ssna .

MODELS'

MODELS 421,
421A AND 421B
GOLDEN EAGLE
AND EXECUTIVE
COMMUTER
FOREWORD

This Service Manual contains factory recommended procedures and

instructions for ground handling, servicing and maintaining the Cessna
421, 421A, 421 Golden Eagle, and 421 Executive Commuter. Where
there is a specific difference, reference has been made to the individual
model aircraft. Besides serving as a reference for the experienced
mechanic, this Service Manual also covers step-byystep procedures for
the less experienced mechanic. This Service Manual should be kept in a
handy place for ready reference. If properly used, it will better enable
the mechanic to maintain the aircraft and, thereby, establish a reputation
for reliable service.

The information in this Service Manual is based on data available at

the time of publication, and is supplemented and lœpt current by Service
Letters and Service News Letters published by Cessna Aircraft Company.
These are sent to all Cessna Dealers so that they have the latest authori,
tative recommendations for servicing Cessna aircraft. Therefore, it is
recommended that Cessna owners utilize the knowledge and experience
of the factory-trained Dealer Service Organization.

In addition to the information in this Service Manual, a group of ven-

dor publications are available from the Cessna Customer Service De-
partment which describe complete disassembly, overhaul and parts
breakdown of some of the various vendor equipment items. A listing
of the available publications is issued periodically in Service Letters.

LATESTCHANGED PAGES SUPERSEDE

THE SAME PAGES OF PREVIOUS DATE
insert changed pages into basic
publication. Destroy supersede'd pages.

NOTE: This reprint

incorporates
of basic Service Manual D817-13 dated April 1970
Change 1 dated August 1970, Change 2 dated De-
SERVKE MANUAL
cember 1970, Change 3 dated April 1971, Change 4 dated De- A PR I L 197 O
cember 1971, Change 5 dated June 1972, Change 6 dated October
1972, Change 7 dated December 1972, Change 8 dated October CHANGED FEBRUARY 1975
1973, Change 9 dated February 1974, Change 10 dated May 1974,
Change 11 dated October 1974 and Change 12 dated February 1975.
D817-13-RAND---2504/75
 421 SERVICE MANUAL

INSERTLATESTCHANGEDPAGES. DESTROYSUPERSEDEDPAGES

ILIST OF EFFECTIVE
PAGES NOTE: The portion
by a vertical
of the text affected by the current change is indicated
line in the outer margin of the page.

Dates of issue for original and changed pages are:

Original . . 0 . . . April 1970 Change . . . 6 . . . October 1972
Change . . . 1 . . . August 1970 Change . . . 7 . . . December 1972
Change . . . 2 . . . December 1970 Change . . . 8 . . . October 1973
Change . . . 3 . . . April 1971 Change . . . 9 . . . February 1974
Change . . . 4 . . . December 1971 Change . . .10 . . . May 1974
Change . . . 5 . . . June 1972 Change . . .11 . . . October 1974
Change . . .12 , . . February 1975

TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 988, CONSISTING OF THE FOLLOWING:

Page Change Page Change Page Change

No. No. No. No. No. No.

*Title . . . . . . . 12 2-40 . . . . . . . 11 3-14A - 3-14B . . . 1

*A D -
. . . . . . . 12 2-40A . . . . . . . 11 3-15 . . . . . . , 1
*E Blank . . . . . . 11 2-40B Blank . . . . 11 3-16 . . . . . . . 4
i . . . . . . . . . 8 2-41 . . . . . . . 9 3-17 - 3-18 . . . . 8
*ii . . . . . . . . 12 *2-42 , . . . . . . 12 3-19 - 3-21 . . . . 11
*1-1 - 1-3 . . . . . 12 *2-42A . . . . . . . 12 *3-22 . . . . . . . 12
1-4 . . . . . . . . 0 2-42B Blank . . . . 9 *3-22A Added . . . . 12
1-5 . . . . . . . . 6 2-43 . . . . . . . 9 *3-22B Blank Added . 12
1-6 . . . . . . . . 1 2-44 . . . . . . . 11 3-23 - 3-26 . . . . 0
1-7 - 1-8 . . . . . 0 2-45 - 2-46 . . . .
11 4-1 . . . . . . . . 6
1-9 -
1-10 . . . . 4 2-47 . . . . . . . 10 4-2 - 4-3 . . . . . 0
1-11 - 1-12 . . . . 11 *2-48 . . . . . . . 12 4-4 . . . . . . . . 4
1-13 - 1-14 . . . . 10 2-48A . . . . . . . 8 4-5 . . . . . . . . 0
1-15 . . . . . . . 5 2-48B Blank . . . . 8 4-6 . . . . . . . . 3
1-16 . . . . . . . 11 *2-49 - 2-50 . . . . 12 4-6A . . . . . . . 7
1-17 - 1-18 . . . . 2 *2-50A - 2-50B . . . 12 4-6B Blank . . . . 7
2-1 . . . . . . . . 11 *2-51 . . . . . . . 12 4-7 - 4-9 . . . . . 11
*2-2 . . . . . . . . 12 2-52 . . . . . . . 8 4-10 . . . . . . . O
2-2A . . . . . . . 11 2-53 . . . . . . . 5 4-11 . . . . . . . 1
2-2B Blank . . . . 11 *2-54 . . . . . . , 12 4-12 . . . . . . . 11
2-3 . . . . . . . . 1 2-55 . . . . . . . 10 4-12A . . . . . . . 4
2-4 . . . . . . . . 11 2-56 - 2-58 . . . . 4 4-12B Blank . . . . 4
2-5 . . . . . . . . 6 2-59 . . . . . . . 11 4-13 - 4-16 . . . . 11
2-6 - 2-7 . . . . . O 2-60 . . . . . . . 10 4-16A . . . . . . . 11
2-8 - 2-9 . . . . . 8 2-61 - 2-62 . . . . 9 4-16B Blank . . . . 11
2-10 - 2-11 . . . . 4 2-63 - 2-66 . . . . 4 4-17 - 4-19 . . . . 9
2-12 . . . . . . . 8 *2-67 . . . . . . . 12 4-20 - 4-23 . . . . 10
2-12A - 2-12F . . . 8 2-68 . . . . . . . 11 4-24 . . . . . . . 11
2-13 . . . . . . . 11 *2-69 . . . . . . , 12 4-24A . . . . . . . 11
2-14 - 2-15 . . . . 8 2-70 - 2-72 . . . . 8 4-24B Blank . . . . 11
2-16 - 2-17 . . . . 11 3-1 . . . . . . . . 2 4-25 . . . . . . . 10
*2-18 - 2-22 . . . . 12 3-2 . . . . . . . . O 4-26 - 4-29 . . . . 2
2-22A . . . . . . . 11 3-3 - 3-4 . . . . . 6 4-30 . . . . . . . 6
2-22B . . . . . . . 7 3-4A - 3-4B . . . . 6 4-31 - 4-32 . . . . 2
2-22C . . . . . . . 8 3-5 - 3-6 . . . . , O 4-33 - 4-34 . . . . 11
2-22D Blank . . . . 8 3-6A . . . . . . . 11 4-34A - 4-34B . . . 11
2-23 . . . . . . . 7 3-6B Blank . . . . 11 4-35 - 4-37 . . . . 11
2-24 - 2-26 . . . . 4 3-7 . . . . . . . . 11 4-38 . . . . . . . 9
2-27 . . . . . . . 6 *3-8 . . . . . . . . 12 4-39 - 4-40 . . . . 2
2-28 - 2-29 . . . . 4 3-9 . . . . . . . . 1 4-41 . . . . . . . 7
2-30 . . . . . . . 5 *3-10 . . . . . . . 12 4-42 . . . . . . . 2
2-31 . . . . . . . 4 3-10A - 3-10B . . . 0 4-42A . . . . . . . 2
2-32 - 2-33 . . . . 11 3-10C . . . . . . . 7 4-42B . . . . . . . 7
2-34 . . . , , . . 10 3-10D - 3-10E . . . 8 4-43 - 4-45 . . . . 0
*2-35 . . . . . . . 12 3-10F - 3-10G . . . 6 4-46 . . . . . . . 4
2-36 Blank . . . . 9 3-10H . . . . . . . 2 4-47 . . . . . . . 11
2-37 . . . . . . . 4 3-11 - 3-12 . . . . O 4-48 . . . . . . . 2
2-38 . . . . . . . 11 3-12A - 3-12B . . . O 4-49 . . . . . . . 0
*2-39 . . . . . . . 12 3-13 - 3-14 . . . . O 4-50 . . . . . . . 9

* The asterisk indicated pages changed, added or deleted by the current change,

à Change 12
 421 SERVICE MANUAL

LISTOF EFFECTIVE
PAGES
Page Change Page Change Page Change
No. No. No. No. No. No.
4-51 - 4-52 . . . - 0 9-4B Blank . . . . 8 9-50B . . . . . . . 10
4-53 - 4-54 . . . . 8 9-5 - 9-6 . . . . . 11 9-51 . . . . . . . O
*4-55 . . . . . . . 12 9-7 - 9-8 . . . . . O 9-52 - 9-55 . . . . 10
4-56 - 4-57 . . . . O 9-8A - 9-8C . . . . O 9-56 Blank . . . . 10
4-58 . . . . . . . 2 9-8D Blank . . . . O *10-1 - 10-9 . . . . 12
4-59 - 4-60 . . . . O 9-9 . . . . . . . . 6 *10-10 Blank . . . . 12
5-1 . . . . . . . . 10 9-10 . . . . . . . 0 *10-11 Deleted . . . 12
5-2 . . . . . . . . 9 9-11 . . . . . . . 7 *10-12 Blank
5-2A . . . . . . . 9 9-12 . . . . . . . O Deleted . . . . . 12
5-2B . . . . . . . 8 9-12A - 9-12B . . . 7 11-1 . . . . . . . 2
5-3 . . . . . . . . 1 9-13 - 9-14 . . . . 11 11-2 . . . . . . . 11
5-4 - 5-5 . . . . . 0 *9-14A . . . . . . . 12 11-2A . . . . . . . 11
5-6 . . . . . . . . 4 9-14B Blank . . . . 9 11-2B . . . . . . . 5
5-7 . . . . . . . . 6 9-15 . . . . . . . 9 11-3 . . . . . . . O
*5-8 . . . . . . . . 12 9-16 - 9-18 . . . . 6 *11-4 . . . . . . . 12
5-9 . . . . . . . . 4 9-18A . . . . . . . 6 *11-4A . . . . . . . 12
5-10 - 5-11 . . . . O 9-18B . . . . . . . 8 11-4B Blank . . . . 11
5-12 - 5-13 . . . . 10 9-19 . . . . . . . 4 *11-5 . . . . . . . 12
5-14 . . . . . . . 0 9-20 . . . . . . . 0 11-6 . . . . . . . 11
5-15 - 5-16 . . . . 9 9-20A . . . . . . . 4 11-6A . . . . . . . 8
6-1 . . . . . . . . 10 9-20B Blank . . . . 4 11-6B . . . . . . . 2
6-2 . . . . . . . . 9 9-21 . . . . . . . 5 *11-6C . . . . . . . 12
*6-3 . . . . . . . . 12 9-22 . . . . . . . 11 11-6D Blank . . . . 2
6-4 . . . . . . . . 9 *9-23 . . . . . . . 12 11-7 . . . . . . . 8
6-4A 6-4C
-
. . . . 9 9-24 . . . . . . . 0 11-8 . . . . . . . 11
6-4D Blank . . . . 9 9-25 . . . . . . . 8 11-8A . . . . . . . 9
*6-5 - 6-6 . . . . . 12 9-26 - 9-28 . .
. . 0 11-8B . . . . . . . 6
6-7 . . . . . . . . 9 9-29 . . . . . . . 9 11-8C . . . . . . . 4
6-8 . . . . . . . . O 9-30 . . . . . . . 10 11-8D . . . . . . . 6
6-9 - 6-10 . . . . 9 9-31 - 9-33 . . . . O 11-9 - 11-10 . . . O
6-11 . . . . . . . 1 9-34 . ... . . . . 9 11-11 . . . . . . . 1
6-12 . . . . . . . O 9-34A . . . . . . . 10 *11-12 . . . . . . . 12
6-13 . . . . . . . 6 9-34B - 9-34C . . . 11 11-12A - 11-12B . . 9
6-14 Blank . . . . 6 9-34D Blank . . . . 11 11-13 . . . . . . . 9
7-1 . . . . . . . . 10 9-35 . . . . . . . 4 11-14 . . . . . . . 6
7-2 - 7-4 . . . . . 9 9-36 . . . . . . . 0 11-15 . . . . . . . 11
7-4A . . . . . . . 9 9-37 . . . . . . . 4 11-16 . . . . . . . 6
7-4B Blank . . . . 9 9-38 . . . . . . . O 11-16A , . . . . . 2
7-5 - 7-6 . . . . . 9 9-38A . . . . . . . O 11-16B - 11-16C . . 1
*7-6A . . . . . . . 12 9-38B . . . . . . . 10 11-16D . . . . . . 11
7-6B Blank . . . . 4 9-39 . . . . . . . 2 *11-17 - 11-18 . . . 12
*7-7 . . . . . . . . 12 9-40 . . . . . . . 0 11-19 11-21
-
. . . O
7-8 - 7-11 . . . . 9 9-41 . . . . . . . 8 11-22 Blank . . . . O
7-12 Blank . . . . 9 9-42 . . . . . . . 0 12-1 . . . . . . . 10
8-1 . . . . . . . , 10 9-42A . . . . . . . 8 12-2 . . . . . . . O
8-2 . . . . . . . . 8 9-42B . . . . . . . 1 12-2A . . . . . . . O
8-2A . . . . . . . 8 9-43 . . . . . . . 1 12-2B Blank . . . . O
8-2B Blank . . . . 8 9-44 . . . . . . . 8 12-3 - 12-6 . . . . O
8-3 - 8-4 . . . . . 8 9-44A . . . . . . . 0 12-6A . . . . . . . 1
*8-5 . . . . . . . . 12 9-44B - 9-44C . . . 4 12-6B - 12-6C . . . 8
8-6 . . . . . . . . 5 9-44D Blank . . . . 4 12-6D . . . . . . . 10
*8-6A . . . . . . . 12 9-45 . . . . . . . 4 12-7 . . . . . . . 7
8-6B Blank . . . . 8 9-46 . . . . . . . 0 12-8 . . . . . . . O
*8-7 - 8-8 . . . . . 12 9-46A - 9-46B . . . 0 12-9 . . . . . . . 11
8-9 . . . . . . . . 9 9-47 . . . . . . . O 12-10 . . . . . . . 10
8-10 . . . . . . . 10 9-48 . . . . . . . 5 12-10A - 12-10B . . 11
8-11 - 8-12 . . . . 9 9-48A . . . . . . . 5 12-11 . . . . . . . 6
9-1 - 9-2 . . . . . 8 9-48B . . . . . . . 4 12-12 . . . . . . . 5
9-3 . . . . . . . . 4 9-49 . . . . . . . 11 12-13 . . . . . . . O
9-4 . . . . . . . . 8 9-50 . . . . . . . O 12-14 . . . . . . . 9
9-4A . . . . . . . 8 9-50A . . . . . . . 4 12-15 . . . . . . . O
12-16 . . . . . . . 4
12-16A - 12-16B . , 11

Chonge 12 O
 421 SERVICE MANUAL

LISTOF EFFECTIVE
PAGES

Page Change Page Change Page Change

No, No- No. No. No. No.

12-17 . . . . . . . 0 13-40B Blank . . . 8 *13-100 Blank Added. 12

12-18 . . . . . . . 9 13-41 . . . . . . . 8 14-1 . . . . . . . 10
12-19 . . . . . . . 4 13-42 . . . . . . . 11 *14-2 . . . . . . . 12
12-20 - 12-21 . . - 9 13-42A - 13-42B . . 11 14-2A . . . . . . . 4
12-22 Blank . . . . 9 13-42BA . . . . . . 11 14-2B Blank . . . . 4
13-1 - 13-2 . . . . 11 13-42BB Blank . . . 11 14-3 . . . . . . . 2
13-2A . . . . . . . 11 13-42C - 13-42E , . 11 14-4 . . . . . . . 0
13-2B . . . . . . . 10 13-42F . . . . . . 6 14-4A . . . . . . . 0
13-2C . . . . . . . 6 13-42G . . . . . . 11 14-4B . . . . . . . 4
13-2D - . . . . . . 8 13-42H - 13-42I . 6 14-4C . . . . .
. . 8
13-3 - 13-4 . . . . 8 13-42J Blank , . . 6 14-4D - 14-4E . . . 11
13-4A . . . . . . . 2 13-43 - 13-46 . . . O 14-4F Blank . . . . 10
13-4B 13-4C
-
. . . 8 13-47 - 13-48 . . . 1 14-5 - 14-6 . . . . 11
13-4D Blank . . . . 8 13-48A - 13-48C . . 1 14-7 - 14-9 . . . . 4
13-5 .
. . . . . . 8 13-48D Blank . . . 1 14-10 . . . . . . . 8
13-6 . . . . . . . 9 13-49 - 13-50 . . . O 14-10A . . . . . . 10
13-7 - 13-8 . . . . 6 13-51 . . . . . . . 9 *14-10B - 14-10D . . 12
13-8A . . . . . . . 6 13-52 . . . . . . . 6 14-10E - 14-10F . . 10
13-8B Blank . . . . 6 13-53 - 13-56 . . . 9 14-11 . . . . . . . 10
13-9 - . . . . . . 6 13-57 - 13-64 . . . 11 14-12 , , . . . . . 11
13-10 -
. . . . . . 2 13-64A - 13-64B . . 11 14-12A . . . . . . 11
13-11 - 13-13 . . . 0 13-64C - 13-64F . . 11 14-12B . . . . . . 4
13-14 - 13-15 . . . 7 13-64G - 13-64H . . 11 14-13 . . . . . . . 10
13-16 . . . . . . . 11 13-64I - 13-64N . . 9 14-14 . . . . . . . 4
13-16A - 13-16B . . 11 13-64NA . . . . . . 11 14-14A - 14-14B . . 11
13-17 - 13-18 . . . 11 13-64NB Blank . . . 11 14-14C . . . . . . 10
13-18A . . . . . . 11 13-640 - 13-64R . . 11 14-14D Blank . . . 10
13-18B Blank . . . 11 13-643 - 13-64V . . 9 14-15 . . . . . . . 1
13-19 . . . . . . . 5 13-65 . . . . . . . 7 14-16 . . . . . . . 4
13-20 . . . . . . . 0 13-66 . . . . . . . 0 14-16A . . . . . . 4
*13-20A . . . . . . 12 13-66A . . . . . . 10 14-16B Blank . . . 4
13-20B . . . . . . 11 13-66B Blank . . . 6 14-17 . . . . . . . 2
*13-20C . . . . . . 12 13-67 . . . . . . . 11 14-18 . . . . . . . 6
13-20D Blank . . . 11 13-68 - 13-70 .
. . 10 14-18A . . . . . . 6
*13-21 - 13-22 . . . 12 13-70A . . . . . . 10 14-18B Blank . . . 6
13-22A . . . . . . 11 13-70B Blank . . . 10 14-19 . . . . . . . 6
*13-22B . . . . . . 12 13-71 . . . . . . . 6 14-20 . . . . . . . 10
13-23 . . . . . . . 11 *13-72 . . . . . . . 12 14-21 . . . . . . . O
*13-24 - . . . . . . 12 13-73 - 13-74 . . . 0 14-22 . . . . . . . 10
13-24A . . . . . . 4 *13-75 . . . . . . . 12 14-22A - 14-22B . . 10
13-24B . . . . . . O 13-76 - 13-77 , . . 10 14-22C . . . . . . 4
13-25 . . . . . . . O 13-78 . . . . . . . 11 *14-22D . . . . . . 12
13-26 · · · · · · · 7 13-78A . . . . . . 11 *14-22DA Added .. . . 12
13-27 . . . . . . . 6 13-78B Blank . . . 11 *14-22DB Blank
13-28 . . . . . . . O 13-79 . . . . . . . 11 Added . . . . . . 12
13-28A . . . . . . 2 13-80 . . . . . . . 10 14-22E - 14-22F . . 10
13-28B Blank . . . 2 13-80A . . . . . . 11 *14-22G - 14-22H . . 12
13-29 . . . . . . . 8 13-80B Blank . . . 11 *14-23 - 14-24 . . . 12
13-30 - . . . . . . 10 13-81 - 13-83 . . . 11 14-25 . . . . . . . 8
*13-31 - 13-32 . . . 12 13-84 - 13-85 . . . 0 14-26 . . . . . . . 0
13-32A . . . . . . 6 13-86 - 13-88 . . . 8 14-27 - 14-28 . . . 4
*13-32B . . . . . . 12 13-88A . . . . . . 8 14-29 - 14-31 . . . O
13-33 . . . . . .
. 8 13-88B - 13-88C , . 9 14-32 . . . . . . . 2
13-34 . . . . .
. . 4 13-88D Blank . . . 9 14-33 - 14-35 . . . O
13-35 - . . . . . . 0 *13-89 . . . . . . . 12 14-36 , , . . . . . 8
13-36 . . . . . . . 8 13-90 - 13-91 . . . 11 *14-37 . . . . . . . 12
13-36A . . . . . . 4 13-92 . . . . . . . 10 14-38 . . . . . . . 8
13-36B . . . . . . 8 13-93 - 13-94 . . . 5 14-39 - 14-41 . . . 0
13-36C - 13-36D . . 11 13-95 . . . . . . . 10 14-42 - 14-43 . . . .4

13-37 - 13-38 . . . 10 13-96 . . . . . . . 5 14-44 - 14-49 . . . 0

13-39 - 13-40 . . . 11 *13-97 - 13-98 . . . 12 14-50 . . . . . . . 10
13-40A - . . . . . 10 *13-99 Added . . . . 12

C Change 12
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PAGES

Page Change Page Change Page Change

No. No. No. No. No. No.

14-51 - 14-52 . . . 0 15-2 . . . . . . . 7 16-62 . . . . . . . 7

14-53 . . . . . . . 8 15-2A - 15-2B . . . 2 16-63 - 16-65 . . . 2
14-54 . . . . . . . 0 *15-2C - 15-2D . . . 12 16-66 . . . . . . . 5
14-55 . . . . . . . 5 *15-2E - 15-2H *16-67 Added . . . . 12
14-56 . . . . . . . 2 Added . . . . . . 12 *16-68 Blank Added . 12
14-57 . . . . . . . 6 15-3 - 15-6 . . . . 0
14-58 . . . . . . . 5 15-6A - 15-6B . . . 0
14-59 . . . . . . . 4 15-7 - 15-9 . . . . 1
14-60 . . . . . . . 2 15-10 . . . . . . . 0
14-61 . . . . . . . 4 15-11 - 15-12 . . . 1
14-62 - 14-63 . . . 2 15-12A . . . . . . 1
14-64 - 14-65 . . . 4 15-12B Blank . . . 1
14-66 . . , . - . . 9 15-13 . . . . . . . 1
14-67 - 14-68 . . . 11 15-14 - 15-15 . . . 0
14-69 . . . . . . . 4 15-16 . . . . . . . 1
14-70 . . . . . . . 0 15-16A . . . . . . 1
14-71 . . . . . . . 9 15-16B . . . . . . 2
14-72 Blank . . . . 9 15-16C . . . . . . 0
14-73 . . . . . . . 11 15-16D . . . . . . 2
14-74 - 14-77 . . . 0 15-16E . . . . . . 1
14-78 . . . . . . . 8 15-16F - 15-16G . . 2
14-79 . . . . . . . 10 15-16H - 15-16J . . 1
14-80 . . . . . . . 1 15-17 - 15-18 . . . 1
14-81 . . . . . . . 10 15-18A . . . . . . 1
14-82 - 14-86 . . . 0 15-18B Blank . . . 1
14-87 - , . . . . . 4 15-19 - 15-20 . . . 1
14-88 . . . . . . . 0 15-20A - 15-20D . . 1
14-89 . . . . . . . 4 15-21 - 15-26 . . . 1
14-90 - 14-92 . . . 0 15-26A - 15-26E . . 1
*14-93 . . . . . . . 12 15-26F . . . . . . 2
14-94 . . . . .
. . 4 15-26G - 15-26H . . 1
*14-95 - 14-96 . . . 12 15-27 - 15-32 . . . 1
14-97 . . . . . . . 10 *15-32A - 15-32D . . 12
14-98 . . . . . . . 11 15-33 - 15-34 . . . 1
14-99 - 14-101 . . 5 15-34A - 15-34B . . 0
14-102 . . . . . . 8 15-35 - 15-46 . . . 0
14-102A - 14-102B . 11 16-1 . . . . . . . 7
14-102C . . . . . . 11 16-2 . . . . . . . 5
14-102D Blank . . . 11 16-3 - 16-4 . . . . 0
*14-103 - 14-104 . . 12 16-5 . . . . . . . 6
14-105 . . . . . . 8 16-6 . . . . . . . 0
14-106 Blank . . . 8 16-6A . . . . .
. . 4
14-107 - 14-109 . . 11 16-6B - 16-6D . . . 8
14-110 - 14-111 . . 6 16-7 . . . . . . . 0
14-112 . . . . . . 8 16-8 . . . . .
. . 5
14-113 . . . . . . 10 16-9 - 16-11 . . . 0
14-114 . . . . . . 11 *16-12 . . . . . . . 12
14-114A . . . . . . 8 *16-12A Added .
. . 12
14-114B Blank . . . 8 *16-12B Blank
14-115 . . . . . . 8 Added . . . . . . 12
14-116 - 14-117 . . 6 16-13 . . . . . . . 0
14-118 - 14-119 . . 11 16-14 . . . . .
. . 8
14-120 . . . . . . 6 16-15 - 16-18 . . . 6
14-120A . . . . . . 8 16-19 . . . . . . . 10
14-120B Blank . . . 8 *16-20 . . . . . . . 12
14-121 . . . . . . 8 16-21 . . . . . . . 8
*14-122 - 14-124 . . 12 16-22 - 16-24 . . . 2
14-125 . . . . . . 8 16-25 - 16-49 . . . 0
14-126 . . . . . . 11 16-50 . . . . . . . 2
14-127 - 14-128 . . 8 16-51 . . . . . . . 0
*14-129 . . . . . . 12 16-52 . . . . . . . 8
*14-130 Blank 12 16-53 16-61
. . . -

. . . 0
*15-1 . . . . . . . 12

Change 12
09/E
 421 SERVICE MANUAL

SECTION
OFCONTENTS
TABLE
PAGE

1 GENER A L INFORM ATION ...................................................................

1-1

2 GROUND HA NDL IN G, SERVICING A ND INSPECT ION ................... 2 -1

3 AIRFRAME ............................................................................................ 3 -l

4 LANDING GEAR AND BRAKE SYSTEM ......----------....-...........--.----- 4-1

5 CONTROL COLUMN,
AILERON A NDTR IMCONTROLSYSTEMS ....................................... 5 -1

6 ELEVATOR AND TRIM CONTROL SYSTEMS ....................................

6-1

7 RUDDER A ND TRIMCONTROLSYSTEMS ....................................... 7 -1

8 FLA PCONTROLSYSTEM ................................................................... 8 -l

9 ENG INE ................................................................................................ 9 -1

10 PROPELLERSYSTEM ............................................................................ 10 -1

11 FUEL SYSTEM .......................................................................................

11-1

l2 INSTRUMENT A NDREL ATEDSYSTEMS ........................................... l2 -l

13 UTILITY A NDOPT I ON A L SYSTEMS ............................................. 13 -1

14 ELECTRICA LSYSTEMS .........................................................................

14 -l

15 ELECTRON ICSSYSTEMS ...................................................................... 15 -1

16 STRUCTUR ALREP AIR ..........................................................................

16 -l

Change 8
 421 SERVICE MANUAL

SERVICE LETTERS AND SERVICE KITS

Service Letters and Service Kits (SK's) provide instructions for making modification changes to
the aircraft in service.

When a Service Letter or Service Kit is initially incorporated into this Service Manual, informa-
tion applicable to the change is referenced in the text or illustrations, and the Service Letter
and/or Service Kit is listed below. At the first revision of the Service Manual, after the infor-
mation is incorporated, the Reference Data will be eliminated from the Data Record below.

REFERENCE ISSUE INCORPORATED

DATA DATE TITLE DATË

Cessna Avionics 8-30-74 ELT System Improvements Feb 1975

Service Letter
AV74-14

Cessna Avionics 9-13-74 ELT Modification Feb 1975

Service Letter
AV74-16

Cessna Service 8-9-74 Voltage Regulator Feb 1975

Letter ME74-13 Modification

Cessna Service 12-18-74 Exhaust System Inspection Feb 1975

Letter ME74-21

CHANGE SYMBOLS

Changes to text and tables in the manual are indicated by a vertical black line in the margin
which extends along the entire length of the area affected. Changes to Illustrations, Charts
and Tables are indicated by miniature pointing hands. Change Symbols are not shown for:

1. Introductory material, indexes and tabular data.

2. Blank spaces which are the result of text, illustration or table deletion.

3. Correction of minor inaccuracies, such as punctuation, relocation of material, etc.,

unless such a correction changes the meaning of instructive information and procedures.

Change 12
 421 SERVICE MANUAL GENERAL INFORMATION Î-l

SECTION 1

GENERAL INFORMATION
Table of Contents

General Description . . . . . . .
1-1
Principal Dimensions . . . . . . .
1-1

MODEL NUMBER AND SERIAL

MODEL YEAR BEGINNING ENDING

421 1968 421-0001 421-0200

421A 1969 421A0001 421A0158
421B 1970 421BOOO1 421B(Í056
421B 1971 421B0101 421B0147
421B 1972 421B0201 421B0275
421B 1973 421B0301 421BO486
421B 1974 421B0501 421BO665
421B 1975 421B0801

GENERAL DESCRIPTION:

The Model 421 is an all-metal, low-wing, pressurized executive aircraft built by Cessna Aircraft Companÿ,
Wichita, Kansas. The pressurized cabin permits flights to 24, 000 feet on aircraft 421-0001 to 421BO301 and
26, 500 feet on aircraft 421B0301 and on, without the use of oxygen. The aircraft is powered by two Continental
Turbocharged GTSIO-520-D and GTSIO-520-H, six cylinder, fuel injected 375 horsepower engines. The en-
gines drive, three blade constant-speed, full-feathering 90-inch McCauley propellers. The landing gear on the
Model 421 is tricycle-type, fully retractable and electrically operated. Trim tabs located on the right elevator,
left aileron, and the rudder are provided to aid in flight adjustment; also provided are split-type electrically-
operated wing flaps to aid in landing.

PRINCIPAL DIMENSIONS:

GROSS WEIGHT
421 . . . . . . . . . . . . 6800 Pounds
421A . . . . . . . . . . . . 6840 Pounds
421 Golden Eagle (421BOOO1 to 421BO201) . . . . 7250 Pounds
421 Executive Commuter (421-0001 to 421B0001) . . 7250 Pounds
. 421 Golden Eagle (421B0201 and On) . . . . . 7450 Pounds
421 Executive Commuter (421BO201 and On) . . . 7450 Pounds

LANDING WEIGHT
421 . . . . . . . . . . . . 6500 Pounds
421A . . . . . . . . . . . . 6500 Pounds
421 Golden Eagle . . . . . . . . . 7200 Pounds
421 Executive Commuter . . . . . . . . 7200 Pounds

Change 12
Î- SENERAL INFORMATION 421 SERVICE MANUAL

PRINCIPAL DIMENSIONS (CONTINUED):

ENGINES: Continental GTSIO-520-D (421-0001 to 421B0001),

Continental GTSIO-520-H (421B0001 and ON),
Opposed, Fuel Injected, Turbocharged, Wet Sump

HP (maximum) . . . . . . . . . . 375 2275 RPM and

39. 5 Hg. Manifold Pressure
Compression Ratio . . . . . . . . . 7. 5:1
Fuel . . . . . . . . . . . . Grade 100/130 Minimum
Oil Capacity Each Engine Sump . . . . . . 13 Quarts
Magnetos . . . . . . . . . . . Bendix S6LN-1205
Delco-Remy
Starters............ 28V,50Amp
Alternators . . . . . . . . . . . 28V, 100 Amp (Optional)
28V, 100 Amp DC; 185 VAC (Optional)

PROPELLER: McCauley (3AF34C92/90LF-0) Constant-

Speed, Three Bladed, Full-Feathering

Diameter . . . . . . . . . . . 90 Inches

BATTERY (LH Stub Wing) . . . . . . . . . 24V, 24 Amp-Hr

FUEL CAPACITY:
Main Tanks (each wing) . . . . . . . . 51. 0 U. S. Gallons
Usable (each wing) . . . . . . . . 50. 0 U. S. Gallons

Auxiliary Tanks (each wing) . . . . . . . 36. 5 U. S. Gallons

Usable (each wing) . . . . . . . . 35. 0 U. S. Gallons

Optional Wing Tanks (each wing) . . . . . . 13. 5 U. S. Gallons

Usable (each wing) . . . . . . . . 13. 0 U. S. Gallons

Wing Locker Tanks (each wing) . . . . . . 26. 3 U. S. Gallons

Usable (each wing) . . . . . . . . 26. 0 U. S. Gallons

CONTROL SURFACE TRAVEL:

Flap
Down...........45°+1°-0°

Aileron
Up............20°+1°-0°
Down...........20°+1°-0°

Aileron Trim Tab

Up............20°+1°-0°
Down...........20°+1°-0°

Change 12
 421 SERVICE MANUAL SENERAL INFORMATION l "Ë
PRINCIPAL DIMENSIONS (CONTINUED):

Rudder (Measured perpendicular to hinge line)

25°

l
+1°
Left (421-0001 to 421B0801)
-0°

. . . . . .

25° +1°
Right (421-0001 to 421B0801)
-0°

. . . . . .

32° +1°
Left (421BO801 and On)
-0°

. . . . . . .

32° +1°
Right (421B0801 and On)
-0°

. . . . . . .

Rudder Trim Tab (Measured perpendicular to hinge line)

...........16°+1°-0°

Left
Right 11° +1° -0°

. . . . . . . . . . .

Elevator
Up . . . . .
25°+1°-0°
. . . . .

Down
15° +1° -0°

. . . . . . . . . . .

Elevator Trim Tab o

10° +1°
Up (421-0001 to 421BOOO1)
-0°

. . . . . .

(421BOOO1and On) . .
12° +1° -0°

. . . . .

Down (421-0001 to 421BOOO1) .

26° +1° -0°

. . . .

20°
.

+1°
(421B0001 and On)
-0°

. . . . . . .

LANDING GEAR:

Main Wheels and Brakes (Five-Piston, Dual Dise Type)

Tire Size . . . . . . . . . . 6. 50 x 10 -

8 Ply Rating
Tire Pressure (421-0001 to 421BOOO1) . . . 65 psi
(421BOOO1 and On) . . . . 70 psi

Main Strut Pressure (without load) (421-0001 to 421BOOO1) 200 psi

(421BOOO1 and On) . 275 psi

Nose Wheel
Tire Size . . . . . . . . . . 6, 00 x 6 -

6 Ply Rating
Tire Pressure (421-0001 to 421B0001) . . . 32 psi
(421BOOO1 and On) . . . . 35 psi

Nose Strut Pressure (without load) . . . . . 65 psi

0°
WING DIHEDRAL (Outboard of Wing Fittings) . . . . 5.

Change 12
1-4 eENERAL INFORMATION 421 SERVICE MANUAL

11. 58'

10.49'
33.75'
17.0

10.00'

39.06'

90" DIA

7.46
14.92' 421-0001 TO 421BOOO1

Figure 1-1. General Dimensions (Sheet 1 of 2)

 421 SERVICE MANUAL GENERAL INFORMATION 1-5

o . 11. 58 '

10. 49'
36. 08'
17. 0'

10. 00'
0 0

- -

1. 86'

90" DIA

8. 46'
16.92'

Figure 1-1. General Dimensions (Sheet 2 of 2)

Change 6
1-6 ENERAL INFORMATioN 421 SERVICE MANUAL

20

19
18 17 16 15 14 1

oL J
O

FUSELAGE BOTTOM

2 3 4 5
1

11 10

LH FUSELAG

101
10
103
104

Detail $
421BOOO1 AND ON
Detail
OPTIONAL 421BOOO1 AND ON
12 2 1

10 11
RH FUSELAGE

4 13

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 1 of 7)

Change 1
 421 SERVICE MANUAL OENERAL INFORMATION

21 22 23 33
30 34

24 25 26 27 28 29

36

UPPER LH WING

39 38

421-0001 TO 421BOOO1
Those indexed items which are denoted
by a star (*) are considered to be struc-
tural support items and must be secured
in place before attempting any taxi or
30 flight operations.

21
29
91 28 27 26 25 24 2 22

34

UPPER RH WING
39
38

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 2 of 7)

1-8 6ENERAL INFORMATION 421 SERVICE MANUAL

49

50

5 53 4
0 41 42 43 44 45 46 47 48

o o o o 2,

58
- OO
38

68 67 66 62 85 64 63 62 60 59

LOWER RH WING 6Û 61

49
421-0001 TO 421B0001
Those indexed items which are denoted
by a star (*) are considered to be struc-
tural support items and must be secured
in place before attempting any taxi or
50 flight operations.
7 3 51
56 55 54 53 52
,

59 83 61 62 63 64 65 62 66 87 88
LOWER LH WING

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 3 of 7)

 421 SERVICE MANUAL GENERAL INFORMATION 1"$

32
31

21 22 23 33
30 34

24 25 26 27 28 29

37

I
I

UPPER LH WING

39 38

31 32 WARNING ]
421B0001 AND ON
Those indexed items which are denoted
by a star (*) are considered to be struc-
tural support items and must be secured
in place before attempting any taxi or
3ÿ flight operations.

21
29
91 28 27 26 25 24 23 22

34

UPPER RH WING
39
38

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 4 of 7)

Change 4
1-10 GENERAL INFORMATION 421 SERVICE MANUAL

49

50

41 42 43 44 45 46 47 48

68 67 66 62 65 84 83 62 60 59

LOWER RH WING 60 61

49 WARNING|
----------

Those indexed items which are denoted

by a star (*) are considered to be struc-
tural support items and must be secured
in place before attempting any taxi or
50 flight operations.
51
5 5 4 2
47 46 45 44 43 42 41 4

59 60 61 62 63 84 65 62 66 67 68
LOWER LH WING

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 5 of 7)

Change 4
 421 SERVICE MANUAL SEN ERAL INFORMATION Î *ÎÎ

74 76 77 78 79 80 81 82 83 84 108

7 71 70 69 107 106 86 94 85
*421B0201 AND ON
84 108 109
421-0001 TO 421B0301

FUSELAGE FLOORBOARDS
421B0301 AND ON 85 110

NOSE COMPARTMENT SHELVES NOSE COMPARTMENT SHELVES 51112004

(421-0001 TO 421B0001) (421B0001 AND OÑ 51112005
51131004
51133003

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 6)

Change 11
1-12 C,ENERAL INFORMATION 421 SERVICE MANUAL

1. Radome 52. Lower Nacelle Access

2. Equipment Access 53. Nacelle Fuel Access
3. Baggage Door 54. Jür Inlet Access
4. Landang Gear Boot Access 55. Fuel Selector Access
5. Rudder Cable Pulley 56. Wing Fitting Access
6. Rudder Trina Actuator 57. Heat Exchanger Access
7. Fin Tip 58. Battery Drain Access
8. Rudder Balance VVeight 59. Inboard Iñain Gkaar I>Dor
9. Upper Sänger 60. Inboard Flap Button
10. Lower Stinger 61. Outboard Main Gear Door
11. Stabilizer Fairing 62. Outboard Flap Button
12. Baggage Door 63. Auxiliary Fuel Indicator Access
13. Heater Access 64. Aileron Stop Access
14. Nose Gear Door 65. Outboard Flap Access
15. Cable Access 66. Aileron Trim Pulley Access
16. Nose Gear Bellerank 67. Aileron Bellerank Button
17. Aileron Servo Access 68. Aileron Pulley Button
18. Elevator Bellerank Access 69. Left Vacuum Valve Access
19. Elevator Trim Access 70. Pilot's Floor Access
20. Elevator Tip 71. Brake Cylinder Access
21. Tip Tank Nose 72. Nose Gear Boot Access
22. Tip Tank Filler Cap 73. Fuel Selector Gear Box Access
23. Tip T'ank Gap Cover 74. Heater Hose Access
24. Tip Tank Fairing Upper 75. Variable Pressure Control Filter
25. Auxiliary Filler Cap (Optional) 76. Copilot's Floor Access
26. Auxiliary Filler Cap (Standard) 77. Front Spar Access
27. Juleron Bellcrank Access 78. Canted Access (421-0001 to 421BO201)
28. Fuel Tank Access 79. Landing Gear Idler Access
29. Upper Nacelle Cowl 80. Center Fwd Moorboard
30. Left Nacelle Cowl 81. Right Fwd Floorboard
31. Upper Nose Nacelle Cowl 82. Center Alt Floorboard
32. Spinner 83. Right Alt Floorboard
33. Right Nacelle Cowl 84. /dt Cabin Floorboard
34. Fuel Selector Access 85. Left Alt Floorboard
35. Forward Wing Structural Skin (Wing Gap) 86. Left Fwd Floorboard
36. Battery Cables Access 87. LH BaggageTVeb Rear
37. Battery Access 88. LH BaggageTVeb Fwd
38. Aft Wing Gap Cover 89. RH Baggage Web Fwd
39. Tip Tank Fairing 90. 101 BaggageiVeb Rear
40. Tip Tank Fairing Lower 91. Air Conditioning Access Cover
41. Tip Tank Wing Access 92. Wing Locker Fuel Filler Cap
42. Optional Fuel Tank Access 93. Main L. G. Seal Boot Access
43. Outboard L.E. Access 94. Júleron Servo Governor Access
44. Tie-Down Ring Access 95. Fwd Avionics Bay Baggage
45. Auxiliary Fuel Tank Indicator Access 96. Fwd RH Baggage Shelf
46. Fuel Line Clamping Access 97. Aft RH Baggage Shelf
47. Inboard L.E. Access 98. Alt LH Baggage Shed
48. Fuel Vent Check Valve 99. Fwd LH Baggage Shelf
49. Lower Nose Nacelle Cowl 100. Avionics Bay Baggage Access
50. Oil Drain Access 101. LH Baggage Access
51. Nacelle Louver 102. RH Baggage Access
103. LH Avionics Bay Baggage Access
104. RH Avionics Bay Baggage Access
105. Heated \Vindshield Inverter Access
106. Flap Actuator and Limit Switch Access
107. Landing Gear Actuator Access
108. ]Pressurization Valve Access
109. Center Aft Baggage Floor Access
110. LH Aft Baggage Floor Access
111. Pressure Bulkhead Access

Figure 1-2. Inspection Plates and Access Covers Callouts (Sheet 7 of 7)

Change 11
 421 SERVICE MANUAL GENERAL INFORMATION Ε•Ñ

B.L. 42.25

B.L. 31.70

VV.S. 217.66. ---VV.S. 46.89

VV.S. 206.74-- VV.S. 75.24
VV.S. 195.75---- YV.S. 94.74
YV.S. 184.74 VV.S. 107.24
VV.S. 173.74 VV.S. 118.24
TV.S. 162.74 VV.S. 129.24
VV.S. 151.24 VV.S. 140.24

VV.L. 71.92

F. S. 392. 00
F. S. 373. 56
F. S. 21. 00 ¯T¯ F. S. 360. 38
F. S. 34. 00 F. S. 349. 65
F.S. 43.00-- -F.S. 336.70¶lg
F.S. 52.00-- -F.S. 321.94
F.S. 61.00 ---F.S. 305.94
F.S. 70.00- --F.S. 289.94
F.S. 88.00 ----F.S. 273.94
F.S. 100.00 ---F.S. 264.47
F.S. 108.50 ----F.S. 255.00
F.S. 118.55 ----F.S. 246.50
F.S. 130.00 ----F.S. 238.13
F.S. 141.35 ----F.S. 225.50
F.S. 154.50 F.S. 212.87
F.S. 166.95 F.S. 200.75 421-0001 TO 421B0001
51202001R
51103002 F.S. 176.50 F.S. 186.15

Figure 1-3. Station Diagram (Sheet 1 of 3)

Change 10
H4 6ENERAL INFORMATION 421 SERVICE MANUAL

B.L. 54.25
--B.L. 42.25
- --B.L. 31.70

VV.S. 229.71- VV.S. 58.94

VV.S. 218.79-- TV.S. 87.29
VV.S. 207.79--- VV.S. 106.79
VV.S. 196.79---- VV.S. 119.29
TV.S. 185.79 TV.S. 130.29
VV.S. 174.79 VV.S. 141.29
TV.S. 163.29 TV.S 152.29

VV.L. 71.92

F. S. -7.
O
F.S. 0.00
--F.S. 392.90
F.S. 14.35
F.S. 31.00- --F.S. 373.56
F.S. 43.00--- --F.S. 360.38
F.S. 52.00---- ---F.S. 349.65
F.S. 61.00 ----F.S. 336.70 -ggg

F.S 70.00 F.S. 321.94

F.S. 79,00 F.S. 305.94
F.S. 88.00 F.S. 289.94
F.S. 94.95 F.S. 273.94 *(277.20)
F.S. 100.00 F.S. 264.47
F.S. 108.50 F.S. 254.96
F.S. 118.55 F.S. 246.50
F.S. 130.00
*421BO301ed4D CIN
F.S. 238.13
F.S. 141.35 F.S. 225.50
F.S. 154.50 F.S. 212.87
51202001R 421BOOO1 AND ON
F. S. 166. 95 F. S. 200. 75
51104003
F.S. 176.50 F.S. 186.15

Figure 1-3. Station Diagram (Sheet 2)

Change 10
 421 SERVICE MANIJAL SENERAL INFORMATION 1"

W. L. 182. 38
W. L. 177, 38

W. L. 165.97
W. L. 164. 85
W.L. 160.70

(,¡ r W.L. 136.33

W.L. 135. /

W.L. 109.90

B.L.
B. L. 34 50 B. L.
B.L. 47.50 20.70 B.L.
B.L. 61.50 20.70
B. L. 76. 50
94. 22

B. L.
75.75
B.L 421BOOO1
96. 31 AND ON
B. L. B. L. B. L.
20.88 35.75 96.31

Figure 1-3. Station Diagram (Sheet 3 of 3)

Change 5
1-16 SENERAL INFORMATION 421 SERVICE MANUAL

RECOMMENDED NUT TORQUES

THE TORQUE VALUES STATED ARE POUND-INCHES, RELATED
ONLY TO STEEL NUTS ON OIL-FREE CADMIUM PLATED THREADS.

FINE THREAD SERIES

TENSION NUTS SHEAR NUTS

TORQUE TORQUE
TAP
SIZE STD ALT STD ALT
(NOTE 1) (NOTE 2) (NOTE 3) (NOTE 2)
8-36 12-15 7-9
10-32 20-25 20-28 12-15 12-19
1/4-28 50-70 50-75 30-40 30-48
5/16-24 100-140 100-150 60-85 60-106
3/8-24 160-190 160-260 95-110 95-170
7/16-20 450-500 450-560 270-300 270-390
1/2-20 480-690 480-730 290-410 290-500
9/16-18 800-1000 800-1070 480-600 480-750
5/8-18 1100-1300 1100-1600 660-780 660-1060
3/4-16 2300-2500 2300-3350 1300-1500 1300-2200
7/8-14 2500-3000 2500-4650 1500-1800 1500-2900
1-14 3700-5500 3700-6650 2200-3300 2200-4400
1-1/8-12 5000-7000 5000-10000 3000-4200 3000-6300
1-1/4-12 9000-11000 9000-16700 5400-6600 5400-10000

COARSE THREAD SERIES

(NOTE 4) (NOTE 5)

8-32 12-15 7-9

10-24 20-25 12-15
1/4-20 40-50 25-30
5/16-18 80-90 48-55
3/8-16 160-185 95-100
7/16-14 235-255 140-155
1/2-13 400-480 240-290
9/16-12 500-700 300-420
5/8-11 700-900 420-540
3/4-10 1150-1600 700-950
7/8-9 2200-3000 1300-1800
1-8 3700-5000 2200-3000
1-1/8-8 5500-6500 3300-4000
1-1/4-8 6500-8000 4000-5000

NOTES
1. Covers AN310, ;MN315, AN345, AN362, AN363, AN366, MS17825, MS20365, MS21044, MS21043, MS21044,
MS21045, MS21046, MS21047, MS21048, MS21078 and other fine thread tension nuts.
2. When using AN310, AN320, MS17825 or MS17826 castellated nuts where alignment between the bolt and
cotter pin hole is not reached using normal torque values, use alternate torque values or replace the nut.
3. Covers AN316, AN320, AN7502, MS17826, MS20364, MS21043, MS21083, MS21245 and other fine thread
shear nuts.
4. Covers MS20341, MS20365, MS21042, MS21043, 14821044, MS21045, MS21046and other coarse thread
tension nuts.
5. Covers AN340, MS20364, MS21083 and other coarse thread shear nuts.
CAUTION

During removal and replacement of component parts, all self-locking

nuts and castellated self-locking nuts must be replaced with new nuts.

These torque values are recommended for all procedures contained in this manual except where other
values are stipulated. They are not to be used for checking tightness of installed parts during service.

Figure 1-4. Torque Values

Change 11
 421 SERVICE MANUAL GENERAL INFORMATION 1"

Cessna,
MANUFACTUtiO BY

CESSNA
. « yp'e==. AIRCRAFT
COMPANY

CES C AFT
COMPANY
wi TA, sAs 421-0001 TO 421-0058

C€SSn3. CESSNA
UNDER
UCENSED U.S.MRPLANE
PATEMS OF ALL MEul[95
L',"|
FATINTS OF
MANUFACTURERS
AIRERAff
ASSOCIAlf0N ogg;

421-0001 TO 421-0118

421-0058 AND ON

421-0118 AND ON

MODE 5 BO T.c.
0 STROKE
MADE IN MUSKEGON MICH. U.S.A. BY
CONTINENTAL MOTORS CORP. P.C.

---- ----
C.R.
RATEDH.P. RATED R.P.M.
TAKEDFFH.P TAKEOFFR.P.M.
FUEL OCT.MIN. MAG.TIMING R.
VENTURI °BTC L.
QUOTEENG.NO.
UNDER PATENTS 2270990, 2657679, 2705479,
-

2759468, 2764143, 782644, 2806752

Figure 1-5. Serial Numbers and Identification Plates

Change 2

I
1•18 6ENERAL INFORMATION 421 SERVICE MANUAL

CABIN
FORWARD LH NOSE ENTRANCE
WHEEL WELL WEB LIGHT LH UPHOLSTERY
PANEL

PLATE
PLATE

I VIEW LOOKING UP AND LEFT

INTO NOSE WHEEL WELL
VIEW LOOKING OUTBOARD AT
LEFT-HAND UPHOLSTERY PANEL

Figure 1-6. Finish and Trim Plate Location Figure 1-7. MAA Plate Location

Change 2
 421 SERVICE MANUAL OROUND HANDLING, 24
SERVICING AND INSPECTION

SECTION 2

GROUND HANDLING, SERVICING AND INSPECTION

Table of Contents

Page Page

GENERAL DESCRIPTION . . . .
2-2A Heater . . . . . . . .
2-30
GROUND HANDLING . . . . . 2-2A Seats . . . . . . . . 2-30
Towing . . . . . . . . 2-2A Seat Belts . . . . . . .
2-31
Taxiing . . . . . . . .
2-2A Upholstery . . . . . . . 2-31
Minimum Turn Radius . . . . 2-4 Carpets . . . . . . . . 2-31
. Parking . . . . . . . . 2-4 Control Quadrant . . . . . .
2-31
Rudder Pedals Gust Lock . . . .
2-4 Empennage . . . . . . . 2-31
Tie-Down .......
2-4 Wing ........2-31

Jacking . . . . . . . .
2-4 Emergency Exit Door . . . . .
2-32
Leveling . . . . . . .
2-4 LANDING GEAR . . . . . .
2-32
Weighing and Measuring . . . .
2-4 Landing Gear Actuator . . . .
2-32
STORAGE OF AIRCRAFT - . . .
2-11 Emergency Manual Extension System .
2-33
Flyable Storage . . . . . .
2-11 Main and Nose Landing Gear Assemblies . 2-34
Temporary Storage . . . . . 2-11 Nose and Main Landing Gear Rigging
Indefinite Storage . . . . . .
2-11 Inspection . . . . . .
2-34
Restoring Aircraft to Service . . .
2-12 Nose and Main Gear Retracting Linkage .
2-34
PAINTING . . . . . . . . 2-12A Shock Strut Servicing . . . . .
2-34
Preparation of Surface . . . . 2-12A Nose Gear Shimmy Dampener . . .
2-34
Paint Stripping . . . . . . 2-12A Nose Wheel Steering System . . .
2-37
Corrosion Treatment . . . . . 2-12A Nose and Main Wheels and Tires . .
2-37
Wash Primer (Type 1-E) Mixture and Brake System Plumbing . . . .
2-37
Application . . . . . . 2-12C Brake Assemblies . . . . .
2-38
Polycarbonate Primer (Type 1-L) Master Cylinders . . . . .
2-38
Mixture and Application . . . 2-12C FLIGHT CONTROLS . . . . .
2-38
Epoxy Primer (Type 1-M) . . . .
2-12C Control Column . . . . . .
2-38
Epoxy Primer . . . . . . 2-12C Aileron and Aileron Trim System . . 2-38
Preparation of 82B Series Vinyl Elevator and Elevator Trim Tab
Enamel Colors . . . . . 2-12D Control System . . . . . 2-39
Application of 82B Series Vinyl Rudder and Rudder Trim Tab System .
2-39
Colors . . . . . . . 2-12D Rudder Pedal Assembly . . . . 2-39
Epoxy Enamel . . . . . . 2-12D Flap System . . . . . . .
2-39
Application . . . . . . 2-12D Control Cable Seals . . . . .
2-40
VHT Paint (Very High Temp) . . . 2-12D ENGINE GROUP . . . . . .
2-40
Aerylic Lacquer and Heat Resistant Engine Cowling . . . . . .
2-40
Paint . . . . . . . .
2-12D Induction Air Filter . . . . .
2-40
Touch Up Vinyl . . . . . . 2-12F Induction Manifold . . . . .
2-40A
Polyurethane Finish . . . . . 2-12F Engine Oil Pressure System . . .
2-41
Touch Up of Polyurethane Finish - .
2-13 Engine Oil Filter Service . . . .
2-41
Metalic Gold Urethane Coating . . .
2-13 Oil Breather-Separator . . . .
2-42
Clear Urethane Top Coat . . . .
2-13 Engine Compartment . . . . .
2-42
Touch Up Landing Gear Finish . . .
2-13 Engine Compartment Fire Extinguisher . 2-42
Rain Erosion Coating Application . . 2-13 Engine Controls . . . . . .
2-42
Engine Wire Bundles . . . . .
2-42
INSPECTION REQUIREMENTS . . .
2-14 Engine Mounts . . . . . .
2-42
INSPECTION CHARTS . . . . .
2-14 Engine Compartment Hoses . . .
2-43
INSPECTION PROGRAM SELECTION . .
2-14 Spark Plugs . . . . . . .
2-43
INSPECTION GUIDE LINES . . . .
2-15 Ignition Cables . . . . . .
2-44
INSPECTION FREQUENCY . . . . 2-16 Magneto . . . . . . . .
2-44
OVERHAUL AND REPLACEMENT CHART .
2-22 Alternator . . . . . . .
2-44
CLEANING, INSPECTION, REPAIR AND Pumps . . . . . . . .
2-44
SERVICING . . . . . . 2-22A Turbocharger . . . . . .
2-44
Fuselage . . . . . . . 2-22B Manifold Pressure Relief Valve . .
2-44
Pressure Cabin . . . . . . 2-22B Engine Exhaust System . . . .
2-44
Windshield and Windows . . . . 2-22C Inspection for Oil Screen . . . .
2-46
Cabin Door . . . . . . .
2-30 PROPELLERS . . . . . . .
2-46
Cabin Door Seal . . . . . .
2-30 Propeller Deice.System . . . .
2-47
Door Latch Pins . . . . . .
2-30 Propeller Unfeathering System .
2-47
Nose Baggage and Wing Locker Doors .
2-30 Propeller Synchronizer . . . .
2-47
Change 11
2-2 ORoUND HANDLINe, 421 SERVICE MANUAL
SERVICIN6 AND INSPECTION
Table of Contents (Continued)

Page Page

FUEL SYSTEM . . . . . . .
2-47 Battery . . . . . . . .
2-50B
Fuel-Air Control . . . . . .
2-47 Battery Box . . . . . . .
2-51
Fuel Manifold . . . . . . 2-47 Starter Relay . . . . . .
2-51
Fuel Discharge Nozzles . . . .
2-48 Emergency Locator Transmitter . .
2-51
Fuel Selector Valve and Strainer . .
2-48 MISCELLANEOUS INSPECTION . . .
2-52
Fuel Selector Valve Control System . .
2-48 Movable Parts . . . . . .
2-52
Fuel System Main -
. . . . .
2-48 Engine Compartment Hoses . . .
2-52
Fuel System Auxiliary
-
. . . .
2-48 Fluid Lines and Hoses . . . .
2-52
Main Tank and Transfer Pump . . .
2-48 Metal Parts . . . . . . .
2-52
OXYGEN SYSTEM . . . . . .
2-48 Wiring . . . . . . . .
2-52
Filler Valve . . . . . . .
2-48 Bolts in Critical Area . . . .
2-52
Oxygen Regulator and Cylinder . . .
2-48A Filters, Screens and Fluids . . .
2-52
Oxygen Masks and Hoses . . . .
2-48A Aircraft File . . . . . .
2-52
VACUUM SYSTEM . . . . . .
2-49 EXTREME WEATHER MAINTENANCE .
2-52
Vacuum System Components . . .
2-49 Cold Weather . . . . . .
2-52
SURFACE DEICE SYSTEM . . . .
2-49 Hot Weather . . . . . . .
2-52
Surface Deice System Components . .
2-49 Dusty Conditions . . . . . .
2-53
PITOT STATIC SYSTEM . . . . .
2-49 Seacoast and Humid Areas . . .
2-53
Pitot Static System Components . .
2-49 MISCELLANEOUS SERVICE ITEMS . .
2-53
AIR CONDITIONING SYSTEM (Belt Driven) .
2-49 Cold Weather Servicing . . . .
2-53
AIR CONDITIONING SYSTEM (Hydraulic Fuel System . . . . . . .
2-53
Driven) . . . . . . . .
2-50 Fuel System Drains . . . . .
2-53
PRESSURIZATION SYSTEM COMPONENTS .
2-50A Defueling . . . . . . .
2-53
Safety Valve and Outflow Valve . . . 2-50A Purging Main Fuel Tanks and Auxiliary
Dump Valves . . . . . . . 2-50A Fuel Cells . . . . . .
2-54
Door Seals . . . . . . .
2-50A
ALCOHOL WINDHSILED DEICE SYSTEM .
2-50A SPECIAL TOOLS AND EQUIPMENT . .
2-54
Alcohol Windshield Deice System LUBRICATION DIAGRAMS . . . .
2-55
Components . . . . . . 2-50A SERVICE CHART . . . . . .
2-67
ELECTRICAL SYSTEM . . . . .
2-50B COMPONENTS LOCATION CHART , .
2-70
Inspection . . . . . . .
2-50B

Change 12
 421 SERVICE MANUAL GROUND HANDLING, 2-2A 2-28
SERVICING AND INSPECTION

GENERAL DESCRIPTION. CAUTION

This section contains routing, servicing and main- e When towing the aircraft, the 55 degree limit
tenance procedures that are most frequently en- shall be strictly observed, as the nose gear
countered. Frequent reference to this section will and/or steering mechanism will be damaged
aid maintenance personnel by providing information if turned beyond the 55 degree stops.
on ground handling and emergency procedures, daily
and periodic servicing procedures and airframe Be sure parking brake is released and the ex-
maintenance and lubrication. When any system or ternal and internal rudder gust locks are re-
unit requires service or maintenance, other than the moved before towing as structural damage
routine procedures as outlined in this section, refer will be incurred.
to the section applicable to that system or unit.
Never push, pull or lift aircraft by the aile-
rons, elevators, flaps, nacelles or unsup-
GROUND HANDLING. ported skin between wing ribs.

The following precautionary measures should be Power towing is not recommended. However, air-
taken when handling the aircraft on the ground: craft can be power towed to move aircraft over soft
a. Control surfaces shall not be locked while tow- or muddy ground or in emergencies by attaching a
ing or taxiing the aircraft. rope harness to the main landing gear. Do not power
b. Do not set parking brake if brakes are over- tow aircraft with towing vehicle attached to nose gear
heated, or the tail skid. When power towing, station a crew
When operating the engines, observe the following: member in the aircraft to apply brakes in case of
a. Remove all towing equipment. emergency. Use extreme caution to avoid jerky
b. Head aircraft into wind and chock wheels. motions, as serious structural damage can result.
c. Remove all control locks.
d. All personnel, work stands, and equipment shall Taxiing.
be clear of danger areas.
e. Parking brake set. Before attempting to taxi the aircraft, ground person-
f. Position nose wheel exactly fore and aft when nel should be checked out by qualified pilots or other
running engine at high RPM. responsible personnel. When it is determined that
the propeller blast area is clear, apply power and
.
start taxi roll and perform the following checks:
Towing.
a. Taxi forward a few feet and apply brakes to de-
termine their effectiveness.
A steering bar, located in the left nacelle baggage
compartment, is provided to aid in ground movement
of the aircraft. The steering bar engages spacers on
the nose gear lower torque link and is used to guide
the aircraft manually. The nose gear will caster a
maximum of 55 degrees to either side of center.

Change 11
 421 SERVICE MANUAL GROUND HANDLINO, "O
SERVICING AND INSPECTION

13'3"

Pivot Point

30'6" 55'2"

15'3"

Propeller Ground Clearance: 10. 55 Inches o

421-0001 TO 421BOOO1

13'11"

Pivot

34'6" 59'2"

17'3"

Propeller Ground Clearance: 10. 55 Inches

421B0001 AND ON

Figure 2-1. Minimum Turning Radius

Change 1
2-4 onoUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

b. While taxiing, make slight turns to determine CAUTION

effectiveness of nose gear steering.
c. Check operation of turn and bank indicator and Do not set parking brake when the brakes are
directional gyro. overheated or during cold weather when ac-
d. Check for sluggish instruments during taxiing. cumulated moisture may freeze the brakes.
In cold weather, make sure all instruments have
warmed sufficiently for normal operation. c. Set trim tabs to neutral, so tabs fair with con-
e. Minimum turning disfance must be strictlý ob- trol surfaces,
served when taxiing the aircraft close to buildings d. Install external gust locks on rudder, elevator
or other stationary objects. and aileron (one each wing) as shown in figure 2-2.
f. Do not operate the engine at high RPM when taxi- NOTE
ing over ground containing loose stones, gravel or
any loose material that may cause damage to the If external rudder gust lock is not available,
propeller blades. turn nose wheel to extreme right or left position.

Minimum Turn Radius. e. (See figure 2-2.) Drive the ground anchor stakes
45°
as shown to provide a rope angle of to the ground.
See figure 2-1 for minimum turning radius. Secure chains or manila rope of 700 pounds or more
tensile strength to the tie-down fittings under the
Parking. wings and secure opposite end to the ground anchor
stakes.
a. When parking the aircraft, head into the wind and f. Tie a manila rope around the nose gear, above
set parking brake, torque link, and secure the outer end to a ground
anchor.
CAUTION g. Tie a manila rope or chain to tailcone bumper
and secure other end to a ground anchor.
Do not set parking brakes when the brakes h. Install pitot tube cover.
are overheated, or during cold weather
when accumulated moisture may freeze the Jacking.
brakes.
b. Close engine cowl flaps (421-0001 to 421B0001) Three jack points are on the underside of the aircraft,
and install internal control lock. Install pitot tube one just aft of the nose wheel well, and one on the
cover and place chocks under all wheels. In parking lower surface of each wing, just alt of the main gear
the aircraft, it is also important to turn the nose attach points. See figure 2-3 for jacking procedures.
gear to its full limit, either right or left, if external
rudder lock is not available. This will place the NOTE
rudder bellerank against the stop and hold it there Special two-ton jacks, ideally suited to the 421,
with spring tension from the nose gear steering can be supplied by the Cessna Aircraft Company.
mechanism• Three jacks are required to lift the aircraft.

Rudder Pedals Gust Lock (Optional). (See figure 2-2.) Leveling.

The rudder pedals gust lock is installed on the left- To level the aircraft longitudinally and laterally, use
hand floorboard with a clamp which permits the lock the three jacking points provided on the aircraft.
to pivot forward to engage the rudder pedals when in Level longitudinally by backing out the two screws at
use, and back to the floorboard for stowage when not "Level Point" on the right hand outside fuselage (op-
in use. The lock is adjustable for rigging purposes. posite cabin door) at Stations 214 and 238 and place
a spirit level on these screws, then level longitudin-
NOTE ally. To level laterally, place a spirit level between
the black marks at Station 154.00 (aft of front spar)
Rig gust control lock so that both rudder on the underside of fuselage.
pedals must be pushed forward a minimum
of 0. 10 inch to engage lock. Weighing and Measuring.

Tie-Down. For weighing and measuring the aircraft refer to

figure 2-5.
Tying-down the aircraft should be accomplished in
anticipation of light winds, or anytime the aircraft is NOTE
to be left outside for lengthy periods, such as over-
night. Tie-down as follows: To prevent the flight hour recorder from re-
a. Head aircraft into the wind, if possible, and cording while the aircraft is on jacks and bat-
close engine cowl flaps. tery switch is in the ON position, remove fuse
b. Set parking brake and install control lock. located in the left console.

Change 11
 421 SERVICE MANUAL 6ROUND HANDLINe,
2-5
SERVICIN6 AND INSPECTION

2' TYP

Detail Detail
8

1. AileronGust Lock 4. Control Lock 7. Lockwasher

2. ElevatorGust Lock 5. Rudder Control Lock 8. Plate
3. Rudder Gust Lock 6. Clamp 9. Screw

Figure 2-2. Tie-Down and Control Lock

Change 6
$ GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

JACKING REQUIREMENTS
HEIGHT HEIGHT
CLOSED EXTENDED CAPACITY

NOSE 26. 5 44. 5 2 TONS

WING 26. 5 44. 5 2 TONS

Note

FOR LANDING GEAR REMOVAL AND MAINTENANCE, USE ALL THREE

JACK POINTS. FOR REMOVAL OF MAIN WHEELS USE APPROPRIATE
WING JACK POINT. FOR REMOVAL OF NOSE WHEEL, USE NOSE JACK
POINT.

PLACE WEIGHT IN NOSE SECTION OF FUSELAGE TO PREVENT

AIRCRAFT FROM TIPPING BACKWARD WHEN NOSE IS RAISED.

WING JACKI O

NOSE JACKING POINT

Figure 2 -3.
Jacking
 421 SERVICE MANUAL 6ROUND HANDLINO,
SERVICING AND INSPECTION

Horizontal Leveling Point

(Using spirit level)

Lateral Leveling Point

(Using spirit level)

o
o I
O
°
o

Figure 2-4. Leveling

28 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

WEIGHING ON JACK POINTS

1398.
20 6C

NOSE JACK PAD MAIN JACK PAD

WEIGHING POINT WEIGHING POINT
+--86. 74
D L HORIZONTAL CG.
186.20
Wn (86. 74)
CG = 186. 20 -

W
CG -
139. 20
/oM.A.C. = (100)
63. 56

51104006

W. S. 103. 25
421B0001 AND ON

W. S. 91. 25 W. S. 91. 25

MAIN JACK POINT L. H.

MAIN JA R. H.

NOSE JACK POINT

LATERAL CG.
NOTE 12. 55(Wn) + 91 25(Wn) + (W1 -
Wr)
CG. =

AIRCRAFT IS WEIGHED WITH GEAR

EXTENDED. MOMENT CHANGE POSITIVE CG. IS LEFT OF AIRCRAFT CL
WITH GEAR RETRACTED IS +889.0
INCH-POUNDS. 12. 55 L. BL.
51104007

Figure 2-5. Weighing and Measuring (Sheet 1 of 2)

Change 8
 421 SERVICE MANUAL OROUND HANDLIN6,
SERVICING AND INSPECTION

WEIGHING ON LANDING GEAR

DATUM
STr.. 0• S *63. 92
139.20 1 63.56--+
*139. 06 M. A. C.

W. L. 102. 01

L MAIN GEAR WEIGHING POINT

125. 95
*125. 82
D
+----
171. 89 HORIZONTAL CG.
NOSE GEAR
*125. 82
WEIGHING POINT
Wn (125. 95)
CG 171. 89
= -

W
CG 139. 20-

ŸoM. A. C. =
(100)
63. 56
*63. 92

*89. 50 -+
*89. 50
NOTE *101. 50 *101. 50

AIRCRAFT IS WEIGHED WITH GEAR

EXTENDED. MOMENT CHANGE *421B0001 AND ON
WITH GEAR RETRACTED IS +889. O
INCH-POUNDS. 51104000

Figure 2-5. Weighing and Measuring (Sheet 2 )

2•10 421 SERVICE MANUAL
GROUND HANDLING,
SERVIClNO AND INSPECTION

LEGEND

W The weight of the aircraft. (Wn + W1 + Wr) C. G. The distance from the datum to the center of
gravity of the aircraft.
D The horizontal distance from the datum to the
main weighing points. Wn The weight at the nose weighing point.

L The horizontal distance from the main weigh- W1 The weight at the left main weighing point.
ing points to the nose weighing point.
Wy The weight at the right main weighing point.
S The horizontal distance from the datum to the
leading edge of the M. A. C. M. A. C. Mean Aerodynamic Chord.

NOTE
(Wn (L)
Formula: C. G. = D -

W AIRCRAFT IS WEIGHED WITH GEAR

EXTENDED. MOMENT CHANGE
/o M. A. C. C. G. -

S WITH GEAR RETRACTED IS +889. O

=

C' (100) y
INCH-POUNDS,

SCALE NET
WEIGHING READING TARE WEIGHT
POINT (LBS) (LBS) (LBS)

W1

Wr

Wn

W (EMPTY WEIGHT)

Table 1.
Preparation for Weighing. weight equals the actual recorded weight
less the weight of the oil in the engines
a. Remove excessive dirt, grease, moisture, etc., (oil weight oil capacity
= in gallons x 7. 5
from the aircraft before weighing. pounds).
b. Weigh the aircraft inside a closed building to
prevent error in scale reading due to wind.
c. To determine the center of gravity, place the g. Properly calibrate, zero and use scales in ac-
aircraft in a level attitude. cordance with the scale manufacturer's instructions.
d. Have all items of equipment included in the h. Place the scales and suitable supports (jacks)
certificated empty weight installed in the aircraft under the aircraft jack pads or wheels and record
when weighing. These items of equipment are listed the scale readings. (See table 1. )
on the equipment list. i. Do not set brakes while taking scale readings.
e. Defuel the aircraft in accordance with defueling j. Note tare when the aircraft is removed from the
procedure and drain the sump. Fuel remaining scales.
aboard after draining is residual fuel and is included
in the empty weight. NOTE
f. Drain all the oil from the engines by opening the
drain cocks. The oil remaining after draining is TARE the weight of the chocks, blocks,
is
residual oil and is included in the empty weight. stands, etc., used when weighing the air-
craft, and is included in the scale readings.
NOTE Tare is deducted from the scale readings at
each respective weighing point where tare
When weighed with full oil, actual empty is involved to obtain the aircraft weight.

Figure 2-5. Weighing and Measuring (Sheet 3 )

Change 4
 421 SERVICE MANUAL OROUND HANDLING, Î"•Ñ
SERVICING AND INSPECTION

STORAGE OF AJRCRAFT. Volatile, Corrosion Inhibited, MIL-L-46002, Grade

1) (221°-250°) through
upper.spark plug hole of each
There are three recommended categories of storage cylinder with the piston
in the down position. Rotate
of the aircraft. crankshaft as each pair of cylinders is sprayed.
a. Flyable Storage Aircraft which will not be
-

Stop crankshaft with no piston at top position. If the

flown for an indefinite period of time but which are aircraft is to be stored outside, 2-bladed propeller
to be kept ready to fly with the least possible pre- position should be as nearly horizontal as possible to
paration. provide maximum clearance with passing aircraft.
b. Temporary Storage Aircraft which will be
-

stored for a period of time up to 60 days. NOTE

c. Indefinite Storage Aircraft which will be stored
-

for an indefinite period of time. Listed below are approved preservative oils
recommended for use in Continental engines.
FLYABLE STORAGE Continental: Nucle Öifl06, Petrotect VA,
Ferro-Gard 1009-G or equivalent.
Aircraft which are not in daily flight should have the
engine rotated by hand-turning the propeller five (5) b. Respray each cylinder without rotating crank.
revolutions at least once each week. In damp climate To thoroughly cover all surfaces of the cylinder in-
and in storage areas where the daily temperature terior, move the nozzle or the spray gun from the
variation can cause condensation, the turning opera- top to the bottom of the cylinder.
tion should be accomplished more frequently. Rota- c. Reinstall spark plugs.
ting the engine an odd number of turns redistributes d. Apply preservative to engine interior by spray-
residual oil on cylinder walls, shaft and gear sur- ing the above specified oil (approximately 2 oz.)
faces and repositions the pistons in the cylinders through the oil filler tube.
thus preventing corrosion accumulation. e. Seal all engine openings exposed to the atmos-
phere using suitable plugs, or non-hygroscopic tape,
and attach red streamers at each point.
CAUTION f. Install pitot tube cover, seal static source, in-
stall ground locks on retractable gear aircraft and
For maximum safety, accomplish engine rota- attach red streamers at each location. Close all
tion as follows. Assure magneto switches are vents and plug cowl openings to prevent bird nests
"OFF", throttle position "CLOSED", and mix- in the engine compartment.
ture control "IDLE CUT-OFF". Do not stand g. Engines, with propellers installed, that are pre-
within the arc of the propeller blades while served for storage in accordance with this section
turning the propeller, should have a tag affixed to the propeller in a con-
spicuous place with the following notation on the tag:
"DO NOT TURN PROPELLER ENGINE PRE-
-

a. Fill fuel tanks full to minimize condensation in SERVED. "

the fuel tanks. Keep battery fully charged to pre- h. Disconnect or remove the battery from the air-
vent the electrolyte from freezing in cold weather. craft. If the battery is disconnected and left in the
If the aircraft is stored outside, tie-down should be aircraft, regular servicing will be required to pre-
accomplished in anticipation of high winds. vent freezing or discharge. Batteries which are
b. Tie ropes or chains to the wing tie-down fittings removed from the aircraft and stored should be
located on the underside of each wing. Secure the checked regularly for state of charge. Recent
opposite ends of the ropes or chains to ground an- production aircraft have the battery serial recorded
chors. in the aircraft equipment list. To assure accurate
c. Secure a rope (no chains or cables ) to the upper warranty records, batteries should be reinstalled
trunnion of the nose gear and secure opposite end of in the same aircraft from which they were removed.
rope to a ground anchor. i. If the aircraft is stored outdoors, place control
d. Secure the middle of a rope to tail tie-down ring. locks on all movable control surfaces and tie the
Pull each end of rope away at 45-degree angle and aircraft down snugly, not tightly, with enough clear-
secure-to ground anchors at each side of tail, ance so wind gusts will not shift aircraft into another-
e. Install surface control locks on ailerons, rudder Leave no long chains dangling. Release the parking
and elevators and aileron, if available, brake to prevent seizing and chock the wheels.
f. Install control lock on pilot control column if
available; if control lock is not available, tie pilot
control wheel back with front seat belt. INDEFINITE STORAGE
g. After thirty (30) days, aircraft should be flown
for thirty (30) minutes or ground run-up until oil has a. Drain the engine oil and service with corrosive
reached operating temperature, preventive mixture.

TEMPORARY STORAGE NOTE

a. Remove top and bottom spark plugs and atomize Corrosion preventive mixture consists of one
spray preservative oil (Lubrication Oil -

Contact and part compound MIL-C-6529, Type I, (Esso

Change 4
2·12 6ROUND HANDLINe, 421 SERVICE MANUAL
SERVICIN6 AND INSPECTION

Rust-Ban 628, Cosmoline No. 1223 or equiv- 1. Install pitot tube

cover, seal static source, in-
alent) mixed with three parts new lubricating stall ground locks on retractable gear aircraft and
oil of the grade recommended for service. attach red streamers at each location. Close all
This mixture should be thoroughly mixed and vents and plug cowl openings to prevent bird nests
221°F
maintained at a temperature of at least in the engine compartment.
at the time it is added to the engine. Im-
mediately after servicing with the corrosion NOTE
preventive mixture, fly the aircraft for a
period of time not to exceed a maximum of As an alternate method of indefinite storage,
30 minutes. the aircraft may be serviced in accordance
with the procedures under Temporary Stor-
b. Remove the top spark plug from each cylinder age providing the aircraft is run-up at maxi-
(221°
and spray with corrosion preventive mixture to mum intervals of ninety (90) days and then
250°F). To thoroughly cover all surfaces of the cyl- reserviced per the temporary storage re-
inder interior, move the nozzle of the spray gun from quirements.
the top to the bottom of the cylinder. If by accident
the propeller is rotated following this spraying, re-
spray the cylinders to insure an unbroken coverage m. Aircraft stored in accordance with the indefinite
of corrosion preventive mixture on all surfaces. storage procedures should be inspected per the follow-
c. Install protex plugs in each of the top spark plug ing instructions:
holes, making sure that each plug is blue in color 1. Aircraft prepared for indefinite storage shall
when installed. Protect and support the spark plug have the cylinder protex plugs inspected weekly. The
leads with AN-4060-1 protectors. plugs should be changed as soon as their color indi-
d. Place a bag of desiccant in the exhaust pipes and cates unsafe conditions of storage. If the dehydrator
seal the openings with moisture resistant tape. plugs have changed color in one half or more of the
e. Seal the cold air inlet to the heater muff with cylinders, all desiccant material on the engine should
moisture resistant tape to exclude moisture and be replaced.
foreign objects. ,
2. The cylinder bores of all engines prepared for
f. Seal the engine breather by inserting a protex indefinite storage should be resprayed with corro-
plug in the breather hose and clamping in place. sion preventive mixture every 6 months. Before
g. Attach a red streamer to each place on the en- spraying, the engines shall be inspected for corro-
gine where bags of desiccant are placed. Either at- sion as follows: Inspect the interior of at least one
tach red streamers outside of the sealed area with cylinder on each engine through the spark plug hole.
tape or to the inside of the sealed area with safety Remove at least one rocker box cover from each
wire to prevent wicking of moisture into the sealed engine and inspect the valve mechanism.
area.
h. Engines, with propellers installed, that are pre-
served for storage in accordance with this section Restoring Aircraft to Service.
should have each propeller tagged in a conspicuous
place with the following notation of the tag: "DO NOT If the proper procedures were followed for extended
TURN PROPELLER ENGINE PRESERVED.
-
" storage, the aircraft should require the following
i. After the engine has been prepared for storage, service:
remove the battery from the aircraft, store in a a. Airframe:
cool dry place and check regularly for state of 1. Remove all covers from vents and air inlets.
charge. Note serial number on battery and reinstall 2. Clean aircraft if required.
in the same aircraft. 3. Lubricate the aircraft.
j. If the aircraft is stored outdoors, place control 4. Check the brake cylinders, struts and shimmy
locks on all movable control surfaces and tie the air- dampener.
Craft down snugly, not tightly, with enough clearance 5. Drain a small amount of fuel from all fuel drains
so wind gusts will not shift aircraft into another- and check for water and sediment.
Leave no long chains dangling. Release the parking 6. Check fuel selector valve for evidence of leaking.
brake to prevent seizing and chock the wheels. b. Battery:
k. Cover the aircraft with moisture resistant paper 1. Charge and check battery.
and tape as necessary. 2. Install battery.
c. Engines:
1. Remove all vent and opening covers installed.
NOTE 2. Remove oil sump drain plugs.
3. Remove plugs from spark plug holes in all cylin-
The necessity of this requirement can be de- ders. Rotate engines, by hand, to remove corrosion
termined by the condition at the storage area. preventive oil from cylinders.

Change 8
 421 SERVICE MANUAL C,ROUND HANDLINS, 2-12A
SERVICING AND INSPECTION

WARNING care must be taken to insure that stripping

fluids do not come in contact with fuel cells.
Magneto switches must be in the off position Paint stripping fluids can inflict severe dam-
when rotating propellers by hand. age to cells which is not readily apparent or
easily detected. For this reason, the cells
4. Install recommended spark plugs which have should be disconnected from their upper skin
been properly cleaned and gapped. covers and hangers and protected with a
5. Remove, clean and reinstall the oil filter plastic sheet during stripping operations.
screens.
6. Install the oil sump drain plugs and fill oil sump c. During paint stripping, the following safety pre-
with recommended oil. cautions should be observed.
7. Lubricate propellers and check for free opera- 1. Have fire extinguisher available,
tion. 2. Provide adequate ventilation in working area.
8. Start engine and give aircraft complete ground 3. Wear goggles, rubber gloves, apron, face shield
runup check. and head coverings.
9. Perform flight test. d. Apply paint stripper as follows:
1. Starting at the top and working down, brush or
spray paint stripper on painted surface. Follow paint
PAINTING. stripper manufacturer's recommendations regarding
use of the stripper.
Preparation of Surface. 2. Rinse area thoroughly and allow to dry.

Thoroughly clean all surfaces, beyond area to be

painted with Turco 800 or Enmar 3094 thinner. Ex- Corrosion Treatment.
treme care should be taken to remove all letters,
grease, bugs, etc. Mask off stripe areas to be a. If corrosion occurs, complete removal of corro-
painted carefully; see that all tapes are firmly ad- sion deposits is required to prevent recurrence. Par-
hered to metal to prevent ragged edges. Class "A" tial removal and covering with paint will not halt con-
wrapping paper and thinner proof masking tape should tinued attack because a small amount of moisture pen-
be used to cover the plexiglas area. This will pre- etrates the surface of all paint and allows corrosion
vent damage from solvent and thinner vapors. (News- to continue.
paper will not provide adequate protection. ) Extreme b. If an area of corrosion exists, the area shall be
care should be taken to assure that no oil seepage cleaned and the paint stripped. If the area is confined
occurs from seams, splices, or rivet heads. and the use of paint stripper is impractical because of
rinsing difficulties paint may be removed with solvent
CAUTION material Federal Specification TT-E-'751 or TT-T-
266. Apply solvent with a soft bristle brush, allow
& Metallic paper, metal, metal foil or metal solvent to remain until paint film is loosened, then
of any kind should never be used as a paint wipe clean with a clean damp cloth.
spray mask on heated windshields. c. Heavy aluminum parts are suspectible to inter- .

granular corrosion attack. Mechanical corrosion

During aircraft painting operations, extreme removal may be used in pitted areas or in conjunction
care must be taken to insure that stripping with chemical corrosion removal in lightly corroded
fluids do not come in contact with fuel cells. areas. Use #400 aluminum grit abrasive paper or
Paint stripping fluids can inflict severe dam- abrasive mat for mechanical corrosion removal.
age to cells which is not readily apparent or d. Chemical corrosion removal must be used on
easily detected. For this reason, the cells clad aluminum parts; such as skin. It is also suitable
should be disconnected from their upper skin for other areas of light corrosion removal. The sur-
covers and hangers and protected with a rounding parts and materials shall be protected from
plastic sheet during stripping operations. damage of the corrosion remover by proper masking
or other appropriate methods. Specific CAUTION
should be exercised in areas where the corrosion re-
Paint Stripping, mover could become entrapped or attack an uncorrod-
ed area.
a. Paint stripping is required to reach paint covered e. For light corrosion and discoloration proceed as
corrosion, repaint an area with paint that is incom- follows:
patible to paint currently on the part etc. 1. Apply Delchem 810 with brush or cloth.
b. Before applying paint stripper, windows, areas 2. Agitate with short fiber brush or abrasive mat
not being painted, openings, rubber and other non- until all corrosion is removed. Do not leave condi-
metallic parts must be masked off. If paint stripper tioner in contact with the surface longer than 20 min-
should accidently get on material, such as plexiglas, utes.
flush parts with water immediately. 3. Rinse off the corrosion remover with a damp
cloth. Rinse the cloth frequently in water.
CAUTION 4. Repeat cycle as required.
5. After all corrosion is removed, thoroughly
During paint stripping operations, extreme rinse treated area with clean water.

Change 8
 2•l28 GROUND HANDLING. 421 SERVICE MANUAL
SERVICING AND INSPECTION

Recommended Materials and Equipment.

NAME NUMBER MANUFACTURER USE

I
GENERAL CLEANING INCLUDING EXHAUST DEPOSITS

Delchem Jet Wash 2271 Pennsalt Chemical Corp. To wash exterior surface
2700 South Eastern Ave. of the aircraft.
Los Angeles, Calif.

Aerowash Wyandotte Chemicals To wash exterior surface

Corp. of the aircraft.
8921 Dick Road
Los Nietos, Calif.

PAINT REMOVER

Delchem E-Z Strip 19B Pennsalt Chemical Corp. To strip polyurethane

2700 South Eastern Ave. paint.
Los Angeles, Calif.

Paint Remover Turco 5556A Turco Products Inc. To strip polyurethane

Box 1055 paint.
Wilmington, Calif.

Paint Remover Turco 5556AF Turco Products Inc. To strip polyurethane

Box 1055 paint.
Wilmington, Calif.

CORROSION REMOVAL

Delchem 810 Pennsalt Chemical Corp. To remove light corrosion

2700 South Eastern Ave. or discoloration,
Los Angeles, Calif.

Pennsalt 715 Pennsalt Chemical Corp. To remove moderate

2700 South Eastern Ave. corrosion.
Los Angeles, Calif.

DEICING EXTERIOR SURFACES

Deicing Fluid WD-20 Jefferson Chemical To remove ice and frost

Corp. from control surfaces.
Houston, Texas

PRE TREATMENT

Iridite 14-2 Allied Research Inc. To prevent aluminum

against corrosion.

Change 8
 421 SERVICE MANUAL OROUND HANDONG, 2,-l Û
SERVIC1NO AND INSPECTlÓN

6. Apply pretreatment (Iridite 14-2) to aluminum Epoxy Primer (Type I-M).

where corrosion was removed in accordance with
manufacturer's instructions. a. Mix thoroughly by volume one part epoxy primer
f. For moderate corrosion proceed as follows: to one part catalyst. Thin this mixture with T-6487
1. Dilute Pennsalt 715 with an equal volume of Thinner to a spray viscosity of 17-19 seconds in a
water in a plastic lined container- number 2 Zahn cup.
2. Apply diluted Pennsalt 715 with a brush or cloth b. Allow mixture to set for one hour before using.
wetting the entire corroded surface thoroughly.
3. Allow the solution to stand as long as necessary NOTE
to remove corrosion but no longer than 20 minutes.
4. Scruff with a short fiber brush just before rins- The work life of the primer is six hours after
ing with water and damp cloth. mixing.
5. Repeat cycle as necessary.
6. After all corrosion is removed, rinse the treat- c. Material should be applied in a wet coat applica-
ed area thoroughly with water and dry. tion to a dry film thickness of 0004 to 0007 inch.
. .

7. Apply pretreatment (Iridite 14-2) to aluminum d. Allow 20 to 30 minutes drying time between appli-
where corrosion was removed in accordance with cations of primer coats. Primed surface should be
manufacturer's instructions. allowed to air dry 30 minutes, then final dry 4 hours
135°F.
at

Wash Primer (Type I-E) -

Mixture and Application.
Epoxy Primer.
NOTE
Fiberglass parts that have been stripped of their
Mix primer only in quantities required for primer should be primed with P-900 Sky Spar Sur-
use within six hours and then only in stain- facer, consisting of the following:
less steel bucket provided.
P-900 Sky Spar Surfacer Base Component
a. Mix primer EX2016G (Enmar) or 818-012 C-918 Catalyst Concentrate Component I
(Dupont) with diluent T670 (Enmar or Dupont) in a 1 C-916 Catalyst Thinner Component II
to 1 volume ratio and stir thoroughly. T-262 Thinner Component III
b. Apply primer in a well-broken up, wet, even
coat. If primer has to be sanded, sand and reprime- a. Surfaces to receive Epoxy primer should be
Sanding breaks film, resulting in poor adhesion. sanded lightly so the outer laminated layer is not
exposed.
NOTE b. Remove residue by wiping with a cloth dampened
with Isopropyl Alcohol.
On all leading edge surfaces, apply cross coat
wet and even. NOTE

c. Allow wash primer to air dry a minimum of 30 Do not use wood filler, lacquer, putty or
minutes or a maximum of 4 hours before applying aerodynamic smoothers, such as White
overcoat. Streak or Bondtite on fiberglass.
d. Clean equipment immediately after use and under
no consideration use primer that has been mixed c. Allow all materials when first mixed with a
longer than six hours. catalyst, to stand in a closed container for approxi-
mately one hour before use.

Polycarbonate Primer (Type I-L) -

Mixture and NOTE
Application.
Mixed material has a usable pot life of 8
a. Surfaces to receive primer shall be solvent wash- hours. When the material becomes thick
ed with isopropyl alcohol. and start to gel, it must be discarded.
b. Primer shall be Lacco 600 SL 9953, White (Red
Spot Paint and Varnish Company) or RV 3649, White
(Duralac Chemical Corporation). This primer shall Materials, Description and Mixing Instructions,
be reduced to spray viscosity by thinning with Red
Spot SL 8381 or Duralac T901 respectively. Use ap- P-900 Surfaces is an epoxy resin and constitutes the
proximately one volume of thinner for one volume of base component of the system. By mixing with the
primer. C-918 Catalyst Concentrate and/or the C-916 Cata-
c. The first coat of reduced primer shall be dry lyst Thinner in varying proportions and thinning with
sprayed. T-262 Thinner, any desired consistency can be ob-
d. The sprayed coating shall be allowed to dry a tained, from heavy putty to a spraying viscosity.
minimum of one hour prior to overcoating.

Change 8
2-120 enoUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

a. Mix 12 parts of the base component with one part Epoxy Enamel.
of Component I (Catalyst Concentrate). Mix thor·-
oughly then cover the container and allow to stand 1 When touch up or refinish of parts becomes neces-
hour. sary, the the
finish adjacent
edge of to the defect
b. The mixture should be a thick, smooth putty and shall be feathered by sanding with #320 followed by
may be applied with a spatula or heavy bristled brush. #400 sandpaper. Avoid sanding through the primer
c. The material may be overcoated immediately if possible. If the primer is penetrated over an area
with P-900 either by brushing or spraying. The ma- of 1/2 inch square or larger, the surface must be
terial will be dry for sanding when it does not gum reprimed.
up in the sandpaper and sands off in a dry powder.
This will occur after air drying for a period of not Epoxy Enamel Application.
170°F
less than 2 hours or is forced dried at for 30
minutes, a. Mix epoxy enamel by adding 1 part by volume of
d. If the material is to be brushed on, take a por_ thinner (Enmar 5400) to 1 part by volume of enamel.
tion of the putty material that has been allowed to set No additional thinning is necessary.
for one hour and thin it to a suitable brushing viscos_ b. Allow mixture to set for 1 hour before using.
ity with Component II (Catalyst Thinner). This ma-
terial is ready to brush on after thinning. NOTE
e. The mixture should be brushed on the part, work-
ing material well into surface and filling all holes. Work life of epoxy enamel is B hours.
f. Allow part to air dry for a period of not less than
two hours or force dry at 170°F for 20 minutes be_ c. Spray coats shall be applied to a dry film thick-
fore sanding. ness of 0008 to 0012 inch.
. .

d. Allow finish to cure for a period of 8 hours at

room temperature. As an alternate finish may be
Preparation of 82B Series Vinyl Enamel Colors. force dried by air for 30 minutes followed by a 30
250°F 130°F.
minute bake at or 2 hours at
Thoroughly mix and stir in original container and
make sure all pigments are in solution. Thin requir-
ed amount of vinyl color with T1866B vinyl thinner in VHT Paint (Very High Temp)
a 1:1 ratio. Mix thoroughly and strain into either a
cup or pressure pot- The cowl flaps (421-0001 to 421BOOO1), are painted
with VHT paint. The following instructions apply to
. the areas where VHT paint is applied.
Apphcation of 82B Series Vinyl Colors.
Priming is not necessary. Area to be refinished
NOTE must be dry; clean and free of dirt and oil and sand-
ed using a 220 grit or finer abrasive paper.
If vinyl is to be applied from pressure pot, do
so under the following conditions: pressure of VHT paint should be thinned for spraying by adding
10 pounds on the pot. Regulate gun pressure an equal volume of Volvene.
at gun with test gauge to 25 pounds, using gun
with FX needle and fluid tip, with fan set wide Thinned material should be sprayed on surface to be
open and yield two turns open. If cups are painted to yield a cured film thickness of 001 inch. .

used, set gun at 30 pounds with EX needle

and fluid tip, fan set one turn open and yield VHT paint shall be allowed to air dry for 30 minutes
wide open 250°F.
followed by a 15 minute force dry at

a. Apply first coat even and wet; second and third

coats in the same manner.
b. Check carefully before second and third coats Acrylic Lacquer and Heat Resistant Paint. (421B0001
for defects and correct before final coats. and ON.) (See figure 2-6.)
c. On second and third colors, mask off and lightly
sand with 400 grit sandpaper the painted surfaces of The lower nose cowl, lower nacelle skin and the al-
previous color that is in area to be painted. ternate air inlet are painted with acrylic lacquer.
The area aft of the exhaust outlet on the underside
NOTE en-
ofdhe wing has been painted with heat resistant
amel.
On all leading edges apply a fourth coat. Af
1. When it is necessary to repaint the areas painted
ter finishing each color coat, burn down with
with acrylic lacquer or heat resistant enamel the
T1411 burn down thinner. Remove all mask- us-
area should be masked off and the area stripped
ing from painted surfaces after each color
ing Delchem E-Z Strip 19B or equivalent, then rins-
application. If you have a Heat Room, turn
ed clean with a water spray.
up the heat and dry paint at temperatures of
125°
to 145°F, for at least three hours. Heat
will give a very good reflow on vinyl paint.

Change 8
 421 SERVICE MANUAL OROUND HANDLINO, 2"•Î2Ë
SERVICING AND INSPECTION

(SEE PAINT
CHART)
ALTERNATE AIR
INLET ASSEMBLY

NOTE
COWLING DOOR
FOR SPRAY COATING PUR-
L 00
(TYPICAL
POSES, ACRYLIC PAINT
TO BE THINNED USING
·

. (1. 25) ONE AND ONE

(SEE PAINT 16. 00 1. 00 FOURTH PART (MINIMUM
CHART) (TYPICA L) F114A-T-7945 THINNER
COWL FLAP EDGE OF FILLET TO (1) ONE PART PAINT.
ENAMEL TO BE THINNED
USING (1) ONE PART
XYLENE OR TOLUENE
TO (4) FOUR PARTS
+. 5 ENAMEL OR PER MANU-
19. 0 -

0 FACTURERS INSTRUC-
TIONS ON CONTAINER.

AREA BETWEEN
(SEE PAINT INBOARD AND
EXHAUST STACK --

CHART) OUTBOARD FLAPS

VIEW LOOKING UP AT BOTTOM OF NACELLE
421-0001 TO 421BOOO1

NLLEER EEMA
ILR
A S

(SEE PAINT 1 1. 00
CHART) (TYPICA L)

16. 00 L 00
(SEE PAINT EDGE OF FILLET (TYPICAL)
CHART)

+. 5
19. 0
. 0 (SEE PAINT
AREA BETWEEN CHART)
INBOARD AND
OUTBOARD FLAPS
EXHAUST STACK
VIEW LOOKING UP AT BOTTOM OF NACELLE
421BOOO1 AND ON
HEAT RESISTANT -

PAINT CHART

LOCATION CESSNA PART NO. VENDOR PART NO. TYPE COLOR

CES 2800-2131 PX114A-51070A ACRYLIC VESTAL WHITE

CES1059-918 PX114A-43026 ACRYLIC SUN YELLOW

CES 1054-917 PX114A-43029 ACRYLIC POLARIS BLUE

CES1054-142 ENMAR 22-11980 ENAMEL GRAY

Figure 2-6. Acrylic Lacquer and Heat Resistant Paint Chart

Change 8
2°12F GROUND HANDLINe, 421SERVICE MANUAL
SERVICING AND INSPECTION

2.Scuff sand and tack rag area to be sprayed. b. When priming with EX2016G, use a light coat of
3.Spray coat Red Iron Oxide Primer (Type 1-8) to MIL-P-8585 zine chromate primer thinned four parts
insure a cure film thickness of 0. 002 to 0. 005 inches toluol to one part primer applied over the EX2016G.
to the area receiving heat resistant enamel. c. Fill the feathered areas by spraying on several
light coats of Acme 538 dark grey surfaces and allow-
NOTE
ing 5 to 8 minutes drying time for each coat.
Thin Red Iron Oxide Primer to a one to one d. Sand the entire area with #400 sandpaper and ap-
ratio with Toluene for spray. ply the top coat.

4. Spray coat areas receiving acrylic lacquer with NOTE

wash primer EX2016G Enmar, or 818-012 Dupont
wash primer to insure a cured film thielmess of Remove dry overspray by burndown (T-1411)
. 0002 to 0003 inch. . or by compounding with Dupont 808 rubbing
compound.
NOTE

Wash primer should be thinned with a one to Polyurethane Finish (optional).

one ratio with T670 Enmar or Dupont equiva-
lent. The mixed primer must be used within a. The surfaces to receive polyurethane paint shall
a six hour period after thinning or discarded. be sanded smooth and solvent cleaned with isopropyl
alcohol.
5. Allow primed surface to air dry approximately b. Mix wash primer C-22 Y7277 (U. S. Paint,
one hour. Lacquer and Chemical Company) in a 1:1 ratio by
6. Sand primed surface irregularities and reprime. volume with 66C-7225 so that the viscosity is 17
7. On surfaced to receive acrylic lacquer cross seconds in a #2 Zahn cup. No induction time is
spray coat lacquer to insure a film thickness of necessary and the pot life is 8 hours.
.0002 to 0004 inch. . c. Apply a light spray coat with a dry film thick-
ness of 0. 005 to 0. 007 inches and allow to air dry
NOTE for a period of 30 minutes.
d. Mix an intermediate primer by mixing two parts
Acrylic lacquer should be thinned using AA-92 to one part Y-43 Urethane Zine Chromate
(1. 25) one and one-fourth part F114A-T¯ Primer, and then combine these parts of this mix-
7945 thinner to one part acrylic paint. The ture with two parts 7-888 thinner. This mixture will
acrylic lacquer should be allowed to air dry have a viscosity of 17 seconds in a #2 Zahn cup, and
for a minimum of 24 hours prior to handling also an induction time of one hour and a pot life of 8
hours.
8. On surfaces to receive heat resistant enamel, e. Apply a spray coat of the intermediate primer
spray coat enamel toinsure a film thickness of 001 .

over the washed primer surface. Spray the AA-92,

to 0015 inch
.
Y-43 film to a dry thickness of 0007 to 0. 001 and
.

80°F
allow to dry one hour at before overcoating.
NOTE f. Mix AA-92 Urethane Enamel in a 1:1 ratio.

Heat resistant enamel should be thinned in a NOTE

one to one ratio with 1 part Xylene or Toluene
to four parts enamel and allowed to air dry For a minimum of Orange peel, the material
for a period of 24 hours· should be thinned to a viscosity of 18 seconds
in a #2 Zahn cup. Induction time is 30 min-
Touch Up Vinyl- utes and pot life is 8 hours. Induction time
is the time required for mixture to set after
When it is necessary to touch up or refinish an area, mixing and before application. At life is the
the edge of the finish adjacent to the defect shall be work life after mixing.
feathered by sanding with #320 followed by #400
sandpaper. Avoid, if possible, sanding through the g. Apply urethane enamel to primed surface in two
primer. If the primer is penetrated over an area of passes such that the dry film thickness is 0. 0013 to
1/2-inch square or larger, the surface must be re- 0. 0017 inches.
140°F
primed. h. Force dry at for a period of 4 hours be-
fore masking for additional painting.
NOTE
NOTE
Avoid spraying metal primer on the adjacent
paint as much as possible.
Applying a heavy film will cause solvent
popping and should be avoided. If anti-
a. When touching up vinyl, use EX2016G primer
cratering solution is used, #92C24 should
mixed one part primer to one part EX2016A activator, be added at the rate of not more than 2
Stir and allow 30 minutes before spraying.
ounces per catalyzed gallon,

Change 8
 421 SERVICE MANUAL GROUND HANDLING,
SERVICING AND INSPECTION

i. Apply W102 white for the topcoat if white is spec- CAUTION

ified.
Metallic gold is not a finish coat in itself,
and must be overcoated. Care should be taken
Touch Up of Polyurethane Finish. that the surface sh 11 not be touched or wiped,
this will cause a discoloration. Overcoat
a. Urethane touch up and design should be accom- must be applied as soon as possible.
plished within 24 hours after the application of the
topcoat. The topcoat must be wiped down with MEK
before touch up or painting stripes. Clear Urethane Top Coat.
b. If the touch up or striping is accomplished after
the 24 hour limitation the area should be scuff sanded. a. Mix the clear urethane C-21C in a 1 to 1 ratio
e. Apply touch up in accordance with Polyurethane with catalyst C-22B. Mixture may be sprayed at
Finish, steps f thru h. this viscosity or thinned with MEK to a viscosity of
no less than 18-20 seconds in a #2 Zahn cup.
Metallic Gold Urethane Coating· b. Apply the clear coating in three uniform 50°/o
overlap spray coats to an approximate thickness of
A metallic gold urethane coating is applied to painted 2-1/2 to 3 mils dry film thickness.
surface of the vertical stabilizer. Should it become c. Allow to air dry 4 to 6 hours or force dry at
necessary to repaint this area, the following proce- 135°F
approximately for 1 hour.
dure will apply.
NOTE
NOTE
If system is to be recoated, lettered or sten-
Touch-up of Polyurethane paint is not recom¯ ciled in anyway, this will have to be applied
mended. The entire area must be stripped Longer times will
within a 36 hour period.
and a new application of Polyurethane applied. necessitate a light sanding (remove gloss)
before recoating or lettering.
a. The area to be painted shall be thoroughly clean-
ed and washed before priming.
NOTE
b. Apply a wash primer (EX2016G Enmar, or 818-
012 Dupont) mixed with diluent (T670 Enmar or should be cleaned immediately
All equipment
Dupont, respectively) in a 1 to 1 volume ratio. T-732A, Methyl Ethyl Ketone, or
after use.
Cellosolve Acetate should be used for cleaning
NOTE equipment.

The mixed wash primer must be used within

a six-hour period or be discarded. Touch Up Landing Gear Finish.

c. Apply wash primer by spray coating to insure a a. The area of the landing gear to receive touch up
film thickness of 0002 to 0003 inch.
. . paint should be masked off, sanded, cleaned and
d. Allow primer to air dry for 30 minutes before primed in accordance with Priming Procedures using
overcoating. Red Oxide Primer P/N BM 111-35.
e. Wash primer surface irregularities should be b. Apply enamel touch up paint Gull Gray P/N 52-
sanded and tack-ragged. New primer should be 9375 in accordance with Touch Up Vinyl Enamel Pro-
applied to sanded areas to prevent a break in primer cedures and allow to air dry. On aircraft 421B0501
film. and On, apply Epoxy White P/N 54E-511 in accord-
f. Wash primer may be overcoated after air drying ance with Epoxy Finish.
a minimum of 30 minutes or a maximum of 4 hours,
g. Mix a small amount of MEK with the metallic
RAIN EROSION COATING APPLICATION.
powder until a paste is formed. Continue adding
thinner, a little at a time, until gold powder is
a. Refer to Section 16 for preparation and applica-
evenly dispersed with no lumps and volume of MEK
added reaches one pint.
tion of rain erosion coating.
h. Mix the clear urethane C-21C in a 1 to 1 ratio
with C-22B catalyst.
i. Slowly add the thinner-powder mixture. The
viscosity will be 15-17 seconds in a #2 Zahn cup.
This mixture should be sprayed immediately.
j. Spray one overlap spray coat and then let flash
off. Add one light dry coat to insure uniformity of
color.
k. Allow to air dry for one hour.

Change 11
 2-14 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION
I INSPECTION REQUIREMENTS

As required by Federal Aviation Regulations, all civil aircraft of U.S. registry must undergo a complete inspection
(ANNUAL) each twelve calendar months. In addition to the required ANNUAL inspection, aircraft operated commercially
(for hire) must also have a complete inspection every 100 hours of operation.

In lieu of the above requirements, an aircraft may be inspected in accordance with progressive inspection schedule,
which allows the work load to be divided into smaller operations that can be accomplished in shorter time periods.

CESSNA PROGRESSIVE CARE PROGRAM has been developed to provide a modern progressive inspection schedule that
satisfies the COMPLETE AIRCRAFT INSPECTION (refer to paragraph II, c., for definition) requirements of both the
100 HOUR and ANNUAL inspection as applicable to Cessna Aircraft.

II INSPECTION CHARTS

The following Inspection Charts show the recommended intervals at which items are to be inspected.

As shown in the charts , there are items to be checked each 50 hours , each 100 hours , each 200 hours , and also Special
Inspection Items which require servicing or inspection at intervals other than 50, 100 or 200 hours.

a. When conducting an inspection at 50 hours, all items marked under EACH 50 HOURS would be inspected, serviced
or otherwise accomplished as necessary to insure continuous airworthiness.

b. At each 100 hours, the 50 hour items would be accomplished in addition to the items marked under EACH 100
HOURS as necessary to insure continuous airworthiness .

c. At each 200 hours, the 50 hour items and 100 hour items would be accomplished in addition to the items marked
under EACH 200 HOURS as necessary to insure continuous airworthiness.

d. The numbers appearing in the SPECIAL INSPECTION ITEMS column refer to data listed at the end of the inspec-
tion charts.These items should be checked at each inspection interval to insure that applicable servicing
and inspection requirements are accomplished at the specified intervals .

e. A COMPLETE AIRCRAFT INSPECTION includes all 50, 100 and 200 hour items plus those Special Inspection
Items which are due at the time of the inspection .

III INSPECTION PROGRAM SELECTION

AS A GUIDE FOR SELECTING THE INSPECTION PROGRAM THAT BEST SUITS THE OPERATION OF THE
AIRCRAFT, THE FOLLOWING IS PROVIDED.

1. IF THE AIRCRAFT IS FLOWN LESS THAN 200 HOURS ANNUALLY

a. IF FLOWN FOR HIRE
An aircraft operation in this category must have a COMPLETE AIRCRAFT INSPECTION each
100 hours of operation and each 12 calendar months of operation (ANNUAL) A COMPLETE .

AIRCRAFT INSPECTION consists of all 50 , 100 , 200 and Special Inspection Items shown in
the inspection charts as defined in paragraph II above.

b . IF NOT FLOWN FOR HIRE

An aircraft operating in this category must have a COMPLETE AIRCRAFT INSPECTION each
12 calendar months of operation (ANNUAL) A COMPLETE AIRCRAFT
.
INSPECTION consists
of all 50, 100, 200 and Special Inspection Items shown in the inspection charts as defined in
paragraph II above. In addition, it is recommended that between annual inspections, all
items be inspected at the intervals specified in the inspection charts.

2. IF THE AIRCRAFT IS FLOWN MORE THAN 200 HOURS ANNUALLY

Whether flown for hire or not, it is recommended that aircraft operating in this category be placed
on the CESSNA PROGRESSIVE CARE PROGRAM. However, if not placed on Progressive Care,
the inspection requirements for aircraft in this category are the same as those defined under para-
graph III, 1., a. and b.

Cessna Progressive Care may be utilized as a total concept program which insures that the inspec-
tion intervals in the inspection charts are not exceeded. Manuals and forms which are required
for conducting Progressive Care inspections are available from the Cessna Service Parts Center.

Change 8
 421 SERVICE MANUAL 6ROUND HANDLIN6, 2-16
SERVICIN6 AND INSPECTION
IV INSPECTION GUIDE LINES

a. MOVABLE PARTS for: lubrication, servicing, security of attachment, binding, excessive wear, safetying,
proper operation, proper adjustment, correct travel, cracked fittings, security of hinges, defective bearings,
cleanliness, corrosion, deformation, sealing and tension.

b .
FLUID LINES AND HOSES for: leaks , cracks , dents , kinks , chafing , proper radius , security , corrosion ,

deterioration, obstruction and foreign matter,

c. METAL PARTS for: security of attachment, cracks, metal distortion, broken spotwelds, corrosion, condition
of paint and any other apparent damage.

d. WIRING for: security, chafing, burning, defective insulation, loose or broken terminals, heat deterioration
and corroded terminals.

e. BOLTS IN CRITICAL AREAS for: correct torque in accordance with torque values given in the chart in Section
1, when installed or when visual inspection indicates the need for a torque check.

NOTE

Torque values listed in Section 1 are derived from oil-free cadmium-plated threads, and
are recommended for all installation procedures contained in this book except where other
values are stipulated. They are not to be used for checking tightness of installed parts
during service .

f. FILTERS, SCREENS & FLUIDS for: cleanliness, contamination and/or replacement at specified intervals.

g. AIRCRAFT FILE.

Miscellaneous data, information and licenses are a part of the aircraft file. Check that the following documents
are up-to-date and in accordance with current Federal Aviation Regulations. Most of the items listed are re-
quired by the United States Federal Aviation Regulations. Since the regulations of other nations may require
other documents and data, owners of exported aircraft should check with their own aviation officials to deter-
mine their individual requirements .

To be displayed in the aircraft at all times:

1. Aircraft Airworthiness Certificate (FAA Form 8100-2) .

2. Aircraft Registration Certificate (FAA Form 8050-3) .

3. Aircraft Radio Station License, if transmitter is installed (FCC Form 556).

To be carried in the aircraft at all times:

1. Weight and Balance, and associated papers (Latest copy of the Repair and Alteration Form, FAA
Form 337, if applicable) .

2 Aircraft
. Equipment List.

To be made available upon request:

1. Aircraft Log Book and Engine Log Book.

h. ENGINE RUN-UP.

Before beginning the step-by-step inspection, start, run-up and shut down the engine in accordance with
instructions in the Owner's Manual. During the run-up, observe the following, making note of any discrepan-
cies or abnormalities:

1. Engine temperatures and pressures .

2. Static rpm.
3. Magneto drop (refer to Owner's Manual) .

4. Engine response to changes in power.

5. Any unusual engine noises.
6. Fuel selector and/or shutoff valve; operate engine(s) on each tank (or cell) position and OFF
position long enough to ensure shutoff and/or selector valve functions properly.
7. Idling speed and mixture; proper idle cut-off.
8. Alternator and ammeter.
9. Suction gage.
10 . Fuel flow indicator .

After the inspection has been completed, an engine run-up should again be performed to determine that any
discrepancies or abnormalities have been corrected.

Change 8
2-16 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

INSPECTION FREQUENCY

1 -
As required or 500 hours 7 -
Every 500 hours
2 -
See Table I 8 -
Next 10 hours of operation
3 -
Check torque first 100 hours then every 100 9 -
Daily
hours thereafter check for security looseness 10 -
Every 3 years
and working. DO NOT TORQUE 11 -
Every 5 years
4 -

Every 1200 hours 12 -

Every 2 years
5 -
First 100 hours and 200 hours thereafter 13 -
Every 50 hours and at tire replacement
6 -
Every 50 hours or sooner when dust conditions 14 -
After rough engine operation
exist 15 -
400 Hours

Spl
IMPORTANT 50 100 200 : Insp

Read all Inspection Requirements and Paragraphs prior to

using this chart.

NOTE

This Inspection Chart should be used in conjunction with the

Cleaning Inspection, Repair and Servicing paragraph imme-
diately following the Overhaul and Replacement Chart.

AIRFRAME

1. Fuselage *
2. Cabin Pressurization Check -
1
3. Pressure Cabin (Type A Inspection) 2
4. Pressure Cabin (Type B Inspection) 2
5. Pressure Cabin (Type C Inspection) 2
6. Windshield and Windows Check for condition -
*
7. Cabin Door -
Check for condition and operation *
8. Cabin Door Seal Check for cuts, abrasions
-
and excessive wear *
9. Door Latch Pin (Upper and Lower) Check for damage, cracks, wear -

and rigging *
10. Door Latch Pin Guides Check for damage, cracks and wear -
*
11. Door Latch Pin Receptacles Check for damage, cracks and wear -
*
12. Baggage Doors Check for condition and operation
-
*
13. Nose Ram Air Check clarnps and hoses to heating and ventilating
- system
for condition and security *
14. Heater -
Check *
15. Seats and Seat Belts Check condition, security -
and operation *
16. Upholstery and Carpet Clean -
*
17. Instrurnents Check condition and marking
-
*
18. Control Quadrant Check for condition and security
-
*
19. Placards and Decals Check for presence and legibility
-
*
20. Empennage *
21. Vertical and Horizontal Stabilizers Check bolts for security -
*
22. Wing -
Check for loose rivets, cracks, loose mounting bolts and security *
-
Check for loose rivets, refer to ME73-22
23. Wing Wheel Well Check for damage and sealing
-
*
24. Wing Spar Fittings Check bolts for torque and security
-
3
25. Wing Locker Doors Check condition and security
-
*
26. Tip Tank Fittings Check bolts for security
-
*
27. Wing and Stub Wing (Type A Inspection)
28. Wing and Stub Wing (Type B Inspection) 4
29. .. Nacelle Firewall Structure Check condition and security -
. *
30. Emergency Exit Door Check for condition and security -
*

Figure 2-7. Inspection Chart (Sheet 1 of 6)

Change 11
 421 SERVICE MANUAL GROU MD MA MDLIF G, 2 7
SERVICING AhD INSPECTION

Spl

LANDING GEAR

1. Main Landing Gear Actuator Check for condition, security and -

specification compliance *
2. Emergency Extension System Check for condition, operation and -

specification compliance *
3. Main and Nose Landing Gear Assemblies Check for condition -
*
4. Rigging Perform
-
Landing Gear Rigging Inspection in accordance with
Figure 2-32 *
5. Torque Links Check wear and condition
-
*
6. Nose and Main Gear Retracting Linkage Check for condition -

*
7. Drive Tube Seals Check for security,
-
position and wear *
8. Shock Strut Servicing Check for proper servicing -

*
9. Nose Gear Shimmy Dampener Check fluid and condition -

*
10. Nose Wheel Steering System Check cable tension, travel and gimbal -

for condition and mounting bolts for proper torque *

11. Nose and Main Wheels and Tires Check wear, condition and tire pressure -
13
12. Wheel Bearings Check and repack
-

5
13. Brake System Plumbing Check for leaks, hoses for bulges and
-

deterioration, parking brake for operation *

14. Brake Assemblies Check wear of lining and dise warpage
-
*
15. Master Cylinders Check fluid level
-
*

FLIGHT CONTROLS

1. Control Column Check for security,

-
looseness, wear and proper rig *
2. Aileron Check hinge, bellerank,
-
stop bolt for looseness and/or jamb
nut for being tight, linkage and bolt for condition, operation and
security, and travel *
3. Aileron Trim Tab Check hinge for cracks, wear; bolts for proper
-

safety and tab travel *

4. Aileron Trim Tab Actuator Check travel linkage for condition and -

security *

I 5.

6.
Aileron and Aileron Trim Cables
turnbuckles for safety
Elevator
Check for tension, fraying and
Check pulleys for condition and security
Check hinges and hinge bolts, belleranks
-
-

and push rod

-

connecting bolt and stop bolts for security and condition *

7. Elevator Trim Tab Check hinge for cracks, wear, bolt for proper
-

safety and tab travel *

8. Elevator Trim Tab Actuator Check travel, condition and security -
*

I 9.

10.
Elevator

Elevtric
and Elevator
turnbuckles for safety
Elevator Trim
Trim Tab Cables

Check for security,

Check tension, fraying and
Check pulleys for condition and security
condition
-
-

and travel
-

*
*
11. Rudder -
Check hinge, bellerank, stop bolts and jamb nut for looseness,
torque tube and connector links for security and safety; check travel *
12. Rudder Trim Tab Check security -
and condition, linkage and travel *
13. Rudder Trim Tab Actuator Check travel, mountings for security -
*

I
14. Rudder and Rudder Trim Tab Cables Check tension, fraying and -

turnbuckles for safety Check pulleys for condition and security -

15. Flaps -
Check linkage, belleranks, pulleys and cables for condition,
tension and security Check hinges for cracks -
*
16. Flap Motor and Position Indicator Check for travel, condition and -

security *
17. Flap Actuator Assembly Check for condition, security, -
and
specification compliance *
18. Cable Seals Check for tears and security
-
*
19. Autopilot (Optional Equipment) Check cables, attachments, pulleys and -

turnbuckles for tension, condition, operation and security *

Figure 2-7. Inspection Chart (Sheet 2)

Change 11
2-1.8 ORoUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

Spl
50 100 200 Insp

ENGINE GROUP

CAUTION

Ground magneto primary circuit before working on the engine.

1. Engine Wash, check for security of accessories

-
*
2. Cowling Wash, check for cracks,
-
evidence of abrasion and wear *
3. Induction Air Filter Clean -
6
4. Induction Manifold Check connections for condition -
*
-

5. Engine Oil Pressure System Check for leaks, bends, cracks and -

security
6. Engine Oil Filter Change oil filter element and inspect -
adapters.
7. Engine Oil Change -

I 8.

9.
Engine Oil Separator
Service Chart
Engine Compartment
Inspect and clean element. Refer -

-
Visually check for condition, oil leaks,
to
fuel
6

leaks, etc. *
10. Engine Controls Check travel and security -
*
11. Engine Wire Bundle Check for condition and security -
*
12. Engine Mounts Check for condition and security
-

13. Engine Compartment Hoses Fuel, (check fuel lines under pressure) -

Oil Vacuum, etc. Check deterioration, leaks, discoloration, -

bleaching and rubber hoses for stiffness

14. Cylinder Compression Refer to Manufacturer's Service Bulletin M73-19 -

15. Engine Cylinders, Rocker Box Covers and Pushrod Housings Check -

for fin damage, cracks, oil leakage, security of attachment and

general condition
16. Crankcase, Oil Sump and Accessory Section Inspect for cracks and -

evidence of oil leakage. Check bolts and nuts for looseness and
retorque as necessary *
17. Plugs Clean and rotate (top right to bottom left, top left to bottom
-

right)
18. Ignition Cables Check condition and security -

19. Magneto Check timing, breaker

-
gap and security 14
20. Alternator Check brushes, leads,
-
bearings and slip rings 7
21. Starter Check brushes,
-
commutator and electrical connections *
22. Propeller Governor Check for oil leaks, condition and security -
*
23. Pumps Fuel, Vacuum and Autopilot
-
Check for leaks, condition -
and
security *
24. Turbocharger Check for condition, bulges,
-
warps and security *
25. Engine Exhaust System- Check for security, cracks, bellows
and spring tension

26. Engine Exhaust System- Check for security, cracks, and

spring tension- Visually inspect slip joint seals.

27. Waste Gate Valve, Variable Absolute Pressure Controller and Rate
Controller -
Check for condition and security. Visually check
springs and linkage *
28. Manifold Pressure Relief Valve Visually check for obstructions, -

condition, security and proper operation *

29. Engine Oil Screen Check for removal. (Refer to expanded paragraph)
-
*
30. Engine Compartment Fire Extinguisher Check system pressure, -

condition and security

Figure 2-7. Inspection Chart (Sheët 3)

Change 12
 421 SERVICE MANUAL CROUt D HANDLIN3, 1"
SERVICIN3 AND INSUECTlf N

Spl
50 100 200 Insp

PROPELLER

1. Blades -
Check for nicks, cracks, scratches and blade angles *
2. Propeller Cylinder Check bolts for security -

*
3. Bulkhead -
Check for cracks and security on crankshaft *
4. Propeller Check for oil leaks
-

* 14
5. Deice System Electrical Leads Check for condition and security . -
*
6. Deice System Brushes Check for wear and seating (see Section 13)
-
*
7. Propeller Spinners Wash, check for cracks and fractures
-
*
8. Propeller Mounting Check nuts for security -
* 14
9. Blades -
Check for condition of epoxy and security of retention nut
(see Section 2) *
10. Deice Slip Ring Mounting Bolts Check for clearance between -

propeller hub and slip ring bolt heads (see Section 10) 8
11. Propeller Unfeathering Accumulator Check for leaks, condition -

and proper charge . *

12. Propeller Synchronizer Check condition and security -

FUEL SYSTEM

1. Metering Unit Filter Screen Clean -

*
2. Fuel Injection System and Manifold Inspect for leaking -
*
3. Fuel Discharge Nozzles Inspect orifices and clean -
*
4. Fuel Selector Valve Perform operational check, feel for detents
-

through 270°; check linkage, bearings, pins for condition and

security *
5. Selector Valve -
Perform an operational check in accordance with
Section 11 7
6. Sediment Bowl Drain -

9
7. Fuel Strainer Clean
-

*
8. Fuel System Main Inspect for leaks, -
and operation 9
9. Fuel System Main Inspect plumbing -
and component mountings for
condition, security, system for leaks *
10. Tip Tanks Inspect mounting bolts for security, tip tank for leaks,
I
-

cracks, and dents, cracks at welds

11. Boost Pumps (Auxiliary) Inspect for leaks, operation, vent and -

overboard drain for obstruction *

12. Tip Tank Vents and Nose Cap Drain Inspect for obstructions -

9
13. Auxiliary Tanks Inspect system
-
for security and operation *
14. Heater Fuel Filter Clean -

*
15. Main Tank Fuel Transfer Pump Check security and mounting -
*
16. Main Tank Fuel Transfer Pump Filter Clean -
*
17. Wing Locker Transfer Pump Check for leaks and security of mounting -
*
18. Auxiliary In-Line Pump Check for leaks and security -
*
19. Auxiliary In-Line Pump Filter Inspect and clean element (see Section -
11) *

OXYGEN SYSTEM

1. Oxygen System Check installation,

-
mountings, and pressure *
2. Oxygen Regulator Check pressure and rate of flow
-
*
3. Oxygen Masks and Hoses Check condition and clean -
*
4. Oxygen Cylinder ICC-3HT/DOT-3HT -
Inspect condition and -

Hydrostatic Test Date 10

5. Oxygen Cylinder ICC-3AA/DOT-3AA -
Inspect condition and -

Hydrostatic Test Date 11

Figure 2-7. Inspection Chart (Sheet 4)

Change 12
2-20 6ROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

Spl

VACUUM SYSTEM

1. Filter -
Clean .
*
2. Relief Valve Check security -
and filter for obstruction *
3. Hoses Inspect for hardness,
-
deterioration, looseness and bulging *

SURFACE DEICE SYSTEM

1. Deice System Check for leaks, condition -

and operation of controls,
lines and clamps for security *
2. Deice Boots Check for abrasions, -
cuts, nicks and security of mounting *
3. Deice Filter Clean -
*

PITOT STATIC SYSTEM

1. Sump Check for cracks,

-
dents, leaks and presence of water *
2. System Leak check
-
*
3. Altimeter Inspect as required
-
by FAR Part 91, paragraph 91. 170 in
accordance with FAR Part 43, Appendix E, by authorized repair
station 12
4. Alternate Static Drain Check -
*

AIR COI ITION SYSTEM (BELT DRIVEN)

1. Compressor Drive Belt Tension Check -

2. Compressor Drive Belt Check condition and security -

3. Compressor Lines Check suction, injection and discharge lines for

-

leaks, cracks, sharp bends and condition

4. Condenser Fan Check blade for nicks, looseness and security
-

5. Evaporator Fans Check blades for nicks, looseness and security

-

6. Component Mounting Check condition and security -

7. Condenser Check inlet and outlets for obstruction,

-
check coils
for debris, etc. *
8. Sight Glass Check proper charge with engine operating
-

9. Condenser Fan Motor Brushes Visually check -

AIR CONDITION SYSTEM (HYDRAULIC DRIVEN)

1. Compressor Lines Check suction, injection and discharge lines for -

leaks, cracks, sharp bends, and condition

2. Compressor and Motor Check condition and security -

3. Condensers Check inlets and outlets for obstruction,

-
check coils for
debris, etc.
4. Sight Glass Check proper charge with engine operating
-
and air
conditioner on *
5. Hydraulic Lines Check for leaks, security and condition -
*
6. Condenser Fan Check blades for nicks, looseness
-
and security *
7. Condenser Fan Motor Brushes Visually check - *
8. Evaporator Fan Check blades for nicks, looseness and security
-
*
9. Hydraulic Fluid and Filter Change fluid and element (P/N 6655567) -

(refer to expanded paragraph)

Figure 2-7. Inspection Chart (Sheet 5)

Change 12
 421 SERVICE MANUAL GROUND HAADLIN3, 2" 1
SERVICING AND INSF ECTK N

Spl
50 100 200 Insp

PRESSURIZATION SYSTEM

1. Safety Valve Check for security and operation

-

*
2. Outflow Valve Check for security and operation
-

*
3. Outflow Valve Filter Clean -

*
4. Safety Valve Filter Clean -

*
5. Variable Pressure Controller Filter (Optional System) Check -

*
6. Heat Exchanger Drain oil. Check for security and air passage
-

obstruction *
7. Dump Valves Check for security-
and proper operation *
8. Door Seals Check for proper installation,
-
cuts, wear and abrasion *
9. Perform Cabin Pressurization Check (refer to Section 13) 1

ALCOHOL WINDSHIELD ANTI-ICE SYSTEM

1. Check reservoir for proper service *

2. Check nozzles for security and obstructions *
3. Anti-ice System Check for leaks, condition and operation -
of controls *
4. Pump -
Check for leaks, condition and security *

ELECTRICAL SYSTEM

1. Junction Box and Circuit Breaker Panel Check wiring and -

terminals
for condition and security *
2. Pedestal and Instrument Panel Check wiring and terminals -
for
condition and security *
3. Regulators Check wiring and terminals for condition and security
-

*
4. Switches Check for security
-
and interference *
5. Landing Gear Relay and Limit Switch Check wiring and terminals for -

condition and security *

6. Flap Limit Switch and Motor Check wiring and terminals for condition-

and security *
7. Wing and Fuselage Check wiring bundle for condition and security
-

*
8. Battery -
Check electrolyte and general condition and security *
9. Battery Cables Check for corrosion, -
condition and security *
10. Battery Box Check for corrosion,
-
condition and security, clean vent tube *
11. Instrument and Interior Lights Check lights for operation -
*
12. Radio and Navigation System Check for condition and security -
*
13. Check bonding between stationary panel and instrument panel for proper
ground resistance
-
must be 0. 010 ohms or less *
14. Emergency Locator Transmitter Check for condition, security, -

operation and battery pack for proper charge *

15. Warning Lamps Check condition -
*
16. Starter Relay Inspect Contact Area -

15
POST INSPE CTION

1. Correct all discrepancies, replace all fairings, doors and access hole
covers
2. Ground check engine, check ignition drop, alternator charging rate, oil
pressure and general operation of components

SERVICE LETTERS

1. Check that all applicable Cessna Service Letters and Service Bulletins
are complied with
2. Check that all applicable current airworthiness regulations are complied
with

Figure 2-7. Inspection Chart (Sheet 6)

Change 12
2-22 OROUND HANDLING, 421 SERVICE MANUAL
SERVICING AND INSPECTION

OVERHAUL AND REPLACEMENT CHART

A -
Every 500 hours H -
Every 500 hours of heater operation
B -
Every 1200 hours J -
Every 12 months
C -
Every 1500 hours K -
Every 2500 hours
D -
On Condition L -
Every 2400 hours
E -
Every 15 years or 4380 eyeles whichever M -
Every 5 years
occurs first N -
At first 5000 hours
F -
Every 8000 hours P -
Every 3 years or 3000 hours
G -
Every 13, 200 hours

Overhaul . Replace
AIRFRAME
1. Oxygen Bottle (ICC or DOT-3HT 1800) (see Section 13) E
2. Oxygen Regulator P
3. Oxygen Pressure Gage P
4. Oxygen Filler Valve P
5. Oxygen Outlets P
6. Heater (see Heater and Components Service/Parts Manual) H
7. Control Cable Seals B
8. Safety Valve K
9. Safety Valve Filter A
10. Outflow Valve C
11. Outflow Valve Filter A
12. Variable Pressure Controller Filter (Optional System) A
13. Pressurization Dump Valve (see Janitrol Instructions P/N43DS7) B
14. Ram Air Valve B
15. Autopilot Filter P/N AMA201442 (see Cessna Nav-O-Matic 800 Service/
Parts Manual) A
16. Upper Cabin Door Latch Pins and Receptacles (421-0001 to 421B0001) F
17. Windshield G
LANDING GEAR
1. Landing Gear Actuator (see Cessna Landing Gear and Flap System
Components Overhaul/Parts Manual) D
2. Actuator Motor (see Cessna Landing Gear and Flap System Components
Overhaul/Parts Manual) D
3. Actuator Reduction Unit D
4. Drive Tube Seals B
5. Shimmy Dampener (see Section 4) D
6. Uplock Hooks (421-0001 to 421A0146) N

FLIGHT CONTROLS
1. Flap Actuator Gearbox
(see Cessna Landing Gear and Flap System
Components
Overhaul/Parts Manual) D
2. Flap Actuator Motor (see Cessna Landing Gear and Flap System
Components Overhaul/Parts Manual) D
3. Rudtler.Trim Tab,Actuator (see Section 7) B
4. Ailerknim Tab Actuator (see Section 5) B
5. Elevator Trim Tab Actuator (see Section 5) B

ENGINE GROUP
1. Engine (see Continental Motors Engine Overhaul Manual) B
2. Magneto (see Bendix Magneto Overhaul Manual) B
3. Alternator 50 AMP (see Cessna Alternator
-
Service/Parts Manual) B
4. Alternator 100 AMP (see Westinghouse Service Manual)
-
B
5. Turbocharger (see Cessna Turbocharger and Controls Service/Parts Manual) B
6. Controllers (see Cessna Turbocharger and Controls Overhaul/Parts Manual) B
7. Manifold Pressure Relief Valve (see Cessna Turbocharger and Controls
Overhaul/Parts Manual) B
8. Waste Gate (see Cessna Turbocharger and Controls Overhaul/Parts Manual) B
9. Vacuum Pump (wet) (see Authorized Repair Station) B
10. Vacuum Pump (dry) (see Authorized Repair Station) B

Figure 2-8. Overhaul and Replacement Chart (Sheet 1 of 2)

Change 12
 421 SERVICE MANUAL GROUND HANDLING, 2-
SERVICING AND INSPECTION

Overhaul Replace

11. Vacuum System Hoses

12. Fuel Pump (refer to Manufacturers Overhaul Manual) B
13. Tach Generator (refer to Manufacturers Overhaul Manual) B
14. Starter (Refer to Manufacturers Overhaul Manual) B
15. Engine Compartment Hoses eg. fuel, oil, deice etc. (Rubber)
16. Engine Compartment Fuel and Oil Hoses (Teflon) L
17. Induction Air Filter (P/N 9910018-1) B
18. Cowl Flap Actuator B
19. Engine Compartment Fire Extinguisher Container M
20. Engine Compartment Fire Extinguisher Cartridge M
21. Vacuum System Filter Element -
Standard (P/N C294501-0103) A
-
Optional (P/N C294501-0203) A
22. Engine Mounts B

PROPELLER
1. Propeller (See McCauley Maintenance and Overhaul Manual) B
2. Governor (See Manufacturer's Overhaul Manual) B
I 3.
4.
Accumulator,
Propeller
Unfeathering (See Manufacturer's
Shaft Oil Seal (See Continental Service
Overhaul Manual
Bulletin M70-3)
B
B

Figure 2-8. Overhaul and Replacement Chart (Sheet 2)

CLEANING, INSPECTION, REPAIR AND SERVICING. the Inspection Chart Figure 2-7. These procedures
are more detailed and provide expansion of the In-
The Cleaning, Inspection, Repair and Servicing Items spection items requiring additional attention.
listed in this section appear in the same sequence as

Change 11
2-228 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION
ration, excessive wear and proper installation. Leaks
AIRFRAME- in the cabin structure may be sealed in accordance
with Sealing Instructions given in Section 16.
Fuselage. 8. Check heater ducting, mounting and sealing for-
ward of pressure bulkhead Station 100. 00,
a. Cleaning. 9. On completion of repairs to the cabin pressuri-
1. Clean the fuselage with mild soap and water, zation area, a flight or ground check should be per-
Use Stoddard Solvent to remove grease and tar then formed in accordance with Section 13.
wash with soap and water and allow to dry. 10. To assure a successful fail-safe structure for
2. The fuselage may be cleaned with any good air- the pressure cabin, periodic inspections are re-
craft cleaner and wax. quired. Three types of inspection are outlined for
b. Inspection. the pressure cabin structure, Types A, B, and C.
1. Inspect exterior surface for damage and cracks The aircraft hour intervals and type of inspection to
loose rivets and nuts, be performed are listed in Table I.
2. Inspect attaching screws, access plates, ex- 11. Type "A" Inspection.
terior paint, nose gear door hinge points, for dam- Type "A" inspection consists of a limited inspection
age and excess wear. of the cabin structure requiring a very minimum of
3. Inspect stiffeners, stringers, doublers, bulk- equipment and upholstery removal for access. The
heads and stinger for loose screws, rivets, cracks shaded areas to each figure are the critical areas to
or damage. be inspected. Use the following procedures:
4. Inspect nose ram air hoses and clamps to heat
and vent system for wear and security and leaks. NOTE
5. Inspect heater installation for evidence of fuel In case of any skin cracks or significant
leaks, exhaust leaks, combustion air leaks, loose rivet damage, upholstery should be removed
wiring and security to structure
in the local damage area to inspect internal
6. Inspect instruments for proper marking, broken structure for damage.
glass, loose fittings and electrical wiring, and for
proper calibration. _ TABLE I.
7. Check all placards and decals for security and
legibility. INSPECTION SCHEDULE FOR CABIN STRUCTURE
8. Inspect all fluid lines and hoses for leaks,
cracks, dents, kinks, chafing, bleaching or discolor- Type of Hours at which Inspections
ation, proper radius, security, corrosion, deterior- Inspection are Required
ation, obstructions and foreign matter.
c. Repair and Servicing. A Every 1200 hours.
1. If cracks are found in stinger, or fuselage area,
refer to Section 16 and repair. B First time at 6000 hours and re-
peat every 3600 hours thereafter.
I 2. Loose or working rivets must be replaced.
Refer to Section 16.
C First time at 13, 200 hours and re-
Pressure CaWin. peat every 3600 hours thereafter.

a.Cleaning. (a) Inspect all external pressure cabin structure

1.Refer to Owner's Manual Section 5 for cleaning for cracks and damage.
pressure cabin windows and painted surfaces, (b) Inspect pressure cabin structure for loose or
b. Inspection, failed fasteners.
1. Any leak at windows or doors, noted during the (c) Inspect pressure cabin skin and skin splices
flight check, should be corrected. If pressurtzation for cracks, loose rivets or failed fasteners,
air dump valve malfunction was detected, the unit (d) Inspect windshield, cockpit side windows and
should be repaired or replaced (see Janitrol Instruc- cabin windows for looseness, cracks, nicks, deep
tions Part No. 43D57), gouges and scratches.
2. Check cabin pressurization ducting fittings in (e) Inspect the cabin door and cabin doorframe
the engine compartment for security, cracks, leaks, for cracks, loose rivets or fasteners.
loose clamps and deterioration. (f) See figure 2-9. Inspect forward cabin pres-
3. Check ram air valve in the nose for operation sure bulkhead at Fuselage Station 100. 00.
and possible leakage or blockage due to foreign ma- (g) See figures 2-22 and 2-23. Inspect aft cabin
terial. pressure bulkhead at Fuselage Station 273. 94 (421-
4, Check electrical operation of the safety valve by 0001 to 421B0301) Fuselage Station 289. 94 (421B0301
actuating the ram air dump control, and On).
5. Check main and nose gear actuating pushrod (h) See figure 2-10. Inspect stationary instrument
boots for loose clamps, cracks or deterioration. panel for cracks at Fuselage Station 118. 55, (421-
6. Check access doors to the cabin for possible 0001 to 421BO301).
seal leaks, check test fittings in forward pressure 12. Type "B" Inspection.
bulkhead in nose wheel well area. Type "B" is a visual inspection of the most critical
7. Check the sealing of any repairs or field elec- areas of the cabin structure. To conduct this inspec-
tronics installation affecting the cabin pressurized tion, only partial upholstery and floorboards neces-
area and the control cable seals for cracks, deterio- sary for these areas must be removed. Inspect all

Change 7
 421 SERVICE MANUAL ORoUND MANDLINO, -

Û
SERVICING AND INSPECTION

cabin structure for fatigue cracks and damaged areas (g) See figure 2-17. Inspect cabin doorframe at
for loose and failed rivets or structural fasteners. Fuselage Station 225. 50.
Shaded areas in each figure are the critical areas to (h) See figures 2-18 and 2-19. Inspect cabin
be inspected. Use the following procedures: doorframe supporting bulkheads at Fuselage Stations
(a) See figure 2-13. Inspect entire front spar 211. 00, 212. 87, 235. 50 and 238. 13. Note critical
bulkhead at Fuselage Station 154, 5 both left-hand and areas.
right-hand, especially around the lightening holes. (i) See figure 2-21. Inspect cabin doorframes,
(b) See figure 2-14. Inspect front spar carry- hinges, hinge pins, hinge support castings, and sup-
thru noting especially the critical points, port castings attachments.
(c) See figure 2-15. Inspect entire rear spar (j) See figure 2-21. Remove cabin door latch pin
bulkhead at Fuselage Station 186. 15. receptacles and guides from cabin door and cabin
(d) See figure 2-16. Inspect rear spar carry- doorframe and inspect for wear, cracks, dents,
thru at Fuselage Station 186. 15. bends and reinstall.
(e) See figures 2-22 and 2-23. Inspect aft pres-
sure bulkhead at Fuselage Station 273. 94 (421-0001 NOTE
to 421B0301) Fuselage Station 289. 74 (421B0301 and
On). If latch pin receptacles or cabin door latch
13. Type "C" Inspection. pins are damaged or worn don't hesitate to
Type "C" is a complete visual inspection of the cabin reject and install new parts.
structure. Should a crack be detected, the structure
must be repaired using the standard structural re- (k) See figure 2-20. Inspect entire bulkhead at
pair as defined in Section 16 of the Service Manual, Fuselage Station 255. 00 especially at the left-hand
with the following exceptions, the windshield, cock- and right-hand mountings as shown.
pit side windows, cabin windows, door latch pin re- (1) See figure 2-10A. Inspect entire bulkhead at
ceptacles, door latch pin guides and lower cabin door Fuselage Station 277. 20 especially at the critical
pins. Any cracks found in any of these components points.
must be replaced. To conduct this inspection, the (m) Inspect skins, skin attaching rivets and skin
floorboards and upholstery must be removed. Shaded splices in pressure cabin area.
areas in each figure are the critical areas to be in- (n) Inspect all stringers behind upholstery and
spected. under the floorboards.

NOTE NOTE

On 421-0001 to 421B0001 the upper cabin door It will be necessary to drill out rivets to re-
latch pins must be replaced at 8000 hours in- move overhead air plenum cover to inspect
terval. On aircraft 421B0001 and On the latch stringer splices at Fuselage Station 160. 50.
pin system is fail-safe. The windshield must See Section 16 for sealing and riveting pro-
be replaced at 13, 200 hours. cedures when reinstalling air plenum cover.

Use the following procedures:

(a) See figure 2-9. Inspect forward pressure Windshield and Windows.
bulkhead at especially noted areas at Fuselage Sta-
tion 100. 00. a. Cleaning.
(b) Inspect windshield, cockpit side windows and 1. Remove dust and dirt from the panels by wash-
cabin windows especially in attaching areas for ing with a solution of mild soap and warm water.
cracks, nicks, dents, deep gouges, loose rivets or 2. Dissolve grease and oil deposits with either
structural fasteners, kerosene or Aliphatic Naphtha, Specification TT-N-
95 (Type II only). Apply this solvent with either a
CAUTION soft, grit-free cloth, chamois, sponge or with bare
hands. Bare hands are the most satisfactory appli-
When inspecting the critical (shaded) areas, cators, as they are least likely to produce scratches.
it may be necessary to remove primer and
dye check. Removal of sealing is not re- CAUTION
commended unless repair is being made.
Do not use any solvent except those specified
(c) See figure 2-10. Inspect instrument panel in step 2, above, as many chemical solvents
structural fastenings at Fuselage Station 118. 55, will soften or craze the surface of the plastic.
(421-0001 to 421B0301). Cleaning sprays and other cleaning solutions
(d) See figure 2-11. Inspect bulkhead structure prepared for use on cellulose-nitrate and
mountings and skin fasteners at Fuselage Station cellulose-acetate base plastics often contain
141. 35, (421-0001 to 421B0301), ingredients harmful to acrylic plastic, which
(e) See figure 2-12. Inspect bulkhead for struc- is the material used in this aircraft. Even
tural mounting left-hand and right-hand at Fuselage a light coat of salt spray or dust should not
Station 166. 95. be wiped off when dry, as small hairline

I (f) Open escape hatch and inspect frame,

and operating mechanism.
seal

Change 8
 421 SERVICE MANUAL eRoUND HANDLINo. 2-23
SERVICING AND INSPECTION

F.S. 100.00 F.S. 100.00

Figure 2-9. Forward Pressure Bulkhead

F. S. 11

421BO301 AND ON

Figure 2-10. Stationary Instrument Panel Figure 2-10A. F. S. 277. 20 Bulkhead

Change 7
2-24 GROUND HANDLING, 421 SERVICE MANUAL
SERVICING AND INSPECTION

SYM SYM
Detail

C
Detail Detan

o\

D
Detail lii

F. S. 141. 35 F. S. 166. 95

Figure 2-11. Canted Windshield Bulkhead Figure 2-12. Left-Hand Bulkhead

F. S. 154. 50

Figure 2-13. Front Spar Bulkhead (Left-Hand) Figure 2-14. Fuselage Front Spar

Change 4
 421 SERVICE MANUAL GRoUND HANDLINe, 2-25
SERVICING AND INSPECTION

STA. 187. 52
STA. 189.88
F.S. 186.15
8 52
Detaii B
sTA.
B 16 6- Detail A

'
A
STA.
4.76

189 88
SYM

--
Detail

Figure 2-15. Rear Spar Bulkhead (Left-Hand) Figure 2-16. Rear Spar Carry-Thru

Detail

Detail

F. S. 225. 50 O

F. S. 211. 00 Detail B
Figure 2-17. Cabin Doorframe Figure 2-18. Fwd Door Bulkhead

Change 4
2•26 GRoDND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

Detail

Detail

Detail

OOD eo
F. S. 255. 00
F. s. 235. So

Figure 2--19. Aft Door Bulkhead Figure 2-20. Left Hand Bulkhead

Detail

Deta

Figure 2- 21. Cabin Door Installation

Change 4
 421 SERVICE MANUAL eRoUND HANDLIN6, 2-27
SERVICING AND INSPECTION

'
F. S. 273. 94 ' F. S. 289. 94
421-0001 TO 421BO301 421BO301 AND ON

Figure 2-22. Aft Pressure Bulkhead (Fwd Side)

:W F. S. 273. 94 F. S. 289. 94
421-0001 TO 421B0301 421B0301 AND ON

Figure 2-23. Aft Pressure Bulkhead (Aft Side)

Change 6
2-28 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

BOTTOM TOP
SKIN SKIN
L/H WING L/H WING

Figure 2-24. Engine Nacelle Figure 2-25. Wing Skin and Splices

Figure 2-26. Front Spar and Leading Edge Assernbly Figure 2-27. Rear Spar

Change 4
 421 SERVICE MANUAL GRoUND HANDLING,
SERVICING AND INSPECTION

Figure 2-28. Front Spar Carry-Thru Structure Figure 2-29. Rear Spar Carry-Thru Structure

Figure 2-30. Stub Wing Figure 2-31. Ailerons

Change 4
2-30 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

scratches will result when gritty particles 1. Clean the door latch pins with Trichloroethelene
are rubbed over the surface. Always flush or suitable solvent.
the surface first with clean water or soap b. Inspection.
solution. Finally, rinse generously with 1. Inspect door latch pins for damage, cracks, and
clean water. wear.
2. Check for proper rigging in accordance with
b. Inspection. rigging procedures (See Section 3).
1. Refer to Section 3 and inspect all windows and 3. Check door latch pin guides for cracks and wear.
windshield in accordance with Plastic Windows In- 4. Check door latch pin receptacles for wear,
spection Criteria. cracks and visible damage.
c. Repair and Servicing. c. Repairs and Servicing.
1. After cleaning plastic window surfaces, allow 1. Refer to Lubrication Diagram for lubrication
to dry, then wax to give surface a maximum trans- of door latch pins.
parency.
2. Minute hairline scratches can often be removed
by rubbing with commercial automobile body cleaner. Nose Baggage and Wing Locker Doors.
Apply the cleaner with a soft, dry, clean cloth or
imitation chamois of flannel. a. Cleaning.
3. If repair to plastic window surfaces becomes 1. Clean upholstery panel with a suitable commer-
necessary, refer to Section 16 and repair them in cial upholstery cleaner,
accordance with Repair of Plastic Window Surfaces. 2. Clean latch assembly, cylinder assembly and
door assembly with suitable solvent and wipe dry
with cloth.
Cabin Door, b. Inspection.
1. Make a visual inspection of latch and cyHnder
a. Cleaning. assemblies for excessive wear or binding.
1. Clean the cabin door and latching mechanisms c. Repair and Servicing.
by wiping with a suitable cloth. 1. Refer to Section 3, replace components which
2. Remove accumulations of grease from cabin show evidence of excessive wear.
door parts by using a suitable solvent and wipe clean 2. Refer to Lubrication Diagram and service com-
with a cloth. ponent parts as shown.
b. Inspection.
1. Make a visual inspection of component parts for
excessive wear, metal breaks and improper threads. Heater.
2. Operate door and observe for proper function of
component parts. Refer to Cessna Heater and Components Overhaul/
c. Repair and Servicing. Parts Manual for cleaning, inspection, servicing and
1. Refer to Section 3, replace components which repair of heater.
show evidence of excessive wear.
2. Refer to Lubrication Diagram, and service
components as shown. Seats.
3. Lubricate the cabin door seal with Sil-Glide, or
equivalent, to aid sealing. a. Cleaning.

NOTE
Cabin Door SeaL
Cleaning fluids used on fabrics having a
a. Cleaning. naphtha base are recommended for use in
1. Remove accumulation of dirt and grease from cleaning fabric covered seats.
cabin door seal by using a suitable solvent and wipe
clean with a clean cloth. CAUTION
b. Inspection.
1. Inspect door seal for cuts, abrasions, and ex- Never use anything except a mild soap solu-
cessive wear. tion on leather and vinyl covered seats. Sol-
c. Repairing and Servicing. vents and cleaners will damage, discolor and
1. Refer to Section 3 for replacement of door seal shorten the life of the seats.
if evidence of excessive wear exists.
2. Refer to Lubrication Diagram, and service door L Clean fabric covered seats as follows:
seal with proper lubricant. (a) Carefully brush off and vacuum all loose
3. If repair to seals is required refer to Section particles of dirt.
16 for repair procedures. (b) Wet a small, clean cloth with cleaning solu-
tion and wring out thoroughly. Then open the cloth
and allow a small part of the fluid to evaporate.
3oor Latch Pins (Upper and Lower). (c) Pat the spot lightly with the cloth, but do not
rub it. Repeat this procedure several times, using
a. Cleaning, a clean part of the cloth each time,
hange 5
 421 SERVICE MANUAL enoUND HANDLING, S
SERVICING AND INSPECTION

NOTE mable solvent while installed in the aircraft Spots

or stains can be removed by following the procedure
Patting the spot lightly will prevent its spread- for cleaning the seats (fabric), as outlined in this
ing and is less likely to leave a ring. section.
b. Inspection.
(d) 1VÏoisten another piece of cloth and allow to 1. Inspect upholstery for general condition and
evaporate until barely damp. Now pat the spot light- wear. Observe areas where chafing from other
ly, working from the outside in toward the center. equipment might occur thus damaging the upholstery
panels.
CAUTION

Do not use too much fluid. Seat cushions are Carpets.

padded with foam rubber, and since volatile
cleaners attack rubber, these pads may be a. Cleaning.
damaged if the material gets soaked with the 1. Use a small whisk broom to loosen dirt; then
cleaner. vacuum the carpet. The more difficult spots or
stains can be removed by using a noninflammable
(e) Brush again to remove any more particles dry-cleaning fluid. General care of the carpet is
which have become loosened. the same as the care of the carpets in your home.
2. Clean.vinyl or leather seats as follows: b. Inspection.
(a) On vinyl or leather seats, use a mild soap 1. Inspect carpet for excessive wear and security
solution and sponge to remove dirt from seats; wipe to the floorboard.
dry with a clean damp cloth.
b. Inspection.
1. Inspect the front seats for binding on seat rails. Control Quadrant.
2. Inspect for proper functioning of adjusting han-
dles and tilting mechanism, a. Cleaning.
3. Seat belts for proper security. Clean all metal parts
1. in a suitable solvent and
4. If electrically operated seats are installed (op- allow to air dry,
tional equipment), actuate switches and observe for b. Inspection.
smooth operation. 1. Inspectall parts for evidence of cracking and
c. Repair and Servicing. excessive wear.
1. Refer to Section 3, replace components which 2. Inspect the racks and ratchet stops on the mix-
show evidence of excessive wear or binding. ture levers for broken teeth and excessive wear.
2. Lubricate seat base rollers with oil as required. c. Repair and Servicing.
3. Wax seat rails with automotive wax to reduce 1. Replace racks, ratchet stops, and ratchet stop
friction between seat rollers and seat rails, springs if worn or too weak to insure positive lock-
ing.
2, Lubrication of control quadrant is not recom-
Seat Belts. mended; however, the control quadrant pedestal does
require lubrication. (Refer to Lubrication Diagram.)
a. Cleaning.

NOTE Empennage.

Seat belts should be removed from the air- a. Cleaning.

craft to clean. 1. Clean the empennage with mild soap and water.
Stoddard Solvent may be used to remove grease and
1. Clean seat belts using a suitable solvent or mild tar then washed with soap and water and allowed to
soap solution, dry.
2. The empennage may be cleaned with any good
CAUTION aircraft cleaner and wax.
b. Inspection.
Never use thinner or strong solutions on seat 1. Inspect exterior surfaces for damage and
belts. See Seat Belt Inspection procedure be- cracks, loose rivets and loose nuts.
fore reinstalling seat belts in aircraft. 2. Inspect attaching bolts and hinge attaching
points for security.
b. Inspection.
1. Inspect webbing material for fraying.
2. Inspect seat belt installation for security. Wing.

a. Cleaning.
Upholstery. Clean the wing as follows:
1.
(a) Use a suitable solvent to remove all grease
a. Cleaning. and dirt from nacelle area and landing gear area.
1. The upholstery can be cleaned with a noninflam-

Change 4
2•3Ž enoUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

CAUTION Should a crack be detected, the structure must be

repaired using the standard structural repair as de-
Never use gasoline, paint thinners, or Ketone fined in Section 16, with the following exceptions:
to remove grease. These are highly inflam- the wing-stub wing spar fittings, tip tank fittings,
mable and fire could result. landing gear and attachment fittings, push-pull tubes,
belleranks, hinges, bolts, rivets, pins bushings and
(b) After washing area with suitable solvent, wash bearings. Any cracks in or failure of these items
the remaining solvent off with soap and water and al- will require that the item be replaced.
low to air dry.
(c) The wing can be cleaned with any good air- CAUTION
craft cleaner and wax.
b. Inspection. When inspecting the critical (shaded) areas
1. Inspect wing skins, wing attach fittings, tip it may be necessary to remove primer and
tank fittings, flap and aileron attach fittings for dye check.
cracks and visible damage.
2. Inspect wheel well, fluid lines and hoses for (a) Inspect all wing and stub wing structure for
leaks, cracks, dents, kinks, chafing, bleaching or cracks and damaged areas.
discoloration, proper radius, security, corrosion, (b) Inspect for loose and failed structural fasten-
deterioration and foreign matter. ers.
3. Inspect wing spar bolts for security and insure (c) See figure 2-25. Inspect wing skin and splices.
they are not working. Torque front spar bolts 60 ±5 (d) Inspect rivets, especially those common to
feet-pounds and rear spar bolts 175 ±15 inch-pounds. front spar and skin.
(e) See figure 2-26. Inspect front spar and lead-
NOTE ing edge assembly.
When checking torque on spar bolts, always (f) See figure 2-28. Inspect front spar carry-
loosen nut first then check torque while tight_ thru structure. (For carry-thru structure inside the
fuselage, refer to "Pressure Cabin Inspection Re-
ening nut. Spar bolts are installed in shear
position. DO NOT OVERTORQUE. It is pos_ quirements. ")
sible wing spar bolts will turn if a slight tor- (g) See figure 2-27. Inspect rear spar and trail-
que is applied to bolt head. ing edge assembly.
(h) See figure 2-29. Inspect rear spar carry-
c. Wing and stub wing area inspection. thru structure. (For carry-thru structure inside the
fuselage, refer to "Pressure Cabin Inspection Re-
1. Two types of inspections are required for the
wing and stub wing area. These inspection, Type quirements. ')
A and Type B, are outlined in the following para- (i) Inspect wheel well, especially gear fittings,
graphs. The aircraft hour intervals and type of in- ribs and spars.
spection to be performed are shown in figure 2-7. (j) See figure 2-24. Inspect engine nacelle,
especially engine mounts, prop unfeathering accumu-
2. Type "A" Inspection.
Type "A" inspection is a limited visual inspection of lator mounting holes and areas shaded.
the wing and stub wing structure. (k) See figure 2-30. Inspect stub wing.
Use the following procedures: (1) Inspect flaps, especially the hinge, scissors,
(a) Inspect all external wing structure for cracks and their attachments and push-pull rod connecting
and damaged areas. the scissor assembly to the bellerank.
(b) Inspect for loose and failed structural (m) See figure 2-31. Inspect ailerons.
fasteners.
(c) Inspect wing skin and splices for cracks, Emergency Exit Door.
wrinkles, abnormal stresses, dents, etc.
(d) Inspect rivets, especially those common to a. Cleaning.
front spar and skin, for loose or working rivets, 1. Clean exit door and latching mechanisms by
stretched rivets, and cracks around dimples. wiping with a suitable cloth.
(e) Inspect gear attach fittings and supporting b. Inspection.
structure for loose bolts, elongated bolt holes, and 1. Inspect general condition, fit and security of
structural member damage resulting in secondary door.
damage such as high shear or stretched rivets. 2. Inspect position of emergency release handle
3. Type "B" Inspection. to verify that the release mechanism has not been
l'ype "B" inspection is a complete visual inspection disturbed.
3f the wing and stub wing using all available access
Toles, lightning holes, etc. To conduct this inspec -

LANDING GEAR.
ion, engine cowls, tip tank fairing, wing stub gap
:over, battery box assembly, prop unfeathering ac-
:umulator and all access doors and panels are to be Landing Gear Actuator.
'emoved. Flaps should be fully extended and ailer-
ms free to move for ease in inspection. Shaded a. Cleaning.
treas in each figure are the critical areas to be in- 1. Clean external parts of landing gear actuator
ipected. assembly and reduction gear by wiping with a clean

Change 11
 421 SERVICE MANUAL eRoUND HANDLIN6, 33
SERVICING AND INSPECTION

cloth.
2. Dampen cloth with a suitable cleaning solvent
to remove oil or grease accumulations* BLACK (BRAKE)
b. Inspection.
1. Inspect assemblies externally for visible dam- POWER
age such as cracks, nicks, dents and scratches. WHITE CCW SUPPLY
Check upper and lower belleranks and splines on
par ruding portions of sector shaft for visible dam¯ GREEN S

i Check landing gear actuator for proper operat- CW

S2
ing times as follows:
(a) Flight check for excessive noise and for
free, proper operation.

NOTE
V =
VOLTMETER, DC, 7. 5/30/75, TYPE DP-11,
NO. 50-202011 RCPF
air- A =
AMMETER, DC, 5/20/50, TYPE DP-11 '
Use maximum placarded
- .

airspeeds in
NO. 50-202111 RXPS
craft for extension and retraction tests.
81 =
SWITCH, SPST 30 AMPERE CAPACITY,
NO. 707
(b) Flight check time for full retraction "UP, " S2 = SWITCH -
PUSH BUTTON NO. CR2940-UA202B
amber light on 10 to 14 seconds. Time for S3 =
SWITCH, DPDT NO. 2565K5
full extension "DOWN, " green lights on 8 to
11 seconds.
(c) If during flight check, the landing gear will
not retract and extend within the time limit Figure 2-31A. Schematic Test Connection Diagram
described in step (b), remove the landing
gear motor and perform the following no described in step (12).
load test: (15) If the motor does not operate within the
(1) Mount motor securely in a horizontal limits as described in step (12), refer
position. to Troubleshooting the Landing Gear
(2) Connect motor as shown in Figure 2-31A Actuator Motor, Section 4.
to
a variable 30 volt, DC power supply. (d) If the motor will not meet operating require-
(3) Connect switch S3 for either direction. ments, after performing no load check, re-
(4) Open switch S2 to read ammeter. place motor and repeat step (b).
(5) Close switch S1 to start motor- (e) If the gear still will not meet flight check re-
(6) Gradually increase voltage from zero quirements, check all linkage and hinge
until the brake releases. points for binding or interference.
(f) If no evidence of binding or interference is
NOTE found, landing gear actuator must be re-
placed or overhauled in accordance with
The brake releasing may be indicated either Cessna Landing Gear and Flap System
by sound or the armature starting to turn. Components Overhaul/Parts Manual.
c. Repair and Servicing.
(7) Read voltmeter when brake releases- 1. Refer to Lubrication Diagram and service com-
Brake must release at or less than 18 ponents as shown.
volts. 2. Disassembly of the landing gear actuator as-
(8) Stop motor, close switch S3 for opposite sembly or reduction unit for repairs are not recom-
rotation and repeat steps (3) thru (7). mended.
(9) Voltage must be within the same limits
as previous rotation. NOTE
(10) If the voltage is not within the limits as
described in step (7), refer to Trouble- Landing gear actuator may be partially dis-
shooting the Landing Gear Actuator assembled to lubricate gears.
Motor, Section 4.
(11) Run motor in each direction as shown
connected in Figure 2-31A with 24 volts Emergency Manual Extension System.
DC applied.
(12) Open switch S2 and read ammeter cur- a. Cleaning.
rent. The ammeter should read approx- 1. Clean all components
with suitable solvent.
imately 7. 5 amperes under no load, b. Inspection.
when the RPM is approximately 4000 1. Inspect miter gears and sprocket for visible
RPM. damage such as chipped or broken teeth, nicks,
(13) Stop motor, close switch $3 for opposite
rotation and repeat step (12).
(14) Motor should operate within limits as
Change 11
2-34 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

dents, cracks or deep scratches• c. Repair and Servicing.

2. Inspect all bolt and pin holes for elongation· 1, Repair of torque link assemblies is limited to
3. Inspect around all welds for cracks replacement of parts, smoothing out of minor
4. Check emergency manual extension system for scratches, nicks, and dents and repainting of areas
specification compliance as follows: where paint has chipped or peeled.
2. Refer to Lubrication Diagram and service com-
NOTE ponents as shown.

This check must be accomplished during flight.

Nose and Main Gear Retracting Linkage.
(a) Place the landing gear actuator switch in the
"OFF" position a. Cleaning.
(b) Manually extend the landing gear, counting the 1. Clean linkage components with cloth saturated
number of turns required to illuminate the green with suitable cleaning solvent.
to fifty-four turns are required
I
lights. Forty-seven
to illuminate the lights·
c. Repair and Servicing.
CAUTION

1. Refer to Lubrication Diagram, and service com¯ or needle bear-

Do not clean sealed bearings
ponents as shown- ings which do not have provisions for lubri-
cation.
Main and Nose Landing Gear Assemblies· b. Inspection.
1. Refer to Inspection Chart for periodical inspec-
a. Cleaning• tion requirements.
1. Clean all metal parts with suitable solvent. c. Repair and Servicing.
1. Repair of main landing gear retracting linkage
CAUTION is limited to replacement of parts, smoothing out of
minor nicks, dents, and scratches and repainting of
If metal parts are not to be assembled im¯ areas where paint has chipped or peeled,
mediately, coat with system hydraulic fluid 2. Refer to Lubrication Diagram and service com-
to prevent rusting. Before assembly it will ponents as shown.
be necessary to again clean with solvent.

2. Clean all O-rings and seals with system hydrau¯

Shock Strut Servicing.
lic fluid.
b. Inspection- a. To fill the main landing gear shock struts, use
1. Inspect all components for excessive wears the following procedures:
cracks, dents, nicks and scratches· 1. Jack aircraft in accordance with Jacking Pro-
2. Inspect outer barrel of the lower strut assembly cedures.
for any defects that may damage seals· 2. Deflate strut by loosening valve body 2-1/2
3. Refer to Inspection Chart for additional periodi¯
turns. (Maximum)
cal inspecton requirements· 3. With strut fully compressed, remove valve and
c. Repair and Servicing· fill with hydraulic fluid. (1VEL-H-5606)
1. Repair of main landing gear is limited to re¯ 4. Stroke strut slowly 3 times. (Minimum)
placement of parts, smoothing out of minor scratches, 5. Top off fluid with strut compressed.
nicks and dents and repainting of areas where paint .6. Replace valve and inflate strut to 200 PSI (275
has chipped or peeled. PSI, 421BOOO1 and ON) with tire clear of ground.
2. Refer to Lubrication Diagram and service com- 7. When aircraft is on the ground, service strut to
ponents as shown. approximately 2. 35 inches (2. 70 inches, 421B0001
and ON) extension until it can be serviced per step 6.
b. To fill nose landing gear shock strut, use the
Nose and Main Landing Gear Rigging Inspection, following procedures:
1. To fill the nose gear shock strut follow proce-
Inspect the nose and main landing gear rigging in dure given above, inflating nose strut to 65 PSI with
accordance with figure 2-32. tire clear of ground.
2. When aircraft is on the ground, service strut to
approximately 1. 37 in. extension until it can be ser-
viced per step 1.
Torque Links.

a. Cleaning. Nose Gear Shimmy Dampener.

1. Clean torque link assemblies with a suitable
solvent and wipe clean with a clean cloth. a. Cleaning.
b. Inspection. 1. Clean all metal parts with suitable solvent.
1. Refer to Inspection Chart for periodical require- 2. Clean all O-rings and seals with clean system
ments. hydraulic fluid.

Change 10
 421 SERVICE MANUAL GROUND HANDLING, ÈÑ
SERVICING AND INSPECTION

2. Inspect disc drive clips for damage, looseness,

CAUTION and excessive wear.
3. Inspect bearing cups for visible damage and
If metal parts are not to be assembled im- wear.
mediately, coat with system hydraulic fluid
to prevent rusting. Before assembly, it will NOTE
be necessary to again clean with suitable
solvent. Do not remove bearing cups unless replace-
ment is required.
b. Inspection.
1. Refer to Inspection Chart for periodical inspec- 4. Inspect bearing cones for visible damage and
tion requirements. wear.
c. Repair and Servicing.
1. Repair of shimmy dampener is limited to re- NOTE
placement of parts, smoothing out of minor nicks,
scratches, and dents, and repainting areas where If more than the usual number of takeoffs
paint has chipped or peeled. and landings are made or the aircraft is
2. Refer to Lubrication Diagram and follow this operated in dusty areas, it is recommended
procedure to fill the shimmy dampener. that cleaning and lubrication of wheel bear-
(a) Using the tow bar, turn the nose wheel strut ings be accomplished at each 100-hour in-
to the extreme left position against the 55-degree spection.
stop. This will place the shimmy dampener piston to
the rear of the cylinder and eliminate the possibility 5. Inspect retainers
and snap rings for damage and
of entrapped air in the cylinder. distortion. Straighten
or replace as necessary.
(b) Remove the filler plug and fill with hydraulic 6. Inspect the tire for breaks, cuts, foreign objects
fluid. embedded in tread and flat spots and/or exposed
(c) Replace filler plug and turn nose wheel strut cords.
through its entire travel several times.
(d) Return strut to the extreme left position CAUTION
against the 55-degree stop.
(e) Remove filler plug and add whatever fluid is Breaks, flat spots, exposed cords and cuts
needed to fill the cylinder. that damage cords are cause for immediate
(f) Replace and safety filler plug. rejection of tire. Should there be any doubt
about a tire's reliability, don't hesitate to
Nose Wheel Steering System• reject it.

a. Cleaning- 7. Refer to Inspection Chart for periodical inspec-

1. Clean metal parts with suitable solvent· tion requirements.
2. Wipe cables and pulleys with a clean dry cloth. c. Repair and servicing.
b. Inspection· 1. Slightly corroded areas on wheel castings can be
1. Refer to Inspection Chart for periodical inspec¯ repaired as follows:
tion requirements· (a) Clean affected area thoroughly.
2. Check gimbal mounting bolts for proper torque (b) Repaint with two coats of zinc chromate prim-
50 to 70 inch-pounds- er on area which has had the protective coating re-
c. Repair and Servicing. moved.
1. Repair of components in the nose gear steering (c) Finish coat casting with two coats of alumi-
system is limited to replacement of parts- num lacquer.
2. Refer to Lubrication Diagram and service sys~ 2. Replace bearing cones with applicable grease as
tem components as shown- shown in Lubrication Diagram.
3. Replace damaged clips.
Nose and Main Wheels and Tires. 4. Lubricate felt seal with light oil.

a. Cleaning. NOTE
1. Clean all metal parts with suitable solvent.
2. Clean felt seals and bearing cones by washing The main wheel tires should be maintained
in suitable solvent and dry thoroughly. at 65 PSI and nose wheel tires at 32 PSI on
b. Inspection. aircraft 421-0001 to 421BOOO1 and at 70 PSI
1. Inspect wheel castings for cracks, nicks, dents, for the main wheel tire and 35 PSI for the
scratches and corrosion. nose wheel tire on aircraft 421B0001 and ON.
Check and examine tires for wear, cuts and
NOTE bruises when checking tire pressures.
Brake System Plumbing.
Replace castings which show evidence of
cracks or heavy corrosion. See step c. for a. Cleaning.
servicing castings which show evidence of 1. Clean hydraulic components with clean system
light corrosion- hydraulic fluid or denatured alcohoL

Change 4
2-38 eRoUND HANDUNe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

b. Inspection. wall is found.

1. Inspect fittings for damaged threads and deform- 2. Repairs to master cylinder components are not
ed flares on ends of tubing; lines for cracks, dents, recommended, only replacement of defective parts,
deep scratches, flattened bends and signs of chafing 3. Refer to Lubrication Diagram, and service as
at points of wear; hose for swelling, cracking, abra- shown.
sions through protective plies and leaks.
2. Refer to InspectionChart for periodical inspec-
tion requirements. FLIGHT CONTROLS.
c. Repair and Servicing.
1. Repairs to brake system plumbing should be Control Column.
made in accordance with best shop practice, using
standard parts and procedures, and be conducted in a. Cleaning.
compliance with applicable regulations. 1.The control column tube assemblies are chemi-
2. Service system as shown in Lubrication Diagram. cally treated with a dry lubricant and should be clean-
ed only with a clean, dry cloth.
2. Clean roller chains and cables with a clean, dry
Brake Assemblies, cloth.
b. Inspection.
a. Cleaning. 1. Check all bolt holes for elongation.
1. Wash metal parts in suitable solvent. 2. Check bearings for excessive wear, binding and
2. Wash O-rings with clean system hydraulic fluid looseness.
or denatured alcohoL 3. Check tube assemblies for cracks and loose
3. If required, clean brake linings with MEK. rivets,
b. Inspection. 4. Check for loose or missing bolts, pins, nuts,
1. Inspect metal parts for wear and thread damage. and rivets on control wheel, aileron sprocket, bear-
2. See Inspection and Replacement of Brake Lin- ing blocks and tube assemblies.
ings, Section 4, for wear tolerances. 5. Check control wheel and control locis Er con-
3. Inspect cylinder walls for corrosion, pitting and dition and operation.
scoring. c. Repair and servicing.
4. Refer to Inspection Chart for periodical inspec- 1. Repair is limited to replacement of parts and
tion requirements. smoothing out minor dents or scratches.
c. Repair and Servicing.
Aileron and Aileron Trim System.
CAUTION
a. Cleaning.
Always release parking brake before servic- 1. Clean ailerons, hinges, pulleys, belleranks,
ing cylinders. trim tab actuator and trim tab mechanism with suit-
able solvent.
1. Replace worn or damaged parts. 2. Remove dirt and grease from cables with a
2. Polish out minor nicks using 400 grit wet-or- clean dry cloth.
dry sandpaper with system hydraulic fluids. b. Inspection,
3. Replace brake dises at each engine overhaul or 1. Inspect aileron and trim system for visible dam-
when wear approaches limits described in Section 4, age such as cracks, dents, nicks, deep gouges and
Replacement of Brake Linings. loose balancing weights.
2. Inspect aileron and trim system hinges for free-
dom of movement, wear and fatigue cracks and attach
Master Cylinders. bolts for security.
3. Inspect aileron and trim control system cables
a. Cleaning. for fraying, proper tension and safeties; fairleads,
1. Clean all metal parts in suitable solvent, pulleys and chains for wear and attachment; all gears
2. Clean O-ring seals with clean system hydraulic and sprockets for wear, missing or broken teeth,
fluid or denatured alcohol. damage, security of attachment, binding and exces-
b. Inspection, sive wear; controls for proper operation, adjustment,
1. Inspect metal parts for wear and thread damage, travel and security of attach bolts.
2. Inspect cylinder walls for corrosion, pitting and 4. Inspect linkage, bellerank and bolt for security,
scores, stop bolts for looseness and security.
3. Inspect O-ring seal and O-ring portion of lock- 5. On aircraft 421-0001 to 421BOOO5, inspect stop
o-seal for swelling, chipping or other evidence of bolts on aileron bellerank stop bracket for looseness,
damage. if bolts can be turned by hand, an MS25082-3 lock nut
4. Refer to Inspection Chart for periodical inspec- should be installed on the near side of stop bolt. If
Jion requirements. the existing aileron bellerank rigging does not allow
c. Repair and Servicing, space for a lock nut, the stop bolt may be safety-
1. Replace master body when damage to cylinder wired instead. This requires the drilling of a 04 .

+. 04 diameter hole in the stop bolt bracket. Safety-

-.
00
wire stop bolt to stop bolt bracket.

Change 11
 421 SERVICE MANUAL GROUND HANDLINO, 2-
SERVICING AND INSPECTION

20°
6. Check travel on aileron up +1°, and and Servicing.
-0°

c. Repair
20°
down +1°, -0°.

1. Refer to Section 16 for repair, and Lubrication

20° +1°,
Check travel on aileron trim tab up
7. Diagram, for lubrication of elevator and trim system.
20° +1°,
and down
-0° -0°.

8. Check aileron cable tension 25 ±5 pounds. Rudder and Rudder Trim Tab System.
9. Check aileron trim tab cable tension 10 ±3
pounds. a. Cleaning.
10. Refer to Lubrication Diagram for lubrication 1. Use a soap solution and clear water rinse to re-
of aileron and trim system. move dirt and grease from the exterior surfaces of
the rudder and rudder trim tab. Wipe the hinges
Elevator and Elevator Trim Tab Control System. and actuator clean using a cloth dampened with a
suitable solvent.
a. Cleaning. 2. Clean grease from the rudder trim tab actuator
1. Use a soap solution and a clear water rinse to with Stoddard Solvent and air dry,
remove dirt and grease from the exterior surfaces b. Inspection,
of the elevator and elevator trim tab. Wipe the 1. Inspect the rudder hinge and attaching points
hinges and actuator clean using a cloth dampened for wear, cracks and excessive looseness.
with suitable solvent. 2. Inspect skin for loose rivets, push rods for
2. Clean grease from elevator trim tab actuator wear, bends, cracks and condition.
with Stoddard Solvent and air dry. 3. Inspect linkage, bellcranks and bolts for loose-
b.
Inspection. ness and security.
Inspect the elevator and trim tab hinges and
1. 4. Inspect rudder trim tab hinge and push rod for
attach points for wear, cracked fittings, defective condtion and security.
bearings, corrosion, deformation of parts, exces_ 5. Inspect rudder trim tab actuator for wear and
sive looseness and attach bolts for security. condition.
2. Inspect the skin for loose rivets, push rods for 6. Inspect the rudder and rudder trim cables for
wear, binds, cracks and condition. proper tension and safeties; fairleads, and pulleys
3. Inspect linkage, belleranks, and bolts for loose_ for proper alignment, wear and attachment.
ness and security, 7. Check travel on rudder (421-0001 to 421B0801),
left
25° +1°, 25° +1°,
4. Inspect elevator trim tab, hinge and push rod right per- -0°
-0°;

measured
for security and condition. pendicular to hinge line or (421BO801 and On) left 32°
5. Inspect elevator trim tab actuator for wear and
+1°, right 32°, +1°,
-0°,
-0°.

condition. 8. Check travel on rudder trim tab, left 16° +1°,

11° +1°,
6. Inspect elevator and elevator trim tab cables -0°;

right measured
-0°

perpendicular to
for fraying, proper tension and safeties; fairleads, hinge line.
pulleys and chains for wear and attachment; all gears 9. Check cable tension on rudder cables 25 ±5
and sprockets for wear, missing or broken teeth, pounds. (Refer to Rigging of Rudder, Section 7.)
damage, security of attachment, binding, and exces- 10. Check cable tension on rudder trim tab cables
sive wear; controls for proper operation, adjustment, 10 ±3 pounds.
travel and security of attach bolts. c. Repair and Servicing.
7. Check travel on elevator up 25° +1°, down -0°;
1. Refer to Section 16 for repair and figure 2-37
15° +1°, -0°.

for lubrication of rudder.

10° +1°,
8. Check travel on elevator trim tab up -0°

Rudder
421-0001 to 421B0001, (12° +1°, Pedal Assembly
421B0001 and On),
-0°

down
26° +1°, 421-0001 to 421B0001 (20° +1°,
-0° -0°

Cleaning
a.
421B0001 and On).
1. Clean component parts with suitable solvent.
9. Check elevator cable tension 32 ±5 pounds.
b. Inspection
10. Check elevator trim tab cable tension 10° ±3 1. Inspect all components for visible damage such
pounds (electric trim cable tension 18 ±3). as dents, cracks and broken welds.
11. Inspect ends of elevator torque tubes for rust, 2. Inspect all bearings
.

for scoring, binding and

exists, the following procedures
. . .

if a rust condition
excessive wear.
are recommended:
3. Inspect all pin and bolt holes for elongation.
(a) Refer to figure 6-1, remove taper pin (19) and
c1. RReeppirr udd
)e nan de-
al assembly by replacing
1 the area and remove any rust with fine
fective parts only.
emery cloth.
2. Refer to Lubrication Diagram, and service as
CAUTION shown.

The clean-up should not remove any more Flap System.

material than necessary and still provide a Cleaning.
a.
minimum wall thickness of 0. 038 on the Use Stoddard
1. Solvent to remove dirt and grease
torque tube ends. in the flap scissor area. After solvent is used the
entire area should be washed with a mild soap and
(c) Apply wet primer to the clean area; reinstall water solution and rinsed with clear water and al-
the flange fitting and taper pin. lowed to air dry.

Change 12
2-40 GROUND HANDLING. 421 SERVICE MANUAL
SERVICING AND INSPECTION

b. Inspection. 1. Inspect all hoses for evidence of internal swell-

1. Inspect the external surface of flaps for dents, ing, chafing, cuts or breaks.
nicks, cracks and proper flush fit in the up position. 2. Inspect all fittings for thread damage, damage
2. Inspect the flap scissors and attaching bolts for to chamfered seats and replace fittings as necessary.
wear and security. Check hinge segments for cracks. 3. Inspect oil separators for evidence of restric-
3. Inspect belleranks and push-pull rods for secu- tions and clean as necessary.
rity. 4. Visually inspect the engine cylinders for cracks,
4. Inspect flap cables for fraying, proper tension loose nuts and studs; baffles and seals for cracks and
and safeties; fairleads and pulleys for proper align- security; push rod housings and rocker box covers for
ment, wear and attachment. leaks, cracks and security; crankcase, oil sump and
15°
5. Check rigging and travel down at the stop oil cooler for loose bolts, cracks and oil leakage.
15° 0°, 45° +1°, 45°
and at the stop. Make necessary and repairs in accord-
-0°
-2°,

corrections
6. Check cable tension direct cable with flaps down ance with best shop practices and in compliance with
85 ±10 pounds. Return cables, flaps up 225 ±25 applicable FAA regulations.
pounds. 5. Perform a cylinder compression check in ac-
7. Check flap operation for specification compli- cordance with the engine manufacturers operator's
ance as follows: manual.
(a) Flight check to verify that flaps fully extend c. Repair and servicing.
in 9 -
13 seconds, and retract in 7 10 seconds. -
1. Refer to Engine Overhaul Manual and Section 9
Check extension and retraction times at 160 MPH for repair and servicing.
IAS. Check actuation to
15°
at 180 MPH IAS.
(b) If during flight check, the flaps will not extend
and retract within the time limits described in step Engine Cowling.
(a), the flap motor must be replaced.
c. Repair and Servícing. a. Cleaning.
1. Refer to Section 16 for repair of flap. 1. Wash cowling with Stoddard Solvent and wipe
2. Lubricate flap hinge as necessary with oil (MIL- dry with a clean cloth.
L-7870).
CAUTION
Control Cable Seals.
Never use thinners or MEK to clean cowling.
a. Cleaning.
1. The control cable seals are packed with a b. Inspection
lubricant; therefore, care must be exercised when 1. Inspect cowling for cracks, elongated holes,
cleaning to prevent dissolving grease within the seal. abrasions and wear due to rubbing.
2. Clean control cables using a clean, dry cloth. c. Repair and Servicing.
b. Inspection. 1. Refer to Section 16 for repair of engine cowling.
1. Check seals for cuts or excessive wear.
2. Check cables and seals for proper lubrication.
c. Repair and servicing. Induction Air Filter.
1. Replace worn or damaged seals as required.
2. Lubricate cables for full length of travel within The induction air filters should be cleaned every 50
the seal with MIL-G-81322A lubricant. hours or more often under dusty conditions and re-
3. Pack seal with MIL-G-81322A lubricant. placed every engine overhaul. Under extremely
4. Place the seal on the cable on the non pressur- dusty conditions, daily maintenance of the filter is
ized side of bulkhead with the small end of seal to- recommended. One method is to use dry compress-
ward bulkhead. ed air at not over 100 PSI and blow through the filter.
5. Insert seal in the bulkhead hole so that bulkhead Blow from the inside to outside to remove dirt and
metal within the retaining groove of seal
is seated dust. At 50 hour intervals clean the filter as follows:
and so that the small end of seal is in the pressur-
ized section. a. Cleaning.
6. Install proper retaining rings in the grooves on 1. Remove the filter from the canister.
the seal (two on small end and one on large end)- 2. Slightly rap the filter to remove heavy dirt ac-
cumulations.
ENGINE GROUP. non-
3. Wash thoroughly, using a mild detergent,
sudsing soap and water solution.
a. Cleamng.
.

4. Rinse filter with a stream of water until water

1. Wash down the engine with Stoddard Solvent and is clear.
dry with a jet of low pressure air.
.

5. Dry thoroughly using dry compressed air. Air

b. Inspection.
pressure should not exceed 100 PSI.
NOTE b. Inspection.
Instructions concerning inspection of particu- 1. Check filter for holes, cracks, deterioration
lar engine components, refer to applicable and pleats for proper bonding.
paragraph in "Engine Maintenance and Over- 2. Install the filter in the canister and safety,
haul Manual, " Continental Motors Corpora- 3. Refer to Overhaul and Replacement chart for
tion- inspection and replacement intervals.

Change 11
 421 SERVICE MANUAL GROUND HANDLINe, 2-40A/2-40B
SERVICING AND INSPECTION

Induction Manifold,

a. Cleaning.
1. Clean the induction manifold when washing down
engine using the same solvent.
b. Inspection.
1. Inspect the induction manifold for security,
loose connections, air leaks and condition.

Change 11
 421 SERVICE MANUAL OROUND HANDLING, -

41
SERVICING AND INSPECTION

c. Repair of induction manifold is limited to replace- cover.

ment of components. (g) Inspect the adapter gasket seat for possible
gouges, excessive scratches, wrench marks or
Engine Oil Pressure System. . other types of mutilation. If defects are found, re-
place the adapter.
Each engine's oil systemhas a capacity of 13 U. S. (h) Inspect threaded hole in the center of the
quarts, which includes 1 quart for oil filter. Do not adapter gasket seat. If the hole is off center more
operate on less than 9 U. S. quarts of oil. The filler than 030 inch, replace the adapter.
.

cap is located on the upper part of the engine or be- (i) Install the assembled oil filter on the adapter
tween the first and second left cylinders. The oil dip- (1) but DO NOT allow the gasket (2) to make contact
stick is located outboard of the filler cap and is used with the gasket seat. Hold the oil filter assembly to
to check the quantity of oiL The gear type engine oil prevent it from turning, torque the filter bolt (8) 15
pump is located on the lower aft end of the engine and to 18 foot-pounds (180 to 216 inch-pounds).
circulates the oil through the oil system.
NOTE
On aircraft 421-0001 to 421BOOO1 the oil filter
screen, which is located in the oil pump housing, If torque wrench is not available, tighten bolt
should be removed at the next 50 hour inspection 1-3/4 turns after gasket (2) snugs against the
except aircraft modified by SL ME70-8. gasket seat.

a. Cleaning. (j) Refill engine with proper grade and quantity

1. Clean line assemblies and fittings with suitable of oil. Start engine and run for 5 minutes at 1000
solvent. RPM and check for leaks after the engine has warmed
b. Inspection. properly, cycle through at least one high power set-
1. Start and run engine for a few moments observ- ting.
ing oil pressure gage for fluctuations. (k) If gasket (2) protrudes more than twice as
2. Shutdown engine and inspect oil pressure lines much on one side as on the other, the gasket has be-
and fittings for leaks.
c. Repair and Servicing.
1. Anytime the oil pressure indicating system has
been removed or repairs have been made the oil pres-
sure system should be serviced as follows:
(a) With all connections tightened, start engine
and allow time for the engine pumps to fill the oil
pressure lines.
(b) After a positive indication of oil pressure has
been noted, loosen the hose fittings on the rear of the
engine gage units and allow a few drops of oil to leak
from the fittings. This will bleed the trapped air
from the lines and provide an accurate oil pressure
indication.

Engine Oil Filter Service. (See figure 2-33. ) 4

a. Installation and inspection. o o o°, 5
1. Inspect and replace filter
I
(See figure 2-33. )
(a) Remove cowling.
element as follows.

(b) Remove oil filter element from adapter by

loosening bolt (8).
(c) Inspect bottom surface of filter case (6) by
placing a straight edge on the washer seat surface.
If any distortion or out-of-flat condition greater
than 0. 010 inch is observed, replace filter case (6).
(d) Lubricate the gasket (4) furnished with filter 7
element kit with a light coat of engine oil or general
purpose grease which allows the gasket to move free-
ly and seat properly.
(e) Assemble bolt (8), washer (7), through case
(6) and filter element (5). Position case (6) so that
element (5) is facing upwards. Assemble gasket (4) 1. Adapter 5. Filter Element
and cover (3) onto bolt (8). 2. Gasket (Cover to Adapter) 6. Filter Case
(f) Assemble new gasket (2) on cover (3), turn 3. Cover 7. Washer
cover (3) so that it is facing downwards. If gasket 4. Gasket (Case to Cover) 8. Bolt
(2) falls off, replace the gasket and repeat test.
Should this gasket fall from cover (3), replace the Figure 2-33. Oil Filter Assembly

Change 9

i
2- 42 GROUND HANDLING. 421 SERVICE MANUAL
SERVICING AND INSPECTION

421-0101 TO 421B0501 421B0501 AND ON

-

gig"
51561008

1. Wing Nut 3. Element 4. Gasket

2. Top 5. Body

Figure 2-34. Oil Breather-Separator

1. Visually inspect the engine compartment for

come unseated during assembly. This condition in¯ evidence of chafing lines and wires, evidence of fuel
dîcates that either the cover or adapter are faulty leaks, oil leaks, burned spots, parts for excessive
and should be replaced· wear, loose connections, loose bolts and entire area
(1) Recheck filter bolt torque and safety wire the for cracks, nicks and bends,
filter assembly· c. Repair and Servicing.
1. Refer to Section 16 for repairs.
Oil Breather-Separator. (See figure 2-34.)
Engine Compartment Fire Extinguisher.
a. Cleaning.
1. Wash metal parts and element in suitable solvent a. Cleaning.
and allow to dry. 1. Wipe with a clean dry cloth.
b. Inspection. b. Inspection.
1. Inspect metal parts for cracks in body and 1. Inspect the fire extinguisher bottles for proper
around the welded tubes. operating pressure. Replace bottle if pressure is
2. Inspect filter element for clogging and general not satisfactory.
deterioration. NOTE

NOTE The pressure-temperature correction table

indicates upper and lower pressure limits
If inspection of filter reveals damage or de- at a specified ambient temperature.
terioration, replace element with P/N
0850694-5. 2. Inspect the extinguisher bottles for security,
electrical connections and replacement schedule.
3. Inspect the deployment tubes for security and
Engine Compartment. outlet obstruction.
c. Repair and Servicing.
a. Cleaning. 1. Repair of components is limited to replacement
1. Spray engine compartment with a suitable sol- of parts.
vent and allow to drain and air dry. 2. Refer to Section 13 for servicing the fire extin-
b. Inspection. guisher.

Change 12
 421 SERVICE MANUAL GROUND HANDLING, 2--4 --42Ñ
SERVICING AND INSPECTION

Engine Controls. Engine Mounts.

a. Cleaning. a. Cleaning.
1. The controls should be cleaned when the engine 1. Clean engine mounts with a suitable solvent.
compartment is cleaned or washed down.
b. Inspection. CAUTION
1. Inspect the engine for security of
controls
mounting, sharp bends, kinks and damage which Never use a wire brush or sandpaper to clean
might affect operation of the control. engine mounts.
c. Repair and Servicing.
1. Repair of engine controls is Emited to replace- b. Inspection.
ment of parts. 1. Refer to the Inspection Chart for interval.
2. Inspect protective boots for discolored areas
or spots.
Engine Wire Bundles. 3. Displace protective boots and inspect engine
mounts for security, safetying, looseness, deterio-
a. Cleaning. ration, cracked fitting, localized burning, blister-
1. The wire bundles should be wiped clean with a ing, sagging and end separation.
dry cloth. DO NOT use solvents.
b. Inspection.
1. Inspect the wire bundles for security, chafing,
burning, defective insulation, loose or broken ter-
minals, heat deterioration and corroded terminals.
2. Inspect wire bundles in high heat areas, such
as close proximity of exhaust stacks or turbocharger
for heat damage.
c. Repair and Servicing.
1. If wire bundles are damaged they should be re-
placed.
2. Wire bundles should be clamped out of high heat
areas.

Change 12
I

421 SERVICE MANUAL GROUND HANDLINO, "$3

SERVICING AND INSPECTION

FLAT (UPPER PAD) CONICAL (LOWER PAD)

Mount Mount Max. "A" Min. "B"

Model Engine Assembly Component Eccentricity Thickness

421 GTSBJ520D J-9613-41 J-9612-25 0.08 1.22

and J-7763-32 0.08 1.02
GTSIO520H J-9613-54 J-9612-30 0.14 1.20
J-7763-34 0.14 1.02

Figure 2-35. Engine Mount Inspection Limits

4. If isolated discolored spots are present on pro- cessive wear, cracks, nicks, bulges, deterioration,
tective boots, rotate the affected area away from the discoloration, bleaching and rubber hoses for hard-
vicinity of the exhaust system. ening.
5. If areas of discoloration or cracks are found in NOTE
protective boots, replace boots.
6. Check engine mount for sag. Teflon hose assemblies exhibit considerable
stiffness throughout their useful life. Rea-
NOTE
sonable stiffness is normal and does not in-
If the area between the exhaust riser of num- dicate that the line should be replaced.
ber six cylinder and the lower cowl panel
does not have a minimum of 0. 40 inch clear- 2. Inspect engine compartment fuel hoses under
ance, refer to Section 9 and install engine pressure for deformation and leaks as follows:
mount shims. (a) Make sure throttles are in idle position and
mixture controls are in idle cutoff.
7. See figure 2-35 for inspection requirements. (b) Turn prime switch on and assure boost pumps
are operating in HI position.
NOTE (c) Check hoses for leaks, bulges, deterioration,
and deformation.
At each engine overhaul period it is recom- 3. Inspect hoses in the high heat areas such as
mended that engine mounts be replaced. En- close proximity of exhaust stacks or turbocharger
gine mounts which have been replaced prior area for heat deterioration and hardening or crack-
to the normal engine overhaul may be reused ing due to age.
providing dimensions are within inspection c. Repair and Servicing.
requirements. 1. Refer to Overhaul and Replacement Chart for
replacement intervals of engine compartment hoses.

Engine Compartment Hoses.

Spark Plugs.
a. Cleaning.
1. Clean engine compartment hoses by washing a. Cleaning.
engine compartment down with mineral spirits or a 1. Clean the spark plugs with an abrasive type
suitable solvent. cleaner.
b. Inspection.
CAUTION 1. Inspect spark plugs for proper gap 0. 015 to
0. 018 inches.
Never use inflammable or combustible sol- 2. Inspect porcelain for cracks and evidence of
vents. arcing.
c. and Servicing.
Repair
b. Inspection. 1. Rotate spark plugs top right to bottom left, and
1. Inspect all engine compartment hoses for ex- top left to bottom right.
Change 9

I
2-44 enoUND HANDLING. 421 SERVICE MANUAL
SERVICING AND INSPECTION

Ignition Cables. b. Inspection.

1. Remove turbocharger heat shield from turbine
a. Cleaning. and inspect housing for cracks or bulges.
1. The ignition cables should be wiped clean using 2. Remove the tail pipe from the turbine and visu-
a clean cloth and DC4 Silicone grease, ally inspect the impellers and visible portions of tur-
b. Inspection. bine for coking, carbonization, oil deposits, nicks
1. Inspect the ignition cable for damaged insulation or dents.
and the end fitting for evidence of cracks and damage. c. Repair and Servicing.
c. Repair and Servicing. 1. If cracks or bulges do appear on the turbine
1. Refer to Section 9 for maintenance and care of housing, replace housing in accordance with the
the ignition cables. Turbocharger and Controls Overhaul/Parts Manual.
2. For removing coke and carbonized oil deposits,
Magneto- refer to the Turbocharger and Controls Overhaul/
Parts ManuaL
a. Cleaning.
1 Clean the magnetos with a suitable solvent such
as Stoddard solvent and dry with dry compressed air. Manifold Pressure Relief Valve.
b. Inspection.
1. Inspect the magneto for proper breaker point a. Cleaning.
gap (refer to Section 9), and evidence of moisture 1. Clean dirt and debris from valve with a suitable
and arcing. cloth.
2. After rough engine operation, inspect magneto b. Inspection.
drive couplings. Refer to Section 9. 1. Inspect relief valve vents for obstructions or
c. Repair and Servicing. foreign materiaL
1. Refer to Section 9 for proper maintenance and 2. Check for proper operation as follows:
care of the magneto. (a) After adequate engine warm up with oil tem-
perature at the lower third of green are, ac-
Alternator. celerate the engine rapidly from idle to maxi-
mum RPM.
a. Cleaning.
1. The alternator should be washed down at the CAUTION
time the engine is cleaned using the same cleaning
procedure. Discontinue acceleration if manifold pressure
b. Inspection. exceeds 43. 5 in. Hg.
1. Check wiring for breaks and evidence of wear.
(b) If maximum manifold pressure exceeds 43. 5
NOTE in. Hg., immediately reduce power and shut
down engine. Manifold pressure relief valve
For electrical output and operational check, is faulty and must be replaced.
refer to Section 14.

c. Repair and Servicing. Engine Exhaust System.

1 Refer to
Section 14 and Overhaul and Replace-
ment Chart (figure 2-8). a. Cleaning.

NOTE
Pumps.
In order to properly inspect the exhaust sys-
a. Cleaning- tem, components must be clean and free of
1. The fuel, vacuum, and autopilot pumps should oil, grease, etc. If required, clean as
be washed down at the same time as the engine, follows:
using the same solvent.
b. Inspection. 1. Spray engine exhaust system components with a
1. Inspect the pumps for evidence of leaking, con- suitable solvent (such as Stoddard Solvent), allow to
dition and security. drain and then wipe dry with a clean cloth.
c. Repair and Servicing.
1. Repair of the engine driven pumps is limited to WARNING
replacement. Refer to Overhaul and Replacement
Chart (figure 2-8). Never use highly flammable solvents on en-
gine exhaust systems.

Turbocharger- Never use a wire brush or abrasives to clean

exhaust systems or mark on the system with
a. Cleaning. lead pencils.
1. Clean outer surface of turbocharger with a
suitable solvent.
Change 11
 421 SERVICE MANUAL eRoUND HANDLINS,
SERVICING AND INSPECTIÒN

SHOULD BE STRAIGHTEDGE -

0. 20 inch
LESS THAN 062
Maximum
.

Seal Retaining Seal Gap

Flange
emale Joint

NUORENIRALNDFLAT)
ale Joint

COUPLING

Figure 2-36. Exhaust Coupling Deformation Limits Figure 2-36A. Exhaust Slip Joint Inspection Limit

b. Inspection. measure installed length of each spring. Those

compressed to less than 0. 45 inch must be replaced.
NOTE (b) Remove all springs and measure free length.
Springs having a free length of less than 0. 57 inch
This inspection should be conducted when the must be replaced.
engine is cool.
NOTE
1. Remove the
heat shields on the turbocharger in
accordance with heat shield removal procedures in Add AN960-10 washers under head of joint
the service manual, bolts as required to obtain correct dimen-
2. Remove shields around the exhaust bellows or sion.
slip joints, multi-segment V-band clamps at joints,
and other items which might hinder inspection of During installation, joint bolts should be
the system. tightened gradually and spring length check-
ed frequently to prevent over compression
NOTE of springs.

Do not remove clamps. (c) Reinstall springs and measure installed

length. Length must be 0. 51 +. 00, 03 inch.
-.

3. Inspect exhaust stacks for burned areas, cracks 6. Inspect multi-segment V-band clamp for de-
and looseness. Insure that attach bolts are properly formation, looseness and leakage (see figure 2-36).
torqued in accordance with the aircraft service man_ (a) Inspect installed clamps for deformation by
ual. checking the flatness of the outer back-up band, es-
4. Inspect exhaust clamps for cracks, looseness pecially within 2 inches of the spot welded tabs which
and proper torque. Refer to figure 9-21. retain the T-bolt fastener. This can be done by plac-
ind a straight edge across the flat part of the outer
NOTE band as shown, then check the gap between the
straight edge and band. This gap should be less than
During inspection ,
particular attention 0. 062 inch.
should be given to condition of the clamp (b) If deformation gap exceeds the 0. 062 inch
flanges, bellows or slip joints and welded limit the clamp must be replaced with a new part.
areas along seams and around the bellows When replacement is required, install the new clamp
or slip joints. over the exhaust flange and torque to the correct
value. As the band is tightened, lightly tap it cir-
5. Inspect exhaust joint springs for correct com- cumferentially in a radial direction with a rawhide
pression only if the joint is disturbed (see figure or soft plastic mallet.
9-5). (c) Clamps found in acceptable condition should
(a) Before removal of exhaust joint springs, then be checked for looseness and leakage. Only

Change 11
2-48 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

highly finished parts separately, exer-

clamps which are obviously loose or leaking should Clean small,
be retorqued. If retorquing is required, refer to cising care not to cause damage, particularly to
figure 9-21. working surfaces.
(d) The flexible connection between the waste- NOTE
gate and overboard duct (when applicable) must be
visually inspected for cracks and security. Inside diameter of counterweight halves and
(e) Any leakage (minor or major) in all other ferrule groove in which they mount, must be
areas of the exhaust system must be corrected. free of all oil. Use solvent only -
not the
mixture -

to clean these surfaces. Should

NOTE mixture or any other lubricant ac-
cleaning
cidentally come into contact with these sur-
If not previously accomplished, the over- faces, clean thoroughly prior to reassembly.
board exhaust stack to turbocharger clamps
(multi-segment V-band type) must be re- 2. Clean non-metallic parts (except gaskets, pack-
placed with a new one-piece V-clamp. ings and seals) by wiping with a soft, lint-free cloth
dampened with cleaning mixture.
The remainder of the bulti-segment V-band 3. Heavy and tightly adhering deposits may be re-
clamp(s) down stream of the aft engine cyl- moved with a soft brush.
inders are "Life Limited" to 400 hours.
These clamps must be replaced on or be- CAUTION
fore 400 hours of service and every 400
hours thereafter. Under no circumstances are any parts to be
cleaned with a steel, other metal, or hard
bristle brush or tool of any type.

4. After cleaning, allow parts toair dry, or re-

move excess mixture with a gentle stream of clean,
dry compressed air. Keep nozzle well away from
parts.
5. Protect parts from collecting dust and dirt dur-
ing storage and handling for overhaul. It is recom-
mended that small parts be kept in transparent plas-
Inspection For Oil Screen. (421-0001 to 421B0001) tic bags.
6. Parts which are to be coated with dry film lubri-
a. Lower the right-hand nacelle cowl to remove the cant are to be cleaned with ethyl acetate immediately
oil screen. prior to application of lubricant.
b. Remove oil filter line from oil discharge port
cap. WARNING
c. Remove discharge cap from oil pump housing.
d. If screen is present, proceed as follows: Under no circumstances should engine opera-
1. Clean all flammable fluids from cap assembly. tion be continued when the presence of a crack
2. Secure cap hexagonal head on a bench vise with in the propeller is suspected.
screen oriented upwards.
3. Apply heat with a propane torch on the general b. Inspection,
area of the screen cap soldered interface, and re- 1. Refer to the Inspection Chart, figure 2-7, and
move screen by pulling with a wire loop or pliers. McCauley Industrial Corporation's Service Manual.
2. Refer to the Inspection Chart, figure 2-7, for
CAUTION interval, and visually examine the condition of the
epoxy sealant by looking through the hole in the
Do not use oxyacetylene equipment since the spinner. The outboard end of the retention nut to
excessive heat could damage oil discharge cap. hub connection will appear as a wide, circumferen-
tial flat with a narrow, light brown colored groove
4. Clean and inspect cap for loose solder or screen in the center. The light brown material is epoxy
wire particles. sealant and should be in place without evidence of
e. Install cap on oil pump discharge port and con- missing portions. A normal appearance may in-
nect hose assembly and fittings. clude several areas with air bubbles on the surface.
If in doubt, rock the blades and check for noticeable
movement between the nut and hub.
PROPELLERS.
CAUTION
a. Cleaning.
1. Clean all metal parts in a mixture consisting of If one propeller is found with missing portions
1/3 lubricating oil, Specification MIL-L-6082, Grade of epoxy sealant and/or loose retention nut,
1030, and 2/3 solvent, Federal Specification P-S-66L remove and repair both propellers even though
the mating propeller appears to be in satis-
factory condition.
Change 11
 421 SERVICE MANUAL 6ROUND HANDLIN6, "$1
SERVICING AND INSPECTION

3. Anytime the propeller attachment has been sub- (d) Always check and make sure the filler valve
jected to excessive engine roughness, inspect in ac- does not leak after charging the accumulator.
cordance with Rough Engine Operation Inspection,
Section 9.
4. Check propeller attachment nuts for 80-85 foot- Propeller Synchronizer.
pounds torque. If torque is less than 80 foot-pounds,
replace nuts with new elastic element lock nuts. a. Cleaning.
c. Repair and Servicing. 1. Clean external parts of propeller synchronizer
1. Any repairs should be made in accordance with actuator by wiping with a clean cloth.
best shop practices as outlined in McCauley Indus- b. Inspection.
trial Corporation's Service Manual and FAA regula- 1.
Check rod ends, actuator housing, flexible shaft
tions. and wiring for condition and security.
2. Refer to McCauley Industrial Corporation's c. Repair and Servicing.
Service Manual and lubricate only on reassembly. 1. Refer to Section 10 for repair and servicing.

Propeller Deice System.

FUEL SYSTEM.
a. Cleaning.
1. Clean brushes and slip ring with a suitable non- Fuel-Air ControL
corrosive solvent.
b. Inspection. a. Cleaning.
1. Inspect for interference between the propeller 1. Remove the metering unit filter screen and
hub and deice slip ring mounting bolts on McCauley clean the screen in fresh cleaning solvent. Reinstall
"K" series propellers. If interference is found, re- and safety.
fer to Section 10 for the corrective procedure. b. Inspection.
2. Inspect propeller deice brushes for correct 1. Check control connections, levers, and linkage
length and alignment in accordance with Section 13. for security of attaching parts, for safetying and lost
motion due to wear.
Propeller Unfeathering System. 2. Check the air control body for cracks and the
fuel-air control unit for overall condition.
a. Cleaning.
1. Clean accumulator with suitable solvent. Fuel Manifold.
2. Wipe hoses and accumulator with a clean cloth.
b. Inspection. a. Cleaning.
1. Inspect hose assemblies for chafing and fittings 1. Disconnect the overboard vent line from the
for tightness. manifold top cover.
2. Inspect accumulator for security in mounting 2. Hold the top cover down against internal spring
brackets. until all four attaching screws have been removed,
3. Always inspect filler valve after charging for then gently lift off the cover. Use care not to damage
leaks. the spring-loaded diaphragm below.
c. Repair and Servicing. 3. Remove the upper spring and lift the diaphragm
1. Repairs to propeller unfeathering system are assembly straight up.
limited to replacement of components.
NOTE
CAUTION
If the valve attached to the diaphragm is stuck
Always release system pressure by placing in the bore of the body, grasp the center nut
propeller control in unfeathered position and and rotate and lift at the same time to work
release accumulator pressure through filler gently out of the body.
valve, before disconnecting hose between ac-
cumulator and governor or removing accumu- WARNING
lator.
Do not attempt to remove needle or spring
2. accumulator
Service as follows: from inside valve. Removal of these items
(a) Place propeller control in the unfeathered from the valve will disturb the 4 PSI factory
position before charging the accumulator to prevent calibration.
the possibility of oil under pressure being trapped
in the accumulator. 4. Remove the flushing plug located opposite the in-
(b) Although the accumulator will function pro- let fitting.
perly when charged with air, dry nitrogen gas is
recommended to minimize corrosion. CAUTION
(c) Either too much pressure or not enough pres-

I
sure in the accumulator
unfeathering
psi.
system.
will reduce efficiency
Service accumulator
of the
to 75-90
The filter
damaged
be removed
stalled.
screen
if removal
is a tight fit and may be
is attempted. It should
only if a new screen is to be in-

Change 10
2-48 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

5. Using clean gasoline, flush out the chamber be- binding of control, travel, proper operation, exces-
low the screen. sive wear, safetying and detent position.
6. Flush above the screen and inside the center
bore making sure that outlet passages are open. CAUTION
Use only a gentle stream of compressed air to re-
move dust and dirt and to dry. The fuel selector valve should always stop in
7. Replace flushing plug. a detent position, never intermediate. If the
8. Clean the diaphragm valve, top cover and fuel selector stops in an intermediate posi-
springs in the same manner. tion, the controls are improperly rigged,
9. Carefully replace diaphragm and valve in mani- and should be rigged in accordance with See-
fold body. Check that valve works freely. tion 11.
10. Place upper spring in position.
11. Align mounting holes in body, diaphragm and
top cover locating the vent fitting hole in the cover Fuel System -
Main.
to the side. Hold the cover down against the spring
while installing and tightening all four attaching a. Visually inspect filler cap gasket. If crushed or
screws. Safety the screws. damaged, replace filler gasket.
12. Connect overboard vent line. b. Remove main tank nose cap (Section 11); visually
inspect area for evidence of fuel leakage.
1. If fuel leakage is evident, defuel the main tank
Fuel Discharge Nozzles. and replace the stat-o-seals and/or panel gaskets
as required.
a. Cleaning.
1. To clean fuel discharge nozzles, immerse in NOTE
fresh cleaning solvent.
When installing new stat-o-seals and gaskets,
CAUTION apply a small amount of rubber lubricant or
petroleum jelly to the new stat-o-seals or
Do not use a wire brush or other sharp metal gaskets. This will prevent damage to the
objects to clean orifices. This will damage seals when screws are tightened and will
orifice. allow the seals to seat evenly,

b. Inspection. c. Purge in accordance with Section 2.

1. Inspect the fuel discharge nozzle for damaged d. Refer to Section 11 for cleaning and inspection of
orifice, dirt and foreign objects. disassembled main fuel system.

Fuel Selector Valve. Fuel System -

Auxiliary.

a. Cleaning. Refer to Inspection Chart and Section 11 for cleaning

1. Fuel selector valve handles OFF. -
and inspecting of auxiliary fuel system.
2. Drain excess fuel from sediment bowl with
quick-drain.
3. Remove the lower access cover plate. Main Tank Fuel Transfer Pump.
4. Remove the eight screws securing sediment
bowl to bottom of selector valve and remove bowl a. Cleaning,
and filter assembly. 1. Refer to Section 11, Main Tank Fuel Transfer
5. Clean filter in fresh solvent and air dry. Pump for cleaning and inspection of main tank trans-
b. Inspection. fer pump.
1. Inspect quick-drain valve, gasket, filter and
fuel selector for nicks, dents, scratches, dirt
accumulation and other foreign matter. OXYGEN SYSTEM.
2. Refer to Inspection Chart for interval of inspec-
tion. Filler Valve.
3. Refer to Section 11, figure 11-8. Reassemble
selector valve. Make sure filter is installed with a. Cleaning.
large hole facing up. Replace gasket with a new 1. The filler valve should be cleaned with trichlor-
gasket. ethylene MIL-T-7003.
2. Clean Freon MIL-C-8638 or Alcohol may be
Fuel Selector Valve Control System. used as an alternate.
b. Inspection.
a. Cleaning. 1. Inspect the filler valve for nicks, cracks and
1. Clean the fuel selector valve with a suitable sol- deep gouges.
vent, wipe clean with a dry cloth. c. Repair and Servicing.
b. Inspection. 1. Repair is.limited to the replacement of parts.
1. Inspect fuel selector valve control system for Refer to Section 13 for servicing oxygen system.

Change 12
 421 SERVICE MANUAL GROUND HANDLIN6, 2-4ÛA 2-48
SERVICING AND INSPECTION

Oxygen Regulator and Cylinder. c. Repair and Servicing.

1. Refer to Section 13 for repair and servicing oxy-
a. Cleaning. gen cylinders and regulators.
1. Clean regulator and cylinder with a clean cloth.
b. Inspection.
1. Refer to Section 13 for inspection requirements Oxygen Masks and Hoses.
and criteria.
2. Refer to Section 13 for Hydrostatic Test Date on a. Cleaning.
oxygen cylinder. 1. Clean the mask and hoses with a mild solution

Change 8
 421 SERVICE MANUAL GROUND HANDLING, "$$
SERVICING AND INSPECTION

of soap and water. Rinse thoroughly with clean water b. Inspection.

and allow to dry. 1. Inspect the deice system for leaks, remove fil-
NOTE ter and clean with Naptha and dry with a jet of dry
compressed air.
c. Repair and Servicing.
Make sure all soap is removed by rinsing.
Masks may be disinfected with a hospital 1. Repair of the deice system components is limit-
spray or Zep Aero SBT-12, ed to the replacement of parts.
type antiseptic
or denatured alcohol. 2. For repair of the deice system boots, refer to
Section 13.
CAUTION 3. For replacement of the filter P/N H95888-36,
refer to Overhaul and Replacement Chart.
Remove microphone from pilot's mask be-
fore cleaning.
PITOT STATIC SYSTEM.
b. Inspection.
1. Inspect mask and hoses for leaks, cracks, and Pitot Static System Components.
deterioration. Check mask stowage compartment
for cleanliness and general condition. Check floW a. Cleaning,
indicator for freedom of movement. 1. Immerse lines in dry cleaning solvent.
2. Inspect couplings and adapters for proper in-
sertion. NOTE
c. Repair and Servicing.
1. Refer to Section 13 for repair and servicing. All pitot static components must be discon-
nected from instruments and removed from
the aircraft when cleaning.
VACUUM SYSTEM.
2. Dry lines with filtered compressed air.
Vacuum System Components. 3. Wipe exterior of lines with a clean, dry cloth,
b. Inspection,
a. Cleaning. 1. Inspect lines for cracks, chafing and abrasions.
1. The vacuum system components may be cleaned 2. Refer to Section 12 for testing.
by immersing lines and hoses in dry cleaning solvent,
and dried with filtered dry compressed air. NOTE
2. Wipe exterior of lines and hoses with a clean,
dry cloth. Make sure alternate static source valve is
3. Clean vacuum system filter with a jet of clean, closed before returning aircraft to service.
dry air and tapping lightly while blowing air over the
filter.
4. Remove the relief valve screen and submerge
in suitable solvent. Allow to soak or wash until all
foreign particles are dislodged. AIR CONDITIONING SYSTEM. (Belt Driven)
5. Clean relief valve if required by washing in
suitable solvent and drying with filtered dry com- a. Cleaning.
pressed air. 1. The air conditioning components should be
b. Inspection. wiped clean with a cloth and a stream of low pres-
1. Inspect the vacuum system for scratches, chips, sure dry air.
nicks, dents, deformed tubes, sharp bends, dirt, 3. Clean and flush condensate valve with water.
proper operation and correct vacuum indication. b. Inspection.
1. Refer to Section 13, figure 13-27 for 421A0001
to 421BOOO1 and figure 13-27F for 421BOOO1 and On,
SURFACE DEICE SYSTEM. for checking compressor oil leveL
2. Remove lint, grease or other debris from evap-
Surface Deice System Components. orator module coils.
3. Clean and flush condensate valve with water.
a. Cleaning, b. Inspection.
1. The deice system components can be washed 1. Refer to Air Conditioning System Service/Parts
down with the engine using Stoddard Solvent. Manual for checking compressor oil.
2. The deice boots can be cleaned using soap and 2. Check lines and fittings for evidence of oil seep-
water. age around compressor.

NOTE

Never use thinners, Ketone or harsh solvents

on deice boots.

Change 12
2- 50 OROUND HANDLINO, 421 SERVICE MANUAL
SERVICING AND INSPECTION

CAUTION AIR CONDITIONING SYSTEM. (Hydraulic Driven)

If evidence of oil seepage is noted around the a. Cleaning,

compressor shaft or at the system fittings, 1. The air conditioning components should be wiped
the compressor seal should be replaced, the clean with a cloth and a stream of low pressure dry
fittings tightened, the oil checked for proper air.
servicing and the refrigerant system checked 2. Remove lint, grease or other debris from evap-
for proper charge. orator module coils.
3. Clean and flush condensate (drain) valve with
3. Check compressor drive belt for fraying, loose- water.
ness, evidence of cuts, nieks, heat deterioration b. Inspection.
hardness, and alignment of pulleys. Refer to Section 1. Refer to Air Conditioning System Service/Parts
13 for drive belt tension. Manual for checking compressor oil level.
2. Check refrigerant lines and fittings for evidence
NOTE of oil seepage around compressor.

If the drive belt is out of alignment it will CAUTION

necessitate adding shims to the compressor
mounting to properly align belt. If evidence of oil seepage is noted around
the compressor shaft or at the system fit-
4. Check compressor discharge and suction lines tings, the compressor seal should be re-
for cracking, fraying or evidence of high tempera- placed, the fittings tightened, the oil level
tures. checked for proper level and the refrigerant
5. Check compressor support bracket bushings for system checked for proper charge.
deterioration or wear.
6. Check condenser fan blade, evaporator motor 3. Check hydraulie lines and fittings for evidence
shaft, condensers, receiver-dryer, condenser fan of hydraulic fluid seepage around pump, motor, mani-
motor and evaporator modules for looseness and fold and valve assembly and reservoir.
security of mounting.
7. Check condenser coil inlets and evaporator coil NOTE
inlets for paper, lint, grease or other debris.
8. Check freon sight glass for bubbles with air If evidence of hydraulic fluid seepage is
conditioning system in operation, add more freon noted, tighten the fittings and check the
until bubbles are not indicated in accordance with hydraulic fluid reservoir for proper level.
the Charging Procedures in the Air Conditioning
System Service/Parts Manual. 4. Check compressor discharge, suction and liquid
9. Check brushes on condenser fan motor for pro- injection lines and hydraulic fluid lines for cracking
per length. If brush length is 1/4" or less new brush- or evidence of high temperatures.
es are required. Refer to Air Conditioning System 5. Check condenser blower fan blade, evaporator
Service/Parts Manual. motor shaft, condensers, receiver-dryer, condenser
10. Check condenser fan blade for excessive nicks, fan motor and evaporator modules for looseness and
cracks or hub looseness. security of mounting.
c. Repair and Servicing. 6. Check condenser coil inlets and evaporator coil
1. Repair of the air conditioning system is limited inlets for paper, lint, grease or other debris.
to component replacement. Refer to Section 13 for 7. Check freon sight glass for bubbles with air con-
the removal, replacement and installation of various ditioning system in operation, add more freon until
air conditioning components, bubbles are not indicated in accordance with the
charging procedures in Air Conditioning Systems
Service/Parts Manual.
8. Check brushes on condenser fan motor for prop-
er length. If brush length is 1/4 or less new brushes
are required. Refer to Replacement of Condenser
Blower Motor Brushes in Air Conditioning Systems
Service/Parts Manual.
9. Check condenser fan blade for excessive nicks,
cracks or hub looseness.
c. Repair and servicing.
1. Repair of the air conditioning system is limited
to component replacement. Refer to Section 13 for
removal, replacement and installation of various air
conditioning components.

Change 12
 421 SERVICE MANUAL eRoUND HANDLINe, 2-50A
SERVICING AND INSPECTION

PRESSURIZATION SYSTEM COMPONENTS. Dump Valve.

Safety Valve and Outflow Valve. a. Cleaning

1. Cleaning the dump valves requires the removal
a. Cleaning, of the valves and cleaning in a suitable solvent (refer
1. Clean the safety valve and outflow valve exterior to Janitrol instructions P/N 43DS7).
surfaces and valve seat faces with a clean cloth satu- b. Inspection.
rated with a suitable solvent such as an 8 to 1 solution 1. Inspect dump valves for proper operation, se-
of Burlin 815 MS or a sponge soaked with diluted as curity, condition and wear.
required solution of NRG No. 678 (National Colloid c. Repair and Servicing.
Corporation, P. O. Box 293, Garden Grove, Califor- 1. Refer to Janitrol instructions P/N 43DB7 for
nia 92642). This will remove tars and nicotine de- repair and servicing dump valves.
posits from valves and valve seat faces.
Door Seals.
CAUTION
180° a. Cleaning.
O Raise outflow valve with hands as nearly 1. Clean door seals with a mild detergent solution
apart as possible. Raising from one side only and dry with a clean cloth.
may damage the outflow valve pilot. Also do b. Inspection.
not use compressed air in the cleaning of any 1. Inspect door seals for cuts, breaks, tears and
part of the unit as serious damage to the dia- abrasions.
phragms may result· c. Repair and Servicing.
1. Refer toSection 16 for repair of the door seals.
O Extreme care must be taken to prevent the 2. Refer toLubrication Diagram for lubrication of
solution from entering the valves internal door seals.
cavities. During cleaning of the assembled
valves, all sense ports must be protected to
prevent solution from entering the internal
parts of the valve. ALCOHOL WINDSHIELD ANTI-ICE SYSTEM.

2. Clean outflow valve and safety valve filters by Alcohol Windshield Anti-Ice System Components.
removing and soaking in a mild detergent and rins-
ing in clear water and allow to air dry, a. Cleaning.
b. Inspection. 1. Immerse lines in a dry cleaning solvent.
1. Inspect the poppet in the safety valve and out-
flow valve for freedom of movement. NOTE
2. Inspect the fittings and lines for security and
condition. Lines not readily removable from aircraft
3. Inspect landing gear safety switch to assure may be flushed with cleaning solvent. Take
actuation of safety valve as described in Adjustment necessary precautions to protect windshield.
of Landing Gear Safety Switch procedures, Section 4.
c. Repair and Servicing. 2. Dry lines with filtered compressed.
1. Repair of the safety valve and outflow valve is 3. Clean pump filter screen in accordance with
limited to the replacement of the valves. Cleaning and Inspection of Main Tank Fuel Transfer
Pump Parts (Section 11).
b. Inspection.
1. Inspect lines for cracks, chafing and abrasions.
2. Inspect lines and adjacent areas for evidence of
leakage.
3. Inspect pump for security and operation.

Change 12
2-50B OROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

ELECTRICAL SYSTEM. Do not allow acid deposits to come in contact

with skin or clothing. Serious acid burns may
Inspection. result unless the affected area is washed im-
mediately with soap and water. Clothing will
a. Inspect the electrical system and components for be ruined upon contact with battery acid.
the following:
1. All aircraft and systems wiring for chafing, 3. Clean battery terminals as needed with a wire
terminals for security, and general condition. brush to brighten the terminals for good electrical
2. Circuit breakers for mounting and condition.
3. Regulators for mounting, terminals for loose
wires.
4. Switches for loose wiring, proper mounting.
5. Relays for wiring and mounting.
6. Motors for proper mounting and wires for
elamping.
7. Battery cables for corrosion and looseness.
8. Battery for electrolyte level and specific gravi-
ty.
9. Instruments and interior lights for operation
and broken glass.
10. Communications and navigation system for
proper installation, security in mounts and proper
operation, antenna for damage.
11. Instrument panel and control pedestal for loose
wiring, clamps and terminals for security.
12. Wing and fuselage wiring for proper wire rout-
ing, clamped properly and loose terminals.
13. External power receptacle for proper door
closing, terminals for corrosion and looseness.
14. Engine compartment wire bundles for proper
clamping, evidence of burning, heat hardness, secu-
rity and chafing.
15. Stall warning vane and heater for proper opera-
tion and security.
16. Electric heated windshield for operation.

Battery.

NOTE 1
If excessive corrosion is detected around
upper portion of battery box, remove the
battery and inspect battery box and sur- 2
rounding area of wing for corrosion.

a. Cleaning. 3
1. Clean batteries with a mild solution of bicarbon-
ate of soda (baking soda) and water to remove acid
corrosion. A
NOTE

Remove batteries from aircraft before clean-

2. Rinse with clear water and sponge off excess

water and allow batteries to dry.

CAUTION 1458P6001

Take special precautions to insure that bat-

tery cell filler caps are tight before cleaning 1. Cover 3. Contact Area
the battery. Entrance of soda water into bat- 2. Contactor 4. Relay
tery cells will neutralize the cell electrolyte.
Figure 2-36B. Starter Relay Inspection W

Change 12
 421 SERVICE MANUAL OROUND HANDLIN6, Öl
SERVICIN6 AND INSPECTION

contact. Coat with Petrolatum to prevent corrosion. NOTE

b. Inspection.
1. Check battery case for possible cracks and de- It is recommended that the bottom of the bat-
terioration. tery box compartment cover and the battery
2. Check electrolyte for specific gravity as follows: box supports be painted with acid proof lac-
(a) Using a hydrometer, check specific gravity quer.
for a reading of 1.265 to 1.285 corrected to
temperature.
(b) Check that specific gravity of the electrolyte Starter Relay. (See figure 3-36B. ) I
does not vary more than 020 between cells.
.
I
(c) Should a greater variation exist, refer to a. Inspection.
Maintenance of Battery, Section 14. 1. Remove starter relay.
2. Remove contact cover.
CAUTION 3. Inspect contact area for burned and pitted area -

if 25°/o of area is burned and pitted, replace relay.

Remove batteries from aircraft when charg-
ing the batteries. Do not use external power
generators for charging purposes. Emergency Locator Transmitter

a. C leaning.
Battery Box- 1. Clean emergency locator transmitter with a
clean dry cloth.
b. Inspection.
NOTE 1. Perform the following periodic inspection at
the prescribed intervals.
At 100 hours, battery removal is not re_ 2. Monthly.
quired if corrosion is not evident around (a) Turn aircraft master switch ON.
upper portion of box, at 200 hours, the (b) Turn aircraft transceiver ON and set frequen-
battery must be removed and the battery cy on local tower frequency.
box thoroughly cleaned and repainted as (c) Contact local tower personnel and alert them
necessary. of the proposed test.
(d) Place the ELT function selector switch in the
ON position until the emergency tone is heard on the
a. Cleaning. aircraft radio (not over 10 seconds). Immediately
1. Battery lead should be cleaned with a strong place the function selector switch in the ARM posi-
solution of bicarbonate of soda (baking soda) and tion. (Ensure that the transmitter has been de-
water. activated. )
2. Clean hard deposits of spilled acid and corro- NOTE
sion products using a wire brush.
3. When all foreign materials have been removed After accumulated test or operation time
from the box, flush it thoroughly with clean water, equals 1 hour, battery pack replacement
4. After cleaning battery box, flush surrounding is required.
skin with clean water to ensure that all corrosive
material has been removed. 3. 100 Hours.
(a) Check ELT operation in accordance with pro-
cedure outlined under "Periodic. "
CAUTION
NOTE
Do not allow acid deposits to come in contact
with skin or clothing. Serious acid burns may Check calendar date for replacement
of
result unless the affected area is washed im- battery pack. This
date is supplied on a
mediately with soap and water. Clothing will sticker attached to the outside of the ELT
be ruined upon contact with battery acid. case and to each battery.
(b) Verify compliance with Cessna Avionics
b. Inspection. Service Letter AV74-10 and 74-14. I
1. Inspect the cleaned battery box for physical 4. 12 Months. Have your dealer check your ELT
damage and for areas lacking proper acid proofing. for the following:
Badly damaged or corroded boxes should be replaced. (a) Power output (refer to Section 13).
2. Inspect surrounding areas of wing adjacent to (b) Carrier frequency,
battery box for damage and corrosion. (c) Modulation.
c. Repair. (d) Sweep.
1. Boxes requiring acid proofing should be painted (e) Sweep rate.
inside and out with TT-L-54 Enmar Acid Proof Black (f) Operation of "g" switch.
lacquer. (g) Replacement of battery pack.
 2-52 6ROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

MISCELLANEOUS INSPECTION. EXTREME WEATHER MAINTENANCE.

To avoid repetition throughout the inspection, general Cold Weather.

points to be checked are given below. In the inspec-
tion, only the items to be checked are listed and de- After the last flight of the day, drain engine oil into
tails as to how to check, or what to check for, are clean containers so it can be preheated. Cover the
excluded. Check as applicable: engines, including the rear air scoop opening, to
prevent ice or snow from collecting inside the cowl-
Movable Parts. ing. When preparing an engine for operation after
using this procedure, preheat the oil. After preheat-
Inspect for lubrication, servicing, security of attach- ing the oil, gasoline may be mixed with the oil in a
ment, binding, excessive wear, safetying, proper ration of one part gasoline to 12 parts oil before
operation, proper adjustment, correct traveÏ, crack- pouring the oil in the engines. If free air tempera-
ed fittings, security of hinges, defective bearings, ture is below -29°C (-20°F), the engine compart-
cleanliness, corrosion, deformation, sealing, and ments should also be preheated with a ground heater.
tensions. Check all engine compartment drain and vent lines
for presence of ice. Remove protective covers
Engine Compartment Hoses. placed on engines and rear cowl opening. Pull pro-
pellers through several revolutions by hand before
Inspect for leaks, cracks, chafing, kinks, deterior- starting the engines.
ation, security, heat hardness, obstructions and for-
eign matter. The hoses and wire bundles in the heat WARNING
areas close to the exhaust and turbocharger should
be inspected for heat hardness, cracking, flexibility Preheat oil before diluting with gasoline, and
do not heat above 121°C
and security during regular (250°F),
engine inspection. (See to prevent
figure 2-7 for intervaL ) the possibility of a flash fire. Before pulling
propellers through by hand, insure the mag-
Fluid Lines and Hoses. neto switches are OFF.

Inspect for leaks, cracks, dents, kinks, chafing, CAUTION

proper radius, security, corrosion, deterioration,
obstructions and foreign matter- Due to the desludging effect of the diluted oil,
engine operation should be observed closely
Metal Parts, during initial warmup of the engines. En-
gines that have a considerable amount of oper-
Inspect for security of attachment, cracks, metal ational hours accumulated since their last
distortion, broken spot-welds, corrosion, condition dilution period may be seriously affected by
of paint and any other apparent damage, the dilution process. This will be caused by
the diluted oil dislodging sludge and carbon
deposits within the eneines. This residue
Wiring. will collect in the oil sumps and possibly clog
the screened inlet to the oil pumps. Small de-
Inspect for security, chafing, burning, defective in- posits may actually enter the oil pumps and
sulation, loose or broken terminals, heat deteriora- be trapped by the main oil filter screens.
tion and corroded terminals. Inspect wire bundles Partial, or in some cases, complete loss of
in high heat areas such as close proximity of exhaust engine lubrication may result from either con-
stacks or turbocharger for heat damage, dition. If these conditions are anticipated af-
ter oil dilution, the engines should be run for
Bolts in Critical Area, several minutes at normal operating temper-
atures and then stopped and inspected for
Inspect for correct torque in accordance with torque evidence of sludge and carbon deposit in the
values given in the chart in Section 1, when installed oil sumps, oil coolers, and oil filter screens.
or when visual inspection indicates the need for a Future occurence of this condition can be pre-
torque check. vented by diluting the oil prior to each oil
change. This will prevent accumulations of
Filters, Screens and Fluids, sludge and carbon deposits within the engines.

Inspect for cleanliness, contamination, and/or re-

placement at specified intervals. Hot Weather.

Aircraft File. In hot weather, with hot engine, fuel may vaporize
at certain points in the fuel system. Vaporized fuel
Inspect for miscellaneous data, information and may be purged by setting the mixture control in IDLE
licenses that are a part of the aircraft file. (See CUT-OFF and operating the auxiliary fuel pump on
Inspection Chart, Figure 2-7. ) "HI. "

Change 8
 421 SERVICE MANUAL eRoUND MANDLIN6,
SERVICING AND INSPECTION

(250°F).
Engine mis-starts characterized by weak, intermit- Heating the oil above this tempera-
tent explosions followed by puffs of black smoke from ture may cause a flash fire. Just before shut-
the exhaust are caused by over-priming or flooding. ting down the engine in cold weather a quart of
This situation is more apt to develop in hot weather, gasoline may be added to the oil in the sump
or when the engine is hot. If it occurs, repeat the to dilute the oil for the next start.
starting routine with the throttle approximately one-
half OPEN, the mixture control in IDLE CUT-OFF,
and the auxiliary fuel pump switch OFF. As the en- Fuel System.
gine fires, move the mixture control to full RICH and
decrease the throttle to desired idling speed. The fuel system is comprised of two main tanks,
holding a total of 51 U. S. gallons each of which 50
Engine mis-starts characterized by sufficient power gallons are usable, four auxiliary tanks holding a
to disengage the starter but dying after 3 to 5 revolu- total of 36. 5 U. S. gallons in each wing, of which 35
tions are the result of an excessively lean mixture gallons are usable, two optional auxiliary tanks hold-
after the start. This can occur in either warm or ing a total of 13. 5 U. S. gallons each, of which 13. O
cold temperatures. Repeat the starting routine but gallons are usable. This provides a total usable fuel
allow additional priming time with the auxiliary fuel capacity of 170 U. S. gallons for aircraft without op-
pump switch to "LO" before cranking is started, or tional auxiliary tanks, or a total usable fuel capacity
place the auxiliary fuel pump switch on "HI" imme- of 196 U. S. gallons for aircraft with optional auxili-
diately for a richer mixture while cranking. ary tanks. The filler caps for the main tanks are
located on the top inboard side of the main tanks.
If prolonged cranking is necessary, allow the starter The filler caps for the auxiliary or optional tanks are
motor to cool at frequent intervals, since excessive located on the top of the wing just inboard of the main
heat may damage the starter. tanks.

NOTE
Dusty Conditions.
Fuel servicing rates on some ground servicing
Dust inducted into intake systems is probably the equipment may tend to exceed the aircraft's
greatest single cause of early engine wear. Under fuel system intake rate, thus creating several
high dust conditions, the induction air filters should false "Full" indications. A slower fueling
be serviced daily. rate is therefore recommended.

Seacoast and Humid Areas. Fuel System Drains.

In salt water areas, special care should be taken to The fuel system has incorporated eight drain valves
keep engines and engine accessories clean to pre- which must be drained before the first flight each day
vent oxidation. Fuel and oil should be checked fre- to check for water or sediment. Two fuel selector
quently and drained of condensed moisture in humid valves and two crossover drain valves are drained by
areas. pushing up on the valve stem. The fuel selector valve
is locate inboard of nacelles and forward of the gear
doors in the leading edge, while the crossover drain
MISCELLANEOUS SERVICE ITEMS· valves are located in the wing gap area inboard of the
fuel selector valves. The main tank drain valves are
Cold Weather Servicing· located in the aft end of the main tanks. To drain the
main tank, engage the screwdriver (with shank re-
If the aircraft is to be frequently used in extremely moved), furnished with the aircraft, and push up.
cold weather, the oil should be drained while the Fuel will flow through the hollow handle of the screw-
engine is hot and stored in a dry warm place until driver. The auxiliary or optional tanks drain valves
needed for next flight. If desired, the oil may be are located outboard of the nacelle and forward of
heated before it is poured into the engine for the flaps. These drain valves are drained by pushing up
next flight on the center plunger.

a. Drain oil system as follows:

1. Start engine and run until oil temperature is Defueling.
within normal operating limits.
2. Stop engine and open oil drain access The defueling procedures given pertain to either wing.
3. Remove drain plug and allow sump to complete- A standard defueling truck or defueling pump is ne-
ly drain· cessary to defuel the aircraft.
4. Install drain plug and close oil drain access.
CAUTION
WARNING
During all defueling, tank purging and tank
When preheating the oil, do not allow the121°C
tem" repairing operation, the aircraft must be lo-
perature of the heated oil to rise above cated a safe distance from other aircraft and

Change 5
2-54 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

buildings. Fire fighting equipment must be SPECIAL TOOLS AND EQUIPMENT.

available. The use of two ground wires from
different points on the aircraft to separate The relative simplicity of easy accessibility of 421
approved grounding stakes shall be used to components eliminates the use of many special tools.
prevent ungrounding of the aircraft due to In most cases, the well equipped shop will find it
accidental disconnecting of one ground wire. necessary to employ only the following special tools
which are available through the Cessna Dealers'
a. Turn off all electrical power, Organization.
b. Turnfuel selector valve handles off.
c. Remove filler cap and insert defueling tube. Re- Part No. Nomenclature
move as much fuel as possible through the filler.
d. Cut safety wire and remove drain valves from C173001-0101 Towing Bar -
Light Duty
the bottom side of the wing and drain remaining fuel P/N 2-170 Jack
in a clean open container. Use defueling pump to re- SK421-33 Fuel Pressure Test Kit
move fuel from container. SE608 Motor Mount Wrench (for use with
e. Drain the crossover lines at the wing gap drain 0851559 lockwasher)
valve. 6090002-1 Tool, Pressure Ratio Controller
SE716 Inclinometer
WARNING 5090006-9 Propeller Torque Wrench Adapter
SK421-1 Pressurization System Leakage
Residual fuel accumulation in the wing is a Test Kit
fire hazard. Use care to prevent the accu- SK310-32 Oxygen Refill Kit
mulation of such fuel. 0880002-3 Hook
0880001-1 Actuator Arm Tension Measuring
Tool
Purging Main Fuel Tanks and Auxiliary Fuel Cells. FT251 Reamer Tool
SK182-43 Cylinder Head Calibration Unit
To reduce the possibility of an explosion during re- 0880004-1 Ring Pack Support Tool
pair, purge fuel tanks and fuel cells with an inert gas 0880004-2 Ring Pack Support Tool
such as Argon. Since Argon is heavier than air, it SK421-40 Exhaust System Seal Replacement
will remain in the fuel tank or cell during the repair. Tool Kit
Repairs shall be made using non-sparking tools (air 1007254 Seal Replacement Tool Kit
motors, plastic scrapers, etc.). The use of a port- SK150-20 Wheel Balancer Kit
able vapor detector (Mine Safety Appliances Explosi- 5090005-1 Alternator Hub Wrench
meter, Model 5 Indicator) to detect the presence of CM3 Screwdriver/Sampler Cup
explosive gases is also recommended.
a. Defuel the aircraft in accordance with defueling
procedure.
b. Insert hose through filler opening into fuel tank
or cell.
c. Attach hose to inert gas container and allow
inert gas to flow into the fuel tank or cell until all
explosible gas vapors are dissipated.

NOTE

The length of time required to fill the fuel

tank or cell with inert gas is dependent upon
rate of flow and tank capacity.

Change 12
 421 SERVICE MANUAL GROUND
AND
HANDLINe, 2 55
SERVICING INSPECTION

FREQUENCY (HOURS) METHOD

O 6 -
* HAND

SQUIRT CAN
100 HOURS

FILLER CAN

200 HOURS
GREASE GUN

NOTE
500 HOURS
Specified lubricants will meet requirements for extreme hot
or extreme cold temperature operations. Use of substitutes
or other lubricants may cause malfunction when operating in

O 1200 HOURS extreme temperature conditions,

wear due to improper lubrication.
or may cause excessive

AS REQUIRED TYPE OF LUBRICANT

GL . . . . . . . . Grease, Low Temperature (MIL-G-21164)

OG . . . . . . . . Oil, General Purpose (MIL-L-7870}

FG . . . . . . . . Graphite, Lubricating (SS-G-659)

P . . . . . . . . . Petrolatum or Terminal Grease (VV-P-236)

OI . . . . . . . . Oil, Lubricating, Aircraft Instrument

(MIL-O-6085)

OH . . . . . . . . Hydraulic Fluid (MIL-H-5606A)

GW . . . . . . . . Grease, Wide Temperature Range

(MIL-G-81322)

GS . . . . . . . . Grease, Medium Consistency Silicone

Dow Corning DC4 (MIL-G-23827)

DS . . . . . . . . Dry Spray Lubricant, Camie No. 1000

Watson Industrial Pack, St. Louis, Mo. ,

or Dupont Slip Spray Dry Film Lubricant.

GSL . . . . . . . . Grease, Light Consistency Silicone

Dow Corning, Midland, Michigan

Do not lubricate roller chains or cables except under seacoast conditions. Wipe with a clean, dry cloth.

Lubricate unsealed pulley bearings, rod ends, oilite bearings, pivot end hinge points, and any other
friction point obviously needing lubrication, with general purpose oil every 500 hours or more often,
if required.

Lubricate door latches with automotive type door latch lubricant, and the latching mechanism with
general purpose oil every 1200 hours, or more often if binding occurs. Lubricate door stop with
Sil-Glyde.

Figure 2-37. Lubrication Diagram (Sheet 1)

Change 10
2-56 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

CABIN DOOR

o
o

421-0001 TO 421-0104

421-0104 AND ON

* USE ANY AUTOMOTIVE TYPE

DOOR LATCH LUBRICANT.

OG 0

GS

421-0085 AND ON

Figure 2-37. Lubrication Diagram (Sheet 2)

Change 4
 421 SERVICE MANUAL GROUND HANDLINO, Î."$1
SERVICING AND INSPECTION

BAGGAGEDOORS

* USE ANY AUTOMOTIVE TYPE

DOOR LATCH LUBRICANT.

OG

GS

Figure 2-37. Lubrication Diagram (Sheet 3)

Change 4
2- OROUND HANDLING, 421 SERVICE MANUAL
SERVICING AND INSPECTION

ADJUSTING SEATS

GL

GL OG

Figure 2-37. Lubrication Diagram (Sheet 4)

Change 4
 421 SERVICE MANUAL OROUND HANDLINe, SW
SERVICING AND INSPECTION

NOTES:
LANDING GEAR MANUAL 1. AFTER LUBRICATING, WIPE OFF EXCESS
LUBRICANT ADJACENT TO CRANKING HANDLE.
EXTENSION MECHANISM 2. DO NOT OIL THE CHAIN; AN OILED CHAIN
MAY COLLECT DIRT AND GRIT. WIPE CHAIN
WITH'A CLEAN DRY CLOTH.
MIT RS

SUPPORT BEARINGS

OG
O
SUPPORT BEARINGS o
O
O GL

SPOOL &
LANDING GEAR ACTUATOR BELLCRANK

GEAR BOX
OG
ZERK
NOTE GL FITT1NGS CRANK HANDLE LINKAGE
APPROXIMATELY 3 PUMPS ON OG
A HAND GREASE GUN WILL
GIVE ADEQUATE LUBRICATION. LINKAGE

NOTE

WHEN GREASING THIS FITTING

REMOVE THIS BOLT TO PRE-
VENT BREAKING SEAL, REIN-
STALL WHEN FINISHED GREAS-
ING.

GL

SHAFT AND
SECTOR GEAR

Figure 2-37. Lubrication Diagram (Sheet 5)

Change 11
-80
GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTlON

SHOCK
MAIN GEB INGLINKAGE

OG

BUSHING
UP LOCK

GS
GL

TORQUE LINK
ZERK FITTING

NOTE:
INSPECT AND REPACK MAIN GEAR SAFETY
SWITCH WITH DC4 DOW CORNING SILICONE
GREASE EVERY 100 HOURS

NOTE:
LUBRICATE ALL SPHERICAL ROD ENDS
WITH A MIXTURE OF LOW TEMPERATURE
AIRCRAFT LUBRICATING GREASE AND
MOLY-KOTE
GW

WHEEL BEARINGS
NOTE:
WIPE POLISHED SURFACE OF LANDING
GEAR SHOCK STRUT WITH A CLEAN,
DRY CLOTH EVERY 50 HOURS.

NOTE:
UNDER EXTREME CONDITIONS CLEAN
's AND LUBRICATE WHEEL BEARINGS
EVERY 100 HOURS.

G THRUST BEARING
(OILIT E)

THRUST BEARING (OILITE)

Figure 2-37. Lubrication Diagram (Sheet 6)

Change 10
 421 SERVICE MANUAL 6ROUND HANDLING, pg
SERVICING AND INSPECTION

NOSE GEAR LINKAGE

SHIMMY DAMPENER

OH

GL

RETRACTION TORQUE
TUBE BEARINGS

BUSHING OG

TRUNNION
PIVOT BUSHING / BEARING

LINK
OG SHOCK STRUT

GL

TORQUE LINK
WHEEL BEARINGS / ZERK FITTINGS

NOTE:
LUBRICATE ALL SPHERICAL ROD ENDS \
WITH A MIXTURE OF LOW TEMPERATURE
AIRCRAFT LUBRICATING GREASE AND .

MOLY-KOTE.

NOTE:
WIPE POLISHED SURFACE OF LANDING GEAR
SHOCK STRUT AND SHIMMY DAMPENER PISTON
ROD WITH A CLEAN DRY CLOTH EVERY 50 HOURS.

Figure 2-37. Lubrication Diagram (Sheet 7)

Change 9
2-62 -OROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

RUDDER PEDAL MECHANISM

RUDDER GUST LOCK

NOTE:
AFTER LUBRICATING, ACTUATE THE
RUDDER PEDALS AND PARKING BRAKE
SEVERAL TÏMES TO INSURE ADEQUATE
PENETRATION OF THE LUBRICANT.
BEAR ALVES THHORROUUDGDHLR DAE OFF ANY ŒLLOONCK.
P

BEAR LVES

OG r i

PEDAL
LINKAGE

OH

BRAKE
MASTER CYLINDERS

OG
PEDAL
LINKAGE

Figure 2-37. Lubrication Diagram (Sheet 8)

Change 9
 421 SERVICE MANUAL OROUND HANDLING, Î"
SERVICING AND INSPECTION

TRIM TAB ACTUATORS

INTERNA L THREADS
NOTE:
CLEAN AND REPACK ACTUATORS
GSL WITH NO. 33 (LIGHT CONSISTENCY)
SILICONE GREASE -
DOW CORNING
MIDLAND MICHIGAN 48641.
ORAB

Detail

' '
ELEVATOR TAB

'
AILERON TA
ACTUATOR
GL

NOTE

ELECTRIC TRIM TAB ACTUA-

TOR DRUM AND CABLE MUST
BE FREE OF GREASE AND OIL.

Detail

Figure 2-37. Lubrication Diagram (Sheet 9)

Change 4
2-84 OROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

COWL FLAP e

os NOTE
GREASE ACTUATOR EACH
TIME ENGINE ASSEMBLY
IS WASHED DOWN.

421-0001 TO 421B0001

LANDING LIGHT
NOTES
1. THE LIGHT MUST BE EXTENDED
TO LUBRICATE THE LARGE SECTOR
GEAR. WIPE OFF EXCESS GREASE
FROM GEAR SECTOR BEFORE RE-
TRACTING THE LIGHT.
2. THE OPTIONAL RIGHT WING LAND-
GL ING LIGHT, IF INSTALLED, MAY BE
LUBRICATED IN THE SAME MANNER.
EXPOSED GEAR SECTOR

OG

HINGE POINT

01

INTERNAL GEARS

Change 4 Figure 2-37. Lubrication Diagram (Sheet 10)

 421 SERVICE MANUAL OROUND HANDLINe, 2-65
SERVICING AND INSPECTION

CONTROL MECHANISM

BEARINGS BEARINGS

OG OG

GL

GEARS AND TRACK

OG

LINKAGE

Figure 2-37. Lubrication Diagram (Sheet 11)

Change 4
2-86 GRoUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

FUEL SELECTOR VALVE

FUEL SELECTOR VALVE

NOTE
CLEAN AND LUBRICATE WITH
It CAMIE NO. 1000 DRY SPRAY
LUBRICANT OR DUPONT SLIP
SPRAY DRY FILM LUBRICANT
EVERY 100 HOURS.

421-0001 TO 421A0092

OG

421A0092 AND ON

Figure 2-37. Lubrication Diagram (Sheet 12)

Change 4
 421 SERVICE MANUAL GROUND HANDLING, $Ÿ
SERVICING AND INSPECTION

2 1

5 2
4
6
1 2

SERVICING PROCEDURES

For convenience, the items listed below are segregated into servicing intervals; that is, all items which
must be checked or serviced daily are listed, then items requiring 50 hour service are listed, etc. The
numbered symbol at each item refers to the item as shown in the Servicing Diagram.

SERVICING CHART

Symbol denotes servicing interval. Number within symbol refers to item to be serviced.

CHECK OR SERVICE AT SERVICE AT SERVICE AT SERVICE

SERVICE DAILY 50 HOURS 100 HOURS 200 HOURS AS REQD.

Figure 2-38. Service Chart (Sheet 1 of 3)

Change 12
2-88 GROUND HANDLING. 421 SERVICE MANUAL
SERVICIN6 AND INSPECTION

DAILY

FUEL TANK FILLERS:

Service after each flight with 100/130 or alternate 115/145 aviation gasoline. The capacity of
each main tank is 51 U. S. Gals. 40. 7 Imp Gals. , or 193. O Liters and the capacity
, of the
standard auxiliary tanks in each wing without optional auxiliary tank installed is 36. 5 U. S.
Gals. , 28. 7 Imp. Gals. or 137. 9 Liters.
,
The capacity of the standard auxiliary tanks in
each wing and optional auxiliary tank is 50 U. S. Gals. 40. O Imp. Gals.
,
or 189. 3 Liters.,

The capacity of each optional wing locker fuel tank is 26. 3 U. S. Gals. , 21. 9 Imp. Gals. , or
99. 5 Liters.
FUEL TANK DRAINS:
On the first flight of each day and after each refueling, drain a small amount of fuel from the
main and auxiliary tanks drain valves.

FUEL SELECTORS:
On the first flight of each day and after each refueling, drain a small amount of fuel from the
fuel selector drain valve.

OIL DIPSTICKS:
Check oil level before each flight. Capacity for each engine oil sump is 13 U. S. quarts which
includes 1 quart for oil filter. (Do not take off on less than 9 quarts. )

OIL FILLER CAPS:

Check oil level before each flight. Capacity for each engine oil sump is 13 U. S. quarts,
which includes one quart for oil filter. (Do not take off on less than 9 quarts. ) When pre-
flight shows less than 9 quarts, service with aviation grade engine oil, SAE 30 below
40°F, SAE 50 above 40°F. The aircraft is delivered from the factory with straight min-
eral oil, therefore it will be necessary during the break in period or first 50 hours of
operation to add straight mineral oil. Multi-viscosity oil with a range of SAE 10W30 is
recommended for improved starting and turbocharger controller operation in cold weath-
MHS-
I er. Ashless dispersant oil, conforming to Continental
24A must be used after the first 50 hours of new or overhauled
Motors Specifications
engine operation.

Og OXYGEN
Check
CYLINDER (OPTIONAL):
oxygen pressure gage for anticipated requirements before first flight. Whenever
Specifi-
pressure drops below 300 PSI, refill with aviator's breathing oxygen, Military
cation MIL-O-27210. Maximum pressure 1800 PSI.

Oy FUEL LINE CROSSOVER DRAINS:

On the first flight of each day, drain two ounces of fuel from each valve.

Og AIR CONDITIONING
Check hydraulic
RESERVOIR:
fluid level before flight. Service with MIL-H-5606A (Red).

50 HOURS

Og BATTERY:
Check level of electrolyte
Maintain level of electrolyte
every 50 hours or at least every 30 days, more often in hot weather.
in the filler hole even with the bottom of the vent well by adding
distilled water. Check battery drain line for corrosion and blockage.

OŽ OIL SUMP DRAINS AND OIL FILTERS:

Change oil and replace filters. After break-in oil (mineral oil) is removed, change engine
oil filter every 100 hours and oil every 100 hours. Change engine oil at least every four
months even though less than 100 hours have accumulated. Reduce periods for prolonged
operation in dusty areas, cold climates, or where short flights and long idle periods are
encountered which cause sludging conditions. Use caution when installing filter element
so as not to overtorque.

Figure 2-38. Service Chart (Sheet 2)

Change 11
 421 SERVICE MANUAL GROUND HANDLINe, 2 W
SERVICING AND INSPECTION

50 HOURS (Cont. )

O INDUCTION AIR FILTERS:

Service
dusty
every 50 hours or more
conditions, daily maintenance
often when operating
of the filter
in dusty conditions.
is recommended.
Under extremely

OIL SEPARATORS:

I O
4 Remove oil separator element
vent, dry with compressed

SHIMMY DAMPER:
air.
of oil separator (P/N 201957) and clean with Stoddard Sol-

O
5 Check
(Red).
fluid level and fill as required with hydraulic fluid, Military Specification MIL-H-5606A

100 HOURS

1 SUCTION RELIEF VALVE:

Check suction relief valve filter for dirt or obstructions if suction gage reading appears
high, Remove, wash with a mild soap and water solution and allow to dry.

FUEL SELECTOR VALVE:

Clean and lubricate detents with Camie 1000 dry spray lubricant.

BATTERY BOX:
Clean and service with 50 grams of sodium nitride or 50 grams of sodium bicarbonate.

200 HOURS

A VACUUM SYSTEM FILTER:

Clean at 200 hours replace
(optional) P/N C294501-0203.
with new filter at 500 hours (standard) P/N C294501-0103 or

SHOCK STRUTS:
Check and fill to level of filler plug with hydraulic fluid, Military Specification MIL-H-5606A
(Red).

BRAKE MASTER CYLINDERS:

Check fluid level in reservoirs and fill as needed through plug on cylinder heads. Fill with
hydraulic fluid, Military Specification MIL-H-5606A (Red).

HEATER FUEL FILTER:

Remove filter and wash thoroughly with unleaded gasoline.

I OIL SEPARATORS:
Remove oil separator and flush with Stoddard

AS REQUIRED
Solvent, dry with compressed air.

TIRES:
Nosewheel tire maintain 32 PSI. Main wheel tire maintain 65 PSI. (421-0001 TO 42180001.)
Nosewheel tire maintain 35 PSI. Main wheel tire maintain 70 PSI. (421BOOO1 AND ON.)

FUEL SELECTOR VALVE GEAR BOX:

Clean thoroughly with suitable solvent, allow to air dry and lubricate, by hand, with general
purpose grease.

ALCOHOL WINDSHIELD ANTI-ICE SYSTEM:

Check fluid level and fill as required with isopropyl
alcohol (MIL-F-5566)

Figure 2-38. Service Chart (Sheet 3)

Change 12
2-70 GROUND HANDLINe, 421 SERVICE MANUAL
SERVICING AND INSPECTION

COMPONENT LOCATION

Air Conditioning System (Belt Driven)

Cluirging Ports (421A0001 to 42180001) . . RH Wing Locker
Clutrging l'orts (42180001 and On) . . . . RH Evaporator
Sight Gage (421A0001 to 42180001) .
. . RH Wing Locker Forward Left Side
Sight Gage (421BOOO1 and On) . . . . . RH Evaporator
Pressure Switch (421B0001 and On) . . . RH Wing Locker Aft Side
Blower Relay (421BOOO1 and On) . . . . Outboard Side of RH Evaporator
Circuit Breakers (421A0001 and On) . . . LH Console
High Pressure Switch (421B0001 and On) . . Located off of Freon Liquid Injection Line leading
to Air Conditioner Manifold
Low Pressure Switch (421BOOO1 and On) . . Located in Manifold
Solenoid Shutoff Valve (421B0001 and On) . . Located in Manifold
Condensate Tank (421-0001 to 421B0001) . . Beneath Floorboard Under Evaporator
Expansion Valve (421A0001 to 421B0001) . . Right Side of Evaporator
Expansion Valve (421B0001 and On) . . . Inboard Side of Evaporator

Air Conditioning System (Hydraulic Driven)

Hydraulic Pump . . . . . . . . RH Engine Compartment
Compressor Drive Assembly . . . . . RH Wing Locker Compartment
Reservoir (hydraulic fluid) . . . . . RH Wing Locker Compartment
Manifold and Valve Assembly . . . . . RH Wing Locker Compartment
Condenser Blower Motor . . . . . . RH Wing Locker Compartment
Condensers . . . . . . . . . RH Wing Locker Compartment
Drain Valve (hydraulic fluid) . . . . . RH Wing Locker Compartment
Low Pressure Switch . . . . . . . RH Wing Locker Compartment
High Temperature Switch . . . . . . RH Wing Locker Compartment
Receiver-Dryer . . . . . . . . RH Wing Locker Compartment
Expansion Valve . . . . . . . . On Each Evaporator
Sight Gage . . . . . . . . . RH Evaporator
Charging Ports . . . . . . . . RH Evaporator
Blower Relay . . . . . . . . . RH Evaporator

Alternate Static Source Valve . . . . . . Forward Side of Left Console

Alternator System
Emergency Field Fuse . . . . . . Left Console Switch Panel
Overvoltage Relay . . . . . . . Inside Left Console
Fail Light Diode . . . . . . . . In Wire Bundle approximately 18 inches from
Alternator
Fail Module . . . . . . . . . Mounted on Alternator
Fail Light . . . . . . . . . In Annunciator Panel
Filter Capacitor . . . . . . . . On Alternator
Ammeter
Shunts . . . . . . . . . Inside Left Console
Autopilot
Pressure Switch . . . . . .
. . Firewall Aft Side of each Engine Compartment
Solenoid Valve . . . . . . . . In Left and Right Engine Nacelles
Filter Element . . . . . . . . Aft of Rear Cabin Pressure Bulkhead
Barometric Switch . . . . .
. . Forward of Instrument Panel
Battery Solenoid . . . . . . . . Left Stub Wing Forward of Battery
Cigar Lighter Resistor . . . . . . . Inside Left Console Lower Aft
Deice System Wing
Timer . . . . . . . . . Left Console
Control Switch . . . . . . . . Left Console
Filter . . . . . . . . . . RH and LH Engine Nacelle
Pressure Switch . .
. . . . . . Under Floorboards Forward of F. S. 158. 00
Deice System (Propeller)
Timer . . . . . . . . . . Under Copilot Seat

Figure 2-39. Components and Location Chart (Sheet 1 of 3)

Change 8
 421 SERVICE MANUAL OROUND HANDLING, •¾

SERVICING AND INSPECTION

COMPONENT LOCATION

Engine
Cylinder Head Temperature Bulb . . . . Lower Side of Number 2 Cylinder
EGT Probe . . . . . . . . . In Exhaust Stack Aft of Engine
Oil Temperature Bulb . . . . . . Aft Side of Engine in Oil Passage
Tachometer Generator . . . . . . Accessory Drive Aft Side of Engine
External Power Receptacle . . . . . . Fuselage Lower Side Forward of Door
Elevator Trim Actuator . . . . . . . In Tailcone Aft of F. S. 273. 94
Flap System
Position Indicator (421-0001 to 421A0001) . . Mounted in Stationary Panel
Position Indicator (421A0001 and On) . . . Part of Preselect Switch
Limit Switches . . . . . . . . Located on Flap Actuator Bracket
400A Autopilot Resistor . . . . . . Located on Flap Actuator
Flap Actuator . . . . . . . . Under Floorboards Aft of Rear Spar
Flight Hour Recorder
Actuator Switch (421-0001 to 421BOO56) . . On Belly of Aircraft F. S. 273. 94
Actuator Switch (421BOO56 and On) . . . Connected to LH Main Landing Gear Safety Switch
Fuse . . . . . . . . . . Located in Wire Bundle Inside LH Console
Finish and Trim Plate . . . . . . . Located on Nose Wheel Well Web Forward LH Side
Fuel System
Drain Valves . . . . . . Wing Gap Area and Under each Fuel Tank
Selector and Strainer . . . . . Outboard of Engine Nacelles in Wing Leading Edge
Boost Pump Relays . . . . . . Inside LH Console
Transfer Pump (Main Tank) . . . . . Aft Side of Main Tank Bulkhead
Pressure Switch . . . . . . . . Engine Nacelle Aft Side of Engine
Signal Conditioner . . . . . . Located on Rib Outboard of each Nacelle
Tank Vent Heaters . . . . . . End of Vent Lines below Fuel Tanks
Wing Locker Transfer Pump . . . . . Outboard of Wing Locker in Wing
In Line Fuel Pump . . . . . . Wing Area Outboard and Forward of Wing Locker
Heater
Filter and Solenoid . . . . . . . Right Wing Leading Edge at W. S. 60. 57
Igniter Plug . . . . . . . . . Located on Heater
Shutoff Valve (Manual) . . . . . . In RH Wing Leading Edge
Thermostat . . . . . . . . . Inside Ducting RH Nose
Fuel Pump (421A0001 to 421B0001) . . . . In RH Leading Edge Outboard of Nacelle
Fuel Pump (421B0001 to 42180149) . . . . RH Stub Wing Leading Edge Inboard of Nacelle
Fuel Pump (421B0149 and On) . . . . . Located on Combustion Blower Motor
Junction Box
Right 1 . . . . . . . . . . Left Side in Nose Compartment
Right 15 . . . . . . . . . . 100. 00 Bulkhead
Landing Gear
Landing Gear Actuator and Motor . . . . Aft of Front Spar Under Floorboards
Landing Gear Limit Switches . . . . . Mounted on Top of Landing Gear Actuator
Landing Gear Safety Switch . . . . . Mounted on Torque Link of Left Gear
Landing Gear Down Relays . . . . . Inside Left Console (421-0001 to 421A0001)
Landing Gear Down Resistor . . . . . Inside Left Console (421-0001 to 421A0001)
Landing Gear Down Resistor . . . . . Under Floorboard at F. S. 170. 00 (421A0001 and On)
Landing Gear Relay . . . . . . . Under Floorboard at F. S. 180. 00 (421A0001 and On)
Landing Gear Up Indicator Switches . . . Mounted on Retracting Linkage in Each Wheel Well
Landing Gear Down Indicator Switches . . . Mounted on Landing Gear Braces in Each Wheel
Well
Landing Gear Diode Assembly . . . . . Inside of Pedestal (See Figure 3-11)
Landing Gear Warning Relay . . . . . Insied Left Console
Landing Gear Relay . . . . . . . . Inside Left Console
Lighting
Landing . . . . . . . . . Tip Tank Tail Cap
Strobe Light Power Supply . . . . . Located in Tail Cone Aft of F. S. 273. 94
Strobe Light Flasher Unit . . . . . . Located under Floorboard of LH Aft Passenger Seat
Cabin Entrance . . . . . . . . Left Upholstery Panel
Wing Locker Baggage . . . . .
. . Wing Locker Baggage Well
Wing Locker Baggage Switch . . . . . Aft of Wing Locker Baggage

Figure 2-39. Components and Location Chart (Sheet 2 )

Change 8
2-72 GRoUND HANDLINo. 421 SERVICE MANUAL
SERVICING AND INSPECTION

COMPONENT LOCATION

MAA Plate . . . . . . . . . . Left Upholstery Panel Forward of Cabin Door

Outside Air Temperature Bulb . . . . . Belly of Aircraft F. S. 151. 14 and L. B. L. 17.29
Oxygen Regulator . . . . . . . . Mounted on Cylinder in Nose Compartment
Oxygen Warning Barometric Pressure Switch . . Forward of Instrument Panel
Pressurization System
Safety Valve . . . . . . . . Mounted on Aft Cabin Pressure Bulkhead
Outflow Valve . . . . . . . Mounted on Aft Cabin Pressure Bulkhead
Dump Valve . . . . . . . . . Mounted in Leading Edge of Stub Wings
Air Venturi- . . . . . . . . Mounted in Aft Engine Compartment
Pitot Static System Sump . . . . . . Mounted on Aft Side of Aft Cabin Pressure Bulkhead
Propeller
Synchronizer Actuator . . . . . . Right Engine Compartment
Synchronizer Control Box . . . . . Under Glove Compartment Box
Unfeathering Accumulator . . . . . Left Side of Engine Mount Beam
Starter
Solenoid . . . . . . . . . In Left Stub Wing
Vibrator . . . . . . . Inside Left Console
Stereo
Resistor . . . . . . . Inside Stereo Cabinet
Relay . . . . . . . . . Inside Stereo Cabinet

I Terminal

Tow Bar
Blocks
Refer to Section
. .
14
. . . . . . . . Stowed in LH Wing Locker
Vacuum
Filter . . . . . . . . Mounted on Forward Cabin Bulkhead in Nose
Compartment Left Side
Regulator . . . . . . . . Wing Gap Area
Variable Pressure Controller . . . . . Mounted on Control Pedestal
Variable Pressure Controller Filter . . . .
Forward of Station 118. 00 Beneath Floorboard
Voltage Regulators . . . . . . . . On Right Side of Forward Cabin Bulkhead

I Warning
Warning
Windshield
Horn
Horn Flasher Unit
(Heated) Control
. . . .

.
.
.

.
.
.

.
.

.
.
.

.
.

.
Inside Left Console
Under Copilot Seat
Inside Left Console
Windshield (Heated) Relay . . . . . . Inside Left Console
Wemac Shutoff Valve . . . . . . . Aft of Pilot in Cabin Divider Area
Wemac Blower . . . . . . . . . In RH Cabin Divider Above Evaporator
Zener Diode (IN3133) . . . . . . . Located Inside Stereo Cabinet

Figure 2-39. Components and Location Chart (Sheet 3 )

Change 8
 421 SERVICE MA1¾IAL AIRFRAME 3-1

SECTION 3

AIRFRAME
Table of Contents

Page Page

FUSELAGE . . . . . . .
3-3 Removal and Installation of Seat
Windshield . . . . . . .
3-3 Belts . . . . . . .
3-10E
Removal of Windshield . . .
3-3 Removal and Installation of Shoulder
Installation of Windshield . . .
3-3 Harness . . . . . .
3-10E
Removal and Replacement of Foul Removal and Installation of Seventh and
Weather Window . . . .
3-3 Eighth Seats . . . . .
3-12A
Cabin Windows . . . . . .
3-3 Removal and Installation of Passenger
Removal and Replacement of Side Bench Seat . . . . .
3-12A
Window . . . . . .
3-3 Removal and Installation of Passenger
Removal and Installation of Escape Ninth and Tenth Seats . . .
3-12A
Hatch . . . . . . .
3-3 Removal of Front Seats . . .
3-13
Removal and Installation of Escape Installation of Front Seats . . .
3-13
Hatch Window . . . . .
3-4A Troubleshooting Individual Seat
Removal and Installation of Escape Assemblies . . . . .
3-13
Hatch Release Mechanism . .
3-4A Removal and Installation of Upholstery
Removal and Replacement of Cabin and Upholstery Trim . . .
3-13
Windows . . . . . .
3-4A Removal and Installation of Carpet .
3-18
Plastic Window Inspection Criteria .
3-5 Removal and Installation of Control
Inspection of Plastic Windshield Pedestal . . . . . .
3-18
andWindows .....
3-6 WING.........3-18
Repair of Plastic Windshield and Removal of Wing . . . . .
3-18
Windows . . . . . .
3-6 Installation of Wing . . . . .
3-21
Doors . . . . . . . .
3-6 Wing Locker . . . . . .
3-22
Removal and Installation of Upper Removal and Installation of Wing Locker
Cabin Door . . . . .
3-6 Door . . . . . . .
3-22
Removal, Installation and Adjustment Removal and Installation of Wing Locker
of Upper Cabin Door Latch . .
3-6 Door Latch . . . . . .
3-22
Checking Cabin Door Stop Tension .
3-9 NOSE . . . . . . . . .
3-23
Adjustment of Cabin Door and Baggage Removal of Nose Baggage Compartment
Door Stop Tension . . . .
3-9 Doors . . . . . . .
3-23
Removal and Installation of Lower Disassembly and Assembly of Nose
Cabin Door . . . . .
3-9 Baggage Compartment Doors . .
3-23
Removal and Installation of Cabin Installation of Nose Baggage Compartment
Door Seal . . . . . .
3-9 Doors . . . . . . .
3-23
Removal, Installation and Adjustment Radome . . . . . . .
3-23
of Lower Cabin Door Latch . .
3-9 Removal and Installation of Radome .
3-24
Removal and Installation of Step Repair of Radome . . . . .
3-24
Mechanism . . . . .
3-10 STABILI2;ERS . . . . . . .
3-24
3-10 Removal of Vertical Stabilizer 3-24

l
Seats . . . . . . . .
. .

Removal of Passenger Seats . .

3-10 Installation of Vertical Stabilizer . .
3-24
Seats 3-10 Removal of Horizontal Stabilizer 3-24
Installation of Passenger . .
. .

of Seventh Seat (Optional) 3-10 Installation of Horizontal Stabilizer 3-24

Removal .
. .

Installation of Seventh Seat (Optional) .

3-10

Change 2
 AIRFRAME 421 SERVICE MANUAL

Detan B
Detail

Detail

1. Windshield 4. Screw 6. Lower LH Retainer

2. Upper Retainer 5. Nut 7. Upper RH Retainer
3. Lower Retainer 8. Grommet

Figure 3-1. Windshield Installation

 421 SERVICE MANUAL AIRFRAME 3"'3

FUSELAGE. g. Align holes in windshield half (1) with holes in

frame and secure retainer (2) to frame with attaching
The fuselage is of semimonocoque construction, pres- screws.
surized to the skin between forward pressure bulk- h. Install Lower center retainer (3) with attaching
head and aft pressure bulkhead. All skin, bulkhead screws. Finish securing screws in LH lower retain-
and structure joints, plumbing, controls, and wiring er (6) and LH upper retainer (7).
connections passing through a pressure wall, access i. Install trim strip and magnetic compass with
doors, windows, control cables, and torque shafts attaching screws and nuts,
are sealed to minimize air leakage. The wing cen-
ter section is an integral part of the fuselage. Ten
(twelve 421B0301 and on) stretched acrylic plastic Removal and Replacement of 'Foul Weather Window.
windows and a two piece windshield are provided in
the fuselage. A pilot's foul weather window, which a. The foul weather window assembly is removed
opens in and forward is provided for pilot and co- by removing four screws securing hinges to the
pilot. An emergency exit is provided on the right frame at the forward side.
side of the fuselage at the second window. To pro- b. Install window assembly by installing the four
vide a convenient stairway for boarding the plane, screws securing the hinges to the frame. Adjust.
the cabin entrance door swings down. Individual hinge until a good seal is provided at the forward
passenger seats are provided. The fuselage nose side of the window.
section provides baggage space and electronics area. c. Adjust striker by closing window and sliding
striker until window latch locks firmly, and a good
Windshield. (See figure 3-1, ) seal is provided around the window.

The windshield is a two piece stretched acrylic plas-

tic section. It is secured to the fuselage by screw Cabin Windows. (See figure 3-2).
fastened retainers. The retainers and screws are
sealed upon installation to adequately maintain pres- The cabin windows are made of one piece stretched
surization capabilities of the cabin section. acrylic plastic. The pilot and copilot windows are
secured to the structure by screw-fastened retainers.
The retainers and screws are sealed upon installa-
Removal of Windshield. (See figure 3-1.) tion to provide adequate pressurization capabilities
of the cabin section. The aft cabin windows are
a. Disconnect electrical wiring tomagnetic compass, secured to the structure by screws, sealing between
remove screw, nut and compass, remove windshield the window and structure to provide a cabin pressure
trim. seal.
NOTE

The following instructions are given for the Removal and Replacement of Side Window. (See
removal of the LH windshield only. The RH figure 3-2.)
windshield is removed in the same manner.
Remove side window as follows:
b. Remove screws and nuts attaching the lower a. Remove side window trim (20).
center retainer (3) and remove retainer. b. Remove the seven screws, nuts and washers
c. Remove upper center retainer (2), LH upper re- attaching upper forward retainer to glass.
tainer (7), and LH lower retainer (6) by removing c. Remove screws (13), nuts (9) and washers (3)
screws and nuts. attaching window retainer (22) to glass.
d. Remove windshield from aircraft- d. Remove the screws attaching retainer (22) to
frame,
e. Remove retainer (22) and remove window (18).
Installation of Windshield. (See figure 3-1.) f. To install window, place glass in position in
frame.
a. Install grommets (8) in each attachment hole of g. Fay seal between window and retainer and
windshield· between skin and retainer in accordance with Section
b. Position windshield half in place and temporarily 16. Install retainer (22).
hold in place with a screw at top and one at bottom of h. Dab sealer in screw holes and attach retainer
glass until installation of retainers (22) to frame with screws and attach retainer to
c. Fill the void around the edges of glass as des- glass with screws, nuts and washers.
cribed in Section 16. i. Install window upholstery trim.
d. Fay seal between retainers, windshield and skin
with sealant using non-crazing accelerator, in accord-
ance with Section 16. Seal all screws by dabbing Removal and Installation of Escape Hatch.
countersink or dimpled area with sealant.
e, Install LH lower retainer (6) but do not tighten a. Remove plexiglass cover (16) from release pan
screws at this time. (14) and turn the handle counterclockwise as far as
f. Install LH upper retainer (7) but do not tighten it will turn, (approximately 1/4 turn).
screws at this time, b. Remove hatch by pulling inboard on the handle.
Change 6
 3-4 AIRFRAME 421 SERVICE MANUAL

1 0
12 9

22

24
'
D

13

22 Detan Û
13

1. Guide 8. Link 15. Handle 22. Retainer

2. Spring 9. Nut 16. Cover 23. Striker
3. Washer 10. Clevis 17. Seal 24. Spacer
4. Latch Bolt 11. Bellerank 18. Window 25. Armrest
5. Roll Pin 12. Channel 19. Clip Bracket
6. Pin 13. Screw 20. Window Trim 26. Inner Window
7. Cotter Pin 14. Pan 21. Frame 27. Seal Strip :

Figure 3-2. Side Window Installation

Change 6
 421 SERVICE MANUAL AIRFRAME 3-4A

NOTE g. Lubricate moving parts in accordance with Sect-

ion 2 before installation.
Check seal for cuts or deterioration before h. The installation of the release mechanism is the
installation of hatch. Replace seal if ques- reversal of the removal procedure.
tionable.
NOTE
c. To install hatch, position hatch in place and turn
handle to locked position. The locking mechanism is rigged in such a
d. Install cover (16), manner that it has a over-center locking
condition.
Removal and Installation of Escape Hatch Window.
(See figure 3-2.) 1. To adjust links, install 1/8" rigging pin through
the hole provided in the guides (1) and through the
a. Remove window trim. 1/8" hole provided in the latch bolts (4).
b. Remove screws, nuts and washers securing glass j. With the handle turned clockwise until it is
to escape hatch frame and remove glass. against the stop, adjust links to a length whereby the
c. Fay seal between glass and skin when placing the pins (6) can be installed with no binding.
glass in position. See Section 16 for sealing proced- k. Install pins (6), cotter pins (7), and secure jamb
ures. nuts (9).
d. Dab sealant in screw holes and secure glass 1. Remove rig pins,
panel with screws, nuts and washers.
e. Install window trim.
Removal and Replacement of Cabin Windows. (See
figure 3-2, Detail B. )
Removal and Installation of Escape Hatch Release
Mechanism. (See figure 3-2.) a. Remove window trim by removing attaching
screws.
a. Remove plexiglass cover (16) from release pan b. Remove nuts securing clips (19). Remove clips
(14) and turn handle counterclockwise. and inner window (26).
b. Remove pan (14) by removing roll pin (5) from c. Remove screws, nuts and washers securing
handle, window to structure.
c. Remove upholstery panel, d. To install window panel, place window in posi-
d. Remove pins from links (8) and remove links. tion. Fay seal between window and structure, using
e. Remove two screws securing channel to frame, a sealant with noncrazing accelerator. Refer to
lift out channel and bellerank (11). Section 16 for detailed instructions.
f. Remove latch bolts (4) and springs (2). e. Secure window in place with screws, washers

421 0001 TO 421B0301

CRITICA L VISION AREA

NON-CRITICAL VISION AREA

NOTE:
LE FT WINDOWS TYPICAL
FOR RIGHT WINDOWS
421BO301 AND ON

Figure 3-3. Critical Vision Diagram

Change 6
3-48 AIRFRAME 421 SERVICE MANUAL

and nuts. On aircraft 421BO301 and on, an inner re- g. Position inner window against seal strip and se-
tainer is installed next to the glass. cure in place with four clips (19) and nuts over ex-
f. Cement new seal strip (27) in position using isting nuts, one each at top, bottom, front and aft
EC2141 adhesive. Cut seal strip to provide a 40
. sides.
inch gap at lower side, h. Install window trim.

Change 6
 421 SERVICE MANUAL AIRFRAME F5

Plastic Windows Inspection Criteria.

DEFECTS CRITICAL VISION AREA NON-CRITICAL VISION AREA

MAXIMUM MAXIMUM MAXIMUM MAXIMUM

REPAIRABLE PERMISSIBLE REPAIRABLE PERMISSIBLE
WITHOUT REPAIRING WITHOUT REPAIRING

NICKS AND DENTS

Maximum Not repairable. 0.025 inch. 0.250 inch. 0.125 inch.

Diameter.

Depth. Not repairable. 0.016 inch• 0.060 inch. 0.032 inch.

Frequency. None 2 per sq. ft. 2 per sq. ft. 1 per sq. ft.

SCRATCHES.

Length. 12 inches total 12 inches total 24 inches total 24 inches total

per area. per area. per area. per area.

Width. 0.020 inch. 0.020 inch. 0.050 inch. 0.020 inch.

Depth. 0. 016 inch. 0. 008 inch. 0. 008 inch. 0. 008 inch.

Frequency. 12 inches total 12 inches total 20°/o of total Total length of scratches
per area. per area. area. equals 3 times longest
dimension of area.

CRACKS.

Length. Not repairable. None. Not repairable. None.

Frequency. Not repairable. None. Not repairable. None.

CRA ZING.

Slight. Not repairable. Crazing adjacent to the Not repairable. Shall be contained in
edges of the glass must a 9. 00 inch circle.
not extend more than 1
inch into the C.V. area.

Severe. Not repairable. Crazing adjacent to the Not repairable. Shall be contained in
edge of the glass must a 6.00 inch circle,
not extend more than 1
inch into C. V. area.

DISCO LORA TION.

Not repairable. None Not repairable. May extend 1 inch from

all edges of non-critical
areas.
3-6 AIRFRAME 421 SERVICE MANUAL

Inspection of Plastic Windshield and Windows. j. (Refer to figure 3-6A.) Adjust pins to a mini-
mum of 0.77 inch engagement with the receptacles
See Inspection Criteria Chart for allowable defects. (1) in the locked position and a minimum of 0.05
Repairable defects after repair are considered per- clearance in the unlocked position and a maximum
manent repairs. "Not repairable" defects may be of 0.21 clearance.
repaired and/or used only as a temporary repair.
NOTE
CAUTION
If required, one spacer (3) or (4) may be add-
If temporary repairs are made, aircraft ed between the lockplate (2) and the doorframe
must be operated in unpressurized mode until at each required pin location.
replacement of window can be made.
k. Secure jam nuts (3) and install cotter pins (12)
on tube assembly (21) and link (13) holding latch pins
Repair of Plastic Windshield and Windows. (10).
1. Adjust door latch receptacles as follows:
See Section 16 for repair of windshield and windows. 1. (See figure 3-5.) Remove window trim.
2. Loosen nut securing receptacle (28) to lock
plate (29).
Doors. 3. Adjust receptacle (28) in forward door jamb and
aft door jam so that when the latch pins (10) are en-
gaged inthe receptacles, the door will produce a
Removal and Installation of Upper Cabin Door. (See tight fit.
figure 3-5.) 4. Secure nuts on receptacle.
m. Close and fully lock cabin doors. The indica-
a. Open cabin doors and carefully pull headliner tors (31) should indicate a locked condition.
out of retainer above door to gain access to upper n. Close and fully lock cabin doors observing the
hinge bolts (1). cabin door not-locked light on the stationary instru-
b. Remove door stay strap assembly. ment panel for a light-out condition. If the light re-
c. With upper door open and supported, remove mains illuminated, adjust switch located just forward
nuts (3), stat-o-seals (2) and bolts (1). of doorframe near guide receptacle (28) using the
d. Remove upper door from aircraft. following steps:
e. Install upper door by reversing removal pro-
cedures.

ROLLER INCREASE
Removal, Installation and Adjustment of Upper Cabin SPRING
TENSION
Door Latch. (See figure 3-5.)

a. Open cabin door and remove handle (17), base

CHANNEL
(16) and window trim panel by removing screws and
pin. o DECREASE STRAP
b. Using Detail C, figure 3-5, disassemble, repair TENSION
TONGUE
and reassemble door latch as necessary.

NOTE
STOP
Refer toOverhaul and Replacement Chart for ASSEMBLY s
replacement interval of latch pin (10), figure
3-5.

e 421-0104 AND ON
c. With the inside handle turned as far as it will go
. . .

in a clockwise rotation, adjust link (13) to give a

positive locking condition of the cam assembly (27).
d. Adjust links (13) and tube assembly (21) until
the pins (11) can be installed with no binding.
e. Install cotter pins (12) except on pins holding
latch pins (10) to link (13) and tube assembly (21). e
f. Secure jamb nut (3) on link (13) holding to cam
assembly (27). 421-0001 TO 421-0104
g. Position handle (17) so that the be11crank (22) is
against the housing stop in the open position.
h. Loosen jamb nuts (3) on tube assembly (21) and
link (13) holding latch pins (10), and remove pins (11). BLOCK
i. Screw tube assembly (21) and link (13) holding
latch pins (10) clockwise or counterclockwise to de-
crease or increase length of them. Figure 3-4. Door Stop Adjustment
 421 SERVICE MANUAL AIRFRAME 3-6A/3-6B

Detail

29

28

etail $

130
1
5

11 23
25
11 Detail 37 B51114oo2
421-0001 TO 421BO801 17 51142046
gir g x es1114ooi
10

1. Bolt 8. Door Frame 16. Base 24. Lock Assembly 32. Stop
2. Stat-O-Seal 9. Guide 17. Handle 25. Spindle 33. Housing
3. Nut 10. Latch Pin 18. Cup 26. Bearing 34. Catch
4. Seal 11. Pin 19. Spring 27. Cam Assembly 35. Cover
5. Seal Retainer 12. Cotter Pin 20. Roll Pin 28. Receptacle Assembly 36. Gasket
6. Window Trim 13. Link 21. Tube Assembly 29. Lock Plate 37. Stop
7. Retainer 14. Clevis 22. Bellerank 30. Spacer Bolt
15. Washer 23. O-Ring 31. Indicator

Figure 3-5. Upper Cabin Door Installation (Sheet 1 of 2)

Change 11
 421 SERVICE MANUAL AIRFRAME 3-7

17
16
12
13

22
1
15
23
20
33
25
19

26

24
17

Detail 34
421BO801 AND ON

Detali E
421BO301 AND ON

014143058
E51141073R

Figure 3-5. Upper Cabin Door Installation (Sheet 2)

Change 11
3-8 AIRFRAME 421 SERVICE MANUAL

85 AND ON

C DetaOil

24
21

Detail

2 14

17
10

24-- , 13
g
3
3
1510
" 421A0001 /
AND ON 4 M111¾œ
1 14 B51112001R
Detaii D camoom

1. Guide 9. Clevis 17. Screw

2. Latch Pin 10. Nut 18. Spacer
3. Bolt 11. Tube Assembly 19. Cap Nut
4. Washer 12. Handle 20. Cable Assembly
5. Bearing 13. Bellerank 21. Seal
6. Bellcrank 14. Spring 22. Indicator Flag
7. Cotter Pin 15. Roll Pin 23. Cup
8. Pin 16. Stop Assembly 24. Receptacle

Figure 3-6. Lower Cabin Door Installation

Change 12
 421 SERVICE MANUAL AIRFRAME ¾9

1. Remove window trim just forward of entrance 4. Secure nuts on receptacles.

door. 5. Install upholstery panels.
2. Loosen screws securing warning switch to
bracket and adjust switch until positive contact with Removal and Installation of Cabin Door Seal. (See
the shaft assembly is made and light on instrument Figure 3-5 or Figure 3-6. )
panel is extinguished.
3. Secure switch in this position by tightening a. Remove door seal from seal retainer being care-
screws. ful not to tear or damage seal. Use a phenolic wedge
4. Reinstall window trim. or plastic tool to help remove door seal.
b. Install seals by gently edging seal into retainer
Checking Cabin Door and Locker Door Stop Tension. using a plastic tool. It is permissible to use talcum
powder, soapstone or water to facilitate installation
a. Open cabin door until upper cabin door is sup- of seals.
ported by the cabin door stop.
b. Install spring scale (0 to 50 pounds) to cabin door NOTE
handle,
c. Check for correct tension. Install upper door seal (4, figure 3-5) with
the holes towards the door opening and the
NOTE lower door seal (21, figure 3-6) with the holes
towards the top of the door. Pressurized air
When checking tension be sure to pull scales from inside-the cabin door enters the holes,
straight and read tension when stop releases inflating the seal to form a pressurized seal.
door free to close. Tension should be 15 ±5
pounds.
Removal, Installation and Adjustment of Lower Cabin
d. If correct tension is not obtained, refer to Adjust- Door Latch. (See Figure 3-6.)
ment of Cabin Door and Baggage Door Stop Tension.
e. Check locker door stop tension and adjust in ac- a. Open lower cabin door and remove necessary
cordance with Adjustment of Cabin Door and Baggage upholstery panels to gain access to latch mechanism.
Door Stop Tension procedures. Tension should be b. Using Detail C, figure 3-6, disassemble, repair
25 ±3 pounds as applied directly to the stop assembly, and reassemble door latch as necessary.

NOTE
Adjustment of Cabin Door and Baggage Door Stop
Tension. (See Figure 3-4. ) Refer to Overhaul and Replacement Chart
for replacement interval of latch pin (2),
a. Adjust tension on stop assembly, using a drift figure 3-6.
punch and hammer as follows:
1. Position stop assembly on block with stop ex- c. Adjust lower receptacles to outboard position.
tended and tongue down. d. Adjust upper receptacles to inboard position to
2. Using drift punch and hammer, tap on roller to insure that the lower door in the closed position will
increase tension. produce a good fit.
3. To decrease tension, turn stop assembly over on e. With the handle in the locked position, adjust the
block and bend tongue down with hammer. Be sure tube assemblies (11) to a length whereby the pins (8)
block is inside of the channel to prevent damage to can be installed with no binding.
the channel flanges. f. Install cotter pins (7) on clevis (9).
g. Position handle (12) in the open position.
h. Loosen jamb nuts (10) on tube assemblies (11)
Removal and Installation of Lower Cabin Door. (See and remove pins (8).
Figure 3-6. ) i. Screw tube assemblies (11) clockwise or counter-
clockwise to decrease or increase their length.
a. With cabin door open and supported, remove nut j. (Refer to figure 3-6A. ) Adjust the upper latch
and screw attaching cable (20) to bellerank (13), pins (2) to a minimum of 77 inch engagement
.
with
b. Remove screws (17) attaching lower hinges to the receptacles (3) in the door locked position and a
door. minimum of 05 clearance
. in the unlocked position
c. Remove lower door from aircraft. and a maximum of 21 clearance.
.

d. Install lower door by reversing removal pro-

cedures. NOTE
e. (See figure 3-5.) Adjust door latch receptacles
as follows: If required, one spacer (5 or 6) may be added
1. Remove uphols.tery side panels, between the lockplate (4) and the doorframe at
2. Loosen nut (3) securing réceptacle (28) to lock each required latch pin (2) location.
plate (29).
3. Adjust receptacles (28), two in forward door k. (Refer to Figure 3-6. ) Adjust the lower latch
jamb and two in aft door jàmb so that when the latch pins for the same engagement and clearance require-
pins (10) are engaged in the receptacles, the door ments as specified for upper latch pins.
will produce a good fit. 1. Secure jamb nuts (10) and install cotter pins (7)

Change 1
3 10 AIRFRAME 421 SERVICE MANUAL

b. Using Detail B, figure 3-6, disassemble repair

UNLOCKED and reassemble as necessary.
c. Reinstall upholstery panel.
LOC

Seats.
1 (MIN.)
21 Removal of Passenger Seats. (See figure 3-8. )
(MAX,) a. Remove rail stops by removing cotter pin.
b. Pull up on the left-hand adjusting handle and
i
p slide the seat over cutout in rail.
Iii 4 c. Disengage seat rollers from rail assemblies.
5 d. Remove seat from aircraft and disassemble and
6 assemble passenger seat in accordance with figure

MlN
e. To remove aft facing seat, lift seat stop (34) and
slide seat to cutouts in rail.

Installation of Passenger Seats. (See figure 3-8. )

·¡

a. Engage seat rollers (9) with track assemblies

(31) along cutouts in tracks.
b. Install rail stops (32) on track assemblies (31)
and secure in place with cotter pin (33).
c. Aft facing passenger seats are installed in the
same manner as the forward facing seats. Seat po-
sition is adjusted by seat stops (34) and the back is
adjusted to clear cabin divider or stereo (optional
equipment) by adjusting bolt (35).

NOTE: MAXIMUM OF ONË SPACER ALLOWED

PER PIN AS REQUIRED. WARNING
5 11110 0 1
Forward facing seats should never be in-
stalled or used as aft facing seats. . When in-
stalling seats make certain dual roller guide
1. Door 5. Spacer (P/N 5111565-1) assembly (26) is installed in the aft side of
2. Latch Pin 6. Spacer (P/N 5111565-2) seat on forward facing seats and in the for-
3. Receptacle 7. Door Jamb ward side of seat on aft facing seats.
4. Lockplate

Figure 3-6A. Cabin Door Latch Pin Requirements WARNING

After the seat has been jointed to rail assem-

blies (31), insure that rail stops are installed
on tube assemblies (11). properly and the seat adjustment mechanisms
m. Adjust lower receptacles inboard as far as pos- function properly.
sible to allow free latch pin movement within the re-
ceptacles.
n. Recheck all latch pins for engagement and clear- Removal of Seventh Seat. (Optional. ) (See figure
ance. 3-7. )
o. Adjust lower door handle stops in the locked and a. Pull up on handle (19) and tilt seatback forward
unlocked position to correspond with engagement and as far as possible.
clearance requirements. b. Lift stop pins (11) and slide seat aft to cutouts in
p. Close doors and check for proper operation, seat rails.
positive locking and observe the door locked indica- c. Slide seat backward until front guide assemblies
tors (22), which should show a locked condition. (15) disengage from seat rail.
q. Install upholstery panels. d. Then slide seat forward until back guide assem-
blies (15) disengage from seat rail.
e. Remove seat from aircraft and disassemble and
Removal and Installation of Step Mechanism. (See assemble in accordance with figure 3-7.
figure 3-6. )
a. Remove upholstery panel from aft side of the Installation of Seventh Seat. (Optional.) (See figure
step well. 3-7.)

Install seat by reversing removal procedure.

:hange 12
 421 SERVICE MANUAL AIRFRAME O ÛA

DOOR OPERATION
PEN
l. CLOSE DOOR
2.lNSERT SAFETY PIN
FROM BOTTOMSIDE
OF HANDLE.
3.CHECK SAFETY PIN
CLOSE FOR POSITIVE Detail A
ENGAGEMENT.

Detail $

Figure 3-6B. Upper Cabin Door Safety Chain Installation

3-108 AIRFRAME 421 SERVICE MANUAL

421-0001 TO 421A0001 421A0001 TO 421B0001

3 4 10 11

5 8 12 13

421 GOLDEN EAGLE 421 EXECUTIVE COMMUTER

1. Refer to figure 3-7. 9. Refer to figure 3-8B.

2. Refer to figure 3-7. 10. Refer to figure 3-8.
3. Refer to figure 3-8. 11. Refer to figure 3-8.
4. Refer to figure 3-8. 12. Refer to figure 3-8.
5. Refer to figure 3-8. 13. Refer to figure 3-8.
8. Refer to figure 3-8. 14. Refer to figure 3-8C.
7. Refer to figure 3-8A. 15. Refer to figure 3-8D.
8. Refer to figure 3-8B. 16. Refer to figure 3-8D.

Figure 3-6C. Seating Arrangement Schematic

 421 SERVICE MANUAL AIRFRAME 3"ÎÛÛ

1
50
51
49

3
47 48

46

45
40
32 33 34 6 35
3 11 12 13

7 14
3 1615
30
1817
28

24 20
23 21
22 25

1. Cover Assembly 14. Handle 27. Pin 40. Screw

2. Seat Belt 15. Arm Assembly 28. Pan Assembly 41. Washer
3. Cover Assembly 16. Pin 29. Bolt 42. Spacer
4. Skirt 17. Actuator Assembly 30. Spacer 43. Washer
5. Screw 18. Bracket 31. Nut 44. Nut
6. Stop Pin 19. Spring 32. Spring 45. Cover
7. Pin 20. Arm Assembly 33. Pin 46. Washer
8. Pin 21. Spacer 34. Pivot 47. Nut
9. Tube 22. Nut 35. Pin 48. Stop Assembly
10. Pin 23. Stop 36. Nut 49. Escutcheon Plate
11. Spacer 24. Screw 37. Washer 50. Screw
12. Pin 25. Bracket 38. Spacer 51. Cover
13. Pin 26. Pin 39. Bolt

Figure 3-7. Front Seat

Change 7
 AIRFRAME 421 SERVICE MANUAL

Detail A

Detail
OPTIONAL INSTALLATION
421B0501 AND ON

10

OPTIONAL
INSTALLATION 51142034
421B0101 AND ON AS1142034
AS4141019

1. Bulkhead, Station 154. 50 5. Seat Belt 9. Spacer

2. Bracket 6. Seat Assembly 10. Nut
3. Shoulder Harness Assembly 7. Bolt 11. Hook
4. Bracket Cover 8. Washer 12. Inertia Reel

Figure 3-7A. Seat Belt and Shoulder Harness Installa.tion

Change 8
 421 SERVICE MANUAL AIRFRAME 3-10E

Removal and Installation of Seat Belts. (See figure Removal and Installation of Shoulder Harness. (See
2-7A.) figure 3-7A.)

a. Remove nut, washers, spacer and bolt from seat a. Remove bracket cover (4).
belt anchor. b. Remove nut, washers, spacer (9), hook (11)
b. Remove seat belt. and bolt securing shoulder harness to bracket (2).
c. Install seat belt by reversing removal proce- c. Install shoulder harness by reversing the re-
dures moval procedures.

NOTE
Removal and Installation of Inertia Reel. (See figure
Make sure seat belts are installed with the 3-7A. )
buckle portion of seat belt on the inboard side
of the seat. a. Remove bracket cover (4) by removing screw anc
spacer. Retain spacer for reinstallation.
b. Remove screws securing inertia reel (12) to
bracket.
c. Install inertia reel by reversing the removal
procedures.

Change &
3-10F AIRFRAME 421 SERVICE 1VIANUAL

22
1

21 15 16

20

19 Detail A

10 3

Detail D
D

6
30
e 3 27
31 32
5

33

33 27

34 Detan

27 28

$3 Detail $ 421-0001 to 421B0001

Figure 3-8. Passenger Seat (Sheet 1 of 3)

Change 6
 421 SERVICE MANUAL

22
"
1
21 15

25

20

35
1
10

Detail D D
4

8 7

33 i 28 a
33 e

Detail
34

29 27 26
/^'

Detail $ 421B0001 AND ON

Figure 3-8. Passenger Seat (Sheet 2 of 3)

Change 6
3-lÛÑ AIRFRAME 421 SERVICE MANUAL

41

40
A

36
31
421 EXECUTIVE COMMUTER
Detail

1. Head Rest G. Bellerank 17. Actuator Assembly 25. Bolt 33. Cotter Pin
2. Back Assembly 10. Brace 18. Arm 26. Guide 34. Seat Stop
3. Panel 11. Pin 19. Link 27. Roller 35. Bolt
4. Seat Belt 12, Support 20. Bellcrank 28. Link 36. Locating Hole
5. Roller 13. Arm 21. Link 29. Pin 37. Railout
6. Skirt 14. Pin 22. Handle 30. Bellerank 38. Spacer
7. Bolt 15. Armrest 23. Spring 31. Seat Track 39. Nut
8. Bottom 16. Seat Cover 24. Stop 32. Rail Stop 40. Seat Frame
Assembly 41. Frame Padding

Figure 3-8. Passenger Seat (Sheet 3 of 3)

Change 2
 421 SERVICE MANUAL AIRFRAME ll

21
29
24
12 5
25

12 4
26 20
1 19
27
1
23 29
26
28

17
14
16 11
1513

Detail

1. Front Skirt 9. Screw 17. Washer 25. Link

2. Side Skirt 10. Cover Seat -
18. Cap Nut 26. Pin
3. Removable Armrest 11. Track Stop Pin 19. Handle 27. Bellerank -
Forward
4. Cover Seatback
-
12. Bolt 20. Nut 28. Actuator Control Arm
5. Headrest 13. Bushing 21. Seat Back Stop 29. Actuator Control Link
6. Cover Assy Back-
14. Spacer 22. Bellerank -
Aft .
30. Spacer
7. Grommet 15. Guide 23. Cotter Pin 31. Actuator
8. Spacer 16. Roller 24. Spring 32. Washer

Figure 3-8A. Passenger Seventh Seat

3-1 AIRFRAME 421 SERVICE MANUAL

13

14
'
15

14
12 15

17

Detail Detail B 6

1. Headrest 10. Washer

2. Seat Back 11. Spacer
3. Seat Bottom 12. Nut
L Screw 13. Seat Back Cover
i. Fastener 14. Seat Belt
i. Forward Leg 15. Seat Belt Attachment
. Seat Bottom Skirt 16. Attachment Bolt
. Rear Leg 17. Stud Fitting
. Bolt

Figure 3-8B. Passenger Seventh and Eighth Seat

 421 SERVICE MANUAL AIRFRAME 3-l A

Removal and Installation of Seventh and Eighth Seats· b. Slide the seat over the cutout in the rail.
(421BOOO1and OÑ c. Disengage seat rollers from rail assemblies.
d. Remove seat from aircraft.
a. Turn fasteners on back legs of chair 1/4 turn
and free back legs from anchors.
b. Turn fasteners on front legs of chair 1/4 turn, Removal and Installation of Passenger Ninth and
free front legs from anchors and remove chair- Tenth Seats. (See figure 3-8D. ) (Executive
e. Install chair by reversing the removal pro- Commuter)
cedures.
Remove and install ninth and tenth seats in the Exee-
utive Commuter in accordance with the Removal and
Removal and Installation of Passenger Bench Seat. Installation of Seventh and Eighth Seat Procedures.
(See figure 3-8C.) (421BOOO1 and ON)
a. Remove seat stops by removing cotter pin.

10
111

Detail

1. Seat Stop 5. Locating Hole 8. Seat Belt Assembly

2. Cotter Pin 6. Rail Cutout 9. Bolt
3. Bottom Cushion 7. Back Cushion 10. Spacer
4. Seat Rail 11. Nut

Figure 3-8C. Passenger Bench Seat

3"Î AIRFRAME 421 SERVICE MANUAL

12

'
14

' 15

4
Detail
15 Detaii B

1. Seat Back 9. Washer

2. Seat Bottom 10. Spacer
3. Screw 11. Nut
4. Fastener 12. Seat Back Cover
5. Forward Leg 13. Seat Belt
6. Seat Bottom Skirt 14, Seat Belt Attachment
'7. Rear Leg 15. Attachment Bolt
8. Bolt 16. Stud Fitting

Figure 3-8D. Passenger Ninth and Tenth Seat

 421 SERVICE MANUAL AIRFRAME 3-13

Removal of Front Seats. (See figure 3-7. ) d. Disassemble and assemble front seats in accord-
ance with figure 3-6.
Removal procedure is the same for either pilot's or
copilot's seat.
a. Pull up on right-hand adjusting handle and tilt Installation of Front Seats. (See figure 3-7.)
the seat back as far as possible.
b. Remove screws securing front seat stops (23) on Install front seats by reversing removal procedure.
left seat rail and pan assembly (28).
c. Pull up on left-hand adjusting handle and slide
seat aft to remove. WARNING

NOTE After the front seats have been installed,

insure that stops (23) are installed properly
If (optional) cabin divider is installed, slide and that seat adjustment mechanisms are
seat forward to remove. functioning properly.

Trouble Shooting Individual Seat Assemblies.

TROUBLE PROBABLE CAUSE CORRECTION

LOCKING MECHANISM FAILS Broken, disconnected or missing Replace spring.

TO ENGAGE IN SEAT SUP- spring.
PORT

Distorted parts.
Repair or replace parts.
SEAT ADJUSTMENT MECH- Broken, disconnected or missing
Replace spring.
ANISM FAILS TO OPERATE spring.

Distorted parts- Repair or replace parts.

SEAT ASSEMBLY FAILS TO Improper lubrication Apply paraffin wax to the seat
SLIDE FREELY ON SEAT rails on the pan assembly.
SUPPORT
Parts bent or broken. Repair or replace parts.

Removal and Installation of Upholstery and Upholstery carefully peeling upholstery from metal.
Trim. (See figure 3-9, sheet 1 of 2.) 8. Remove headliner from curtain track (11 and
15) by unsnapping retainer (14 and 10) from curtain
a. Remove front and passenger seats in accordance track working from front to aft.
with seat removal procedures. 9. Carefully remove headliner from pronged retain-
b. Remove headliner as follows: er (12) above entrance door and at aft cabin bulkhead.
10. Remove headliner by carefully working from
NOTE left to right and front to rear releasing the headliner
wires (16) from support hooks.
Removal of LH headliner is given, removal 11. Remove screws securing retainer (19) to struct-
of RH headliner is the same. ure and remove headliner.
c. Remove aft cabin bulkhead upholstery as follows:
1. Remove sun visor by removing clamp screws 1. The side flaps of the center panel (27) are held
securing clamps to support. Remove supports by by hook and pile. To remove pull sides loose.
screwing counterclockwise out of retainer. 2. Raise panel approximately 1/2 inch and pull
2. Remove cover plate on individual combination bottom of panel forward to release upper support
light assemblies by removing oxygen outlet port from clips. Remove panel.
cover, retaining nut and attaching screws. 3. Remove aft cabin bulkhead side upholstery
3. Remove upper windshield trim (22). (26 and 28) by carefully peeling the upholstery loose
4. Remove LH side window trim (39). and around the edges.
5. Starting at the left side of the windshield, re -

4. Raise panel approximately 1/2 inch and pull

move headliner (13) from prongs of upholstery retain- panel forward to release support from clips at top
er (18). edge.
6. Remove headliner from side window retainer d. Remove set screw (6) at the end of curtain
prongs (17), tracks and slide curtain from curtain track.
7. Remove headliner from overhead plenum by e. Remove window trim (32, 35 and 36) by remov-
3-14 AIRFRAME 421 SERVICE MANUAL

4
3
2

20 / /

32

34

35
22

28

1925

33

A 37 40
38

Figure 3- 9. Upholstery and Upholstery Trim (Sheet 1 of 4)

 421 SERVICE MANUAL AIRFRAME 3"Î$A

4
3

0 20

32

34

22 36

"
21 g 39 -

10

27
28
3,12

23
18

23

37 421 EXECUTIVE COMMUTER

38

Figure 3-9. Upholstery and Upholstery Trim (Sheet 2 of 4)

Change 1
3-148 AIRFRAME 421 SERVICE MANUAL

Detail Detail Detail $

421-0001TO 421A0001 421A0001 and ON 421-0084ANDON

41
5
41
11
41 41

42

421-0001 TO 42130001

Figure 3-9. Upholstery and Upholstery Trim (Sheet 3 of 4)

Change 1
 421 SERVICE MANUAL AIRFRAME F15

41

41

Detail
421B0001 AND ON WITH
OPTIONAL AIR CONDITIONING

41
421 EXECUTIVE CM TER

421B0001 AND ON

1. Emergency Window Trim 15. LH Forward Curtain Track 29. LH Aft Lower Curtain Track
2. RH Forward Window Trim 16. Headliner Wire 30. LH Aft Side Panel
3. RH Center Window Trim 17. Retainer 31. Retainer
4. RH Aft Window Trim 18. Retainer 32. LH Aft Window Trim
5. RH Upper Curtain Track 19. Retainer 33. LH Center Side Panel
6. Set Screw 20. RH Side Window Trim 34. Upper Cabin Door Trim
7. RH Headliner 21. Center Windshield Trim 35. LH Center Window Trim
8. Center Cover Support 22. Upper Windshield Trîm 36. LH Forward Window Trim
9. Aft Headliner Retainer 23. RH Forward Side Panel 37. LH Forward Side Panel
10. Aft Retainer 24. Arm Rest Upholstery 38. LH Forward Panel
11. LH Aft Curtain Track 25. RH Side Upholstery Panel 39. LH Side Window Trim
12. Retainer 26. RH Aft Bulkhead Upholstery 40. LH Forward Lower Curtain Track
13. LH Headliner 27. Center Aft Bulkhead Upholstery 41. Curtain
14. Retainer 28. LH Aft Bulkhead Upholstery 42. Forward Cabin Divider

Figure 3-9. Upholstery and Upholstery Trim (Sheet 4 of 4)

Change 1
3-l6 AIRFRAME 421 SERVICE MANUAL

19

Detail
421B0201 AND ON
6

11
12
13
14
15
g
16

17

i. Forward Bulkhead Carpet 8. Rear Carpet 14. Kick Plate

2. Cover Plate 9. Step Plate 15. Cover Plate
>. Kick Plate 10. LH Center Carpet 16. Forward Bulkhead Carpet
1, Kick Plate 11. LH Outboard Carpet 17. Baggage Shelf Carpet
i. RH Outboard Carpet 12. Carpet Retainer 18. LH Scuff Plate
3. RH Center Carpet 13, Kick Plate 19. RH Scuff Plate
r. Center Carpet 20. Carpet

Figure 3-10. Carpet Installation

Change 4
 421 SERVICE MANUAL AIRFRAME 3"ÎÎ

421-0001 TO 421A0001

14 8
Detail

15 4
3 y

16

14

13 11
12

421A0001 and ON
51153013

1. Face Plate 6. Bulkhead 12. Cover

2. Quadrant 7. Terminal Block 6 13. Cover
3. Screw 8. Pulley Bracket 14. Alternate Air Controls
4. Bearing Pad 9. Terminal Block 5 15. Diode Assembly
5. Cover 10. Cover Plate 16. Heat Exchange Controls
11. Filler

Figure 3-11. Control Pedestal Installation

Change 8
3--18 AIRFRAME 421 SERVICE MANUAL

ing retaining screws and slipping trim out from plates.

behind upper and lower eurtain tracks. b. Remove cover (5), right and left side filler (11)
f. Remove LH and RH forward side panels (23 and and cover (12).
37) as follows: c. Remove control quadrant in accordance with
1. Remove ash receivers and armrest cover Section 9.
assembly by removing attaching screws. d. Remove elevator trim contial in accordance with
2. Remove bonded armrest upholstery cover and Section 6.
pad by carefully peeling from armrest base. e. Remove rudder trim control in accordance with
3. Remove attaching screws and forward panel (38). Section 7.
g. Remove LH center panel (33) as follows: f. Disconnect aileron trim cable in accordance with
1. Remove ash receivers, lighter assembly and Section 5.
safety chain. g. Route elevator, rudder and trim cables from
2. Remove screws securing panel to structure at pedestal,
forward edge, bottom edge and along center at each h. Remove throttle mixture, and propeller controls
bulkhead. in accordance with Section 9.
3. Pull panel out of aft retainer and curtain track i. Remove alternate air control cover (13) and cover
(40). plate (10) in accordance with Section 9, and remove
4. Disconnect courtesy light and switch wires. controls from bracket as follows:
5. Disconnect clamp and hose from air outlet duct 1. Remove nut securing controls to bracket.
and remove panel. 2. Pull control aft until cable will slip out of slots
h. Remove RH center panel (25) in a similar manner. In bracket.
i. Remove LH aft side panel as follows: j. Remove bearing pad (4) by removing screws
1. Remove cabin door cable fitting. securing pad to pedestal.
2. Remove screws from aft and lower sides of k. Remove terminal blocks (7 and 9) and diode
panel. assembly (15).
3. Pull panel from the forward retainer and from 1. Remove two screws (3) securing pedestal to
under curtain track and remove panel. instrument panel.
j. Install upholstery panels by reversing removal m. Remove pedestal side panels by drilling out
procedures and bonding affected panels with cement rivets at floor and forward cabin bulkhead. Drill out
(ECB80 Minnesota Mining and Manufacturing Co., rivets securing side panels to bulkhead and pulley
or equivalent). brackets.
k. Install headliner by reversing removal proced- n. Replace damaged parts and reassemble by
ures and bonding affected areas with cement (EC880 reversing the removal procedures.
Minnesota Mining and Manufacturing Co., or
equivalent). NOTE

Removal and Installation of Carpet. (See figure 3-10.) When assembling parts to forward cabin
pressure bulkhead, be sure that parts are
a. Remove front and passenger seats in accordance sealed in accordance with Section 16.
with seat removal procedures.
b. Remove kick plates (3, 4, 13 and 14) by remov- WING.
ing attaching screws.
c. Remove screws attaching cover plates (2 and Removal of Wing. (See figure 3-12.)
15) to floorboards and pedestal installation, remove
cover plates. a. Drain fuel system at four places: cross feed
d. Remove carpet retainers (12) by removing attach- drain, sediment bowl, main tank and sump drain,
ing screws. and auxiliary tank and sump drain.
e. Remove carpets (5, 6, 7, 10, 11 and 8) by re-
moving attaching screws. NOTE
I, Remove forward bulkhead carpet (1) by carefully
peeling the bonded carpet from metal. Wings can be removed with fuel tanks installed.
g. Install carpets by reversing removal procedures If fuel tank removal is desired, remove in ac-
and bonding affected carpets using cement (EC880 cordance with Section 11.
Minnesota Mining and Manufacturing Co., or equiva-
lent), b. Remove engines in accordance with removal pro-
cedures in Section 9.

Removal and Installation of Control Pedestal. (See CAUTION

figure 3-11. )
If one or both engines are removed, the air-
NOTE craft may become tail heavy. To balance
aircraft use weights (such as shot bags or
The control pedestal is riveted to the forward sand bags) in the nose compartment and sup-
cabin bulkhead and should not be removed port the tailcone.
unless damaged.
c. Jack aircraft in accordance with jacking proced-
a. Remove front seats, front carpet and kick ures in Section 2.
Change 8
 421 SERVICE MANUAL AIRFRAME 3-19

Detail $
1 2
Detail A

A A
. 15 ±. ois )
20° ±30'

0811350 †
FITTING \

VIEW
CHAMFER AS SHOWN A52203001
0 o 00
Detail

1. Nut 4. Nut 6. Bolt

2. Washer 5. Washer 7. Countersunk Washer
3. Bolt

Figure 3-12. Wing Installation

Change 11
3-20 AIRFRAME 421 SERVICE MANUAL

d. Place suitable padded supports (cradles) beneath spars 35. 50 inches from fuselage centerline
each stub wing, tailcone, and wing; then remove on stub wings, beneath tailcone bumper, and
jacks. wing root, and tip ribs. If both engines were
NOTE removed and weight was placed in nacelles,
remove weight after removing jacks.
To prevent damage to skin and rib sections,
place padded supports beneath front and rear

1
5
6

4
12
1514 10
13
11

1. Vacuum Line 10. Electrical Wire Bundle

2. Brake Line 11. Cabin Pressure Duct
3. Oil Pressure Line 12. Heater Fuel Line (RH wing only)
4. Electrical Wire Bundle 13. Autopilot Supply Line
5. Fuel Line 14. Fuel Line
6. Supercharger Pressure Line 15. Throttle Control
7. Manifold Pressure Line 16. Alternate Air Control
8. Fuel Pressure Line 17. Propeller Control
9. Fuel Selector Control 18. Mixture Control

Figure 3-13. Wing Root Connections

Change 11
 421 SERVICE MANUAL AIRPRAME 3• l

CAUTION a. Route engine control cables (15, 16, 17 and 18,

figure 3-13) through proper wing leading edge holes
If only one wing is being removed and the as wing is moved toward fuselage.
engine on the opposite wing remains install- b. Guiding main gear drive tube through wing, move
ed; relieve the engine weight on opposite wing toward fuselage until wing fittings engage and
wing by using engine hoist before removing attach drive tube in accordance with Section 4.
wing or serious damage, due to tipping, may c. Guide fuel selector cable (9, figure 3-13) through
result. opening in wing root rib.
d. Align bolt holes in front and rear spar fittings
e. Remove wing structural skins by removing at- and install bolts (3), washers (2), and nuts (1) on
taching screws. front spar fittings; and bolts (6), washers (5 and 7),
f. Disconnect or remove landing gear drive tube in and nuts (4) on rear spar fitting.
accordance with removal procedures outlined in Sec-
tion 4.
g. Remove flap cables from wing in accordance
with Section 8· NOTE
h. Remove aileron cables in accordance with Sec-
tion 5. Install front spar bolts with heads forward
i. On left wing only, remove aileron trim cables in and rear spar bolts with heads aft. Place
accordance with Section 5- countersunk washers (7) under heads of bolts
j. Remove engine controls in nacelle in accordance (6). Torque front spar nuts (1) to 60 ±5 foot
with Section 9. pounds, and rear spar nuts (4) to 175 ±15
k. (See figure 3-13. ) Disconnect and tag the follow- inch pounds.
ing items;
1. Vacuum line at union (1). NOTE
2. Wing wiring disconnect (4).
3. Fuel lines (5) and (14). Spar bolts are installed in a shear position.
4. Brake line at fitting (2). DO NOT OVERTORQUE. It is possible wing
5. Oil pressure line at fitting (3)- spar bolts will turn if a slight torque is ap-
6. Supercharger pressure line at fitting (6). plied to bolt head.
7. Manifold pressure line at fitting (7).
8. Fuel pressure line at fitting (8), e. If wing deice system (optional equipment) is
9. Fuel selector control (9). installed, connect the two ends of cut nylon line with
10. Electrical disconnect (10). two Cessna Part Number 81130-4 Nuts and one
11. Cabin pressure line at duct (11). S1132-4 Union.
12. Heater fuel line (12). Right wing only. f. Remove tags and connect the following items:
1. With engine controls (15), (16), (17) and (18) dis- 1. Vacuum line at fitting (1).
connected at engine, route cables through wing toward 2. Wing wiring disconnect (4).
the fuselage until the wing root is cleared. 3. Brake line at fitting (2).
m. If wing de-ice system (optional equipment) is 4. Oil pressure line at fitting (3).
installed, cut nylon line in wing root area. 5. Fuel lines (5 and 14).
n. (See figure 3-11. ) From wing attachment fittings, 6. Supercharger line at fitting (6).
remove nuts (1 and 4), washers (2, 5 and 7), and 7. Manifold pressure line at fitting (7).
bolts (3 and 6). 8. Fuel pressure line at fitting (8).
NOTE 9. Fuel selector control (9).
10. Electrical disconnect (10).
If difficulty is encountered in driving out wing 11. Cabin pressure duct (11).
bolts or disengaging fittings, it may be nec- 12. Heater fuel line (right wing only) at fitting (12).
essary to rock wing slightly. g. On left wing only, route and connect aileron trim
cables to trim tab in accordance with Section 5.
o. Move wing and padded supports outboard until h. Route and connect aileron cables to aileron and
wing attachment fittings have disengaged. rig in accordance with Section 5.
i. Route and connect flap cables to flap and rig in
3-12. ) accordance with Section 8.
Installation of Wing. (See figure
j. Connect landing gear drive tube to landing gear
NOTE in accordance with Section 4.
k. Jack aircraft in accordance with procedure out-
If a new wing(s), wing front spar (s), or front lined in Section 2.
spar fitting(s) is being installed on the aircraft,
the fuselage front spar fittings may have to be CAUTION
modified in accordance with figure. After per-
forming this modification, all bare surfaces If one or both engines were removed, the air-
must be color chemical filmed (Irridite 14-2), craft may become tail heavy. To balance
Allied Research Produet) per manufacturer's aircraft use weights (such as shot bags or
instructions, then primed with zinc chromate sand bags) in the nose compartment and sup-
primer. port the tailcone.

Change 11
 AIRFRAME 421 SERVICE MANUAL

Detail

Detail $
10542007
Detail A10543002
B
C10542009

1. Bolt 14. Nut 26. Support 38. Spring

2. Washer 15. Screw 27. Screw 39. Cylinder Assembly
3. Stat-o-seal 16. Support 28. Screw 40. Screw
4. Hinge Strap 17. Cotter Pin 29. Lockwasher 41. Lockwasher
5. Nut 18. Screw 30. Lock Arm 42. Latch Handle Retainer
6. Door Assembly 19. Screw 31. Nut 43. Button
7. Screw 20. Cotter Pin 32. Pin 44. Spring
8. Washer 21. Bolt Latch 33. Screw 45. Spacer
9. Spacer 22. Spring 34. Pin 46. Latch Handle
10. Stop Assembly 23. Pin 35. Screw 47. Link
11. Screw 24. Block Guide 36. Washer 48. Spacer
12. Spacer 25. Spacer 37. Shell 49. Seal
13. Bracket

Figure 3-14. Wing Locker Installation

Change 12
 421 SERVICE MANUAL AIRFRAME 3-22A/3-22B

1. Leave tailcone support in place, remove padded key that operates the cabin door. Door stays are
supports from beneath fuselage and wings, provided to support the door when it is open,
m. Install engines in accordance with installation
procedures of Section 9.
n. Remove tailcone support and jack. Removal and Installation of Wing Locker Door. (See
o. Check for correct cable tensions, proper opera- figure 3-14.)
tion, and correct travel of flaps, ailerons, and ailer-
on trim tabs. Refer to rigging procedures for limits a. Open wing locker door.
and tolerances. b. Remove screw (11), washer (12), and spacer (13)
p. Service aircraft, then check for fuel leaks at from lower end of stop assembly (10).
fuel tank and wing root connects. c. Remove nuts (5), washers (2), stat-o-seals (3)
q. Install structural skins. Start engines and check and bolts (1) from door hinge (4) and remove door
operation of electrical equipment and engine controls. from nacelle.
d. Install wing locker door by reversing removal
Wing Locker procedures.

The wing locker compartments are located just aft of

the engine nacelle compartment in each wing nacelle. Removal and Installation of Wing Locker Door Latch.
The wing locker door is located on the aft side of the
wing and can be opened by a push type, flush mounted Removal and installation of wing locker door latch is
snap latch. The door locks are opened by the same not recommended unless replacement or repair is

Change 12
 421 SERVICE 1VIANUAL AIRFRAME 3 Û
I

Detail
421A0001 and ON

421-0001 TO 421A0001

1. Fastener 3. Glide Slope Antenna 4. Screw

2. Seal 5. Washer
Figure 3-15. Radome Installation

necessary. Use figure 3-14 as a guide for removal Should replacement of the lock assembly be necessary,
and installation. loosen nut securing the lock assembly to door and
remove. Assembly of nose baggage compartment
door is the reversal of disassembly procedure.
NOSE

The nose section of the fuselage provides a baggage Installation of Nose Baggage Compartment Doors.
area accessible through two baggage compartment
doors. The lower center section of the nose pro- a. To install nose baggage compartment doors,
vides a housing for the rectractable nose gear with position door in place and install bolts and nuts
space on the right side for the cabin heater and through hinges making sure the spacers are in place
space on the left side for electronics equipment. in the hinges.
The nose cap area may be used for optional elect-
ronics equipment and radome installation NOTE

The installation procedure is the same for

Removal of Nose Baggage Compartment Doors. either left or right hand nose baggage com-
partment.
a. The removal of the nose baggage doors is the
same for either left or right nose baggage door. Radome.
b. Remove nuts and screws in door hinges and re-
move door. The radome is a covering designed to protect the
radar antenna from the elements. It is part of the
NOTE nose section and has certain physical and electrical
properties. Physically, the radome must withstand
Do not lose spacers out of door hinges, airloads subjected to it and also minimize drag.
Electrically, the radome must permit passage of the
radar transmitted signals and return echoes with min-
Disassembly and Assembly of Nose Baggage Compart- imum distortion and absorption. In order to do this,
ment Doors. it must have a certain electrical thickness and this is
related to the physical thickness, operating frequency
No disassembly of nose baggage compartment doors and type of material and construction. This relation-
is recommended. If hinges are to be replaced, rivets ship is defined by a number of complex mathematical
securing the hinge to door must be drilled out. equations. These equations show that for given phy-
3-24 AIRFRAME 421 SERVICE MANUAL

sical properties a radome will have certain electrical i. Removerudder trim tab actuator cables from
thickness for a narrow range of operating frequencies. Verticalstabilizer in accordance with Section 7.
This is why C-band radomes will not give optimum j. Remove screws securing rudder trim tab cable
performance with X-band radar and vice-versa. Also, bracket (10) to vertical stabilizer spar.
a very small variation in physical thickness will k. Remove screws (3) in dorsal fin.
cause a sizeable variation in electrical thickness. 1. Remove forward spar nuts (6), washer and bolt
This can mean the difference between an efficient (4).
radome and an inefficient radome that can reduce m. Remove nuts, washers and aft spar bolts (7).
radar range, distort displays and cause inaccurate n. Disconnect antenna lead at fuselage.
directions and false targets. o. Disconnect deice line inside of tailcone if optional
deice is installed.
Removal and Installation of Radome (See figure 3-15. ) p. Lift vertical stabilizer vertically until front spar
has cleared fuselage and remove from aircraft.

NOTE Installation of Vertical Stabilizer.

Installation and removal is the same The installation of the vertical stabilizer is the
for standard nose cap or for radome, reversal of the removal procedures.

a. Unfasten lock fasteners or screws around the

periphery of the radome. Removal of Horizontal Stabilizer. (See figure 3-17. )
b. Slide radome forward sufficiently to disconnect
glideslope antenna lead. a. Place a suitable support under tailcone.
c. Reverse this procedure for installation. b. Remove rudder in accordance with Section 7.
c. (See figure 1-2.) Remove access cover (19).
d. Remove elevator trim tab cables from the stab-
Repair of Radome. ilizer in accordance with Section 6,
e. Remove nuts (3), Washers (4) and bolts (1) in
Refer to Section 16 for repairs of radome. rear spar cap (2).
f. Remove nuts (3), washers (4) and bolts (9) in
front spar.
STABILIZERS g. Lift rear spar sufficiently to clear trim tab
pulley brackets and move horizontal stabilizer aft to
Removal of Vertical Stabilizer (See figure 3-16.) remove.

a. (See figure 3-16.) Remove fairings and stinger NOTE

cap.
b. (See figure 1-2.) Remove access covers (5, 6 Elevators need not be removed to remove
and 18). stabilizer from empennage. However, if
c. Place suitable support under tailcone. elevators are to be removed, see Section 6
d. Remove rudder in accordance with Section 7. for removal procedures.
e. Remove rudder cables from vertical stabilizer
pulley bracket. Installation of the Horizontal Stabilizer.
f. Disconnect elevator cables from elevator bell-
crank in accordance with Section 6. The installation of the horizontal stabilizer is the
g. Disconnect elevator downspring from elevator reversal of the removal procedures,
bellerank.
h. Remove elevator trim cables in accordance with
Section 6.
 421 SERVICE MANUAL AIRFRAME 3-25

34b6 7

Detail

øø
10

1. Fiberglass Tip 4. Bolt 8. Rudder Bellcrank Stop Bolt

2. Vertical Stabilizer 5. Washer 9. Lower Hingë Assembly
3. Screw 6. Nut 10. Pulley Bracket
7. Bolt

Figure 3-16. Vertical Stabilizer Installation

 AIRFRAME 421 SERVICE MANUAL

11 2
1

Detail / Detail

9
10

Detail

1. Bolt 5. Horizontal Stabilizer 9. Bolt

2. Stabilizer Rear Spar 6. Left stabilizer Fairing 10. Stabilizer Front Spar
3. Nut 7. Screw 11. Fuselage Stinger
4. Washer 8. Right Stabilizer Fairing

Figure 3-17. Horizontal Stabilizer Installation

 421 SERVICE MANUAL LANDING GEAR AND 4-1
BRAKE SYSTEM

SECTION 4

LANDING GEAR AND BRAKE SYSTEM

Table of Contents

Page Page

LANDING GEAR SYSTEM

Troubleshooting . . . . . .
4-2 Nose Gear Shimmy Dampener . .
4-42B
Landing Gear Actuator . . . .
4-6 Removal . . . . . .
4-42B
Troubleshooting Landing Gear Motor .
4-6 Disassembly . . . . .
4-44
Removal . . . . . . .
4-6A Assembly . . . . . .
4-44
Installation . . . . . .
4-6A Installation . . . . .
4-44
Manual Extension System . . . .
4-7 Nose Gear Steering System . .
4-44
Removal . . . . . . .
4-9 Removal . . . . . .
4-44
Installation . . . . . .
4-9 Installation . . . . .
4-46
Main Landing Gear . . . . .
4-11 Rigging . . . . . .
4-46
Removal . . . . . . .
4-11 Nose Wheel and Tire Assembly . .
4-46
Disassembly . . . . . .
4-13 Removal . . . . . . .
4-46
Assembly . . . . . .
4-13 Disassembly and Assembly . .
4-46
Installation . . . . . .
4-16 Installation . . . . . .
4-46
Main Wheel Alignment . . . .
4-16 Main Wheel and Tire Assembly . .
4-46
Removal of Main Gear Torque Links .
4-16B Removal . . . . . . .
4-46
Disassembly of Main Gear Torque Disassembly . . . . . .
4-48
Links . . . . . . .
4-16B Cleaning and Inspection . . .
4-48
Assembly of Main Gear Torque Links .
4-16B Replacement of Bearing Cup . .
4-50
Installation of Main Gear Torque Replacement of Keyway Liner . .
4-50
Links . . . . . . .
4-16B Retreating and Repainting of Main
Main Landing Gear Doors . . .
4-17 Whee1Repaired Surfaces . .
4-50
Removal . . . . . .
4-17 Assembly . . . . . .
4-50
Installation . . . . .
4-17 Installation . .
4-51
Rigging . . . 4-17 BRAKE SYSTEM -
MAIN AND PARKING .
4-51
Main Landing Gear Retracting Troubleshooting . . . . . .
4-51
Linkage . . . . .
4-19 Removal . . . . . . .
4-52
Removal . . . . . .
4-19 Installation . . . . . . .
4-52
Installation . . . . .
4-24 Checking of the Wearing of Brake Dises .
4-54
Rigging of Main and Nose Landing Gear 4-25 Removal and Disassembly of Main
Adjustment of Landing Gear Safety Wheel Brake Assembly . . .
4-54
Switch . . . . . .
4-33 Cleaning of Brake Assembly Parts . .
4-54
Adjustment of Landing Gear Warning Inspection of Brake Assembly Parts .
4-55
System . . . . . .
4-33 Replacement of Wear Pads on Pressure
Nose Gear . . . . . . .
4-34 Plate and Back Plate . . . .
4-56
Removal . . . . . . .
4-34 Applying Protective Coating . . .
4-56
Disassembly . . . . . .
4-35 Repairing Torque Tube . . . .
4-57
Assembly . . . . . .
4-35 Repairing the Housing . . . .
4-57
Installation . . . . . .
4-37 Repairing the Piston . . . . .
4-57
Removal and Disassembly of Nose Retreating and Repainting Brake
Gear Torque Link Assemblies .
4-37 Housing . . . . . . .
4-57
Assembly and Installation of Nose Installation and Assembly of Main
Gear Torque Link Assetnblies .
4-37 Wheel Brake . . . . . .
4-57
Nose Gear Doors . . . . .
4-39 Bleeding the Brake System . . .
4-57
Removal . . . . . .
4-39 Parking Brake Valves . . . .
4-57
Installation . . . . .
4-39 Master Cylinder . . . . . .
4-58
Rigging . . . . . .
4-39 Removal . . . . . . .
4-58
Nose Gear Retracting Linkage . .
4-40 Disassembly . . . . . .
4-60
Removal . . . . . .
4-40 Assembly . . . . . .
4-60
Installation . . . . .
4-41 Installation . . . . . .
4-60

Change 6
4--2 LANDIN6 GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

LANDING GEAR. at the right side of the pilot's seat. Limit switches
control the UP and DOWN limits and prevent over-
The landing gear is a fully-retractable tricycle land- travel by opening the electrical circuits to the motor
ing gear consisting of a main gear located aft of each when the correct amount of travel has been attained.
engine nacelle, and a nose gear located in the nose There is a position indicator switch located on each
section of the fuselage. Each landing gear is con- gear to indicate when the landing gear is down and
nected mechanically to a single gear box driven by an locked. A safety switch prevents accidental retrac-
electric motor. In the event of landing gear electri- tion on the ground by opening the landing gear elec-
cal system failure, the landing gear can be extended trical circuit while the weight of the aircraft is on
by operating the manual extension hand crank located the landing gear.

Trouble Shooting the Land ng Gear System.

TROUBLE PROBABLE CAUSE CORRECTION

LANDING GEAR FAILS Manual extension crank improperly Stow crank properly.
TO RETRACT GEAR -

stowed.
MOTOR OPERATES
Defective landing gear actuator. Replace actuator.

Defective reduction unit. Replace reduction unit.

Pin sheared on gear motor shaft. Replace pin.

Broken bolts or retracting linkage, Replace broken parts. Connect linkage if

or disconnected retracting linkage, disconnected.

LANDING GEAR FAILS Circuit breaker out. Reset circuit breaker.

TO RETRACT GEAR -

MOTOR DOES NOT Defective circuit breaker. Replace circuit breaker.

OPERATE
Insufficient electrical power. Recharge batteries. Check voltage regula-
tors.
Defective UP limit switch. Replace switch. Adjust in accordance with
rigging procedure.

Defective landing gear safety switch. Replace switch.

Incorrectly adjusted landing gear Adjust safety switch,

safety switch.

Defective landing gear relay. Replace relay.

Defective landing gear switch. Replace switch.

Defective landing gear motor. Replace motor.

Defective UP electrical circuit. Repair circuit.

LANDING GEAR FAILS Landing gear incorrectly rigged Rig in accordance with rigging procedure.
TO RETRACT COM- for retracted position.
PLETELY
Circuit breaker out, due to over- Reset circuit breaker and rig in accordance
load caused by incorrect landing with rigging procedure.
gear rigging.

Circuit breaker out, due to over- Reset circuit breaker, replace defective
load caused by defective retracting linkage, rig in accordance with rigging
linkage. procedure.

UP limit switch incorrectly adjusted. Adjust in accordance with rigging procedure.

ONE LANDING GEAR Retracting linkage to affected gear Replace broken parts. Connect linkage if
FAILS TO RETRACT broken or disconnected. disconnected. Rig in accordance with
rigging procedure.
 421 SERVICE MANUAL LANDING SEAR AND
BRAKE SYSTEM
-------mmmmmmmmmimmr

TROUBLE PROBABLE CAUSE CORRECTION

ONE LANDING GEAR Affected landing gear incorrectly Rig in accordance with rigging procedure.
FAIIß TO RETRACT rigged for retracted position.

Defective retracting linkage to Replace defective linkage and rig in accord-

affected landing gear. ance with rigging procedure.

LANDING GEAR FAIIß Manual extension crank improperly Stow crank properly.
TO EXTEND- GEAR stowed.
MOTOR OPERATES
Defective landing gear actuator. Replace actuator.

Defective reduction unit. Replace reduction unit.

Pin sheared on gear motor shaft. Replace pin.

Broken bolts or retracting linkage, Replace broken parts. Connect linkage if

or disconnected retracting linkage. disconnected.

LANDING GEAR FAILS Circuit breaker out. Reset circuit breaker.

TO EXTEND GEAR -

MOTOR DOES NOT Defective circuit breaker. Replace circuit breaker.

OPERATE
Insufficient electrical power. Recharge batteries. Check voltage regu-
lators.

Defective DOWN limit switch. Replace switch. Adjust in accordance

with rigging procedure.

Defective landing gear switch. Replace switch.

Defective landing gear motor. Replace motor.

Defective DOWN electrical circuit. Repair circuit.

LANDING GEAR FAILS DOWN limit switch incorrectly Adjust in accordance with rigging procedure.
TO EXTEND COM- adjusted.
PLETELY
Landing gear incorrectly rigged Rig in accordance with rigging procedure.
for the DOWN position.

Circuit breaker out, due to over- Reset circuit breaker and rig in accordance
load caused by incorrect rigging. with rigging procedure.

Circuit breaker out, due to over- Reset circuit breaker, replace defective
load caused by defective retracting linkage, and rig in accordance with rigging
linkage. procedure.

ONE LANDING GEAR Retracting linkage to affected gear Replace broken parts. Connect linkage if
FAILS TO EXTEND broken or disconnected. disconnected. Rig in accordance with rig-
ging procedure.

ONE LANDING GEAR Affected landing gear incorrectly Rig in accordance with rigging procedure.
FAILS TO EXTEND rigged for the DOWN position.
COMPLETELY
Defective retracting linkage to Replace defective linkage and rig in accord-
affected gear. ance with rigging procedure.

MANUAL EXTENSION Manual extension crank not fully Engage crank fully.
SYSTEM FAILS TO EX- engaged.
TEND LANDING GEAR
Incorrect adjustment of manual Adjust linkage in accordance with rigging
extension linkage. procedure.

Defective manual extension linkage. Replace defective linkage.

4-4 LANDING GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

TROUBLE PROBABLE CAUSE CORRECTION

MANUAL EXTENSION SYS- Defective landing gear retracting Replace defective linkage or actuator
TEM FAILS TO EXTEND linkage or actuator.
LANDING GEAR (CONT.)
Landing gear improperly rigged. Rig landing gear in accordance with
rigging procedure.

I
GEAR UP (AMBER) LIGHT Circuit breaker out. Reset circuit breaker.
FAILS TO LIGHT*
Defective circuit breaker. Replace circuit breaker.
*421-0001 to 421BO201
Lamp burned out. Replace lamp.

Lamp loose. Repair or replace receptacle.

Defective electrical circuit. Repair circuit.

Landing gear not fully retracted. Retract fully.

Defective or incorrectly adjusted Replace and/or adjust switch in ac-

UP limit switch. cordance with rigging procedure.

I
GEAR UP (AMBER) LIGHT Defective UP limit switch. Replace switch and ad3ust in accord-
REMAINS ON WHEN GEAR ance with rigging procedure.
IS DOWN*
Circuit shorted to another system. Locate and repair.

LEFT GEAR DOWN (GREEN) Circuit breaker out. Reset circuit breaker.
RIGHT GEAR DOWN (GREEN)
NOSE GEAR DOWN (GREEN) Defective circuit breaker or elect- Replace circuit breaker. Replace
LIGHTS FAIL TO LIGHT rical circuit. defective electrical circuit.

Lamps burned out. Replace lamps.

Lamps loose. Repair or replace receptacle.

Landing gear not fully extended. Extend fully.

One or more DOWN indicator switches Replace defective switches and/or

defective or incorrectly adjusted, adjust in accordance with rigging
procedure.

LEFT GEAR DOWN (GREEN) Circuit shorted to another system. Locate and repair.
RIGHT GEAR DOWN (GREEN)
NOSE GEAR DOWN (GREEN) Defective switch. Locate and repair or replace.
LIGHT REMAINS ON WHEN
GEAR IS UP

LEFT GEAR DOWN (GREEN) One or more DOWN indicator switches Replace defective switches and/or
RIGHT GEAR DOWN (GREEN) defectiveor incorrectly adjusted. adjust in accordance with rigging
NOSE GEAR DOWN (GREEN) procedure.
LIGHT FLICKERS WHEN
GEAR IS DOWN Loose lamp. Repair or replace receptacle.

GEAR WARNING HORN Defective gear DOWN indicator switch. Replace defective switch and adjust
SOUNDS IN FLIGHT WHEN in accordance with rigging proce-
LANDING GEAR IS DOWN dure.
AND THROTTLES ARE
RETARDED

GEAR WARNING HORN Defective throttle microswitch. Replace switch and adjust in accord-
SOUNDS IN FLIGHT WHEN ance with rigging procedure.
LANDING GEAR IS UP AND
THROTTLES ARE NOT Incorrectly adjusted throttle micro- Adjust in accordance with rigging
RETARDED switch. procedure.

Change 4
 421 SERVICE MANUAL LANDING OEAR AND 4-5
BRAKE SYSTEM

TROUBLE PROBABLE CAUSE CORRECTION

GEAR WARNING HORN Incorrectly adjusted gear DOWN Replace switch and adjust in accordance
SOUNDS ON THE indicator switches. with rigging procedure.
GROUND WHILE LAND-
ING GEAR SWITCH IS Defective gear DOWN indicator Replace switch and adjust in accordance
DOWN switches. with rigging procedure.

GEAR WARNING HORN Circuit shorted to another system. Locate and repair.
SOUNDS WHEN BAT-
TERY SWITCH IS incorrectly adjusted gear DOWN Adjust switch in accordance with rigging
TURNED ON, OR indicator switches. procedure.
SOUNDS WHEN AN
UNRELATED SYSTEM Defective gear DOWN indicator Replace switch and adjust in accordance
IS TURNED ON switches. with rigging procedure.

GEAR WARNING HORN Circuit breaker out. Reset circuit breaker.

FAILS TO SOUND WHEN
LANDING GEAR SWITCH Defective circuit breaker. Replace circuit breaker.
IS PLACED UP WHILE
ON THE GROUND Landing gear safety switch incor- Adjust in accordance with rigging procedure.
rectly adjusted.

Defective landing gear safety switch. Replace switch and adjust in accordance
with rigging procedure.

Defective electrical circuit. Repair circuit.

Defective warning horn or flasher Replace horn or flasher unit.

unit.

GEAR WARNING HORN Circuit breaker out. Reset circuit breaker.

FAILS TO SOUND IN
FLIGHT WHEN LAND- Defective circuit breaker. Replace circuit breaker.
ING GEAR IS UP AND
THROTTLES ARE Defective gear DOWN indicator Replace switch and adjust in accordance
RETARDED switches. with rigging procedure.

Defective electrical circuit. Repair circuit.

Defective warning horn. Replace horn.

Throttle microswitch incorrectly Adjust in accordance with rigging procedure.

adjusted.

Defective throttle microswitch. Replace switch and adjust in accordance

with rigging procedure.

LANDING GEAR DOORS Doors incorrectly rigged. Rig doors in accordance with rigging
FAIL TO OPERATE procedure.
PROPERLY
Defective door operating linkage. Replace defective linkage.

LANDING GEAR SHIM- Insufficient fluid in shimmy damp- Service shimmy dampener in accordance
MIES DURING FAST ener. with Section 2.
TAXI, TAKEOFF, OR
LANDING Internal leakage in shimmy damp- Replace defective seals and/or piston.
ener.

Roll pin attaching piston to piston Replace roll pin,

rod sheared.

Shimmy dampener loose at mount- Replace worn housing and/or attaching bolt.
ing.

Tires out of balance, Replace tires when tread is worn unevenly

or has flat spots.
4-6 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

TROUBLE PROBABLE CAUSE CORRECTION

LANDING GEAR SHIM- Worn or loose wheel bearings. Replace and/or adjust bearings.
MIES DURING FAST
TAXI, TAKEOFF, OR Excessive clearance between upper Adjust clearance in accordance with align-
LANDING (CONTINUED) and lower torque links. ment procedure.

Worn torque link bushings. Replace bushings.

EXCESSIVE OR UN- Incorrect operating pressure. Inflate to correct pressure.

EVEN WEAR ON
TIRES Incorrect wheel alignment. Align in accordance with alignment proce-
dure.

Wear resulting from shimmy. See the preceding corrections for shimmy.

NOSE GEAR FAILS TO Incorrect rigging of nose gear Rig in accordance with nose gear steering
STEER PROPERLY steering system. procedure.

One brake dragging. Determine cause and correct.

Defective nose gear steering springs. Replace springs.

NOSE GEAR FAILS TO Gimbal broken or damaged at the Replace defective gimbaL
STRAIGHTEN WHEN top of the nose strut.
LANDING GEAR EX-
TENDS Incorrect rigging of nose gear Rig in accordance with nose gea.r steering
steering system. procedure.

NOSE GEAR FAILS TO Gimbal broken or damaged on top Replace defective gimbal.
STRAIGHTEN WHEN of the nose strut.
LANDING GEAR RE-
TRACTS

ATTITUDE OF AIR- Landing gear struts incorrectly Inflate struts correctly.

CRAFT ON GROUND inflated.
IS INCORRECT

STRUT BOTTOMS ON Insufficient air and/or fluid in strut. Service strut with proper amount of fluid
NORMAL LANDING OR and air.
TAXIING ON ROUGH
GROUND Defective internal parts in strut. Replace defective parts.

STRUT DEFLATED Defective Ò-rings. Determine which O-rings are defective and
WITH EVIDENCE OF replace.
FLUID LEAKAGE

Landing Gear Actuator. actuator worm gear. The bellerank that operates the
main landing gear drive tubes is attached to the upper
The landing gear actuator consists of an electric mo- end of the sector shaft, which extends vertically
tor, a reduction unit, and a worm-and-sector assem- through the actuator assembly, and the bellerank that
bly. The actuator is normally operated by the elec- operates the nose gear drive tube is attached to the
tric motor; however línkage is provided to disengage lower end of the sector shaft. Adjustable limit
the motor-driven reduction unit and engage the man- switches are provided so that correct landing gear
ual extension system, which is linked directly to the travel can be obtained.

Troubleshooting the Landing Gear Actuator Motor.

TROUBLE PROBABLE CAUSE CORRECTION

BRAKE DOES NOT Loosen or open connections or cir- Check test connections; if all right, test mo-
RESPOND AS cuits. Improper assembly. tor circuits for proper resistance, check
REQUIRED for proper brake air gap. Adjust or replace
defective parts.

Change 3

i
 421 SERVICE MANUAL LANDING GEAR AND 4-SA 4"$$
BRAKE SYSTEM

Troubleshooting the Landing Gea.r Actuator Motor (Continued).

TROUBLE PROBABLE CAUSE CORRECTION

SPEED IS TOO LOW Incorrect end play, shorted Check motor for correct
OR CURRENT IS armature circuit, excessive end play. If all right, test
TOO HIGH bea.ring friction. motor circuits for shorts.
Replace defective parts.

MOTOR WILL NOT Circuit breaker out. Reset breaker; if breaker

RUN will not remain set, check
for shorted wiring in field
circuit. If field circuit is
shorted, refer to Landing
Gear and Flap System Com-
ponents Overhaul/Parts
Manual and repair or re-
place motor.

MOTOR NOISY Faulty bearings or armature Refer to Landing Gear and

dragging. Flap System Components
Overhaul/Parts Manual
and repair or replace
motor.

Removal of Landing Gear Actuator. (See figure 4-1. ) NOTE

a. Jack the aircraft in accordance with Section 2. When removing the motor, disconnect and tag
b. Remove the rear seats and carpet. all electrical wires at the quick-disconnects
c. Remove cabin floor above landing gear actuator provided.
and access hole cover from underside of fuselage be-
neath landing gear actuator. m. Remove switch brackets from actuator assembly.
d. Release tension on retracting linkage by engag- Do not disturb switch adjustments except to replace
ing manual extension crank and operating a few turns switches or brackets.
toward the UP position.
e. Disconnect both main landing gear drive tubes NOTE
from idler belleranks.
f. Remove nut (5), washer (6), caps (7 and 40) and If switches are to be replaced, tag wires be-
bolt (39) securing upper and lower belleranks to the fore disconnecting.
sector shaft.
g. Lift upper bellerank (12) enough to allow main n. Remove the two bolts, washers, and nuts attach-
gear drive tubes to be disconnected. Remove nuts, ing actuator assembly to forward bracket,
washers, and bolts attaching main gear drive tubes o. Lift actuator assembly vertically and remove
(10 and 48) to upper bellerank (12) and slide both from aircraft.
tubes outboard so they will not interfere with re-
moval of actuator. Installation of Landing Gear Actuator. (See figure
h. Lower bellerank (41) enough to allow nose gear 4-1.)
drive tube (37) to be disconnected. Remove nut and
bolt attaching nose gear drive tube to bellerank. a. Install lower bellerank on lower end of sector
i. Temporarily reinstall bolt (39), caps, washers shaft,
and nuts to prevent loss of belleranks and spacers NOTE
(13 and 42).
j. Disconnect manual extension disengage rod by When installing lower bellerank, align the
removing cotter pin and elevis pin. index punch mark on the bellerank with the
k. Disconnect the manual extension drive tubes by chamfered spline on the sector shaft.
removing the three clevis pins, washers, and cotter
pins; then slide outer shaft aft and inner shaft for- b. Position actuator assembly in position, aligning
ward to disconnect. On 421-0182 and ON aircraft manual extension outer and inner shaft so they will
slide torque shaft and universal joint forwa.rd to dis- mate.
connect
1. Remove safetywire from bolts to be removed; NOTE
then remove the four bolts and washers attaching re-
duction unit and actuator assembly to the aft bulkhead. To facilitate installation, install all actua-
tor attaching bolts before any bolts are
tightened.

Change 7
 421 SERVICE MANUAL LANDING OEAR AND 4-Î
BRAKE SYSTEM

c. Install the two bolts attaching the actuator to the

I
forward
securing
mounting
actuator
bracket and bolt, washers
to side support.
d. Install the four bolts and washers attaching
ator assembly and reduction unit to bulkhead.
and nut

actu-
1. Place spacer and upper

NOTE
bellerank on sector shaft.

NOTE When installing upper bellerank, align the

index punch mark on the bellerank with the
Shim as required between reduction unit (3) chamfered spline on the sector shaft.
and bulkhead (4) to align reduction unit gear
with the drive gear in the actuator. m. Attach nose gear drive tube to lower bellerank
with bolt, washer, and nut.
CAUTION n. Insure that lower bellerank and spacers are
correctly in position and install bolt, caps, washers,
Use of bolts of improper length may cause and nut.
damage or binding. o. Connect main landing gear drive tubes to idler
belleranks with bolts, spacers, and nuts.
e. If motor was removed, connect the electrical p. Connect forward push-pull tube to fork bolt with
wires at the quick-disconnect provided. bolt and nut.
f. Install switch brackets with bolts, washers, and q. Perform an operational check of landing gear,
nuts. check especially that limit switches are correctly
adjusted and landing gear is correctly rigged.
CAUTION r. Install cabin floor panel and access hole cover on
underside of fuselage beneath landing gear actuator.
Check switches thoroughly for proper opera- 8. Install rear carpet and seats removed for remov-
tion. A faulty switch may cause damage to al of actuator,
the landing gear actuator. t. After making sure landing gear is DOWN and
locked, remove aircraft from jacks.
g. Tighten all nuts and bolts which were installed
but not tightened.
h. Safetywire bolts attaching actuator to the bulk- Manual Extension System.
head.
i. Connect manual extension drive tubes with clevis The manual extension system consists of a hand
pins and washers, and safety with cotter pins. On crank, which is connected to the landing gear ac-
421-0182 and ON aircraft connect torque shaft and tuator by an arrangement of chain and sprockets,
universal joint with clevis pins and washers, and belleranks, miter gears, and push-pull rods. The
safety with cotter pins. hand crank, located at the right of the pilot's seat,
j. Connect the manual extension disengage rod with is provided with a spring-loaded release button
elevis pin and safety with cotter pin. which unlocks the hand crank so that it can be
k. Position upper bellerank above actuator assem- folded into the stowed position. When the hand
bly, slide main gear drive tubes inboard and attach crank is folded, it disengages the manual extension
to bellerank with bolts, washers, and nuts. Install system; when unfolded, into its operating position,
bolts with their threaded ends UP. the hand crank disengages the normal landing gear
operating system.
NOTE

Main gear drive tubes must be installed with

half-round side of end fitting upwards.

Change 11
4-8 LANDIN6 GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

30 50 35 34

421-0182 AND ON
3

Detail

49

47
46 29
26

"
29

as A e

Figure 4-1. Landing Gear Actuator Installation

Change 11
 421 SERVICE MANUAL LANDING OEAR AND 4-0
BRAKE SYSTEM

Figure 4-1. Landing Gear Actuator Installation Callouts

1. Landing Gear Motor 19. Washer 37. Nose Gear Drive Tube
2. Bolt 20. Bolt 38. Bolt
3. Reduction Unit 21. Washer 39. Bolt
4. Bulkhead , 22. Switch Bracket 40. Cap
5. Nut 23. Actuator Assembly 41. Lower Bellerank
6. Washer 24. Washer 42. Spacer
7. Cap 25. Nut 43. Manual Extension
8. Nut 26. Mounting Bracket Disengage Rod
9. Washer 27. Nut 44. Down Limit Switch
10. Main Landing Gear Drive Tube 28. Gear Shaft 45. Grease Fitting
11. Bolt 29. Cotter Pin 46. Bolt
12. Upper Bellcrank 30. Pin 47. Washer
13. Spacer 31. Washer 48. Main Gear Drive Tube
14. Bolt 32. Outer Shaft 49. Support
15. Washer 33. Inner Shaft 50. Torque Shaft
16. Switch Bracket 34. Cotter Pin 51. U-Joint
17. Up Limit Switch 35. Washer
18. Bolt 36. Nut

Removal of Manual Extension System. (See figure replaced, the landing gear actuator must be
4-2. ) removed; then the support bracket removed
from front spar. The oilite bearings in which
a. Remove pilot's seat, the gear shafts rotate are a press fit, and
b. Remove left rear seats and carpet to gain access should be removed only for replacement.
to cover over extension system.
c. Remove access hole cover from cabin floor above Cleaning, Inspection, and Lubrication of Manual
the landing gear actuator. Extension System. (See Section 2. )
d. Remove chain guards by removing the three at-
taching seres. Installation of Manual Extension System. (See
e. Remove chain by disconnecting at the master Figure 4-2.)
link.
f. Remove crank handle and shaft assembly as fol- a. If the support bracket has been disassembled
lows: without removing the landing gear actuator, assemble
1. Remove roll pin and washer from shaft. as follows:
2. Remove cotter pin and clevis pin from spool. 1. Insert actuator drive tube thru the aft bushing;
3. Pull crank handle and shaft from supports, re- then install miter gear on shaft and insert roll pin.
moving spool as shaft is pulled through it. 2. Holding sprocket and other miter gear in posi-
g. Remove upper rod assembly by removing cotter tion, slide the shaft thru the gear and sprocket, then
pins, washers, and clevis pins attaching rod assem- insert the two roll pins.
bly to the belleranks. b. Connect drive tubes from landing gear actuator.
h. Remove upper bellerank by removing nut, wash- On 421-0182 and ON aircraft connect universal joint
er, and bolt; then remove bushing from bellerank. and torque shaft.
i. Remove lower rod assembly by removing cotter
pins, washer, and clevis pins attaching rod assembly NOTE
to lower bellerank and landing gear actuator.
j. Remove lower bellerank by removing nut, wash- AN3-6A bolt and MS428C nut with AN960-10
er, spacer, and bolt, washers may be installed in lieu of clevis pin
k. Remove chain tighteners by removing attaching (50), washer (51) and cotter pin (52) on univer-
screws and washers, then remove the adjusting sal joint if clevis pins are excessively loose.
screw, washers, and nut.
1. If support bracket is to be disassembled further, c. Install chain tighteners with attaching screws
proceed as follows: and washers; then install adjusting screw, washers,
1. Remove roll pins from sprocket and miter gear and nut, but do not tighten at this time.
and slide shaft out of bracket and remove sprocket d. Install lower bellerank with bolt, spacer, wash-
and miter gear. er and nut.
2. Disconnect drive tube from actuator by remov- e. Insert bushing into upper bellcrank then install
ing cotter pin, washer, and clevis pin. On 421-0182 bellcrank with bolts, washers, and nuts.
and ON aircraft disconnect universal joint from actu- f. II disassembled, reassemble crank handle and
ator by removing cotter pin, washer, and clevis pin. shaft with pins, cotter pins, nut and bolt.
3. Slide shaft with other miter aft and remove roll g. Install er ank handle and shaft assembly as follows:
pin; then remove the other miter gear. 1. Insert crank handle and shaft through inboard
support, spool, and the outboard support.
NOTE 2. Engage upper bellerank with spool, align spool
If bushings in the support bracket are to be attaching holes, and install pin and cotter pin.

Change 11
4-10 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

34

65--
28
66
0

62

52
73

51 52
A Detail A
58 421-0182 AND ON

421-0001 TO 421-0182

Figure 4-2. Manual Extension System Installation

 421 SERVICE MANUAL LANDING OEAR AND 4-11
BRAKE SYSTEM

Figure 4-2. Manual Extension System Installation Callouts

1. Clevis Pin 20. Clevis Pin 39. Screw 58. Actuator Assembly
2. Spacer 21. Clevis Pin 40. Screw 59. Clevis Pin
3. Spool 22. Cotter Pin 41. Chain Guard 60. Washer
4. Clevis Pin 23. Washer 42. Roll Pin 61. Cotter Pin
5. Spacer 24. Nut 43. Sprocket 62. Manual Extension
6. Shaft Assembly 25. Cotter Pin 44. Chain Disengage
7. Lug 26. Spacer 45. Gear Rod
8. Cotter Pin 27. Clevis Pin 46. Ring 63. Bellerank
9. Apool 28. Sprocket 47. Gear 64. Washer
10. Crank Assembly 29. Screw 48. Gear Shaft 65. Nut
11. Washer 30. Washer 49. Roll Pin 66. Spacer
12. Nut 31. Spacer 50. Clevis Pin 67. Cotter Pin
13. Pin Lock 32. Sprocket 51. Washer 68. Rod
14. Cotter Pin 33. Spacer 52. Cotter Pin 69. Bellerank
15. Spring 34. Washer 53. Shaft 70. Bushing
16. Clevis Pin 35. Nut 54. Clevis Pin 71. Screw
17. Bolt 36. Clevis Pin 55. Mounting Bracket 72. Cotter Pin
18. Cotter Pin 37. Spacer 56. Inner Shaft 73. Torque Shaft
19. Link 38. Washer 57. Outer Shaft 74. U-Joint

3. Place washer and collar on the shaft and install m. Install chain guards with attaching screws.
roll pin and safety. This washer is to remove end n. Install access hole cover on cabin floor above
play. the landing gear actuator.
h. Install chain on sprockets and connect with mas- o. Install rear carpet and seats.
ter link. Adjust chain tighteners and tighten adjust-
ing screw and nut.
i. Attach the lower rod assembly to the lower bell- Main Landing Gear.
crank and landing gear actuator with pins and wash-
ers and safety with cotter pins. Each main landing gear consists of a wheel and tire
j. Attach upper rod assembly to belleranks with assembly, brake assembly, lower piston assembly,
pins, washers, and cotter pins. cantilever axle, upper cylinder assembly, and
k. If the length of the upper or lower rod has been torque links. The Air·-oleo shock strut contains an
changed, adjust as follows: orifice and tapered metering pin which vary the re-
1. Place crank in operating position. sistance to shock according to its severity. During
2. Adjust lower rod assembly to a length of approx- extension and retraction, the landing gear pivots on
imately 18. 10 inches, measured between the rod end heavy-duty needle bearings by means of trunnion
bolt holes, and install. shafts attached to the upper cylinder assembly.
3. Pull lower rod assembly forward until internal
gear, in landing gear actuator, reaches the end of its
travel; adjust upper rod assembly so that rod and Removal of Main Landing Gear. (See figure 4-3. )
bolt holes align with holes in upper and lower bell-
cranks. a. Jack the aircraft in accordance with Section 2.
4. Lengthen upper rod assembly one-half turn and b. Drain brake system by loosening bleeder plug.
install. c. Disconnect brake hose at forward wheel well
bulkhead union. Plug hose and cap fittings to pre-
NOTE vent entry of foreign matter.
d. Remove safety switch and down indicator switch
If the upper rod assembly adjustment cannot by removing attaching screws and nuts.
be obtained because an excessive amount of e. Remove wire clamps and tie switches where they
threads would be exposed, readjust the lower will not interfere with gear removal.
rod assembly to obtain the desired result, and f. Release tension on retracting linkage by engaging
repeat steps "3" and "4. " manual extension crank and operating a few turns to-
ward the UP position.
1. Perform an operational check to see that manual g. Disconnect the main landing gear doors.
extension functions properly. h. Disconnect retracting linkage as follows:
1. Disconnect outboard push-pull tube from bell-
CAUTION crank by removing nuts, washers, and bolts. •

Do not use the manual extension system to

fully retract the landing gear, except when
manually pushing upward on all landing gears
to relieve strain on manual extension system.

Change 1
4-12 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

Detail
o ' 421-0001 W Detail 8
TO 421B502 i 5
6
421BOOO1 TO 421B0502

Detail

421B0502 & ON
10413007
lÎ A, C10413001
D,F10413001
Detaii F Detali D asisiioos
E51481001

1. Landing Gear Safety Switch 9. Bearing 17. Outboard Push-Pull Tube

2. Screw 10. Washer 18. Spacer
3. Bracket 11. Attaching Shaft 19. Down Indicator Switch
4. Screw 12. Truss Assembly 20. Spacer
5. Washer 13. Bolt 21. Screw
6. Nut 14. Bellerank 22. Side Lock Link
7. Nut 15. Washer 23. Bracket
8. Landing Gear Support 16. Nut 24. Nut

Figure 4-3. Main Landing Gear Installation

Change 11
 421 SERVICE MANUAL LANDING OEAR AND 4-lŽA A"Î$
BRAKE SYSTEM

2. Disconnect upper side link from lower side link only for replacement. Bearings must be re-
by removing nuts, washers, and bolts. moved by driving them toward the wheel well.
i. Remove roll pins from attaching shafts, and in-
sert AN6 bolt or puller tool. CAUTION
j. Support gear and pull attaching shafts.
NOTE the amount of thickness of washers re-
NOTE moved. These washers should be installed
exactly as they were located before removal
Needle bearings, in which the attaching shafts to insure proper alignment of side link assem-
pivot, are a press fit and should be removed bly.

ALL DIMENSIONS ARE IN INCHES

2. 750 2. 600
2. 150

1.375 1.075 1.300

4.00
MAIN LANDING DEAR
6 00
P/N 0880004-1

NOSE LANDING GEAR PN 0880004-2

2.750
2. 480
2. 100

1. 375 1. 050 1. 240

2. 00
1, 00
NOTES

1. Material to
be 4130 Type I steel.
2. Finish inside bore to smooth finish.
3. Cut cylinder on center line to form two halves.
4. Wrap cylinder with mystic tape 5812 (Stock Code
F840022) or equivalent. Cut tape on one side to
permit halves to hinge open.
5. Coat tool with light oil to prevent rust.

Figure 4-3A. Landing Gear Ring Pack Support Tool

Change 4
 421 SERVICE MANUAL LANDING OEAR AND 4"Î $
BRAKE SYSTEM

Disassembly of Main Landing Gear. (See figure 4-4. ) NOTE

On 421BOOO1 and On add shims (61) and/or
a. Completely deflate strut, and after all the air washers (62) as required between metering
has been expelled, remove the valve body and drain pin (5) and seal support (7) to maintain 112 .

fluid• ±. 005 inch between top of pin (5) and opening

b. Remove lower strut assembly from upper truss of orifice.
assembly as follows:
1. Disconnect brake hose from brake at elbow and
remove hose.
2. Remove wheel and tire assembly and brake as- 4. Slide lock ring (27), scraper ring (28), and in-
sembly from axle fitting. ternal lock ring (29) on piston barrel (10).
3. Disconnect torque links (14) by removing cotter 5. Install poly-pak seal (63) inside ring pack sup-
pin, nut (20), washer (21), spacer (19), clamp and port (34); then work O-ring (30) on the outside into
bolt (15). groove on ring pack support (34) and slide onto piston
4. Remove lock ring (27), scraper ring (28), and barrel (10).
internal lock ring (29).
5. Pull piston assembly (10) from upper trunnion
assembly (46). CAUTION
NOTE
Install poly-pak seal with wide lip up (toward
Lower piston barrel and axle fittings are a pressure area).
press fit and drilled on assembly. Disassem-
bly is not recommended. 6. Install spacer (35) on piston barrel (10).
7. Install inner bearing (36) on piston barrel (10)
CAUTION and secure with external lock ring (37).

NOTE
Removal and handling of the lower strut
should be done with care to prevent the
Install inner bearing with chamfered end up
possibility of damage to exposed parts.
in order to seat against external lock ring.
c. (See figure 4-4) Disassemble upper trunnion
assembly as follows: 8. Carefully O-ring (3) into groove in orifice
work
1. Remove bolts (48), washers (47), and nut (54). tube (4) and insert into trunnion assembly (46) from
2. Remove metering tube (4) from trunnion assem- the bottom, taking care to align holes.
bly (46) by pulling straight out. 9. Align holes and install two bolts (48), washers
(47), and nuts (54).
CAUTION 10. Carefully work piston barrel into trunnion as-
sembly (46) and slide ring pack support (34), internal
If the metering pin and seal support are to lock ring (29), scraper ring (28), and lock ring (27)
be reinstalled, use extreme caution during into trunnion assembly and secure.
removal.
NOTE
3. See Section 2 for cleaning and inspection of main
To prevent damage to piston barrel and ring
landing gear.
pack support during installation, a ring pack
support tool P/N 0880004-1 available from
your Cessna Dealers' Organization should be
used. (See Figure 4-3A. )
Assembly of Main Landing Gear. (See figure 4-4.)
b. Assemble torque links (14), if removed, to strut
NOTE assembly in accordance with installation of main gear
torque link procedures.
Before each component of the main landing e. Install brake assembly, wheel and tire assembly;
gear shock strut is assembled, assure that then connect hoses and clamp.
it isthoroughly clean, then lubricate with sys- d. Service strut with hydraulic fluid in accordance
tem hydraulic fluid- with Section 2. Do not fill with air at this time.
e. Install new O-ring (2) on valve body (1) and in-
a. Assemble landing gear as follows: stall in top of orifice tube (4).
1. Carefully work O-ring (6) over threads of meter- f. Install side braces removed with bolts, washers,
ing pin (5) and install in seal support (7) with nut (9). and nuts.
2. Install O-ring (8) in groove on outside of seal
support (7).
3. Insert seal support (7), with metering pin assem-
bled, into lower piston barrel (10).

Change 11
4-14 LANDING OEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

95051f2544753

55

4
11
36 20
35

li
Change
63

11
Figure 4-4.
13

Main Landing Gear Strut

51413004
10411010
 421 SERVICE MANUAL LANDING BEAR AND 4-15
BRAKE SYSTEM

Figure 4-4. Main Landing Gear Strut Callouts

1. Valve Body 17. Bushing 33. Deleted 49. Serew
2. Packing 18. Bushing 34. Ring Pack Support 50. Clamp
3. "O" Ring 19. Spacer 35. Spacer 51. Clamp
4. Metering Tube 20. Nut 36. Inner Bearing 52. Spacer
5. Metering Pin 21. Washer 37. External Lock Ring 53. Nut
6. "O" Ring 22. Deleted 38. Deleted 54. Nut
7. Seal Support 23. Cotter Pin 39. Screw 55. Bushing
8. "O" Ring 24. Deleted 40. Deleted 56. Deleted
9. Nut 25. Set Screw 41. Spacer 57. Placard
10. Barrel Piston 26. Bushing 42. Clamp 58. Spacer
11. Bolt 27. Lock Ring 43. Deleted 59. Spacer
12. Shaft 28. Scraper Ring 44. Nut 60. Reamer Tool
13. Roll Pin 29. Internal Lock Ring 45. Orifice 61. Shim
14. Torque Link 30. "O" Ring 46. Trunnion 62. Washer
15. Bolt 31. Deleted 47. Washer 63. Poly Pak Seal
16. Clamp 32. Deleted 48. Bolt

Installation of Main Landing Gear. k. Service strut in accordance with Servicing

Instructions in Section 2, then remove jacks.
a. If needle bearings were removed, install as fol- 1. Check landing gear alignment in accordance with
lows: Main Wheel Alignment and Figure 4--5.
1. Press needle bearings into landing gear sup-
ports. Bearings must seat against shoulders provided Main Wheel Alignment. (See figure 4-5.)
in supports,
b. Position gear in place; then install washers be-
Correct alignment of the main landing wheels is nec-
tween supports and trunnion and align holes• essary to minimize tire wear. If the tires are wear-
c. Install attaching shafts into gear trunnion and ing excessively or unevenly, the wheel alignment
align gear trunnion, washer, and bearing in the land- should be checked and corrected in accordance with
ing gear supports, then work the shafts into positions the following procedure:
using care to align holes in shaft and trunnion for the a. Position the aircraft with the main wheels rest-
mstallation of roll pin.
ing on grease plates.
NOTE
NOTE
The attaching shafts are a slip fit and should For each set of grease plates, use two alum-
be lubricated with light oil to aid in the in" inum sheets approximately 18 inches square
stallation of the shafts• with sufficient grease spread between them to
permit the top plates to slide freely on the
d. Remove AN6 bolt used in removal and installa¯ bottom plates.
tion of attaching shafts and install roll pin,
e. Connect side brace and push-pull tubes and gear b. Set a straightedge in place against the main
door using bolts, washers, and nuts, wheel tires at axle height as illustrated.
f. Install safety switch and down indicator switch c. Place one leg of a carpenter's framing square
with screws and nuts and adjust in accordance with against the straightedge, with the other leg against
Rigging of Main Landing Gear. the inboard side of the wheel being checked. Mea-
sure the distance from framing square leg adjacent
NOTE to wheel, to wheel rim, at extreme aft circumfer-
ence of wheel rim. The difference between the two
Make sure landing gear limit switches have measurements will be the toe-in or toe-out for that
all holes in switch housing plugged and packed wheel. Toe-out for either wheel is 06 ±. 05 inch.
.

with DC-4 Silicone Compound to prevent mois- Toe-out must remain in tolerance throughout the en-
ture entering limit switches. tire range of free play in the system. If tolerance
cannot be retained, replace bushings. (See Disas-
g. Remove plug and caps and connect brake hose to sembly and Assembly of Main Gear Torque Links.)
union at bulkhead at forward wheel well. Use suit-
able lubricant on threads. NOTE
h. Install clamps securing switch wire bundle and
brake hose. Remove weight from gear by jacking aircraft
i. Service and bleed brake system in accordance before attempting to add or remove washers
with Servicing Instructions, Section 4. to torque links.
j. Perform operational check on landing gear.
d. Add washers between torque links to correct for
excessive toe-in. Wheel alignment after adjustment
must be within limits prescribed in step "e".
Change 11
4-16 421 SERVICE MANUAL
LANDIN6 GEAR AND
BRAKE SYSTEM

MAIN GEA0 0SO4RUO

0. 2 0 INCH

A A
TORQUE LINKS
SECTION A--A

REPOSITION WASHERS
BETWEEN TORQUE LINKS
AS NECESSARY TO OBTAIN
CORRECT WHEEL ALIGNMENT.

PLACE STRAIGHTEDGE
AT AXLE HEIGHT,
VIEW LOOKING
FWD LH SIDE

STRAIGHTEDGE

TOE-OUT 0. 06 ±0. 05 INCHES

MEASURED ON WHEEL RIM TAKE MEASUREMENTS
IN A HORIZONTAL PLANE AT EDGES OF WHEEL
THROUGH CL OF AXLE. RIM.

FORWARD

CHECKING MAIN WHEEL ALIGNMENT

14412002
10411008

Change 11 Figure 4-5. Main Wheel Alignment

 421 SERVICE MANUAL LANDING C,EAR AND 4-16A/4-16B
BRAKE SYSTEM

NOTE CAUTÏON

(See Figure 4-5) AN960-716 and AN960-716L Take precaution when removing bushings to
washers are used as shims between the upper - prevent damage to torque link.
and lower torque links. Combinations of thick
and thin washers can be used between the tor"
Assembly of Main Gear Torque Links. (See figure
que links to obtain the correct wheel alignment. 4_4
Washers that are added or removed between a. Press in bushings (18 and 26) using bench vise
the torque links must also be removed or add- with necessary wood block and proper size punch.
ed to the outside end of the spacer to maintain
an 004 to 020 side play of the torque links'
. .
NOTE
Be sure that the spacer washers are centered
on the spacer as the nut is being torqued up to Bushings (18 and 26) must be pressed in wet
proper value (refer to Figure 1-4)· using MIL-P-8585 zinc chromate primer or
equivalent, and lube fitting holes of bushings
Removal of Main Gear Torque Links. (See figure aligned with torque brace lube fitting holes.
4-4. )
b, Mill and finish installed bushings (18 and 26)
The removal procedures are the same for either left flush with outside edge of torque link brace (14),
or right main landing gear torque links. break sharp edges 0. 005 radius minimum. Bush-
a. Check alignment of main landing gear wheels in ings must not extend past edge of torque link brace.
accordance with alignment procedures.
b. With main landing gear wheels aligned and jacks NOTE
removed, mark the relative position of each main
landing gear piston and axle assembly, and trunnion Mill an equal amount on each bushing (26)
assembly to facilitate aligning of parts for installa- using a flat mill file to provide a slip fit
tion. between lugs on the torque link and the lugs
NOTE on the trunnion and/or the lugs on the axle.

pencil
c. Insure lube fitting holes are clean and install
Use a grease for marking.
lube fittings.

c. Mark extension of landing gear strut.

d. Jack the aircraft in accordance with Section 2. Installation of Main Gear Torque Links. (See figure
4-4.)
NOTE a. Install upper torque link brace (14) on barrel
assembly (38), with shaft (12), spacer (59) and the
jack is positioned to allow removal necessary shims to align pin hole in shaft with pin
Make sure
hole in spacer.
of wheel and brake assembly.
CAUTION
e. Remove brake, wheel and tire assembly in
It may be necessary to remove the finish
accordance with Section 4. from shaft (12). DO NOT FORCE. If stop
f. Deflate strut in accordance with Section 2° welds on the inside of spacer interfere
g. Disconnect landing gear door and tie out of way. smooth welds with file.
h. Disconnect torque link braces by removing cotter
pins (23), nut (20), bolt (15), washers (21) and spacer NOTE
(19). Adjust set screw (25) against strut to pre-
NOTE vent spacer (59) from pivoting, then stake
set screw.
Washers located between torque link braces
control toe-out, and must be retained and b. Install pin (13) and safety wire in place by rout-
replaced in removal order, for proper wheel ing wire through roll pin and around the bushing.
and torque link brace alignment, c. Install lower torque link brace (14) on barrel
assembly (38) using same lirocedures as the upper
i. Remove roll pin (13) using a suitable drift punch. torque link.
j. Remove shaft (12) using a suitable drift punch. d. Align main landing gear barrel piston (10) and
k. Remove torque links (14). axle assembly in position as previously marked.
e. Block landing gear strut up using wood blocks
Disassembly of Main Gear Torque Links. (See to previously marked extension to facilitate aligning
figure 4-4.) torque link braces.
f. Align upper and lower torque link braces (14)
Bushings (18 and 26) are press fit and should be re- using same number of retained washers positioned
moved only for replacement. When replacement be- between braces in the same order they were removed.
comes necessaly proceed as follows: g. Use a .4300 diameter pilot (bolt or rod) to align
a. Remove grease fittings. torque link braces and washers.
b. Using a bench vise, wood blocks_and proper size h. Clamp torque link bfaces in position using two
shaft or punch, press out bushings (18 and 26). small "C" clamps.

Change 11
 421 SERVICE MANUAL LANDING OEAR AND 4-ÎÏ
BRAKE SYSTEM
i. Using a standard 29/64 (. 4531) reamer, having b. Remove wheel well door as follows:
a 0.75 length, 0.430 diameter pilot or Cessna Spec- 1. Jack aircraft and engage manual extension, and
ial Tool FT251 reamer, ream bushings, to insure release tension on gear retraction system.
a straight true hole in both parts. 2. Remove access hole covers from wheel well
door.
CAUTION 3. Disconnect the door link tube from actuator arm.
4. Remove wheel well door by removing nuts,
Turn reamer by hand, using a "T" handle. washers, and bolts attaching hinge arms to door.
Do not use power tools. c. If desired, remove hinge arms as follows:
1. Remove lower wing root fillet and hinge covers
j. Remove clamps and clean torque link braces with by removing attaching screws.
suitable solvent. 2. Remove hinge arms from brackets by removing
k. Install retained lube fitting in torque link braces nuts, washers, spacers, and bolts.
and flush grease to insure bushings are free of dirt
and remove grease.
1. Position brake hose and clamp on bolt (15) and Installation of Main Landing Gear Door. (See figure
connect upper and lower torque link at hinge point 4-6.)
using bolt (15), spacer (19), washers (21) and nut
(20).
·
a. If hinge arms were removed, attach to brackets
with bolts, spacers, washers, and nuts. Install
NOTE hinge covers and lower wing root fillet with attaching
screws.
Make sure all new and existing washers at b. Install wheel well door as follows:
torque link hinge point are in place and free 1. Jack aircraft and engage manual extension to re-
in movement, tighten bolt and nut to insure lease tension on gear retraction system.
a side play of 0. 004 to 0. 020 is maintained 2. Place wheel well door in position, align mount-
between torque link braces. It may be nec- ing holes, and attach to hinge arms with bolts, wash-
essary to position the washers in a different ers, and nuts.
location to maintain alignment and side play 3. Attach door link tube to actuator arm with bolt
simultaneous. and nut.
NOTE
m. Insure brake line is clear of all structure and
secure. If length of door link tube has been changed
n.Safety bolt (15) and nut (20) with cotter pin (23). .
'
or new door components are bemg mstalled
.

o.
Install wheel and brake assembly in accordance '
rig in accordance with Rigging Procedures
with installation procedures.
of Mam Landing Gear Doors.
.

p. Torque all nuts properly, and safety.

q. Lubricate upper and lower torque link fittings· 4. Install access hole cover on wheel well door,
r. Inflate landing gear strut in accordance with c. Install strut door as follows:
Section 2- 1. Place door in position and secure in place with
s. Connect landing gear door and cycle landing gear nine screws.
to make sure door fits properly and all lines are 2. Attach door link rod to strut with bolt and nut.
clear.
t. Remove aircraft from jacks. NOTE

Main Landing Gear Doors. If length of door link rod has been changed or
new door components are being installed, rig
The main landing gear is equipped with wheel well in accordance with Rigging Procedures of
doors and strut doors. Each strut door, pivoting on Main Landing Gear Doors.
a continuous hinge located at its outboard end, is
operated by a push-pull rod attached to the main. Gear Door. (See figure 4-6.)
Rigging Main Landing
landing gear strut. Each wheel well door, pivotmg
on forged aluminum hinges located at its inboard end
a. Jack aircraft in accordance with Section 2,
is operated by a bellerank and push-pull tube, which'
b. Disconnect wheel well door by removing nut (14),
is connected to the landing gear retracting linkage,
The operating mechanism is so arranged that the attaching door link tube (15) to actuator arm (16).
c. Disconnect strut door by removing nut (27) at-
wheel well door is closed when the main gear is either
fully retracted or fully extended.
taching door link rod (28) to strut.
d.. Using the normal landing gear retraction system,
operate gear to the UP position.
Gear Doors. (See figure
.

Removal of Mam Landing

4-6.) NOTE
a. strut door as follows:
Remove The use of an external power source is re-
1. Disconnect door link rod from strut by removing commended for operation of electrical units
nut and bolt. while engines are not being operated. Low
securing door to structure; voltage could cause low downlock tension
I 2. Remove screws
remove door. readings.

Change 9
i
4-18 LANOWS GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

21
29
22
27 24
Detail A
28
29 3

0
Det4ail Û 7

11

16 151311
(
12

13
Detail
A52273001
B14274002
Detail C C52141005
D52411005

Figure 4-6. Main Landing Gear Door Installation

Change 9
 421 SERVICE MANUAL LANDING OEAR AND 4-1@
BRAKE SYSTEM

Figure 4-6. Main Landing Gear Door Installation Callouts

1. Washer 11. Washer 20. Hinge

2. Nut 12. Nut 21. Main Landing Gear
3. Bracket 13. Spacer 22. Nut
4. Hinge Cover 14. Nut 23. Snubber
5. Screw 15. Door Link Tube 24. Cotter Pin
6. Nut 16. Door Actuator Arm 25. Hinge Pin
7. Bolt 17. Bolt 26. Bolt
8. Spacer 18. Washer 27. Nut
9. Bolt 19. Nut 28. Door Link Rod
10. Main Wheel Well Door 29. Spacer

e. Close strut door and adjust door link rod (28) so rigging of the main landing gear system will
that door fits flush• be necessary.
f. Adjust snubber (23) so there is 0 to 0. 06 inches
clearance between door and main gear torque link. m. Install access hole cover on wheel well door.
g. Operate gear to the DOWN position. n. Insure that the landing gear is DOWN and locked,
h. Close wheel well door and adjust door link tube remove jacks.
(15) so that door just fits flush.
1. Adjust rod end on door link tube one-half turn Main Landing Gear Retracting Linkage.
shorter and connect.
The main landing gear retracting linkage consists of
NOTE push-pull tubes, belleranks, torque tubes, braces,
Make sure door link tube adjustment does not and links interconnected between the landing gear act-
cause deformation of door. uator and the main landing gear. A positive downlock
is obtained by rigging the main side links to an over-
i. Operate gear to the UP position, center position. The link assemblies which hold the
main side links in an over-center position are also
CAUTION rigged over-center. Downlock springs, which apply
spring tension to the over-center position of the link
When retracting gear while rigging door, be assemblies, are provided as an added safety feature.
prepared to stop before damage can occur. Hook-type mechanical locks are provided to lock the
landing gear in its retracted position. The main land-
j. If necessary, readjust door link tube (15) so that ing gear retracting linkage also operates the main
door fits flush. landing gear door operating mechanism.
k. Repeat steps "d" thru "j" as necessary to obtain
proper fit of doors, checking that wheel well door Removal of Main Landing Gear Retracting Linkage.
clears tire and wheel. (See figures 4-7 and 4-8.)
1. The door push-pull tube is to be 5 degrees over-
a. Jack the aircraft in accordance with Section 2.
center with the door actuator arm against its stop, as
b. Disconnect main landing gear doors.
shown in figure 4-6A, in both gear Up and gear Down
iosition.
c. Release tension on retracting linkage by engaging
hand crank and operating a few turns toward the UP
position.
d. (See figure 1-2. ) Remove access covers (56, 36,
16 and 4),
e. Remove rear seats, carpet and floorboard to
gain access to the landing gear actuator.
f. Remove inboard drive tube (35) as follows: (See
figure 4-7. )
1. Disconnect drive tube from landing gear actua-
tor bellerank.
2. Disconnect drive tube from idler bellerank (7)
/ 5° by removing nut (36), washer (34) and bolt (32).
OVER-CENTER 3. Remove clamp (48) securing seal boot (49) to
drive tube; then remove drive tube by pulling tube
into cabin area.
g. Remove seal boot as follows: (See figure 4-7.)
1. The following procedures are given for the left
side. The right side procedures are the same.
Figure 4-6A. Door Actuator Arm 2. Remove the landing gear drive tube in accor-
Overcenter Adjustment dance with the preceding instructions.
CAUTION 3. (See figure 1-2.) Remove cover plates (36 and 4).
4. Remove clamps (48) and remove boot.
If the door actuator arm stop is moved, re-
Change 9
4-20 LANDING GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

44

43

41

40

44

51
Detail
RH Side Only
40

43

'
A B
C
35

50
48

49

Detail B

A51411004
14403001R
214412007

Figure 4-7. Main Landing Gear Retracting Linkage-Inboard Components (Sheet 1 of 2).

Change 10
 421 SERVICE MANUAL LAND1NO GEAR AND 4- I
BRAKE SYSTEM

4 10
5

Detail
16421B0558 AND ON
39
"
38 ' 13
30 6
37 ," to
14
12
35 16

15

Det3
3
17
2
D

D14412006
C14412005

1. Nut 18. Nut 35. LH Inboard Drive Tube

2. Washer 19. Washer 36. Nut
3. Door Link Tube 20. Nut 37. Bearing
4. Nut 21. Thrust Bearing Washer 38. Nut
5. Washer 22. Bolt 39. Bolt
6. Upper Connecting Link 23. Rocker Arm Lower Link 40. Intermediate Drive Tube
7. Idler Bellerank 24. Washer 41. Washer
8. Washer 25. Nut 42. Bolt
9. LH Outboard Drive Tube 26. Screw 43. RH Inboard Drive Tube
10. Door Actuator Assembly 27. Washer 44. Bolt
11. Bolt 28. Nut 45. Bushing
12. Thrust Bearing Washer 29. Nutplate 46. Idler Bellerank
13. Bellerank Rocker Arm 30. Thrust Bearing Washer 47. Nut
14. Spacer 31. Spacer 48. Clamp
15. Nutplate 32. Bolt 49. Seal Boot
16. Bolt 33. Bolt 50. Adapter
17. Spar 34. Washer 51. RH Outboard Drive Tube

Figure 4-7. Main Landing Gear Retracting Linkage - Inboard Components (Sheet 2)

Change 10
4-22 LANDING GEAR ANo 421 SERVICE MANUAL
BRAKE SYSTEM

A
21
14
15 17

B
C

24
Detal

34

59
58
18
37
56
39

54
53

49
Detail $ 14413002R
A14411001
BlA413003

Figure 4-8. Main Gear Retracting Linkage -

Outboard Components (Sheet 1 of 2)

Ohange 10
 421 SERVICE MANUAL LANDING SEAR AND 4-
BRAKE SYSTEM

12
6 61 66 65 62 67 68 69

1
2
3
68

63

64

Detail (

052412001

1. LH Push-Pull Tube 18. Upper Side Link 36. Pin 54. Bolt
2. Bolt 19. Uplock Assembly 37. Down Indicator Switch 55. Nut
3. Torque Tube 20. Bolt 38. Spacer 56. Bolt
4. Bolt 21. Nut 39. Nut 57. Lower Side Link
5. Nut 22. Nut 40. Screw 58. Washer
6. Nut 23. Washer 41. Setscrew 59. Nut
7. Washer 24. Bolt 42. Side Brace Lock Link 60. Washer
8. Bolt 25. Screw 43. Adjusting Screw 61. Nut
9. Nut 26. Spacer 44. End Fitting 62. Bolt
10. Uplock Push-Pull 27. Nut 45. Bolt 63. Torque Tube
Tube 28. Washer 46. Nut 64. LH Outboard Drive
11. Washer 29. Nut 47. Spacer Tube
12. Mounting Bracket 30. Spacer 48. Bolt 65. Washer
13. Rib Assembly 31. Nut 49. Nut 66. Nut
14. Nut 32. Washer 50. Door Link Rod 67. Torque Tube Support
15. Support 33. Bolt 51. Nut 68. Washer
16. Bolt 34. Bolt 52. Washer 69. Bolt
17. Bolt 35. Bellerank 53. Spacer 70. Spring

Figure 4-8. Main Gear Retracting Linkage-Outboard Components (Sheet 2)

Change 10
4 4 LANDING GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

5. Installation of seal boot is the reversal of the j. Remove uplock assembly as follows:
removal procedures. 1. Disconnect uplock push-pull tube (10) from up-
lock assembly by removing cotter pin, nut (22), wash-
NOTE er (23), and bolt (24).
2. Remove screw (25) attaching uplock assembly
Clamp seal boot to drive tube with gear down to side link (18).
and with boot extended approximately 11"• k. Remove side links (18 and 57) as follows:
Install clamps with the clamp body aft to 1. Disconnect lower side link (57) from upper bar-
clear the rib when gear retracts. Install rel by removing nut (49), door link rod (50), nut (51),
boot so that the majority of folds in the boot, washers (52), spacers (53) and bolt (54).
when compressed, are in the aft position• 2. Disconnect lower side link from upper side link
Check neoprene gasket for cuts or tears be- by removing cotter pin, nut, washer and bolt (56).
fore reinstalling cover plate (4)• 3. Disconnect upper side link (18) from support
(15) by removing cotter pin, nut, washer and bolt
g. Remove idler bellerank (7) and door operating (17).
linkage as follows: 1. Remove torque tube (3) as follows:
1. Remove nut (25) and bolt (22) and four screws 1. Disconnect uplock push-pull tube (10) from tor-
attaching bearing housing to web• que tube by removing cotter pin, nut (6), washer (7),
2. Remove nut (18) and thrust bearing washer (21) and bolt (8).
then pull door actuator arm (10) thru web- 2. Remove nut (9), washer (11), bolt (2) attach-
ing torque tube to rib mounting bracket.
NOTE 3. Remove nut (61), washer (68), and bolt (69)
attaching torque tube to torque tube support (67).
Door actuator arm assembly (10) is a matched
set. Disassembly is not recommended. Installation of-Main Landing Gear Retracting Linkage.
(See figure 4-8.)
3. Remove bolt (39) and thrust bearing washers
(30), attaching idler bellerank (7) to front spar and a. Install torque tube as follows:
support web. 1. Attach torque tube (3) to torque tube support
4. Remove bolt (11) and thrust bearing washers (67) with bolt (69), washer (68), and nut (61).
(12), attaching bellerank rocker arm (13) to front 2. Attach torque tube (3) to rib mounting bracket
spar and support web. (12) with bolt (2), washer (11) and nut (9).
5. Pull belleranks and attached linkage from be- 3. Connect uplock push-pull tube (10) to torque
tween front spar and support web. tube (3) with bolt (8), washer (7), nut (6), and cotter
6. Remove the spacers (14 and 31) from the idler pin.
bellei-ank (7) and bellerank rocker arm (13). b. Install side links (18 and 57) as follows:
7. Remove upper connecting links (6) by removmg 1. Attach upper side link (18) to lower side link
nuts (4), washers (2), and bolts (16). (57) with bolt (56), washer (58), and nut (59). Tor-
8. Remove rocker arm lower link (23) by removing que nut to 110 ±5 inch-pounds. Install cotter pin.
nuts (20 and 25), washers (19 and 24), and bolts (22 2. Attach upper side link (18) to support with bolt
and 16). (17), washer (28), and nut (27). Torque nut (27) to
NOTE 200 ±25 inch-pounds. Install cotter pin.
3. Attach lower side link (57) to upper barrel with
See figure 4-8 for the following steps. bolts (54), washers (52), spacers (53), and nut (51).
Torque nut (51) to 110 ±5 inch-pounds. Install door
link rod (50) on bolt (54) with nut (49).
h. Remove LH push-pull tube (1) as follows: c. Install uplock assembly as follows:
1. Disconnect the push-pull tube from the bellerank 1. Insert uplock hook (19) into upper side link (18)
(35) by removing cotter pin, nut (31), washer (32) and and secure uplock assembly with screw (25).
bolt (34). 2. Attach uplock push-pull tube (10) to uplock as-
2. Disconnect push-pull tube from torque tube (3) sembly with bolt (24), washer (23), nut (22) and
by removing cotter pin, nut (5), washers and bolt (4). cotter pin.
i. Remove bellerank (35) and side brace (42) lock d. Install bellerank (35) and side brace lock link
link as follows: (42) as follows:
1. Disconnect DOWN indicator switch (37) by re- 1. Attach side brace lock link (42) to bellerank
moving nuts (39) and screws (40). (35) with pin (36), Secure set screw (41) and stake.
2. Rernove downlock spring. Do not stake over existing stakes.
3. Disconnect side brace lock link from lower side
link (57) by removing nut (55), washer (60), and bolt NOTE
(45).
4, Disconnect bellerank (35) from the upper barrel Ensure arrow (indicating flat surface) lo-
by removing cotter pin, nut (29), spacer (30), and cated on end of pin (36) is aligned towards
bolt (33)- set screw (41).
5. Remove the side brace lock link (42) from the
bellcrank (35) by removing setscrew (41) and pin (36).

Change 11
 421 SERVICE MANUAL LANDING OEAR AND 4-24A/4-24B
BRAKE SYSTEM

2. Attach bellerank (35) to upper barrel with bolt (34), washer (32), nut (31) and cotter pin.
(33), spacer (30), nut (29) and cotter pin. 2. Attach push-pull tube to torque tube (3) with bolt
3. Attach side brace lock link (42) to lower side (4), nut (5) and cotter pin.
link (57) with bolt (45), washer (60), and nut (55). 3. Insert push-pull tube and verify that the heads
4. Install down lock spring (70)- of the three in-line rivets are facing down.
5. Install DOWN indicator switch (37) with attach-
ing screws and nuts. NOTE
e. Install LH push-pull tube (1) as follows:
1. Attach push-pull tube to bellerank (35) with bolt See figure 4-7 for the following steps.

f. Install idler bellerank (7) and door operating

linkage as follows:

Change 11
 LANDING SEAR ANo 4-25
421 SERVICE IVIANUAL
BRAKE SYSTEM

1. Attach rocker arm lower link (23) to bellerank and idler in the fuselage.
rocker arm (13) and bellerank (10) with bolts (16 and
22), washers (19 and 24), and nuts (20 and 24). CAUTION
2. Attach upper connecting links (6) to bellerank
rocker arm (13) and idler bellerank (7) with bolts Anytime the floorboards are removed a tem-
(16), washers (2), and nuts (4). porary protective cover should always be
3. Install spacers (14 and 31) in idler bellerank (7) used to prevent damage and improper settings
and bellerank rocker arm (13). of the landing gear actuator limit switches.
4. Place belleranks and attached linkage in position
between front spar and support web. c. Release compression on retracting linkage by
5. Install bellerank rocker arm (13) with bolt (11), engaging manual extension crank and operating a

I
and thrust bearing washers
6. Install idler bellerank
thrust bearing washers (30).
(12).
(7) with bolt (39) and

7. Insert door actuating arm assembly

then install thrust bearing washer (21) and nut (18).
(10) thru web;
sufficient number
open the inboard
of turns toward the up position
main gear door 20°

NOTE
30°.
to
-

8. Install four screws attaching bearing housing to Prior to any operation of the landing gear by
web and bolt (22) and nut (25). Safety with locktite the manual extension crank, assure the land-
sealant. ing gear switch is in the neutral position and
g. Install landing gear drive tube (35) as follows: circuit breaker is pulled.
1. Insert drive tube into position from the cabin
area and attach to idler bellerank (7) with bolt (32), d. (See figure 4-6. ) Disconnect main wheel well
washer (34), and nut (36). door link tube (15) by removing nut (14) and washer
2. Attach drive tube to landing gear actuator bell- (11) from the door actuators. (See figure 4-16.)
crank. Disconnect door link tubes (3 and 15) by removing
h. (See figure 4-8) Install outboard drive tube (64) nuts and bolts.
as follows:
1. Attach drive tube to torque tube (63) with bolt NOTE
(62), washer (65), and nut (66).
2. (See figure 4-7) Attach drive tube to idler bell- Always disconnect nose gear door link tubes
crank (7) with bolt (33), washer (8), and nut (38). from the upper connection to prevent the pos-
i. Rig main landing gear in accordance with rigging sibility of connecting the lower connection to
procedure. the wrong side of the hinge.
j, Install access hole covers on underside of wing
forward of wheel well. e. (See figure 4-10.) Disconnect nose gear retract-
k. Install floorboard and rear carpet. ing linkage in the nose gear wheel well by removing
L Connect landing gear doors and rig per Main nuts and bolts attaching nose push-pull tube (7) to
Landing Gear Door Rigging Procedure. fork bolt (8) and connector link (3) and removing
m. Insure that landing gear is DOWN and locked, push-pull tube (7).
then remove aircraft from jacks. f. Disconnect the inboard end of both outboard drive
n. Install rear seats. tubes (15) by removing nut, spacers and bolt.
g. Disconnect LH inboard drive tube (21) and RH
inboard drive tube (17) at door actuator bellcranks
Rigging of Main Landing and Nose Gear. (See figure (16).
4-9.)
CAUTION
The following landing gear rigging procedure is de-
signed specifically for the Model 421. A faithful During operation of landing gear actuator be
following of this procedure will result in a proper prepared to stop to prevent any possible dam-
rigged and efficient operating system. Before start- age.
ing the rigging the "toe-out" should be checked in ac-
cordance with main wheel alignment procedures, the CAUTION
tires inflated to proper pressures and main gear door
link tube should be checked for proper overcenter ad- It is recommended that the inboard drive tubes
justment, in accordance with main landing gear door be held during actuation to prevent damage to
rigging procedures. the structure. It may be necessary to install
a length of safety-wire in the drive tube ends
a. Jack aircraft using the three provided jack points. to help hold tubes in position during operation.
One point is located on the underside of the fuselage,
just aft of the nose wheel well, and one point is lo-
cated on the lower surface of each wing on the wing h. (See figure 4-1. ) Adjust the UP and DOWN limit
rear spar, just aft of the main gear attach points, switches (17 and 44) on the landing gear actuator as
Position jacks to clear movement of main gear strut follows:
door. 1. Adjust both limit switches to the end of their
b. Remove carpet and floorboards covering and nec- adjusting slots in a direction which will permit max-
essary access plates to gain access to the gear box imum bellerank traveL

Change 10
4-26 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

A
1234567 654321

11 12 13 14 15 16 21 20 19 18 17 16 15 14 13 12

8
22
22

14 2

ADJUST
Dimension D

15
mens

NOTE: DIMENSIONS ARE FOR

T¯ß
4
ILLUSTRATING PRINCIPLE ONLY.
14
Dimension C

30" NOTE: DIMENSIONS ARE FOR

Dimension A ILLUSTRATING PRINCIPLE ONLY.

Detail Detail B

1. Main Landing Gear Strut 8. Lock Link End Fitting 16. Door Actuator Bellcrank
2. Push-Pull Tube 9. Side Brace Lock Link 17. RH Inboard Drive Tube
3. Uplock 10. Bellerank 18. Bellerank
4. Fork Bolt 11 Lower Side Link 19. Intermediate Drive Tube
5. Door Actuator Arm Stop 12. Upper Side Link 20. Landing Gear Actuator
6. Door Actuator Arm 13. Uplock Push-Pull Tube 21. LH Inboard Drive Tube
7. Bellerank 14. Torque Tube 22. Adjusting Screw
15. Outboard Drive Tube

Figure 4-9. Schematic of Main Gear Retracting Linkage

Change 2
 LANDING OEAR AND
$¯ 7
421 SERVICE MANUAL
BRAKE SYSTEM

5
e g
4

17 16 15
+

A
18

10

NOT ACCEPTABLE

ADJUST
DESIRED

FORK BOLT

g ACCEPTABLE
9
Detail Detail B

1. Nose Gear Strut 10. Forward Drive Tube

2. Adjusting Fork 11. Idler Bellcrank
3. Connector Link 12. Aft Drive Tube
4. Adjusting Rod End 13. Actuator Bellerank
5. Uplock Torque Tube 14. Landing Gear Actuator
6. Spring 15. Torque Tube Assembly
7. Nose Push-Pull Tube 16. Outboard Bellerank
8. Fork Bolt 17. Truss Assembly
9. Adjusting Bellcrank 18. Drag Brace

Figure 4-10. Schematic of Nose Gear Retracting Linkage

Change 2
 28 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

NOTE two turns. If necessary, adjust the down limit switch

to meet this requirement.
When adjusting either limit switch, align
switch so that roller is contacted 10. Actuate gear electrically to the down position.
squarely
by the Manually place the door actuator arm (6) against its
bellerank or drive tube
stop. Adjust RH and LH inboard drive tubes (17 and
2. Engage manual extension to- 21) to align with hole in bellerank door actuator (16);
crank and operate
ward the up position until the internal then lengthen the rod ends on the drive tubes (17 and
stop in the act-
uator is reached. 21) two turns. Actuate gear electrically toward the
To prevent possible damage to the
actuator, do not force against the internal up position as required to install bolts, washers and
stop.
3. (See figure 4-1. ) Note the angular position of nuts.
the crank when internal stop is reached, back crank
off toward the down position 2 turns of the hand crank, CAUTION
then advance crank 1/2 turn toward the up position.
Adjust the up limit switch (17) so that it is just actu- Bolt (32, figure 4-7) must be installed with
ated at this point. head of bolt forward.
4. Engage manual extension crank and operate to¯
11. (See figure 4-11.) Actuate gear electrically
ward the down position until the internal stop in the to the DOWN position and check the pull force re-
actuator is reached. Do not force against the inter¯ quired to move the door actuator arms from their
nal stop• stops as illustrated.
5. (See figure 4-1. ) Note the angular position of
the crank when internal NOTE
stop is reached, back crank
off toward the up position 2 turns of the hand crank
adjust the down limit switch (44) so that it is just a'ct- The pull required to move door actuator arm
uated at this point. from stop must be measured at a right angle
6. After these preliminary adjustments to the limit to the arm. The tool illustrated in figure
switches have been made, stow the manual extension
4-11 can be made to facilitate this measure-
crank and operate the actuator electrically ment,
to the up
position until the up limit switch is actuated
12. Adjust the length of both inboard drive tubes
CAUTION (17 and 21) as necessary to
obtain a force of 25 ±10
pounds required to move door actuator arms (6) from
Caution must be observed actuation to stops (5) in the down position.
during
insure that no damage is incurred by the dis- 13. Anfuaie gear eléctrically to the UP position
and adjust the up limit switch as necessary to obtain
connected ends of the main drive tubes.
a force of 25 ±10 pounds and a maximum difference
of 10 pounds from the down position required to move
NOTE the door actuator arms (6) from stop (5) in the up po-
sition.
To facilitate rigging of the landing gear, a
NOTE
two-position momentary ON switch with suit-
able lengths of electrical wires can be con~
nected to the landing gear electrical If the up limit switch is readjusted recheck
circuit in Step 7.
in such a manner that the landing gear can be the minimum turn requirement
observed while being operated during rigging.
The use of an external i. Adjust side brace lock links (9) as follows:
power source is also adjust
recommended. 1. With landing gear in the down position,
end fitting (8) so that lower side link (11) and upper
side link (12) are held firmly in overcenter position
7. Engage the manual extension crank and note the
angular position of the crank. Operate crank toward when side brace lock link (9) is firmly overcenter.
the up position noting the number of turns required to 2. During retraction check for clearance between
reach the internal stop in the actuator. The minimum bellerank (10) and push-pull tube (2). It may be nec-
number of turns required in the up position is three_ essary to add or subtract washers to provide clear-
fourths of one turn. The desired is 1-1/2 turns. If ance.
necessary, adjust the up limit switch to obtain this 3. Manually "Break" the lock link from its over-
requirement. center position and move the landing gear to a posi-
8. Stow the manual extension crank and operate the tion five to six inches inboard from the down and
actuator electrically to the down position until the locked position, then release. The landing gear must
down limit switch is actuated. free fall and lock when released from this position.
9. Engage the manual extension crank and note the
position of the crank. Operate crank toward the down NOTE
position and note the number of turns required to
reach the internal stop in the actuator. The minimum Lengthen side brace lock link end fitting (8)
number of turns required in the down position is one in 1/2 turn increments until the gear will
and the maximum (and desired) number of turns is not free fall down and locked.

Change 2
 421 SERVICE MANUAL LANDING OEAR AND (-g
BRAKE SYSTEÑ

SPRING SCALE
25± 10 POUNDS

.188"
.75" .13"

WELD
.28" .19"

SE
ION'g--A 5.00 "
.13
DOUBLE SIZE Ã .
' DRI3 (.281)
'"K"

28

3.06"

.375"R o
DRILL "K" 1)

MATERIAL-STEEL

Figure 4-1L Fabrication and Usage of Tool for Measuring Door Actuator Arm Tension

Change 2
4-30 LANDING 6EAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

4. On aircraft 421-0001 to 421A0070 shorten lock NOTE

link end fitting (8) in 1/2 turn increments until gear
will free fall down and locked. Detail A illustrates this adjustment. Length-
5. On aircraft 421A0070 and On shorten adjusting ening the fork bolt increases dimension "B, "
screw (22) in small increments until the gear will, the longer dimension "B" is, the higher the
free fall down and locked. Double safety wire screw gear will retract.
in adjusted position.
6. Adjust both main landing gear side brace lock 2. The axle dust cover should make light contact
links in this manner- with the corrugated reinforcement at the top of wheel
then drop down a specified distance (drop-off).
well,
NOTE Refer to step "m. "
m. Adjust the amount of drop-off as follows:
After the preceding steps have been completed 1. Determine whether drop-off is too little or too
the main landing gear retracting system is rig-
much. The minimum and desired amount of drop-off '
ged from the limit switches through the door measured at the center of the wheel, is 1/8 inch.
actuator belleranks, and both side brace lock The maximum is 1/4 inch.
links are adjusted at the landing gear. The
2. If drop-off is too much, lengthen outboard drive
following procedure is to rig the retraction tube (15) in half-turn increments until drop-off is
s stem from the door actuator belleranks to
correct.
the side brace lock links. 3. If drop-off is too little, shorten outboard drive
tube (15) in half-turn increments until drop-off is
j. Make the following preliminary preparations:
correct.
1. Remove uplocks (3) and uplock push-pull tubes 4. Adjust the amount of drop-off for both main land-
(13) by removing attaching bolts.
ing gears in this manner '
2. Adjust the length of outboard drive tubes (15) to
1/4 inch from as short as possible and install.
NOTE
NOTE
Detail B illustrates the principle used to ob-
tain drop-off. Notice that dimension "C" is
Bolt (33, figure 4-7) must be installed with
head of bolt forward.
35 inches. If we continue to rotate the torque
tube fork bolt past its parallel position with
3. Disconnect push-pull tube (2) from fork bolt (4). the push-pull tube, dimension "C" will de-
4. Screw fork bolts (4) into torque tuhes (14) as far crease as illustrated by dimension "D. "
as possible. Dimension "C" represents the highest posi-
5. Operate landing gear actuator to DOWN position. tion reached by the main landing gear during
6. With landing gear DOWN, adjust length of push- retraction. If the fork bolt is rotated past
pull tubes (2) so that rod end holes align with the its parallel position, we actually cause the
main gear to start extending. This slight
holes in fork bolts (4), then shorten one turn. Oper-
past center extension is defined as drop-off.
ate landing gear actuator toward the UP position far
enough to permit installation and install push-pull
tubes (2). INSTALL WITH THE COLLAR-END n. Adjust the down lock tension as follows:
OF
THE HI-SHEAR RIVETS POINTING UPWARD FOR 1. (See figure 4-12. ) Operate the landing gear to
CLEARANCE.
the DOWN position. The main landing gear down
lock tension should be 40 to 50 pounds.
CAUTION 2. If down lock tension is too high, lengthen push-
pull tube (2) until the correct down lock tension is
The bolt installing push-pull obtained.
tube (2) to the push-pull
fork bolt (4), must be installed 3. If down lock tension is too low shorten
with the bolt
head forward. tube (2) until the correct down lock tension is obtain-
ed.
NOTE
NOTE
The preceding preparations will result in in-
complete retraction, thus eliminating the pos- Since the highest position during retraction is
sibility of damage to the wing structure caused
controlled by the combined length of the push-
by retracting too far.
pull tube (2) and the fork bolt (4), this com-
bined length must remain unchanged to main-
k. Operate landing gear to the UP position and ob-
tain the correct highest position. When ad-
serve the highest position reached by the gear during
justing the push-pull tube to obtain the spe-
retraction and the amount of drop-off.
cified down lock tension, the fork bolt must
1. Adjust the highest position reached by the gear
be readjusted a corresponding amount in the
during retraction as follows:
direction that will not change the combined
1. Lengthen fork bolt (4) in half-turns to
.

increase
length of the push-pull tube and fork bolt.
the highest position during retraction.

Change 6
 MANUAL LANDING GEAR AND (·-31
421 SERVICE
BRAKE SYSTEM

SPRING SCALE
MODEL 140 HEAVY DUTY
0-200 LBS.
JOHN H. CHATILLON AND SON
83-28 KEW GARDENS
KEW GARDENS, NEW YORK

40-50 LBS DURING RIGGING

40-60 LBS FOR ROUTINE IN-SERVICE INSPECTION

Figure 4-12. Main Landing Gear Down Lock Requirements

4. Adjust the down lock tension for both main land- must engage and disengage freely and smoothly with
ing gear in this manner. no indication of binding.
o. Install and adjust uplocks as follows: 7. VISUALLY CHECK THE ALIGNMENT OF ALL
1. Connect uplock push-pull tubes (13) to uplock ROD ENDS TO INSURE THAT THEY ALIGN WITH
assemblies with bolts, washers and nuts. THEIR ATTACH FITTINGS.
2. (See figure 4-8.) Position uplock assemblies
in place and attach to upper side links with screws p. Refer to figure 4-10 for the following steps q.
(25). Do not tighten attachment. thru z. for rigging the nose gear.
3. Adjust uplock push-pull tubes (13) to a prelimi- q. Disconnect downlock assist spring (6) in nose
nary length of 5. 15 inches and attach to torque tube gear wheel well.
(14) with bolts, washers and nuts.
4. Operate landing gear to the UP position. NOTE

Because the aft drive tube (12) is a fixed

CAUTION length, the idler bellerank (11) is correct-
ly positioned to the actuator bellerank (13).
Use caution when landing gear nears the UP
position before adjustment of uplock push-
r. Operate the actuator to the DOWN position, then
pull tubes has been completed. If necessary'
adjust the length of the forward drive tube (10) as
readjust the push-pull tube and/or uplock follows:
hooks to prevent damage.
forward drive tube (10) from out-
1. Disconnect
board bellerank (16).
5. Adjust uplock push-pull tubes so that uplock 2. Adjust the length of forward drive tube (10) so
assemblies fully engage the spacers provided on the that fork bolt (8) is parallel with the upper flange of
landing gear and tighten nuts. the wheel well former adjacent to the fork bolt. The
forward end of the fork bolt will point downward any
NOTE amount caused by less than one turn of the threaded
end of the forward drive tube (10). Detail "A" illus-
Elongated slots are provided in the uplock trates three possible conditions. The straight config-
hooks so that each uplock hook can be ad¯ uration is most desired. The fork bolt must never
justed vertically to contact the spacers. point up.

6. Operate the landing gear several times, observ-

ing uplock assemblies. Uplock hooks must engage
fully with the spacers provided on the gear, and

Change 2
4-32 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

NOTE NOTE

The collar-end of the forward horizontal hi- If the auxiliary switch described in paragraph
shear rivet must point inboard for clearance- h. , step 6. , of Rigging of Main Landing Gear,
is not being used to rig the landing gear, use
s. Make the following preliminary adjustments: the normal retraction system. The use of an
1. Screw fork bolt (8) into adjusting bellerank (9) as external power source is recommended for
far as possible, operation of electrical units while engines
2. Screw adjusting rod end (4) into uplock torque are not being operated.
tube (5) as far as possible.
3. Shorten adjusting fork (2) as much as possible. 4. Check the uplock tension at the nose gear door
4. (See figure 4-17. ) Adjust uplock hook (52) to actuator arm, as illustrated in figure 4-13. The
the end of its adjusting slots in the direction that will force required to move the connector link from its
prevent hook from fully engaging- position against uplock torque tube must be 75 +10,
t. Adjust connector link (3) as follows: -15
pounds.
1. With nose gear DOWN, check the over-center 5. Shorten nose push-pull tube (7) in half-turn in-
position of connector link (3)• crements to increase uplock tension; lengthen to de-
crease.
NOTE 6. Operate landing gear to the DOWN position and
check the downlock tension in the same manner. The
A slight force should be required to snap con- force required to move the connector link from its
nector link into its over-center position. position against the uplock torque tube must be 25
±10 pounds.
2. Lengthen adjusting rod end (4) in half-turn in- Lengthen fork bolt (8) in half-turn increments
7.
crements to increase the force required to snap con- toincrease downlock tension; shorten to decrease.
nector link over-center; shorten to decrease. DO NOT adjust nose push-pull tube (7).
3. Manually place nose gear UP, push upward on
door actuator arm to lock connector link over-center, NOTE
and check the retracted position.
Detail "B" illustrates the principle for ad-
NOTE justing the uplock and downlock tension. Ad-
just length of nose push-pull tube for uplock
The nose gear should retract to a position tension and the length of the fork bolt for
that will align the center of the uplock hook downlock tension,
with the spacer provided on the gear for
hook engagement.
8. Operate landing gear to the UP position and re-
check the uplock tension. If necessary, readjust
4. If the retracted position is too low, lengthen ad- nose push-pull tube (7) in accordance with step 5.
justing rod end (4) and shorten adjusting fork (2) in
half-turn increments.
5. If the retracted position is too high, shorten
adjusting rod end (4) and lengthen adjusting fork (2)
in half-turn increments.
o c
NOTE o

Since the combined length of adjusting rod end

(4) and adjusting fork (2) determines the force SPRING SCALE
required to snap link over-center in the DOWN
° °
position, this combined length must remain un- UP
changed. When changing the length of adjust-
75 10 LBS
+
ing rod end (4) to obtain the correct retracted
position, change the length of adjusting fork 15
-

(2) a corresponding amount in the direction

that will not change their combined length. DOWN
u. Adjust uplock tensions as follows:
and downlock 25 *
- 10 LBS
1. Lengthen nose push-þull tube (7) as much as
possible. Insure rod end is visible through the in-
spection hole for thread engagement.
2. Temporarily install nose push-pull tube (7).
3. Retract landing gear electrically.

Figure 4-13. Nose Gear Tension Requirements

Change 2
 421 SERVICE MANUAL LANDING 6EAR AND 4"33
BRAKE SYSTEM

NOTE c. Insure that battery switch is OFF.

d. (Aircraft 421-0001 to 421B0502. ) Adjust safety
Since the combined length of fork bolt (8) and switch as follows:
nose push-pull tube (7) determines the down- 1. With left main landing gear strut fully extended,
lock tension, this combined length must re¯ adjust arm of landing gear safety switch so that
main unchanged. When changing the length switch is actuated when the arm is raised to a posi-
of the nose push-pull tube to obtain the cor¯ tion of 0. 30 +. 05, 00 inches.
-.
Assure pressuriza-
rect uplock tension, change the length of the tion portion of the landing gear safety switch provides
fork bolt to a corresponding amount in the an open circuit to pressurization safety valve. Move-
direction that will not change their combined ment of the landing gear safety switch arm should
length· provide an audible actuation of the safety valve sole-
noid. If either the landing gear safety switch portion
v. Adjust the uplock
hook as follows: or pressurization safety valve portion does not oper-
L With landing gear in the UP position, check the ate within the prescribed limits, the switch must be
clearance between uplock hook and the spacer on the replaced.
strut with which the hook engages.
NOTE
NOTE
The arm is adjusted by removing the cotter
An access is provided in the top of the
cover
pin and nut which attach the arm to the
nose gear wheel well to check uplock hooks
switch, repositioning the arm, and rein-
in the gear UP position with doors closed.
. .

stalling the nut and cotter pin.

2. Adjust uplock hook to obtain a minimum clear¯
e. (Aircraft 421-0001 to 421BO472.) Check the ad-
ance of 0. 003 to 0. 060 inch and a maximum clearance justment of the landing gear safety switch as follows:
of 0. 06 inch at the closest point, which should be at
the underside of the spacer, near the fully engage po- WARNING
sition of the hook.
Since landing gear may retract if adjustment
NOTE of safety switch is incorrect, insure that all
wheel well areas are clear while performing
For adjustment of uplock hook, elongated holes the following checks.
are provided in the supports to which the hook
is attached· 1. If available, connect an external power source;
if not available, turn battery switch ON.
3. Operate landing gear several times to observe 2. Raise the switch arm to the position adjusted in
the hook. The hook must engage
uplock and disen~ step d. While holding the switch arm in this position
gage freely, with no indication of binding between the have an assistant place the landing gear switch in the
hook and the spacer' UP position. Landing gear should NOT retract.
w. Connect downlock assist spring and cycle landing 3. Continue to raise the switch arm upward to the
gear. The spring must cause no interference with end of its travel. Landing gear should NOT retract.
gear operation· 4. Release the switch arm. Landing gear SHOULD
x. (See figure 4-16.) Connect door link tubes (3 retract.
and 15) with bolts and nuts and rig nose gear doors 5. Operate landing gear through several cycles,
in accordance with Nose Gear Door Rigging Proce~ checking landing gear for proper operation.
dures f. (Aircraft 421B0472 and On. ) Adjust safety switch
y. (See figure 4-6. ) Connect main wheel well door
link tubes (15) with washer (11) and nut (14). Rig 1. Adjust the landing gear safety switch to operate
doors in accordance with Main Gear Landing Doors on the centerline of the stop plate.
Rigging Procedure. 2. Remove bottom left-hand wing gap fairing.
z. Reinstall floorboards, seats, carpet and access 3. Place jack under axle and raise strut to 0.75
lock-
covers. Insure that landing gear is DOWN and +0.75, from full extended position.
-0.12 Cut safety
ed, then remove jacks. wire and adjust the switch to actuate at this position.
NOTE
Adjustment of Landing Gear Safety Switch. (See
4-13A. To ensure switch is actuating at position
figure )
described above, refer to Section 14 and
The landing gear safety switch is located on the aft make a continuity check of safety switch.
side of the left main landing gear and is actuated by
the upper torque link. 4. Tighten jam nuts at safety switch and safety
a. Jack aircraft in accordance with Section 2. wire nuts,
b. Place landing gear switch in the DOWN position. 5. Remove jack from under axle.

Change 11
4-¾ LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

6. If available connect external power source; if the position marked on the control quadrant during
not available, turn battery switch ON. flight.
9. Adjust the throttle microswitch to actuate at
WARNING this position. Turn battery switch ON and check that
warning horn sounds as throttle levers are retarded
Since landing gear may retract if adjustment to this position, then turn battery switch OFF.
of safety switch is incorrect, insure that all
wheel well areas are clear while performing NOTE
operational check.
Elongated slots are provided for vertical ad-
7. Place the landing
gear switch in the UP position. justment and an adjusting screw positions the
Landing gear SHOULD retract. microswitch horizontally.
8. Operate landing gear through several cycles,
check landing gear for proper operation. b. On aircraft 421B0201 and On, adjust flap gear
9. Reinstall bottom left-hand wing gap fairing. warning as follows:
g. Insure that landing gear switch and landing gear 1. Fully advance throttle levers. +2°
o
are DOWN and battery switch is OFF, then remove 2. Position flap preselect lever to 16 -0°¯

jacks. 3. Turn off electrical power.

4. (See figure 8-3.) Loosen screws (39) and adjust
switch (38) to operate at this position. A definite
Adjustment of Landing Gear Warning System- click should be felt when switch actuates.
5. (See figure 8-3. ) Tighten screws (39) and turn
a. Adjust the throttle microswitch as follows: electrical power on.
6. Operate the landing gear to full up position.
NOTE 7. Operate flaps to full down position and note flap
position when warning horn sounds.
To properly adjust the throttle microswitch,

I
it is necessary to fly the aircraft. As a pre- NOTE
liminary adjustment before flight, adjust mi-
croswitch to actuate when the aft edges of the Anytime the flap preselect lever is placed
15° detent, the landing gear warn-
throttle levers are approximately 3/4 inch below the
from the fully closed position. ing horn should sound when the flaps reach
16° +2°o travel.
-0

1. Obtain a pressure altitude of 2500 feet.

2.
Adjust propeller pitch levers to obtain 2300 rpm 8. It may be necessary to repeat steps 4 through 7
on both engines. to properly adjust the landing gear warning system.
3. Place mixture levers in FULL RICH. 9. After microswitch adjustment is completed,
4. Retard throttle levers to obtain 12 to 14 inches place throttle levers in the CLOSED position and the
I
of manifold pressure.
NOTE
mixture levers in IDLE CUT-OFF.
c. Adjust DOWN indicator switches as follows:
1. (See figure 4-6) Disconnect main wheel door Ïink
tubes (15) from main wheel well door (10).
If throttle levers are retarded below the 2. (See figure 4-16) Disconnect nose gear door link
specified manifold pressure, advance them tube (15) from nose gear door hinge (21).
and repeat the retarding procedure.
3. Release tension on retracting linkage by engag-
ing manual extension crank and operating a few turns
5. Using a pencil, tape, or other suitable means
toward the UP position.
of marking, index the position of the throttle levers
4. (See figure 4-17) Disconnect nose gear nose
in the control quadrant. push-pull tube (37) from fork bolt (39) by removing
nut and bolt.
NOTE
5. (See figure 4-7) Disconnect main gear LH out-
board drive tube (9) idler bellerank (7) by re-
from
The remainder of the adjusting procedure must
moving nut, spacers and bolt.
be accomplished with the aircraft on the ground. 6. Adjust all three DOWN indicator switches so
that they are not actuated until landing gear is DOWN
6. With engines not being operated, place mixture
and locked by the over-center linkage. Adjust the
levers in FULL RICH. main landing gear switches by repositioning. Adjust
the nose gear switch by adjusting the switch actuating
WARNING
bolt.
Insure that fuel selector
7. Attach the push-pull tubes disconnected in steps
valve handles and
fuel boost pump switches are in the OFF
"4" and "5 "
8. Using the normal landing gear retraction sys -

position,
tem, operate landing gear to the UP position.
7. Jack aircraft in accordance with Section 2. 9. Place landing gear switch in a neutral position,
8. Fully advance throttle levers, then retard to engage the manual extension crank, and lower the

Change 11
 421 SERVICE MANUAL LANDING OEAR AND 4"34A
BRAKE SYSTEM

landing gear. Stop cranking immediately when the sembly, torque links, and shimmy dampener. The
green light illuminates, and note the exact angular Air-oleo shock strut contains an orifice and tapered
position of the crank. metering pin which vary the resistance to shock ac-
10. Check that both main gear and nose gear are cording to its severity. During extension and re-
DOWN and locked in the over-center position. traction, the nose gear pivots on heavy-duty needle
11. Resume cranking toward the DOWN position bearings by means of sleeved lugs on the trunnion
noting the number of turns required, until the inter- assembly. A wheel straightener and steering mech-
nal stop in the landing gear actuator is reached. The anism are provided so that the nose wheel turns while
number of turns required should not be less than four, taxiing, but is straightened during retraction,
nor more than eight for the main landing gears. The
number of turns should not be less than eight nor Removal of Nose Gear. (See figure 4-14.)
more than fourteen for the nose gear.
readjust DOWN indicator switch¯
12. If necessary, a. Jack aircraft in accordance with Section 2.
es as required to meet the conditions of steps "6" b. Remove taxi light (if installed, optional).
and "11. " c. Release tension on retracting linkage by engag-
13. Connect nose gear nose push-pull tube (7) to ing manual extension crank and operating a few turns
fork bolt (8)- toward the UP position.
14. (See figure 4-7) Connect main gear LH out¯ d. Disconnect nose gear doors.
board drive tube (9) to idler bellerank (7)- e. Disconnect retracting linkage as follows:
15. Insure that landing gear is DOWN, then remove 1. Remove nut (20), washer (19), and bolt (22)
jacks. attaching drag brace (23) to strut.

NOTE
NOSE GEAR.
To facilitate installation, note the number and
The nose gear consists of a wheel and tire assembly, position of attaching clamps and the routing of
yoke, axle, lower strut, upper strut, trunnion as- electrical wires.

SAFETY SWITCH
ADJUSTMENT
421-0001 TO 421BO472

ARM
SAFETY SWITCH
+0.75
TO ACTUATE AT 0.75
0. 12
FROM FULLY
0. 30 +0. 05 EXTENDED STRUT
-0.
00 Inche

TORQUE LINK

SAFETY SWITCH
ADJUSTMENT
421B0472 AND ON

10411002

Figure 4-13A. Adjustment of Landing Gear Safety Switch

Change 11
4•348 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

2. bolts (25 and 29), washers (26 and 30),

Remove Cleaning, Inspection, and Repair of Nose Gear,
and spacers (27 and 28).
3. Remove four nuts (17), washers (16), and bolts The instructions for cleaning, inspection, and repair
(14) on both left and right side of wheel well; then of the main landing gear also applies to the nose gear,
turnnose gear and slide retainer and gear aft to re-
move gear. Assembly of Nose Gear. (See figure 4-15. )

NOTE Before each component of the nose gear shock strut

is assembled, assure that it is thoroughly clean,

I To facilitate removal,
applied to retainer
wax or paraffin was
(13) upon installation,
then lubricate with system hydraulic fluid.
a. If metering
follows:
pin was disassembled, assemble as

1. Install O-rings (2) as shown and install pin (1)

in pin plug base (3) and install nut (4).
2. Install metering pin in inner tube and fork (5).
Align holes and install bolt (9), washer, and nut (12).
Disassembly of Nose Gear. (See figure 4-15. )
NOTE
WARNING
On 421BOOO1 and On add shims (65) and/or
Deflate the nose gear strut before removing washers (66) as required between metering
or disconnecting nose gear torque links- pin (1) and plug pin base (3) to maintain 486 ,

±. 005 inch between top of pin (1) and opening

a. Remove fender (if installed, optional). of orifice.
b. Remove wheel and tire assembly,
c. Remove retainers from trunnion assembly, b. Slide lock ring (27), ring pack retainer (26), and
scraper ring (25) on inner tube and fork (5).
NOTE
c. Install back up ring (22), O-ring (23), and back
Needle bearings are a press fit and should be up ring (24) or poly-pak seal (67) inside ring pack
removed only for replacement, support (21); and O-ring (20) in the groove on the
outside of ring pack support (21).
d. Remove shimmy dampener by removing nuts,
washers, and bolts. CAUTION
e. Completely deflate strut and after all air has
been expelled remove valve assembly and drain fluid. Install poly-pak seal with wide lip up (toward
f. Remove snap ring (28) and stop (34) then pull pressure side).
trunnion (30) from upper barrel (59).
g. Remove ball bearing (33) and packing (32) from d. Slide ring pack support on inner tube and fork (5)
trunnion (30). then install shim (19) and spacer (18).
h. Remove cotter pin (35), washer (36), and pin (60) e. Install bearing (17) on inner tube and fork (5) and
from upper barrel (59). install lock ring (16).
i. Remove cotter pin (42), nut (43), washers (44
and 50), and bolt (49). Then disconnect torque links NOTE
(46 and 51).
j. Pull inner tube and fork assembly (5) and upper Install bearing with chamfered end up in order
barrel (59) far enough apart to remove lock ring (27); to seat against external lock ring.
then remove lock ring (27) and separate upper barrel
(59) and inner tube (5). f. Screw orifice(15) in bottom of orifice tube (14)
k. Pull orifice tube (14) from inner tube and fork and install O-ring (13) in groove in orifice tube (14).
(5), then unserew orifice (15) from orifice tube (14), g. Insert assembled orifice tube (14) into upper
1. Remove lock ring (16) from inner tube and fork barrel (59); align holes and install pin (60), washer
(5) and remove bearing (17). (36), and safety with cotter pin (35).
m. Slide spacer (18), shim (19), ring pack support
(21), scraper ring (25), and ring pack retainer (26) NOTE
up and off of inner tube and fork (5),
n. Remove metering pin as follows: Lubricate O-ring (13) or tape sharp edges of
1. Remove nut (12) and bolt (9) from wheel fork. lower strut to prevent O-ring damage.
2. Pull metering pin from inner tube and wheel fork.
3. Remove nut and disassemble metering pin as h. Install assembled inner tube and fork (5) into
shown. upper barrel (59). Carefully work scraper ring (25)
o. Remove back up ring (22), O-ring (23), and back and retainer ring (26) into place and install lock ring
up ring (24) from ring pack support (21). (27).

NOTE
NOTE
Inner tube and fork are a press fit and drilled Lubricate O-ring (20) or tape sharp edges of
on assembly. Disassembly is not recommended. lower strut to prevent O-ring damage.

Change 11
 421 SERVICE MANUAL LANDING BEAR AND
4-35
BRAKE SYSTEM
NOTE
Removal and Disassembly of Nose Gear Torque Link
To prevent damage to piston barrel and ring Assemblies.
pack support during installation, a ring pack
support tool P/N 0880004-2, available from a. Nose Gear (see figure 4-15).
your Cessna Dealers' Organization, should
be used. (See Figure 4-3A. ) WARNING

i. Connect torque links (46 and 51) together with If the aircraft is on jacks, it is advisable to
bolt (49), washer (50), bushing (52), washer (53), deflate struts before removing torque links
spacer (54), washer (53), bushing (55), washers (44), to avoid possible damage.
nut (43), and cotter pin (42).
j. Install packing (32) and ball bearing (33) into 1. Remove cotter pins (11, 37 and 42).
trunnion (30) and lubricate. 2. Remove nuts (10, 38 and 43).
3. Remove washers (7, 39 and 44).
CAUTION 4. Remove spacers (8, 48 and 57).
5. Remove bolts (6, 49 and 56) attaching links to
Do not use high pressure grease gun on fitting strut and attaching the upper torque links to the lower
(31). Damage may result to trunnion (30)• torque links.
NOTE
k. Install ball bearing (29) in top of trunnion (30) and
fit trunnion on upper barrel• Observe the number of washers (53) installed
1. Install stop (34) and snap ring (28)- to facilitate reinstallation.
m. Press needle bearings into place on trunnion (30),
n. Install shimmy dampener in accordance with 6. Remove nose gear torque links by pulling for-
installation procedure'
ward.
o. Install fender (if required, optional).
P. Install wheel and tire assembly. NOTE
q. With strut completely deflated, fill with hydraulic
fluid as specified in Section 2 and install valve body. The bushings and spacers in the torque links
Do not inflate strut at this time. are a press fit and should be removed only
for replacement.

Installation of Nose Gear. (See figure 4-14. ) b. Remove grease fittings from torque links.

Assembly and Installation of Nose Gear Torque Link

a. Make sure bearings (12) are in place, then in- Assemblies.
stall retainers (13) and shims on trunnion (11).
a. Nose Gear (see figure 4-15).
1. Install grease fitting in torque link.
NOTE
2. If removed, install bushings (40, 45, 47, 52,
Shim as required to center nosegear and to 55 and 58).
limit side play to not exceed 0. 020. NOTE
O Mill an equal amount on each busing (40,
b. Place nose gear in wheel well and turn into po- 45, 47 and 58) using a flat mill file to pro-
sition for installation. Force nose gear forward and vide a slip fit between the lugs on the torque
align mounting holes. link and the trunnion and/or lugs on the axle.

O Make sure holes in spacers (52 and 55) are

NOTE
aligned with grease fittings.
To facilitate installation, rub wax or paraffin 3. Install spacers (8, 48 and 57).
on the wheel well bulkheads against which the 4. Insert nose gear torque links (51 and 46) into
retainers must slide; and move forward evenly• position and install washers (7 and 39) and bolts (6
c. Install eight bolts (14), washers (16), and nuts
(17) attaching retainers to airframe. Torque heads
of bolts to 85 ±15 inch-pounds,
d. Align Gimbal fitting on nose gear steering unit
and install spacers (27 and 28), washers (26 and 30)
and bolts (25 and 29). Torque bolts 50 to 70 inch-
pounds.

Change 11
 4-36 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

13
14

15

18

18
Detail

10

9 6 24 20
23

Detail Ë

31

25
30 27
29

Detail
14424001

Figure 4-14. Nose Gear Installation

Change 11
 421 SERVICE MANUAL LANDING GEAR AND
$¯3
BRAKE SYSTEM

Figure 4-14. Nose Gear Installation Callouts

1. Connector Link 12. Bearing 22. Bolt

2. Washer 13. Retainer 23. Drag Brace
3. Retracting Arm 14. Bolt 24. Nose Gear Down Indicator Switch
4. Bolt 15. Shim 25. Bolt
5. Nut 16. Washer 26. Washer
6. Truss Assembly 17. Nut 27. Spacer
7. Washer 18. Web 28. Spacer
8. Bolt 19. Washer 29. Bolt
9. Retainer 20. Nut 30. Washer
10. Nut 21. Trunnion 31. Nose Gear Steering Assembly
11. Trunnion

Change 11
4--38 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

28
13
29

5
14

30 15
18
17

1
--31

23 2

64 i -34
3
-27
4

67

42
53 43
52
44
56
49 45
46
47 52423001R
48 ^

Figure 4-15. Nose Gear Strut

Change 9
 421 SERVICE MANUAL LANDING SEAR AND 4-3Û
BRAKE SYSTEM

and 56). 1. Install hinges in brackets using bolts, washers,

5. Install nuts (10 and 38) and safety with cotter spacers, and nuts.
pins (11 and 37). 2. Replace radio shelves and equipment removed
6. Install correct number of washers (53) pre- previously.
viously removed. b. Install nose gear doors at the four hinges with
7. Install bolt (49), washers (44), nut (43) and the three bolts and nuts.
safety with cotter pin (42). c. Connect door link tubes with bolt, washers, and
nut to the forward side of hinge (21).
NOTE d. Rig nose gear doors in accordance with rigging
procedure.
Washers should be installed in the same posi^
CAUTION
tion from which they were removed. If new
components are being installed, align landing Damage will result if door link tube is not
gear in accordance with Main Wheel Align- connected on the proper side of hinge (21).
\4 ment Procedures.
Rigging Nose Gear Door. (See figure 4-16.)
b. If aircraft was placed on jacks, insure the gear
is DOWN and locked and remove aircraft from jacks. a. Jack aircraft in accordance with Section 2.
c. Inflate struts in accordance with Section 2. b. Disconnect main door link tubes (3 and 15) from
d. Lubricate torque links in accordance with Lubri- center hinges (8 and 21) by removing cotter pins,
cation Chart. nuts, washers, and bolts.
c. Using the normal landing gear retraction system,
Nose Gear Doors.
operate gear to the UP position.
Right and left main doors are used to enclose the nose
gear in its retracted position. The doors are connec- NOTE
ted to the nose gear retracting linkage and hinged at
their outboard ends, pivoting downward during nose The use of an external power source is recom-
gear extension and remaining down while the nose mended for operation of electrical units while
gear is down. engines are not being operated.
Removal of Nose Gear Doors. (See figure 4-16. ) CAUTION

a. Remove nut, washers, and bolt from door link When operating gear before door rigging is
tubes (3 and 15). completed, be prepared to stop before damage
b. Remove the three nuts and bolts from four hinge can occur. On new doors, operation by hand
brackets and doors; then remove doors. is necessary to make sure of clearance between
c. Remove nose gear door hinges as follows: fuselage skin and door.
1. Remove necessary radio equipment and shelves
to gain access to hinge bolts.
2. Remove nuts, spacers, washers, and bolts from d. Connect and adjust main door link tubes (3 and
hinge brackets and remove hinges. 15) until main doors close snugly when gear is in the
UP position.
Installation of Nose Gear Doors.

a. If nose gear door hinges were removed, install

as follows:
Figure 4-15. Nose Gear Strut Callouts

1. Metering Pin 19. Shim 37. Cotter Pin

2. O-Ring 20. O-Ring 38. Nut 55. Bushing
3. Plug Pin Base 21. Ring Pack Support 39. Washer 56. Bolt
4. Nut 22. Back Up Ring 40. Bushing 57. Spacer
5. Inner Tube and Fork 23. O-Ring 41. Lube Fitting 58. Bushing
6. Bolt 24. Back Up Ring 42. Cotter Pin 59. Upper Barrel
7. Washer 25. Scraper Ring 43. 11ut Assembly
8. Spacer 26. Ring Pacli Retainer 44. Washer 60. Pin
9. Bolt 27. Lock Ring 45. Bushing 61. Gasket
10. Nut 28. Snap Ring 46. Torque Link 62, Valve
11. Cotter Pin 29. Bearing Ball 47. Bushing Assembly
12. Nut 30. Trunnion 48. Spacer 63. Placard
13. O-Ring 31. Lube Fitting 49. Bolt 64. Placard
14. Orifice Tube Assembly 32. Packing 50. Washer 65. Shim
15. Orifice 33. Bearing Ball 51. Torque Link 66. Washer
16. Lock Ring 34. Stop Assembly 52. Bushing 67. Poly Pak Seal
17. Bearing 35. Cotter Pin 53. Washer
18. Spacer 36. Washer 54. Spacer

Change 2
4-40 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

e. Extend and retract gear, check for clearance be- center position is also rigged over-center. A hook-
tween nose tire and doors, and readjust door link type mechanical lock is provided to lock the nose
tubes (3 and 15) as necessary to obtain clearance. gear in its retracted position. The nose gear re-
f. Insure that landing gear is DOWN and locked, tracting linkage also operates the main nose gear
then remove jacks. doors.

Nose Gear Retracting Linkage· Removal of Nose Gear Retracting Linkage. (See fig-
ure 4-17.) I
The nose gear retracting linkage consists of a drag
brace, truss assembly, belleranks, torque tubes, a. Jack the aircraft in accordance with Section 2.
push-pull tubes and drive tubes interconnected be- b. Remove pilot's seat and front carpet.
tween the landing gear actuator and the nose gear. c. Remove covers from access holes from underside
A positive down lock is obtained by rigging the drag of fuselage and left front cabin floor.
brace to an overcenter position. The connector link
assembly which holds the drag brace in an over-

I
1. Nut 8. Hinge 14. Nut 20. Spacer
2. Washer 9. Washer 15. Door Link Tube 21. Hinge
3. Door Link Tube 10. Washer 16. Bolt 22. Nut
4. Washer 11. Nut 17. Washer 23. Washer
5. Bolt 12. Cotter Pin 18. Bolt 24. Washer
6. Bolt 13. Bolt 19. Washer 25. Cotter Pin
7. Washer 26. Nut

Figure 4-16. Nose Gear Doors Installation

Change 2
 LANDING SEAR AND 4-41
421 SERVICE MANUAL
BRAKE SYSTEM

d. Disconnect main nose gear doors. k. Remove connector link assembly (48) as follows:
e. Release tension on retracting linkage by engaging 1. Remove nut (29) and bolt (65) attaching connec-
manual extension crank and operating a few turns to- tor link assembly to retracting arm (78).
ward the UP position. 2. Remove nut (50), washer (49), and bolt (47) at-
f. Remove nose push-pull tube (37) as follows: taching connector link assembly to adjusting rod end
1. Remove nut and bolt attaching nose push-pull (51).
tube to fork bolt.
2. Remove nut, Washer, and bolt attaching nose NOTE
push-pull tube to connector link.
Access to bolt (47) is provided by a hole in the
NOTE adjacent structure. Rotate connector link as-
sembly to align hole.
During removal of nose gear linkage, manually
move gear as required for access to attaching 1. Remove drag brace (61) as follows:
bolts and nuts• 1. Remove nut (58), washer (59), and bolt (62) at-
taching drag brace to truss assembly (55).
Remove aft drive tube (1) as follows: to

I
g. 2. Remove nut and bolt attaching drag brace
1. Disconnect alt drive tube from actuator in ac- strut.
cordance with Removal of Landing Gear Actuator, m. Remove up lock torque tube (41) as follows:
steps f and h. 1. Remove nut (44) and washer (45) from each end
2. Move aft drive tube (1) forward as far as pos- of assembly, then unhook spring (82).
sible to gain access to idler bellcrank attachment
point, and remove nut, washer, spacers, and bolt. NOTE
h. Remove forward drive tube (8) as follows:
1. Remove nut, washer, spacers, and bolt attach- Up lock torque tube (41) must be removed with
ing forward drive tube to idler bellerank. bearing assemblies in place.
2. Remove nut and bolt attaching forward drive
tube to outboard bellerank. 2. Remove the bearing assemblies (46) by remov-
i. Remove idler bellerank by removing bolt and ing attaching nuts (43) and bolts (42).
washers. Then remove spacer from idler bellerank.
NOTE

NOTE Bearings are a press fit, and should be re-

moved from supports only for replacement.
Access to bolt (3) is provided by a hole in the
cabin floor above the bolt head. 3. If desired, up lock hook (52) and adjusting rod
end (51) can be removed from up lock torque tube.
j. Remove torque tube (25) as follows: n. Remove truss assembly (55), retracting arm (78),
1. Remove adjusting bellerank (18) by removing and adjusting fork (68) as an assembly as follows:
cotter pin (40) and pin (16). If desired, the fork bolt 1. Remove nut (63) and bolt (56) attaching switch
(39) can be removed from adjusting bellerank. bracket (57) to truss assembly.
2. Remove inboard support bearing (20) by remov- 2. Remove clamps attaching switch wires to retract
ing four nuts (21) and bolts (19). Then remove wash- ing linkage and tilt switch where it will not interfere
er (22). with linkage removal.
3. Pull torque tube (25) inboard until it clears out-· 3. Remove nuts (70), washers (71), and bolts (73)
board support bearing (30), then tilt the outboard end attaching truss assembly to retainers (72).
upward and remove from nose section. Then remove 4. Pull truss assembly forward and remove from
washer (33). aircraft.
4. If desired, outboard support bearing (30) can be 5. If desired, retracting arm (78) and adjusting
removed by removing attaching nuts (31) and bolts fork (68) can be removed from truss assembly by re-
(32). moving attaching nuts and bolts.
5. Remove stop collar (24) from torque tube by re- 6. If desired, retainers (72) can be removed from
moving cotter pin (35) and pin (23). aircraft by removing nuts (76), washers (75), and
bolts (74).
NOTE
Installation of Nose Gear Retracting Linkage. (See
Removal of collar (26) and outboard bellcrank figure 4-17. )
(28) from torque tube (25) is not recommended.
These are matched parts and collar (26) is a a. Install truss assembly (55) as follows:
press fit. 1. If removed, install retracting arm (78) and ad-
justing fork (68) on truss assembly.

NOTE

Lower retracting arm bolt (67) is inaccessible

after truss assembly is installed.
Change 7
4-42 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

38 37

90
88

52 51
90
88 Detail
421A0001 and oN ""
D notan C
37
48 90

80
666

768

63-"
..---60

74 Detai62

Î 7 Detail E

Figure 4-17. Nose Gear Retracting Linkage

Change 2
 MANUAL $¯4
421 SERVICE LANDING GEAR AND A
BRAKE SYSTEM

2. If removed, install retainers (72) with bolts (74), NOTE

washers (75), and nuts (76).
3. Place truss assembly in position and attach to Access to bolt (47) is provided by a hole in the
retainers with bolts (73), washers (71), and nuts (70). adjacentstructure. Rotate connector link as-
4. Install clamps attaching switch wires to retract- sembly to align hole.
ing linkage and attach switch bracket (57) to truss
assembly with bolt (56) and nut (63). e. Install torque tube (25) as follows:
b. Install up lock torque tube assembly (41) as fol- 1. Install stop collar (24) on torque tube with pin
lows: (23) and safety with cotter pin (35).
1. If removed, attach up lock hook (52) and adjust- 2. If removed, install outboard support bearing (30)
ing rod end (51) to up lock torque tube. with bolts (32) and nuts (31).
2. Install bearing assemblies (46) with bolts (42)
and nuts (43). NOTE
3. Install washer (45) and nut (44) on each end of
up lock torque tube assembly. Torque the nuts attaching inboard and outboard
c. Install drag brace (61) as follows: support bearings to 13. 5 ±1. 5 inch-pounds.
1. Attach drag brace to truss assembly (55) with
bolt (62), washer (59), and nut (58). 3. Install outboard washer (33) on torque tube and
NOTE place in position.
NOTE
When installing bolt (62), insure that down
indicator switch bracket (57) is properly in Insert inboard end of torque tube through the
place. inboard mounting hole from the left, pull into
wheel well area until outboard end of torque
2. Connect drag brace to strut with attaching bolt tube can be inserted into outboard support
and nuts. bearing.
d. Install connector link assembly (48) as follows:
link assembly to retracting
4. Place inboard washer (22), then inboard support
1. Attach connector
arm (78) with bolt (65) and nut (79).
bearing (20), on inboard end of torque tube. Install
support bearing with bolts (19) and nuts (21).
2. Attach connector link assembly to adjusting rod
5. II removed, install fork bolt (39) in adjusting
end (51) with bolt (47), washer (49), and nut (50).
bellerank (18).

Figure 4-17. Nose Gear Retracting Linkage Callouts

1. Aft Drive Tube 31. Nut 62. Bolt

2. Bolt 32. Bolt 63. Nut
3. Bolt 33. Washer 64. Bolt
4. Washer 34. Nut 65. Bolt
5. Spacer 35. Cotter Pin 66. Bolt
6. Washer 36. Nut 67. Bolt
7. Bolt 37. Nose Push-Pull Tube 68. Adjusting Fork
8. Forward Drive Tube 38. Bolt 69. Bolt
9. Nut 39. Fork Bolt 70. Nut
10. Washer 40. Cotter Pin 71. Washer
11. Washer 41. Uplock Torque Tube 72. Retainer
12. Bracket 42. Bolt 73. Bolt
13. Idler Bellcrank 43. Nut 74. Bolt
14. Nut 44. Nut 75. Washer
15. Bolt 45. Washer 76. Nut
16. Pin 46. Bearing Assembly 77. Nut
17. Nut 47. Bolt 78. Retracting Arm
18. Adjusting Bellcrank 48. Connector Link Assembly 79. Nut
19. Bolt 49. Washer 80. Washer
20. Inboard Support Bearing 50. Nut 8 1. Nut
21. Nut 51. Adjusting Rod End 82. Spring
22. Washer 52. Uplock Hook 83. Clamp
23. Pin 53. Nut 84. Seal Boot
24. Collar 54. Bolt 85. Spacer
25. Torque Tube 55. Truss Assembly 86. Clamp
26. Collar 56. Bolt 87. Fender
27. Pin 57. Switch Bracket 88. Bolt
28. Outboard Bellerank 58. Nut 89. Nut
29. Bolt 59. Washer 90. Washer
30. Outboard Support Bearing 60. Adjusting Bolt 91. Bracket Assembly
61. Drag Brace

Change 2
4-42 8 LANDING BEAR. AND 421 SERVICE MANUAL
BRAKE SYSTEM

6. Install adjusting bellerank (18) on torque tube NOTE

with pin (16) and safety with cotter pin (40).
Access to lower bellerank is gained through
NOTE
an access hole on underside of fuselage.
Splines must align so that pin (16) can be in-
i. Install nose push-pull tube (37) as follows:
stalled and belleranks (18 and 28) both extend 1. Using the manual extension system, operate the
forward from torque tube. landing gear to the DOWN position, then crank a few
f. Insert spacer (5) into idler bellerank (13), place turns toward the UP position.
bellerank in position and install with bolt (3) and 2. Attach nose push-pull tube (37) to connector link
washers (4 and 6). assembly (48) with bolts, washers, and nuts.
3. Attach nose push-pull tube (37) to fork bolt (39)
g. forward
Install drive tube (8) as follows: with bolt and nut.
1. Attach forward drive tube (8) to outboard bell- j. Rig nose gear retracting linkage in accordance
crank (28) with bolt (29) and nut (34). with rigging procedure,
2. Attach forward drive tube (8) to idler bellerank k. Connect nose gear doors and rig nose gear doors
(13) with bolt (7), washer (10), and nut (9). in accordance with rigging procedure,
1. Install access hole covers and carpet.
NOTE m. Install pilot's seat, insure that landing gear is
DOWN and locked; then remove aircraft from jacks.
To gain access to idler bellerank attach-
ment points, rotate bellerank forward as Nose Gear Shimmy Dampener.
far as possible.
The shimmy dampener provided for the nose gear
3. If seal boot (84) was removed; install boot but offers resistance to shimmy by forcing hydraulic fluid
do not clamp to forward drive tube (8) at this time. through small orifices in the piston. The outer hous-
ing is attached to the upper nose strut and moves as
NOTE the strut turns, while the piston and piston rod are
attached to the trunnion assembly which does not turn,
After gear is rigged, cement rubber spacer thus causing motion between the housing and the piston.
(85) to forward drive tube (8) and clamp boot
to spacer at a position approximately 5 inch-
es from the Station 100. 00 bulkhead while Removal of Nose Gear Shimmy Dampener. (See fig-
gear is in the down position. ure 4-18.)

h. Install aft drive tube (1) as follows: a. Disconnect piston rod (23) from trunnion assem-
1. Attach aft drive tube (1) to idler bellerank (13) bly by removing nut (26), washer (25), spacer (24),
with bolt (2), washer (6), washers (11), and nut (9). washer (22), bolt (21), and cotter pin (28).
2. Attach aft drive tube (1) to landing gear acutator b. Rernove shimmy dampener by removing nut (11),
lower bellerank with bolt. Refer Ìo removal and in- bushing (18), washer (19) and bolt (20).
stallation of landing gear actuator.

Change 7
 MANUAL LANDING SEAR AND
421 SERVICE
BRAKE SYSTEM

4
67 10
11
12

1516
17

421A0001 and ON '

18
20 -

1
3
4
5
' 6 4
4
1 21
10
11 22
o 23
' 121314
, 24
15 25
16 26
7 17 |28

22
23
24
421-0001 TO 421A0001
26
28

19. Washer
1. Lock Ring 10. O-Ring 20. Bolt
2. Internal Retaining Ring 11. Nut 21. Bolt
3. Wiper Ring 12. Cotter Pin 22. Washer
4. Backup Ring 13. Backup Ring 23. Piston Rod
5. O-Ring 14. O-Ring 24. Spacer
6. Bearing Head 15. Roll Pin 25. Washer
7. O-Ring 16. Piston 26. Nut
8. Barrel 17. Bearing Head 27. Retainer
9. Filler Plug 18. Bushing 28. Cotter Pin
Figure 4-18. Shimmy Dampener
 4--44 LANDING GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

Disassembly of Nose Gear Shimmy Dampener. (See Installation of Nose Gear Shimmy Dampener. (See
figure 4-18.) figure 4-18.)

a. Push piston rod (23) into shimmy dampener, re- a. Place bushing (18) in barrel (8), align mounting
move filler plug (9) and O-ring (10), and drain fluid. holes and install bolt (20), washer (19) and nut (11).
b. Remove lock ring (1) from forward end of shim-
my dampener and pull piston and rod assembly from NOTE
barrel (8).
Lubricate bushing (18) with light oil during in-
CAUTION stallation.

Remove bearing heads and piston assemblies b. Connect the piston rod (23) to the trunnion assem-
with care to prevent damage to O-rings. bly with bolt (21), washer (22), spacer (24), washer
(25), nut (26), and cotter pin (28) .

c. Remove O-rings,backup ring and retainer, as c. If not filled with hydraulic fluid during assembly,
applicable, from piston (16). service shimmy dampener in accordance with Section
d. Remove roll pin (15) and remove piston (16) from 2.
piston rod (23).
e. Remove bearing head (17) from piston rod (23).
f. Remove lock ring (1) from aft end of shimmy Nose Gear Steering System.
dampener and pull bearing head (6) from barrel (8).
g. Remove outer O-rings (7) from bearing heads The nose gear steering system permits nose gear
(6 and 17), steering with the rudder pedals, for angles up to 18
h. Remove internal retaining rings, wiper rings, degrees, either right or left of center. Spring loaded
backup rings and O-rings, as applicable, from bear -
nose gear steering cables permit continued resisted
ing heads (6 and 17). turning action of the nose gear for steering angles
greater than 18 degrees, up to a maximum of 55 de-
Assembly of Nose Gear Shimmy Dampener. (See grees. Steering arms, welded to the rudder torque
figure 4--18.) tubes, are connected by the steering cables, to a
steering gimbal, which pivots in a support mounted
Before each component of the shimmy dampener is directly above the nose gear trunnion assembly. The
assemblied, assure that it is thoroughly clean, then gimbal allows nose gear steering when the gear is
lubricate with system hydrualic fluid. down. When gear is retracted, the gimbal serves as
a. Install internal retaining rings, wiper rings, an idler, permitting free wheeling of the nose gear
backup rings and O-rings, as applicable, inside steering.
bearing heads (6 and 17).
b. Install outer O-rings (7) on bearing heads (6 and
17). Removal of Nose Gear Steering System. (See figure
c. Install bearing head (6) in barrel (8) and secure 4-19.)
with aft lock ring (1).
d. Position beai-ing head (17) on piston rod (23), a. Remove pilot's and copilot's seats.
then assemble piston (16) to piston rod (23) with roll b. Remove scuff plates from front carpet by re-
pin (15). moving attaching screws, then remove carpet and
e. Install O-rings, backup ring and retainer, as access panels on pilot's and copilot's side of aircraft.
applicable, on piston (16). c. Remove cable access panel from underside of
f. Insert piston and piston rod assembly into barrel aircraft.
(8), slide bearing head (17) into position, and secure d. Disconnect the nose gear steering cables at the
with forward lock ring (1). forward bellerank in the nose wheel well by loosening
the, turnbuckles.
CAUTION
CAUTION
Insert piston and bearing heads with care to
prevent damage to O-rings. Do not remove clevis pin from nose gear steer-
ing bellerank without first releasing tension on
g. Completely fill shimmy dampener with hydraulic the nose gear steering cables.
fluid, as specified in Section 2, and install filler plug
(9) and O-ring (10). e. Remove necessary radio shelving to gain access
to nose gear steering cable pulleys and remove cable
NOTE guard pins.
f. Disconnect nose gear steering cable from rudder
For proper operation, shimmy dampener must torque tube by removing cotter pin, nut, and bolt,
be completely full of hydraulic fluid, with no g. Remove seals (15) from forward cabin pressure
trapped air present. Push piston rod into the bulkhead.
shimmy dampener to the limit of its travel, h. Pull forward cable through wheel well web into
then fill with hydraulic fluid. If desired, shim- nose section then pull cable forward and remove from
my dampener can be serviced after installation aircraft.
in accordance with Section 2. i. Disassemble cables from spring by removing
 421 SERVICE MANUAL LANDING SEAR ANo 4-45
BRAKE SYSTEM

10 11

2
1

16 13
1

12
Detail 5
3

1. Nose Gear Steering Bellerank 6. Eye 11. Bolt 16. Guide

2. Link 7. Turnbuckle Assembly 12. Cable Pin 17. Cable Assembly
3. Screw 8. Cable Assembly 13. Cotter Pin 18. Spring
4. Nut 9. Pulley 14. Nut 19. Cable Assembly
5. Spacer 10. Washer 15. Seal Assembly 20. Bolt

Figure 4-19. Nose Gear Steering System

 4-46 LANDING OEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

cotter pins, nuts and bolts. seats in hardened steel cups. The nose wheel rotates
j. If desired, remove nose gear steering bellerank around a tubular axle attached to the nose strut fork.
as follows:
1. Remove the two bolts in the gimbaL
2. Remove the nut, washer and bolt in bellerank Removal of Nose Wheel and Tire Assembly. (See
and remove bellerank. figure 4-20.)

a. Jack the aircraft in accordance with Section 2.

Installation of Nose Gear Steering System. (See b. Remove cotter pin (2), nut (3) and bolt (7).
figure 4-19.) c. Remove axle bolt buckets (4). After removal of
buckets, the wheel and tire assembly can be removed
a. If removed, install nose gear steering bellerank from fork (1).
as follows:
d. Remove spacers (5) and axle tube (6) from wheel.
1. Position bellerank in place and install the two

I
washers and bolts in gimbal and torque 50 to 70 inch-
pounds.
2.Align upper hole in bellcrank
ture and install bolt, washer and nut.
with hole in strue-
Disassembly
Assembly.
and Assembly of Nose Wheel and Tire

b. Attach forward end of turnbuckles to bellerank Instructions for the disassembly and reassembly of
with screws, washers and nuts. the main wheel and tire assembly also applies to the
c. Assemble forward and aft cables to spring with nose wheel and tire assembly,
bolts, nuts and safety with cotter pins.
d. Route the aft cable through the spring housing
to the rudder torque tube and connect with bolt and Installation of Nose Wheel and Tire Assembly. (See
nut and safety with cotter pin. figure 4-20.)
e. Route the forward cable through nose wheel well
web. a. Insert axle tube (6) in wheel and place spacers (5)
f. Install seals (15) as follows:
cable on ends of axle tube.
1. Insure that the cables are lubricated for the full b. Place wheel and tire assembly in position, align
length of its travel within the seals, with mounting holes in fork (1), and install axle bolt
2. Pack the seals with MIL-G-7187 lubricant, buckets (4).
3. Place seals on cable on the non-pressurized c. Install bolt (7) and nut (3).
side of bulkhead with small end of seal toward bulk-
head. NOTE
4. Insert seal in bulkhead hole so that bulkhead
metal is seated within the retaining groove of seals Tighten nut (3) until a slight bearing drag is
and so that the small end of the seal is on the pres- felt as wheel is rotated. Loosen nut to the
surized side of the bulkhead. nearest slot that will align cotter pin hole.
5. Install proper retaining rings in the grooves on
the seals (two on small end and one on large end). d. Install cotter pin (2).
g. Install cable guard pins and replace radio equip. e. Insure gear is DOWN and locked, then remove
ment shelves removed during removal. aircraft from jacks.
h. Connect nose steering cables to turnbuckles and
tighten. Rig cable tension in accordance with Rig- Main Wheel and Tire Assembly.
ging of Rudder Control System (Section 7). Re-
safety turnbuckles. The main wheel is a two-piece magnesium alloy cast-
i. Install carpet, scuff plates, pilot and copilot ing. The two halves of the wheel can be separated
seats. to install the tube and tire. Tapered roller bearings,
seated in hardened steel cups, are provided in each
NOTE wheel half. The brake side of the main wheel is
equipped with steel drive keys and provisions to
Nose steering springs are pre-set at the accommodate a dual dise type brake,
factory to 85 pounds.

Removal of Main Wheel and Tire Assembly. (See

Rigging the Nose Gear Steering System• figure 4-21.)
Rig nose gear steering system in accordance with a. Jack aircraft in accordance with Section 2.
Section 7• b. Remove snap ring (1), bearing cap (2), cotter
pin (3), nut (4) and washer from axle.
c. Remove wheel and tire assembly from axle using
Nose Wheel and Tire Assembly• caution to prevent damage to axle threads and to
keep bearings clean.
The nose wheel is a two-piece, magnesium alloy cast¯ d. Remove outer bearing cone (6) from wheel to
ing. Two halves of the wheel, which are bolted to¯ prevent it from dropping out of wheel after wheel
gether, can be separated to install the tire. Each removal,
wheel half contains a tapered roller bearing, which

Change 4
 LANDING SEAR AND 4-4Î
421 SERVICE MANUAL
BRAKE SYSTEM

4 11
7

12

3
5
6 14
17

5
13

14

421BO816 TO 421BOB67
8
16

1. Nose Wheel Fork 7. Bolt 12. Inner Wheel Half

2. Cotter Pin 8. Retainer 13. Tire
3. Nut 9. Bearing Cone 14. Tube
4. Axle Bolt Bucket 10. Nut 15. Outer Wheel Half
5. Spacer 11. Washer. 16. Washer
6. Axle Tube 17. Bolt
Figure 4-20. Nose Wheel and Tire Assembly

Change 11
4-48 LANDING OEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

CAUTION
Disassembly of Main Wheel and Tire Assembly.
(See figure 4-21.)
a. Remove tire (11) as follows: Do not spin bearings with compressed air.
1. Deflate tire by removing valve core from tube.
3. Inspect and repack bearing cones and coat bear-
WARNING ing cups with c ean bearing grease, Specification
Always deflate tire before separating wheel MIL-G-81322.
halves. 4. Wash inboard bearing seal in denatured alcohol
and dry with a clean, soft cloth.
2, Remove nuts (7), washers (8) and bolts (16) and b. Make the following inspection as specified in the
separate wheel halves (9 and 12). following procedures:
3. Remove each wheel half from tire and remove 1. Inspect all parts of wheel for cracks, nicks,
tim and tube corrosion, or other damage. Replace all cracked
b. Remove snap ring (20), felt retainers (18), felt or severely damaged parts.
seal (19) and bearing cone (17) from wheel half (12). 2. Inspect inboard bearing seal for wear of dam-
c. Bearing cups (Ï0and 13) are a shrink fit and age to sealing lip or to metal reinforcing ring. Re-
should be removed only for replacement. place if damaged or deformed.
d. Keyway liners (14) are attached with rivets and 3. Visually inspect bearing cones for nicks,
should not be removed unless replacement is re- scratches, water staining, spalling, heat discolora-
quired, tion, roller wear, cage damage, cracks, or distor-
tion. Replace if defective or worn.

I
CAUTION
4. Inspect wheel halves for cracks, corrosion,
During disassembly be careful not to gouge, and other damage. Areas having suspected cracks
nick or scratch the rim in the tire bead seat should be inspected by Zyglo or other dye-penetrant
area, this could cause wheel rim to crack. method. Cracked or badly corroded castings should
be replaced. Smäll nicks, scratches, or pits in the
Cleaning and Inspection of Main Wheel Assembly. castings should be blended out with fine (400 grit)
wet-or-dry sandpaper,
a. Remove dirt and grease as specified in the fol 5. Inspect bearing cups for looseness, scratches,
lowing procedures: pitting, corrosion, or evidence of overheating. If
evidence of añy defect exists; replace cup as ex-
WARNING
plained in the Replacement of Bearing Cup Procedures.
Dry-cleaning solutions are toxic and volatile. 6. Inspect valve hole of outboard wheel half for
Use in a well-ventilated area. Avoid contact cracks or corrosion. Replace cracked wheels.
with skin or clothing. Do not inhale vapors. Pits or nicks may be polished out with fine (400 grit)
wet-or-dry sandpaper.
1. Clean 11 metal parts with dry-cleaning 7. Inspect wheel bolts. Carefully check for cracks
solutidn '
Federal Specification P-D-680. in radius under bolt head and in the threads adjacent
A soft bristle brush
may be used to remove hardened grease, dust, or to the bolt shank. Replace cracked bolts,
dirt.
NOTE
CAUTION
No reworking of bolts is permissible.
Clean bearing cones in a separate container
8. Inspect self-locking nuts for self-locking fea-
of clean solvent.
ture. Replace if nut can be turned onto bolt with the
- 2. Dry bearing cones thoroughly, fingers past the nut's locking section.
using filtered and
dried compressed air.

Figure 4-21. Main Wheel, Tire and Brake Assembly Callouts

1. Lock Ring 14. Keyway Liner 28. Esion Insulator

2. Cap 15. Countersunk Washer 29. Nut
3. Cotter Pin 16. Bolt 30. Bleeder Plug
4. Nut 17. Bearing Cone 31. Torque Tube
5. Washer 18. Grease Seal Ring 32. Pressure Plate
6. Bearing Cone 19. Grease Seal Felt 33. Rotating Disc
7. Nut 20. Snap Ring 34. Stationary Disc
8. Washer 21. Bolt 35. Spacer
9. Wheel Half 22. Bolt 36. Wear Pad
10. Bearing Cup 23. Countersunk Washer 37. Back Plate
p. Tire and Tube Assembly 24. Housing 38. Nut
12. Wheel Half 25. Union 39. Spacer
fi. Bearing Cup 26. "O" Ring 40. Rivet
27. Piston 41. Wear Pad

Change 2
 421 SERVICE MANUAL LANDING GEAR AND 4-4Û
BRAKE SYSTEM

11
9
10

17
18
19
18
20

37 14 13
O
36
35

33
34

32
31
30
29
2

22

41 21

RH WHEEL ASSEMBLY SHOWN

Figure 4-21. Main Wheel, Tire and Brake Assembly

4-50 LANDING SEAR 421 SERVICE MANUAL
AND BRAKE SYSTEM

9. Inspect keyway liners on inboard wheel half for CAUTION

wear. If distance between surfaces of liners across
any tang slot of inboard wheel half exceeds 0. 680 Peened head of rivet must be on outside of
inch, replace liners as explained in the Replacement keyway liner. Chamfered head of rivet must
of Keyway Liners Procedures in Section 4. be installed in countersink in wheel flange.
10. Inspect keyway liners for tightness. If loose,
either tighten or replace rivets.
Retreating and Repainting of Main Wheel Repaired
NOTE Surfaces.

Replace all parts of brake assembly which a. Thoroughly clean repaired surfaces and areas
are cracked, unrepairable, or otherwise of the wheel from which paint has been removed.
unserviceable. b. Treat cleaned surfaces with Dow No. 1 solution,
Specification MIL-M-3171, and paint with two coats
Replacement of Bearing Cup. (See figure 4-21.) of zinc chromate primer, Specification MIL-P-8585A,
and two coats of aluminum lacquer, Specification TT-
a. Heat wheel half in boiling water for one hour, or L-32
250°F (121°C)
in an oven not exceeding for 30 min-
utes. CAUTION
b. Remove wheel half from source of heat and re-
move bearing cup. Never paint working surfaces of bearing cups.
NOTE Wheel register surfaces and bolt bosses
should receive one mist coat of zinc chromate
After heating wheel half, bearing cup should primer only.
be loose enough to fall out of bearing bore
when inverted. If cup does not drop out, tap NOTE
evenly from bore with a fiber drift pin.
Wheel halves between bead flanges should be
c. Place wheel half (9 or 12) in boiling water for kept painted with zine chromate primer and
one hour, or in an oven not exceeding 250°F (121°C) aluminum lacquer. This will help to prevent
for 30 minutes. Chill bearing cup on dry ice. corrosion.
d. Remove wheel half from source of heat.
e. Dry chilled bearing cup thoroughly and coat con-
tacting surfaces of cup with zinc chromate primer or Assembly of Main Wheel and Tire Assembly. (See
paste. figure 4-21.)
f. Install chilled bearing cup in heated wheel half
and tap into place evenly with a fiber drift pin. a. If removed, replace bearing cups (10 and 13).
b. Install tube, yellow stripe on base of tube align-
NOTE ed with red dot on tire to obtain proper balance in
tire, and leave deflated.
Bearing cup should be installed while primer c. Place wheel halves (9 and 12) in position on tire.
or paste is still wet. d. Install bolts (16), countersunk washers (15),
washers (8) and nuts (7). The countersink of wash-
Replacement of Keyway Liner. (See figure 4-21. ) ers (15) must be facing the bolt head. Torque bolts
to 120 inch-pounds.
a. Grind off rivet head.
b. Punch out rivet and remove keyway liner (14). CAUTION

CAUTION Tighten nuts evenly and torque correctly in

a criss cross pattern to lessen the possibil-
Support flange solidly when punching out ity of bolt failure. Make sure at least one
rivets. Be careful not to enlarge rivet full thread is through nut.
holes.
e. Inflate tire enough to seat the beads on the wheels,
c. Inspect area under keyway liners for corrosion. deflate completely, then reinflate to approximately
Blend out corrosion pits to 0. 010 inch deep and re- one-half operating pressure.
treat and repaint reworked areas in accordance with f. Install bearing cone (17), felt seal (19), grease
the Retreating and Repainting Procedures. seal rings (18) and snap ring (20).

d. Position new liner (14) on inboard wheel half CAUTION

with tab extension on ends of liner toward the center-
line of the wheel. The outer edge of the liner should Insure that bearing cones (6 and 17) are pro-
be flush with the outer edge of the wheel. perly greased before installing.
e. Install rivet (40) through wheel flange and key-
way liner (14). g. Check wheel balance using Service Kit SK150-20.

Change 9
 421SERVICE MANUAL LANDING GEAR
4-51
AND BRAKE SYSTEM

Installation of Main Wheel and Tire Assembly. (See c. Install cotter pin (3), bearing cap (2) and lock
figure 4-21.) ring (1).
d. Check that wheel rotates freely, then remove
a. Place the wheel and tire assembly in position on jack and inflate tire to correct operating pressure.
the axle, aligning brake dises with dise drive slots
in wheel.
BRAKE SYSTEM -

MAIN AND PARKING.

NOTE
The aircraft has a hydraulically actuated braking
Ascertain that the seven keyway liners (14) system. A hydraulic master cylinder is attached to
are properly installed in the wheel flange. each pilot's rudder pedal with lines routed to the
brake assemblies on each main gear. The brakes
b. Install outer bearing cone (6), washer (5) and are dual-disc, non-adjustable type with five actuat-
nut (4). ing cylinders in each brake assembly. The brakes
may be operated from either pilot's or copilot's
NOTE pedals. The parking brake system consists of a
manually operated handle assembly connected to the
Tighten wheel bearing nut (4) to 40 pound- parking brake valves located in each main brake line.
inches while rotating wheel, back off nut When pressure is applied to the brake system and the
and retighten to 20 pound-inches while rotat- parking brake handle is pulled, the valve holds pres-
ing wheel, continue to first locking position sure on the brake assemblies until released. To
and install cotter pin. release parking brakes, push parking brake handle
in. It is not necessary to depress rudder pedals
when releasing parking brakes.

Trouble Shooting the Brt ke System.

TROUBLE PROBABLE CAUSE CORRECTION

BRAKE PEDAL BOT- Insufficient brake fluid in system. Bleed and fill system in accordance with
TOMS Section 2.

Brake disc warped, causing exces- Replace disc.

sive clearance.

Loose bleeder screw, faulty bleeder Tighten bleeder screw. Replace washer,
screw washer, or adapter not tight. Tighten adapter.

Leaking connections or broken lines Tighten connections. Replace or repair

or hoses. lines or hoses.

Rudder pedals not connected to Connect pilot's rudder pedals to master

master cylinders, cylinders.

Damaged O-ring seal in master cyl- Replace O-ring seal,

inder or in brake actuating cylinder.

Lock-o-seal in master Replace Lock-o-seal,

Damaged
cylinder.

"SPONGY" BRAKES Air trapped in system. Bleed system.

Swollen hose. Replace hose.

BRAKES DRAG Binding brake pedal linkage. Free linkage to prevent binding.

Brake disc badly dished or warped. Replace brake disc.

Internally swollen hoses and/or Replace hoses and/or O-ring seals. Flush
swollen O-ring seals due to system with denatured alcohol. Bleed and
improper hydraulic fluid in system. fill system in accordance with Section 2.
4-52 LANDING SEAR AND 421 SERVICE lVÏANUAL
BRAKE SYSTEM

Trouble Shooting the Brake System Cont'd.

TROUBLE PROBABLE CAUSE CORRE CTION

BRAKES FAIL TO Brake dises worn out. Replace dises in accordance with Section 2.
HOLD

New discs just installed. Taxi aircraft and apply brakes several
times to condition dises.

Air in system. Bleed and fill system in accordance with

Section 4.

Oil, grease, or other foreign ma- Clean and flush with carbon tetrachloride,
terial on dises. then taxi the aircraft slowly, apply the
brakes several times to condition the discs.

Rudder pedals positioned so that Reposition pedals.

brakes cannot be fully applied.

Brakes too hot from extensive use, Allow time for brakes to cool.

Removal of Brake System. (See figure 4-22.) line from stub wing section.
m. Remove clamps from lines (18 and 20) then dis-
a. Drain fluid from system by removing bleeder connect union (19) and elbow (22) and remove lines
screw. thru access holes in wing.
b. Remove pilot's and copilot's seats in accordance n. Remove clamps from lines (21 and 23) then dis-
with Section 3. connect at elbows (22 and 25) and remove into wheel
c. Remove front carpet and scuff plates from front well area.
floorboards. o. Remove clamps from line (24) on right wing and
d. Remove the access panels in front floorboard disconnect at elbow (25).
area and on bottom of fuselage. p. Remove elbow (25) from structure of wing by
e. Remove covers frorì around rudder pedals. removing the nut and washer and disconnecting hoses
f. Disconnect master cylinders (29) from rudder (26).
pedals and rudder torque tube by removing cotter q. Remove clamps (27) from main gear strut and
pins and clevis pins. disconnect hose at brake unit, then remove hose,
g. Remove hoses (1 and 2) from master cylinders r. Remove brake units by removing the six bolts
and parking brake valve. securing unit to strut and remove union (28).
h. On aircraft 421-0001 to 421B0001 disconnect link s. If removal of parking brake control is desired,
(11), cable (31), and stop (10), and lines (12 and 13) remove as follows:
from parking brake valves (5). Remove parking 1. Remove clamps (6) by removing nut (9), spacer
brake valves (5) by removing nuts, washers, and (7), and screw (8).
screws attaching valves to bulkhead. 2. Remove stop (10) from cable.
i. On aircraft 421B0001 and ON disconnect cable 3. Remove nut securing cable (31) in panel bracket
(31) and lines (12 and 13) from parking brake valve and pull cable (31) aft out into cabin area.
(5). Remove parking brake valve (5) by removing
nuts, washers, and screws attaching valve to brack-
et (32). Installation of Brake System. (See figure 4-22.)
j. Remove clamps from lines (12 and 13) then dis-
connect lines from elbow (14) and union (15) and re- a. If removed, install parking brake control as
move line, follows:
1. Route cable (31) thru panel bracket, forward
NOTE thru grommet, and around down and aft into parking
brake valve area. Then clamp to brackets with
Removal of brake lines is not recommended clamps (6), spacers (7), screw (8), and nut (9).
except for replacement.
CAUTION
k. Remove access panels on lower side of inboard
leading edge, wing gap covers, left and right wings. Do not bend cable in too sharp a radius to pre-
1. Remove clamps from lines (16 and 17) then dis- vent binding in cable action.
connect at wing gap from unions (15 and 19) and pull
 421 SERVICE MANUAL LANDING GEAR AND 4-53
BRAKE SYSTEM

4 12 2 3
32

Detail Detail
421-0001 TO 421B0001 421B0001 Al ) ON
5

15
17
12 19

3
25
A54471001
Detail B 27
26
A54472001 3Û
51473001 28 /
B51473001

1. Hose LH (To Master Cylinder) 12. Line LH 22. Elbow

2. Hose RH (To Master Cylinder) 13. Line RH 23. Line Assy. LH Brake
3. Elbow 14. Elbow 24. Line Assy. RH Brake
4. Elbow 15. Union 25. Elbow
5. Valve Parking Brake 16. Line Assy. RH Brake 26. Hose
6. Clamp 17. Line Assy. LH Brake 27. Clamp
7. Spacer 18. Line Assy. RH Brake 28. Union
8. Screw 19. Union 29. Master Cylinder
9. Nut 20. Line Assy. LH Brake 30. Brake Assembly Main Wheel
10. Stop 21. Line Assy. RH Brake 31. Cable
11. Link

Figure 4-22. Brake System Plumbing Installation

Change 8
4-54 LANDING GEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

2. Install stop (10) with screw and nut, and tighten

only snug at this time,
b. Install brake units on main strut with six bolts
and nuts and install elbow (28) in brake unit.
c. Install hose (26) and clamp to strut with clamps
(27),
d. Install elbow (25) in bulkhead with washer and
nut.
e. Connect hose (26) to brake unit and elbow (25).
'
SS 60" s
f. Route lines (23 and 24) in position. Connect to 4 p
elbow (25) and clamp. O,
g. Install elbow (22) on lines (21 and 20). Route in
place and connect to lines (23 and 24) and clamp in
place.
h. Install unions (19) on lines (17 and 21) then route
in wing and clamp in place.
i. Install unions (15) on lines (12 and 16) and route
in wing position and connect to line (17) and clamp as
required.
j. Install line (13) to elbow (14) and connect to line
(16) then clamp.

NOTE Figure 4-22A. Wear Pad Wear Limits

When installing lines, it may be neeëssary to

bend lines to work into position. However, b. Apply 600 psi pressure to the brake and hold.
excessive bending should be avoided. c. Measure distance between inside face of brake
housing and pressure plate. If this distance mea-
k. Assemble parking brake valves (5). sures 0. 234 inch or greater, remove brake for in-
1. On aircraft 421-0001 to 421B0001 perform the spection.
following procedures:
1. Install fittings (4) and valve link (11).
2. Install valves (5) in place with screws and nuts. Removal and Disassembly of Main Wheel Brake
3. Connect valve link (11) with bolt, and connect Assembly. (See figure 4-21. )
cable (31) to link bolt at time of installation.
4. Rig stop (10) so the valve link (11) movement To remove either brake assembly, proceed as fol-
is stopped, in forward direction, approximately lows
1/16 inch before it reaches the full forward direc- a. Reiove wheel and tire assembly.
tion of the valve arms. Loosen stop to set, then b. Disconnect brake line from union (25).
tighten stop screw. c. Remove brake assembly from axle by removing
m. On aircraft 421B0001 and ON perform the fol- eight nuts (29), washers and bolts (21).
lowing procedures: d. Lay brake assembly on a clean flat surface and
1. Install fitting (4) to valve. remove nuts (38), bolts (22) and countersunk washers
2. Install valve (5) to bracket (32) with screws and (23) releasing back plate (37).
nuts- e. Remove rotating disc (33), stationary disc (34),
3. Connect cable (31) to valve assembly. second rotating disc (33) and pressure plate (32).
n. Connect lines (12 and 13) and install hoses (1 and f. Remove spacer (35).
2). g. Remove piston insulators (28) and pistons (27)
o. Assemble master cylinders and place in position from housing (24), then remove O-ring seals (26)
and connect hoses (1 and 2). from brake housingt
p. Install lower end of master cylinders with spa-
cers, clevis pins, and safety with cotter pins.
q. Connect top end of master cylinders with clevis Cleaning of Brake Assembly Parts.
pins and safety with cotter pins.
r. Fill master cylinders and bleed in accordance a. Clean all metal parts of brake assembly, except
with the bleeding procedure. Check system for leaks. rotating dises, in dry-cleaning solution, Federal
s. Replace all access covers, forward wing struc- Specification P-D-680, and dry with filtered com-
tural skin, floorboard covers and carpet. pressed air. A soft bristle brush may be used where
t. Replace pilot's and copilot's seats. necessary.

Checking of the Wearing of Brake Dises. WARNING

Dry-cleaning solvents are toxic and volatile.

Brake dise wear can be determined while brake is on Use in a we11·-ventilated area. Do not inhale
aircraft as follows: solvent vapors or allow solvent to contact
a. Apply and release brakes twice. skin or clothing.
Change 8
 421 SERVICE MANUAL LANDING 6EAR AND 4-55
BRAKE SYSTEM

b. Clean rotating dises with compressed air and a

soft wire or stiff bristle brush. c. Inspect pressure plate subassembly (32) as fol-
c. Clean piston insulators with denatured alcohol. lows:
Dry with compressed air or a clean cloth.
1. Inspect pressure plate subassembly for cracks
NOTE in corners of keyslots. Discard if cracked.
2. Inspect subassembly for thickness. Replace if
It is recommended that new O-ring packings worn to 0. 225 inch or less in thickness measured
be installed at each overhauL If packings between wear pad rivets.
must be reused, they should be cleaned with 3. Inspect wear pads (41) for thickness. Replace
denatured alcohol and dried with a clean, all pads if any rivet is sheared, any pad is cracked,
soft cloth. Reinstall packings in same lo- or if one or more pads are worn to a width of 2. 75
cation from which they were removed. inches or less, as shown in Figure 4-22A. Install
new pads in accordance with applicable instructions.
4. Discard if key slot width is less than U. 61b or
Inspection of Brake Assembly Parts. (See figure 4-21.) greater than 0. 640 inch.
5. Inspect for dishing. Replace pressure plate
Inspect all parts for cracks, nicks, scratches, dam- dished in excess of 0. 015 inch.
aged threads, or other damage. Discard all cracked 6. Discard pressure plate which is 0. 120 inch or
parts and all parts having damaged threads. more out-of-round.
a. Inspect rotating discs (33) as follows: d. Inspect back plate subassembly (37) as follows:
1. Inspect relief slot terminal holes and drive tang 1. Inspect for cracks. Pay particular attention to
radii for cracks. Discard cracked discs. relief slot terminal holes. Discard cracked back
2. Inspect disc for wear. Discard disc when min- plate.
imum thickness across unchipped mix becomes 0. 143 2. Inspect wear pads (36) for thickness. Replace
inch or less or if mix is worn to 0. 015 inch thick at all pads if one or more pads are worn to 0, 090 inch
any location on either face of disc. or less in thickness when measured from face of pad
to surface of back plate, or if pad width is less than
2. 75 inches, as shown in Figure 4-22A. Install new
pads in accordance with applicable instructions.
NOTE 3. Inspect for dishing. Replace back plate if dish-
ed 0. 015 inch or more.
As much as 25 percent of mix may be lost e. Inspect the torque tube (31) as follows:
through chipping, provided mix loss is 1. Inspect for cracks. Discard cracked torque
scattered. tube.
2. Inspect for key width. Discard torque tube if
3. Inspect discs for dishing. Discs can be.dished key is worn to a width of 0.550 inch or less at any
a maximum of 0. 015 inch if they are to be used with point on any key,
other dished discs. f. Inspect the brake housing (24) as follows:
4. Discard dises that are 0. 125 inch or more out 1. Inspect housing for cracks. Discard cracked
of round. housing.
5. Inspect disc tangs for battering. Discard disc 2. Discard housing having stripped or badly dam-
when one or more tangs becomes less than 0. 615 aged threads in inlet and bleeder bosses.
inch in width. 3. Inspect piston cavities for wear. Discard hous-
6. Inspect disc for shrinkage. Discard discs that ing if any cavity exceeds 1. 386 inches in diameter.
have shrunk to an inside diameter of 7. 750 inches or 4. Inspect for nicks, scratches, and corrosion.
less. Rework in accordance with applicable instructions,
b. Inspect stationary disc (34) as follows: g. Ïnspect the pistons (27) as follows:
1. Inspect relief slot terminal holes and key slot 1. Inspect pistons for wear. Measure diameter of
corners for cracks. Discard cracked discs. pistons at three places around circumference. Dis-
2. Inspect disc for wear. Discard dise when worn card any piston if diameter at any location measures

lto a thickness of 0. 146 inches or less on aircraft

421-0001 to 421B0001 or when worn to a thickness of
0.170 inches or less on aircraft 421B0001 and On.
3. Inspect for dishing. Dise can be dished a max-
imum of 0. 015 inch if it will be used with other dish-
1. 362 inches or less.
2. Inspect pistons for burrs, scratches,
Discard any piston having damage greater than 0. 003
inch deep on seal contacting surfaces.
tons with damage less than 0.003 inch deep.
or nicks.

Repair pis-

ed discs, h. Inspect the piston insulators (28) as follows:

4. Check inside diameter of disc for size by as- 1. Inspect piston insulators for deterioration or
certaining that it can be installed on the torque tube wear. Discard insulators worn to 0. 215 inch or
without interference. less in thickness.
5. Check key slots for wear and battering. Dis- 2. Remove blisters and raised areas not exceeding
card dise wita keyslots less than 0. 590 inch or 0. 010 inch from insulators with a file or by grinding,
greater than 0. 640 inch in width. making .certain a minimum thickness of 0. 215 inch is
6. Inspect disc for shrinkage. Discard disc if maintained, and that both faces are parallel.
shrunk to an inside diameter of 7. 10 inches or less i. Carefully inspect brake bolts for thread damage
measured between ends of key slot tangs. and cracks under head and in threads adjacent to bolt
Change 12
4-56 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

ment of the wear pads. A maximum of one

crack is permitted in the shop head of a tu-
bular rivet, but it must not extend into the
rivet shank. To check rivets that appear
0. 105 MAX unseated, insert a 0, 0015 inch feeler gage
0. 251 MAX 0, 095 MIN between the disc and the pad. It should not
0. 247 MIN slide past the rivet,

d. After repadding, grind the wear-padded subas-

sembly to the thickness as shown in Figure 4-22B.

NOTE

Wear pads must be ground flat to each other

with assurance that the minimum dimensions
shown in Figure 4-22B are held. No more
than 25 percent of the rivet head shall be re-
PRESSURE PLATE
moved by grinding as shown in Figure 4-22C.

BACK PLATE Applying Protective Coating.

Treat newly ground back and pressure plates which

are not to be put immediately into service as follows:
a. Degrease dises in a vapor degreaser to remove
all oil and grinding residue.
Figure 4-22B. Limits For Repadded Pressure b. Immerse disc in Houghton's Rust Veto 377 or
and Back Plates equivalent. Use in the "as-received" condition with-
out dilution. Let dises drip and air dry for five min-
shank. Discard bent or cracked bolts or ones with utes or more. Clean, compressed air may be used
thread damage. No refinishing of these parts is per- to speed drying.
missible.
j. Inspect self-locking nuts for self-locking feature. WARNING
Replace if nut can be spun onto brake bolt with the
fingers past the nut's locking section. Rust Veto is highly flammable. Observe all
fire precautions during its use.

Replacement of Wear Pads on Pressure Plate and

Back Plate. (See figure 4-21. )

a. Using a 7/32 (0. 218) inch drill, remove wear NOTE

pads (36 or 41) from back. plate or pressure plate by
drilling out shop heads of old rivets and punching out SHADED PORTION INDICATES AREA
rivets. GROUND FROM RIVET HEAD.

CAUTION

Exercise care to avoid damaging or enlarging

rivet holes. TOTAL RIVET
HEAD AREA
b. Inspect base plate of pressure plate or back
plate for cracks, using Magnaflux or equivalent
method. Discard cracked base plates or base plates
dished 0. 015 inch or more.
c. Using the proper rivets, install new wear pads \ /

and rivets. Rivets shall be installed by the conr-

pression method so that formed head or rivet is
flush with or below the surface of the wear pad.

NOTE

When installation is complete, rivets must

be snug. A slight movement of wear pads
is desirable. It should be determined that Figure 4-22C. Rivet Head Grinding Limits
a force of not less than 2 pounds or more
than 100 pounds is required to cause move-
 4-5·/
421 SERVICE MANUAL LANDING SEAR AND
BRAKE SYSTEM

Repairing Torque Tube. tube (31).

8. Install five bolts (22), countersunk washers (23)
a. Repair worn disc drive keys which have not worn and nuts (38) securing the assembly as a unit. Draw
to 0. 550 inch or less by blending out indentations in up bolts evenly and torque to 120 inch-pounds.
keys.
CAUTION
Repairing the Housing.
Countersunk washers (23) must be installed
a. Blend out and polish burrs, nicks, and scratches under the bolt heads with the countersink fac-
to 0. 030 inch deep on outside of housing with 280 grit ing the bolt head.
(wet-or-dry) sandpaper.
b. Blend and polish out scratches in piston cavities b. Place brake assembly on axle with bleeder
not exceeding 0. 003 inbh deep with fine 400 grit (wet- ports at top and secure to axle flange with eight
or-dry) sandpaper. Remove burrs and rough edges bolts (21), washers and nuts (31). Draw up nuts
from seal grooves to a 0. 010 to 0. 015 inch radius evenly and torque to 100-120 inch-pounds.
with 400 grit (wet-or-dry) sandpaper. Avoid heavy c. Connect hydraulic brake line to elbow (25).
localized polishing as this can promote leakage. d. Fill and bleed brake system in accordance with
bleeding procedure.
Repairing the Piston.

a. Blend out and polish scratches, nicks, and burrs Bleeding the Brake System· (See figure 4-21.)
on edges and seal contacting surfaces of piston to
0. 003 inch deep. In order to assure proper brake action, it is neces-
b. Blend repairs to avoid local indentation of piston sary to have positive transfer of hydraulic pressure
seal surfaces. Discard pistons damaged deeper than through the system. Any air trapped in the system
0. 003 inch. must be removed. This is accomplished by bleeding,
c. Retreat reworked areas with Dow No. 1 Solution, which can be done in any one of several different
MIL-M-3171, Type I. ways. The following procedure is bleeding by pres-
sure with a bleeder pump:
Retreating and Repainting Brake Housing. a. Fill reservoir of bleeder pump with clean s ys-
tem hydraulic fluid. (See Section 2 for hydraulic
a. Rinse
reworked areas with hot water and dry fluid specifications.)
thoroughly with filtered, dried compressed air. b. Remove filler plug from master cylinder.
b. Retreat reworked areas with Dow No. 1 Solution,
MIL-M-3171, Type L NOTE
c. Repaint reworked areas with two coats of zinc
chromate primer, Specification MIL-P-8585, and When bleeding the brake system, it is advis-
two coats of aluminum lacquer, Specification TT-L- able to wrap the master cylinder with rags to
32. prevent fluid from spilling or leaking on the
carpet.

Installation and Assembly of Main Wheel Brake. c. Remove bleeder screw and open bleeder plug
(See figure 4-21.) and allow hydraulic fluid to drain from the system
into a suitable container.
a. Assemble main wheel brake as follows: d. Connect the hose to the bleeder pump to the
1. Lubricate o-rings (26) with hydraulic oil and bleeder valve on top of brake unit.
install in the groove of each cylinder of housing (24). e. Pump slowly until fluid in master cylinder re-

I 2. Install pistons
ricate pistons
(27) in brake housing (24).
with MIL-G-7711 Grease.
3. Install on piston insulator (28) in recess
Lub.

of each
servoir is within 1/2 inch of the top.
f. Close bleeder
hose connection.
plug (30) and detach bleeder pump

piston (27), g. Check brake operation.

4. Position torque tube (31), scalloped side toward
brake housing and align the bolt holes. NOTE
5. Install pressure plate (32), wear pads facing
away from and directly over the pistons. If brakes are "spongy" and do not have a solid
feel in the pedals, repeat the above procedure.
CAUTION
h. Install bleeder screw in brake unit and replace
Be sure the five key ways of the pressure plate filler plug in master cylinder,
and stationary disc engage the five keys of
the torque plate.
Parking Brake Valves.
6. Install one rotating disc (33), one stationary
disc (34) and a second rotating disc in sequence. The removal and installation of the parking brake
7. Position back plate (37) on torque tube spacer valves is included in the Removal and Installation
(35) aligning the bolt holes and position on torque of the Brake System.
4-58 LANDING SEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

5 6
9 10 8 1

6 54 3 2

421-0001 TO 421B0001
421B0001 AND ON

1. Valve Seat 4. Washer 7. Spacer 10. O-ring

2. Elbow 5. Ball 8. Elbow 11. Seal
3. Spring 6. Plunger 9. Lockwasher

Figure 4-23. Parking Brake Valve

Master Cylinder. (See figure 4-24.) servoir to enter the cylinder. This positive unseating
also allows unrestricted passage of fluid from cylin-
Each vertical mounting type
master cylinder used on der to reservoir while the piston is in the static po-
the aircraft incorporates a fluid reservoir and cylin- sition. This is to compensate for any excess fluid
der within the same body (11). A plastic filler plug which may be present in the system due to pumping
(3) is used to close the filler opening in the cover (5), or from thermal expansion. The effective stroke of
which is threaded into the body. The filler plug is the piston is 1. 437 inches with maximum displace-
vented, as sufficient ventilation is not provided by ment of 5327 cubic inch.
. Reservoir capacity is
clearance between the piston rod (6) and piston rod approximately 3. 391 cubin inches.
passage through the cover (5). With the exception
of the piston return spring (12), all internal operat-
ing parts are assembled onto the piston rod; piston Removal of Master Cylinder. (See figure 4-24.)
(17), piston spring (15), lock-o-seal (19), and com-
pensating sleeve (20). A seal between the piston (17) Removal of either master cylinder can be accom-
and the cylinder walls is provided by a packing O-ring plished as follows:
(16) installed in a groove around the piston. As pres- a. Remove pilot's seat in accordance with Section 2.
sure is applied to advance the piston rod into the cyl- b. Remove carpet, left scuff plate, and left access
inder, the piston remains stationary until the lock-o- hole cover.
seal is seated on the piston (. 030 to 040 inch move- . c. Drain hydraulic fluid from master cylinder by
ment). Proper operation of the master cylinder de- removing the line at the main wheel, then connect the
pends upon this seating action. When the lock-o-seal line after draining fluid to prevent entry of foreign
is seated, fluid cannot get past the piston and with material into brake.
continued movement of the piston rod forcing the
piston farther into the cylinder, pressure in the cyl- NOTE
inder is increased. At any time during the stroke
that pressure on the piston is eased, the piston spring When making connections on hydraulic lines,
will tend to keep the piston seated against the lock-o- use only system fluid as a lubricant.
seal, maintaining pressure in advance of the piston.
As the pressure is further eased, allowing the piston d. Disconnect clevis (1) from rudder pedal (21) by
return spring to force the piston to retreat, the upper removing cotter pin (24) and pin (25).
end of the compensating sleeve will contact the cover e. Disconnect lower end of master cylinder by re-
boss, forcing the piston to unseat itself from the lock- moving cotter pin (23), pin (21), and spacers (22).
o-seal. This will allow additional fluid from the re- f. Disconnect hose from fitting (7) in base of master

Change 2
 421 SERVICE MANUAL LANDIN6 GEAR 4"
AND BRAKE SYSTEM

16 2

.040

18
15 4

20
10

24

Detail

22
21

1. Clevis 10. Setscrew 18. Lock-O-Seal

2. Jamb Nut 11. Body 19. Compensating Sleeve
3. Filler Plug 12. Piston Return Spring 20. Pilot's Rudder Pedal
4. Screw 13. VVasher 21. Pin
5. Cover 14. Nut 22. Spacer
6. Piston Rod 15. Piston Spring 23. Cotter Pin
7. Elbow 16. O-Ring 24. Cotter Pin
8. Nut 17. Piston 25. Pin
9. O-Ring 26. O-Ring

Figure 4-24, Brake Master Cylinder Installation

4-60 LANDING BEAR AND 421 SERVICE MANUAL
BRAKE SYSTEM

cylinder body (11) by lifting master cylinder enough (17) against nut, adjust clearance between piston and
to allow removal of hose. lock-o-seal (18) to 0. 040 inch as illustrated, using
g. Remove master cylinder and cap hose to prevent feeler gage or 0. 040 to check measurement.
entry of foreign material into system.
CAUTION
Disassembly of Master Cylinder. (See figure 4-24. )
Be careful, when inserting feeler gage or
Disassembly of either master cylinder can be accom- wire, not to damage lock-o-seal.
plished as follows:
a. Remove filler plug (3) and drain residual hydrau- NOTE
lic fluid from reservoir portion of master cylinder.
The 0. 030 to 0. 040 inch dimension between
Screw (4) serves no purpose in this assembly except
the lock-o-seal and the
piston determines the
as a plug for the threaded hole in the cover, and need
between piston rod travel and
.

not be removed. relationship

Pro-
b. Remove setscrew (10) and unscrew cover (5) to seating of the lock-o-seal to the piston.
per master cylinder operation depends upon
remove cover and piston rod (6) along with the other
illustrated parts which are attached to the piston rod. this dimension being set correctly.
The piston return spring (12) will remain inside the sec-
d. Place piston return spring (12) into cylinder
body (11); to remove, lift from position.
c. Remove nut (14) from piston rod (6), to remove tion of body (11).
piston spring (15), piston (17), lock-o-seal (18), and
NOTE
compensating sleeve (19).
d. Back off jamb nut (2) from its locking position On aircraft 421-0001 to 421A0005 make sure
against base of clevis (1) and remove both parts from piston return spring (12) is installed correct-
piston rod (6)- ly with broad base down.
e. Remove O-ring (16) from piston (17).
f. Remove elbow (7) from body (11), if required. e. Lubricate cylinder walls and piston (17) with
clean system hydraulic fluid and insert nut (14)
NOTE against piston return spring.
Clean all metal parts with a suitable solvent. f. Place compensating sleeve (19) notched end to-
O-ring seals should be washed in clean sys ward piston, over piston rod (6). Slide cover (5)
tem hydraulic fluid or denatured alcohol. In over piston rod, and tighten into body. Install set-
screw (10) and tighten to prevent movement of cover
spect metal parts for wear and thread damage.
Inspect cylinder walls for corrosion, pitting
(5).
and scores. Damaged cylinder g. Screw jamb nut (2) and clevis (1) onto piston rod
walls require
replacement of the body (11). Inspect Œring end.
seal (16) and O-ring portion of lock-o-seal h. Install filler plug (3), and elbow (7), if removed
(18) for swelling, chipping, or other evidence during disassembly.
of damage. Replace as necessary. Repairs NOTE
to master cylinder components are not re- lub-
If elbow is being installed, use a suitable
commended. Damaged or defective parts
should be replaced. ricant on O-ring (9) and threads before screw-
ing into master cylinder.
Assembly of Master Cylinder. (See figure 4-24. ) 4-24. )
Installation of Master Cylinder. (See figure
Assemble either master cylinder as follows:
a. Install lock-o-seal
Install either master cylinder as follows:
(18) on shank of piston rod (6). (7).
a. Lift hose end and connect to lower elbow
CAUTION
NOTE
Lubricate O-ring portion of lock-o-seal with
Use only system hydraulic fluid for lubricant
system hydraulic fluid and install carefully
when making this connection.
prevent damage from the threaded portion of
the piston rod shank. b. Insert pin (21) through master cylinder mounting
brackets and hole in body of master cylinder (11) with
b. Slip O-ring (16) into groove in piston (17) as il- spacers (22) in place as,illustrated. Secure pin (21)
lustrated, using clean system hydraulic fluid as a with cotter pin (23).
lubricant. c. Connect clevis (1) to rudder pedal (20) with pin
(25). Adjust clevis (1) to align tips of rudder pedals
CAUTION
(20) with rudder pedals in a neutral position. Secure
Install O-ring carefully to prevent chipping on pin (25) with cotter pin (24), and secure clevis with
sharp corner of piston. jamb nut (2).
d. Install access hole cover, carpet, and scuff plates.
c. Install piston (17), piston spring (15), and nut e. Fill master cylinder and bleed brakes in accord-
(14) on piston rod (6) as illustrated. Tighten nut (14) ance with bleeding procedure in Section 4.
and with piston spring (15) compressed to seat piston f. Install pilot's seat.
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 51
AND TRIM CONTROL SYSTEMS

SECTION 5

CONTROL COLUMN, AILERON AND TRIM CONTROL SYSTEMS

Table of Contents

Page Page

CONTROL COLUMN . . . . . .
5-1 Removal of Aileron Wing Bellerank . .
5-7
Removal . . . . . . . .
5-1 Installation of Aileron Wing Bellerank .
5-7
Disassembly . . . . . . .
5-1 Rigging Aileron Control System . . .
5-9
Assembly . . . . . . . .
5-3 AILERON TRIM CONTROL SYSTEM . .
5-9
Installation . . . . . . .
5-3 Troubleshooting . . . . . .
5-9
Rigging . . . . . . . .
5-3 Removal of Aileron Trim Control Cables
AILERON . . . . . . . .
5-3 and Chains . . . . . . .
5-11
Removal . . . . . . . .
5-3 Installation of Aileron Trim Control
Installation . . . . . . .
5-4 Cables and Chains . . . . .
5-11
AILERON TRIM TAB . . . . . .
5-4 Removal of Aileron Trim Tab Actuator .
5-11
Removal . . . . . . . .
5-4 Disassembly, Overhaul and Assembly of
Installation . . . . . , .
5-4 Trim Tab Actuators . . . .
5-13
AILERON CONTROL SYSTEM . . . .
5-4 Installation of Aileron Trim Tab Actuator. 5-13
Troubleshooting . . . . . .
5-4 Removal of Aileron Trim Control Knob
Removal of Aileron Control Cables . .
5-5 and Pointer Assembly . . . . 5-15
Installation of Aileron Control Cables .
5-5 Installation of Aileron Trim Control Knob
Removal of Aileron Fuselage Bellerank .
5-7 and Pointer Assembly . . . .
5-15
Installation of Aileron Fuselage Bellerank. 5-7 Rigging Aileron Trim Control System .
5-15

CAUTION

Primary and secondary flight control cables, push pull tubes, bellcranks and mountings
on late model aircraft use dual locking fasteners. The lock nuts for these fasteners incor-
porate a fiber lock, and are castellated for safetying with a cotter pin. When any of these
areas are disconnected on any aircraft, new dual locking fasteners should be installed.
See the Aircraft Parts Catalog for part numbers and location of these fasteners.

CONTROL COLUMN.
NOTE
The control column assembly consists of two teles-
copic tube assemblies which rotate within each other. To remove nut (15), remove cover (17) and
The control column incorporates the use of roller- gasket (16) from the forward side of forward
bearings for the purpose of easing the forward and cabin pressure bulkhead (18).
aft motions of the tube assemblies. Each control
column is attached to the forward cabin bulkhead and
is supported by a bearing block. A roller-bearing e. Remove safety and loosen turnbuckle (13) to
block assembly supports the control column at the relieve tension on rigging chain (14) and disengage
stationary instrument panel. The control column as- chain from sprocket.
semblies are physically coupled by an interconnect f. Disconnect push rods (9) from bearing sleeve (8)
assembly located at the forward cabin bulkhead. by removing bolt and washer.
g. Remove screws, washers and nuts retaining the
control column support block (3) and cover (2) to in-
Removal of Control Column. (See figure 5-1.) strument panel.
h. Compress control column and remove by lifting
a. Remove secondary instrument shock panel in upwards and to the rear until the stationary instru-
accordance with Section 12. ment panel is cleared.
b. Position front seats to the most aft position.
c. Disconnect electrical wiring to control wheels
and remove control wheel (1) from tube assembly (10) Disassembly of Control Column. (See figure 5-1.)
by removing nuts and bolts.
d. Remove nut (15) from control column sprocket a. Remove control column from stationary panel,
shaft.

Change 10
5-2 coNTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

'
Detail A 5
14
7" 12

18
17
421-0001 TO 421B-0301

A14152012
51612005R

1. Control Wheel 6. Slide 10. Tube Assembly 14. Chain

2. Cover 7. External Retainer 11. Roller Support 15. Nut
3. Support Block 8. Bearing Sleeve 12. Tube Assembly 16. Gasket
4. Clevis Assembly 9. Push Rod 13. Turnbuckle 17. Cover
5. Screw 18. Bulkhead

Figure 5-1. Control Column (Sheet 1 of 2)

Change 9
 421 SERVICE MANUAL coNTROL COLUMN, AILERON 5-8
AND TRIM CONTROL SYSTEMS

1
2 .

10

11

421B-0301 & ON

51154015

Figure 5-1. Control Column (Sheet 2)

Change. 9
5-28 CONTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

NOTE
assembly (10).
Disassembly and repair of control column is c. Compress tube assembly (10) and (12) together
limited to the replacement of worn or defee- and remove screw (5) and slide (6),
tive shafts, bearings, bushings, rollers or d. Remove tube assembly (12) from inside tube as-
other replaceable components. sembly (10) by pulling apart.
e. Expand external retainer (7) and remove bearing
b. Loosen clevis assembly (4) on control support sleeve (8) and retainer from tube assembly (10).
block (3) and remove column support block from tube f. Remove roller support (11) by drilling out the

Change 8
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 5 3
AND TRIM CONTROL SYSTEMS

four rivets attaching roller support to the sleeve on 4. Align interconnect assembly with sprockets as
tube assembly (10). shown in figure 5-2, and engage chain on sprockets.
5. Tighten turnbuckle and install safety wire.
NOTE
NOTE
Do not remove roller support (11) from tube
assembly (10) except when replacement of When tightening turnbuckles, chain tension
roller support is required. should not exceed the minimum necessary
to remove excess slack.

Assembly of Control Column. (See figure 5-1.)

AILERONS.
a. Assemble component parts of the control column
by reversing disassembly procedures. The all metal ailerons attach to the rear spar of each
wing at two hinge points, each hinge point is bolted
NOTE to the rear spar and incorporates a sealed bearing.
The aileron trim tab actuator fastens to the left
When assembling the control support block (3) aileron by a full length hinge and operates from a
to the column tube assembly (10), set the ad- push-pull tube. The ailerons are 100/o static bal-
justable lower bearing to provide 008 clear- . anced at the time of installation.
ance with the two upper bearings in direct
contact with tube assembly. Removal of Aileron. (See figure 5-4.)

Installation of Control Column. (See figure 5-1.) a. When the left aileron assembly is being removed,
move aileron trim tab to the extreme UP position and
a. Compress control column together and insert remove cotter pin, nut, bolt and spacer from aileron
into slot provided in the stationary instrument panel· trim tab push-pull tube (6).
b. Align holes in cover (2) and support block (3) b. Lower flaps and disconnect aileron push-pull rod
with stationary instrument panel and attach with assembly (10) by removing bolt and washer.
screws, washers and nuts• c. Disconnect bonding strap from aileron by remov-
c. Extend control column, align aileron sprocket
ing attaching screw.
with bearing block attached to bulkhead and secure d. Remove bolt attaching aileron to hinge assembly.
with nut (15).
d. Install gasket (16) and cover (17) with six attach-
ing screws.
e. Connect push rods (9) to bearing sleeve (8) with
bolts and washers.
f. Place chain (14) on sprocket and rig inter-
connect assembly in accordance with rigging proce-
dure.
g. Secure turnbuckle (13) by safetying.

Rigging Control Column. (See figure 5-3.)

a. (See figure 5-2.) Align interconnect assembly

(3) as shown. 4
NOTE

Check and/or adjust length of interconnect as-

sembly to provide 16. 10 inches span, measur- N /
ing from center to center of clevis holes. If
adjustment is made to interconnect assembly, 16.10"
recheck aileron cable tensions.

b. With interconnect assembly centered, check

pilot's and copilot's control wheels for the neutral
position. If control wheels do not assume the neutral
position, or are not aligned together, proceed with
the following steps:
1. Loosen turnbuckle (43) on chain (45) and remove
chain from control column sprockets.
2. Rotate pilot's control wheel to the neutral posi- 1. Sprocket 3. Interconnect Assembly
tion and install control column lock. 2. Turnbuckle 4. Lock Nut
3. Visually align copilot's control wheel with pilot's
control wheel. Figure 5-2. Interconnect Assembly Adjustment

Change 1
 5-4 CONTROL COLUMN, AILERON
421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

e. To remove aileron, move aileron to the rear, connect bonding strap by removing screw.
clearing hinge assembly, and slightly inboard until b. Remove cotter pin, nut and bolt attaching aileron
outboard hinge pin (9) is free of bearing. trim tab push-pull tube (6) to aileron trim tab,
c. Remove cotter pins in hinge half and remove
hinge pin.
Installation of Aileron. d. Remove aileron trim tab from aileron.

NOTE
Installation of Aileron Trim Tab. (See figure 5-4.)
If rigging was correct prior to aileron re-
moval and aileron push-pull rod end adjust- a. Install aileron trim tab by reversing removal
ment was not disturbed, it should not be ne- procedures.
cessary to rerig the aileron control system.
If the push-pull rod end adjustment was dis- NOTE
turbed, adjust rod ends to provide 9.65 inches
span measuring from center to center of rod Check aileron trim tab travel, alignment and
end attach holes. rerig, if necessary, in accordance with rig-
ging procedure,
a. Installation of Ailerons is the reversal of the
removal procedures.
AILERON CONTROL SYSTEM.
NOTE
The ailerons are actuated by the rotational movement
After installation of ailerons, check the travel of either control wheel. The actuation of ailerons is
and alignment and rerig if necessary. accomplished by cable assemblies which are attached
to the control column interconnect assembly and
routed through the fuselage to the fuselage bellerank
AILERON TRIM TAB. located just forward of the rear spar. From the fuse-
lage bellerank, cable assemblies are then routed
The all metal aileron trim tab is attached to the left through each wing to a wing bellerank assembly where
aileron by a single hinge extending the entire length a push-pull tube is connected to the aileron. An ail-
of the trim tab. The trim tab must be installed when eron trim system is provided and is routed directly
static balancing the left aileron. through the fuselage and left hand wing to the aileron
trim tab actuator. An aileron trim control knob is
provided on the control pedestal.
Removal of Aileron Trim Tab. (See figure 5-4.)

a. Position aileron trim tab to full DOWN and dis-

Trouble Shooting Aileron Control System.

TROUBLE PROBABLE CAUSE CORRECTION

LOST MOTION BETWEEN Cable tension too low. Adjust cable tension in accordance
CONTROL WHEEL AND with rigging procedures.
AILERON
Broken pulley. Replace pulley.

Cables not in place on pulleys or wing Install cables correctly. Check cable
belleranks. guards.

RESISTANCE TO CON- Cable tension too high. Adjust cable tension in accordance
TROL WHEEL with rigging procedures.
ROTATION
Wing bellerank bolts over-torqued. Loosen bolts.

Pulleys binding or rubbing. Replace binding pulleys. Provide

clearance if rubbing pulley brackets
or cable guards.

Clevis assembly in control column Provide proper clearance between

support block adjusted too close to bearing and control tube assembly.
control tube assembly.
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 5-5
AND TRIM CONTROL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

RESISTANCE TO CON- Control column crossover chains too Adjust in accordance with control
TROL WHEEL tight. column rigging procedures.
ROTATION (CONT.)
Cables not in place on pulleys or wing Install cables correctly,
bellerank.

Bent aileron. Repair or replace aileron.

CONTROL WHEELS Incorrect control column rigging. Rig in accordance with control column
NOT SYNCHRONIZED rigging procedures.

Aileron system tension greater than Adjust tensions in accordance with

control column crossover tension. rigging procedures.

CONTROL WHEELS NOT Incorrect aileron system rigging. Rig in accordance with rigging proce-
HORIZONTAL WHEN dures.
AILERONS ARE
NEUTRAL

INCORRECT AILERON Aileron quadrant stops incorrectly Adjust in accordance with rigging pro-
TRAVEL adjusted. cedures.

CORRECT AILERON Incorrect rigging of quadrant cables, Rig in accordance with rigging proce-
TRAVEL CANNOT BE compensated for by incorrect adjust- dures.
OBTAINED BY ADJUST- ment of push-pull rods.
ING WING BELLCRANK
STOPS Incorrect rigging of aileron belleranks. Rig in accordance with rigging proce-
dures.

Removal of Aileron Control Cables. (See figure 5-3.) h.

Remove pulley (30) from pulley bracket.
Remove
i. cable seals (56).
NOTE j. Remove wing aileron cables from aircraft through
wing access panel.
See figure 1-2 and remove floorboard ac-
cess panels (80, 81 and 86), fuselage panel NOTE
(15), and wing access panels (64, 65 and
66). Leave the guide wires in the aircraft to serve
as a guide for cable reinstallation.
a. Remove cable guard pins from fuselage and/or
wing aileron pulley brackets.
b. Relieve aileron cable tension by loosening cable Installation of Aileron Cables. (See figure 5-3.)
turnbuckles at the fuselage bellerank assembly (6).
a. Attach guide wires to wing aileron and/or fuse-
NOTE lage aileron cable terminals and route cable through
aircraft toward fuselage bellerank (6).
The following procedure is for removing aileron b. Secure wing aileron cables to wing bellerank as-
cables with turnbuckle forks remaining attached sembly (26) with bolts, nuts and cotter pins.
to the fuselage bellerank. c. Install cable guard pins, washers and cotter pins
on wing bellerank assembly (26).
c. Remove turnbuckle barrels connecting turnbuckle d. Install pulley (30) in pulley bracket.
forks to cable terminals and attach guide wire to cable
terminals. CAUTION
d. Disconnect forward aileron cables from inter-
connect assembly (54) by removing cotter pin, nut Be sure spacer (31) is correctly installed be-
and bolt. neath pulley (30) or cable will misalign with
e. Remove fuselage aileron cables from aircraft wing bellerank and damage may occur.
through cabin forward access panel.
f. Ðisconnect wing aileron cables at the wing bell- e. Connect fuselage aileron cables to the intercon-
crank assembly (26) by removing cotter pin, nut and nect assembly (54) with bolts, nuts and cotter pins.
bolt. f. Assemble turnbuckle barrels to aileron cable
g. Remove cable guard pins, washers and cotter terminals and forks on fuselage bellerank assembly
pins from wing bellerank assembly (26). (6).
 ..g CONTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

54 16 19
25 e
28

10 223

35 4 24 30
Detail

Detaii D

'
42 cete F
49
Detaa E

Figure 5-3. Aileron Control System

Change 4
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 54
AND TRIM CONTROL SYSTEMS

Figure 5-3. Aileron Control System Callouts

1. Bolt 16. Bolt 29. Cable Guard Pin 44. Bolt

2. Nut 17. Pulley 30. Pulley 45. Chain
3. Cotter Pin 18. Nut 31. Spacer 46. Nut
4. Pivot Bolt 19. Bolt 32. Washer 47. Cotter Pin
5. Washer 20. Pulley 33. Bolt 48. Pulley
6. Fuselage Bellcrank 21. Nut 34. Cotter Pin 49. Cable Guard Pin
7. Washer 22. Washer 35. Washer 50. Bolt
8. Washer 23. Bolt 36. Pivot Bolt 51. Washer
9. Nut 24. Nut 37. Nut 52. Pulley
10. Link 25. Screw 38. Bolt 53. Cable Guard Pin
11. Cable Pin 26. Wing Bellerank 39. Washer 54. Interconnect Assembly
12. Bolt Assembly 40. Cable Guard Pin 55. Retaining Ring
13. Washer 27. Aileron 41. Pulley 56. Cable Seal
14. Pulley Push-pull Tube 42. Nut 57. Stop Bolt
15. Nut 28. Pin 43. Turnbuckle 58. Safety Wire

g. Install guard pins in pulley brackets.

cable reversal of the removal procedures.
h. Installcable seals (56) as follows; b. Rig aileron control system in accordance with
1. Insure that the cables are lubricated for the full rigging procedures.
length of its travel within the seals. c. Safety turnbuckles by installing clips.
2. Pack the seals with MIL-G-81322A lubricant, d. Install access panel.
3. Place the seals on cable on nonpressurized side
of bulkhead with small end of seal toward bulkhead. WARNING
4. Insert seal in the bulkhead hole so that bulkhead
metal is seated within the retaining groove of seals Make sure ailerons move in the correct di-
and so that the small end of seal is in the pressurized rection when operated by the control wheel.
section.
5. Install proper retaining rings in the grooves on Removal of Aileron Wing Bellerank. (See figure 5-3.)
the seal (two on small end and one on large end).
i. Rig aileron control system in accordance with NOTE
rigging procedure.
j. Install safety on turnbuckles. See figure 1-2 and remove floorboard access
k. Reinstall all access panels. panel (80), wing plug buttons (67 and 68) and
wing access panel (27).

Removal of Aileron Fuselage Bellerank. (See figure a. Relieve tension on aileron control system by
5-3.) loosening the alleron control cable turnbuckles at the
fuselage bellerank assembly (6).
NOTE b. Disconnect wing aileron cables from wing bell-
crank assembly (26) by removing the cable guard
See figure 1-2 and remove floorboard access pins, washers and cotter pins and attaching screws
panel (80). and nuts.
c. Disconnect aileron push-pull tube (27) from wing
a. Relieve tension on aileron control system by re- bellerank assembly (26) by removing attaching nut,
moving turnbuckle clips and loosening the aileron washer and bolt.
cable turnbuckles. d. Remove pivot bolt (36) from wing bellcrank as-
b. Disconnect turnbuckle forks from bellerank by sembly (26) and work bellerank through wing access
removing nuts, washers and bolts. hole.
c. Remove pivot bolt (4) and work bellerank through
floorboard access hole. NOTE

NOTE Repair of aileron wing bellerank is limited to

replacement of defective bearings and spacers.
Repair of aileron fuselage bellerank is limited
to replacement of defective bearings and spa-
cers.
Installation of Aileron Wing Bellerank. (See figure
Installation of Aileron Fuselage Bellerank. (See 5-3.)
figure 5-3.)
a. Installation of wing bellerank is the reversal of
a. Installation of aileron fuselage bellcrank is the the removal procedures.

Change 6
5-8 coNTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

Detan $
o

12 5

Detail e

*13
O ostati C
10 B10242002
* A MAXIMUM WASHER THICKNESS OF 10242001
C10242002
0.126 MAY BE USED ADJACENT TO 8 A10242002
EACH SIDE OF ROD END.

1. Hinge Pin 5. Nut 10. Aileron Push-Pull Rod

2. Cotter Pin 6. Aileron Trim Tab Push-Puu Tube 11. Bolt
3. Aileron Trim Tab 7. Bolt 12. Cotter Pin
4. Spacer 8. Aileron 13. Washer
9. Hinge Pin

Figure 5-4. Aileron and Aileron Trim Tab Installation

Change 12
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 59
AND TRIM CONTROL SYSTEMS

CAUTION b. Loosen fuselage and wing aileron cable turn-

buckles to provide free swivel of fuselage bellerank
Do not over-torque pivot bolt (36) or serious assembly (6).
binding may result. c. Adjust fuselage aileron cables as necessary to
bring fuselage bellerank to neutral position,
b. Rig aileron control system in accordance with d. Rig fuselage aileron cables to provide 25 ± 5
rigging procedures. pounds tension.
c. Safety turnbuckles by installing clips, e. Retain control column gust lock in place; stream-
d. Install fuselage and wing access panels. line trailing edge of aileron with edge of flap and se-
cure aileron in place with a temporary locking device.
WARNING NOTE

Make sure ailerons move in the correct di- Rig each wing aileron separately.
rection when operated by the control wheel.
f. Remove excess slack in wing aileron cables by
tightening turnbuckles.
Rigging Aileron Control System. (See figure 5-3.) g. Rig wing aileron cables to 25 ±5 pounds tension.
NOTE NOTE

See figure 1-2 and remove center floorboard Cable tension should be adjusted when ambi-
60°F 90°F.
access panel (80), fuselage access panel (15) ent temperature is to Allow air-
and wing access panel (27). craft temperature to stabilize for a period of
4 hours,
a. Place pilot's control wheel in neutral position.
and install control column gust lock. h. Remove control column gust lock and temporary
NOTE aileron locking device and check aileron for the neu-
tral position..
The next steps may be omitted if copilot's i. Adjust wing aileron bellcrank stop bolts (57) to
20°
wheel is aligned in neutral with pilot's con- provide up and down travel with a plus one and
trol wheel. minus zero tolerance.
j. Tighten jam nuts, safety turnbuckles and bell-
1. Loosen turnbuckle on
crossover chain and ad- crank stop bolts (57) and check for obstructed travel.
just copilot's
control column sprocket to provide the k. Check all pulleys for cable guard pins in place.
neutral position. Chain tension should be the mini-
mum necessary to remove slack from chain. WARNING.
2. Align interconnect assembly as shown in figure
.5-2.

Insure that ailerons move in the proper di-

AILERON TRIM CONTROL SYSTEM. rection when operated by the control wheel.
Trouble Shooting Aileron Trim Control System.

TROUBLE PROBABLE CAUSE CORRECTION

TRIM CONTROL WHEEL Cable tension too high. Adjust tension in accordance with
MOVES WITH EXCESSIVE rigging procedure.
RESISTANCE
Pulleys binding or rubbing. Replace binding pulleys. Provide
clearance if rubbing pulley brackets
or cable guards.

Cables not in place on pulleys dur- Install cables on pulleys correctly,

ing installation.

Trim tab hinge binding. Lubricate hinge. If necessary, re-

place.

LOST MOTION BETWEEN Cable tension too low. Adjust tension in accordance with
TRIM CONTROL WHEEL rigging procedures.
AND TRIM TAB
Broken pulley. Replace pulley.

Cables not in place on pulleys. Install cable on pulleys correctly and

check cable guards.

Worn trim tab actuator. Repair or replace actuator.

Change 4
5-10 CONTROL COLUMN, AILERON MANUAL
421SERVICE
AND TRIM CONTROL SYSTEMS

18

51 1
3

11
10
Detail

54

55

Detail Detaii E

47 4 49 50

33

33 31 50 30 24
27
Detail Ir
y gg

Figure 5-5. Aileron Trim Control System

 421 SERVICE MANUAL CONTROL COLUMN, AILERON 5-11
AND TRIM CONTRO.L SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

TRIM INDICATOR FAILS Indicator incorrectly engaged with Engage indicator on track.
TO INDICATE CORRECT wheel track.
TRIM POSITION

INCORRECT TRIM TAB Travel stop blocks loose or in- Adjust stop blocks in accordance with
TRAVEL correctly adjusted. rigging procedures.

CORRECT TRAVEL CAN- Actuator screw incorrectly ad- Adjust in accordance with rigging
NOT BE OBTAINED BY justed. procedures.
ADJUSTING STOP
BLOCKS

1. Install access panels in aircraft. f. Remove stop blocks (42) from main aileron trim
cables in LH wing.
NOTE g. Connect guide wires to main aileron trim cable
terminals in fuselage area and remove aileron trim
An Inclinometer for measuring control surface cable from aircraft through wing access panel.
travel is available from Cessna Service Parts
Center. (See figure 5-8.) NOTE

Leave guide wires in aircraft to serve as a

Removal of Aileron Trim Control Cables and Chains. guide for cable reinstallation.
(See figure 5-5.)

NOTE
Installation of Aileron Trim Control Cables and
Chains. (See figure 5-5.)
See figure 1-2 and remove fuselage access
panel (15), floorboard access panels (80 and a. Install aileron trim cables by reversing removal
86) and left wing panels (27, 64 and 66). procedures and rig in accordance with aileron trim
rigging procedure.
a. Remove RH access cover on pedestal. b. Install aileron trim cable seals (55) in accord-
b. Disconnect turnbuckles (45 and 49) and remove ance with aileron cable seal installation procedures.
forward fuselage aileron trim cable and chain (46)
from aircraft through fuselage cable access.
c. Remove cable guard pins from fuselage and wing Removal of Aileron Trim Tab Actuator. (See figure
aileron trim pulley brackets. 5-5.)
d. Remove chain guard (29) from trim tab actuator
(27). a. Remove LH aileron in accordance with aileron
e. Remove cable seals (55). removal procedure.
b. Disconnect turnbuckles on aileron trim cables.

Figure 5-5. Aileron Trim Control System Callouts

1. Nut 19. Pulley 37. Clamp

2. Washer 20. Nut 38. Bolt
3. Pulley 21. Washer 39. Pulley
4. Bolt 22. Cotter Pin 40. Washer
5. Cable Pin 23. Nut 41. Nut
6. Cable Pin 24. Bolt 42. Stop Block
7. Bolt 25. Push-pull Tube 43. Nut
8. Cable Pin 26. Screw 44. Bolt
9. Washer 27. Trim Tab Actuator 45. Turnbuckle
10. Nut 28. Nut 46. Forward Aileron Trim Cable
11. Pulley 29. Chain Guard 47. Bolt
12. Bolt 30. Chain 48. Pulley
13. Cable Pin 31. Nut 49. Turnbuckle
14. Pulley 32. Bolt 50. RH Aileron Trim Cable
15. Washer 33. Cable Guard 51. LH Aileron Trim Cable
16. Nut -34.
Clip 52. Chain
17. Bolt 35. Screw 53. Sprocket
18. Cotter Pin 36. Nut 54. Retaining Ring
55. Cable Seal
5-12 CONTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

4
5

10

15
RUDDER TRIM TAB ACTUATOR
10
14 11
10

13
16

10
11
12 AILERON AND ELEVATOR
TRIM TAB ACTUATOR
. 13
14
15
16

1. Screw 6. Bearing 12. Groov-Pin

2. Deleted 7. Collar 13. Bearing
3. Retaining Ring 8. O-ring Packing 14. Sprocket
4. Bearing 9. Housing 15. Chain Guard
5. Screw 10. Groov-Pin 16. Nut
11. Screw

Figure 5-6. Trim Tab Actuators

Change 10
 421 SERVICE MANUAL coNTROL COLUMN, AILERON 5-0
AND TRIM CONTROL SYSTEMS

c. Relieve tension on aileron trim control system f. Examine screws (5 and 11) for damaged threads
by disconnecting turnbuckles in forward cabin section. or dirt particles that may impair smooth operation,
d. At the aileron trim tab actuator assembly, re- g. Check sprocket (14) for broken, chipped and/or
move chain guard (29) and disengage chain (30) from worn teeth.
sprocket. h. Check bearing (4) for smoothness of operation.
e. Remove cotter pin, nut, washer and bolt attach- i. Do not attempt to repair damaged or worn parts
ing push-pull tube (25) to aileron trim actuator (27). of the actuator assembly. Discard all defective
f. On forward side of rear spar, remove nuts, bolts, items and install new parts during reassembly.
and clips (34). j. Always discard the following items and install
g. On aft side of rear spar, remove nut, bolt and new parts during reassembly: nuts (16), groov-pins
clamp (37). (10 and 12) and O-ring packing (8).
h. (See figure 5-6.) Remove forward retaining ring k. During reassembly, lubricate collars (7) and
(3) from housing (9). screw (11) with general purpose lubricating grease,
i. Remove aileron trim tab actuator (27) from air- 1. Reassemble actuator in accordance with the fol-
craft through rear spar. lowing:
m. Slip bearing (13) and collar (7) on screw (11).
Disassembly, Overhaul and Assembly of Trim Tab n. Press sprocket (14) into hollow end of screw
Actuators (See figure 5-6.) (11), making sure pin holes are aligned. Press two
new groov-pins (12) into pin holes.
a. Disassemble aileron trim tab actuator assembly o. Insert screw (11), with assembled parts, into
in accordance with exploded view, figure 5-6. This housing (9).
view clearly illustrates the proper relationship of all
component parts.
b. Do not remove bearing (4) from screw (5) unless
replacement of parts is required. NOTE
c. Clean all component parts, except bearing (4),
by washing in suitable solvent. Do not clean sealed Locate sprocket (14) at the end of housing (9)
bearing (4). which is farthest from the groove for retain-
d. Inspect all component parts for obvious indica- ing ring (3).
tions of damage such as stripped threads, cracks,
deep nicks and dents. p. Align pin holes in bearing (13) and housing (9).
e. Check bearings (6 and 13) and screws (5 and 11) Press new groov-pin (10) into pin holes.
for excessive wear and scoring. Dimensions of parts q. Insert collar (7), new O-ring (8) and bearing (6)
shall be as follows; into end of housing (9). Align pin holes in bearing
and housing and install new groov-pin (10).
Front bearing (13) ID ...... 0.373 in. min. r. If new parts are required, press bearing (4) into
...... 0.380 in. max. boss at end of screw (5). Be sure force bears against
outer race of bearing. Install screw (5) in housing
Rear bearing (6): (9) and screw (11).
Small hole ID . . . . . . . . . 0. 248 in. min. s. Install retaining rings (3) in grooves provided on
......... 0.253 in. max. outside of housing (9).
Large hole ID . . . . . . . . . 0. 373 in. min. t. Test actuator assembly by rotating sprocket (14)
......... 0.380 in. max. with fingers while holding bearing end of screw (5).
Screw (5) should travel in and out of housing (9) smo-
Screw (5) OD (Shank) . . . . . . . 0. 242 in. min. othly, with no indication of binding.
....... 0.246 in. max.
NOTE
Screw (11) OD ......... 0.367 in. min.
......... 0.370 in. max. Relative end movement between screw (5)
and collar (7) should be 0.008 to 0.012 inch
when set a room temperature.
NOTE

Relative linear movement between internal Installation of Aileron Trim Tab Actuator. (See fig-
threaded screw (11) and bearing (6) should ure 5-5.)
be 0. 008 to 0. 012 inch on rudder trim tab
actuator when set at room temperature, a. Secure aileron trim tab actuator (27) in position
with clamp (37) and clips (34).
NOTE b. Engage chain (30) on sprocket and install chain
guard (29) with screws and nuts.
Relative linear movement between internal c. Reconnect forward and main aileron trim cables
threaded screw (11) and bearing (6) should with turnbuckles (45 and 49) and tighten cables to 10
be 0. 004 to 0. 010 on aileron and elevator ±3 pounds tension and safety turnbuckle.
trim tab actuator when set at room temper-
ature.

Change 10
5-14 CONTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

2 3
4
7 8 9

13

17 pg
14
15

I
1. Pointer 7. Shaft 12. Roll Pin
2. Screw 8. Roll Pin 13. Screw
3. Bracket 9. Sprocket 14. Washer
4. Washer 10. Chain 15. Nut
5. Nut 11. Gear 16. Roll Pin
6. Gear Assembly 17. Knob
Figure 5-7. Aileron Trim Control Knob and Pointer Assembly.
 421 SERVICE MANUAL CONTROL COLUMN, AILERON 5B
AND TRIM CONTRQL SYSTEMS

NOTE c. Remove pointer assembly (1) by removing four

attaching screws (13).
Cable tension should be adjusted when ambi- d. Relieve tension on aileron trim control system
60°F to 90°F. turnbuckles,
ent temperature is Allow air- by loosening
craft temperature to stabilize for a period of e. Disengage roller chain (10) from sprocket (9)
4 hours. and slide sprocket from shaft (7).
f. Remove roll pin (12) from gear (11) and slide
d. Connect aileron trim tab push-pull tube (25) to shaft (7) from pedestal assembly.
actuator (27) with bolt, washer, nut and cotter pin.
e. Install left aileron in accordance with installation Installation of Aileron Trim Control Knob and Pointer
and rigging procedures. Assembly (See figure 5-7.)
f. Rotate aileron trim control knob to the neutral
position and align aileron with the trailing edge of a. Installation of trim control knob and pointer is
wing. the reversal of the removal procedure.
g. Position the trailing edge of trim tab with aileron b. Check rigging and rig, if necessary, in accord-
trailing edge. ance with Rigging of Aileron Trim Control System.
h. Align push-pull tube (25) with trim tab horn and
secure with bolt and nut.
i. Check aileron trim tab for proper operation, cor- Rigging of Aileron Trim Control System. (See fig-
rect travel and rigging. ure 5-5.)
j. Install access covers.
NOTE

Removal of Aileron Trim Control Knob and Pointer See figure 1-2 and remove cable access panel
Assembly. (See figure 5-7.) (15),floorboard access panels (80 and 83) and
wing access panels (27, 65 and 66).
a. Remove pedestal access covers.
b. Remove gear assembly (6) and bracket (3) from a. Remove safety from turnbuckles (45 and 49) and
pedestal assembly. adjust cable tension to 10 ± 3 pounds.

Figure 5-8. Inclinometer SE716 for Measuring Control Surface Travel

Change 9
5-16 CONTROL COLUMN, AILERON 421 SERVICE MANUAL
AND TRIM CONTROL SYSTEMS

NOTE i. Loosen stop blocks (42), move trim tab to 20 plus

one, minus zero degrees DOWN, slide outboard stop
Cable tension should be adjusted when ambi- block against outboard rib assembly at station 129. 24
ent temperature is
60°F
to 90°F. Allow air- and tighten stop block.
craft temperature to stabilize for a period of
4 hours. NOTE

b. Move aileron trim control system to neutral by Stop blocks (42) should be installed so that
rotating control knob. bottom cable passes through bushing and
c. Check to make sure ends of chain (30) are equal top cable is clamped by stop blocks.
in length from sprocket on actuator (27) and ends of
chain (52) are equal in length from sprocket (53). j. Move trim tab to 20 plus one, minus zero de-
d. (See figure 5-7.) Adjust aileron trim indicator grees UP, slide inboard stop block against inboard
to neutral by removing screw and raising bracket (3) rib assembly at station 118.24 and tighten stop
to allow pointer (1) to move to the center, block.
e. (See Figure 5-5.) Remove cotter pin (22), nut
(23) and bolt (24) attaching push-pull tube (25) to WARNING
aileron trim tab.
f. Align aileron with trailing edge of wing and place Insure that aileron moves in the proper
trim tab in neutral. direction when operated by trim knob.
g. (See figure 5-5.) Adjust screw of trim tab actuator
(27) so that hole in push-pull tube (25) is in line with k. Install all access panels.
hole in trim tab horn.
h. (See figure 5-5.) Install bolt (24), nut (23) and
cotter pin (22).

Change 9
 421 SERVICE MANUAL ELEVATOR AND TRIM 6-1
CONTROL SYSTEMS

SECTION 6

ELEVATOR AND TRIM CONTROL SYSTEMS

Table of Contents

Page Page

ELEVATORS . . . . . . . .
6-1 Rigging . . . . . . .
6-6
Removal . . . . . . . .
6-1 ELEVATOR TRIM TAB CONTROL SYSTEM .
6-6
Installation. . . . . . .
.6-4

Troubleshooting. . . . . .
6-6
ELEVATOR TORQUE TUBE , . . .
6-4 Removal of Elevator Trim Control
ELEVATOR TRIM TAB. . . . . .
6-4A Cables and Chains . .
6-7. . .

Removal . . . . . . . .
6-4A Installation of Elevator Trim Control
Disassembly and Assembly . . . . 6 4B -

Cables and Chains . .

6-7. . .

Installation. . . . . .
.6-4B RemovalofTrimTabActuator. 6-7 . .

ELEVATOR CONTROL SYSTEM . .

6-4B.
Disassembly of Trim Tab Actuator 6-7 . .

Troubleshooting. . . . . .
.6-4B InstallationofTrimTabActuator .
.6-10

Removal of Elevator Control Cables . . 6 C -4

Removal of Elevator Trim Control Wheel,
Removal of Elevator Control Quadrant. . 6 -4
C Sprocket and Indicator Assembly 6-10 . .

Installation of Elevator Control Quadrant . 6 -4

C Installation of Elevator Trim Control Wheel,
Installation of Elevator Control Cables. . 6 -4
C Sprocket and Indicator Assembly 6-10 . .

Removal of Elevator Bellerank . . . 6 C -4

Rigging . . . . .
6-10. . .

Installation of Elevator Bellerank . . . 6 C -4

ELECTRIC ELEVATOR TRIM CONTROL 6-10 .

Removal of Elevator Arm . . . .

6-4C Removal of Elevator Trim Actuator
InstallationofElevatorArm. . .
.6-4C Assembly. . . . . .
.6-13

Removal and Installation of Elevator Dissassembly and Assembly of

Down Spring . . . . . . .
6 -4
C Elevator Trim Actuator Assembly. . 6-13
Removal and Installation of Aft Elevator Installation of Elevator Trim Actuator
Push-Pull Tube - · · - - ·

6 -4

C Assembly . . . . . . .
6-13

CAUTION

Primary and secondary flight control cables, push pull tubes, belleranks and mountings
on late model aircraft use dual locking fasteners. The look nuts for these fasteners incor-
porate a fiber lock, and are castellated for safetying with a cotter pin. When any of these
areas are disconnected on any aircraft, new dual locking fasteners should be installed.
See the Aircraft Parts Catalog for part numbers and location of these fasteners.

ELEVATORS. c. (See figure 6-2, ) Remove push-pull tube (19) by

unscrewing from actuator.
The elevator control surfaces consist of two elevator d. Disconnect bonding strap (16) by removing attach-
assemblies connected by a torque tube, and an eleva- ing screws.
tor trim tab located at the trailing edge of the right e. Remove fiberglass tip (15) by removing attaching
elevator. Each elevator is attached to the rear spar screws.
of the horizontal stabilizer at two hinge points. Each f. Remove nut (21), washer (22) and remove pin (19)
hinge has a sealed bearing. The elevators are opera- by installing washers and nut on the opposite end of
ted by an arm to which the elevator torque tubes are pin and tighten nut as required to free pin.
bolted. Each elevator is 1009'ostatic balanced with g. Remove nuts (47) and screws (48) securing eleva-
the elevator trim tab and elevator arm attached, at the tor collar to elevator arm.
time of installation. h. Remove elevator hinge by removing cotter pins,
nuts (27), washers (26) and bolts (25).
i. Remove collar (46) from torque tube.
Removal of Elevators. (See figure 6-1. )
CAUTION
a. Refer to Section 3 (Removal of Horizontal Stabi-
lizer) and remove stinger and access covers. The elevator collar (46) and elevator torque
b. (See figure 6-2. ) Disconnect elevator trim tab tube (45) are drilled and taper reamed as a
push-pull tube (19) by removing cotter pin, nut, wash- matched set and must be replaced as a match-
er and bolt. ed set.

Change 10
8-2 ELEVATOR AND TRIM 421 SERVICE MANUAL
coNTROL SYSTEMS

14

4 2
Detan B

E A

anE

to C

prK " '

11

12
5
A,asiissoio
siis4oisa Detan D oetan C
C51154010 38 5
D52612005 's
"
E51154010

Figure 6-1. Elevator and Elevator Bellcrank (Sheet 1 of 2)

 421 SERVICE MANUAL ELEVATOR AND TRIM Û•3
CONTROL SYSTEMS

r 26

26 27 -

26
"Detail 6

3 41 Detail
Detaii H 25
1

28 21 22 45 47 46 19
41
14 38 488

29
13

o N ON

34

31
36 32

F52342002
G51151006
H52342002
Detail J51154016R
K52612004

1. Cable Guard Pin 13. Right Forward Cable 25. Bolt 37. Bolt
2. Bolt 14. Quadrant 26. Washer 38. Up Stop Bolt
3. Cotter Pin 15. Fiberglass Tip 27. Nut 39. Gasket
4. Pulley 16. Bonding Strap 28. Down Stop Bolt 40. Seal
5. Pulley Bracket 17. Nut 29. Right Aft Cable 41. Bearing Pad
6. Push Rod 18. Washer 30. Nut 42. Support
7. Washer 19. Pin 31. Washer 43. Rigging Pin Hole
8. Nut 20. Bolt 32. Spacer 44. Rigging Pin Hole
9. Screw 21. Nut 33. Elevator Bellerank 45. Torque Tube
10. Bob Weight 22. Washer 34. Down Spring Arm 46. Collar
11. Left Forward Cable 23. Push-pull Tube 35. Down Spring 47. Nut
12. Turnbuckles 24. Elevator Arm 36. Left Aft Cable 48. Screw

Figure 6-1. Elevator and Elevator Bellerank (Sheet 2)

Change 12
 8-4 ELEVATOR AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

j. Remove the elevator by pulling aft and outboard 2. Using external control locks, lock elevators
while guiding the torque tube through the horizontal in a neutral position.
stabilizer ribs. 3. Using the pilot holes in the collar, drill a 1/8"
(. 125) hole through elevator torque tube.
NOTE 4. Enlarge hole in stages until small end of a
Number 4 B&S taper reamer will enter the hole.
Counterweights are located in the forward 5. Line ream hole with number 4 reamer to a
outboard elevator tips. Support the eleva- diameter wh ich will permit taper pin to extend not
tor tips during removal to prevent damage more than 1/16 inch above surface of collar.
to elevator during removal. 6. Install taper pin (19) with wet primer, position
AN975-5 washer (22) over pin and secure with nut
(21). Tighten nut to 50 +10, inch-pound torque.
-10

Installation of Elevators. (See figure 6-1.) Do not over-torque nut.

c. Check elevator and elevator trim tab for proper
a. Reverse the elevator removal procedure. operation and correct travel.
NOTE
ELEVATOR TORQUE TUBE.
Install pin (19) with wet primer and tighten
nut (21) to 50 +10, inch-pound
-10
torque. Removal of Elevator Torque Tube. (See figure
6-1A.)
b. If a new collar is being installed on an original
elevator, proceed as follows: a. Remove elevator from aircraft in accordance
1. Install elevator on aircraft with new collar in with elevator removal procedures.
place. Install screws securing collar (46) to ele- b. Drill out rivets (4) from leading edge of elevator
vator arm (24). to gain access to torque tube (1) by spreading leading
edge skins (3).
NOTE
CAUTION
The replacement collar will be 1. 85 inch long.
Make sure of identification of part because During all drilling operations, take precau-
right and left hand parts are not interchange- tions to prevent enlarging holes or damaging
able. , existing structure.

1. Torque Tube 3. Leading Edge Skin 4. Rivet

2. Screw 5. Rivet

Figure 6-1A. Elevator Torque Tube

Change 9
 421 SERVICE MANUAL ELEVATOR AND TRIM A
CONTROL SYSTEMS

c. Drill out rivets (5) securing torque tube to rib. b. Drill holes through torque tube flange to match
d. Remove four screws (2) and withdraw torque drilled out rivet holes in elevator assembly rib.
tube. c. Secure torque tube flange to rib using same size
and type rivets removed.
Installation of Elevator Torque Tube. (See figure d. Resecure elevator skin using the same size and
6-1A. ) type rivets as that removed.

a. Install torque tube in position and secure with

four screws (2)• ELEVATOR TRIM TAB.
NOTE

To facilitate installation of torque tube, drill Removal of Elevator Trim Tab. (See figure 6-2.)
out attaching rivets at rib and spar as re-
quired to gain access for bucking rivets- a. Disconnect the elevator trim tab push-pull tube
(19) by removing cotter pin, nut, washer and bolt.
b. Remove cotter pin (17) from each end of hinge
pin (18).
c. Remove trim tab by removing hinge pin (18).

Change 9
 421 SERVICE MANUAL
.4
8 ELEVATOR AND TRIM
CONTROL SYSTEMS

Disassembly and Assembly of Elevator Trim Tab. ELEVATOR CONTROL SYSTEM.

Disassembly and assembly of the trim tab is limited The elevators are operated by the fore and aft move-
to removal and installation of trim tab horn. To re- ment of the control column. The quadrant assembly
move the elevator trim tab horn, proceed as follows: is attached to the control column by links which are
a. Remove nuts, washers and screws securing trim attached to a swivel bearing on the control column.
tab horn to trim tab. The elevator cable assemblies and adjustable turn-
b. To install trim tab horn, install screws through buckles are attached to the quadrant assembly and
horn and secure with washers and nuts. then routed down under the floor panel and through
the fuselage by pulleys to the elevator bellcrank in
Installation of Elevator Trim Tab. (See figure 6-2. ) the tail section. A push-pull tube connects the bell-
crank to the elevator arm which is attached to the
a. Reverse the elevator trim tab removal proce- elevator torque tube. The elevator travel stops,
dures. consisting of bolts mounted in a bracket just aft of
b. Check the elevator trim tab for proper operation the bellerank, are provided for the recommended
and travel in accordance with the rigging of elevator adjustment. The elevator bob weight is attached to
trim tab control system. the quadrant assembly torque tube and is provided
to stabilize the aircraft in flight. The elevator down
spring is attached to the bellerank and is provided for
better elevator balance during flight.

Troubleshooting Elevator Control

TROUBLE PROBABLE CAUSE CORRECTION

LOST MOTION BETWEEN Cable tension too low. Adjust cable tension in accordance with
CONTROL WHEEL AND elevator rigging instructions.
ELEVATORS
Broken pulley. Replace pulley.

Cables not in place on pulleys. Install cables correctly. Check cable

guards.

Aft push-pull tube disconnected. Connect push-pull tube.

Cable disconnected. Connect cables.

RESISTANCE TO Cable tension too high. Adjust cable tension in accordance with
ELEVATOR CONTROL elevator rigging instructions.
MOVEMENT
Pulleys binding or rubbing. Replace binding pulleys. Provide clear-
ance if rubbing pulley brackets or cable
guards.

Cable not in place on pulleys. Install cable correctly.

Bent elevator or hinge. Repair or replace elevator or hinge.

Defective bearing or bushing in Replace defective bearing or bushing.

control column or interconnect
assembly.

INCORRECT ELEVATOR Elevator bellerank stops incor- Adjust in accordance with elevator
TRAVEL rectly adjusted. rigging instructions.

CORRECT ELEVATOR Elevator cables incorrectly Rig cables in accordance with elevator
TRAVEL CANNOT BE rigged. rigging instructions.
OBTAINED BY ADJUST-
ING BELLCRANK Control wheel is not rigged in the Rig cables in accordance with elevator
STOPS neutral position. rigging procedures.

Bob weights contacting or rubbing. Provide clearance if rubbing or contact-

ing other equipment.

Change 9
 421 SERVICE MANUAL ELEVATOR AND TRIM -4G|6-40
CONTROL SYSTEMS

Removal of Elevator Control Cables. (See figure a. Remove cabin tailcone access door.
6-1.) b. Remove left access cover from pedestal.
c. Unsafety and loosen either turnbuckle (12) (to
a. Remove seat, cabin divider (optional equipment), release tension on elevator cables).
refreshment bar (optional equipment), toilet (optional d. Disconnect elevator cables (29 and 36) from ele-
equipment), carpet, tailcone access and pedestal left vator bellerank (33) by removing cotter pins, nuts
access in accordance with Section 3. and bolts.
b. (See figure 1-2.) Remove floorboards access
(73, 77, 80, 82, and 84) and cable access (15). NOTE
c. Unsafety turnbuckles (12) and remove; disconnect
elevator cables (11 and 13) from quadrant (14) by re- If an autopilot (optional equipment) is installed,
moving nuts (8), washers (7) and screw (9). disconnect from elevator bellerank.
d. Disconnect elevator cables (29 and 36) from ele-
vator bellerank (33) by removing cotter pins, nuts, e. Disconnect elevator push-pull tube (23) from
and bolts. elevator bellerank (33) by removing cotter pin, nut,
e. Remove cable seal (40) and gasket (39)· washer and bolt.
f. Tie guide wires to forward ends of elevator f. Disconnect elevator down spring (35) from brac-
cables (29 and 36), remove cables by pulling them out ket and remove cotter pin, nut and bolt from down
aft of cabin compartment, and disconnect guide wires. spring arm (34) at the bellerank (33).
g. Remove elevator bellerank (33) by removing nut
NOTE (30), washer (31), bolt (37) and spacers (32).

When removing or installing the elevator cable

(29), check the correct routing through the Installation of Elevator Bellerank. (See figure 6-1.)
down spring arm (34).
a. Reverse the removal of elevator bellerank pro-
Removal of Elevator Control Quadrant. (See figure cedures, except the installation of the access door
6-1.) and panel.
b. Rig the elevator control system in accordance
a. Remove pilot's and copilot's seats in accordance with rigging of elevator control system.
with Section 3.
b. Remove elevator cables cover by removing Removal of Elevator Arm. (See figure 6-1.)
screws.
c. Disconnect cables (29 and 36) at turnbuckles (12). a. Remove stinger in accordance with Section 3.
d. Disconnect push rods (6) by removing nuts from b. Remove elevators in accordance with the removal
each control column assembly. of elevator procedure.
e. Disconnect bearing pad (41) from supports (42) c. Disconnect elevator push-pull tube (23) from
and the center pedestal structure by removing nuts elevator arm (24) by removing cotter pin, nut,
and bolts. washer and bolt.
f. Remove the elevator control quadrant by tilting d. Remove elevator arm by removing nuts (17),
the right side up and working the quadrant assembly washers (18) and bolts (20) from hinge bracket.
out on the left hand side of the aircraft.
Installation of Elevator Arm. (See figure 6-1.)
Installation of Elevator Control Quadrant. (See fig-
ure 6-1.)
a. Reverse the removal of elevator arm procedures.
b. Check elevator for proper operation and correct
control quadrant is the
travel,
a. Installation of elevator
reversal of the removal procedure.
b. Check rigging in accordance with rigging proce-
Removal and Installation of Elevator Down Spring.
dures
(See figure 6-1.)

a. Refer to Section 3, remove rear upholstery

Installation of Elevator Control Cables. (See figure panel to tailcone.
6-1.) b. Remove cotter pin, nut and screw from down
spring arm (34).
a. Reverse the elevator control cable removal pro- c. Remove down spring (35) by unhooking from
cedure except the installation of seats, cabin dividers structure.
(optional equipment), refreshment bar (optional equip- d. Installation of the elevator down spring is the
ment), toilet (optional equipment), carpet and cabin reversal of the above procedure.
tailcone access door.
b. Rig elevator control system in accordance with
rigging the elevator control surface. Removal and Installation of Aft Elevator Push-Pull
Tube. (See figure 6-1.)

Removal of Elevator Bellerank. (See figure 6-1.) a. Refer to Section 3, remove rear upholstery panel

Change 9
 421 SERVICE MANUAL ELEVATOR AND TRIM $4
CONTROL SYSTEMS

to tailcone and stinger- c. On aircraft 421-0001 to 421-0050 rig controls as

b. Remove cotter pin, nut, washer and bolt attach- follows:
ing push-pull tube (23) to elevator bellerank (33)- 1. Adjust elevator bellerank up stop (38) so that
c. Remove cotter pin, nut, washer and bolt attach- elevator travel is 25 +1, degrees
-0
up.
ing push-pull tube (23) to elevator arm (24) and re- 2. Adjust elevator bellerank down stop (28) so that
move push-pull tube. elevator travel is 15 +1, degrees
-0
down.
d. To install aft elevator push-pull tube, reverse 3. Adjust turnbuckles (12) until tension on elevator
the above procedure. cables (29 and 36) is 32 ±5 pounds with 5/32" diameter
rig pins installed in rigging pin holes (43 and 44).
Rigging of Elevator Control System. (See figure 6-1.) 4. Safetywire turnbuckles (12) and remove rigging
pins.
a. Remove access cover from pedestal, tailcone d. On aircraft 421-0050 and On, rig controls as
access door and necessary covers to gain access to follows;
elevator push-pull tube- 1. Disconnect elevator push-pull tube (23) from
b. Place a suitable support under tailcone at F. S· elevator arm (24), by removing cotter pin, nut
305. 94- washer and bolt.
2. Install external control locks between elevator
NOTE horns and the horizontal stabilizer.

Cable tension should be measured aft of F. S. NOTE

255. 00 in tailcone. Cable tension should be
adjusted when ambient temperature is 60°F. On aircraft with a royalite cover over the
Allow aircraft temperature to stabilize for a control column, remove cover and slide aft
period of four hours. to facilitate installation of holding tool.
An inclinometer for measuring control sur-
face travel is available from the Cessna
Dealers' Organization. (See figure 5-8. )

CONTROL
. M5
COLUMN
View A
INSTRUMENT
PANEL

STREAMER

HOLDING TOOL FABRICATE TOOL FROM . 187 DIA. 1025 CARBON STEEL.
CONTROL COLUMN BEND RADIUS TO BE 12 .

52801001

Figure 6-1B. Control Column Holding Tool

Change 12
6-6 ELEVATOR AND TRiu 421 SERVICE MANUAL
CONTROL SYSTEMS

3. Fabricate and install a control columnholding 10. Safety turnbuckles

and secure all bolts and
tool (see figure 6-1B) to secure control column in nuts. nuts with cotter pins.
Safety
position. e. Install access covers, center pedestal cover,
tailcone access panels, seats and upholstery.

l
NOTE

Elevator
WARNING
down spring must be disconnected
when adjusting cable tension.
Insure that elevator controls have freedom
of movement and elevator moves in proper
4. Adjust turnbuckles (12) connecting cables (13 to direction when operated by the control wheel.
29) and (11 to 36) until elevator bellerank (33) is ver¯ Make sure aileron controls have freedom of
tical (cable attachment holes equal distance from movement at the extreme positions of the
bulkhead) and cable tension on cables (29 and 36) is elevator control.
32 +5 pounds.
5. Adjust push-pull tube length to obtain slip fit of
push-pull tube attachment bolt and secure to elevator ELEVATOR TRIM TAB CONTROL SYSTEM.
with bolt, washer, nut and cotter pin.
6. Remove external elevator locks. The elevator trim tab is operated by a control wheel
7. Remove control column holding tool. (Refer to mounted on the left side of the pedestal. The control
step 6. ) wheel is attached to a sprocket which drives a chain
and cables. The chain and cables are routed to pul-
CAUTION leys, forward and down through the pedestal under
the floor and aft to the tailcone of the aircraft. In
Do not operate elevator from the tips, dam- the tailcone, the cables are routed aft to pulleys just
age could result. forward of the horizontal stabilizer rear spar, then
up and through the right horizontal stabilizer to a
8. Adjust elevator bellerank up stop to provide an chain which operates the trim tab actuator. The
up travel
of 25 +1°, -0°.

trim tab push rod connects the trim tab actuator to

9. Adjust elevator bellerank down stop to provide the elevator trim tab which is mounted to the right
a down travel of 15 +1°, -0°.

elevator by a continuous hinge. The adjustable turn-

buckles are located in the forward inspection panel
CAUTION for cable tension adjustment. The stop blocks are
located in the tailcone for the adjustment of the ele-
Make sure elevator bellerank is striking stops vator trim tab travel.
and is not limited by other structural inter-
ference.

Troubleshooting Elevator Trim Tab Control System.

TROUBLE PROBABLE CAUSE CORRECTION

LOST MOTION BETWEEN Cable tension too low. Adjust cables in accordance with elevator
TRIM CONTROL WHEEL trim control rigging instructions.
AND TRIM TAB
Broken pulley. Replace pulley.

Cables not in place on pulley. Install cables correctly. Check cable

guards.

Worn trim tab actuator. Repair or replace actuator.

RESISTANCE TO Cable tension too high. Adjust cable in accordance with elevator
CONTROL WHEEL trim control rigging instructions.
MOVEMENT
Pulleys binding or rubbing. Replace binding pulleys. Provide clear-
ance if rubbing pulley brackets or cable
guards.

Cable not in place on pulleys. Install cable correctly.

Trim tab actuator defective. Repair or replace actuator.

INCORRECT ELEVATOR Stop block loose or incorrectly Adjust stop block or chain in accordance
TRIM TAB TRAVEL adjusted or control wheel not with elevator trim control rigging in-
indexed properly on chain, structions.

Change 12
 421 SERVICE MANUAL ELEVATOR AND TRIM 6
CONTROL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

CORRECT ELEVATOR Actuator screw incorrectly Adjust in accordance with elevator trim
TRIM TAB TRAVEL adjusted. control rigging instructions.
CANNOT BE OBTAINED
BY ADJUSTING STOP
BLOCK

INDICATOR DOES NOT Indicator incorrectly engaged Adjust in accordance with elevator trim
INDICATE THE CORRECT with wheel track. control rigging instructions.
TRIM POSITION

Removal of Elevator Trim Control Cables and Chains, e. Install cable pulley (27) by installing bolt, washer,
(See figure 6-2.) nut and cable guard pins at pulleys (27 and 28).
f. Attach guide wire to turnbuckle ends of cables
a. Remove seats, cabin dividers (optional equip- (20 and 21) in the tailcone and pull into position and
ment), refreshment bar (optional equipment), toilet remove guide wires. Engage cables in rub block
(optional equipment), carpet, tailcone access and (34).
pedestal aft and right access in accordance with g. Connect the left cables (11 and 14) and right
Section 3. cables (10 and 13) using turnbuckles (15).
b. (See Figure 1-2.) Remove floorboard access (77, h. Install cable guard pins (12) and two seals (31).
80, 82, and 84), fuel selector gearbox access (73) i. Install seals (31) as follows:
and cable access (15). 1. Insure that cables are lubricated for the full
c. (See figure 1-2.) Remove stabilizer fairing (11), length of travel within the seals.
stinger (10) and elevator trim tab actuator access 2. Pack the seals with MIL-G-81322A lubricant,
panel (19). 3. Place seals on cable on non-pressurized side of
d. Remove elevator trim stop blocks (29) and bush- bulkhead with small end toward bulkhead.
ings (30) by removing nut, washer and screw. 4. Insert seal in the bulkhead hole so that bulkhead
e. Unsafety turnbuckles (15) and disconnect cables metal is seated within the retaining groove with the
by removing turnbuckles. small end of the seal in the pressurized section.
f. Remove chain guard (25) from elevator trim act- 5. Install proper retaining rings in the grooves of
uator (26) by removing nuts and screw. the seal (two on small end and one on large end).
g. Remove elevator push-pull tube (23, figure 6-1) 3. Install stop block (29) and bushings (30) with
to gain access to guard pin at pulley (28). screws, nuts and washers. Do not tighten at this
h. Remove pulley (27) by removing nut, washer, time.
bolt and cable guard pins at pulleys (27 and 28). k. Rig elevator trim control in accordance with
i. Disengage chain (22) from actuator sprocket rigging of elevator trim control system.
1. Install elevator push-pull tube (23, figure 6-1)
(24), attach a guide wire to the chain, and remove
cables and chain from stabilizer by pulling out with bolt, washer and nut. Safety nuts with cotter
through opening in tailcone. pms.
j. Remove three cable guard pins (12) and two seals m. Install stabilizer fairings, stinger, and elevator
(31) and disengage cables from rub block (34). actuator access panel.
k. Attach guide wire to aft cables (13 and 14) at fuel n. Install access cover on pedestal, floorboard fuel
selector valve access and remove by pulling out selector gearbox access, and cable access door.
through opening in tailcone. o. Install tailcone access door, carpet, seats,
1. Remove eight cable guard pins (16). cabin divider (optional equipment), refreshment bar
m. Attach guide wires to forward cables (10 and 11) (optional equipment), and toilet (optional equipment).
at fuel selector valve access and remove by pulling Removal of Elevator Trim Tab Actuator. (See figure
out through opening in pedestal. 6-2.)
a. (See Figure 1-2.) Remove fuel selector gearbox
Installation of Elevator Trim Control Cables and access (73) and elevator trim access panel (19).
Chains. (See figure 6-2.) b. Unsafety and loosen turnbuckles (15) to release
tension on elevator trim control cables.
a. Tie guide wires at pedestal to turnbuckle end of c. Remove right elevator in accordance with re-
cables (10 and 11), pull into position, and remove moval of elevator procedures.
guide wires, d. Disconnect the elevator trim tab push-pull tube
b. Engage chain (9) with trim control wheel sproc- (19) by removing cotter pin, nut, washer and bolt.
ket (6) and install eight cable guard pins (16). e. Remove chain guard (25) from elevator trim tab
c. Attach chain (22) to guide wire in tailcone and actuator (26) by removing nuts and screw; disengage
pull into position and remove guide wire. chain from sprocket.
d. Engage chain (22) with actuator sprocket (24) and f. Remove clamps (23) by removing nut, washer and
install chain guard (25) with screws and nuts. screw and remove elevator trim tab actuator.

Change 9
8-8 ELEVATOR AND TRIM 421 SERVICE MANUAL
ONTROL SYS

12
/* ' '
4 Detail
14

13 15

Detail

Detaii D

Detail

11 1
EDC

18 12

" " 14
Detail F is / se

Detail E oetaii A

1. Cotter Pin 7. Trim Indicator 12, Cable Guard Pin

2. Nut 8. Control Wheel 13. Aft Right Cable
3. Bolt 9. Chain 14. Aft Left Cable
4. Washer 10. Forward Right Cable 15. Turnbuckle -
5. Bearing 11. Forward Left Cable 16. Cable Guard Pin
6. Sprocket

Figure 6-2 Elevator Trim Control System (Sheet 1 of 2 )

 421 SERVICE MANUAL ELEVATOR AND TRIM 6-9
CONTROL SYSTEMS

17

26
31
19

25
21 2
2423

22
14 3

30 Detaii Ñ
421B0301 AND ON
Detail A J52613001
54613003
421-0001 TO 421B0301 H51611011 .

JS16il012

17. Cotter Pin 23. Clamp 29. Stop Block

18. Hinge Pin 24. Sprocket 30. Bushing

120.
19.

21.
Push-Pull
Guard Pin
Bolt
Tube 25.
26.
27.
Chain Guard
Trim Actuator
Pulley
31.
32.
33.
Seal
Trim Tab
Shield
22. Chain 28. Pulley 34. Rub Block

Figure 6-2. Elevator Trim Control System (Sheet 2 of 2)

Change 9
 6-10 ELEVATOR AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

Disassembly of Elevator Trim Tab Actuator.

. NOTE
For elevator trim tab actuator disassembly, over-
If an electric elevator trim control is in-
haul, and reassembly procedure, see Section 5,
stalled, in addition to the autopilot, adjust
Disassembly, Overhaul and Reassembly of Trim
Tab Actuator
tension on elevator trim control cables to
18 ±3 pounds for the Nav-O-Matic 800 or
Installation of Elevator Trim Tab Actuator. (See 22 ±2 pounds for the400A Nav-O-Matic.
figure 6-2.)
e. Disconnect elevator trim push-pull tube (19) from
a. Reverse the elevator trim tab actuator removal elevator trim tab by removing attaching cotter pin,
procedure except installation of inspection panel and nut, washer and bolt.
trim actuator access panel. f. Rotate elevator trim control wheel (8) forward
b. Rig the elevator trim control system in accord- (nose down) until forward chain (9) and aft chain
ance with rigging of the elevator trim control system. (22) have approximately two links clearing the sproc-
Removal of Elevator Trim Control Wheel, Sprocket, kets.
NOTE
and Indicator Assembly. (See figure 6-2.)
a. (See Figure 1-2.) Remove fuel selector gearbox If the elevator trim indicator (7) reaches its
access (73)- extreme travel during rigging, it can be re-
located by removing elevator trim control
b.Unsafety and loosen turnbuckles (15) to release
wheel, moving the indicator, and reinstall-
tension onelevator trim control system.
ing wheel. (See figure 6-2.)
c. Remove elevator trim control wheel by removing
four screws and washers. g. With the elevator in neutral (elevator horns
d. Remove the quadrant cover, right side panel and aligned with stabilizer) and the chains in the above
forward panel from control pedestal. position, adjust trim actuator (26) by rotating push-
NOTE pull tube (19) so that the push-pull tube hole and the
elevator trim tab attaching holes align with the trim
To remove the elevator trim indicator assem- tab positioned approximately 12° up from neutral
bly, the rivet, around which the indicator (neutral position is alignment of the outboard trailing
pivots, must be removed. edge of the trim tab with the elevator trailing edge).
e. Disengage chain (9) from sprocket (6) and remove Connect push-pull tube to the elevator trim tab with
sprocket (6) by removing cotter pin (1), nut (2), wash_ attaching bolt, washer, nut and cotter pin.
er (4), bearing (5) and bolt (3), h. Rotate elevator trim control wheel so elevator
tab is 10° +1°, up on 421-0001 to 421B0001,
-0°

Installation of Elevator Trim Control Wheel, Sprocket, 12° +1°,

up on 421B0001 and On. On aircraft
-0°

and Indicator Assembly. (See figure 6-2.) 421-0001 to 421B0301, locate center stop (29) ap-
proximately three inches forward of Fuselage Station
a. Reverse the elevator trim control wheel, sproc~ 305. 94 and tighten. Slide the forward stop block (29)
ket, and indicator assembly removal procedures ex¯
aft against center stop block and tighten. On aircraft
cept the installation of the inspection panel• 421B0301 and On, slide aft stop block forward against
b. Rig elevator trim control system in accordance rub block (34) and tighten.
With rigging of the elevator trim control system' i. Rotate trim control wheel so elevator trim
elevator
26°
tab is down on 421-0001
+1°, to 421BOOO1
-0°

Rigging of Elevator Trim Control System. (See fig- 20° +1°,

ure 6-2.) down on 421BOOO1 and On. On aircraft
-0°,

421-0001 to 421B0301, slide aft stop block (29) forward

a. Remove the tailcone door and RH pedestal cover. against center stop block and tighten. On aircraft
b. (See Figure 1-2.) Remove fuel selector gearbox 421BO301 and On, slide forward stop block against rub
access (73) and elevator trim access (19). block (34) and tighten.
c. Loosen stop blocks (29) by loosening attaching
nuts and bolts. WARNING
d. Check and adjust the cable tension on the eleva- Insure that elevator trim tab moves in the
tor trim control cables to 10 ±3 pounds• proper direction when operated by the trim
NOTE control wheel,
j. (See figure 1-2. ) Install fuel selector gearbox
Cable tension should be adjusted when ambi¯
90°F. access (73) and elevator trim access (19),
ent temperature is 60 F to Allow air¯ k. Install tailcone door and RH pedestal cover.
craft temperature to stabilize for a period of
4 hours.
NOTE ELECTRIC ELEVATOR TRIM CONTROL. (Optional
421A0001 and ON.)
If the Nav-O-Matic 800 autopilot is installed,
adjust tension on elevator trim control ca- The electric elevator trim control system is com-
bles to 16 ±3 pounds. If the 400A Nav-O-Matic is prised of a single pole, single throw switch and a
| installed, adjust tension to 19 ±3 pounds, slider switch mounted in the pilot's control wheel;
an actuator assembly mounted on a support under

Change 9
 421 SERVICE MANUAL ELEVATOR AND TRIM $ ll
CONTROL SYSTEMS

1 2
3

Detail A

D
4 8

421A0001 and ON

Detail $

1. Control Wheel 4. Screw 7. Turnbuckle

2. Switch 5. Control Cable 8. Actuator Assembly
3. Switch 6. Locking Clip 9. Support

Figure 6-3. Electric Elevator Trim Control System (Sheet 1 of 2)

Change 1
6-12 ELEVATOR AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

NOTE

TOP OF HOUSING
OMITTED FOR
Detail CLARITY.

10 27 11

12
5
13

14

20

19 28

Detail

10. Turnbuckle 16. Cover 22. Screw

11. Motor Assembly 17. Screw 23. Cover Assembly
12. Screw 18. Housing 24. Screw
13. Pin 19. Screw 25. Clutch Assembly
14. Sprocket 20. Cover 26. Cable Guard
15. Chain Assembly 21. Cover Assembly 27. Electrical Wire

Figure 6-3. Electric Elevator Trim Control System (Sheet 2 of 2)

 421 SERVICE MANUAL ELEVATOR AND TRIM Û-13 f6•Í4
CONTROL SYSTEMS

the cabin floorboard at Station 225. 50; a control j. (See figure 2-9.) During reassembly, lubricate
cable attached to the elevator trim control cable and clutch assembly (25).
routed around the actuator clutch assembly cable k. Install motor assembly (11) in housing (18).
drum; and associated electrical wiring. The electric 1. Install control cable (5) on clutch assembly (25).
elevator trim control system is energized when the
single pole, single throw switch is placed in the EN- NOTE
GAGE position and the slider switch is moved to the
forward (DOWN) or aft (UP) position. The actuator Clutch assembly cable drum and control
motor drives the clutch assembly, which moves the cable must be free of grease and oil and con-
elevator trim control cable and places the elevator trol cable must make 3 full wraps around the
trim tab in the corresponding UP or DOWN position. cable drum.
Manual override is accomplished by operating the
elevator trim control wheel mounted on the left side m. Install chain assembly (15) on sprocket (14) and
of the pedestal. clutch assembly sprocket and slide clutch assembly
into housing (18).
Removal of Elevator Trim Actuator Assembly. (See n. Install support assembly (23), cover assembly
figure 6-3). (21) and secure with screws (22 and 24).
o. Install cable guard (26) in housing (18).
a. Remove seats and center carpets in accordance p. Install top and side covers (16 and 20) and se-
with Section 3. cure with screws (12, 17 and 19).
b. (See figure 1-2.) Remove floorboard center ac-
cess panels, as necessary, to gain access to the Installation of Elevator Trim Actuator Assembly
elevator trim control cable turnbuckles. (See figure 6-3).
d. Loosen and disconnect turnbuckles (7 and 10)
from the control cable. a. Install actuator assembly (8) on support (9) and
e. Remove screws (4) attaching actuator assembly secure with screws (4).
(8) to support (9) and disconnect electrical wiring b. Connect electrical wiring (27),
(27). c. Connect turnbuckles (7 and 10) to elevator trim
f. Remove actuator assembly (8) and control cable control cable.
(5). d. Install locking clips (6) in turnbuckles.
e. Rig elevator trim control system in accordance
Disassembly and Assembly of Elevator Trim Actua- with the Elevator Trim Control System Rigging Pro-
tor Assembly. cedures, except cable tension should be 18±3 pounds.

a. Loosen screws (12, 17 and 19) and remove top NOTE

and side covers (16 and 20).
b. Loosen screws (22 and 24) and remove cover as- Cable tension should be adjusted when am-
60°F
sembly (21), support assembly (23) and cable guard bient temperature is to 90°F. Allow
(26). aircraft temperature to stabilize for a peri-
c. Slide clutch assembly (25) from housing (18) and od of 4 hours,
remove chain assembly (15) from clutch assembly
sprocket and sprocket (14), f. (See figure 1-2.) Install removed floorboard ac-
d. Remove control cable (5) from clutch assembly cess panels.
(25). g. Install carpets and seats in accordance with Sec-
e. Remove motor assembly (11) from housing (18). tion 3.
f. Clean component parts by wiping with a clean
cloth saturated with a suitable solvent.
g. Check clutch assembly sprocket and sprocket
(14) for broken, chipped and worn teeth,
h. Do not attempt to repair damaged or worn parts
of the actuator assembly. Discard all defective
parts and install new parts during reassembly.
i. Adjust clutch assembly (25) to slip at 25 ±3 inch-
pounds.

Change 6
 421 SERVICE MANUAL RUDDER AND TRIM UÎ
CONTROL SYSTEMS

SECTION 7

RUDDER AND TRIM CONTROL SYSTEMS

Table of Contents

Page Page

RUDDER . . . . . . . .
7-1 Rigging of Rudder Control System . .
7-7
Removal . . . . . . .
7-1 RUDDER TRIM CONTROL SYSTEM . .
7-7
Installation . . . . . . .
7-1 Troubleshooting . . . . .
7-7
RUDDER TRIM TAB . . . . .
7-4 Removal of Rudder Trim Control Cables
Removal . . . . . . .
7-4 and Chains . . . . . .
7-10
Installation . . . . . . .
7-4 Installation of Rudder Trim Control
RUDDER CONTROL SYSTEM . . .
7-4 Cables and Chains . . . .
7-10
Troubleshooting . . . . .
7-4 Removal of Rudder Trim Tab Actuator .
7-10
Removal of Rudder Control Cables .
7-4A Disassembly, Overhaul and Assembly
Installation of Rudder Control Cables .
7-6 of Rudder Trim Tab Actuator . .
7-11
Removal of Rudder Bellerank . . .
7-6 Installation of Rudder Trim Tab Actuator 7-11
Installation of Rudder Bellerank. . . 7-6 Removal of Rudder Trim Control Wheel
Removal of Rudder Pedal Assembly . 7-6 Sprocket, and Indicator Assembly .
7-11
Disassembly of Rudder Pedal Assembly 7-6 Installation of Rudder Trim Control Wheel,
Assembly of Rudder Pedal Assembly . 7-6 Sprocket, and Indicator Assembly .
7-11
Installation of Rudder Pedal Assembly . 7-6 Rigging Rudder Trim Control System .
7-11

CAUTION

Primary and secondary flight control cables, push pull tubes, belleranks and mountings
on late model aircraft use dual locking fasteners The lock nuts for these fasteners
.
incor-
porate a fiber lock, and are castellated for safetying with a cotter pin. When any of these
areas are disconnected on any aircraft, new dual locking fasteners should be installed.
See the Aircraft Parts Catalog for part numbers and location of these fasteners.

RUDDER. e. Disconnect rotating beacon light wire at upper

hinge.
The all metal rudder has a fiberglass tip which en- f. Support the rudder and remove the three hinge
closes a rotating beacon. The rudder is 100°/ostatic cotter pins, nuts, washers and bolts.
balanced by means of lead weight enclosed in lead- g. Remove rudder by pulling aft while guiding rud-
ing edge at the time of installation. The rudder trim der trim tab push rod out through the rudder.
tab, located at the trailing edge of the rudder, is
actuated by a push-pull rod whidÏfis routed through
the rudder to an actuator in the vertical stabilizer.
The rudder, attached to the vertical stabilizer with Installation of Rudder. (See figure 7-1. )
three hinges, is operated by cables attached to a
bellerank at the bottom of the rudder. a. Reverse the rudder removal procedure except
the installation of the stabilizer fairing.

Removal of Rudder. (See figure 7-1.) NOTE

a. (See figure 1-2.) Remove stabilizer fairings Washers may be required between rudder hinge
(9, 10 and 11). brackets and hinge bearings to prevent defor-
b. (See figure 7-3.) Disconnect the push rod (17) mation of hinge brackets.
from the rudder trim tab (14) by removing cotter pin,
nut, washer and bolt. b. Check rudder and rudder trim tab for proper op-
c. Disconnect the bonding strap (11) by removing eration and travel in accordance with rigging of the
nut, washer and screw. rudder control system and rigging of the rudder trim
d. Disconnect cable links (16) from bellerank (13) control system.
by removing screw and nut. c. Install the stabilizer fairings.

Change 10
7- RUDDER AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

Detail

Detail 51154002
AS4612001
B54612001

Fi ure 7-1. Rudder and Rudder Control (Sheet 1 of 2)

Change 9
 421 SERVICE MANUAL RUDDER AND TRIM ί
CONTROL SYSTEMS

Detail
i D
2 21
14

Detail

14 Detail

11 a oo

Detail

BONDING JUMPER ON
CENTER HINGE ONLY

13

C51613005

H H D,E,F,G54613003
Detail Detail DetailF »,a,xs4eisoos

1. Right Steering Cable 8. Right Rudder CabÍe(Fwd) li T rminal

2. Left Steering Cable 9. Turnbuckle 16. Link.
3. Right Torque Tube 10. Seal 17. Stop Bolt
4. Turnbuckle 11. Bonding Strap 18. Stop Block
5. Left Torque Tube 12. Rudder Torque Tube 19. Seal
6. Position Cable 13. Rudder Bellerank 20. Right Rudder Cable (Aft)
7. Left Rudder Cable (Fwd) 14. Turnbuckle 21. Left Rudder Cable (Aft) i

Figure 7-1. Rudder and Rudder Control System (Sheet 2)

Change 9
 7-4 RUDDER AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

RUDDER TRIM TAB. (See figure 7-3.) RUDDER CONTROL SYSTEM.

The all-metal rudder trim tab is operated by a push- The rudder is operated by the movement of the right
pull tube extending through the rudder and attached and left pilot's or copilot's rudder pedals. The
to an actuator in the vertical fin. The tab is attached pedals are connected to torque tubes which have
to the lower trailing edge of the rudder by a contin- link arms for the attachment of the rudder cables.
uous hinge and is adjustable in flight. The rudder cables are attached to the torque link
arms and routed forward over pulleys, then aft
under the floorboards through pulleys to turnbuckles
Removal of Rudder Trim Tab. (See figure 7-3.) in the tailcone, then routed over pulleys to the
rudder bellerank. The bellerank is attached direct-
a. Disconnect the rudder trim tab push rod (17) by ly to the rudder torque tube. The rudder travel
removing cotter pin, nut, washer and bolt. stops, consisting of bolts mounted in brackets
b. Remove cotter pin from each end of hinge pin attached to the lower hinge bracket, are provided
(16). for the recommended travel adjustment. The po-
c. Remove trim tab by removing hinge pin (16). sition cable is attached to the left rudder pedal
torque tube and is routed aft around a pulley and
then forward to right rudder pedal torque tube to
Installation of Rudder Trim Tab. (See figure 7-3.) complete the rudder control cable system. The
nose gear steering cables are attached to the right
a. Reverse the rudder trim tab removal procedures. and left rudder pedal torque tubes; routed forward
b. Check the rudder trim tab for proper operation to springs and then to the nose gear steering yoke.
and travel in accordance with the rigging of rudder
trim tab control system.

Troubleshooting Rudder Control System.

TROUBLE PROBABLE CAUSE CORRECTION

LOST MOTION BETWEEN Cable Tension too low. Adjust cable tension in accordance with
RUDDER PEDAL AND rudder rigging instructions.
RUDDER
Broken pulley. Replace pulley.

Bolts attaching rudder bellerank Tighten bellerank bolts.

RESISTANCE TO RUDDER Cable tension too high. Adjust cable tension in accordance with
CONTROL MOVEMENT rudder rigging instructions.

Pulley binding or rubbing. Replace binding pulleys. Provide clear-

ance if rubbing pulley brackets or cable
guards.

Cable not in place on pulley. Install cables correctly.

Bent hinges or faulty hinge bear- Replace hinges and/or bearings.

ings.

Bent rudder. Repair and/or replace rudder.

CORRECT RUDDER Rudder cables incorrectly rigged. Rig cables in accordance with rudder
TRAVEL CANNOT rigging instructions.
BE OBTAINED BY
ADJUSTING BELL- Rudder pedals contacting fuselage Rig position cables, nose wheel steer-
CRANK STOPS bulkhead. ing cables, and rudder cables in
accordance with rudder rigging instru-
tions.

RUDDER PEDALS NOT Aft rudder cables incorrectly Rig in accordance with rudder rigging
NEUTRAL WHEN RUDDER rigged. instructions.
IS STREAMLINED

Change 9
 421 SERVICE MANUAL RUDDER AND TRIM J-(g ).gg
CONTROL SYSTEMS

Removal of Rudder Control Cables. (See figure 7-1.) c. Remove turnbuckle clip and turnbuckles (14) and
disconnect cables (20 and 21) from bellerank (13) by
a. Remove seats, cabin dividers (optional) refresh- removing cotter pins, nuts and bolts.
ment bar (optional), carpet, LH and RH rudder cover d. Disconnect rudder cables (7 and 8) from pedal
plates and tailcone access in accordance with Section torque tubes (3 and 5) by removing cotter pins, nuts
3. and bolts.
b. (See figure 1-2.) Remove cables access (15), e. Remove seals (19).
front spar access (77), center control access (79), f. Remove cable guard pins; attach guide wires to
front pilot's floor access (70), brake cylinder access cables (7, 8, 20 and 21) and withdraw.cables. Dis-
(71), floorboards (80, 82, 84) and stabilizer fairing connect guide wires and leave in place until ready to
(11). reinstall cables.

NOTE CAUTION

If an autopilot (optional equipment) is in- Tension on nose wheel steering cables must
stalled, disconnect from rudder bellerank be released before rudder position cable
when removing cables (20 and 21). (6) is disconnected,

g. Remove turnbuckle clip and turnbuckle (4), from

position cable (6); remove cotter pin, nut and screw
securing cable to torque tube (3).

Change 9
 421 SERVICE MANUAL RUDDER AND TRIM
CONTROL SYSTEMS

FORWARD CABIN BHD.

7.60" to 7.80"

RUDDER PEDAL NEUTRAL

9
1

1. Brake Link 4. Pin 7. Brake Torque Tube

2. Brake Master Cylinder 5. Spring 8. Rudder Torque Tube
3. Roll Pins 6. Spacer 9. Bearing

Figure 7-2. Rudder Pedal Assembly

Change 9
7-6. RUDDER AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

Ih. Remove cable guard pins

and route cable from aircraft.
from pulley bracket torque tubes by removing cotter pins,
pins.
g. Remove rudder pedal assemblies
spacers

by removing
and

eight bolts, four upper and four lower bearing halves.

Installation of Rudder Control Cables. (See figure
7-1.) NOTE

a. Reverse the rudder control cables removal pro- The upper and lower halves of each bearing
cedures except the installation of seats, cabin divid- are matched parts and should be tagged and
ers (optional), refreshment bar (optional), carpet, kept in pairs.
access panels, rudder cover plates, floorboards and
stabilizer fairings.
b. Install seals (10) on steering cables and seals Disassembly of Rudder Pedal Assembly. (See figure
(19) on rudder cables as follows: 7-2.)
1. Insure that cables are lubricated for the full
length of its travel within the seals. a. Remove brake links (1) by removing cotter pins
2. Pack the seals with MIIrG-81322A lubricant. and pins.
3. Place seals on cable on non-pressurized side b. Remove pilot's and copilot's rudder pedals by
of bulkhead with small end toward bulkhead. driving out roll pins (3) and removing pins (4),
4. Insert seal in the bulkhead hole so that bulk- springs (5) and spacers (6).
head metal is seated within the retaining groove
of seals and the small end of seal is in the pressur- NOTE
ized section.
5. Install proper retaining rings in the grooves of Copilot's rudder pedals do not have springs
the seal (two on small end and one on large end. (5) and spacers (6) installed.
c. Rig rudder control system in accordance with
rigging of the rudder control system, c. Remove brake torque tubes (7) from rudder pedal
torque tubes (8) by removing cotter pins, pins and
couplers.
Removal of Rudder Bellerank. (See figure 7-1.) d. Bearing (9) in rudder pedal torque tube and tor-
que arm are a press fit and should be removed only,
a. (See figure 1-2.) Remove stabilizer fairings if during an inspection, it is determined that the
(11). bearings need to be replaced,
b. Remove turnbuckle clips and loosen either turn-
buckle (4) (to release tension on rudder cables). Assembly of Rudder Pedal Assembly. (See figure
c. Disconnect rudder cables (20 and 21) from rudder 7-2.)
bellerank (13) by removing cotter pins, nuts, wash-
ers and bolts. a. Insert brake torque tubes (7) into rudder pedal
d. Remove nut, washer and bolt from rudder bell- torque tubes (8) and install couplings using pins and
crank hinge- cotter pins,
e. Remove rudder bellerank (13) from the rudder b. Install rudder pedals on rudder pedal torque tube
torque tube by removing nut, washer and bolt. arms using spacers (6), springs (5), pins (4), and
roll pins (3).
Installation of Rudder Bellcrank. (See figure 7-1.)
NOTE
a. Reverse the rudder bellerank removal procedures
except the installation of the stabilizer fairings. Copilot's rudder pedals do not have springs
b. Rig rudder control system in accordance with (5) and spacers (6) installed.
rigging of rudder control system.
c. Install brake links (1) using pins and cotter pins.
Removal of Rudder Pedal Assembly. (See figure 7-2.)

a. Remove pilot's seat and copilot's seat, cabin Installation of Rudder Pedal Assembly. (See figure
divider (optional), cover plates, kick plates, carpet 7-2.)
and pedestal filler in accordance with Section 3.
b. (See figure 1-2.) Remove pilot's floor access a. Install the rudder pedal assembly by placing the
(70), copilot's floor access (76), and brake cylinder lower half of each bearing over attached nutplates and
access (71). locate the rudder pedal assembly in the bearing, then
c. Release tension on nose wheel steering cables, placing the upper bearing half and installing the
rudder cables and rudder position cable, screws.
d. Remove five cables from rudder torque tubes (8)
by removing cotter pins, nuts, washers and bolts. . NOTE
e. Disconnect brake master cylinders (2) from the
pilot's rudder pedals by removing cotter pins and During the installation of rudder pedal assem-
Pins. blies, lubricate in accordance with Section 2.
f. Remove four brake links (1) from rudder pedal Rudder pedal torque tubes must rotate freely
Change 9
 421 SERVICE MANUAL RuoDER AND TRIM ]•$A 7-68
CONTROL SYSTEMS

(2 X 4) VERTICAL FIN

RUDDER

BLOCK

BLOCK RUDDER HALF WIRE POINTER

THE DISTANCE BE-
TWEEN STRAIGHTEDGES
MEASURING
ESTABLISHING NEUTRAL RUDDER
POSITION OF RUDDER TRAVEL

1. Establish neutral position of rudder by clamping straightedge (such as wooden 2 x 4) on each side of
fin and rudder and blocking trailing edge of rudder half the distance between straightedges as shown.

2. Tape a length of soft wire to the stinger in such a manner that it can be bent to index at the lower
corner of the rudder trailing edge.
3. Using soft lead pencil, mark rudder at point corresponding to soft wire indexing point (neutral).

4. Remove straightedges and blocks.

5. Hold rudder against right, then left, rudder stop. Measure distance from pointer to pencil mark
on rudder in each direction of travel. Distance should be between 14.25" and 14.87" (421-0001
to 421B0801) or 15.90 to 16.52 (421BO801 and On).

Figure 7-2A. Checking Rudder Travel

Change 12
 421 SERVICE MANUAL RUDDER AND TRIM
CONTROL SYSTEMS

in bearings. NOTE

b. Connect brake links (1) to rudder pedal torque Cable tension should be adjusted when ambi-
60°F
tubes (8) with pins, spacers and cotter pins. ent temperature is to 90°F. Allow air-
c. Connect brake master cylinders (2) to pilot's craft temperature to stabilize for a period of
rudder pedals with pins and cotter pins. 4 hours.
d. Attach rudder cables, nose wheel steering cable
g. Adjust the rudder bellerank stop bolts (17) so
and position cable to rudder pedal torque tube with
that the rudder travel is (421-0001 to 421B0801) 25
bolts, washers, nuts and cotter pins. +1° -0°

left and
25° +1°
right (measured
-0°

per-
e. Rig rudder control system in accordance with ' '
to the rudder hinge line) or (421B0801
.

pendicular
rigging of the rudder control system. 32° +1° 32° +1°
and On) left and
-0°

' right.
-0°

f. Install pilot's floor access, copilot's floor access

See figure 7-2A for alternate method of measuring
and brake cylinder access.
filler, carpet, kick plate, cover rudder travel.
Install pedestal
.
h. Resafety stop bolts (17) and install turnbuckle
cabin divider (optional), and pilot's and co-
. .

plate, clip on all turnbuckles.

pilot's seats. i. Check the tips of the pilot's rudder pedals for
alignment and if needed, adjust clevis rod ends (2)
Rigging of Rudder Control System. (See figure 7-1.) on brakes master cylinders. Check and adjust the
copilot's rudder pedals for alignment. (See figure
cabin dividers
. .

a. Remove seats, (optional), cover y

plates, kick plates and carpet in accordance with
Section 3. WARNING
b. (See figure 1-2.) Remove cable access (15),
stabilizer fairings (11) and fuel selector gear box Insure that rudder moves the proper direct-
access (73). tion when operated by the rudder pedals.
c. Remove turnbuckle clips from the rudder system
turnbuckles (14). j. Install cable access, stabilizer fairings and fuel
d. Adjust the position cable (6), which is a "balance" selector valve access.
cable, used to close the rudder system. The position k. Install seats, cabin dividers (optional), cover
cable turnbuckle (4) should be adjusted so that the pi- plates, kick plates and carpet.
vot point of the rudder pedals are 7. 60 to 7. 80 inches
from the forward cabin bulkhead (see figure 7-2). RUDDER TRIM CONTROL SYSTEM.
e. With the nose wheel and rudder pedals in neutral
position, adjust the nose wheel steering cables ten- The rudder trim tab is operated by a control wheel
sion to 20 ±5 pounds. mounted on the aft side of tne pedestal. The control
f. With the nose wheel, rudder pedals and rudder wheel is attached to a sprocket which drives a chain
in neutral position, adjust the rudder cable turn- and cables. The chain and cables are routed by pul-
buckles so that the cable tension is 25 ±5 pounds. leys, forward and down through the pedestal under
the floor and aft to the tailcone of the aircraft. In
the tailcone, the cables are routed aft to pulleys
NOTE mounted on the aft side of the vertical stabilizer rear
spar, then up and through the vertical stabilizer, to
The tension on the nose wheel steering cables a chain which operates the trim tab actuator. The
and the aft rudder cables operate in the same trim tab push rod connects the trim actuator to the
direction. If either cables are adjusted, it rudder trim tab which is mounted to the rudder by a
will be necessary to recheck the tension on continuous hinge. The adjustable turnbuckles, for
the cables which were not adjusted. cable tension adjustment, are located under the fuel
selector gear box access panel. The stop blocks are
located in the tailcone for adjustment of the rudder
Troubleshooting Rudder Trim Control System. trim tab travel.

TROUBLE PROBABLE CAUSE CORRECTION

RESISTANCE TO CON- Cable tension too high. Adjust cables in accordance with
TROL WHEEL rudder trim control rigging
MOVEMENT instructions.

Pulleys binding or rubbing. Replace binding pulleys. Pro-

vide clearance if rubbing pulley
brackets or cable guards.

Cable not in place on pulleys. Install cable correctly.

Trim tab actuator defective. Repair or replace actuator.

Trim tab hinge binding. Lubricate hinge. If necessary,

replace.

Change 12
7-Ñ RUDDER AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

E
D

/
4 8
g5 10
3

Detail
10

Deta 1 B
3

Sus3oil '
Es16no13 's
22
csus4oos
usussoo9 23-
Detail
E54613003
A14153018
-
Detati D netan C

Figure 7-3. Rudder Trim Control System (Sheet 1 of 2)

Change 9
 421 SERVICE MANUAL RUDDER AND TRIM
CONTROL SYSTEMS

17 .

13 14

12 15

11
16

27
222 23
8
Detail Û
22 22
23 25

21 Detail
24
23

421-0001 TO 42 B0301

421BO301 AND ON F54613004

GS4613004
Detail) Detail H «s4612oos
J51611010
J52613001
K54613004

1. Control Wheel 9. Right Cable (Fwd) 16. Hinge Pin 23. Left Cable (Aft)
2. Pin 10. Guard Pin 17. Push Rod 24. Bushing
3. Shaft 11. Sprocket 18. Clamp 25. Pulley
4. Sprocket 12. Chain Guard 19. Chain 26. Seal
5. Chain 13. Trim Actuator 20. Pulley 27. Nut
6. Guard Pin 14. Trim Tab 21. Stop Block 28. Washer
7. Turnbuckle 15. Trim Tab Horn 22. Right Cable (Aft) 29. Screw
8. Left Cable (Fwd) 30. Cable Stop

Figure 7-3. Rudder Trim Control System (Sheet 2)

Change 9
 1-10 RUDDER AND TRIM 421 SERVICE MANUAL
CONTROL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

LOST MOTION BETWEEN Cable tension too low. Adjust cables in accordance with
TRIM CONTROL WHEEL rudder trim control rigging
AND TRIM TAB instructions.

Broken pulley. Replace pulley.

Worn trim tab actuator. Repair or replace actuator.

INCORRECT TRIM TAB Stop block loose or incorrectly adjusted. Adjust stop block in accordance
TRAVEL with rudder trim control rig-
ging instructions.

CORRECT RUDDER TRIM Actuator screw incorrectly adjusted. Adjust in accordance with rudder
TAB TRAVEL CANNOT trim control rigging instructions.
BE OBTAINED BY AD-
JUSTING STOP BLOCK

INDICATOR DOES NOT Indicator incorrectly engaged with Adjust in accordance with rudder
INDICATE THE COR- control wheel. trim control rigging instructions.
RECT TRIM POSITION

Removal of Rudder Trim Control Cables and Chains.

(See figure 7-3.) a. Tie guide wires at pedestal to turnbuckle end of
cables (8 and 9), pull into position and remove guide
a. Remove seats, cabin dividers (optional), refresh- wires.
ment bar (optional), carpet, pedestal cover and tail- b. Engage chain (5) with trim control wheel sproc-
cone access door in accordance with Section 3. ket and install five cable guard pins (10).
b. (See figure 1-2.) Remove fuel selector gear box c. Attach chain (19) to guide wire in vertical
access (73), center control access (79), center floor- stabilizer and pull into position and remove guide
boards (80, 82, and 84) and cable access (15) to gain wire.
access to forward cables, pulleys and attachment d. Engage chain (19) with actuator sprocket (11)
points. and install chain guard (12) with screws, washers
c. (See figure 1-2.) Remove stabilizer fairing (11), and nuts.
vertical stabilizer access (6) and tailcone access e. Install cables pulleys'(20 and 25) by installing
(18). bolts, washers, nuts and cable guard pins.
d. Remove rudder trim stop blocks (21) and bush- f. Attach guide wire to turnbuckle end of cables
ings (24) by removing nut, washer, and screw. (22 and 23) in tailcone, pull into position and remove
e. Remove cable stop (30) by removing guide wires,
Inuts.
f. Unsafety turnbuckles (7) and disconnect cables
screws and
g. Connect the left cables (8 and 23) and right cables
(9 and 22) using turnbuckles (7).
by removing turnbuckles. h. Install stop block (21) and bushing (24) with
g. Remove chain guard (12) from rudder trim actu- screws, nuts and washers. Do not tighten at this
ator (13) by removing nuts, washers and screws. time,
h. Remove pulleys (20 and 25) by removing nuts, i. Install cable stop (30) with screws and nuts.
washers, bolts and cable guard pins. j. Install seals (26) in accordance with instructions
i. Disengage chain (19) from actuator sprocket (11), for installing rudder seals.
attach a guide wire to the chain and remove cables k. Rig rudder trim control in accordance with rig-
and chain from vertical stabilizer by pulling out ging of rudder trim control system.
through opening in tailcone, 1. Install stabilizer fairing and rudder actuator
j. Remove seals (26). access panel.
k. Remove two cable guard pins (6). m. Install access cover on pedestal, floor, and
1. Attach guide wire to aft cables (22 and 23) at fuel fuel selector valve access.
selector gear box access and remove by pulling out n. Install tailcone access door, seats, cabin divi-
through opening in tailcone. der (optional), refreshment bar (optional), carpet,
m. Remove forward cables by removing five cable and pedestal cover.
guard pins (10) and remove chain (5) from sprocket
(4). Removal of Rudder Trim Tab Actuator. (See figure
n. Attach guide wires to forward cables (8 and9) 7-3.)
at cable access (15, figure 1-2) and remove by pull-
ing out through pedestal. a. (See figure 1-2.) Remove fuel selector gear box
access (73) and rudder trim access (6).
Installation of Rudder Trim Control Cables and b. Unsafety and loosen turnbuckles- (7) to release
Chains. (See figure 7-3.) tension on rudder trim control cables.
Change 9
 421SERVICE MANUAL RUDDER AND TRIM
CONTROL SYSTEMS

c. Disconnect the rudder trim tab push rod (17) by Rigging of Rudder Trim Control System. (See figure
removing the cotter pin, nut, washer and bolt. - 7-3.)
d. Reniove cable guard from rudder trim tab actu-
ator (13) by removing nuts, washers and screws, and a. (See figure 1-2.) Remove tailcone access door,
disengage chain from sprocket. fuel selector gear box access (73), pedestal access,
e. Remove nuts (27), washers (28), and screws (29) and rudder trim access (6).
and remove actuator through access hole. b. Loosen stop block (21) by loosening attaching
nuts and screws.
c. Check and adjust the cable tension on the rudder
Disassembly, Overhaul and Assembly of Rudder trim control cables to 10 ±3 pounds.
Trim Tab Actuator.
NOTE
The instructions for disassembly, overhaul and as-
sembly of the aileron trim tab actuator, given in Cable tension should be adjusted when ambi-
Section 5, also applies to the rudder trim tab actua- ent temperature is
60°F
to 90°F. Allow air-
tor. craft temperature to stabilize for a period of
4 hours.

Installation of Rudder Trim Tab Actuator. (See fig-

ure 7-3.) d. Move rudder trim control system to neutral by
rotating trim control wheel so that the ends of the
a. Reverse the rudder trim tab actuator removal chains are equal length from actuator and control
procedure except installation of fuel selector gear wheel sprocket.
box access and rudder trim access. e. Check the rudder trim indicator to indicate
b. Rig the rudder control system in accordance neutral position and if requiring adjustment, insert
with rigging of rudder trim control system. a screwdriver beneath the indicator and prying out of
track in the trim control wheel, moving the indicator
to neutral, and re-engaging with the track.
Removal of Rudder Trim Control Wheel, Sprocket, f. Disconnect rudder trim tab push rod (17) from
and Indicator Assembly. (See figure 7-3.) rudder trim tab (14) by removing attaching cotter pÏn,
nut, washer and bolt.
a. Remove from the pedestal lower access cover, g. With the control wheel (1), rudder and rudder
right access cover, and autopilot cover to autopilot trim tab (14) in neutral, adjust the trim actuator
panel (optional). (13) so that the hole in the push-pull tube (17) is
b. Remove fuel selector gear box access and aligned with the hole in the trim tab horn (15); attach
loosen turnbuckles (7) to release tension on rudder with bolt, washer, nut and cotter pin.
trim control system. h. Rotate rudder trim control wheel (1) so rudder
chain and drive out pins (2) from con- trim tab (14) is 11° +1°, perpen-
-0°

c. Disengage right (measured

trol wheel (1) and sprocket (4). dicular to rudder hinge line). On aircraft 421-0001 to
d. Remove the control wheel and sprocket by re- 421BO301 locate center stop block (21) approximately
moving shaft (3). 24 inches aft of cabin bulkhead and tighten. Slide for-
ward stop block (21) against center stop block (21)
NOTE and tighten. On aircraft 421BO301 and On, slide aft
stop block (21) against cable stop (30) and tighten.
To remove the rudder trim indicator assembly, i. Rotate rudder trim control wheel (1) so rudder
the rivet, around which the indicator pivots, trim tab (14) is 16° +1°, -0°

left (measured perpen-

must be removed. dicular to rudder hinge line). On aircraft 421-0001
to 421B0301, slide aft stop block (21) against center
stop block and tighten. On aircraft 421B0301 and On,
Installation of Rudder Trim Control Wheel, Sprocket, slide forward stop block against cable stop (30) and
and Indicator Assembly. (See figure 7-3.) tighten.
a. Reverse the rudder trim control wheel, sprocket WARNING
and indicator assembly removal procedure except
the installation of the access cover and panels. Insure that rudder trim tab moves in the
b. Rig rudder trim control system in accordance proper direction when operated by the trim
with rigging of the rudder trim control system. control wheel.

j. Install the tailcone access door, fuel selector

valve access, pedestal access, and rudder trim
access.

Change 9
 421 SERVICE MANUAL FLAP CONTROL SYSTEM Û

SECTION 8

FLAP CONTROL SYSTEM

Table of Contents

Page Page
FLAP CONTROL SYSTEM - - - · 8-1 Installation of Limit Switch Bracket .
8-6
Troubleshooting . - - - · · 8-2 Installation of Flap Actuator Assembly .
8-8
Removal of Flaps - - - · · 8-2A Rigging Flap Control System . . .
8-8
Installation of Flaps - - - - - 8-2A Operational Flight Check . . . . 8-11
Removal of Flap Control Cables and Removal of Flap Preselect Lever
Chain - · · · · · · 8-2A Assembly . . . . . .
8-11
Installation of Flap Control Cables Disassembly and Assembly of Flap
and Chain . . . . . .
8-3 Preselect Lever Assembly . . .
8-11
Removal of Flap Bellerank . . .
8-3 Installation of Flap Preselect Lever
Installation of Flap Bellcrank . . .
8-3 Assembly . . . . . .
8-11
Removal and Installation of Flap Removal of Flap Preselect Control
Scissors Assembly . . . .
8-3 Cable . . . . . . .
8-11
Troubleshooting Flap Actuator Motor .
8-6 Installation of Flap Preselect Control
Removal of Flap Actuator Assembly .
8-6 Cable . . . . . . .
8-11
Removal of Limit Switch Bracket . .
8-6 Rigging Flap Preselect System . .
8-12
Adjustment of Landing Gear Warning
System . . . . . . .
8-12

CAUTION

Primary and secondary flight control cables, push pull tubes , belleranks and mountings
on late model aircraft use dual locking fasteners. The lock nuts for these fasteners incor-
porate a fiber lock, and are castellated for safetying with a cotter pin. When any of these
areas are disconnected on any aircraft, new dual locking fasteners should be installed.
See the Aircraft Parts Catalog for part numbers and location of these fasteners.

FLAP CONTROL SYSTEM. lever assembly and routed aft under the cabin floor-
board and attached to the flap control cable, and as-
The flap control system is operated by an electric sociated electrical wiring. When the preselect lever
drives a gear reduction unit. Two is placed in the
0° (UP) or 15°, 30° 45°
motor which assembly or
sprockets, connected in tandem to the reduction unit (DOWN) position, the preselect lever assembly mi-
output shaft by special rivets, drive four chain- croswitches are energized and actuates the flap mo-
connected cables which actuates the flap belleranks. tor, which drives the flaps until the corresponding
The four belleranks in each wing are interconnected flap position is reached. As the flaps reach the pre-
by push-pull tubes. A cam, driven by a gear attach- selected position, the preselect lever assembly mi-
ed to the aft output shaft of the reduction unit, oper- croswitches are de-energized. On aircraft 421B0201
ates two limit switches. On aircraft 421A0001 and and ON, a warning switch is mounted on the flap pre-
ON, a flap preselect system is provided. The flap select mounting bracket to provide an aural warning
preselect system is comprised of a preselect lever when the flap preselect handle is lowered past the
15°
assembly, mounted on the instrument panel; a flap position with the landing gear not down and lock-
preselect control cable, attached to the preselect ed.

Change 10
8-2 FLAP CONTROL SYSTEM 421 SERVICE MANUAL

Troubleshooting Flap Control System.

TROUBLE PROBABLE CAUSE CORRECTION

FLAP FAILS TO EXTEND Battery switch OFF. Turn switch ON.

OR RETRACT
Circuit breaker out. Reset circuit breaker.

Defective flap switch and/or limit Replace flap switch and/or limit
switches. switches.

Defective flap motor. Replace flap motor.

Stripped or broken drive gear on Replace flap motor.

flap motor.

Stripped or broken gears in re- Replace reduction unit.

duction unit.

Drive sprockets not secured to re- Replace special rivets and/or

duction unit output shaft. sprockets.

FLAPS FAIL TO RETRACT Up limit switch incorrectly adjusted. Adjust in accordance with rigging
procedures.

Incorrect rigging of flap cables, com- Rig in accordance with rigging pro-
pensated for by incorrect adjustment cedures.
of push-pull rods.

FLAPS FAIL TO EXTEND DOWN limit switch incorrectly ad- Adjust in accordance with rigging
COMPLETELY justed. procedures.
Incorrect rigging of flap cables, Rig in accordance with rigging pro-
compensated for by incorrect ad- cedures.
justment of push-pull rods.

adjustment of push-pull Rig in accordance with rigging pro-

Incorrect
rods, cedure.

FLAPS NOT SYNCHRO- Incorrect adjustment of push-pull Adjust in accordance with riggíng
NIZED OR FAIL TO FIT rods. procedure.
EVENLY WHEN
RETRACTED Bent push-pull rods. Straighten or replace.

Incorrect adjustment of bellerank Adjust in accordance with rigging

interconnecting push-pull tubes. procedure.

Incorrect rigging of cables and Rig in accordance with rigging pro-

chains. cedures.

Bent flap. Repair or replace flap.

FLAPS ON ONE SIDE Drive sprocket for inoperative side Replace special rivets and/or
FAIL TO OPERATE not secured to reduction unit output sprocket.
shaft.

Broken chain, cable or attaching pin. Replace broken parts.

Change 8
 421 SERVICE MANUAL FLAP CONTROL SYSTEM $" A $Ñ.Ñ

Removal of Flaps. (See figure 8-1.) d. Check flap for proper operation and correct tra-
vel. If adjustment is necessary, refer to rigging
The following is a removal procedure for the left in- procedure.
board flap. Remove the other flaps in a similar
manner.
a. Extend flaps. Removal of Flap Control Cables and Chains. (See
b. (See figure 1-2.) Remove access cover (38). figure 8-1.)
c. Disconnect lower scissors link assemblies (10)
from flap structure by removing nuts (15), washers a. Remove cabin seats and carpet on LH and RH
(14), spacers (12 and 13) and bolts (9). sides of aircraft in accordance with Section 3.
.d. Remove safety wire from bent end of hinge pin b. (See figure 1-2) Remove floorboard access
(24), and detach flap by removing hinge pin. panels (80, 81 and 86).
c. (See figure 1-2) Remove wing structural sRin
NOTE (35) and access plates (58, 64, 65, and 66).
d. Remove four inspection plates on forward side of
If difficulty is encountered in removing out- rear spars adjacent to wheel well.
board flap binge pin, it may be necessary to e. Lower flaps several degrees to decrease tension
remove alleron to gain better access to hinge on cables, remove safety and disconnect the turn-
pin. buckles.
f. Disengage chains from sprockets.
Installation of Flaps. (See figure 8-1.) g. Disconnect flap extendcable (25)and return cable
(27) from cable attachment links (26) by removing
a. Attach flap to wing with hinge pin (24). Safety cotter pins, screws and nuts.
wire bent end of hinge pin. h. Remove outboard pulley (28) by removing nut and
bolt.
NOTE
NOTE
To facilitate hinge pin installation, check
hinges and pin for distortion, lubricate Outboard pulley cable guard cotter pins are
hinge pin, and taper end of hinge pin. quite difficult to remove and install and
should be removed only for replacement.
b. Connect
lower scissors link assemblies (10) to
flap structure by installing bolts (9), spacers (12 i. Remove pulleys (29 and 30) located on wing stub
and 13), washers (14) and nuts (15). by removing nuts and bolts.
c. (See figure 1-2) Replace wing access cover (38)• j. Remove pulleys (31 and 32) located under floor-

Change 8
 421 SERVICE MANUAL FLAP CONTROL SYSTEM

board access panel by removing bolts. (27) from cable attachment links (26) by removing
k. Remove seal assemblies (42) through access cotter pins, screws and nuts.
holes (58)- NOTE
1. Üisconnect chain (33) from extend cable (25) and
return cable (27) by removing cotter pins, nuts, The above steps apply only to removal of the
washers and bolts. inboard bellerank for the inboard flaps. To
m. Tie guide wires to flap cables and pull out through remove other belleranks, remove access hole
fuselage, covers from rear spar adjacent to affected
n. Untie guide wires and remove cables from air- bellerank.
craft.
o. Removal procedures are for LH wing only. Re- f. Disconnect push-pull rod (11) from bellerank
move right cables and chain in a similar manner. (17) by removing cotter pin, nut, spacers and bolt.
g. Disconnect inter connecting push-pull tube (19)
Installation of Flap Control Cables and Chains. (See from bellerank (17) by removing cotter pin, nut,
figure 8-1.) spacers and bolts.
h. Unsafety bolt (22) retaining bellerank (17) and
a. Tie cables (25 and 27) to guide wire and route remove bolt by gaining access through plug button
into position through the fuselage and wing. from the underside of wing beneath bolt,
b. Attach flap extend cable (25) and return cable i. Remove bellerank through rear spar access
(27) to links (26) on bellerank (17) with screws, panels taking care that bushing (21) does not fall
washers, nuts and cotter pins. from bellerank during removal.
c. Place return cables (27) in position on pulleys
(28, 29, and 31) and install pulleys with bolts and nuts. Installation of Flap Bellcrank. (See figure 8-1.)
d. Place extend cables (25) in position on pulleys
(32 and 30) and install pulleys with bolts and nuts. a. Insert bellerank through access hole and install
e. With turnbuckle ends attached to extend cable (25) with washers (23) and bolt (22). Safety bolt and in-
and return cable (27), secure cables to chain (33) with stall plug button on underside of wing beneath bolt.
screws, washers, nuts and cotter pins. NOTE
f. Engage chains (33) on reduction unit sprocket and
rig cables m accordance with flap rigging procedures. Washers (23) and bushing (21) must be in place
g. Install seal assemblies (42) as follows. before installing bolt (22).
1. Insure that cables are lubricated for the full push-pull
b. Attach interconnecting tube (19) to
length of its travel within the seals• with attaching
bellerank bolt, spacers, nut and
2. Pack the seals with MIL-G-81322A lubricant. cotter pin.
3. Place seals on cable on non-pressurized side of c. Connect push-pull rod (11) to bellerank (17) with
bulkhead with small end toward bulkhead.
attaching bolt, spacers, nut and cotter pin.
4. Insert seal in the bulkhead hole so that bulkhead d. On bellerank (17) connect flap extend cable (25)
metal is seated within the retaining groove with the and return cable (27) to cable attachment links (26)
small end of seal in the pressurized section. by installing nuts and cotter pins.
screws,
5. Install proper retaining rings in the grooves of e. Rig flaps in accordance with rigging procedure.
the seal (two on small end and one on large end).
f. Reinstall access hole covers, carpets and seats
h. Install inspection plates, wing access panels, wing
.

as necessary,
gap skin, floorboard access panels, carpet and seats.
i. Installation procedures are for LH wing only.
Install RH cables and chain in a similar manner.
Removal and Installation of Flap Scissors Assembly.
of Flap (See figure 8-1.) (See figure 8-1.)
Removal Bellerank.

NOTE a. Removal of flap scissors as follows:

1. Extend flaps.
Eight belleranks are used to operate the flaps. 2. Disconnect upper and lower scissors links (3
The following procedure is used for removing and 10) by removing cotter pins, nuts, washers,
the inboard bellerank on the inboard flaps. spacers and bolts.
Removal of the remaining belleranks may be 3. Disconnect push-pull rod (11) by removing
accomplished in a similar manner. cotter pin, nut, washer, spacers and bolts attaching
push-pull rod to.scissors.
a. Remove cabin seats and carpet in accordance b. Install flap scissors as follows:
with Section 3. 1. Attach scissor links (3 and 10) to push-pull rod
b. (See figure 1-2.) Remove floorboard access using bolt, spacers, washer, nut and cotter pin.
panels (80, 81 and 86). 2. Connect upper and lower scissor links (3 and
c. (See figure 1-2) Remove plug button (60) and 10) using bolts, spacers, washers, nuts and cotter
rear spar access cover adjacent to bellerank. pins.
d. Lower flaps several degrees to decrease tension 3. Check flaps for proper operation and correct
on return cable (27), remove safety and loosen turn- travel. See Rigging of Flap Control System for
.

buckles to release tension on cables, limits and tolerances,

i e. Disconnect extend cable (25) and return cable
Change 8
8-4 FLAP CONTROL SYSTEM 421 SERVICE MANUAL

Detail
11

24

1. Nut 16. Scissors Assembly 31. Upper Inboard Pulley LH

2. Washer 17. Bellerank 32. Lower Inboard Pulley LH
3. Upper Link Assembly 18. Center
Interconnecting Push-pull Tube 33. Flap Chain LH
4. Spacer 19. Inboard
Interconnecting Push-pull Tube 34. Extend Cable RH
5. Spacer 20. Outboard Bellerank 35. Return Cable RH
6. Spacer 21. Bushing 36. Flap Chain RH
7. Bolt 22. Bolt 37. Lower Inboard Pulley RH
8. Bolt 23. Washer 38. Upper Inboard Pulley RH
9. Bolt 24. Hinge Pin 39. Lower Center Pulley LH
10. Lower Link Assembly Ë25. LH Extend Cable 40. Upper Center Pulley LH
11. Push-pull Rod 26. Cable Attachment Link 41. Flap Actuator
12. Spacer 27. LH Return Cable 42. Seal Assembly
13. Spacer 28. Outboard Pulley LH 43. Bellerank RH
14. Washer 29. Upper Center Pulley LH 44. Outboard Pulley RH
15. Nut 30. Lower Center Pulley LH 45. Cotter Pin

Figure 8-1. Flap Control System (Sheet 1 of 2)

Change 8
 421 SERVICE MANUAL FLAP CONTROL SYSTEM 8-5

25 26 23

17

28

44 43
28

40 Detail B 2
38 22
34
39
*
38 ch 23

33
37
35 27
41
31

Detail F _ 2,
·
17
25
32
42
30

30
Detail E 25 7 notan C

25 E51612006
9 O F51154006
G51612006

Figure 8-1. Flap Control System (Sheet 2 of 2)

Change 12
8•6 FLAP CONTROL SYSTEM 421 SERVICE MANUAL

Troubleshooting the Flap Actuator Motor.

TROUBLE PROBABLE CAUSE CORRECTION

BRAKE DOES NOT Loosen or open connections Check test connections; if all right, test
RESPOND AS or circuits. Improper motor circuits for proper resistance,
REQUIRED assembly. check for proper brake air gap. Adjust
or replace defective parts.

SPEED IS TOO LOW Incorrect end play, shorted Check motor for correct end play. If all
OR CURRENT IS armature circuit, exces- right, test motor circuits for shorts. Re-
TOO HIGH sive bearing friction. place defective parts.

MOTOR WILL NOT Circuit breaker out. Reset breaker, if breaker will not remain
RUN set, check for shorted wiring in field cir-
cuit. If field circuit is shorted, refer to
Landing Gear and Flap System Compo-
nents Overhaul/Parts Manual and repair
or replace motor.

MOTOR NOISY Faulty bearings or arma- Refer to Landing Gear and Flap System
ture dragging. Components Overhaul/Parts Manual and
repair or replace motor.

Removal of Flap Actuator Assembly. (See figure Removal of Limit Switch Bracket. (See figure 8-2.)
8-2.)
a. Disconnect and tag electrical wires and route
a. Flap motor and/or position transmitter (421¯ from bracket.
0001 to 421A0001) can be removed without removing b. Remove safety wire from bolts (1).
reduction unit; however, due to limited working space c. Remove screw (38) and bolt (1). The lower bolt
it is desirable to remove reduction unit, flap motor, only needs to be loosened. Bracket hole is slotted
and transmitter as an assembly· for removal.
b. (See Section 3) Remove cabin seats and carpet d. Remove bracket (3) and switch assembly.
on LH side of aircraft.
c. (See figure 1-2) Remove floorboard access
Installation of Limit Switch Bracket. (See figure 8-2.)
panels (80, 81 and 86).
d. Lower flaps several degrees to release tension a. Position bracket (3) and switch assembly to
on return cables, remove safety from turnbuckles motor (2) and secure with bolts (1), screw (38) and
and loosen turnbuckles enough to disengage chains
lockwasher (39). Safety wire bolts (1).
from sprockets. b. Route electrical wires through bracket and
e. On aircraft 421-0001 to 421A0001, disconnect
grommet. Connect wires and remove tags.
electrical connector from position transmitter (25). c. Check that the reduction unit output shaft (14)
f. Remove nuts and screws attaching reduction unit
does not turn when 800 pound-inches torque is ap-
to fuselage rear spar. plied.
g. Move complete actuator assembly forward until
d. Adjust setscrew (33) to provide 0. 005 maximum
it clears the rear spar, tilt assembly slightly and re transfer shaft movement and secure with locknuts
move through floorboard access hole. (34).
Care should be exercised when working flap
actuator assembly through control cables. NOTE

h. Disconnect and tag wires leading from wire bun- Shaft movement measurement should be
dle to limit switches (21). measured between miter gear (30) and miter
gear (32).
NOTE

If optional 400A Nav-O-Matic autopîlot flap

actuator is installed, tag and disconnect
wires from resistor (28).

Change 5
 421 SERVICE MANUAL FLAP CONTROL SYSTEM Û-BA

23 421-0001 To 421A0001 16
3
15
22 14
20

Detail A 19

421-0001 TO 421-0183

Detail
421-0183 TO 421A0001

1. Bolt 11. Screw 20. Limit Switch Actuator 30. Miter Gear
2. Flap Motor 12. Sprocket 21. Limit Switch (Down) 31. Roll Pin
3. Bracket 13. Pin 22. Spacer 32. Miter Gear
4. Screw 14. Output Shaft 23. Nut 33. Setserew
5. Nut 15. Reduction Unit 24. Spacer 34. Locknut
6. Setscrew Plate Cover 25. Position Transmitter 35. Spacer Bushing
7. Reduction Unit 16. Pinion Gear 26. Limit Switch (Up) 36. Resistor Bracket
8. Nut 17. Roll Pin 27. Guard Assembly 37. Resistor
9. Screw 18. Cam 28. Shaft 38. Screw
10. Dowel Pin 19. Screw 29. Spacer 39. Lockwasher
40. Gear
Figure 8-2. Flap Actuator Assembly (Sheet 1 of 2)
Change 12
 421 SERVICE MANUAL FLAP CONTROL SYSTEM $"

36 *37

40 32 5

NOTE
26
*USED WITH 400A 19
NAV-O-MATIC
AUTOPILOT ONLY
18 3 23 33 34 2 1
Detail B
421A0067 AND ON

1 17
32 34
2
31
23

33

126

13 40
28
34
10 9 8 37* 30 29

14152019
421A0001 AND ON
51152007

Figure 8-2. Flap Actuator Assembly (Sheet 2)

Change 12
8-8 FLAP CONTROL SYSTEM 421 SERVICE MANUAL

Installation of Flap Actuator Assembly. (See figure Inboard interconnecting

8-2, ), push-pull tubes . . . . . . . . . . . . . 23. 80 inches

a. Place flap actuator assembly near floorboard ac- f. Adjust remaining push-pull rods from belleranks
cess hole and attach wires from wire bundle to res- to scissors so flaps fit evenly when in the UP position.
pective limit switch and remove tags. g. (See figure 8-2) Adjust limit switches as follows:
1. Loosen limit switches (21 and 26) and position
NOTE them where they will be activated by the cam (18).
2. With the flaps in the UP position on 421-0001 to
Insure that terminals of the limit switches 421A0001 aircraft, flex flap switch bracket (3) aft to
are covered with insulated sleeving and wir- disengage cam (18) from pinion gear (16). Rotate
ing is secure and clear of all control cables cam to a point where it actuates the UP limit switch
and moving parts. (26), (upper switch) and re-engage cam with pinion
gear by releasing tension on bracket (3).
b. Insert actuator assembly through floorboard ac- 3. With the flaps in the UP position on 421A0001
cess hole and install with screws and nuts. and ON aircraft, loosen setscrew (6), rotate cam
c. On aircraft 421-0001 to 421A0001 connect the (18) to a point where it actuates the UP limit switch
electrical connector to the position transmitter (25). (26), and then tighten setscrew (6).
d. Engage chains with sprockets (12) and rig flap h. (See figure 8-1) With flaps in the UP position,
control system in accordance with rigging procedure, check for correct positioning of the flap chains on
e. Install fuselage and floorboard access panels. sprockets and, if necessary, adjust as follows:
f. Install carpets and cabin seats in accordance 1. Engage right chain (36) with forward sprocket so
with Section 3. that approximately 2-1/2 links extend around bottom
side of sprocket.
2. Engage left chain with aft sprocket so that 3
Rigging of Flap Control System. (See figure 8-1.) links extend around the top side of sprocket.
3. Connect RH extend cable (34) to the long end of
The flap control system should be rigged using a 24 chain (top side of forward sprocket) and route over
volt external power source, with a two-position mo- pulleys (38 and 39) to bellerank (43).
mentary switch, attached to the flap motor wires so 4. Connect RH return cable (35) to the short end
the flaps may be observed while being operated dur- of chain (bottom side of forward sprocket) and route Ë
ing rigging. over pulleys (37 and 40) around outboard pulley (44)
and back to bellcrank (43).
CAUTION 5. Connect LH extend cable (25) to the long end of
chain (bottom side of aft sprocket) and route over
Use caution while operating flaps with an ex- pulleys (30 and 32) to bellerank (17).
ternal power source, as the limit switches 6. Connect return cable (27) to the short end of
are inoperative, chain (top side of aft sprocket) and route over pulleys
(29 and 31) around outboard pulley (28) and back to I
a. Remove center seats and center carpet in ac- bellerank (17).
cordance with Section 3. 7. With flaps secured in UP position tighten turn-
b. (See figure 1-2) Remove floorboard access buckles until all slack is out of cables. Temporarily
panels (80, 81 and 86). rig both return cables (27 and 35) with 185 lbs. ten-
c. Remove four inspection plates on the forward sion. Final tension on return cables should be 200
side of rear spar adjacent to wheel well. to 250 lbs. with flaps in the UP position. The dif-
d. Check length of inboard push-pull rod (11) on ferential tension between left and right should not
each inboard flap and adjust to 10. 45 inches, exceed 25 lbs.

NOTE NOTE

Length of push-pull rods is measured between At this point, recheck flap position as to being
the centerlines of rod end bolt holes. in proper position with respect to wing trail-
ing edge. Should further adjustment of push
e. Check length of interconnecting push-pull tubes rods be necessary, this must be accomplished
and adjust, if necessary, to the following dimensions: before final setting of cable tension.

Outboard interconnecting Remove tape or other means of securing

8. flaps
push-pull tubes . . . . . . . . . . . . . 33. 35 inches in the UP position and lower flaps a few degrees at
a time, observing for any unusual tension build-up
Center interconnecting in the cables or binding of the push-pull tubes and
push-pull tubes . . . . . . . . . . . . . 23. 80 inches push rods, until flaps reach their bottom position as

Change 12
 421 SERVICE MANUAL FLAP CONTROL SYSTEM S-Û.

30
Detail
51144004
Detail
A51151005
B
421A0001 AND ON

1. Bolt 9. Control Cable 17. Phenolie Washer

2. Bracket Assembly 10. Rod End 18. Spacer
3. Nutplate 11. Nut 19. Flap Preselect Lever
4. Spring Washer 12. Limit Switches 20. Knob
5. Arm Assembly 13. Cam 21. Set Screw
6. Washer 14. Cam 22. Teflon Washer
7. Nut 15. Nut 23. Spacer
8. Screw 16. Washer 24. Pivot Bellcrank

Figure 8-3. Flap Preselect Installation (Sheet 1 of 2)

Change 9
8-10 FLAP CONTROL SYSTEM 421 SERVICE MANUAL

Detail
421A0001 TO 421B0469 a
Detail LF
4 421B0469 TO 421B0594
I)etail
421BO201 AND ON

421A0001 TO 421B0301

4
D
22 23
6
18
E 11 Detaii E
421A0001 TO 421B0618

051153016
Detail C E51153016
C51153015
F51153016

25. Flap Cable (Extend) 30. Nut 35. Indicator Block

26. Flap Cable Pulley 31. Clamp 36. Guard Block
27. Nut 32. Bolt 37. Instrument Panel
28. Nut 33. Stop Bolt 38. Warning Switch
29. Nut 34. Pointer 39. Screw

Figure 8-3. Flap Preselect Installation (Sheet 2)

Change 10
 421 SERVICE MANUAL FLAP CONTROL SYSTEM $•ll

measured with a protractor. Tolerance for flap

travel is plus one degree, minus zero degrees. NOTE
9. Rig both extend cables (25 and 34) with 85 lbs.
of tension. (Final tension of extend cables, with Install knob with a minimum clearance of 0. 12
flaps down should be 75 to 95 lbs., with the differ- from instrument panel structure.
ential tension between left and right not exceeding
25 lbs. ) e. Rig flap preselect system in accordance with rig-
10. Raise flaps and make final tension check of ing procedure.
return cables (27 and 35) when stopped by the limit
switch. (200 to 250 lbs.) NOTE

NOTE When removing flap preselect lever assembly

from bracket assembly, make sure spring
If the return cable tension is readjusted at washers do not fall into center console.
this time, it will be necessary to recheck
the extend cable tension with the flaps in the Disassembly and Assembly of Flap Preselect Lever
down position and adjust as required. It Assembly. (See figure 8-3.) 421A0001 and ON
will always be necessary to make the last
tension adjustment on the extend cables with
flaps down. a. Disassemble lever assembly in accordance to
the applicable detail in figure 8-3.
Cable tension should be adjusted when ambi-
60°F
ent temperature is to 90°F. Allow air- NOTE
craft temperature to stabilize for a period of
4 hours- To facilitate assembly of preselect lever (19)
and cam (14), mark position of assemblies
11. (See figure 8-2) Lower flaps to 45 degrees and before loosening nut (15).
adjust down limit switch (21) to actuate and stop flap
travel at this point. Safety turnbuckles.
b. Assemble flap preselect lever assembly by re-
NOTE versing disassembly procedure.

On aircraft 421A0001 and On, adjust limit Installation of Flap Preselect Lever Assembly. (See
switches and cable tension in accordance figure 8-3.) 421A0001 and ON
with Flap Preselect Rigging Procedures.
a. Place flap preselect lever assembly into position
i. If used, disconnect the switch and outside power in bracket assembly (2).
source which were wired into the flap circuit. b. Install bolt (11) to nutplate (3).
j. Replace access hole covers. c. Align holes in rod end (10) and arm assembly (5),
k. Install rear carpet in accordance with Section 3. install screw (8) and secure with nut (11).
1. Install rear seat in accordance with Section 3. d. Install knob (20) on lever assembly (19) and se-
cure with set screw (21).
Operational Flight Check.

The operational flight check of the flaps consists of

flying the aircraft at 165 MPH CAS and operating the
flaps down, noting the extension time. The flaps
should extend in 10 to 14 seconds. Operate the flaps Removal of Flap Preselect Control Cable. (See
up and note the retraction time. The flaps should figure 8-3.) 421A0001 and ON
retract in 6 to 10 seconds.
a. Remove pilot's, copilot's and forward passenger
NOTE
seats in accordance with Section 3.
If the flaps will not extend or retract within b. Remove center carpets and floorboard in accor-
the correct time, it will be necessary to re- dance with Section 3 to gain access to flap preselect
place the flap motor. control cable,
c. Loosen nut (11) and remove screw (8).
Removal of Flap Preselect Lever Assembly. (See d. Loosen nut (30) and remove bolt (32) and
figure 8-3.) 421A0001 and ON clamp (31) from flap cable (25) and control cable (9).
e. Remove clamps securing control cable (9) to
a. Loosen set screw (21) and remove knob (20) from bulkheads.
lever assembly (19). f. Remove control cable (9) from aircraft,
b. Loosen nut (11) and remove screw (8) from rod
end (10).
c. Remove bolt (1) from nutplate (3). Installation of Flap Preselect Control Cable. (See
d. Remove flap preselect lever assembly from figure 8-3. ) 421A0001 and ON
bracket assembly (2).
Change 9
$" FLAP CONTROL SYSTEM 421 SERVICE MANUAL

a. Install flap preselect control cable by reversing (DOWN) position.

30° ±0°
removal procedure and rig in accordance with rig- p. Operate flap motor until flaps are in the
ging procedure. (DOWN) position.
q. Check preselect limit switches (12) for proper
Rigging Flap Preselect System. (See figure 8-3.) adjustment, to ensure limit switches are de-ener-
30°
421A0001 and On gized when the flaps reach the (DOWN) position.

a. Remove passenger seats and center carpets in NOTE

accordance with Section 3 to gain access to the
right-hand When the preselect lever assembly is placed
forward floorboard. 30°
in the (DOWN) position, the flap angular
b. Remove right-hand floorboard.
c. Loosen nut (30) and remove
travel must be 30 o ±2 o .

bolt (32) from

clamp (31).
r. Match pointer are with indicator block (35) and
d. Remove clamp (31) from flap cable (25) and
guard block (36) by adjusting blocks vertically.
control cable (9).
(Slotted holes provided.)
e. Connect a 24 volt external power source.
s. On aircraft 421A0001 to 421BO469, adjust flap
NOTE handle stop bolts (33) so that switch rollers are still
0° 45°
on cam (14) when and flap motor limit switches
To facilitate rigging of the flap preselect
-

are actuated. This will take 12 inch to 16 inch

system, a two position momentary
. .

switch

If.
handle travel measured at the intersection of the panel
with suitable lengths of electrical wires
slot.
can be connected to the flap actuator limit 421B0469 and On, adjust flap pre-
switches in such a manner that the flaps
t. On aírcraft
0°
lever up stop (33) to hmit flap setting with
. .

dur- select
can be observed while being operated
225 ±25 pounds return cable tension,
ing rigging.
u. Adjust flap preselect lever down stop to limît
45° +1°
f1a travel to
-0°

On aircraft 421A0001 to 421B0469, adjust flap ' '

0° v. Check flap surface travel tolerances at the fol-
motor lunit switches to provide
. .

(UP) position and 15° ±0° 30° ±2° DOWN; 45°,

lowing locations: DOWN;
45 +1 position flap travel in accordance
-0

with +1° 15° +0°

, ,
from DOWN to UP.
-2°

DOWN; ' '

-0°

the adjusting procedures.

g. On aircraft 421B0469 and On, adjust flap motor
w. Disconnect the 24 volt external power source
limit switches to provide 0° (UP) with cable tension from flap motor wiring.
of 280 ±20 pounds and
46°
(DOWN) with cable ten-
x. Perform operational check out of flap and pre-
sion of 85 ±10 pounds. select system, using the aircraft power system, to
ensure that proper operation of limit switches, pre-
h. Operate flaps full down and retract control cable
(9) to full in position at aft end. select switches and flap angular movements are
within specified tolerances.
. .

i. Move control cable (9) out 10 inch and install

y. Install right-hand
.

floorboard.
clamp (31) to flap cable (25) with bolt (32) and secure
z. Install center carpets and center seats in accord-
with nut (30). Clamping block to be located 50 ±25 .

ance with Section 3.

inch from edge of flap pulley (26). Use conduit and/
or cable end thread adjustment to attain 50 inch di- .
Adjustment of Flap-Gear Warning System. (421B0201
mension. Operate flaps to full up position. and On)
j. Adjust limit switch (12) rollers snug against cam
(14) at the flap preselect control. Refer to Adjustment of Landing Gear Warning System
k. Adjust tension on flap control bolt (1) to prevent Section 4.
flap preselect lever (19) from moving when limit
switch roller falls off cam (14).
1. Attach rod end (10) to preselect arm (5) and ad-
just rod end (10) and/or cable housing to locate pre-
select arm (5) to the dimension shown in figure 8-4.
15°
m. Move flap preselect lever (19) to position
detent. Loosen adjustment screw (17) between the
flap preselect lever (19) and pivot bellerank (24).
Measure flap control surface and move cam (14)
as required to provide a flap surface position of 15° /
±0°.
Tighten adjustment screw (17) at flap preselect Q(
lever (19) and pivot bellerank (24). \ \
y
NOTE J '\
When the preselect lever /
' ¯ .2O
assembly is placed r
15° '
in the (DOWN) position, the flap angular
travel must be 15° ±0°. +,

15°
n. Adjust pointer (34) to center on mark on
indicator block (35) by bending wire.
30° 8-4.
o. Place preselect lever assembly (19) in the Figure Flap Preselect Dimension Requirement

Change 9
 421 SERVICE MANUAL ENGINE Û"1

SECTION 9

ENGINE

Table of Contents

Page Page

GENERAL INFORMATION . . . .
9-2 FUEL INJECTION PUMP . . . .
9-32
Detail Engine Specifications . . .
9-2
TROUBLESHOOTING THE ENGINE . .
9-3 Removal . . . . . .
9-32
ENGINE COWLING . . . . . .
9-8B Installation . . . . . .
9-32
Removal . . . . . . .
9-8B Fuel Mixture Check . . . . .
9-33
Installation . . . . . .
9-8C Unmetered Fuel Test Hook-up Check
COWL FLAPS . . . . . . .
9-8C and Adjustment . . . . .
9-33
Removal . . . . . .
9-8C ENGINE IGNITION SYSTEM . . . .
9-34
Installation . . . . . . .
9-8C Troubleshooting . . . . . .
9-34
Rigging the Cowl Flap . . . .
9-8C MAGNETOS . . . . . .
9-34A
ENGINE . . . . . . .
9-10 Removal . . . . . .
9-35
Engine Removal . . . . . .
9-10 Inspection . . . . . .
9-35
Disassembly and Assembly . . .
9-11 Internal Timing . . . . . .
9-35
Inspection of Engine . . . . .
9-14 Installation and Timing . . . .
9-36
Installation of Engine . . . .
9-14 IGNITION CABLES . . . . . .
9-38
Installation Inspection . . . .
9-14A Removal . . . . ,
9-38
Rough Engine Operation Inspection . .
9-14A Installation . . . . . .
9-38
9-15 SPARK PLUGS 9-38B
Installation Inspection . . . . . .

9-38B
.

Engine Operational Check 9-15 ENGINE OIL SYSTEM . . . . .

9-16 Oil Pressure Adjustment 9-38B

ENGINE MOUNTS .
. . .

9-38B
Removal 9-16 Removal of Oil Pressure Lines .

9-40
.

9-16 Installation of Oil Pressure Lines

Shimming
. .

9-40
.

Installation 9-17 Troubleshooting . .

ENGINE EXHAUST SYSTEM . . . .

9-17
9-17 AIR INDUCTION SYSTEM 9-44
Removal . . . . . . .
- . . .

Slip Removal and Installation 9-44

Removal and Installation of Exhaust . . . .

9-18B Rigging of Alternate Air Canister

I Joint Seals
Installation
and Expansion
.
Ring
. . .
.

.
.

.
9-18B Control Door
WASTE-GATE ACTUATOR, CONTROLLERS,
. . . . .
.
9-44

9-19 AND TURBOCHARGER 9-44

ENGINE BAFFLES .
.
.
,

Removal 9-19 Turbocharger Control System Functions

. . . . .

Installation 9-19 and Operations . . . . .

9-44
. . . . .

ENGINE CONTROLS . . .
9-20A Troubleshooting . - . . . .
9-48
.

Removal and Installation . . . .

9-21 Turbocharger Insulation . . .
.
9-48B
Throttle Control Installation . . .
9-21 Removal · · -
. . .
.
9-48B
Rigging Mixture and Throttle Controls .
9-21 Installation . . . . . .
9-48B
9-24 Checking Turbine Shaft Drag 9-48B
Rigging Procedures Chart . . .
. . .

Removal, Installation and Rigging of

Removal of Turbocharger .
. ,
9-49
9-27 Installation of Turbocharger 9-49
Propeller Controls . . . .
. . .

9-27 Removal and Installation of Rate of

ENGINE CONTROL QUADRANT . . .

9-27 Change Controller 9-49

Removal . .
. .
. ,

9-49
. . . .

9-27 Rate of Change Controller Adjustment

Disassembly . . . . .
.

9-27 Removal and Installation of Variable

Assembly . . . . .

Absolute Pressure
.

9-27 Controller 9-51

Installation . . . . .
. ,

Variable Absolute Pressure

.

FUEL INJECTION SYSTEM . . . .

9-27 Controller
9-28 Adjustment 9-51
Troubleshooting . . . . . .

Waste-Gate
. . . . . .

9-29 and Actuator 9-52

FUEL AIR CONTROL UNIT . . . .
. . . .

9-29 Removal 9-52

Removal . . . . . .
- . . . . .

9-29 Installation 9-52

Installation . . . . . .

of Waste-Gate
. . . . . . .

9-30 Adjustment
Adjustment of . . . . .
.

9-30 and Actuator 9-54

FUEL MANIFOLD . . . . . .
. . . . .

Removal . . . . .
9-30 Turbocharger Operational Flight
9-32 Check Procedure 9-54
Installation . . . . .
. . . . .

9-54
. .

9-32 MANIFOLD PRESSURE RELIEF VALVE

FUEL DISCHARGE NOZZLES . . .
.

9-32 Removal and Installation of Manifold

Removal . . . . . . .

9-32 Pressure Relief Valve 9-54

Installation . . . . . . .
. . .

Change 8
9-2 ENSINE 421 SERVICE MANUAL

GENERA L INFORMATION. and various adapters, clamps and brackets for

mounting these items on the engine. Each engine
drives an all-metal, three-bladed, constant-speed
Two Continental GTSIO-520D (421-0001 to 421B0001) full-feathering propeller. In addition to the propel-
or GTSIO-520H (421B0001 and ON) engines are ler and the above mentioned engine accessories, the
mounted on the aircraft. The engine is geared, tur- complete engine assembly consists of the following
bocharged, six-cylinder, fuel injected, horizontally Cessna installed items: propeller governor, engine
opposed and developes 375 horsepower at 2275 pro- baffles, induction air filter, vacuum pump, oil filter,
peller RPM. Installed on each engine are two mag- turbocharger with pressurization bleed off, control-
netos, twelve spark plugs, ignition harness and wir- 1ers, waste-gate actuator, alternators, exhaust
ing, primer distribution lines and fittings, engine- stack assemblies, cylinder head temperature bulb,
driven fuel pump, low pressure, multi-nozzle, con- oil temperature bulb, cowl flap assembly, erankcase
tinuous flow fuel injection system, pressure type in- breather line and various other lines, hoses, fittings
take manifold piping, integral oil pump and external- and brackets necessary for the proper assembly and
ly mounted oil cooler, intake air intercooler, starter operation of the engine.

Detail Engine Specifications.

Model (421-0001 to 421B0001) . . . . . . . . . . . .

GTSIO-520D
(421B0001 and On) . . . . . . . . . . . . . .
GTSIO-520H

Propeller Drive Ratio . . . . . . . . . . . . . . . . 667:1

Propeller Shaft Rotation (Looking Forward) . . . . . . . . . . .

Clockwise*

Propeller Attachment (Flange) . . . . . . . . . . . . . APR 502 Type I

Bore, Inches . . . . . . . . . . . . . . . . . . 5.250

Stroke,Inches........... ......4.000

Displacement, Cubic Inches . . . . . . . . . . . . . . . 520

CompressionRatio.................7.5:1

Turbosupercharged (Maximum RPM) . . . . . . . . . . . . . 75, 000

OilSAENumberAbove40°F..............
SAE#50
Below 40°F . . . . . . . . . 10W30 Multi-Viscosity or SAE #30

Oil Sump Capacity . . . . . . . . . . . . . . . . . 13 Qts.

Fuel, Aviation Grade, Octane (Minimum) (Low Lead Fuels are approved for use) . . 100/130

Fuel System . . . . . . . . . . . . . . Continental Fuel Injection

Fuel Injector . . . . . . . . . . . . . Continental Fuel Injection

Magneto Drive, Ratio to Crankshaft . . . . . . . . . . . . . 1. 5:1

Magnetos (1) Bendix S6LN-1201 (Left Magneto on LH and RH Engines) . . . . .

Clockwise*
(1) Bendix S6LN-1205 (Right Magneto on LH and RH Engines) . . . .
Clockwise*

Tachometer Drive, Ratio to Crankshaft . . . . . . . . . . . . .

. 5:1
Rotation . . . . . . . . . . . . , ,
Clockwise*

*Direction of rotation facing engine drive pad.

Change 8
 421 SERVICE MANUAL ENGINE S-3

Detail Engine Specifications (Cont.)

Starter Drive, Ratio to Crankshaft . . . . . . . . . . . . 32:1

Rotation . . . . . . . . . . . . .
Counterclockwise*

Alternator Drive, Ratio to Crankshaft . . . . . . . . 3:1

Rotation . . . . . . . . . . . .
Counterclockwise*

Vacuum Pump Drive, Ratio to Crankshaft . . . . . . . . . . 1. 14: 1

Rotation . . . . . . . . . . . .
Counterclockwise*

Vacuum Pump Drive, (Deice) . . . . . . . . . . . . . 1. 14: 1

Rotation . . . . . . . . . . .
Counterclockwise*

Vacuum Pump Drive, (Autopilot) . . . . . . . . . . . . 1. 14: 1

Rotation . . . . . . . . . . .
Counterclockwise*

Propener Governor Drive, Ratio to Crankshaft . . . . . . . . . . 809:1

Rotation . . . . . . . . . . .
Clockwise*

Spark Plug Type, AC . . . . . . . . . . . . . . .

AC 273
20°
Breaker Point Setting (Both Magnetos) . . . . . . . . .
BTC

Spark Plug Gap . . . . . . . . . . . . . . . .

0.017-0.018

Firing Order . . . . . . . . . . . . . . . .
1-4-5-2-3-6

Fuel Pressure (Lbs. Unmetered @ 450 Propeller RPM

Per Sq. Inch) . . . . 6.0 PSI
Auxiliary Pump Resistor @ 450 Propeller RPM . 5.5 ±.25 PSI
Maximum Metered Fuel Pressure @39. 5" Hg MP & 2275 Propeller RPM 16.0 -
17.0 PSI
Metered Fuel Pressure Shown Here is Referenced to Compressor Discharge Pressure
Minimum Auxiliary Pump Pressure Switch @450 Propeller RPM 4.0 ±.25 PSI
Oil Pressure (Lbs. Per Sq. Inch)
Normal ................ 30to60
Maximum ............... 100
Idling (Minimum) . . . . . . . . . . . . . . 10
(°F)
Oil Temperature
170°
Normal ................

240°
Maximum ...............

(°F)
Cylinder Head Temperature
460°
Maximum ...............

200°
Minimum (Takeoff) . . . . . . . . . . . . .

Standard Engine Dry Weight (Lbs.) . . . . . . . . . . . 550.39

* Direction of rotation facing engine drive pad.

Change 4
9-4 ENGINE 421 SERVICE MANUAL

Troubleshooting the Engine.

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE WILL NOT START Fuel tank empty. Fill with correct grade of fuel.

Improper starting procedure. Refer to Pilot's Checklist for

starting procedure and check
for performance of each item.

Cylinder overprimed. With auxiliary fuel pump switch

OFF, allow manifold to drain
at least 5 minutes or until fuel
ceases to flow out of the drain
under the nacelle.

If circumstances do not allow

natural draining periods re-
commended above, with the
auxiliary pump switch OFF,
magneto switches OFF, mix-
ture idle cut-off and throttle
full open, turn engine with
starter and/or by unfeather-
ing for a minimum of 15
revolutions.

CAUTION

If the primer switch is activated for excessive periods of time

with the engine inoperative on the ground or during flight, dam-
age may be incurred to the engine and/or aircraft due to fuel
accumulation in the induction system. Similar conditions may
develop when the engine is shutdown with the auxiliary pump
switch in the ON position.

ENGINE WILL NOT START Manifold valve sticking closed. Repair or replace manifold
(CONT.) valve.

Induction system leak. Tighten or replace loose or

damaged hose connections.

Excessive starter slippage. Replace starter adapter.

Fuel system malfunction. Isolate cause and correct.

(See Engine Maintenance and
Overhaul Manual.)

Ignition system malfunction. Isolate cause and correct.

(See Engine Maintenance and
Overhaul Manual.)

Intercooler and risers system Tighten or replace clamps or

leak. faulty hose connections.

Change 8
 421 SERVICE MANUAL ENGINE 9--4A -48

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE WILL NOT RUN AT Propeller levers set in high pitch Use low pitch (INCREASE
AT IDLING SPEED (DECREASE RPM) position. RPM) position for all ground
operations.

Fuel injection system improperly See Section 11.

adjusted.

Air leak in intake manifold. Tighten loose connection or -

replace damaged part.

Spark plugs fouled by oil escaping Top overhaul.

past piston rings,

Intercooler and risers system Tighten or replace clamps or

leak. faulty hose connections.

ROUGH IDLING Fuel injection system improperly See Section 11.

adjusted.

[) Mixture levers set for lean mix- Use FULL RICH position for
ture. all ground operation.

Fouled spark plugs. Remove and clean. Adjust

gaps.

Discharge nozzle air vent mani- Set fuel control in FULL RICH
fold restricted or defective, position, turn auxiliary pump
ON, check to be sure feed
lines and filters are not re-
stricted. Clean or replace
defective components.

Hydraulic lifters fouled. Remove and clean lifters. In-

spect and clean oil filter at
more frequent intervals.

Burned or warped exhaustvalves, Top overhaul.

worn seats, scored valve guides.

ENGINE RUNS TOO LEAN AT Improper manualleaning proce- Operate in FULL RICH position
CRUISING POWER dure. below 5000 feet. Above 5000
feet retard mixture levers un-
til a slight drop in RPM is
noted, then advance levers ap-
proximately one inch toward
FULL RICH position.

Turbine pressurization air leak at Tighten or replace faulty

controlling venturi inlet coupling or components.
at variable absolute pressure con-
troller mounting flange.
Turbocompressor discharge air Tighten or replace faulty
leak at throttle body coupling. components.

Fuel injection malfunction, See Fuel Injection System.

Change 8
 421 SERVICE MANUAL ENGINE 9-5

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE RUNS TOO RICH Fuel flow too low. Check fuel strainer for clogging.
A T CRUISING POWER Clean screen.

Restrictions in air intake passages. Check passages and remove restric-

tions.
Intercooler or induction system Tighten or replace clamps or faulty
leak. hose connections.

ENGINE RUNS TOO LEAN Fuel injection malfunction. See Fuel Injection System.
OR TOO RICH AT
THROTTLE SETTINGS
OTHER THAN CRUISE

CONTINUOUS FOULING Piston rings excessively worn or Replace rings. Replace cylinder if
SPARK PLUGS broken. damaged.

Oil leakage from turbocharger Check turbocharger oil drain lines,

into intake system. separator and scavenger oil pump.
If positive identification is made of
this type of malfunction, it is im-
portant to thoroughly clean the pres-
surization air ducts, intercooler
and heater system.

Piston rings inverted or not seated. Install with side marked TOP toward
piston head. Allow approximately 25
hours for new rings to wear in.

Cold cylinder operation. Check cylinder baffles.

ENGINE RUNS ROUGH AT Loose mounting bolts or damaged Tighten mounting bolts. Replace
HIGH SPEED mount pads. mount pads.

Plugged nozzle. Clean.

Propeller out of balance. Remove and repair.

Ignition system malfunction. See Ignition Trouble Shooting Chart.

CAUTION
After rough engine operation, inspect in accordance with Rough or Malfunctioning
Engine Operation Inspection.

REGULAR MISSING AT Broken valve spring. Replace.

HIGH SPEED
Plugged nozzle. Clean.

Spark plugs fouled. Clean or replace.

Burned or warped valve. Top overhaul.

Hydraulic tappet dirty or worn. Remove and clean or replace.

SLUGGISH OPERATION Throttle not opening wide. Check and adjust linkage.
AND LOW POWER
Exhaust system leakage. Locate and correct.

Restriction in air intake passages. Check passages; remove retrictions.

Turbocharger wheels rubbing. Replace turbocharger.

Ignition system malfunction. See Ignition Trouble Shooting Chart.

Change 11
 421 SERVICE MANUAL
¯$

ENSINE

TROUBLE PROBABLE CAUSE CORRECTION

SLUGGISH OPERATION Fuel injection malfunction. See Fuel Injection System.

AND LOW POWER
(CONT.) Valve seats worn and leaking. Top overhaul.
Piston rings worn or stuck in
grooves.

Bypass valve stuck open or control- Repair or replace faulty components.

lers and actuators inoperative.

Variable absolute pressure control- Adjust low pressure setting of vari-

ler low setting improperly adjusted. able absolute pressure controller.

HIGH CYLINDER HEAD Low octane fuel. Drain tanks and replace with correct
TEMPERATURE grade of fuel.

Lean fuel/air mixture due to im- See CORRECTION under Engine Runs
proper manual leaning procedure. too Lean at Cruising Power.

Dirt between cylinder fins. Clean thoroughly.

Excessive carbon deposits in cyl- Top overhaul.

inder head and on pistons.

Exhaust system gas leakage. Locate and adjust.

Exhaust valves leaking. Top overhaul.

Improper magneto timing. See installation and timing of magne-

tos.
Improper seating of bypass valve in Repair or replace valve or actuator
closed position. system.

OIL LEAKS At front of engine; damaged crank- Replace.

shaft oil seal.

At top of engine; discontinuity on Repair or replace lines or hose

erankcase breather system. connections.

Around push-rod housings; damaged Replace.

push-rod housing packing.

At aft engine compartment: exhaust Tighten or replace faulty seals, lines

valve controllers or actuators. or fittings.

Around propeller mounting flange; Replace.

damaged hub O-ring seal.

Around plugs, fittings and gaskets Tighten or replace,

due to looseness or damage.

oil temper-
I EXCESSIVE OIL DIS-
Around oil temperature

Faulty vacuum
bulb.

pumps or breather
Remove crush
ature and install
Repair
washer

or replace
from
MS28774-4 packing.
faulty components.
CHARGE OVERBOARD oil separators: restricted oil re-
turn line.

Crankcase breather line; stuck rings High power engine operation to clear
due to prolonged operation at low rings with close monitoring of cylin-
power. der temperatures.

LOW COMPRESSION Piston rings excessively worn. Top overhaul.

Valve faces and seats worn.

Change 11
 421 SERVICE MANUAL ENGINE $-7

TROUBLE PROBABLE CAUSE CORRECTION

LOW COMPRESSION Excessively worn cylinder walls. Replace cylinders and piston rings.
(CONT. )

ENGINE WILL NOT AC- Unmetered fuel pressure too high. See Unmetered Fuel Pressure Adjust-
CELERATE PROPERLY ment.

Waste-gate does not close properly. Replace waste-gate and actuator.

Manifold pressure relief valve Replace manifold pressure relief

sluggish or stuck open. valve.

Leak in turbocharger discharge Inspect turbocharger installation.

pressure system. (See Note.)

NOTE

Leak in turbocharger discharge system is characterized by

the engine leaning out at idle, but when acceleration is at-
tempted, it will not accelerate because of an over-rich mix-
ture. However, when the mixture control is leaned the max-
imum RPM will be low and the engine will be very rough.

Variable absolute pressure control- Adjust cam on variable controller as

ler improperly adjusted, to advance point of contact with valve
plunger.

Premature opening of waste-gate: Check and clear all lines: desensi-

hydraulic system obstruction or tize rate controller up to the over-
oversensitive rate controller adjust- boost limits under rapid accelera-
ment. tion.
SLOW ENGINE ACCEL- Mixture too rich. Momentarily pull mixture control
ERATION ON A HOT DAY back until engine acceleration picks
up, then move mixture control to full
forward again.

ROUGH IDLE AT AIR- Mixture too rich. Pull mixture control back to where
FIELDS WITH GROUND the engine operates the smoothest
ELEVATION OF 3500 at IDLE RPM.
FEET OR HIGHER

SLOW ENGINE ACCEL- Mixture too rich. Pull mixture control back to where
ERATION AT AIR- engine operates at IDLE RPM. En-
FIELDS WITH A GROUND gine should accelerate normally.
ELEVATION OF 3500
FEET OR HIGHER

MANIFOLD PRESSURE Engine acceleration too rapid from Open throttles about half-way. Let
OVERSHOOT ON ENGINE idle to full power, engines accelerate to 30" Hg. and
ACCELERATION peak. Move throttles to full open
position.

Manifold pressure relief valve Replace manifold pressure relief

stuck closed. valve.

Rate controller improperly adjusted. Adjust rate controller.

ERRATIC ENGINE OPER- Loose or failed compressor dis- Tighten or replace coupling. Re-rig-
A TION, WITH UNAS- charge to throttle body coupling, ging of throttle and mixture may be
SISTED POWER CHANGES affecting throttle and mixture con- necessary.
trol lever positions.
Û¯$ ENSINE 421 SERVICE MANUAL

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE MANIFOLD Variable absolute pressure con- Adjust variable pressure controller.
PRESSURE TOO HIGH troller improperly adjusted.

Manifold pressure relief valve Replace manifold pressure relief

stuck closed. valve.

LOW CRITICAL ALTI- Induction, pressurization air, Conduct air leak check and tighten
TUDES AT CORRES- and/or exhaust systems leaking. or replace faulty components.
PONDING ENGINE POWER

ENGINE DOES NOT DE- Variable absolute pressure control- Adjust high pressure setting on vari-
VELOP MAXIMUM POWER ler high setting improperly adjusted, able absolute pressure controller,

Loose or failed compressor dis- Tighten or replace coupling.

charge to throttle body coupling.

ENGINE WILL NOT STOP Fuel manifold valve not seating Repair or replace manifold valve.
AT IDLE CUT-OFF tightly.
ENGINE WILL NOT START Fuel manifold valve sticking closed. Repair or replace manifold valve.

HIGH FUEL PRESSURE Fuel manifold valve sticking closed. Repair or replace manifold valve.
AT ENGINE IDLE IM-
POSSIBLE TO OBTAIN

ERRATIC ENGINE Fuel manifold valve sticking part- Repair or replace manifold valve.
OPERATION way, or not free,

MANIFOLD PRESSURE Ram air pressure changes with air- Normal turbocharged engines charac-
VARIES WITH AIRSPEED. speed while RPM remains constant. teristics.
INCREASE WHEN AIR-
SPEED INCREASED,
DECREASE WHEN AIR-
SPEED DECREASED

NOTE

The left engine manifold pressure will normally increase or

decrease more than right engine because of location of left
engine air intake duct.

MANIFOLD PRESSURE Waste-gate OPEN, RPM increase, Normal turbocharged engines charac-
VARIES WITH ENGINE manifold pressure slight decrease. teristics.
RPM RPM decrease, manifold pressure
slight increase.

Waste-gate CLOSED, RPM in- Normal turbocharged engines charac-

crease, manifold pressure slight teristics.
increase. RPM decrease, manifold
pressure slight decrease.

MANIFOLD PRESSURE Waste-gate CLOSED, fuel flow in- Normal turbocharged engines charac-
VARIES WITH INCREAS- creased, turbine turns faster more teristics.
ING OR DECREASING induction air furnished engine re-
. FUEL FLOW sulting in manifold pressure increase,

I
 421 SERVICE MANUAL ENGINE 9-8A

TROUBLE PROBABLE CAUSE CORRECTION

INDICATED FUEL FLOW Compressor discharge air pres- Flush and clear lines. Rework air refer-
HESITATES OR LAGS sure line to fuel flow gage ob- ence pressure lines in conformance with
OVER THREE SECONDS structed with oil. provisions defined on SK421-6.
AFTER THROTTLE IS
ADVANCED TO FULL
OPEN POSITION

FUEL FLOW FLUCTU- Low pressure output from aux- Reset low boost adjustment in conform-
ATES WITHIN A RANGE iliary pump. ance with the adjustment procedures
OF ± 1. O GALLONS/HR. defined in Section 11. Adjustment must
IN FLIGHT WITH ENGINE be performed with the opposite engine
OPERATING ON MAIN operating at 1000 rpm to insure correct
TANK, AND WITH AUX- electrical power supply.
ILIARY PUMP SWITCH IN
THE LOW POSITION

FUEL FLOW FLUCTU- Defective fuel pressure switch. To isolate malfunction reset auxiliary
ATES OVER A RANGE OF pump switch to LOW position. If fuel
± 3. O GALLONS/HR. IN flow fluctuations are arrested, replace
FLIGHT WITH ENGINE fuel pressure switch installed on unmet-
OPERATING ON MAIN ered fuel line to metering unit.
TANK AND WITH AUX-
ILIARY PUMP SWITCH
IN THE ON POSITION

FUEL FLOW FLUCTU- Very low pressure output from To isolate malfunction alternatively
ATIONS EXCEEDING A auxiliary pump or complete activate and deactivate auxiliary pump
RANGE OF ± 1. O GAL- auxiliary pump failure, for not less than 40 seconds in each mode
LONS/HR. IN FLIGHT and observe fuel flow changes:
WITH ENGINE OPERAT-
ING ON MAIN TANK, 1. If fluctuations decrease with auxiliary
AND WITH AUXILIARY pump "ON", the auxiliary pump
PUMP SWITCH IN THE requires readjustment in conformance
LOW POSITION, with the adjustment procedures de-
fined in Section 11. Adjustment must
be performed with the opposite eng-
ine operating at 100 rpm to insure
correct electrical power supply.

2. In the event that no change is detected

in fuel flow fluctuations with or with-
out auxiliary pump "ON", the auxili-
ary pump and/or the associated
electrical system is malfunctioning.
Refer to Section 11.

FUEL FLOW FLUCTU- Auxiliary tank pump failure. To isolate malfunction alternatively move
ATIONS EXCEEDING O ±3. the auxiliary pump switch from "OFF" to
GALLONS/HR. OR POWER "LOW" for not less than 40 seconds in
LOSS IN FLIGHT WITH each mode and observe fuel flow changes.
ENGINE OPERATING ON
AUXILIARY TANKS, AND If no change takes place, select main
WITH AUXILIARY PUMP tank with auxiliary pump switch in "LOW".
SWITCH IN THE "LOW" In the event that power is regained or
POSITION fluctuations are eliminated by this opera-
tions, the auxiliary tank in-line pump
must be replaced.
$•Û ENGINE 421 SERVICE MANUAL

TROUBLE PROBABLE CAUSE CORRECTION

EXCESSIVE FUEL FLOW Pressure relief provisions on To verify malfunction observe mixture
INDICATION AND/OR CIR- auxiliary tank pump out of control positions between both engines at
CUIT BREAKER OPENS calibration. comparable power settings and fuel flows.
WITH ENGINE OPERATING If severe lean out is required on the affec-
FROM AUXILIARY TANK ted engine when auxiliary tanks are sel-
WITH PUMP SWITCH ON ected with pump switch on "LOW", the
"LOW" auxiliary tank in-line pump must be re-
placed. Refer to SK421-14.

ENGINE FAILS AFTER Auxiliary pump failure or in- Replace pump or adjust low boost pressure
LANDING AND/OR correct boost pressure output. in conformance with adjustment proce-
TAXIING WITH AUXILI- dures defined in Section 11. Adjustment
ARY PUMP ON "ON" must be performed with the opposite
engine operating at 1000 rpm in insure
correct electrical power supply.

SEVERE FUEL FLOW Inherent fuel injection system Adjust engíne driven fuel injection pump
CALIBRATION CHANGES characteristics. to obtain fuel flows within the prescribed
AT MAXIMUM POWER gage white arc during take-off, under the
AND FULL RICH COND- average operating ambient conditions.
ITIONS, DURING OPERA- The following procedure is suggested in
TION FROM HIGH order to facilitate pump high pressure
ALTITUDE FIELDS OR adjustment during ground static maximum
HIGH AMBIENT power run-ups.
TEMPERATURES
1. For operation from field altitudes
below 2000 feet and ambient tempera-
tures below 60°F, adjust ground
static maximum power fuel flow to
40-42 gals/hour.

2. For operation from field altitudes

above 2000 ft. , reduce an additional
1 gal/hour for each 1000 ft.

3. For operation at ambient tempera-

tures above 60°F, reduce an addit-
10°F.
ional l gal/hour for each

ENGINE COWLING. (See figure 9-1.) a. Release cowl door fasteners to open cowl doors
(2 and 7).
Removal of Engine Cowling. b. Release upper cowl section fasteners and remove
upper cowl section (1),
NOTE c. Remove screws on cowl doors (2 and 7) and re-
This procedure is the same for either engine.
 421 SERVICE MANUAL ENSINE 9-80/9-80

move doors, d. To remove cowl flap (8) remove pin (7) from
d. Remove nose cowl by removing the screws in the cowl flap hinge (6).
lower nose cowl (5) and then removing screws (4) e. To remove actuator (3), disconnect the electri-
that attach upper nose cowl (6) and lower nose cowl cal leads and remove cotter pin, washer and pin.
(5) together, f. To remove torque tube (2), remove nuts and
e. Remove clamp from cooling air duct. screws from bearing block (1), and disconnect the
cowl flap transmitter arm.

Installation of Engine Cowling. (See figure 9-1.)

Installation of Cowl Flap and Actuator. (See figure
NOTE 9-2.)

This procedure is the same for either engine. a. Reverse the cowl flap and actuator removal pro-
cedure.
a. Install the upper and lower nose cowl (5 and 6) b. Rig the cowl flap and actuator assembly in ac-
together and to nacelle structure using screws (4). cordance with the rigging procedure.
b. Install the upper cowl section (1) in place and
fasten to nose cowl (6) and nacelle structure,
c. Install doors (2 and 7) with screws and fasteners. Rigging the Cowl Flap. (See figure 9-2.)

a. Extend cowl flap to the full DOWN position.

COWL FLAPS. (421-0001 to 421B0001) b. Attach an inclineometer to cowl flap and check
for 40 degrees down travel.
Removal of Cowl Flap and Actuator. (See figure 9-2.) c. If adjustment is necessary, proceed as follows:
1. Remove pins, washers, and cotter pins attach-
a. Release cowl doors (2 and 7) fasteners and open ing push-pull rods (5) to torque tube (2).
doors. (See figure 9-1.) 2. Lengthen or shorten push-pull rods as necessary,
b. Turn battery switch ON and open cowl flap (Full 3. Install pins, washers and cotter pins attaching
Open). Turn battery switch OFF. push-pull rods (5) to torque tube (2),
c. Remove cotter pins, washers, and pins attaching d. Remove inclineometer and actuate cowl flaps to
adjustable push-rods (5) to cowl flaps (8). full UP position.
 421 SERVICE MANUAL ENetNE $"$

4
421-0001 TO 421B0001

421B0001 AND ON

1. Upper Cowl Section 4. Screw 6. Upper Nose Cowl

2. Left Cowl Door 5. Lower Nose Cowl 7. Right Cowl Door
3. Cowl Flap Assembly 8. Cooling Scoop

Figure 9-1. Engine Cowling

Change 6
 9-lÛ ENGINE 421 SERVICE MANUAL

ENGINE. NOTE

Engine Removal. (See figure 9-3.) Plug or cap all disconnected lines and hoses.

The removal procedure is the same for either en- a. Turn all cockpit switches and the fuel selector
gine. Although the routing of wire bundles, cables, valves OFF.
lines, hoses and conduit varies between engines, the b. Open the battery circuit by disconnecting the
following description will be typical for either engine, ground cable.
Identify each item as it is disconnected to aid in re- c. Remove engine cowling (29, 30, 31 and 33). (See
installation. Cover the open ends of all lines and figure 1-2.)
hoses to prevent entry of foreign materials. d. Disconnect magneto ground wires at the magnetos
(21) alternator cables at the alternator (20), and with-
NOTE draw wire bundle aft through the rear engine baffle (5).
e. If installed, disconnect connector and ground wire
,
If engine being removed is tobe placed in to optional propeller de-ice.
storage, proper preparatory steps should f. Drain the oil in accordance with Section 2. Re-
be taken prior to beginning the removal place the drain plug.
procedure. g. Remove the propeller in accordance with Section 10.

4°
oc
o °
421-0001 TO 42180001 4

Detail
421A0001 o
TO 421BOOO1 o

1. Bearing Block 4. Structure Attachment 7. Hinge Pin

2. Torque Tube 5. Adjustable Push-rod 8. Cowl Flap
3. Actuator 6. Hinge 9. Brace

Figure 9-2. Cowl Flap Control System

 421 SERVICE MANUAL ENGINE S-ll

h. Disconnect the propeller control (18) at the NOTE

governor (19) by removing nut, washer and bolt.
Remove the propeller control bracket (16) from If the aircraft has the optional propeller un-
the engine sump by removing the two bolts and feathering system installed, check the ac-
washers, cumulator for pressure and disconnect hose
i. Disconnect wires and cables as follows: at the governor after all pressure has been
1. Disconnect starter cable at starter. released. (Refer to Section 10 for unfeather-
2. Disconnect electrical connector at tachometer. ing procedures.)
3. Disconnect oil temperature electrical connector
(12) located directly below the oil cooler (13) and the 17. Disconnect cylinder head drain cross to over-
ground terminal, board outlet hoses (35) at the cross (36).
4. Disconnect the electrical leads from the cylinder 18. Remove hose and clamps which connect intake
head temperature bulb located on the lower side of air duct (6) to the throttle body (24).
No. 2 eylinder. k. Disconnect exhaust stack ball joints at forward
5. Remove all clamps attaching wires and cables end of exhaust stack bellows (11).
to the engine assembly. Locate wire to clear engine 1. Attach a hoist to the lifting eyes of the engine
for removal. crankcase. Lift the engine just enough to relieve the
6. Remove ground strap from oil sump bolt aft of weight from the engine mounts.
No. 5 cylinder.
j. Disconnect lines and hoses as follows: CAUTION
1. Disconnect oil separator overboard drain hose
from oil separator. Place a stand under the aircraft tailcone bum-
per before removing engine. The loss of en-
WARNING gine weight may allow the tail to drop.

Fuel and oil draining from lines and hoses is m. Remove the engine as follows: (See figure 9-4.)
a fire hazard. Prevent fuel and oil from col- 1. Remove engine mount bolt (11).
lecting in the engine nacelle. 2. Hoist engine out of the nacelle and clear of the
aircraft.
2. Disconnect vacuum pump to firewall hose from
vacuum pump. NOTE
NOTE
Determine location and number of spacers,
If surface deice system is installed, an ad- boots, and bolt lengths used on each forward
ditional oil separator exists and more hoses engine mount so that proper reinstallation
must be disconnected. may be attained.

CAUTION
3. Disconnect the fuel flow gage line (1) at the aft
side of engine rear baffle (5). Hoist engine slowly and make certain that all
4. Disconnect the controller to air injection mani- wires, lines and hoses have been disconnec-
fold hose (25) at the manifold. ted.
5. Disconnect the ram air tube (14) at the engine
rear baffle (5).
6. Disconnect the manifold pressure gage hose (3) Engine Disassembly and Assembly.
at the aft side of engine baffle (5).
7. Disconneet the controller oil return hose (7) a. The disassembly procedure is the same for
from the aft end of engine crankcase, either engine and is intended to cover only those
8. Disconnect the vapor return hose (29) from the items which could normally be expected to require
fuel pump. removal or are not covered by Continental Motor
9. Disconnect fuel bypass to fuel pump hose (30) at Corporation Engine Maintenance and Overhaul
the fuel pump. Manual.
10. Disconnect fuel pump to mixture control hose 1. Hoist engine assembly to a convenient working
(26) at the fuel pump. height.
11. Disconnect firewall to fuel pump hose (28) at 2. Spray engine assembly with suitable solvent to
the fuel pump, clean off any dirt accumulation and allow to drain.
12. Disconnect.oil filter to oil pump screen hose at Blow off residual dirt and solvent with compressed
the oil pump screen, air.
13. Disconnect turbocharger oil return hose (37) CAUTION
from scavenger oil pump.
14. Disconnect oil filter to oil cooler hose (10) at Particular care should be given to electrical
the oil cooler (13)• components and bearings before cleaning.
15. Disconnect fuel pump drain hose from fuel Solvents should not be allowed to enter mag-
pump· netos, starters, alternators, compressor
16. Disconnect oil pressure hose (39) and turbo- idler pulley bearings, and any lubricated con-
charger oil supply hose (38) at "tee" fitting. trol. These items must be protected with
Change 7
 ENSINE 421 SERVICE MANUAL

6 31 23 7 24

r 0

10

19 9

18 17 18 15 12 13 11 B
C 421-0001 TO 421A0001
4

32

21

2
14

20

22

421-0001 TO 421B0001

Figure 9-3. Engine Installation (Sheet 1 of 3)

 421 SERVICE MANUAL ENGINE $"1 A

4 6 31 23 24

10

19 9

> 3 9
A

52 21 3 5 1 22 14 43 45

48

50 ,:
47

20----

51

44
2

49

32 .
-
48

52
421BOOO1 AND ON

Figure 9-3. Engine Installation (Sheet 2)

Change 'l
9-12 8 EN6lNE 421 SERVICE MANUAL

40
27
37
29
25
Detail

35
39
Detail Detail B
1. Fuel Flow Gage Line 19. Governor 37. Turbocharger to Scavenger
2. Manifold Valve 20. Alternator Pump Line
3. Manifold Pressure Line 21. Magneto 38. Turbocharger Oil Supply Line
4. Intercooler 22. Oil Separator 39. Oil Pressure Line
5. Rear Engine Baffle 23. Air Injection Manifold 40. Fuel to Metering Unit Line
6. Intake Air Duct Hose 41. Cooling Duct
7. Oil Line (Controller to 24. Throttle Body 42. Air Inlet
Crankcase) 25. Fuel Manifold and Pump 43. Manifold Pressure Relief Valve
8. Rate of Change Controller Drain Line 44. Turbocharger (Turbine)
9. Oil Filter 26. Mixture Control to Fuel 45. Variable Absolute Pressure
10. Oil Line (Filter to Pump Hose Controller
Crankcase) 27. Fuel Pump 46. Air Canister
11. Exhaust Stack Bellows 28. Fue1Inlet 47. Fuel Pressure Regulator
12. Oil Temperature Connector 29. Vapor Return Line 48. Exhaust Pipe
13. Oil Cooler 30. Fuel Return 49. Waste-Gate Actuator
14. Ram Air Tube 31. Vacuum Pump Inlet Hose 50. Alternator Fail Indicator
15. Accumulator 32. Hoisting Lug Module
16. Prop Control Bracket 33. Prop Synchronizer Lead 51. Turbocharger (Compressor)
17. Accumulator Hose 34. Prop Deice Lead 52. Nozzle Pressurization Line
18. Prop Control Cable 35. Cylinder Head Drain Line 53. Wing Deice Light
36. Cross

Figure 9-3. Engine Installation (Sheet 3)

Change 7
 421 SERVICE MANUAL ENSINE Û Î3
cover before saturating the engine with sol-
vent. Any oil, fuel, and air openings on the 3. Remove engine exhaust system in accordance
engine accessories should be covered before with removal of exhaust system.
washing down the engine with solvent. Caus- 4. Remove cylinder head drain lines by disconnect-
tic cleaning solutions should be used cautious- ing at cylinder heads and removing clamp at cross,
ly and should always be properly neutralized 5. Remove engine baffles in accordance with re-
after their use. moval of engine baffle.
6. Remove the vacuum pump in accordance with
NOTE Section 12.
7. Remove the tachometer generator by removing
As each item is removed from the engine, four nuts and pulling it free of the tachometer gen-
place a temporary cover over the hole left erator dríve adapter.
by the removal of the item. This will pre- 8. Remove oil temperature bulb.
vent the accidental entry of foreign material
which could cause engine damage or lead to NOTE
engine malfunction.
When reinstalling oil temperature bulb, re-
move crush washer and install MS28778-4
packing.

b. To assemble the engine, reverse the engine dis-

assembly procedure.

Change 11
9-14 ENGINE 421 SERVICE MANUAL

Inspection of Engine. (see Section 2.) NOTE

Installation of Engine. (See figures 9-3 and 9-4.) If aircraft has the optional propeller unfeather-
ing system installed, connect hose (17) from
The installation procedure is the same for either accumulator (15) to governor (19),
engine. Although there is some difference in the
routing of wire bundles, lines, hoses and conduit. 3. Connect oil pressure hose (39) and turbocharger
This procedure is typical for installation of either oil supply hose (38) at "tee" fitting.
engine. 4. Connect oil filter to oil cooler hose (10) at oil
a. Hoist engine to a point just above the nacelle, cooler (13).
b. Install engine on engine mounts as follows (see 5. Connect fuel pump drain hose to fuel pump (27).
figure 9-4): 6. Connect turbocharger oil return hose (37) to
1. On aircraft 421-0001 to 421B0201, temporarily scavenger oil pump.
install mount pads (4 and 7), spacer (5), boot (8), 7. Connect filter to oil pump hose to oil pump.
retainer (9), to all four engine mounts (1) using bolts 8. Connect firewall to fuel pump hose (28) to fuel
(11) and lockwashers (10). Ascertain that the mount- pump (27).
íng pad (7) will locate over pin (12) in the lower sur- 9. With ram air tube installed and pushed aft, con-
face of mount bracket (6) and lockwasher (10) fits in nect the mixture control to fuel pump hose (26).
hole in retainer (9) and mount pad (7). 10. Connect the fuel pump to mixture control hose
(a) On aircraft 421BO201 and On, temporarily in- (26).
stall mount pads (4 and 7), spacer (5) and shield (13) 11. Conneet fuel pump to firewall vapor return line
to all four engine mounts (1) using bolts (11) and lock- (29) at fuel pump (27).
washers (10). Ascertain that the mounting pad (7) 12. Connect the controller to erankcase oil return
will locate over pin (12) in the lower surface of mount hose (7) to the crankease.
bracket (6) and lockwasher (10) fits in hole in retainer 13. Connect the baffle to firewall fuel flow gage
(9) and mount pad (7). hose (33).
2. Be certain that the propeller control conduit and 14. With the aft end of the ram air tube (14) in-
bracket is outside of engine mounts, stalled, and tube clamped. Connect ram air tube (14)
3. On aircraft 421-0001 to 421B0201, with upper to baffle.
mount pads (4) located on mount brackets (6) and boot 15. Connect the firewall to engine baffle manifold
(2) installed on engine mount (1), lower engine onto pressure gage hose (3) to the baffle fitting.
mount pads (4) and install lower pads (7) by locating 16. Connect vacuum pump inlet hose (31) to vacuum
hole in pads over pin (12) then install boot (8), re- pump.
tainer (9), lockwashers (10) and bolts (11). Be sure
lockwasher extends through retainer into hole in low- NOTE
er pad.
(a) On aircraft 421B0201 and On, with the upper If surface deice system is installed, an ad-
mount pads located on mount brackets (6) and spacers ditional oil separator exists and more hoses
(3) as required in place, lower engine onto mount must be connected,
pads (4) and install lower pads (7) by locating hole in
pads over pin (12) then install shield (13), lockwash-
ers (10) and bolts (11). Be sure lockwasher extends 17. Connect oil separator overboard drain hose to
through retainer into hole in lower pad. oil separator (22).
4. Torque bolts (11) to 300, +50, inch-pounds
-00
d. Fasten engine ground strap to the sump bolt att
and bend tab on lockwasher (10) over bolt head. of No. 5 cylinder.

NOTE
NOTE
Locate spacers (3) between upper mount pads (4)
and engine on the forward mounts only as re- Use a multimeter to assure proper bond be-
quired to align propeller spinner with cowling. tween engine and aircraft structure. Resis-
Be sure proper length bolts are used on each mount. tance should be 0. 00 ohms.

5. (See figure 9-3.) Connect exhaust stack ball e. Install the propeller control cable bracket (16)
joint to exhaust bellows (11) in accordance with ex- using the two engine sump washers and bolts.
haust system installation. f. Connect propeller control cable (18) at the gov-
c. (See figure 9-3.) Install lines and hoses as fol- ernor by installing bolt, washer and nut.
lows: g. Connect wires and cables as follows:
1. Install hose and clamps which connect intake air 1. Route starter cable forward and attach to starter
duct (6) to throttle body (24). terminal.
2. Connect cylinder head drain hose (35) to cross 2. Route magneto grounding and alternator wires
(36). forward through aft engine baffle (5) and clamps.
Attach alternator wires to alternator.
3. Route the tachometer wire to the tachometer and
connect.

Change 11
 421 SERVICE MANUAL ENGINE 9-14A $••148

4. Route temperature wire to oil tempera-

the oil w. Turbocharger assembly secure.
ture bulb, locate
directly below oil cooler (13) and x. Vacuum line and vacuum pump outlet hose and
safety. Connect ground wire to engine baffle (5). connection secure.
5. Route the cylinder head temperature wire for- y. Engine controls properly rigged.
ward along right side of engine to the number 2 cyl- z. Oil drain plugs tight and safetied.
inder. aa. Oil quantity check (see Section 2).
h. Install the propeller in accordance with Section ab. Hose and lines secure at firewall.
10. ac. Fuel air control unit secure.
i. Connect the battery cables in accordance with ad. Shrouds installed on engine-driven fuel pump,
Section 14. and fuel-air control unit. Ram air tube installed and
j. Inspect installation for safeties, loose connec- clamped.
tions, missing bolts, clamps, screws or nuts; ae. Air leak check should be made on the induction
proper routing of cables, hoses and lines, and for system to insure optimum performance from the
correct connection. turbocharger. The following procedure is recom-
k. Make a magneto switch ground-out and continuity mended:
check. Connect magneto ground wires to the mag- 1. Remove the flexible duct between the air induc-
netos• tion filter and the air inlet scoop, then by use of an
1. Service the engine in accordance with Section 2· adapter plug, attach the pressure side of an indus-
m. Install the engine cowling in accordance with in¯ trial vacuum cleaner to the air filter inlet,
stallation of engine cowling• 2. Fabricate a baffle plate and install between fuel
control body and pressurization venturi to block the
Installation Inspection. (See figure 9-3.) flow of air to cabin.
The following check may be used as a guide for in- CAUTION
specting the installation of either engine.
a. Propeller mounting nuts torqued. The inside of the vacuum cleaner should be
b. Engine mounts secure. free of any contamination that might be blown
c. Oil temperature bulb electrical connector secure into the engine induction system.
and safetied, ground wire connection tight.
d. Oil pressure relief valve plug safetied. 3. With the vacuum cleaner on, all joints may be
e. Tachometer generator electrical connector se- checked for leaks by using a soap solution and watch-
cure and safetied, ing for bubbles. All joints should be free of air leaks
f. Starter cable connection secure and insulating with the exception that some small bubbles will ap-
boot in place. pear at the joint of the turbocharger compressor and
g. Cylinder head temperature bulb installed and bearing housing,
ground wire connection bonded properly.
h. Alternator cable connection secure and case NOTE
ground wire installed (100 Amp alternator only).
i. All wiring securely clamped in place. The manifold pressure indicator should indi-
j. Fuel pump connection tight. cate two to three inches of pressure above
k. Manifold pressure hose connections tight. atmospheric pressure, when the vacuum
1. Oil pressure connections clamped and tight. cleaner is on.
m. Fuel injection nozzles tight.
n. Fuel pressurization line tight· af. Exhaust system secure. Conduct air leak check
o. Fuel injection lines clamped and tight· in accordance with Inspection of Exhaust System pro-
p. Fuel manifold secure. cedures.
q. Turbocharger oil supply line tight. ag. Spark plugs tight. Ignition harness connections
r. Oil filter lines tight. tight and harness properly clamped.
s. Controller lines secure and tight. ah. Magneto ground wires connected.
t. All flexible tubing in place and clamped. ai. Engine nacelle for loose objects (tools, nuts,
u. Crankcase breather line connections secure. rag, etc.).
v. Air-oil separator exhaust and return hoses se- aj. Cowl flaps free.
cure. ak. Cowling and access doors for security.
NOTE

On aircraft 421B0001 to 421B0501, make Rough or Malfunctioning Engine Operation Inspection.

Certain oil separator return line check
valves are installed horizontally with the The purpose of the tachometer yellow are and asso-
word "HINGE" stamped on the hex flat in ciated placard is to minimize the possibility of op-
UP position and tue flow arrow pointing eration with a rough or malfunctioning engine at these
toward the scavenge pump. RPM's. The GTSIO-520 engine has no restrictions

Change 12
. •···
I
 421 SERVICE MANUAL ENOINE -16

or critical vibration characteristics when operating e. If magneto rubbers show severe distress, the
normally (e.g. all cylinders firing equally); however, following additional items must be inspected:
certain malfunctions within the engine cause torsional 1. Alternator couplings, starter adapter drive
vibrations to be excited in the crankshaft and drive gear, and tachometer drive for galling, pitting, dis-
system. These vibrations, when forced at certain tortion or heavy wear distress. Items found to be
levels and frequencies, will damage numerous com- unserviceable must be replaced.
ponents of the engine and possibly the propeller and 2. Remove propeller and inspect quill shaft for
its attachment. This condition may be characterized evidence of blueing or discoloration from heat. If
as a roughness such as that resulting from a misfir- discoloration is found, the quill shaft must be re-
ing or dead cylinder caused by one or more of the placed and also the propeller dowels anTtuds must
following malfunctions: be replaced.

a. Both spark plugs of a cylinder fouled or shorted. NOTE

b. Broken valve spring.
c. Burned valve guide. To inspect quill shaft, remove cover plate
d. Sticking or broken valve. located on the crankcase below the propeller
e. Broken rocker arm or pushrod. shaft. (Refer to Continental Overhaul Manual,
f. Loose cylinder Figure 4-12) Remove retaining ring (16), and
g. Cracked cylinder head. pull shaft out for inspection.

CAUTION
Specific items which show early damage from these
torsional vibrations are: the magneto rubbers, al-
Failure of the valve actuating mechanism
ternator drives, starter adapter gears, tachometer for one valve in any cylinder will usually
drive shaft, and quill shaft. cause the other valve pushrod in the same
cylinder to bend or twist and finally fail
If it is necessary to keep a rough engine in operation, since it is operating beyond capacity in try-
the speed of least destructive resonance is 1800 RPM; ing to open the valve against full compres-
however, it is recommended that a rough engine be sion pressure. It is therefore necessary
shutdown whenever possible- to fully inspect both valve trains in any cyl-
inder which has experienced lifter, pushrod,
In addition to the normal troubleshooting required to rocker arm or rocker shaft failure.
determine cause and correct engine roughness, the
following inspection must be conducted.
Engine Operational Check,
a. Check magneto rubber drive couplings for back-
lash, and possible damage or tearing. CAUTION
1. Drive coupling backlash may be inspected by
removing the timing inspection plug from each mag- Ground operation time should be held to a
neto and moving the distributer gear with a flat blade minimum to prevent overheating the engine.
screwdriver. Total backlash should not exceed At no time should the engine temperatures
1-3/4 teeth with a 3 pound load each direction on the be allowed to exceed their maximum limits.
screwdriver. Backlash exceeding 1-3/4 teeth re- Do not operate the engine with cowling re-
quires removal of both magnetos for visual drive moved.
rubber inspection.
b. If magneto rubbers are in good serviceable con- a. Park aircraft with nose headed into prevailing
dition, accomplish the following propeller inspection: wind and clear an area directly in front and to the
1. Check torque of propeller attach nuts to deter- rear of all objects that may be affected by the pro-
mine if they are loose. If any nuts are found exces- peller and propeller slipstream.
sively loose (70 foot-pounds or less), remove pro-
peller and check dowel pins and mounting studs for CAUTION
possible damage. If damage is found, the affected
parts should be replaced by an approved propeller Avoid engine run-up with aircraft parked in
overhaul shop. a loose gravel area. The propeller will pick
up small stones which can damage propeller
NOTE blades.

When reinstalling the propellers, new A1639-2 b. Install wheel chocks and position a fire extinguis-
(MS21044-N8) attach nuts are to be used. Do her for easy access in the event of engine fire.
not reuse old nuts. c. Release parking brake if previously set, and
test-operate brakes. Take note of any sponginess or

Change 9
Û~ ŸI ENSINE 421 SERVICE MANUAL

excessive pedal travel. Reset parking brake after ENGINE MOUNTS.

completion of test
The engine is mounted to the nacelle structure by
CAUTION four engine mounts. Each mount incorporates two
rubber pads capable of sustaining operational loads
If parking brake action is not normal do not and provide absorption for engine vibrations. On
perform engine run-up until corrective action aircraft 421-0001 to 421B0201, these mounts are
is accomplished on the brake system. covered by an elastomeric rubber boot to provide a
shield for the rubber mounting pads against heat.
d. Refer to Model 421 Owner's Manual and perform On aircraft 421BO201 and On, a metal heat shield
"Before Starting Engine" and "Starting Engines" is provided.
procedures.
e. Warm-up engines as follows: Removal of Engine Mounts. (See Figure 9-4.)
Throttles -
750 to 900 RPM.
1. Leave cowl flap to full OPEN position. (421- NOTE
0001 to 421BOOO1)
2. Perform magneto ground-out check as follows: Engine must be supported before removal is
(a) Throttle engine back to idle RPM. attempted. If engine is going to be removed,
(b) Momentarily switch both magnetos OFF. see Removal of Engine for the attaching parts
RESULT: The tachometer will indicate a sudden to be disconnected.
RPM drop when magnetos cease firing.
a. Bend ears down on locking washers (10) and re-
CAUTION move bolts (11) locking washers (10), retainers (9),
boots (8), lower mount pads (7) and spacers (5).
If magneto switches are left OFF for a pro- b. Lift the engine just enough to relieve the weight
longed period, after firing may occur when from engine mounts (1).
they are switched back on. If the engine con- c. Remove upper mount pads (4) and on forward en-
tinues to run with switches OFF, stop engine . gine mounts, remove spacer washers (3).
by placing control in IDLE CUT-OFF and
check magneto ground. Shimming the Engine Mounts. (See Figure 9-4. )

3. Advance throttle to 1500 RPM and perform a Although engine mount sag is normal and occurs over
magneto check as follows: a period of time in-service, it can be corrected by
(a) Place right magneto switch to OFF position shimming the mount back to its original position with
and note RPM drop. Return switch to ON posi- special spacers.
tion. Repeat check with left magneto switch.
RESULT: Engine speed drop of 100 RPM maximum Engine mount sag which has resulted in a loss of
or if the drop in RPM between the left and right clearance between engine, mount and or cowling
magneto differs by 50 RPM maximum. components should be corrected by shimming. If the
4. With engine at 1700 RPM, exercise the propel- area between the exhaust riser of number six cylin-
ler. der and the lower cowl panel does not have sufficient
(a) Retard the propeller pitch lever to obtain a clearance, (0, 40 inch minimum) install shims to obtain
1000 RPM tachometer indication. proper clearance.
RESULT: Exercise propeller and watch for any in- a. Hoist engine and support as required to insert
dication of sluggish or erratic operation. spacers.
5. Make a mixture control check by slowly moving
the mixture lever toward IDLE CUT-OFF. NOTE
RESULT: When a slight drop in RPM is noted, im- Spacers may be obtained form the Cessna
mediately return mixture lever to FULL RICH po- Dealers' Organization. Refer to Table I
sition. for part number and thickness. If a total
6. Stop engine by placing the mixture lever in IDLE thickness of spacers on any mount exceeds
CUT-OFF. As soon as propeller has stopped turn- 0.312 inch the mount must be removed and
ing, place ignition switches OFF. Turn all switches inspected in accordance with Section 2.
OFF.
CAUTION ENGINE MOUNT SPACER SPECIFICATIONS
PART NUMBER DESCRIPTION THICKNESS
After extended periods of ground engine opera-
tion above 1600 rpm or when the cylinder head 5056010-1 Spacer 0. 125 inch
temperature indicator shows values within the
5056010-2 Spacer 0. 188 inch
upper half of the green operating arc, reduce
power to speeds between 600 and 800 rpm for 5056010-3 Spacer 0. 250 inch
a period not less than 2 to 3 minutes prior to
is intended TABLE I
engine shutdown. This expedient
to reduce internal turbocharger temperatures b. Insert spacers between the engine mount bracket
and preclude the possibility of premature ac- (1) and the upper pad (4) as required to obtain 0. 40
cumulation of carbon on the turbine shaft seals. inch minimum clearance.

Change 6
 421 SERVICE MANUAL ENOINE Û-D

CAUTION Engine Exhaust System.

For each 0. 125 inch of spacer thickness add The exhaust system consists of a riser pipe attached
ed it will be necessary to add the next size to the exhaust port of each cylinder. The three ris-
longer length engine mount bolt- ers at each bank of cylinders are joined together into
a common pipe to form a stack assembly. The in-
c. Secure engine mount in place and safety in accor- board stack assembly is joined by a forward cross-
dance with engine mount installation procedures. over pipe to the outboard stack. The outboard stack
d. Recheck all clearances, especially in the exhaust assembly is routed aft through a flexible bellows to a
stack area. bypass valve assembly which is mounted to the tur-
bine side of the turbocharger. From the exhaust
port of the turbine, the tailpipe routes the exhaust out
Installation of Engine Mounts. (See Figure 9-4.) of the aircraft through the lower nacelle. The ex-
haust port of the waste-gate assembly is teed into the
a. Install the upper mount pads (4) on mount brack- tailpipe for the exhaust to be expelled from the sys-
ets (6) and on forward engine mounts install spacer tem when not required at the turbine. The waste-gate
washers (3). is automatically controlled by the turbo controlsystem.
b. Lower engine slowly into place on mount pads (4)
Removal of Exhaust System. (See figure 9-5.)
and spacer washer (3), forward engine mounts only.
c. Install spacers (5) and lower mount pads (7) with a. Remove engine cowling in accordance with re-
hole located over pin (12) in mount brackets (6). moval procedures.
d. Install boots (8), retainers (9), lockwashers (10) b. Remove cotter pin, washer and pin from the for-
and bolts (11). On aircraft 421B0201 and On, install ward support brackets.
shield (13), lockwashers (10) and bolts (11). c. Remove cotter pins, nuts, washers, springs,
e. Torque bolts (11) 300, +50, pound-inches.
-00

and bolts from the crossover (3) and elbow (2).

d. Remove crossover (3) and elbow (2) from engine.
NOTE e. Remove cotter pins, nuts, washers, springs and
bolts from heat shield (5) and bellows (12).
Lock washers (10) with a break tool. This f. Remove the exhaust stacks by removing the four
break tool is available from Cessna Dealers' nuts securing each riser to its cylinder.
Organization (Tool No. SE608). g. Work riser down and free of cylinder studs and
remove stacks from engine.

'N SE608 ENGINE MOUNT WRENCH

OPERATING PROCEDURE (SE608)

1. Instalt tool on rachet wrench or other

2 2.
suitable
Position
tool.
tool over bolt head making sure
it seats flat against engine mount pad face.
4 NOTE

Washer ears should either be splitting

421-0001 TO 421B0201 corners or on flat of bolt hr
42180201 AND ON
3. Turn tool until ears are positioned flat
against corners of flat of bolt.

1. Engine Mount 5. Spacer 9. Retainer

2. Boot 6. Mount Bracket 10. Lockwasher
3. Spacer "[. Lower Pad 11. Bolt
(Front Mount only) 8. Boot 12. Pin
4. Upper Pad 13. Shield

Figure 9-4, Typical Engine Mount Installation

Change 6
9-18 ENSINE 421 SERVICE MANUAL

De a 1

Detail $
TYPICAL
B0001 AND ON

RH ENGINE

4 421-0001ENOGIN2E1B201

. Stack Assembly 7. Waste-gate Valve Assembly 12. Bellows 17. Clamp

' Elbow 18. Flex Joint
.
8. Coupling 13. Coupling
:. Crossover 9. Tailpipe 14. Spring 19. Expansion Ring
2
. Stack Assembly 10. Coupling 15. Joint Flange 20. Seal
i . Heat Shield 11. Coupling 16. Slip Joint 21. Clamp
i . Elbow 22. Retention Bracket

Figure 9-5. Engine Exhaust Stack Assemblies (Sheet 1 of 2)

Change 6
 421 SERVICE MANUAL ENGINE -jg&

0 00
0. 51

CUTAWAY VIEW
OF SLIP JOINT

Detail $
TYPICAL

18
o°
A 16

Detail --"'

16

3
1
RH ENGINE
O
o 8
O |
o

5 ,

21"
22*

2
10
11

LH ENGINE

4421BO201 AND ON
B 421B0301 AND ON

Figure 9-5. Exhaust Stack Assemblies (Sheet 2)

Change 6
9-188 ENGINE 421 SERVICE MANUAL

NOTE Installation of Exhaust System. (See Figure 9-5.)

Discard metallic gaskets at risers and engine a. Install new spirotallic gaskets between each
mounting pads and replace with new gaskets. riser and its mounting pad then work riser up on
cylinder studs,
h. Remove coupling (11) connecting elbow (6) to b. Install nuts and torque to 100 110 inch-pounds.
-

waste-gate (7) and remove elbow.

i. On aircraft 421-0001 to 421B0201, remove cou¯
NOTE
pling (10) connecting waste-gate (7) to tailpipe (9) and
coupling (8) connecting tailpipe to turbine to remove Apply Fel-Pro C-5 or equivalent (Felt Pro-
tailpipe. ducts Manufacturing Company, Chicago 7,
j. On aircraft 421B0201 and On, remove coupling Illinois) high temperature anti-seize com-
(8) and clamps (17) to remove tailpipe (9) and flex pound to attaching nuts and bolts in extreme
joint (18). high heat areas of the exhaust system.

Removal and Installation of Exhaust Slip Joint Seals

and Expansion Ring, (See figure 9-5.) c. Install crossover (3) securing it with bolts,
springs, and washers,
a. Remove exhaust system in accordance with re-
NOTE
moval procedures.
b. Remove seal and expansion rings. Check free length of exhaust springs before in-
c. Install new expansion ring and seal in accordance stallation. If the free length is less than 0. 57
with SK421-40. inch, the springs must be replaced. Compress
springs to a length of 0.51 +0.000, inch
-0.030

CAUTION by adding or removing washers during installation.

re- d. Secure elbow (6) to waste-gate (7) with couplings

Do not bend or flex exhaust system after aligning elbow with bellows (12).
(11),
placing seals. This could cause leakage.

Change 8
 421 SERVICE MANUAL ENOINE S-lÛ

e. Install bellows (12) securing it with bolts, springs, 4. Remove air injection line at air injection mani-
and washers. The heat shield will be supported by fold and at nozzle.
two of the aft bolts. 5. Disconnect manifold pressure line at baffle and
f. On aircraft 421-0001 to 421B0201, install tail- cap lines to prevent entry of dirt or foreign objects.
pipe (9) securing it at the waste-gate (7) and to the 6. Disconnect cooling shrouds from baffle adapter
turbine with couplings (8) and (10). and disconnect fuel line at distributor valve and route
g. On aircraft 421B0201 and On, install flex joint aft through baffle adapter.
(18) and tailpipe securing tailpipe to turbine with 7. Remove screws attaching baffle (1) to support
coupling (8) and flex joint with clamps (17). (3).
h. Torque coupling bolts to torque values given in 8. Remove lower RH nut on vacuum pump and re-
Figure 9-21. move baffle (1).
1. Remove support (3) from engine by removing
bolt from aft engine body.
ENGINE BAFFLES. m. Remove baffle (2) by removing induction air
coupling and removing five screws attaching baffle to
inter cooler.
Removal of Engine Baffles. (See Figure 9-6.) n. Remove baffle (6) as follows:
1. Remove ram air hose from baffle to fuel pump
a. Remove engine cowling in accordance with cowl- housing at the baffle.
ing removal procedures. 2. Remove air injection line at air injection mani-
b. Remove baffles (9 and 17) as follows: fold and at nozzle.
1. Remove nuts attaching upper straps to intake 3. Remove screws attaching baffle (6) to oil cooler.
manifold (2 places). 4. Remove screws attaching baffle (6) to baffle (7).
2. Remove screws attaching lower straps to engine o. Remove baffle (7) by removing attaching screws
rocker arm assemblies (3 places). from baffle (9) and baffle (20).
3. Remove screws attaching baffle (9) to baffle (7). p. Remove baffle (20) and support (5) together by
4. Remove screws attaching baffle (17) to baffle removing attaching screws.
(1). q. Remove baffle (4) from baffle (8) by removing
5. Remove screws attaching baffles (9 and 17) to attaching screws and pulling aft clearing rear cylin-
baffles (15 and 16). der.
6. Remove baffles (9 and 17) from engine. r. Remove baffle (8) by pulling down and aft clear-
c. Remove bolts (19) connecting supports (18) to ing tabon baffle from cooling fins and index fin to
baffle assemblies (11) and remove supports from en- facilitate installation,
gine.
d. Remove screws attaching baffle bases (10), to
baffle assemblies and remove baffle assemblies from Installation of Engine Baffles. (See Figure 9-6.)
engine.
e. Reaching in between the engine cylinders, re- NOTE
trieve bafflebases (10 and 11).
f. Remove shield (14) from baffle (15) by removing Seal all holes left in baffles due to bend re-
screws and washers. liefs with Sealant EC801 (Minnesota Mining
g. Remove exhaust support (13) by removing attach- and Manufacturing Co., or equivalent).
ing screws.
h. Remove baffles (15 and 12) from engine by re- a. Align baffle (8) on index mark made on removal
moving attaching screws and washers on baffle (15). and guide baffle into position aft of No. 2 cylinder.
i. Remove screws fastening baffle (12) to baffle (15) b. Mount baffle (5) with baffle (8) using attaching
if baffle (12) is being replaced. screws.
j. Remove baffle (16) as follows: c. With baffle (20) and support (5) affixed together,
1. Disconnect and remove exhaust manifold sup- guide into position aligning holes in baffle (8) with
ports at the exhaust manifold, engine body, and alter- support (5) and secure with attaching screws.
nator bracket, d. Secure baffle (7) to baffle (20) with attaching
2. Remove bolts and washers attaching baffle (16) screws.
to front engine body, e. Install baffle (6) as follows:
3. Remove baffle (16) by lifting slightly upwards, 1. Secure baffle (6) to baffle (7) and engine oil
clearing tab on exhaust manifold and remove baffle cooler using attaching screws.
from front of engine. 2. Install air injection line through baffle and se-
k. Remove baffle (1) as follows: cure to air injection manifold and to nozzle.
1. Disconnect oil breather line hoses at the oil 3. Install ram air to fuel pump hose.
separator and tee assembly, route breather line
through engine baffle. NOTE
2. Tag and disconnect the following wires:
(a) Alternator wires. Make sure that seal is installed properly be-
(b) Propeller deice wires (Optional), tween oil cooler and engine.
(c) Magneto wires.
3. Route engine wire bundle aft through baffle. f. Install baffle (2) by securing to intercooler with

Change 4
9-20 ENGINE 421 SERVICE MANUAL

421A 00 1 A D ON

o Detan
421B0001 AND ON

Detail g Detan D
421B0001 AND ON 421B0001 AND ON
I
1. Baffle Assembly 8. #2 Cylinder Baffle 14. Shield
2. Baffle Assembly 9. Baffle Assembly 15. Baffle Assembly
3. 41 Cylinder Baffle 10. Base 16. Baffle Assembly
4. Upper Baffle 11. Baffle Assembly 17. Baffle Assembly
5. Angle 12. Baffle Assembly 18. Support
6. Baffle Assembly 13. Support 19. Bolt
7. Baffle Assembly 20. Baffle Assembly

Figure 9-6. Engine Baffles

Change 1
 421 SERVICE MANUAL ENSINE 9-20A/9-20B

three screws and to baffle (1) with two screws. Con- j. Install baffle (12) on baffle (15) and secure with
nect induction air coupling, screws, if removed, from baffle (15).
g. Install support (3) using existing bolt on aft engine k. Install baffles (15 and 12) on engine and secure
body. with washers and screw.
h. Install baffle (1) as follows: 1. Install exhaust support (13) and secure with
1. Position baffle (1) in position and secure to screws.
baffle (3) with screws. m. Install shield (14) on baffle (15) and secure with
2. Secure baffle (1) to lower RH nut of vacuum screws.
pump using existing nut. n. Position baffle bases (10) between engine cylinders.
3. Route engine wire bundle through baffle, o. Secure baffle assemblies (11) to bases (10) with
4. Connect and remove tags on the following wires: screws.
(a) Magneto wires. p. Position supports (18) on engine cylinders with
(b) Propeller deice wires (Optional). inner leg between #13 and #14 fins from engine crank-
(c) Alternator wires. case and secure to baffle assemblies (11) with bolts (19)
5. Route breather line through engine baffle and Make sure baffle (11) is mounted to proper cylinders,
connect to oil separator and tee assembly using ex- q. Install baffles (9 and 17) as follows:
isting clamps. 1. Position baffles (9 and 17) on engine and secure
6. Route air injection line through baffle and con- to rocker arm assemblies with screws (3 places) and
nect to air injection manifold and at nozzle. to intake manifold with washers and nuts (2 places).
7. Connect manifold pressure line. 2. Secure baffles (9 and 17) to front baffles (15 and
8. Route fuel line through baffle to distributor 16) with screws.
valve, then secure cooling shrouds to baffle adapter 3. Secure baffle (9) to rear baffle (9) with screws.
using existing clamps. 4. Secure baffle (17) to rear baffle (1) with screws.
i. Install baffle (16) as follows: r. Install engine cowling in accordance with instal-
1. Position baffle (16) on front of engine by lifting lation procedures.
upwards slightly to clear tab on exhaust manifold. s. Start engine and check for intake manifold leaks
2. Secure baffle (16) to front engine body using ex-- by observing manifold pressure gage on instrument
isting nuts and washers. panel.
3. Install exhaust manifold brackets and supports.

ENGINE CONTROLS.

Removal and Installation of Engine Controls. (See

Figure 9-8.)

a. Remove pilot and copilot seats, cabin divider

(optional equipment), carpet and pedestal access
covers in accordance with Section 3.

Change 4
 421 SERVICE MANUAL ENGINE $ 2l

b. (See Figure 1-2.) Remove access panels (73 and a. Install cable as follows:
77). 1. Lay cable out on floor with arrow at control end
c. (See Figure 1-2.) Remove engine cowls (29, 30 facing up (fixed race up).
and 33) and wing access panels (54, 55, 56 and 57). 2. Straighten ribbon by establishing a bend or hump
d. Disconnect the throttle, propeller and mixture in the control and carrying the hump from one end of
controls from quadrant levers. Note the direction control to the other,
that each pin is installed and position of each hous- 3. Start cable into wing through nacelle firewall
ing, so they may be reinstalled in the same position. and route cable to the control pedestal, exercising
e. Disconnect each control from its respective en- extreme care to prevent damage to the control.
gine component, and remove rod ends and jam nuts 4. Check control for freedom of movement before
from each end of controls. securing cable.
f. Disconnect cable housings from brackets at each 5. Secure each end of cable housing to control
end of controls, and remove washers and nuts. brackets.
g. Remove block assembly (1) from the housings. 6. Secure control to quadrant control lever and fuel
h. Loosen the shield (16) through which the engine control lever making sure the control cannot be
controls pass at the engine firewall. bottomed.
i. Remove seal assembly (17) as follows:
1. Remove nuts and screws securing seal assem- Rigging Mixture and Throttle Controls. (See Figure
bly to cabin skin. 9-7.)
2. Carefully remove seal assembly from cabin skin
and separate seal halves to remove from controls. a. Adjustment of the idle mixture is accomplished
j. Remove the controls from clamps under the by the use of locknut (6) which is attached to mixture
floorboards and from clamps securing the controls control lever (5) on the mixture control (4). Tight-
along their routing to the engine compartment. ening locknut (6) to shorten the interconnecting link-
k. Pull the controls into the cabin and remove, age provides a leaner mixture. Adjust to obtain a
slight and momentary gain in idle speed as the mix-
ture control is slowly moved toward IDLE CUT-OFF
(if set too lean, idle speed will drop under the same-
CAUTION condition). Mixture control levers in the cabin should
end their travels approximately 1/4 of an inch before
Due to the design of the throttle control, ex- reaching the quadrant stops. At the same time, the
treme care should be exercised to prevent mixture levers on the engines should rest against the
damage to the control during removal. See corresponding stops.
Throttle Control Installation. b. Mixture levers should be uniform within 1/2 of a
knob through the cruising range. This can be checked
1. Reverse this procedure to install the controls, by adjusting both flow meter readings to an identical
then rig each control. value at uniform RPM and manifold pressure on both
m. Install seal halves and seal in accordance with engines.
Section 16 sealing procedures. c. Adjust the throttle control levers in the cabin so
that their travel ends 1/4 of an inch before reaching
the quadrant stops. At the same time the throttle
levers on the engines should rest against the corres-

I Safety wire
CAUTION

all ball joints and locknuts.

ponding stops.
d. Throttle control levers should be uniform
1/8 of an inch of the knobs through the entire travel.
The rigging procedures
structions
chart provides
within

corrective
in order to meet the above control require-
in-

Throttle Control Installation. ments.

e. Rig control cables on throttle valve and mixture
The throttle control cable is an anti-friction bearing control as follows:
type control having a center blade or ribbon sus- 1. Find the neutral position on shafts (3 and 8) and
pended and guided by balls which are separated by scribe an index mark on body of throttle valve (2)
ball separators. Due to the geometry of the ribbon and mixture control (4),
and balls, care should be exercised in handling, re- 2. Align serrated spacer (9) on shafts (3 and 8) so
moving and installing the control to prevent damage. that serration lines on the face of the spacer are per-
To make bends in different planes it is necessary to pendicular to the neutral position of the shafts.
helix or twist the control so that the axis of the two
planes are separated by one inch per ten degrees of CAUTION
angular difference in the two planes.
Care should be exercised in order to maintain
NOTE original factory setting of serrated spacer (9)
on shafts (3 and 8).
Minimum bend radius can not be less than
eight inches. Do not coil the cable as a rope 3. Install lever (10) on shafts (3 and 8) aligning the
or force into position when storing but fold serration marks on spacer (9),
cable in a lazy figure eight. 4. Install washer (11) and nut (12) on shafts (3 and 8).

Change 5
9-22 ENOINE 421 SERVICE MANUAL

1 2

4
13

6 5
LH ENGINE (Closed Position)

o
4
13
A
RH ENGINE ( Closed Position)
11 10 9 :

3
~

Detail

1. Idle Speed Adjustment 6. Idle Mixture A u ment Nut 10. Lever

2. Throttle Valve 7. Stop Pin 11. Washer
3. Throttle Shaft 8. Mixture Control Shaft 12. Nut
4. Mixture Control 9. Serrated Spacer 13. Metering Unit Filter
5. Mixture Control Lever

Figure 9-7. Engine Controls

Change 11
 421 SERVICE MANUAL ENGINE Û¯Ž3

Detail E
4
" 1·l
10

1 20
Detail Ë 12

14 etail

Detail

Detail D

1. Block Assembly 6. Control Cable 11. Rod End 16. Shield

2. Pedestal Bracket 7. Housing Bracket 12. Bolt 17. Seal Assembly
3. Control Housing 8. Washer 13. Washer 18. Cabin Skin
4. Screw 9. Nut 14. Nut 19. Ball Joint
5. Clamp 10. Jam Nut 15. Lever 20. Safety Wire i

Figure 9-8. Engine Control Cables

Change 12
9-24 ENOINE 421 SERVICE MANUAL

5. On the control quadrant place the throttle and rant were not set at a true mid-point as de-
mixture controls at the mid-point between stops. scribed in step 5 above, the 1/4 inch toler-
6. With shafts (3 and 8) in the NEUTRAL position ance as noted in steps a. and c. will not be
and the controls on quadrant set at the mid-point, ad- available. Readjustment for 1/4 inch travel
just control cables ends so that when attached to will be necessary and should be made at the
levers (10) a 90 degree angle is formed between cen- control quadrant,
terline of lever (10) and centerline of control cables.
NOTE

NOTE Control actions must be corrected in the order

presented in Rigging Chart. Start at the top of
If throttle and mixture controls at the quad- the chart and work toward the bottom.

Rigging Procedures Chart for Throttle and Mixture Controls. (See Figures 9-7 and 9-8.)

TROUBLE PROBABLE CAUSE CORRECTION

MIXTURE CONTROL LEVER Insufficient mixture control lever (See Figure 9-7.) Shorten travel
REACHES QUADRANT BE- travel on fuel-air control unit. of serrated lever (10) by reset-
FORE COVERING FULL ting lever lower on serrated
TRAVEL spacer (9).

MIXTURE CONTROL LEVER Excessive mixture control lever (See Figure 9-7.) Lengthen travel
STOPS SHORT AT BOTH travel on fuel-air control unit. of serrated lever (10) by resetting
ENDS OF QUADRANT lever higher on serrated spacer (9).

MIXTURE CONTROL LEVER Uneven control travel adjust- (See Figure 9-8.) Reset control
STOPS SHORT A T ONE END ment. cable travel by removing bolt (12),
OF TRAVEL AND STRIKES . washer (13), nut (14) and loosen-
QUADRANT STOP AT THE ing nut (10) and turning rod end
OTHER END (11) to achieve desired adjustment.

UNEVEN MIXTURE RESPONSE Different mixture control sensi- Refer to Rigging Mixture and
BETWEEN ENGINES (MORE tivities. Throttle Controls.
THAN HALF KNOB DIFFER-
ENCE AT BALANCED FLOW
. METER READINGS. RPM
AND MANIFOLD PRESSURE

THROTTLE CONTROL LEVER Insufficient throttle control lever (See Figure 9-7.) Shorten travel
REACHES QUADRANT BE- travel on fuel-air control unit. of serrated lever (10) by resetting
FORE COVERING FULL TRAVEL lever lower on serrated spacer (9).

THROTTLE CONTROL LEVER Excessive throttle control lever (See Figure 9-7.) Lengthen travel
STOPS SHORT AT BOTH END travel on fuel-air control. of serrated lever by resetting
OF QUADRANT lever higher on serrated spacer.

THROTTLE CONTROL LEVER Uneven control travel adjustment. (See Figure 9-8.) Reset control
STOPS SHORT AT ONE END cable travel by removing bolts (12)
OF TRAVEL AND STRIKES washer (13), nut (14) and loosen-
THE QUADRANT STOP AT ing nut (10) and turning rod and
THE OTHER END (11) to achieve desired adjustment.

UNEVEN THROTTLE SETTING Different throttle control sensi- Refer to Rigging Mxiture and
RESPONSE BETWEEN ENGINES, tivities. .
Throttle Controls.
MORE THAN 1/8 INCH DIFFER-
ENCE BETWEEN KNOBS (AT
SAME FLOW METER MANIFOLD
PRESSURE AND RPM READINGS)

NOTE

If described corrective measures do not provide adequate

throttle control operation, check throttle body, control
valve operation and air intake system for leaks.
 421 SERVICE MÁNUAL ENGINE 9-25

13 /

Detail
421-0001 TO 421A0001

3 4 5 6

10

16
14

421A0001 and ON

1. Control Pedestal 7. Terminal Block 6 12. Friction Knob

2. Metalcal 8. Terminal Block 5 13. Alternate Air Controls
3. Throttle Levers 9. Screw 14. Heat Exchange Controls
4. Propeller Levers 10. Cover Plate 15. Screw
5. Mixture Levers 11. Control Cable Assembly 16. Cover Plate
6. Screw 17. Cover Plate

Figure 9-9. Control Quadrant

Change 8
9-26 ENGINE 421 SERVICE MANUAL

3
4
5
6

39
Detail A
34

1. Screw 15. Right Mounting Plate 29. Screw

2. Lockscrew 16. Friction Knob 30. Pitch Lever Knob
3. Retainer 17. Center Stud 31. Terminal
4. Left Mounting Plate 18. Washer 32. Washer
5. Spacer 19. Spring 33. Cotter Pin
6, Rack 20. Spacer 34. Screw
7. Spacer 21. Friction Disc 35. Spacer
8. Guide Rod 22. Mixture Lever 36. Switch
9. Mixture Lever Knob 23. Spacer 37. Lug
10. Screw 24. Propeller Pitch Lever 38. Screw
11. Ratchet Stop 25. Throttle Lever 39. Spacer
12. Spring 26. Spacer 40. Pin
13. Housing 27. Hub 41. Bolt
14. Screw 28. Throttle Lever Knob 42. Nut

Figure 9-10. Control Quadrant Disassembly

 421 SERVICE MANUAL ENSINE 9-D

Removal, Installation and Rigging of Propeller Con- Assembly of Control Quadrant. (See Figure 9-10.)
trols.
a. Install gear warning switch using bolts, spacers
For removal, installation and rigging of propeller and nuts as illustrated,
controls see Section 10. b. Screw center stud (17) into retainer (3).
c. Screw retainer (3) into hub (27) and install hub
in left mounting plate with lockscrew (2).
ENGINE CONTROL QUADRANT.
NOTE
Removal of Control Quadrant. (See Figure 9-9.)
Prick punch edge of lockscrew after instal-
a. Remove elevator trim control wheel and sprocket ling to prevent it from becoming loose and
in accordance with Section 6. dropping out.
b. Remove cover plate (10) and unserew friction knob
(12) from right hand side of control pedestal (1). d. Install three guide rods on left mounting plate
c. Remove cotter pins and pins which connect the (4) with three attaching screws (1).
cable assemblies (11) to the control levers (3, 4 e.. Assemble control levers, spacers, guides, etc.
and 5). on hub and guide rods as illustrated.
d. Disconnect the wires from the gear warning
switches and tag. NOTE
e. Remove control quadrant by removing screws
(6) which attach the control quadrant to the pedes- Do not lubricate the parts to be assembled
tal (1). on the hub. These parts must remain dry
for proper operation of the control friction
lock.
Disassembly of Control Quadrant. (See Figure
9-10.) f. Install right mounting plate (15) with three
screws (1), attaching mounting plate to guide rods
a. Remove the three screws (1) attaching right (8).
mounting plate (15) to guide rods (8). g. Install the two lugs (37) with the spacers (39),
b. Remove cotter pins (33), washers (32) and pins bolts (41) and nuts (42).
(40) from terminal (31). h. Install screws (38) in lugs (37) and terminals
c. Remove nut (42), spacers (39), lugs (37) and (31) on screws (38), then with terminals (31) located
bolt (41) from right and left mounting plates (4 on spacer lugs, install pins (40), washers (32), and
and 15). cotter pins (33).
d. Remove washer (18) and spring (19) from end of i. Adjust forward screw (34) on the gear warn-
center stud (17). ing switches (36) so that when the throttle levers
e. Remove spacer (7), rack (6) and spacers (7) (25) are CLOSED, the switches (36) are closed.
from guide rods, then remove spacer (20), friction
dise (21) and control lever (22) from hub (27). Fol-
low this sequence and remove the remaining parts Installation of Control Quadrant. (See Figure 9-8.)
assembled on the guide rods and hub.
Reverse the removal of control quadrant proce-
NOTE dure.

The spacers are of different thickness.

f. Remove three screws (1) attaching guide rods FUEL INJECTION SYSTEM.
to the left mounting plate (4) and remove guide
rods. The fuel injection system is a simple, low pressure
system of injecting fuel into the intake valve port in
CAUTION the cylinder head. It is a multi-nozzle, continuous
flow type system which controls fuel flow to match
Hold the ratchet stop (11) on the mixture engine airflow. Any change in throttle position,
levers (22) down when removing the racks engine speed, or a combination of both, causes
to prevent them from springing out of changes in fuel flow in correct relation to the en-
their housings. gine airflow. A manual mixture control and a flow
gage, indicating metered fuel pressure, are pro-
g. Remove lockscrew (2) from left mounting plate vided for precise leaning at any combination of alti-
(4) and remove hub (27) from mounting plate. tude and power setting. The continuous flow system
h. Unscrew retainer (3) from hub (27) and cen- uses a typical rotary vane fuel pump. There are no
ter stud (17) from retainer, to complete disassem- running parts in this system except for the engine-
bly. driven fuel injection pump.
i. To remove stall warning switches (36) from
spacer (35), remove nut (42), spacer (35), and
screws (34).
EN ENGINE 421 SERVICE MANUAL

Trouble Shooting The Fuel Injection System.

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE WILL NOT START No fuel to engine. Check tank fuel level.
---

WITH NO FUEL FLOW

GAGE INDICATION Mixture control improperly rigged. Check mixture control for proper
rigging.

Engine not primed. Auxiliary pump switch in PRIME

position.

Selector valve in wrong position. Position selector valve to MAIN

TANK position.

ENGINE WILL NOT START Engine flooded. Open throttle, close mixture,
---
WITH FUEL FLOW clear engine of excess fuel, try
GAGE INDICATION another start.

No fuel to engine. Loosen one line at nozzle. If no

fuel flow shows, with fuel flow on
gage, replace fuel manifold valve.

ROUGH IDLE Nozzle restricted. Remove nozzles and clean.

Improper idle mixture. Adjust miiture per Engine Opera-

tional Check.
POOR ACCELERATION Idle mixture incorrect. Adjust mixture as required. See
Engine Operational Check.

Unmetered fuel pressure too high. Lower unmetered fuel pressure.

Worn linkage. Replace worn elements of línkage.

ENGINE RUNS ROUGH Restricted nozzle. Remove and clean all nozzles.
Check adjustment of fuel pump,
Improper mixture. if unable to adjust properly re-
place fuel pump.

LOW FUEL FLOW GAGE Restricted flow to metering valve. Check mixture control for full
INDICATION travel. Check for clogged fuel
filters.

Inadequate flow from pump. Adjust engine-driven fuel pump.

Altitude compensator stuck. Repair or replace engine-driven

fuel pump.

Distribution valve stuck open. Repair or replace distribution

valve.

HIGH FUEL FLOW GAGE Restricted flow beyond metering Check for restricted nozzles or
INDICATION valve. fuel manifold valve. Clean or re-
place as required.

Air in gage line. Loosen line to remove trapped

air.

Restricted recirculation passage Replace engine-driven fuel pump.

in pump.

FLUCTUATING OR Vapor in system, excess fuel If not cleared with auxiliary pump,
ERRONEOUS FUEL temperature. check for clogged ejector jet in va-
FLOW INDICATIONS por separator cover. Clean only
with solvent no wires.
 421 SERVICE MANUAL ENGINE $

TROUBLE PROBABLE CAUSE CORRECTION

FLUCTUATING OR Aneroid in pump stuck. Repair òr replace injection fuel

ERRÖNEOUS FUEL pump.
FLOW INDICRI'IONS
(CONT.) Distribution valve stuck closed. Repair or replace distribution
valve.

Air in fuel flow gage line. Leak Repair leak and purge line.
at gage connection.

ERRATIC IDLE FUEL (Not associated with vapor) Clean relief valve. Refer to
PRESSURE Dírty Relief Valve. Continental M73-22.

POOR IDLE CUTOFF Engine getting fuel. Check mixture control in full IDLE
CUT-OFF. Check auxiliary pump
is OFF. If neither, replace mani-
fold valve.

UNMETERED FUEL Internal orifices plugged. Clean internal orifices in engine-

PRESSURE RAISE driven fuel pump. Set aneroid.

UNMETERED FUEL Relief valve stuck open. Replace engine-driven fuel pump.
PRESSURE DROP Check supercharger discharge
pressure.

VERY HIGH IDLE AND Relief valve stuck closed. Replace engine-driven fuel pump.
FULL THROTTLE FUEL
PRESSURE PRESENT

FUEL DISCHARGED INTO Leaking diaphragm. Replace engine-driven fuel pump.

ENGINE COMPARTMENT
AND RELIEF VALVE WILL
NOT PROPERLY OPEN

LOW FUEL PRESSURE AT No turbocharger discharge Check turbocharger lines and fit-
HIGH POWER pressure. tings. Check discharge pressure.

NO FUEL PRESSURE Check valve stuck open. Replace engine-driven fuel pump.

FUEL-AIR CONTROL UNIT• a. Place the fuel selector valve handle in OFF position.
b. Remove the engine cowling.
The function of the fuel-air control unit is to control
engine air intake and to set the metered fuel pressure NOTE
for proper fuel-air ratio. There are three control
elements in this unit, one for air, and two for fuel; Plug or cap all open lines, hoses and fittings.
one of which is for fuel mixture and the other for
fuel metering- c. Loosen clamps securing flexible ducts to the
bottom of the fuel control unit shroud and slide ducting
Main fuel enters the control unit through a strainer down. Disconnect the three fuel lines.
and passes to the metering valve. The position of d. Disconnect the fuel pressure switch wiring.
the metering valve controls the fuel passed to the e. Remove fuel-air control cover.
manifold valve and nozzles. A linkage connecting f. Remove bolts securing fuel-air control to throttle
the metering valve to the air throttle proportions body.
air-flow to fuel-flow. The position of the mixture g. Remove the fuel-air control unit.
valve determines the amount of fuel returned to the
fuel pump. The fuel control portions of the fuel-air Installation of Fuel-Air Control Unit.
control unit is enclosed in a shroud and is blast air
cooled to help prevent vapor lock. A fuel pressure a. Place the fuel-air control in position on the throttle
switch, connected to the fuel control unit, actuates body,
to cause the auxiliary fuel pump to operate at a high NOTE
speed if the engine-driven pump pressure drops be-
low 5 PSI. The auxiliary fuel pump switch must be When replacing fuel lines, use only a fuel sol-
ON for the fuel pressure switch to operate. uble lubricant (such as engine oil) on the fitting
threads. DO NOT USE ANY OTHER FORM OF
Removal of Fuel-Air Control Unit. THREAD COMPOUND.

Change 9
9-30 EN6lNE 421 SERVICE MANUAL

b. Install bolts securíng fuel-air control to the FUEL MANIFOLD.

throttle body.
c. Install fuel-air control lever. From the fuel control unit, fuel is delivered to the
d. Before connecting the three fuel lines, which run fuel manifold which provides a central point for di-
between the fuel control unit and the fuel pump and viding fuel to the individual cylinders,
engine, make certain that the three flexible ducts are
installed on these lines. Connect these three lines at In the fuel manifold, a diaphragm and plunger valve
the fuel-air control unit. Install the flexible ducts on raises or lowers, by fuel pressure, to open or close
the air tubes located at the bottom of the fuel-air con- the individual cylinder fuel supply ports simultane-
trol shroud and secure with clamps, ously. A piston type check valve serves to insure
e. Connect electrical wiring at fuel pressure switch. that the plunger fully opens the outlet ports before
f. Rig engine controls in accordance with rigging fuel flow starts. Thus, there is no unbalance re-
instructions. strictions to fuel flow in the fuel manifold. A fine
g. Check the operation of mechanical linkage and mesh screen is included in the fuel manifold as ad-
ground run as required for adjustments. ditional protection of the injection nozzles against
h. Install engine cowling. dirt or foreign matter.

Adjustment of Fuel-Air Control Unit. (See Figure Removal of Fuel Manifold.

9-11.)
NOTE
The idle speed adjustment is a conventional spring-
loaded screw located in the air throttle lever. Ad- Plug or cap all disconnected lines, hoses and

\
just idle speed adjustment
500 RPM.
screw to obtain 450 to
Turn screw CW to increase
to decrease RPM. The idle mixture adjustment
RPM; CCW

the locknut at the metering valve end of the linkage.

Tightening the nut, to shorten the linkage, provides
is
fittings.

a. Disconnect fuel supply line and fuel flow gage

line at the fuel manifold.
b. Disconnect the six fuel injection lines at the fuel
a leaner mixture. A richer mixture is obtained by manifold.
backing off the nut to lengthen the linkage. Adjust c. Disconnect the manifold overboard vent line.
to obtain a slight and momentary gain in idle speed d. Remove the fuel manifold by removing the crank-
as the mixture control is slowly moved toward IDLE case bolts which secures it.
CUT-OFF. If set too lean, idle speed will drop
under the same conditions.

Idle Speed Adjustment

Idle Mixture Adjustment

Figure 9-11. Fuel Air Control Unit Adjustment

Change 10
 421 SERVICE MANUAL ENGINE -3Î

CHECK VALVE
THROTTLE
BODY

TURBOCHARGER FUEL AIR

CONTROL

FUEL
INLET

PRESSURE
RELIEF
VALVE

VAPOR RETURN
ALTITUDE COMPENSATOR PART THROTTLE
LINE
(ANEROID VALVE) POSITION

FUEL cauin
FLOW POWER

OVERBOARD
DRAIN

FUEL FLOW GAGE

FUEL
MANIFOLD
VALVE

:i: FUEL FROM TANK

UNMETERED PUMP FUEL

RETURN FUEL

METERED FUEL

TURBOCHARGER DISCHARGE INJE CTOR

AIR PRESSURE
VAPOR RETURN

421A0001 TO 421BOOO1

Figure 9-12. Fuel Injection System Schematic (Sheet 1 of 2)

 421 SERVICE MANUAL
9-32 ENGINE

CHECK VALVE
THROTTLE
BODY

TURBOCHARGER FUEL AIR

NTROL

FUEL
INLET

PRESSURE
RELIEF
VALVE

VAPOR RETURN
LINE
ALTITUDE COMPENSATOR PART THROTTLE
(ANEROID VALVE) POSITION

FUEL cacius
FLOW pown

OVERBOARD
DRAIN

FUEL FLOW GAGE

FUEL
MANIFOLD
VALVE

FUEL FROM TANK

UNMETERED PUMP FUEL

RETURN FUEL

METERED FUEL

TURBOCHARGER DISCHARGE INJE CTOR

AIR PRESSURE
VAPOR RETURN

421BOOO1 AND ON

Figure 9-12. Fuel Injection System Schematic (Sheet 2 of 2)

 421 SERVICE MANUAL ENGINE $"33

Cleaning and Inspection of Fuel Manifold. Refer to c. Connect nozzle pressurization hose at the fuel
Section 2. discharge nozzle,
d. Check installation for crimped lines and loose
Installation of Fuel Manifold. fittings.

NOTE
FUEL INJECTION PUMP.
When replacing fuel lines, use only a fuel sol-
uble lubricant (such as engine oil) on the thread The fuel pump is a single rotor pump incorporating
fittings. DO NOT USE ANY OTHER FORM OF a splined shaft for connection to the accessory unit.
THREAD COMPOUND. Since the pump is engine-driven, changes in engine
speed affect total pump flow proportionally. The
a. Installthe fuel manifold using crankcase bolts. pump supplies more fuel than is required by the en-
b. Connect fuel supply line and fuel flow gage line. gines. Therefore, a relief valve is provided to
c. Connect the manifold overboard vent line. maintain a constant fuel pump pressure. A check
d. Connect the six fuel injection lines at the fuel valve is provided so that the auxiliary pump pres-
manifold. sure can bypass the engine-driven fuel injection
e. Check for leaks and proper operation. pump for starting. In case of engine-driven fuel
injection pump failure, the auxiliary fuel pump will
operate automatically when the auxiliary fuel pump
FUEL DISCHARGE NOZZLES. switch is ON. Incorporated on the fuel injection
pump is a variable orifice controlled by an aneroid
From the fuel manifold, individual fuel lines carry on the pump. The aneroid is controlled by the super-
the metered fuel to the fuel discharge nozzles, one charger discharge pressure.
for each cylinder. These nozzles are installed in the
cylinder heads outside each intake valve. An air
bleed and nozzle pressurization arrangement supplies Removal of Fuel Injection Pump.
pressurized air to the nozzle. The air bleed arrange-
ment aids in vaporization of fuel and by breaking the a. Place fuel selector valve handles in the OFF
high vacuum at idle, maintains the fuel lines solidly position.
filled and ready for instant acceleration of the engine. b. Remove the engine cowling.
Nozzles are stamped with a letter on the hex of the c. Remove necessary lines and hoses for accessi-
nozzle body. Replacement nozzles must match, but bility to pump.
a matched set of another letter may be used.
NOTE

Removal of Fuel Discharge Nozzles. Plug or cap and tag for identification all
lines, hoses and fittings.
a. Disconnect the fuel injection lines at the fuel dis-
charge nozzles. d. Remove the shroud surrounding the fuel pump.
e. Remove the four nuts and washers attaching the
NOTE pump to the engine.
f. Remove fuel pump and gasket.
Plug or cap all disconnected lines and fittings.
WARNING
b. Disconnect nozzle pressurization hose.
c. Remove the fuel discharge nozzles from the Residual fuel draining from lines and hoses
cylinders. is a fire hazard. Use care to prevent the
accumulation of such fuel when lines or
hoses are disconnected.
Installation of Fuel Discharge Nozzles.
g. If a replacement pump is not being installed im-
NOTE mediately, a temporary cover should be installed
on the fuel pump mount pad.
When replacing fuel lines, use only a fuel
soluble lubricant (such as engine oil) on the
fitting threads. DO NOT USE ANY OTHER Installation of Fuel Injection Pump.
FORM OF THREAD COMPOUND.
a. Position a new gasket and fuel pump on four
a. Install the fuel discharge nozzles in the cylin- mounting studs with the fuel pump inlet to the left.
ders, b. Secure pump to engine with four plain washers,
b. Connect fuel injection lines at the fuel discharge four internal tooth lockwashers and nuts.
nozzles.
9-34 ENGINE 421 SERVICE MANUAL

NOTE Fuel Mixture Check.

When replacing fuel lines, use only a fuel sol- a. Perform a fuel mixture check as follows:
uble lubricant (such as engine oil) on the fitting 1. Warm-up engine, move throttle back to idle
threads. DO NOT USE ANY OTHER FORM OF position (450 RPM).
THREAD COMPOUND. 2. Place mixture control to full rich and propeller
control full forward.
c. Install the cooling shroud on the fuel pump. 3. Position auxiliary fuel pump to LOW, advance
d. Install all fittings and connect all lines as tagged throttle to 1000 RPM and slowly reduce mixture con-
at removal, trol, if both the fuel mixture control unit and fuel in-
e. Run operational check and adjust as required. jection pumps are set properly, RPM should decrease
f. Replace the engine cowling. when the mixture control is gradually moved towards
IDLE CUT-OFF.

421B0001 AND N

TO NIPPLE (13)
' TO ELBOW (3)
421-0001 TO 421B0001

\1.
51562001
14981008

Hose (fuel inlet from tank) 5. Compensator Valve Adjusting Screw 10. Hose
2. Hose (fuel pump to metering unit) 6. Gage 11. Nipple
3. Elbow 7. Hose 12. Tee
4. Low Unmetered Pressure 8. Nipple 13. Nipple
Adjusting Screw 9. Reducer

Figure 9-13. Fuel Injection Pump Adjustment

Change 9
 421 SERVICE MANUAL EN6fNE Û•34A

NOTE tions and readjust each pressure valve until

the proper balance and pressure settings are
If RPM increases when mixture is reduced, achieved.
fuel mixture is too rich; conversely, if RPM
diminishes rapidly when mixture is reduced, 3. Maximum fuel flow adjustment (see figures 9-3
fuel mixture is too lean. and 9-13) (42180001 and ON and aircraft incorporat-
ing SK421-38).
b. If fuel mixture check indicates a too rich or
too lean idle condition, refer to Fuel-Air Control NOTE
Unit Adjustments paragraph and adjust as neces- Propeller and manifold pressure adjustments
sary. must be accomplished before fuel flow adjust-
ments.

Unmetered Fuel Injection Pump Test Hook-Up, Check (a) Disconnect hose from return center port of
pressure regulator and plug.the end of detached hose
and Adjustment. (See figure 9-13.)
and cap center port on regulator.
a. Test procedures are the same for left and right (b) Allow engine oil to reach a temperature indi-
Connect test gage to pump as follows: cation in the upper 1/3 of green are on temperature
fuel pumps.
indicator.
1. Install fitting in pressure port of gage (6) and
connect hose (7). CAUTION
2. Install nipples (11 and 13) and reducer (9) and
nipple (8) in tee (12). Do not disconnect or plug line connected to
3. Connect hose (10) to nipple (11) and hose (7) inlet (side) port of pressure regulator. Com-
to nipple (8). plete failure of pressure regulator could oc-
4. Disconnect hose (2) (engine-driven pump to cur.
metering unit) from fuel pump elbow (3) and connect
hose (10) to elbow (3). Connect hose (2) to nipple (c) With throttle full open, mixture full rich, low
(13). boost and propeller control retarded to maintain 2100
RPM reading aircrafts fuel flow gage, set high pres-
sure adjustment to obtain a fuel flow gage reading of
b. Adjust compensator valve (aneroid) and pressure 233 to 238 pounds per hour.
relief valve to obtain the following:
1. Low unmetered pressure adjustment: Allow en- NOTE
gine warm-up, then idle engine at idle RPM. Pres-
sure should indicate 5. 5 to 6. 5 PSI on test hook-uP The above adjustment is accomplished by
pressure gage. If the indicated pressure is not with- loosening locknut and turning adjustment
in prescribed tolerances, turn adjusting screw (4) on screw (5) on altitude compensator (turn
pressure relief valve (turn IN to increase fuel pres- OUT to increase or turn IN to decrease).
sure or turn OUT to decrease fuel pressure) until
proper fuel pressure is obtained. Position auxiliarY (d) Shutdown engine, remove plug and connect
pump to LOW, observe that unmetered fuel pressure hose to return (center) port of pressure regulator.
does not exceed 6. 5 PSI. (e) Start engine and allow to warm up.
fuel flow adjustment (421-0001 to to ob-
2. Maximum (f) Adjust top screw of pressure regulator
42180001): Allow engine oil to reach a temperature tain aircraft fuel flow gage reading of 255 to 260
indication in the upper 1/3 of green arc on the oil pounds per hour with throttle full open, mixture full
temperature indicator. With the engine power set- rich, auxiliary boost pumps on low, and maximum
ting at maximum RPM and 39. 5 in. Hg manifold pres- static RPM settings.
sure, reading from the aircraft's fuel flow indicator
set the fuel flow to 42. 6 to 44. 3 GPH with auxiliary NOTE
fuel pumps in the OFF position. Position auxiliary
fuel pumps to ON, check that fuel flow does not ex- This setting will override the setting made
ceed 44. 8 GPH. If the indicated GPH is not within at the engine-driven fuel pump. Therefore,
prescribed tolerance, loosen locknut and turn adjust- it is important to follow these procedures
ment screw (5) on altitude compensator valve (turn correctly to assure proper fuel flow.
OUT to increase or turn IN to decrease) until proper
GPH is obtained. (g) Turn the auxiliary boost pump ON and check
that fuel flow does not exceed (260 lbs/hr) on instru-
NOTE ment panel gage. If fuel flow exceeds (260 lbs/hr)
with auxiliary boost pumps ON, the fuel pressure re-
Adjustments made to either the pressure re- lief valve is malfunctioning or the auxiliary boost
lief valve or the altitude compensator will pump pressure is set too high. (See Section 11 for
affect the pressure setting of the other valve- auxiliary boost pump adjustment. )
Therefore, recheck low and high RPM indica-
NOTE

Adjustments made to either the pressure re-

lief valve (4) or the altitude compensator (5)
Change 10
9-348 ENGINE 421 SERVICE MANUAL

will affect the pressure setting of the other 5. Remove test hook-up.
valve. Therefore, recheck low and high 6. After completion of unmetered fuel adjustments
RPM indications and readjust each pressure with test equipment removed and fuel lines connected
valve until the proper balance and pressure in normal position, it may be necessary to purge air
settings are achieved. from the fuel lines to prevent indicator needle fluc-
4. After adjusting the low unmetered fuel pressure tuations or erroneous readings.
and the maximum fuel flow, check idle RPM and idle
mixture in accordance with the FUEL MIXTURE
CHECK.

4
8
421B0001 TO 421B0301 1

8 5 4
421BO301 AND ON

51162006
51162005

1. Fuel Flow Gage 4. Fuel Pressure Line 7. Glove Compartment

2. Snubber 5. Turbocharger Discharge Line 8. Elevator Torque Tube
3. Snubber Tee 6. Cap Support

Figure 9-13A. Purging Fuel Pressure Lines

Change 11
 421 SERVICE MANUAL ENSINE 9-34C/9-34D

Purging Fuel Pressure Lines. (See figure 9-13A.) NOTE

WARNING On aircraft 421-0001 to 421B0001, the lines

will have to be disconnected at the fuel flow
Considerable fuel will run from the intake gage,
drain under each nacelle during purging
procedures. An appropriate receptacle c. Reinstall caps (6) or lines, tightening finger tight
should be provided to prevent a pool of raw then backing off one-half turn.
fuel from accumulating under each nacelle. d. Operate auxiliary pump until solid fuel is dis-
charged from the cap connection. Tighten cap with
a. Place throttle in full open position and mixture pump still operating then turn pump off.
to full rich,
b. Remove caps (6) from fuel pressure lines and NOTE
operate auxiliary fuel pump until at least one pint of
fuel has discharged from each pressure line. Verify that snubbers (2) and snubber tees (3)
are properly installed if excessive fuel flow
fluctuations are encountered.

Trouble Shooting the Ignition System. ENGINE IGNITION SYSTEM.

TROUBLE PROBA BLE CAUSE CORRE CTION

ENGINE FAILS TO START Ignition switch OFF or grounded Flip switch ON, check for grounded
DUE TO IGNITION switch wires. wires.
TROUBLE
Spark plugs fouled, improperly Remove and clean, adjust to proper
gapped, or loose. gap. Tighten to specified torque.
Magnetos improperly timed to en- See 1gnition Timing.
gine.

Shorted condenser. Replace condenser.

Magneto internal timing incorrect Install correctly timed magneto.

or timed for opposite rotation.

ROUGH IDLING Spark plugs fouled or improperly Clean spark plugs. Adjust spark plug
gapped. gap.

Weak condenser. Replace condenser.

ROUGH AT SPEEDS Loose or improperly gapped spark Tighten to specified torque. Adjust
ABOVE IDLE plugs. to proper gap.

High tension leak in ignition harness. Check for faulty insulation.

Weak or burned out condenser as Replace points and condenser.

evidenced by burned or pitted
breaker points.

SLUGGISH OPERATION Fouled or dead spark plugs. Clean spark plugs. Replace dead spark
AND/OR EXCESSIVE plugs.
RPM DROP
Improperly gapped spark plugs. Adjust to proper gap.

Magnetos out of time with engine. See Installation of Magnetos and

Ignition Timing.

Damaged magneto breaker points or See Installation of Magnetos and

condenser. Ignition Timing.

HIGH CYLINDER HEAD Improper magneto timing. See Installation of Magnetos and
TEMPERA TURE Ignition Timing.

Change 11
 421 SERVICE MANUAL ENGINE 945
MAGNETOS. ing and steel retainer in the gear hub to make
sure they will not drop out.
Engine ignition for the aircraft is provided by two
Bendix-Scintilla magnetos mounted on each engine. Inspection of Magnetos
Each magneto has a ground wire to a two position
switch mounted on the console paneL The left mag- NOTE
neto has a retard contact assembly which is so posi-
tioned that its points open at a predetermined number Anytime the engine and propeller have been
of degrees after the main contact points open. A subjected to excessive roughness the mag-
battery operated starting vibrator used with this mag- netos should be removed for a drive coupling
neto provides retarded ignition for starting. The vi- inspection.
brator is electrically actuated by the starter switch
mounted on the left console. Routed from the left a. Inspect the rubber drive bushings in the drive
magneto are six shielded, high tension cables, with gear hub for deformation and damage.
three to the upper spark plugs on the left bank of cyl-
inders and the other three routed to the lower spark NOTE
plugs on the right bank of cylinders. The right mag-
neto and wiring harness fires the remaining spark If magneto rubber shows severe distress,
plugs on that engine. inspect the quill shaft, alternator couplings,
starter adapter drive gear and tachometer
Removal of Magnetos., (See Figure 9-3.) drive for galling, pitting, or heavy wear
distress.
NOTE
Replace with new parts if they will not fit the
The magneto removal procedures are identical magneto coupling lugs closely.
for removing either magneto from either en-
gine, b. Remove the magneto breaker cover plate and in-
spect the points. They should have a gray, frosty
a. Remove the engine cowling· appearance. If burning or pitting is apparent, de-
b. Remove induction air intercooler as follows: termine the cause and correct it before replacing the
1. Remove clamp from induction air coupling at aft points. If the breaker points are oily, they can be
end of intercooler. cleaned with clear unleaded gasoline. Avoid getting
2. Remove clamp from coupling at forward end of any gasoline on the breaker felt as this will wash
cooling air plenum. away the lubricant. Breaker point gap is ±.003.
.016

3. Disconnect manifold pressure line.

4. Loosen clamps and slide hoses of intake mani- Internal Timing. (See Figure 9-25.)
fold tubes off of intake air plenum.
5. Remove intercooler assembly. a. On each side of the breaker compartment there
c. Remove magneto ground wire from magneto. are five timing marks. The marks on the left-hand
side, viewed from the breaker compartment, are for
WARNING clockwise rotation viewed from the drive end. The
marks on the right-hand side are for counterclockwise
The magneto is in a switch ON position when rotation. The timing marks indicate "O" position,
the switch ground wire is disconnected. "E" gap, and various degrees of magneto retard.
(See Figure 9-25.) The point in the center of the "E"
NOTE gap boss indicates the exact "E" gap position. The
width of the boss on either side of the point is the
±4°.
When both magnetos are being removed, tag allowable tolerance of In addition to these marks,
each ground wire for identification. the cam has an indented line across its end for loca-
ting neutral position. The number of degrees retard
d. Detach the high tension outlet plate from the mag- for a particular magneto is stamped at the bottom of
neto to be removed. the breaker compartment.
e. Remove the two magneto flange clamp nuts,
washers and clamps. Pull the magneto forward from NOTE
the crankcase mounting pad.
25°
When retard is required, advance pointer
20°
NOTE until it is over the mark. Then turn rotor
45°
untilpointer is over the mark. This will
the crankcase 25°
As the magneto flange clears give a total of retard,
accessory hole, watch the rubber drive bush-

Change 4
9-36 ENGINE 421 SERVICE MANUAL

b. Turn rotor in direction of rotation until painted ing a timing light, adjust retard breaker contacts to
chamfered tooth of distributor gear is just becoming open at this point. A tolerance of 1/16 inch past the
visible in timing window. Continue turning rotor of point can be used to get proper contact clearance.
magneto until line on end of cam is aligned with Continue rotating rotor until cam follower is on the
neutral mark in housing, high point of the lobe. Measure contact clearance.
c. Fabricate a timing pointer from a piece of wire It should be 0.016 ± 0.003. If not, readjust breaker
(approximately 2-1/2 inches) as follows: and recheck to be sure that contacts will open within
1. Remove the cam screw and flat washer from retard degree tolerance. Replace breaker assembly
cam, if retard degree tolerance and contact clearance can-
2. Bend one end of wire around the threads of the not be obtained.
screw, loose enough to allow wire to be rotated.
3. At the outside diameter of the large washer, bend NOTE
wire straight up parallel to the screw.
4. Install assembly on cam shaft and tighten screw Extreme care must be taken not to move the
just enough to hold wire in position and yet allowing rotor from the main breaker opening position
it to be rotated. when returning the pointer back to the zero
5. At a height sufficient to clear breaker housing, mark.
make a right angle bend in the wire.
Installation and Timing of Magnetos. (See Figure
NOTE
9-15.)
Pointer should be over timing marks, but not
touching the housing,
a. Check magneto to see that it is internally timed
for left hand drive rotation as viewed from the drive
d. On the retard breaker magnetos, it is necessary end.
to set the retard breaker to open a predetermined
number of degrees after the main breaker opens with- NOTE
in +2°, The number of degrees retard for a
-0°.

particular magneto is stamped at the bottom of the The magneto installation procedure is identical
breaker compartment. After main breaker has been for installing either magneto on either engine.
15° 2°
set to open a "E" gap ± move pointer back un-
til it is over the zero mark without moving rotor from b. (See Figure 9-15.) Remove the timing inspection
its position where main breaker just opened. Turn plug located on the side of the crankease and forward
rotor until pointer is over correct retard mark. Us- of No. 6 cylinder.

REFERENCE MARK

FABRICATED TIMING

®® POINTER

o o

0152535 35255

O 45 30 45
RETARD /
BREAKER

ADJUSTMENT NUMBER OF
SCREW DEGREES RETARD
MAIN BREAKER

CAPACITOR LEAD

RETARD LEAD PRIMARY LEAD

Figure 9-14. Magneto Timing Adjustment

 421 SERVICE MANUAL ENGINE $"O

I
TOP CENTER
-
TIMING MARK

ALTERNATOR DRIVE GEAR

PAINTED
ENGINE TIMING INSPECTION CHAMFERED
HOLE WITH PLUG REMOVED TOOTH
.J:LIIILIL alJLU.

20 DEGREE MARK

MAGNETO TIMING INSPECTION

r HOLE WITH PLUG REMOVED

ENGINE TIMING
INSPECTION PLUG
UPPER SPARK PLUGS

LOWER SPARK PLUGS

NOTE

NUMBER 1 CYLINDER
LEAD IS MARKED ON
MAGNETO CASE'

MAGNETO TIMING
INSPECTION PLUG

e13 46.*

5 • • 2
O .

LEFT • • RIGHT
MAGNETO MAGNE TO

TO MAGNETO SWITCHES

TO STARTING VIBRATOR

9-15. Magneto and Cable Numbering

Change 4
9-38 ENSINE 421 SERVICE MANUAL

c. Remove the upper No. 1 cylinder spark plug. 4. Remove the slotted-head screw and brass
d. Rotate the propeller by hand until the No. 1 cylin- washer from plate grommet base which is in line with
der is on the compression stroke and the timing mark cable to be detached.
on the ring gear is visible through the crankease tim- 5. Withdraw cable.
ing inspection hole.
e. Turn magneto coupling until the painted chamfered
tooth on the distributor gear is centered in the inspec- Installation of Ignition Cables. (See Figure 9-15.)
tion hole and hold magneto in its approximate position
while installing. a. All cables can be installed in the same manner.
f. Set the magneto in place on the crankcase acces- If a new cable is being installed, check it for correct
sory mounting pad. length by comparing it with the cable which is being
g. Attach a timing light to the magneto in accordance replaced.
with the timing light manufacturer's instructions. b. To install ignition cable:
h. If timing light is extinguished, rotate magneto 1. Connect cable to high tension outlet by inserting
housing in direction of its magneto rotation a few degrees cable end, with ferrule and coupling nut in place,
beyond point where light illuminates. Slowly rotate mag- through high tension cable outlet plate and into proper
neto in opposite direction until light is extinguished. hole in outlet plate grommet.
i. Tighten magneto clamp nuts to prevent any fur- 2. Fasten cable in place with cable piercing screw
ther movement of the magneto. and brass washer.

CAUTION CAUTION

Do not adjust breaker points to compensate Do not over-tighten screws.

for ignition timing. Breaker point adjustment
is for internal magneto timing only. This ad- 3. Attach high tension outlet plate, with cables in
justment of magneto breaker points to com- place, to magneto with four attaching screws.
pensate for ignition timing will ultimately pro- 4. Replace cable on proper spark plug.
duce a weak ignition spark and reduce engine 5. Install the engine cowling removed.
performance. c. By using good ignition maintenance practices in
addition to the Do's and Don'ts listed herein, the nor-
j. Rotate propeller in opposite direction of normal mal life expectancy of the harness can be reached,
rotation for a few degrees after light illuminates. Avoid sloppy installation and maintenance to gain full
k. Rotate propeller in direction of normal rotation harness service life. Don't let poor practices reduce
until light extinguishes. If timing mark is visible, reliability.
through the crankcase timing inspection hole, when
light extinguishes, the magneto is correctly timed to Do -

Use the Bendix 11-8950 High-Tension Lead

the engine. Tester to avoid unnecessary handling and replace-
1. Repeat timing procedure for other magneto, if ment of leads.
applicable.
m. When ignition timing has been checked (breaker Do -
Route leads to avoid all contact with engine,
20° mag-
points open on both magnetos at BTC) retighten engine components, oil lines, airframes, etc.
neto clamp nuts to prevent movement of the magnetos.
n. Remove timing light from the magneto and engine. Don't -
Allow leads to chafe on engine, engine com-
o. Replace magneto timing inspection hole plug and ponents, oil lines, airframes, etc.
attach high tension outlet plate to magneto.
Do Make necessary
-

bends as gradual as possible.

WARNING Keep leads stright wherever possible. Use an el-
bow clamp P/N 10-320283, screw P/N 10-35936-6
The magneto is in a switch ON position when and nut P/N 10-90404-4 where a bend at the spark
the switch wire is disconnected. plug is required.

p. Install timing inspection plug. Don't -

Make sharp bends or stretch leads.
q. Attach the magneto ground wire to magneto.
r. Replace the removed spark plug. Do Torque spark plug coupling
-
nuts accurately;
s. Install the engine cowling. 90-95 inch-pound for 5/8"-24 nut and 110-120 inch-
pound for the 3/4"-20 coupling nut.
IGNITION CABLES
Removal of Ignition Cables. (See Figure 9-15.) CAUTION

a. Remove the
engine cowling in accordance with Don't over-torque or under-torque spark
engine cowling removal procedure. plug coupling nuts. Always use a torque
b. To remove any ignition cable: wrench.
1. Remove the cable from the spark plug and with-
draw the contactor from the spark plug barrel. Do Hold the hex-shaped
-
crimped portion of the
2. Loosen attaching clamps. spark plug terminal ferrule with a crescent wrench.
3. Remove screws which secure high tension plate This will prevent the ferrule from turning and twist-
to magnetos.
 421 SERVICE MANUAL ENGINE
Û¯ ÛA

IELDING BRAID
PULLED BACK FROM
LEAD INSULATION

--
PUSH TOWARD
PLUG TERMINAL
RUPTURED LEAD INSULATION TO FLATTEN BRAID

Figure 9-15A. Ignition Harness

ing the lead while tightening or loosening the coup- Do -

Remember to clean the spark plug well ce-
ling nut. A four-inch crescent-type wrench is about ramic and terminal insulating sleeve. Clean with
the right size. a cloth dampened in alcohol.

Don't Allow -
theleads to twist while coupling. Don't -
Touch the terminal insulating sleeve after
Twisting leads may rupture the insulating material. washing.

Do Use as many clamps and wire bundle ties as

-
Do -
Use a high-temperature mold (MS-122 Fluoro-
necessary. When in doubt, use another clamp or carbon Spray, Miller-Stepenson Chemical Co., Inc.,
tie. 16 Sugar Hollow Rd., Danbury, Connecticut), re-
lease on terminal sleeves and on grommets at the
Do Redress
-
harnesses when engines are mounted magneto cable outlet plates. This will help pre-
in their nacelles to prevent chafing against airframe vent the hotter running plug insulating sleeves from
components, etc. Change nylon ties or clamps if sticking.
theu will hold better in a new position. Check har-
nesses, ties and clamps when other checks are Don't -
Apply mold release to dirty plugs or insula-
being made on the engine. ting sleeves.
Don't Allow leads and wire bundles to hang loose-
-
d. During maintenance check, carefully inspect the
ly from their clamps. Don't allow leads to come silicone lead insulating between the braided conduit
near the exhaust manifold keep them as far away
-
and insulating sleeve. Remove the elbow clamp, if
as possible. Retighten or reposition clamps or ties installed, to facilitate this inspection. Any lead that
if they are loosened for any reason. is torn or cut must be replaced. A longitudinal or
cross-shaped tear may be caused by spark plug leak-
Do Check lead terminals, especially
-
bottom cylin- age. This leakage usually causes a gray or black
der plug terminals (which seem to run the hottest). discoloration of the lead at the torn area.
The heat may cause the insulating sleeve of the plug
terminal to stick in the barrel of the spark plug. If CAUTION
stuck, the insulating sleeve should be removed
from the spark plug in such a manner as to protect Avoid bending the lead over the edge of the
the silicone insulating on the lead as much as pos- harness ferrule; this may result in cutting
sible. The insulating sleeve, which is readily re- the lead.
placeable, will receive most of any damage incur-
red during removal. e, Whenever a 3/4-20 spark plug is used, insure
that the compression spring is fully seated in the
Don't Bend and twist the spark plug lead until the
-

ferrule counterbore. If this precautions is not ob-

insulation is damaged or cut by the edge of the ter- served, a "Z" or "S" shaped bend can occur in the
minal ferrule. Do not damage the 5mm high- in the lead when assembled to the plug and the con-
tension wire by allowing a screwdriver blade or ductor may eventually puncture the silicone lead in-
other sharp tool to pierce it. sulation. As shown in Figure 9-15A, the braided
 9-388 ENOINE 421 SERVICE MANUAL

conduit should always be pushed along the lead to its purpose on the engine turbocharger and for control-
original position before assembling the lead to the ling purposes at the waste gate. Engine oil is filtered
spark plug. through an internally mounted outlet filter screen in
the oil pump and a externally mounted oil filter. A
SPARK PLUGS. bypass valve will route the oil around the oil filter if
it should become clogged. Oil pressure is maintained
a. There are two 18mm short-reach type spark by a spring-loaded pressure relief valve. The oil
plugs for each cylinder. The spark plugs are screwed temperature bulb is located directly below the oil
into a heli-coil insert in each cylinder. The spark cooler. The bulbs are heat variable resistor type and
plugs have an internal resistor to provide longer gap are attached to the oil temperature gage by a single
life and are shielded to prevent radio interference. electrical wire.
An average life of 200 hours can be expected, how-
ever, this time will vary with operating conditions.
The spark plugs are installed in the engine ata torque Oil Pressure Adjustment.
of 330 ±30 pound-inches. The correct gap setting is
. 016 to 018 inch.
. The oil pressure relief valve, located on the oil pump
is adjustable to increase or decrease oil pressure.
Refer to figure 9-15B and adjust oil pressure to 30 to
ENGINE OIL SYSTEM. 60 psi.

The engines installed in the aircraft have wet pump

pressure lubrication system. Oil temperature in each Removal of Oil Pressure Lines. (See Figure 9-17.)
is controlled by a thermally operated valve which
either bypasses the oil around the externally mounted a. Remove engine cowling.
cooler or routes it through the cooler passages for b. Remove oil filter element and drain oil filter.
cooling. Drilled and cored internal passages route the
oil to all moving engine parts which require lubrica- NOTE
tion. Oil furnished to the propeller governor for pro-
peller operation is also routed through internal pas- Cap all hose and line openings on removal,
sages. Engine oil is used externally for lubrication

1. Oil Pump 3. Washer (Copper) 4. Locknut

2. Housing 5. Adjusting Screw

Figure 9-15B. Oil Pressure Adjustment

Change 10
 421 SERVICE MANUAL ENSINE $ $

CODE

SUMP OIL

ENGINE OIL
PROPELLER GEAR
REDUCTION GEAR GOVERNOR
OIL

PROPELLER GOVERNOR

CAMSHAFT BEARING

MAIN BEARING

OIL GALLEY

OIL COOLER

PRESSURE RATE
....

CONTROLLER
.....-..
.
421-0001 TO 421A-0001
VARIABLE
VERNATHERM .
. ABSOLUTE
PRESSURE
CONTROLLER

WCA
STU
EAGAO
RE

FILTER

BYPASS VALVE SCAVENGER PUMP

ENGINE COMBINATION GAGE UNIT

PRESSURE RELIEF VALVE TURBOCRARGER

Figure 9-16. Engine Oil Schematic

Change 2
9-40 ENGINE 421 SERVICE MANUAL

le Shooting Engine Oil System

TROUBLE PROBABLE CAUSE CORRECTION

HIGH OIL TEMPERA- Low oil supply. Replenish.

TURE INDICA TION
Cooler air passages clogged. Clean thoroughly.

Cooler core plugged. Remove cooler and flush thoroughly.

Thermostat damaged or held open by Remove, clean valve and seat. If

solid matter. still inoperative, replace.

Oil viscosity too high. Drain and refill with correct

seasonal weight. (See Section 2.)

Prolonged ground operation. Limit ground operation to a minimum.

Malfunctioning gage or bulb unit. Check wiring. Check bulb unit.

Check gage. Replace defective parts.

LOW OIL PRESSURE Low oil supply. Replenish.

INDICA Í'IÒN
Oil viscosity too low. Drain and refill with correct seasonal
weight. (See Section 2.)

Foam in oil due to presence of alka- Drain and refill with fresh oil. (It
line solids in system, may be necessary to flush cooler
core if presence of alkaline solids is
due to a previous cleaning with alka-
line materials.

Defective pressure pump. Replace pump.

Malfunctioning pressure gage. Check gage. Clean plumbing. Re-

place if required.

Weak or broken oil pressure relief Replace spring. Adjust pressure to

valvespring. 30-60 PSI by adjusting screw.

Clogged oil filter. Replace oil filter.

c. Disconnect hose (9) from turbocharger (27) and remove.

ten at engine mounting bracket. 1. Disconneet hose (13) from oil cooler and remove,
d. Disconnect hose (10) from turbocharger (27) to m. Disconnect line (12) from actuator and remove,
sc¾enger pump and remove, n. Disconnect hose (26) and lines (16) and (23) from
e. Disconnect hose (7) from tee to firewall fitting rate controller (17),
and remove. o. Disconnect hose (26) from engine and remove.
f. To remove line (6) from between firewall and p. Disconnect line (14) from waste-gate actuator
wing gap, remove wing access (34, 54, 55, and 56, (19) and variable pressure controller (15) and remove.
figure 1-2). q. Disconnect (23) and (16) from variable pressure
g. To remove line (5) from between fuselage skin controller and remove.
and wing gap, remove heat exchanger in accordance r. Disconnect hose (18) from variable pressure con-
with removal procedures, Section 13. Disconnect troller (15) and engine, and remove.
line at each end, using caution to prevent breaking s. Disconnect line (24) from variable pressure con-
seal at cabin bulkhead fitting, and remove line, troller (15) and tee, and remove.
h. '‡o remove line (4) from between support bracket
and fuselagé uliîon, remove upholstery side panel in
ac ordance with Section 3, pilot's seat, carpet and
front spar access (78, figure 1-2). Disconnect line Installation of Oil Pressure Lines. (See Figure 9-17.)
at each end and remove through access (78),
i. Disconnect hoses (2 and 3) from between engine a. Reverse the oil pressure line removal proce-
gage and support bracket and remove. dures.
j. Disconnect line (12) and hoses (11) and (13) from
oil filter, let all excess oil drain from hoses,
k. Disconnect hose (11) from engine oil screen and
 421 SERVICE MANUAL ENOINE Û•$l

B C D E

Detail E

1. Engine Gage 16. Line (Variable Pressure Controller to Rate

2. Left Oil Pressure Hose Controller)
3. Right Oil Pressure Hose 17. Rate Controller
4. Cabin Oil Pressure Line 18. Hose (Variable Pressure Controller to Sump)
5. Stub Wing Oil Pressure Line 19. Actuator
6. Wing Oil Pressure Line 20. Oil Filter
7. Nacelle Oil Pressure Hose 21. Actuator Drain Line
8. Engine Oil Pressure Line 22. Hose (Turbocharger Manifold to Rate
9. Hose (Turbocharger to Oil Supply) Controller)
10. Hose (Turbocharger to Öil Pump) 23. Oil Line (Variable Pressure Controller to Rate
11. Hose (Oil Screen to Filter) Controller)
12. Line (Oil Filter to Actuator) 24. Line (Variable Pressure Controller to Tee)
13. Hose (Oil Filter to Oil Cooler) 25. Line (Tee to Rate Controller)
14. Line (Actuator to Variable Pressure 26. Hose (Rate Controller to Sump)
Controller) 27. Turbocharger
15. Variable Pressure Controller 28. Oil Separator
29. Line (Separator to Crankcase)

Figure 9-17. Engine Oil Pressure System (Sheet 1 of 3)

Change 8
9-42 EN61NE 421 SERVICE MANUAL

23

11 12
20

LH ENGINE

23 10 g
20
13
1
10

RH ENGINE 421-0001 TO 421A0001

Figure 9-17. Engine Oil Pressure System (Sheet 2 of 3)

 421 SERVICE MANUAL ENGINE 9-4 A

27

18

114

18 10
28
11 12

Detail

ENGINE 421B0501 and ON

LH

27

10
12
0

13
10
18 421B0501 and ON

RH ENGINE
421A0001 and ON

Figure 9-17. Engine Oil Pressure System (Sheet 3 of 3)

Change 8
 -428
ENC,INE 421 SERVICE MANUAL

FILTERED AIR

ALTERNATE HEATED AIR

RAM AIR

(CLOSED)
ALTERNATE COLD AIR

INDUCTION AIR

1
6

\ 4
RAM AIR

421-0001 (OPEN)
TO 421BOOO1

ALTERNATE AIR

1. Ram Air 5. Manually Controlled 7. Magnetically Controlled

2. Intercooler Alternate Heated Air Alternate Air Door
3. Throttle Body 6. Filter 8. Filtered Air
4. Turbocharger 9. Induction Air

Figure 9-18. Induction Air System Schematic (Sheet 1 of 2)

Change 1
 421 SERVICE MANUAL ENGINE S-43

9 FILTERED AIR

ALTERNATE HEATED AIR

RAM AIR

ALTERNATE COLD AIR

(CLOSED)
INDUCTION AIR
8

1
6

RAM AIR

421B0001 AND ON

(OPEN) 7

4
I
ALTERNATE AIR 5

Figure 9-18. Induction Air System Schematic (Sheet 2 of 2)

Change 1
9-44 ENSINE 421 SERVICE MANUAL

NOTE WASTE-GATE ACTUATOR, CONTROLLERS AND

TURBOCHARGER.
When installing oil pressure hoses and lines,
coat threads of fittings with a suitable thread
lubricant to facilitate installation. Turbocharger Control System Functions and Opera-
tions,
b. Start engines and observe for oil leaks while
bringing engines up to operating temperatures< a. Functions. The turbocharger is driven by ex-
c. Install all access covers, upholstery panels, haust gases to provide engine induction air and cabin
seats, carpet and engine cowling. pressurization air. An actuator controls the position
of the waste gate which allows exhaust gases to by-
pass the turbocharger when less pressure is re-
AIR INDUCTION SYSTEM quired as determined by the controllers. A variable
absolute pressure controller is mounted integrally
Induction air enters the system through a ram air
with the throttle body and its sensing head is exposed
duct located on the mboard and
.

side of each nacelle

is directed through a filter mounted to the turbocharg-
to the pressurization airflow. The variable absolute
pressure controller automatically maintains a pre-
er-compressor air inlet. A magnetically controlled
selected compressor discharge pressure at levels
alternate air door incorporated in the air filter per- deter-
that exceed the engine manifold pressures,
mits compressor suction to open the door and admit
mined by the position of the throttle lever. On 421-
alternate air if the air induction system becomes ob-
0001 to 421A0001 aircraft, a rate-of-change control-
structed. A manually controlled alternate air door com-
ler controls the rate of which the turbocharger
within the nacelle permits the pilot to open it to ad¯ pressor discharge will increase under rapid or
mit alternate (heated engine compartment air) if the moderate movements of the throttle by governing the
air induction system should become obstructed and flow of oil to the waste-gate actuator. On 421A0001
the automatic system failed to operate. An exhaust and ON aircraft, a manifold pressure relief valve is
driven turbocharger is automatically controlled by mounted on the venturi which provides protection to
controllers to maintain a manifold pressure at 39. 5 the engine from excessive intake manifold pressure
inches Hg. from sea level to a critical altitude (16,000 by assuming the function of rate control.
feet) regardless of temperature. The turbocharger
is completely automatic requiring no pilot action to
critical altitude• b. Operation. The waste-gate actuator is spring
loaded to
position the waste-gate to the normally
Removal and Installation of Induction Air Filter• open position when there is not adequate oil pressure
(See figure 9-19). in the actuator power cylinder during engine shut
down. When the engine is started, oil pressure is
a. Remove cowling in accordance with removal pro" power cylinder through a capil-
fed into the actuator
cedures. the flow and dampens any
lary tube which restricts
b. Unlock and disconnect air filter clamp• sudden changes of the position of the waste-gate.
c. Remove air filter from cannister•
As the actuator cylinder and lines leading to the con-
d. Installation of induction air filter is the reversal will block the flow
trollers are filled, the controllers
of the above procedure. of oil by normally closed metering and/or poppet
NOTE valves. As the oil pressure builds up i.n the actuator
cylinder, it overcomes the force of the actuator open
Before installing the induction air filter, the spring, closing the waste-gate. When the waste-gate
filter should be cleaned accordance
-in
with begins to close, the exhaust gases are routed through
Cleaning Procedures, Section 2· the turbocharger turbine. As the engine increases
its power and speed, the increase of temperature and
Rigging of Alternate Air Canister Control Door pressure of the exhaust causes the turbocharger to
(See figure 9-18A.) rotate faster, raising the turbocharger compressor
a. Position door to CLOSE. outlet pressure. As the compressor outlet pres-
b. Adjust travel of alternate air control cloor by sure rises, the aneroid bellows in the variable ab-
loosing nut (18) to increase or decrease length of solute pressure controller senses the increase in
cable.
c. Position door to OPEN.
d. Check the extension of control handle for not
more than 3. 00 inches of travel from control pedestal.

Change 8
 421 SERVICE MANUAL ENSINE -44A

·
7 12

10

11

8
14

18

Detail

18 17

1 2

1. Air Inlet Scoop 7. End Cap 13. Valve

2. Duct 8. Door 14. Seal
3. Canister 9. Hinge-Half 15. Dry Air Filter
4. Container 10. Door 16. Alternate Air
5. Latch 11. Hinge-Half Control
6. Latch 12. Hinge-Half .
17. Bracket- Control
Pedestal
18. Nut

Figure 9-18A. Turbocharger Induction Air Components

9-448 ENGINE 421 SERVICE MANUAL

vetaii A 421-0096 TO 421A0001

421-0001 TO 421-0096

Detail $ 421-0096 To 421A0001

9 12 8 46 12
421-0001 TO 421-0096

1. Throttle Valve 6. Oil Pressure Line 11. Variable Absolute

2. Coupling 7. Bracket Pressure Controller
3. Bypass Valve Assembly 8. Clamp 12. Tail Pipe
4. Compressor 9. Air Filter Assembly 13. Rate Controller
5. Coupling 10. Air Intake Duct 14. Manifold Pressure Relief Valve

Figure 9--19. Turbocharger and Induction System (Sheet 1)

Change 4
 421 SERVICE MANUAL ENOINE 9-440/9-440

14

Detail

421A0001 TO 421B0001

Figure 9-19. Turbocharger & Induction System (Sheet 2)

Change 4
e.
 421 SERVICE MANUAL ENGINE 9-45

LEFT ENGINE (421BOOO1 AND ON)

RIGHT ENGINE (421BOOO1 AND ON)

Detan D

Figure 9-19. Turbocharger & Induction System (Sheet 3)

Change 4
9-46 ENGINE 421SERVICE MANUAL

WASTE-GATE
WASTE-GATE
ACTUATOR

OVERBOARD o

RAM AIR
COMPRESSOR

EXHAUST GASES

OIL FILTER

TURBINE

PRESSURE RATE CONTROLLER

OIL PUMP--
EAXLHAEUST

INTAKE
VALVE

THROTTLE BODY -VARIABLE ABSOLUTE

PRESSURE CONTROLLER OIL SUMP

421-0001 TO 421A0001

LH ENGINE

Figure 9-20. Turbocharger, ControHers and Waste-Gate Actuator System Schematic (Sheet 1 of 4)
 421 SERVICE MANUAL ENGINE 9-46

WASTUEATGOATE
WASTE-GATE

OVERBOARD

RAM AIR COMPRESSOR

IP EXHAUST GASES Ì

TURBINE

PRESSURE RATE
CONTROLLER O
OIL
FILTER

EXHAUST
VALVE

INTAKE -

VALVE

OIL PUMP

THROTTLE
BODY

VARIABLE ABSOLUTE-
PRESSURE CONTROLLER

OIL SUMP
RH ENGINE
421-0001 TO 421A000L

Figure 9-20. Turbocharger, Controllers and Waste-Gate Actuator System Schematic (Sheet 2 of 4)
-488 ENOINE 421 SERVICE MANUAL

. ¯¯

-WASTE-GATE WASTE-GATE
ACTUATOR

OVERBOARD .. L

RAM AIR -COMPRESSOR

EXHAUST GASES

OIL ---

DimlNE- FILTER

INTERCOOLER

OIL PUMP--
EXHAUST/ r--THROTTLE .

VALVE / | BODY

OIL SUMP

VARIBLE ABSOLUTE
INTAKE PRESSURE CONTROLLER
-

VALVE
RELLEF
VALVE
TO
PRESSURIZATION
SYSTEM

LH ENGINE
421A0001 and ON
--a no wwwwoiewomewwwwawara-amm m.m m, -- - um mmmmewwwarma symmmmm,mwema snowmamm a- .. -am--mma - --owannemmwowrtwemammeewsmemvmesmnmuuuma un-

Figure 9-20. Turbocharger, Controllers and Waste-Gate Actuator System Schematic (Sheet 3 of 4)
 421 SERVICE MANUAL EN6INE Û·4Î

ACTUATOR

OVERBOARD i

RAM AIR COMPRESSOR

EXHAUST GASES

TURBINE

INTERCOOLER

OIL FILTER

THROTTLE VARIABLE ABSOLUTE

EXHAUST BODY PRESSURE CONTROLLER
VALVE

NAL OIL PUMP

LLIEEF

OIL SUMP

TO
PRESSURIZATION
SYSTEM

RH ENGINE
421A0001 and ON

Figure 9-20. Turbocharger, Controllers and Waste-Gate Actuator System Schematic (Sheet 4 of 4)
9-48 ENOINE 421 SERVICE MANUAL

'roubleshooting Controllers, Waste-gate Actuator, and Turbocharger

TROUBLE PROBABLE CAUSE CORRECTION

UNABLE TO GET RATED Controller not getting enough oil pres- Check pump outlet pressure, oil filter,
POWER BECAUSE MANI- sure to close the waste-gate. and external lines for obstructions.
FOLD PRESSURE IS LOW
Chips under metering and/or poppet Flush chips out of controller. Re-
valves in controllers holding them place controller if necessary.
open.

Capillary tube in actuator plugged. Remove actuator and clean capillary.

Actuator piston seal failed and leak- Replace actuator,

ing oil excessively.

Leak in exhaust system. Replace defective exhaust components.

ENGINE SURGES OR Metering valve stem seal broken in Replace controller.

SMOKES one of the controllers, leaking oil
into manifold.

Actuator waste-gate linkage binding. Correct cause of binding.

Turbine seal leaking. Replace seal (see Turbocharger and

Controls Overhaul/Parts ManuaL
TURBOCHARGER NOISY, Turbocharger overspeeding, control- Adjust or replace controller assem-
POWER ADEQUATE lers not opening, aneroid bellows blies and turbocharger.
leaking or not properly adjusted.

Waste-gate sticking closed. Replace waste-gate, waste-gate actua-

tor, or correct binding linkage.

ENGINE POWER IN- 421-0001 to 421A0001

CREASES SLOWLY, OR
SEVERE FLUCTUATIONS Controller drain line obstructed. Clean or replace line.
OF MANIFOLD PRESSURE
ON RAPID THROTTLE AD- Capilliary tube plugged in rate of Replace absolute pressure and rate-
VANCE change controller, of-change controller.

Rate-of-change controller out of Calibrate or replace absolute pres-

calibration. sure and rate-of-change controller.

Waste-gate operation is sluggish. Replace waste-gate, waste-gate

actuator or correct binding linkage.

421A0001 and ON

Controller drain line obstructed. Clean or replace line.

Waste-gate operation is sluggish. Replace waste-gate, waste-gate

actuator, or correct binding
linkage.

Manifold Pressure relief valve is Check or replace valve.

popping open too soon.

Change 5
 421 SERVICE MANUAL ENGINE $•48A

TROUBLE PROBABLE CAUSE CORRECTION

ENGINE POWER IN- Allow engine to warm up. Oil temperature low.
CREASES RAPIDLY AND
MANIFOLD PRESSURE 421-0001 to 421A0001
OVERBOOSTS ON RAPID
THROTTLE ADVANCE Rate-of-change controller out of Calibrate or replace absolute pres-
calibration. sure and rate-of-change controller.

Waste-gate operation is sluggish. Replace waste-gate, waste-gate

actuator or correct binding linkage.

421A0001 and ON

Waste-gate operation is sluggish. Replace waste-gate, waste-gate

actuator or correct binding linkage.

Manifold pressure relief valve Check or replace valve.

stuck closed.

MANIFOLD PRESSURE Manifold pressure relief valve Repair or replace relief valve.
OVERBOOSTS DURING stuck closed.
FLIGHT
Waste-gate actuator sluggish. Repair or replace waste-gate.

Waste-gate butterfly clearances Reference Turbocharger and Controls

set improperly. Overhaul/Parts Manual and set butter-
fly valve clearances properly.

SLUGGISH OR LOW Rust deposits in seal ring Soak or spray the area behind
POWER ENGINE area. turbine wheel with *KANO
OPERATION Aerokroil penetrating oil.
*KANO LABORATORY INC.
1000 South Thompson Lane
Nashville, Tennessee 37211

pressure. When at high engine speed and load and senses the compressor outlet pressure in the upper
the proper absolute pressure is reached as deter- chamber and through an internal capillary restrictor
mined by the throttle position, the force on the aner- tube in the lower chamber. When the compressor
oid bellows opens the normally closed metering valve discharge pressure increases more rapidly than
in the controller. When the oil pressure in the actu- approximately 6. 5 inches of mercury per second, a
ator is lowered sufficiently, the actuator open spring pressure differential exists between the upper and
forces the mechanical linkage to open the waste-gate. lower chambers of the diaphragm. As the pressure
A portion of the exhaust gases then bypasses the tur- in the upper chamber becomes greater than that of
bocharger turbine, thus preventing further increase the lower chamber, the diaphragm between the upper
of turbocharger speed and holding the compressor and lower chamber is forced downwards causing the
discharge absolute pressure to the desired value. poppet valve to open and lowers the oil pressure in
Conversely at engine idle, the turbocharger runs the actuator power cylinder causing the waste-gate
slowly with low compressor pressure output; there- to open. This prevents the turbocharger from in-
fore, low pressure applied to aneroid bellows is not creasing at too fast a rate and prevents overboosting
sufficient to affect the unseating of the normally the engine. On 421A0001 and ON, a manifold pres-
closed metering valve. Consequently, engine oil sure relief valve protects the engine from overboost-
pressure keeps the waste-gate closed. On 421-0001 ing by actuating if the intake manifold pressure ex-
to 421A0001 aircraft, a rate-of-change controller ceeds 43. 5 in. Hg.

Change 5
9-488 ENGINE 421 SERVICE MANUAL

07

421B0201 AND ON

VIEW LOOKING AFT AT LH TURBOCHARGER

1. Wrap Button 3. 0. 032 Monel Wire 5. Shield

2. Insulation Blanket 4. Hinge 6. Turbine II

Figure 9-20A. Turbocharger Insulation Installation

TURBOCHARGER INSULATION. d. Lace insulation blankets together with number

0. 032 Monel wire.
On aircraft 421-0001 to 421B0201, the turbocharger
insulation installation consists of three individual NOTE
blankets which are wrapped around the turbocharger
turbine and held in place with Monel wire. Each When lacing, wrap Monel wire tightly around
blanket is made from material which consists of high buttonson the insulation blankets.
temperature insulation sandwiched between two thin
jackets of quilted stainless steeL Small holes are On aircraft 421B0201 and On, the turbocharger is in-
provided on the inside of each blanket to provide the sulated by a shield, the shield consists of two shield
necessary breathing. These blankets, when installed, halves hinged together which are fitted around the
will contain the high temperatures which are.emitted turbocharger turbine and held in place with Monel
by the turbocharger turbine, wire.

Removal and Installation of Turbocharger Insulation Removal and Installation of Turbocharger Shield.
Blankets. (See figure 9-20A.) (See figure 9-20A.)

CAUTION a. Cut safety wire securing the turbocharger shield

in place.
Extreme care should be taken when removing, b. Open shield assembly and remove from turbo-
installing, or working near the turbocharger charger.
blankets to prevent puncturing the stainless c. Install shield assembly by placing the shield
steel jackets. around the turbocharger turbine with the hinge at the
top,
a. Cut and unlace the Monel wire securing the tur- d. Lace the shield halves together on each side with
bocharger insulation blankets in place. 0. 032 Monel wire.
b. Carefully remove the three insulation blankets
from the turbocharger turbine. Checking Turbine Shaft Drag.
c. Install insulation blankets by placing the large
blanket on turbocharger turbine. Position each of Excessive turbine shaft drag can be verified by man-
the two smaller blankets over the large blanket and ually rotating the compressor wheel through the air
turbine. filter opening. This shaft drag is caused by the for-

Change 4
 421 SERVICE MANUAL ENOINE 9-49

mation of rust deposits in the area of the turbine exhaust stack and conduct an engine power check to
shaft piston ring area as a result of water vapor ac- confirm proper turbocharger output.
cumulation. Though not detrimental to the integrity
of the turbocharger, these deposits may momentarily NOTE
restrict or impede rotation of the turbine assembly,
resulting in sluggish or low-power engine operation. The above turbine shaft drag problem con-
Where this condition exists, the turbine shaft can be cerns only formation of rust deposits in new
freed by the method described below. or low-time turbochargers, those in which
combustion product have not yet formed a
a. Remove the overboard exhaust stack and liber- protective coating on seal surfaces. This
ally spray the area behind the turbine wheelwith the problem should not be confused with turbine
following approved or equivalent penetrating oil: shaft binding caused by excessive internal
Kano Aerokroi (Kano Laboratories, 1000 S. coking, which can occur on high-time turbo-
Thompson Lane, Nashville, Tennessee 37211), chargers. Units which are binding after a
b. After a soaking period of not less than 10 min- long time in-service must be removed for
utes, turn the turbine by hand. Lightly tapping the cleaning or replacement. Turbocharger
shaft end with a soft mallet may be required to free coke removal procedures are given in the
the shaft in the most severe cases- Cessna Turbocharger and Controls Overhaul/
c. Once the shaft is free, reinstall the overboard Parts Manual.

CAUTION

The variable absolute pressure and rate-of-change, controllers

are set at the factory and should not be tampered with except for
prescribed minor adjustments to obtain rated manifold pressure.

Removal of Turbocharger. (See Figure 9-19.) pressor air openings to prevent the entry of
foreign materials.
a. Remove air induction filter assembly (9) by re-
moving clamps (8) at air compressor (4 ) and at air
intake duct (10). Installation of Turbocharger. (See Figure 9-19.)
b. Remove coupling (2) which attaches throttle body
to compressor (4), a. Remove covers or seals from turbine and induc-
c. Remove couplings securing tail pipe (12) to tur- tion air openings.
bine outlet and bypass valve assembly. b. Lower turbine-compressor assembly into place
d. Disconnect turbine assembly from bypass valve and install bolts and nuts securing turbine to bracket
assembly by removing four nuts, washers and bolts. (7).
e. Disconnect oil pressure line (6) and oil return c. Install four bolts, washers, and nuts securing
line from turbocharger. turbine to support bracket and waste-gate assembly.
f. Remove two bolts at aft side of turbine assembly
attaching turbine to bracket (7).
NOTE
NOTE
Apply Fel-Pro C-5 or equivalent (Felt Prod-
Cap and plug oil lines and seal turbine-com- ucts Manufacturing Company, Chicago 7,

ENGINE TORQUE VALUES IN POUND INCHES

Engine Mount Bolts 300-350

Turbine Flange Bolts . . . . . . . . . . . .
150-160
Compressor Housing Coupling Bolt . . . . . . . . .
40-60
Turbine to Center Housing Bolts . . . . . . . . .
160-190
Compressor Discharge to Throttle Body Coupling Bolts . . . .
70-75
Turbine Exhaust to Tailpipe Clamp . . . . . . . . . 40
Tailpipe Duct to Waste-gate Assembly . . . . . . .
65-70
Venturi Inlet to Throttle Body Coupling Bolt . . . . . .
45-50
Intercooler Outlet to Riser Coupling Bolt . . . . . . .
45-50
Air Filter to Compressor Inlet Clamp . . . . . . . .
70-75
Exhaust Elbow to Waste-gate Inlet Clamp . . . . . . .
70-90
Exhaust Riser to Cylinder Studs . . . . . . . . .
100-110

Figure 9-21. Engine Torque Values

Change 11
S-6Û ENetNE 421 SERVICE MANUAL

THROTTLE VALVE SHAFT STOP

THROTTLE BODY PIN

THROTTLE LINK

SPRING FORCE OF 8
TO 10 LBS IS ADEQUATE
TO MAINTAIN CONTROLLER
AGAINST HIGH STOP

INCREASE

HIGH PRESSURE
DECREASE SETTING ADJEJSTMENT

LOW PRESSURE /g RATE OF CHANGE

SETTING ADJUSTMENT CONTROLLER
421-0001 TO 421A0001
' INCREASE

LOW PRESSURE SETTING

REFERENCE MARKINGS U

LOCK NUT

CAM NEEDLE BEARING

FLAT BLADED BELLOWS
SCREWDRIVER ASSEMBLY BOOT

INLET PORT

5090002-1 TOOL DRAIN PORT

VARIABLE ABSOLUTE
PRESSURE CONTROLLER

Figure 9-22. Controller Adjustments

 421 SERVICE MANUAL ENSINE 9-50A

5
1

Detail

421A0001 AND ON
AND AIRCRAFT
MODIFIED BY
SK421-22

1. Screw 4. Adapter Pad

2. Relief Valve 5. Washer
3. O-ring

Figure 9-22A. Manifold Pressure Relief Valve

Change 4
9-50 B ENSINE 421 SERVICE MANUAL

Illinois) high temperature anti-seize com- Removal and Installation of Rate of Change Controller.
pound to attaching nuts and bolts when in- (See Figure 9-17.) 421-0001 TO 421A0001
stalling turbocharger to bypass assembly.
a. Disconneet oil line assemblies and discharge air
d. Connect oil pressure line and oil return line to line assembly from controller.
turbocharger.
NOTE
CAUTION
Cap all lines and fittings to prevent entry of
If oil inlet adapter was removed, do not over- foreign materials.
torque inlet fitting or adapter mounting bolts
on installation. b. Remove two nuts and bolts attaching controller to
mounting bracket.
e. Install tailpipe and secure with couplings at tur-
bine and waste-gate assembly, Rate of Change Controller Adjustment. (See figure
f. Install air filter and secure with clamp (8) at 9-22.) 421-0001 TO 421A0001
turbine.
a. Remove rate of change controller in accordance
NOTE with removal procedures.
b. Remove ambient air plug from low pressure port.
For bolt torque and coupling torque values Remove oil line assembly from drain port.
see figure 9-2L

Change 10
 421 SERVICE MANUAL EN61NE 9- O

c. Insert tool 5090002-1 into drain port. Insert NOTE

small bladed screwdriver into low pressure port.
Rotate poppet assembly until screwdriver blade en- The above settings must be carried out with
gages slot provided in bellows assembly boot. the throttle lever in contact with the quadrant
d. Holding bellows assembly boot, rotate poppet as- full open stop against the cushion force.
sembly (1/16th of one full turn changes manifold pres-
sure 1 inch Hg.), clockwise to increase, counter-
clockwise to decrease. High Pressure Settings.
e. Install ambient air plug and oil line assembly.
f. Install rate of change controller and connect a. After adequate engine-warm up with oil tempera-
lines. ture at upper third of green arc, accelerate the en-
g. Install engine cowling in accordance with instal. gine gradually to maximum RPM. Manifold pressure
lation procedures. at maximum RPM should be 39. 5 ±. 5 in. Hg.
h. Check operation in accordance with controller
operation flight check procedures. CAUTION

Discontinue acceleration if manifold pres-

Removal and Installation of Variable Absolute Pres- sure exceeds 40. O in. Hg.
sure Controller. (See Figure 9-20.)
a. Remove engine cowling in accordance with re- b. If maximum manifold pressure does not conform
moval procedures. with the limits defined above, reduce power to idle
b. Disconnect oil line assemblies. and loosen the high setting screw lock nut. Hold the
c. Disconnect throttle link at throttle lever. screw while loosening the lock nut to prevent change
d. Remove screws securing controller to throttle of setting.
body and lift of controller out. c. When adjusting, the fork and pin arrangement
e. Install controller by reversing removal proce- should be turned in the direction of the markings
dures. stamped at the edge of the cam arm, UP to increase
manifold pressure and DN to decrease manifold pres-
NOTE sure. Approximately one turn of the adjusting screw
should provide a 1-inch Hg. variation of manifold
If controller is being replaced, use existing pressure.
fittings with new packings. The use of Teflon d. Repeat adjustments as required to obtain a set-
tape is permissible on all controller fittings ting within the limits specified in step "c" with the
to provide sealing. high setting screw lock nut properly tightened. Shut
down engine.

Variable Absolute Pressure Controller Adjustment.

Low Pressure Setting.
The variable absolute pressure controller may be ad-
justed as much as 2" Hg. increase or decrease in the a. Align the index marks on the side of the cam arm
high pressure setting by the following procedure and and edge of cast bearing support by moving the engine
not change the low stop setting more than 1" Hg. from throttle lever. Tighten the control quadrant friction
its nominal setting while maintaining the 30 ± 2° knob to prevent control movement.
alpha angle. b. Loosen the low pressure setting screw lock nut
and adjust the screw so that the cam needle bearing
NOTE just starts to contact the cam follower. This can
best be determined by rotating the needle bearing
The alpha angle is the degree of travel of the with the fingers to detect the point of initial drag.
cam starting with the cam arm against the Tighten the low setting screw lock nut.
the high setting stop pin to where cam dis-
engages the cam follower.
Low Pressure Setting and Cam Angle Verification
Procedure,
a. Remove engine cowling in accordance with re-
moval procedures. In order to establish an adequate low pressure adjust-
b. (See figure 9-22. ) Adjust linkage as follows: ment, the following concurrent ground and flight tests
1. Make sure controller mounting screw , fittings must be conducted.
and lines are torqued properly.
2. With the corresponding throttle lever against a. Ground Test.
the full open cushion force, verify that the throttle After completion of the adjustment defined by the
valve shaft stop rests solidly against the pin on the high pressure setting and low pressure setting, con-
throttle body. nect a standard dual manifold pressure gauge to the
3. The throttle linkage adjustment nut must be ad- test ports provided at the corresponding compressor
justed to provide a clearance of 015 to 025 between
. . discharge connections of the fuel flow gauge. This
the nut and the link rod end with the cam arm in solid test gauge provides compressor discharge pressure
contact against the high setting controller stop. readings required on the following verification tests:
9-52 ENOINE 421 SERVICE MANUAL

1. Start the engine and after adequate warm up, ad- Installation of Waste-gate and Actuator,
just the propeller control to maintain a constant 1800
RPM during the following verification. a. Before installation of waste-gate and a actuator
2. With the manifold pressure setting at 29. O inch·- assembly check adjustments in accordance with ad-
es Hg. the compressor discharge pressure should justment procedures.
read 31. 3 ±. 6 inches Hg. b. Attach waste-gate assembly to turbine with four
3. With the manifold pressure setting at 26. O inch- bolts, washers and nuts.
es Hg. the compressor discharge pressure should
read 30. 7 ±. 6 inches Hg.. NOTE

NOTE Install new gaskets between waste-gate,

support and turbine. Apply Fel-Pro C-5 or
To attain the above manifold pressure settings equivalent on all bolts in extreme high heat
it will be necessary to adjust the throttle con- area.
trol along with the propeller control.
c. Install tailpipe and bypass duct and secure with
4. (See figure 9-22. ) To increase compressor dis- couplings. Torque couplings to values shown in fig-
charge pressure loosen the low pressure setting ure 9-21.
screw lock nut and turn screw clockwise as shown. d. Connect exhaust elbow to waste-gate with coup-
To decrease compressor discharge pressure, the ling. See torque chart figure 9-21.
reverse process should be adopted. Tighten lock e. Connect actuator drain line.
nut holding adjusting screw stationary after adjust- f. Connect oil inlet and oil outlet lines to actuator.
ment. g. Install upper cowl.
b. Flight Check. _
h. Start engine in accordance with operational pro-
1. The dual pressure test gauge must be connected cedure to check for oil leaks and proper operation,
to the right hand and left hand compressor discharge
pressure connections at the fuel flow gauge test ports Adjustment of Waste-gate and Actuator.
during the flight tests.
2. Flight verification for the low pressure adjust- a. See Turbocharger and Controls Overhaul/Parts
ment to be conducted at a pressure altitude of 12, 000 Manual.
feet and at 1950 RPM. Adjust the throttle to a mani-
fold pressure of 23. O inches Hg. and the correspond-
ing compressor discharge pressure should be 31. O Turbocharger Operational Flight Check Procedure.
±. 3 inches Hg.
3. After low setting flight verification is complete, The flight check procedure details the method of
remove compressor discharge pressure test gauge checking the turbocharger, variable absolute pres-
and reinstall caps. sure and rate-of-change controllers. This procedure
is to be used for aircraft suspected of improper
turbocharger operation in order for the discrepancy
Waste-gate and Actuator,
to be correctly diagnosed. To aid in recording the
necessary flight readings, a sample form, as shown
Removal of waste-gate and Actuator.
in figure 9-24, is provided. This sample form, or
one with similar content, should be used in conjunc-
NOTE
tion with the flight check procedure. To determine
at which conditions bootstrapping is most likely to
The waste-gate and actuator are considered
occur, refer to the Bootstrapping Tolerance Chart in
as a matched set and must be removed and
figure 9-23.
replaced as sets.

a. Remove upper cowl in accordance with removal TAKEOFF VARIABLE ABSOLUTE CONTROL-
1. -

procedures. LER
b. (See Figure 9-17.) Disconnect actuator drain a. Cowl flaps open (421-0001 to 421B0001)
-

line. b. Airspeed 120 MPH IAS

-

c. Disconnect oil inlet and oil outlet lines from ac- c. Oil temperature upper 1/3 of green are
-

tuator and plug open lines. d. RPM -

2275 ±25 RPM
d. Remove three bolts securing waste-gate to con- e. Fuel flow full rich -

troller bracket. f. Full throttle M. P. 39. 5 ±5 in. Hg. -

e. Remove four nuts, washers and bolts securing 2. CLIMB- VARIABLE ABSOLUTE CONTROLLER
waste-gate to turbocharger. a. Cowl flaps open (421-0001 to 421BOOO1)
-

f. Remove couplings from waste-gate valve to ex- b. Airspeed 120 MPH IAS
-

haust tailpipe and from exhaust elbow to waste-gate. c. Pressure altitude 16, 000 ft. -

g. Remove the waste-gate and actuator combina- d. RPM 2275 ±25 RPM
-

tion from the aircraft.

Change 10
 421 SERVICE MANUAL ENGINE 9-53

24

IN THIS AREA
ANYGIVEN ENGINE
MAYOR MAYNOT
BOOTSTRAP
22

ALL ENGINES SHOULD NO ENGI¾E

20 BOOTSTRAPIN THIS SHOULD
AREA -
BOOTSTRAP
IN THIS AREA

18

16

30 40 50 60 70 80
ENGINE POWER %BHP -

421-0001 TO 421B0001

au
3û" HG. MANIFOLD PRESSURE
2200 RP 23,000 FEET PRESSUREALTITUDE
2100 ppg
2000 RPR
70
i900 ppy
WIS

60
1800 RPM-

1700 Rpg

50 -

1600 Rpg-.
1500 Rpg

-40 -20
0 20 40
TEMPERATURE °F -

(OAT GAGEAT 140 KNOTS)

51986002
421B0001 AND ON 51986003

Figure 9-23. Bootstrapping Tolerance Chart

Change 10
9-54 ENGINE 421 SERVICE MANUAL

e. Fuel flow -
full rich 6. CRUISE -
BOOTSTRAPPING DETERMINATION
f. Full throttle M. P. in. Hg. -
39. 5 ±5 (421B0001 and ON. )
3. CRUISE - RATE-OF-CHANGE CONTROLLER a. Airspeed level flight
-

a. Cowl flaps closed (421-0001 to 421B0001) -

b. Pressure altitude 23, 000 ft.
b. Airspeed level flight -
c. RPM -
2200 RPM
c. Pressure altitude 16, 000 ft. -
d. Fuel flow lean -

5°
d. RPM 2275 ±
-
RPM e. Throttle 30 in. Hg.
-

e. Fuel flow full rich -

f. Prop control (one engine at a time)
f. Throttle (one engine at a time) (1) Slowly decrease RPM until M. P. drop
(1) Idle until M. P. stabilizes indicates waste-gate is closed
(2) Rapidly advance to full throttle (2) The M. P. RPM, and OAT at the in-
(3) Obtain time for M. P. to increase stant of waste-gate closing should be
from 20 to 30 in. Hg. recorded
(a) Should require between 1. 25 and (3) The actual power being developed
2 seconds (5 to 8 in. Hg. /sec.) should be less than 60/o power
g. RPM increase
-
50 RPM
4. CRUISE MANIFOLD PRESSURE RELIEF
-
h. Mixture normal
-
lean
VALVE (421A0001 and ON. ) i. Engine should not bootstrap

5. CRUISE BOOTSTRAPPING
-
DETERMINATION MANIFOLD PRESSURE RELIEF VALVE.
(421-0001 to
421B0001)
a. Cowl flaps closed -
A manifold pressure relief valve, mounted on the
b. Airspeed level flight -

venturi adapter plate, is provided on aircraft 421A-

c. Pressure altitude 20, 000 ft. -

0001 and ON to prevent engine damage from exces-

d. RPM 2100 RPM
-
sive intake manifold pressure. The non-adjustable
e. Fuel flow lean -
manifold pressure relief valve will be actuated if the
f. Throttle 26 in. Hg. -

manifold pressure exceeds 43. 5 in. Hg.

g. Prop control (one engine at a time)
(1) Slowly decrease RPM until M. P. drop Removal and Installation of Manifold Pressure Relief
indicates waste-gate is closed Valve. (See figure 9-22A.) 421A0001 and ON
(2) The M. P. , RPM, OAT, and Hp at the
instant of waste-gate closing should be Removal and installation procedures of the manifold
recorded pressure relief valve is the same on either engine.
(3) The actual power being developed a. (See figure 9-1.) Remove engine cowling in
should be less than 60°/o power accordance with removal procedure.
h. RPM Increase 50 RPM
-
b. Remove screws (1) and washers (5) attaching
i. Mixture normal lean
-

manifold pressure relief valve (2) to venturi adapter

j. Engine should not boot-strap pad (4) and remove manifold pressure relief valve
with O-ring (3).
c. Install manifold pressure relief valve by revers-
ing removal procedure.

CAUTION

Be sure that G-ring remains in groove on

relief valve when installing to adapter plate.

Change 10
 421 SERVICE MANUAL EN61NE 9-55/9-56

6 LEVEL OFF 20, 000 FT

COWL FLAPS CLOSED -

1. Perform Controller Operation Flight Check
421-0001 to 421B0001 Procedure step 4.

5 CLIMB 20, 000 FT ..

SET THROTTLE
MAX RPM
MIXTURE-LEAN
READINGS AT 20,000 FT. OAT
(COWL FLAPS-OPEN \
421-0001 TO 421B0001 |
M.P. Number 1 In. RPM Number 1 Fuel Flow Gal/Hr
CLIMB SPEED-120 MPH IAS
M. P. Number 2 In. RPM Number 2 Fuel Flow Gal/Hr
CAUTION
SEE MP OPERATIONS
LIMITATIONS PLACARD

4 CLIMB 16, 000 FT .. 1. Observe manifold pressure at approx. 16,000 ft.

II 39. 5 t0. 5 in. Hg. is available, absolute 421-0001 TO
M. P. 39. 5 ±0. 5 IN. HG. pressure controller is functioning properly•
421A0001
FULL RPM 2. If 39. 5 ±0. 5 in. Hg. is not available, perform
MIXTURE -
RICH Controller Operation Flight Check, step 3.
(COWL FLAPS OPEN -

3. Observe manifold pressure at 16, 000 ft. If

421-0001 TO 421BOOO1/ 39. 5 ±0. 5 in. Hg. is available, absolute pres-
CLIMB SPEED 120 MPH -

sure controller is functioning properly.

421A0001 AND ON
IAS 4. If 39. 5 ±0. 5 in. Hg. is not available, the man-
ifold pressure relief valve is popping open too
soon.
READINGS AT 16, 000 FT. OAT

3 CLIMB 14, 000 FT. -- M. P. Number 1 In. RPM Number 1 Fuel Flow Gal/Hr
M. P. Number 2 In. RPM Number 2 Fuel Flow Gal/Hr
M. P. 32. 5 ±. 5 IN. HG.
RPM 2100
MIXTURE RICH -

READINGS AT 14, 000 FT. OAT

(COWL FLAPS
421-0001
OPEN -

\ Fuel
TO 421B0001) M. P. Number 1 In. RPM Number 1 Flow Gal/Hr
CLIMB SPEED 120 MPH -

, M.P. Number 2 In. RPM Number 2 Fuel Flow Gal/Hr

IAS
1. Observe and record altitude where ALTITUDE READINGS AT
manifold pressure (M. P.) falls off. M. P. FA LL OFF
If altitude is unusually low (below
8,000 or 9,000 ft. on a hot day) Altutide Number 1 Ft
2 TAKEOFF suspect exhaust system leak. Altitude Number 2 Ft

M. P. 39. 5 t0. 5 IN. HG.

FULL RPM
MIXTURE RICH
-

OIL TEMPERATURE UPPER - 1/3 GREEN ARC

READINGS AT TAKEOFF OAT

M. P. Number 1 In. RPM Number 1 Fuel Flow Gal/Hr

M. P. Number 2 In, RPM Number 2 Fuel Flow Gal/Hr

] SET ALTIMETER

29. 92 IN. HG

Figure 9-24. Turbocharger System Operational Check Chart

Change 10
 421 SERVICE MANUAL PROPELLER SYSTEM 10-1

SECTION 10

PROPELLER SYSTEM

Table of Contents

Page Page

PROPELLER - . . . . . .
10-1 PROPELLER GOVERNOR . . . .
10-6
Troubleshooting . . . . . .
10-1 Removal . . . . . . .
10-6
Removal . . . . . . .
10-3 Installation . . . . . . .
10-9
Installation . . . . . . .
10-5 Rigging Propeller Governor Controls .
10-9
Operational Check of Propellers . .
10-5

PROPELLER. pump, and supplied to the propeller hub through en-

gine shaft flange. When the engine is not in opera-
The Model 421 is equipped with all metal, three tion, the high pitch latch mechanism prevents the
bladed, constant-speed, full-feathering, single- propeller blades from moving into the feathered posi-
acting, and governor regulated propellers. Each tion. To feather the propeller blades, the propeller
propeller utilizes hydraulic pressure which opposes control levers on the control pedestal must be placed
the forces of springs and counterweights to obtain in the feathered position. Unfeathering the propeller
the correct pitch for engine load. Hydraulic pres- is accomplished by positioning the propeller control
sure from the engine-mounted governor urges blades levers to increase rpm position and rotating the
toward low pitch (increasing rpm) while the springs blades to the low pitch position, or by starting the
and counterweights urge blades toward high pitch (de- engines. If installed, the optional unfeathering sys-
creasing rpm). The source of hydraulic pressure tem uses accumulator air and oil to force the pro-
for propeller operation is furnished by the engine oil peller to the low pitch condition.
system, boosted in pressure by the governor gear

Troubleshooting the Propellers.

TROUBLE PROBABLE CAUSE CORRECTION

PROPELLER DOES NOT Control linkage disconnected. Check visually, connect or replace
RESPOND TO MOVE- control linkage.
MENT OF PROPELLER
PITCH LEVER OR FAILS Governor not correct for propeller, Check that correct governor is
TO CHANGE PITCH installed.

Governor speeder spring broken. Overhaul or replace governor.

Screen in governor mounting gasket Remove governor and replace gasket.

clogged.

Governor drive shaft sheared. Overhaul or replace governor.

Defective pitch changing mechanism Check propeller manually, repair or

or excessive blade friction, replace parts as required.

Change 12
10-2 PROPELLER SYSTEM 421 SERVICE MANUAL

TROUBLE PROBABLE CAUSE CORRECTION

FAILURE TO CHANGE Improper rigging of governor control. Check that arm on governor has full
PITCH FULLY travel and rig correctly.

Defective governor. Overhaul or replace governor.

SLUGGISH PROPELLER Excessive propeller blade friction. Overhaul propeller.

MOVEMENT TO EITHER
HIGH OR LOW PITCH

ENGINE SPEED WILL Governor relief valve sticking. Overhaul or replace governor.
NOT STABILIZE
Excessive clearance in pilot valve, Overhaul or replace governor.

Air trapped in propeller actuating Trapped air should be purged by ex-

cylinder. ercising the propeller several times
prior to takeoff, after the propeller
has been reinstalled or has been
idle for an extended period.

Excessive friction in pitch chang- Check propeller manually, repair or

ing mechanism or excessive blade replace parts as required.
friction.

Excessive governor oil pump clear- Overhaul or replace governor.

ance.

EXCESSIVE RPM Sludge in governor. Remove and clean governor. Drain

CHANGES WITH AIR- engine oil, clean oil filter, service
SPEED OR POWER engine with new oil.
CHANGES

FAILURE OF PRO- Improper rigging of governor Refer to Operational Check of Pro-

PELLER TO GO TO control system. pellers.
FULL LOW PITCH
(HIGH RPM) Governor arm reaches stop be- Adjust in accordance with Operational
fore maximum RPM is obtained. Check of Propellers.

Defective governor. Overþaul or replace governor.

STATIC RPM TOO HIGH Incorrect propeller or incorrect Install correct propeller, with cor-
low pitch blade angle. rect blade angle.

STATIC RPM TOO LOW Governor high RPM stop set too low. See Note 1 at the end of this chart and
rig.

Defective governor. See Note 2 at the end of this chart.

Incorrect propeller or incorrect Install correct propeller with cor-

low pitch blade angle, rect blade angle.

PROPELLER FEATHERS Latching mechanism does not engage. Due to unusual circumstances, a pro-
DURING ENGINE SHUT- peller may occasionally feather during
DOWN engine shutdown. If this occurs re-
peatedly, the latching mechanism is
defective. Propeller repair or re-
placement is required.

FAILURE TO FEATHER Defective governor. See Note 2 at the end of this chart.

Defective pitch changing mechan- Check propeller manually, repair or

ism or excessive blade friction. replace parts as required.

Change 12
 421 SERVICE MANUAL PROPELLER SYSTEM lÛ=

TROUBLE PROBABLE CAUSE CORRECTION

FAILURE TO FEATHER Incorrect rigging of governor con- Check that arm on governor has full
(CONTINUED) trol. travel and rig.

Defective latching mechanism in- Propeller repair or replacement is

side propeller. required.

Attempting to feather from too Increase RPM and attempt to feather

low an engine RPM. again. (See feathering procedures.)

Feathering spring weak or Overhaul propeller.

broken.

OIL LEAKAGE AT Damaged O-ring seal between Check visually for oil leakage and re-
MOUNTING FLANGE engine and propeller. place O-ring seal.

Foreign material between engine Check visually for oil leakage and
and propeller mating surfaces or clean propeller and engine mating
nuts not tight, and tighten nuts properly.

OIL OR GREASE Defective seals, gaskets, etc., Check visually for oil or grease
LEAKAGE AT ANY or incorrect assembly. leakage, repair or replace propeller
OTHER PLACE as required.

NOTE 1. It is possible for either the propeller low pitch (high RPM) stop or the governor high RPM
stop to be the high RPM limiting factor. It is desirable for the governor stop to limit the
high RPM at the maximum rated RPM. Due to climatic conditions, field elevation, low
pitch blade angle, and other considerations, an engine should not reach rated RPM on the
ground. It may be necessary to readjust the governor stop after test flying to obtain maxi-
mum rated RPM when airborne.

NOTE 2. When trouble shooting a propeller-governor combination, it is recommended that a governor

known to be in good condition be installed to check whether the propeller or the governor is
at fault. Removal and replacement, high-speed stop adjustment, desludging, and replace-
ment of the mounting gasket are not major repairs and may be accomplished in the field.
Repairs to governors-are classed as propeller major repairs in Federal Aviation Regulations,
which also defines who may accomplish such repairs.

Removal of Propellers. (See Figure 10-1.) fails to feather at idling (470 RPM), increase
the RPM slightly and attempt to feather again.
The removal procedure is the same for either pro-
If the Optional Unfeathering System is Installed:
peller. It is not necessary to feather the propeller
1. After the propeller has been feathered and the
for removal or installation but if blade angles are to
engine shutdown, move the propeller control out of
be changed, which would require removal of the dome'
FEATHER position until blades start to unfeather
it is then necessary to feather the propeller. Blade
then quickly pull the control back into FEATHER.
angles may be changed without removing the propel- the pressure
This procedure is known as "milking"
ler.
out of the unfeathering system. This procedure
should be continued until the propeller will no longer
a. Feather the propeller by thefollowing procedure:
15 to 20 movements of the
Check- move, which may require
1. Start engine in accordance with "Pilot's
propeller control.
list " blades to rotate
2. Do not allow propeller far
2. engine at normal
Operate idle (470 RPM).
enough to let high-pitch latches engage or engine
3.Place propeller pitch lever in the FEATHER
must be restarted, propeller feathered again, and
position and at the same time place the mixture lever
CUT-OFF the procedure repeated.
in the IDLE position,
b. Remove the nose cap cowling and spinner.
c. Remove the six attaching nuts securing propeller
CAUTION
to crankshaft mounting flange. On aircraft 421B0376
and On, remove eight nuts and eight spacers. Retain
Do not feather from a high RPM as this will
spacers for installation.
cause excessive manifold pressure and pos-
d. Remove propeller from engine crankshaft.
sible damage to the engine. If the propeller
e. If optional propeller deice system is installed,
Change 12
10-4 PROPELLER SYSTEM 421 SERVICE MANUAL

13
12
10
6

421B0376 AND ON

11
5

8 1
421B0001 TO 421B0376

421-0001 TO 421BOOO1 9

PART NUMBER

SPINNER SCREWS BLADE ANGLES

TORQUETO40-45IN. LB. (16.9°ÌO.2°
LOW
FEATHER
84-5°ì 0 3°
PROPELLER MOUNTING NUTS
TORQUE TO 80 85 FT. LBS. -
APPROVED FOR CESSNA
AIRCRAFT MODEL NUMBER(S)
"O" RING FURNISHED
WITH PROPELLER 421

PROPELLER Detail 51502003

ASSY. A51501004
14502004

1. Spinner 4. Cylinder 8. Screw 12. Crankshaft

2. Support 5. Propeller 9. Washer 13. A-4472
3. Shim 6. Bulkhead 10. Adapter Spacer
7. Nut 11. O-Ring

Figure 10-1. Propeller Installation

Change 12
 421 SERVICE MANUAL PROPELLER SYSTEM Û¯$

remove wiring at terminal block then remove the NOTE

slip rings and spinner bulkhead from propeller hub.
Insure that all washers are reinstalled pro-
perly. Slip rings should run in a true plane
NOTE relative to brush block. Total deviation not
to exceed . 005 true indicator reading, with
Refer to McCauley Service/Parts Manual no more than 002 deviation within any 4. 00
.

for maintenance, overhaul and repair of inch interval. Approximately, 012 inch ad-
.

propeller. justment may be made by varying torque on

attach bolts (maintain as near 65 inch-pounds
as possible). Shims may be used between
Installation of Propeller. (See figure 10-1.)
slip ring and spinner bulkhead under mount-
ing bolts.
The installation procedure is the same for either
propeller.
a. Position spinner bulkhead over propeller hub 7. Reinstall propeller.
attach studs. h. Install spinner: (See figure 10-1.)
b. Wipe all dust and foreign particles from the pro- 1. Install shims (3) and support (2).
peller hub flange, the propeller hub oil passage, the 2. Lightly press spinner (1) to hold snug against
crankshaft flange and the crankshaft oil passage with support and check alignment of spinner holes with
a clean cloth, bulkhead (6).
c. Install or check "O"-ring seal in the propeller 3. Alignment lack of 3/64 is approximate fit: add
hub and lubricate lightly with engine oil. or remove shims to produce this condition.
d. Position propeller and spinner bulkhead on the 4. Pushing hard on the shell, install screws (8)
crankshaft, and washers (9). Remove shims, if necessary, until
e. Secure propeller to crankshaft with six new nuts. just possible to install screws.
On aircraft 421BO376 and On, secure propeller to i. Replace nose cap cowling and check propeller
crankshaft with eight A-4472 spacers and eight new for operation in accordance with the operational
elastic element locknuts. check procedure.
WARNING

Do not use all steel locknuts. Use only new Operational Check of Propellers.
elastic element locknuts when installing pro-
peller. Anytime the propellers or propeller governors have
been removed, the following check should be perfor-
f. Torque nuts to 80 to 85 foot-pounds. med after reinstallation, this will insure that the
g. (See figure 10-2.) On McCauley "K" series engine-propeller-governor combination is in good
propellers (421-0001 to 421BOOO1), if optional deice operating adjustment and will give maximum perfor-
system is installed, check for interference between mance.
propeller hub (8) and deice slip ring mounting bolts a. Start engines and perform normal ground runup.
(7). If clearance is not sufficient (0. 001 inches),
proceed with the following steps: CAUTION
1. Remove propeller.
2. Remove bolts (7), one at a time to eliminate Avoid running up engines where loose stones
aligning of holes of spinner bulkhead (1), spacer (2), or cinders can be sucked up by inflow of air
and slip ring (3). and damage the propeller blades.
3. Grind the head of each bolt (7), as shown in
Section A-A of figure 10-2, to assure positive
clearance of (. 001 shim or cigarette paper) between b. Check tachometer indication during power check.
head of bolt and the hub forging (8) of the propeller Static RPM should be approximately 2225 RPM.
when the propeller is fully torqued in place. 1. If static RPM is too high, reduce by adjusting
4. Blend out any nicks or gouges in propeller hub governor stop screw (12). Turn clockwise one revo-
caused by bolt interference. lution for each 17 RPM decrease. This reduction
5. Paint chamfered metal of bolt heads and propel- prevents possible overspeeding at takeoff.
ler hub using zine chromate primer (MIL-P-8585) 2. If static RPM is too low, it is possible that
for corrosion protection. either the governor stop or the propeller low pitch
6, Secure locknuts (6) on bolts (7) making sure stop is the limiting factor. Increase the engine RPM
that ground side of head of bolts are positioned to- and move the propeller pitch lever back and forth,
ward the hub forging of the propeller. If the maximum obtainable RPM is reached at the
same time as the governor stop is reached, the gov-
NOTE

(See figure 13-30. ) Replace star lockwasher

(16) and locknuts (21) when making reinstalla-
tion.

Change 12
10-8 PROPELLER SYSTEM 421 SERVICE MANUAL

ernor is the limiting factor. Correct by adjusting PROPELLER GOVERNORS.

the governor stop screw (12). Turn counterclockwise
one revolution for each 17 RPM increase. If the One base-mounted, centrifugal, single-acting gover-
maximum obtainable RPM is reached before the gov- nor is installed on each engine to control propeller
ernor stop is reached, the propeller low pitch stop pitch. The governors are engine-driven and are
is the limiting factor. This would require an ad- mounted on the left side of each crankcase just be-
justment of the propeller blades to decrease the low low and forward of the most forward cylinder. A
pitch angle. This adjustment should be made only by gear type pump and relief valve are incorporated in
an authorized propeller overhaul station, each governor to boost engine oil pressure to the
pressure required to actuate the propeller piston,
CAUTION (approximately 275 psi). Internal flyweights are at-
tached to the pilot valve which directs high pressure
Do not allow engine temperatures to exceed oil to the propeller piston or allows oil to drain from
operating limits while these checks are the piston. Pitch changing links connect the propeller
being performed. piston to the propeller blades. The position of the
NOTE piston determines the propeller blade angle which is
either increased or decreased by the governor as
To avoid propeller surging on takeoff, it is flight conditions vary, to maintain a constant RPM.
desirable for the governor stop to limit the
high static RPM, with the propeller stop
reached at 50 to 100 RPM beyond. ·

Removal of Propeller Governors. (See figure 10-3. )

3. Anytime the propeller attachment has been sub- The removal procedure is the same for either pro-
jected to excessive engine roughness the propeller pener governor,
should be removed and the dowel pin inspected for a. Remove the engine cowling,
looseness, cracks, and visual damage as part of the
Rough Engine Operation Inspection defined in Sec-
tion 9.

Change 12
 421 SERVICE MANUAL PROPELLER SYSTEM 1Û"I

FWD

i
6
(.001) POSITIVE
CLEARANCE

Detail Å
GRIND HEAD OF AN4 BOLTS THAT
SECURE DEICE SLIP RING TO SPINNER
BULKHEAD AS REQUIRED TO ASSURE
POSITIVE CLEARANCE (. 001 SHIM OR
CIGARETTE PAPER) AT EACH LOCA-
TION BETWEEN HEADS OF BOLTS AND
'
THE HUB FORGING OF THE PROPELLER,
421-0001 TO 421B0001 WITH THE PROPELLER FULLY TORQUED A-A
VIEW
IN PLACE.

1. Spinner Bulkhead 3. Deice Slip Ring 5. Nut 7. Bolt

2. Spacer Ring 4. Deice Brush Block 6. Locknut 8. Propeller Hub

Figure 10-2. Checking of Propeller Hub Clearance

Change 12
lÛ-8 PROPELLER SYSTEM 421 SERVICE MANUAL

10

Detail

54551001
A10551007

1. Plug 5. Control Arm 10. Control Cable

2. Nut 6. High RPM Stop 11. Bolt
3. Screw Adjustment 7. Spacer 12. Locknut
4. Feather Stop 8. Rod End 13. Washer
9. Locknut

Figure 10-3. Propeller Governor

Change 12
 421 SERVICE MANUAL PROPELLER SYSTEM ÎÛ¯$ ÍÎÛ"lÛ

b. Remove the left forward engine baffle and heat unfeathering system is installed.
shield. e. Rig the propeller governor in accordance with
c. Disconnect propeller control from governor the propeller governor rigging procedure.
I control arm.
d. If optional unfeathering system is installed, dis-
f. Replace
baffle.
governor heat shield and forward engine

connect the accumulator hose from the governor. g. Replace the engine cowling and make Operational
Check as described in Operational Check of Propel-
CAUTION lers.

Make sure all pressure is removed from the Rigging of Propeller Governor Control.
accumulator before disconnecting hose. Re-
fer to alternate unfeathering method* a. Disconnect the propeller control at the propeller
governor arm.
e. Remove governor and mounting gasket by remov-
ing the four nuts, lockwashers, and plain washers, b. Place propellerpitch lever in the control pedes-
tal in the FULL INCREASE RPM position against the
forward stop. Retard the lever approximately 1/4
Installation of Propeller Governor. (See figure inch from stop and lock lever in this position by
10-3. ) tightening the friction knob on the control quadrant.
c. Place governor arm with the full forward posi-
a. Place the mounting gasket over the governor tion against the stop (FULL INCREASE RPM).
mount studs with the raised surface of gasket screen d. Loosen locknut on propeller control and adjust
facing away from the engine. the position of the control rod end by s.crewing in or
out until the bolt can be inserted through the rod end
NOTE and governor arm without binding.

Do not use sealing compound of any kind on

the mounting gasket. NOTE

b. Align the splines on the governor shaft with the Do not allow propeller pitch lever or propel-
engine drive and slide the governor into position. ler governor arm to move from position dur-
c. Secure the governor in place with the four plain ing adjustment of the control rod end.

I washers, lockwashers
mount studs.
d. Connect accumulator
system
and nuts on the governor

hose to governor if optional

e. Install the bolt, washer,
spacer
en nut then tighten locknut.
spacer and nut with
between the rod end and governor arm. Tight-
unfeathering is installed.
f. Unlock propeller pitch lever in the control pedes-
taL Move the pitch lever to the FEATHER position
(full aft). Check to see that the propeller governor
arm is against its stop in the full aft position. With
the governor arm against either stop, the pitch lever
should be approximately 1/4 inch from the quadrant
stop. This unused travel provides the necessary
cushion to assure full travel of the governor arm.

Change 12
 412 SERVICE MANUAL FUEL SYSTEM ÎÎ"1

SECTION 11

FUEL SYSTEM
Table of Contents

Page Page

FUEL SYSTEM . . . . . . .
11-1 Installation of Fuel Quantity Sending Units -

Troubleshooting . . . . . .
11-2B Main Tank (421-0001 to 421B0001) .
11-9
MAIN TANKS . . . . . . .
11-4 Fue1Quantity Sending Units Operational
Removal . . . . . . .
11-4 Check (421-0001 to 421B0001) . .
11-9
Disassembly . . . . . .
11-4 Removal of Outboard, Auxiliary and
Inspection and Repair . . . .
11-4 Inboard Fuel Cell Tank Units
Assembly . . . . . . .
11-4 (421B0001 and On) . .
. .
11-9
Installation . . . . . .
11-6 Installation of Outboard, Auxiliai'y and
SNIFFLE VALVE . . . . . .
11-6 Inboard Fuel Cell Tank Units
Removal . . . . . . .
11-6 (421B0001 and On) . . . .
11-9
Installation . . . . . . .
11-6 Removal of Main Fuel Tank Unit
MAIN TANK FUEL TRANSFER PUMP .
11-6 (421BOOO1 and On) . . . .
11-9
Removal . . . . . . .
11-6 Installation of Main Fuel Tank Unit
Disassembly . . . . . .
11-6 (421B0001 and On) . . . .
11-14
Cleaning and Inspection . . . .
11-6 Removal and Installation of Signal
Assembly . . . . . . .
11-6A Conditioner (421BOOO1 and On) . .
11-14
Installation . . . . . . .
11-6A Removal of Auxiliary Fuel Quantity
AUXILIARY FUEL PUMP . . . .
11-7 Tank Units (421BOOO1 and On) . .
11-14
Removal . . . . . . .
11-7 Installation of Auxiliary Fuel Quantity
Installation . . . . . . .
11-7 Tank Units (421B0001 and On) . .
11-14
Auxiliary Fuel Pump Low Adjustment .
11-7 Fuel Quantity System Calibration . .
11-14
AUXILIARY WING CELLS . . . .
11-8 Dry Calibration . . . . . .
11-14
Removal . . . . . . .
11-8 Alternate Method . . . . .
11-16
Inspection and Repair . . . .
11-8 FUEL LINES AND VENTS . . . .
11-16B
Installation . . . . . . .
11-8 Removal of Fuel Lines . . . .
11-16B
AUXILIARY TANK IN-LINE FUEL PUMP .
11-8 Installation of Fuel Lines . . . .
11-16B
Removal of Auxiliary Tank In-Line Fuel WING LOCKER FUEL (Optional) . . .
11-16B
Pump . . . . . . .
11-8 Troubleshooting . . . . . .
11-16D
Installation of Auxiliary Tank In-Line Removal . . . . . . .
11-16D
Fuel Pump . . . . . .
11-8A Installation . . . . . . .
11-16D
Removal of Auxiliary Tank In-Line Fuel Removal of Wing Locker Fuel
Pump Filter . . . . . .
11-8A Plumbing . . . . . .
11-16D
Cleaning and Inspection of Auxiliary Tank Installation of Wing Locker Fuel
In-Line Fuel Pump Filter . . .
11-8A Plumbing . . . . . .
11-16D
Installation of Auxiliary Tank In-Line Fuel VENT HEATERS . . . . . .
11-16D
Pump Filter . . . . . .
11-8A SELECTOR VALVES . . . . .
1-17
INDICATOR SYSTEM . . . . .
11-8A Removal of Fuel Selector Valves . .
1-17
Troubleshooting . . . . . -
11-8B Installation of Fuel Selector
Removal of Fue1Quantity Sending Unit Valves . . . . . . .
11-17
Wing Cells (421-0001 to 421B0001) .
11-8D FUEL SELECTOR CONTROL SYSTEM . .
11-17
Installation of Fuel Quantity Sending Unit Removal . . . . . . .
11-17
Wing Cells (421-0001 to 421B0001) .
11-8D Installation . . . . . . .
11-21
Removal of Fuel Quantity Sending Units -

Rigging . . . . . . . .
11-21
Main Tank (421-0001 to 421BOOO1) .
11-9 Operational Check . . . . .
11-21

FUEL SYSTEM. craft 421A0112 and ON and all aircraft modified by

SK421-26A there are two electrically operated fuel
The aircraft standard fuel system consists of an in- pumps mounted in each main tip tank, the auxiliary
tegrally sealed (wet) tank mounted to each wing tip fuel pump and the fuel transfer pump. The auxiliary
and two interconnected auxiliary tanks (synthetic rub- fuel pump, mounted in the bottom of the main tank,
ber cell) mounted within each wing. Optional wing provides fuel pressure for priming during engine
fuel tanks are provided to increase fuel capacity and starting and supplies fuel to the engine in an emer-
are interconnected to the auxiliary tanks. Optional gency. The fuel transfer pump is mounted on the aft
wing locker fuel tanks are also provided, located in side of the tip tank rear bulkhead and transfers fuel
the forward section of the wing locker. Fuel capac- from the nose section of the main tank to the center
ities for each system are given in Section 1. On air- baffle area, where it is picked up and routed to the

Change 2
ll- 2 FUEL SYSTEM 421 SERVICE MANUAL

RIGFIT YILLER CAP

RIGHT AUX. (STANDARD FUEL SYSTEM)
FUEL TANKS

421A0112 AND ON
AND ALL AIRCRAFT VENTLINE
MODIFIED BY SK421-26A \
au^«"à,,'^1"cLL

DRAINVALVE

TWG R FUELQUANTITYINDICA OR
E STANDARD FUEL SYSTEM

TLOR FILI.ER CAP

E LV FILLER CAP Qi]B

VENT

LEFT FILLER CAP RIGHT FILLER CAP

(OPTIONAL) TUELSYBTEM DRADI VALVE DRAIN VALVE (OPTIONAL) FUEL BYSTEM

LEFT OPT. Lt.FT AUX RIGRT AUX. HIGHT OPT.

FUELTA URLny FUELTANKS DELTANK

VENTL1 V TLINE
FILLERCAP ER

TM SFER
SFER

PU

AUX. FUEL PUMPSWCE DRAIN VALVE AUX. FUEL PUMP SWITCH

SELECTOR V VE SEL CTORVALVE

DRAIN VALVE DitAIN VALVE

PRIME SWITCH

VAP LEFT RIGHT 4 LINE

F
VAPOR VAPOR
SEPARATOR SEPARATOR
CODE
LEPT ENGINg m
;--]
FUEL SUPPLY LINE
L
PUEL PUMP VAPOR RETURN LINE
MECHANICAL ACTUATION
ELECTRICAL ACTUATION
CHECK VALVE ALTITUDE COMPENSATOR
ALTITUDE COMPENSATOR- (ANEROID VALVE)
PRESSUftE RELIEF VALVE
(ANEROIDVALVE)

----FDEL PRESSURE W GE FUEL PRESSURE

FUE
PRESSURE ADJUSTING SCREW ADJUSTING SCREW
FORAUX. PUMPS FOR AUX. PUMPS

FILTER SCHEEN
FILTER SCREEN

LEFT ENGINE RIGHT ENGINE

FUNHLCONTROL EL CONTROL

THROTTLE UR THROTTLE
TURE
CONTROL CONTROL

TO To To TO
CYLINDERS CYLINDERS CYLINDERS CYLINDERS

421-0001 to 421BOOO1
FUEL INJECTION LEPT ENGINE R1GELTENGINE FUEL INJECTION
NOZ2LE FUEL MANIFOLO FUEL MANimLD NO2ZLE

Figure 11-1. Fuel System Schematic (Sheet 1 of 2)

Change 11
 421 SERVICE MANUAL FUEL SYSTEM ÎΕ A

RIGHT F[LLER CAP

YSTEM)

AUX. TANK FUEL

QUANTITY DIDICATOR
DRAIN Vr,LVr

STANDARD FUEL SYSTEM

FFT G R FUELQ OTOR

INTERCONNECT FILLER CAP RIGHT WING LOCKKR

FELLEIIECK VALVE FILLER CAP FUEL TANK (OPT)

LEFT RIGHT FILIÆR CAP

(OPflONAL) FUEL SYSTEM DRAIN VALVE DRAIN VALVE (OPTIONAL) FUELBYSTEM

LEFT OPT, -LEFT AUX. RIGIIT AUX. RIGHT OPT

FUEL TANK FUEL TANK" NSFER FUEL TANKS FUEL TAN
VENT LINE VENT LINE
FILLER CAP FILLER CAP,
MAIN MAIN

R SFER
R

AUX.PUMP INDLCATO VINE

AUX.PUMP
A

AUX, FUEL PUMP S CH DRAIN VALVE AUX TUEL PUMP SWITCH

SELECTOR VA VE SEL CTOR VALVE

DRAIN VALVE DRAIN VALVE

VAPO LEFT JGHT LE

VAPOR VAPOR
SEPARATOR / SEPARATOR
CODE ,

LEFT ENGINE FUELSUPPLY LINE

FUEL PUMP VAPOR RETURN LINE
- MECHANICAL ACTUATION
L

ELECTRICAL ACTUATloN
CHEC< VALVE
ALTE VCAL ENSATOIl PRELERE RELIEF VALVE LT UDE CAOM NSATOR
OD

.LEU
A DUAL FUEL TO RIGHT
FUEL PRESSURE FLOW GAGE FUEL PRESSURE
AUX. PUMP
FUEL
PRESSURE ADJUSTING SCREW ADJUFflNG SCREW FUEL
FOR AUX. PUMPS PHESSURE SWITCH
FOR AUX. PUMPS
FILTER SCREEN
FILTER SCR

WHEOL CEN
---
OL

TUR TTLE
THR TTLE
Rno
N

CYLMODElis
CYLI ERS CYL ERS CYLINDERS

FUEL INJECTION LEIT ENGINE 421B0001 AND ON RlGHT ENGINE FUEL INJECTlON
NOzZLE FUEL MANIFDLD FUEL MANIFOLD NOZZLE

Figure 11-1. Fuel System Schematic (Sheet 2 of 2)

Change 11
11-28 Fuet sysTeu 421 SERVICE MANUAL

engine by.either the engine-driven or the auxiliary locker to the main tanks. Fuel is routed from the
fuel pump. The fuel transfer pump prevents the pos- wing locker tank to each respective tank through
sibility of fuel starvation to the engine during steep lines routed in the leading edge of the wing. There
angles of descent and a low quantity of fuel. An elec- are no return lines in the wing locker system, there-
trically operated auxiliary fuel pump feeds fuel to the fore, it is necessary the aircraft be flown with the
selector valve, located outboard of each engine na- fuel selector on MAIN for at least sixty minutes or
celle and in turn routes fuel to the engine-driven fuel until thirty gallons of fuel remain in the main tanks
pumps on each engine. A vapor return line is in- before transferring fuel from the wing locker tanks.
stalled from the engine-driven fuel pump to the main A pressure switch is installed in the fuel line to op-
tank to return unused fuel A line is installed from erate a pilot indicator light mounted on the lower left
each auxiliary fuel cell to the respective fuel selec- side of the instrument panel. Quick-drain valves are
tor. The auxiliary fuel cells are equipped with an in- provided in the bottom of each main auxiliary and
line fuel pump for vapor clearing, there is no vapor wing locker tanks, in addition to a drain valve locat-
return line to the auxiliary tanks. When fuel is used ed in the crossover drain line and fuel selector sedi-
from the main tanks, the fuel vapor from the fuel ment bowl to drain trapped moisture and sediment.
pump is returned to the main tank. Fuel from the The fuel system is vented to a common vent located
optional wing tants is gravity fed into the auxiliary on the underside of each tip tank and incorporates a
tanks. The wing locker fuel system is equipped with heater to prevent icing. A sniffle valve located aft
a transfer pump mounted outboard of the wing locker of the filler cap, provides a secondary vent for the
on the rib. These pumps transfer fuel from the wing main tank.
Trouble Shooting the Fuel System.

TROUBLE PROBABLE CAUSE CORRECTION

ÑO FUEL QUANŸITY Fuel tank empty. FÏll tank with correct grade
INDICA TION of fuel.

Fuel quantity indicator circuit breaker Reset circuit breaker.

open.

Broken or loose wiring. Check circuit with multime-

ter.
Loose connection or open circuit. Tighten connections and
check wiring.

Defectivesignal conditioner. Replace signal conditioner.

(421BOOO1 and on)

Defective fuel quantity indicator. Replace fuel quantity indica-

tor.
Defective fuel quantity sending unit. Replace fuel quantity send-
ing unit.

Defective fuel tank unit. (421B0001 Verify tank unit is defective

using Field Calibration Unit i
and on)
Test Box.
FUEL DRIPS FROM OVER- Mixture lever not in IDLE CUT-OFF. Place mixture lever in
BOARD DRAIN TUBE IN IDLE CUT-OFF.
NACELLE
Mixture lever not in IDLE CUT-OFF Rig mixture control in accor-
due to improper rigging. dance with rigging procedure.

Distribution valve is leaking. Repair or replace.

Broken fuel line or loose fitting. Check fuel lines and fittings.

AUXILIARY FUEL PUMP Master switch OFF. Turn master switch ON.
INOPERA TIVE
Circuit breaker open. Reset circuit breaker.

Open circuit or loose connection. Check circuit and repair.

Defective fuel pump. Replace fuel pump.

Change 5
 421 SERVICE MANUAL FUEL SYSTEM ÎÎÑ

TROUBLE PROBABLE CAUSE CORRECTION

AUXILIARY FUEL PUMP Defective fuel pressure switch. Replace fuel pressure switch.
RUNS AT HIGH SPEED WITH
AUXILIARY FUEL PUMP Prime switch has been actuated Move auxiliary pump switch
SWITCH IN "ON" POSITION momentarily. to the
OFF position.
WITH ENGINE RUNNING

AUXILIARY FUEL PUMP Defective auxiliary fuel pump. Replace auxiliary fuel pump.
RUNS AT SLOW SPEED
WITH AUXILIARY FUEL
PUMP SWITCH "ON" AND
ENGINE NOT RUNNING

ENGINES WILL NOT Fuel tank empty. Fill tank with correct grade
START OR CONTINUE TO of fuel.
RUN AFTER STARTING
Fuel selector valve in OFF position. Move fuel selector valve to
desired tank.

Mixture in IDLE CUT-OFF. Set mixture to FULL RICH.

Engine overprimed. Place mixture control in

IDLE CUT-OFF, turn en-
gine over several revolutions
with throttle WIDE OPEN.

Fuel strainer in fuel control unit Clean fuel control unit

dirty. strainer.

Auxiliary fuel pump switch not in Place auxiliary fuel pump

PRIME position. switch in PRIME position.

Plugged fuel cap vent. Clean vent.

Bypass valve in engine-driven fuel Replace engine-driven fuel

pump stuck. pump.

HIGH FUEL FLOW INDICA- Gage vent line plugged or leaking. Clean, tighten or replace
TION AT FULL THROTTLE vent line.
AFTER RAP1D ENGINE
ACCELERATION ON GROUND

LOW FUEL FLOW Mixture control lever does not Rig mixture control in
contact the full-rich stop. accordance with Section
9, Rigging Mixture Throttle
Controls.

No turbocharger discharge pressure Check turbocharger and fuel

to fuel pump, pump aneroid.

ROUGH AND ERRATIC Fuel mixture control lever does not Rig mixture control in
ENGINE SHUTDOWN contact idle cut-off stops firmly. accordance with Section
9. Rigging Mixture and
Throttle Controls.

FUEL SHUTOFF INCOM- Misaligned linkage or fuel control Align linkage or re-rig
PLETE levers hitting stops too hard. mixture control.

Distribution valve stuck. Repair or replace.

FUEL FLOW INCREASES, Pressure switch set too high. Reset fuel pressure switch
ENGINE DIES to actuate between 4 to 5
PSL

Pressure switch stuck. Replace pressure switch.

11-4 FUEL SYSTEM 421 SERVICE MANUAL

TROUBLE :PROBABLE CAUSE CORRECTION

AUXILIARY PUMP WILL Pressure switch stuck. Replace pressure switch.

NOT SWITCH TO HIGH
SPEED

AUXILIARY WING Circuit breaker open. Reset circuit breaker.

LOCKER FUEL PUMP
INOPERATIVE Open circuit or loose connections. Check circuit and repair.

Defective fuel pump. Replace pump.

AUXILIARY W1NG LOCK- Open circuit or loose connection. Check circuit and repair.
ER FUEL TRANSFER
LIGHTS INOPERATIVE Defective pressure switch. Replace pressure switch.

MAIN FUEL TANKS. Disassembly of Main Fuel Tank.

Each main tank is attached to the outboard end of both Disassemble main fuel tank in accordance with figure
spars and is streamlined to the wing by fairing strips, figure 11-2 and figure 11-3.
A flush-type filler cap is incorporated for servicing.
The tanks are integrally sealed (wet) tanks and have CAUTION
an electrically operated fuel boost pump installed in
the bottom of each tank. On aircraft 421A0112 and If drain cock has been removed, replace
ON, and all aircraft modified by SK421-26A an elec- existing seal with aluminum crush washer
trically operated fuel transfer pump is located on the (P/N AN960-616D).in order to prevent leak-
aft side of the main tank rear bulkhead. On aircraft age from overtightening drain cock when in-
421-0001 to aircraft 421BOOO1 a sending unit operated stalling it,
by a float arm inside the main tank is also installed.
On aircraft 421BOOO1 and ON, afuel capacitance send- Inspection and Repair of Main Fuel Tanks.
ing unit is mounted in the upright position to provide
fuel quantity measurements. Access to the auxiliary a. Inspect filler cap gasket. If crushed or damaged,
fuel pump is gained by removing upper and lower replace filler gasket. On integrally sealed (wet)
fairing strips. Access to the fuel transfer pump is tanks, inspect sealing gasket, loose rivets, cracks
made by removing tail cap assemblies from the wing or dents for leaks and attaching mounts.
main fuel tanks. Access to the fuel capacitance tank b. Purge in accordance with Section 2.
unit is gained by removing the main tank filler cap. c. Repair in accordance with Section 16.
Access to the fuel quantity sending unit is gained by
removing the main fuel tank tail cap. A quick drain
valve is incorporated in the bottom of each fuel tank Assembly of Main Fuel Tanks.
for draining moisture and sediment.
Assemble main fuel tank in accordance with figure
figure 11-2 and figure 11-3.
Removal of Main Fuel Tank. (See figure 11-2.)
NOTE
The removal procedure is the same for either main
tank. When replacing fuel lines, use only a fuel
a. Selector valve handles -
OFF. soluble lubricant (such as engine oil) on the
thread fittings. DO NOT USE ANY OTHER
CAUTION FORM OF THREAD COMPOUND.

Make sure handle is in detent in the OFF po- All access openings must be sealed and checked on
sition to prevent fuel leakage. assembly. Seal and check as follows:
a. Clean all surfaces to be sealed with a low mois-
b. Defuel main tank in accordance with Section 2. ture solvent using a lintless cloth for solvent appli-
c. Remove wing fairings and tail cap. cation.
d. Disconnect electrical wiring,
e. Disconnect fuel lines, fittings and vent lines. NOTE
f. Remove mounting nuts, washers and bolts,
g. Remove main tank. Do not allow cleaning solvent to evaporate;
wipe dry.

Change 12
 421 SER.VICE MANUAL FUEL SYSTEM 11-4A 11-4B

32 35 34 17 36 37 3 A
10
2
4
38

21

20
23
12
15 24
D 12 11 2 i 2 is
C 12 14
A e
5

W 38
9
2
Detail Û 51264007
421-0001 TO 421B0502 A10261008

Figure 11-2. Main Fuel Tank Installation (Sheet 1 of 2)

Change 12
 421 SERVICE MANUAL FUEL SYSTEM 11-6

Detail

28

Detail

26----·- '
1. 00

. 06 MAX

Detail
421-0001 TO 421B0801
10261016

1. Tail Cap 13. Front Fairing 26. Heater

2. Screw 14. Inlet Vapor Return Line 27. Main Fuel Tank Fitting
3. Fuel Tank 15. Hose 28. Front Spar
4. Filler Cap 16. Nut 29. Bracket
5. Gasket 17. Auxiliary Fuel Pump 30. Sniffle Valve
6. Nutplate Cover 18. O-ring 31. Vent Scoop
7. Nose Door Assembly 19. Nipple 32. Hose
8. Nose Cap 20. Fuel Pump Drain Line 33. Clamp
9. Bolt 21. Upper Fairing 34. O-ring
10. Washer 22. Lower Fairing 35. Fitting
11. Fuel Supply Line 23. Elbow 36. Line
12. Clamp 24. Fuel Pump Drain Plug 37. Union
25. Vent Tube 38. Stat-O-Seal

Figure 11-2. Main Fuel Tank Installation (Sheet 2)

Change 12
11-6 FUEL SYSTEM 421 SERVICE MANUAL

b. Mix Sealant MIL-S-8802 pèr manufacturer's in- valve, washer and gasket.
structions and apply with a spatula over all seams, e. Remove sniffle valve.
rivets, fittings and possible leak areas.
c. Inspect tank as follows:
1. Seal off all access holes in tanks. Close vent Installation of Sniffle Valve. (See figure 11-2.)
hole by covering inside with tape.
2. Saturate a clean rag with 25 cubic centimeters The installation procedure of the sniffle valve is the
of household ammonia. Insert rag in fuel tank and reversal of the removal procedures.
close filler cap.
3. Pressurize fuel tank to a maximum of 2 psi.
4. Saturate a large clean cloth with indicated solu- MAIN TANK FUEL TRANSFER PUMP.
tion (1/2 gallon distilled water, 1/2 gallon denatured (421BOOO1 and ON)
alcohol, and 1/2 ounce of phenopthalein crystals or
powder) and spread smoothly on surface of tank. One main tank fuel transfer pump is mounted on the
5. A leak will appear as a pink spot on the cloth. aft side of each main tank rear bulkhead. The func-
Repair all leaks and repeat testing until entire tank tion of these pumps is to transfer fuel from the for-
surface has been tested. ward end of the main tanks to the center baffle area,
where it is picked up and routed to the engine by
WARNING either the engine-driven pump or the auxiliary fuel
pump.
Remove tape from filler cap, rag from inside
fuel tank, and allow fuel tank to air out before Removal of the Main Tank Fuel Transfer Pump,
using. (See figure 11-3. )

Installation of Main Fuel Tank. (See figure 11-2.) The removal procedure is the same for either main
tank fuel transfer pump.
The installation procedure is the same for either a. Make sure fuel selector handles are OFF.
main fuel tank. For installation of main fuel tanks, b. Defuel main tank in accordance with Section 2.
reverse removal procedure. c. Remove tail cap assemblies from wing main
fuel tanks by removing attaching screws.
CAUTION d. Disconnect electrical wiring,
e. Disconnect fuel lines from pump.
If vent scoop is installed, lower fairing, f. Remove two nuts attaching pump to bulkhead and
tail
cap and drip fence must be sealed with Pro- remove pump from aft end of main tank.
Seal 890 to prevent entry of fuel to wing
structure. Disassembly of Main Tank Fuel Transfer Pump.
(See figure 11-2A. )
NOTE
NOTE

I Torque main
inch-pounds-
tank mounting bolts to 50 ±10
The interrupter
transfer
end of the main tank fuel
pump is sealed with air removed
SNIFFLE VALVE (See figure 11-2. ) and an atmosphere of a special dry gas in-
jected. Should any of the electrical compo-
The sniffle valve is located in the top of each main nents become inoperative, the fuel pump
tank aft of the filler cap. This valve will vent the must be replaced. The gas seal is located
main tank should the overboard vent become clogged in the center of the mounting bracket and no
or obstructed. attempt should be made to break this seal,
as it would render the pump useless.

Removal Sniffle Valve. (See figure 11-2.) a. Hold the pump body securely in one hand and re-
lease the bottom cover from the bayonet fittings by
The removal procedures given pertain to either main rotating it counterclockwise with a 5/8 inch wrench.
tank. b. Remove the gasket from the cover.
c. Carefully remove the filter screen.
CAUTION d. Remove the three screws that hold the plunger
spring cup to the pump body.
Care should be taken to guard against foreign e. Remove the gasket and plunger spring.
matter entering the tank. f. Carefully withdraw the plunger from the pump
body. Do not drop or mutilate the plunger.
a. Defuel main tip tank in accordance with defueling
procedures. Cleaning and Inspection of Main Tank Fuel Transfer
b. Remove screw securing cover. Pump Parts,
c. Remove tip tank filler cap in accordance with
removal procedure. a. Wash the plunger assembly in Stoddard Solvent
d. Holding top half of valve, remove bottom of or gasoline. If it fails to become thoroughly clean or

Change 11
 421 SERVICE MANUAL FUEL SYSTEM
ÎίË

if any rough spots are present, dress the surface Assembly of Main Tank Fuel Transfer Pump.
carefully with crocus cloth. Rinse thoroughly to re-
move all foreign material a. Insert the plunger assembly (8) in the tube with
b. Dip the pump body in clean solvent, shake it the buffer-spring end first. Check for proper fit by
lightly, then remove it and dry with compressed air' slowly raising and lowering the plunger in the tube;
c. Blow out the plunger tube with compressed air it should move freely without any tendency of stick-
and check for any rough spots, deposits or foreign ing. A click should be heard each time the plunger
material. If not smooth, wrap a piece of cloth approaches the top of the tube. If this click cannot
around a wood dowel, dip the cloth in Stoddard Sol¯ be heard, the interrupter assembly in the sealed por-
vent (Federal Specification P-D-680), and swab the tion of the pump is not functioning properly, and the
plunger tube until clean- pump assembly must be replaced.
b. Install the plunger spring (7).
c. Place the spring cup gasket (6) in position on the
plunger spring cup (5) and carefully attach this as-
sembly to the pump body (9), with the three screws
(4). Tighten screws securely.
d. Carefully install the screen (3), place cover gas-
ket (2) in position in cover (1) and attach the cover to
the pump body (9).
e. Hold the pump body securely with one hand and
,,, tighten the cover (1) into place on the pump body bay-
onets with a 5/8 inch open-end wrench or box socket.

Installation of Main Tank Fuel Transfer Pump.

/ (See figure 11-3. )
7
The installation procedure is the same for either
main tank fuel transfer pump.
5 a. Install pump to bulkhead.
A3 V b. Connect fuel lines to pump.

CAUTION

Observe "IN" and "OUT" markings on pump

relative to lines being connected for correct
1. Bottom Cover 6. Gasket installation. Outlet port of pump must be to
2. Cover Gasket 7. Plunger Spring the top of pump.
3. Filter Screen 8. Plunger
4. Screw 9. Pump Body c. Connect electrical wiring,
5. Plunger Spring Cup d. Perform following operational check of trans-
fer pump:
Figure 11-2A. Main Transfer Pump 1. Pour approximately 5 gallons of fuel into main
tank.
2. Turn master switch ON.
d. Rinse remaining parts in the solvent and dry
with compressed air. Exercise care when drying
3. Observe that pump is functioning properly.
the screen (3) to prevent damage.
NOTE
e. Inspect all parts visually for damage.
f. Inspect the fuel pump electrical resistance by
ter- Transfer pump must be pumping from for-
connecting an ohmmeter between the connector to center baffle
ward section of maintank
minal and ground on the pump housing. Resistance
area.
should be between 19. 0 and 19. 5 ohms. If the re-
sistance is not within limits, replace the pump as- tank.
e. Install tail cap assemblies to main fuel
sembly. f. Refuel aircraft.

AUXILIARY FUEL PUMP.

One auxiliary fuel pump is installed in the bottom of

each main tank. These pumps are submerged, elec-
trically controlled by three switches. The prime

Change 8
 11-68 FUEL SYSTEM 421 SERVICE MANUAL

4
6 5

421A0001 AND ON
Detail A

1. Seat Support 3. Resistor 5. Resistor

2. Clip Assembly 4. Clip Assembly 6. Mounting Bracket

Figure 11-2B. Auxiliary Fuel Pump Resistors

I Change 2
 421 SERVICE MANUAL FUEL SYSTEM 11-6Û

2 20

e
e= -

18 1 19 20

17

8
4 |
421-0001 TO 421B0001 15
14

Detail

421B0001 AND ON
I

10

6
A
A51261008

1. Auxiliary Fuel Pump 8. Hose 15. Fuel Line (Transfer Outlet)

2. Gasket 9. Elbow 16. Union
3. Doubler 10. Bolt 17. Fuel Line (Transfer Inlet)
4. O-ring 1L Fuel Pump Drain Line 18. Main Fuel Transfer Pump
5. Nut 12. Nipple 19. Access Plate
6. Fuel Supply Line 13. Fuel Tank 20. Aft Bulkhead
7. Clamp 14. Baffle 21. Stat-O-Seal

Figure 11-3, Auxiliary Fuel and Transfer Pumps Installation

Change 12
 421 SERVICE MANUAL FUEL SYSTEM lίÎ

switch is a momentary on, center off switch. When 2. On aircraft

421A0001 and On, adjust resistor
the prime switch is placed in the left position, the until required auxiliary fuel pump pressure is ob-
left auxiliary pump provides priming for the left en- tained (see figure 11-2B).
gine. When the prime switch is placed in the right
position, the right auxiliary pump provides priming NOTE
for the right engine. During the priming operation,
the auxiliary pumps operate at high speed. The aux- The left resistor is for the left auxiliary fuel
iliary pump switches are a two-position center off pump and the right resistor is for the right
switch. When placed in the LOW position, the aux- auxiliary fuel pump.
iliary pump and also the auxiliary tank in-line fuel
pump provides pressure for purging. When the
auxiliary pump switch is placed in the ON position, 3. On aircraft 421-0001 to 421A0001, remove left
the auxiliary pump operates at low speed. In case console panel and adjust resistor until required aux-
of an engine-driven fuel pump failure, the auxiliary iliary fuel pump pressure is obtained (see figure
pump will automatically operate at high-speed. Prior 14-2).
to switching to auxiliary tanks, place the auxiliary
pump switch in the LOW position. During take-off NOTE
and landing, the auxiliary pump switch is placed in
the ON position. The upper resistor is for the left auxiliary
fuel pump and the lower resistor is for the
right auxiliary fuel pump.
Removal of Auxiliary Fuel Pump. (See figure 11-3.)
The removal procedure is the same for either auxili-
ary fuel pump. 4. Turn all switches OFF, place fuel selector
a. Make sure fuel selector handles are OFF. valve handle to OFF position.
b. Defuel main tank in accordance wiU1 Section 2. 5. Replace left console side cover and install
c. Remove wing fairings. pilot's seat.
d. Disconnect electrical wiring. h. Remove test pressure gage.
e. Remove fittings, lines, and hoses required.
f. Remove tail cap, rear access plate and gasket.
g. Remove the four auxiliary pump mounting bolts,
and remove pump from inside the fuel tank.

Installation of Auxiliary Fuel Pump.

The installation procedure is the same for either

auxiliary fuel pump. For installation of auxiliary
fuel pump, reverse removal procedures as outlined
in preceding paragraph.

NOTE 10
9 *8

Anytime the auxiliary fuel pump has been *7

replaced or altered the auxiliary fuel pump *g
4
low adjustment must be performed. *Deleted on
421B0238 AND ON
Auxiliary Fuel Pump Low Adjustment.
' 0. 531
a. Fill main tank with proper grade of fuel (see 2
Section 2).
'
b. Install a calibrated fuel pressure gage in the
engine-driven fuel pump inlet line by use of a tee,
hose and unions.
valve handles to main tanks.
Detail A 5
c. Place fuel selector
d. Start both engines and allow to warm-up.
e. Set engine being adjusted to 450 rpm and the
opposite engine to 1250 rpm with all electrical 1. In-line Fuel Pump 6. Spring
equipment turned off to insure maximum bus voltage• 2. Leaf Spring 7. Filter
f. Position auxiliary fuel pump to LOW position for 3. Screw 8. Pilot
engine being checked. The fuel pressure gage should 4. Lockwasher 9. Seal Ring
indicate 5. 5 ±. 25 psi. 5. Relief Valve Cover 10. Bypass Valve
g. If fuel auxiliary fuel pump pressure is not 5. 5
±. 25 psi, adjust as follows: Figure.11-3A. Auxiliary Tank In-Line Fuel Pump
1. Remove pilot's seat. Filter Installation

Change 8
 114 FUEL SYSTEM 421 SERVICE MANUAL

AUXILIARY WING CELLS i. On the two outboard fuel cells, thru the bottom
access in the leading edge, remove the fuel quantity
The auxiliary fuel system consists of two wing cells sending unit wires, then remove the fuel quantity
in each wing on standard aircraft. These cells are sending unit. Refer to "Removal of Fuel Quantity
synthetic rubber, interconnected fuel cells located Sending Unit Wing Cell" paragraph.
outboard of the nacelle in each wing, having a com- j. Remove top access cover and filler cap assembly.
bined capacity of 36. 5 U. S. gallons. On the optional k, Disconnect interconnects and clamps.
fuel system, there is another fuel cell installed just 1. Disconnect bayonet fasteners and carefully re-
outboard of the standard auxiliary cells and in inter- move the fuel cell thru the top access hole, using
connected to provide a combined capacity of 50 U. S. care not to puncture or tear bladder.
gallons in each wing. When the optional tank is in- NOTE
stalled, the fuel filler is located outboard allowing a
greater fuel capacity in each wing. A finger strainer Retain sending unit gaskets for replacement
is provided at the fuel outlet. Fuel is fed to the se- if they are not damaged.
lector valve through an auxiliary tank in-line fuel
pump. The auxiliary fuel system has a separate fuel Inspection and Repair of Auxiliary Wing Fuel Cells.
quantity indicating system and each cell has a send-
ing unit calibrated for either a standard fuel system a. Inspect filler cap gasket. If crushed or damaged,
or a optional system. Located on the bottom of each replace filler gasket. Inspect fuel cell for cuts,
inboard wing cell, there is a drain valve for drain- tears, abrasions and deterioration.
ing moisture and sediment- b. Purge in accordance with Section 2.
c. Repair in accordance with repair procedures,
Removal of Auxiliary Wing Cells. (See figure 11-4.) Section16.

Removal procedure is the same for either wing out¯ Inspection of Fuel Cell Cavity Following Fuel Cell
board and center cells·
Removal.
a. Fuel selector valve handles OFF.
-

b. Defuel main tank in accordance with Section 2• a. Inspect carefully the interior of the fuel cell
WARNING cavity and cell bulkheads or supports for possible
damage or corrosion.
Residual fuel draining from lines and hoses b. All internal rivets and protrusions must be pro-
is a fire hazard. Use care to prevent the tected by the proper type of tape,
accumulation of such fuel ·

Installation of Wing Cells. (See figure 11-4.)

c. Remove top access covers on the upper surface
of the wing and the bottom access covers to gain ac- Installation procedure is the same for either wing.
cess to fuel outlet connection and fuel quantity send- a. Make sure the cell cavities are free from dirt,
ing units. rough edges, and rivets.
b. On the inboard fuel cell, carefully work the tank
NOTE thru the access hole and position in place. Then
fasten the bayonet fasteners.
It may be necessary to drill off the access c. Install fuel quantity sending unit as shown in fig-
hole doublers to gain access to the fuel lines. ure 11-5.
d. Install finger strainer, connect outlet lines and
install drain valve.
d. On inboard fuel cells, remove safety wire and e. On the outboard wing cells, carefully work the
bolts from the inner bar, closing the fuel cells and tanks thru access hole and into position.
interconnects, clamps and lines. f. Pull the fuel cell aft far enough to install the fuel
e. Disconnect outlet line and remove finger strain- quantity sending unit.
er from cell, g. Install the fuel quantity sending unit in cell, as
f. Remove and tag fuel quantity sending units wires. shown in figure 11-5, with five screws; then position
g. On the inboard fuel cell, remove the five bolts gasket between spar and cell unit and secure sending
securing the sending units to the inboard wing rib unit to front spar; connect the fuel quantity sending
and remove the fuel quantity sending unit. unit wires.
h. Remove two screws securing drain valve adapter, h. Install bayonets in position, and install intercon-
then thru the top access holes, disconnect the bay- nects and clamps in each cell. Then install the two
onet fasteners and carefully remove the fuel tank, screws in drain valve adapter on the underside of
using care not to puncture or tear the bladder. the wing.
i. Install filler cap and adapter assembly on out-
CAUTION
board fuel cells.
During all defueling, tank purging, and tank
3. Close inboard fuel cells as shown. Torque bolts
(12) 75 to 85 inch-pounds. Safetywire bolts and in-
repairing operafíons, two ground wires, from
stall covers.
different pomts on the aircraft to separate
approved grounding stakes, shall be used to AUXILIARY TANK IN-LINE FUEL PUMP
prevent ungrounding of the aircraft due to The auxiliary tank in-line fuel pump supplies fuel
accidental disconnecting of one ground wire• from the auxiliary tank to the fuel injection pump and

Change 11
 421 SERVICE MANUAL FUEL SYSTEM lÎ"O
prevents vapor from forming in the auxiliary fuel a. Cleaning.
lines. The auxiliary tank in-line fuel pump operates 1. Clean filter (7) with a suitable solvent and jet of
simultaneous with the auxiliary fuel pump when the low pressure dry air not to exceed 10 PSI.
auxiliary fuel pump switch is placed in the "LOW" b. Inspection.
position. The fuel pressure setting is preset at 5 1. Inspect filter for any damage to main filter
PSI and cannot be adjusted. body, pilot (8), and spring (6).

Removal of Auxiliary Tank In-Line Fuel Pump. (See NOTE

figure 11-6.)
If there is any damage to any portion of filter
The removal procedure is the same for either auxi- (7), replace filter.
liary tank in-line fuel pump.
a. Place fuel selector valve handles in the OFF 2. Inspect leaf spring (2) for a dimension not to
position. exceed 0. 531 inch as shown in illustration or less
b. Defuel auxiliary tanks in accordance with Section than 0. 500 inch. The leaf spring may be bent slight-
2. ly to meet the requirement when necessary.
c. (See figure 1-2.) Remove access plates 47, 48, 3. Inspect seal ring (9) for damage, replace if
and 63. necessary.
d. Tag and disconnect electrical wiring.
e. Disconnect fuel lines (7) and (42) and drain line (48)- Installation of Auxiliary Tank In-Line Fuel Pump
f. Loosen nut on band clamp securing pump to pump Filter (421-0001 to 421B0238) (See figure 11-3A.)
mounting bracket.
g. Slip fuel pump from band clamp. The installation procedure is the same for either
auxiliary tank in-line fuel pump filters.
Installation of Auxiliary Tank In-Line Fuel Pump. a. Align marked lines of relief valve cover (5) and
in-line fuel pump housing to insure original position
The installation procedure is the same for either of cover.
auxiliary tank in-line fuel pump. For installation of b. Position relief valve cover (5) on face of pump
auxiliary tank in-line fuel pump, reverse removal housing, aligned with coil spring (6) of installed
procedures as outlined in preceding paragraph. filter and leaf spring (2) of cover in contact with
bypass valve (10) of pump.
Removal of Auxiliary Tank In-Line Fuel Pump Filter. c. Secure relief valve (5) with screws (3) and lock-
(421-0001 to 421B0238) (See figure 11-3A.) washers (4).

The removal procedure is the same for either auxil- NOTE

iary tank in-line fuel pump filter.
a. Place fuel selector valve handles in the OFF po- Tighten screws (3) finger-tight before using
sition. screwdriver. Tighten screws (3) to approxi-
b. Defuel auxiliary tanks in accordance with Section mately 15 inch-pounds torque,

c. (See figure 1-2.) Remove access plates 47, 48, d. Refuel auxiliary tanks partially.
and 63. e. Place fuel selector valve handles in the ON posi-
tion and inspect relief valve cover plate (5) on in-line
NOTE fuel pump for leaks while pump is operating.
f. Complete refueling if no leaks occur.
Mark or scribe a line on applicable in-line g. If leaks occur, place fuel selector in OFF posi-
fuel pump relief cover (5) and pump housing tion, defuel in accordance with Section 2, remove
to insure original position for reinstallation cover plate (5) and check that filter (7) is in proper
of relief valve cover. position, and also that seal ring (9) is properly in-
stalled.
d. Loosen screws (3) attaching relief valve cover h. Reinstall cover plate (5), refuel aircraft, and
to pump (1). place fuel selector valve in ON position.
i. (See figure 1-2.) Install access plates 47, 48,
CAUTION and 63.

Be sure to loosen all four screws before re- FUEL INDICATOR SYSTEM.
moval thus to prevent damage to leaf spring
(2) attached to relief valve cover (5). On aircraft 421-0001 to 421BOOO1 the main and auxil-
iary fuel systems have individual indicators and each
e. Remove screws (3), lockwashers (4), and relief fuel tank has an individual sending unit. The two sys-
valve cover (5) by pulling cover gently forward and tems are float arm actuated, variable resistor type
inboard until clear of pump housing to prevent dam- sending units, powered by the aircraft electrical sys-
age to leaf spring (2). tem, which sends an electrical signal to the fuel
quantity indicators in the cabin. On aircraft
Cleaning and Inspection of Auxiliary Tank In-Line 421B0001 and ON, a capacitance type fuel quantity in-
Fuel Pump Filter (421-0001 to 421B0238) (See dicating system, that is compensated for specific
figure 11-3A.) gravity and reads in both pounds and gallons, is in-
Change 9
11-88 FUEL SYSTEM . 421 SERVICE MANUAL

stalled. The system components include an indica- the tank units which are part of the system bridge
tor, a fuel indicator selector switch mounted on the circuit, provide a continuous signal to the signal
instrument panel, a signal conditioner mounted on a conditioner and is amplified to the indicator. The
rib just outboard of each engine nacelle and six tank indicator is a dual indicator providing a left and
units mounted in each main tank and each auxiliary right hand indication for the main fuel tanks as well
fuel celL Each tank unit consists of two concentric as left and right hand indication for the auxiliary fuel
electrodes. The inner electrode consists of a main cells. When the fuel selector handle is placed in the
body of insulating material with two conducting sur- main position, the fuel quantity indicator will indicate
faces, separately insulated around the outside face fuel in the main tanks. When the fuel selector handle
of the tank unit. One conducting surface is grounded is placed in the auxiliary position, an indicator light
and the other surface is connected to the signal con-. located under the indicator will be turned on, indicat-
ditioner input bridge circuit. The outer electrode is ing that the selector valve is in the auxiliary position
an aluminum tube coated with insulating material on and the fuel quantity indicator will indicate auxiliary
the outside. Openings in the unit allow fuel to flow fuel. An override switch is provided for monitoring
between electrodes to the same level as that in the the fuel quantity in the opposite system. When the
tank. Fuel between the electrodes is the variable fuel selector handles are placed in the main position
dielectric factor of the capacitor. Capacitance of and the override switch is pressed, the indicator
troubleshooting the Fuel Quanti y Indicator System. (The troubleshooting chart is the same for either system.

TROUBLE PROBABLE CAUSE . CORRECTION

INCORRECT QUANTITY Defective wiring. Replace or repair defective wiring.

INDICATION
Defective sending unit. Remove wires at the sending unit and
attach an ohmmeter to unit terminals.
Operate float by hand. If the unit is
good, the meter should read approxi-
mately 15 ohms when empty and 180
ohms when full.

NO INDICATION ON GAGE Circuit breaker out. Reset circuit breaker.

AND TANK IS FULL
Defective circuit breaker. Replace circuit breaker.

421B0001 AND ON

POWER SWITCH ON No power. Use a voltmeter to check that power

POINTER BELOW 0 is being applied to the system.
Defective indicator. Substitute a known good indicator. If
proper indication is obtained, original
indicator is defective.

Open wiring in harness or Use an ohmmeter to check continuity.

probe.

Defective probe. Verify probe is defective using Field

Calibration Unit Test Box.

Open HiZ line to probe. Use an ohmmeter to check for open.

POWER SWITCH ON Open HiZ to compensator. Use an ohmmeter to check for open.
POINTER ABOVE 310
LBS. (INTO STOP) Defective tank unit. Check for defective probe.

Defective indication. Check for defective indicator.

Defective tank fuel valve Check switch and relays with ohm-
switch and/or selector meter.
switch relays.

Change 6
 421 SERVICE MANUAL FUEL SYSTEM Îl¯ÑÛ

TROUBLE PROBABLE CAUSE CORRECTION

INACCURATE FUEL Defective indicator. Check for defective indicator.

Contaminated probe. Check for defective probe.

Capacitance leakage in Refer to wiring manual. Check all

wiring. connections, shields and components.

POWER ON AND BOTH LoZ to ground short. Use ohmmeter to check for short on
POINTERS AT MID LoZ leads.
SCALE REGARDLESS
OF FUEL LEVEL Defective.indicator. Check for defective indicator.

POWER ON AND Defective fuel valve switch. Use ohmmeter to check switch.
POINTER READS
APPROXIMATELY Defective selector switch Use ohmmeter to check relay.
80 TO 100 LB HIGH relay.

POWER ON AND HiZ shield shorted to Use ohmmeter to check for short be-
POINTERS CHANGE ground. tween HiZ and shield (with indicator
READING WHEN OTHER disconnected).
AVIONICS ARE
OPERATED Defective indicator. Check for defective indicator.

POWER ON AND POINTER Defective indicator. Check for defective indicator.

POSITION SENSITIVE TO
BATTERY VOLTAGE Battery voltage too low. Check battery voltage.
7
ERRATIC INDICATOR Defective indicator. .
Check for defective indicator.
READINGS
Defective harness. Check all grounds.

Defective probe. Check for defective probe.

STICKY POINTER Defective tank selector. Check switch with ohmmeter.

Defective indicator. Replace indicator.

Change 4
11-80 FUEL SYSTEM 421 SERVICE MANUAL

lights will light along with the indicator reading aux- 2. Remove interconnects, clamps and bayonet
iliary fuel quantity. When the fuel selector handles fittings as necessary to pull the fuel cell aft far
are placed in the auxiliary position and the override enough to remove sending unit.
switch is pressed the indicator will read main fuel 3. Remove the five bolts securing fuel quantity
quantity. sending unit to front spar.
4. Remove fuel quantity sending unti aft thru upper
NOTE access panel.

Fuel quantity system is solid state. There

are no moving parts. Installation of Fuel Quantity Sending Unit. Wing Cells.
(421-0001 to 421B0001)

Removal of Fue1Quantity Sending Unit. Wing Cells. The installation of fuel cells fuel quantity
the optional
(421-0001 to 421B0001) sending units is the for either wing; likewise,
same
the installation of the auxiliary and inboard wing cell
The removal of the optional fuel cell (extreme out- fuel quantity sending unit is the same for either wing.
board) fuel quantity sending unit is the same for a. On the optional fuel cells, make sure wing cavity
either wing; likewise, the removal of the inboard is free from dirt, rough edges, and protruding rivets;
and auxiliary cells fuel quantity sending units are pull cell aft sufficiently to install fuel quantity send-
the same for either wing. ing unit.
a. Fuel shutoff valves handles OFF. -

b. Install fuel quantity sending unit as shown in fig-

b. Defuel main tank in accordance with Section 2. ure 11-5, Detail C.
c. Install gasket and sending unit in position thru
CAUTION the front spar and secure with five bolts provided.
d. Connect wires.
During all defueling, tank purging and tank e. Install bayonet fittings, interconnects and clamps,
repairing operations, two ground wires, from filler cap and adapter assembly.
different points on the aircraft to separate ap- f. When installing the auxiliary fuel cell fuel quan-
proved grounding stakes, shall be used to pre- tity sending unit, place gasket on the sending unit and
vent ungrounding of the aircraft due to acci- position unit in place forward of front spar.
dental disconnecting of one ground wire.
NOTE
c. On the inboard fuel cells, remove lower access.
d. Disconnect fuel quantity sending unit wiring. When installing fuel quantity sending unit, it
e. Remove the five bolts securing the sending unit may be necessary to loosen clamp on the main
to the wing rib and remove sending unit. fuel lines in the leading edge of the wing.

WARNING g. Secure fuel quantity sending unit to fuel cell

through spar with five bolts, making sure bonding
Residual fuel draining from fuel cells is a fire strap is placed under one of the bolts for sufficient
hazard. Use care to prevent the accumulation ground.
of such fueL h. Connect wires,
i. On the inboard fuel cell, place gasket and send-
f. To remove the fuel quantity sending unit on the ing unit in position securing to wing rib with five
auxiliary fuel cell, remove lower access covers. bolts, making sure bonding strap is placed under
g. Remove and tag fuel quantity sending unit wires. one of the bolts for sufficient ground,
h. Remove the five bolts securing the fuel quantity j. Connect wires.
sending unit to the front spar.
i. Remove the clamps on the main fuel and vent NOTE
lines if necessary and remove fuel quantity sending
unit from cell. After the removal and installation of fuel
j. When removing the fuel quantity sending units on quantity sending units, the fuel cells should
the optional fuel cells (extreme outboard, removal be checked for leaks. Service aircraft in
of the fuel quantity sending unti is accomplished as accordance with Section 2 and allow to re-
follows: main for a long enough period of time to in-
1. Remove top access hole cover and filler, sure cells are not leaking.

Change 6
 421 SERVICE MANUAL FUEL SYSTEM 11-9

I
Removal of Fuel Quantity Sending Units Main Tank. fully remove tank unit (18) from fuel cell (6).
-

(421-0001 to 421B0001) f. (See figure 11-4. ) On the auxiliary fuel cell, if

optional outboard cell is not installed, remove filler
Either fuel quantity sending unit can be removed by cap (1) and adapter assembly (2) from fuel cell. If
the following procedure; optional outboard cell is installed, remove access
a. Fuel shutoff valve handles OFF. -
cover (18) from auxiliary fuel cell.
b. Drain fuel from main tank. g. Tag and disconnect electrical bundles (17) from
c. Remove tail caps. tank unit (18).
d. Remove wires and tag. h. Remove tank unit from clip.
e. Remove fuel quantity sending unit. i. Working through filler cap opening or access
cover opening carefully remove tank unit (18) from
auxiliary fuel cell (6).
j. (See figure 11-4.) On the inboard fuel cell, re-
I
Installation
(421-0001 to 421B0001)
of Fuel Quantity Sending Unit -
Main Tank
move cover (7), support (10), outer bar (9), and
inner bar (8) from inboard fuel cell.
Either fuel quantity sending unit can be installed by k. Tag and disconnect electrical bundles (17) from
the following procedure: tank unit (18),
a. Install new gasket and sending unit; secure with 1. Remove tank unit from clip.
five bolts. m. Working through access opening carefully re-
b. Connect wires. move tank unit (18) from inboard fuel cell (6).
c. Install tail cap.
Installation of Outboard, Auxiliary, and Inboard Fuel
Cell Tank Units. (See figure 11-5. ) 421BOOO1 and

I
Fuel Quantity
(421-0001 to 421B0001)
Sending Units Operational Check. ON

The installation of the optional fuel cell (extreme

a. With the fuel tanks completely drained, place the outboard) fuel quantity tank unit is the same for
quick-drain valves in the closed position. either wing; likewise, the installation of the aux-
b. Turn battery switch to the ON position. iliary and inboard wing cell quantity tank units are
c. Add 1 gallon of fuel to each tank (the amount de- the same for either wing.
termined as unusable fuel) and the fuel quantíty indi-
cator should read empty (E). a. Reverse the removal procedures for installing
d. Add fuel in five gallon increments until a total of tank units.
50 gallons has been added to each tank. Check fuel b. Service fuel cell in accordance with fueling pro-
quantity indicator reading for each five gallons of cedures and check for leaks.
fuel added, c. Perform the operational and calibration check
in accordance with the Fuel Quantity System Opera-
tional Check and Calibration Procedure.
Removal of Outboard, Auxiliary, and Inboard Fuel
Cell Tank Units. (See figure 11-5. ) 421B0001 and
ON Removal of Main Fuel Tank Unit. (See figure 11-5. )
(421BOOO1 and ON)
The removal of the optional fuel cell (extreme out-
board) fuel quantity tank unit is the same for either The removal procedure is the same for either main
wing; likewise, the removal of the inboard and aux- fuel quantity sending unit.
iliary cells fuel quantity tank units are the same for a. Defuel aircraft in accordance with section 2.
either wing.
CAUTION
a. Defuel aircraft in accordance with Section 2.
During all defueling, tank purging and tank
CAUTION repairing operations, two ground wires from
different points on the aircraft to separate
During all defueling, tank purging and tank approved grounding stakes shall be used to
repairing operations, two ground wires, from prevent ungrounding of the aircraft due to
different points on the aircraft to separate ap- accidental disconnection of one ground wire.
proved grounding stakes, shall be used to pre-
vent ungrounding of the aircraft due to acci- b. (See figure 11-2.) Remove filler cap (4) and
dental disconnecting of one ground wire- gasket (5) from main fuel tank.
c. Tag and disconnect electrical bundle (17) from
b. (See figure 11-4. ) On the extreme outboard op- tank unit (18),
tional cell, remove filler cap (1) and adapter assem- d. Remove four bolts attaching brackets (19) to
bly (2) from fuel cell. bulkhead.
c. Tag and disconnect electrical bundles (17) from e. Working through filler cap access opening,
tank unit (18). carefully remove tank unit (18) from fuel cell (6).
d. Remove tank unit from clip.
e. Working through filler cap access opening care-
11-10 FUEL SYSTEM 421 SERVICE MANUAL

Detail $

Detail

B C
D

5
18

Detail Detail D
8

1. Filler Cap 7. Cover , 13. Sleeve

2. Adapter Assembly 8. Inner Bar 14. Shield
3. Wing Skin 9. Outer Bar 15. Adapter
4. Gasket 10. Support 16. Screw
5. Fuel Cell 11. Washer 17. Drain Cock
6. Fuel Injection Pump 12. Bolt 18. Access Cover

Figure 11-4. Wing Fuel Cells

 421 SERVICE MANUAL FUEL SYSTEM Îl-ll

6
5
4 .

5 3
6

Detail

Detail
"
D

^
c
421-0001 TO 421B0001

'il
6
5
9 4
3

c 12

ta 1 Ë
Detail

1. Bonding Cable 5. Gasket 9. Bolt

2. Wing Rib 6. Fuel Cell 10. Auxiliary Fuel Gage
3. Screw 7. Fuel Quantity Sending Unit 11. Main Fuel Gage
4. Adapter Assembly 8. Washer 12. Front Spar

Figure 11-5. Fuel Indicator System (Sheet 1 of 2)

Change 1
11-12 FUEL SYSTEM 421 SERVICE MANUAL

20
Detail E ostan F

E14262007
F10261007
R
Detail Detail e
421BOOO1 AND ON H51282001

13. Bracket Assembly .

17. Electrical Bundle 21. Terminal Board
14. Bracket 18. Nut 22. Relay
15. Sensor Unit 19. Tank Unit Bracket 23. Nutplate
16. Signal Conditioner 20. Access Plate 24. Doubler

Figure 11-5. Fuel Indicator System (Sheet 2 of 2)

Change 12
 421 SERVICE MANUAL FUEL SYSTEM 11-l A

51264010

1. Line (crossover, selector valve to union) RH 21. Line (main fuel, selector valve to firewall) LH
2. Line (crossover, selector valve to union) LH 22. Line (main fuel, selector valve to firewall) RH
3. Line (crossover, selector valve to 23. Line (heater fuel, tee to shutoff valve)
drain valve) LH 24. Line (heater fuel, shutoff valve to pump)
4. Line (crossover, selector valve to tee) RH 25. Line (heater fuel, pump to filter)
5. Line (auxiliary, selector valve to 26. Line (heater fuel, filter to solenoid)
bulkhead elbow) LH 27. Line (heater fuel, solenoid valve to heater)
6. Line (auxiliary, selector valve to 28. Shutoff Valve
bulkhead elbow) RH 29. Heater Fuel Pump
7. Line (auxiliary, bulkhead elbow to fuel pump) LH 30. Fuel Filter
8. Line (auxiliary, bulkhead elbow to fuel pump) RH 31. Solenoid Valve
9. Line (auxiliary vent, auxiliary tank to 32. Check Valve
main tank) LH 33. Selector Valve LH
10. Line (auxiliary vent, auxiliary tank to 34. Selector Valve RH
main tank) RH 35. Tee
11. Line (vapor return, check valve to 36. Elbow
main tank) LH 37. Union
12. Line (vapor return, check valve to 38. Hose
main tank) RH 39. Drain Valve
13. Line (vapor return, firewall to check valve) LH 40. Strainer Assembly
14. Line (vapor return, firewall to check valve) RH 41. Auxiliary Tank In-Line Fuel Pump
15. Line (main fuel, main tank to union) LH 42. Line (auxiliary, pump to elbow) LH
16. Line (main fuel, main tank to union) RH 43. Line (auxiliary, pump to elbow) RH
17. Line (main fuel, union to union) LH 44. Line (crossover, tee to union) RH
18. Line (main fuel, union to union) RH 45. Line (crossover, union to union) RH
19. Line (main fuel, union to selector valve) LH 46. Line (crossover, union to union) LH
20. Line (main fuel, union to selector valve) RH 47. Line (heater fuel, pump to solenoid)
48. Line (pump drain)

Figure 11-6. Fuel System Plumbing (Sheet 1 of 3)

Change 9
11-128 ÈÙEL. SYSTEM 421 SERVICE MANUAL

10
40
36 36
43
37
41

38
12
37
18
32
37
20 6
14 36
35
22
4 23

45
Detail
421-0001 TO 421A0092

3735 37 46
5
40
2 19
36

35
39
37
3

36
3
3T
33 9
37

21
Detail 13 38
37 15
421-0001 TO 421A0092 37
11
38 51263011

Figure 11-6. Fuel System Plumbing (Sheet 2)

Change 9
 421 SERVICE MANUAL FUEL SYSTEM ÎÎ"l3

40
37
10 36
36 43
37
41*

38
12
37
32
37
14 D ON

421ADetailA
ON y,

47 37 27 37 39 35 37 48
37 1 37

3
37
36
17

35
37
3

35
36

Detail 15
421A0092 AND ON As1263oio
N 5 O E R U M B51263012

Figure 11-6. Fuel System Plumbing (Sheet 3)

Change 9
11-14 FUEL SYSTEM 421 SERVICE MANUAL

Installation of Main Fuel Tank Unit. (See figure quantity tank unit is the same for either left or right
11-5. ) (421BOOO1 and ON) auxiliary fuel cell.
a. Carefully position auxiliary fuel tank unit into
The installation procedure is the same for either cell and secure into place with bolts. Torque bolts
main tank unit. to 50 ±5 inch-pounds.
a. Install main fuel tank unit (17) in position and b. Conneet electrical wires.
secure with brackets (19) and bracket bolts. c. Service fuel cell in accordance with fueling pro-
b. Position electrical connector in main tank and cedures and check for leaks.
secure with nut. d. Replace cover plates and perform operational
c. Connect electrical plug to connector. and calibration check.
d. (See figure 11-2.) Install filler cap (3) and
gasket (5) to main fuel tank.
e. Refuel main tanks
f. Check for leaks.
Fuel Quantity System Calibration (42180001 and On).

g. Check operation of fuel quantity indicating sys- Two methods of calibrating thefuel quantity system
tem. are given. Dry Calibration and Alternate Calibra-
h. Check calibration in accordance with calibration tion.
procedures.
Dry Calibration is the preferred method, being the
Removal and Installation of Signal Conditioner. (See most accurate. Dry Calibration uses the actual tank
figure 11-5. ) (421BOOO1 and ON) units for Zero Calibration, this compensates for the
tank unit and wiring harness tolerances. A fixed
a. Remove access plate (46, figure 1-2) to remove capacitance is added in parallel with the actual dry
signal conditioner (16). tank unit to represent the fuel in the tank to provide
b. Remove four screws and washers attaching the for calibration in the full condition.
signal conditioner to bracket (14).
c. Remove signal conditioner through access hole To calibrate the fuel system with the Dry method, it
(48, figure 1-2), will be necessary to fabricate a capacitance test box
d. Install the signal conditioner by reversing the in accordance with Figure 11-6A or use the Field
removal procedures. Calibration Unit Test Box. The parts for fabricating
the capacitance test box may be purchased locally or
Removal of Auxiliary Fuel Quantity Tank Units. (See through your Cessna Dealers' Organization. The
figure 11-5. ) (421BOOO1 and ON) Field Calibration Unit Test Box is designed for com-
plete maintenance, troubleshooting and calibration,
The removal procedure for the auxiliary fuel tank enabling the technician to measure capacitance of
units is the same for either side. system, individual components, harness insulation
breakdown, resistance of system components and
a. Remove the access cover located just outboard substitute capacitance to simulate the tank sensors
of the engine nacelle on the upper surface of the wing, or actual fuel in the tank.
b. Defuel aircraft in accordance with section 2.
The Alternate method of calibrating the fuel quantity
CAUTION system may be accomplished without the capacitance
test box. This method checks fuel temperature and
During all defueling, tank purging and tank re- density versus total capacitance of fuel. The Alter-
pairing operations, two ground wires from nate method of calibration has a greater chance for
different points on the aircraft to separate error than the Dry Fuel System Calibration.
approved grounding stakes shall be used to
prevent ungrounding of the aircraft due to
accidental disconnecting of one ground wire. Dry Calibration.

a. Defuel aircraft in accordance with Defueling

e. Tag and disconnect electrical wires. Procedures in Section 2.
d. Remove bolts securing the auxiliary fuel tank
unit and carefully remove the unit from the aircraft.
CAUTION

WARNING During all defueling and tank calibration, the

aircraft must be located a safe distance from
Residual fuel accumulation in the wing is a other aircraft and buildings. Fire fighting
fire hazard. Use care to prevent the accu- equipment must be available. Two ground
mulation of such fuel, wires from different points on the aircraft
to separate approved grounding sta.kes shall
Installation of Auxiliary Fuel Quantity Tank Unit. be used to prevent accidental disconnecting
(See figure 11-5.) (421BOOO1 andON) of one ground wire.

The installation procedure for the auxiliary fuel b. Apply electrical power -
If battery is used be

Change 6
 421 SERVICE MANUAL FUEL SYSTEM ll-16

Mb3106E-18-15- ~--------
MS3102A-18-1P
UG RECEPTACLE
CREEN
BLUE Part Number Descrlption Quantity
F
YELLOW MS3100E-18-IS (Pl) Plug I
C
BLACK CU3003A Mini Box 1
RED
MS3102A-18-1P (Jl) Receptacle i

VYl3C33R21F (C2) 33.21 PF Capacitor 1

HI-Z D15 (Alternate C2) 1

33.21 PF Capacitor
HI-Z MST-105D Swltch 1
(s3)
MS35489-5 Grommet i
C2

53

E (MAIN) LO-Z GRAY E

D (AUX) LO-2 WHITE D

(Sg) SWITCH POSlT10NS
-- LCU3003A L off
NOTES: MINI BOX 2. Main Fun
U- A c. 111 vr 1 -vd re:rplacle
1. Plug (PI) mates tCi rece <

(Jy) mates with .r:al er -Ett er Erfer 9 T..vD.ptem -preinzer

wiring diagram in Section 14.

2. All wire except for HT-Z wire tote 22 gage per MIL-W-16878D/4 Type
"E" or equivalent. HI wires to be per MIL-W-1687BD Type "E" 20
gage shleided with T<Dr insulatlon over shield.

421B0001 TO 421BO301

MS3106E-LB-1S -- ----------- -MS3102A-18-lP

RECEPTACLE PartNumber De I,:Ion Quantity
GREEN
F .. BLUE MS3106E-18-lS (P1

C YELLOW Cuson3A MM < 1

BLACK
RED
MS3101A-LB-1P (J
1 ) Rec c:le 1

VYl3C32R6F (C2) 32.6 PF Capacitor 1

IH-
D15 (Alternate C2) 32. 6 PF Capacitar 1

MST-105D ($3) 6G uhmet

S3

E (MAIN) LO-Z GRAY

(S3) SWITCH POSITlONS

D (AUX) LO Z WHITE
ain Full
¯¯
-

CU3003A
MINI BOX

NOTES:
L Plug (P
(J1) mate
) - 1
r
le hi I: rt
miu. -r
-, i a,ar
wiringdu ran MNew 14
2. AllwireroptMrN1ZainlaWW rdL T- 87 .

"E" or equivalent. HI-Z wire Io opr VIL W-16878D Type "E" 2D

.
.

gage shielded with Teflon ins.51 : e er Mield.

421BO301 AND ON

Figure 11-6A. Fabrication of Fuel Quantity Test Box

Change 11
11-18 FUEL SYSTEM 421 SERVICE MANUAL

sure voltage is not less than 22 volts. n. Turn power Off.

c. Place fuel selector handle to "Main" position. o. Interconnect capacitance test box in accordance
d. Adjust the "Main Empty" potentiometer on signal with Figure 11-6A, and recheck "Main Full" indica-
conditioner to read exact zero pounds indication on tion.
fuel quantity indicator. p. If calibration has changed repeat steps c thru 1
until a full indication without change in both main and
NOTE auxiliary zero indication is obtained.
q. After both LH and RH systems have been re-
Tap the indicator slightly when reading indi- stored to their original configurations, read indica-
cator, this will help overcome friction of the tion on auxiliary tank by actuating the override switch
needle when the indicator is in a static con- located below the fuel quantity indicator and verify
dition. that auxiliary zero corresponds to that of main,
r. Turn off electrical power and service fuel sys-
e. Interconnect capacitance test box in accordance tems in accordance with Section 2.
with Figure 11-6A.

NOTE
Alternate Method.
Fabricate test box in accordance with Figure
11-6A. The Alternate method of calibrating the fuel system
should be used only as a temporary calibration until
the preferred method of calibration can be accom-

I
f. Position selector switch on capacitance test box plished. The alternate method of calibration will re-
-30°F
to "Main Full"- quire a thermometer with a scale reading of
g. Adjust the "Main Full" potentiometer on the sig- 150°F.
to
nal conditioner to read 50 gallons on the indicator.
a. Defuel aircraft in accordance with Defueling
Procedures in Section 2.
NOTE

Tap indicator when reading indicator. CAUTION

h. Position selector switch on the capacitance test During all defueling and tank calibration the
box to "Off" and recheck sero indication. aircraft must be located a safe distance from
other aircraft and buildings. Fire fighting
NOTE equipment must be available. Two ground
wires from different points on the aircraft
If the zero indication has changed readjust to separate approved grounding stakes shall
zero and full indications until no change is be used to prevent accidental disconnecting
evident by the adjustment setting of the other, of one ground wire.

i. Turn off power and return aircraft to original

configuration and remove capacitance test box. b. Turn on electrical power.
j. Turn power on and recheck main zero indication. c. Place fuel selector control valve to "Main" posi-
tion.
NOTE d. Adjust the "Main Empty" potentiometer on the
signal conditioner to exact zero on the fuel quantity
This will assure that calibration of the main indicator.
tank was good and not affected by a defective
test box.
NOTE
k. Place fuel selector valve to "Aux" position.
1. Adjust the "Empty Auxiliary" potentiometer on Tap the indicator lightly when reading indi-
the signal conditioner, to read exact zero on the in- cator. This will overcome friction of the
dicator. needle when the indicator is in a static con-
m. With power on the aircraft place fuel selector dition.
handles to "Main" position and check "Main Empty"
potentiometer setting, e. Position fuel selector valve handles to "Auxili-
ary" and adjust the "Auxiliary Empty" potentiometer
NOTE exact zero on the fuel indicator.
f. Using a thermometer measure the temperature
It may be necessary to readjust main and of the fuel and determine density of the fuel from
auxiliary empty potentiometers by switching Figure 11-6B, Temperature Conversion Chart.
back and forth the main and auxiliary posi- g. Fuel the system or tank being calibrated in ac-
tions respectively until NO deviation reading cordance with Fueling Procedures, Section 2.
is evident. h. Record the total number of gallons in the tank.

Change 6
 421 SERVICE MANUAL FUEL SYSTEM Îl-ISA

i. Multiply the density of the fuel as determined

in step f by the total number gallons of fuel in the
tank to obtain total pounds of fuel. < g a

O 6 2
NOTE

This should be the exact number of pounds of -

e i
fuel as indicated on the fuel quantity indicator. I
6 O

j. If the total pounds of fuel as indicated on the fuel

quantity indicator is other than the total number
pounds of fuel as determined in step h, adjust the
"Main Full" potentiometer on the signal conditioner -

to the correct number of pounds. a 5 a

k. Place fuel selector valve to "Auxiliary" position u-
and check fuel quantity gage.
1. Determine total pounds of fuel from Figure
11-6B using same procedure as for the main tank.
5.6

WARNING

When using the Alternate Method of calibra- -so -20 -10

0 10 i T 4 5Ò 80 90 100 10 20

tion allow 10°/oerror in total quantity pounds TEMPERATURE DEGREES FAHRENHEIT

of fuel.
EXAMPLE: A -
Temperature, 30
B -

Density, 6. O Pounds Per Gallon

TOTAL FUEL IN TANK 51. O gal

FUEL DENSITY 6. 00 lbs/gäl

TOTAL POUNDS IN TANK 306. 00 lbs

MINUS UNMEASURED FUEL 6. 00 lbs =

1 gal ±0. 5 gal

APPROXIMATE GAUGED FUEL 300 lbs

Figure 11-6B. Temperature Conversion Chart

Change 2
11-1 FUEL SYSTEM 421 SERVICE MANUAL

FUEL LINES AND VENTS. (See figure 11-6.) NOTE

Fuel from either main tank may be routed to either It will be necessary to remove turbocharger
engine. Fuel vapor from the vapor separator, loca- and remove access plate behind turbocharger
ted in the engine-driven fuel pump, is returned to the to gain access to the elbow fitting.
fuel tank through a vapor return line. The main sup-
ply line and vapor return line are routed through the
wing forward of the main spar. The cross feed lines
between the selector valves are routed aft of the fire-
wall and forward of the main spar to the fuselage. j. Disconnect auxiliary fuel line (8) from elbow (36)
A fuel line drain valve, located at each wing root, and strainer (40) and remove through access hole
is installed in the low point of each cross feed line. (63, see figure 1-2).
These drain valves are accessible by removing the
wing gap covers. It is not necessary to remove the
wing gap covers to drain the valves. The main fuel k. Disconnect auxiliary vent line (10) and remove
tanks are vented through an overboard vent line and through wing tip rib.
the auxiliary fuel cells are vented into the main tank. 1. Loosen clamp which secures auxiliary vent line
(42) in fuel cell and remove through access hole.
Removal of Fuel Lines. (See figure 11-6.) NOTE

Removal procedure is given for the right wing. It will be necessary to open the outboard
Removal of the left wing fuel lines is the same auxiliary fuel cell to gain access to the clamp
except the heater fuel lines which are installed in the that secures the vent line.
right wing only.

a. (See figure 1-2.) Remove access panels (41, 42, m. Disconnect crossover line (1) at selector valve
43, 46, 47, 48, 53, 63, 54, 55, 56 and 34), and union at wing gap and remove through selector
b. (See figure 1-2.) Remove forward wing gap skin valve access.
(35).
c. Remove tip tank fairing. n. Disconnect crossover line (4) at selector valve
d. Defuel main tank in accordance and unions and remove through selector access,
with Section 2.
o. Remove heater lines (23, 24, 25 and 26) through
access holes in lower side of wing.

WARNING Installation of Fuel Lines. (See figure 11-6. )

Residual fuel draining from lines is a fire To install fuel lines, reverse removal procedure.
hazard. Use care to prevent accumulation
of such fuel when lines and hoses are being
disconnected. NOTE

Use a suitable thread lubricant on the male

e. Disconnect right main fuel lines (16, 18, and 20) threads of all fittings. Fuel soluble lubricant
at hose (38), unions (37), and tee (35). only should be used. DO NOT USE ANY OTHER
f. Remove clamps securing line and remove lines. FORM OF THREAD COMPOUND.

NOTE WING LOCKER FUEL. (Optional)

It will be necessary to remove tip tank to Optional wing locker fuel consists of a fuel cell (26. 0
withdraw the main fuel line, vapor return U. S. gallons usable each wing) mounted in the for-
line and vent line, ward portion of each wing locker, an electrical oper-
ated, manually controlled fuel pump, a pressure
switch to control the panel warning lights and neces-
sary plumbing. There are no separate fuel selector
g. Disconnect vapor return line at hose (38) and controls or fuel quantity gages for the optional wing
check valve (32) and remove through tip rib. locker fuel tanks. Optional fuel is pumped directly
h. Disconnect vapor return line (14) from firewall into the main fuel tanks with independent fuel trans-
fitting and remove through access hole, fer pumps. Switches are provided on the panel to
i. Disconnect auxiliary fuel line (6) from selector control each pump. Indicator lights mounted directly
valve (34) and elbow mounted through spar web. above the switches are illuminated by pressure switch-
Then remove through fuel selector access hole. es to indicate fuel has been transferred. There is no
fuel quantity indicating system in the wing locker fuel
tanks.

Change 1
 421 SERVICE MANUAL FUEL SYSTEM 11-16Û

25 5
6
2 11

24 Detail

Detail

421-00D0el
T 21B0001

3
E D
24

19

Detail
421B0001 AND ON l2
21 13

18
17
16
23 20

22 14

21
Detaii E ,

*421A0151 AND ON
AND ALL AIRCRAFT 15
MODIFIED PER SERVICE LETTER ME69-34. Detail D
1. Adapter 7. Drain Line 13. Vent Line 19. Wing Locker Fuel Transfer Pump
Assembly 8. Screw 14. Spacer 20. Pressure Switch
2. Nacelle Skin 9. Drain Valve 15. Heater 21. Fuel Line
3. Gasket 10. Strainer 16. Fuel Line 22. Fuel Line
4. Support 11. Fuel Line 17. Tee Assembly' 23. Drain Line
5. Fuel Cell 12. Vent Line 18. Check Valve 24. Filler Neck
6. Clamp 25. Vent Hole

Figure 11-7. Wing Locker Fuel Installation (Optional)

Change 1
11-100 FUEL sYSTEM 421 SERVICE MANUAL

Trouble Shooting the Wing Locker Fuel System.

TROUBLE PROBABLE CAUSE CORRECTION

WING LOCKER FUEL Circuit breaker open. Reset circuit breaker.

PUMP INOPERATIVE
(OPTIONAL FUEL) Open circuit or loose connections. Check circuit and repair.

Defective fuel pump. Replace pump.

INDICATOR LIGHTS WILL Open circuit or loose connections. Check circuit and repair.
NOT LIGHT (OPTIONAL
FUEL) Defective pressure switch. Replace pressure switch.

Removal of Wing Locker Fuel Cell. (Optional) (See d. Remove nut, spacer (14) and screw securing vent
figure 11-7. ) line (13) to structure, disconnect heater wires to vent
heater (15), remove through lower access opening.
a. Refer to Section 2 and defuel aircraft. e. Disconnect drain line (7) from drain valve and
b. Remove screws attaching adapter assembly (1) to remove.
nacelle skin and to support (4). f. Remove two screws securing drain valve (9) and
c. Remove screws attaching support (4) to fuel cell bracket assembly and remove drain valve through
(5). wheel well access,
d. Reaching through filler opening, remove the g. Disconnect fuel line (11), fuel line (22) and drain
clamp securing vent line (12) to the fuel cell (5). line (23) from fuel pump (19). Disconnect electrical
e. In the wheel well area, remove clamp securing wires to fuel pump. Remove four nuts, washers and
drain line (7) to fuel cell. bolts securing pump to structure and remove pump.
f. Disconnect strainer (10) from fuel line (11), re-
h. Disconnect fuel line (21) from tee. Disconnect
move clamp securing strainer (10) to fuel cell and re- electrical wires from pressure switch (20) and re-
move line (22) and pressure switch (20) as an assem-
move strainer,
through open bly.
g. Carefully fold fuel cell and remove
ing vacated by the support and adapter assembly. 1. Disconnect fuel line (21) from check valve (18)
and remove through wing leading edge access open-
Installation of Wing Locker Fuel Cell. (Optional) ing.
(See figure 11-7. ) j. Remove clamps securing fuel line (16) in wíng
leading edge. Disconnect fuel line (16) from tee (17)
a. Carefully insert fuel cell through the filler open- and at main fuel tank. Remove line through outboard
ing and arrange the cell in the correct position. wing leading edge rib.
b. Insert strainer (i0) iilto fuel cell and secure with Installation of Wing Locker Fuel Plumbing. (Optional)
clamp (6). (See figure 11-7.)
c. Insert drain line (7) into fuel cell and secure with
clamp (6)- a. Install wing locker fuel plumbing by reversing
d. Insert vent line (12) into fuel cell and secure to the removal procedure.
cell with clamp. b. Connect all electrical wires,
e. Install a new gasket (3) between support (4) and c. Service fuel system with proper grade of fuel and
fuel cell (5) and secure with screws. check for leaks.
f. Install a new gasket (3) between support (4) and d. Check vent heater for proper operation,
adapter assembly (1) and secure with screws.
VENT HEATERS
g. Attach adapter assembly (1) to nacelle skin with
screws.
Vent heaters are installed on the fuel tank vent tubes
Removal of Wing Locker Fuel Plumbing. (Optional) to prevent freezing of vapors. Care must be exer-
(See figure 11-7. ) cised in removing and installing the vent tubes to pre-
vent damage to the heaters and electrical leads.
a. Refer to Section 2 and defuel aircraft. a. Replace heaters in accordance with following
procedures:
NOTE 1. Clean vent tube surface in area where heater is
to be installed with 280 grit sandpaper and ketone
Removal procedure is the same for either (MEK).
wing locker fuel plumbing. 2. Install in accordance with detail A, figure 11-2,
and bond vent heater to vent tube using epoxy cement
b. (See figure 1-3.) Remove wing access covers Epon 834 with curing agent TTA in accordance with
(40, 41, 42, 43, 44, 45, 46, 49, 48 and 63). Remove the manufacturers instructions.
applicable cover plates in wheel well area. 3. Pot the heater wires to protect them from dam-
c. (See Removal of Wing Locker Fuel Cell.) Ac- age using EC2273 or Hysol EA9309, mixed in accord-
complish steps b, c, d, e and f. ance with the manufacturer's instructions.

Change 11
 421 SERVICE MANUAL FUEL SYSTEM 11-17

SELECTOR VALVES. FUEL SELECTOR CONTROL SYSTEM.

One fuel selector valve is located in each wing just The fuel selector valve controls are located between
forward of the main spar, between the fuselage and the front seats on the cabin floor. The valve control
nacelle. Each valve is cam operated from the cabin on the right controls fuel flow to the right engine and
thru flex cables. Each valve has four positions which the valve control on the left controls the fuel flow to
allows fuel to flow to the respective engine from the the left engine. The handles are of rotary-type and
270°
left tank, the right tank, the auxiliary tank, or stops are operated mechanically with a flex cable to
all fuel flow thru the valve. Each fuel selector the fuel selector valve assemblies mounted between
valve has a fuel strainer located on the bottom of the the nacelles and the fuselage in the leading edge of
valve and a quick-drain is provided to remove mois- the wing. The four valve positions which:are marked
ture and sediment. on the "metalcals" are: LEFT MAIN, RIGHT MAIN,
LEFT AUXILIARY, and OFF; RIGHT MAIN, LEFT
Removal of Fuel Selector Valves. (See figure 11-9.) MAIN, RIGHT AUXILIARY, and OFF. The fuel se-
lector valve handles indicate the position of the fuel
The removal of the fuel selector valves is essentially selector valves. The valve handles are protected
the same for either valve; however, there are left by a guard to prevent the possibility of switching or
and right brackets which mount the valve into movement by pilot's or copilot's feet.
position.
a. Defuel main tank in accordance with Section 2.
b. Remove upper and lower access cover plates. Removal of Fuel Selector Control System. (See fig-
c. Disconnect lines and fittings. ure figure 11-9. )

CAUTION Removal of fuel selector control system is the same

for either selector.
Plug or cap all open lines or fittings. a. Fuel selector valve handles OFF.
-

b. Remove pilot and copilot seats,

d. Disconnect selector linkage at valve arm. c. (See figure 1-2.) Remove carpet as required and
e. Remove the three bolts securing valve and remove remove access covers (73 and 77).
the valve from wing. d. (See figure 1-2.) Remove access covers (34, 35,
56 and 57).
e. Remove fuel selector handle.
Installation of Fuel Selector Valves. f. (See figure 11-9.) Disconnect cable (7) by re-
moving cotter pin, nut and bolt.
The installation of the fuel selector valves is essen- g. Remove two screws attaching gear box to bracket
tially the same for either valve; however, there are and remove gear box.
left and right brackets which mount the valve into po- h. Disconnect cable from selector valve in wing by
sition. removing cotter pin, nut and screw.
a. Install fittings in valve and clock to correct po- i. Remove cable terminals, jam nuts, clamps and
sition. pressure seal assembly.

NOTE NOTE

It is permissable to use teflon tape to improve To remove pressure seal at fuselage skin and
sealing ability of fittings used in fuel selector to facilitate routing of cable, remove the
valve. Lay end of tape on male threads of heat exchanger in accordance with Section 13.
fitting leaving one and one half threads ex-
posed, wrap around once, stretching tightly j. Remove cable through heat exchanger access ,

so that the threads show through the tape. opening.

Overlap end of tape approximately 3/8" and
cut tape. Assemble joint.

b. Install valve, securing in position with three

bolts, then connect lines.
c. Connect selector linkage and safety.

WARNING

Residual fuel draining from the lines and hoses

is a fire hazard. Care should be exercised in
disposal of such fue? when lines or hoses are
disconnected to prevent its accumulation in
the wing.

Change 12
11-18 FUEL SYSTEM 421 SERVICE MANUAL

421-0001 TO 421A0092

421A0092 AND ON

1. Fuel Inlet 4. Filter 6. Bowl Assembly

2. Gasket 5. Drain Valve Push-Rod 7. Fuel Outlet
3. Screw 8. Spring

Figure 11-8. Fuel Selector Valve and Strainer

Change 12
 421 SERVICE MANUAL FUEL SYSTEM ll-l$

11

"
11
10 1-

°
I 5

/ O

7 Detail
421-0001 TO 421A0092
Detail $

1 Screw 5. Bracket 9. Nut

2. Spacer 6. Gear Box 10. Terminal
3. Handle 7. Cable 11. Bolt
4. Floorboard 8. Cotter Pin 12. Fuel Selector Valve

Figure 11-9, Fuel Selector Control Handle

ll-2Û FUEL SYSTEM 421 SERVICE MANUAL

--FLEX FLEX CABLE TERMINAL

CABLE TERMINAL
FUEL SELECTOR VALVE
LEVER ARM
FWD
SEAL FUEL SELECTOR
VALVE

FLEX CABLE O
RBL WING ROOT I
HANDLE 32. 55

POSITION MARKER (Typical)

-FUEL SELECTOR GEAR BOX

GEAR BOX LEVER ARM

VIEW OF RH WING SHOWN, LH WING IS SIMILAR

421A0092 AND ON

FLEX CABLE TERMINAL

-FLEX CABLE TERMINAL
FUEL SELECTOR VALVE
LEVER ARM
FWD
SEAL FUELSELECTOR
Ma VALVE

FLEX CABLE
RBL WING ROOT
HANDLE 32. 55

POSITION MARKER (Typical) STOP PIN -

STOP PIN

--FUEL SELECTOR GEAR BOX LEFT MAIN (CROSSOVER) ---

OFF
GEAR BOX LEVER ARM
RIGHT AUXILIARY RIGHT MAIN
VIEW OF RH WING SHOWN, LH WING IS SIMILAR

421-0001 TO 421A0092

Figure 11-10. Fuel Selector Rigging Schematic

 421 SERVICE MANUAL FUEL SYSTEM Îl• 1 /11-22

Installation of Fuel Selector Control System. (See dles to the LEFT MAIN and RIGHT MAIN positions
figure 11-9. ) respectively.
j. Observe that the pointer end of handle nearly
a. Place gear box in position and secure to bracket aligns with marker on placard after traveling approx-
90°
(5) with two screws. imately from the OFF position and the fuel se-
b. Install selector handle (3) with spacer and screw. lector valve lever arm seats in the respective main
c. Route cable through heat exchanger access tank detent on the fuel selector valve.
opening into cabin and into wing root rib. (The k. If the fuel selector valve lever arm has not
shortest telescoping unit into fuselage.) seated in proper detent after handle has been rotated
90°
d. Secure cable housing to wing root rib with from the OFF position, lengthen or shorten ter-
jamb nuts and to bracket under floor with jamb nuts. minals and/or flex cables as necessary to achieve
e. Install jamb nuts and terminals to cable ends and proper rigging.
secure terminals to gear box and selector valve. 1. Continue from the LEFT MAIN and RIGHT MAIN
f. Install and seal pressure seal assembly in acc- position, rotate handles to the LEFT AUXILIARY and
ordance with sealing procedures in Section 16. RIGHT AUXILIARY positions respectively.
g. Check operation for binding and smooth actuation. m. Observe that the pointer end of handle nearly
h. Check for proper rigging. aligns with marker on placard after traveling ap-
180°
i. Install heat exchanger in accordance with Section proximately from the OFF position and the fuel
13. selector valve lever arm seats in the respective aux-
NOTE iliary tank detent on the fuel selector valve.
n. If the fuel selector valve lever arm has not seat-
Support and security of the fuel selector cables ed in proper detent after handle has been rotated 180°
is most essential to provide the optimum fuel from the OFF position, lengthen or shorten terminals
selector valve operation. Inspect the fuel and/or flex cable as necessary to achieve proper rig-
selector cable support points for adequate ging.
tightness and security. o. Continue from the LEFT AUXILIARY and RIGHT
AUXILIARY position, rotate LH handle to the RIGHT
Rigging the Fuel Selector Valve. . (See figure 11-10.) MAIN (crossover) and RH handle to the LEFT MAIN
(crossover).
a. (See figure 3-9.) Remove scuff plates and fold p. Observe that the pointer end of handle nearly
back carpet (9) just enough to remove floorboard aligns with marker on placard after traveling approx-
270°
access plate (93, figure 1-2). imately from the OFF position and the fuel se-
b. (See figure 1-2.) Remove wing access plates (34 lector valve lever arm seats in the respective in-
and 35). board crossover tank detent on the fuel selector valve.
c. Position lever arm on fuel selector valve in wing q. If the fuel selector valve lever arm has not seat-
to the most inboard position. ed in proper detent after handle has been rotated 270°
from the OFF position, lengthen or shorten terminals
NOTE and/or flex cable as necessary to achieve proper rig-
ging.
Observe that the attachment hole in lever arm NOTE
is pointing inboard· If terminal and/or flex cable adjustments have
been made at any one of the fuel selector posi-
d. Connect terminal on flex cable to the fuel selec~ tions, repeat steps i, j, 1, m, o and p to ver-
tor valve lever arm with attaching bolt, nut and cot¯ ify correct rigging and make further adjust-
ter pin• ments as necessary.
e. On the cabin floorboard, rotate (counterclock-
wise for LH and clockwise for RH) the handle on the Operational Check.
gear box until lever af-m comes to rest against gear a. Place left selector valve in the left position.
box bracket. Place right selector valve in the right position and
f. Rotate handle (clockwise for LH and counterclock- start both engines.
5°
wise for RH) approximately until a pointer on han- b. When the engines are sufficiently warmed, ad-
dle is aligned with the OFF position marker- vance the throttles to 1500 RPM. Observe the fuel
flow gage to assure there are no radical fluctuations
CAUTION and that fuel flows at proper pressure. Observe the
engine for a proper short continuous run.
Observe that the handle is parallel with the c. Place both selector valves in RIGHT position,
centerline of aircraft and pointer on handle Make observations given in step b.
is indexed to the OFF position (aft)· d. Place both selector valves in AUXILIARY posi-
tion. Make observations given in step b.
g. With the handles in the position described in e. Place both selector valves in LEFT position.
step f. above, adjust terminal and flex cable until Make observations given in step b.
attach holes on gear box lever arm and terminal are f. Place left selector valve in OFF position with
aligned. engine at idle RPM. Engine should run momentarily,
h. Connect terminal to gear box lever arm with then fail.
attaching screw, nut and cotter pin- g. Place right selector valve in OFF position with
i. Start from the OFF position and rotate (clock- engine at idle RPM, Engine should run momentarily,
wise for LH and counterclockwise for RH) the han- then fail.
 421 SERVICE MANUAL INSTRUMENTS AND Î -l

RELATED SYSTEMS

SECTION 12

INSTRUMENTS AND RELATED SYSTEMS

Table of Contents

Page Page

GENERAL . . . . . . .
12-1 Installation of Vacuum Air Filter . .
12-13
INSTRUMENTS . . . . .
12-2 Removal of Vacuum Relief Valve . .
12-13
Troubleshooting . . . . . .
12-2 Installation of Vacuum Relief Valve . .
12-13
Vacuum System . . . . . .
12-6C Adjustment of Vacuum Relief Valve . .
12-14
Pitot-Static System . . . . .
12-6C Removal of Vacuum System Plumbing .
12-14
Engine . . . . . . .
12-7 Installation of Vacuum System Plumbing .
12-14
Miscellaneous . . . . . .
12-7 PITOT-STATIC SYSTEM . . . .
12-14
Typical Instrument Removal . . .
12-9 Removal of Pitot and Static Lines . .
12-14
Typical Instrument Installation . .
12-9 Installation of Pitot and Static Lines .
12-15
Removal of Magnetic Compass . .
12-9 Testing Static Pressure System . .
12-15
Installation of Magnetic Compass . .
12-9 Dual Pitot System . . . . .
12-16A
Compass Alignment Procedure . . .
12-9 Isolation of Excessive Static System
Index Error Alignment . . . .
12-10 Leakage . . . . . . .
12-18
Compensator Adjustments . . . .
12-10 Testing Pitot Pressure Lines . . .
12-19
Compensation Calculations . . .
12-10 Purging Pitot or Static Lines . . .
12-19
Compass Compensation . . . .
12-10 Removal of Pitot Tube . . . .
12-21
Typical Bulb Removal and Installation .
12-10A Installation of Pitot Tube . . . .
12-21
INSTRUMENT PANELS . . . .
,
12-10A MANIFOLD PRESSURE SYSTEM . . .
12-21
Removal . . . . . . . .
12-10A Removal of Manifold Pressure
Installation . . . . . . .
12-10A Plumbing . . . . . .
12-21
VACUUM SYSTEM . . . . . .
12-10B Installation of Manifold Pressure
Troubleshooting . . . . . .
12-11 Plumbing . . . . . .
12-21
Removal of Vacuum Pumps . . .
12-11
Installation of Vacuum Pumps . . .
12-13
Removal of Vacuum Air Filter . . .
12-13
Replacement of Vacuum Air Filter
Element . . . . . . . 12-13

GENERAL. and installation is provided as a guide for the re-

moval and installation of all instruments. The instru-
All instruments, except the magnetic compass which ments are grouped and listed according to systems:
is mounted on the windshield centerstrip, are located the vacuum system and the pitot static system. The
on the shock-mounted instrument panel or the station- remainder of the instruments are listed under engine
ary panel. Specific locations are illustrated in fig- or miscellaneous instruments.
ure 12-1. For ease of maintenance, each instrument
may be removed individually or the shock-mounted
panel with instruments attached may be removed. NOTE
The instruments are positioned in back of and attach-
ed to the instrument panel by three or four attaching Disassembly or overhaul of instruments
bolts and nuts. Since all instruments are mounted in should be performed only in approved ships
a similar manner, a description of a typical removal by authorized personnel.

Change 10
2. INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

INSTRUMENTS.

Troubleshooting the Instruments.

TROUBLE PROBABLE CAUSE CORRECTION

VACUUM SYSTEM INSTRUMENTS

BOTH VACUUM INSTRUMENTS Dirty filter element. Restricted Clean and replace filter. Adjust
MALFUNCTIONING airflow or improper adjustment. vacuum relief valve.

ONE VACUUM INSTRUMENT Defective instrument. Replace instrument.

MALFUNCTIONING, OTHER
VACUUM INSTRUMENT
OPERATING NORMAL

DIRECTIONAL Insufficient suction. Repair or replace vacuum pump and/

GYRO PRECESSES or check system.
AND/OR SPINS
Filter element dirty. Replace filter element.

Excessive vibration of instrument Replace instrument panel shock

panel. mounts.

Operational limits exceeded. Replace or overhaul directional gyro.

GYRO HORIZON WILL Insufficient suction. Repair or replace vacuum pump

NOT ERECT, TUMBLES, and/or check system.
AND IS SLUGGISH IN
OPERATION Filter element dirty. Replace filter element.

Excessive vibration of instrument Replace instrument panel shock

panel. mounts.

Operational limits exceeded. Replace or overhaul gyro horizon.

SENSITIVE ALTIMETER

INDICATING POINTERS Static line obstructed. Disconnect static line from all in-
FAIL TO RESPOND struments and altitude hold on auto-
pilot computer, and blow out line
with dry compressed air.

EXCESSIVE POINTER Excessive vibration of static Secure to aircraft structure or com-

VIBRATION line or hose. ponents.

ERRONEOUS INDICATIONS Water or foreign matter in static Disconnect static line from all in-
line. struments and altitude hold on auto-
pilot computer, and blow out line
with dry low pressure air.

Loose static line connection. Test and repair in accordance with

testing static pressure system.

Defective instrument. Replace instrument.

AIRSPEED INDICATOR
POINTER FAILS TO RESPOND Clogged pitot line, Disconnect pitot line and altitude
hold on autopilot computer from in-
strument and blow out line with dry
compressed air.

ERRONEOUS INDICATIONS Water or restriction in pitot and/ Disconnect tube from all pitot static
or static line. system instruments and altitude hold
on autopilot computer and blow out
lines with dry compressed air.
 421SERVICE MANUAL INSTRUMENTS AND• l2-2Afl2•26
RELATED SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

ERRONEOUS INDICATIONS Leak in pitot and/or static line. Test and repair in accordance with
testing of pitot pressure system.

Pitot and/or static line improp- Connect lines as illustrated in fig-

erly connected. ure 12-9.

VERTICAL SPEED INDICATOR

POINTER FAILS TO RESPOND Water or restriction in static line. Disconnect static line from all pitot
static system instruments and alti-
tude hold on autopilot computer and
blow out with dry compressed air.

Defective instrument. Replace instrument.

TURN-AND-BANK INDICATOR

NOTE

To operate any of the electrical instruments, the battery

switch must be in the ON position.

BALL OFF CENTER Incorrectly mounted. Mount correctly.

Defective instrument. Replace instrument.

TURN INDICATED Open circuit, Reset circuit breaker. Check and

repair circuit.

Defective instrument. Replace instrument.

DUAL TACHOMETER

ERRONEOUS INDICATION Defective circuit. Check and repair circuit.

OR INDICATOR INOPERA-
TIVE Defective instrument. Replace instrument.

Defective tachometer generator. Replace tachometer generator.

DUAL FUEL QUANTITY INDICATOR

NO INDICATION Sunken float. (421-0001 to 421B0001) Replace float.

Defective tank unit. (421BOOO1 and on) Repair or replace tank unit.

Open circuit. Reset circuit breaker. Check

and repair circuit.

Defective fuel quantity sending unit. Replace fuel quantity sending

(421-0001 to 421BOOO1) unit.

Defective fuel quantity signal condi- Replace fuel quantity signal

tioner (421B0001 and on) conditioner.

Defective indicator. Replace indicator.

ERRONEOUS INDICATOR Damaged float. (421-0001 to Replace float.

421BOOO1)

Defective fuel tank unit. (421BOOO1 Repair or replace tank unit.

and on)
 421 SERVICE MANCAL INSTRUMENTS AND
RELATED SYSTEMS

TROUBLE PROBABLg CAUSE CORRECTION

ERRONEOUS INDICATOR Defective circuit. Check and repair circuit.

Malfunctioning fuel quantity sending Check in accordance with

unit. (421-0001 to 421B0001) Section 11. Replace if neces-
sary.
Malfunctioning fuel quantity signal Check in accordance with
conditioner. (42120001 and on) Section 11. Replace if neces-
sary.

Defective indicator. Replace indicator.

Improper calibration. Calibrate in accordance with

calibration procedures.

FLAP POSITION INDICATOR

NO INDICATION WITH Open circuit. Reset circuit breaker. Check and

FLAPS DOWN repair circuit.

Defective indicator. Replace indicator.

Defective transmitter. Replace transmitter.

ERRONEOUS INDICATION Improper engagement of trans- Rig in accordance with Section 8.

WITH FLAPS DOWN mitter cam with pinion gear.

Defective circuit. Check and repair circuit.

Defective indicator. Replace indicator.

Defective transmitter. : Replace transmitter.

OUTSIDE AIR TEMPERATURE

INDICATOR
POINTER FAILS TO RESPOND
Open circuit. Reset circuit breaker. Check and
repair circuit.
ERRONEOUS INDICATION
Defective circuit. Check and repair circuit.

Defective air temperature bulb. Replace air temperature bulb.

Defective indicator. Replace indicator.

STALL WARNING INDICATOR

HORN FAILS TO OPERATE Open circuit. Reset circuit breaker. Check and
repair circuit.

Defective transmitter. Replace transmitter.

Defective horn. Replace horn.

COMBINATION GAGES

NO INDICATION ON OIL Open circuit. Reset circuit breaker. Check and

TEMPERATURE GAGE repair circuit.

Defective oil temperature bulb, Replace oil temperature bulb.

Defective instrument. Replace instrument.

12--4 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

ERRONEOUS INDICATION OF Defective circuit. Check and repair circuit.

CYLINDER TEMPERATURE
GAGE Defective cylinder head tempera- Replace cylinder head temperature
ture bulb. bulb.

Defective instrument. Replace instrument.

HIGH CYLINDER HEAD Improper ground. Remove ground wire and door
TEMPERATURE INDICATOR bonding area. Replace bonding
wire.

ERRONEOUS OIL PRES- Defective instrument. Replace instrument.

SURE INDICATION
Broken or restricted oil pres- Repair or replace oil pressure line,
sure line.

Defective oil pressure relief valve. Repair or replace relief valve.

MANIFOLD PRESSURE GAGE

SLUGGISH POINTER Damaged or restricted lines. Remove line and blow out restriction.
OPERATION Replace line or hoses as necessary.

Defective instrument. Replace instrument.

MAGNETIC COMPASS

EXCESSIVE COMPASS Improper compensation. Compensate the compass.

ERROR
External magnetic interference. Locate the interference and elimi-
nate if possible.

FAILURE TO RESPOND Compensating magnets de- Replace instrument.

TO COMPENSATION magnetized.

FUEL FLOW GAGE

ERRONEOUS FUEL PRES- Clogged or restricted fuel lines. Clean fuel lines and fuel strainer.
SURE INDICATION
Broken or restricted fuel flow lines. Replace fuel flow lines.

Defective fuel pump. Replace fuel pump.

Defective instrument. Replace instrument.

VOLTAMMETER
NO INDICATION ON VOLT-
AMMETER Defective voltammeter. Check/replace voltammeter.

Defective voltammeter leads. Check/repair or replace.

 421 SERVICE MANUAL INSTRUMENTS AND 12-5
RELATED SYSTEMS

Detail A
14
5 6 7 8 9 10 11 12 1 15 16 17 18 19 20 21

5 31 30 29 28 25 24 23 22
C

Detail C Detail B
421-0001 TO 421A0001

1. Nut 10. Clock 18. Fuel Flow Gage

2. Bonding Strap 11. Altimeter 19. Outside Air Temperature Gage
3. Shock Mount 12. Vertical Speed Indicator 20. Prop Deice Ammeter
4. Washer 13. Economy Mixture Indicator 21. Optional Right Panel
5. Optional Instrument 14. Compass 22. Right Engine Combination Gage
6. Airspeed Indicator 15. Tachometer 23. Left Engine Combination Gage
7. Turn and Bank Indicator 16. Manifold Pressure 24. Auxiliary Fuel Gage
8. Directional Gyro 17. Fuel Gage 25. Flap Position Indicator
9. Horizontal Gyro 26. Oxygen Gage

Figure 12-1. Instrument Panel (Sheet 1 of 3)

12-6 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

145

5 7 8 5 8 9 10 11 1/2 13 16 17 18 19 20 21

5 31 30 29 32 24 23 22
a
C D
26

27

Detail

Detail D 421A0001 TO 421B0001

27. Variable Cabin Pressure Rate 31. Cabin Rate of Climb Indicator 36. Pressurization Controls
Controller (Optional) 32. Flap Preselect Indicator 37. Light Dimming Controls
28. Suction Gage 33. Annunciator Panel 38. Gyro Slaving Ammeter
29. Cowl Flap Position Indicator 34. Radio Panel 39. Cabin Heat Controls
30. Cabin Differential Pressure Gage 35. Screw 40. Cigar Lighter (Optional)

Figure 12-1. Instrument Panel (Sheet 2 of 3)

 421 SERVICE MANUAL INSTRUMENTS AND 1 "$$
RELATED SYSTEMS

14
10 6 2
9 11 12 8 16 15 18 17 23 22 13 6 7 19 9 38 20 11

35
37 30 31 Detail A

Detail g 36
28 26 32 39 4]

Detail 421B0001 AND ON

Figure 12-1. Instrument Panel (Sheet 3 of 3)

Change 1
12-68 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

11

12 13 14 14 15 4 16 17 8
1 23456789 10

'
30

2e

3 18
2 27 26 18 25 24
23 2201

421BO301 TO 421BOSO1

is 24 31 32 y
421B0501 AND ON

Figure 12-1A. Instrument Panel

Change 8
 INSTRUMENTS AND
MANUAL
-

421 SERVICE RELATED SYSTEMS

Figure 12-1A. Instrument Panel Callouts

1. Slaving Meter 18. ADF Ind.

2. Clock 19. Flap Position Ind.
3. Turn and Slip Ind. 20. Autopilot Controller
4. Airspeed Ind. 21. Yaw Damper Switch
5. ADI Attitude Director Ind. 22. Variable Cabin Pressure Controller
6. HSI Horizontal Situation Ind. 23. Dimming Control
7. Vertical Speed Ind. 24. OBS Ind.
8. Altimeter 25. Mode Selector
9. Manifold Pressure Ind. 26. Cabin Rate-of-Climb
10. Tachometer 27. Oxygen Pressure Ind.
11 Magnetic Compass 28. Circuit Breakers
12. Fuel Flow Ind. 29. Suction Gage
13. Fuel Quantity Ind. 30. Differential Pressure Gage
14. Engine Combination Gage 31. Annunciator Panel
15. EGT Ind. 32. Fire Detect Panels
16. Outside Air Temperature Ind. 33. DME Indicator
17. Propeller Deice Ammeter 34. Radar Altimeter

1. Screw 3. Padded Control Wheel 5. LH Stationary Panel

2. Padded Glareshield 4. RH Stationary Panel Padding Padding

Figure 12-1B. Padded Glareshield and Stationary Panel

Change 8
12-60 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

CABIN DIFFERENTIAL PRESSURE

GAGE

ERRONEOUS INDICATIONS Static line obstructed. Disconnect static line from

all instrument and altitude
hold on autopilot computer,
and blow out line with dry
compressed air.

Defective instrument. Replace instrument.

CABIN RATE OF CLIMB INDICATOR

POINTER FAILS TO Static ports obstructed. Remove obstructions.

RESPOND
Defective instrument. Replace instrument.

PROPELLER DEICE AMMETER

NO INDICATION ON Defective ammeter. Check/replace ammeter.

AMMETER
Defective ammeter leads. Check/repair ammeter.

Vacuum System Instruments. from the true horizon. The indicator is marked from
zero to 90 degrees.
a. The Directional Gyro. A flight instrument in- d. Directional and Attitude Gyro Precession. Ac-
4°
corporating an air-driven gyro stabilized in the ver- ceptable limits for gyro drift is in either direction
tical plane. The gyro is rotated at high speed by from a heading during a ten minute period. Exces-
lowering the pressure in the airtight case with the sive gyro precession can be caused by low vacuum
engine-driven vacuum pumps and simultaneously system pressure; therefore, the following items
allowing air at atmospheric pressure to enter against should specifically be checked prior to gyro removal
the gyro buckets. Due to gyroscopic inertia, the and/or replacement:
spin axis continues to point in the same direction, 1. Vacuum system lines for kinks or leaks.
even though the aircraft yaws to the left or right. 2. Central air filter or instrument filter for dirt.
This relative motion between the gyro and the instru- The filter should be cleaned and/or replaced.
ment case is shown on the instrument dial which is 3. Suction gage for proper operation.
similar to a compass card. The dial, when set to 4. Vacuum relief valve for proper adjustment.
agree with the aircraft's magnetic compass, provides Adjustment instructions are outlined in "Adjustment
a "dead beat" azimuth indicator that is free from of Vacuum Relief Valve. "
"swing. "
b. The Slaved Directional Gyro includes a single, NOTE
synchro-driven pointer and in some gyros, a dual A gage reading of 5.0 inches of mercury is
pointer for use with ADF/VOR inputs to provide con- desirable for gyro instruments; however, a
tinuous indication of the bearing to specific ground range of 4.75 to 5.25 inches of mercury is
stations. The slaved directional gyro operates with acceptable.
a slaving meter and a flux detector, to produce input
to the electronic compass circuit in the gyro. The e. The Suction Gage is calibrated in inches of mer-
flux detector is remotely located in the tailcone of cury and indicates the amount of vacuum created by
the aircraft. Refer to Compass Alignment procedure the engine-driven vacuum pumps. The suction gage
for compensating the slaved directional gyro, has four connecting lines. The upper outboard line
c. The Horizontal Gyro is essentially an air-driven is routed directly to the directional gyro to monitor
gyroscope rotating in a horizontal plane, operated by vacuum. The lower lines are attached to the vacuum
the same supply of vacuum as the directional gyro. system manifold for the purpose of monitoring vacu-
Due to gyroscopic inertia, the spin axis continues to um pump function. The upper inboard line is routed
point in the vertical direction providing a constant to static air.
Visual reference to the attitude of the aircraft relative
to its pitch and roll axis. A bar across the face of Pitot-Static Instruments.
the indicator represents the horizon and a miniature
adjustable aircraft is mounted to the case. Aligning a. Altimeter is a pressure
The Sensitive instrument
the miniature aircraft to the horizon bar simulates that measures the change in static pressure and by
the alignment of the aircraft to the actual horizon and means of an indicator, translates this change into
any deviation simulates the deviation of the aircraft altitude above sea level. A barometric scale is in-

Change 10
 421 SERVICE MANUAL INSTRUMENTS AND O"
RELATED SYSTEMS

corporated in the instrument. The barometric pres- ture in degrees Fahrenheit. The oil temperature is
sure scale is calibrated in inches of mercury and is electrically received from the oil temperature bulb,
set manually by a knob on the lower left-hand corner located in the engine oil passage and calibrated in
of the altimeter case. Three pointers on the dial of degrees Fahrenheit. Oil pressure is taken directly
the instrument indicate altitude in units of 100 feet, from the pressurized engine oil passage. It is
1000 and 10, 000 feet. routed through small lines and hoses to the combina-
b. The Airspeed Indicator measures the differential tion gage which calibrates the pressure to pounds per
between ram, or impact air pressure taken at the square inch.
pitot tube, and static air pressure. The instrument e. The Dual Tachometer is a remote electrical in-
dial is calibrated in both knots and miles per hour. strument that is connected by electrical leads to a
Should airspeed indicator require maintenance and tachometer generator on each engine. The tachom-
recalibration, recalibrate in accordance with FAA eter calibrates electrical current from the tachom-
TSO-2C. eter generator to revolutions per minute. The point-
c. The Vertical Velocity Indicator measures the ers, one marked for each engine, are concentrically
rate of change in static pressure when the aircraft mounted so that the engines may be synchronized
is climbing or descending. By means of a pointer visually by over-lapping the pointers.
and dial it indicates the rate of ascent and descent
of the aircraft in feet per minute. Miscellaneous Instruments.
d. The Cabin Altitude and Differential Pressure
instrument is a dual purpose instrument which indi- a. The Turn-and-Bank Indicator is a combination
cates cabin altitude in feet. It also indicates differ- instrument. The turn indicator is an electrically-
ential pressure between cabin pressure and atmos- driven gyro mounted in a horizontal gimbal that is
pheric pressure. This function is given in PSI. attached to a pointer which indicates the rate of turn.
e. The Cabin Altitude Rate of Change indicates the The slip indicator consists of a curved, liquid-filled
rate in feet per minute at which the cabin pressure glass tube in which an inclinometer ball, moving with
is changing. The instrument dial is calibrated in dampened motion, changes positions according to the
100 feet increments. The cabin altitude rate of gravitational and centrifugal force acting upon the
change is similar in function to the vertical velocity aircraft.
indicator except the cabin altitude rate of change in- b. The Voltammeter, located on the left console,
dicator is referenced to cabin pressure instead of measures the current received from each alternator,
static air pressure. individually or simultaneous, the battery drain or
the battery bus voltage, whichever is desired, using
Engine Instruments. the Voltammeter Selector Switch.
c. The Magnetic Compass is located on the wind-
a. A Fuel Quantity Indicator with two pointers on shield centerstrip. It consists of a pair of parallel
the dial, one for each wing tip tank, is located in the magnetic bars surrounded by a circular calibrated
upper right-hand portion of the instrument panel- compass card visible through a window in the com-
The fuel quantity indicator receives electrical signals pass case. The compass case is a metal bowl filled
from the variable resistor type fuel quantity sending with liquid to dampen dial oscillation. Lighting is
units located inside the wing tip tanks and indicates, integral and controlled by a rheostat on the switch
in gallons, the amount of remaining usable fuel. An panel. The compass has two adjusting set screws,
auxiliary fuel quantity indicator with two pointers on one for N-S headings and one for E-W headings.
the dial, one for each wing tank, is located in the These set screws are located on lower face of com-
lower right-hand portion of the instrument panel in- pass behind the metal disc.
dicating the amount of remaining usable fuel in the d. The Stall Warning Unit is mounted in the left
auxiliary tanks. console. A stall warning transmitter, mounted on
b. The Dual Fuel Flow Gage senses the pressure at the leading edge of the left wing, energizes the elec-
which fuel is delivered to the fuel injection nozzles- trical circuit when the aircraft approaches a stall
The gage is marked as a flowmeter. Two pointers and causes the horn to operate. The stall warning
indicate the fuel-flow for the left and right engines. transmitter incorporates a heater element, operated
The gage is a direct reading pressure gage. by the pitot heater switch, to prevent ice from ham-
c. The Manifold Pressure Gage is a direct readin pering its operation.
gage used to indicate the pressure of the induction e. The Outside Air Temperature Gage is calibrated
air in the engine intake system. Two pointers indi- in degrees Fahrenheit and operated electrically from
cate the manifold pressure in inches of mercury a free air temperature bulb located in the heat ex-
absolute. changer ram air duct, in the right stub wing.
d. The Engine Combination Gages, (Cylinder Head f. (421-0001 to 421A0001) The flap position indica-
Temperature, Oil Temperature and Oil Pressure), tor is electrically operated and indicates the position
one for each engine, are remote electrical indicators- of the flaps from zero to 45 degrees. The indicator
Each gage is connected electrically to a cylinder head operates in conjunction with a flap position trans-
temperature bulb located underneath the number two mitter located just aft of the fuselage spar. Refer
cylinder of the respective engine. As the tempera- to Section 8 for flap position transmitter removal
ture of the bulb changes, the combination gage meas- and installation procedures.
ures the change and the pointer indicates the tempera-

Change 7
12-8 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

1
2
3

1. Lighting Fixture 4. Instrument 8. Connector

2. Spacer 5. Electrical Connector 9. Hose Fittings
3. Instrument Panel 6. Lockwasher 10. Vent Plug
7. Nut

Figure 12-2. Typical Instrument Installation

1. Oil Pressure Line 3. Cylinder Head Wiring Bundle

2. Oil Temperature 4. Instrument Panel

Figure 12-3. Engine Combination Gauge

 421 SERVICE MANUAL INSTRUMENTS AND -Û
RELATED SYSTEMS

g. (421A0001 and On) The flap position is indicated by Removal of Magnetic Compass. (See figure 12-4.)
the flap preselect system pointer on the stationary in-
strument panel. a. Remove screw (4) securing compass light wire
h. The cowl flap position indicator (421-0001 to to compass card light.
421BOOO1), mounted on the stationary panel in front of b. Remove two mounting screws (6) securing com-
the pilot, is an electrically operated instrument using a pass to mounting bracket (2).
transmitter connected to the cowl flap actuator for in- c. Retain the compass card bracket for reassembly.
dicating degrees of travel.
i. The clock is a standard eight-day aircraft clock with Installation of Magnetic Compass. (See figure 12-4.)
a sweep second hand. A winding stem is provided in the
lower left hand portion of the case. a. Position compass (7) and compass card bracket on
windshield and secure with two screws (6).
centerstrip
Typical Instrument Removal. (See figure 12-2. ) b. Connect compass light wire to compass card light
terminal with Screw (4),
a. If instrument is not accessible, remove instru-
ment panel in accordance with procedures for instru-
ment panel removal.
b. Disconnect and tag electrical wires, hoses or , o
tubes from back of instrument being removed. 1
c. Plug all hoses and cap fittings to prevent the
entry of foreign matter,
d. Remove the connector (8), nut (7), washer (6),
and spacer (2) from the lighting fixture (1) if installed
on instrument.
e. Remove instrument (4) from panel (3) by remov-
ing nuts and screws.

OObeEreplaced,

If the iñstrument is remove the

hose or tube fittings and install the replace-
ment unit.

Typical Instrument Installation. (See figure 12-2.)

NOTE

Lubricate straight threads with specification

petrolatum; tapered threads with specifica-
tion anti-seize compound. Apply lubricant
to male threads only, omitting the first two
threads.

a. Position instrument (4) on back of instrument 1. Windshield Centerstrip 6. Mounting Screw

panel (3) and secure with attaching screws and nuts• 2. Mounting Bracket 7. Compass
3. Centerstrip Trim 8. Compass Card
NOTE 4. Terminal Screw Bracket
5. Compass Light Wire 9. Compass Card
Steps "b" and "c" should be omitted if no light-
ing fixtures are used to attach instrument. Figure 12-4. Magnetic Compass

b. Install lighting fixtures using spacers (2), wash-

ers (6) and nuts (7). Compass Alignment Procedure.
c. Attach connectors (8) to lighting fixtures (1).
d. Connect hoses, tubing and electrical wires as The following procedures pertain to alignment of the
tagged at removal. magnetic (standby) compass and the flux detector on
e. Reinstall panel if removed. the slaved directional gyro. A calibrated compass
rose must be used to accomplish the alignment pro-
cedures.
a. Insure compensator adjustments are set to a
neutral position. The compensators are located on
flux detector or gyro, depending on system.
b. Using a hand held magnetic compass, check all
ferrous material parts for magnetism near the mag-
netic compass and flux detector.
Change 11
12-10 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

c. Degauss any parts within two feet which cause d. Repeat compass alignment procedure step j, 1
10°
greater than deflection of the magnetic compass, thru 8.
and any part within four feet which cause greater e. The remaining error at the cardinal headings as
than 90° deflection of the magnetic compass. received in step d should equal the difference between
d. Insure that each of the applicable systems are the initial cardinal heading errors obtained originally
controlled from the proper circuit breakers, and in compass alignment procedure step j, 1 thru 8.
the corresponding "HDG" flag appears when the cir- f. Recalculate error and assure the remaining
cuit breaker is disengaged. error is 0 ±0. 5 degrees.
e. Insure slave meter is operative.
f. Insure the systems fast slaving circuitry is Compensator Adjustments.
operational.
g. Insure all electrical instruments for the aircraft a. If the corrected error as calculated in index
±2°
are installed and operative, error alignment paragraph step a is greater than
h. Insure other aircraft and vehicles are a safe out the compensators must be adjusted. The index cor-
of the way distance. rected errors are used to calculate the required
270°
i. Position aircraft on the heading of the com- amount of degrees of compensation required for the
pass rose- remote compass. The errors obtained in the com-
j. With both engines running 1000 RPM, turn on the pass alignment procedure step j, 1 thru 8, for the
following: standby compass will be used to determine the re-
1. All circuit breakers- quired amount and degree of compensation for the
2. Inverters. standby compass.
3. All lights except landing lights and reading
lights. Compensation Calculations.
4. All avionics systems.
5. All electrical systems except pitot heat, stall a. Using cardinal heading errors calculated in in-
and static heaters. dex error alignment, step e for remote compass sys-
6. Allow slaved gyro system to stabilize (stabili- tem and compass alignment procedure for the stand-
zation speed may be increased by using fast slave). by compass, algebraically sum the north and south
7. Record the slaved gyro system error in degrees errors, divide this sum by two and change the sign
and direction with the slave meter nulled. of the result. The resulting number is the amount
8. Record the standby compass error in degrees and direction of north/sourth compensator adjust-
and direction- ment.
b. Repeat step a for east/west errors.
NOTE
Compass Compensation.
High readings are positive errors, low read-
ings are negative errors. a. At one cardinal heading, adjust the appropriate
compensator the amount calculated in the compensa-
360°
9. Position aircraft on the heading of the com- tion calculations paragraph step a.
90°
pass rose and repeat steps 1 thru 8. b. Rotate the aircraft and adjust the appropriate
90°
10. Position aircraft on the heading of the com- compensator the amount calculated.
pass rose and repeat steps 1 thru 8. c. Rotate the aircraft to the next two cardinal head-
180°
11. Position aircraft on the heading of the com- ings and insure that no errors greater than two de-
pass rose and repeat steps 1 thru 8. grees for slaved gyro systems or five degrees for
the standby compass are present.
Index Error Alignment. d. With normal aircraft power, all electrical sys-
30° headings (includ-
tems on, rotate the aircraft to
This alignment should insure that the compass sys- ing cardinals). Stop on each reading long enough to
tems flux detector is positioned for minimum index allow the gyros to stabilize and the slave meter to
error, null.
a. Algebraically sum the four cordinal heading e. Observe and record the headings indicated by the
errors obtained in preceding paragraph, steps 1 thru slaved gyro system.
8. f. Record the headings indicated by the standby com-
b. Divide the sum obtained by four. 30°
This result is pass at the positions.
±5°
the index error correction and direction of rotation g. No error greater than shall be indicated by
of the flux detector. the standby compass.
c. Rotate flux detector the direction and amount as
calculated in steps a and b. CCW rotation of the flux NOTE
detector is required to correct a positive error.
The errors determined in step f shall be re-
NOTE corded on the compass correction card.
Approximately five degrees rotation equals
approximately 1/8 inch distance measured h. Turn off all electronic systems and shut down
on the outer circumference of the flux detec- engines.
I tor.

Change 10
 421 SERVICE MANUAL INSTRUMENTS AND 12-10A
RELATED SYSTEMS

b. (421B0301 to 421B0801), remove the hinged in- |

strument panels as follows:
1. Remove the two holdown screws at aft end of
glareshield. Lift shield up and pull aft. Remove
from aircraft.
2. Remove two screws from Royalite cover over
steering column and lift cover away from column.
3. Remove two screws from block holding steering
column in place against instrument panel structure.
2 4. Remove two screws holding instrument panel to
structure, swing panel out and down.
5. Disconnect tubing and electrical leads, tag and
stow. Cap and plug hose connections.
6. Remove six mount screws from hinge at base of
panel assembly.
7. Remove panel from aircraft.
c. Remove the instrument paneÏs not shock-mounted
as follows:
3 1. Remove screws, nuts, and washers from instru-
ment panel and pull panel aft enough to disconnect in-
struments electrical leads.
', 2. Tag all electrical leads and remove panel.

Installation of Instrument Panels. (See figure 12-1. )

a. (421-0001 to 421B0301 and 421B0801 and On),

install the shock-mounted instrument panels as follows:g
1. Electrical Connector 2. Bulb 3. Flange
CAUTION
Figure 12-5. Indicator Bulb
Clean bonding area between stationary panel
Typical Bulb Removal and Installation. (See figure and instrument panel before starting to install
12-5.) instrument panel.

a. Tag and disconnect electrical connector (1). NOTE

b. Remove bulb (2).
c. Install bulb by reversing removal procedures. Inspect rubber shock-mounts (3) and bonding
strap (2) for deterioration and cracks. If
either is damaged, replace before installing
INSTRUMENT PANELS. instrument panel.

The stationary instrument panel is a part of the fuse- 1. Position instrument panel, to attach hoses and
lage structure and is not ordinarily considered re- electrical leads as tagged at removal.
movable. (421-0001 to 421BO301 and 421B0801 and
On), the pilot's and copilot's panels contain the flight NOTE
instruments and are removable. (421BO301 to
421B0801), the pilot's and copilot's panels are hinged Lubricate straight threads with specification
for easier access to instruments and fittings. The petrolatum; tapered threads with specification
radio or radio panel is directly attached to the sta- anti-seize compound. Apply lubricant to male
tionary panel depending upon the optional radio equip- threads only, omitting the first two threads.
ment installed. The removal of these panels will de-
pend upon the individual or group of instruments re-
quired to be removed. 2. Position instrument panel on shock mounts (3)
and install nuts (1).
Removal of Instrument Panels. (See figure 12-1. ) 3. Connect tubing lines to instruments.
b. Install the instrument panel not shock-mounted
a. (421-0001 to 421B0301 and 421B0801 and On), as follows:

I
remove
follows:
the shock-mounted

1. Disconnect
instrument

tubing lines to instruments

panels as

and tag.
1. Position the instrument
trical leads as tagged at removal.
2. Locate instrument
panel, to attach elec-
panel and install screws,
2. Remove nuts (1) from shock mounts (3) on in- washers, and nuts.
strument panel and pull panel aft enough to disconnect
instrument hoses and electrical leads. Tag all hoses
and electrical leads.

Change 11
12-10B INSTRUMENTS AND 421SERVICE MANUAL
RELATED SYSTEMS

c. (421BO301 to 421B0801), install the hinge mount- sure bulkhead and to the suction gage. The suction
I ed instrument panels as follows:
1. Position panel to align hinge assembly with
gage is vented to ambient air through a fitting mounted
in the forward cabin bulkhead. The suction gage indi-
structure. Secure panel to structure with six attach- cates amount of vacuum present in the system; also
ing screws. provided are operational indicator buttons for each
2. Check condition of hoses, connectors, and wire pump. The vacuum air filter is provided to remove
bundles. dust particles and vapor from the air, providing dry,
3. Attach hoses and electrical leads as tagged at clean air for the instruments. Vacuum air is routed
removal. to a vacuum operated dump valve located on the att
4. Swing panel up taking care not to allow hoses or cabin pressure bulkhead. The dump function of this
wires to kink or bind. Secure in place with two valve is governed by an electric solenoid which opens
screws. the vacuum line to open the dump valve and closes the
5. Reinstall block, cover, and glareshield. vacuum line to close the dump valve.
NOTE

VACUUM SYSTEM. All flexible and fixed line fittings, clamps, re-

lief valves, and filters must be cleaned and

A dry vacuum pump, which requires no lubrication of suitably protected by caps or bags until instal-
any kind, is located on the att right accessory mount led in aircraft. The vacuum system shall not
pad of each engine. The pump outlets are exhausted be open while awaiting the remaining parts to
into the engine nacelle. The vacuum line plumbing is be installed. Prior to running of the vacuum
routed from the vacuum pumps through the nacelles to pumps, the lines shall be flushed with air to
the relief valves mounted in the wing root area. From approximately seven (7) cubic feet per minute
the relief valves, the lines are routed through the stub while alternately closing off the ends of the
wing, through the cabin to the vacuum manifold loca- lines. This will create pressure pulses to
ted on the left side of the forward cabin bulkhead. dislodge and eject foreign particles.
The manifold has check valves included to prevent re-
verse flow, in the event of failure of either vacuum
pump. Hoses are routed from the manifold to the di-
rectional gyro, horizontal gyro, and suction gage.
Other hoses connect the gyros to a vacuum air filter
located on the forward side of the forward cabin pres-

Change 11
 421 SERVICE MANUAL INSTRUMENTS AND l ll
RELATED SYSTEMS
Trouble Shooting the Vacuum System.

TROUBLE PROBABLE CAUSE CORRECTION

NO SUCTION INDICATED Defective vacuum pump. Check suction at pump.

AT ONE SOURCE Replace pump.

Disconnected, broken or plugged Check suction through lines and hoses.

lines or hoses. Clean or replace lines and hoses.

Defective relief valve. Check suction to and from relief

valve. Replace relief valve.

.Defective suction gage. Check suction at applicable line to

test indicator buttons. Replace
suction gage.

NO SUCTION INDICATED, Defective suction gage. Check suction to gage. Replace

BUT GYROS OPERATE gage.
NORMA LLY

LOW SUCTION Defective vacuum pump. Check suction at pump. Replace

pump.

Leaking or restricted lines or Clean or replace lines and hoses.

hoses. Check suction through lines and hoses.

Defective or improperly adjusted Check suction to relief valves. Ad-

relief valves. just relief valve in accordance with
adjusting procedures. Replace if
defective.

Defective check valves. Check operation of check valves.

Replace manifold assembly.

HIGH SUCTION Relief valve air filters dirty. Check operation with filters removed.
Clean or replace filters.

Defective or improperly adjusted Check suction to relief valves. Ad-

relief valves. just relief valves in accordance with
adjusting procedures. Replace if
defective.

SUCTION GAGE Excessive vibration. Visually check for panel, gage or

FLUCTUATES plumbing vibration. Determine cause
of vibration and correct.

Defective suction gage. Check for fluctuating suction to gage.

Replace gage.

Removal of Vacuum Pumps. (See figure 12-6.)

NOTE
a. Remove upper nacelle cowl.
b. Loosen the two hose clamps securing hoses (1 Do not clean vacuum pump (2) in solvent.
and 3) to the vacuum pump (2). Clean by wiping with a clean cloth.
c. Remove vacuum pump (2) by removing four at-
taching nuts and washers.

Change 6
12-·12 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

21
13
23

19

13 14

18

Sta. 100. 00
Forward
421-0001 TO 421B0101
Pressure 20
'
11

17
421B0101 AND ON

1. Outlet Hose 9. Manifold Line 17. Left Indicator Hose

2. Vacuum Pump 10. Pressure Indicator Hose 18. Vacuum Manifold
3. Inlet Hose 11. Left Filter Hose 19. Right Indicator Hose
4. Wing Line 12. Horizontal Gyro Hose 20. Vacuum Air Filter
5. Stub Wing Line 13. Horizontal Gyro 21. Suction Gage
6. Aft Line 14. Directional Gyro 22. Relief Valve
7. Intermediate Line 15. Right Filter Hose 23. Static Line
8. Forward Line .
16. Directional Gyro Hose 24. Pressurization Line

Figure 12-6. Vacuum System

Change 5
 421 SERVICE MANUAL INSTRUMENTS AND 12"ÎÊ
RELATED SYSTEMS

Installation of Vacuum Pumps. (See figure 12-6.) Replacement of Vacuum Air Filter Element.

NOTE NOTE

If a new vacuum pump is being installed, re- It is not required to remove air filter to re-
move the serviceable fittings from the old place the element.
pump and install the fittings on the new pump.
Use no oil of any sort, no thread lubricant of a. Remove wing nut from the bottom of the vacuum
any description on any fitting used on the in- air filter (20).
let side of the vacuum pumps. Make sure in- b. Remove vacuum air filter element.
let fitting on the dry vacuum pump has an inlet c. Install new vacuum air filter element.
screen. d. Fasten element in place using wing nut,

a. Align splines on the vacuum pump drive (2) with

splines on the engine drive and slide vacuum pump Installation of Vacuum Air Filter. (See figure 12-6.)
into position so the ports are facing to the right.
b. Secure vacuum pump (2) to the engine with four Reverse the vacuum air filter removal procedures.
washers and nuts.
c. Slide vacuum line hose (3) and clamp onto the in
port of the vacuum pump and secure clamp. Removal of Vacuum Relief Valve. (See figure 12-6.)
d. Slide vacuum pump outlet hose (1) and clamp onto
the out port of the vacuum pump and secure clamp. a. Remove wing gap skin (35). (See figure 1-2.)
e. Install upper nacelle cowl. b. Remove relief valve (7) by loosening hose clamps,
then slide hoses off of valve.
c. Remove valve (7).
Removal of Vacuum Air Filter. (See figure 12-6. )
a. Disconnect filter hoses (11 and 15) from filter Installation of Vacuum Relief Valve. (See figure
fittings. 12-6.)
b. Remove vacuum air filter (20) from forward
side of the left hand cabin bulkhead by removing two Reverse the vacuum relief valve removal procedures.
screws.

---Sta. Directional Gyro Horizontal Gyro

100. 00
Forward
Static , Pressure
Source Bulkhead

Vacuum Air Filter

Suction Gage

-l I-I I-I
Check Valve And
Vacuum Manifold

Relief Valve Relief Valve

Dump Valve Vacuum Pump Vacuum Pump

Outlet Outlet

Figure 12-7. Vacuum System Schematic

12-14 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

Adjustment of Vacuum Relief Valve, 1. Remove manifold (18) by disconnecting all hoses
from manifold and removing two screws.
Since a relief valve is used for each vacuum source, m. Remove hose from manifold (18) to instrument
each relief valve must be adjusted separately. and instrument to filter by removing clamps at mani-
a. Remove wing gap skin (35), (See figure 1-2.) fold and disconnecting hoses at instrument.
b. Remove safety wire from adjusting screw lock-
nut.
c. Start the engines and idle the right engine. Installation of Vacuum System Plumbing. (See figure
d. With left engine operating and tachometer read- 12-6.)
ing 1700 RPM, the suction gage should read 4.80
inches of mercury. NOTE
e. Adjust the left relief valve by loosening the knur-
led screw locknut and adjusting to obtain the desired Slight bending of the vacuum line may be re-
vacuum reading, clockwise rotation of the adjusting quired to facilitate installation, however,
screw increases the vacuum. excessive bending should be avoided. Use
f. Idle the left engine and operate the right engine no oil of any sort, no thread lubricant of any
so tachometer reads 1700 RPM. description on any fitting used on the inlet
g. Adjust the right relief valve by loosening the side of the vacuum pumps.
knurled screw locknut and adjusting to obtain the de-
sired vacuum reading. Clockwise rotation of the ad- a. Reverse the vacuum system plumbing removal
justing screw increases the vacuum. procedure except installation of the upholstery panel,
h. With both engines operating at tachometer RPM wing panels, access panels, carpet, kick plates,
of 1700, the suction gage should read 5,00 ±.25 inches pilot's seat, copilot's seat and cabin divider (optional).
of mercury. If the gage reading is not within these b. Check vacuum system and adjust the relief valves
limits, the relief valves should be readjusted to if system vacuum gage indication is not within the
these limits. specified limits.
i. Shutdown both engines and check that the locknuts c. Install the upholstery panel, wing panels, access
on the knurled adjusting screw are tight. panels, carpet, kick plates, pilot's seat, copilot's
seat, cabin divider (optional) and nacelle cowls.
Removal of Vacuum System Plumbing, (See figure
12-6.)
PITOT STATIC SYSTEM.
NOTE
The pitot tube mounted in the nose of the fuselage and
Removal procedure will be given for left engine connected with plastic tubing to the airspeed indicator
installation only. Removal of right engine in- provides it with ram air pressure. An electrical
stallation is basically the same. heating element is installed within the pitot tube to
prevent ice from obstructing the pitot tube opening
a. (See figure 1-2.) Remove engine nacelle cowls during severe weather conditions. The static pres-
(29, 30 and 33). sure is provided by two holes mounted on opposite
b. Remove hose (1) by loosening clamp and remov- sides of the fuselage, aft of the cabin compartment.
ing. These are connected with plastic tubing and routed
c. Remove hose (3) by loosening clamp at vacuum forward through the right side of the fuselage to a
pump and detaching from union at wing rib. tee. The static drain valve is forward of the tee and
d. Removal of line (4) is not recommended except is accessible through the copilot's side pocket. The
as required for replacement. The replacement of static pressure line is routed from the tee up the
the line with a hose to facilitate installation is per- right side and across to the altimeter, vertical speed
missible. indicator and airspeed indicator. The alternate static
e. Remove pilot's seat, copilot's seat, cabin di- source valve which substitutes an alternate ambient
vider (optional) kick plates and carpet in accordance air pressure for atmospheric air pressure in emer-
with Section 3. gencies is located forward of the left hand switch and
f. Remove line (5) by detaching at the fuselage skin circuit breaker console. The valve is attached by
union and relief valve. Remove through wing gap, plastic tubing to the airspeed indicator.
g. Remove aft cabin vacuum line (6) by disconnect-
ing at fuselage skin union and intermediate line union.
h. Remove intermediate line (7) by disconnecting at Removal of Pitot and Static Lines. (See figure 12-9.)
aft line union and forward line union.
i. Remove left upholstery side panel in accordance The location of all pitot and static lines are shown in
with Section 3. figure 12-9. All lines are standard nylon or aluminum
J. Remove forward vacuum line (8) by disconnecting tubing and fittings. (All of the lines are equipped with
from intermediate line union, and from union at sup- conventional fittings and may be removed when neces-
port bracket. sary.) Lines and fittings may be cleaned by immer-
k. Remove manifold line (9) by disconnecting from sing in denatured alcohol or tri-ethyl alcohol and dry
union at support bracket and from union at manifold with filtered compressed air.
(18).

Change 9
 421 SERVICE MANUAL INSTRUMENTS AND l -16

RELATED SYSTEMS

Installation of Pitot and Static Lines. (See figure NOTE

12-9.)
Do not use positive pressure in the static
a. Install lines as illustrated in figure 12-9. system with the instruments connected.
When applying or releasing vacuum from
NOTE the static system, care should be taken not
to exceed the range of the rate of climb in-
Apply a small amount of suitable thread lub- dicator as instrument damage could result.
ricant to male threads of all metal fittings
before installation.
h. Close pitot control valve to protect airspeed in-
dicators during the test in step (i).
Testing Static Pressure System. (See figure 12-9.) i. With the alternate static valve (16) closed apply
vacuum to the line between the vacuum source attach-
When testing the static pressure system, it will be ment and the alternate static valve (16) until 9550
necessary to evacuate the system using a vacuum feet is indicated on the altimeter. Lock pressure in
source capable of 9 inches Hg. to provide an instru- the line by closing the vacuum control valve and im-
ment altitude indication of 9550 feet. See figure 12- mediately check leak down rate for one minute. The
11 for test equipment and connection schematic, indicated altitude loss should not exceed 190 feet per
minute. Tap indicator lightly during leak down check.
NOTE j. Release vacuum slowly and change alternate stat-
ic valve (6) to the open position.
If autopilot is installed turn off all electrical k. Apply vacuum to the static system until altime-
power. ters indicate approximately 3500. Slowly open pitot
control valve to apply enough vacuum to equalize
a. Set all altimeters to zero. pressure and stabilize the airspeed indicators.
b. Close static drain valve (15).
c. Alternate static system valve (16) must be NOTE
closed.
d. Carefully seal static ports (11) in tail cone with Care must be taken during evacuation of the
masking tape. static system above 3500 feet indicated alti-
e. Connect vacuum source to the alternate static tude to prevent damaging airspeed indicators.
system bulkhead fitting (12) at station 100. 00 lower This can be done by metering vacuum to the
left side of nose compartment. pitot system through the pitot control valve,
f. Disconnect pitot line at aft cabin airspeed indi- to keep from exceeding instrument range.
cator.
g. Attach vacuum line to airspeed pitot tube. This 1. Continue to evacuate the static system until 9550
is to equalize pressure within the cockpit airspeed feet is indicated on the altimeters. Lock pressure in
instruments to prevent damage when vacuum is ap- the static and pitot systems by closing both test con-
plied to the static system. trol valves and immediately check leak down rate for
one minute, tap altimeter lightly during leak down
check.

Static Port Static Port

Altimeter Airspeed Indicator

Static Sump

-F. S. 255. 00
Aft Pressure Alternate Static
Bulkhead Selector Valve
L/H Side Panel
Alternate
Dual Pressure, Static Source
Gage
Sta.

O
R/H Side Panel 100. 00
Vertical Speed Drain Valve Forward
Indicator Pressure
Bulkhead

Figure 12-8. Pitot Static System Schematic

12-16 INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

Detail

Detai
Detail

12

21 Detail E m.E oetan D oetan D

421-0001 TO 421BOOO1 421-0106 AND ON 421-0001 to 421-0106

1. Forward Static Line 8. Sump 16. Selector Valve

2. Altimeter 9. Static Crossover Line 17. Pitot Tube Bracket
3. Pitot Pressure Line 10. Aft Static Line 18. Receptacle
4. Airspeed Indicator 11. Static Port 19. Pitot Tube
5. Static Source Line 12. Alternate Static Line 20. Pitot Line
6. Dual Pressure Gauge 13. Support Bracket 21. Screw
7. Vertical Speed Indicator 14. Static Line 22. Instrument Static Line
15. Drain Valve

Figure 12-9. Pitot Static System (Sheet 1 of 2)

Change 4
 421 SERVICE MANUAL INSTRUMENTS AND lhlÛA
RELATED SYSTEMS

Detali E oetaii F
(OPTIONAL) (STANDARD)
421BOOO1 AND ON 52143002R
E51161102R

Figure 12-9. Pitot Static System (Sheet 2)

To Static
Source Pitot Tubes
Airspeed
Indicators

To Static RH
Source
TowStaetic

Airspeed Pitot Tubes Vertical Speed

RR Indicator
rs

Altirneter

421B0001 TO 421B0801
421BO801 AND ON 10987010

Figure 12-9A. Dual Pitot System Schematic

Change 11
12-16B INSTRUMENTS AND 421 SERVICE MANUAL
RELATED SYSTEMS

Dual Pitot and Static System. (See figure 12-9A. ) source is provided for the copilot's flight instruments.
It is identical to but independent of the pilot's flight
On aircraft 421BOOO1 and On, an optional pitot system instruments static.system.
is provided for the copilot's airspeed indicator. It is
independent of the pilot's airspeed indicator but uses For maintenance and servicing of the dual pitot and
a common static air source. static systems, refer to procedures for removal,
installation, testing and purging of the standard
On aircraft 421B0801 and On, an optional static air systems.

Change 11
 421 SERVICE MANUAL INSTRUMENTS AND Î ÎÎ
RELATED SYSTEMS
I

NOTE

Air bulb with check valves may be obtained

locally from a surgical supply company. This
is the type used in measuring blood pressure.

THICK-WALLED
PRESSURE
SURGICAL HOSE

PRESSURE BLEED-OFF /
SCREW (CLOSED)

AIR BULB
WITH CHECK Rw?
VALVES

CLAMP

THICK-WALLED CLAMP
SURGICAL HOSE

CHECK VALVE

SUCTION CHECK VALVE

TO TEST PITOT PRESSURE SYSTEM

1. Connect pressure hose to pitot tube.

2. Slowly squeeze air bulb to apply desired pressure to pitot system. Desired pressure may be
maintained by repeatedly squeezing bulb to replace any air escaping through leaks.

3. Release pressure by slowly opening pressure bleed-off screw, then remove test equipment.

Figure 12-10. -Pitot System Test Equipment

l -18

INSTRUMENTS AND 421 SERVICE MANUAL

RELATED SYSTEMS

m. A leak down rate of 190 feet per minute or less the system and conduct leak check for one minute.
indicates the static system is within the allowable e. A lea.k rate of less than 190 feet per minute in-
tolerance and has satisfactorily completed the test. dicates cockpit instrument system is satisfactory
n. Slowly release the vacuum from the pitot and and excessive system leakage is isolated to the re-
static systems, remove the test equipment, close mainder of the system in the fuselage.
the alternate static valve (16) and remove tape from 1. Remove line fittings at static system drain
static buttons (11) in tail cone. Reconnect aft cabin valve, aft cabin bulkhead and tail cone sump and
airspeed indicator if installed to return aircraft to make sure fitting line inserts (P/N S-1130-1) are
service. installed and that fittings are not cracked. Rein-
stall fittings using a light coating of Parker thread
Isolation of Excessive Static System Leakage. lube or equivalent for sealant.

If the system leak down rate exceeds 190 feet per NOTE
minute, the leakage must be located and corrected.
Possible sources are the static port assemblies, Care must be used when installing and tight-
system connections and fittings, selector and drain ening nylon line connection nuts to prevent
valves and instrument case leakage, damage due to over-torque.

NOTE 2. Reconnect the cockpit instrument system and

the fuselage system at the static drain valve. Apply
All system connections require plastic line vacuum to the test altitude to check leak down rate.
inserts (P/N 8-1131-1) to seal properly, any If leakage is less than 190 feet per minute the system
connection without inserts must have them is satisfactory.
installed before resealing. f. A leak down rate in excess of 190 feet per minute
while testing cockpit instruments, as described in
When checking for excessive leakage proceed as fol- item (d) above, requires that the leakage be isolated
lows: and corrected.
1. Release vacuum from the cockpit instrument
a. Remove the static line from one of the tail cone system and remove the glove box for easier access .

static ports (11) and plug the line. Apply vacuum to to lines behind the instrument panel.
the system and leak check for one minute as de- 2. Disconnect and plug pitot and static lines be-
scribed above. Check the leakage rate. Repeat the tween pilot and copilot instrument group (copilot op-
above test with the other static port disconnected tional instruments) behind the copilots instrument
from the system. If system leak down rate is im- panel.
proved with static ports out of the system, either or 3. With pilots instruments isolated, apply vacuum
both ports are leaking and should be resealed or re- to the pitot and static systems (monitor airspeed
placed as follows: pitot vacuum above 3, 500 feet) until 9, 550 feet alti-
1. Remove static port by drilling out four rivets. tude is reached and conduct leak check for one min-
Install a tube in the static port, seal the vent hole ute.
securely, apply positive pressure while static port 4. If leak rate for the pilots instrument group is
is immersed in water to detect leakage. If the static less than 190 feet per minute, release vacuum slowly
port is leaking replace it. from the system, reconnect pilot and static lines be-
2. If the static port assembly does not leak it tween pilot and copilot instrument groups coupling
should be reinstalled and sealed using PR1422 the cockpit instruments together again.
(MIL-S-8802). 5. The above test indicated excess leakage in the
copilot instrument group. Check for leak as follows:
NOTE (a) Isolate copilot instruments in the following
order, one at a time -
airspeed rate of climb
Insert a wire through the vent hole to prevent indicator and altimeter. Disconnect and plug
sealant from plugging hole. Do not apply vac- the static line at the instrument (both pitot
uum to port, for a period of 4 hours after re- and static lines for airspeed) and apply vac-
sealing to allow sealant to set. Remove wire uum to the remainder of the system, until a
after sealant has set. 9, 550 foot altitude is reached and conduct
leak down check for one minute.
b. Connect static port lines together and apply vac- (b) After each instrument is tested by removing
uum to 9, 550 feet altitude and check leak down rate it from the system, lines should be reconnect-
for one minute. ed to each acceptable instrument before pro-
c. If static system leak down rate is still in excess ceeding. The results of these tests will show
of 190 feet per minute, slowly remove the vacuum the source of leakage,
source, disconnect and plug cockpit instrument static (c) Instruments found to be leaking excessively
line at the instrument side of the drain valve (located should be replaced.
at the copilots side pocket). This isolates the cock- 6. If the test of the pilots instruments (f. 4. above)
pit instruments from the remainder of the system. indicates a leak rate over 190 feet per minute, the
d. Slowly apply vacuum to the static and pitot sys- following isolation procedure is required:
tems of the cockpit instruments as described pre- (a) Release vacuum from the system and isolate
viously (monitor pitot vacuum above 3, 500 feet) until instruments in the following order, one at a
9, 550 feet altitude is indicated. Lock pressure in time -
airspeed, rate of climb, cabin differ-

Change 9
 421 SERVICE MANUAL INSTRUMENTS AND 12-19
RELATED SYSTEMS

PITOT CONTROL VALVE

SUC ON GAGE (NEEDLE ALVE)

TO PITOT SYSTEM

VACUUM SOURCE
TO STATIC SYSTEM
VACUUM CONTROL VALVE
(NEEDLE VALVE)

NOTE
RATE OF CLIMB 't
VACUUM SOURCE MUST BE CAPABLE OF
INDICATOR
SENSITIVE 9 INCHES OF MERCURY.
ALTIMETER

Figure 12-11. Typical Static System Test Equipment

ential pressure gage and altimeter. Discon- Testing Pitot Pressure Lines. (See figure 12-9.)
nect and plug the static line at the instrument
(both pitot and static lines for airspeed). Ap- a. Connect a pressure source to opening in pitot
ply vacuum to the remainder of the system tube assembly (19).
until the test altitude is reached and check b. Apply pressure slowly until airspeed indicator
leak down rate for one minute. reads 150 MPH; shut off pressure, seal opening and
(b) Reconnect each acceptable instrument to the wait one minute.
static system before proceeding. E instru- CAUTION
ments leak replace instruments.
The amount of pressure required for a 150
NOTE MPH indication is less than 1/2 PSI. Avoid
high pressures as instrument damage will
If leakage is indicated at a point other than result.
the pilots instruments, be sure to test the
static line to the autopilot computer, c. If airspeed indicator (4) drops more than 10 MPH
in one minute, disconnect hose from airspeed indica-
7. With leakage isolated and corrected in the cock- tor (4).
pit instrument system and in the fuselage system, d. Plug hose and apply pressure.
reconnect lines to the tail cone static ports (11). e. Coat lines and connections with a solution of soap
Check security of connections of static lines at the and water to locate leak.
drain valve. f. Tighten or repair faulty connections or replace
8. Apply vacuum to the complete system (monitor lines. Connect hose to instrument and repeat step
airspeed pitot vacuum above 3, 500 f eet) until 9, 550 "b" to be certain connections and lines do not leak.
feet is indicated on the altimeters. Lock pressure
in the static and pitot systems and check leak down CAUTION
rate for one minute. The altitude loss should not
exceed 190 feet per minute- Do not apply suction to pitot pressure system
9. Replace glove box, remove test equipment, re- static system is being tested.
unless
connect pitot line at the aft cabin airspeed, close al-
ternate static valve and replace access openings to Purging Pitot or Static Lines.
return the aircraft to service.
Although the pitot system is designed to drain down
CAUTION to the pitot tube opening, condensation may collect at
other points in the system and produce a partial ob-
If static drain valve is left open during flight, struction. To clear the line, disconnect it at the air-
damage to instruments can occur, speed indicator and, using low pressure air, blow
from the indicator end of the line toward the pitot
tube.

Change 4
 INSTRUMENTS ANo 421 SERVICE MANUAL
RELATED SYSTEMS

CAUTION

Never blow through the pitot lines toward the Like the pitot lines, the static pressure lines must be
instruments. Doing so may damage them. If kept clear and the connections tight. The system has
autopilot is installed with altitude hold, dis- static source sumps that collect moisture and keep
connect the static line from the computer be- the system clear. However, when necessary, purge
fore purging static lines. the system as follows:

Detail

1. Manifold Line 4. Gage Line

2. Wing Line 5. Manifold Pressure Gage
3. Cabin Line 6. Stub Wing Line

Figure 12-12. Manifold Pressure System

Change 9
 421 SERVICE MANUAL INSTRUMENTS AND lŽ-Ž1/ÎŽ-
RELATED SYSTEMS

a. On aircraft 421-0001 to 421-0107: Removal of Manifold Pressure Plumbing. (See fig-

1. Disconnect static line to instruments from the ure 12-12. )
static line drain valve tee.
2. Cap or plug open end of tee. NOTE
3. Open static source drain valve.
4. Plug one static port. Removal procedure will be given for left en-
5. Purge the system from the drain valve with gine installation only. Removal of right en-
clean moisture free air for a period of at least two gine is basically the same.
minutes.
6. Plug opposite static port and repeat step 5- a. (See figure 1-2. ) Remove engine nacelle cowls
7. Remove cap or plug from static line drain valve (29, 30 and 33).
tee. b. Remove cabin divider (optional), pilot's seat,
8. Connect static line to instruments to the static copilot's seat, kick plates, carpet, and left forward
line drain valve tee. upholstery side panel in accordance with Section 3.
9. Leak check static system in accordance with c. (See figure 1-2. ) Remove forward wing strue-
testing procedures· tural skin (35), heat exchanger access (57), air
b. On aircraft 421-0107 and On: inlet access (54), fuel selector access (55), wing
1. Turn static source selector valve to "Alternate fitting access (56), access (69) and front spar
Source. " access (77).
2. Open static source line drain valve. d. Remove manifold line (1) by disconnecting at
3. Plug one static port. rear baffle and firewall bulkhead.
4. Purge system from the drain valve with clean e. Remove wing line (2) by disconnecting from union
moisture free air for a period of at least two minutes at firewall bulkhead and from wing splice union.
5. Plug opposite static port and repeat step 4.
6. Close static line drain valve and turn static NOTE
source selector valve to main system.
It may be necessary to bend the line slightly
to facilitate removal, however, excessive
Removal of Pitot Tube. (See figure 12-9.) bending should be avoided to prevent possible
damage to the lines.
a. Remove screw (21) and pull pitot tube (19) for-
ward· f. Remove stub wing line (6) by disconnecting at .

b. Disconnect heat element receptacle (18)· unions.

c. Disconnect line (20) from pitot tube (19)· g. Remove cabin line (3) by disconnecting from
d. Use denatured alcohol or tri-ethyl alcohol for union at wing splice and at support angle remove
cleaning the pitot tube· clamps then remove line.
e. Dry all parts with filtered compressed air· h. Remove gage line (4) by disconnecting from
union at support angle and from elbow at manifold
gage (5).
Installation of Pitot Tube. (See figure 12-9.)

a. Connect line (20) to pitot tube assembly (19). Installation of Manifold Pressure Plumbing. (See
b. Connect heat element receptacle (18). figure 12-12. )
c. Position pitot tube (19) into sleeve and install
screws (21). Reverse the Manifold Pressure Plumbing procedures,

NOTE
MANIFOLD PRESSURE SYSTEM.
Apply a small amount of suitable thread lubri-
The manifold pressure system consists of a dual cant to male threads of all fittings before in-
manifold pressure gage mounted in the instrument stallation. Slight bending of the manifold pres-
panel. The manifold pressure lines are routed from sure lines may be required to facilitate install-
the intake manifold of each engine to separate con- ation, however, excessive bending should be
nections at the back of the gage. The gage is cali- avoided,
brated in inches of mercury, it indicates the absolute
pressure in the intake manifold of each engine.

Change 9
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

SECTION 13

UTILITY AND OPTIONAL SYSTEMS

Table of Contents

Pae:e Page
HEATING, VENTILATING AND Removal and Installation of Plenum
DEFROSTING SYSTEM . . . . .
13-2C Ducts . . . . . . .
13-10
Description of Heater and Basic Cabin Warm Air Vents and Ducting .
13-14
Components . . . . . .
13-2C Removal and Installation . . .
13-14
Operating Procedures . . . . .
13-2C Cabin Fresh Air Vents and Ducting .
13-14
Troubleshooting the Heater Removal and Installation . . .
13-14
(421-0001 to 421B0229) . . . .
13-4 Cabin Pressurized Air Ducting . .
13-14
Troubleshooting the Heater Removal and Installation . . .
13-14
(421B0149 and On) . . . . .
13-4B PRESSURIZATION SYSTEM . . . .
13-14
Electrical Continuity Checks . . .
13-5 Troubleshooting . . . . . .
13-15
Functional Check of Heater Fuel Supply .
13-6 Heat Exchanger and Pressurization
Removal and Installation of Heater Air Dump Valve . . . . .
13-20A
Assembly (421-0001 to 421BO229) . .
13-6 Removal and Installation of Heat
Removal and Installation of Heater Exchanger, Dump Valve and
Assembly (421B0229 and On) . .
13-6 Pressurization Air Venturi . .
13-20A
Ventilating Air Blower . . . .
13-6 Outflow and Safety Valves . . . .
13-20A
Removal and Installation of Ventilating Removal and Installation . . .
13-20A
Air Blower (421-0001 to 421B0229) .
13-6 Removal and Installation of Safety
Removal and Installation of Ventilating Valve Plumbing . . . . .
13-21
Air Blower (421B0229 and On) . .
13-6 Variable Cabin Pressure System
Combustion Air Blower . . . .
13-7 (Optional) . . . . . . .
13-21
Removal and Installation of Combustion Outflow Valve . . . . . .
13-21
Air Blower (421-0001 to 421B0229) .
13-7 Removal . . . . . . .
13-21
Removal and Installation of Combustion Installation . . . . . .
13-21
Air Blower (421B0229 and On) . .
13-7 Variable Pressure Controller . . .
13-21
Spark Plug . . . . . . .
13-7 Removal . . . . . . .
13-21
Vibrator Assembly . . . . .
13-7 Installation . . . . . .
13-21
Thermostat . . . . . . .
13-7 Removal and Installation of Pressure
Removal and Installation . . .
13-7 Controller Plumbing . . .
13-21
Fuel Solenoid Valve . . . . .
13-7 Preflight Ground Checkout Procedure
Removal and Installation . . .
13-7 (421-0001 to 421B0801) (Optional
Heater Fuel Pump . .
. . .
13-8 System) . . . . . .
13-22A
Removal and Installation Preflight Ground Checkout Procedure
(421-0001 to 421B0229) . . .
13-8 (421B0801 and On) (Optional
Removal and Installation System) . . . . . .
13-22A
(421B0229 and On) . . . .
13-8 CABIN PRESSURIZATION CHECK . .
13-23
Heater Fuel Filter . . . . .
13-8 Standard Cabin Pressurization System
Removal, Cleaning and Installation Flight Check . . . . . .
13-23
(421-0001 to 421A0092) . . .
13-8 Optional Cabin Pressurization System
Removal, Cleaning and Installation Flight Check . . . . . .
13-23
(421A0092 to 42180229) . . .
13-8 Cabin Pressurization System Ground
Removal, Cleaning and Installation Check , , . . . .
13-24
(421B0229 and On. . . . .
13-8 Troubleshooting . . . . . .
13-24A
Cabin Heat Switch . . . . .
13-8 OXYGEN SYSTEM . . . . . .
13-27
Cabin Fan Switch . . . . . .
13-8 Troubleshooting . . . . . .
13-27
Removal and Installation of Cabin Heat Maintenance . . . . . .
13-30
Switch and Cabin Fan Switch . .
13-8 Bleeding . . . . . . .
13-30
Temperature Control . . . . .
13-8 Removal of Oxygen Cylinder -

Removal . . . . . . .
13-10 Regulator Assembly . . . .
13-30
Installation . . . . . .
13-10 Installation of Oxygen Cylinder -

Airflow Controls . . . . . .
13-10 Regulator Assembly . . . .
13-30
Removal . . . . . . .
13-10 Removal of Altitude Compensating
Installation . . . . . .
13-10 Oxygen Regulator . . . . .
13-31
Removal and Installation of Ram Air Installation of Altitude Compensating
Valve Assembly . . . . .
13-10 Regulator . . . . . .
13-31
Removal and Installation of Ram Air Removal of Oxygen Pressure Gage . .
13-31
Control . . . . . . .
13-10 Installation of Oxygen Pressure Gage .
13-31

Change 11
13-2 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Table of Contents (Continued)

Page Page

Inspection Criteria for Acceptance of YAW DAMPER SYSTEM . . . . .

13-42E
Oxygen Cylinders 13-32 13-42E
. . . . .

Troubleshooting . . . . . .

Removal of Oxygen Filler Valve . .

13-32A Removal and Installation . . . .
13-42E
Installation of Oxygen Filler Valve . .
13-32A Rigging . . . . . . . .
13-42E
Removal and Installation of Oxygen Actuator Centering Adjustment . . .
13-42E
Control Cable . . . . .
13-32A INTEGRATED FLIGHT CONTROL SYSTEM .
13-42I
Oxygen Cylinder Identification . . .
13-32B Removal and Installation . . . .
13-42I
Servicing and Inspection of Oxygen NAV-O-MATIC 800 AUTOPILOT SYSTEM .
13-42I
System . . . . . . .
13-32B Removal and Installation of Autopilot
Purging . . . . . . . .
13-33 Aileron Cables . .
13-46
Charging . . . . . . .
13-33 Removal and Installation of Autopilot
Leak Testing . . . . . . .
13-33 Rudder Cables . . .
13-46
Functional Testing . . . . .
13-33 Removal and Installation of Autopilot
SURFACE DEICE SYSTEM . . . .
13-36 Elevator Cables . 13-46
. . . .

Removal of Deice Lines . . . .

13-36 Removal and Installation of Autopilot
Removal of Deice Filter, Control Elevator Trim Control Cables . .
13-46
Valve and Shuttle Valve . . . .
13-36 Removal and Installation of Autopilot
Installation of Deice Filter Control Pneumatic System . . . .
13-46
Valve and Shuttle Valve . . . .
13-36 Removal and Installation of Autopilot
Surface Deice System Check . . .
13-36B Servos . . . . . . .
13-49
SURFACE DEICE SYSTEM (421B0120 Removal and Installation of Autopilot
and On) . . . . . . .
13-36B Flight Controller . . . . .
13-49
Removal of Deice Lines . . . .
13-36B Removal and Installation of Autopilot
Surface Deice System Check . . ,
13-36D Computer . . . . . .
13-49
Cold Patch Repair of Deicer Boots . .
13-37 Rigging Autopilot Control System . .
13-50
Replacement of Deice Boots . . . 13-40A Autopilot Pressure Check and
NAV-O-MATIC 400 AUTOPILOT SYSTEM .
13-40A Adjustment . . . . . .
13-50
Removal and Installation of Autopilot AIR CONDITIONING SYSTEM
Elevator and Control Cables . .
13-41 (421-0001 to 421BOOO1) . . . .
13-51
Removal and Installation of Autopilot Troubleshooting . . . . . .
13-51
Aileron Control Cables . . .
13-41 Removal of Compressor and Condenser
Removal and Installation of Aileron Unit . . . . . . . .
13-52
Servo . . . . . . .
13-41 Installation of Compressor and Condenser
Removal and Installation of Elevator Unit . . . . . . . .
13-52
Servo and Computer . . . .
13-41 Removal of Evaporator, Blower and Cabin
Removal and Installation of Autopilot Divider . . . . . . .
13-52
Gyros . . . . . . -
13-43 Installation of Evaporator, Blower and
Removal and Installation of Autopilot Cabin Divider . . . . . .
13-52
Switches . . . . . . .
13-42 Removal of Condensate Tank and Valve .
13-52
Removal and Installation of Controller .
13-42 Installation of Condensate Tank and
Rigging Autopilot Control System . .
13-42 Valve . . . . . . .
13-52
400A NAV-O-MATIC AUTOPILOT SYSTEM .
13-42 Removal and Installation of Wemac
Removal and Installation of Autopilot Plenum . . . . . . .
13-52
Elevator Control Cables . . .
13-42 Removal of Wemac Shutoff Valve . .
13-52
Removal and Installation of Autopilot Installation of Wemac Shutoff Valve .
13-52
Aileron Control Cables . . .
13-42A Removal of Air Conditioning Plumbing .
13-52
Removal and Installation of Autopilot Installation of Air Conditioning Plumbing .
13-57
Servo . . . . . . .
13-42A AIR CONDITIONING SYSTEM
Removal and Installation of Autopilot (421B0001 to 421B0501) . . . .
13-57
Flap Actuator . . . . .
13-42A Troubleshooting . . . . . . 13-60
Removal and Installation of Autopilot Removal of Compressor . . . .
13-60
Elevator Servo and Computer . .
13-42A Installation of Compressor . . . 13-59
Removal and Installation of Autopilot Removal and Installation of Compressor
Elevator Trim Follow-Up Sensor . .
13-42A Drive Belt . . . . . .
13-64C
Removal and Installation of Autopilot Removal of Manifold Assembly . .
13-64C
Elevator Trim Follow-Up Motor . .
13-42D Installation of Manifold Assembly . .
13-64C
Removal and Installation of Controller .
13-42D Removal of Low Pressure Switch . .
13-64C
Removal and Installation of Autopilot
Gyros . . . . . . .
13-42D
Removal and Installation of Autopilot
Switches . . . . . . .
13-42D
Rigging of Autopilot Control System .
13-42D

Change 11
 421 SERVICE MANUAL UTILITY AND l3- A
OPTIONAL SYSTEMS

Table of Contents (Continued)

Page Page
Installation of Low Pressure Switch . .
13-64D Installation of Temperature Control
Removal of Temperature Control Assembly . . . . . . . 13-64T
Assembly . . . . . . .
13-64D Removal of Evaporator Blower Motor . 13-64T
Installation of Temperature Control Installation of Evaporator Blower Motor . 13-64T
Assembly . . . . . .
13-64D Removal of Expansion Valve . . . 13-64T
Removal of Blower Motor . . . .
13-64D Installation of Expansion Valve . . . 13-64T
Installation of Blower Motor . . .
13-64D Removal of Evaporators . . . . 13-64U
Removal of Expansion Valve . . .
13-64D Installation of Evaporators . . . 13-64U
Installation of Expansion Valve . .
13-64D Removal and Installation of Evaporator
Removal of High Pressure Switch . .
13-64E Condensate Drain . . . . . 13-64U
Installation of High Pressure Switch .
13-64E Removal of Air Conditioning Plumbing . 13-64U
Removal of Blower Fan Blade . . .
13-64E Installation of Air Conditioning Plumbing . 13-64U
Installation of Blower Fan Blade . .
13-64E FIRE EXTINGUISHER . . . . . 13-64V
Removal of Condenser Blower Motor .
13-64E RELIEF TUBE . . . . . . . 13-64V
Installation of Condenser Blower Motor .
13-64F PROPELLER DEICE SYSTEM . . .
13-66
Removal of Receiver-Dryer . . .
13-64F Troubleshooting . . . . . .
13-66
Installation of Receiver-Dryer . . .
13-64F Removal of Slip Ring . . . . .
13-66
Removal of Liquid Trap . . . .
13-64F Installation of Slip Ring . . . .
13-66
Installation of Liquid Trap . . .
13-64F Removal of Brush Holder Assembly .
13-66
Removal of Bypass Valve . . . .
13-64F Installation of Brush Holder Assembly .
13-66
Installation and Adjustment of Bypass Adjustment of Brush Assembly . .
13-69
Valve . . . . . . . .
13-64F Replacement of Brush Assembly . .
13-70
Removal of Latching Pressure Switch .
13-64F Removal and Installation of Propeller
Installation of Latching Pressure Deice Ammeter . . . . .
13-70
Switch . . . . . . .
13-64G Removal of Propeller Deice Timer . .
13-70
Removal of Evaporators . . . .
13-64G Installation of Propeller Deice Timer .
13-70
Installation of Evaporators . . .
13-64G Inspection and Testing of Propeller
Removal of Condensers . . . .
13-64G Deice Timer . . . . . . 13-70
Installation of Condensers . . . .
13-64G Removal of Propeller Deice Boots . . 13-70
Removal and Installation of Evaporator Installation of Propeller Deice Boots . 13-70
Condensate Drain . . . . .
13-64G PROPELLER UNFEATHERING SYSTEM .
13-71
Removal of Air Conditioning Plumbing .
13-64G Troubleshooting . . . . . .
13-72
Installation of Air Conditioning Plumbing .
13-64H Removal, Service, Maintenance and
AIR CONDITIONING SYSTEM Installation of Propeller Governor .
13-72
(421B0501 and On) . . . . .
13-64H Removal and Installtion of Propeller
Troubleshooting Air Conditioner Unfeathering Accumulator . . .
13-73
Hydraulic System . . . . .
13-64L Operational Check of Propeller
Hydraulic System Operational Test . .
13-64L Unfeathering System . . .
13-73
.

Removal of Hydraulic Pump . . .

13-64M PROPELLER SYNCHRONIZER SYSTEM .
13-73
Installation of Hydraulic Pump . . .
13-64M Troubleshooting . . . . . .
13-73
Removal of Hydraulic Motor . . .
13-64M Operation . . . . . . .
13-73
Installation of Hydraulic Motor . . .
13-64M Removal of Propeller Synchronizer
Removal of Compressor . . . .
13-64N Components . . . . . .
13-74
Installation of Compressor . . .
13-64N Installation of Propeller Synchronizer
Removal of Hydraulic Reservoir . .
13-64N Components . . . . . .
13-74
Installation of Hydraulic Reservoir . .
13-64N Adjustment . . . . . . .
13-74
Removal of Manifold and Valve Assembly. 13-64N PROPELLER SYNCHRONIZER WIRING
Installation of Manifold and Valve CONTINUITY CHECK . . . .
13-76
Assembly . . . . . . .
13-64N PROPELLER SYNCHRONIZER VOLTAGE
Removal of Condenser Blower Motor .
13-64N CHECK . . . . . . .
13-76
Installation of Condenser Blower Motor .
13-645 Synchronizer Wiring Test . . .
13-77
Removal of Fan Blade . . . .
13-64S Removal and Installation of Magnetic
Installation of Fan Blade . . . .
13-64S Pickup in Propeller Governor . .
13-77
Removal of Condensers . . . .
13-645 Functional Test of Synchronizer System .
13-77
Installation of Condensers . . . .
13-64S HEATED STATIC PORTS . . . .
13-78
Removal of Receiver-Dryer . . .
13-645 Removal and Installation . . . .
13-78
Installation of Receiver-Dryer . . .
13-64S FLIGHT HOUR RECORDER . . . .
13-78
Removal of Low Pressure Switch . .
13-64S Removal and Installation . . . .
13-78
Installation of Low Pressure Switch . .
13-64S CESSNA ECONOMY MIXTURE INDICATOR .
13-78
Removal of High Temperature Switch .
13-64T Troubleshooting . . . . . .
13-78A
Installation of High Temperature Switch .
13-64T Removal and Installation . . . .
13-78A
Removal of Temperature Control Calibration . . . . . . . 13-78A
Assembly . . . . . . .
13-64T
Change 11
13-2 8 UTILITY AND- 421 SERVICE MANUAL
OPTIONAL SYSTEMS
Table of Contents (Continued)
Page Page

TRUE AIRSPEED INDICATOR . . .

13-79 EMERGENCY LOCATOR TRANSMITTER .
13-90
Removal and Installation . . . .
13-79 Description . . . . . . .
13-90
HEATED WINDSHIELD , . . . .
13-79 Operation . . . . . . .
13-90
Troubleshooting . . . . . .
13-82 Removal . . . . . .
13-90
Removal . . . . . . .
13-82 Installation . . . . . . .
13-90
Installation . . . . . . .
13-82 Removal and Installation of Emergency
Removal and Installation of Heated Locator Transmitter Antenna . .
13-91
Windshield Components . . .
13-82 Removal and Replacement of Battery
Operational Check . . . . .
13-82 Pack . . . . . . . .
13-91
Removal and Installation of Heated Troubleshooting . . . . . .
13-92
Windshield Components . . .
13-83 PILOT AND COPILOT MANUAL AND
Operational Check . . . . .
13-83 ELECTRICAL ADJUSTABLE
STEREO TAPE PLAYER . . . .
13-83 SEAT . . . . . . . .
13-93
Removal and Installation . . . .
13-84 Removal . . . . . . .
13-93
Crosstalk or Misaligned Head Disassembly . . . . . . .
13-93
Adjustment . . . . . .
13-84 Installation . . . . . . .
13-93
Speed Control Adjustment , . .
13-84 ALCOHOL WINDSHIELD ANTI-ICE
ELECTRIC ELEVATOR TRIM CONTROL .
13-84 SYSTEM . . . . . . .
13-95
STROBE LIGHT SYSTEM . . . .
13-84 - Removal . . . . . . .
13-95
WING LOCKER FUEL SYSTEM . . .
13-84 Installation « . . . . . .
13-95
SEVENTH, EIGHTH, NINTH AND TENTH Operational Check . . . . .
13-95
SEATS . . . . . . . .
13-84 ANGLE OF ATTACK SYSTEM . . .
13-97
ELECTRIC SEAT . . . . . .
13-85 Removal of Angle of Attack Indicator .
13-97
ENGINE COMPARTMENT FIRE Installation of Angle of Attack Indicator .
13-97
EXTINGUISHER . . . . .
13-88 Removal of Angle of Attack Transducer .
13-97
Troubleshooting .
..
. . . .
13-88 . Installation of Angle of Attack
Removal . . . . . . .
13-88B Transducer . . . . . .
13-97
Installation . . . . . . .
13-88B Operational Check . . . . .
13-97
Removal and Installation of Fire
Extinguisher Thermo Detectors . .
13-88B
Removal and Installation of Annunciator
Panel . . . . . . .
13-88B
Servicing .. . . . . . .
13-88B

Change 10
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

HEATING, VENTILATING AND DEFROSTING tion. As the combustion air flow increases, the com-
SYSTEM. (See figure 13-1.) bustion air pressure switch closes and actuates the
ignition coil and heater solenoid valve. Fuel then
The heating and ventilating system provides air for flows through the heater solenoid valve into the com-
cabin heating, cooling, ventilation, defrosting, and bustion chamber spray nozzle which injects a conical
also provides an air source for cabin pressurization. sh¾ped spray cone of fuel into the combustion cham-
Air enters the cabin through controllable outlets. ber where the spark plug is already sparking, thus
Two outlets are located at the base of the windshield combustion occurs. As the heated air flowing from
for defrosting purposes, two are located on the for- the heater to the cabin exceeds the thermostat setting,
ward cabin pressure bulkhead just forward of each the thermostat automatically closes the solenoid
set of rudder pedals and one is mounted on each side valve, stopping fuel flow into the heater. As the
of the cabin. There are also seven overhead wemac heater cools, the thermostat opens the solenoid
valves. valve, allowing fuel to flow and combustion takes
place since the spark plug is continually sparking.
During unpressurized ground operation, fresh air By cycling on and off the heater maintains an even
enters a ram air scoop located in the nose of the air- air temperature in the cabin. The heater combus-
craft and is forced through the cabin outlets by use of tion chamber is completely separate from the ven-
the cabin heater fan acting as a ventilating fan. The tilating system to prevent any exhaust gases from
cabin heater controls the temperature of the ventila- contaminating the cabin air. All exhaust gases are
ting air. The ventilating fan is operated by the use vented overboard through an exhaust tube directly
of either the cabin fan switch or the cabin heat switch. beneath the heater.
During unpressurized flight operation, air also enters
the ventilation system through a duct located under- Operating Procedure,
neath the fuselage and is routed through ducts to in-
dividual adjustable overhead wemac valves. a. Place the CABIN HEAT switch in the ON position.
The heater should fire and continue to operate.
During pressurized flight, ventilating air is ducted
NOTE
from the turbine compressor, through a heat ex-
changer which cools the air, into the cabin ventilating A short time lag, not more than 10 seconds,
system. Fresh air continually enters the cabin and unless fuel line has been drained, may be
is exhausted through a cabin pressure regulating required for the fuel pump to purge the fuel
valve located on the aft pressure bulkhead. line of air bubbles.

b. Open cabin heat vents.

Description of Heater and Basic Components. c. The cabin air temperature control knob, labeled
CABIN HEAT, can be set to regulate the cabin tem-
The heater is a gasoline combustion type and is perature for desired comfort level. If this switch is
mounted in the right side of the nose section. On set for ground operating comfort, it may be neces-
aircraft 421-0001 thru 421B0229, fuel is routed from sary to reset it after airborne, since ram air will
a tee in the fuel crossfeed line through a filter and increase the ventilating air flow and heater output.
pulsating pump to the solenoid valve-regulator which
regulates the fuel pressure to 7. 5 ±0. 5 psi. On air-
craft 421B0229 and on the fuel pump is mounted in
the combustion blower. Fuel from the solenoid
valve-regulator is routed through the fuel line as-
sembly to the heater. The heater fuel line assembly
fitting, at the heater, is enclosed in a metal housing.
The housing is vented and drained as a precaution
against fire in the event of a fitting leakage. Fuel
routed through the fuel line assembly enters the
heater solenoid valve which allows fuel to pass
through the combustion chamber spray nozzle. Elec-
trical current is supplied to the combustion air blow-
er, combustion air pressure switch and ignition coil
when the heater switch is placed in the HEAT posi-

Change 6
13-2 0 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

HEATER FUEL PUMP FUEL SUPPLY SOLENOID

CABIN HEAT CABIN FAN
TO FUE L SUPPLY LINE ....

ON HI
AFT '
CABIN STRAINER OVER
HEAT HEAT OFF
LIGHT OVERHEAT o o
A' SWITCH OF
,U NOR
SPARK
PLUG
COMBUSTION
IGNITION AIR BLOWER
COIL AIRFLOW
RAM AIR
SWITCH
THERMOSTAT VALVE
RAM AIR
(INLET AT
NOSE OF
AIRCRAFT)
COMBUSTION /

CHAMBER
-VENTILATION
FAN
DEFROSTER
' OUTLETS ' v' SOLENOID
.,
VALVE
CHECK VALVE

y' CHECK VALVE NOZZLE .

\ 97 / COMPRESSOR
PILOT/ COMPRESSOR INLET
CHO LEOR INLET
CYCLING
REGISTER SWITCH PILOT'S CHECKVALVE
AIR VENT
O a RESTRICTOR
o
CABIN
COPILOT'S RAM AIR
,

AIR
AIR VENT INLET AT
CLOSED VENTS O BOTTOM OF
AIRCRAFT
CHECK VALVE
CABIN

F DUMP
VALVE

CODE

gF-¯¯¯ COMBUSTION AIR FLOW

lHEATED OR COLD AIR
IW//////AFUEL
CHECK VALVE
- --MECHANICAL ACTUATION 421-0001 TO 421B0001
ELECTRICAL ACTUATION

51983002

Change 8
 421 SERVICE MANUAL UTILITY AND 13-3
OPTIONAL SYSTEMS

TO FUEL SUPPLY LINE ' STRAINER CABIN HEAT CABIN FAN

HEATER FUEL
FUEL SUPPLY SOLENOID ON HI
PUMP
OVER
HEAT OFF
LIGIIT OVERHEAT o o
'.. SWITCH OF NOR
AFT
CABIN SPARK
COMBUSTION
HEAT PLUG
AIR BLOWER
COMBUSTION
CHAMBER ' IGNITION AIRFLOW
COIL SWITCH
RAM AIR
THE RMOSTAT VAL VE
EAŒA
T
NOSE OF
AIRCRAFT)

CYCLING / VENTILATION
SWITCH FAN
DEFROSTER --SOLENOID
OUTLETS / / VALVE
NCOHECCLKEVALVE
/
/ CHECK VALVE COMPRESSOR
PILOT/
\ y/
INLET
COPILOT'S COMPRESSOR
HEATER / INLET
REGISTER PILOT'S L-CHECK
• V
o 17
..
/ AIR VENT
VALVE
/ 0 RESTRICTOR
COPILOT'S

CLOSED

CABIN CABIN
DUMP
VALVE VENTS

P
CODE

/ |||||5 COMBUSTION AIR FLOW RH BLEED AIR

g' LH BLEED AIR OR COLD AIR
¡ ¡ HEATED DUMP VALVE
DUMPV A LVE B7//////A
FUEL
\ ICHECK VALVE
-

---MECHANICAL ACTUATION
ELECTRICAL ACTUATION 421BOOO1AND ON
51983001 * EXECUTIVE COMMUTER

Change 8
13-4 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Troubleshooting the Heater. (421-0001 To 421BO229)

TROUBLE PROBABLE CAUSE CORRECTION

HEATER FAILS TO Heater switch or circuit breaker Position heater switch to HEAT or
LIGHT open. close circuit breaker.

Low voltage. Connect to auxiliary power supply.

No fuel to system. Turn on fuel shutoff valve.

Insufficient fuel pressure caused by Correct faulty fuel pump wiring or re-
faulty fuel pump or no pump current, pair or replace fuel pump.

Fuel pump operating but not building Remove and repair or replace fuel
up sufficient pressure. pump.

Fuel nozzle clogged in heater. Remove the nozzle and clean or re-
place it.

Fuel solenoid valves not operating. Remove and check solenoid. Replace
it if faulty.

Fuel lines clogged or broken. Inspect all lines and connections. It

may be necessary to disconnect lines
at various points to determine where
the restriction is located.

Fuel filter clogged. Clean fuel filter element.

Ignition vibrator defective. Replace

Manual reset overheat switch open. Press reset button and recheck to de-
termine reason for switch opening.

Combustion air flow switch open. Check for low blower output and cor-
rect it, If switch is defective, replace
it.

Cycle switch open. Replace if defective.

Thermostat switch open. Operate control to see if switch will

come on. Replace switch if defec-
tive.

Change 8
 421 SERVICE MANUAL UTILITY AND 13-4A
OPTIONAL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

VENTILATING Heater switch OFF. Broken or loose Turn heater switch to FAN. Check and re-
AIR BLOWER wiring to motor. pair wiring.
FAILS TO RUN
Circuit breaker out. Close circuit breaker.

Worn motor brushes. Replace motor brushes.

Blower fan jammed. Remove and repair the ventilating-air blower.

Motor burned out. Remove blower assembly and replace defec-

tivemotor.

Defective radio-noise capacitor. Replace capacitor.

COMBUSTION Faulty wiring to motor. Inspect and replace faulty wiring.

AIR BLOWER
FAILS TO RUN Poor ground connection. Tighten ground screw.

Worn motor brushes. Replace motor brushes.

Blower wheel jammed. (Usually in- Overhaul the combustion-air blower.

dicated by hot motor housing. )

Short-circuited radio-noise capacitor. Replace capacitor.

Faulty or burned-out motor. Remove combustion air blower for overhaul

or replacement.

HEATER FIRES Insufficient fuel supply. Inspect fuel supply to heater, including shut-
BUT BURNS off valve, solenoid valve, fuel filter, fuel
UNSTEADILY pump and fuel lines. Make necessary repairs.

Spark plug partially fouled. Replace spark plug.

Loose primary connection at ignition Tighten connection.

assembly.

Faulty vibrator. Replace vibrator.

Combustion-air blower speed fluctu- Remove and overhaul the combustion-air

ates. (Can be caused by low fluctua- blower assembly as required.
ting voltage, loose blower wheel,
worn brushes or defective motor. )

Insufficient combustion-air supply. Seal by use of Arno Ductape No. C-506 or

equivalent and clamps, as required.

High voltage leak in lead between Replace ignition assembly.

ignition assembly and spark plug.

Defective ignition assembly. Replace ignition assembly.

Restriction in fuel nozzle orifice. Remove nozzle for cleaning or replacement.

Nozzle loose in retainer or protruding Tighten or replace the nozzle as required.

improper spray angle.

HEATER Lack of fuel at heater. Check fuel supply through all components
STARTS from the tank to the heater. Make necessary
THEN corrections.
GOES
OUT Defective combustion-air pressure Replace switch assembly.
switch.

Change 2
 13-4B UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

HEATER STARTS THEN Damaged overheat switch. Replace the switch.

GOES OUT (CONT.)
Damaged cycling switch. Adjust or replace the switch.

Fouled spark plug. Replace spark plug.

HEATER FAILS TO Fuel solenoid valve in heater Remove and replace solenoid assembly.
SHUTOFF stuck open.

Defective heater switch. Replace the heater switch.

COLD HEATER OUTPUT Combustion air supply is low. Perform functional check of air pres-
AT HIGH AIR SPEEDS sure switch with voltmeter.

Defective thermostat. Perform functional check of thermostat.

Defective pressure switch. Replace pressure switch.

INSUFFICIENT HEATEË Malfunction inheater fuel Perform checks in accordance with

OUTPUT AT HIGH AIR supply. functional check of heater fuel supply
SPEEDS and heater fuel nozzle. Replace com-
ponents as necessary.

Troubleshooting the Heater. (42 B0229 AND ON)

TROUBLE PROBABLE CAUSE CORRECTION

HEATER WILL NOT START, Open circuit breaker. Reset circuit breaker.
BLOWERS DO NØr RUN
Defective heater switch or Replace switch or wiring as necessary.
wiring.

VENT AIR BLOWER RUNS Overheat switch tripped. Reset switch and find cause of over-
BUT COMBUSTION AIR heating.
BLOWER DOES NOT START
Defective combustion air Replace blower assembly.
blower.

BOTH BLOWERS RUN BUT Ignition vibrator defective. Replace vibrator.

HEATER FAILS TO START
Defective spark plug. Replace plug.

Defective airvane switch. Replace switch assembly.

Obstruction in combustion Remove obstruction.

air passage.

Defective ignition coil. Replace coil.

Open circuit in thermostat. Replace thermostat.

Defective solenoid or Replace nozzle solenoid assembly.
I obstructed nozzle.

Open circuit in duct limit Replace switch.

switch.

Defective fuel pump. Replace blower assembly.

Defective supply solenoid. Replace solenoid.

Change 8
 421 SERVICE MANUAL UTILITY AND 13-4Û l3-40
OPTIONAL SYSTEMS

TROUBLE PROBABLE CAUSE REMEDY

BOTH BLOWERS RUN BUT Airflow switch open. Recalibrate switch or correct cause of
HEATER FAILS TO START low combustion air flow.
(CONT. )

HEATER OPERATES ON Insufficient combustion air. Check ducts for obstruction

GROUND, BUT NOT IN
FLIGHT Check blower motor for proper speed.

Check fan blades for damage and free-

dom of rotation.

Weak ignition. Check spark plug. A good ignition sys-

tem check may be performed by using a
long reach automotive spark plug opened
up to a 3/32 inch gap. If the ignition
system is operating properly the spark
in this gap will ignite a business card
or a manila tag.

NOTE

Heater spark plug will not work

for this check, due to the annular
spark gap.

Check ignition unit.

Lack of fuel. Check power to heater solenoid terminal

(#8). If no voltage is present, check
thermostat calibration, air flow switch,
and cycling switch.

Check fuel pressure between fuel pump

and heater. Refer to Cessna Heater and
Components Overhaul/Parts Manual.

Check fuel supply to pump (remote sole-

noid,filter manual valves, etc. ).

Refer to Cessna Heater and Components

Overhaul/Parts Manual and perform
Fuel Nozzle and Solenoid test.

HEATER OPERATES IN Poor thermostat operation. Check thermostat calibration and free-
FLIGHT, OUTPUT IS LOW dom of movement.

Poor fuel atomization in Check fuel pressure to heater.

burner.
Refer to Cessna Heater and Components
Overhaul/Parts Manual and perform
Fuel Nozzle and Solenoid test.

HEATER BURNS BUT Defective thermostat. Replace thermostat.

THERMOSTAT WILL NOT
CONTROL TEMPERATURE Defective fuel solenoid. Replace solenoid.

OUTLET AIR TEMPERA- Insufficient vent air. Increase vent air flow.
TURE TOO HIGH
Defective thermostat. Replace or adjust thermostat.

Change 8
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

TROUBLE PROBABLE CAUSE CORRE CTION

OUTLET AIR TEMPERA- Excessive vent air flow. Reduce vent air flow.
TURE TOO LOW
Defective thermostat. Replace thermostat.
Defective duct limit switch. Replace switch.

Low fuel pressure. Repair or replace pump.

Dirty fuel nozzle. Replace nozzle.

Defective solenoid valve. Replace solenoid valve.

HEATER TRIPS OVER- Defective overheat switch. Replace switch.

HEAT SWITCH
Insufficient vent air plus Replace duct limit switch and increase
defective duct limit switch. air rate.

SMOKING HEATER EXHAUST Defective nozzle. Replace nozzle.

Slow combustion blower. Replace combustion blower.

Leaking solenoid valve. Replace valve.

HEATER POPS OR BANGS Leaking solenoid valve. Replace valve.

WHEN STARTING OR
CYCLING Delayed ignition caused by Replace spark plug or coil as necessary.
intermittent spark.

Defective fuel nozzle. Replace nozzle.

RUMBLE OR COMBUSTION Loose burner assembly Tighten mounting screws.

NOISE IN HEATER mounting screws.

Defective nozzle. Replace nozzle.

Electrical Continuity Checks.

For electrical continuity checks, refer to Section 14 and

to the Heater and Components Service/Parts Manual.

Change 8
 -g
UTILITY AND
SYSTEMS
421 SERVICE MANUAL
OPTIONAL

Functional Check of Heater Fuel Supply Removal and Installation of Heater Assembly.
421B0229 and on. (See Figure 13-2A. )
a. Heater Fuel Supply. Install a pressure gage in
the heater fuel supply line (between the heater sole- a. Remove necessary access plates, radio and
noid valve and heater). Start the heater and observe radio shelves to gain access to heater.
pressure gage, on aircraft 421-0001 to 421B0229 it b. Remove RH engine control access cover. Un-
should indicate 7 to 8 psi, on aircraft 421BOOO1 and safety knob on shutoff valve and turn heater fuel
On it should indicate 18 to 24 psi. If this pressure valve off.
is low, check: c. Tag and disconnect all electi-ical wires from
1. Heater Fuel Shutoff Valve (Located in right wing the combustion blower motor and heater terminal
leading edge at station 60. 57 Check that valve is
-
strip.
open. d. Remove hose clamp from fuel lines (3 and 7)
2. Heater Fuel Pump with a supply source to the from fuel pump housing and fuel inlet shroud,

l
-

pump (inlet hose in a container of fuel), pump outlet e. Remove fuel pump housing vent line.
pressure should be 7 to 8 psi on aircraft 421-0001 to f. Disconnect vent line (7), and fuel inlet shroud
421B0229, on aircraft 421B0229 and On it should in- vent lines from shroud on air flow switch (12).
dicate 18 to 24 psi. Replace fuel pump if defective. g. Remove clamp from heater at plenum (1).
3. Heater Solenoid Valve (Remote valve in wing h. Remove clamp from forward inlet valve (10)
right-hand leading edge) Check that solenoid valve
-
and remove clamp (11) from ram air tube.
is open. Replace valve if defective. i. Remove mounting clamps and lift heater out.
4. Fuel Strainer and Lines Clean filter and check
-

lines for obstructions. WARNING

Fuel accumulation in the nose is a fire haz-

Removal and Installation of Heater Assembly. 421. ard. Use caution when removing heater to
0001 to 421B0229. (See Figure 13-2. ) prevent residual fuel from draining.

a. (See Figure
1-2.) Remove baggage shelf (90) j. Cap all fuel lines to prevent dirt accumulation or
located in the right nose section. contamination of fuel.
b. Close heater fuel shutoff valve located in the k. Install the heater by reversing the removal pro-
right leading edge at wing station 60. 57. cedures.
c. Tag and disconnect all electrical wires from 1. Turn fuel shutoff valve on and safety in the ON
heater terminal strip necessary for removal of position.
heater.
d. Loosen clamps and slide hoses from fuel inlet Ventilating Air Blower. (See Figure 13-2. )
shroud (23).
e. Loosen clamp attaching fuel inlet shroud to
heater; separate shroud halves by removing two The ventilating air blower is attached to the inlet end
attaching screws. of the heater assembly to provide a source of venti-
f. Disconnect fuel line (16) from the heater and re- lating air through the heater and ram air from the
move. ventilating-air intake scoop.

CAUTION Removal and Installation of Ventilating Blower.

421-0001 to 421B0229. (See Figure 13-2.)
A small amount of fuel will drain from fuel
line. Do not permit accumulation of fuel in a. (See Figure 1-2. ) Remove baggage shelf (90)
the area. located in right nose section.
b. Remove electrical connector.
g. Disconnect combustion air blower outlet tube (13) c. Remove clamps (17, 11 and 4).
from heater elbow by removing attaching nut and bolt. d. Slide sleeve (19) forward, then lift blower out as
h. Disconnect drain line (15). a unit, independent of the heater.
i. Remove mounting clamps (11) at front and rear e. Installation of the blower is the reversal of the
of heater. removal procedures.
j. Loosen clamps (17 and 24) to gain clearance,
then lift out heater. Removal and Installation of Ventilating Blower.
421B0229 and on. (See Figure 11-2A. )

NOTE a. Remove necessary access plates, radio and

radio shelves to gain access to heater.
For disassembly and inspection of heater and b. Remove ventilating blower clamp, duct assembly
heater components, see Cessna Heater and (10), and clamp (11) from heater.
Components Overhaul/Parts Manual. c. Tag and disconnect wires.
d. Route shutoff valve and duct assembly (10) out of
k. Install heater by reversing removal procedures. the way enough to remove ventilating blower.
1. Turn fuel valve on and perform functional check e. Install ventilating blower by reversing the re-
for proper operation. moval procedures.

Change 9
 421 SERVICE MANUAL UTILITY AND g-
OPTIONAL SYSTEMS

Combustion Air Blower. (See Figure 13-2. ) Install plug by reversing above procedure.
3. spark

The combustion air blower is a centrifugal type NOTE

blower, located above the heater assembly, that sup-
plies combustion air to the combustion chamber in A new spark plug gasket should be installed
the heater- on the spark plug. Torque plug to 28 foot-
pounds. Torque nut on high voltage lead to
of Combustion Air Blower•
I
Removal and Installation
421-0001 to 421B0229.

a.(See Figure
(See Figure 13-2. )
1-2. ) Remove baggage shelf (90)
20 foot-pounds.

Vibrator Assembly.

located in the right nose section- a. Remove the necessary access panels to reach the
b. Disconnect electrical wire· ignition unit on the heater assembly.
c. Remove tubes (12 and 13) from blower assembly b. Measure the distance the vibrator protrudes out
by removing nuts and bolts securing tubes to adapter of the ignition assembly to determine when the new
d. Remove clamps (7) securing blower assembly to unit is inserted properly. Grasp the vibrator and
support (8). with slight back and forth movement, pull it straight
out of the ignition unit. (For a friction grip, it may
NOTE be necessary to use a piece of masking or friction
tape around the exposed portion of vibrator.)
Check combustion air supply joints for leak¯ c. Carefully rotate the new vibrator until the index
age, seal by the use of Arno Ductape No. C¯ marks are aligned and the connector pins on the vi-
506 or equivalent and clamps as required· brator can be felt entering the pin sockets in the ig-
nition unit socket, then press the vibrator fully and
e. Installation of the combustion air blower is the firmly into position,
reversal of the removal procedure• d. Check the heater for operation and close all
access openings.
Removal and Installation of Combustion Blower.
I 421BO229 and on. (See Figure 11-2A. ) Thermostat.

a. Remove necessary access covers, radios and The thermostat is located in the plenum at the aft
radio shelves to gain access to the combustion blower end of the heater. It senses the ventilating air out-
b. Tag and disconnect wiring· let temperature. To select the desired cabin air
c. Remove right engine control access cover and temperature, the thermostat may be manually con-
unsafety heater fuel shutoff valve and turn shutoff trolled through a temperature range of 200°F, down
valve off. 70°F.
to
d. Disconnect inlet air duct (17) and combustion air
duct (15)- Removal and Installation of Thermostat.
e. Disconnect heater fuel pump drain line, inlet
fuel line and vent lines by removing hose connections· a. Disconnect electrical wires from terminals.
b. Loosen screw securing control wire to thermo-
WARNING stat actuating arm.
c. Remove four screws securing thermostat to
Fuel accumulation in the nose is a fire haz¯ plenum duct then carefully remove thermostat and
ard. Use caution when removing heater to gasket.
prevent residual fuel from draining, d. Installation is the reversal of the removal pro-
cedures.
f. Remove mounting screws from bracket and re- e. Adjust control wire in thermostat actuating arm.
move combustion blower from aircraft· for proper operation.
g. Install the combustion blower by reversing the
removal procedures· Fuel Solenoid Valve,

Spark Plug. A fuel solenoid valve is located in the RH leading

edge wing (421-0001 to 421B0001) and in the RH
a. Removal and Installation· leading edge stub wing (421BOOO1 and On). It is
1. Remove high voltage lead connector at spark electrically operated and controls the fuel supply
plug and grommet. and regulates fuel pressure to the heater. The
2. Remove spark plug with a 7/8-inch deep socket· pressure regulator function of the solenoid valve
Make sure spark plug gasket is removed with plug- is adjusted to control fuel pressures to 6. 5 to 7 psi.

Removal and Installation of Fuel Solenoid Valve.

NOTE
a. Remove access hole cover from lower leading
I On aircraft
essary to
421BO229 and On it will be nec-
remove the
. .

igmtion unit before

edge at RH wing or RH stub wing area.

removing spark plug.

Change 6
13¯Ê UTILITY AND
421 SERVICE MANUAL
OPTIONAL SYSTEMS

b. Shut off fuel at fuel shutoff valve located in wing filter is located in the heater fuel pump, which is lo-
leading edge adjacent to the fuel pump. cated in the right wing leading edge at wing station
c. Disconnect electrical leads and disconnect fuel 60. 57. Refer to figure 2-34, Inspection Chart, for
lines. inspection and cleaning intervaL
d. Remove screws securing solenoid valve to rib.
Removal, Cleaning and Installation of Fuel Filter.
e, Install valve by reversing removal procedures.
f. Turn fuel shutoff valve on and check for leaks.
421A0092 to 421B0229
WARNING
Heater Fuel Pump.
Residual fuel accumulation in the wing is a
The heater fuel pump is an electrically operated fuel
fire hazard. Use care to prevent the accu-
pump, located in the RH leading edge wing (421-0001
mulation of such fueL
to 421B0001) and in the RH leading edge stub wing
(421B0001 to 421B0229). On 421BO229 and on the a. (See figure 1-2.) Remove access plate (55) from
heater fuel pump is mounted on the combustion air lower right leading edge.
blower. b. Remove bottom cover of heater fuel pump and re-
move filter screen.
Removal and Installation of Heater Fuel Pump.
421-0001 c. Clean filter screen with unleaded gas and a jet of
to 421B0229.
low-pressure air.
a. Remove access hole cover from lower leading d. Install filter by reversing the removal procedure.
edge at RH wing or RH stub wing area.
b. Shut off fuel at fuel valve located adjacent to the Removal, Cleaning and Installation of Fuel Filter,
fuel pump. 421B0229 and on.
c. Disconnect electrical lead and fuel lines. Tag On aircraft 421B0229 and on the heater fuel filter is
fuel lines so proper reinstallation can be attained and located in the leading edge of the RH stub wing. The
remove pump. removal, cleaning and installation of fuel filter (421-
0001 to 421A0092) procedures apply to 421B0229 and
NOTE
on, except the fuel filter is located in the stub wing.
Do not lose insulator in the electrical connector.
Cabin Heat Switch.
d. Installation is the reversal of the removal pro~
The cabin heater is controlled by a two position tog-
cedures gle switch labeled CABIN HEAT located on the left

I
Removal and Installation of Heater
421B0229 and on. (See Figure
Fuel Pump.
13-2A. )
console.
the switch
heater
Switch
in the
operation
positions are ON and OFF. Placing
ON position starts and maintains
and also turns the cabin fan on low.
a. Remove
necessary access plates, radio and
radio shelves to gain access to combustion blower.
Cabin Fan Switch,
b. Remove combustion air blower in accordance
with removal procedures.
The ventilating fan which is integrated into the heat-
c. Refer to Heater and Components Overhaul/Parts er assembly is controlled by a three position switch
Manual for disassembly of heater fuel pump.
labeled CABIN FAN located on the left console.
Heater Fuel Filter. Switch positions are NORMAL, OFF, and HIGH.
421-0001 Placing the switch in either the normal or high posi-
On aircraft to 421A0092 the fuel filter is tion operates the ventilating fan.
located in the right wing leading edge at wing station
65. 57 in the fuel line between the heater, fuel pump Removal and Installation of Cabin Heat Switch and
and heater shutoff solenoid. Refer to figure 2-34' Cabin Fan Switch.
Inspection Chart, for inspection and cleaning intervaL
Removal, Cleaning and Installation of Heater Fuel a. Remove and replace switches in accordance with
Filter. 421-0001 to 421A0092. Section 14.
WARNING
Residual fuel accumulation in the wing is a Temperature ControL
fire hazard. Use care to prevent the accu-
mulation of such fuel. The temperature control is located below and slightly
1-2-)
to the left of the right control column. It is a rotary
a. (See figure Remove access cover (55) type knob and is labeled CABIN HEAT. Clockwise
from lower right leading edge at wing station 70. 57. rotation of the temperature control knob increases
Shut off fuel at fuel valve located adjacent to the
.

b. de-
cabin temperature and counterclockwise rotation
fuel pump.
creases it. This knob mechanically controls the
c. Disconnect fuel lines and remove
,

screw securing
setting of a thermostat located within the outlet
filter to rib.
adapter just aft of the heater. The thermostat in
d. Clean filter with unleaded gas and a jet of low-
turn cycles the heater to maintain the cabin tem--
aressure air.
proce- perature setting selected with the control knob.
e. Install filter by reversing the removal
lures.
On aircraft 421A0092 to 421B0229 the heater fuel

Change 6
 421 SERVICE MANUAL UTILITY AND $3 Î3-SS
OPTIONAL SYSTEMS

Detail 3Û

31 29
5
34
4
2 .
1
28
27 24
26 11

419 421-0001 TO 421BOOO1

421B0001 TO 421B0229

1. Vent Air Inlet Line 10. Thermostat Control 19. Sleeve 29. Spark Plug
2. Duct Assembly 11. Clamp 20. Valve Assembly 30. Vibrator
3. Sleeve 12. Blower Inlet Tube 21. Gasket 31. Pin
4. Clamp 13. Blower Outlet Tube 22. Adapter 32. Disc
5. Duct 14. Vent Air Outlet 23. Inlet Fuel Shroud 33. O-ring
6. Combustion Air Line 24. Clamp 34. Housing
Blower Assembly 15. Drain Line 25. Blower Housing 35. Stop Bolt
7. Clamps 16. Fuel Line 26. Bolt 36. Shatt
8. Support 17. Clamp Assembly 27. Washer 37. Arm
9. Plenum Assembly 18. Ram Air Control 28. Nut 38. Scoop

Figure 13-2. Heater Installation

Change 6
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

16
17
15

421B0229 AND ON

1. Plenum Assembly 10. Duct Assembly

2. Thermostat Control 11. Clamp
3. Fuel Supply Line 12. Airflow Switch
4. Combustion Chamber 13. Fuel Pump
5. Exhaust Outlet 14. Fuel Supply Line
6. Fuel Drain Line 15. Combustion Air Duct
7. Vent Line 16. Combustion Fan
8. Ram Air Duct 17. Inlet Air Duct
9. Valve Assembly

Figure 13-2A. Heater Installation

Change 6
13-10 UTILITV AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Removal of Temperature Control. trol wires through the valve actuating arm clamps
and secure by tightening clamp nuts.
a. Loosen screw securing control wire to thermo- e. Seal control cables at forward cabin bulkhead in
stat actuating arm, accordance with instructions given in Section 16 for
b. Remove clamp securing coil wire housing to the sealing continuous wire bundles.
plenum.
c. Remove control knob by rernoving knob set
screw. Removal and Installation of Ram Air Valve Assembly.
d. Remove nut securing temperature control as- (See figure 13-2.)
sembly to the stationary instrument panel. Slide
temperature control assembly forward until free of a. (See figure 1-2.) Remove baggage shelf (90) lo-
stationary instrument panel and then aft beneath cated in right nose section,
stationary panel until coiled wire housing is removed b. Remove screws securing radio shelf located just
from forward cabin bulkhead. forward of heater and raise it to gain access to bolts
(26).
c. Disconnect control (18) from valve by removing
Installation of Temperature Control. cotter key, nut and screw.
d. Remove nuts (28), washers (27) and bolts (26).
a. Route temperature control wire housing through e. It is possible to lift valve out but for conven-
forward cabin bulkhead and attach to plenum with ience in reinstallation, remove duct assembly (2) by
attaching clamp. removing clamps (4) and sliding flex ducts aft. Re-
b. Insert temperature control assembly through tain gasket (21) for reinstallation if not torn or muti-
hole in stationary instrument panel and secure with lated.
nut. f. Installation of the ram air valve is the reversal
c. Place control knob on temperature control as. of the removal procedures.
sembly and secure with set screws.
d. With control knob turned to the LOW position and Removal and Installation of Ram Air Control.
the thermostat arm forward, secure arm to the con-
trol wire by tightening clamp screw, a. Remove nut and bolt securing control to valve.
e. Seal control cable at forward cabin bulkhead y b. Remove clevis, jam nuts, and control housing
accordance with instructions given in Section 16 for retaining nuts, remove from support bracket.
sealing continuous wire bundles. c. Remove cotter key, nut and screw securing con-
trol to control lever located just forward of the
switch panel.
Airflow Controls. d. Remove clevis, jam nut, and control housing
retaining nuts, then remove from support bracket.
Removal of Airflow Controls, e. Remove clamps securing control located under
the forward cabin floor,
a. Loosen clamp and nuts securing control wires to f. Slide control through the seal at forward cabin
the cabin air defroster valve arms. bulkhead.
b. Work cabin air control coiled wire housing from g. Install control by reversing removal procedure.
seal assembly, h. Seal control cable at forward bulkhead in accord-
c. Work defroster control coiled wire housing from ance with instructions given in Section 16 for sealing
seal assembly supporting it at forward cabin bulk- continuous wire bundles.
head, i. Check control adjustment for positive sealing of
d. Loosen nuts securing control assemblies to low- the inlet duct when in the closed position.
er instrument panel and slide assemblies aft through
mounting holes. Removal and Installation of Plenum Ducts.
(See figure 13-3.)
a. To remove lower plenum duct (9), remove
Installation of Airflow Controls. heater in accordance with procedures for removing
heater.
a. Insert control assemblies through mounting holes b. Remove temperature control from thermostat (8)
in lower instrument panel'
and aft cabin control cable from valve (13).
b. Slide lockwashers and nuts over coiled wire c. Remove clamps (1) and remove flex duct (7).
housings and secure control assemblies to lower in- d. Remove clamp (15) securing duct to support,
strument panel by tightening nuts onto threaded fit¯ e. Remove screws (12) securing duct assembly to
tings on control ends• forward cabin bulkhead (11).
c. Route defroster control through seal assembly f. Remove duct by pulling forward and up,
at forward cabin bulkhead, and cabin air control g. To remove upper plenum duct (2), disconnect
through seal assembk• forward cabin air control from valve lever and de-
d. With control knobs locked in the closed position frost control from defrost valve,
and plenum chamber valves closed, insert the con- h. Remove clamps (3) securing defrost ducts (4) to

Change 2
 421 SERVICE MANUAL UTILITY AND
¯

OPTIONAL SYSTEMS

B C K

D
E

N HF L

P A ,

Detail K Detail K
421BOOO1 AND ON EXECUTIVE COMMUTER

Detail
i Detail M Detail N oetaii P

Figure 13-3. Air Distribution System (Sheet 1 of 3)

13-12 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

18

421A0001 and ON
2

16
1
'
16 x
421-0001 TO 421A0001

tail

Detail

Detail
24

"
22

421A0001 and ON
23
48 45

24
25 28
22
29 1 1
' s 30 ( ss'
3231
26 1 n
33 2¯/ Detati D
421-0001 TO 421A0001

Detail F octati E

Figure 13-3. Air Distribution System (Sheet 2 of 3)

 421 SERVICE MANUAL UTILITY AND 13-13
OPTIONAL SYSTEMS

e--* 7 ,

1 ·

40 '

1 42 Detan Û
43 ,

1
1
Detail ' y /
'
43 1
1
44

Detail

1. Clamp 16. Forward Cabin Duct 31. Gasket

2. Upper Plenum 17. Adapter 32. Screen
3. Clamp 18. Center Cabin Duct 33. Scoop
4. Defrost Duct 19. Right Cabin Duct 34. Stat-O-Seal
5. Screw 20. Duct Assembly 35. Coupling
6. Bracket 21. Left Cabin Duct 36. Gasket
7. Duct 22. Clamp Assembly 37. Check Valve
8. Thermostat 23. Upholstery Panel 38. Fuselage Skin
9. Plenum 24. Left Pressure Duct 39. Adapter
10. Gasket 25. Adapter 40. Nozzle Adapter
11. Forward Cabin Bulkhead 26. Vent Duct 41. Nozzle Assembly
12. Screw 27. Adapter 42. Center Pressure Duct
13. Aft Cabin Air Control 28. Upper Vent Duct 43. Forward Pressure Duct
14. Insulation Strip 29. Retainer 44. Check Valve Assembly
15. Clamp 30. Check Valve 45. Baffle Plate
46. Seal
Figure 13-3. Air Distribution System (Sheet 3 of 3)
 13-14 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

plenum (2) and slide tubes off. d. Remove clamps securing duct (28) to overhead
i. Remove screws (5) securing top of plenum to plenum and adapter (27).
support. e. Remove adapter (27) by removing four nuts,
j. Remove screws (5) securing bottom bracket (6) washers and screws.
to structure. f. Remove restrictor duct (25), retainer (29), check
k. Install plenum by reversing removal procedure. valve (20), gasket (21) and screen (32) by removing
eight nuts, washers and screws.
NOTE g. Remove screws securing scoop (33) to skin,
break seal carefully and remove scoop.
Install new gaskets as necessary to insure a h. Remove the ducts from the overhead plenum to
good seal, the individual wemacs by removing the headliner as
necessary to gain access to the clamps and ducts.
Cabin Warm Air Vents and Ducting. i. Install ducting by reversing removal procedures.

The cabin is heated by six Warm air vents. The NOTE

warm air is routed from the heater through warm
air ducting and expelled through heat outlets, along Fay seal scoop (33) in accordance with in-
the sides of the aft cabin near the floor, defrost out- structions given in Section 16.
lets, and the forward cabin direct outlets. The out-
lets are controlled by controls located on the right- Cabin Pressurized Air Ducting.
hand switch panel.
The cabin pressurization system utilizes the air-
Removal and Installation of Warm Air Ducting. (See craft's air distribution system through which the
figure 13-3.) cabin is pressurized. Pressurized air enters the
cabin through a system of check valves and ducts to
a. (See figure 1-2.) Remove all seats, carpeting, the heater inlet. The ram air inlet being closed, the
floorboards (78, 79, 80, 81, 82, 83, 85 and 86) and air enters the normal ventilation system. Pressur-
access plates (73, 74 and 72). ized air is also ducted to the overhead outlets through
b. Remove forward duct (16) by removing clamps a restrictor which is an integral part of one of the
at plenum (9) and adapter (17) through floorboard ducts.
access holes.
c. Remove duct (18) by removing clamps at adapter Removal and Installation of the Cabin Pressurized
(17) and duct (20). Air Ducting. (See figure 13-3.)
d. Remove duct (19) by removing clamps at duct
(20). It will be necessary to remove lower uphol- a. Remove forward cabin carpet and access plates
stery panel (23) to gain access to the adapter on (77, 73, 74, 76 and 69). (See figure 1-2.)
right and left sides. b. Remove duct (43) by removing clamps at forward
e. Remove duct (21) by removing clamps at duct check valve assembly (44) and adapter (40).
(20) and left side adapter (22). Remove adapter (22) c. Remove nozzle assembly (41) by removing
by removing four nuts, washers and screws clamps securing the nozzle to the structure.
f. Remove adapter (17) and duct (20) by removing d. To remove center pressure duct (42), remove
screws attaching them to the structure, clamps, slide the flex ducts off, then remove nuts,
g. Install ducting by reversal of removal proce- washers and screws that secure the duct to the
dures. structure.
e. Remove adapter (24) by disconnecting clamps and
Cabin Fresh Air Vents and Ducting. slide off flex ducts.
f. Remove coupling (35), check valve (37) and adapt-
Fresh air is supplied to the cabin when in unpressur- er (39) by removing eight nuts, washers, stat-o-
ized mode, by ram air taken in at the nose and rout- seals and screws.
ed through the heater and enters the cabin as either g. Install by reversing removal procedures.
heated or cool air. In addition, secondary ram air
is supplied to the cabin by a scoop mounted on the NOTE
bottom of the fuselage. Air is taken in through the
bottom scoop, routed through ducting and enters the Install all butterfly type check valves with
cabin through overhead outlets. the hinge line in a vertical plane. Be sure
air will flow in the proper direction.
Removal and Installation of Fresh Air Ducting. (See
figure 13-3.)
PRESSURIZATION SYSTEM.
a. Remove seats, carpet, floorboards (77, 79 and
86) and left side upholstery panel (See figure 1-2.) The pressurization system provides a constant 8000
b. Remove clamps securing duct (7) to adapter (24), foot cabin altitude from 8000 to the altitude at which
restrictor duct (25) and remove duct (7) nominal differential pressure is reached. No pres-
c. Remove clamps securing duct (26) to restrictor surization is provided below 8000 feet with the stand-
duct (25) and adapter (27) and remove duct, ard system. Above 20, 180 feet a nominal differential

Change 7
 421 SERVICE MANUAL UTILITY AND 1>15
OPTIONAL SYSTEMS

pressure of 4. 2 ±. 10 is maintained on aircraft 421- cabin pressure bulkhead which controls cabin air out-
0001 to 421B0201. On aircraft 421B0201 to 421B0301 flow and is automatic in operation A combination
a nominal differential pressure of 4. 4 ±.10 psig is safety and cabin air dump valve is located on the aft
maintained above 20, 860 feet. On aircraft 421B0301 cabin pressure bulkhead. The dump function of the
and On a nominal differential pressure of 5. 0 ±. 10 valve is solenoid operated, vacuum actuated, and
psig is maintained above 23, 120 feet. Pressurization controlled by the pilot by means of a switch lever
of the cabin is developed by the use of the engine- mounted on the control panel. An override switch
driven turbocharger which provides compressed air interlocked with the gear squat switch insures de-
for engine induction air and for cabin pressurization. compression when the aircraft is on the ground. Two
One compressor is mounted in each engine nacelle, small restrictor valves are installed in the dump
either of which will supply adequate pressurization valve sensing lines to provide a controlled opening
in the event of failure of one. Ram air is taken and closing rate. This reduces the "pressure bump"
through a scoop on the side of the nacelle, compress- to a minimum when making the transition from the
ed by the turbocharger and directed through a sonic unpressurized mode to the pressurized mode and
venturi type flow limiter to a ram air heat exchanger vice versa. Upon actuation it should take approxi-
mounted in the leading edge of the stub wing, which mately 30 seconds for the valve to open and approxi-
reduces the temperature of the pressurized air enter- mately 20 seconds for it to close. A pressure con-
ing the cabin. From the heat exchanger, air ís rout- trol panel is located on the stationary panel consist-
ed through check valves which are provided to pre- ing of a combination cabin altitude and cabin ambient
vent back flow of air in the event of failure of either differential pressure gage, cabin altitude rate-of-
compressor or single engine operation, into the cabin change instrument, left and right pressurization air
air system. The pressurized air is routed through dump valve switches, a cabin altitude warning light,
the air distribution system and enters the cabin and a manual ram air shutoff valve control located
through the overhead fresh air wemacs and heater to the right side of the panel The cabin altitude and
outlets at a controlled temperature. In the unpres- differential pressure instrument indicates cabin alti-
surized, conventional mode of operation, the pres- tude in feet and also indicates differential pressure
surized air is dumped overboard by means of two between cabin and atmosphere. The cabin altitude
pressurization air dump valves located in each stub rate-of-change instrument tells the pilot the rate in
wing, adjacent to the heat exchangers. On aircraft feet per minute at which the cabin altitude is chang-
421-0001 to 421B0001 the pressurization air dump ing. It is calibrated in 100-foot increments to 6000
valves are solenoid actuated and may be actuated feet in both up and down directions. A cabin altitude
independently by switches mounted on the control light is provided to warn the pilot of an oxygen re-
panel. On aircraft 421BOOO1 and On the dump valves quirement. This light is connected to a barometric
are manually actuated and may be actuated independ- pressure switch which is set to come on at cabin alti-
ently by push pull controls on the control panel. A tude of 10, 000 ±350 feet and go off at 9000 feet mini-
cabin pressure regulator valve is located in the aft mum. The ram air shutoff valve control is located

Troubleshooting the Pressurization System.

TROUBLE PROBABLE CAUSE CORRECTION

CABIN WILL NOT Dump valves open. Check electrical circuit.

PRESSURIZE
Outflow valve defective. Replace outflow valve.

Inadequate air supply to Repair or adjust air supply

cabin. equipment.

Safety valve defective. Replace sa.fety valve.

Foreign object between Clean safety or outflow valve

safety valve or outflow seat.
valve.

Defective landing gear Replace switch.

squat switch.

Filter clogged. Clean or replace filter.

Defective electrical cir- Check electrical circuit.

cuits.

Inadequate vacuum Adjust vacuum supply to

supply to altitude and 4. 2 ±. 10 in. Hg. less than
rate of change controllers. cabin pressure.

Change 7
13-16 UTILITY AND
SYSTEMS
421 SERVICE MANUAL
OPTIONAL

1 2
57 3
uu u i

BUS BAR)

VARIABLE PRESSURIZATION
CONTROL SYSTEM (OPTIONAL) 13 11
2
421-0001 TO 421-0013, 421-0014 TO
421-0025 AND 421-0026 TO 421-0029

1. Vacuum Manifold 29. Variable Controller

2. Ram Air Valve 30. Turbocharger
3. Vacuum Shutoff Valve 31. Waste-Gate Actuator
4. Variable Pressure Outflow Controller 32. Rate Controller
5. Filter 33. Alternate Air Door
6. Outflow Valve Vacuum Line 34. Pressurization Air Dump Valve
7. Static Pressure Line 35. Heat Exchanger
8. Safety Valve Vacuum Line 36. Check Valve
9. Static Shutoff Valve 37. Passenger Air Outlets
10. Static Line 38. Safety Valve
11. Outflow Valve 39. Tailcone
12. Restrictor 40. Aft Cabin Pressure Bulkhead
13. Safety Valve 41. Static Pressure Reference
14. Safety Valve Solenoid 42. Outflow Valve
15. Left Gear Safety Switch 43. Cabin Outlets
16. Left Dump Valve 44. Ram Air Inlet and Check Valve
17. Right Dump Valve 45. Pilot and Crew Air Outlet
18. Ram Air Control Lever 46. Windshield Defog Outlets
19. Switch 47. Forward Cabin Heating Outlets
20. Circuit Breaker 48. Forward Cabin Pressure Bulkhead
21. Aft Cabin Pressure Bulkhead 49. Windshield Defog Control Valve
22. Ram Air Inlet 50. Forward Cabin Heat and Ventilation Valve
23. Ram Air Shutoff Valve 51. Recirculating Air Duct
24. Ventilating Air Blower 52. Inlet
25. Combustion Air Blower 53. Exhaust
26. Nacelle Ram Air Valve 54. Inlet Air Valve
27. Intercooler 55. Manifold Pressure Relief Valve
28., Throttle Air Valve 56. Left-Hand Pressure Check Valve Open

Figure 13-4. Pressurization Schematic (Sheet 1 of 6)

Change 11
 421 SERVICE MANUÁL UTIUTY AND Î3-16A
OPTIONAL SYSTEMS

BUS BAR
o o 5
19
7

16 17

15

12-- 5
9

VARIABLE PRESSURIZATION
CONTROL SYSTEM (OPTIONAL) 10
421-0013, 421-0025 AND
421-0029 TO 421B0801 g 12

2 1 2
57

US BA

16 17
0 0
15

14 2
5
21

12
PRESSURIZATION CONTROL 11 lÛ 13
SYSTEM (STANDARD)
421-0001 TO 421B0801 y

Figure 13-4. Pressurization Schematic (Sheet 2)

Change 1
13·168 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

51
22
50
23
24
49 25
26

48
27
52
47 53
.28

46

45

364

34
43
35
42 36

37
41

40 39
-38

HEAT AND VENT AIR

PRESSURI2.ED AIR

RAM AIR
421-0001 TO 421A0001
EXHAUST

Figure 13-4. Pressurization Schematic (Sheet 3)

hange 11
 421 SERVICE MANUAL UTILITY AND Î3•-Î7
OPTIONAL SYSTEMS

51
22
50
23
24
49 '
25
26

5253 2
55

54 '28
48
29
45

33

4
43
35
42 36

37
41

40 L38
39

BW§§ HEAT AND VENT AIR

E. .
I PRESSURIZED AIR

I | RAM AIR

421A0001 TO 421BOOO1 N EXHAUST

Figure 13-4. Pressurization Schematic (Sheet 4)

Change 11
 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

22
PRESSURIZED AIR

HEAT AND VENT AIR

36 54 5 3455 28

45 29

30

56
31

37
*USED ON * *
EXECUTIVE
COMMUTER

421BOOO1 AND ON

Figure 13-4. Pressurization Schematic (Sheet 5)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-18A/13-18B
OPTIONAL SYSTEMS

1 5

14 e 15

BUS BAR
20

10 17

421BO801 AND ON
PRESSURIZATION CONTROL SYSTEM (STANDARD)

558

57

14
60

15
BUS BAR 20

21 10
421BORO1 AND ON
PRESSURIZATION CONTROL SYSTEM (OPTIONAL)
14983003

57. Cabin Air Dump Switch 59. Rate-of-Change Selector

58. Cabin Altitude Control 60. Volume Tank

Figure 13-4. Pressurization Schematic (Sheet 6)

change 11
 421 SERVICE MANUAL UTILITY AND 13-1
OPTIONAL SYSTEMS

TROUBLE PROBABLE CAUSE CORRECTION

CABIN WILL NOT Excessive cabin leakage. Locate and repair.

PRESSURIZE
Control knob on altitude controller Turn control knob of altitude
improperly set, controller to desired setting.
Defective pressure controller. Replace controller.
(Optional system. )
CABIN PRESSURE Defective outflow valve. Replace valve.
EXCESSIVELY HIGH
Shutoff valve or valves closed. Open shutoff valve or valves.

Defective safety valve. Replace valve.

Outflow valve static line loose or Tighten line or clear obstruction.

restricted.

Ground test valve in TEST ONLY-ALL Place valve in FLIGHT position.

OFF position.

Defective rate of change controller. Replace rate of change controller.

Defective rate of change selector. Replace rate of change selector.

OUTFLOW OR SAFETY Defective safety or outflow valve. Replace safety or outflow valve.
VALVE FAILS TO OPEN
DURING VACUUM
RELIEF CYCLE

CABIN AIR PRESSURE Loose or damaged pneumatic fittings Repair or replace fittings.
RATE OF CHANGE DOES on rate of change controller or selector.
NOT RESPOND TO RATE
OF CHANGE SELECTOR Defective rate of change controller Replace rate of change controller.

Pressure ports of rate of change Remove connections and clean

controller clogged with foreign matter. ports.

CABIN PRESSURIZES Shutoff valve in vacuum line is closed. Open valve and safety.
IMMEDIATELY TO
MAXIMUM DIFFER- Shutoff valve in static line is closed. Open valve and safety.
ENTIAL

CABIN PRESSURE WILL Defective safety valve. Replace safety valve.

NOT DUMP WHEN SAFE-
TY VALVE SWITCH IS Defective electrical circuit. Check circuitry.
SET TO OPEN
Safety valve vacuum line restricted. Clean or replace restrictor.

Safety valve vacuum line loose or Tighten vacuum line.

disconnected.

Vacuum control filter restricted. Clean or replace filter.

Leak in deice flow valves. Refer to deice system trouble-

shooting, Remove deice flow
valves and clean.

Change 5
13-20 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

17

I etail $

16 15 13 14 13

Detail

Detail

421B0001 AND ON

1. Coupling 8. Gasket 14. Duct

2. Heat Exchanger 9. Retainer 15. Door
3. Adapter 10. Venturi 16. Inlet Air Valve
4. Dump Valve 11. Bolt 17. Heat Exchanger Control
5. Gasket 12. Spacer 18. Control Pedestal
6. Duct 13. Clamp 19. Instrument Panel
7, Sleeve 20. Dump Valve Control

Figure 13-5. Heat Exchanger Installation

 421 SERVICE MANUAL UTILITY AND Î3-2ÛA
OPTIONAL SYSTEMS

below the heater controls. This control is mechani- i. Install heat exchanger and dump valve by revers-
cally linked to a butterfly valve located in the nose ing removal procedures.
inlet scoop just forward of the heater. It is electri-
cally linked to the cabin pressure safety valve. As
the ram air control is moved to the DEPRESSURIZED Outflow and Safety Valves,
position, the cabin dump valve is actuated to the open
position. When the control is moved to the PRES- An outflow valve is located on the aft cabin pressure
SURIZED position, the cabin dump valve is actuated bulkhead. It is completely automatic in operation,
closed provided the gear is in extended position, set to maintain a nominal cabin pressure altitude of
When the control lever is moved to the RAM (dump) 8000 feet to 20, 180 feet and a nominal pressure dif-
position the butterfly valve in the nose is opened and ferential of 4. 1 to 4. 3 psi above 30, 180 feet on air-
ram air is allowed to enter the cabin. craft 421-0001 to 421B0201 On aircraft 421B0201
to 421BO301 a nominal pressure differential of 4. 3
Heat Exchanger and Pressurization Aír Dump Valve, to 4. 5 psi is maintained above 20, 860 feet. On air-
craft 421B0301 and On a nominal pressure differen-
A heat exchanger is located in each stub wing leading tial of 4. 9 to 5. 1 psi is maintained above 23, 120 feet.
edge. Pressurized air passing through the heat ex- There is no adjustment of the outflow valve. A com -

changer is cooled to within 10 degrees of ambient bination cabin safety and dump valve is also located
temperature by ram air entering the wing leading on the a.ft cabin pressure bulkhead. This valve is
edge air íntake and passing through the heat exchang- provided for cabin depressurization and as a safety
er. On aircra.ft 421-0001 to 421A0001 the dump valve backup for the outflow valve. On aircraft 421-0001
is solenoid operated. On aircraft 421B0001 and On to 421B0201 the safety valve pressure relief is fac-
the dump valve is manually controlled. The dump tory set at 4. 2 to 4. 4 psi and should not be reset.
valves may be individually controlled by the pilot. In On aircraft 421B0201 to 421BO301 the safety valve
case of noxious fumes or contamination entering pressure relief is factory set at 4. 5 to 4. 6 psi and
the cabin, either dump valve may be opened to allow should not be reset. On 421B0301 and On the safety
fumes to be dumped overboard and still maintain valve pressure is factorÿ set at 5. 2 to 5. 4 psi and
pressurization from the opposite side. should not be reset. The safety valve also incorpo-
rates a dump function which is solenoid operated,
vacuum actuated and controlled by the pilot.
Removal and Installation of Heat Exchanger Dump
Valve and Pressurization Air Venturi. (See figure
13-5.) Removal and Installation of Outflow Valve and Safety
Valve. (See figure 13-5A.)
Removal and installation is given for left-hand side;
right-hand side is similar. Remove heat exchanger a. Remove tailcone access door.
as follows: b. Disconnect static line (13), vacuum line (12) and
a. Remove access plates (54, 55, 56, 57 and 35). electrical connection at safety valve (10).
(See figure 1-2.) c. Remove screws (8) securing valve to aft cabin
b. Remove door (15) and overboard drain tube. bulkhead (5).
c. Remove clamps securing ducts to heat exchanger, d. Disconnect static pressure line (16) from outflow
d. Remove bolt (11) and spacer (12), then slide valve (3).
dump valve assembly outboard to disengage adapter e. From aft side of cabin bulkhead, remove screws
(3) from heat exchanger. (8), washers (7) and stat-o-seals (6) while holding
e. Remove screws securing heat exchanger to strue- valve to prevent damage from falling.
ture at forward side and lower heat exchanger from
stub wing. NOTE
f. Remove the remaining bolts securing the dump
valve to adapter to remove dump valve. On aircraft 421-0801 and On, discard re-
g. Ducting is then removed by removing clamps (13) moved gaskets and seal valves to bulkhead
and sleeve (7), with approximately 1/8" diameter head of
RTV-106 sealant. Torque attaching screws
h. Remove screws securing retainer (9) and three
gaskets (8), then remove venturi (10) through firewall to 4-6 inch-pound in a diametrically opposed
into nacelle area. sequence. Safetywire screws in accordance
with standard procedures.

f. Installation is a reversal of removal procedures.

Change 12
13-20B UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

5
4
3
2

8 5 9 421-0001 TO 42180301

Deta
421B0301 TO 421BO801

"
5 1 51143009«
51142014R

1. Filter 7. Washer 13. Static Line 19. Vacuum Hose

2. Lever 8. Screw 14. Filter 20. Manifold
3. Outflow Valve 9. Static Ports 15. Restrictor 21. Tee
4. Gasket 10. Safety Valve 16. Static Line 22. Doubler
5. Aft Cabin Bulkhead 11. Restrictor 17. Gasket 23. Solenoid Valve
6. Stat-O-Seal 12. Vacuum Line 18. Lock-O-Seal 24. Controller

Figure 13-5A. Cabin Outflow and Safety Valve Installation (Sheet 1 of 2)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-20C/13-20D
OPTIONAL SYSTEMS

'
13

24

421B0801 AND ON

Detail D
51143066
D51143070

Figure 13-5A. Cabin Outflow Valve and Safety Valve Installation (Sheet 2)

Change 12
 421 SERVICE MANUAL UTILITY AND
l3-2l
OPTIONAL SYSTEMS
Removal and Installation of Safety Valve Plumbing· Installation of Outflow Valve. (See Figure 13-6.)
(See figure 13-5A. )
a. Assemble flow rings (23), stat-o-seals (24) and
a. Remove right-hand upholstery panel in accord_ gaskets (12) to valve (25) with the stat-o-seals be-
ance with Section 3. tween flow rings and valve, held in position with the
b. Remove vacuum hose (19) from "tee" (21) and attaching screws (22).
from adapter located at right side of cabin, forward b. Place assembly in position on aft cabin bulkhead
of instrument panel. and secure with nuts (11).
c. Remove clamps securing vacuum lines to bulk_ c. Adjust flow rings (23) to a minimum clearance of
heads along the right side of cabin. .05 inch between flow rings and valve (25).
d. Disconnect line at unions and safety valve, then d. Connect static and vacuum lines.
remove in five sections. e. Install safety valve and outflow valve shroud.
e. Remove static pressure lines (13) from safety f. Install tailcone access door.
valve to aft pressure bulkhead.
f. Installation is a reversal of removal procedures· Variable Pressure Controller.
The variable pressure controller incorporates a ref-
Variable Cabin Pressure System. (Optional) erence chamber which controls the outflow valve
The variable cabin pressure system provides the which in turn governs the cabin pressure. The con-
troller is referenced to a static air system, indepen-
maximum for passenger comfort by allowing selection
of any cabin pressure altitude above sea level. This dent of the aircraft's static air system. The control
selected cabin altitude is automatically maintained by is shock mounted and located on the control pedestal.
the control system until the aircraft reaches an alti-
tude creating ±. 10 PSI differential pressure. The Removal of Pressure Controller. (See figure 13-6.)
pressure rate-of-change for this system can be se-
a. Remove screws (22) securing panel (28) to lower
lected by the pilot providing maximum passenger
side of pedestal.
comfort regardless of aircraft rate of ascent or de-
scent b. Disconnect filter hose (14), outflow hose (15),
static hose (16) and vacuum hose (17).
c. Remove cap nuts (1) and pull control out far
The variable cabin pressure system utilizes the com¯ enough to disconnect post light wire.
ponents of the standard system with the following ad¯
face plate (2) to
d. Remove four screws securing
ditions: a variable rate cabin pressure outflow valve, control (4).
a controller mounted on the pedestal which governs
the outflow valve and plumbing interconnecting the CAUTION
valve and controller.
No adjustments should be attempted on con-
troller or outflow valve. Repair is limited
Outflow Valve. to replacement of parts.
The outflow valve governs cabin pressure and is act-
uated by a reference chamber in the variable control- Installation of Pressure Controller. (See Figure 13-6.)
ler. It is located in the aft cabin pressure bulkhead. controller the reversal of
Installation of pressure is
removal procedures.

Removal of Outflow Valve. (See Figure 13-6.)

Removal and Installation of Pressure Controller
a. Remove tailcone access door. Plumbing. (See figure 13-6.)
b. Remove safety valve and outflow valve shroud,
c. Disconnect static and vacuum lines from valve, a. Remove safety valve and outflow valve shroud.
b. Remove right side seats, pilot's seat, copilot's
d. Remove nuts, stat-o-seals and screws securing
seat, kick plates and carpet as required in accord-
flow rings (23) to valve (25) and valve to doubler (26),
ance with Section 3.
NOTE
c. Remove right lower side panels in accordance
with Section 3.
On aircraft 421-0801 re- d. Remove floor access cover (73) and access cover
and On, discard
(15) from lower side of fuselage. (See Figure 1-2.)
moved gaskets and seal valves to bulkhead
e. Lower panel (28) and disconnect hoses (14, 15,
with approximately 1/8" diameter bead of
RTV-106 sealant. 16 and 17) from pressure controller (4).
Torque attaching screws
f. Disconnect hoses (14, 15, 16 and 17) from elbow
to 4-6 inch-pound in a diametrically opposed
fittings and remove through access in bottom of the
sequence. Safetywire screws in accordance
fuselage.
with standard procedures.
g. Remove clamps securing static line (6) and out-
NOTE flow hose (15) seven places, disconnect at forward
end and at aft fittings; then remove.
To preclude possible leaks on assembly, dis- h. Disconnect vacuum line (5) at fittings and remove
card all stat-o-seals and gaskets removed in sections.
and install new ones. i. Installation is a reversal of removal procedures.

Change 12
13-2Ž UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

16
24
23

Detail A
13 421-0029 TO 421BO301

2128
6

|
l DetailÃ
421B0801 AND ON

51143063
A5114301l
A51143071R

Figure 13-6. Variable Pressure Installation (Sheet 1 of 2)

Change 12
 421 SERVICE MANUAL UTILITY AND 13-22A
OPTIONAL SYSTEMS

25

12

Detail B
421-0001 TO 421-0013
421-0014 TO 421-0025
421-0026

25

27

4 23 24 6 7 18

Detail
421B0301 TO 421B0801

28 22
Detail D es1142o4s
DS1141004

1. Cap Nut 10. Elbow 18. Shutoff Valve 26. Doubler

2. Face Plate 11. Nut 19. Tee 27. Lock-O-Seal
3. Shock Mount 12. Gasket 20. Shutoff Valve 28. Panel
4. Outflow Valve Control 13. Filter 21. Safety Valve 29. Restrictor
5. Vacuum Line 14. Filter Hose 22. Screw 30. Aft Pressure Bulkhead
6. Static Line 15. Outflow Hose 23. Flow Ring 31. Coupling
7. Outflow Line 16. Static Hose 24. Stat-O-Seal 32. Packing
8. Coupling 17. Vacuum Hose 25. Outflow Valve 33. Solenoid Valve
9. Union 34. Volume Tank

Figure 13-6. Variable Pressure Installation (Sheet 2)

Change 11
13-22B UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Preflight Ground Checkout Procedure. (421-0001 CAUTION

to 42180801. ) (Optional System. )
Controller unit will be damaged if more than
a. Place aircraft
in pressurized mode: doors and 1 in. hg. vacuum is applied to line.
windows closed, cabin pressurize switch in PRES-
SURIZE position, ram air valve control and dump
valve control pushed full in. g. At completion of leak check reconnect line to
b. Disconnect electrical plug from cabin pressuri- outflow valve and remove ANB14-5D plug from con-
zation dump valve. troller and install orifice fitting.
c. Start and run engines at 20 inches of manifold h. Remove plug from vacuum line and reconnect
pressure. line to tee (19).
d. On cabin altitude control, place cabin altitude
needle on -1
(1000 feet below sea level). Preflight Ground Checkout Procedure. (421BO801
e. Set rate control arrow at midpoint (500 feet per and On. ) (Optional System. )
minute) immediately after setting cabin altitude.
f. Observe cabin rate of change gage. It should a. Place aircraft in pressurized mode: doors and
refleet a minus 500 ft. per minute reading for ap- windows closed, pressurized air switches in PRES-
proximately four and one-half minutes after setting SURIZE position, ram air valve control and dump
the rate control knob. After this time, it should valve control pushed full in.
drop back to zero. b. Pull CABIN PRESS circuit breaker.
g. Observe cabin differential gage. It should in- c. Start and run engines at 22 inches of manifold
crease to and then stabilize at approximately 1.2 pressure. Confirm that aircraft vacuum is in the
psi. If erratic readings are observed check all green range.
associated lines for loose fittings. Also check for d. On cabin altitude control, place cabin altitude
clogged air filter and obstructed static sensing port• pointer at a minimum of 1000 feet below field eleva-
tion.
e. Set rate control arrow straight up (12 o'clock
Leak Check of Pressurization Components. (See position) immediately after setting cabin altitude.
figure 13-6.) (421B0801 and On.) f. Observe cabin rate-of-change gage. It should
reflect approximately 500 feet per minute reading
a. Remove the orifice fitting from the rear of the until cabin altitude approaches the selected altitude
controller. In its place screw an ANB14-5D plug. setting.
b. Disconnect the vacuum line from tee (19) to con- g. Observe cabin differential pressure gage. It
troller (4) at tee. Plug open end of line, should increase and then stabilize at approximately
c. Disconnect the line connecting the outflow valve . 00 psi at sea level. The cabin differential pressure
(25) to controller (4) at the outflow valve. will increase approximately 50 psi per 1000 feet in-
.

d. Connect an alternate source of vacuum to the crease above sea level. See figure 13-6A,
disconnected line.
e. Set controller altitude and rate selection knobs
to maximum values.
f. Pull a vacuum on the line. With 1 in. hg. vacu-
um (1000 ft. on altimeter), there should be no leak-
age observed for three minutes.

ALTITUDE X DIFFERENTIAL ALTITUDE X DIFFERENTIAL

1000 FT PRESSURE PSI 1000 FT PRESSURE PSI

1 .52 9 4.19
2 1.03 10 4.58
3 1.52 11 4.97
4 2.00 12 5.35
5 2.47 13 5.71
6 2.92 14 6.06
7 3.35 15 6.40
8 3.78 16 6.72

(STANDARD DAY)

Figure 13-6A. Pressure/Altitude Chart

Change 12
 421 SERVICE MANUAL UTILITY AND 3
OPTIONAL SYSTEMS

CABIN PRESSURIZATION CHECK. Maximum differential of 4. 2 (4. 4) 5. 0 PSIG ±. 3

should be reached at 20, 180 (20, 86T23, 120 feet.
NOTE c. If the engines and turbochargers are functioning
normally, according to the Turbocharger Operation
Pressure and altitude readings given in pa- Flight Check Procedure, Section 9, any malfunction
rentheses apply to aircraft 421B0201 to of the cabin pressurization system should be isolated
421B0301. Readings underlined apply to to the cabin area, its ducting seals and/or regulating
aircraft 421B0301 and On. equipment.

The cabin pressurization check should be conducted NOTE

anytime 4. 2 (4. 4) 5. 0 PSIG ±. 3 cabin differential can-
not be maintained and/or during every 500 hour in- If engines are not performing properly at al-
spection. Outlined below are two cabin pressuriza- titude, the engine trouble should be corrected
tion checks that may be utilized to recognize cabin before proceeding further with this check.
pressurization leakage or equipment malfunction.
The cabin pressurization flight check procedure is d. While at cruise power and maximum differential
the preferred method and requires no test equipment. pressure, check the following for air leaks: around
An alternate ground check procedure using SK421-1 the main cabin door, emergency exit window, cock-
may be conducted in lieu of the flight check to obtain pit storm windows, etc. Refer to Pressurization
the same basic results. Troubleshooting Checklist in this section for addi-
tional areas to check.
If the systemis not functioning properly, obtain all e. Check cabin pressure regulator and safety valve
information available as to the nature of the malfunc- for escaping air pressure; both valves should be
tion such as; when it occurs, altitude, maximum dif- closed if 4. 2 (4. 4) 5. O PSIG ±. 3 differential is not
ferential obtained, engine power settings, cabin pres- being maintained ati, 180 (20, 860) 23, 120 feet or
surization control settings, any recent repairs or above.
major equipment installation affecting the pressur- f. Check the operation of each engine system and
ized cabin section. the pressurization air dump valves by dumping one
valve at a time. A normal system will show a mo-
There are two principal areas to be considered in mentary rise in cabin altitude followed by a return
troubleshooting the cabin pressurization system. to a stable condition on the cabin rate-of-climb indi-
a. Engine and turbochargers. cator. Close the valve returning the system to pres-
b. Pressurized cabin section and its regulating surization from both engines. Dump the opposite
controls. valve and observe the cabin rate-of-climb indicator
for change. The rate should become stable after a
To isolate the source of the trouble, a flight check is momentary rise in cabin altitude.
recommended, this will accomplish the following:
a. Check the performance of the engines and turbo- CAUTION
chargers (refer to Section 9 for Turbocharger Opera-
tion Flight Check Procedures). Severe personnel discomfort will be encount-
b. Check the cabin pressurization system in accord- ered if both dump valves are opened at the
ance with the Cabin Pressurization System Flight same time.
Check Preferred Method of this section.
A continuing rate-of-change indication and a loss of
Standard Cabin Pressurization System Flight Check differential pressure at a constant power setting,
(Preferred Method). while pressurizing with one engine, could indicate
leaking in the dump valves or ducting in that system.
a. Conduct a Turbocharger System Operational g. If 4. 2 (4. 4) 5. O PSIG ±. 3 differential pressure
Flight Check, refer to Section 9 for Turbocharger was not maintainiduring the check flight, refer to
Operation Flight Check Procedure. the Pressurization Troubleshooting Checklist and
b. During climb, pressurize the cabin and observe perform the Cabin Pressurization System Inspection
operation of the system, noting the differential and found in Section 2.
comparing cabin altitude with the cabin pressuriza-
tion operational flight check chart, figure 13-8A.

Change 11
13-24 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Optional Cabin Pressurization System Flight Check The following cabin pressurization ground check pro-
(Preferred Method). cedures, which is the alternate method, can be per-
formed in lieu of the Cabin ressurization Flight
a. Conduct a Turbocharger System Operational Check Procedures, using Cabin Pressurization Sys-
Flight Check, refer to Section 9 for Turbocharger tem Test Kit, SK421-1.
Operation Flight Check Procedures.
b. During the climb to altitude, set cabin altitude CAUTION
control for a sea level cabin. A properly functioning
system should maintain a sea level cabin to 9000 feet To prevent damage to the engine due to over-
altitude. A 4. 2 (4. 4) 5. O PSIG ±. 3 differential pres- heating, this check should not be conducted
85°F.
sure should be maintalid throughout the remainder when ambient temperature is above
of the climb. Monitor cabin altitude during the climb
and compare cabin pressurization with the cabin pres- a. Park the aircraft heading into the wind.
surization schedule in the 421 Owner's Manual.
c. If the engines and turbochargers are functioning CAUTION
normally, according to the Turbocharger Operation
Flight Check Procedures Section 9, any malfunction Conduct engine runup during this check with the
of the cabin pressurization system should be isolated cowling installed to prevent overheating. This
to the cabin area, its ducting seals and/or regulating check can be run using either engine.
equipment.
NOTE b. Remove plugs (421-0001 to 421-0014), cover
plates (421-0014 to 421A0001) and manifold pressure
If engines are not performing properly at alti- relief valve (421A0001 and On) and connect gages as
tude, the trouble should be corrected before shown in figure 13-7.
proceeding further with this check· c. Route instrument hoses out of nacelle through the
cowl flap opening, Place instruments close to tip tank
d. While at cruise power and maximum differential and tape lines to wing.
pressure, check the following for air leaks: around d. Remove sump from thermos console to gain ac-
the main cabin door, emergency exit window, cockpit cess to the cabin outflow valve and turn lever (2,
storm windows, and etc., refer to Pressurization figure 13-5A) to TEST (Standard System) or close
Troubleshooting Checklist in this Section for addi- vacuum shutoff valve (20, figure 13-6) and static shut-
tional areas to check. off valve (18, figure 13-6) in the optional system.
e. Check cabin pressure regulator and safety valve Access to the vacuum shutoff valve is gained by un-
for escaping air pressure, both valves should be snapping the right-hand front upholstery panel next to
closed if 4. 2 (4. 4) 5. O PSIG ±. 3 differential pressure the static drain valve. The static shutoff valve is in
is not being maintaid, the aft cabin below the thermos console.
f. Check operation of each engine and the pressuri- e. (See figure 13-6.) Turn shutoff valve (20) to
zation air dump valves by dumping one valve at a closed position to deactivate system.
time. A normal system will show a momentary rise f. Position master switch to ON and pressurization
in cabin altitude followed by a return to a stable con- dump valve switches to NORMAL.
dition on the cabin rate-of-change indicator. Close g. Place ram air valve control to PRESSURIZED.
the valve, returning the system to pressurization h. Close cabin doors and windows.
from both engines. Dump the opposite valve and ob- i. Set aircraft altimeter to 29.92 in. Hg. and re-
serve the cabin rate-of-change indicator for change. cord field pressure altitude.
The rate should become stáble after a momentary j. Start instrumented engine in accordance with
rise in cabin altitude. Starting Procedures in aircraft Owner's Manual.

CAUTION CAUTION

Severe personnel discomfort will be encount- Do not allow engine manifold pressure to ex-
ered if both dump valves are opened at the ceed 28. O in. Hg. when starting, to prevent
same time. damage to the differential pressure test gage.
After the engines are started, the manifold
A continuing rate-of-change indication and a loss of pressure can be increased; however, the dif-
differential pressure at a constant power setting, ferential pressure test gage must be moni-
while pressurizing with one engine, could indicate tored to prevent rapid acceleration. To pro-
leaking in the dump valves or ducting in that system. vide for personnel comfort, throttle move-
g. If 4. 2 (4. 4) 5. O PSIG ±. 3 differential pressure ments (increase or decrease) should be moni-
was not maintainiduring the check flight, refer to tored to maintain a cabin pressure rate-of-
the Pressurization Troubleshooting Checklist and change of not more than 1000 feet per minute.
perform the Cabin Pressurization System Inspection
found in Section 2.
k, (See figure 13-8.) The following step by step

I
Cabin Pressurization System Ground Check (Alternate procedures are given to determine if the cabin is
Method) (Standard and Optional Systems) (421-0001 to
421BO801).
Change 12
 421 SERVICE MANUAL UTILITY AND l3 4A
OPTIONAL SYSTEMS

pressurizing properly. NOTE

1. Starting at field pressure altitude, recorded in
step i., on chart A, project a line from field pressure Check gasket, if damaged replace with a new
altitude to the diagonal guide line then to absolute gasket.
pressure reading.
2. Increase engine RPM until absolute pressure CAUTION
gage reading, as determined in step 1., is reached,
and hold this reading for one minute. Record the dif- Be sure that "O" ring remains in groove on
ferential pressure gage reading. This is measured reliefvalve when installing to adapter plate.
cabin differential pressure.
3. Record the aircraft outside air temperature,
then starting from this point on chart B, project a n. (See figure 13-5A.) On the standard cabin pres-
line to the guide line then to differential pressure surization system, set cabin outflow valve (3) to
gage reading. FLIGHT position and safety.
4. If the differential pressure gage reading obtained o. (See figure 13-6.) On the optional cabin pres-
from chart B is equal to or more than the actual dif- surization system, return vacuum shutoff valve (20)
ferential pressure gage reading obtained in step 2., and static shutoff valve (18) to the open position.
the cabin differential pressure rate is acceptable. Safety static shutoff valve (18) in the open position.
1. If the differential pressure is greater than that
obtained from Chart B, the cabin pressurization sys- NOTE
tem is not maintaining a proper differential pressure
and the Cabin Pressurization System Inspection On the optional pressurization system the vacu-
found in Section 2 should be performed. um and static shutoff valves must be open for the
m. After test is completed, remove all test equip- cabin pressurization system to function properly.
ment and restore to original configuration. The vacuum shutoff valve must be safetied open.

PRESSURIZATION TROUBLE SHOOTING CHECKLIST.

LOCATION PROBABLE CAUSE CORRECTION

Entrance Door* Faulty seals and/or Lock-O-Seals Repair or replace seal

Refer to SK421-2
Emergency Exit* Faulty seal Replace seal
Foul Weather Windows Faulty seals Replace seals
Wire Bundles at Sta. 100. 00 Bulkhead Sealant broken Reseal bundle
Access Doors Faulty seals Replace seals
Windows Sealant broken Replace sealant
Nose Gear Push-pull Tube Boot loose or torn Replace boot

Main Gear Push-pull Tube Boot loose or torn Replace boot

Control Column Bearing Cover Gasket Reseal gasket
Controls at Sta. 100. 00 Bulkhead Sealant broken Reseal controls
Controls at Stub Wing Sealant broken Reseal controls

Safety Valve and Outflow Valve Faulty gaskets and/or Replace gaskets
Lock-O-Seals

*A small amount of leakage around these areas is normal.

Change 4
13-248 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

GASKET P/N 5155136-2

*PLATE P/N 5199001-10
*GAGE ADAPTER ASSEMBLY
o P/N 5199001-8
*O-RING
P/N MS27039-1-12

421-0014 AND ON
*DIFFERENTIAL PRESSURE
GAGE P/N 1038B10-04
PRESSURIZATION AIR
VENTURI *SCREWS
P/N MS28778-16
4 REQUIRED

*ABSOLUTE PRESSURE
GAGE P/N 2635L3 HIGH PRESSURE PORT

LO PRESSURE PORT

HIGH PRESSURE PORT

P/N AN816-2D
*GAGE ADAPTER ASSEMBLY
P/N 5199001-8 )
*O-RING
P/N MS27039-1-12
*ELBOW
P/N MS20822-2D
LOW PRESSURE PORT
*INTERCONNECT HOSE
P/N CM2944-2-12
HIGH PRESSURE
PORT

*TEE P/N MS20826-2D

*NIPPLE P/N ANB16-2D *INSTRUMENT HOSE

P/N CM2944-2-180

*PARTS SUPPLIED IN SK421-1

Figure 13-7. Cabin Pressurization Test Equipment

 421 SERVICE MANUAL UTILITY AND U-25
OPTIONAL SYSTEMS

SAMPLE PROBELM; (for Chart A) SAMPLE PROBLEM: (for Chart B)

1. Field Pressure Altitude 3400 Ft.
-
1. Outside Air Ternperature -
88°F
2. Guide Line 2. Guide Line
3. Absolute Pressure Gage Reading 31. 4 in. Hg.
-

3. Differential Pressure Gage

Ahowance -
83 in. H2O.

CHART CHART

38. 0 160

37.0 150

36.0 140

35.0 130

34.0 120

33.0 - -

110 -

32.0 100

m 31.0 90

30.0 80

29.0 < 70

28.0 60

27. o 50

26.0 40 -

25.
oooooooooo
o o o o o o o o o 78 80 82 84 86 88
ooooooooo

FIELD PRESSURE ALTITUDE IN FEET DIFFERENTIAL PRESSURE

(ALTIMETER SET TO 29.92 IN. HG.) GAGE (MAX ALLOWABLE)
INCHESH2O

Figure 13-8. Leak Rate Chart

13- UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

5. Cabin Rate-of-Change Indicator and Cabin Altitude

Indicator will rise with 4. 2 (4. 4) 5..0 PSIG ±. 3

I 5 ABOVE 20, 180 FEET

(20, 860)
23, 120 4.
Differential Remaining

Cabin Rate-of-Change
Constant.

Indicator should remain at 0

from 8000 feet to 20, 180 feet during climb at 4. 2
differential pressure only. Differential Pressure

I 4 CRUISE 20,180 FEET

(20, 860)
23, 120
Indicator should increase from 0 to 4.2 (4.4) 5.0
PSIG ±. 3. Check left and right Pressurization
Dump valves. Observe Cabin Rate-of-Climb
Air
Indi-
cator. Check main cabin door, emergency exit,
pilot's storm window, cabin safety and outflow
valves for leaks.

3. Check Rate-of-Change
-

Indicator will start to de-

crease relative to aircraft Rate-of-Climb Indicator.
3 CLIMB 8000 FEET Refer to Standard Pressurization Schedule in air-
craft Owner's Manual from 8000 to 20, 180 feet.

2. Check Cabin Altimeter

-

and Aircraft Altimeter

should read within ±600 feet from takeoff to 8000
2 TAKEOFF feet.
NOTE

Readings given in parentheses apply to

I SET ALTIMETER aircraft 421B0201 to 421B0301. Read-
29.92 IN. HG ings underlined apply to aircraft
421B0301 and On.

CABIN PRESSURIZATION SYSTEM STANDARD

ABOVE 5. Cabin Rate-of-Change Indicator and Cabin Altitude

5 CRUISE 9000 FEET Indicator will rise with 4. 2 (4. 4) 5. O PSIG ±, 3
MAX Differential Pressure HoldinRonstant.
See
Optional Pressurization Schedule in aircraft Owner's
Manual. Check left and right dump valves, cabin
main door, cabin outflow and safety valve for leaks
(see Cabin Pressurization Check and Troubleshoot-
ing Chart).

4 CLIMB 9000 FEET 4. Climb -

Cabin Altitude should read Sea Level and
Differential Pressure Indicator should read 4. 2
(4. 4) 5. O PSIG ±. 3.

2. 500 feet above pattern altitude and Cabin Rate

3 TAKEOFF
Control to MIN.

NOTE
SET CABIN ALTITUDE
CONTROL Readings given in parentheses apply to
aircraft 421B0201 to 421B0301. Read-
ings underlined apply to aircraft
1 SET ALTIMETER
421B0301 and On.
29. 92 IN. HG
CABIN PRESSURIZATION SYSTEM OPTIONAL

Figure 13-8A. Cabin Pressurization Operation Flight Check Chart

Thange 7
 421 SERVICE MANUAL UTILITY AND l3" I
OPTIONAL SYSTEMS
OXYGEN SYSTEM. . valve which requires no manual opening of closing.
A protective cap screws over the filler valve to
The optional oxygen system is designed to supply prevent entry of foreign particles. The oxygen
oxygen for a pilot and five passengers. The optional to the regulator-shutoff
pressure gage is connected
system consists of an oxygen cylinder, filler valve valve by a tube and indicates the amount of oxygen
(inside left nose baggage door), plumbing, oxygen pressure in the oxygen cylinder.
pressure gage, six outlet couplings, two permanent
oxygen masks and four dispósable type oxygenmasks.
WARNING
Two optional bottle sizes are provided, an 11.0 cubic
foot capacity bottle and a 114.9 cubic foot capacity Oil, grease or other lubricants in contact with
bottle which meets the air carrier oxygen require -

oxygen create a serious fire hazard, and such

ments. On aircraft 421BO301 and ON the 48. 3 and contact must be avoided. Do not permit smok-
76. 6 cubic foot oxygen installations incorporate an ing or open flame in or near aircraft while
oxygen altitude compensator in the line from the work is performed on oxygen system, or when
regualtor to the cabin outlets. This compensator the system is in operation. Guard against in-
reduces asygen expenditures at lower altitudes and
advertently turning the master switch on.
increases the oxygen duration.
All aircraft are equipped with standard WARNING
plumbing from the forward cabin bulkhead to the six
standard oxygen outlet couplings. Oxygen is routed USE NO OIL. Also keep equipment free of or-
from the high pressure cylinder through a regulator¯ ganic material (dust, lint, etc.). Be sure
shutoff valve. The regulator-shutoff valve reduces hands and clothing are free of oil, grease,
high cylinder pressure to a low usable pressure, soap, lipstick, lip balm and other fatty
and is controlled by a knob located just left of the materials.
pedestal. The low oxygen pressure is routed to six,
outlet couplings which supply a continuous flow of CAUTION
oxygen to the oxygen mask whenever the mask hoses
are plugged into the couplings. Each coupling con- Prior to initial use, the oxygen system shall
tains a spring-loaded valve which prevents the flow be purged with oxygen for a period of ten (10)
of oxygen until the mask hose is plugged into the minutes by inserting mask fitting at each of
coupling. Each mask hose contains a flow indicator the outlets and allowing the oxygen to flow
for visual proof of oxygen flow. The filler valve is through slowly. If the system has not been
located inside of the nose baggage door and elim- used for a period of two (2) years, the regu-
inates the removal of the oxygen cylinder for re-- lator shall be inspected and rubber materials
filling. The filler valve is a self-sealing automatic replaced.

Trouble Shooting the Oxygen System.

TROUBLE PROBABLE CAUSE CORRECTION

NO PRESSURE INDICATION Leak in system has exhausted pres- Visually check pressure gage.
ON PRESSURE GAGE sure. Charge system and use detector
fluids, type CG-1, MIL-25561A,
or its equivalent, to check lines
and fittings. Tighten or re-
place fittings as necessary.

Defective pressure gage. Pull knob out, insert mask hose

into outlet and note flow indica-
tor, Replace gage.

PRESSURE INDICATION Defective oxygen cylinder- Replace oxgyen cylinder-regu-

NORMAL BUT OXYGEN regulator assembly. lator assembly.
FAILS TO FLOW

OXYGEN DURATION TOO Leak in system. Draw a line on gage cover glass
SHORT directly over pointer with a
grease pencil, Loss of oxygen:
should not exceed one percent
of total supply for a 24-hour
period. Charge system and
use detector fluids. Type CG-1
MIL-25567A, or its equiva-
lent, to check lines and fittings.
Tighten or replace fittings as
necessary,
I

Change 6
13¯ Û UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

OXYGEN CYLINDER AND

PRESSURE REGULATOR ASSY.

PRESSURE
GAGE

OVERHEAD CONSOLE PANEL

PULL

OXYGEN CONTROL

FILLER VALVE AND

PROTECTIVE CAP

TO PILOT'S
FACE MASK w

TO OPTIONAL SEVENTH AND EIGHTH

PASSENGER FACE MASKS

CODE:

§¾Ð HIGH PRESSURE OXYGEN

LOW PRESSURE OXYGEN
CONTINUOUS FLOW COUPLING

FLOW INDICATOR (SPRING

DISAPPEARS WHEN OXYGEN IS FLOWING)
] FLOW INDICATOR (SPRING DISAPPEARS
WHEN OXYGEN IS NOT FLOWING) AND TENTH
TO OPTIONAL NINTH
-

MECHANICAL ACTUATION PASSENGER FACE MASKS

(EXE CUTIVE COMMUTER)

Figure 13-9. Oxygen System Schematic

 421 SERVICE MANUAL UTILITY AND 13=SQl3-268
OPTIONAL SYSTEMS

13
15
22

A C
21 17
DETAIL DETAIL
421-0001 TO 421A0024
"
o
23
o

10
24
19
20
16
25

DETAIL $ 21

421A0024 AND ON SEE SERVlCE MANUAL FOR

SERvlCING INSTRUCTIONS

421-0001 TO 421BOOO1

1. Oxygen Outlet 5. Union 8. Oxygen Cylinder Regulator

2. Line 6. Filler Valve Assembly (11. O cu. It.)
3. Tee 7. Mounting Clamp 9. Shutoff Valve
4. Elbow 10. Control Cable

Figure 13-10. Oxygen System Installation (Sheet 1 of 2)

Change 2
 421 SERVICE MANUAL UTILITY AND 13" $
OPTIONAL SYSTEMS

26
Detail
Detail
EXECUTIVE COMMUTER

Detaii D
10
24 16
25

21

Detail 421BOOO1 AND ON Detaii E

1. Mask Hose 17. Low Pressure Line 23. Oxygen Cylinder Regulator
2. Oxygen Mask 18. Pressure Relief Valve Assembly (114. 9 cu. ft. )
3. Disposable Oxygen Mask 19. Cotter Pin 24. Bulkhead Sta. 94. 75
4. Seal Assembly 20. Control Mounting Clamp 25. Bulkhead Fitting
5. Oxygen Control Knob 21. Filler Valve Line 26. Altitude Compensating
6. Capillary Line 22. Pressure Gage Oxygen Regulator
27. Oxygen Cylinder

Figure 13-10. Oxygen System Installation (Sheet 2 of 2)

Change 8
13-30 UTILITY AND -

421 SERVICE MANUAL

OPTIONAL SYSTEMS

Maintenance of Oxygen System. NOTE

Before and during maintenance on oxygen systems, Cap lines at both ends immediately after dry-
the following general rules must be followed: ing to prevent moisture from entering.
a. Clean hands, tools, and working area.
b. Keep grease, oil, water and all foreign matter Bleeding the Oxygen System. (See figure 13-10.)
from system,
c. Keep all lines dry and capped until installed. a. Pull oxygen control knob (15) to ON position.
d. All compounds used on fittings must conform to b. Remove tubing from mask end of one of the pas-
MIL-T-5542. No compound shall be used on alumi- senger's oxygen masks and insert into oxygen outlet
num alloy flared fittings. Compounds are used only and route the hose outside the cabin area through the
on the first three threads of male fittings. No com- pilot's foul weather window.
pound is used on coupling sleeves, or outside of tube
flares. WARN1NG
CAUTION
The bleeding procedure should be accom-
plished outdoors. If the bleeding is done in-
Whenever a component of the oxygen system
(lines, gages, cylinders
doors extreme care must be exercised to
or regulators, etc. ) con-
prevent oxygen flow from oils, grease,
has been removed, reinstalled, replaced, or
system has been disassembled taminants and electrical sparks. The area
in any way '
should be roped off and no smoking or open
the oxygen system must be leak checked and
flame in or near the area.
purged as per procedures outlined in this
section
c. Bleeding the oxygen system into the cabin area
is not recommended.
e. Inspection of the cylinder is required before
charging. Do not attempt to charge the cylinder if Removal of Oxygen Cylinder-Regulator Assembly.
any of the following conditions exist: (See figure 13-10. )
1. Contamination or corroded fitting on cascade
cylinder of filler valve· The following procedures are for the 11. O cu. ft.
2. Cylinder out of hydrostatic test date- capacity cylinder. The 114. 9 cu. ft. cylinder is lo-
3. Cylinder bears no I. C. C. designation- cated in nose baggage compartment, mounted on the
4. Cylinder completely empty after shutoff valve compartment floor. Access to the filler valve is
has been turned off for a length of time. Must be through the right baggage compartment access door.
completely disassembled and inspected in an FAA Removal and installation of the 114, 9 cu. ft. capacity
approved facility before charging• . cylinder is the same as for the 11. O cu. ft. cylinder.
f. Fabrication of pressure lines is not recommen-
ded. Lines should be replaced from factory by part a. Remove nose baggage compartment floor to gain
number- access to oxygen cylinder and regulator.
g. Lines and fittings shall be clean and dry. One b. Push oxygen control knob (15) to OFF position
of the following methods may be used to clean lines: and disconnect lines (16, 17 and 21) from oxygen
1. A vapor degreasing solution of stabilized tri- cylinder-regulator assembly (8).
chlorethylene conforming to Specification MIL-T-7003 c. Disconnect control cable (10) from oxygen
cylinder-regulator
Iof
followed by blowing tubing clean and dry with a stream
clean, nitrogen gas (BB-N-411)
Grade A or technical Argon (MIL-A-18455).
Type 1, Class 1, d. Remove control
cylinder-regulator
assembly

assembly
(8).
mounting clamp (20) from oxygen
(8).
e. Loosen mounting straps (7) and lift oxygen cylin-
CAUTION der from aircraft.

Most air compressors are oil lubricated, and CAUTION

a minute amount of oil may be carried by the
air stream. A water lubricated compressor Do not rotate control lever to the ON position
should be used to blow tubing clean· with outlet ports (low pressure) open to atmos-
phere. Damage to regulator metering poppet
2. Flush with naphtha conforming to Specification will occur.
TT-N-95, then blow clean and dry with clean, dry,
nitrogen gas (BB-N-411) Type 1, Class 1, Grade A Installation of Oxygen Cylinder-Regulator Assembly,
or technical Argon (MIL-A-18455). Flush with anti- (See figure 13-10.)
icing fluid conforming to MIL-F-5566 or anhydrous
ethyl alcohol. Rinse thoroughly with fresh water and WARNING
dry with clean, nitrogen gas (BB-N-411) Type 1,
Class 1, Grade A or technical Argon (MIL-A-18455). Extreme care must be taken when installing
3. Flush with hot inhibited alkaline cleaner until or working near the cylinder-regulator to
free from oil and grease. Rinse with fresh water prevent damaging the cylinder. The slightest
and dry with clean, nitrogen gas (BB-N-411) Type 1, scratch, nick or dent is cause for immediate
Class 1, Grade A or technical Argon (MIL-A-18455). condemnation of the cylinder.

Change 10
 421 SERVICE MANUAL UTILITY AND 13¯3l
OPTIONAL SYSTEMS

a. Install oxygen cylinder-regulator assembly (8) NOTE

in the
nose compartment position in mounting clamps
(7). Do not tighten at this time. Repair or maintenance of this unit is not re-
b. Align oxygen cylinder-regulator assembly (8) commended. If malfunction should occur,
with control cable (10) and three line assemblies (16, remove and replace.
17 and 21). Tighten nuts on mounting straps (7).
c. Install three line assemblies (16, 17 and 21) on b. Disconnect inlet and outlet lines from compen-
the oxygen cylinder-regulator assembly (8). sating regulator (26).
c. 'Removeicompensating regulator from aircraft.
CAUTION d. Install clean dry caps in inlet and outlet ports of
compensating regulator and install clean dry plugs in
On aircraft 421BOO58 and On, an overboard disconnected oxygen lines.
vent line is incorporated. Make sure vent
line is connected. Installation of Altitude Compensating Oxygen Regula-
tor. (See figure 13-10. ) (421B0301 and On)
d. Install control mounting clamp (20) on the oxygen
a. Remove protective caps and plugs from compen-
cylinder-regulator assembly (8) and connect control
sating and supply lines.
regulator
cable (10) to the control actuator with cotter pin (19).
b. Position compensating
.

regulator in place and

e. Install nose baggage compartment floor.
connect supply lines to compensating regulator.
c. Move oxygen control knob to the ON position and
check for leaks.
Removal of Altitude Compensating Oxygen Regulator. Removal of Oxygen Pressure Gage. (See figure 13-
(See figure 13-10. ) (421BO301 and On) 10. )

a. Move oxygen control knob to the OFF position. The oxygen pressure gage may be removed without
bleeding the oxygen pressure. A check valve is in-
stalled in the gage pressure outlet of the regulator

Each interconnected series of oxygen cylinders is equipped with a single gage. The trailer type
cascade may also be equipped with a nitrogen cylinder (shown reversed) for filling landing gear
struts, accumulators, etc. Cylinders are not available for direct purchase, but are usually
leased and refilled by a local compressed gas supplier.

Service Kit SK310-32 (available from the Cessna Dealers' Organization) contains an adapter, a
pressure gage, hose, lines, and fittings for equipping two oxygen cylinders to service oxygen
systems. As noted in the Service Kit, a tee (Part No. 11844) and a pigtail (Part No. 1243-2)
should be ordered for each additional cylinder to be used in the cascade of eylinders. Be sure
to ground the aircraft and ground servicing equipment before use,
OXYGEN CYLINDER
NITROGEN CYLINDER

PRESSURE GAGE

ZGH204 ADAPTER

C ZS711-12 LINE ASSY OXYGEN PURIFIER /

W/REPLACEABLE
Detail CARTRIDGE

Figure 13-11. Typical Portable Oxygen Cascades

Change 12
13-32 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS
to shutoff the flow of oxygen from the cylinder when b. Disconnect capillary line (16) at gage from nipple
the capillary line is disconnected at the oxygen in back of pressure gage (22). I
cylinder-regulator. c. Cap all lines immediately after disconnecting.
d. Remove pressure gage by removing the mounting
WARNING screws.

Use non-sparking tools, make sure tools, Installation of Oxygen Pressure Gage. (See figure
and hands are free from oils, grease and 13-10.)
other contaminants when working with oxy- a. Installation of oxygen pressure gage is the re-
gen, versal of removal procedures.

a. Disconnect capillary line (16) at regulator. The

I
check valve should close as tne line is loosened.
Removal of Oxygen Filler Valve. (See figure 13-5. )
CAUTION
The oxygen filler valve may be removed without bleed-
If oxygen continues to flow, reconnect line ing the oxygen pressure system. A check valve is
and bleed off pressure in accordance with incorporated in the high pressure side of the oxygen
bleeding procedures.

INSPECTION CRITERIA FOR ACCEPTANCE OF OXYGEN CYLINDERS

The following data may be used to determine that oxygen cylinders are acceptable for service. This cri-
teria should be used prior to charging cylinders.

Cylinder Classification

Discrepancies ICC-3AA 1800 ICC-8HT 1800

Isolated pitting or corrosion . 020 2 3 . 010 2 3

(Depth)
Local pitting or corrosion or line corrosion
(Depth) . 010 3 4 . 005 3 4

General corrosion Not allowed 5 Not allowed 5

Cuts, Digs, gouges .010 6 . 005 6
(Depth)
Dents (Depth) . 062 7 . 031 7
Fire Damage Not allowed 8 Not allowed 8
Bulges Not allowed 9 Not allowed 9

2 Isolated pits of small cross section involving loss of wall thickness by corrosive media. Small
isolated pits with a maximum depth as shown are acceptable.
3 If depth exceeds figure shown, cylinder must be returned to the manufacturer for disposition.
4 Local pitting or corrosion or line corrosion involving loss of wall thickness by corrosive media
with a pattern of pits which are connected to others in a band or line. A sma11 area with a mini-
mum depth as shown is acceptable. Areas extending beyond 3 inches in diameter or 4 inches
long shall be considered general corrosion.
5 General corrosion (someümes accompanied by pitting) involving loss of wall thickness by cor-
rosive media covering a considerable area. Cylinder must be returned to the manufacturer for
hydrostatic testing.
6 Deformations caused by contact with a sharp object cutting or upsetting the material of the cylin-
der, decreasing the wall thickness. Maximum defect permissible without corrective action. If
this depth is exceeded, the cylinder must be returned to the manufacturer for removal of defects
and verification of cylinder strength by hydrostatic tesung.
7 Deformations caused by contact with blunt objects in such manner that the thickness of the metal
is not materially impaired. The major diameter of the dent must be equal to or greater than 32
times the depth of the dent. Sharper dents (or deeper dents) than this are considered too abrupt
and must be returned to the cylinder manufacturer for disposition.
8 Fire damage is indicated by charring or burning or sintering of the metal, charring or burning
of the paint, distortion of the cylinder, functioned safety relief devices, melting of valve parts,
etc. Cylinders must be returned to the cylinder manufacturer for disposition.
9 Bulged cylinders are not acceptable. Cylinders must be returned to the cylinder manufacturer
for disposition.

Change 12 Figure 13--11A. Inspection Criteria for Acceptance of Oxygen Cylinder

 421 SERVICE MANUAL UTILITY AND jg-ggg
OPTIONAL SYSTEMS

regulator to shutoff the flow of oxygen from the cylin" d. Connect filler valve line (21) to oxygen regulator.
der when the high pressure line is disconnected from e. Replace filler valve protective cap.
the oxygen cylinder.

a. Disconnect filler valve line (21) at oxygen regula- Removal of Oxygen Control Cable. (See figure 13-10.)
tor.
a. Remove cotter pin securing control cable to oxy-
CAUTION gen regulator valve. On aircraft 421B0001 and On
loosen set screws in collars and set screw in clamp,
If oxygen continues to flow when line is re- to remove clamp assembly.
moved reconnect the line and bleed off oxy- b. Remove nut and washer securing control to sup-
gen pressure in accordance with bleeding port bracket.
procedures. c. Remove clamps securing control cable to struc-
ture.
b. Disconnect the filler line (21) from filler valve d. Remove nut on forward side of oxygen control
(6). bracket.
c. Cap all lines immediately after disconnecting. e. Pull control aft through forward cabin bulkhead
d. Remove filler valve protective cap. seal and remove cable.
e. Remove filler valve by removing three nuts and
bolts.
Installation of Oxygen Control Cable. (See figure
13-10. )
Installation of Oxygen Filler Valve. (See figure 13-
10. ) a. Install oxygen control cable by reversing the re-
moval procedures.
a. Position filler
valve in mounting bracket and b. Seal cable at forward cabin bulkhead; seal fitting
secure with three attaching bolts and nuts. in accordance with Section 16.
b. Remove filler valve protective cap.
c. Connect filler valve line (21) to filler valve.

Change 6
13-328 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Oxygen Cylinder Identification. 2. At any time upon notification of decaying cylin-

der pressure when oxygen is not in use, immediately
a. Cyunder specification followed by service pres- check the system until leak is found (use only leak
sure such as "ICC-3AA1800" or "ICC-3HT1800" will detector conforming to MIL-L-25567B).
be stamped on the shoulder, or neck of each cylinder. d. Oxygen Inspection requirements:
1. A careful visual inspection of the cylinders
NOTE should be performed during routine maintenance and
periodic inspections. If any bad dents, scratches or
Effective January 1, 1970, all newly manu- areas of corrosion are found, the cylinder must be
factured cylinders will be stamped "DOT" carefully checked per the criteria Table I.
(Department of Transportation) in Heu of
"ICC" (Interstate Commerce Commission). NOTE
An example for the new designation would
be: "DOT-3HT1800. 't If the acceptability of the cylinder is ques-
tionable after using criteria Table I, do not
b. Cylinder serial number will be stamped below or hesitate to return cylinder to manufacturer.
directly following the cylinder specification.
c. Hydrostatic test date will be stamped directly be- e. Regulator shall be removed and overhauled by
low the original manufacturer date and shall include manufacturer or an FAA approved facility during
the month and year of the hydrostatic test date. hydrostatic testing.
f. Pressure Gage. The pressure gage shall be
Servicing and Inspection of Oxygen System, checked for accuracy and cleaned by the manufactur-
er every 3 years or 3000 flight hours, whichever
Servicing and inspection of oxygen slill be accom- occurs first.
plished as follows: g. Individual outlets shall be disassembled and in-
a. Hydrostatic Test requirement: spected, and the sealing core, and/or all rubber
1. Standand weight (ICC or DOT-3AA1800) cylin- parts replaced, regardless of condition every 3
ders must be hydrostatically tested to 5/3 their work- years or 3000 flight hours, whichever occurs first.
ing pressure every five years starting with the date h. On 421-0001 to 421A0141, the filler valve should
of the last hydrostatic test. be disassembled, inspected and the o-rings replaced,
2. Lightweight (ICC or DOT-3HT1800) cylinders regardless of condition every 3 years or 3000 flight
must be hydrostatically tested to 5/3 their working hours, whichever occurs first.
pressure every three years starting with the date of i. High pressure lines should be inspected for
the last hydrostatic test. scratches, dents, cracks, deep gouges if a leak is
indicated. Lines should be tested to not less than
NOTE 3000 PSIG if trouble is indicated.

These test requirements are established by WARNING

the Interstate Commerce Commission code
of Federal Regulations, title 49, chapter 1, Whenever components have been removed
paragraph 73. 34. and replaced or oxygen system has been
allowed to deplete to below 50 PSIG, the sys-
b. Service Life requirements: tem must be purged in accordance with purg-
1. Standard weight (ICC or DOT-3AA1800) cylin- ing procedures before charging the system.
ders have no life limitations, and may continue to be
used until they fail hydrostatic testing. j. Mask and Hose.
2. Lightweight (ICC or DOT-3HT1800) cylinders 1. Cleaning Clean mask and hose with a mild so-
-

must be retired from service after 15 years or 4380 lution of soap and water. Rinse thoroughly with clean
filling eycles after date of manufacture, whichever water and allow to dry. Make sure all soap is re-
occurs first. moved after rinsing. Masks may be disinfected with
c. Servicing requii-ements: a hospital type antiseptic spray or Zep Aero SBT-12.
Oxygen system regulators/reducers, mask mounted
regulators, valves, outlets, hoses, lines and cylin- NOTE
ders must be serviced every year or 1000 flight
hours, whichever occurs first. Remove mike from pilots mask when cleaning.
1. Service shall include for the above items, check
of system line pressure, functional check of all mov- 2. Inspection. Inspect mask and hoses for breaks,
ing components for operation and excessive wear, cracks, deterioration. Check mask storage compart-
visual check for damage to components, visual check ment for cleanliness and general condition. Check
for the presence of contaminants (oil, grease, dirt, flow indicators for free movement, and inspect coup-
etc.); visual examination of both low and high pres- lings for proper insertion.
sure regulator relief mechanisms for damage and to
insure freedom from obstruction.

Change 12
 421 SERVICE MANUAL UTILITY AND 13-33
OPTIONAL SYSTEMS
WARNING
TABLE OF FILLING PRESSURES
Whenever components have been removed or
replaced or oxygen system has been allowed Initial temperature refers to ambient temperature in
25°F
to deplete to below 50 psi, the system must filling room. A rise of approximately may be
be purged before charging. expected as a result of compression. The cylinder
should be filled as quickly as possible and allowed
WARNING to cool by ambient air only.

When purging the oxygen system, the aircraft Initial Filling Initial Filling
should be outdoors. If purging is done indoors Temp. Pressure Temp. Pressure
extreme caution must be taken to prevent oxy- °F °F
Psig Psig
gen flow from contacting oils, grease, contam-
inants and electrical sparks. The area should 0 1, 600 70 1, 925
be roped off, with no smoking or open flames 10 1, 650 80 1, 950
allowed in or near the area. Make sure there 20 1, 675 90 2, 000
is adequate ventilation in the area. 30 1.725 100 2, 050
Purging the Oxygen System. 40 1, 775 110 2, 100
50 1, 825 120 2, 150
a. Charge the oxygen system
60 1,875 130 2, 200
in accordance with
charging procedures.
b. Plug all masks into all outlets and purge system
the System,
.

Functional Testing Oxygen

by allowing the oxygen to flow for at least 10 min-
utes. Smell the oxygen flowing from the outlets and
continue to purge until the oxygen is odorless. Re- Whenever the oxygen system regulator (or regulator-
fill cylinder as required during and after purging. cylinder assembly) has been replaced or overhauled,
perform the following flow and internal leakage tests
Charging the Oxygen System. to check that the system functions properly.
a. Fully charge the oxygen system per charging
The following procedures may be used in conjunction instructions.
with the table of pressure/temperature values for b. Install an oxygen outlet adapter (Cessna Part
charging the cylinder. Number 0166005-0506) into a pressure gage (gage
a. Connect the cascade connection to filler valve. should be calibrated in one-pound increments from 0
b. Slowly open valve of cylinder to be charged and to 100 PSIG), and insert adapter into pilots' oxygen
observe pressure on cascade system. outlet. Place control knob in tþe "ON" position.
The gage pressure should be 70 ±10 PSI.
NOTE c. Insert adapters (or mask and line assemblies if
they are operating properly) into all remaining out-
The oxygen bottle service line utilizes an lets. With oxygen flowing from all outlets, the pres-
AN805-3 nut and AN800-3 cone union. If nut shall be
sure should still be 70 ±10 PSI. Flow check
or cone union is damaged replace defective accomplished with a ground check flow meter model
parts• 40400, or equivalent.
c. Slowly open valve on cascade cylinders having d. Place oxygen control knob in the "OFF" posi-
lowest pressure and allow pressure to equalize. tion and allow pressure to fall to O PSI. Remove all
d. Close cylinder valve on cascade cylinders, and
adapter assemblies except the one with the pressure
slowly open valve on cylinder with next highest pres. Œage. The pressure must not rise above 0 PSI when
sure until cylinder has been charged in accordance observed for one minute. Remove pressure gage and
adapter from oxygen outlet.
with chart.

NOTE

Leak Testing the Oxygen System. If pressures specified in the foregoing pro-
cedures are not obtained, the oxygen regula-
Test the oxygen system for leakage by applying de- tor is not operating properly. Remove and
tector fluids, which have been compounded for use replace cylinder-regulator assembly with
with oxygen systems, to each fitting and observe for another unit and repeat test procedure.
formation of bubbles. No visible leakage should e. Connect oxygen masks to each outlet and check
occur. Remove all traces of solution and repair or eadh mask for proper operation.
replace leaky fittings and repeat preceding procedure· f. Check proper function of pilot's mask micro-
Further test the oxygen system for leakage by pres phone and control wheel switch. After checking, re-
surizing it to service pressure. The leak rate should turn all masks to mask case,
not exceed one percent of total supply per 24-hour g. Recharge oxygen system as required.
period. After the test has been completed, wash
away all traces of the leak detector.

Change 8
13-34 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

STABILIZER DEICE

WING DEICE

TO GYROS TO GYROS

SHUTTLE PRESSURE CONTROL SW. SHUTTLE

VALVE SWITCH VALVE

PRESSURE
INDICATOR O Il
LIGHT
FILTER FILTER
CIRCUIT
BREAKER
T. & B. NO. 1

CONTROL VALVE CONTROL VALVE

VACUUM --- VACUUM
PUMP PUMP

OIL OVERBOARD OVERBOARD OIL

SEPARATOR DUMP DUMP SEPARATOR

TO ENGINE TO ENGINE
CRANKCASE CRANKCASE

IIIIIIIIHlllIIIII
PRESSURE AND VACUUM
WW//APIVACUUM
N PRESSURE
ELECTRICAL ACTUATION
421-0001 TO 421BO120

Figure 13-12. Surface Deice System Schematic

Change 4
 421 SERVICE MANUAL UTILITY AND 13-35
OPTIONAL SYSTEMS

2
1

DETAIL

23

AIL D

15 31
16
DETAIL $
20 |
21

DETAIL

32

Figure 13-13. Surface Deice System

13-36 UTILITY AND
421 SERVICE MANUAL
oPTioNAL SYSTEMS

Figure 13-13. Surface Deice System Callouts

1. Right Stabilizer Boot 18. Pressure Switch

2. Hose and Clamps 19. Line Cross To RH Wing Gap
3. Line To Right Stabilizer 20. Line Tee To Left Wing Boot
4. Line To Vertical Stabilizer 21. Line Elbow To Tee
5. Vertical Stabilizer Boot 22. Existing Vacuum Line
6. Line Tee To Union 23. Line Filter To Shuttle Valve
7. Line Tee To Tee 24. Filter
8. Line To Left Stabilizer 25. Support
9. Left Stabilizer Boot 26. Control Valve
10. Aft Cabin Pressure Bulkhead 27. Line Control Valve To Oil Separator
11. Lock-O-Seal 28. Support
12. Line Union To Cross 29. Shuttle Valve
13. Line Cross To LH Wing Gap 30. Pneumatic Pump
14. Seal Fitting 31. Oil Separator
15. Line Elbow To E1bow 32. Left Wing Boot
16. Line Wing Gap To Tee 33. Line Shuttle Valve To Elbow
17. Cabin Skin 34. Line Shuttle Valve To Tee

SURFACE DEICE SYSTEM. (421-0001 TO 421B0120.) NOTE

The optional surface deice system consists of gear To remove line (20) from tee to wing boot,
driven wet vacuum pumps, inflatable rubber deice it is necessary to remove the turbine to gain
boots cemented to the leading edges of the horizontal access to the line clamps through the firewall
and vertical stabilizer and outer wing leading edge access. Remove turbine in accordance with
panels. Air for inflation of the boots is supplied by Section 9.
the pressure side of the vacuum pump. Operation of
the deicing system is through a six-second delay ac- f. Remove nylon insert and nut from line (13),
tion control, labeled "Surface Deice" located on the break seal at seal fitting (14) and withdraw tube
left hand switch and circuit breaker console. When into cabin area.
the control is positioned to ON, the control valve g. The right side removal procedures are the same.
closes its overboard air valve and redirects the air h. Remove clamps securing lines to structure in cabin
from the pressure side of the vacuum pump through section, disconnect lines at cross and aft cabin pres-
a filter, shuttle valve, and into the deice boots for sure bulkhead, remove inserts and nuts, then remove
the inflation cycle. After the six-second inflation lines.
cycÏeis complete, the system returns to its off po- i. Remove tailcone access door.
sition. Everytime an inflation cycle is desired, the j. Remove clamps securing line to tailcone structure,
control must be momentarily positioned to ON. After disconnect lines and remove.
six-second inflation is completed, the deflation cycle k. To remove lines (3 and 8) from stabilizer boots,
begins. Air pressure returns through the system and remove stabilizer in accordance with Section 3, then
overboard through the control valve. When the shut- remove lines.
tle valve has less than 1 PSI against it, it closes and 1. Remove line (4) through vertical stabilizer access
the vacuum side of the vacuum pump holds the boots (5). (See figure 1-2.)
in a deflated position. The pressure indicator should m. Installation of deice lines is the reversal of
light when the system reaches 10 PSI. An optional removal procedures.
left wing ice light is incorporated on the outboard o. Seal line at seal fitting (14) in accordance with
side of the left engine nacelle to provide an aid in sealing procedures outlined in Section 16.
observing ice formation during night operation.

Removal of Deice Filter, Control Valve, and Shuttle

Removal of Deice Lines. (See figure 13-13.) Valves. (See figure 13-13.)
Remove deice lines as follows: a. Remove engine cowling,
a. (See figure 1-2) Remove aft passenger seats, b. Remove the clamps and hoses from the control
carpet and floorboards (78, 79, 80, 82, 84, 85 and and shuttle valves.
86) in accordance with Section 3. c. Remove nuts, washers and bolts from control and
b. Remove wing access covers (35, 48, 54, 55, 56 shuttle valves.
and 36) Typical right and left wings. d. Remove filter (24), control valve (26) and shuttle
c. (See figure 1-2.) Remove engine cowl (29). valve (29).
d. Remove hoses in engine compartment by remov-
ing hose clamps and hoses from pneumatic pump
(30), oil separator (31), filter (24), control valve Installation of Deice Filter, Control Valve, and Shut-
(26), shuttle valve (29) and firewall fittings. tle Valves. (See figure 13-13.)
e. Remove clamps securing-lines in wing leading
edge, disconnect from fittings and remove lines. Reverse the deice filter, control valve and shuttle
Change 8
 421 SERVICE MANUAL
·

UTILITY AND "MA

OPTIONAL SYSTEMS

STABILIZER

PRASSURE SWITCH

IIIIIIIIIIIIIMlllIB
PRESSURE AND VACUUM
N VACUUM
A\\ \\\\ \\ \\ NPRESSURE
ELECTRICAL ACTUATION
FLOW _-

VALVE
PRESSURE
INDICATOR
\ LIGHT

OUTBOARD OUTBOARD
WING BEÀV777777r WING

FLOW FLOW
VALVE VALVE

INBOARD INBOARD
WING WING

VACUUM
MANIFOLD

FILTER FILTER

CONTROL li il CONTROL
VALVE VALVE

VACUUM VACUUM
PUMP PUMP
OIL OIL ,

SEPARATOR SEPARATOR

OVERBOARD OVERBOARD \
DUMP . DUMP

TIMER MODULE
TO ENGINE TO ENGINE
CRANKCASE CRANKCASE

CIRCUIT CONTROL
421B0120 BREAKER SWITCH
AND ON

Figure 13-13A. Surface Deice System Schematic

Change 4
13-368 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

valves removal procedures. installed in the pressure line of each engine driven
system to prevent loss of pressure if either pressure
NOTE source fails. Operation of the deicing system is
through a six second timer module and a "Surface
Apply a small amount of suitable thread lub- Deice" switch located on the left switch and circuit
ricant to male threads of a11 metal fittings breaker console. When the switch is momentarily
before installation. positioned ON, the control valve closes its over-
board air valve and directs the air from the pressure
side of the vacuum pump through a filter and a check
Surface Deice System Check. valve to the three flow valves. The timer module
electrically opens the stabilizer flow valve allowing
a. Electrical Test: the stabilizer boots to inflate. After the six-second
1. Reconnect battery cables. inflation is completed,
cycle the timer module elec-
2. Position deice control to OFF position. trically the
closes stabilizer flow valve, then opens
3. Position aircraft battery switch to ON position. the wing flow valves. After a six-second inflation
4. Close the T & B No. 1 (CB-9) circuit breaker. cycle, the wing flow valve closes, completing the
5. Press pressure indicator light to check light cycle. After each inflation cycle, air pressure from
circuit and bulb. the boots is vented from the flow valve through a
6. Position deice control to ON position and repeat relief. When vent air pressure drops to approxi-
step 5. mately 1 PSI, the relief closes and the vacuum pump
7. If indicator light does not function in steps 5 and then holds the boots in a deflated position. The pres-
6, the circuit breaker may have opened. Check for sure indicator light will illuminate when the stabili-
short in system. Reset circuit breaker and recheck zer boot pressure reaches 10 PSI. Optional wing ice
step 4. lights are incorporated on the outboard side of the
b. Air Leakage Test: engine nacelles to provide an aid in observing ice
1. This test can be performed in either the left or formation during night operation.
right nacelles. The following steps refer to the left
nacelle.
2. Disconneet pressure hose from the control valve Removal of Deice Lines. (See Figure 13-13B.)
inlet fitting. (421B0120 and on.)
3. Disconnect tube from overboard port and plug the
port with an AN933-4 plug. Remove deice lines as follows:
4. Connect a source of clean air to the control valve a. (See Figure 1-2.) Remove seats, carpets, floor-
inlet port. It is necessary that the inlet pressure be boards, aft cabin access panel and upholstery as
a minimum of 18 20 PSIG to perform
-
this test. In- necessary to facilitate removal of deice system.
clude a pressure gage in the air line to observe the b. Remove left and right engine cowlings, wing gap
system pressures. covers, wing and fuselage access covers as neces-
5. Apply 18 PSIG pressure to the system and by sary to facilitate removal of deice system.
means of a hand-operated valve, trap the pressure in c. Remove hoses in engine compartment by remov-
the deicer system. Observe the system for leakage. ing hose clamps and hoses from pneumatic pump (44),
The leakage rate should not exceed a pressure drop oil separator (42), filter (37), control valve (39) and
of 4. O PSIG per minute. firewall fittings.
6. To check the pressure switch, apply 18 PSIG d. Remove clamps securing lines in wing leading
pressure to the system, turn on the aircraft battery edges, disconnect from fittings and remove lines.
switch with the T & B No. 1 (CB-9) closed. The in- e. Remove nylon insert and nut from lines (19) and
dicator light should glow. Release the pressure and (21), break seal at seal fitting (23) and withdraw
the indicator light should extinguish between 8 and 12 tubes into cabin area.
PSIG. f. The right side removal procedures are the same.
7. Remove test equipment, lubricate all threads g. Remove clamps securing lines to structure in
and replace all system components. the cabin section, disconnect lines at tee assemblies
8. Disassembly or rework of the operating equip- and at aft cabin pressure bulkhead, remove inserts
ment in this system should not be attempted, replace and nuts, then remove lines.
any unit which does not function correctly. h. Remove clamps securing lines to tailcone struc-
ture, disconnect lines at aft cabin pressure bulkhead,
flow valve and pressure switch and remove lines.
i. To remove lines (3 and 9) from stabilizer boots,
SURFACE DEICE SYSTEM. (421B0120 and on.) remove stabilizer in accordance with Section 3, then
remove lines.
The optional surface deice system consists of infla- j. Remove line (4) through vertical stabilizer ac-
tablerubber deice boots cemented to the leading cess panel.
the k. Installation of deice lines is the reversal of re-
edges of the horizontal and vertical stabilizers,
outboard wing leading edge and inboard wing leading moval procedures.
1. Seal lines at seal fitting (23) in accordance with
edge. Air for inflation is supplied by the pressure
side of gear driven vacuum pumps. A check valve is sealing procedures outlined in Section 16.

Change 8
 421 SERVICE MANUAL UTILITY AND 13-38Û
OPTIONAL SYSTEMS

2
10

Detail

421B0801 AND ON

17

421B012 1BO801
Detail M1i64004
Detail
C5l164003
421B0120 AND ON c51164005

Figure 13-13B. Surface Deice System (Sheet 1)

Change 11
3-36Û UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

D51264012
as1264ois
Detaii D
1. Right Stabilizer Boot 16. Lock-O-Seal 31. Line Tee to Hose
2. Hose and Clamps 17. Vacuum Line 32. Line Hose to Hose
3. Line to Right Stabilizer 18. Line Union to Tee 33. Left Wing Outboard Boot
4. Line to Vertical Stabilizer 19. Line Tee to LH Wing Gap 34. Line Elbow to Check Valve
5. Vertical Stabilizer Boot 20. Line Tee to RH Wing Gap 35. Check Valve
6. Line Tee to Flow Valve 21. Vacuum Line 36. Packing
7. Line Tee to Pressure Switch 22. Cabin Skin 37. Filter
8. Pressure Switch 23. Seal Fitting 38, Line Filter to Tee
9. Line to Left Stabilizer 24. Union 39. Control Valve
10. Left Stabilizer Boot 25. Tube 40. Overboard Valve
11. Flow Valve 26. Flow Valve 41. Existing Vacuum Line
12. Vacuum Line ' 27. Line Tee toElbow 42. Oil Separator
13. Tube Flow Valve 28. Line Tee toUnion 43. Line Oil Separator to Tee
14. Line Tube to Union 29. Left Wing Inboard Boot 44. Pneumatic Pump
15. Aft Pressure Bulkhead 30. Line Tee to Boot 45. Line to Engine Crankcase

Figure 13-13B. Surface Deice System (Sheet 2)

Surface Deice System Check. (421B0120 and on.) 5. With engines running, momentarily position
deice switch to ON position.
a. Operational Test. 6. Check that timer cycles the stabilizer boots
1. Close surface deice circuit breaker. first for a period of approximately six seconds and
2. Position deice control switch to OFF position. then cycles the wing boots for a period of approxi-
3. Position aircraft battery switch to ON position. mately six seconds and then deactivates itself.
4. Press annunciator panel test switch to check
light circuit and bulb.
Change 11
 421 SERVICE MANUAL UTILITY AND l3 3Î
OPTIONAL SYSTEMS

7. The surface deice light in the annunciator panel cedures. An alternate method of repair is to
will illuminate during the first (stabilizer) cycle to peel the deice boot back using Keystone sol-
indicate the system is operating. vent, and reapply using normal adhesives.
8. Position wing deice light switch to ON position
and check that deice light illuminates. a. Scuff or Surface Damage. This type of damage
9. Position all switches to OFF position. is the most commonly encountered and is usually
b. Air Leakage Test. caused by scuffing the outer surface of the deice
1. This test can be performed in either the left or boots while using scaffolds, refueling hoses, ladders,
right nacelles. The following steps refer to the left etc. Repair is generally not necessary because the
nacelle. thick outer veneer provides protection to the natural
2. Disconnect the pressure hose from the pneu- rubber underneath. If the scuff is severe and has
matic pump (hose routed to oil separator). caused removal of the entire thickness of veneer (ex-
3. Connect a source of 18-20 PSI clean air with an posing the brown natural rubber underneath) the dam-
inline hand operated valve and an18-20 PSI pressure age should be repaired as outlined below:
gauge, to the disconnected deice hose. 1. Select a patch (Part Number 3306-1, 3306-2 or
4. Disconnect tube from overboard port of the con- 3306-3) of ample size to cover the damaged area.
trol valve and plug the port with an AN933-4 plug. 2. Clean the area to be repaired with a cloth damp-
5. Disconnect the electrical power lead to each of ened slightly with solvent.
the three flow valves- 3. Buff the area around the damage with steel wool
so that the area is moderately but completely rough-
CAUTION ened.
4. Wipe the buffed area clean with a cloth slightly
Do not attempt air leakage test with deice dampened in solvent to remove all loose particles.
timer module connected in circuit. 5. Apply one even thorough coat of cement (Part
Number 3306-16) to the patch and to the correspond-
6. Connect a 28VDC electrical source to each flow ing damaged area of the deice boot. Allow cement
valve to energize the valves. to set a couple of minutes until it becomes tacky.
6. Apply patch to the deice boot with an edge or the
NOTE center adhering first, and work the remainder of the
patch down being careful to avoid trapping air pockets.
For test or troubleshooting, one valve may 7. Roll the patch thoroughly with a stitcher-roller
be actuated at a time to test and isolate each (Part Number 3306-10) and allow to set for ten to
system. fifteen minutes.
8. Wipe the patch and surrounding area from the
7. Apply 18 PSI pressure to the deice system and center of the patch outwärd, with a cloth slightly
by means of the inline hand operated valve, trap the dampened with solvent.
pressure in the deice system· 9. Apply one light coat of A-56-B conductive ce-
(a). Observe the deice system for leaks. The ment (Part Number 3306-13) to the patched area.
leakage rate should not exceed a pressure
drop of 4. O PSI per minute' NOTE
8. Insure that all deice boots inflate and that there
are no leaks, remove test equipment and reconnect Satisfactory adhesion should be obtained in
hose to pneumatic pump, remove plug from control four hours, however, if the patch is allowed
valve and connect tube to cure for a minimum of 20 minutes, the
9. Remove 28VDC electrical source and reconnect deice boots may be inflated to check the
electrical leads to aircraft system.
repair.

Cold Patch Repair of Deice Boots, b. Damage to Tube Area. This type of damage con-
sists of cuts, tears, or ruptures to the inflatable tube
There are four types or areas of damage that are area and a fabric reinforced patch must be used for
most common to the deice boots. An outline of the this repair. Damage to the tube area should be re-
cold patch repair procedure for each follows: paired as outlined below:

1. Select a patch (Part Number 3306-4, 3306-5, or

NOTE 3306-6) of ample size to extend at least 5/8" beyond
the damaged area.
When repairing the deice boots and replace-
ment layers are being installed, exercise care NOTE
to prevent trapping air beneath the replace-
ment layers. If air blisters appear after ma- If none of these patches are of the proper size,
terial is applied, remove them with a hypo- one may be cut to the size desired from one
dermic needle. Should air blisters appear of the larger patches. If this is done, the
after boots have been installed for a length of edge should be beveled by cutting with the
time, it is permissible to cut a slit in the de- shears at an angle. These patches are manu-
ice boot, apply adhesive and repair in accord- factured so they will stretch in one direction
ance with the following cold patch repair pro- only. Be sure to cut the patch selected so

Change 10
13-38 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

that the stretch is in the widthwise direction center tape under all edges of cutout.
of the inflatable tubes. 10. Roll down tape on wing skin with stitcher-roller
(Part Number 3306-10) to assure good adhesion being
2. Clean the area to be repaired with a cloth damp- careful to avoid air pockets.
ened slightly with solvent. 11. Apply one coat of EC-1300 cement to top sur-
3. Buff the area around the damage with steel wool face of tape and allow to dry approximately 5 to 10
so that the area is moderately but completely rough- mintues.
ened. 12. Reactivate cemented surfaces with solvent.
4. Wipe the buffed area clean with a cloth slightly Working toward the cutout, roll down the edges of the
dampened in solvent to remove all loose particles. loosened deice boot being careful to avoid trapping air
5. Apply one even thorough coat of cement (Part pockets. The edges should overlap on the tape ap-
Number 3306-16) to the patch and the corresponding roximately 1 inch.
damaged area of the deice boot. Allow the cement to 13. Roughen back surface of inlay repair material
set for a couple of minutes until it becomes tacky. (Part Number 3306-7, previously cut to size) with
6. Apply the patch to the deice boot with the stretch steel wool. Clean with solvent and apply one coat of
in the widthwise direction of the inflatable tubes, EC-1300 cement.
sticking edge of patch in place first and working re- 14. Apply one coat of EC-1300 cement to wing skin
mainder down with a very slight pulling action so the inside of the cutout area and allow to dry,
injury is closed. Use care not to trap air between 15. Apply the second coat of EC-1300 cement to
patch and deicer surface. back side of inlay material and allow to dry.
7. Roll the patch thoroughly with a stitcher-roller 16. Reactivate cemented surfaces with solvent and
(Part Number 3306-10) and allow to set for ten to fif- carefully insert inlay material with feathered edge aft.
teen minutes. Working from the leading edge of wing aft, roll down
8. Wipe the patch and surrounding area, from the the inlay material carefully to avoid trapping air,
center outward, with a cloth slightly dampened with 17. Roughen area on outer surface of deice boot and
solvent. inlay with steel wool 1-1/4" on each side of splice.
9. Apply one light coat of S-56-B conductive cement Clean with solvent and apply one coat of EC-1300
(Part Number 3306-13) to restore conductivity. cement to this area.
18. Apply one coat of EC-1300 cement to one side
NOTE of 2" wide neoprene coated fabric tape (Part Number
3306-8) trim to size and center tape over splice on all
Satisfactory adhesion of patch to deice boot three sides.
should be reached in four hours, however, if 19. Roll down tape on deice boot with stitcher-roll-
the patch is allowed to cure for a minimum of er (Part Number 3306-10) to assure good adhesion,
20 minutes the deice boots may be inflated to being careful to avoid air pockets.
check the repair. 20. Apply one light coat of A-56-B conductive ce-
ment (Part Number 3306-13) to restore conductivity.
c. Damage to Fillet Area. This includes any tears d. Damaged Veneer -
Loose from Deice Boot. If
or cuts to the tapered area aft of the inflatable tubes. the veneer should become loosened from the deice
Damage to the fillet area should be repaired as out- boot, repairs should be made as outlined below:
lined below: 1. Peel and trim the loose veneer to the point
1. Trim damaged area square and remove excess where the adhesion of veneer to the deice is good.
material. Cut must be sharp and clean to permit 2. Roughen the area in which veneer is removed
good butt joint of inlay. with steel wool, rubbing parallel to cut-edge of
2. Cut inlay from tapered fillet (Part Number 3306- veneer ply to prevent loosening it.
7) to match cutout area. 3. Taper edges of veneer down to the tan rubber
3. Using solvent, loosen edges of deice boot around ply by rubbing parallel to the edges with steel wool
area approximately 1-1/2" from all edges. and solvent.
4. Clean the area to be repaired with a cloth damp- 4. Cut a piece of veneer material (Part Number
ened slightly with solvent. 3306-9) to cover the damaged area and extend at
5. Lift back edges of cutout and apply one coat of least 1" beyond in all directions.
EC-1300 cement to the underneath side of the loosen- 5. Mask off an area 1/2" Iarger in length and width
ed portion of the boot. than the size of veneer patch.
6. Apply one coat of EC-1300 cement to the wing 6. Apply one coat of EC-1300 cement to the damag-
skin underneath the loosened edges of deice boot and ed area and one coat to the veneer ply. Allow cement
extending 1-1/2" beyond edges of deice boot into the to set a couple of minutes until it becomes tacky.
cutout area. 7. Roll the veneer ply to the deicer with a 2" rub-
7. Apply second coat of cement to underneath side ber roller, applying a slight tension on the veneer ply
of deice as outlined in step 5. when applying to prevent trapping air.
8. Apply one coat of EC-1300 to one side of a 2" 8. Wipe the patch and surrounding area, from the
wide neoprene coated fabric tape (Part Number 3306- center of the patch outward, with a cloth slightly
8) and allow to dry and trim to size. dampened with solvent.
9. Reactivate cemented surfaces with solvent and 9. Apply one light coat of A-56-B conductive ce-
apply reinforcing tape to wing skin, using care to ment (Part Number 3306-13) to restore conductivity.

Change 10
 421 SERVICE MANUAL UTILITY AND ]3-39
OPTIONAL SYSTEMS

Detail $
8
421-0001 to 421B0001
C51l51007

1. Disengage Switch 17. Cable Assembly (Computer to Controller)

2. Attitude Gyro 18. Cable Assembly (Computer to Elevator Servo)
3. Directional Gyro 19. Cable Assembly (Computer to Aileron Servo)
4. Omni Selector Switch 20. Sprocket
5. Bezel 21. Aileron Cable (Servo to Bellerank)
6. Flight Controller 22. Aileron Servo
7. Retainer 23. Bracket
8. Control Quadrant 24. Aileron Cable
9. Shock Mounted Instrument Panel 25. Aileron Quadrant
10. Elevator Bellerank 26. Turnbuckle
11. Connector Link 27. Chain Assembly
12. Elevator Cable Upper (Servo to Bellcrank) 28. Aileron Cable Pulley
13. Elevator Cable Lower (Servo to Bellerank) 29. Aileron Cable Pulley
14. Elevator Servo 30. Chain Assembly (Elevator Cable)
15. Static Line 31. Turnbuckle
16. Computer 32. Sprocket

Figure 13-14. Nav-O-Matic 400 Autopilot Installation (Sheet 1 of 2)

Change 11
13-4ÛUTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Detail D

15
14 10
20 11

Detaii E

21 29 31 32

24 25 28 23 27 22
Detail F
E51142047 421-0001 to 421B0001
F51152005

Figure 13-14. Nav-O-Matic 400 Autopilot Insta11ation (Sheet 2)

Change 11
 421 SERVICE MANUAL UTILITY AND l3"$ÛA Í3-408
OPTIONAL SYSTEMS

Replacement of Surface Deice Boots. NAV-O-MATIC 400 AUTOPILOT SYSTEM. (See

figure 13-14.) (421-0001 to 421BOOO1)
a. Remove wing tip tank front fairings.
b. (LH wing only) Remove four screws securing the CAUTION
stall warning transmitter.
c. Refer to Removal and Installation of Propeller Primary and secondary flight control cables,
Deice Boots procedures and remove and install deice push pull tubes, belleranks and mountings on
boots. late model aircraft use dual locking fasteners.
d. Install stall warning transmitter screws on left The lock nuts for these fasteners incorporate
wing. a fiber lock, and are castellated for safety-
e. Replace tip tank front fairings. ing with a cotter pin. When any of these
areas are disconnected on any aircraft, new
dual locking fasteners should be installed.
See the Aircraft Parts Catalog for part num-
bers and location of these fasteners.

The Cessna Nav-O-Matic 400 Autopilot is a two-axis

automatic flight control system that controls the po-
sition of the ailerons and elevators. In addition to
holding the wing level and compensating for rotation
about the pitch axis, the system incorporates an au-
tomatic intercept and hold of any magnetic heading
or VOR radiaL Also included are a command turn,
a command pitch and altitude hold feature. For de-
scription of Cessna Nav-O-Matic 400 Autopilot com-
ponents and trouble shooting procedures, refer to
Cessna Nav-O-Matic 400 Autopilot Service/Parts
Manual.

Change 10
 421 SERVICE MANUAL UTILITY AND Î3"$1
OPTIONAL SYSTEMS

Removal and Installation of Autopilot Elevator Con- Removal and Installation of Aileron Servo. (See fig-
trol Cables. (See figure 13-14.) ure 13-14.)

a. Refer to Section 3 and remove tailcone access a. Refer to Section 3 and remove aft cabin seats,
door and necessary access covers. rear carpet and necessary access panels.
b. Remove safety and disconnect turnbuckle (26) b. Remove safety and loosen turnbuckle (31).
and remove cable (12) from elevator bellerank (10) c. Disengage chain assembly (27) from sprocket
by removing cotter pin, nuts, washers and bolts. (32).
c. Route cable (12) from sprocket (20) and remove d. Remove aileron servo attaching nuts, washers,
cable. and bolts. Disconnect electrical plug and remove
d. Install control cables by reversing the removal servo from aircraft.
procedure. e. Install aileron servo by reversing the removal
procedures.
NOTE
NOTE
When installing chain over sprocket (20), the
elevators must be neutral and the actuator in When installing aileron servo make sure
the center of travel. chain is centered over sprocket (32) and
ailerons are in neutral.
e. Rig autopilot elevator cables in accordance with
rigging procedures. f. Rig autopilot aileron control cables in accordance
with rigging procedures.
NOTE g. Turn autopilot on and make sure ailerons oper-
ate in the correct direction.
After rigging is complete, turn on autopilot
and verify that theelevator responds in the
correct direction. Assist the movement of Removal and Installation of Elevator Servo and Com-
the elevator by pulling back on the control puter. (See figure 13-14.)
wheel, this will aid in overcoming the coun-
terbalance of the elevator bob weight. a. Place suitable support under tailcone.
b. Remove tailcone access panel and elevator bell-
crank access covers.
Removal and Installation of Autopilot Aileron Control c. Remove safety and loosen turnbuckle (26).
Cables. (See figure 13-14.) d. Disengage chain assembly (30) from sprocket
(20).
a. Refer to Section 3 and remove aft cabin seats, e. Remove elevator servo attaching nuts, washers
rear carpet and necessary access panels. and bolts.
b. Remove safety and disconnect turnbuckle (31) f. Disconnect electrical plug and remove servo.
connecting cable (21) to chain assembly (27). Tie g. Disconnect static line (15) from autopilot com-
guide wire to cable end. puter (16).
c. Remove pulleys (28 and 29) from brackets (23). h. Remove attaching nuts, washers, and bolts and
d. Remove cable by routing cable aft from around remove computer from aircraft.
aileron quadrant (25). i. Install the elevator servo and computer by re-
e. Install the control cables by reversing the re- versing the removal procedures.
moval procedure.
NOTE NOTE

Note when installing chain over sprocket (32) When installing elevator servo make sure
the ailerons must be neutral and the actuator chain is centered over sprocket (20) and
in the center of travel. elevator is in the neutral position,

j. Rig autopilot elevator cables in accordance with

f. Rig autopilot aileron control cables in accordance rigging procedures.
with rigging procedures.

NOTE

After rigging is complete; turn on autopilot

and verify that the ailerons respond in the
correct direction.

Change 8
13-42 UTILITY AND
421 SERVICE MANUAL
OPTIONAL SYSTEMS

NOTE 6. Safety turnbuckle.

b. Rig autopilot elevator control system as follows:
After rigging is complete turn on autopilot 1. Refer to Section 6 and verify that the elevator
and verify that the elevator responds in the control system is properly rigged.
correct direction. Assist the movement of 2. Place elevator control surfaces in neutral po-
the elevator by pulling back on the control sition and secure using a clamping device,
wheel, this will aid in overcoming the coun- 3. With elevator control surface in neutral position,
terbalance of the elevator bob weight- center chain assembly (30) on elevator servo sprocket
(20), and attach cables (12 and 13) to links (11) on
bellerank (10).
Removal and Installation of Autopilot Gyros. (See 4. Ïtig elevator actuator cables (12 and 13) to 12 ±3
figure 13-14.) pounds tension by tightening turnbuckle (26).
5. Safety turnbuckle.
a. Refer to Section 12 and remove gyros in accor- c. Remove locking devices from control surfaces
dance with typical instrument removal and installa- and move through entire travel. Observe chain as-
tion. semblies (27 and 30) on servo sprockets for suffi-
cient remaining links at extreme travel limits.
NOTE

Disconnect electrical connection before re-

400A NAV-O-MATIC AUTOPILOT SYSTEM. (See
mova1· figure 13-14A. ) 421BOOO1 AND ON

The Cessna 400A Nav-O-Matic Autopilot is a two-

Removal and Installation of Autopilot Switches. (See axis flight control system featuring vacuum gyros,
figure 13-14,) altitude hold, synchronous pitch trim, heading pre-
select, omni intercept and track, turn command.
a. Refer to Section 14 for typical removal and in-
stallation of electrical switches- The following offerings are options to the basic auto-
pilot: Automatic pitch trim ILS approach coupler,
and slaved directional gyro. The automatic pitch
Removal and Installation of Controller. (See figure trim operates in conjunction with the aircrafts ele-
13-14.) vator trim tab. A sensor installed in the elevator
servo cables actuates the elevator trim servo motor
a. Remove screws attaching controller to pedestal- and in turn operates the elevator trim tab to provide
b. Pull controller out from center pedestal and dis- a follow up system. The ILS approach coupler en-
connect electrical plug· ables the pilot to fly inbound on ILS front course on
c. Install controller by connecting electrical plug back course, this option is installed in the computer
and inserting controller in center pedestal and in¯ and connects to the indicator at the nose junction box.
stalling screws· The slaved directional gyro replaces the standard
d. Check operation of controller and verify auto- directional gyro and provides heading information for
pilot in operating the control surfaces in correct di¯
the 400A Nav-O-Matic.
rection.

For additional description of the 400A Nav-O-Matic

Autopilot and components refer to Cessna 400A Nav-
Rigging Autopilot Control System. (See figure 13- O-Matic Autopilot Service/Parts manual.
14.)
Removal and Installation of Autopilot Elevator Con-
a. Rig autopilot aileron control system as follows: trol Cables. (See figure 13-14A. )
1. Refer to Section 6 and verify that aileron con-
trol system is properly rigged. a. Refer to Section 3 and remove tailcone access
2. Place aileron control surfaces to the neutral door and necessary access covers.
position and secure with a clamping device. b. Remove safety and disconnect turnbuckle (26)
3. Insure that cable (21) is properly routed on and remove cable (12) from elevator bellcrank (10)
pulleys (28 and 29) and check the installation of cable by removing cotter pin, nuts, washers and bolts.
guard pins. c. Remove cable guard posts (34) from sensor unit
4. Center chain assembly (27) on sprocket (32) and (33) to free cables (12 and 13).
route cable over aileron control quadrant. d. Route cable (12) from sprocket (20) and remove
5. Rig autopilot aileron cable (21) to 12 ±3 pounds cable.
by tightening turnbuckle (31). e. Install control cables by reversing the removal
procedure.
NOTE
NOTE
Cable tension should be adjusted when ambi-
ent temperature is
60°F to 90°F. Allow air- When installing chain over sprocket (20), the
craft temperature to stabilize for a period of elevators must be neutral and the actuator in
4 hours. the center of travel.

Change 11
 421 SERVICE MANUAL UTILITY AND 13•4 A
OPTIONAL SYSTEMS

f. Rig autopilot elevator cables in accordance with NOTE

rigging procedures.
After rigging is completed, turn autopilot on
NOTE and make sure ailerons operate in the cor-
rect direction.
After rigging is complete, turn on autopilot
and verify that the elevator responds in the Removal and Installation of Autopilot Flap Actuator.
correct direction. Assist the movement of
the elevator by pulling back on the control For removal and installation of autopilot flap actuator
wheel, this will aid in overcoming the coun- refer to Section 8.
terbalance of the elevator bob weight.
Removal and Installation of Elevator Servo and Com-
puter. (See figure 13-14A.)
Removal and Installation of Autopilot Aileron Control
Cables. (See figure 13-14A. ) a. Place a suitable support under tailcone.
b. Remove tailcone access panel and elevator bell-
a. .Refer to Section 3 and remove aft cabin seats, crank access covers.
rear carpet and necessary access panels. c. Remove safety and loosen turnbuckle (26).
b. Remove safety and disconnect turnbuckle (31) d. Disengage chain assembly (30) from sprocket
connecting cable (21) to chain assembly (27). Tie (20).
guide wire to cable end. e. Remove elevator servo attaching nuts, washers
c. Remove pulleys (28 and 29) from brackets (23). and bolts.
d. Remove cable by routing cable aft from around f. Disconnect electrical plug and remove servo.
aileron quadrant (25). g. Disconnect static line (15) from autopilot com-
e. Install the aileron control cables by reversing puter (16).
the removal procedure. h. Remove attaching nuts, washers, and bolts and
remove computer from aircraft.
NOTE i. Install the elevator servo and computer by re-
versing the removal procedures.
When installing chain over sprocket (32) the
ailerons must be neutral and the actuator in NOTE
the center of travel.
When installing elevator servo make sure
f. Rig autopilot aileron control cables in accordance chain is centered over sprocket (20) and
with rigging procedures. elevator is in the neutral position.

NOTE j. Rig elevator cables in accordance with rigging

procedures.
After rigging is complete, turn on autopilot
and verify that the ailerons respond in the NOTE
correct direction.
After rigging is complete turn on autopilot,
Removal and Installation of Aileron Servo. (See fig- and verify that the elevator responds in the
ure 13-14A. ) correct direction. Assist the movement of
the elevator by pulling back on the control
a. Refer to Section 3 and remove aft cabin seats, wheel, this will aid in overcoming the coun-
rear carpet and necessary access panels. terbalance of the elevator bob weight.
b. Remove safety and loosen turnbuckle (31).
c. Disengage chain assembly (27) from sprocket Removal and Installation of Autopilot Elevator Trim
(32). Follow-Up Sensor. (See figure 13-14A. )
d. Remove aileron servo attaching nuts, washers,
and bolts. Disconnect electrical plug and remove a. Place a suitable support under tailcone.
servo from aircraft. b. Remove tailcone access panel and elevator bell-
e. Install aileron servo by reversing the removal crank access covers.
procedures. c. Remove cable guard posts (34) from sensor unit
(33) to free cables (12 and 13).
NOTE d. Disconnect electrical plug from sensor unit.
e. Remove sensor unit (33) from bracket by remov-
When installing aileron servo make sure ing attaching screws and nuts.
chain is centered over sprocket (32) and
ailerons are in neutral. NOTE

f. Rig autopilot aileron control cables in accordance Make sure sensor unit (33) is installed with
with rigging procedures. over-hanging pulley (35) forward.

Change 11
13-428 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

5
Detail
Detail

A51141092
851141091
C51l51007 Detail
421BOOO1 AND ON
51143057

1. Disengage Switch 21. Aileron Cable (Servo to Bellcrank)

2. Horizontal Gyro 22. Aileron Servo
3. Directional Gyro 23. Bracket
4. Omni Selector Switch 24. Aileron Cable
5. Bezel 25. Aileron Quadrant
6. Flight Controller 26. Turnbuckle
7. Retainer 27. Chain Assembly
8. Control Quadrant 28. Aileron Cable Pulley
9. Flight Instrument Panel 29. Aileron Cable Pulley
10. Elevator Bellerank 30. Chain Assembly (Elevator Cable)
11. Connector Link 31. Turnbuckle
12. Elevator Cable Upper (Servo to Bellerank) 32. Sprocket
13. Elevator Cable Lower (Servo to Bellerank) 33. Sensor Unit
14. Elevator Servo 34. Bracket
15. Static Line 35. Pulley
16. Computer 36. Elevator Trim Servo
17. Cable Assembly (Computer to Controller) 37. Bracket
18. Cable Assembly (Computer to Elevator Servo) 38. Elevator Trim Follow-Up Cable
19. Cable Assembly (Computer to Aileron Servo) 39. Autopilot Flap Actuator
20. Sprocket 40. Elevator Trim Tab Cable
Figure 13-14A. 400A Nav-O-Matic Autopilot Installation (Sheet 1 of 3)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-42BA/13-42BB
OPTIONAL SYSTEMS

1235 "
'
19
34
3313

Detail

18

Detail E
421B0001 TO 421B0301

12
35
15 D as
'
10 30

Detail

Detaii E 14 av
421B0301 AND ON 36 D14141052
E51142047
E54143020
F51142047

Figure 13-14A. 400A Nav-O-Matic Autopilot Installation (Sheet 2)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-42C
OPTIONAL SYSTEMS

25 21 29 31

27 22
24
Detaii G
38
40 37

36

Detali H

41

Detail
421B0232 AND ON
AND AIRCRAFT MODIFIED
BY SK 421-46

G51152005
H51141090
314142022

Figure 13-14A. 400A Nav-O-Matic Autopilot Installation (Sheet 3)

Change 11
13-420 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

f. Install sensor unit by reversing the removal pro- Rigging Autopilot Control System. (See figure 13-
cedures. 14A. )

NOTE a. Rig autopilot aileron control system as follows:

1. Refer to Section 6 and verify that aileron con-
After installation is completed, check tension trol system is properly rigged.
on elevator control cables in accordance with 2. Place aileron control surfaces to the neutral
the Rigging of Autopilot Elevator Control Sys- position and secure with a clamping device.
tem procedures. 3. Insure that cable (21) is properly routed on
pulleys (28 and 29) and check the installation of cable
Removal and Installation of Autopilot Elevator Trim guard pins.
Follow-Up Servo. (See figure 13-14A.) 4. Center chain assembly (27) on sprocket (32) and
route cable over aileron control quadrant.
a. Place a suitable support under tailcone. 5. Rig aileron autopilot cable (21) to 12 ±3 pounds
b. Remove tailcone access panel and elevator bell- by tightening turnbuckle (31).
crank access covers.
c. Disconnect electrical plug from servo (36).
d. Loosen screws attaching servo to bracket (37). NOTE
e. Remove servo from cable (38).
f. Install servo by reversing the removal proce- Cable tension should be adjusted when ambi-
dures. ent temperature is
60°F
to 90°F. Allow air-
craft temperature to stabilize for a period of
NOTE 4 hours.

Elevator trim control cable must make 2 6. Safety turnbuckle.

full loops around the cable drum. .-
b. Rig autopilotelevator control system as follows:
1. Refer to Section 6 and verify that the elevator
NOTE control system is properly rigged.
2. Place elevator control surfaces in neutral posi-
After installation is completed, check ten- tion and secure using a clamping device.
sion on elevator trim control cables in ac- 3. With elevator control surface in neutral position,
cordance with the Rigging of Elevator Trim center chain assembly (30) on elevator servo sprock-
Contro1System procedures found in Section et (20), and attach cables (12 and 13) to links (11) on
6. bellcrank (10).
4. Rig elevator actuator cables (12 and 13) to 22 ±2
Removal and Installation of Controller. (See figure pounds tension by tightening turnbuckle (26).
13-14A. ) 5. Safety turnbuckle.
c. Rig autopilot elevator trim control system as
a. Remove screws attaching controller to pedestal. follows:
b. Pull controller out from center pedestal and dis- 1. Refer to Section 6 and verify that the elevator
connect electrical plug. trim control is properly rigged.
c. Install controller by connecting electrical plug 2. Place elevator trim control surfaces in neutral
and inserting controller in center pedestal and in- position and secure using a clamping device,
stalling screws. 3. With elevator trim control surface in neutral
d. Check operation of controller and verify auto- position, check to see that cable (38) is looped twice
pilot is operating the control surfaces in correct di- around cable drum.
rection. 4. Rig cable (38) to 19 ±3 pounds of tension.

Removal and Installation of Autopilot Gyros, (See NOTE

figure 13-14A. )
If optional electric elevator trim control
a. Refer to Section 12 and remove gyros in accord- motor is installed, rig cable (38) to 22 ±2
ance with typical instrument removal and installation. pounds of tension.

NOTE d. Remove locking devices from control surfaces

and move through entire travel. Observe chain as-
Disconnect electrical connection before re- semblies (27 and 30) on servo sprockets for suffi-
moval. cient remaining links at extreme travel limits.

Removal and Installation of Autopilot Switches. (See

figure 13-14A. )

a. Refer to Section 14 for typical removal and in-

stallation of electrical switches.

Change 11
 421 SERVICE MANUAL UTILITY ANo 13-42 E
OPTIONAL SYSTEMS

YAW DAMPER SYSTEM. (See figure 13-14B. )

f. Install the rudder yaw actuator by reversing the
The yaw damper system is an independent system removal procedures,
consisting of a gyro computer (turn and bank indica g. Rig cables in accordance with rigging proce-
dures.
tor), control switch, yaw actuator, and the disengage
switch.
Rigging Yaw Damper System. (Refer to Figure 13-
The gyro computer picks up the signal, routes it
through a built-in computer in the gyro, amplifies 14C.)
the signal and sends the amplified signal to the yaw
actuator. a. Refer to Section 7 and verify that rudder control
system is properly rigged.
The yaw damper control switch is mounted separate- b. Rig yaw actuator cables (5) and (13) to 16 ±2
ly from the flight controller on all installations ex- pounds tension by tightening turnbuckle (14).
cept the 800 integrated flight control system. On c. Safety turnbuckle.
aircraft incorporating the 800 integrated flight con- d. Adjust actuator in accordance with Actuator
trol system the yaw damper control switch is part of Centering Adjustment procedures.
the autopilot flight controller. The yaw damper dis-
engage switch in the control wheel is connected to the
autopilot disengage switch; disengaging the autopilot Actuator Centering Adjustment. (421B0301 to
will also disengage the yaw damper. 421BO801. )
Before making actuator centering adjustments, as-
Troubleshooting- sure that rudder system and yaw damper system is
rigged in accordance with rigging procedures.
For troubleshooting the yaw damper system, refer to
the Yaw Damper System Service/Parts manual. a. Turn yaw damper system "ON. "
b. Check position of rudder. If rudder deflects
Removal and Installation of Yaw Damper Actuator. from neutral position, manually hold rudder in the
(See figure 13-14C. ) assumed position and disengage yaw damper switch.
Refer to figure 13-14C, turn and hold centering screw
a. Place a suitable support under tailcone. (16) in a full (CW) position while returning rudder to
b. Remove tailcone access panel and rudder bell- neutral position. Release adjusting screw on actua-
crank access covers,
c. Remove chain guard (17), loosen turnbuckle (14)

I
and remove chain assembly from sprocket.
d. Disassemble
ance with applicable
e. Disconnect
tuator from aircraft.
actuator from structure
detail in figure,
electrical connector
in accord-

and remove ac-

Change 11
13-42F UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

1 3

Detail

Detail

4
- ¯,

-
lit IMHLIII19 RIlli 0011101 -

300 AND 400 SERIES IFCS 800 IFCS

Detail

1. Turn and Bank Indicator 3. Autopilot Disengage Switch

2. Actuator 4. Yaw Actuator Switch

Figure 13-14B. Yaw Damper Control System

Change 6
 421 SERVICE MANUAL UTILITY AND Î3-AÎÛ
OPTIONAL SYSTEMS

B
4
1
12 11 10

2 3 4 15 14 13

Detail
421B0801 AND ON 17 15 5 14 13

Detail
421B0301 TO 421B0801

51613010
A51613011
E54613001

1. Actuator 5. Cable 9. Bellcrank 13. Cable

2. Washer 6. Bracket 10. Cotter Pin 14. Turnbuckle
3. Lockwasher 7. Bracket 1L Nut 15. Chain
4. Screw 8. Bolt 12. Cable, Rudder 16. Centering Screw
17. Chain Guard
Figure 13-14C. Yaw Damper Installation

Change 11
13-428 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

C
6
5
9
4
7

ostan 8

Detan

1. ADI Indicator 4. Pitch Synchronization Switch 7. Autopilot Controller

2. HSI Indicator 5. Autopilot Disengage Switch 8. Inverter
3. Mode Selector 6. Go-Around Switch 9. Gyro

Figure 13-14D. Integrated Flight Control System

Change 6
 421 SERVICE MANUAL UTIUTY AND Î3-4Ž (fÎ3*4)

Itor.
OPTIONAL SYSTEMS

couplers and turn and pitch command. Simultaneous

c. Turn yaw damper system "ON" and recheck for or independent operation of the autopilot and flight
zero rudder deflection. director is provided and in addition to the autopilot
features, the flight director includes pitch synchro-
nization and go-around commands as selceted by the
FLIGHT CONTROL SYSTEM. pilot. The 800 Integrated Flight Control System in-
I INTEGRATED
(421B0201 AND ON). (See figure 13-14D.) cludes a vacuum,
presentation
slaved directional
and an horizontal situation
gyro with ADF
indicator
The Integrated Flight Control System is a two-axis (HSI). Nav 1 is connected to the HSI and Nav 2 is
(aileron and elevator) automatic flight control system connected to an individual course indicator. 400 or
consisting of the autopilot and flight director. Either 800 avionics system may be used with the 800 Inte-
the flight director or the autopilot may be used sepa- grated Flight Control System.
rately or as a combination. As an autopilot, in addi-
tion to holding the wings level and compensating for Removal, Installation and Rigging the Integrated
rotation about the pitch axis, the autopilot provides Flight Control System Components. (See figure
an automatic intercept and track of any magnetic 13-14D.)
heading or VOR radiaL Also included is an automat-
ic pitch trim, turn command, pitch command, alti- Refer to Removal, Installation and Rigging Proce-
tude hold and an ILS approach feature. As a flight dures for the Nav-O-Matic 400A Autopilot Section 13
director the Integrated Flight Control System pro- and Typical Instrument Removal and Installation Pro-
vides steering information, visually presented on the cedures Section 12 for removal, installation and rig-
altitude director indicator (ADI), for climb, cruise, ging the Integrated Flight Control System Components,
descent and altitude hold. Heading, VOR navigation,
glide slope and ILS approaches are visually presented
on the horizontal situation indicator (HSI). Removal, Installation and Rigging the Integrated
Flight Control System Components. (See figure 12-2
For additional description, installation adjustments, and figure 13-14. )
troubleshooting, schematics and parts listing, refer
to Cessna Integrated Flight Control System Service/ Refer to Removal, Installation and Rigging proce-
Parts ManuaL dures for the Nav-O-Matic 400A Autopilot, Section 13
and Typical Instrument Removal and Installation pro-
300 And 400 Series Integrated Flight Control Systems. cedures, Section 12 for removal, installation and
rigging the Integrated Flight Control System compo-
The 300 and 400 Integrated Flight Control Systems nents.
consist of the 400A Nav-O-Matic autopilot and flight
director, ILS coupler, slaved directional gyro, pitch
synchronization and associated avionics. The 300
Integrated Flight Control System usese 300 avionics, NAV-O-MATIC 800 SYSTEM.
while the 400 Integrated Flight Control System uses
400 avionics. Simultaneous or independent operation The Nav-O-Matic 800 Autopilot consists of the-follow-
of the autopilot and flight director are provided. Go- ing components: three gyroscopic sensors, a flight
around commands selectable by the pilot are provided controller, a transistorized electronic computer,
in addition to the pitch synchronization. three electrically-controlled pneumatic powered
servos which actuate the rudder, elevator, and ail-
eron, one elevator trim pneumatic actuator, and a
800 Series Integrated Flight Control System. pump and pressure system to operate servos. Op-
tional components to the basic autopilot installation
The 800 Integrated Control System consists of
Flight are a heading selector and altitude controller. For
the 400A Nav-O-Matic autopilot and flight director, adjustment, trouble shooting, and maintenance, re-
with yaw damper, altitude hold, automatic pitch trim, fer to the Cessna Nav-O-Matic 800 Service/Parts
. pitch synchronization, heading preselect, omni/ILS Manual.

Change 6
 421 SERVICE MANUAL UTILITY AND 13-43
OPTIONAL SYSTEMS

ELEVATOR TRIM SERVO

PRESSURE REGULATOR --

421A0001 AND ON ELEVATOR SERVO

AILERON SERVO---- - PRESSURE REGULATOR

421A0001 AND ON

RUDDER SERVO

FILTER

STATIC AIR
SOURCE t
| CHECK VALVE
ADJUSTING
SCREW
D G ll
CHECK VALVE CHECK VALVE

PUMP FAIL r SOLENOID

LIGHT PRESSURE SWITCH ---VALVE

!! RELIEF VALVE RELIEF VALVE

SOLENOID

UMP PUMP

FILTER FILTER

Figure 13-15. Cessna Nav-O-Matic 800 Autopilot Pneumatic Schematic

13-44 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

'
11

10

Detail
Detail B
(

1. Elevator Trim Servo 6. Autopilot Warning Lights 10. Ground Adapter

2. Flight Controller 7. Directional Gyro 11. Computer
3. Solenoid 8. Attitude Gyro . 12. Rudder Servo
4. Circuit Breaker 9. Turn and Bank 13. Elevator Servo
5. Pilot's Disengage Switch 14. Aileron Servo

Figure 13-16. Cessna Nav-O-Matic 800 Autopilot Components Location

 421 SERVICE MANUAL UTILITY AND 13-45
OPTIONAL SYSTEMS

10 11
Detail
2
--13

20 17 16 Detail C 15 14

Detail

"
29

31
21

Detail
29 30 25
Detail E I

Figure 13-17. Cessna Nav-O-Matic 800 Autopilot Servos and Cables Installation
 13-46 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Figure 13-17. Cessna Nav-O-Matic Autopilot Servos and Cables Installation Callouts

1. Rudder Bellerank 11. Aileron Servo 22. Cotter Pin

2. Turnbuckle 12. Support 23. Spacer
3. Rudder Cable 13. Cable Guard Assembly 24. Cable GuardAssembly
4. Autopilot Rudder Cable 14. Cable Drum 25. Clamp
5. Guard Pin 15. Pulley Bracket 26. Elevator Trim Pulley Bracket
6. Pulley Bracket 16. Autopilot Aileron Cable 27. Elevator Trim Cable
7. Pulley 17. Aileron Quadrant Assembly 28. Elevator Trim Servo
8. Pulley Bracket 18. Clamp 29. Autopilot Elevator Cable
9. Aileron Bellerank 19. Support 30. Turnbuckle
10. Turnbuckle 20. Rudder Servo 31. Elevator Bellerank
21. Elevator Servo

Removal and Installation of Autopilot Aileron Cables, dures.

(See figure 13-17. ) i. Rig autopilot rudder cables in accordance with
rigging procedures of this section.
Remove autopilot aileron cable as follows:
a. Remove front seats, middle seats and aft seats
in accordance with Section 3. Removal and Installation of Autopilot Elevator Cables.
b. Remove rear carpet as necessary to gain access (See figure 13-17.)
to cables.
c. (See figure 1-2.) Remove floorboards (80 and 86) a. Place a suitable support under tailcone.
and access cover (17) on fuselage bottom. b. Remove tailcone access door,
d. Remove safety and disconnect turnbuckle (10). c. Remove safety and disconnect turnbuckle (30),
e. Remove pulleys from pulley brackets (15). d. Remove cotter pin, nut and washer securing
f. Loosen clamp (18) securing cable to quadrant (17). autopilot elevator cable to bellerank links.
g. Through fuselage bottom access, remove screws e. Remove screws and spacers (23) from cable
and spacers (23) from cable guard assembly (13). guard assembly (24).
h. Remove two outer screws from cable drum f. Remove the two outer screws from cable drum
clamp (25), then loosen the remaining two screws clamp (25), then loosen the two remaining screws
allowing cable to become free, allowing the cable to become free,
i. Remove cable through lower access. g. Install autopilot elevator cables by reversing the
j. If autopilot aileron quadrant (17) is to be removed, removal procedures,
the quadrant may be removed by removing the three h. Rig cables in accordance with rigging procedures
attaching nuts and bolts. of this section,
k. Install autopilot aileron cables by reversing the
removal procedures.
1. Rig aileron and check cable tension in accordance Removal and Installation of Autopilot Elevator Trim
with rigging procedures of the section. Control Cables. (See figure 13-17.)

NOTE a. Place a suitable support under tailcone.

b. Remove tailcone access door.
The turnbuckle must be located midway between c. Remove safety and disconnect turnbuckle on
aileron servo drum and the adjacent pulley cable,
when in a neutral position, d. Remove pulleys from bracket (26) and dis-
engage cable from elevator trim servo (28).
Removal and Installation of Autopilot Rudder Cables. e. Remove cable in accordance with Section 6.
(See figure 13-17.)
NOTE
Remove autopilot rudder cables as follows:
a. Place a suitable support under tailcone. The removal procedures for the autopilot
b. Remove tailcone access door. elevator trim cable is the same as removal
c. Remove stabilizer fairings (9 and 11) and access procedures for the elevator trim cables.
cover (5). (See figure 1-2.)
d. Remove safety and disconnect turnbuckles (2) f. of the elevator
Installation trim control cables
from left and right autopilot rudder cables (4). is the
reversal of removal procedures,
e. Remove guard pins (5) from pulley brackets (6 g. Rig elevator trim control cables in accordance
and 8). with rigging procedures of this section.
f. Remove screws and spacers (23) from cable guard
assembly of rudder servo (20).
g. Remove two outer screws from cable drum clamp, Removal and Installation of Autopilot Pneuthatic
then loosen the two remaining screws allowing cable to System. (See figure 13-18.)
become free.
h. The installation procedure of the autopilot Remove autopilot pneumatic system as follows:
rudder cables is the reversal of the removal proce- a. (See figure 1-2.) Remove engine cowls (29),
 421 SERVICE MANUAL UTILtTY AND 13-47
OPTIONAL SYSTEMS

33

43 --

42

440

Detail
14

12

11

17 23

Detail
21 25 421-0001 To421sooo1
I

Figure 13-18. Cessna Nav-O-Matic 800 Autopilot Pneumatic System Installation (Sheet 1 of 5)

Change 1
13-48 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

32

4
2
3

Detail D 16
' Ûg 421-0001 TO 421B0001

1. Aft Pressure Bulkhead 17. Pneumatic Pump 35. Line Elevator Trim Servo
2. Lock-O-Seal 18. Cooling Air Adapter to Elevator Servo
3. Pressure Line Assembly 19. Inlet Air Filter 36. Elevator Trim Servo
4. Aileron Servo Pressure Line 20. Pressure Relief Valve 37. Elevator Servo Support
5. Servo Bleed Line 21. Dump Valve 38. Filter
6. Line Union to Aileron 22. Pressure Switch 39. Line Filter to Check Valve
Servo 23. "O" Ring Gasket 40. Check Valve
7. Beam Web 24. Firewall 41. Line Tee to Union
8. Line Tee to Elbow 25. Hose Tee to Tee 42. Line Filter to Tee
9. Line Elbow to Elbow .26. Line Union to Elbow 43. Line Tee to Elevator Servo
10. Aileron Servo 27. Line Elbow to Elbow 44. Elevator Servo
11. Line Check Valve to 28. Line Union to Elbow 45. Line Tee to Pressure
Firewall 29. Line Elbow to Elbow Regulator
12. Check Valve 30. Line Elbow to Elbow 46. Pressure Regulator
13. Line Check Valve to 31. Line Elbow to Tee 47. Pre,ssure Regulator to Filter
Union 32. Line Elevator Servo to 48. Line Union to Pressure
14. Line Union to Union Elevator Trim Servo Regulator i

15. Cabin Skin 33. Line Rudder Servo to Tee 49. Pressure Regulator
16. Shroud 34. Rudder Servo 50. Elbow

Figure 13-18. Cessna Nav-O-Matic 800 Autopilot Pneumatic System Installation (Sheet 2 of 5)

Change 1
 421 SERVICE MANUAL UTILITY AND 13-48A
OPTIONAL SYSTEMS

46
47
4

Detail E
421A0001 TO 421BOOO1
AND AIRCRAFT MODIFIED
BY SK421-20.

49

Detail F
421A0001 TO 421BOOO1
Ai) AND AIRCRAFT MODIFIED
BY SK421-20.

NOTE
*ON
AIRCRAFT 421A0046 TO 421BOOO1
SERVO BLEED LINE (5) HAS BEEN
DELETED BACK TO AILERON
SERVO (10) INCLUDING ELBOW (50).
Detail
ON AIRCRAFT MODIFIED PER
SK421-21 AND ON AIRCRAFT
421A0030 TO 421A0046

421-0001 TO 421BOOO1

Figure 13-18. Cessna Nav-O-Matic 800 Autopilot Pneumatic System Installation (Sheet 3 of 5)

Change 1
13-488 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

C D

48

Detail

421BOOO1 AND ON

Figure 13-18. Cessna Nav-O-Matic 800 Autopilot Pneumatic System Installation (Sheet 4 of 5)

Change 1
 421 SERVICE MANUAL UTILITY AND 13-480/13-480
OPTIONAL SYSTEMS

41
43

44

3634 Detan D

TO AILERON
-

SERVO

48
1 2
4 49

TORH '
ENGINE 3

31 14

12

11

181

Detail $
25

421BOOO1 AND ON

Figure 13-18. Cessna Nav-O-Matic 800 Autopilot Pneumatic System Installation (Sheet 5 of 5)

Change 1
 421 SERVICE MANUAL UTILITY AND 13
OPTIONAL SYSTEMS

lower wing access doors (53, 54, 55, 56 and 57) and a. Remove autopilot aileron servo (11) as follows:
wing gap skin (35). 1. Remove seats, carpet, floorboard access panels
b. Remove pilot, copilot and aft seats in accordance necessary to gain access to aileron servo.
with Section 3. 2. Remove safety and disconnect turnbuckle (10).
c. Remove carpet and floorboards (77, 78, 79, 80, 3. Remove cable from aileron servo drum by
81, 82, 83, 84, 85 and 86 in accordance with Section loosening clamp securing cable to drum.
3. (See figure 1-2.) 4. Remove aileron servo attaching nuts, washers,
d. Remove tailcone access door. bolts and electrical plug and remove servo from air-
NOTE craft.
5. Install aileron servo by reversing the removal
All lines and fittings must be kept clean and procedure.
suita,bly protected by caps, plugs or bags 6. Rig autopilot aileron cables in accordance with
until installed in the system. rigging procedures.
b. Remove autopilot rudder servo as follows:
e. (See figure 13-18.) Remove plumbing from pneu- 1. Place a suitable support under tailcone.
matic pump (17) to firewall (24) by disconnecting 2. Remove tailcone access door.
hoses from pump (17), pressure relief valve (20), 3. Remove safety and disconnect turnbuckle (2),
dump valve and pressure switch tee. 4. Remove cable from rudder servo by loosening
f. Disconnect and remove line (11) from firewall clamp securing cable to the servo drum.
(24) to check valve (12). 5. Remove rudder servò attaching nuts,.washers,
g. Disconnect and remove line (13) from check bolts and electrical plug and remove servo from air-
valve (12) to union located in wing gap area. craft,
h. It will be necessary to remove the heat exchanger 6. Installation of autopilot rudder servo is the re-
to gain access to stub wing line (14). Remove heat versal of removal procedures.
exchanger in accordance with Section 13. 7. Rig autopilot rudder cables in accordance with
i. Disconnect line (14) from cabin skin fitting and rigging procedures.
remove. c. Remove autopilot elevator servo as follows:
NOTE 1. Place a suitable support under tailcone.
2. Remove tailcone access door.
The removal procedures are the same for 3. Remove safety and disconnect turnbuckle (30),
right and left wings. 4. Remove clamp from elevator servo drum and
remove cable from drum.
j. Remove clamps securing lines to structure• 5. Remove elevator servo attaching nuts, washers,
k. Disconnect lines (26 and 28) from cabin skin fit¯ bolts and electrical plug and remove servo from air-
ting. Hold fittmg through skm to prevent it from craft.
turning, thus breaking the seal. 6. Installation of elevator servo is the reversal of
1. On aircraft 421-0001 to 421A0001, disconnect
the removal procedures,
aileron servo pressure line (4) and aileron servo 7. Rig autopilot elevator cables in accordance with
bleed line (5) from aft pressure bulkhead fittings. On rigging procedures,
aircraft 421A0001 and ON, remove pressure regula-
d. Remove autopilot elevator trim servo as follows:
tor (49) by disconnecting line union to pressure 1. Place a suitable support under tailcone.
regulator (48) and aileron servo pressure line (4)' 2. Remove tailcone access door.
Hold fittings at bulkhead to prevent turning and break- 3. Remove safety from elevator trim cable and dis-
ing cabin pressurization seal• connect elevator trim cable from elevator trim servo.
NOTE
4. Remove elevator trim servo attaching nuts,
washers and bolts and remove servo from aircraft.
5. Installation of elevator tritn servo is the rever-
On aircraft 421A0046 and ON, servo bleed
sal of removal procedures.
line (5) has been deleted.
6. Rig elevator trim servo system in accordance
m. Disconnect lines in the cabin area in accordance with rigging procedures,
with figure 13-18.
n. In the tailcone area, remove pressure line (33)
from tee to rudder servo (34) and pressure line (43) Removal and Installation of Autopilot Flight Controller
from tee to elevator servo (44).
o. Disconnect and remove lines (32 and 35) from a. Remove the four screws attaching the flight
elevator trim servo (36) to elevator servo (44). controller to pedestal,
p. Disconnect and remove line (41) from tee to b. Pull flight controller aft and disconnect electri-
pressure bulkhead fitting. cal plug and remove flight controller from pedestal.
q. On aircraft 421-0001 to 421A0001 remove filter c. Install by reversing the above procedure.
lines (39 and 42). On aircraft 421A0001 and ON re-
move filter lines (45 and 47) from pressure regula-
tor (46). Removal and Installation of Autopilot Computer.
r. Installation is the reversal of the removal pro-
cedures. a. Open left nose access door and remove rear
baggage shelf.
Removal and Installation of Autopilot Servos. (See b. Loosen wing nuts securing computer and pull
figure 13-17.) computer straight out of rack.
13-50 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

c. Reverse the removal procedure for installation. 4. Rotate the elevator trim control wheel so ele-
vator trim tab is 26° +1°, down and set stop on
-0°

Rigging Autopilot Control System. (See figure 13-17.) the elevator trim tab cable.
5. Rotate the elevator trim control wheel so ele-
control system as follows: 10° +1°, up and set stop on
a. Rig autopilot aileron vator trim tab is
-0°

1. Refer to Section 6 and verify that the aileron the elevator trim tab cables,
control system is rigged properly.
2. Place aileron control surfaces to the NEUTRAL NOTE
position and secure with a clamping device.
3. With drum (14) and servo (11) in NEUTRAL The elevator trim tab stop block must be 10-
position, clamp cable to drum (14) in such a manner cated where they will not come in contact
that the turnbuckle is midway between drum and the with the elevator trim servo pulley.
adjacent pulley.
4. Rig tension on cable (16) to 12 ±3 pounds. 6. Check neutral position of elevator trim servo
and trim tab.
NOTE 7. Check operation in accordance with Nav-O-
Matic 800 Service and Parts Manual.
Cable tension should be adjusted when ambi-
60°F
ent temperature is to 90°F. Allow air- NOTE
craft temperature to stabilize for a period of
4 hours. For installation of checkout patch cable, re-
move the LH forward cabin vent located just
5. If ailerons and servo are both still in neutral, forward of the pilot's rudder pedals.
install clamp (18), insure that cable guard pins (5)
and guard spacers (23) are in place and safety turn-
buckle (10). Autopilot Pressure Check and Adjustment. (See
6. Remove aileron clamping device· figure 13-18). (421-0001 to 421A0001)
b. Rig the rudder control system as follows:
1. Refer to Section 7 and verify that the rudder a. Disconnect line (33) from tee.
control system is properly rigged. b. Connect a pressure gage to the tee fitting.
2. Place rudder control surface in NEUTRAL posi- c. Start one engine and run at cruise RPM.
tion and clamp and secure with clamping device. d. Pressure at the filter outlet should read 10
3. Insure that cable is properly clamped to servo + . 75 0 PSI.
-

drum and properly routed over pulleys. e. If pressure reading is below prescribed toler-
4. Rig control cable to 15 ±5 pounds tension, keep- ance, adjust pressure relief valve (20) in the engine
ing rudder and rudder servo in NEUTRAL position. compartment to obtain correct pressure.
5. Remove clamping device and check rudder for f. Shut down engine and start opposite engine and
full travel and centering. perform the same check. Adjust if necessary.
6. Safety turnbuckle and verify that all cable
guards are in place.
c. Rig the autopilot elevator control cables as Autopilot Pressure Check and Adjustment. (See fig-
follows: ure 13-18. ) (421A0001 and ON)
1. Refer to Section 6 and verify that the elevator
control system is properly rigged, a. Disconnect line (42) from tee.
2. Place elevator control surface to the NEUTRAL b. Connect a 0 to 20 PSI pressure gauge to line (42).
position and clamp with suitable clamping device. c. Start one engine and run at cruise RPM.
3. Check the autopilot elevator control cables for d. Pressure at the filter outlet should read 11. O
proper routing and mounting on the elevator servo. +. 75, PSI.
-0

4. Make sure elevator servo drum is in the e. If pressure reading is above or below the pre-
NEUTRAL position, scribed tolerance, adjust pressure regulator (20) in
5. Rig elevator control cables (29) to 15 ±5 pounds the engine compartment to obtain correct pressure,
tension. f. Shutdown engine and start opposite engine and
6. Remove clamping device and clamps and oper- perform the same check. Adjust if necessary,
ate elevator up and down. g. With engine running at cruise RPM, remove
7. Verify that elevator control surfaces and cable pressure gauge and connect line (42) to pressure
drum are neutral, regulator (46).
8. Refer to Section 7 and check travel of elevator h. Connect the pressure gauge to the test port of
control surface. pressure regulator (46).
d. Rig autopilot elevator trim control as follows: i. Pressure should be 10. 0 +. 75, PSI.
-0

1. Refer to Section 6 and ríg elevator trim control j. If pressure reading is not within prescribed tol-
system in accordance with rigging procedures. erance adjust pressure regulator by turning pressure
2. Check routing of elevator trim control cables, regulator adjusting screw full in, with engine operat-
make sure cables are routed over pulleys and around ing at cruise RPM turn pressure regulator adjusting
the elevator trim servo drum, screw out until correct pressure setting is reached.
3. Rig the elevator cables to 16 ±3 pounds tension. k. Remove pressure gauge and install plug in test
port.
 421 SERVICE MANUAL uTILITY AND U-51
OPTIONAL SYSTEMS

1. Connectpressure gage to the test port of pres- The Wemac air shutoff valve is a solenoid operated
sure regulator (49) at access plate (93, figure 1-2). butterfly valve located in the lower portion of the
m. Pressure reading should be 6. 0 +. 50, on -0
Wemac plenum, and prevents mixing warm pressur-
421-0001 to 421BOOO1 aircraft and 7. 0 +. 50, on -0
ized air or ambient air (depending on the mode of op-
421BOOO1 and ON aircraft. eration) with refrigerated air in the upper plenum.
n. If pressure reading is not within the prescribed The pressurized air will continue to be directed
tolerance adjust pressure regulator by turning pres- through the lower heating and ventilating outlet sys-
sure regulator adjusting screw full in, with engine tem. The shutoff valve is closed when the compres-
operating at cruise RPM turn pressure regulator ad- sor switch is turned on.
justing screw out until correct pressure setting is
reached. The condensate tank is installed below the evaporator
o, Remove pressure gauge and install plug in test unit to collect and store evaporator condensation. An
port. electrically actuated dump valve is wired through the
p. Shutdown engine. gear squat switch to provide stored fluid to drain
overboard upon aircraft landing and depressurization.

ÁIR CONDITIONING SYSTEM. (See figure 13-19.) The switch controls consisting of three toggle switch-
(421-0001 TO 421B0001) es are located on the upper forward face of the cabin
The air conditioning system is composed of six ma- divider. The cooling switch turns on the compressor
the compressor-conden- and the evaporator blower to high speed. The fan
jor component installations;
ser unit, the evaporator and blower cabin divider, switch allows the evaporator blower to operate inde-
the Wemac plenum check valve, the Wemac air shut- pendent of the compressor unit and has two speeds,
off valve, the condensate tank and drain, and the high and low. The Wemac air switch controls the
switch controls. Wemac air blower.

The compressor-condenser unit mounted in the right- When the cooling switch is placed in the ON position,
hand forward wing locker area consists of the com- the compressor, driven by an electric motor, com-
pressor, the condenser, the electric drive motor and presses the Freon gas to a high pressure and high
the cooling fan. Inlet air is provided from the out- temperature. This gas is routed to the condenser
board side of the nacelle and outlet air is expelled on where cooling from the fan removes heat from gas,
the inboard side of the nacelle. Plumbing and wiring condensing it to a liquid. The liquid is then stored
is routed through the wing to the cabin area with a in the receiver-dryer, adjacent to the compressor,
pressure seal installed at the fuselage skin. until it is used. The Freon is metered to the evapo-
rator through the expansion valve at a rate to allow
The evaporator and blower cabin divider unit is a all the liquid to evaporate and return to the compres-
special designed unit mounted in the forward right- sor at a reduced pressure. The heat required for
hand cabin divider. This unit consists of the evapo- the evaporation is absorbed from air passing over
rator, evaporator air blower, upper Wemac air the evaporator cooling fins. Refrigerated air is then
blower, control switches, and the adjustable air out- routed to the Wemac plenum and cabin outlets by the
lets. This unit also serves as a plenum for cabin air Wemac blower.
distribution. Air is routed from the forward lower
part of the cabin divider and pulled through the evap-
orator by the evaporator air blower. Refrigerated CAUTION
air is delivered to the passenger and crew overhead
vents by the Wemac air blower located inside the If for any reason the air conditioner is turned
divider plenum. Refrigerated air is also delivered off, it is recommended that a minimum of three
from the upper portion of the cabin divider through minutes elapse before it is turned on again;
the adjustable louvers located on the forward and aft this allows the compressor head pressure to
side of the cabin divider. bleed off and bring the starting load to normal.

The Wemac air plenum check valve is located inside Troubleshooting.

the Wemac plenum to prevent back flow from the
Wemac plenum air system when the air conditioner For troubleshooting the air conditioning system, refer
is not in use. to the Air Conditioning System Service/Parts manual.

Change 9
13-52 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Removal of Compressor and Condenser Unit. (See Removal of Condensate Tank and Valve. (See figure
figure13-19. ) 13-19. )

a. Turn off all electrical power, a. Remove copilots seat in accordance with Remov-
b. (See figure 1-2. ) Remove air conditioning ac- al Procedures.
cess panel cover (91). b. Remove carpet in front of cabin divider on right
c. Loosen screws and remove cover shield. side.
d. Tag and disconnect electrical wiring. c. Remove cabin divider in accordance with Remov-
e. Discharge pressure in accordance with Discharge al Procedures.
Procedures and disconnect lines, d. Remove evaporator mounting screws and lift
fa Remove bolts from mount and remove the com- evaporator up enough to remove floorboard plates.
pressor and condenser unit by lifting straight out of e. Remove condensate tank and valve.
nacelle.

Ig. If further disassembly

Conditioning Systems Service/Parts
is required,
ManuaL
refer to Air
Installation
ure 13-19. )
of Condensate Tank and Valve. (See fig-

Installation of Compressor and Condenser Unit. (See a. The Installation Procedure for the condensate
figure 13-19. ) tank and valve is the reversal of the Removal Proce-
dures.
a.Position compressor and condenser unit in na-
celle and install shock mount bolts,
b. Connect wiring and remove tags. Removal and Installation of Wemac Plenum. (See
c. Connect refrigerant lines. figure 13-19.)
d. Evacuate and charge the refrigerant system in
accordance with the Air Conditioning Systems a. Removal and installation of the Wemac plenum
Service/Parts Manual. is not recommended.
e. Check operation.
f. Install cover shield and air conditioning access
cover. Removal of Wemac Shutoff Valve. (See figure 13-
19.)

Removal of Evaporator, Blower and Cabin Divider a. Remove pilot's seat in accordance with Removal
Unit. (See figure 13-19. ) Procedures in Section 3.
b. Remove carpets and floorboards in accordance
a. Remove screws from panel on cabin divider. with Removal Procedures in Section 3.
b. Tag and disconnect wiring from evaporator blow- c. Tag and disconnect electrical wiring.
er and Wemac blower. d. Remove bolts (67) securing shutoff valve (69) to
c. Remove screws securing the cabin divider to shutoff valve bracket assembly (70).
floorboard, side bulkhead and top bulkhead. Remove e. Remove valve and both gaskets (68).
cabin divider from the aircraft.

I
d. Discharge pressure in accordance with Air
Conditioning Systems Service/Parts Manual and dis- Installation of Wemac Shutoff Valve.
connect lines.
e. Remove screws securing Wemac blower and re- a. Install new gaskets (68).
move clamp on Wemac blower outlet.
f. Remove screws securing evaporator to mounts, NOTE
loosen clamp to condensate tank and lift evaporator
from aircraft. When installing shutoff valve always use new
gaskets (68).

Installation of Evaporator, Blower and Cabin Divider b. Install shutoff valve (69) in bracket assembly (70)
Unit. (See figure 13-19. ) c. Install bolts (67) and nuts (71).
a. The Installation Procedure for the evaporator, d. Connect electrical wiring.
blower and cabin divider unit is the reversal of the e. Install carpets and floorboards in accordance
Removal Procedure, with Installation Procedures in Section 3.
b. Evacuate and charge the refrigerant system in f. Install pilot's seat in accordance with Installa-

l
accordance with Air Conditioning Systems Service/
Parts Manual.
tion Procedures in Section 3.

Removal of Air Conditioning Plumbing. (See figure

13-19. )

a. (See figure 1-2. ) Remove access covers (35),

(58) and (91).
b. Discharge pressure in accordance with Air
Change 6
 421 SERVICE MANUAL UTILITY ANo O ·53

OPTIONAL SYSTEMS
I

H G F

1. Motor 10. Shaft 17. Line (Receiver Dryer to Expansion

2. Charging Port (Low Pressure) 11. Bolt Valve)
3. Pulley (Motor Drive) 12. Bolt 18. Bearing
4. Charging Port (High Pressure) 13. Line (Compressor 19. Bearing Retainer
5. Belt (Motor to Compressor) Discharge) 20. Line (Evaporator to Compressor)
6. Belt (Motor to Fan) 14. Line (Condenser to 21. Electrical Cable
7. Fan Receiver Dryer 22. Relay
8. Condenser 15. Bolt 23. Compressor
9. Fan Pulley 16. Receiver Dryer .
24. Allen Bolt

Figure 13-19. Air Conditioning System Installation (Sheet 1 of 4)

Change 9
13-54 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

21 22 21 23 24
1

19 / 2
19
3

4
17
16
20

14
13
'
12

11
'
64
10
9
25
28

27
3

"'
DetailA
25 y

29

Figure 13-19. Air Conditioning System Installation (Sheet 2 of 4)

Change 9
 421 SERVICE MANUAL UTILITY AND 13 55
OPTIONAL SYSTEMS

32

37

38
43

42 34

35

41

Detail

37

39
Detail $ 40

25. Grommet 39. Hose Assembly (Elbow to 54. Evaporator Coil

26. Screw Evaporator) (Low Pressure) 55. Cabinet Bottom
27. Aft Support 40. Hose Assembly (Elbow to 56. Mounting Clip
28. Cabinet Assembly Evaporator) (High Pressure) 57. Brace
29. Forward Support 41. Seal Half 58. Cabinet Top
30. Duct 42. Fuselage Skin 59. Blower Housing
31. Hose Assembly Condenser 43. Seal Half 60. Blower Wheel
to Bulkhead (Low Pressure) 44. Duct 61. Inlet Ring
32. Hose Assembly (Rec. Dryer 45. Clamp 62. Motor Mount
to Bulkhead) (High Pressure) 46. Wemac Blower 63. Motor
33. Elbow .
47. Adapter 64. Pulley (Compressor)
34. Line Assembly Bulkhead to 48. Adapter Ring 65. Clamp
.Wing Root (High Pressure) 49. Condensate Tank 66. Duct
35. Line Assembly Bulkhead to 50. Floorboard 67. Bolt
Wing Root (Low Pressure) .
51. Drain Tube 68. Gasket
36. Clamp 52. Solenoid Valve 69. Valve (Shutoff)
37. Union 53. Expansion Valve 70. Bracket Assy
38. Screw 71. Nut

Figure 13-19. Air Conditioning System Installation (Sheet 3 of 4)

Change 9
13-56 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

61 59
Detail Û

Detail

53
40 '
51
39
54 52
Detail E

D
71
69
56 70 e
Detaii F
Figure 13-19. Air Conditioning System Installation (Sheet 4 of 4)

Change 9
 421 SERVICE MANUAL UTILITY ANo lb57
OPTIONAL SYSTEMS

Conditioning System Service/Parts ManuaL disengaged by an electromagnetic clutch when the air
c. Disconnect hoses (31) and (32) at nacelle, re- conditioning switch is placed in the air conditioning
move clamps (36), disconnect lines (34) and (35) at mode position. The compressor does not cycle on
elbows (33) and unions (37) and carefully work lines and off for cooling. A bypass valve has been incor-
from wing. porated to unload the compressor when less R-12 is
needed by the system.
NOTE
To protect the compressor from excessive liquid
Use care when removing lines to prevent ingestion, a liquid trap is incorporated in the suction
scratches, nicks and bends. line located just aft of the firewall.

d. Remove right front passenger seat and floorboard The right hand wing locker houses the two condenser
in accordance with Removal Procedures. modules, receiver-dryer, bypass valve, and conden-
e. Disconnect lines (39) and (40) from hose elbows ser blower assembly. In flight cooling is provided by
from under floorboard. air drawn in through the inlet scoop on the outboard
side of the engine nacelle being passed over the con-
NOTE denser and expelled through the nacelle outlet on the
inboard side of the nacelle. The condenser blower
Cap lines and hoses when not in use, is wired through the landing gear safety switch and
operates during ground operation only except, during
f. Disconnect clamps and remove the pressure seal flight in the event the condenser temperature be-
at fuselage and route lines from stub wing. comes excessively high causing the output pressure
to increase, the fan will be turned on by the conden-
ser fan control switch, and will remain on until the
Installation of Air Conditioning Plumbing. (See fig- temperature of the condensers are reduced, lower-
ure 13-19. ) ing the output pressure. When the output pressure
is reduced the condenser fan control switch will turn
a. The Installation Procedures for the air condition- the fan off.
ing plumbing is the reversal of the Removal Proce-
dures.
The receiver-dryer stores liquid refrigerant and
NOTE draws the moisture out of the Freon during the cycle
of operation. The bypass valve provides refrigerant
When connecting aluminum
fittings in the re- flow to the compressor whenever the refrigerant so-
frigerant system, lubricate
all fittings with lenoid valve is closed, and will maintain suction at a
Capella "E"; torque all 5/8-inch fittings 18 minimum pressure to prevent evaporator coil freez-
to 21 foot-pounds and all 1/2-inch fittings ing. The bypass valve will unload the compressor
11 to 13 foot-pounds. when less R-12 is needed by the system.

b. Reseal in accordance with resealing procedures The latching pressure switch is located in the high
in Section 16. pressure line and provides protection for the refrig-
c. Evacuate and charge the refrigerant system in erant system. Should the thermostatic switch in the
accordance with Air Conditioning System Service/ compressor fail or the temperature rise enough to
Parts Manual. cause the pressure to exceed 350 PSI the latching
d. Check system operation. pressure switch will open and disable the magnetic
clutch on the compressor. If the latching pressure
switch is activated it will be necessary to remove
AIR CONDITIONING SYSTEM. (See figure 13-20. ) the access plate on the inboard forward side of the
(421B0001 to 421B0501. ) right wing locker baggage compartment and manually
reset the latching pressure switch.
The air conditioning system is comprised of three
major installations; right engine compartment, right A cover is provided for access to the right wing
wing locker and cockpit cabin area. The air condi- locker area for service and maintenance of compo-
tioning system utilizing the vapor cycle concept and nents.
R-12 Freon as the refrigerant will deliver 14, 500
100° In the cabin cockpit area are mounted two evaporator
BTU of cooling with an O. A. T. of Fahrenheit.
modules, the control panel and temperature control
The right-hand engine compartment installation con- assembly, the refrigerant manifold assembly, the
I
sists of a piston type light-weight
ed on the aft outboard
pressor is mounted
compressor
side of the engine.
to the nacelle structure
mount-
The com-
and is
condensate drain valve, the air distribution
the sight glass and charging ports,
The evaporator
ducts and

modules each contain an evaporator

belt driven from a pulley mounted on the aft side of coil, an expansion valve, a shroud, and a scroll and
the viscus damper. The compressor is engaged and blower assembly. The evaporator modules are re-
cessed behind the pilot and copilot seats. Cabin air

Change 11
13-58 orie:Tv A_ND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

CODE C

--ELECTRICAL ACTUATION
SYSTEM y
COLD Am

COOLE

coNDENSER

COMPRESSOR

CREW OUTLET LOW PRESSURE

LINE

EVAPORATOR
HIGH PRESSURE
EXPANSION VALVE
LINE
AND BLOWER
ASSEMBLY LIQUID TRAP

RECEIVER-
AIR OUTLET AIR DRYER FILTER
RETURN
CONDENSER

MANIFOLD LINBYP SYLE

PASSENGER
OVERHEAD
ASSENGER
DUCTING
OVERHEAD
DUCTING

Detail
421Bi201 AND ON

51983003
A51983003
BS2983002

Figure 13-20. Air Conditioning Distribution Schematic

Change 11
 421 SERVICE MANUAL UTILITY AND U-59
OPTIONAL SYSTEMS

is drawn through each evaporator coil and refriger-. A temperature control assembly mounted on the RH
ated air is routed into the distribution ducts into the evaporator module (copilot's seat) senses evaporator
cockpit cabin area. The blower motor is manually inlet air. When surrounding air approaches the pre-
controlled and has dual speed which may be used to selected value, the temperature control switch will
provide cockpit cabin ventilation or air recirculation close to provide voltage to the temperature relay.
when the air conditioner is turned off or when the
cabin heater is operating- The temperature control switch provides power to
the compressor clutch through the temperature relay.
located under the cabin
I
The refrigerant
floor, consists
switch and distribution
manifold,
of a temperature relay,
manifold.
low pressure
The manifold is The low pressure switch provides system protection
the junction point for the gaseous and liquid freon in the event of loss of freon or operation during ex-
distributed between the evaporator modules and the tremely low outside ambient temperatures.
compressor.

Change 11
13-60 UTIUTY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

The condensate drain valve is located under the cabin d. Remove compressor drive belt in accordance
floor and automatically drains the condensate from with the Removal of Compressor Drive Belt Tro-
the evaporator modules during ground operation and cedures.
in flight. The valve provides a two stage orifice e. Remove suction hose and discharge hose.
which permits maximum drainage at ground opera- Cap open ports and hoses.
tion and limited drainage during cabin pressurized f. Disconnect electrical wires at splices.
flight. The second stage orifice assures no signifi- g. Remove bolt and nut securing rod end (127) to
cant loss in cabin pressurization. bracket.
h. Remove bolt, nut and washers securing support
The control panel is located on the inboard side of the assembly (130) to support fitting.
right-hand evaporator module and consists of a mode i. Remove compressor, torque link and support
switch, evaporator blower speed selector switch and assembly as a unit.
temperature selector rheostat. A.special service fit- j. Disassemble compressor assembly components
ting assembly is provided which permits system serv- in accordance with figure 13-21.
icing and diagnosis. The fitting is located in the liq-
uid line to the right-hand evaporator module expan- a
sion valve. The fitting contains a sight glass and Installation of Compressor (See figure 13-21. )
service valve. Another service valve is located in
the right-hand evaporator module suction line. This a. Drain all oil from the compressor in accordance
valve is used for charging freon to the system. with Air Conditioning System Service/Parts ManuaL
b. Refill the compressor with 4 ounces of Suniso
System operation in the air conditioning mode, re- No. 5 or Texaco Capella E Grade, 500 viscosity oil
quires that the right-hand engine be operating at a or equivalent.
minimum tachometer reading of 950 RPM in order to
drive the freon compressor at its design ground ca_ NOTE
pacity. Whenever the system mode switch is selected
to the air conditioning mode, with the right-hand en- Special care should be taken to assure that
gine operating, the magnetic clutch is energized and the system is not over-charged with oil,
the compressor starts delivering a high pressure and since an over-charge of oil in the system
temperature freon gas to the condensers. This gas will decrease system performance.
is routed through the condensers where cool air from
the fan assembly removes heat from the gas and con_ NOTE
denses it into a high pressure liquid.
All openings in compressor shall be capped
The liquid then enters the receiver -dryer where it is off to assure that oil in the compressor does
not drain out during installation.
filtered, dried and gas is separated from the liquid.
c. Assemble torque link (129) and support assembly
From the receiver-dryer, the flows to the freon
liquid
(130) to compressor. Refer to figure for proper
distribution manifold which directs the 11quid to each
. .

placement of components.
evaporator module expansion valve. The expansion
valve throttles the liquid into a sub-cooled gas before
NOTE
it enters the evaporator coil. Air from the cabin is
pulled across the evaporator coil and is cooled by the wi th Dow-
sub-cooled Bushings (131) may be lubricated
freon gas. The refrigerated air is then (MIL-G-3278)
Corning DC4 silicone grease
routed into the air distribution ducting and exhausted '
to facilitate installation. Bolts and nuts
.

through directional louvered outlets, into the cabin

.

securing bushings must be snug but not so

.

and cockpit.
tight as to deform bushings. Secure nuts
. with cotter pins.
Troubleshoottng.

d. Position compressor assembly in place and

For troubleshooting the air conditioning system, refer
to the Air Conditioning System Service/Parts secure support assembly (130) to support fitting
Manual.
with bolt, nut and washers.

Removal of Compressor. (See figure 13-21. ) NOTE

a. Verify system power switch is in OFF position. Shift placement of washers as required to
b. Remove RH cowling. provide a static alignment'of compressor
c. Discharge refrigerant system. Refer to Air Con- pulley 15 inches forward
. of the engine
ditioning System Service/Parts Manual, drive pulley.

e. Position compressor drive belt on pulleys and

secure torque link rod end (127) to bracket. Washers
may be added between rod end and bracket if required
to align pulleys. Make certain a minimum of 1-1/2
threads protrude through the nut.
Change 11
 421 SERVICE MANUAL UTILITY AND l3 61
OPTIONAL SYSTEMS

L
K J
H
G

51542006

Figure 13-21. Air Conditioning System (Sheet 1 of 5)

Change 11
13-0 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

I 33
111

35
129
128
127
Detail A
128
46 42

3132

30 55

33
125
27

Detail B 34 26 2e 21244004
814144015

Figure 13-21. Air Conditioning Systern (Sheet 2)

change 11
 421 SERVICE MANUAL UTILITY AND 13-63
OPTIONAL SYSTEMS

0
45

47 113

50

45

4 3 58

47

Detaii D
Detail F
421BOOO1 TO 421BO332

61
59
60 28
28
58

Detail E

C51141099
54143019R

Figure 13-21. Air Conditioning System (Sheet 3)

Change 11
13-64 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

71

7e

28

73

72

"
TO RH ,
APORATOR

112 85

79 84

83
TORH
EVAPORATOR

LH EVAPORATOR

119

Detail Û
G54143018R

Figure 13-21. Air Conditioninz Systern 1Shot._O

 421 SERVICE MANUAL UTILITY AND l3-Û$A
OPTIONAL SYSTEMS

RH EVAPORATOR
" ONLY

Detail
421B0001 TO 421B0109

*124

Detan N
RH SEAT SUPPORT

Detail
109 0
' 95
99 12 100 101 21
93

NOOCIL

,
e- Detail L
HLEVAPORATOR

120
1
Detail M *USED ONLY ON AIRCRAFT INCORPORATING
SK421-58 WITH A 12 VOLT CLUTCH COIL Detail K
421B0109 TO 421B0501 K51141077R
(NOT REQUIRED WITH A 12 VOLT SYSTEM) L14141028
* *USED ONLY ON AIRCRAFT INCORPORATING M54981001
SK421-58 N51141086

Figure 13-21. Air Conditioning System (Sheet 5)

Change 11
13-64Ñ UTILITY AND .421 SERVICE MANUAL
OPTIONAL SYSTEMS

Figure 13-21. Air Conditioning System Callouts

1. Thru 24. Deleted 6L Freon Liquid Injection Line 83. Motor

25. Firewall (Union to High Pressure 84. Blower Housing
26. Freon Discharge Line (Firewall Switch Tee) 85. Fan
Elbow to Condenser Union)
127.
to
Freon Discharge
Compressor)
Hose (Firewall
62. Freon Liquid Injection
(High Pressure
to Manifold Union)
Line
Switch Tee
86.
87.
Setscrew
LH Evaporator
Valve
Expansion

28. Union 63. High Pressure Switch 88. LH Evaporator Module

29. Condenser 64. Low Pressure Switch 89. Condensate Drain
30. Freon Discharge Line (Condenser 65. Manifold Shutoff Solenoid 90. Drain Line From RH
Union to Receiver-Dryer) Valve Evaporator
31. Receiver-Dryer 66. Manifold 91. Drain Line From LH
32. Freon Discharge Line (Receiver- 67. Manifold Mounting Bracket Evaporator
Dryer to Cross) 68. RH Evaporator Expansion 92. Evaporator Condensate
33. Freon Suction Hose (Compressor Valve Line (Manifold to Drain
Elbow to Firewall Elbow) Union) 93. Temperature Control
34. Crossover Line 69. LH Evaporator Expansion Switch
35. Compressor Drive Belt Valve Line (Manifold to 94. Heat Temperature
36. Tee Union) Control
37. Compressor Drive Sheave 70. LH Evaporator Outlet Line 95. Bracket Temperature
38. Reducer (Manifold to Union) Control
39. -Plug 7L RH Evaporator Outlet Line 96. RH Evaporator
40. Blower Motor Mount (Manifold to Union) 97. RH Evaporator Back
41. Blower Motor 72. RH Evaporator Outlet Line Cover
42. Gaseous Freon Suction Line (Union to Service Valve) 98. RH Evaporator Side
(Firewall Elbow to Nacelle 73. RH Evaporator Expansion Cover
Skin Elbow) Valve Line (Union to Floor- 99. Rheostat
43. Line (Elbow to Bypass Valve) board Union) 100. Blower Switch
44. Bypass Valve 74. LH Evaporator Outlet Line 101. Cool-Circulate System
45. Line (Bypass Valve to Cross) (Elbow to Floorboard Elbow) Switch
46. Cross 75. LH Evaporator Expansion 102. Thru 110. Deleted Ñ
47. Gaseous Freon Suction Line Valve Line (Elbow to Floor- 111. Compressor
(Nacelle Skin Elbow to Elbow) board Elbow) 112. Line (Sight Glass -

48. Wing Skin 76. Floorboard Service Port to RH

49. Spier 77. Service Valve Evaporator)
50. ÜaseousFreon Suction Line 78. RH Evaporator Outlet Line 113. Latching Pressure Switch
(Elbow to Union) (Service Valve to RH 114. Thru 118. Deleted
51. Doubler Evaporator) 119. Temperature Sense Bulb
52. Seal 79. Sight Glass -

Service Port 120. Instrument Panel

53. Fuselage Skin 80. RH Evaporator 121. Pan
54. Nacelle Skin Expansion Valve Line 122. Grommet
55. Freon Liquid Injection Line (Floorboard Union to Sight 123. Temperature Control Relay
(Cross to Nacelle Skin Elbow) Glass Service Port) 124. Resistor
56. Freon Liquid Injection Line 81. LH Evaporator Outlet Line 125. Liquid Trap
(Nacelle Skin Elbow to Elbow) (Floorboard Elbow to LH 126. Cap
57. Freon Liquid Injection Line Evaporator) 127. Rod End
(Elbow to Union) 82. LH Evaporator Expansion 128. Nut
58. Gaseous Freon Suction Line Valve Line (Floorboard 129. Torque Link
(Union to Union) Elbow to LH Evaporator 130. Support Assembly
59. Freon Liquid Injection Line Expansion Valve) 131. Bushing
(Union to Union)
60. Gaseous Freon Suction Line
(Union to Manifold Elbow)

Change 11
 421 SERVICE MANUAL UTILITY AND jg-ggg
OPTIONAL SYSTEMS

f. Adjust belt tension in accordance with Removal Removal of Manifold Assembly (See figure 13-21.)
and Installation of Compressor Drive Belt Procedures.
g. Connect eleotrical wires.
a. Remove cabin seats, carpeting and flooring in
NOTE the area between F. S. 200 and 212. 50 on right hand
section of cabin.
When replacing a compressor having a 12 volt b. Discharge refrigerant system. Refer to Air
clutch assembly with a compressor having a Conditioning System Service/Parts Manual.
24 volt clutch, make sure resistors (119, fig- c. Disconnect wiring to solenoid (65) and low pres-
ure 13-37) are removed from the circuit. sure switch (64) and tag.
d. Disconnect suction and discharge plumbing and
h. Connect suction hose and discharge hose. cap off.
L Evacuate and charge system. Refer to Air Con- e. Remove four mounting bolts and remove mani-
ditioning System Service/Parts Manual. fold.
j. Leak check fittings. No leakage is allowed.
k. Install cowling- Installation of Manifold Assembly. (See figure
13-21. )
Removal and Installation of Compressor Drive Belt.
(See figure 13-21. ) a. Installation of the refrigerant manifold assembly
is the reversal of the removal procedure.
a. Remove and install drive belt as follows: b. Evacuate and charge system. Refer to Air Con-
1. Remove RH engine cowling. ditioning System Service/Parts Manual.
2. Cut safety wire from nuts (128) and screw nut c. Check for leaks with leak detector H-10 or
onto rod end (127) until belt can be removed. equivalent.
3. Remove belt from compressor pulley and engine d. Replace flooring, carpeting and seats in cabin.
drive pulley.
4. Install new belt and adjust nuts (128) on rod end Removal of Low Pressure Switch. (See figure
(127) to obtain proper tension. Belt tension to be 13-21.)
measured by loading center of belt with 25 pounds
tension pulling up and measuring 5 inch deflection,
. a. Remove cabin seats, carpeting and flooring in
with a straight edge across top belt between pulleys. the area between F. S. 200. 00 and F. S. 212. 50 on
5. Safety wire adjusting nuts (128) to each other. right section of cabin.

NOTE

Recheck belt tension after a 10 minute ground

run. After 2 to 5 flight hours, check belt for
stretching.

6. Replace right hand engine cowling.

Change 11
13-640 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

b. Discharge system in accordance with Air Con- g. Remove two motor support nuts and lock wash-
ditioning System Service/Parts Manual- ers. Pull motor away from scroll and motor support
c. Disconnect switch (64), wires and tag. ring,
d. Turn pressure switch CCW to remove. Cap off
hole.
Installation of Blower Motor. (See figure 13-21.)

Installation of Low Pressure Switch. (See figure

13-21. ) a. Place new motor in support ring, align mount-
ing studs and press motor in place.
a. Place small strip of teflon tape on pressure b. Replace motor mount lock washers and nuts and
switch threads, remove hole cap and install pressure tighten nuts.
switch (64) in manifold. c. Slide blower wheel on motor shaft until it stops.
Tighten set screw.
CAUTION
NOTE
Do not allow teflon tape to hand over threads
and enter system when torqued. Verify that the back side of the wheel does not
strike the motor mount studs.
b. Screw switch CW until it is tight.
c. Connect electrical wires on switch and charge d. Clean off both scroll mating surfaces and apply
the system as outlined in system charging proce- small bead of silicone rubber (RTV 102) on scroll
dures, mating surface.
d. Leak check at threads. If leak is observed, e. Install motor scroll assembly and align mount-
tighten pressure switch fitting until no leakage is ob- ing screw holes and install screws.
served. f. Place locknuts on mounting screws and tighten
e. Replace flooring, carpeting and cabin seats. in random pattern.
g. Connect motor electrical wiring and check motor
operation at both speeds.
Removal of Temperature Control Assembly. (See
figure 13-21. ) NOTE

a. Verify system mode switch is in off position. During motor operation listen for any exces-
b. Place copilot seat in full forward position with sive noises or rubbing,
back down.
c. Disconnect switch and heater wiring and tag. h. Turn motor off, install evaporator in accordance
d. Remove two mounting screws and locknuts and with the installation procedures.
left switch and heater assembly free.

NOTE Removal of Expansion Valve. (See figure 13-21. )

Temperature control assembly support brack-

et is bonded to the evaporator module shroud a. Verify system power switch OFF.
and normally does not require removaL b. Discharge system in accordance with the Air
Conditioning System Service/Parts Manual.
c. Remove expansion valve temperature sense bulb
Installation of Temperature Control Assembly. (See clamps (119) and remove bulb.
figure 13-21.)
CAUTION
a. Installation of the temperature control assembly
is the reversal of the removal procedure. Do not damage bulb or sense line during dis-
assembly.

Removal of Blower Motor. (See figure 13-21.) d. Disconnect blower motor (83), wiring and tag,
e. Remove five screws and locknuts for blower
seroll and remove motor-scroll assembly from
a. Verify system power switch OFF. module.
b. Remove evaporator in accordance with the re- f. Disconnect 1/4" line at valve inlet (87).
moval procedure. g. Loosen 1/2" jam nut on valve outlet (87) and un-
c. Disconnect motor wiring and tag, screw valve.
d. Remove five screws and locknuts from blower h. Remove O-ring and jam nut. Discard O-ring.
scroll (84).
e. Pull motor and front portion of scroll assembly Installation of Expansion Valve. (See figure 13-21. )
away from module (88).
f. Remove blower wheel setscrew and slide wheel
off motor shaft. a. Install jam nut and new O-ring (NAS-1595-8) on

Change 11
 MANUAL UTILITY AND 13-64E
421 SERVICE
OPTIONAL SYSTEMS

valve outlet fitting. CAUTION

b. Screw valve assembly into coil inlet fitting until
O-ring touches the inlet fitting. Do not allow teflon tape to hang over threads
c. Position valve to mate with inlet line and screw and enter system when torqued.
on inlet line fitting until finger tight,
d. Tighten jam nut while using back up wrench on b. Screw switch CW until it is tight.
valve body flat. c. Connect electrical wires on switch and charge
the system as outlined in system charging proce-
CAUTION dures.
d. Leak check at threads. If leak is observed,
Do not wrench on valve outlet fitting. Wrench tighten pressure switch fitting until no leakage is ob-
on valve body only. served.
e. Replace flooring, carpeting and cabin seats.
e. Tighten fitting on 1/4" inlet line.
f. Replace valve temperature sensing bulb (119) on
suction line using two straps. Removal of Blower Fan Blade. (See figure 13-21. )
NOTE
a. Verify system mode switch is in off position.
Locate bulb on bottom of horizontal section b. Remove access cover from top section of right
of suction line. Mounting straps must be hand nacelle.
tight, overtightening will crush bulb. Fail- c. For complete protection during fan blade remov-
ure to assure the above may result in ex- al, it is suggested that condenser motor ground lead
pansion valve hunting. be disconnected.
d. Remove cotter pin and retaining nut.
e. Remove two Allen Head set screws and loosen
g. Wrap suction line and sense bulb with refriger- fan blade on shaft.
ant, moisture proof, tape. Thickness to be 1/4" f. Loosen clamps securing electric motor and slide
minimum. motor inboard.
h. Clean blower scroll mating surface and apply g. Remove fan blade from shroud.
small bead of silicone rubber (RTV 102).
i. Remove motor-scroll assembly on module scroll
and align mounting holes. Installation of Blower Fan Blade. (See figure 13-21.)
j. Install five mounting screws and locknuts and
tighten at random.
k. Connect motor electrical wiring and checkout a. Install new fan blade on motor shaft with fan hub
motor operation at both speeds. Listen for exces- 1/8 inch from motor front face.
sive noise or rubbing. b. Tighten set screws retaining nut and install
1. Reposition seat back and seat, if required. cotter pin.
c. Move fan motor outboard until fan blade pro-
trudes 2/3 of its blade width into the shroud.
Removal of High Pressure Switch. (See figure
13-21. ) NOTE

a. Remove cabin seats, carpeting and flooring in Clearance between fan blade and inside diam-
the area between F. S. 200. 00 and F. S. 212. 50 on eter of shroud should be 3/16 inch min.
right hand section of cabin.
b. Discharge refrigerant system as outlined in sys- d. Tighten electric motor mounting straps.
tem discharge procedures. e. Connect motor ground lead,
c. Locate high pressure switch between lines (61 f. Install access cover.
and 62). g. Place system mode switch to air conditioning and
d. Disconnect switch (63), wires and tag. check blower assembly operation.
e. Turn pressure switch CCW to remove from re-
ducer (38). Cap off hole. WARNING

Take special care to keep fingers and debris

Installation of High Pressure Switch. (See figure from fan inlet.
13-21. )
h. Turn mode switch OFF.
a. Place small strip of teflon tape on pressure
switch threads, remove hole cap and install pressure
switch in reducer (38). Removal of Condenser Blower Motor. (See figure
13-21. )

a. Verify system mode switch in off position.

b. Remove access cover on top section of right

Change 11
13-64F UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

hand nacelle. CAUTION

c. Disconnect electrical wiring and tag.
d. Remove mounting clamps and slide motor (41) Care must be taken in removal and install-
inboard. ation of the liquid trap to prevent twisting
e. Remove cotter pin, retaining nut and blade set of the fittings which may cause cracks.
screws.
f. Slide fan blade off motor shaft.
g. Remove motor.
Installation of Liquid Trap, (See figure 13-21. )

Installation of Condenser Blower Motor. (See figure a. Position liquid trap in place with the outlet
13-21. ) (curved tube) forward.
b. Tighten tube fittings while holding the elbow fit-
a. Installation of the electric motor is the reversal tings to prevent twisting the fittings.
of the removal procedure.
NOTE
NOTE
Install liquid trap so that the body is within
Fan blade alignment and spacing must be per- 5 degrees of vertical. Insulate liquid trap
formed as outlined in fan blade removal and and elbow using P-2 (2 in. wide x 19 thick) .

replacement procedure. foam tape two layer wrap.

b. Perform electrical checkout of motor operation c. Evacuate and charge system. Refer to Air
Conditioning System Service/Parts Manual.
d. Leak check with H-10 leak detector. No leak-
Removal of Receiver-Dryer. (See figure 13-21.) age is allowed.
e. Install nacelle access cover,

a. Discharge refrigerant system. Refer to Air

Conditioning System Service/Parts Manual and re- Removal of Bypass Valve. (See figure 13-21. )
move access cover in top section of right hand na-
celle.
b. Remove inlet and outlet refrigerant plumbing and a. Discharge refrigerant system. Refer to Air
cap. Conditioning System Service/Parts Manual.
c. Loosen mounting straps and remove receiver- b. Remove access cover in top section of right hand
dryer (31). nacelle.
c. Disconnect valve inlet and outlet plumbing and
cap off.
Installation of Receiver-Dryer. (See figure 13-21. ) d. Remove valve (44).

Installation and Adjustment of Bypass Valve. (See

a. Installation of the receiver-dryer (31) is the re- 13-21. )
versal of the removal procedure.
figure

NOTE a. Installation of bypass valve (44) is the reversal

of the removal procedure.
The "1N" port of the receiver-dryer is con-
nected to the plumbing from the last conden- NOTE
ser outlet port.
The bypass valve is preset from the factory
b. Evacuate and recharge system. Refer to Air and should not be tampered with.
Conditioning System Service/Parts Manual.
b. Evacuate and charge the system. Refer to Air
c. Leak check with H-10 leak detector. No leakage
Conditioning System Service/Parts ManuaL
allowed.
d. Install access cover. c. Leak check valve plumbing. No leakage allowed.
d. Replace access cover.

Removal of Latching Pressure Switch. (See Figure

Removal of Liquid Trap. (See figure 13-21. ) .
13-21. )

a. Discharge refrigerant system. Refer to Air a. Discharge the system. Refer to Air Condition-
Conditioning System Service/Parts Manual. ing System Service/Parts Manual.
b. Remove RH nacelle air conditioning access cover. b. Remove air conditioner access cover in right
c. Disconnect fittings and remove liquid trap from nacelle.
system,

Change 11
 421 SERVICE MANUAL UTILITY AND 13--640
OPTIONAL SYSTEMS

c. Tag and disconnect wires. g. Fasten expansion valve temperature sense bulb
d. Disconnect lines and remove latching pressure (99) to the bottom run of line (96) at approximate 5
switch (113). to 7 o-clock position and as close to the evaporator
e. Cap lines. as possible. Insulate temperature sense bulbs and
lines by wrapping with P-2 foam tape.
h. Evacuate and charge system in accordance with
Installation of Latching Pressure Switch. (See figure Air Conditioning System Service/Parts Manual.
13-21. ) i. Perform operational check of system.
j. Install forward divider.
a. Installation of latching pressure switch is the k. Install pilot's seat in accordance with Section 3.
reversal of the removal procedures.
b. Evacuate and charge system in accordance with
Air Conditioning System Service/Parts Manual. Removal of Condensers. (See figure 13-21.)
c. Operational check in accordance with Operation-
al procedures. a. Remove access cover from top section of right
hand nacelle.
Removal of Evaporators. (See figure 13-21.) b. Discharge system
in accordance with Air Condi-
tioning System Service/Parts Manual.
c. Disconnect lines (26, 30, and 34) from con-
The removal procedures given pertain to the left hand denser units (29).
evaporator unit; however, the procedures are the d. Remove upper channel holding condensers in
same for the right hand evaporator. Where there is place and remove condensers.
a specific difference, reference will be made to the
individual evaporator unit.
Installation of Condensers. (See figure 13-21. )
a. Remove pilot's seat in accordance with Section 3.
b. Remove forward divider.
a. Install condensers by reversing the removal
NOTE procedures.
b. Evacuate and charge system in accordance with
On right hand evaporator remove control the Air Conditioning System Service/Parts ManuaL
panel (98), back cover (97) and disconnect
temperature control switch (93) in accord-
ance with Details J and K. Removal and Installation of Evaporator Condensate
Drain. (See figure 13-21. )
c. Discharge the refrigerant system in accordance
with the Air Conditioning System Service/Parts a. (See figure 1-2. ) Remove front spar access (77).
Manual. b. Remove hose connections from evaporator con-
d. Remove expansion valve temperature sense bulb densate drain (92).
clamps and remove bulb. c. Loosen screws attaching condensate drain to
e. Disconnect lines (81 and 82) from right hand front spar and remove condensate drain from bottom
evaporator, of aircraft.
f. Tag and disconnect electrical wiring. d. Install condensate drain by reversing the remov-
g. Remove bolts securing evaporator to floorboard, al procedures.
h. Disconnect drain tube from bottom of evaporator
unit. NOTE
i. Remove air duct from evaporator.
j. Remove evaporator from aircraft. After condensate drain has been installed in
place, use Sealant CES2602, Class III, Type
II to reseal drain hose in bottom of fuselage.
Installation of Evaporator. (See figure 13-21. )
Removal of Air Conditioning Plumbing. (See figure
The installation procedures given pertain to the left 13-21.)
hand evaporator unit; however, the procedures are
the same for the right hand evaporator unit. Where a. Remove all RH passenger seats, pilot and co-
there is a specific difference, reference will be pilot seats, and RH side of cabin carpeting.
made to the individual evaporator unti. b. (See figure 1-2.) Remove all necessary access
covers in RH floorboard area, RH engine cowling,
a. Place evaporator in mounting position. access cover from top section of RH nacelle, and
b. Connect air duct with clamp. lower flaps to gain access to air conditioning plumb-
c. Connect drain tube to bottom of evaporator unit. ing.
d. Secure evaporator to floorboard with bolts. c. Discharge system in accordance with the Air
e. Connect electrical wiring. Conditioning Systems Service/Parts Manual.
f. Connect lines (81 and 82) to evaporator.

Change 11
13-64H UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

d. Refer to figure and remove lines as required. The purpose of the receiver-dryer is to store liquid
refrigerant and filter out any moisture in the Freon
during the system operation cycle.

Installation of Air Conditioning Plumbing. (See fig- The low pressure switch is utilized in the high pres-
ure 13-21.) sure line and provides system protection in the event
of loss of Freon or operation during extremely low
a. Installation of the air conditioning plumbing is outside ambient temperature. The switch senses
the reversal of the removal procedures. Freon low pressure and opens the electrical circuit
and disables the manifold and valve assembly which
NOTE disengages the compressor.
The manifold and valve assembly is electrically op-
Lubricate all fitting threads with Capella "E" pres-
lubricant on installation.
erated and contains a solenoid by-pass valve,
sure relief valve and filter. The manifold and valve
assembly is mounted in the hydraulic line from the
engine driven pump to the hydraulic reservoir. The
b. Reseal fuselage skin (53) in accordance with re_
manifold and valve assembly is controlled by the
sealing procedures in Section 16 if lines (58 and 59) temperature control on the air conditioning panel.
have been removed or replaced. When cooling is selected the manifold and valve as-
c. Evacuate and charge the refrigerant system in sembly is energized and allows the hydraulic fluid
accordance with Air Conditioning Systems Service/ under pressure to operate the motor on trie compres-
Parts Manual. sor. After the temperature demand is reached, the
d. Check for leaks with leak detector H-10 or manifold and valve assembly will de-energize and
equivalent. compressor rotation ceases. A pressure switch is
e. Perform operational check of air conditioning installed in the hydraulic pressure line at the valve
system. assembly. The switch will actuate and illuminate
the A COND HYD light on the annunciator panel with
the air conditioning system ON and right engine run-
AIR CONDITIONING SYSTEM. (See figure 13-22. ning. The switch will deactivate and the light will go
)
(421B0501 and On. ) out when hydraulic fluid pressure falls below 400 psi.
A conver is provided for access to the right wing
locker area, for servicing and maintenance of com-
The air conditioning system is comprised of three
major installations; right-hand ponents,
engine compartment,
right-hand wing locker area, and the fuselage cabin In the cockpit area are mounted two evaporator mod-
area. The air conditioning system utilizes the vapor ules, the control panel and temperature control as-
cycle concept and R-12 Freon as the refrigerant. The sembly, the condensate drain valve, the air distribu-
system will deliver 14, 500 BTU of cooling with an tion ducts, the sight glass and charging ports.
100°
OAT of Fahrenheit.
The evaporator modules each contain an evaporator
The right engine compartment installation consists of coil, an expansion valve, a shroud, and a scroll and
a hydraulic pump mounted on the accessory pad of the blower assembly. The evaporator modules are locat-
engine with necessary lines and fittings routing to the ed aft in the cabin under the baggage shelf. Cabin air
wing locker. Is drawn through each evaporator coil and refriger-
ated air is routed into the distribution duct and cabin
The right wing locker houses the condensers, the cockpit area.
compressor and its hydraulic drive motor, receiver-
dryer, hydraulic manifold and valve assembly, con- The blower motor is manually controlled and has dual
denser blower motor and fan, hydraulic fluid reser- speed which may be used to provide cockpit cabin
voir and drain valve, associated wing locker wiring ventilation or air recirculation when the air condition-
and plumbing, In flight cooling is provided by air er is turned off or when the cabin heater is operating.
drawn through the inlet scoop on the outboard side of
the engine nacelle being passed over the condensers A temperature control assembly is mounted on the
and expelled through the nacelle outlet on the inboard left-hand evaporator module. Whenever the surround-
side of the nacelle. The condenser blower is wired ing air approaches the preselected valve, the control
through the landing gear safety switch and normally assembly will open the manifold and valve assembly,
operates during ground operation only; however, dur- shutting off hydraulic fluid to the compressor motor,
ing flight in the event condenser temperature becomes
excessively high, causing the output pressure temper- The condensate drain valve is located under the cabin
ature to increase, the fan will be turned on by the floor and automatically drains the condensate from
condenser high temperature switch, and remain on the evaporator modules during ground operation and
until temperature of the condensers are reduced, in flight. The valve provides a two stage orifice
lowering the output pressure temperature. When which permits maximum drainage at ground opera-
the output pressure temperature is reduced the con- tion and limited drainage during cabin pressurized
denser high temperature switch will turn the fan off. flight. The second stage orifice assures no signifi-
cant loss of cabin pressurization.
 421 SERVICE MANUAL UTILITY AND
13~Û$l
OPTIONAL SYSTEMS

The control panel, located on the right-hand side of Whenever the system mode switch is selected to air
the crew compartment, consists of a temperature conditioning mode, the manifold and valve assembly
selector rheostat, a mode switch and blower speed is closed and hydraulic fluid is supplied to the com-
selector switch. pressor motor which drives the compressor. The
compressor starts delivering a high pressure and
Special service fittings for diagnosis and charging temperature Freon gas to the condensers. This gas
the Freon system are installed in the liquid line to is routed through the condensers where cool air from
the right-hand evaporator module expansion valve the fan assembly removes heat from the gas and con-
and in the suction line in the sight gage. These fit- denses it into a high pressure liquid.
tings contain a valve to prevent loss of Freon during
servicing. Service fittings are also located on the The liquid then enters the receiver-dryer where it is
aft face of the compressor. filtered, dried and gas is separated from the liquid.
From the receiver-dryer, the liquid flows to each
System operation in the air conditioning mode, re- evaporator module expansion valve. The expansion
quires the right engine to be operating at a minimum valve throttles the liquid into a sub-cooled gas before
tachometer reading of 950 RPM to drive the Freon it enters the evaporator coil. Air from the cabin is
compressor at its designed ground capacity pulled across the evaporator coil and is cooled by the
sub-cooled Freon gas. The refrigerated air is then
routed into the air distribution ducts and exhausted
into the cabin and cockpit.

Change 9
13-64J UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

STATIONARY
PANEL LOW PRESSURE
SWITCH
PILOT'S RE CEIVER-DRYER
OUTLET FILTER
REGISTER HYDRAULIC PUMP
EVAPORATOR ...
:9 ÈDRAULIC MOTOR
EXPANSION VALVE fi
MANIFOLD-VALVE
AND BLOWER ASSEMBLY .-

HIGH PRESSURE
LINE

CONDENSER
COOLING FAN

HIGH
TEMPERATURE
SWITCH

CONDENSERS

REFRIGERANT
LINES

PASSENGER
OVERHEAD
DUCTING
CODE

COLD AIR 52981001

51982007

Figure 13-22. Air Conditioning Distribution Schematic

Change 9
 ENGINE DRIVEN HYDRAULIC PUMP
HYDRAULIC PUMP CASE DRAIN
FILLER CAP

CONDENSER COOLING
ROA LDETENT
OVER

FLUID-RETURCNOLND

NSER FAN

ENGINE FLUID SUPPLY LINE

HYDRAULIC
COMPARTMENT
DE-AERIATION FLUID RESERVOIR
BAFFLE

PUMP HIGH PRESSURE DISCHARGE LINE

RELIEF AND INACTIVE

HYDRAULIC
MODE RETURN FLOW
FLUID COOLER
CONDENSERS
FUNCTION LIGHT
HYDRAULIC MOTOR
PRESSURE SWITCH
AIR CONDITIONER
COMPRESSOR

-
PRESSURE CONTROL gg
SOLENOID VALVE

o 2 REFRIGERANT
HYDRAULIC RECEIVER-DRYER
MANIFOLD
ASSEMBLY
-t
HYDRAULIC FLUID FILTER

CONDENSER COOLING C
-I
AIR FLOW EXIT ItEFRIGERANT LINES TO PASSENGER CABIN
ELISES EALVE
R AFT NACELLE BOUNDARY

mo
13-64L UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYsTEMS

Troubleshooting Air Conditioner Hydiaulic System.

TROUBLE PROBABLE CAUSE CORRECTION

CABIN PRESSURE LIGHT Defective or misadjusted Check pressure switch and

OUT WITH SYSTEM IN pressure switch. associated components. Re-
OPERATION place or adjust as necessary.
Refer to Air Conditioning
System Service/Parts ManuaL

Defective pressure light. Replace light.

HYDRAULIC MOTOR Defective solenoid. Check solenoid for 24 VDC.

FAILS TO TURN WHEN Replace if necessary.
AIR CONDITIONER IS
ACTIVATED Defective pressure relief Test manifold valve and ad-
valve. just relief valve as necessary.
Refer to Air Conditioning
System Service/Parts Manual.

Clogged filter. Determine reason for con-

tamination.

Air conditioner compressor Check compressor for proper

over-serviced. freon charge. Refer to Air
Conditioning System Service/
Parts Manual

Hydraulic pump inoperative. Check drive spline for pos-

sible shear and/or that
spacer is installed in the
internal bore of the
splined
engine accessory drive shaft.

Defective pump. Replace if

necessary.

Incorrect hydraulic pump.

Check Parts Catalog for cor-
rect pump part number.

Hydraulic motor defective. Replace hydraulic motor.

Defective manifold. Pressure test manifold. Re-

place if necessary. Refer to
Air Conditioning System
Service/Parts Manual.

I
Hydraulic System Operational Test. 5. Connect 28 VDC power source to aircraft.
6. Adjust hydraulic test cart to 3 gpm.
a. Conduct operational test using a hydraulic test 7. Turn air conditioner to COOL mode.
cart as follows: ,
8. Check hydraulic system for leaks.
1. Ensure that all air conditioning system fittings,
clamps and lines are tight. NOTE
2. Service air conditioner hydraulic reservoir with
2. 75 quarts of MIL-H-5606 hydraulic fluid (red). Use caution in the area of the condenser fan.
3. Ensure air conditioner compressor is serviced
with proper amount of Freon. Refer to Air Condi·- 9. Increase hydraulic pressure to 1250 psi and
tioning System Service/Parts Manual. observe that air conditioner panel light is ON and
4. Connect hydraulic test cart to inlet and outlet hydraulic motor is rotating.
lines at the engine driven hydraulic pump.

Change 9
 421 SERVICE MANUAL UTILITY AND 13-64M
OPTIONAL SYSTEMS

10. Increase hydraulic flow to 6 gpm and main- CAUTION

taining 1250 psi turn air conditioner mode switch
OFF, observe theair conditioner panel light OUT. Hydraulic system must be serviced and sys-
11. Turn air conditioner mode switch to COOL tem complete before engine operation or pump
and observe panel light ON and hydraulic motor ro- should be removed from pad and pad cover in-
tation, stalled. Pump inlet must be primed before
12. Operate air conditioner in this configuration cranking engine.
for a period of not less than ten minutes. Observe
for leaks and proper air conditioning operation. c. Check system operation and for hydraulic fluid
13. Remove hydraulic test cart, reconnect inlet leakage.
and outlet lines to hydraulic pump and check hydrau- d. Install engine cowling.
lic reservoir fluid level
b. Conduct operational test using engine operation
as follows:
1. Ensure that all air conditioning system fittings,
clamps and lines are tight.
2. Service air conditioner hydraulic reservoir with
2.75 quarts of MIL-H-5606 hydraulic fluid (red). Removal of Hydraulie Motor. (See figure 13-23.)

CAUTION a. Remove RH wing nacelle air conditioning access

cover.
Hydraulic system must be complete and ser- b. Place container under reservoir drain.
viced before starting RH engine and pump c. Cut safety wire; open drain valve (8) and drain
inlet must be primed, fluid from the reservoir.
d. Disconnect line (25) from manifold and valve
3. Ensure conditioner compressor
air is serviced assembly (9) and firewall fitting. Cap all openings.
with the proper amount of Freon. Refer to Air Con- e. Disconnect line (12) and hose (24) from hydraulic
ditioning Service/Parts Manual, motor (22). Cap all openings.
4. Start RH engine and operate at approximately f. Remove nuts, washers and bolts, securing hy-
1000 rpm and check for hydraulic fluid leaks. draulic motor (22) to adapter (89).
5. Select COOL mode on the air conditioner switch g. Pull hydraulic motor (22) outboard and remove
and observe the air conditioner panel light is ON and motor from compartment.
hydraulic motor rotation.
6. Increase rpm to 1600 rpm. NOTE
7. Turn air conditioner mode switch to OFF posi-
tion and observe that air conditioner panel light is Coupling half may be connected to motor
OFF. spline, when motor is removed from the
8. Turn air conditioner mode switch to COOL and adapter. If coupling half is attached to
observe the air conditioner panel light is ON and spline, remove.
hydraulic motor rotating.
9. Operate engine at various rpm's while checking h. If further disassembly of hydraulic motor (22) is
air conditioner hydraulic operation and air condition- required, refer to Air Conditioning System Service/
er operation for a period of not less than 10 minutes. Parts Manual.
10. Shut down engine and recheck reservoir fluid
leveL
Installation of Hydraulic Motor. (See figure 13-23. )

Removal of Hydraulic Pump. (See figure 13-23. ) NOTE

a. Remove RH engine cowling. Before installing hydraulic motor, lubricate

b. Remove clamps from shroud (30) and remove spline of motor with Dow Corning No. 4
adapter (28). Compound.
c. Disconnect hoses (2 and 26) and drain lines (27
and 101) from hydraulic pump (1) and cap all openings. For ease of installation, assemble coupling
d. Remove nuts and remove hydraulic pump (1) from half on motor spline before installing motor
engine. in adapter,

a. Insure spacer (90) is properly positioned in the

Installation of Hydraulic Pump. (See figure 13-23.) opposite coupling half inside the adapter (89), before
installing the hydraulic motor (22).
a. Installation of the hydraulic pump (1) is the re- b. Slide the hydraulic motor (22) with couplíng half
versal of the removal procedures. attached to spline into the adapter. Insure that the
b. Fill reservoir (4) with hydraulic fluid. two coupling halves and spacer are engaged properly.
c. Secure the hydraulic motor (22) to adapter (89)
with bolts, washers and nuts.
d. Connection of lines and hose is the reversal of

Change 9
13-64N UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

the removal procedures. Removal of Hydraulic Reservoir. (See figure 13-23. )

e. Close drain valve (8) and safety wire.
f. Fill reservoir (4) with hydraulic fluid. a. Remove RH nacelle air conditioning access cover.
g. Check system for operation and leakage. b. Place container under reservoir drain.
h. Install RH nacelle air conditioning access cover. c. Cut safety wire; open drain valve (8) and drain
hydraulic fluid from reservoir.
d. Disconnect vent line (5), line (7), hose (6), line
Removal of Compressor. (See figure 13-23.) (3) and drain line (30) from reservoir (4). Remove
fittings and cap all openings.
a. Discharge refrigerant system. Refer to Air e. Remove nuts, washers and bolts, securing mani-
Conditioning System Service/Parts Manual. fold and valve assembly (9) to reservoir (4).
b. Remove RH wing nacelle air conditioning access f. Remove bolts and washers from reservoir (4);
cover. remove reservoir (4).
c. Disconnect lines (41 and 50) from compressor
(53). Cap all openings.
d. Disconnect line (39) from receiver-dryer and low Installation of Hydraulic Reservoir. (See figure
pressure switch (51) if necessary. Cap all openings. 13-23. )
e. Loosen bolts, securing adapter (89) to compres-
sor (53). a. Installation of reservoir (4) is the reversal of
f. Remove nuts, washers and mounting bolts, se- the removal procedures.
curing compressor (53) to brackets (52). Slide com- b. Close drain valve (8) and safety wire.
pressor (53) inboard and lift it out of the compart- c. Fill reservoir (4) with hydraulic fluid.
ment. d. Check system operation.
g. Remove screws, securing baffle to compressor
(53).
h. If further disassembly of compressor (53) is re- Removal of Manifold and Valve Assembly. (See fig-
quired refer to Air Conditioning System Service/ ure13-23. )
Parts Manual.
a. Verify electrical power to air conditioning sys-
tem is turned OFF.
Installation of Compressor. (See figure 13-23. ) b. Remove RH nacelle air conditioning access cover.
c. Place container under reservoir drain,
a. Drain all oil from the compressor (53) in accord- d. Cut safety wire; open drain valve (8) and drain
ance with Air Conditioning System Service/Parts hydraulic fluid from reservoir (4).
Manual. e. Identify electrical wiring and disconnect.
b. Refill the compressor with 4 ounces of Suniso f. Disconnect lines (12 and 25) and tee (13) from
No. 5 or Texaco Capella E Grade, 500 viscosity oil manifold and valve assembly (9). Cap all openings.
or equivalent. g. Remove nuts, washers and bolts; remove mani-
fold and valve assembly (9).
NOTE

Special care shall be taken to assure that Installation of Manifold and Valve Assembly. (See
the system is not over-charged with oil, figure 13-23. )
since an over-charge of oil in the system
will decrease system performance. a. Installation of manifold and valve assembly (9) is
the reversal of the
removal procedures.
All openings in compressor shall be capped b. Close drain valve (8) and safety wire.
off to assure that oil in the compressor does c. Fill reservoir with hydraulic fluid.
not drain out during installation· d. Check system operation.

c. Secure baffle to compressor (53) with screws,

before installation. Removal of Condenser Blower Motor. (See figure
d. Position compressor (53) in the compartment. 13-23. )
Slide the compressor (53) into the adapter (89). In-
sure compressor engages properly in the adapter. a. Verify electrical power to air conditioning sys-
e. Secure compressor (53) to brackets (52) with tem is turned OFF.
bolts, washer and nuts. b. Remove RH nacelle air conditioning access cover.
f. Torque adapter bolts to 125 inch-pounds +0, -10. c. Disconnect electrical wiring and tag.
g. Connect lines (41-and 50) to the compressor (53). d. Remove mounting clamps (35) and slide blower
h. If line (39) between receiver-dryer (38) and low motor (36) inboard and remove motor.
pressure switch was disconnected, reconnect line. e. If removal of fan blade is required, refer to
i. Evacuate and charge system. Refer to Air Con- Removal and Installation of Fan Blade procedures.
ditioning System Service/Parts Manual.
j. Leak check system.
k. Install RH nacelle air conditioning access cover.

Change 9
 421 SERVICE MANUAL UTILITY AND 13-64NA/13-64NB
OPTIONAL SYSTEMS

A DF N

P H G

Detail
51143052
A51144013

1. Pump (Hyd. ) 10. Line 19. Clip

2. Hose-Supply 11. Pressure Switch (Hyd. ) 20. Cooling Coil
3. Line-Supply 12. Line 21. Grommet
4. Reservoir (Hyd. ) 13. Tee 22. Motor (Hyd. )
5. Vent Line 14. Bracket (Lower) 23. Elbow
6. Hose 15. Spacer 24. Hose
7. Line 16. Bracket 25. Line
8. Drain Valve 17. Retainer 26. Hose
9. Manifold and Valve Assembly 18. Spring 27. Drain Line

Figure 13-23. Air Conditioning System (Sheet 1 of 5)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-640
OPTIONAL SYSTEMS

102

100
Detail B
421B0501 TO 421BO823 Detail (
421B0823 AND ON

Detan D

B51144014
C51141107
D51141099

Figure 13-23. Air Conditioning System (Sheet 2)

Change 11
13-64P UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

INSURE THAT THESE HOSES

35
30
343

29
30
28
29

28
Detali E
Detau E 421BO823 AND ON

421BO501 TO 421B0823
41 42
4) 43 44
39

Detaii F E14143045
E51143064
Fl4144012

28. Adapter 37. Mount 45. Condensers

29. Clamp 38. Receiver-Dryer 46. Line
30. Shroud 39. Line 47. Line
31. Adapter 40. Line 48. Line
32. Adapter 41. Line 49. Line
33. Hose 42. Line 50. Line
34. Clamp 43. High Temperature Switch 51. Low Pressure Switch
35. Clamp 44. Line 52. Bracket
36. Blower Motor 53. Compressor

Figure 13-23. Air Conditioning System (Sheet 3)

Change 11
 421 SERVICE MANUAL UTILITY AND 13 -64
Q
OPTIONAL SYSTEMS

61
80
62

Detail

80

79 LH EVAPORATOR

RH EVAPORATOR H
Detail
78 ONLY G51144010
H54143015
Detail J Ji4141028

54. Line 65. Line 76. Expansion Valve

55. Line 66. Line 77. Temperature Control Bracket
56. Service Body 67. Line 78. Heat Temperature Control
57. Valve Core 68. Line 79. Temperature Control Switch
58. Cap 69. Line 80. Condensate Drain Line
59. Service Valve 70. Line 81. Temperature Sense Bulb
60. Line 71. Line 82. Motor
61. Line 72. LH Evaporator 83. Blower Housing
62. Seal Fitting 73. Line 84. Wheel (Fan)
63. Line 74. Line 85. Set Screw
64. Line 75. RH Evaporator

Figure 13-23. Air Conditioning System (Sheet 4)

Change 11
13-64R UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

90 93
92

Detail L

Detail

Kl4144013 Detaii N
L52143027 RH EVAPORATOR
M52143027 ONLY
N54143009 Detail
P14141029

36. Coupling Half 91. Nut 95. Support 99. Evaporator Cover
37. Washer 92. Coupling Half 96. Clamp 100. Gasket
38. Snap Ring 93. Baffle 97. Drain Tube 101. Drain Line
39. Adapter 94. Air Seal 98. Condensate Drain Valve 102. Drain Line
30. Spacer

Figure 13-23. Air Conditioning System (Sheet 5)

Change 11
 421 SERVICE MANUAL UTILITY AND
13-848
OPTIONAL SYSTEMS

Installation of Condenser Blower Motor. (See figure c. Disconnect lines (41, 42 and 44) from condensers
13-23. ) (45). Cap all lines and openings.
d. Remove retainers (17), springs (18) and washers
a. Installation of the blower motor (36) is the rever- securing cooling coil (20) to condensers (45).
sal of the removal procedures. e. Remove air seal securing condensers (45) and
remove condensers.
NOTE

Fan blade alignment and spacing must be per- Installation of Condensers. (See figure 13-23.)
formed as outlined in the fan blade removal
and installation procedures. a. Installation of the condensers (45) is the reversal
of the removal procedures.
b. Evacuate and charge the refrigerant system.
Removal of Blower Fan Blade. (See figure 13-23. ) Refer to Air Conditioning Systems Service/Parts
Manual.
a. Verify system mode switch is in the OFF posi- c. Leak check all fittings. No leakage is allowed.
tion.
b. Remove RH nacelle air conditioning access cover.
c. For complete protection during fan blade remov- Removal of Receiver-Dryer. (See figure 13-23.)
al, disconnect and isolate condenser blower motor
ground lead. a. Discharge refrigerant system. Refer to Air
d. Loosen clamps, securing electric motor and Conditioning System Service/Parts Manual.
slide motor inboard. b. Remove RH wing nacelle air conditioning access
e. Remove cotter pin and retaining nut. cover.
f. Remove two allen head set screws and loosen fan c. Disconnect lines (39 and 42) at receiver-dryer
blade on shaft. (38). Cap all lines and openings.
g. Remove fan blade from shroud. d. Loosen mounting clamp and remove receiver-
dryer (38).

Installation of Blower Fan Blade. (See figure 13-

23.) Installation of Receiver-Dryer. (See figure 13-23. )

a. Install fan blade on the motor shaft with fan hub a. Installation of receiver-dryer (38) is the rever-
1/8 inch from motor front face. sal of the removal procedures.
b. Tighten set screws, retaining nut; install cotter
pin. NOTE
c. Move fan motor outboard until fan blade pro-
trudes 2/3 of its blade width into the shroud. The IN port of the receiver-dryer is connect-
ed to the plumbing from the condenser.

CAUTION b. Evacuate and charge system. Refer to Air Con-

ditioning System Service/Parts Manual.
Make sure there is sufficient clearance be- c. Leak check with H-10 leak detector. No leakage
tween the fan blade and inside diameter of allowed.
shroud. d. Install access panel.

d. Tighten blower motor mounting clamps (35).

e. Connect motor ground lead; if disconnected. Removal of Low Pressure Switch. (See figure 13-
f. Apply electrical power to system; position air 23. )
conditioning switch to COOL and check blower opera-
tion, a. Discharge refrigerant system. Refer to Air
Conditioning System/Parts Manual.
CAUTION b. Remove RH wing nacelle air conditioning access
cover.
Take special care to keep fingers and debris c. Locate low pressure switch (51) between lines
from fan inlet. (39 and 40).
d. Disconnect and tag electrical wires to low pres-
g. Turn switch OFF. sure switch (51).
h. Install access cover. e. Turn low pressure switch (51) CCW to remove
from tee. Cap off hole.

Removal of Condensers. (See figure 13-23. )

Installation of Low Pressure Switch. (See figure
a. Remove RH nacelle air conditioning access cover. 13-23. )
b. Discharge system in accordance with Air Condi-
tioning System Service/Parts Manual. a. Place small strip of Teflon tape on low pressure

Change 9
 13-64T UTILITY 421 SERVICE MANUAL
ANo
OPTIONAL SYSTEMS

switch threads, remove hole cap and install low pres- Installation of Evaporator Blower Motor. (See figure
sure switch (51) in tee. 13-23. )

CAUTION a. Place motor in support ring, align mounting

studs and press motor in place.
Do not allow Teflon tape toextend over b. Replace motor mount lock washers and nuts and
threads and enter system when torqued. tighten nuts.
c. Slide wheel (84) on motor shaft until it stops.
b. Screw low pressure switch (51) in tee until it is Tighten set screw (85) -

tight.
c. Connect electrical wires, evacuate and charge NOTE
the system. Refer to Air Conditioning System
Service/Parts Manual. Verify that the back side of the wheel does
d. Leak check at threads. If leak is observed, not strike the motor mount studs.
tighten low pressure switch (51) fitting until no leak-
age is observed. d. Clean off both scroll mating surfaces and apply
e. Install access cover. small bead of silicone rubber (RTV102) on scroll mat-
ing surface.
e. Install motor scroll assembly and align mounting
Removal of High Temperature Switch. (See figure
13-23. screw holes and install screws.
)
f. Place lock nuts on mounting screws and tighten in
a. Remove RH wing nacelle access random pattern.
air conditioning
cover. g. Connect motor electrical wiring and check motor
operation at both speeds.
b. Verify electrical power to system is turned OFF.
c. Disconnect and tag electrical wires to switch.
NOTE
d. Remove nut and bolt and remove high tempera-
ture switch (43) from line (44).
listen for any exces-
During motor operation
-Installation sive noise or rubbing.
of High Temperature Switch. (See figure
13-23. ) h. Turn motor off, install evaporator in accordance
with the Installation of Evaporator procedures.
a. Installation of high temperature switch (43) is the
reverse of the removal procedures.
13-23.
Removal of Expansion Valve. (See figure )

Removal of Temperature Control Assembly. (See The removal procedures are the same for the LH or
figure 13-23. ) RH evaporator expansion valve except for the valve
being located in a different place on the evaporator.
a. Verify electrical power to system is turned OFF.
b. Remove baggage compartment floorboards. a. Verify system power switch is OFF.
c. Disconnect electrical wiring and tag. b. Remove evaporator in accordance with the Re-
d. Remove mounting screws and nuts and lift switch moval of Evaporator Procedures.
and heater assembly free. c. Disconnect blower motor (82) , wiring and tag.
d. Remove screws and lock nuts from module hous-
Installation of Temperature Control Assembly. (See ing and remove motor housing assembly from evapo-
figure 13-23. ) rator module.
e. Disconnect 1/4 inch inlet line (73) from expansion
a. Installation of the temperature control assembly valve.
is the reversal of the removal procedures. f. Loosen jamb nut on valve (76) and unscrew valve.

Removal of Evaporator Blower Motor. (See figure CAUTION

13-23. )
While loosening jamb nut on valve use back-
a. Verify electrical power to system is turned OFF. up wrench on evaporator boss.
b. Remove evaporator in accordance with the Re-
moval of Evaporator procedures. g. Remove O-ring and jamb nut. Discard O-ring.
c. Disconnect motor (82) wiring and tag.
d. Remove screws and locknuts from blower housing Installation of Expansion Valve. (See figure 13-23. )
(83).
e. Pull motor and front portion of scroll assembly The installation procedures are the samefor the LH
away from evaporator module (72). or RH evaporator expansion valve except for the valve
f. Renove blower wheel set screw (85) and slide being located in a different place on the evaporator.
wheel (84) off motor shaft.
g. Remove two motor support nuts and lock washers, a. Install jamb nut and new O-ring (NAS-1595-8) on
Pull motor away from scroll and motor support ring, the valve outlet fitting.

Change 9
 421 SERVICE MANUAL UTILITY AND 13-64U
OPTIONAL SYSTEMS

b. Screw valve assembly into coil inlet fitting until h. Evacuate and charge the refrigerant system.
O-ring touches the inlet fitting. Refer to Air Conditioning Systems Service/Parts
c. Position valve to mate with inlet line and screw Manual.
on inlet line fitting until finger tight. i. Perform operational check of system.
d. Tighten jamb nut while using back-up wrench on j. Install baggage shelf.
evaporator boss. k. Install carpets and seats.

CAUTION Removal and Installation of Evaporator Condensate

Drain. (See figure 13-23. )
Do not use wrench on valve outlet fitting.
a. (See figure 1-3. ) Remove floorboards necessary
e. Tighten fitting on 1/4 inch inlet line (73). to gain access.
f. Clean motor housing and module housing mating b. Remove hose connections from evaporator con-
surfaces and apply small bead of silicone rubber densate tank (98).
(RTV102). c. Loosen screws attaching condensate drain to
g. Install motor housing assembly to module hous- front spar and remove condensate drain from bottom
ing and align mounting holes. of aircraft.
h. Install mounting screws and lock nuts and tighten d. Install condensate drain by reversing the remov-
at random. al procedures.
i. Connect motor electrical wiring and checkout NOTE
motor operation at both speeds. Listen for excessive
noise or rubbing. After condensate drain has been installed in
j. Install evaporator in accordance with the Installa- place, use Sealant CES2602, Class IH, Type
tion of Evaporator Procedures. II to reseal drain hose in bottom of fuselage.

Removal of Evaporators. (See figure 13-23. ) Removal of Air Conditioning Plumbing. (See figure
13-23. )
The removal procedures given pertaín to the LH
evaporator unit; however, the procedures are the a. Remove all RH passenger seats, pilot and copilot
same for the RH evaporator. Where there is a seats, RH side of cabin carpeting.
specific difference, reference will be made to the b. (See figure 1-3. ) Remove all necessary access
individual evaporator unit. covers in RH floorboard area, RH engine cowling,
RH nacelle air conditioning access cover and lower
a. Remove seats and carpet. flaps to gain access to plumbing in the wing.
b. Remove aft baggage compartment cover. c. Discharge system. Refer to Air Conditioning
c. Discharge the refrigerant system. Refer to Air Systems Service/Parts Manual.
Conditioning Systems Service/Parts Manual. d. Cut safety wire and open drain valve (8) and
d. Remove expansion valve temperature sense bulb drain hydraulic fluid from reservoir.
clamps and remove bulb· NOTE
e. Disconnect lines from evaporator.
f. Tag and disconnect electrical wiring. Step d. applies only if hydraulic fluid plumb-
g. Remove bolts securing evaporator, ing of the air conditioning system is disturbed.
h. Disconnect drain tube from bottom of evaporator 13-23 for removal
e. Refer to figure of air condi-
unit.
tioning plumbing.
i. Remove air duct from evaporator.
NOTE
j. Remove evaporator from aircraft.
Installation of Evaporators. (See figure 13-23. ) All lines and openings shall be capped.

The installation procedures given pertain to the LH Installation of Air Conditioning Plumbing. (See fig-
evaporator unit; however, the procedures are the ure 13-23. )
same for the RH evaporator unit. Where there is
a specific difference, reference will be made to the a. Installation of the air conditioning plumbing is
individual evaporator unit. the reverse of the removal procedures.
b. Install lock-o-seals (63 and 64) on pressure side
a. Placeevaporator in mounting position. of fuselage if lines (65 and 70) have been removed.
b. Connect air duct with clamp· c. Reseal seal fitting (62) in accordance with
c. Connect drain tube to bottom of evaporator unit· sealing procedures in Section 16. If lines (60 and 61)
d. Secure evaporator with bolts. have been removed and replaced.
e. Connect electrical wiring. d. Evacuate and charge the refrigerant system.
f. Connect lines to evaporator. Refer to Air Conditioning Systems Service/Parts
g. Fasten expansion valve temperature sense bulb Manual.
(75) to the bottom run of line at the approximate 5 to e. Check for leaks with leak detector H-10 or
7 o'clock position and as close to the evaporator as equivalent.
possible. Insulate temperature sense bulbs and f. Perform an operational check of the air condition-
lines by wrapping with P-2 foam tape. ing system.

Change 9
13-64V UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

FIRE EXTINGUISHER. (See figure 13-28.) RELIEF TUBE. (See figure 13-29.)

The Fire Extinguisher mounted on the floor, forward The relief tube is located behind the compartment
of the copilot's seat contains a pressurized Dry door on the upper forward right-hand side of the
Chemical Charge. The fire extinguisher may be toilet. On aircraft 421B0001 and On the relief tube
used on combustible, liquid, or electrical fires. may be installed behind the right-hand upholstery
The dry charge is non-toxic and non-corrosive. panel at F. S. 238. 13. The relief tube should be
Residue left after use may be wiped off with a damp cleaned on each post flight with a commercial dis-
cloth or picked up with a vacuum source. The fire infectant.
extinguisher may be recharged by most Fire Equip-
ment Dealers.

5
8

1. Seat Support 3. Bracket 5. Nut

2. Fire Extinguisher 4. Screw 6. Floorboard

Figure 13-28. Fire Extinguisher Installation

Change 9
 421 SERVICE MANUAL UTILITY AND 13·-65
OPTIONAL SYSTEMS

10

45

6
3 12

4
5

1. Toilet Assembly 5. Bracket 9. Adapter

2. Tissue Holder 6. Hose 10. Cover
3. Compartment Door 7. Grommet 11. Line
4. Horn 8. Toilet Lid 12. Clamp

Figure 13-29. Relief Tube Installation

Change 7
13-86 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

PROPELLER DEICE SYSTEM, force removes ice.the The cycle timer used on the
deicing system heats the propeller deicer from 28
The propeller deice system is the electrothermal type to 40 seconds. The deicer outer elements cycle on
system. It consists of the_following items: propeller the right propeller element from 28 to 40 seconds,then
blade dei.cers bonded to the propeller blades. slip ring on the inner elements. It then cycles to the left pro-
assembly mounted to the engine crankshaft, brush peller outer elements from 28 to 40 seconds then to
holder assembly mounted to the engine crankcase, a the left inner elements. It then returns to the right
repeat cycle timer, ammeter mounted in the instru- outer elements on the right propeller and continues
ment panel, a switch, and a circuit breaker. The cycling action. The cycling is done in order to main-
deicing is accomplished by raising the temperature of tain a balance between the left and right propellers
the deice interface to a point, at which, centrifugal and reduce power drain on the electrical system.

Troubleshooting the Propeller Deice System.

TROUBLE PROBABLE CAUSE CORRECTION

NO HEAT AT PROPELLER Circuit breaker out. Reset circuit breaker.

BLADE ELEMENTS
Timer inoperative. Replace timer.

Brushes improperly adjusted or Repair or adjust brushes.

broken.

Wiring broken. Repair or replace wiring.

DEICE SYSTEM INTER- Elements damaged. Refer to inspection and testing

MITTENT procedures.

Timer defective. Repair/replace timer. Refer

to inspection and testing pro-
cedures.

Brushes broken or improperly Repair or replace brushes.

adjusted. Refer to adjustment procedures.

Removal of Slip Ring. (See figure 13-30. ) NOTE

a. Remove propeller in accordance with Propeller Slip ring (8) should run in a true plane relative
Removal Procedures found in Section 10, removing to brush block (10). Run out should not exceed
propeller, bulkhead and slip ring as one assembly. .005 inch. Adjustment may be made by vary-
b. Identify and remove deice boot and slip ring ing torque on attach bolts while maintaining
electrical leads from spinner bulkhead. as near 65 inch-pounds as possible.
c. Remove nuts, washers and bolts securing slip
ring to spacer and bulkhead. c. Torque slip ring attach bolts and connect elect-
rical leads to proper terminals on terminal strip.

Installation of Slip Ring. (See figure 13-30. )

Removal of Brush Holder Assembly. (See figure
a. With the six attachment bolts in position in bulk- 13-30. )
head (6), assemble in sequence; spacer (9), washer
(11), star lockwasher (16), washer (11) and slip a. (See figure 1-2.) Remove upÿër nacelle cowl (29).
ring (8), guiding slip ring electrical leads through b. Disconnect electrical leads from brush holder
bulkhead as it is assembled. Secure with washers (14),
and nuts but do not torque at this time. c. Remove nuts (12), washers (11), and bolts (15)
b. Place assembly over propeller studs and install from brush holder bracket and crankcase. Be care-
propeller in accordance with Propeller Installation ful not to apply any side loading on the brushes during
Procedures found in Section 10. the removal.
 421 SERVICE MANUAL UTILITY AND 13'"Û$$ 3'"$$
OPTIONAL SYSTEMS

14
34 + 6 SECONDs
15
ON TIME (TYP) 12
'
11
CYCLE 1 10
1 SECOND MAX.
OFF TIME (TYP)
PIN C

11
PIN E o

CYCLE 3

11
14

51583002
51583002 20
A14502005 DetRil N
51141096 421B0001 AND ON

1. Spinner 8. Slip Ring 15. Bolt

2. Support 9. Crankshaft Flange 16. Star Lockwasher
3. Spacer 10. Brush Assembly 17. Terminal Strip
4. Electrical Lead 11. Washer 18. Clamp
5. Deice Boot 12. Nut 19. Timer
6. Spinner Bulkhead 13. Screw 20. Copilot Seat Support
7. Spacer 14. Brush Holder 21. Antislip Ring

Figure 13-30. Propeller De-ice Installation (Sheet 1 of 2)

Change 10
 421 SERVICE MANUAL UTILITY AND l3 $Î
OPTIONAL SYSTEMS

0.50

CABLE DIMENSIONS

Detail

21 17
8
421BODe0

D ON

421BOOO1 AND ON

814581001
C14581002
51583001

Figure 13-30. Propeller De-ice Installation (Sheet 2)

Change 11
13-88 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS
I

4
PROP
TWIST 90 ROTATION

I
2

1/16 ± 1/32

1/16

Excess material
2 may be removed.

421-0001 to 421BOOO1

0. 063 ± 0. 015

0.063 ± 0.015
1 '
4

3
2
SIDE VIEW

421BOOO1 AND ON
TOP VIEW
PROP
ROTATION

1. Screw 3. Bracket Assembly 5. Washer

2. Brush Holder .
4. Slip Ring
Figure 13-31. Deice Brush Holder Installation
Change 10
 421 SERVICE MANUAL UTILITY AND 0""$Û
oPTIONAL SYSTEMS

d. Remove screws (13), washers (11) and spacers NOTE

(3) attaching brush holder to bracket.
If this chattering or screeching is noticed over
idling engine noises, the trouble is severe and
Installation of Brush Holder Assembly. (See figure should be remedied immediately. A less se-
13-30. ) vere chattering or screeching may be detected
by pulling each propeller through slowly in the
NOTE direction of rotation.

When installing brush holder, hold the brushes b. The brush block assembly should be positioned
back in the holder until the mounting bolts have as follows:
been inserted through the crankcase. Be care- 1. Loosen the screws through bracket assembly and
ful not to apply any side loading on the brushes brush holder (1, 2 and 3).
during installation. 2. Adjust the brush block assembly, twist brush
block assembly in brackets so that the brushes contact
Allow a minimum of engine running
of 5 hours the slip rings in such a manner that the angle of the
deice sys- 2°
time before turning on the propeller brushes to the slip rings is approximately from
tem. Ground checkout of the system is allowed, a perpendicular to the slip ring surfaces. The angle
with the engines not running. is measured toward the direction of rotation of the
slip rings.
Reverse the brush holder assembly removal pro- .3. Check each brush for correct alignment with
cedure. slip ring surfaces through
360°
rotation of slip rings.
Add or remove washers (5) as required to obtain
correct alignment.
4. Check the brush block assemblies for clearance
Adjustment of Brush Assembly. (See figure 13-31.) from slip ring surfaces, on Aircraft 421A0001 to
421BOOO1 a distance of 1/16 ±1/32" should be main-
a. When a chattering or screeching nose is emitted tained. On Aircraft 421B0001 and On maintain a dis-
from the brush slip ring area, the probable cause is tance of 0. 063 ±0. 015 inches. If a portion of the
the improper alignment of the brushes and slip ring. brush block assembly is closer to the slip ring sur-
360°
face through rotation, the excess material on
the brush block should be removed.

421-0001 to 421B0001
421B0001 AND ON

1. Brush Block 3. Spring 4. Brush Bracket

2. Brush Assembly 5. Brush

Figure 13-32. Brush Holder Assembly

Change 10
13-70 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Replacement of Brush Assembly. (See figure 13-32. ) Inspection and Testing of Propeller Deice System.

NOTE a. Visually check the completed installation.

1. Check propeller deicers for wrinkling or loose
The brushes are deemed replaceable when 1/4 spots.
inch of brush material remains. It is consid- 2. Check wiring connections for correctness and
ered good practice, however, to replace the tightness,
brushes when 3/8 inch of the brush material 3. Check continuity of wiring. Remove plug from
still remains. The brush block should be dis- timer. Using ohmmeter, check continuity from:
mantled and the brush length measured period- (a) Pin C of the plug to Terminal A of one prop
ically in order to determine usable remaining shoe on the right engine.
brush lengths. (b) Pin D of the plug to Terminal B of one prop
shoe on the right engine.
(c) Pin E of the plug to Terminal A of one prop
a. Remove the four screws and washers which hold shoe on the left engine.
the connector plate to the block. Note the orientation (d) Pin F of the plug to Terminal B of one prop
of the connector plate relative to the brush block so shoe on the left engine.
that it may be removed and then replaced in the exact (e) Pin G of the plug to ground.
same position. (f) Terminal C of one prop shoe on the right en-
b. Disassemble the brush block (1) by pulling it gine to ground.
apart in a direction perpendicular to brush travel, (g) Terminal C of one prop shoe on the left en-
as shown in figure 13-32. gine to ground.
c. Discard the old brush assembly (2) and the springs b. System Tests.
(3). Place new springs (3) into the counterbored holes. 1. Propeller Deicer Resistance Check:
d. Take a new brush assembly (2) and insert the (a) Using an ohmmeter, check the resistance be-
rods of the brushes through the spring (3) and into tween terminals A-C, B-C of prop shoes in
the holes of the brush block (1). This will partially both engines. Resistance should be 2. 23 to
compress the springs. 2. 58.
e. Reassemble the other half of the brush block as-
sembly (1) by placing the slots of the block over each
brush, brush rod, and brush leads. Engage the Removal of Propeller Deice Boots.
block with pins.
CAUTION
NOTE
Do not use sharp tools or objects to remove
Care must be used so as not to damage the boot as damage to the propeller may result.
brush leads.
a. Remove deice boot from the propeller by soften-
f. Install the four screws and washers which hold ing the bond line of boot with Toluol until loosened.
the connector plate to the block. b. Pull deice boot slowly from propeller blade as
bond line is loosened.

Removal and Installation of Propeller Deice Ammeter. Installation of Propeller Deice Boots.

To remove or install ammeter, see Section 12. a. Place deice boot on hub end of propeller blade,
centered on blade leading edge and lead strap (ter-
minal end) of boot aligned and against attach holes
Removal of Propeller Deice Timer.(See figure 13-30.) of installed terminal bracket.
b. Mark off an area on propeller blade (using mask-
a. Remove copilot's seat in accordance with Section ing tape) 1/2 inch from each side and outer end of de-
3. ice boot.
b. Remove access plate in top of seat support. c. Remove boot and clean the masked area of pro-
c. Remove connector plug. peller blade using Methyl-Ethyl-Keytone (MEK) clean-
d. Remove nuts, washers and screws securing ing solvent. For final cleaning, wipe the solvent film
timer to seat support web, off quickly with a clean dry cloth before it has time to
dry.

Installation of Propeller Deice Timer. CAUTION

Reverse the propeller deice timer removal procedure. Methyl-Ethyl-Ketone (MEK) must be used in
a well ventilated area; avoid prolonged breath-
ing of fumes. During all surface cleaning
operations take precaution to guard against
spark or open flame in work area.

Change 10
 421 SERVICE MANUAL UTILITY AND 13-70A/13-70B
OPTIONAL SYSTEMS

d. Mix thoroughly the EC1300LP cement and apply j. Roll outwardly from the centerline to the edge.
one brush coat evenly to the cleaned metal surface. If excessive material at the edges tend to form
Allow to air dry for a minimum of one hour and then puckers, work them out smoothly and carefully with
apply a second coat of EC1300LP cement. fingers.
e. Moisten a clean cloth with MEK and clean the un- k. Roll the tapered edges of the deice boot with a
glazed back surface of the deice boot, changing cloth metal hand-stitch roller and ensure there are no
frequently to avoid contaminating of the area. bubbles entrapped under the boot and that all edges
f. Apply an even brush coat of EC1300LP cement to firmly adhere to the propeller.
the unglazed back surface of the deice boot.
g. Allow cement to dry; then using a silver (non- NOTE
graphite, greaseless) pencil, mark a centerline along
the leading edge of the propeller blade and a corres- In the event it becomes necessary to remove
ponding centerline on the cemented side of the deice or loosen installed deice boots, Toluol shall
boot. be used to soften the "cement" line. A mini-
h. Reactivate the surfaces of the cement using a mum amount of this solvent should be applied
clean, lint-free cloth, heavily moistened with Toluol to the cement line as tension is applied to
solvent. Avoid excessive rubbing of cement which peel back the deice boot. The removal should
would remove it from surfaces. be slow enough to allow the solvent to under-
i. Position the deice boot centerline on the propeller cut the cement so that parts will not be dam-
leading edge, with all marks and terminal leads aged,
aligned. Tack the deice boot centerline to the lead-
ing edge of the propeller blade. 1. Apply one brush coat of EC539P coating, mixed
per manufacturer's instructions, evenly around the
NOTE edges of the installed deice boot.
m. Remove masking tape from the propeller blade
If the deice boot is allowed to get off center- and clean the surface of the blade with a clean cloth
lines, pull up with a quick motion and repo- dampened with Toluol.
sition properly. Roll firmly along center-
line with a rubber roller.

Change 10
 421 SERVICE MANUAL UTILITY AND 13-71
OPTIONAL¯ŠYSTEMS

2. Timer Tests: on, place a hand on each of the two deicer

(a) Connect a jumper wire from Pin B of the timer areas which should be heated per paragraph
receptacle to Terminal B of the connector b. 2. (d).
plug and from Pin G of the timer receptacle (c) The assistant in the cabin should note and re-
to ground. cord the prop deicer system ammeter read-
(b) Place the prop deicing system switch in the ing. This should be 11 to 18 amps. Keep a
"ON" position, close watch on the ammeter needle. The am-
(c) Using a voltmeter check the DC volts to meter needle will deflect every 30 seconds be-
ground from Pin B of the timer. This should cause of the switching action of the timer.
be approximately 24 volts DC. Each deflection will indicate a change in the
(d) Check DC volts to ground from Pins C, D, E, heating areas of the prop deicers.
F; they are the points at which the system
voltage is impressed in sequence to cycle NOTE
power to the propeller deicers. The follow-
ing cycling action of the timer should be: The observer in the cabin should call out these
(1) Timing sequence Pin C, 30 seconds, right 30 second interval deflections and the inspector
engine propeller outboard halves. at the propellers should change the position of
(2) Timing sequence Pin D, 30 seconds, right his hands on the prop deicers accordingly, to
engine propeller inboard halves. check proper heating sequence of the prop de-
(3) Timing sequence Pin E, 30 seconds, left icer areas.
engine propeller outboard halves.
(4) Timing sequence Pin F, 30 seconds, left NOTE
engine propeller inboard halves.
If any irregularities are noted, recheck the
NOTE wiring from the timer to the brush holder as-
sembly and the prop deicer terminal connec-
On time is approximately 30 seconds when oP- tions. Make corrections as necessary and
erating on alternator voltage. When operating retest.
on battery voltage as in this checkout proce-
dure, on time may be longer. c. Slip Ring and Holder Assembly Check.
1. Check for out of flatness:
NOTE (a) Allowable tolerance is 008. If 008 is ex-
. .

ceeded, shim under mounting bolts to bring

The timer does not reposition itself to start at within tolerance.
pin C when the system is turned off, but will 2. On all new brush and/or slip ring installations,
begin its cycling at the same position in which allow five hours engine running time before using de-
it was last turned off. Cycling will then pro- ice system.
ceedintheorderofC, D, E, F, as shown.
NOTE

NOTE Ground checkout of the system is allowed, with

engines not running. Allow a minimum of 5
Check pins C, D, E, F, until a voltage read- hours of engine running time before turning on
ing of approximately 24 volts DC is obtained- the propeller deice system.
Hold the voltmeter probe on the pin until the
voltage drops to 0. Move the probe to the
next pin in the sequence C, D, E, F. Check
volts DC at each pin in sequence, 24 volts DC
should be measured at each pin in the sequence PROPELLER UNFEATHERING SYSTEM.
C, D, E, F. When correctness of the cycling
sequence is established, turn prop deicing sys- The optional unfeathering system consists of a nitro-
tem switch off at the beginning of one of the on gen charged accumulator, a special governor, and a
time periods and record the letter of the pin hose running from the governor to the accumulator.
at which the voltage supply is present. The governor contains a spring-10aded check valve
which is unseated while the propeller control is in any
3. Propeller Deicer Heat Test: position except FEATHER thus permitting governor
(a) Remove the jumper wire installed in para- pressurized oil to flow to and from the accumulator.
graph b. 2. (a), and replace the connector plug When the propeller control is moved to the FEATHER
in the timer receptacle, position, the check valve is seated and oil under gov-
(b) Referring to the position in which the time ernor pressure is trapped in the accumulator and
was left in paragraph b. 2. (d), have an as. hose. As the propeller control is moved out of the
sistant place the prop deice system switch in FEATHER position, the trapped oil flows back through
the "ON" position. As the switch is turned the governor to the propeller to unfeather it.

Change 6
13-72 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Troubleshooting the Propeller Unfeathering System.

TROUBLE PROBABLE CAUSE CORRECTION

PROPELLER FAILS Improper accumulator pressure. Charge accumulator in accordance with

TO UNFEATHER Section 2.

Defective governor. Repair or replace/Rerig governor

control.

Removal, Service, Maintenance, and Installation of a. Place propeller control in the UNFEATHER po-
Propeller Governor, sition before charging the accumulator to prevent the
possibility of oil under pressure being trapped in the
For removal and installation of propeller governor accumulator,
refer to Removal and Installation of Propeller Gover- b. Although the accumulator will function properly
nor Procedures found in Section 10. when charged with compressed air, dry nitrogen gas
is recommended to minimize corrosion.
CAUTION c. Either too much pressure or not enough pressure
in the accumulator will reduce efficiency of the un-
Always release system pressure by placing the feathering system. Refer to Section 2 for proper ser-
propeller control in UNFEATHER position, and vicing.
release accumulator pressure through the filler d. Always check that the filler valve does not leak
valve, before disconnecting the hose between after charging an accumulator.
accumulator and governor ortemoving accum-
ulator.

* 421BO801 AND ON 10553005

L Governor 3. Hose 5. Accumulator

2. Elbow 4. Heat Shield 6. Filler Valve

Figure 13-33. Propeller Unfeathering System

 421 SERVICE MANUAL UTILITY AND "Ö
OPTIONAL SYSTEMS

Removal and Installation of Propeller Unfeathering to engage high pitch stop, bleed off accumu-
Accumulator, lator pressure to 100 110 psi, -

then recheck
operation.
a. Remove engine cowling.
b. Disconnect the pressure line.
PROPELLER SYNCHRONIZER SYSTEM.
CAUTION
The component parts of the propeller synchronizer
Always make sure pressure is bled off the ac- system are two electrical pulse pickups, trimmer
cumulator before disconnecting pressure line. assembly, actuator motor assembly, switch, inter-
connecting electrical cable assemblies, and an indi-
c. Remove the four screws securing accumulator to cator light. The control box assembly, located under
the engine mount and remove the accumulator. the glove compartment box, contains an all transis-
torized circuitry. The actuator motor is a stepping
NOTE type that operates on command from the control box
and is located in the right engine nacelle. The flex-
The elbow in the accumulator is installed and ible rotary shaft is connected to the actuator motor
leak tested by the manufacturer; therefore, and trimmer assembly to trim the right engine speed
removal of the elbow is not recommended. setting. Magnetic pickups are mounted in each pro-
peller governor to provide engine speed indications
to the control box assembly. The function of the
The installation of the propeller unfeathering accum- propeller synchronizer system is to automatically
ulator is a reversal of the removal procedure. match the RPM between the two engines, therefore,
the left engine is designated as the "master" engine
while the right engine is termed the "slave" engine.
Operational Check of Propeller Unfeathering System. The electrical pulses from both magnetic pickups are
fed into the control box from the governors, Any
a. With engines operating at 2000 RPM, move pro- difference in these pulse rates will cause the control
peller controls to the FEATHER position, then po- box assembly to run the actuator motor and through
sition mixture to IDLE-CUTOFF. The propellers the flexible shaft, trim the "slave" engine governor
should move to feathered position, speed set ting to exactly match the "masterii engine
b. Move propeller controls to an unfeathered po- RPM. Normal governor operations and functions are
sition. Propellers should unfeather, unchanged but the synchronizer system will continu-
c. If propellers do not unfeather, check system for ously monitor engine RPM and reset the "slave" en-
leaks and proper pressure, gine governor as required. The limited range feature
prevents the "slave" engine losing more than a žixed
NOTE amount of RPM in case the "master" engine is feather
ered with the synchronizer on.
When propellers do not unfeather sufficiently

Troubleshooting the Propeller Synchronizer System.

TROUBLE PROBABLE CAUSE CORRECTION

PROPELLER Circuit breaker out. Reset circuit breaker.

SYNCHRONIZ ER
SYSTEM WILL Actuator motor defective. Repair or replace.
NOT OPERATE
Magnetic pickup out. Replace. Refer to Testing Procedures.

Defective governor. Repair or replace governor.

Wiring defective. Perform Continuity Check in accordance

with Synchronizer Wiring Test Proce-
dures.

Operation of Propeller Synchronizer System. which trims the slave governor speed to match that
of the master engine exactly. Normal governor op-
Electrical pulses from the magnetic pickup in each eration is unaffected. The synchronizer will con-
governor are fed into the control box (Figure 13-34.) tinuously monitor the engine speeds and reset the
As any difference in the number of pulses is detected, slave engine speed setting as required. Operating
a signal is sent from the control box to the actuator, range of the actuator is approximately ± 50 RPM.
13-74 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

CAUTION a. Install components by reversing removal proce-

dures.
Disconnect the propeller synchronizer control b. Adjust in accordance with adjusting procedures.
box before doing any work on the governor pick-
up leads. Turning the propeller synchronizer
switch to the off position WILL NOT give this
protection. Battery master switch must be
OFF. Adjustment of the Propeller Synchronizer System.
(See figure 13-35. )

Removal of Propeller Synchronizer Components. (See a. Start rigging procedures by disconnecting flex-
figure 13-35. ) ible shaft (2) from actuator motor (1).
b. Rotate free end of flexible shaft (2), counting
a. Remove engine cowling. total turns available on the "slave" governor trimmer
b. Disconnect electrical plug and flexible shaft (2) assembly (3).
from actuator (1). c. Return trimmer assembly (3) to its center range.
c. Remove nuts and screws securing actuator to d. When trimmer assembly (3) is centered, rig
bracket and remove actuator from engine nacelle. governor (9) and control cable (15) in accordance with
d. Disconnect flex shaft (2) and control (15) from Rigging Propeller Controls,
trimmer assembly (3). e. Manually rotate trimmer assembly (3) to either
e. Loosen nuts securing control (15) from bracket end of its travel.
(16) remove forward nut and route control aft thru f. Move propeller pitch levers on the pedestal
the bracket (16). through its entire range, observing the governor
f. Remove nut (7), washers (4) and bolts (5) con- speed adjusting lever to be certain it travels to the
necting rod (8) to trimmer assembly (3) and remove maximum and minimum RPM limits.
trimmer assembly (3)- g. Manually rotate the trimmer assembly (3) to
g. Remove nuts (7), washers (4) and screw (14) opposite end of its travel.
from rub block (13) and shield (6) and remove from h. Perform step f. again.
support (12)- i. Recenter the trimmer assembly (3).
h. Remove nuts (7), washers (4) and bolt (5) from j. Insert a squared shaft into drive of actuator
governor (9), and loosen jamb nut and remove.rod motor (1) and count total turns available.
end (10). k. Place actuator motor (1) in its center range.
i. If the switch or light is to be removed, the panel 1. With both actuator motor (1) and trimmer assem-
(19) can be removed by removing autopilot controller, bly (3) centered, connect the flexible shaft (2) to ac-
if installed, and removing the screws fastening the tuator motor.
panel to the pedestal. m. Check flexible shaft (2) for binding and clearance
in the full RPM position.
n. Perform functional test.
Installation of Propeller Synchronizer Components.
(See figure 13·-35.)

MASTER GOVERNOR
( LH ENGINE )

CONTROL BOX o

SLAVE GOVERNOR
( RH ENGINE )

' FLEXIBLE SHAFT

MAGNETIC
PICKUP

ACTUATOR

Figure 13-34. Schematic Diagram of Synchronizer Operation

 421 SERVICE MANUAL UTILITY AND 13 5
OPTIONAL SYSTEMS

1
16

19

2
18

15
14

0 8

12
3

1. Actuator 7. Nut 13. Rub Block

2. Flexible Shaft 8. Rod Assembly 14. Screw
3. Trimmer Assembly 9. Governor 15. Control
4. Washer 10. Rod End 16. Bracket
5. Bolt 11. Spacer 17. Control Box
6. Shield 12. Support 18. Prop Synchronizer
19. Switch and Light Panel
Figure 13-35. Propeller Synchronizer System Installation
Change 12
13-78 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS
Synchronizer Wiring Test
NOTE
CAUTION
If another accessory uses the same circuit
Do not plug in control box until this test has breaker, turn this accessory off before start-
been satisfactorily completed. Even with ing tests. The control box must be unplugged
switch "off" the box could be seriously damaged, for these tests.

a. Before starting this test, be sure the control box b. Make the following tests, using an ohmmeter to
is unplugged, the master switch is off, and the syn- the pin receptacles in the Jones cinch socket number
chronizer circuit breaker is pulled. On a new instal- 233032: zero the ohmmeter and read on the X1 or
lation, connect the actuator assembly and the mag- X10 scale.
netic pickups to the cables. Either pickup wire may
be connected to pin receptacle No. 8 of the Jones CAUTION
cinch socket. Connect the other wire to pin recepta-
cle No. 6 for slave engine, and No. 7 for the master Do not use a probe that exceeds 045 inch in .

engine. Before tying down pickup wires, complete thickness. Insert and remove probe carefully.
continuity checks given in chart below between pins 8 Failure to do so will result in loose pin con-
and 6 and between pins 8 and 7. nectors and faulty synchronizer operation.

PROPELLER SYNCHRONIZER WIRING CONTINUITY CHECK.

OBTAIN
Test 180°
between With Actuator Uncentered ACTION
receptacle With Actuator Centered Turn Clockwise Counterclockwise (If out of limits)
numbers: (Facing Drive End) (Facing Drive End)
To Uncenter To Uncenter

5 & 1 open circuit 6. 5 -

8. 5 OHM 6. 5 -
8. 5 OHM Bench check the actu-
(high resistance) ator in accordance
with Woodward Syn-
5 &3 open circuit closed circuit 13 -
17 OHM chronizer Manual,
(high resistance) (0 -

1.0 OHM) Bulletin 33049.

5 &4 open circuit 13 -

17 OHM closed circuit
(high resistance) (0 -

1.0 OHM)

4 &1 6. 5 -
8. 5 OHM 6. 5 -

8. 5 OHM 6. 5 -

8. 5 OHM

4&3 13-17OHM 13-17OHM 13-17OHM

3 & 1 6. 5 -

8. 5 OHM 6. 5 , 8. 5 OHM 6. 5 -

8. 5 OHM

ACTION
Test between receptacle numbers: OBTAIN (if out of limits)

8 & 7 (with 6 disconnected at pickup) 90 -

110 OHM Repair wiring if at fault; Replace
52 68 OHM**
-

governor if pickup is at fault;

8 & 6 (with 7 disconnected at pickup) 90 110 OHM
-
Replace pickup (Approved
52 68 OHM**
-
Governor Shop).
8 & aircraft ground open circuit
(very high resistance)

1 & aircraft ground short circuit zero OHMS Trace wiring to determine poor
ground.

2 & aircraft ground* open circuit Trace wiring to remove fault.

(very high resistance)

*2 & aircraft ground will read some low OHM value if you cannot open the circuit breaker. If the
synchronizer shares a circuit breaker with another circuit, you may read an OHM value of the
other circuit.
**Solid steel pickup end with first length of sheathing out from the pickup colored white and carries
P/N 723061WG21318 on its outer diameter immediately below the knurled diameter.

Change 10
 421 SERVICE MANUAL UTIUTY AND Î3-7|
OPTIONAL SYSTEMS

c. When the system meets all of the preceding test chronizer circuit breaker (CONTROL BOX must still
values, turn the master switch on and reset the syn- be unplugged) and make the following voltage check:

PROPELLER SYNCHRONIZER VOLTAGE CHECK

ACTION
TEST BETWEEN RECEPTACLE METER READING
(If out of hmits)
. .

2 & 1 Same as supply voltage and Trace wiring to determine fault

polarity of pin No. 2 must be or reversed polarity.
positive and pin No. 1 must be
negative.

d. Check magnetic pickup output with the engine d. Install magnetic pickup as follows:
running at any cruise RPM. Check potential between 1. Set governor for maximum RPM, slowly rotat-
pin receptacles 6 and 8. Also check potential be- ing the governor drive shaft.
tween pin receptacles 7 and 8. Voltage must be a 2. Screw in pickup, tighten with fingers until pick-
minimum of 1/2 volt at minimum cruise RPM, and a up makes contact internally with the rotating fly-
maximum of 3 volts at maximum cruise RPM. Volt- weight head.
ages and RMS voltages as read on a 5000 OHM/volt
AC voltmeter. If you do not obtain this voltage re-
place governor or have approved governor repair CAUTION
shop adjust or repair the pickup.
e. When the system complies with the specifica- Do not use wrench or pliers to tighten mag-
tions above, the control box may be connected. netic pickup.
f. If the synchronizer malfunctions now, the cause
of the malfunction can probably be traced to the con-
trol box, or the mechanical function of the flexible NOTE
shaft or governor speed trimming device. Check for
a high friction level in the trimming mechanism. Be When installing new pickup always install
sure to center the actuator and trimming device be- new O-ring.
fore mating cable.
3. Tighten the pickup 1/8 turn counterclockwise
NOTE and lightly tighten lock nut.
4. Connect a 5000 Ohm/Voltmeter across the pick-
To check magnetic pickup resistance at the up leads.
governor, disconnect both connectors and 5. Drive the propeller governor at minimum cruise
measure resistance with an ohmmeter. Use RPM and adjust pickup output to obtain 1. O ±. 2 volt.
X1 or X10 scale. Replace pickup if reading Screw pickup in to increase voltage, out to decrease
is other than 90-110 OHMS. On aircraft with voltage.
first length of sheathing out from the pickup 6. Tighten pickup lock nut and safety with lock wire.
colored white and carries P/N 723061WG21318
on its outer diameter immediately below the CAUTION
knurled diameter, replace pickup if reading
is other than 52-68 OHMS. Do not torque lock nut over 25 inch-pounds.

e. Install propeller governor in accordance with the

Removal and Installation of Magnetic Pickup in Pro- Propeller Governor Installation Procedures found
peller Governor. in Section 10.
f. Connect wires and remove tags.
a. Remove propeller governor in accordance with
Propeller Removal Procedures found in Section 10. Functional Test of Synchronizer System. (Optional)
b. Tag and disconnect wiring to pickup.
c. Unscrew magnetic pickup from propeller gover- To test the operation of the synchronizer in flight,
nor. first synchronize propellers manually and turn the

Change 10
13-7$ UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

synchronizer switch ON. Then slowly adjust the 3. Disconnect electrical wiring and remove static
master engine propeller governor control lever, in port.
small increments, to increase or decrease RPM. 4. Install static port by assembling static port and
The RPM range over which the slave engine will re- spacer to outside of fuselage skin and retainer on the
main synchronized with the master engine is the inside and secure with countersunk rivets.
limited range mentioned above. With the synchroni- 5. Connect electrical wiring.
zer ON, move the master engine propeller governor 6. Perform static system test in accordance with
control lever to a point which is close to the end of Section 12.
this limited traveL Turn the synchronizer OFF. An
unsynchronized condition will develop as the actuator
moves to its mid-position. When the synchronizer is FLIGHT HOUR RECORDER.
turned ON again, synchronization will result. If the
units do not become synchronized, the actuator has The flight hour recorder instrument is mounted on
reached the end of its travel and must be recentered the lower portion of the cabin outflow valve shroud.
in this manner. On aircraft 421BOO56 and On, the recorder is
mounted on the stationary instrument panel. On
a. Turn the switch OFF. aircraft 421-0001 to 421B0001 the recorder is
b. Synchronize the engines manually. actuated by a vane switch located on the bottom of
c. Turn the switch ON. the aft fuselage. The vane switch is actuated by a
40 ±5 MPH air flow over the vane. On aircraft
HEATED STATIC PORTS 421BOOO1 and Oli the recorder is actuated by the
landing gear safety switch. Whenever the landing
Static port heaters may be installed-toprevent freez- gear strut is extended it will actuate the safety
ing the static ports due to moisture or ice formation. switch and allow the recorder to operate.
Care must be exercised in removing and installing
the static ports to prevent damage to the heaters and
electrical leads. NOTE

On aircraft 421BOOO1 and On it is possible

Removal and Installation of Heated Static Port. if the aircraft is on jacks and the battery
switch is in the ON position, the flight hour
a. On aircraft 421-0001 to 421B0001, replace static recorder will record time.
port as follows:
1. Disconnect static line and remove fitting from Removal and Installation of Flight Hour Recorder.
static port.
2. Drill out rivets securing static port and plate a. Remove aft tailcone access door.
to fuselage skin. b. Disconnect wires from switch, remove screws
3. Disconnect electrical wiring and remove static attaching switch to fuselage skin. Retain the spacers
port. for reinstallation.
c. On aircraft 421-0001 to 421BOO56, remove the
CAUTION outflow valve shroud.
d. Remove two nuts securing flight hour meter to
Use extreme care in removing static port shroud.
and plate from fuselage skin so as not to e. On aircraft 421B0056 and On, refer to typical
damage skin. instrument removal procedures for flight hour meter.
is the reversal of the removal pro-
f. Installation
4. Clean sealant from skin with a cleaning solvent cedure.
before installingnew parts.
5. Fay seal with PR1422 (MIL-S-8802) an area 30 .

wide around edges of, and between plate, skin and CESSNA ECONOMY MIXTURE INDICATOR.
static port. Apply sealant to attaching rivets upon
installation. Fillet seal edges of static port after The exhaust gas temperature (commonly referred to
installation. as EGT) sensing device is used to aid the pilot in se-
6. Trim rivet heads flush with spherical surface lecting the most economical fuel-air mixture for
of plate. cruising flight at a power setting of 75% or less.
7. Connect electrical wiring. Exhaust gas temperature (EGT) varies with the ratio
8. Install fitting and connect static line. of fuel-to-air mixture entering the engine cylinders.
9. Perform static system test in accordance with Refer to the appropriate Owner's Manual for correct
Section 12. operation procedures of system.
b. On aircraft 421B0001 and On, replace static port
as follows:
1. Disconnect static line and remove fitting from
static port.
2. Drill out rivets securing static port, spacer and
retainer to fuselage skin.

Change 11
 421 SERVICE MANUAL UTILITY AND 13-78A/13-78B
OPTIONAL SYSTEMS

Troubleshooting the Exhaust-Gas Temperature Gage.

TROUBLE PROBABLE CAUSE CORRECTION

GAGE INOPERATIVE Defective gage, probe or wiring. Isolate defective circuit, replace
defective probe or gage.

INCORRECT READING Indicator needs calibrating. Calibrate in accordance with

calibration procedure.

FLUCTUATING READING Loose, frayed or broken electrical Tighten connections, and repair
lead. or replace defective leads.

Removal and Installation of EGT System. (See figure NOTE

13-36. )
To obtain peak exhaust temperature, lean out
a. Disconnect wires at probe by removing two mixture control slowly enough for pointer to
screws connecting wires together. follow. When the pointer stops goingup and
b. Loosen clamp and remove from exhaust stack. starts a downward movement, enrich mixture
c. Remove EGT indicator in accordance with Typi- enough to regain peak reading.
cal Instrument Removal Procedures found in Section 12.
d. If wire is to be removed, pull wires from b. Record reading achieved after system has sta-
bundles routed to engine nacelle- bilized.
c. Repeat step a. several times to insure a positive
NOTE reading has been achieved.
25°
The wiring is a thermocouple wire and is cali- d. Lean mixture to a setting of not less than F
brated for a fixed resistance. below peak exhaust gas temperature.
Do not lengthen
and posi-
.

or shorten. e. Use adjust screw on face of mdicator

tion pointer to 4/5 scale.
e. Installation of EGT system is the reversal of the NOTE
removal procedures.
75°
Adjustment should not exceed ± F or
Calibration of EGT System. (See figure 13-36. ) three divisions.
75°F
a. To check calibration, obtain an average cruise f. If adjustment for more than ± is required,
condition of 65°/opower at 7500 feet and lean mixture perform the following steps:
to peak exhaust temperature on indicator. 1. Gain access to rear of indicator.

TAN 4/5 OF SCALE REAR VIEW

RED
0 0
PROBE
CALIBRATION /
J
ADJUSTMEN / '4,
g g
SCREW .¾"^¾5
""°"
|
CLAMP ° • 0

FRONT VIEV/
CALIBRATION
ADJUSTMENT
THERMOECOUPL

TAN

/ RED
EXHAUST STACK

Figure 13-36. Exhaust Gas Temperature System Installation

Change 11
 421 SERVICE MANUAL UTILITY AND 13-79
OPTIONAL SYSTEMS

2. Viewing meter from rear, turn calibration b. On aircraft 421BO201 and On, remove and install
screws one turn clockwise for increase in indicator the true airspeed indicator as follows:
25°F 1. Disconnect clamp securing temperature probe
reading of (one division) or one turn counter-
clockwise for decrease, on bottom skin.
2. Loosen feed thru nut on temperature tube and
TRUE AIRSPEED INDICATOR work tube up and into the cockpit area.

The True Airspeed Indicator is composed of three CAUTION

elements: airspeed, altitude and temperature. The
altitude and temperature mechanisms are correlated Avoid sharp bends, nicks or dents in tem-
to operate a rotating dial over which the indicated perature tube. Incorrect readings could
airspeed indicates the true airspeed. The true air- result.
speed indicator senses changes in pressure and tem-
perature. This combination of altitude and temper- 3. Remove indicator in accordance with Typical
ature change results in a sum total of airspeed cor- Instrument procedures Section 12.
rections to indicate true airspeed. 4. Install true airspeed indicator by reversing
removal procedures.
Removal and Installation of True Airspeed Indicator.
NOTE
(See figure 13-37. )
a. On aircraft 421A0001 to 421B0201, remove and Seal around feed thru fitting after installa-
install the true airspeed indicator in accordance with tion in accordance with Fay Sealing proce-
Typical Instrument Removal and Installation proce- dures Section 16 with Class B type sealant
dures. material.

Change 11
13•80 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Deta

11 4
Detail

Detail 10 421A0001 TO 421B0201

421BO201 AND ON

Detali D asii41ois
B51141014
51141095

I
1. Air Scoop 5. True Airspeed Indicator 9. Clock
D51141094
51143058
C51141017

2. Skin 6. Pitot Pressure Line 10. Altimeter

3. Airscoop Static Line 7. Static Port 11. Insulation
4. Airscoop Pressure Line 8. Static Line 12. Temperature Probe i

Figure 13-37. True Airspeed Installation

Change 10
 421 SERVICE 1VÏANUAL UTILITY AND 13-80A/13-80B
OPTIONAL SYSTEMS

* 421B0403 TO 421B0801
**421-0001 TO 421BO403

10

12

' O •
Detail A

11 51143061
A51141101

1. Decal 5. Heated Windshield 9. Capacitor

2. Access Cover 6. Relay 10. Fuse
3. Inverter 7. Controller 11. Spare Fuse
4. Shelf 8. Circuit Breaker Panel 12. Bulkhead

Figure 13-38. Heated Windshield Components Installation (Sheet 1 of 2)

Change 11
 421 SERVICE MANUAL UTILITY AND 13-81
OPTIONAL SYSTEMS

Detail
421BO801 AND ON A51142044

Figure 13-38. Heated Windshield Components Installation (Sheet 2)

Change 11
13•82 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SŸSTEMS

HEATED WINDSHIELD. operating with a wire sensor

imbedded in the wind-
shield. Actuation of the windshield
anti-ice switch
The heated windshield is electrically heated to pre- activates the controller which senses windshield
vent ice formation on the heated area while flying in heat. If the windshield heat is not within the limits
icing conditions. The windshield is a laminated established by the sensor and controller, the con-
stretched acrylic construction utilizing a deposited troller closes the relay which controls AC power
metallic film for the heating element. On aircraft from the inverter to the windshield. When the wind-
421-0001 to 421A0118, electrical power is supplied shield reaches the cutout temperature, the control-
from an auxiliary winding in the AC-DC 100 amp ler will open the relay, removing power from the
alternators and a alternate selector switch allows the windshield. On aircraft 421BO801 and On, the relay
pilot to use either alternator for the power source, is not required.
On aircraft 421A0118 and On and aircraft incorpora-
ting SK421-47 and SK421-50, the electrical power is
supplied from an inverter. Temperature control is
accomplished by using an ON-OFF type controller

"roubleshooting the Heated Wincshield.

TROUBLE PROBABLE CAUSE CORRECTION

WINDSHIELD WILL NOT Open circuit. Reset circuit breaker.

Defective relay. Replace relay.

Defective temperature controller. Replace temperature controller.

Loose or faulty wiring. Check, tighten or replace wiring.

Defective switch. Replace switch.

Defective windshield sensing element. Replace windshield.

Faulty inverter (421A0118 and On and Replace inverter.

aircraft incorporating SK421-47 and
SK421-50).

WINDSHIELD HEATS Defective relay. Replace relay.

CON.TINUOUSLY
WITHOUT CYCLING Defective temperature controller. Replace temperature controller.

Defective windshield sensing element. Replace windshield.

INVERTER INOPERATIVE Fuse blown Replace fuse/or inverter.

Removal 01 Heatea Windshield. NOTE

a. Disconnect electrical wiring to magnetic com- If installing heated windshield other than one
pass, remove compass. that was in aircraft, measure resistance
b. Tag and disconnect windshield wiring, across power terminals of heated windshield.
c. Remove windshield in accordance with the Wind- Refer to decal on underside of inverter ac-
shield Removal Procedures found in Section 3. cess cover for proper tap setting.
Installation of Heated Windshield. c. Install magnetic compass and connect wiring,
d. Check operation of heated windshield.
a. Install windshield in accordance with Windshield
Installation Procedures found in Section 3• Removal and Installation of Heated Windshield Com-
b. Connect wiring and remove tags· ponents. (See figure 13-38. )

a. Remove access covers as required to gain ac-

Change 11
 421 SERVICE MANUAL UTILITY AND ""Ô
OPTIONAL SYSTEMS

cess to components. Operational Check of Heated Windshield. (421A0118

b. Tag and disconnect wiring. and On and aircraft incorporating SK421-47 and
c. Remove screws securing temperature control SK421-50))
and relay.
d. Remove temperature control and relay from air- a. heated windshield switch ON. Observe in-
Turn
craft. dicator light on the annunciator panel. If the indica-
e, Remove capacitor by removing clamps secureing tor light is out, check press-to-test for defective
capacitor to side of bulkhead- bulb. If the bulb is defective, replace bulb. If the
bulb is not defective, refer to Troubleshooting Chart
NOTE and replace the temperature controller. The tem-
perature controller is operating when the light is ON.
The capacitor is not to be relocated because b. Allow approximately one minute for windshield
of transit voltage interference. to warm-up after switch is turned ON.
c. Check for heat in the heated area of the wind-
f. Remove screws securing inverter to shelving. shield. If the area is not warm, make the following
g. Remove inverter from aircraft, checks:
h. Install temperature control, relay, capacitor and 1. Measure the voltage at the electrical terminal
inverter by reversing the removal procedures. connections of the windshield. On 421-0001 to
421B0801 voltage should be 190 to 208 volts AC.
On 421B0801 and On the voltage should be 198 to
Operational Check of Heated Windshield. (421-0001 211 volts.
to 421A0118) 2. If AC voltage is present, measure the resis-
tance of the heated windshield terminals. Resistance
Because the heated windshield operates on AC volt- should be within limits given on decal (1).
age it will be necessary to operate either engine
when performing an operational check. CAUTION

a. Park aircraft into wind. When making the above resistance measure-
b. Start aircraft engine and allow to warm-up. ments, always disconneet wiring at terminals
c. After engine wartn-up, adjust throttle to 1000 and make sure battery is turned off.
RPM.
d. Turn heated windshield switch ON. OBserve in- 3. If resistance is within tolerance, measure re-
dicator light. If the indicator light is out, check sistance from ground terminal to primary structure.
press-to-test for defective bulb. If the bulb is de- Resistance should be no greater than 005 ohms.
.

fective replace bulb. If the bulb is not defective re- 4. If AC voltage is not present at windshield con-
fer to troubleshooting chart and replace the temper- nection terminals, disconnect AC wiring at termi-
ature controller. The temperature controller is nals of inverter.
operating when the light is ON. 5. Measure AC voltage at inverter output termi-
e. Allow approximately one minute for windshield nals, if AC voltage is not present, disconnect DC
to warm-up after switch is turned ON. voltage terminal wires and check for 28 volts DC.
f. Check for heat in the heated area of the wind- 6. If DC voltage is present, inverter is inopera-
shield. If the area is not warm make the following tive.
checks: 7.If AC voltage is present, at the inverter termi-
1. Measure the voltage at the electrical terminal nals, check for wiring continuity between inverter
connections of the windshield. Voltage should be 100 and the heated windshield.
to 300 volts AC. 8. If DC voltage is not present, check relay.
2. Shutdown engine and disconnect wiring from 9. If relay is good, disconnect wiring from sens-
sensing element. ing unit at windshield terminals.
3. Measure resistance of sensing element. Resis- 10. Measure resistance of sensing element. Re-
tance should be from 300 to 500 ohms, depending on sistance should be from 300 to 365 ohms, depending
the ambient temperature of the windshield. on the ambient temperature of the windshield.
4. Measure resistance of the heated area at termi- 11. If when checking the heated area, and the area
nals. Resistance should be from 30 to 50 ohms. is warm, the heated portion of the windshield should
be operating satisfactorily. This should also be
NOTE shown by the indicator light cycling on and off indica-
ting the temperature controller is cycling.
When making the above resistance measure-
ments always disconnect wiring at terminals STEREO TAPE PLAYER.
and make sure battery is turned OFF.
The optional stereo tape player is installed behind
the left-handforward divider in the stereo cabinet.
g. If, when checking the heated area, and the area The eight track stereo player has a tape speed of
is warm, the heated portion of the windshield should 3.75 in/sec., with a motor speed of 300 RPM. It
be operating satisfactorily. This should also be has automatic switching of programs with continuous
shown by the indicator light cycling on and off indi- play and push button control for immediate program
cating the temperature controller is cycling. change.
Change 11
13-84 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

cartridge first (by substitution). Select a vocal tape

of an artist whose singing voice you are familiar
with. Turn unit on, and insert the cartridge, listen-
ing for the pitch of the artist's voice. Should the
/ voice pitch be high, the unit is running fast; or if the
voice pitch is low, the unit is running slow. To cor-
rect either the high or low pitch condition, follow the
speed correction outline procedure below:
a. Remove the two right-hand knobs from the con-
trol shaft on the tape only, noting an access hole to
the right of the control shaft.
Red Painted Screw b. Using a small screwdriver (inserted into access
on Bottom of Unit hole), make the speed control adjustment. Should
the unit be running fast, a counterclockwise rotation
of the screwdriver will slow the unit down; should the
Figure 13-39. Crosstalk Adjustment unit be running slow, a clockwise rotation of the
screwdriver will speed it up. Set the speed control
at that point where the artist's voice sounds correct
Removal and Installation of the Stereo Tape Player. to your ear.

a. Disconnect electrical plug connector from stereo

player.
b. Remove three screws fastening stereo cabinet to
floorboard.
c. Remove stereo cabinet with stereo player from
floorboard.
d. To further disassemble stereo player from /

cabinet, remove four nuts and washers holding

stereo player to cabinet bracket, and remove
stereo player.
e. To install stereo player to cabinet, and stereo
cabinet back in its original position, reverse the re- Speed control
'
moval procedures. knob on bot-
tom of unit.
NOTE

Do not use four track tape on this eight track

stereo player.
Figure 13-40. Speed Control Adjustment
Crosstalk or Misaligned Head Adjustment on Stereo
Player. (See figure 13-39.)

Check several cartridges for the crosstalk condition. ELECTRIC ELEVATOR TRIM CONTROL.
If only one cartridge produces crosstalk, the cart-
ridge is defective. However, should the majority of See Section 6 for removal, installation and rigging
the cartridges produce crosstalk, the unit requires of electric elevator trim control system.
adjustment. To make the adjustment to eliminate
crosstalk or misadjusted playback head position, STROBE LIGHT SYSTEM.
follow the step-by-step procedure below:
See Section 14 for removal and installation of strobe
a. Use a cartridge of known
good performance. lights system.
b. Note red painted screw on bottom of unit.
c. Insert cartridge, noting if crosstalk is present. WING LOCKER FUEL SYSTEM.
d. Using a screwdriver, adjust the red painted
screw. Should the interference become louder, re- See Section 11 for removal and installation of wing
verse the screw adjustment until the unit plays with- locker fuel system.
out interference.
e. Secure the adjustment in position with plastic SEVENTH, EIGHTH, NINTH, AND TENTH SEATS.
glue.
See Section 3 for removal and installation of the
Speed Control Adjustment on Stereo Player. (See seventh, eighth, ninth and tenth seats.
figure 13-40. )
Should speed variation be present, always check the
 421 SERVICE MANUAL UTILITY AND "$
OPTIONAL SYSTEMS

ELECTRIC SEAT. (See figure 13-4L ) moval of the seat.

Removal and installation of pilot's or copilot's elec- CAUTION

tric seat is the same as the standard seats, except
the wires must be removed and tagged before re- Make sure the master switch is in the OFF
position before removing the electric seat.

4 3
I

1. Bottom Assembly 6. Circuit Breaker

2. Seat Belt 7. Bolt
3. Seat Lock 8. Screw
4. Actuator Switches 9. Armrest
5. Electrical Cable 10. Armrest Stop

Figure 13-41. Electric Seat Installation

13-88 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

B C
D E F

B
C

H
E

12

4
1
3
5

' 4 8 9
51542005R
Detail Detail Detail A14541004
BS1541016
c51541015

1. Discharge Hose 8. Nut 16. Instrument Panel

2. Mounting Clip 9. Washer 17. Control Panel
3. Crankease Thru Bolts 10. Thermo Detector 18. Test Switch
4. Clamp 11. Bracket 19. Post Light
5. Bolt 12. Rubber Nipple 20. Squib Terminal
6. Screw 13. Shield 21. Ground Terminal
7. Baffle 14. Engine Mount Beam 22. Discharge Sensor Lead
15. Fire Extinguisher

Figure 13-42. Engine Compartment Fire Extinguisher (Sheet 1 of 2)

Change 8
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

12

9 FIRE EX INGUISHER

4
1
4 8 19 E

Detail D
Detaii E 18

Detail F
20

21 22

Legend Color Cause of Illumination

Fire Red Fire condition existing

in engine compartment

E Amber Fire extinguisher

container empty

OK Green Fire cartridge and

associated wiring is in
operational condition

Detail
8 5

11
11 6

1 2 10
3
6 10
4

15 Detaii H
Detail Û
D51541014
E51541015
F14141021
G51541014
R51543004
J14541008

Figure 13-42. Engine Compartment Fire Extinguisher (Sheet 2 of 2)

Change 8
 .gg UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

ENGINE COMPARTMENT FIRE EXTINGUISHER. NOTE

The engine compartment fire extinguisher consists The test switch does not check detector sys-
of three major components, control panel, thermal tem (refer to Servicing paragraph).
detectors, and the extinguisher unit. The annuncia-
tor panel may be mounted in any unused standard If an overheat condition is detected, the appropriate
three-inch instrument hole, the three thermal detec- "Fire" light will annunciate the engine to be extin-
tors are mounted in the high heat areas of the engine guished. To activate the extinguisher, open the
nacelle and the fire extinguisher is mounted in the guard for the appropriate engine and press the
nacelle area. An exit line is routed from the fire "Fire" light. Freon, under pressure, will be dis-
extinguisher into the forward section of the engine charged to the engine and engine accessory compart-
where the freon gas is expelled. A smaller dis- ments. The amber light E (figure 13-42) will illu-
charge hose which routes off of the large discharge minate after the extinguisher has been discharged
hose expells freon gas from the center of the nacelle and will continue to show empty until a new bottle is
area towards the inboard side of the nacelle, installed. The "Fire" light will remain illuminated
until compartment temperatures cooL
A test function is provided to test the system circuit-
ry. When the test switch is pushed (shown in figure NOTE
13-42), all lights should illuminate.
Only one discharge is available per engine.

Troubleshooting Engine Fire Extinguisher.

TROUBLE PROBAELE CAUSE CORRECTION

POWER ON TO INDICATOR Open circuit breaker. Close circuit breaker.

PANEL TEST SWITCH
DEPRESSED ALL LIGHTS Open circuit between pin A Repair wiring.
FAIL TO ILLUMINATE and B of connector at panel.
(Pin A is ground. )

Voltage present between Pin Replace panel.

A and B at panel connector.
Faulty panel.

GREEN LIGHT(S) ILLUMINATED Defective light,bulb(s). Replace bulb(s).

LIGHT(S) FAIL TO LIGHT
(Bulb(s) good. ) Disconnect Replace cartridge.
wire from bottom stud of
cartridge. Ground wire,
light(s) illuminate. Defective
cartridge.

(Light(s) fail to illuminate. ) Repair wiring.

Open circuit between bottom
stud wire of cartridge and
panel connector.

(Circuit exists between bottom Replace panel.

wire of cartridge and connec-
tor. ) Faulty panel.
RED (FIRE) LIGHT(S) FAIL TO Defective light bulb(s). Replace bulb(s).
ILLUMINATE
(Bulb(s) good. ) Defective Replace panel.
paneL

AMBER LIGHT (E) LIGHT(S) Defective light bulb(s). Replace bulb(s).

FAIL TO LIGHT
(Bulb(s) good. ) Defective Replace panel.
panel.

Change 8
 421 SERVICE MANUAL UTILITY AND D-88 A
OPTIONAL SYSTEMS

Troubleshooting Engine Fire Extinguisher (Cont. )

TROUBLE PROBABLE CAUSE CORRE CTION

POWER ON TO INDICATOR Shorted detectors or shorts in Replace shorted detector or

PANEL TEST SWITCH NOT detector wiring. (Check for correct shorted wiring.
DEPRESSED. REg (FIRE) shorts in detector wiring be-
LIGHT(S) LIGHTED tween pin C or D of harness
connector and ground. )

(No short in wiring or detec- Replace detector.

tor. ) Indicator panel defective.

GREEN LIGHTS OUT LIGHT(S) (Depress test switch. ) If Replace indicator panel.
LIGHTED light(s) stay on, indicator panel
defective. Also, check affected
cartridge for bridge-wire re-
sistance.

AMBER (E) LIGHT(S) Empty container. Replace container.

FLICKERING

If container is full, unscrew Replace container.

cartridge, scratch some
anodize off cartridge thread
and reinstall. Torque 90 to
100 inch-pounds. If light is
still intermittent, ground sen-
sor wire to aircraft. Light
goes out.

If light does not go out. Repair wiring.

Probable open circuit between
sensor wire and connector pin
H or G.

If circuit exists between sen- Replace indicator panel.

sor wire and connector pin H
or G. ,Faulty panel.

AMBER (E) LIGHT)S) ON Empty container. Replace container.

If container is full, unscrew Replace container.

cartridge, scratch some
anodize of cartridge thread
and reinstall. Torque 90 to
100 inch-pounds. If light is
still on ground sensor wire
to aircraft. Light goes out.

If light does not go out. Repair wiring.

Probable open circuit between
sensor wire and connector pin
H or G.

If circuit exists between sen- Replace indicator panel.

sor wire and connector pin H
or G. Faulty panel.

Change 8
13-888 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Removal of Fire Extinguisher, (See figure 13-42.) Servicing Fire Extinguisher.

a. Remove engine cowling. The following item should be checked at every 100
b. Make sure battery switch is OFF. hour inspection. Check the pressure gage on each
c. Disconnect electrical wires from extinguisher. bottle to ensure the pressures indicated in the
d. Disconnect discharge hose (1). Pressure-Temperature Correction Table. If these
e. Remove clamps (2) securing extinguisher unit pressures are not indicated, the bottle must be ser-
to mounting clips. viced.
f. Remove extinguisher from nacelle.

Installation of Fire Extinguisher. (See figure 13-42.)

PRESSURE-TEMPERATURE
a. Position fire extinguisher in place and connect CORRECTION TABLE
hose (21).
with clamps F°
b. Clamp fire extinguisher in place Temp -60 -40 -20

0 +20
(8). Ind 110 127 148 174 207
c. Connect electrical wires- Pressure 134 155 180 212 251
F° +120
Temp +40 +60 +80 +100
WARNING Ind 249 304 367 442 532
Pressure 299 354 417 492 582
to

l
Before connecting electrical connectors
cartridges, check connectors with multi-
meter to ensure no voltage is present at
connector• Every six months, remove containers and weigh.
(The scale used must be a 5 to 10 pound scale with
d. Continuity check detector circuitry in accord- an accuracy of ±. 1°/ofull scale. ) Weight of 25 pound .

ance with Servicing Fire Extinguisher. below marked weight indicates a leaky container.
e. Turn on electrical power and check system for After bottle has been replaced check the following:
proper operation at the control panel. Press the
test switch. a.Check the test function; if any light fails, replace
f. Install engine cowling. bulb. If green light (OK) does not light after replac-
ing bulb, replace firing cartridge *P/N 13083-5 in
fire extinguisher. Any other light failure, after re-
Removal and Installation of Fire Extinguisher placing bulbs and firing cartridge, indicates malfune-
Thermal Detectors. (See figure 13-42.) tion in the unit or associated wiring circuit.
a. Make sure battery switch is OFF.
b. Remove engine cowling. NOTE
c. Loosen and remove bolts, Washers and nuts at-
taching thermal detector to bracket or clamp. The test switch does not check the detector
d. Disconnect electrical wire from detector. circuit.
e. Remove detector from nacelle.
f. The installation procedure for the fire extinguish- b. Conduct a continuity check of detector circuitry
er thermal detector is the reversal of the removal as follows:
procedure. 1. Apply power to the aircraft.
g. Continuity check detector circuitry in accordance 2. Disconnect sensor wire from fire extinguisher
with Servicing Fire Extinguisher. bottle. The EMPTY light should come on.
3. With sensor wire disconnected, press the Press-
Removal and Installation of Annunciator Panel. (See To-Test switch on the control panel. The OK light
figure 13-42.) should come on indicating the squib is in operational
condition.
a. The removal and installationprocedures for the 4. Reconnect sensor wire to bottle,
annunciator panel is the same as any Typical Instru-
ment Removal and Installation Procedures found in WARNING
Section 12.
Do not attempt to check the continuity of the
NOTE sensor and/or the squib with a V.O. M. tester,
Most V. O. M. testers have enough AMP cap-
When removing annunciator panel or install- ability to fire the cartridge. Continuity of the
ing annunciator panel light bulbs, always make circuit shall be checked only when using a
sure the battery switch is in the OFF position. 100 MA current regulated source.

*P/N of HTL Industries, 1900 Walker Avenue,

Monrovia, California, 91016.

Change 9
 421 SERVICE MANUAL UTILITY AND 13-·$$Ûl3-880
OPTIONAL SYSTEMS

c. Conduct fire detect thermo detector check as NOTE

follows:
500°F
1. Apply power to the aircraft. Heat gun must have a capacity of or
2. Using an Alpha Heat gun, apply heat to each higher.
thermo detector body for approximately ten seconds
and observe that fire light on panel comes on. 3. If light does not come on, remove thermo de-
tector and check further in a temperature oven.
Switch should actuate 450°F.
at

Change 9
 421 SERVICE MANUAL UTILITY AND
OPTIONAL SYSTEMS

Detail

CIR10

Detail
SHARC-7

Bl4142021
*USED WITH MAGNESIUM BATTERIES 51181036

1. Panel Switch 6. Screw 11. Lock Washer

2. Power Switch 7. Battery Access 12. Doubler
3. Terminal Block 8. Fuselage Side Skin .13.
Upper Tailcone Skin
4. Function Switch 9. Antenna Coaxial 14. Antenna
5. Mount 10. Nut 15. Suppressor

Figure 13-43. Emergency Locator Transmitter

Change 12
 .gg UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

EMERGENCY LOCATOR TRANSMITTER emergency signals. In the OFF position, the unit is
inoperative. Placing the switch in the ARM position
Description. will set the unit to start transmitting emergency sig-
nals only after the unit has received a 5G (tolerances
The emergency locator transmitter (ELT) is a self- are +2G and -OG) impact force. On emergency loca-
contained, solid state unit, having its own power sup- tor transmitter P/N C1R10-4, a remote on-off switch
ply with an external mounted antenna. The transmit- on the instrument panel is provided in addition to the
ter is designed to transmit on dual emergency fre- switch located on the front end of the transmitter.
quencies of 121.5 and 243.0 megahertz simultaneous-
ly. The CIR10 emergency locator transmitter is CAUTION
located in the leading edge of the dorsal fin at approx-
imately fuselage station 309. 56 and water line 125. 00. Do not leave the emergency locator trans-
The antenna is also enclosed in the dorsal. The mitter in the ON position longer than 10
SHARC-7 emergency locator transmitter is mounted seconds or you may activate downed air-
in the tailcone on the side of the fuselage. craft procedures by C. A. P. D. O. T. or,

F. A. A. personnel.
On the CIR10 transmitter, power is supplied from the
aircraft system through a switch on the panel or the
battery pack located inside the transmitter. The Removal of Emergency Locator Transmitter. (See
SHARC-7 transmitter is entirely portable operating figure 13-43.)
on the power supplied by a battery pack. The battery
pack service life is placarded on the batteries and The following steps "a" through "d" pertain to the
also on the outside of the cover on ttle end of the CIR10 emergency locator transmitter.
transmitter.
a. Refer to figure 1-2 and remove fin access cover.
b. Assure aircraft electrical power is off and the
The transmitter broadcast tone is audio modulated in on-off switch on the front of the transmitter is in the
a swept manner over the range of 1600 to 300 Hz and OFF position.
is a distinct, easily recognizable distress signal for c. Disconnect electrical leads from transmitter.
reception by search and rescue personnel, and others d. Remove screws securing transmitter to mount
monitoring the emergency frequencies. and remove transmitter from dorsal fin.

The transmitter meets or exceeds the requirements Steps "e" through "g" pertain to the SHARC-7 emer-
of the following specifications: gency locator transmitter.

(1) R. S. S. 147 Issue 2, D. O. C. e. Remove tailcone access door.

(2) TSO C612, F. A. A. f. Disconnect co-axial cable from end of transmit-
(3) F. C. C. Part 87, F. C. C. ter.
(4) TSO C91, F. A. A. g. Cut sta-straps securing transmitter and remove
transmitter from mounting bracket.
Under favorable conditions, a distress signal from
the ELT can be intercepted at a distance of 100 miles.
It exhibits line of sight transmission characteristics Installation of Emergency Locator Transmitter,
which correspond approximately to 100 miles at a (See figure 13-43. )
search altitude of 10, 000 feet.
The following steps "a" through "c" pertain to the
When battery inspection and replacement schedules CIR10 emergency locator transmitter.
are adhered to, the transmitter will broadcast an
emergency signal at rated power, for a continuous a. Position transmitter in mount and install four
period of at least 48 hours at temperatures from mounting screws.
+55°C to -20°C
after an emergency landing.
NOTE
The military monitors 243. O MHz. The 121. 5 MHz
frequency is monitored by the general aviation air- Before installing the emergency locator trans-
craft as well as C. A. P. , D. O. T. F. A. A. and some
,
mitter to the mount, check condition of battery
commercial aircraft. pack and make sure function switch is in the
ARM position and the power switch is in the
OFF position.
Operation.
b. Connect electrical leads to terminals.
A three position switch on the forward end of the unit c. Install dorsal fin access cover.
controls operation. Placing the switch in the ON po-
sition will energize the unit to start transmitting Steps "d" through "h" pertain to the SHARC-7 emer-
gency locator transmitter.

Change 11
 421 SERVICE MANUAL UTILITY AND 13-Ol
OPTIONAL SYSTEMS

d. Assure that the direction of flight arrows (plac- NOTE

arded on the transmitter) are pointing towards the
nose of the aircraft. Before installing the new battery pack, check
e. Install transmitter in bracket and secure with to ensure that its voltage is 10. 8 volts or
new sta-straps. greater.
f. Connect co-axial cable to antenna.
g. Position on-off switch to ARM position NOTE
h. Check operation of emergency locator transmit-
ter in accordance with Section 2. After relatively short periods of inactiva-
tion, the magnesium cell develops a coat-
ing over its anode which drastically reduc-
es self-discharge and thereby gives the cell
Removal and Installation of Emergency Locator an extremely long storage life. This coat-
Transmitter Antenna. (SHARC-7) ing will exhibit a high resistance to the flow
of electric current when the battery is first
a. Disconnect co-axial cable from base of antenna. switched on. After a short while (less than
b. Remove nut and lockwasher attaching the antenna 15 seconds), the battery current will com-
base to the fuselage and the antenna will be free to pletely dissolve this coating and enable the
remove. battery to operate normally. If this coating
c. Install the antenna by reversing the removal pro- is present when your ELT is activated, there
cedures. may be a few seconds delay before the trans-
mitter reaches full power.

Removal and Replacement of Battery Pack d. Replace the transmitter cover by positioning the
rubber gasket on the cover and pressing the cover
a. Remove emergency locator transmitter in accord- and case together and attach with nine screws. Care
ance with removal procedures. should be taken to avoid trapping the gasket and over-
b. Remove screws attaching the cover to the case tightening screws.
and remove cover. Remove rubber gasket to gain e. Remove the old battery placard from the end of
access to battery pack. transmitter and replace with new battery placard
c. When the battery pack is supplied with a plastic supplied with the new battery pack.
connector attached to the battery leads, merely dis-
connect the old battery pack and replace with a new CAUTION
battery pack, making sure the plastic connectors
are completely mated. Be sure to enter the new battery.pack expira-
tiondate in the aircraft records.
CAUTION
If the emergency locator transmitter.is
Some early transmitters were delivered with equipped with magnesium battery-pack, in-
transmitter leads soldered directly to the sure the static noise suppressor is installed
battery pack. Failure to observe proper po_ between the antenna and transmitter refer
-

Iarity in connecting pack in the to Service Letter AV74-16.

a new battery
transmitter may result in immediate failure
of transistorized components attached to the
printed circuit board in the transmitter. f. Check operation in accordance with Section 2.
g. Refer to Section 2 and Inspection Chart for in-
spection intervals.

Change 11
13-92 UTIMTY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

TROUBLESHOOTING. In performing the following troubleshooting procedure

to test, peak effective radiated power, you will be
Should your Emergency Locator Transmitter fail the able to determine if battery replacement is necessary
Periodic or 100 Hours performance checks, it is pos- or if your unit should be returned to your dealer for
sible to a limited degree, to isolate the fault to a par- repair.
ticular area of the equipment. CAUTION

CAUTION Do not leave the emergency locator trans-

mitter in the ON position longer than 10
In order to protect your warranty, trouble- seconds. This could initiate downed air-
shooting should be conducted without remov- craft search procedures by C. A. P. ,
ing the unit cover. D. O. T. or F. A. A. personnel.

TROUBLE PROBABLE CAUSE CORRE CTION

*POWER LOW Low battery voltage. 1. Set toggle switch to OFF.

SHARC-7 2. Remove plastic plug from the remote jack
and by means of a Switcheraft #750 jackplug,
connect a Simpson 260 model voltmeter and
measure voltage. If the voltage is 10-volts or
less, the battery is below specification.

Faulty transmitter. 3. If the battery voltage is 10. 8 volts or more,

it is O. K. If the battery is O. K. check the
,

transmitter as follows:
a. Remove the voltmeter,
b. By means of a Switcheraft #750 jackplug
and 3 inch long maximum leads, connect a
Simpson Model 1223 ammeter to the jack.
c. Set the toggle switch to ON and observe
the ammeter current drain. If it is in the
range 0-50 MA, the transmitter or the
coaxial cable is faulty.

Faulty coaxial antenna cable. 4. Check coaxial antenna cable for high re-
sistance joints. If this is found to be the case,
the cable should be replaced.

*This test should be carried out with the coaxial cable provided with your unit.

POWER LOW Low battery voltage. 1. Pull cabin lights circuit breaker.
CIR10 2. Remove access cover to transmitter.
3. Remove transmitter from mount.
4. Remove battery access cover.
5. Measure voltage at battery contacts.

NOTE

Transmitter should be turned on when

measuring battery voltage.

6. If the battery voltage is 10 volts or less, the

battery pack should be replaced.

Faulty transmitter. If the battery voltage is greater than 10 volts, in-

sert a 0-150 MA meter in series with power leads
and check as follows:

1. Set power switch on transmitter to ON and ob-

serve current drain.
2. If current drain is 0-50 MS, the transmitter
or the antenna is faulty and should be bench tested.

Change 10
 421 SERVICE MANUAL UTILITY AND D-g
OPTIONAL SYSTEMS

Installation of Pilot's and Copilot's Manual and Elec-

trical Adjustable Seat. (See figure 13-44.)

a. Insert seat on seat rails and slide forward.

b. Pull up on seat stop handle and allow seat to
move forward far enough to install seat stops.
c. Connect wiring and remove tags.
d. Install seat stops with screws and nuts.
e. Turn on electrical power and check operation,
f. If seat is not electrical, check operation using
crank provided on the front of the seats.

PILOT AND COPILOT MANUA L AND E LE CTRICA L

ADJUSTABLE SEAT.

Removal of Pilot and Copilot Manual and Electrical

Adjustable Seat. (See figure 13-44. )

The procedures given pertain to either the pilot's or

copilot's manual or electrical adjustable seat. The
difference between the manual and electrical is the
electrical seat utilizes an electric motor in lieu of
the manual crank for the up and down and tilting
movements.

a.. Raise seat to the highest position,

b. Remove seat stops on each side of the rail by re-
moving nuts and screws.
c. Tag and disconnect wiring.
d. Pull up on seat stop handle and slide seat aft and
remove seat from its mounting.
5 4 3 2 1

Disassembly of Pilot and Copilot Manual and Electri- 1. Adjust Handle 3. Nut 4. Screw
cal Adjustable Seat. 2. Seat Stop 5. Seat Rail

a. Disassemble pilot's and copilot's manual and Figure 13-44. Pilot and Copilot Manual and
electrical adjustable seat in accordance with Figure Electrical Seat Installation
13-45.

Figure 13-45. Pilot and Copilot's Manual and Electrical Adjustable Seat Callouts

1. Seat Back 9. Seat Bellerank 18. Bearing Block

2. Screw 10. Seat Stop 19. Seat Bottom
3. Bolt 11. Nut 20. Arm Rest
4. Washer 12. Shaft 21. Arm Rest Stop
5. Spacer 13. Crank 22. Escutcheon
6. Seat Belt 14. Seat Stop Handle 23. Wire Bundle
7. Nut 15. Seat Base 24. Vertical Adjust Motor
8, Side Skirt 16. Shaft 25. Recline Motor
17. Housing

Change 5
13-94 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

1315

25

14

10
13

12 11
23

421B0101 AND ON

Detail
1

Figure 13-45. Pilot and Copilot's Manual and Electrical Adjustable Seat

Change 5
 UTILITY AND Q.g
421 SERVICE MANUAL
OPTIONAL SYSTEMS

AL COHOL WINDSHIELD ANTI-ICE SYSTEM.

b. Install pump (4) with two bolts (5) and washers.
The alcohol windshield anti-ice system consists of a c. Install lines (7) and (8).
three gallon capacity tank which provides approxi- d. Install lines (9) and (19) and clamp in place.
mately one hour anti-icing capability, an electrically
operated pump actuated by a switch breaker located NOTE
on the LH console, and orificed tubes to disperse the
anti-ice fluid over the windshield. A restrictor Hold union (17) with wrench when installing
orifice is provided in the dispersal system to meter lines to prevent turning and subsequent break-
the alcohol for maximum effeciency. The system is ing of seal at cabin skin.
serviced with isopropyl alcohol,
e. Install line (18) and clamp in place.
Removal of Alcohol Windshield Anti-Ice System. f. Install line (20) and restrictor tee (21).
(See figure 13-46.)
NOTE
a. Remove aft nacelle baggage compartment up-
holstery panel. Restrictor tee must be installed with re-
b. Disconnect line (7) at elbow (12) and using a suit_ strictor end upstream and arrow pointing
able tube attached to the line, pump remaining fluid downstream of flow.
from tank (3).
c. Disconnect line (7) from tank and remove line g. Install tubes (22) and (23) and clamp in place.
(8).
d. Disconnect electrical wire from pump (4) at NOTE
splice.
e. Remove pump (4) from tank by removing bolts Make certain tubes (22) and (23) maintain a
(5). minimum gap of 0. 10" between tubes and
f. Remove screws (1) securing tank (3) to structure. windshield retainer.
g. Lift forward end of tank until vent tube clears
bottom skin and carefully slide tank forward until h. Install forward right cabin upholstery panel,
clear of structure, then lift tank from aircraft. wing gap fairings and access covers,
h. Extend flaps and remove i. Install aft nacelle baggage compartment uphol-
RH wing gap fairings
to gain access to lines, stery panel.
i. Remove clamps and remove lines (9) and (19).
j. Remove RH forward side upholstery panel to gain Operational Check of Windshield Anti-Ice System.
access to line (18). Remove clamp and remove line.
a. Fill reservoir with isopropyl alcohol (MIL-F-
NOTE 5566),
b. Turn master switch ON.
Hold union (17) with wrench when removing c. Switch windshield anti-ice switch ON.
lines to prevent turning and subsequent break- d. Assure alcohol flows evenly from all five holes
ing of seal at cabin skin. on each side. Nominal flow rate is approximately
20 minutes per gallon.
k. Working through RH nose baggage door, remove
line (20), restrictor tee (21) and tubes (22) and (23)· NOTE

The left-hand spray pattern may be slightly

Installation of Alcohol Windshield Anti-Ice System- the
greater than right spray pattern. Spray
(See figure 13-46.) should extend approximately 4 to 6 inches
above nozzles during ground operation,
a. Position tank in place and secure in place with
screws (1)- e. Turn windshield anti-ice switch OFF. Alcohol
NOTE flow should cease.
f. If alcohol flow is irregular or fails to shut off
Make certain vent extends below lower skin properly, check pressure at pump. Pressure should
0.40" and scarfed side is forward- be 4.0 to 4.75 PSIG.

Figure 13-46. Alcohol Windshield Anti-Ice System Callouts

1. Screw 9. Line (Elbow to Elbow) 17. Union

2. Filler 10. Nut 18. Line (Union to Union)
3. Tank 11. Washer 19. Line (Union to Elbow)
4. Pump 12. Elbow 20. Line (Union to Tee)
5. Bolt 13. Elbow 21. Restrictor Tee
6. Elbow 14. Line (Union to Union) 22. Tube RH
7. Line (Pump to Elbow) 15. Cabin Skin 23. Tube LH
8. Line (Tank to Pump) 16. Lock-O-Seal 24. Clamp

Change 10
13-96 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

54

Detail

421B0201 AND ON 24.----

Detail $
Figure 13-46. Alcohol Windshield Anti-Ice System

Change 5
 421 SERVICE MANUAL UTILITY AND
""
OPTIONAL SYSTEMS

ANGLE OF ATTACK SYSTEM. (421BO501 and On. ) Operational Check of Angle of Attack System.

The angle of attack system consists of an indicator a. Ground Check.

incorporating a press to test circuit (for ground test 1. Move battery switch to ON position.
or flight test of the system) and a transducer. The 2. Push the "PRESS TO TEST" button on the indi-
indicator is mounted forward of the glareshield and cator and check that the indicator needle moves to
visually displays the angle of attack of the aircraft. the left (SLOW) end of scale and the stall warning
The transducer is located on the leading edge of the horn sounds with the needle in the red zone. The
left wing and transmits electrical signals to the indi- needle should return to the SLOW diamond wh en
cator for angle of attack display. The transducer in- the button is released.
corporates a heater element operated by the pitot 3. Turn the pitot heat switch ON and check to see
heater switch, to prevent ice from hampering the that the transducer mounting plate on the left wing
transducer operation. The system also incorporates leading edge heats up.
a stall warning circuit, when energized causes the 4. Turn pitot heat OFF.
stall warning horn to sound.
NOTE
Removal of Angle of Attack Indicator. (See figure
13-47. ) The pitot heat switch should not be left on
any longer than necessary to determine that
a. Assure aircraft electrical power is off- mounting plate is heating.
b. Disconnect electrical connector to indicator.
c. Remove screws securing indicator to mounting 5. Push the transducer vane gently aft (down).
bracket. Check that the needle moves to the right (FAST) end
d. Remove grommet from deck cover; remove indi- of scale. When released, the vane should return to
cator- the approximate center of its travel and the needle
should return to the SLOW diamond.
Installation of Angle of Attack Indicator. (See figure 6. Push the transducer vane gently forward (up).
13-47. ) The indicator needle should move to the left (SLOW)
end of scale and the stall warning horn should sound.
a. Insert wire cable of indicator through hole in When released, the vane should return to the approx-
deck cover. imate center of travel, the needle to the slow dia-
b. Install grommet in deck cover• mond, and the stall warning horn should stop.
c. Position
indicator on mounting bracket and se- 7. Turn battery switch OFF.
cure with screws· b. Ground Adjustment Check,
d. Reconnect electrical plug· 1. Before applying electrical power to the system,
cheek the SLOW/FAST needle position. It should be
Removal of Angle of Attack Transducer. (See figure at a position midway between the SLOW (left) dia-
13-47. ) mond and the SLOW legend.
2. Turn on battery master switch. Check that the
NOTE aircraft voltage is at least 24 volts.
3. Press the test button on the front of the indica-
Before removal of transducer, it is impor¯ tor. The needle shall move to the left end of the
tant that the exact fore-aft location of the scale and the pre-stall warning horn shall sound.
vane be marked on the wing so that the re- Release the test button. The SLOW/FAST needle
placement unit may be adjusted identically. shall return to a position near the SLOW diamond
and the pre-stall warning horn shall stop.
a.
Assure aircraft electrical power is off. 4. Remove cover, using a small screwdriver, turn
b.
Remove access cover. the adjustment screw marked PSW (Pre-Stall Warn-
c. Disconnect electrical plug to transducer. ing), located on the side of tne indicator, clockwise
d. Remove screws securing transducer to leading until the pre-stall warning horn sounds. Then turn
edge and remove transducer. the PSW screw counterclockwise until the horn stops.
5. Push the vane on the litt transducer, located on
Installation of Angle of Attack Transducer. (See
the leading edge of the left wing forward (up). The
figure 13-47. ) pre-sta11 warning horn shall sound. Release the vane
and the horn shall stop. If it does not stop within 3 to
a. Insert wire cable of transducer through trans~ 4 seconds after the vane is released, turn the PSW
ducer mounting hole' adjustment screw counterclockwise one complete
b. Secure transducer to leading edge with screws. turn. Recheck by pushing the vane forward and re-
c. Reconnect transducer electrical plug.
leasing it to ensure that the horn will stop within 3
d. Replace access cover.
to 4 seconds after the vane is released. The system
is now ready for flight check and adjustment.
c. Flight Check and Adjustment.
1. The flight check should be performed in smooth
air at a safe altitude to perform stalls. Using the
data recorded in the Flight Check portion of the Op-

Change 12
13-98 UTILITY AND 421 SERVICE MANUAL
OPTIONAL SYSTEMS

Detail

Detail
51143047
A51143048
B14141039

1. Screw S. Deck Cover 9. Screw

2. Cover 6. Mounting Bracket 10. Access Cover
3. Indicator 7. Wing Leading Edge 11. PSW Screw
4. Grommet 8. Transducer 12. CM Screw

Figure 13-47. Angle of Attack System

Change 12
 421 SERVICE MANUAL UTILITY AND 13-99/13-100
OPTIONAL SYSTEMS

erational Check of Stall Warning System (Section 14), holes in the corners of the lift transducer mounting
adjust the angle of attack system to provide an "on plate, and slide the transducer forward (up) on the
speed" indication when the indicated airspeed is with- wing. Retighten screws and repeat step 2., and step
in ±2 knots of the approach speed determined from 3., if necessary. Do not attempt to increase the
the Approach and Stall Speed Chart, correct for warning horn speed by turning the PSW adjustment
weight at the time of the test for the following con- screw clockwise, as the maximum clockwise setting
figurations: was determined in the ground adjustment check steps
(a) Landing gear down. 4. and 5. Any further clockwise adjustment will
(b) Flaps full down. cause the horn to sound when the aircraft is at rest
(c) Power as required to maintain a stable rate on the ground.
of descent at 500 FPM. 5. After the pre-stall warning horn is properly ad-
2. With power off (IDLE), flaps down, gear down, justed, determine the weight af the aircraft. Using
trim the aircraft for a speed appraximately 20 knots the Approach and Speed Chart, find the approach
above the stall speed determined from the Approach speed.
and Stall Speed Chart. Then slowly reduce speed at 6. With flaps and gear down, trim the aircraft for
no more than 1 knot per second, and observe the level flight at speed determined in step 5. Altitude
speed at which the pre-stall warning horn sounds. hold may be used to facilitate this adjustment, if
Continue to reduce speed at no more than 1 knot per available. Maintaining this speed, observe the posi-
second until the aircraft stalls, and observe the stall tion of the SLOW/FAST needle. It should be at the
speed. The pre-stall warning horn shall sound 3 to center mark. If the needle is to the left of the center
5 knots before stall. If it does not, proceed as in mark, turn the adjustment screw marked CM (Center
steps 3 and 4. Mark), located on the side of the indicator, clockwise.
3. If the speed at which the horn sounded was If it is to the right of the center mark, turn the ad-
greater than 5 knots before stall, turn tne PSW justing screw counterclockwise. Make the adjust-
(Pre-Stall Warning) adjustment screw on the side of ment in steps of 2 to 3 turns in the appropriate direc-
the indicator counterclockwise approximately 1/2 tion, then recheck the needle position and the air-
turn for each knot the warning speed must be re- speed to insure that the speed is being maintained
duced. Then repeat step 2., until the warning horn at the proper value.
sounds at 3 to 5 knots before stall speed. Do not 7. After completion of the flight check and align-
allow the speed to decrease at greater than 1 knot ment, replace the cover on the indicator and secure
per second during the checks. in place.
4. If the speed at which the pre-stall warning
sounded was less than 3 knots before stall, adjust-
ment of the lift transducer location on the wing is
required. Land and loosen the screws in the slotted

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-1

SE CTION 14

ELECTRICAL SYSTEMS
Table of Contents

Page Page

POWER DISTRIBUTION . . . . .
14-2 Removal and Installation of Starter
Battery and Starter Circuit . . .
14-2A Switches . . . . . . . 14-12B
Troubleshooting . . . . .
14-2A LIGHTING SYSTEM . . . . . .
14-12B
Removal of Battery . . . . .
14-2A Troubleshooting . . . . . .
14-12B
Maintenance of Battery . . . .
14-2A Removal and Installation of Heat Sink
Installation of Battery . . . . .
14-4E Assembly . . . . . . .
14-14B
Removal of Battery Box . . . .
14-4E Removal and Installation of Dimming
Installation of Battery Box . . .
14-4E. Control Assembly . . . . . 14-14B
EXTERNAL POWER . . . . . .
14-4E Removal of Landing Gear Switch and
Removal of External Power Receptacle .
14-4E Indicator Light (421-0001 to 421B0201). 14-14B
Installation of External Power Receptacle. 14-6 Installation of Landing Gear Switch and
ALTERNATORS AND REGULATORS Indicator Light .
Gear¯. . . . 14-14B
(Delco-Remy) (421-0001 to 421A0001) .
14-7 Removal and Installation of Landing
Troubleshooting the 50 Amp Alternator Indicator Lights (421BO201 and On) .
14-16
and Regulator System . . .
14-7 Removal and Installation of Overhead
ALTERNATORS AND REGULATORS Console Light Rheostat . . . . 14-16
(Westinghouse) (421-0001 to 421A0001) .
14-8 Removal and Installation of Instrument
ALTERNATORS AND REGULATORS Lights . . . . . . . 14-16
(421A0001 and On) . . . . .
14-9 Removal and Replacement of Left Hand
Troubleshooting 100 Amp Alternator Console Lights . . . . .
14-16
and Regulator System . . .
14-9 Fuel Selector Valve Lights . . .
14-16
Overvoltage Troubleshooting Removal and Replacement of Fuel
Information . . . . . .
14-10 Selector Valve Lights . . . . 14-16
Removal of Alternator . . . .
14-10D Removal and Replacement of Rear
Alternator Hub Replacement . . 14-10D Dome Lights . . . . . .
14-16A
Installation of Alternator . . .
14-10D Removal and Replacement of Individual
Removal and Installation of Voltage Reading Lights . . . . . 14-16A
Regulator . . . . . .
14-10D Removal and Replacement of Cabin Door
Operational Check and Adjustment Entrance Light . . . . . 14-16A
of Alternator and Regulator . .
14-10E Removal and Replacement of Cabin
Operational Check of Alternator Courtesy Light . . . . . 14-19
Failure Circuit . . . . .
14-10E Removal and Installation of Wing
Operational Check of Alternator Locker Baggage Light . . . .
14-19
Warning System . . . . .
14-10E Removal and Installation of Wing
Operational Check and Adjustment Locker Baggage Light Switch . .
14-19
of Alternators and Regulators . .
14-10E Removal and Installation of Wing
BATTERY MASTER AND ALTERNATOR Navigation Lights . . . . .
14-19
SWITCHES , . . . . .
14-11 Removal and Installation of Tail
Removal . . . . . . . .
14-11 Navigation Lights . . . . . 14-19
Installation . . . . . . .
14-11 Removal and Installation of Rotating
Removal and Installation of Side Beacons . . . . . . .
14-19
Console . . . . . . .
14-12 Removal of Landing Light . . . .
14-19
Removal and Installation of Side Installation of Landing Light . . .
14-20
Console Circuit Breaker Panel . .
14-12 Adjustment of Landing Light . . .
14-21
ANNUNCIATOR PANEL . . . . .
14-12 Removal and Installation of Taxi Light .
14-22
Removal . . . . . . . .
14-12 Adjustment of Taxi Light . . . .
14-22
Removal and Replacement of Diodes . .
14-12 Removal and Installation of Deice Light .
14-22
Removal and Replacement of Light Strobe Light System . . . . . 14-22B
Assembly . . . . . . .
14-12 Removal and Installation of the Strobe
Installation . . . . . . .
14-12 Light System Components . . .
14-22C
Removal and Replacement of Light Bulbs .
14-12 STALL WARNING SYSTEM . . . .
14-22D
Removal and Replacement of Light Lens .
14-12B Removal of Stall Warning Transmitter .
14-22D
STATIONARY INSTRUMENT PANEL Installation of Stall Warning
SWITCHES . . . . . .
14-12B Transmitter . . . . . .
14-22D
Typical Switch Removal . . . .
14-12B Operational Check of Stall Warning
Typical Switch Installation . . . .
14-12B System . . . . . . .
14-22D
Adjustment of Stall Warning System . .
14-22D

Change 10
14-2 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Table of Contents (Continued)

Page Page
CIGAR LIGHTER CIRCUIT . . . . 14-22D ELECTROLUMINESCENT PANEL LIGHTS .
14-22E
PITOT AND STALL WARNING HEAT Removal . . . . . . . .
14-22E
SYSTEMS . . . . . . .
14-22D Installation . . . . . . .
14-22E
WIRING DIAGRAM INDEX . . . .
14-23
WIRING DIAGRAM INDEX . . . . 14-103

POWER DISTRIBUTION• on the underside of the fuselage. Lighting inside the

cabin area includes a dome light, four reading lights,
Electrical energy for the aircraft is supplied by a 24 a map light, fuel selector lights, three overhead
volt direct-current, single wire, negative ground flood lights, three side console lights located in un-
One 24 volt storage battery sup-

lis
electrical system. derside of pilot's armrest, and a cabin door light.
plies power for starting and furnishes a reserve The instrument panel lighting consists of two post ligh
source of power for electrical components in the lights over each instrument, a compass light, and
event of an alternator failure. A battery voltage a call number light. Optional equipment lights in-
monitor light in the annunciator panel provides a clude a right hand landing light, taxi light, and wing
warning when illuminated that the electrical system deice light, outside the cabin area. Inside the cabin
operating on low voltage. The monitor assembly area, a lighted seat belt sign, oxygen sign and post
will illuminate the warning light with decreasing lights for the optional instruments are the only op-
voltage between 24. 5 and 25. 5 volts and remain ON tional lights.
with voltage lower than turn on voltage. The warning
light will turn OFF with increasing voltage between Battery and Starter Circuit.
24. 5 and 26. O and remain off with voltage higher than
turn off voltage. Two engine-driven 24 volt 50 am. A 24 volt, 24 ampere-hour battery is installed in the
pere alternators supply the current needed to oper. Ieft stub wing. Positive and negative terminals are
ate the electrical equipment and to charge the storage clearly marked on the battery posts. The battery is
battery. The standard 50 AMP alternator system held in place by the cover. The battery supplies
has two regulators, one is used for regulation of the power for the starter system and electrical system
system, and the second is used as a spare in event when the engines are not operating. A battery box
of regulator failure. The system is protected again drain is provided to drain and vent battery fluids and
against overvoltages by two circuit breaker type vapors.
overvoltage devices. The alternator switches are CAUTION
mounted on the instrument panel, one on each side of
the battery switch. All other switches with the ex- The use of ah external power source is re-
ception of the landing gear, flap and cowl flap switch- commended for ground operation and start-
ex, are located on the left console. All electrical ing the aircraft engines,
circuits in the aircraft are protected by circuit
breakers and switch breakers, located in the left con-
sole panel. The 421 aircraft is equipped with stand-
ard navigation lights, a retractable landing light lo-
cated in the main tank tail cap of the left wing, and
two rotating beacon lights. One rotating beacon is
mounted on the top of the rudder and one is mounted

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS ÎÊ" A Î4- S
cabin area includes a dome light, four reading lights, Battery and Starter Circuit.
a map light located in each control wheel, fuel selec-
tor lights, three overhead flood lights, three side A 24 volt, 24 ampere-hour battery is installed in the
console lights located in underside of pilot's armrest, left stub wing. Positive and negative terminals are
and a cabin door light. The instrument panel lighting clearly marked on the battery posts. The battery is
consists of two post lights over each instrument, a held in place by the cover. The battery supplies
compass light, and a call uumber light. Optional power for the starter system and electrical system
equipment lights include a right hand landing light, when the engines are not operating. A battery box
taxi light, and wing deice light, outside the cabin drain is provided to drain and vent battery fluids and
area. Inside the cabin area, a lighted seat belt sign, vapors,
oxygen sign and post lights for the optional instru-
ments are the only optional lights. CAUTION
The use of an external power source is re-
commended for ground operation and start-
Troubleshooting the Battery and Starter Circuit. ing the aircraft engines.

TROUBLE PROBABLE CAUSE CORRECTION

SLOW ENGINE CRANKING Partially discharged battery. Charge or change battery.

SPEED
Low capacity battery. Cycle battery to improve
capacity or replace it.
Faulty battery cell. Replace battery.
Loose or corroded terminals. Clean and tighten terminals.
Burned starter solenoid switch Replace solenoid.
contacts.
Starter motor drags. Overhaul starter motor.
STARTER ENGAGES BUT Partially discharged battery. Charge or change battery.
WILL NOT CRANK ENGINE
Faulty battery cells. Replace battery.
Damaged or shorted starter motor. Overhaul starter motor.
Faulty armature or field in starter Overhaul starter motor.
motor.
STARTER WILL NOT Battery full discharged. Replace or charge battery.
ENGAGE Replace faulty cable.
Disconnected battery cable.
Shorted or open starter solenoid Replace solenoid.

I---

Removal of Battery. clean battery, use a mild solution of bicarbonate of

soda (baking soda) and water to remove acid corro-
a. Removethe battery access cover by loosening sion. Rinse with clear water and sponge off excess.
the air lockscrews. Allow to air-dry or blow excess water off battery
b. Remove the NEGATIVE battery terminal by re- with dry air.
moving the nut and bolt securing ground strap to
structure.
CAUTION
CAUTION
Take special precaution to insure that battery
Always remove the ground cable first and in- cell filler caps are tight before cleaning tlie
stall it last to prevent accidental short cir- battery. Entrance of soda water into a bat-
cuits, tery cell will neutralize the cell electrolyte.

c. Disconnect the POSITIVE terminal and stow in a If additional cleaning of the battery terminals is
place not to interfere with removal of battery. needed, use a wire brush and brighten up the termin-
d. Lift battery from box. als to insure a good electrical connection. For best
results the battery electrolyte should be kept level
with the horizontal baffle plate (the plate with the hole
Maintenance of Battery. in it), which is approximately two inches below the
filler plug, by the addition of water as required.
For maximum efficiency, the battery and the battery This water level should be maintained when the bat-
connections should be kept clean at all times. To tery is in a level position.
Change 4
 421SERVICE MANUAL ELECTRICAL SYSTEMS 14-3

18
19
17

12

1. Rotating Beacon 19. Alternator

2. Tail Light 20. Wing Disconnect Plug
3. Courtesy Light 21. Dual Warning Unit
4. Flap Actuator 22. Prop Synchronizer -
Located Under Glove Compart-
5. External Power Receptacle ment
6. Landing Gear Actuator 23. Radio Junction Box RJBI Located in Nose
-

7. Battery 24. Heater

8. Battery Relay 25. Pitot Heat
9. Starter Relay 26. Map Lights
10. Landing Light 27. Stall Warning Horn Located
-
Under Copilot Seat
11. Left Auxiliary Fuel Pump 28. Prop Deice Timer - Located Under Copilot Seat
12. Left Wing Position Light 29. Voltage Regulators
13. Auxiliary Fuel Tank Sending Unit (Opt.) 30. Right Wing Position Lights
14. Stroke Adjusting Panel 31. Right Wing Fuel Pump
15. Auxiliary Fuel Tank Sending Units 32. Console Panel Lights
16. Deice Light 33. Overhead Console Lights
17. Tach Generator 34. LH and RH Reading Lights
18. Starter 35. Dome Light

Figure 14-1. Equipment Location

Change 2
14-4 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Q OoCO©@oo
/ o 02

lDetai
1 112

12 13
10

27 28 25 24 23

C 22 21
30
31 29
33 28

Detail Detail
421-0001 TO 421A0001

1. Circuit Breakers 13. RH Auxiliary Fuel 26. Pilot's Cigar Lighter Resistor
2. Overvoltage Protectors Pump Resistor 27. Ventilation Air Blower Resistor
3. Switch Breakers 14. Spare Fuses 28. LH Fuel Boost Relay
4. Switch Panel 15. Terminal Block TB-2 29. RH Fuel Boost Relay
5. Voltammeter 16. Terminal Block TB-7 30. Landing Gear Relay
6. Engine Control Switch Panel 17. Terminal Block TB-1 31. Gear Down Relay
7. Emergency Switch 18. Barometric Switch 32. Gear Down Relay
8. Heat Sink Diode 19. Starter Vibrator 33. Capacitors
9. LH Ammeter Shunt 20. Warning Unit (Optional 100 Amp Alternator)
10. RH Ammeter Shunt 21. Courtesy Light Relay 34. Heated Windshield Controller
11. Voltage Shunt 22. Gear Warning Relay (Optional)
12. LH Auxiliary Fuel 23. Landing Gear Down Resistor 35. Heated Windshield Relay
Pump Resistor 24. LH Rear Cigar Lighter Resistor (Optional)
25. RH Rear Cigar Lighter Resistor 36. Spare Fuse

Figure 14-2. Switch and Circuit Breaker Panel (Sheet 1 of 3)

 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-4A

oooooo
oooooCOOO

co 000000 000 e
o oooooo og e
oooooooo
as 40 41 42 43
av as av
Detail E

49
48
47

44 Detail F 42140001 To 421soooi

37. Circuit Breakers 48. Battery Shunt 58. Terminal Board TB-2
38. Overvoltage Protector 49. Main Overvoltage Relay 59. Terminal Board TB-1
39. Circuit Breaker Panel 50. Standby Overvoltage Relay 60. Terminal Board TB-4
40. Switch Breakers 51. Cabin Fan Resistor 61. Terminal Board TB-12
41. Switch Panel 52. Cigar Lighter Resistor 62. Electric Windshield Relay
42. Voltammeter 53. LH Fuel Boost Relay (Optional)
43. Engine Control Switch Panel 54. RH Fuel Boost Relay 63. Starting Vibrator
44. Voltage Regulator 55. Electric Windshield 64. Landing Gear Horn Assembly
45. LH Alternator Shunt Controller 65. Stall Warning Horn Assembly
46. RH Alternator Shunt 56. Terminal Board TB-3 66. Flap Position Switch
47. Emergency Switch 57. Cowl Flap Position Relays 67. Horn Assembly Resistor

Figure 14-2. Switch and Circuit Breaker Panel (Sheet 2 of 3)

14-48 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

FLAP GEAR & STALL LDG STALL FLAP --LOG CEAR, SUFFAGFU·F FLN GEAN, TALL START &
G R M R R C

LH RH
LCOWL FLAP
LNSb L FLUEL PU AUX PUMRP, yPLEL QTYp
FUEL PUMPl pAUX PUMP, FFUEL QTY
NO START

LTRANS PUMP

TRANS PUMP-
INST WING TANK DOOR L ENG R ENG r ENG GAGE CABIN DOOR
NA UCX LMPR GH

LF
PUMP DOOR FLOOD
WARN LIGRTS--- LDG LT
LTS
AIR GYRO

GYRO POWER T B T B
A O
C 2 N 2 A 2
CO2MM- NAV TO

COMM 3 DME XPDR T & B

NO. 2 CABIN FIRE TRIM [ELECT SEAT 1
W P R
FIA FUEL QTUX
CIGAR LTRS
CKNR AMDIO
XPDR DME

COMM AV AAUMDIO

R ALT WWRXRM LDG LT-

CRADARA CLTGAR LECTSEAT]

GS

GEAR CAB CAB CAB SHAVER

CONTROL LTS FAN PRESS INV

AIR CABIN CABIN ELECT TRIM

,
,
, COND FAN PWR WSELD PWR

PI T nME XPDR RMI RADAR

VR MAIN
M

LH ALT RH ALT
M
V T A Y --AC INV D SHAVER CIGAR
OVER VOLTAGE
Y N
FIE FIELD

STBY

Detaii D Detan G Detail Û

TYPICAL 421 421A0001 TO 421B0201 421B0201 AND ON

Figure 14-2. Switch and Circuit Breaker Panel (Sheet 3 of 3)

Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14•4Û

10

11

30
20
|

' 23
2 ,, 24
1 25
29

421BOOO1 TO 421BO301

1. LH and RH Alternator Field 10. Engine Control Switch Panel 21. Ground Plug
Diodes 11. Electric Windshield Relay 22. LH and RH Fuel Boost Relays
2. LH and RH Alternator Shunts 112. Terminal Board TB-7 23. Electric Windshield Controller
3. LH and RH Battery Shunts 13. LH and RH Alternator Fuses 24. Standby Overvoltage Relay
4. Circuit Breaker Panel 14. Starting Vibrator 25. Regulator Filter
| 5. Terminal Board TB-8 15. Stall Warning Horn Assembly 26. Cigar Lighter Resistor
6. Alternator Fail Module 16. Landing Gear Horn Assembly 27. Cabin Fan Resistor
7. Terminal Board TB-9 |17. Flasher 28. Regulator Filter
8. Terminal Board TB-4 18. Horn Assembly Resistor 29. Main Overvoltage Regulator
9. Switch Panel 19. Diode 30. Deice Timer Module (Opt.)
20. Ground Plug

Figure 14-2A. Side Console

Change 8
14-40 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

*NOT REQUIRED ON 421B0801 AND ON 7

REQUIRED ON 421BOB01 AND ON

19
27 26 25 24 * 322 21 20
4218301 AND ON 51183010

1. Alternator Field Fuse 12. Landing Gear Warning Horn 23. Cigar Lighter Resistor
2. Circuit Breaker Panel 13. Landing Gear Horn Resistor 24. RH Voltage Regulator
3. Terminal Board TB-8 14. Surface Deice Timer Module 25. LH Voltage Regulator
4. Terminal
. Board TB-9 15. Flasher 26. Terminal Board TB-1
5. Terminal Board TB-4 16. Ground Plug 27. 1N4721 Diode
6. Air Conditioner Relay 17. Electric Windshield Controller 28. Alternator Field Switch
7. Switch Panel 18. RH Overvoltage Relay 29. RH Alternator Shunt
8. Terminal Board TB-7 19. LH Overvoltage Relay 30. LH Alternator Shunt
9. Spare Alternator Field Fuses 20. LH and RH Fuel Boost Relays 31. Low Voltage Monitor
10. Starter Vibrator 21. Cabin Heat Diode 32. Voltage Monitor Fuse
11. Stall Warning Horn 22. Cabin Fan Resistor
Figure 14-2B. Side Console

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-4 E/14-4 F

13

421-00D0e1
21

13
1

12

11

12 421B0801 AND ON

421-0001 TO 421B0801 AS1281003

51283004
* 421B0209 TO 421B0801 51283003

1. Power Cable 6. Battery 12. Grommet

2. Ground Cable 7. Sump Cover 13. Bus Bar
3. Tie Down Strap 8. Battery Box 14. Battery Access Cover
4. Wing Nut 9. Seal 15. Angle Assembly
5. Lockwasher 10. Vent Tube 16. Bonding Jumper
11. Drain Tube

Figure 14-3. Battery and Battery Box Installation

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-5

NOTE:

POWER CABLE (11) CONNECTS THE

EXTERNALPOWERRECEPTACLETO I
THE BATTERY SOLENOID LOCATED IN
THE LEFNGFNGINE NACELLE OR

4 1

421-001 TO 421BO501
51283002
421B0501 AND ON 51283001

1. Nut 6. Screw 8. Lower Skin

2. Lockwasher 6. Receptacle 9. Access Door
3. Ground Strap 7. Bracket 10. Washer
4. Rubber Nipple 11. Cable

Figure 14-3A. External Power Receptacle

Change 11
14-6 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

Installation of Battery. (See figure 14-3.) External Power.

a. Install and assemble components in accordance On aircraft 421-0001 to 421B0801, an optional exter-

I
with figure. Make sure all connectors
nents are secure.

NOTE
and compo- nal power

receptacle
receptacle

is installed
is installed on the underside
the fuselage just forward of the cabin door. On air-
craft 421BO801 and On, the optional external power
under the aft end of the left
of

nacelle. With an external power source connected

When attaching the battery cables to the bat- to the external power receptacle, power is fed to the
tery, be sure cable grommets are properly main bus when the master switch is OFF. To con-
placed over the edges of the battery box. serve the battery, external power should be used for
engine starting in cold temperatures and when testing
CAUTION electrical equipment on the ground. The external
power plug pins should be lubricated periodically with
Make sure battery Master Switch is OFF. petroleum jelly.
Use voltmeter to determine polarity. Re-
verse polarity will damage diodes in the Removal of External Power Receptacle. (See figure
alternators. 14-3A. )

b. Replace the battery access cover and secure a. Remove receptacle in accordance with figure.
with fasteners.
CAUTION
Removal of Battery Box. (See figure 14-3. )
The battery switch must remain in the OFF
a. Remove battery in accordance with battery re- position while the external power receptacle
moval procedure. is being removed or installed. If there is
b. Remove battery box in accordance with figure. any possibility of the switch being turned ON
during this procedure, it is advisable to dis-
Installation of Battery Box. (See figure 14-3.) connect the ground cable from the battery.

a. Install and assemble battery box in accordance Installation of External Power Receptacle. (See
with figure. figure 14-3A. )

CAUTION a. Install and assemble components in accordance

with figure.
Make sure battery box is properly vented
overboard.

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS Î4-7

IALTERNATORS AND REGULATORS. (421-0001 TO composed principally of transistors, diodes, conden-

421A0001) (Delco-Remy) sers, and resistors to form a completely static unit
containing no moving parts. The transistor is an
The alternator is designed and constructed to give electrical device which limits the alternator voltage
long periods of trouble-free service with a minimum to a preset value by controlling the alternator field
amount of maintenance. The rotor is mounted on a current. The diodes, condensers and resistors act
ball bearing at the drive end, and each bearing has a together to aid the transistor in performing this func-
grease reservoir. Only two brushes are required to tion, which is the only function that the regulator
carry through the two slip rings to the field coil performs in the charging circuit. The voltage at
which is mounted on the rotor. The brushes are which the alternator operates is determined by the
extra long and under normal operating conditions regulator adjustment. Once adjusted, the voltage
will provide long periods of service. The stator remains almost constant, since the regulator is un-
windings are assembled on the inside of a laminated affected by either length of service, by change in
core that forms part of the alternator frame. Six temperature, or by changes in the alternator output
rectifier diodes are mounted on the slip ring end and speed. Two regulators are installed on the
frame and are connected to the stator windings. The standard aircraft; however, only one is used, the
six diodes replace the separately mounted rectifier second is a spare. In event of a regulator failure,
as used in other types of applications, and they act the regulator switch can be positioned in STANDBY.
to change the alternator AC voltages to DC voltage Should adjustments be required, an allen screw must
which appears at the battery terminals on the alter- be removed in the top of the regulator to gain access
nators. The transistor regulator is an assembly to adjustment screw. (See figure 14-4.)

Troubleshooting the 50 AMP Alternator and Regulator System. (421-0001 to 421A0001) (Delco-Remy)

TROUBLE PROBABLE CAUSE CORRECTION

BOTH ALTERNATORS FAIL Regulator power circuit breaker Reset.

TO OPERATE open.

Switch faulty. Replace.

Overvoltage protector tripped Reset or replace.

or faulty.

Regulator faulty. Replace.

ALTERNATOR OUTPUT Faulty wiring. Correct as required.

CONTINUOUSLY HIGH
Regulator set too high. Adjust to 27, 5 DC Volts.

Regulator faulty. Replace.

BATTERY CONSUMES Faulty battery. Replace.

WATER RAPIDLY
Regulator set too high. Adjust to 27. 5 DC Volts.

NO VOLTAGE AT BUS Fuse blown. Replace.

BATTERY DOES NOT COME Faulty battery. Replace.

UP TO FULL CHARGE -

ALTERNATORS OPERATING Faulty wiring. Correct as required.

Regulator set too low. Adjust to 27. 5 DC Volts.

AMMETER SHOWN HIGH Shorted diode inside alternator. Disconnect negative battery terminal.
DISCHARGE WHEN ALTER- Connect a #313 light bulb in series with
NATOR SWITCH & BATTERY a 24 volt battery. Connect test leads
SWITCH TURNED ON from battery and bulb to output terminal
(ENGINE NOT RUNNING) of alternator and alternator case. Re-
verse leads light should light on one
-

polarity only if no diodes are shorted.

Replace shorted diodes.

Change 4
14-8 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

Troubleshooting the 50 AMP Alternator and Regulator System. (421-0001 to 421A0001) (Delco-Remy) (Cont.)

TROUBLE PROB ABL E CAUSE CORRE CTION

REGULATOR POWER CIR- Short in regulator or overvoltage Switch to standby regulator. Reset regu-
CUIT BREAKER OPENS protector. lator power breaker. If breaker does
not reopen, determine and replace
faulty regulator or overvoltage protec-
tor.
Faulty wiring (opens in standby Locate and repair,
regulator also).

ALTERNATOR FIELD FUSE Wiring shorted. Locate and repair.

OPENS
Alternator field shorted. Replace alternator.

OVERVOLTAGE PROTECTOR Regulator set too high. Adjust to 27.5 DC Volts.

TRIPS
Protector f aulty. Replace.

NO OUTPUT FROM ONE Alternator field fuse blown. Replace.

ALTERNATOR WITH BOTH
ALTERNATOR SWITCHES Alternator brushes worn. Replace.
ON
Faulty wiring. Repair.

Faulty switch. Replace.

ONE ALTERNATOR OUTPUT Faulty wiring. Repair.

LOW
Faulty alternator field. Replace alternator.

Faulty alternator diode. Replace diode.

NOTE

Any problem which seems to be in the voltage regulator or the overvoltage protector
may be quickly isolated by simply switching the voltage regulator switch to STANDBY
position. If the system then operates properly, the problem is with main voltage
regulator, overvoltage protector, or their wiring. If the same problem still exists,
the problem can then be assumed to be in some other portion of the system, probably
in the alternators themselves.

1100 AMP Alternators

(Optional).
and Regulator
(421-0001 TO 421A0001)
(Westinghouse) voltage is higher than the regulated
citer alternator consists
level.
of a stationary
The ex-
DC field and
a rotating three-phase AC armature. The three-
The optional 100 AMP alternator is a brushless al- phase armature is connected to the main alternator
ternator consisting of two alternators in the same DC field through a half wave rectifier assembly.
housing. One of the alternators produces the DC These rectifiers are mounted on the alternator shaft
power used to supply the load. The second machine between the exciter armature and the rotor field.
supplies the excitation power required by the first When the alternator shaft is rotating and excitation is
alternator. This exciter receives its excitation from applied to the exciter field, an AC voltage is induced
the voltage regulator. The voltage regulator senses in the exciter armature. This voltage is rectified by
the alternator output voltage and in turn delivers a the rectifier assembly and applied to the rotor field.
DC signal to the exciter field. This signal will in- As a result, an AC voltage is induced in the main
crease or decrease in magnitude depending upon alternator stationary winding. This three-phase
whether the alternator output voltage must be raised voltage is applied to a full wave rectifier assembly
or lowered. If the alternator output voltage is lower and is converted to a DC voltage at the output termi-
than the regulated level, the excitation signal will be nals. A capacitor is connected across the output
of a greater magnitude than if the alternator output terminals to act as a voltage spike suppressor.
Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS Î4"$

Experience has shown that a suppressor is required stator, the rotor, the slip ring end head, the drive
to reduce voltage spikes which could destroy the end head and the rectifiers. The stator consists of
diodes. The alternator is engaged to the engine a laminated iron core on which three phase windings
through a gear drive. A special cushion is used in are wound in slots around the inside circumference.
the drive assembly to isolate torsional vibration and The manner in which the three windings are connec-
insure a longer life. Sealed precision bearings are ted together makes the stator a "WYE" type. Leads
used in the 100 Amp alternator and need replacing are connected to each of the three points of the phase
at approximately 1500 hours of operation. The 100 windings and each lead is connected to a pair of
Amp alternator system uses a transistorized regula- diodes, one negative and one positive. The rotor
tor having no moving parts and does not depend upon consists of a single field coil encased between two
a mechanical action for its operation. Instead of four-poled, interleaved iron sections assembled on
mechanical action, the regulator utilizes transistors the shaft. The ends of the field coil are connected to
and diodes. Basically the regulator consists of three a pair of slip rings which are insulated from each
circuits; voltage reference, voltage error detector other and from the shaft. The slip ring end head
and power switch. The voltage reference circuit supports the rectifier mounting plate and the negative
supplies a constant reference voltage which is used rectifiers, a prelubricated bearing in which the rotor
for comparison with the line voltage to determine shaft rotates, the brush holders and brushes, the
voltage error. The error detector circuit makes the field and output terminals, and a ground screw or
comparison between the reference voltage and the terminal. The drive end head supports a sealed,
line voltage, then sends a signal to the transistor prelubricated ball bearing in which the drive end of
power switch. The power switch is the output stage the rotor shaft rotates. The negative rectifiers are
of the regulator, it controls the alternator field volt- pressed in the slip ring end head and the positive
age. Since the field resistance remains virtually rectifiers are pressed into the heat sink (rectifier
constant, due to a temperature compensating winding, mounting plate) and are connected to the stator leads.
the field current is controlled also. The majority of
the regulator components are mounted on a printed The principal components of the regulator are the
circuit board. This provides a more rugged unit, transistors, the rectifier diode, the
zener diode,
with a greater freedom from vibration, and simpli- and the resistors. Thetransistor is an electronic
fies repair. A potentiometer is provided, at the switch which can turn on and turn off the flow of cur-
front of the regulator, to permit adjustment of the rent in an electric circuit. It has no mechanical or
bus voltage to any desired level between 25. O to 28. 5 moving parts to wear out. The zener diode, in
volts. This allows compensation to be made at time addition to passing current in the forward direction,
of installation for the differences in feeder drops be- will pass current in the reverse directîon only when
tween systems. After the adjustment has been made, a particular value of voltage is applied in the re-
a lock is provided to secure potentiometer. verse direction. It is this zener action which makes
it adaptable for use as a voltage sensing device in
the regulator. The resistors are used to limit the
ALTERNATORS AND REGULATORS. (421A0001 and flow of current. The voltage at which the alternator
ON) (Prestolite) operates is determined by the regulator adjustment.

The principal components of the alternator are the

Troubleshooting the 100 AMP Alternator and Regulator System.

I
TROUBLE PROBABLE CAUSE CORRECTION

BATTERY CONSUMES WATER Faulty battery. Replace.

RAPIDLY
Regulator set too high. Adjust to 27. 5 DC Volts.

BATTERY DOES NOT COME Faulty battery. Replace.

UP TO FULL CHARGE -

ALTERNATORS FUNCTION- Faulty wiring. Correct as required.

ING PROPERLY
Regulators set too low. Adjust to 27. 5 DC Volts.

ONE ALTERNATOR FAILS Alternator field fuse open. Replace.

TO OPERATE
Switch faulty. Replace.

Wiring faulty. Correct as required.

Overvoltage protector open. Reset.

Change 4
14-10 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Troubleshooting the 100 AMP Alternator and Regulator System (Cont.)

TROUBLE PROBABLE CAUSE CORRECTION

ONE ALTERNATOR FAILS Regulator faulty. Replace.

TO OPERATE (CONT.)
Alternator faulty. Replace.

BOTH ALTERNATORS FAIL Battery switch open or faulty. Close switch or replace as required.
TO OPERATE

ONE ALTERNATOR OUTPUT Regulator set too low. Adjust to 27. 5 DC Volts.
CONTINUOUSLY LOW
Regulator faulty. Replace.

Wiring faulty. Correct as required.

Faulty alternator field. Replace alternator.

Faulty alternator diode. Replace diode.

ONE ALTERNATOR OUTPUT Regulator set too high. Adjust to 27. 5 DC Volts.
CONTINUOUSLY HIGH
Regulator faulty. Replace

Wiring faulty. Correct as required.

Alternator faulty. Replace.

AMMETER SHOWS HIGH DIS- Shorted diode inside alternator. Disconnect negative battery terminal.
CHARGE WHEN ALTERNATOR Connect a #313 light bulb in series
SWITCH AND BATTERY with a 24 volt battery. Connect test
SWITCH ARE ON (ENGINES leads from battery and bulb to output
NOT RUNNING) terminal of alternator and alternator
case. Reverse leads light should
-

light on one polarity only if no

diodes are shorted. Replace shorted
diode.

ALTERNATOR FIELD FUSE Wiring shorted. Correct as required.

OPENS
Regulator faulty. Replace.

Alternator field shorted. Replace alternator.

OVERVOLTAGE RELAY TRIPS Transient voltage. Turn off both alternator switches and
battery switch to reset relay.

Regulator set too high. Adjust to 27. 5 DC Volts.

Relay faulty. Replace relay.

NO VOLTAGE AT BUS Blown fuse. Replace.

Overvoltage Troubleshooting Information (100 Amp volts DC. The following procedures are typical for
Westinghouse Alternator). right and left alternator systems.

If an overvoltage has occurred the following checks NOTE

should be performed.
When testing trip voltage setting, the 500 uf
a. Overvoltage relays. capacitor and 51 ohm resistor must be a part
1. (See figure 14-2. ) Check overvoltage protectors of the test circuit.
(2 or 38) that trip voltage is between 32. O and 36. O

Change 8
 421 SERVICE MANUAL ELECTRICAL SYSTEMS l4 ÎÛA

CAUTION ening process.

c. Battery.
Overvoltage protectors must be isolated from 1. Insure that battery is properly serviced and that
the aircraft wiring system when checking trip .
ground bus bar is making good ground with the battery
setting, box. Bus bar to battery box mating surface should be
free of all paint, corrosion or other insulating mate-
(a) Insure that overvoltage protector part number rial.
is 9MC7-3-28 V. d. Wiring.
(b) Refer to applicable wiring diagram and isolate 1. Check field sensing leads and alternator output
overvoltage protector, capacitor and resistor power and ground wires for shorts and breaks.
from aircraft wiring.
(c) Using a variable voltage supply, apply voltage NOTE
until protector breaks.
(d) If voltage is within limits remove voltage sup- An intermittently shorted field wire between
ply, restore aircraft wiring and reset over- the regulator and the alternator can cause
voltage protector. overvoltage conditions and a direct shorted
On aircraft equipped with Prestolite Alternators, the field lead can cause damage to the voltage
overvoltage relay may be checked on the bench or in regulator that could result in overvoltage
the aircraft. If the overvoltage relay is to be check- conditions or complete loss of output.
ed installed in the aircraft it will be necessary to
disconnect wiring at the electrical terminals and NOTE
proceed as follows:
a. Connect a 28 VDC test lamp across the field and A directly shorted output wire can create an
ground terminals. overshoot of the alternator voltage which may
b. Connecf a DC voltmeter across the battery and cause local damage where the short occurs.
ground terminals.
2. Check ground return on alternator for good re-
NOTE turn to the engine case and then thr ough the engine
bonding strap to the airframe.
Voltmeter must have an accuracy of ±270.
CAUTION
c. Connect a variable DC power supply 0-50 VDC.
Connect positive lead to battery terminal on the over- Copper terminals or splices should never be
voltage relay and the negative to the ground terminal used to repair aluminum wiring.
on the overvoltage relay.
d. Turn on power supply and adjust output voltage 3. Inspect all terminals in the power generating
for 28 volts. Observe that the test lamp is illuminat- circuit for any loose or damaged connections. A
ed. If lamp is not ON, the relay is defective and loose connection can create unbalanced conditions
must be replaced. in load, voltage and possible failure of the junction.
e. Allow the relay to operate at 28 volts for three e. Generating circuit components.
hours and check that the test lamp remains on. If 1. Check alternator and battery shunts for loose
the lamp does not remain on, the relay must be re- conducting bars at solder joints.
placed. 2. Inspect fuse holders for good solder joint con-
f. Check the relay trip voltage by slowly increasing nections and for cracked or broken housings. Insure
the output voltage. Increase the output voltage using that current carrying metal parts are free of corro-
a rate of approximately three volts per second until sion, check field fuses for continuity.
the test lamp goes out. Check that voltmeter indi- 3. Check battery and alternator field switches for
cates 33 Y ±. 5 volts. If the test lamp does not go out damage or excessive resistance through the contacts.
the relay is defective and must be replaced. 4. Check alternator power circuit breakers for
loose connections, damage or resistance through
NOTE contacts.
5. Check battery relay for proper operation and
Due to variations in operating conditions and bus bars for corrosion.
the rate at which voltage is applied, the value 6. Check all external diodes on the field circuit for
of the voltage could vary ±1. 5 volts and be open or short circuits,
acceptable. 7. Inspect the ammeter select switch for damage
and shorts.
b. Voltage regulators. 8. Check alternator and regulator RFI filters for
1. Insure that
regulator voltage settings are cor- open or short circuits. Use only approved filters
rect. as follows:
2. Regulators must be adjusted to carry equal loads Alternator Filter P/N 93874 Sprague Shunt or
at 1200 prop RPM and a total of 40 to 50 amp load Capacitor P/N CA275X Mallory.
(20 to 25 amp load per alternator). Regulator Filter P/N TC3501A Cornell-Dubilier.
3. Insure that regulator adjustment locknut is prop- 9. Inspect defrost air duct adjacent to voltage reg-
erly tightened and setting is not changed during tight-
Change 10
14-10B ELECTRICAL SYSTEMS 421 SERVICE MANUAL

COTTER PIN HEAD

IN SLOT

CUT AND BEND AS SHOWN.

MUST NOT TOUCH THRUST
WASHER AND MUST NOT I /
EXTEND BEYOND END
OF SHAFT.

Detail D 12

POSITIVE a
TERMINAL Detail A

1 NEAL
Û l 1 15

*16
e 16 16

17
100 AMP n
50 AMP
ALTERNATOR Detail D
ALTERNATOR
421B0129 AND ON
*421-0001 TO 421B0129 10503003
A10502002
Detail $ 351181022

I
1. Left Alternator 9. Gasket 14. Key
C10581001
010282001

5. Right Alternator
2. Console Panel 6. Lockwasher 10. Hub 15. Alternator-Out Sensor
3. Main Regulator 7. Nut 11. Washer 16. Diode
4. Spare Regulator 8. Washer 12. Nut 17. Capacitor
13. Cotter Pin 18. Ground Cable

Figure 14-4. Alternator and Regulator Installation (Sheet 1 of 2)

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-10C

REGULATOR ADJUSTING SCREW REGULATOR ADJUSTING SCREW

50 AMP REGULATOR 100 AMP REGULATOR
421-0001 TO 421A0001 421-0001 TO 421A0001

Detail E notaii E

VARIRESISTOR
USED WITH 9910126-1
REGULATOR ONLY

505 GND

.. 421BO301 AND ON

REGULATOR ADJUSTING SCREW

50 OR 100 AMP REGULATOR
421A0001 TO 421BO301

Detail Ë

Figure 14-4. Alternator and Regulator Installation (Sheet 2)

Change 12
14-100 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

ulators for damage or leaks. Excessive localized Installation of Alternator.

heating may cause intermittent failure of the regula-
tor. The installation of the alternators is the same for
both engines and either 50 Amp or 100 Amp alterna-
NOTE tor.
a. Make sure gasket has not been damaged or has
On aircraft incorporating SK421-51 an inter- been replaced.
rupter is added on the alternator output line b. Position alternator on engine pad.
to prevent possibility of damage to equipment
in the event of an uncontrolled alternator. CAUTION
The interrupter is controlled by the alternator
field switch to insure that power is removed Before installing alternator always make sure
from the line when the alternator field switch the nut on the drive shaft of the alternator is
is opened. safetied with the cotter pin installed as shown
in Figure 14-4. If the nut is not safetied pro-
perly damage could result to the gears and
Removal of Alternator. (See figure 14-4.) alternator shaft.

The removal of the alternators is the same for both c. Work alternator in position and install washers,
engines and either 50 Amp or 100 Amp alternator. lockwashers, and install nuts securing alternator.
d. Torque nuts to 155 to 175 inch-pounds.
a. Remove the upper cowling. e. Connect electrical wiring.
b. Remove the nose cap cowling.
c. Disconnect and tag wires from alternator and CAUTION
stow out of the area.
d. Remove nuts, lockwashers and plain washers Be sure alternator wiring is connected prop-
securing alternator to engine. perly. Reverse polarity will destroy diodes
e. Carefully work the alternator from the engine in the electrical system.
pad.
NOTE
CAUTION
When replacing 50 amp alternator with a 100
Use care when removing alternator to pre- amp alternator, add ground wire from alter-
vent damage to splines on the alternator- nator to engine case bolt.

f. Install nose cap cowling.

g. Install upper and lower cowl.
Alternator Hub Replacement. (See figure 14-4. )

a. Remove alternator hub as follows: Removal and Installation of Voltage Regulator. (See
1. Remove cotter pin (13); then using special figure 14-4.)
wrench, P/N 5090005-1, to hold shaft from turning,
remove nut (12) and thrust washer (11). The removal and installation of the voltage regulator
2. Pull alternator drive gear hub (10) from alter- is the same for either 50 Amp or 100 Amp system.
nator shaft using care not to damage hub assembly.
b. Install alternator hub as follows: a. Remove voltage regulator covers (aft and for-
1. Apply clean engine oil to shaft of alternator and ward) by removing screws attaching covers to side
install key (14). console.
2. Slide alternator drive gear hub (10) onto shaft b. Tag and disconnect electrical wiring.
and onto key (14). c. Remove screws securing voltage regulator to
3. Install thrust washer (11) on alternator shaft shelving.
with bearing material (copper color) side toward the d. Remove regulator.
hub. e. Install regulator by reversing the removal pro-
4. Install nut (12); then using a special wrench cedure.
P/N 5090005-1 to hold shaft from turning, torque
nut to 450-500 inch-pounds.
NOTE
NOTE
After voltage regulator has been mounted in
Ensure wrench 5090005-1 is aligned and position and wired, perform the Operational
seated in notch of alternator drive gear hub Check and Adjustment of Alternators and
flange so that no damage will occur when Regulators.
tor que is applied to nut.

5. Install cotter pin as shown in Detail¾.

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMs 14-10E

Operational Check of Alternator and Regulator. light loads, the alternator which
is set at
421B0001 and On and Aircraft Modified by SK421-47 higher RPM will tend to take all
of the load
and SK421-50. and the alternator running at lower RPM
will be at a no load condition which will tend
a. With both engines operating at 1000 RPM, and to give a false alternator out indication.
the battery and alternator switches on, check the
following: Operational Check of Alternator Warning System.
1. Select voltage position on voltmeter and assure 421B0001 and On and Aircraft Modified by SK421-47
bus voltage is 27. 5 ±1. 0 volts. and SK421-50.
2. Select battery position on voltmeter and note
battery is charging; charging amperage indication a. With both engines operating 1700 RPM and nor-
will vary as the battery builds up to normal charge. mal electrical load applied, push the press-to-test
3. Load electrical system with all external lights, switch and hold in for at least 30 seconds, and in-
fuel pumps, pitot heat, etc., and check the alterna- sure both alternator out lights are on.
tor output; it should be positive and equal within 10 b. Insure that pushing the press-to-test switch
amps when loaded up to 100 amps total load- does not trip the landing gear motor breaker.

NOTE
PRECAUTIONS TO BE OBSERVED WHEN TESTING
If total load is below 15 amps, one alternator OR SERVICING THE ELECTRICAL SYSTEM.
may show little or no output. If so, turn pro-
ducing alternator OFF; the other alternator a. Disconnect the battery, before connecting or dis-
should then pick up the load. Also, when one connecting test instruments (except voltmeter) or be-
alternator is not carrying any load, the cor- fore removing or replacing any unit or wiring. Ac-
responding light may come on or flicker on cidental grounding or shorting at the regulator, alter-
and off. This is normal. nator, ammeter , or accessories, will cause severe
damage to the units and/or wiring.
Operational Check of Alternator Failure Circuit. b. The alternator output lead must not be removed
421B0001 and On and Aircraft Modified by SK421-47 from the alternator with the field circuit energized
and SK421-50. and the alternator operating.
c. Do not attempt to polarize the alternator. No
a. With both engines operating at idle RPM, place polarization is required. Any attempt to do so may
battery switch and alternator switches to OFF, and result in damage to the alternator, regulator or cir-
observe that failure lights are out. cuits.
b. Reduce electrical load to minimum to avoid dis- d. Grounding of the alternator output terminal may
charging the battery. damage the alternator and/or circuit and components.
c. Turn on battery switch and observe both alterna- e. Reversed battery connections may damage the
tor failure lights illuminate full on. rectifiers, vehicle wiring or other components of the
d. Increase engine RPM to 1800 and insure failure charging system. Battery polarity should be checked
light remain ON. with a voltmeter before connecting the battery. Most
vehicles are negative ground.
NOTE f. If a booster battery or fast charger is used, its
polarity must be connected correctly to prevent dam-
The reference voltage used for alternator age to the electrical system components.
out indication is approximately one half of g. When using an auxiliary power unit, make sure
whatever voltage the alternator is produc- the voltage and polarity are set to correspond with
ing. When the alternator is turned OFF, it the vehicle system voltage and polarity.
is capable of producing some voltage which
will be a function of load and RPM of unit.
At high RPM such as maximum power, the Operational Check and Adjustment of Alternators and
Regulators. (421-0001 to 421A0118) (Westinghouse)
residual voltage at times can exceed the
fail triggering level of the sensor, turning
the failure lights OFF; this is acceptable. a. Remove wire No. P39C12 (left regulator) and
P40C12 (right regulator) from field terminals of
e. With both alternators and battery switches ON voltage regulators and check their resistance to
and light electrical load of 15 amps operate both en- ground; their resistance should be approximately 15
gines at idle RPM and observe that lights remain off ohms. Replace each wire after resistance measure-
without any flickering. Increase RPM on both engines ment.
together, to 1800 RPM and again observe for any b. Remove wire No. P81A14 (left regulator) and
flickering. P82AA (right regulator) from Positive (+)terminal
of voltage regulator and measure voltage with battery
NOTE and applicable alternator field switch on. Voltage
should be battery voltage, approximately 24 volts DC.
It is important that both engine RPM be as Each wire voltage should be interrupted by either
close to each other as possible because at opening battery switch or its own alternator field
switch. Replace each wire after measuring voltage.

Change 10
14-10F ELECTRICAL SYSTEMS 421 SERVICE MANUAL

c. Connect a orecision voltmeter with minimum of meter reading 30 to 50 amps output, by loading the
29 accuracy to the aircraft main bus and aircraft system with equipment when operating requires this
ground. (Note that the main bus referred to herein amount of load. Adjust voltage regulator to 27. 5
is all the wiring and bus bars connected between the ±0. 25 volts DC. Record exact alternator output am-
two alternator power circuit breakers and all the perage. Shut down engine.
distribution circuit breakers and not the plus termi- d. Start right engine and repeat above procedure;
nal at the regulators or any other location.) except after warm-up, adjust regulator to obtain the
d. Start left engine per normal starting procedure. same ammeter reading as recorded on left engine.
With the battery and left alternator switches on, in- e. Operate both engines and warm-up per above
crease RPM slowly and monitor alternator output procedure. Check voltage setting for 27. 5 volts on
voltage so as not to exceed 29 volts DC. If voltage each alternator. Left and right alternator voltage
exceeds 29 volts when 600 prop RPM is reached, should be within 0. 50 volts of each other.
adjust left-hand regulator setting to a level of 27 to f. Repeat the above procedures for setting the
29 volts. standby voltage regulator.
e. Start right engine per normal starting proce-
dures and maintain at low idle. Turn left alternator
switch off and right alternator switch on, increase Operational Check and Adjustment of Alternators and
RPM slowly and monitor alternator output voltage as Regulators (421B0301 and On).
outlined in step d.
f. Turn on left alternator switch and observe that a. Install a 270 voltmeter connected to the aircraft
the bus voltage does not exceed 29 volts. power bus. (The power bus is considered to be be-
g. Turn off right alternator switch and operate left tween the alternator power circuit breakers and the
engine at 1000 RPM. Load the system with approxi- individual circuit breakers for each system and not
mately 20 to 30 amps by turning on equipment (Rota- at the cigar lighter.)
ting Beacon, Landing Lights, Taxi Light, etc.). b. Disconnect the paralleling wire (terminal marked
Allow system to warm-up a minimum of 10 minutes. "PAR") from either regulator and leave it disconnect-
h. Turn off all equipment; a DC load of zero to 7 ed thru step k.
amp should now be on the aircraft's meter.
NOTE
NOTE
All adjustments are performed while operat-
On aircraft with AC-DC alternator, do not ing only the LH engine. (RH engine shall not
turn on the AC windshield while regulator be running.)
setting is being made.
c. With LH engine running at 1200 prop RPM, turn
i. With left engine operating between 1000 and 1200 LH alternator field switch ON. (RH alternator switch
RPM, set the voltage regulator adjustment so that must be OFF.) Add 10 to 15 amp load to LH alter-
the voltage at the bus is at 27. 5 ±0. 25 volts DC. nator. Run this load for at least 2 minutes.
j. With right engine operating at the same RPM as
that of the left, turn on the RH alternator switch and NOTE
operate both alternators in parallel. Turn on 30 to
40 amp load and adjust right regulator to equally To adjust voltage regulator, remove the snap
share the load. plug from the upper face of the regulator and
insert allen wrench.
Operational Check and Adjustment of Alternators and
Regulators (421A0118 to 421B0301 and aircraft incor- d. Adjust LH regulator adjustment to read 27.5
porating SK421-47 and SK421-50). volts on the voltmeter connected to the aircraft bus.
Allow sufficient time for voltage to stabilize between
a. Remove wires from field terminal of the main adjustment.
voltage regulator and check resistance of alternator
field; resistance should be approximately 15 ohms. NOTE
Replace wire after resistance measurement.
b. Remove wire from positive (÷)terminal of the The aircraft voltammeter shall not be used
voltage regulator and measure voltage with battery for voltage setting.
and applicable alternator field switch on. Voltage
should be battery voltage, approximately 24 volts DC. e. Replace the snap plug in the LH regulator adjust-
Voltage should be interrupted by either opening bat- ment access hole and do not make any further adjust-
tery switch or its own alternator field switch. Re- ments on the LH regulator.
place wire after measuring voltage. f. While continuing to operate the LH engine and
c. Start left engine per normal starting procedure. alternator with the same electrical load as before,
With left alternator switch ON, increase RPM slowly turn the RH alternator field switch ON. (RH engine
and monitor alternator output voltage. Adjust volt- is still not running.)
age if required to prevent voltage exceeding 29 volts g. The remaining adjustments should be made using
DC. Operate engine at 1500 RPM. Allow system to either a Simpson 260 or a Triplett 630 VOM.
warm-up a minimum of 10 minutes with aircraft am-

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMS S-D

CAUTION BATTERY MASTER AND ALTERNA TOR SWITCHES.

Observe with caution that the field circuits A battery master switch is located between the left
of either system never touch ground or and right alternator switches on the left side of the
other electrical circuits, even for an in- stationary panel. A switch bar is installed across
stant, or the regulators may be damaged. the top of the three switches to permit simultaneous
shut off. When the battery is placed in the ON posi-
h. Select VOM to 0-50V scale and connect VOM be- tion it actuates a heavy duty relay which connects the
tween the field terminals of the left and right regula- battery to the bus bar. The alternator switches are
tors (plus side meter to LH regulator). connected electrically in the alternator field circuit.
i. Now very slowly rotate the RH regulator voltage
adjustment while observing the voltmeter which has
been connected to the two field terminals. Removal of Battery and Alternator Switches.
1. If a reverse (downscale) reading is obtained,
turn the RH regulator adjustment counterclockwise, a. Remove nut securing switch to stationary panel.
this should bring the meter upscale. b. Tag and remove wires from the switch.
2. Then very slowly turn RH regulator adjustment
clockwise to the point where the field voltmeter will CAUTION
read near zero.
During of any switch except the bat-
removal
NOTE tery switch, the
battery switch must remain
OFF. When removing the battery switch, dis-
A stable reading should not be expected, connect the ground cable from the battery to
voltage will fluctuate. prevent an accidental short circuit.

3. Then using the 0-10 volt and 0-2. 5 volt scales on

the VOM continue adjustment of the RH regulator to a Installation of Battery and Alternator Switches.
lower voltage differential. (The 0-2. 5 volt scale is (See figure 14-5.)
recommended for making the final adjustment.) The
correct adjustment has been achieved when the meter a. Connect the wires to proper switches and remove
will remain briefly in the vicinity of zero, swinging tags.
both upscale and downscale. b. Insert switch in proper position in the switch
j. Replace the snap plug in the RH regulator adjust- panel and secure with nut.
ment hole.
k. Shut down all power to the aircraft and discon-
nect VOM from field terminals.
1. Restore the paralleling wire removed by step b.
above.
m. After aircraft has been restored to original
configuration, the RH engine should be started, both
alternators turned on and system should be operated
at different loads to verify that paralleling is within
10Ÿoof load and bus voltage has remained within the
27. 5 ±. 25 volt limit.

Change 10
14-12 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

mounting screws.
Removal and Installation of Side Console.
c. Tag and disconnect wiring.
d. Disconnect electrical plug.
a. Remove upholstery panel on side of console.
e. Remove the four screws securing annunciator
b. Remove screws attaching console to structure,
panel.
c. Lift console from floor to gain easier access to f. Remove press to test switch.
connectors and.leads. Disconnect electrical con-
g. Carefully remove annunciator panel,
nectors. Tag and disconnect cables and leads,
d. Remove console from aircraft.
e. Install console using reverse order.
and Replacement of Annunciator
.

Removal Panel
Diodes. (See figure 14-4A.)
Removal and Installation of Side Console Circuit
Breaker Panel.
a. Using a soldering iron and needle nose pliers,
NOTE unsolder and remove old diode.
b. Solder new diode in place.
When optional electroluminescent panels are
NOTE
installed, these panels must be removed
first, in order to gain access to circuit break-
er panel attaching screws. When soldering printed circuit boards and
diodes always use some means of heat sink
a. Remove the four attaching such as needle nose pliers. Heat could
screws, one at each
cause damage to diodes.
corner, and lift panel up and out.

NOTE Removal and Replacement of Individual Light Assem-

bly. (See figure 14-4A.)
Panel is still attached to console by a wire
bundle assembly. Components may be re- a. With annunciator panel removed from shock
moved, replaced, or installed with panel in panel remove mounting brackets, top or bottom, de-
this position. pending which is closest to light assembly to be re-
moved.
b. Remove and replace components as may be re- b. Unsolder light from printed circuit board and
quired. remove light assembly.
c. If panel is to be removed, tag and disconnect c. Replace light assembly using caution to prevent
electrical leads. damage to circuit board and diodes.
d. Remove panel from aircraft. d. Install mounting brackets.
e. Install panel using reverse order.

Installation of Annunciator Panel. (See figure 14-4A.)

ANNUNCIATOR PANEL (421B0001 and ON)
a. Position annunciator panel in place and install
Sixteen annunciator lights stacked side by side, cou- four screws.
pled by a printed circuit board on the rear and mount- b. Connect electrical plug.
ing brackets on the top and bottom make up the an- c. Install press to test switch,
nunciator panel. These multi-colored lights will il- d. Connect wiring and remove tags.
luminate within a circuit to indicate various functions, e. Install instrument pnael in place.
operations and failures during flight. A press to test f. Turn on power and check operation of annuncia-
button located to the left of the annunciator panelwill, for panel.
when pressed, cause all lights on the annunciator g. Refer to figure 14-4A for proper color coding.
panel, along with the propeller synchronizer if in-
stalled, and auxiliary fuel tank indicator to illumi-
nate. Removal and Replacement of Annunciator Light
Bulbs. (See figure 14-4A.)

a. On the light with the bulb to be replaced push in

Removal of Annunciator Panel. (See figure 14-4A.) on the frame of the light assembly and allow light to
pop out.
a. Turn off all power. b. Rotate the light capsule 90 degrees.
b. Lower left hand instrument panel by removing c. Lift bulb out of light capsule and insert new bulb.
d. Rotate light capsule in place and insert into posi-
tion. Press firmly into proper place.

Change 11
 14-Î A
421 SERVICE MANUAL ELECTRICAL SYSTEMS

10

8
Detail
5

421B0001 AND ON

i. Bracket 5. Light Capsule 9. Lamp

. Circuit Board 6. Clear Lens 10. Press To Test
C Basic Unit 7. Legend Switch
Diode 8. Color Filter 11 Plug

Figure 14-4A. Annunciator Panel Installation

Change 11
14-128- ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Removal and Replacement of Annunciator Light b. Install switch in panel and secure with decorative
Lens. (See figure 14-4A.) nut,

a. Press light in and allow light capsule to pop out,

b. Rotate clip on each side of the lens housing, one Removal and Installation of Starter Switches.
side up, the other side down.
c. Carefully pull lens housing from light capsule. a. Remove left console side cover.
d. Press out clear lens, filter, legend disperser, b. Loosen switch guard and remove nut securing
and clear lens. guard and switch to panel.
c. Tag and remove wires from the switch.
CAUTION
CAUTION
Do not attempt to pry lens housing apart
from lens; the housing will break. When removing starter switches, it is advis-
able to remove negative cable from the bat-
e. Insert the clear lens, filter, legend disperser tery to prevent the starter circuit from being
and clear lens in proper order, energized during removal of switch,
f. Insert lens housing and lock into place with clip,
one up, the other down. d. To install switch, connect the wires to the switch
g. Press light into panel. and remove tags,
e. Install switch in the panel, secure with guard and
nut.
f. Replace console panel cover.
STATIONARY INSTRUMENT PANEL.

Mounted on the stationary instrument panel are the

cowl flap switches, landing gear switch and the flap Removal and Installation Switches and Circuit
switch. There are six rheostats mounted on the Breakers. (Typical) (See figure 14-2A.)
stationary instrument panel to control the dimming
of the left hand console lights, flight instrument a. Turn off all power.
lights, switch panel lights, radio panel lights, com- b. Remove pilot's seat.
pass light and engine instrument lights. c. Remove console side cover to gain access to
applicable switch or circuit breaker.
d. Remove electroluminescent light panel as re-
SWITCHES. quired.
e. Identify, tag and remove wires from switch or
Typical Switch Removal. (See figure 14-5.) circuit breaker.
f. Remove nut and washer securing switch or cir-
a. Loosen and remove the decorative nut securing cuit breaker to panel. Remove switch.
switch to the switch panel and remove switch from g. Install switch or circuit breakers by reversing
the panel. the removal procedures.
b. Tag and remove the wires from the switch.
Typical Switch Installation. (See figure 14-5.) LIGHTING SYSTEM

a. Connect wires to proper switches and remove The standard exterior lighting system consists of the
tags. navigation lights, tail light, top and bottom rotating
beacors and a left landing light. Optional exterior
lights consist of the right landing light, deice light,
Trouble Shooting the Lighting System.

TROUBLE PROBABLE CAUSE CORRECTION

ONE NAVIGATION LIGHT IS Lamp burned out. Replace lamp.

OUT
Defective wiring. Check/repair or replace wiring.

Defective lamp socket. Replace light assembly.

Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14 13

10 2
Detail
7

Detail

14
3
3

Detail

Detail Ô

421-0001 TO 421B0201

A D B C

421-0001 TO 421B0001 51182009

1. Lens Cap 6. Switch 10. Bracket

2. Bulb 7. Switch Bar 11. Knob
3. Nut 8. Pin 12. Keyed Washer
4. Lockwasher 9. Cotter Pin 13. Instrument Panel
5. Light Body 14. Rheostat

Figure 14-5. Stationary Panel Components Installation

Change 10
14-14 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

1
2
3

10
6
Detail Detail B

GEAR UNLÓCKED GEAR DOWN AND LOCKED

INDICATOR LIGHT INDICATOR LIGHT

421B0201 AND ON

1. Light Assembly 5. Lens Assembly 9. Lens Assembly

2. Locking Cam 6. Lamps 10. Lamps
3. Screw 7. Screw 11. Locking Cam
4. Instrument Panel 8. Lamp Socket Assembly 12. Backshell

Figure 14-5A. Landing Gear Indicator Lights

Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-14A

TROUBLE PROBABLE CAUSE CORRE CTION

ALL NAVIGATION LIGHTS Circuit breaker out. Check/reset circuit breaker.

ARE OUT
Defective wiring or navigation Check/repair or replace wiring.
light switch. Replace navigation light switch.

LANDING LIGHT EXTENDS Circuit breaker out. Check/reset.circuit breaker.

BUT DOES NOT LIGHT
Lamp burned out. Replace lamp.

Defective wiring. Check/repair or replace wiring.

LANDING LIGHT WILL NOT Circuit breaker out. Check/reset circuit breaker.
EXTEND OR WHEN EX-
TENDED WILL NOT Defective wiring. Check/repair or replace wiring.
RETRACT
Defective switch. Replace switch.

Defective landing gear light. Replace landing light.

ROTATING BEACON LIGHTS, Defective motor. Replace light.

BUT WILL NOT ROTATE
Defective wiring. Check jumper wire in connector.

ROTATING BEACON LIGHT Lamp burned out. Replace lamp.

WILL NOT LIGHT
Defective wiring. Check/repair wiring.

TAXI LIGHT DOES NOT Circuit breaker out. Check/repair wiring and/or
OPERATE replace switch.

Lamp burned out. Replace lamp.

COURTESY LIGHT OUT Circuit breaker out. Check/reset circuit breaker.

Defective switch or wiring. Check/repair wiring and/or

replace switch.

Lamp burned out. Replace lamp.

DEICE LIGHT OUT Circuit breaker out. Check/reset circuit breaker.

Defective switch or wiring. Check/repair wiring and/or

replace switch.

Lamp burned out. Replace lamp.

INSTRUMENT LIGHTS OUT Lamp(s) burned out. Replace lamps.

GROUP OF INSTRUMENT Defective transistor heat sink Replace transistor.

LIGHTS OUT assembly.

Defective dimmer control. Replace defective resistor.

and/or efective potentiometer.

Change 11
14-14B ELECTRICAL SYSTEMs 421 SERVICE MANUAL

taxi light, and a strobe light. The standard interior e. Transistors (4) may be removed from the heat
lights consist of a cabin door light, a dome light, sink assembly by removing nut, screw, lockwasher
four cabin reading lights, overhead console lights, and mica washer.
a map light, three left hand console panel lights lo- d. Identify electrical leads from transistor to side
cated in the pilot's armrest and fuel selector lights. in reinstallation and disconnect leads.
The instrument panel lights consist of the warning e. Install transistors and heat sink assembly by
lights, compass light, a call letter light, and the reversing the removal procedures.
instrument lights. If desired, an optional lighted
seat belt sign, oxygen sign and post lights for option- Removal and Installation of Dimming Control Assem-
al instruments may be installed. On aircraft bly. (See figure 14-5B.)
421B0001 and On a dimmer control and a transistor
heat sink controls the lighting intensity. On aircraft a. Disconnect electrical wiring at electrical plug
421BOOO1 to 421B0301, the transistor heat sink as- (7).
sembly is located on the right aft side of the forward b. Remove switch handles (12) from dimming con-
pressure bulkhead. On aircraft 421B0301 and On, the trol assembly (6).
transistor heat sink is located on the forward center c. Remove four screws securing dimming control to
side of the forward pressure bulkhead. On aircraft stationary panel (11) and remove dimming control
421B0001 to 421BO301, the dimmer control is mount- from behind panel.
ed on the stationary panel; on aircraft 421B0301 and d. Remove screws, nuts and spacers securing cir-
On, the dimmer control is mounted on the center cuit board (8) to dimming control assembly.
pedestal. On aircraft 421B0001 to 421BO301 a dim- e. Resistors (9) and potentiometers (10) may be
ming control for auxiliary fuel quantity lights is replaced if required by unsoldering electrical con-
mounted on the forward side of the stationary switch nections.
panel at the inboard side of the glove compartment; f. Install resistors, potentiometers, circuit board
on aircraft 421B0301 and On it is mounted above the and dimming control assembly by reversing the re-
center pedestal. moval procedures.

Removal of Landing Gear Switch and Indicator Light.

Removal and Installation of Heat Sink Assembly. (See figure 14-5.) (421-0001 to 421B0201)
(See figure 14-5B. )
a. Unserew and remove wheel shaped knob from
a. Disconnect connector from aircraft wire bundle. switch.
b. Remove four screws securing heat sink assem- b. Remove the nut securing swítch to panel and re-
bly (2) to forward pressure bulkhead (1) and remove move the switch from the rear of the panel.
heat sink. c. Tag and disconnect wires from the switch.
d. To remove the indicator lights, remove the lens
and bulb.
e. Loosen nut securing light to panel and pull light
forward from paneL
f. Unsolder and tag wires from light.

Installation of Landing Gear Switch and Indicator

Light. (See figure 14-5.) (421-0201 to 421BO201)

a. To install indicator light, solder wires to light

and remove tags.

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-14C/14-14D

3
4
5

Detail
TYPICAL INSTALLATION

421B0001 T 421Bo301 5

421BO301 AND ON

51183014
A51181015
B51181032
BS5181023

1. Forward Pressure Bulkhead 7. Electrical Plug 12. Switch Handle

2. Heat Sink Assembly 8. Circuit Board 13. Center Pedestal
3. Mica Washer 9. Resistor 14. Hex Spacer
4. Transistor 10. Potentiometer 15. Spacer
5. Lockwasher 11. Stationary Panel 16. Bracket
6. Dimming Control Assembly 17. Switch

Figure 14-5B. Instrument Lighting Controls

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMs
14-15

10 2
" '
15 10
2

4
DetailA 3
Detail A 421-0001 TO 421B0001 5
421B0001 AND ON 6 Detail $
421BOOO1 AND ON
A B C
8

'
Detali F
421-0001 TO 42180001

12

E D 13

Deta

17
4 18
3 7
Detaii E 3
ostan D

1. Transistor Unit 6. Headset Jack 11. Armrest 16. Lockwasher

2. Escutcheon 7. Bulb 12. Shield 17. Washer
3. Lens 8. Reflector 13. Light 18. Socket
4. Cover 9. Knob 14. Connector 19. Gasket
5. Mike Jack 10. Rheostat 15. Nut

Figure 14-6. Cockpit Lighting

Change 1
14-18 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

b. Install light in panel and secure with nut. NOTE

c. Install bulb and lens,
d. To install landing gear switch, connect wires to An assembled fire warning light must be dis-
switch and remove tags from wires. assembled in accordance with the removal
e. Place two nuts on the switch shaft and run them procedures prior to installation.
down finger-tight against the switch body.
f. Place another nut on the switch shaft from front m. Turn screws (7) clockwise until locking cams
of the instrument paneL Tighten only finger-tight. (11) are engaged against the backshell (12). Tighten
g. Tighten the nut on the front side of the paneL screws.
h. Tighten nuts on the back side of panel (counter- n. Swing light socket assembly (8) into position and
clockwise) on switch shaft until the switch is secured push in until a stop is reached (approximately 1/2
against paneL Be sure the keyed washer mates the inch from panel), Rotate lens (9) clockwise 90 de-
small hole in the panel below switch mounting hole. grees and push lens (9) until it snaps into position.
i. Screw the wheel shaped knob on the switch toggle. o. Connect electrical wires and verify proper oper-
ation of switch.
Removal and Installation of Landing Gear Indicator Removal and Installation of Overhead Console Light
Lights. (See figure 14-SA.) (42180201 and On.) Rheostats.

a. To remove gear unlocked light, identify, tag and a. Loosen setscrew securing rheostat knob using a
disconnect electrical wires at connector. 3/32-inch allen wrench, then remove rheostat knob.
b. Remove screws securing cover panel and remove
cover.
NOTE c. Remove nut securing rheostat to bracket and re-
move rheostat from bracket.
To replace lamps, it is only necessary to d. Tag and remove wires by unsoldering from rheo-
comply with steps (b) and (c). stat connections.
e. To install overhead console light rheostats re-
b. Press the lens assembly (5). The lens will snap verse this procedure,
back and extend approximately 1/2 inch.
c. The lens assembly can then be pulled from light
assembly (1) to expose lamps (6). Removal and Installation of Instrument Lights. (See
d. Turn screws (3) counterclockwise until locking figure 14-6.)
cams (2) are unlocked.
e. Remove light assembly from instrument panel a. To remove post type instrument panel lights,
(4). remove wire from connector and remove nut, lock-
f. Installation of the gear unlocked light is the re- washers and spacer (if used) securing light to instru-
versal of the removal procedures. ment panel or stationary panel.
g. To remove the down-and-locked indicator light, b. To install post instrument lights, reverse the
identify, tag and disconnect electrical wires at con- above procedure.
nector.

Removal and Replacement of Left Hand Console

NOTE Lights.

To replace lamps, it is only necessary to a. Remove the screws securing the metal shield on
comply with steps (h) and (i). the arm rest console.
b. Remove lights by removing lens, bulb and base
h. With finger tips, pull out on lens (9) until it of light.
reaches a stop (approximately 1/2 inch). c. Installation of left hand console panel lights is
i. Rotate lens assembly (9) 90 degrees counterclock- the reversal of the above procedure.
wise. The lens and lamp socket assembly (8) will
then extend further. The lens and lamp socket as-
sembly (8) can then be pivoted down to expose lamps Fuel Selector Valve Lights.
(10).
j. With the lamp socket assembly (8) pivoted out of The fuel selector valve lights are located on the in-
the way, turn screws (7) counterclockwise until the board side of pilot's and copilot's seats. These
locking cams (11) are unlocked. lights are controlled by the engine rheostat on the
k. Slide backshell (12) from the light assembly and stationary panel.
remove light assembly from instrument panel (4).
1. To install the down-and-locked indicator light, Removal and Replacement of Fuel Selector Valve
insert the light assembly through the instrument Light.
panel (4), then slide the backshell (12) onto the light
assembly until it is against the backside of the in- a. To remove fuel selector valve light, pry light
strument panel. . loose from seat base.

Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14"Î$A 14-1 B

b. To install fuel selector valve light, make sure e. Pull escutcheon up and out of bracket.
wire is connected and insert light into hole. Press f. Remove four screws securing light retainer to
in firmly to insure tight fit. plate.

CAUTION
Removal and Replacement of Rear Dome Light. (See
figure 14-7.) Before disconnecting any wires from the
individual reading lights or cabin courtesy
a. Remove rear dome light lens by removing retain- light always disconnect the ground lead of the
ing screws. battery. These lights are not connected thru
b. Remove dome light switch by removing the two the master switch and damage may result to
screws securing switch to bracket. the circuit wiring.
NOTE g, Removal of the individual reading light switch is
accomplished by removing the screws securing the
Because the dome light is riveted to outside switch to the escuthcheon.
skin, no further disassembly should be at-
tempted unless absolutely necessary.
NOTE
c. Replacement of rear dome light is the reversal
of the above procedure. For convenience of replacing bulbs, the lens
is removable from the light by an expansion
type lens and is removed by slipping lens
Removal and Replacement of Individual Reading off of light.
Lights. (See figure 14-7.)
Removal and Replacement of Cabin Door Entrance
a. Remove light socket (3) by screwing counter- Light. (Optional, 421BOOO1 and ON) (See figure
clockwise out of retainer• 14-7. )
b. Pull socket out, tag and disconnect wires.
c. Remove air outlet by screwing counterclockwise a. Remove two screws securing light assembly to
out of retainer. cabin door forward door post.
d. Remove oxygen outlet cover (6) by removing out¯ b. Pull assembly out and disconnect wires.
let cover retainer nut (7)- c. To install, connect electrical leads and install

Change 4
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-17

17 10 1

14 2
4 5

Detail Detail 13 \
Detail B
EXECUTIVE COMMUTER
2
E

Detail E

Detail D

Detail
Detail C
1. Light (Dome) 7. Bracket 12. Light (Reading)
2. Bulb 8. Light (Entrance) 13. Air Outlet Valve
3. Socket 9. Gasket 14. Air Outlet
4. Escutcheon 10. Retainer 15. Outlet Cap
5. Lens 11. Switch 16. Nut
6. Screw 17. Oxygen Outlet

Figure 14-7. Cabin Lighting

Change 2
14-18 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

10
19 15

Detail

D z'
4
14
5

Detail
5 Detati F s s

etail E

1. Wire 5. Screw 9. Rudder Cap 13. Skin (Lower) 17. Light -

Nose Baggage
2. Socket 6. Clamp 10. Bracket 14. Mounting Ring 18. Bulb
3. Bulb 7. Gasket 11. Base 15. Plug 19. Light Socket
4. Lens 8. Beacon 12. Lens Retainer 16. Drain Hole 20. Switch

Figure 14-8. Exterior Lighting

Change 6
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-lAA/14-16B

two retaining screws. e. To reinstall light assembly, reconnect to socket

assembly, insert light assembly into mount bracket,
NOTE push up with a firm even haed pressure until spring
tabs latch light assembly in place.
For convenience of replacing bulbs, the lens f. Close door, secure with locking fasteners.
is removable from the light by an expansion
type lens ring and is removed by slipping
lens off of light. REMOVAL AND INSTALLATION OF NOSE BAGGAGE
COMPARTMENT LIGHT SWITCHES. (See figure
14-8.) (421B0301 AND ON.)
Removal and Replacement of Cabin Courtesy Light.
(See figure 14-7.) a. Open nose baggage doors.
b. Remove the two mount screws (5) securing switch
a. Remove two screws securing light assembly to (20) in place.
side panel armrest.
b. Pull assembly out and disconnect wires. NOTE
c. To install, connect electrical leads and install
two retaining screws. The switches are mounted at aft end of door-
frame, one on the left and one on the right.
NOTE
c. Tag and disconnect wires.
For convenience of replacing bulbs, the lens d. Remove switch from aircraft.
is removable from the light by an expansion e. Install switch by reversing the foregoing pro-
type lens ring and is removed by slipping cedure.
lens off of light f. Close and secure doors with locking fasteners.

Removal and Replacement of (Fasten Seat Belt) and

(Oxygen) Sign Lights (Optional).
Removal and Installation of Wing Locker Courtesy
Light. (See figure 14-7. )
The optional "Fasten Seat Belt" and "Oxygen" sign
. lights are mounted on the cabin divider and are oper-
a. Pull wing locker light circu1t breaker.
.

ated by switches mounted on the left side of the in-

b. Remove the three screws securing the light and
strument panel.
remove light from nacelle.
a. To remove either light, remove the top panel
c. Installation of the wing locker courtesy light is
from the forward side of the cabin divider.
the reversal of the removal procedures. b. Remove the two screws securing the light to the
d. Reset circuit breaker and check operation. . .

cabin divider.
c. Disconnect and tag wires.
Removal and Installation of Wing Locker Courtesy d. Installation of the lights is the reversal of the
Light Switch. (See figure 14-7.)
above procedure.
a. Pull wing locker light circuit breaker. Removal and Installation of Wing Navigation Lights.
b. Remove two screws securing switch· (See figure 14-8.)
c. Tag and disconnect wires to switch.
d. Installation of the nacelle wing locker light
switch is the reversal of the removal procedures. a. Remove the tip tank nose cap.
e. Reset circuit breaker and check operation. b. (See figure 14-8.) Remove and install navigation
light in sequence as shown.

REMOVAL AND INSTALLATION OF NOSE BAGGAGE

COMPARTMENT LIGHT. (See Figure 14-8.) Removal and Installation of Tail Navigation Lights.
(421BO301 AND ON.) (See figure 14-8.)

a. Open nose baggage door. a. Two screws secure the tail light assembly to the
b. Pull light assembly (17) down and lift out of stinger. Removing these two screws and disconnect-
mount bracket. ing the electrical connector from the rear of the light
assembly will allow the tail light to be removed.
NOTE b. To replace the tail light, reverse the above
procedure.
Light assembly (17) is held in place by spring
Removal and Installation of Rotating Beacons. (See
tabs
figure 14-8.)
c. Disconnect socket assembly (19) and remove light
from aircraft.
a. To remove the rudder-mounted rotating beacon,
assembly
d. To replace light bulb (18) remove from socket remove the screws in the fiberglass tip and lift
rotating beacon out.
assembly and install new bulb.

Change 6
 ELECTRICAL SYSTEMS Î4- S
421 SERVICE MANUAL

b. Disconnect electrical plug. from bayonet fittings. This will prevent

c. To remove the belly mounted rotating beacon, motor drive spring damage,
remove the screws in the flange mounting and lower
rotating beacon from fuselage. Removal of Landing Light. (See figure 14-9.)
d. Disconnect the electrical plug.
e. Installation of the rotating beacons may be ac- a. Support the light assembly and remove screws
complished by reversal of the above procedure. which secure lamp housing to retainer band.
b. Lower the light assembly out of the tip tank
NOTE tail cap and place on a stand of suitable height.

On the belly-mounted make NOTE

rotating beacon,
sure the gasket is installed between fuselage
The wiring to the light contains sufficient
skin and rotating beacon. Seal around beacon
slack to permit the light assembly to be
from inside of fuselage in accordance with
brought down below the tip tank tail cap for
sealing procedures in Section 16.
removal of light wiring.

CAUTION c. Tag and remove the wires from the terminal

block on the light.
When replacing the bulb in the rotating bea- d. To remove the lamp from the landing light,
cons do not allow the reflector to move. Al- extend the light approximately 60 degrees and remove
ways grasp the bulb base and unscrew bulb the lamp retainer ring. Pull the lamp from the inner
canopy and disconnect the wires from the lamp.

Change 6
14-20 ELECTRICAL SYSTEMS 421 SERVICE IVÏANUAL

NOTE assembly and secure with two screws.

b. To install a new lamp, conneet the wires to the
When the light assembly is removed from lamp and position the lamp within the canopy with
the aircraft, the light may be extended by the filament shield inboard. Position the lamp re-
applying a 28 volt power source across the tainer band over the edges of the lamp and canopy
OPEN and ground terminals. with the flat side toward the apex of the canopy.
Using needle nose pliers, pull the retainer band tight
e. Remove the two screws securing the power unit around the lamp and canopy and fasten the clip on
to the housing. the band.

Installation of Landing Light. (See figure 14-9.) NOTE

a. Position power unit within drive housing of light Before installing a new lamp, it will be neces-

3
Detail $

AS1182010
B51183013

1. Retainer Band 5. Lamp Assembly 8. Nut

2. Lamp Housing 6. Canopy Assembly 9. Lamp
3. Screw 7. Bracket 10. Gasket
4. Power Unit 11. Retainer Ring

Figure 14-9. Landing and Taxi Light Installation

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMS -$

sary to extend the light approximately 60 de- Landing lights are adjusted in the factory to extend
grees to gain access to the retainer band. to an angle of 80 degrees from the fully retracted
position. The angle of extension may be altered by
c. Position the retainer ring inside the tip tank tail means of an adjustment screw as illustrated in figure
cap with the open side forward and tape it to the tip 14-10.
tank tail cap to hold it in position temporarily while
the light assembly is installed. NOTE
d. Connect the wires to the light assembly and re-
move the identification tags. Do not turn the adjusting screw counterclock-
e. Place the light assembly into the wing and secure wise more than three full turns without closing
with screws. and opening the light before further adjust-
ment. Excessive turns of the screw in a
NOTE counterclockwise direction will distort an
actuator contact within the assembly, thus
Start all screws through the nutplates on the changing the fixed setting which controls the
retainer band before attempting to tighten light retract position.
any of them to prevent distortion of mis-
alignment of the band. The angle of extension of the landing light may be
checked with a bubble protractor. Check the degree
of opening according to.the following steps:
Adjustment of Landing Light. (See figure 14-10.) a. Retract the landing light and place the flat sur-
face of the protractor across the retainer band which
secures the lamp within the inner canopy.

Adjustment Screw
Cap Screw: Must be
removed to gain access
to adjustment screw.

90

FIIID -
TO ADJUST DEGREE OF OPENING (RANGE 60 TO 90 DEGREES)
REMOVE CAP SCREW AND USE REGULAR SCREWDRIVER.
INCREASE DEGREE OF OPENING-TURN CLOCKWISE. EACH
FULL TURN CHANGES OPENING ABOUT ONE DEGREE.
DECREASE DEGREE OF OPENING-TURN COUNTER-CLOCKWISE.

CAUTION-NEVER TURN COUNTER-CLOCKWISE MORE THAN 3

TURNS WITHOUT CLOSING AND OPENING LIGHT FOR FURTHER
ADJUSTMENT.

Figure 14-10. Adjustment of Landing Light

14-22 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

NOTE imately three degrees below horizontal. The light

should also be adjusted to point in the direction of the
Two blocks of equal thickness may be placed nose wheel. The fore and aft positions of the light
on the retainer band to raise the protractor may be adjusted by removing the cotter pin and loosen-
so it will clear the surface of the lamp for a ing the nut to free the mounting bracket. The light
more positive location of the protractor. may be aligned with the nose wheel by loosening the
mounting nut and pivoting the light on the mounting
b. Run the landing light full down and measure the bracket.
angle of extension. If the light has not reached the
desired degree of extension, turn the landing light CAUTION
adjustment screw in the direction necessary to
achieve the desired angle of extension. After adjustment, make sure the nut secur-
c. Retract the light to the full up position, fully ing light to the bracket is tight and the bolt
extend the light, and check the angle of extension. securing the bracket is tight and cotter pin
installed.

Removal and Installation of Taxi Light. (See figure Removal and Installation of Deice Light. (See figure
14-9. ) 14 -11.

)
a. Tag and disconnect electrical wires. a. Remove upper cowling from left engine.

I
b. Remove nut securing lamp and remove lamp. b. Remove screws securing socket assembly and
c. Remove cotter pin, nut and washer securing clamp holding wires.
light to strut bracket. c. Pull socket assembly apart from lamp shield to
d. Installation of taxi light is a reversal of this remove bulb.
procedure. d. If further disassembly is required, tag and re-
move wires. Drill out rivets securing shield assem-
bly to nacelle skin.
Adjustment of Taxi Light. e. Installation of deice light is accomplished by
reversing this procedure.
The taxi light should be adjusted to an angle of approx-

\1. Screw 4. Lamp 6. Lens

2. Plastic Clamp 5. Shield 7. Doubler
3. Socket Assembly 8. Nacelle Skin

Figure 14-11. Wing Deice Light Installation

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-22A

e ,"
6

*
1 ./

F D

7 C
8 16

* 421B 099 & ON

B
A

LTS
EB N

Detail

A14281004
'S Detail B51182003
C54181034
C54181001

1. Circuit Breaker 6. Navigation Light 11. Gasket 16. Trigger Gri<

2. Flasher Unit 7. Power Supply (31-1721-1) 12. Lens 17. Fuse Holder
3. Bracket 8. Flash Tube 13. Retainer 18. Fuse (3 AGC)
4. Nut 9. Bracket 14. Power Supply (60-1520-1) 19. Aluminum
5. Screw 10. Lamp 15. Tailcone Stringer Tape

Figure 14-12. Strobe Light System Installation (Sheet 1 of 2)

Change 10
14-228 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

Strobe Light System. (Optional) forward facing passenger seat, a power supply unit
located in the tail section of the aircraft, a switch
The high intensity strobe light system consists of a circuit breaker located on the side console, and a
strobe light located on each wing tip, a flasher unit tail light unit located in the stringer. The wiring is
located beneath the floorboard under the left-hand aft shielded to guard against radio noise interference.

15 14

Detaii F oetaii E
421BOOO1 THRU 421BOO98

D51181033
E51181035
F52181002

Figure 14-12. Strobe Light System Installation (Sheet 2 of 2)

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14- Û
Troubleshooting the Strobe Light System.

TROUBLE PROBABLE CAUSE CORRE CTION

ONE STROBE Flash tube burned out. Replace flash tube.

LIGHT OUT
Power supply defective. Replace power supply.

ALL STROBE Circuit breaker out. Reset breaker.

LIGHTS OUT
Defective switch. Replace switch.

Power supply defective Replace power supply.

Timer inoperative. Replace timer.

STROBE LIGHT Defective timer. Replace timer.
WILL NOT FLASH

Removal and Installation of the Strobe Light System b. Disconnect electrical wiring to strobe light.
Components. (See figure 14-12.) c. Remove strobe light unit from supporting
bracket.
a. Remove nose cap on each wing tip. d. (See figure 1-2.) Remove access cover (82) to
gain access to flasher.
NOTE e. Disconnect electrical wiring from flasher.
f. Remove flasher from supporting beam.
If strobe light bulb is burned out, unsafety g. (See figure 1-2.) Remove access cover (21) to
and remove from clips. Reinstall new bulb gain access to power supply unit.
and safety. h. Disconnect electrical plug.
i. Remove power supply unit from supporting

\
CAUTION bracket
j. Remove tail light in accordance with figure
Install bulb with trigger grid facing toward k. The installation of the strobe system components
the lens and away from the reflector is the reversal of the removal procedure.

1 2 3 4

7 6 5

1. Left Fuel Supply Line 3. Stall Warning Transmitter 6. Electrical Wires

2. Vapor Return Line 4. Wing Skin 7. Access Hole Cover
5. Screw

Figure 14-13. Stall Warning Transmitter

Change 4
14-220 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

STALL WARNING SYSTEM. Operational Check of Stall Warning System.

The stall warnirg system is comprised of a stall and a. Ground Check.

landing gear warning horn mounted in the left con- 1. Turn electrical power on.
sole and the actuating switch mounted on the leading 2. Activate vane on stall warning transmitter and
edge of the left wing. When the aircraft approaches observe audible warning signal.
a stall the switch energizes the electrical circuit and b. Flight Check.
causes the warning horn to sound. A heater element 1. Check the stall warning in two configurations:
is provided in the actuating switch, to prevent ice landing gear up, flaps up and gear down, flaps full
from hampering the operation, is energized when the down.
pitot heat switch is turned on. 2. Check each configuration in step a at 65Ÿo power
using power computer furnished with aircraft and at
Removal of Stall Warning Transmitter. (See figure idle power.
14-13.) 3. Approach the stall by reducing airspeed at a
rate as close as possible to 1 knot per second. In
NOTE the stall the aircraft roll attitude should be controll-
able up to the time the aircraft nose pitches down-
Before removal of stall warning transmitter, ward or full up elevator stop is reached. The fuel
it is important that the exact location of the should be managed to minimize asymmetric fuel
vane be marked on the wing so that the re- prior to conducting the stall.
placement unit may be adjusted identically. 4. The indicating stall speed in the landing config-
uration at idle power shall fall within ±4 knots of a
a. Remove access hole cover (7). line drawn from the light weight stalling speed to the
b. Remove four screws (5) attaching stall warning heavy weight stalling speed as shown by the appro-
transmitter (3) to wing skin (4). priate chart in Figure 14-13A. The weight at the
c. Tag and disconnect electrical wires (6) and re- time of takeoff minus the fuel used shall be used for
move stall warning transmitter (3). the weight at stall.

Adjustment of Stall Warning System.

Installation of Stall Warning Transmitter. (See fig-
ure 14-13.) a. Using the data recorded in the Flight Check por-
tion of the Operational Check of Stall Warning Sys-
a. Attach electrical wires (6) as tagged at removal- tem, adjust the stall warning vane to provide a stall
b. Secure stall warning transmitter (3) to wing skin warning horn at 4 to 9 knots IAS prior to the idle
(4) with four attaching screws (5). power landing configuration stall.
c. Replace access hole cover ('7). b. Raising the stall warning vane position will in-
crease the stall warning indication and lowering the
stall warning vane will lower the stall warning indi-
cation.

PITOT AND STALL WARNING HEAT SYSTEMS.

The pitot and stall warning heaters are resistance
units mounted integrally in the pitot tube and stall
warning transmitter. Both units are controlled by
one switch.

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-22DA/14-22DB

TAKEOFF WEIGHT RANGE -

LBS TAKEOFF C.G. RANGE -
°/o

6000 -
6750 18 -
20

±4LLNEOTS
SApNED
TROOLEMRSANACEL

/¿UU
"

7000

6800
A B _ g

6400

6200

C
6000 ••

5800

5600

0 70 80 90 100 11)
AIRSPEED -
KIAS

gilW EXAMPLE
"A" POINT "A" WEIGHT (HEAVY WEIGHT)
"B" STALL SPEED AT POINT "A" WEIGHT (72. O KIAS)
"C" POINT "C" WEIGHT (LIGHT WEIGHT)
"D" STALL SPEED AT POINT "C" WEIGHT (68. 2 KIAS)
"E" APPROACH SPEED AT POINT "A" WEIGHT (99. 0 KIAS)
"F" APPROACH SPEED AT POINT "C" WEIGHT (93. 5 KIAS)

51986001

Figure 14-13A. Approach and Stall Speed Chart

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-22E

ELECTROLUMINESCENT PANEL LIGHTS NOTE

The electroluminescent panel emanates light ffom Operational checks on the electroluminescent
crystalline powders, or phosphors, sandwiched be- panels should be performed using 120 volt
tween two electrically conducted surfaces, of which 400 cycle AC. However, panel will operate
one surface is translucent. When the panel lights without damage on 120 volt, 60 cycle AC.
are turned on, the powders absorb electrical AC
energy and convert it to light without the use of
starters, or ballasts and with minimal heat. Installation of Electroluminescent Panels. (See
figure 14-14,)

Removal of Electroluminescent Panels. (See figure a. The installation procedure for the electrolumi-
14-14.) nescent panels is the reversal of the removal pro-
cedures.
a. Turn off power.
b. Remove the necessary switch circuit breaker
nuts.
c. Lift panel off and tag and disconnect wiring.

ALRY A3UX
AURX
A Y AIJ A Y A A Y
5LOEGAL 50GA- 5LOGAL. 5R GAL 50GAL 5ROGHAL 50GAL. 50GHAL.

MAIN
' MAIN MAIN A
MAIN MAIN

RIGHT ENGINE LEFT ENG NE LEFTENGlNE RIGHT ENGlNE

OFF OFF OFF OFF

2 3 4

10

9
421B0001 AND ON a
Detail A

1. RH Auxiliary Fuel Select (48 Gal) 12. Flap Indicator Guard

2. LH Auxiliary Fuel Select (48 Gal) 13. Propeller Synchronizer Control
3. LH Auxiliary Fuel Select (35 Gal) 14. Master Dimming Control
4. RH Auxiliary Furl Select (35 Gal) 15. Cabin Pressure and Fuel Transfer
5. Wing Locker Fuel Select 16. Flight Light Control
6. Manual Gear Extension and Fuel Select 17. Flap Indicator Block
7. Fasten Seat Belts and Oxygen 18. Cabin Heat Control
8. Fasten Seat Belts 19. Forward Switch Console
9. Oxygen 20. Forward Circuit Breaker Console
10. Landing Gear Control 21. Center Circuit Breaker Console
11. Manifold Pressure 22. Aft Circuit Breaker and Switch Console

Figure 14-14. Electroluminescent Panels (Sheet 1 of 2)

Change 10
14-22F ELECTRICAL SYSTEMs 421 SERVICE MANUAL

is C
o
LISHTS
L

Detail F Detail $
D
F
E H

18
Detail (

Detail H
Detail Û
•

22
Detail D 15

Detail
Detail E

421BOOO1 AND ON

Figure 14-14. Electroluminescent Panels (Sheet 2 of 2)

Change 10
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-22G

NOTE

This load chart is to be used for determining electrical

load on the aircraft power distribution system. Amps
given are approximate and based on the maximum allow-
able load in each installation. The loads are not to be
used for troubleshooting.

CONTINUOUS ELECTRICAL LOAD CHART Amp Required

Tip Tank Auxiliary Fuel Pump (2) . . . . . . . . 11. 40

Inline Auxiliary Fuel Pump (2) . . . . . . . . . 3. 80
Fuel Transfer Pump (2) . . . . . . . . . . . 2.20
Fuel Quantity System (2) . . . . . . . . . . . .20

Heater Combustion Air Blower . . . . . . . . . 3. 00

Heater Vent Blower . . . . . . . . . . . . . 11. 00
Fuel Pump (Cabin Heater) . . . . . . . . . . 1. 00
HeaterFuelValve ............ .20

Heater Ignition . . . . . . . . . . . . . . 75
Stall Warning Heater . . . . . . . . . . . 1. 30
Pitot Tube Heater (Single) . . . . . . . . . . 4. 30
Tip Tank Vent Heater (2) . . . . . . . . . . . 58
Flap Position Indicator (6) . . . . . . . . . . .24

Engine Gauges (2) . . . . . . . . . . . . . 64

Air Temperature Indicator . . . . . . . . . . . 08
Turn and Bank Indicator . . . . . . . . . . . . 15
BatteryRelay ............. .60

Landing Gear Up Indicator Light (2) . . . . . . . . . 08

Navigation Lights (3) . . . . . . . . . . . 2. 88
Rotating Beacons (2) . . . . . . . . . . . 3. 60
MapLights(2)............. .52

Reading Lights (4) . . . . . . . . . . . . 1. 20

Fuel Select Lights (2) . . . . . . . . . . . . 40
CompassLight............. .04

Post Lights (47) . . . . . . . . . . . . 1. 48

Side Console Lights (3) . . . . . . . . . . . . 34
Flood Lights (2) . . . - . . . . . . . . . 1. 04
DomeLight. ............ .51

Voltage Regulator (2) . . . . . . . . . . . 2. 00

Pressurization Air Dump Valves . . . . . . . . . . 30
Cowl Flaps (Each) . . . . . . . . . . . . 2. 00
Cowl Flap Position Indicator . . . . . . . . . . .06

Windshield Deice System (Electric) . . . . . . . . 50. 00

Windshield Deice System (Alcohol) . . . . . . . . 40.

Stereo Tape Player System . . . . . . . . . . 1. 50

Auxiliary Fuel Pump Wing Locker (2) . . . . . . . . 6. 00
Propeller Synchronizer System . . . . . . . . . 1. 00
PropeHer Synchronizer Indicator (1) . . . . . . . . 04 .

Oxygen Sign Lights (2) . . . . . . . . . . . .20

Seat Belt Sign Lights (2) . . . . . . . . . . . .20

StrobeLights .............3.00

Propeller Deice Boots (3) . . . . . . . . . . 14.70

Static Source Heater (2) . . . . . . . . . . . .72

Wing Locker Vent Heater (2) . . . . . . . . . . . 58

Turn and Bank Indicator RH . . . . . . . . . . . 15
Flight Hour Recorder . . . . . . . . . . . . 04
Air Conditioner System (Total Package) . . . . . . . 50. 00
WemacBlower.............1.90
Electroluminescent Lighting System . . . . . . . . 1. 25
Electroluminescent Lighting Avionics -
Personalized Panel . . . 30.

NOTE

Total continuous load should not exceed 80°/o of the total

rated alternator capacity.

Change 12
14-22H ELECTRicAL SYSTEMS 421 SERVICE MANUAL

NON-CONTINUOUS ELECTRICAL LOAD CHART

Amp Required

Landing Gear Do Indicator (4) . . . . . . . . . .20

Landing Gear Motor . . . . . . . . . . . . 25. 00

FlapMotor..............13.00
Heater Overheat Light . . . . . . . . . . . . 04
Cigar Lighter (Each) . . . . . . . . . . . 6.80
Landing Gear Relay . . . . . . . . , . . . . 45
Fuel Boost Relay (2) . . . . . . . . . . . . 18
Landing Gear Warning (Horn and Flasher) . . . . . . . . 60
StallWarning ............. .20

Door Warning Indicator . . . . . . . . . . . . 04

Door Courtesy Light . . . . . . . . . . . . 30
Landing Light LH (Lamp) . . . . . . . . . . 9. 00
Landing Light Extension and Retraction Motor . . . . . . 1.25
Alternator Failure Indicator (2) . . . . . . . . . . 08
Cabin Altitude Warning Light (2) . . . . . . . . . . 04
Turn and Bank Test Light (2) . . . . . . . . . . . 15
Press-To-Test Light (2) . . . . . . . . . . . . 08
SpareLight(2)............. .08

ShaverInverter............. .60

Electric Seat (2) . . . . . . . . . . . . 20. 00

DeiceLight-Wing(2) ...........1.40

Intercom Call Light . . . . . . . . . . . . . 04

Surface Deice System . . . . . . . . . . . 6. 25
Surface Deice Indicator . . . . . . . . . . . . 04
ElectricTrim............. .60

TaxiLight..............3.64
Landing Light RH (Lamp) . . . . . . . . . . 9. 00
Landing Light Motor RH . . . . . . . . . . . 1. 25

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14- 3

WIRING DIAGRAM INDEX

421-0001 TO 421A0001

\ TITLE
STANDARD AND OPTIONAL

PAGE

Plug Chart and Terminal Boards . . . . . . . . . . . 14-26

Instruments, Flap and Fuel Control . . . . . . . . . . . 14-27
LandingGear................14-28
Lighting.................14-29
Audio and Door Warning . . . . . . . . . . . . .
14-30
Audio . . . . . . . . . . . . . . . . . . 14-31
Starter, Ignition, Alternator and Power Distribution . . . . . . .
14-32
Cabin Pressure, Cabin Heat, Cowl Flap Actuators and Cigar Lighters . . . 14-33
Optional Equipment (Prop Deice, Surface Deice, Flight Hour Recorder,
Shaver Inverter, and Electric Seat) . . . . . . . . . . 14-34
Optional Equipment (Prop Synchronizer) Air Conditioner, Aux Wing Locker Fuel . 14-35
Optional Equipment (100 AMP Alternator and Electric Heated Windshield) . . 14-36
Alternator (Westinghouse to Prestolite Modification) . . . . . . . 14-37

421A0001 TO 421BOOO1

l Alternator Conversion (Westinghouse

STANDARD

to
AND OPTIONAL

Prestolite) . . . . . . . 14-38
Connectors ................14-39

Terminal Boards . . . . . . . . . . . . . . . 14-40

Starter Ignition
-
. . . . . . . . . . . . . . .
14-41
Alternator 50 AMP Prestolite
-
. . . . . . . . . . . . 14-42
Landing Gear, Flap Control, Vent Heater and Stall Warning . . . . . 14-43
Instruments and Fuel Controls . . . . . . . . . . . . 14-44
Lighting Interior
-
. . . . . . . . . . . . . . . 14-45
Lighting-Exterior ..............14-46

Audio and Door Warning . . . . . . . . . . . . . 14-47

Cabin Press, Cabin Heat, Cowl Flap, Cigar Lighters . . . . . .
. . 14-48
Optional Equipment (Stereo) . . . . . . . . . . . . . 14-49
Optional Equipment (External Power, Air Conditioner, RH Control Wheel,
and Reading, Oxygen and Seat Belt Lights) . . . . . . . . . 14-50
Optional Equipment (Propeller Synchronizer, Surface Deice, Propeller Anti-Ice) . 14-51
Optional Equipment (Static Heaters, Electric Seat, Flight Hour Recorder,
Electric Elevator Trim, Auxiliary Fuel Transfer Pumps) . . . . . 14-52
Alternator (Optional 100 AMP Westinghouse) . . . . . . . . . 14-53
Intercomm, Boom Mike, Fwd and Aft P. A. . . . . . . . . . 14-54

I Connectors . . . . .
421BOOO1 TO 421BO301

.
STANDARD

. . . . . . . . . . 14-55
Terminal Boards . . . . . . . . . . . . . . . 14-56
Starter Ignition . . . . . . . . . . . . . . . 14-57
Prestolite Alternator (50 AMP, Std and 100 AMP, Opt) . . . . . . 14-58
Landing Gear, Flap Control, Vent Heater and Stall Warning . . . . . 14-59
Tach. Generator, Engine Instruments, O.A.T., Turn and Bank, Fuel Pumps . . 14-60
Dimmable Interior Lighting, Door Courtesy Light, and Reading Lights . . . 14-61
Lighting Exterior,
-
and Tip Tank Transfer Pumps . . . . . . . 14-62
Map Lights, Audio and Door Warning . . . . . . . . . . 14-63
Cabin Pressure, Cabin Heat, and Cigar Lighters . . . . . . . . 14-64
Capacitance Fuel System . . . . . . . . . . . . . 14-65

Change 12
14-24 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

WIRING DIAGRAM INDEX

421B0001 AND ON EXCEPT AS NOTED

OPTIONAL

TITLE PAGE

Propeller Deice . . . . . . . . . . . . . . .
14-66
SurfaceDeice................14-67
Heated Windshield . . . . . . . . . . . . . . .
14-68
Propeller Synchronizer . . . . . . . . . . . . . .
14-69
StrobeLight.......,........14-70
Stereo . . . . . . . . . . . . . . . . . 14-71
External Power Receptacle . . . . . . . . . . . . .
14-73
Auxiliary Cabin Ventilating System . . . . . . . . . . .
14-74
No.2PitotHeat ................14-75

Wing Locker Fuel Transfer Pump, and Vent Heaters RH and LH . . . . 14-76
ElectricSeats................14-77
Static Source Heaters . . . . . . . . . . . . . . . 14-78
Electric Elevator Trim . . . . . . . . . . . . . .
14-79
FlightHourRecorder..............14-80
Shaver Inverter . . . . . . . . . . . . . . . 14-81
TaxiLight ................14-82

Radio Noise Filter Magneto -

. . . . . . . . . . . .
14-83
RH Turn and Bank, Left and Right Hand Turn Coordinator . . . . . .
14-84
Radio Noise Filter Regulators -
. . . . . . . . . . . .
14-85
RH Landing Light, and Surface Deice . . . . . . . . . .
14-86
External P. A., Intercomm, Aft P. A., Boom Mike . . . . . . .
14-87
Electroluminescent Panels . . . . . . . . . . . . .
14-88
E. G. T. Lights, Optional Pilot Instrument Lights, Optional Copilot Instrument
Lights.................14-90
Oxygen and Seat Belt Lights . . . . . . . . . . . .
14-91
Power Bus and Wire Installation Side Console -
. . . . . . . .
14-92
Air Conditioner 421BOOO1 to 421B0501 . . . . . . . . . .
14-93
Reading Lights, Ten Places . . . . . . . . . . . . .
14-94
Nacelle Courtesy Light . . . . . . . . . . . . . .
14-95
Fire Detect System . . . . . . . . . . . . . .
14-96
Crash Locator Beacon . . . . . . . . . . . . .. .
14-97
SurfaceDeice................14-98
Alcohol Windshield Deice . . . . . . . . . . . . .
14-99
Light, Dimmer Control . . . . . . . . . . . . .
14-100
Transistor and Heat Sink . . . . . . . . . . . . .
14-101
Annunciator . . . . . . . . . . . . . . . .
14-102
United Kingdom ARB Wiring Diagram . . . . . . . . . . . .
14-102B
Wiring Diagram Index . . . . . . . . . . . . . .
14-103

NOTE

\ See page 14-103 for standard

diagrams
and additional
wiring
index for 421B0301 and On
optional wiring diagrams
for 421BOOO1 and On as noted.

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-25

NOTE

Part Numbers referred to on Wiring Diagrams are for reference only. When
ordering spare or replacement parts, refer to applicable Parts Catalog.

The wiring diagrams contained in this section clearly show the complete wiring
on each item of electrical component listed in the Wiring Diagram Index. The
first portion of wire number indicates the Aircraft System, the center portion
indicates Wire Number, and the last portion indicates Wire Gage Size. Each
wiring diagram contains part number and nomenclature for each component.

EXAMPLE: C14B22
14B

AIRCRAFT 22 WIRE
SYSTEM CODE GÁUGE
WIRE NUMBER
AND SEGMENT

Change 8
14-26 ELECTRicAL SYSTEMS 421 SERVICE MANUAL

WL.UG GM

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 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-73

0- --PS45AL
JIOI
EXTERNAL
PWR
RECEPTACLE 88 of
- P54GA2O /

42)ßooo/17/Li IP i

PG45A2

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CRIO* INZ*S2 O/ODE-FXT PWR RELIPT

CRios IN2462 AFOOE-ET7 PWRITELAY

71525036-126 T£ RM/IVAL. I u G.
MS23D3G-/23 T£RMl/VAL JUG
NSZid36-/O2 TERMlWAL LUG
NS2503G-/27 TERMHVAL. LUG 421BOOO1 AND ON
MSP.5836-ISO 7ERMIWAL LUC.

Ym.E.

EXT£R/Vy9L PWR RECEP7ACLE

WIR/A/S RSSY.
(oRT)
sizE coomioExtmo, onAwinano.

C 71379 6 //8 4-38 c .

Change 11
14-74 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Part Number Nomenclature

1. 66-01-5 Aux Cabin Blower

2. S-382-1 Sw Evap Fan Control
-

3. 1-20-37-39-6 Recept Fwd Side Cons

-

4. 1-20-37-35-5 Plug Fwd Side Cons

-

5. 7277-2-15 Circuit Bkr

SP I
I
HV---c
H5GOM S C YELLOW
C OF F
E¯
1
LO
H50NS GREEN
SPl
2
BLACK

H5138/8

3 ) /
F. S. 120. 00
4 421BOOO1 AND ON

CONTRACT No y gay ggyy

AIRCRAFT
MILrTARY Ik TWIN DiviBION
CO. WicNiYA. KANSAS 67201
DATE

TITLE:
DBAWN C FRIEDLY
osoa 4. AUX CASM NENT\LAT\NG
CHEcK 70-27
£f

15 s,s.ss \N \ PON G D\AGRAM

Peoa
sizE coDE IDENT. NO. DRAWING NO.

-
C 71379 5|\84-33
scALE: NONE nur suser i DE 1
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-75

1 yy Part Number Nomenclature

1. 112-507-101 No. 2 Pitot Heat Sw Ckt Bkr

-

2. 1-203735-5 Plug -
Fwd Side Cons
3. 1-203739-6 Recept Fwd Side Cons
-

4. DSO4-27-25S Recept Nose Bhd

-

5. DSOT-27-25P Plug Nose Bhd

-

6. AN3115-1 Plug No. 2 Pitot Heat

-

7. AN5812-1 No. 2 Pitot Tube Assy

F. S. 120. 00

FSO2B /8

F. S. 100. 00

FSOFC/ 8

FSO+/)/8/y

6 8 A

7 421BOOO1 AND ON

onAw" WALTRAN
"°""
/?tMa. Jo/w/
No.2 PITOT HEAT I
WIRING DIAGRAM ¯
14-78 ELECTRICAL SYSTEMS . 421 SERVICE MANUAL

Part Number Nomenclature Part Number Nomenclature

1. 7277-2-5 Transfer Pump LH -

Ckt Bkr 12. DSO4-37S Recept RH Wing -

2. 1-203739-6 Recept -
Fwd Side Cons 13. 17-1030 Recept Annunciator
-

3. 1-203735-5 Plug -

Fwd Side Cons 14. 17-20370 Plug Annunciator

-

4. MST-205N LH Nac Aux Fuel SW -

15. 5618009-1 Annunciator Assy

5. DSO4-37S Recept LH Wing -

16. 7277-2-5 Transfer Pump RH Ckt Bkr -

6. DSO7-37P Plug LH Wing

-

17. 105880 Vent Htr LH Wing Locker -

7. 9910058-1 Sw LH Nac Fuel Press

-

18. 105880 Vent Htr RH Wing Locker -

8. 4140-00-153 Fuel Pump LH Nac -

19. MST-205N RH Nac Aux Fuel Sw -

9, 4140-00-153 Fuel Pump RH Nac -

20. CM2990-2 Post Lt Radio Call Placard

-
Lt
10, 9910058-1 Sw RH Nac Fuel Press
-

21. CM2990-2 Post Lt Fuel Transfer-

Sw Lt
11. DSO7-37P Plug RH Wing
-

1 16 a2c2°
20 21

2 120.00
|F.s. at
3
St3820 ß2e Ll2A20 --f

U2D10
4 -----
19
15
) 14 .

118. 00
16/20 Gl6BRO

5 F.S. /
12 STALL E YEA/T HTAT STALLgVBVT HEAT
S l 150.00 g (REF RPPL/CABLE -SThHDARD (REE APPL/G9BLE STß¾'39RD)
- •

\ W/RINE D/BGIFabi i WVIR///B DIACS9/i )

916820 af 820 I
H48Els H 48dl8

GIFB2D

sp-; SP-I
SP-/
SF-I

7 10 17 18
->LOW WNifE WHITE
SP2
-- - -
+LOW 5P-2
80 WC 80 NC

421B0001 AND ON

c" RJ/Ak; « ptPIP f VENT HTR NH¢ LN

ess ¢-¢yg (OP7) W/R/NG D/A6RAM

D 71379 f//8 M/
ocata= MSWE ase asesy ¡ pg y
 421 SERVICE MANUAL ELECTRICAL SYSTEMS Î4"Ï7

1 8
O (+) (+) H

BU)C /<

L /KK
WIG T£
wiii TE

Part Number Nomenclature

1. 919J10000-3 Motor RH Elec Seat

-

M60/8 /G 2. 5618111-1 Wire Coil

3. 1-203739-6 Recept Lwr Side Cons -

M502 6 I 6 4. 1-203735-5 Plug Lwr Side Cons

-

F. S. 132. 00 5. 7277-2-10 LH Elec Seat Ckt Bkr -

6. 7277-2-10 RH Elec Seat Ckt Bkr -

7. 5618111-1 Wire Coil

)
8. 919J10000-3 Motor LH Elec Seat
4) -

M602 /4/G

M60l AIG

O5 0 6

421BOOO1 AND ON

AIRCRAFT

TITLE:
onAwN WILTMAN ...

smo- yo/2/n
ELECTRICSEATS
CHECK
747274, WIRING DIAGRAM

PROJ.
SIZE CODE IDENT. No. DRAWING NO.

5\\ 844-2
¯

OTHER
D 71379
SCALE: gQgg REF SHEET / Û
14-78 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

EQU PMENT L)ST

STALL | VENT HE T S/NßOL RART A/S P/9RT A/BU1E'
s C..S

IO
CP/2933-5 SOURC£¯ HTR-RH
HRIOS STATIC
HR709 C/12933-5 STRTIC SOURCPHTR-¿H

FIDIS
*B4sus

EP-I .
S- 70-1 SPA/[E
6/D£ CDIi/LOLE P SR-2 S-\6¯lO-L SPL/C£
LOWlER CONN J
MS¿SD36-/43 TERff/A//1C LUS

FIEl9
H SK

-----
89 MiB ---

) (7EF STALL / VEN7 AfflT)

SP-2

- H42718------1 (BCF SFÆL /VENT BERT)

* 421B0301 AND ON

*Fso/Gis
F2G /8

SR-i stil

LH 5T/4TIC HTYIDB 421BOOO1 AND ON

HRIO9 lìH ST/iTIC
ggyg,
\ r/ERT£R

s'na.^'"T^"
"rzi
TATICSOüRCE H£ATERS
WIRINGOtAGRAM
(OPT)
512E CODE IDENT. NO. DRAWlNG NO.

5!! 844-3
¯

D 71379
SCALE g REF SHEEf / Û

Change 8
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-79

S/ÐF CO/1/JOLE
-
CONN

yppy TR/MRt/VRCletinT BREAKER

CBS22

TRIFI LONTROL SW RED

5 BA . I I

rE

CN
I

C5mAt?-
rt?/M D/SENGAGE ShV

3
C7AB.2 62 e,p

4 4
--- -
-4- -4

C5\DAL2 L
CONTROL WH t. AssY

lEFF 47.1-601.01
4 o!4 (EF 413-80001 T½R 47.t-Blosoo)

CI A22N

LH INSTR PML

GMD PLU

EQUlPNENT L/ST
Syr;Sol. R/4RT IVO Any NAnv.

SP\
BLMM-r
RTO BLACK 81 5//F231-/ ELECT. TRIP1 ACW ASST

e e
7212-5-6 (fr éWL&r/R-TRI/1PUR
CB

F7 [4 RI3tS3DR

l CL TEM
YKii 51863 2 TERAf/N/N

1-320551-2 TE utBA\..
61 lŒCT TRW1 ACTUATOR A gy

421BOOO1 AND ON 39-1 2106

51 305-4320A sv0cemte couTROL
SWITCH-WM DISINGMiE
52. T2003 7

AIRCTIAFT
HA a i IV ION

TITLC

. ELECTRIC ELEVATORTRIM i
WIRING DAGRAM I
¯

(opT)
se co7osioen77 o. onAwmo o

scAi.e-
A/0/VE REF SHEET / Û j

Change 10
14-80 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

(REF STD Wl2ING DIAGRAMt way STD wiRIME DINRAF1,

ALTERNATOÆ
S EFT St.TE.RMATOR SHEET

1
1 stot austt¾
TERMitãAL BOARb (RET)

SIDF CDIV50LE
PS36 O

Ifß 0

2
3
4 5
F 820

3
4

F509B10
SPI

FL AED

6
10

(Rev si unRING)
F509AZO
REF STD Wig)NG
omaam aram 421BOO56 AND ON
SME T MBe

o Part Number Nomenclature

1. IN1201 Diode -
Cabin Lt
2. AGC 3. 0 Amp Fuse -
Flight Hour Recorder
3. 1-203739-6 Recept -
Fwd Side Cons
4. 1-203735-5 Plug -

Fwd Side Cons

421BOOO1 TO 42180056 5. CM2926-1 Recorder Flight Hour -

6. S-1498-2 Sw Flight Hour

-

7. MS24525-22 Sw Battery
-

8. DSO4-37S Recpt LH Wing -

9. DSO7-37P Plug LH Wing -

10. 2VA20 Sw Gear Safety

-

couraner so.

/oysy/sy SSna,
AmenAFT
co. :
e.o.ao2

11 as°27
len

^*N
W/lLTRAN
"°""Ñza14. lo/n/J7 PLIGHTHOURRECORDER
CHECK
P¿rx A yony,a -
WlhG DIAGAM
(OPT)
sizE coDE loENT, No, osAwiNa No.

°2"'
D 71379 I 5118445

Change 1
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-8Î

5 ER INV

C8

VIA 0 TD

5tDF CO/V40/E
LCWER CO/Viv
( (

EQU/PP'lENT L/ST
SY/YROL RART IVO. OnRT /V/9ME
J/02
(/00v/ld)
G/0/ /2SP2Ñ IblVE.RTER
/15 SGT PLUS
J/02 7777½/ RECEPTl\C.LE -
00VAL
R /0/ OR-4O-5 RESISTOR
Cß 7277- 5 CIRCUti SREAKER

502/120,
MSEGO3fo-IOR TERMWAL
V GA20
MS2.603/s~I+9 TERMINAL

xsouro 421BOOO1 TO 421B0394

i G 02 EM242 INVERTŒK
J502. 1977K¿ PECEPOCL.E

FIO/
421B0394 AND ON

GIO/ INVERTTR

Pl/S

421BOOO1 TO 421B0394
V3DM20
Cuc.)

| P5
d5
Si t
LWR
COMLOLE
CONhL

V3D 20
JEANEA
d50L U VAC
G50L v)BixE Réct.PTKAL
L.

421B0394 AND ON

AIRCRAFT

TIAm-
5HA\/ER I N\lERTER 22N)
W\R\NG ASSN.
sizic coortoENTNo. DBAwtNaNo.

D 11379 : 5HBIOS

Change 10
14"ÊÎ ELECTRICAL SYSTEMS 421 SERVICE MANUAL

- LSO6A2Dlv

1
o

CEC20
Part Number Nomenclature

1. 0842215-8 Taxi Lt
2. DSO4-27-25S Recept Nose Bhd -

3. DSO7-27-25P Plug Nose Bhd

-

F.S. 100.00 4. 1-203735-5 Plug Fwd Side Cons

-

5. 1-203739-6 Recept Fwd Side Cons

-

6. 112-205-101 Taxi Lts Sw Ckt Bkr -

LEB20

F. S, 120. 00

L5A RD

421BOOO1 AND ON

CONTRACTNO. DI7VISloN
MILITA 8: 1
WICHITA. KANSAS 67201
DATE

YlTLE:
DRAWN WALTHRAf
TAX/ C/GH7 COPT1
\A//RHVC D/AGRAM
STRESS

"°
SIZE CODE IDENT NO, DRAWING NO

OTHER,
C 71379 : 5!!8447
GCALE: fg£ pf REF 5HEET I ÔŸ \
 421 SERVICE MANUAL ELECTRICAL SYSTEMS Î4-63

J 20
J3C20

ri 5 6
1 2 u
LJ LJ

3 4

J6 D20 J8020
J 7 20 JSD20

STARTER R£2 ST/WTE

/GNIT/0N \ /GNITIOW

Part Number Nomenclature

1. S6LN-1201 LH Mag LH Eng

-

2. S6LN-1205 RH Mag RH Eng

-

3. MF-3A Radio Noise Filter

4. MF-3A Radio Noise Filter
5. S6LN-1205 RH Mag RH Eng -

6. S6LN-1201 LH Mag LH Eng -

7. MF-3A Radio Noise Filter

8. MF-3A Radio Noise Filter

421BOOO1 AND ON

CONTRA/CT

TITLE:
^WN W/lLTAIAN
"°"
/?wisla io/rr/m
RADIO NOISEFILT£R-MAGNETO
CHECK , WIRING DIAGRAM
STREss

PROL
S E CODE'IDE Os DRAWING No

OTHER

SCALE: gdÑÿ REF SHEET / Û

14-84 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Part Number Nomenclature

1. 7277-2-5 Turn & Bank No. 2 Ckt Bkr -

2. 1-203739-6 Recept Fwd Side Cons

-

3. 1-203735-5 Plug Fwd Side Cons

-

4. CM2651-L1 Turn & Bank Ind No. 2

5. 201298-1 Recept RH Grd Inst Pnl
-

6. 203540-1 Plug RH Grd Inst Pnl

-

7. C661003-0202 Turn Coordinator LH -

8. MS3106A-10SL-3S Plug LH Turn Coordinator

-

9. 1-201298-6 Recept LH Grd Inst Pnl

-

10. 1-203540-1 Plug LH Grd Inst Pnl

-

11. C661003-0202 Turn Coordinator RH -

12. MS3106A-10SL-3S Plug RH Turn Coordinator

-

5 6
F4820 F504B20 FSOGA20N

F.S. 120.00
F. S. 118. 00

F. S. 120. 00

F. S. 118. 00

F. S. 120. 00

F. S. 118. 00

421B0001 AND ON

Aals join/ RN TSB LEFT&RIGHT HAND

esec
PAR A ming TURN COORDINATOR WikiWG

6 E CODE IDENT. NO. DRAWING NO.

//
°2"="
D 71379 5 li 8449
 421 SERVICE MANUAL ELECTRICAL SYSTEMs 14-85

REF
N PPL/C9LTLE
t STD
/FING
O/AGMAN
P3/Al4N A32AI4N P3 Al+W P3 /fN

C C 3
1 2 3 4

DLUE
RED
BLUE

V26AIS

6
I
LACK
5
pg,
B CW
BLACK

SLUE
---RED BL E RED -

P26A/S
SFI

P27A18
RTF
I APPL/CAß'Ú
STD WIR/A/6
D/RO/7ð?1
REER/8 i gy í ?30/4 l‡
A LTER/V/)TOR
IA//R/NG'

Part Number Nomenclature

1. 635837 Voltage Reg Main -

2. 138-3 O. V. Relay Main -

3. 635837 Voltage Reg Stby -

4. 138-3 O. V. Relay Stby -

5. JN114-1357B-1 Radio Noise Filter

6. JN114-1357B-1 Radio Noise Filter
42120001 AND ON

coNTRAC
AIRCRAFT
M tcT V ION

TITLE:
answN W/lLTAJAN '
sa°= A Ja dwo
RADio NOISE FILTER-REGULATORS I
WIRING DIAGRAM
¯

CHECK
AN, ,,,27,4,
STRESS

-
D 11379 5/l8450
=^I-r gdNE nre wrrr / Of ¡
14-86 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Part Number Nomenclature

1 7277-2-10
p' 1. RH Ldg Lt Ckt Bkr -

2. MS24524-21 Plug Ldg Lt -

3. 1-203739-6 Recept Lwr Side Cons

-

4. 1-203735-5 Plug Lwr Side Cons

-

<160/6 5. DSO4-37S Recept RH Wing -

2 6. DSO7-37P Plug RH Wing-

7. 0870132-1 Ldg Lt RH -

8. 877 Wire Assy

9. 0820501-1 Wing Ice Lt LH -

-1
10. 0820501-1 Wing Ice Lt RH -

11. DSO4-37S Recept LH Wing -

- - 12. DSO7-37P Plug LH Wing

-

13. 112-205-101 Surface Deice Lt Ckt Bkr -

UGRIS
LMis
13

L2DI20

3
F. S. 132. 00
4

L2?820

LSBl8(16,

LlbB/8 Pl

L40BIS
LE2E20
UnczoOut

F.S. 150.00
F. S. 150. 00 F. S. 150, 00
11
L2 F 2C)

L4CCl8 L/6C/8
LOC /8

C6
421B0001 AND ON
(RL F1
-

L5/44I N gy, y
CONTRACT NO
TRANSFER P. O, SDX 1877
-¿'.=^;1•,:',",'.""'°"
PUMP o,
yo7227, SSnao ce

onAwN WilLTMAN
amour
a RWLANDINGL GHT É SURFACE
DE-¡CE LIGHT (OPT)
casos
y
SYRESS - W/ I G G M
"°
SIZE CODE IDENT, NO. DRAWING NO.

THER
D 71379 5 H 84ö I
sexo ¿V0/VE are sneer / Off
 421 SERVICE MANUAL ELECTRICAL SYSTEMs 14-97

TO CAMN LIGul5
6ATTEAT EMEKG

IDF CONSDLE
TERMIMAL SUARD

TO CAEW LIGHTS (_8

P35C1D

PG36D20

I| TPSGDA20N

4
P501A20

TPEO2A20

EAASH LOCATOR 6EACON WlEING ASSy

Part Number Nomenclature

L IN2482 Diode-Overhead Flood Lts

2. 1-203739-5 Recept Side Console
3. 1-203739-6 Plug Side Console
4. 8-1696-1 Switch
5. CIR-10 Transmitter

421B0101 AND ON

Change 10
14-98 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

M\CA TiMEL MODULE

W TO ti CAP
3Lbl VilU ; 4;

YLLtò

37 20 ATO

LW IKEM FI It KB FKIM
017L61 V/ty CD H CTGA nyya¿l VALVI

1 -Stet - --gogn)- R O(RE -C r. e

au-C-I
mitog -- 9¾B20(JE -->stAc Lt04
a WING
I ow vAlvF
kJ&BL i ,] wrx

LOAl vALVF 0A20

1..103

asuvectAToR
IA2û(M ADSi 651

@¾-1
BLUK-t
TAIL
JALVE BL b¾

5109 PElí5
NWiTCW

4150L cKE MAh1E

MID4
.IO! LM
Till
f
if
'
L\OL 1 E-a

05 0 ihNt: ilm vAL¾f

L\og . WtuG 46¾ .JWf
FAlt Low VAL
PKFSS SWITCH
D DE di wiTCM

\ CIRfviT BEEAKFÆ

EPUCE

tel TERP,1|MAL

N1$¾027. TERMlN41

CPI MS2E274 2 CAŸ

LLui 3D234FOt 4.8 PftESS CONT VALVE
LiDit 302341-0) RH PilESS CONT VALVE
$403 10034-3 PRI.555t]\TCB

vm.:

NG ASSY ~
Su 40
421B0120 AND ON E (DET)

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-$$

1 2 3 5
6 Ce- MilA10 HMS20-- H5llC20- HEIID20 BLAC

1 P
FWD slDE
CON56LE CONNE R

I NG Aî5V~ ßLCDHOL WHUDSHIELD DEMEE

Part Number Nomenclature

1. 112-205-101 Switch Circuit Breaker

2. DSO7-3P Plug
3. DSO4-3S Receptacle
4. WC106 Connector Assembly
5. 476411 Pump and Filter Assembly

421B0201 AND ON ALCOHOL WINDSHIELO

DEICE WIRING

18464
DNF

Change 5
14-100 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

1 4
RED
RED

Part Number Nomenclature

2 RED

4 -------WillTE 1. DB-25S Receptacle

2. RC-20GF151K Resistor
3. CM3535 Potentiometer
5 WHITE
4. DA-15P
-

Plug
7 GREEÑ
5. IN5061 Diode
6. 2N3053 Transistor
8 ---GREEN 7. RC20GF682K Resistor
atos 8. RC20GF152K Resistor
LUE

3
YELLCD
REFER TO SHEET 15
FOR SYSTEM WIRING
14 YELLOW

f6 GREY

F. S. 118. 00
F. S. 118. 00
LIGHT DIMMER CONTROL

5
m . Y] DI DI -

e 5 5 REFER TO SHEET 19
FOR WIRING S TE M
5

Tel (io) (a ) Ò (2 (a) (9 ( F. S. 118. 00

sna.^'"::^" =EE=
DIMMER CONTROL
AUXILIARY FUEL QUANTITY LIGHT LIGHT DIMMER
CONTROL WIRING

42180001 AND ON ""'I """"""° """"*

D 71379 -
5618007
son NOME

hange 5,
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-101

2
BROWN I
1
RED 3
E
ORANGE 2

C Part Number Nomenclature

YELLOW 4
1. MJE3055 Transistor
2. DB-25S Receptacle
GREEW G
E
LIGHT ßLUE 5
C
VlOLET 7
1
GREY- 9
WHITE 8
C
BLACK 10
B
TA N I2.
E
PINK ll
C
DARKBLUE 13
1
WH)TE BLACK 15
E
WHITE RED 14

WHITE C,REEN 16
8 1
WHITE/YELLOh! 18
E
WHITE/BLUE 17

REFER TO SHEET 15
FOR SYSTEM WIRING

F.S. 100.00

TRANSISTOR & HEAT

421BOOO1AND ON SINK ASSEMBLY
sus many.no. omwigNo.

D 71379 5618008

Change 5
14-102 ELECTRICAL SYSTEMs 421 SERVICE MANUAL

FUSELAGE
STATION
118. 00
1 2

28VDepowER sounct geo

YELLow
VTERC0tiM

LR ELLLO

PART NUMBER NOMENCLATURE

1. 17-10370 RECEPTACLE
2. 17-20370 PLUG
3. 1786-7 SWITCH -
PRESS TO TEST
4. GE327 BULB
5. IN5061 DIODE
6. 9910072-6 CIRCUIT BOARD

ANNUNCIATOR INTERNAL
ANHUNClATOR ASSY
SCHEMATIC ONLY
sitt cobs iomr. No. naAWINr, No.

56 8009
J
scAtt
71379
I OF 1
2 / 1

Change 8
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-102A

1 2

MARKER SCN-- GREN

BLACK
2.SVDC- POLO PsElPURC. 860
FUEL QUANTITy -
HITE

BACK COURA -
23 -YELLOW 16

40 4
L TRANS -
¿4 -YEttov/ 42

R Tanma -
25 -YELLOW

T #8 TEST - Eh -YELLOW †9

Jf2 PI2.
4
* A COND HYD 421B0501 AND ON

PART NUMBER NOMENCLATURE

1. 17-10370 RECEPTACLE
2. 17-20370 PLUG
3. SA24SDX11-1 SWITCH -
PRESS TO TEST
4. GE329 BULB
5. 1N5061 DIODE
6. 9910072-13 CIRCUIT BOARD

P. O. BOX 1977
WALLACE.PROSPECTPLANT
WICHITA, KANSAS

ANNUNCIATOR INTERNAL
SCHEMATIC ONLY MNUMCIATOR4557

421B0301 TO 421BO801 D 71379 36|80 9

y -

NONE SNEET

Chang'e 11
14-102B ELECTRICAL SYSTEMS 421 SERVICE MANUAL

1 2

AIP.to o.

PART NUMBER NOMENCLATURE

1. 17-10370 RECEPTACLE
2. 17-20370 PLUG
3. SA24SDX11-1 SWITCH-PRESS TO TEST
4. GE327 BULB
5. 1N5061 DIODE
6. 9910072-13 CIRCUIT BOARD

r. o. Box 1977
WAt1ACE4t0SPECT PLANT
WICHITA. KANSAS

ANNUNCIATOR INTERNAL
SCHEMATIC ONLY : A watcarom assy
Szi CODE1000. W DIAWNG No.

g 421BO801 AND ON D 71379 60 8° S

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-103

WIRING DIAGRAM INDEX

421BO301 AND ON

TITLE PAGE

Wiring Reference Designators . . . . . . . . . . . .

14-105
Connectors . . . . . . . . . . . . . . . . 14-107
Terminal Boards . . . . . . . . . . . . . . . 14-108
Alternator System . . . . . . . . . . . . . . . 14-109
Power Distribution Bus . . . . . . . . . . . . . . 14-110
Starter-Ignition . . . . . . . . . . . . . . . 14-111
Landing Gear . . . . . . . . . . . . . . . .
14-112
FlapControl................14-112
Vent Heater and Stall Warning . . . . . . . . . . . .
14-112
Tach. Generator . . . . . . . . . . . . . . . 14-113
Engine Instruments . . . . . . . . . . . . . .
14-113
Outside Air Temperature . . . . . . . . . . . . .
14-113
Turn and Bank . . . . . . . . . . . . . . . .
14-113
FuelPumps ................14-113

Fuel Quantity System (Capacitance) . . . . . . . . . . .

14-114
Dimmable Panel Lights . . . . . . . . . . . . . .
14-115
Interior Overhead Lighting . . . . . . . . . . . . . 14-116
Light -
Exterior and Tip Tank . . . . . . . . . . . .
14-117
TransferPumps ...............14-117

Cabin Pressurization . . . . . . . . . . . . . .
14-118
CabinHeat ................14-118

Cigar Lighters and Door Warning . . . . . . . . . . . 14-118

Map Lights and Audio . . . . . . . . . . . . . .
14-119
Electroluminescent Instrument Panel . . . . . . . . . . 14-120
AvionicsBus................14-120A
Flight Hour Recorder . . . . . . . . . . . . . . 14-121
Optional Pilot, Copilot Instrument Lights . . . . . . . . . 14-122
Power Distribution Side Console (Optional) -
. . . . . . . . . 14-123
Oxygen, Seat Belt and Smoking Lights (Optional) . . . . . . . . 14-124
Auxiliary Cabin Ventilating System . . . . . . . . . . . 14-125
AngleofAttack ...............14-126

Air Conditioner . . . . . . . . . . . . . . . 14-127

Heated Windshield . . . . . . . . . . . . . . . 14-128
Avionics Cooling Blower . . . . . . . . . . . . . . 14-129

Change 12
14-104 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

WIRING DIAGRAMS

RE FERENCE DESIGNATOR CODE:

Reference designators are used in these diagrams to more quickly identify and locate a part or
assembly used in an electrical system. A part is identified by reference number on a diagram.
The reference number is called out in page 14-105 and identified by part number, description,
and diagram sheet location.

EXAMPLE -

REF. DESIGNATOR DIAGRAM SHT. NO. PART NO. DESÇRIPTION

BB20 6 0820001-1 BATTERY BUS

NOTE

Part Numbers referred to on Wiring Diagrams are for reference only.

When ordering spare or replacement parts, refer to applicable Parts
Catalog.

The wiring diagrams contained in this section clearly show the com-
plete wiring on each item of electrical component listed in the Wiring
Diagram Index. The first portion of wire number indicated the Air-
craft System, the center portion indicates Wire Number, and the last
portion indicates Wire Gauge Size. Each wiring diagram contains
part number and nomenclature for each component.

EXAMPLE: C14B22

14B

AIRCRAFT WIRE NUMBER WIRE GAUGE

SYSTEM CODE AND SEGMENT

Three types of wire numbers are shown for optional equipment. An example of
the various wire numbers is as follows:
E27B18 E327B18 E527B18

The only difference in the wire is in the installation schedule. The E27B wire
numbering system was used on aircraft 421-0001 thru 421BO301. At 421BO301
and On, the same wire would be indicated as E327B18 or E527B18.

Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-120A 4-1 ÛÊ

As 1 CoalsocE

TJ LP Ta gy
ALIFRNATDA ALTERivATOR

COMM NAV AUDIO

Cß41 C64l caso te gg 37

P AG 38405

PS43Al2

DF -CL1DE-
THF.5E kHRES TOBE ADD£b
45 STANDARD ON ALLAlRCRATT BB 06 BBIOl

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¼TTERY comPAciriENT
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-- Pl3AU-
MT coM30tE
P54 DIE
POWER Te.m 80.

PS43C12
I

P5OlAtO

QUlFMENT Lif T ( REF ONLY )

SYt18OL PART NO. PAR.T NAME

l 2-36161-5 TERMtNAL
2 2-3E0568-2 TE.RB\NAL
2-3Gißt-3 TERMINAL
2-320568-3 TERM\MAL
2-3616§-4 TERMINAL
6 322005 TE.RT1\NAL
7 .321670 TERMINAL
BB106 5113410- BUS BÞsR
BBLOL SilB4t0- 3 BUSBÞsR
BBIO3 5\184IΠBUSB/-R
8810¾ 5118403-\ BUS BAR
BB105 5118409-1 BUS BÞsR
BBlofo 5tiB403-1 BUSBAR
BB107 508403-1 BUS BAR
0837 7277-5 CKT BKR, AUDIO AMŸ
CB3B 7277-5- CKT BKR, NAv 2
CB33 7277-5- CKT BER, NAV \
CBAO 7277-5- CKT BKR, COnn 3
CB4\ 7277-5- CKT BKR, COMM 2
CB42 7277 5 -
CKT SKR, C.OMM I
CB43 7277-5- CKT SKR GLIDESLOPE2
CB44 7277-5- CKTBKR GLIDESLDPit
CB45 7277 5- CKT BKR ADF E
CB46 7277-5- CKT BRR ADF I
CB47 7277-5- CKT SKR NKR BCN 421BO301 AND ON
0843 7277-5- CKTBKR RMÍ
CSSO 7277-5- CKT SKR XPDR 1
CBSI 7277-5- CKT SKR DME
CB52 7277-5- CKT BNR AUTOP1LOT
CBGB 785H5-50 CKT BKR Avt0NICS(k\Nf
cat., cw'* 1°="
SCO
,ta,.s-4
C.M-5583-40 SW CB,AV10N\CS
*°"
ALT
na."e "="A""."
C-8 -7654-15-50

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E
AV\0N\CS BUS
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Change 8
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-Î21

(REF STD WictiMGi OtAGRMA

POWER DisT SHERT)

P555 1

FilAI SATTERN SW stDE CONSOt..E

FaAt.o Fa o

(REF STO Wlatuca Da A 1 J P Linithy 4-tealA

AL.NLAMATOR SHEE.T .] RECORose

69\

FOALO

a tw what4
P cond

CEAR ON G,ROLINO

r , resto
LEFT PAIMM
laEAR %AFTEN S

REF STO WIRINor

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EQU\PMENT L\5T
mano, war so e as a mm 421BO301 AND ON
NatO(o C.bALSlu-t R.EC.ORDER -
WLT AR

FtOi ACuf.. 3.O FUSE

SPt Si3]D-i SPL.tc.E

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FLtâ½T MOUR RECOROER

-

\NIRINCa A%W4
(OPT.)
srzt. conEloaNY,No unAw:NaNo.

D 71379 Scota2O2
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Change 8
14-122 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

REF STD WIRIM6 DIA6IMM

REF STDh/lRIN6 DJAGAAM IMtAAlbLL INTEMOR L16H15
DP1MASLE \NTERIOR L16MTS

T
L 2A2O
LSli. O

PROP DE.-lCE. I

LE1OALO

L533A10

CLOC DiR. C,YRO SLAVE \MD

AVtOMICS INSTR LX
TO EbE DETERNAtNED l

1 HO =NR IMO my AMioMK.S E.O.

MAY SullTcMES
FUEL T MSFER. 5

pTicMAL ptLOT ¡MSTRubAF.AlT L.iúßi%

LEb362

AL SP2. T.)RM 4BAhlk \MO.

LE33CTO

\R G.YRO 692. PEED \blo

PTioNAt.. CD-Pit0T \¾STRUNAENT LtGMTS

EGU\PMENT L\ST
5VMß0L PAki h]DMER PART MAME

D5 tos C/12990-G1 PDST tGHT- WAY SW

DS toi D.E SLAVE
05 108 D%Gtmo
DS tou ti MRD
D5 440 PRoP DEIŒ
DS tu AtR bêEF.O
OntìI. MR.SPERO
06 tt3 40RSLANRD
D5 04 RORif.4tWD
D¾ 05 AUltMEILS
DS 06 ALT) AETER
DS 09 Igh 40.

421B0301 AND ON
05

DS LI5 CIALSSO-61 no
POST Libül FuEL 39]
592. 3tosat seau.a OPJiOWAL P\LOT INSTRUMm3 UGHTSL
DPTIONALCD-PW.0T
IN5TRDMENTL1GHTS
h/lR\N6 ASSV

618205
NONE NEV A swarr 10F1

C iange 12
 SERVICE MANUAL ELECTRICAL SYSTEMS 14-l 3

SEACON NAv
5;MbE 135 L15
LIS (SEF1 LVET
IAflDAI Of TitE
5 St 5 5:3 E

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5 USED:

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FLAŸ LD6 GR LOG GT,

illAFACE NOIDA \/AN MðTOP
0 t F) F)

EB 5

y; übíRET)

FML Ellyt. AUX AUX

PDMP PilMP MMP PUNP
L R L K
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met ra to <ss esf EßlIPMENT UTT
SYMEDL PART NUriMR ESERIPTiok)
BBlRET]
CB 111] 5-5 CMI BR6AKER-SUHFACE DE-KE
SS
(MD C L 18ANSFLM PUMP
CS -
K IRiW36ER FilMP
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CL 100-100-30 -AllAJN*2
(8 5 (6 i (8 CS 5 in 200-100-30 Ci3 MEAMER AttBV1 -
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BB(REF1 itL-705-101
SCE -
TAXI LT
SCE 112-205-181 SHut0MHff
SCS 112-L20-101 -PROF ANTHC£
506 112-203-101 -DE-ICE LT
EnbiN SCS 111-205-101 -flTOTHEAT*l
FAN FM RIM EI6M, LTP 50.6 C.w l5M-40 Sum ibRiktixr Ammluh Wmr.
fikF) hiiRN PL/R (REF) L-52.05t=El-5 ikR.mtMAL
Eb309 Silb410-(o ßb5 ßAR
p p
5118410-3
(SHS & 5 E645 ca 15 80110 BUS SAR
85111 511M10-1 805 BM

BBIAEV3

LI GYß0 6YAO Giñ0

CS 5 En S [6 5

BBfREF)

421B0301 AND ON

na.^'"
TiTLE

POWER D\STR\¾T\OM WIRiNG

AssN
S\DE C.OMSOLE. (OPT)
sizz coozinawr.No. onAwinaNo.

D 11379 : 5618204
seu ragME

Change 12
14-124 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

SEAT BEt T UTS

RED

06

01NGEM SibN LTS

SPL XDS \3D LtSWT ASEY

WHITE

LSSGALO
SP1

L555ATO

SEWT BELT OMORM M69T

-¯

LtüßT SWiCTH [40 hiL j i b30 RC I SWtTLB

slos L_ L__ '_A L sus

LT MTO L.1 PRO

1 TERtom. Os]ERMLAD
u RTIMO
REF.5TO. whRis1Ga OtA62AM

EQU\PMENT L\ST won-osaa

SNMBOL PART MO. PART MANtE MOTE

DS Yl.9 321 LAMP

Y,Db\LO 9000 O\ MORT AkiftÞ.biN
LOS t34 IO-OI.Ma-i Múa y Ahm-CAbin

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S us mkT-Loso swTc,w,OWN6E.M
5-433 MST-1054 SWtTCH,SMovJub
SQL %-1570-L SPUCE-
D310551-3 TERNAtMAL-

421B0301 AND ON

AINcnAFT

OXVéaEM , SEAT BELT 4

SMOW MG LTS,
WIRtMB ASSN. (ORT.
srze coaEmeNT me. onAwiNomo.

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Change 12
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-125

S ILO RM IniY

OPIW(sL CAbtN ELOlutR

001 a04 BLA k

MSOktie

gi bÞL

LO & SP1

bin E.vAP FAM R5048\b

t.0NTRbL RES

401 &Oi

. .
PÆD RM Atht
itLD CASIM B.LOWER

Detail
SLAC..w.
E.FF. Att0050t 3RT.LI 411aosoo

MSTR, PAI(EL
CMO. PLub P -

RED>Atta
QDi

i E.VAP FA RU)

I COIJTROL

4503DIIe
401 ADL QDi

BLACK

I
RD

AU
LOWER

L...------A- ---..I
AIR (.OMDíTIDMER
S c..tWLutT BREARER.

EQUl9MENT UST
SNMLSOL ARI MO PART MAME.

312.0 Ft-DGet-i RM Aux Et.OwtR

BU.\ UGocas-I LH AUX BLOWER
S 41 TAS 35 53 -11 Switikw-ENAP FAh3
USkew-D TULMik3AL

001. 5-¾\-\ SPLICL

SPL 5-1510-2. Louce

421B0301 AND ON

ontvisloN
AIRCRAFT
MILITA Ta
Co. wrcNiranAnsAse7xoi
g
rivte:

AUX CABtM \ÆMT\\..ATIM6

-

SNSTENA
-
\MRING AssN -

atxt conitinzNT.No. onAwrNano.

D 71379 i 508207 Ai

Change 8
14-128 ELECTRicAL sYSTEMS 421 SERVICE MANUAL

i I Ct7A2ON
STALL
CONSOLE HORN
GNO PL%

CICA20- CIGB20 -
3 -
GREY

C2A20 CECC3 -
RED
STALL WÞRN CB
M 501
ANGLE
FulO 6 OR
COhiSOLE CONN
ATTACK
IND\CATOR
YELLOW -
( Gjc2 C gge ---
( -YELLO
MT 50\
ANGLE OFATTACK ORANGE -
2 -
ClSA20 C1582O 2 ---ORANGE
TFfANSOUGER
3 GREEN -
5 C304820 C304A2O 5 -
GREEN

BLACK-
*e3e ß BLo sc3of.42.o -7
7 C305820 CT5A20 -
BLACK
--CAA20ht
ww RED 4

Nt4 L553H20- 8 -
BLUE
\dBITE
P503 J505
WHITE
'y- L51G2
SLACK
H5 A20 (RET PILOT \NST L16HTs) JSO4 PSM

(RET STALL¢VEMY RE-AT)

CAP4GN

421BO501 AND ON

MRNG ASEY -

ANGLE.OFEMCK

\8208

Change 11
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-129/14-130

J37 P37
(18)-ME(18)- (EBLU)
ADRFEAKER MP37-F304 (18)--<> (BLK)-GRD(20)
(RED -
|I
CIRCUT
FILTER BLOWER

10986005

Cessna "-

AVloWICS CDDUNG BLOWE

10NG DIAGRAM

Change 12
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-1

SECTION 15

ELECTRONICS SYSTEMS

Table of Contents

Page Page

GENERAL DESCRIPTION .
. . . 15-1 Cessna 800 RMI . . . . . .
15-16E
Wiring Code . . . . . . .
15-1 Cessna 800 Nav . . . . . .
15-16F
AVIONICS MASTER SWITCH BREAKERS .
15-2 Cessna 800 Com . . . . . .
15-16G
ELECTRONIC INTERFERENCE . . .
15-2 Cessna 800 Glideslope . . . .
15-16H
Radio Noise , . . . . . .
15-2 Cessna 800 Antenna Interconnects . .
15-16I
Alternator Noise . . . . .
15-2 Cessna 800 Transponder . . . .
15-16J
Ignition Noise . . . . . .
15-2 Cessna Nav-O-Matic 800 Autopilot .
15-17
Flap and Landing Gear Motor Noise .
15-2A 12310-1144 Ground Adapter . . .
15-20A
Auxiliary Fuel Pump Noise . . .
15-2A DG104B-1 Ground Adapter . . .
15-20B
Lighting Circuit Noise . . .
.
15-2A Cessna Nav-O-Matic 400 . . . .
15-20C
ELECTRONIC INTERFERENCE Cessna Transceiver 500 . . . .
15-20D
TROUBLESHOOTING GUIDE . .
15-2A Cessna Nav/Com 500 . . . .
15-21
Alternator Noise . . . . .
15-2A Cessna 500 Series Antenna
Regulator Noise . . . . . .
15-2A Interconnects . . . . . .
15-22
E. L. Inverter Noise . .
. .
.
15-2A Cessna ADF 500 (Rotatable Loop) . .
15-23
Electric Trim Motor Noise . .
.
15-2B Cessna Dual ADF 500 (Rotatable Loop) .
15-24
Fuel Boost and Auxiliary Transfer Cessna ADF 500 (Fixed Loop) . . .
15-25
Pump Noise . . . . . .
15-2B Cessna Nav/Omni 500 . . . .
15-26
Tip Tank Transfer Pump Noise . .
15-2B Cessna Nav/Com 400 . . . .
15-26A
Rotating Beacon Noise . . . .
15-2B Cessna Transceiver 400 . . . .
15-26B
Strobe Light Noise . . . . .
15-2B Cessna Nav/Omni 400 . . . .
15-26C
AVIONICS COOLING BLOWER . . .
15-2C Cessna ADF 400 . . . . . .
15-26D
Removal . . . . . . . .
15-2C Cessna 400 ADF - - . . . .
15-26E
Installation . . . . . . .
15-2C Cessna Glideslope 400 . . . .
15-26F
FLIGHT PHONE . . . . . .
15-2C Cessna Transponder 400 - . . . 15-26G
Removal and Installation . . . .
15-2C Cessna 400 ADF (Fixed Loop) . . . 15-26H
WIRING DIAGRAMS Cessna Marker Beacon 300 . . .
15-27
Cessna Transceiver 800 15-2H Weather Radar · - - · ·
15-28
AVQ-55
. . ·
. .

Cessna Transmitter 800 . . . .

15-3 WeatherRadar . . . .
15-29
Cessna Nav/Omni 800 . . . .
15-4 T22RA HF Transceiver . . . .
15-30
Cessna Dual Nav/Omni 800 . . .
15-5 PN101 Pictorial Navigation System .
15-31
Cessna Glide Slope 800 . .
15-6 PN101 Pictorial Navigation System .
15-32
Cessna ADF 400 . .
15-6A Audio Amplifier and Audio Wiring
Cessna Dual ADF 400 . . . .
15-6B Diagram - . . . . . .
15-32A
Cessna ADF 800 (Fixed Loop) . .
15-7 Radio Junction Box Terminations . .
15-33
Cessna ADF 800 (Rotatable Loop) . .
15-8 Radio Cooling Blower . . . .
15-34A
Cessna Dual ADF 800 (Rotatable Loop) .
15-9 Audio Code Filter . . . . .
15-34B
Cessna Marker Beacon 800 . . .
15-10 Continuous Load Chart - · · ·
15-35
Cessna DME 800 . . . . .
15-11 Table of Electronic Equipment
Cessna Transponder 800 . . . .
15-14 Loading · - - - - · ·
15-36
Cessna RMI 800 . . . . . .
15-15
AIM 400 Gyro . . . . . .
15-16
Cessna 800 ADF . . . . . .
15-16A
Cessna 800 Dual ADF . . . .
15-16B
Cessna 800 Transponder . . . .
15-16C
Cessna 800 Marker Beacon . . .
15-16D

GENERAL DESCRIPTION. Wiring Code.

This section contains wiring diagrams which clearly Each wire used in the electronics system is identi-
show the complete wiring on each item of electronic fied by code. This coding provides a convenient way
equipment listed in the wiring diagram index. The of identifying wires when installing new wiring or
last portion of the section contains tables showing servicing existing wires. The wire code is shown
the electronic loading of various components on the on each diagram. Some cabling is supplied by ven-
shelves and rack in the aircraft. dors on the electronics equipment and do not carry

Change 12
 ELECTRONICS 421 SERVICE MANUAL
-2 SYSTEMS

Example C14B22 14B

AIRCRAFT WIRE GAUGE

SYSTEM CODE
WIRE NUMBER
AND SEGMENT

NOTE

The wiring diagrams in this section pertain to Aircraft 421-0001

to 421B0001.

For wiring diagrams on Aircraft 421B0001 and On, refer to the

applicable wiring diagram book furnished with your aircraft.

Cessna identification. The diagrams covering such properly installing capacitive and inductive devices
wiring may refer to the instruction manuals of such these circuits, the noise can usually be reduced
in
equipment where a more complete wiring diagram to a tolerable level. A more difficult type of noise
may be found. The wiring code used by Cessna on to suppress, is that generated by friction between
the 421 is shown above. two components or by rectification. Another diffi-
cult problem is noise that is carried to sensitive
areas by grounding loops. The following paragraphs
AVIONICS MASTER SWITCH BREAKERS contain solutions that have been effective for the fac-
tory. It is important to remember that each aircraft
Two Avionics Master Switches are provided with may present a slightly different problem and, there-
factory-installed avionics. Power is supplied from fore, a "fix" on one aircraft will not necessarily be
the battery through a circuit breaker located in the effective in all cases.
left-hand stub wing circuit breaker panel to the avion-
ics switch breaker located on the left side console.
The ALTERNATE AVIONICS power switch circuit Alternator Noise.
breaker located next to the avionics switch circuit
breaker on the left console provides, power in the While the alternators are relatively free from radio
event the avionics circuit breaker, switch breaker or noise, there is the possibility
the alternators will
their associated wiring and battery circuits become produce an audible noise in the radio and electronic
inoperative. Access to the avionics circuit breaker systems. Inside the alternator a three phase AC
is gained by removing access cover (36), figure 1-2. voltage is applied to a full wave rectifier assembly,
thus converting the AC voltage to DC. During the
rectification, an AC ripple appears on top of the DC
ELECTRONIC INTERFERENCE voltage, thus the bus voltage is actually fluctuating.
While the battery acts as a capacitance, it is also
Radio Noise. necessary to have additional filtering. This is ac-
complished by the use of a capacitor from the output
Radio noise is a problem of great importance to the terminal to ground at the alternator. The use of
aircra.ft industry. A noisy radio system may actu- solid state regulators reduces the possibility of reg-
ally imperil the safety of the aircraft occupants. ulator noise to a minimum and will not require filter-
The performance of radio navigation equipment can ing.
be completely erroneous if radio noise is excessive.
For this reason, radio installations should be made
only by persons who are qualified. Radio noise is Ignition Noise.
not generated in a properly operating radio set, but
is merely presented to the listener in an audible form The sound of ignition noise is easily identified be-
exactly the same way that a radio station is received. cause of its timing. The 421 has a shielded magneto
Many forms of noise can exist in any particular air- ignition system. Each econdary lead from the mag-
craft and, ironically, sometimes certain aircraft can neto to the plug is a shielded wire. Double shielded
be amazingly quiet. This condition is unusual and wiring is used in the primary circuit with a special
even though the aircraft is quiet without noise sup- suppressor in series with the switch lead. The sup-
pression, it cannot be released without proper sup- pressor is constructed coaxially with a shielded lead
pression. A quite aircraft without suppression may coming out of the end which is connected to the mag-
degenerate into a noisy aircraft with changes in age, neto cigarette cartridge. The double shielded wire
temperature, and humidity. Common radio noise is is connected to the terminal end of the filter (the
generated by ordinary electrical devices in the air- shield is grounded). The double shielded wire enters
craft such as flap or gear motors, navigation light the cabin area through connectors in the wing root rib
flashers and ignition or alternator systems. By to prevent noise transfer to the junction box wiring.
Change 7
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 5-2A

The double shielding is continued to the inside of the tems to determine which component or components
cabin to the magneto switch. The magneto switches are causing the noise, by observing which compo-
are enclosed in a shielded case to which the double nents are actually operating when the noise occurs.
shield of wire is grounded. If ignition noise is pre- c. Check the component for proper operat1on or
valent in the radio system, the entire magneto sys- damage.
tem should be checked for tight connections, espe- d. Check wiring connections and wiring coming in
cially in the root rib connectors and at the switch contact with moving parts.
and suppressor. All ground connections in the cir- e. Check wire routing for proper separation.
cuit are critical and any oil or dirt accumulation f. Check wire shielding where applicable.
should be cleaned from the connection and the metal g. Check all system grounds.
should be brightened to provide the best possible
ground. Ignition harness should be replaced if shield-
ing becomes questionable. Alternator Noise.

If alternator noise is experienced and it is deter-

Flap and Landing Gear Motor Noise. mined it is coming from the output of the alternator,
the following troubleshooting should'be accomplished
During a landing approach, an unfiltered motor in the before attempting additional filtering.
flap or gear circuits can produce a startling volume
of noise which is very distracting. There is also the a. Check attenuator output bypass filter for broken
possibility of the noise blanketing a message from the leads or inadequate ground.
tower during the approach. It is possible that suffi- b. Check the lead attaching to alternator power (+)
cient noise could be created through these circuits to terminal is as short as possible or approximately 1
blanket an ILS signal, creating a hazardous situation. to 2 inches long.
For these reasons, the circuits have a filter section c. Check alternator ground wire for any damage or
built into the motor. The filter should be very ef- improper contact or corrosion between terminal and
fective if the unit is properly grounded. If noise be- grounding point.
comes excessive with good grounding, a motor over- d. Check alternator brushes for damage that could
haul or replacement may be necessary. be arcing.
e. Check alternator brush tension for proper seat-
ing.
Auxiliary Fuel Pump Noise.

Coaxial type capacitors produce effective results Regulator Noise.

when installed on the base of the fuel boost pumps.
Because of the location of the fuel pump and capaci- If regulator noise is present and traced to the regu-
tors, the connections must be kept tight to avoid any lator and its associated control leads, the following
possible arcing. When proper filtering and ground- checks should be made before attempting to add addi-
ing do not produce the desired filtering results, a tional filtering.
new pump should be tried.
a. Check regulator adjustment for proper setting
(27. 25 to 27. 75 volts).
Lighting Circuit Noise. b. Check regulator noise filter for damage, loose
wires, broken leads, or improper connections.
All lighting components on the 421 have internal fil- c. Check shield wire on regulator to alternator
ters and usually do not require external capacity- field wires for proper temination (single point
The light wiring, however, because of its route to ground), shield damage, check for adequate coverage
the extremities of the aircraft can, in unusual cases, at termination ends.
conduct noise to vital areas. The light wires and d. Check alternator for brush arcing.
electrical wiring bundles should be routed away from
the antenna and loop antenna cables to prevent picking
up noise in the radio systems. Shielding should be E. L. Inverter Noise.
properly grounded.
In most cases noise produced by the E. L. inverters
could be due to the light capacitive load on inverter.
ELECTRONIC INTERFERENCE TROUBLESHOOTING When this problem occurs, it can be eliminated by
GUIDE. the addition of 01 to 05 udf 200 WV capacitor
. . to the
output terminals of the inverter. If the noise cannot
The following general troubleshooting information is be eliminated, it should be determined whether the
presented as a guide to determine the system or sys- noise is due to one of the following.
tems producing the interference.
a. Radiation from AC arcing requiring shielding.
a. Pinpoint the particular system causing the noise b. Noise conducted to the power bus by the DC in-
by the process of elimination. put, requiring filtering.
b. Once the system causing a particular noise is c. Radiation from DC power leads requiring shield-
isolated, investigate the particular system or sys- ing.

Change 2
15-28 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

d. Radiation from inverter, necessitating replace- NOTE

ment of inverter.
e. If the aircraft has an ADF installed, the follow- If the cause of the noise cannot be eliminated,
ing guidelines may be used to locate E. L. inverter a 47 microfarad
. 50 WV feed-thru capacitor
noise: should be installed in the power (AX) lead as
1. Tune ADF to a low frequency band. close to the pump as possible and insure the
2. Place all panel light controls in the lowest po- case of the capacitor is properly grounded to
sition. the airframe.
3. Turn each.panel cotitrol fully on, one at a time,
and listen for a high-pitched buzzing sound similar
to an electric drill motor. Tip Tank Transfer Pump Noise.
4. After isolation of the noisy control, check
panels on that control for operation. If the tip tank transfer pump is causing noise in the
5. If the inverter has a capacitor across its output audio system, check the following.
terminals, check the capacitor for damage or sub-
stitute a capacitor known to be good. a. Check capacitor case ground.
b. Check capacitor for damage, open circuit, short
circuit, loose wiring and damaged shielding.
Electric Trim Motor Noise. c. Substitute a capacitor of the same value known
to be good in place of the original capacitor.
In the event of noise difficulties caused by the trim
system motors, the following should be checked to
insure standard noise suppression equipment is Rotating Beacon Noise.
properly installed.
If the rotating beacons are causing noise in the audio
a. Check that motor frame and actuator assembly system, the following should be checked.
are properly grounded.
b. Check capacitors inside of motor for broken a. Filter for proper ground.
leads or damage. b. Lamp circuit for loose connections and wiring.
c. Check to make sure shielded wires are properly c. Bulb for loose socket.
grounded at the actuator assembly and that the d. Internal filter for damage.
shields are not shorted in other areas to structure e. External light for proper ground to frame or
which could create noise loops. structure of aircraft.
d. If the filters are good and noise is not totally
eliminated, the following procedures should be at-
tempted to eliminate the noise: Strobe Light Noise.
1. Change C1 to 05 microfarad.
.

2s Add a 1.0 microfarad feed-thru capacitor with If the strobe lights are causing noise in the audio
shielded lead to (+)lead of the side producing the system from radiation or in-line interference, the
noise. Attach the housing or capacitance ground to following should be checked.
the actuator housing assembly.
3. Make sure shielding wire and motor frame are a. Make sure all power supply units are grounded
making good ground. properly to the airframe.
4. If the motor is noisy in both directions of rota- b. Insure the shielded wires and twisted pairs
tion, add a 1.0 microfarad feed-thru capacitor to both from the tail light are grounded.
leads and insure that shield and housing or capacitor
ground are attached to the actuator housing assembly.
5. The addition of larger capacitors, inductors or NOTE
RF chokes is not recommended; experience has
proven no significant change in additional filtering. Grounds must be terminated at the power
supply.

Fuel Boost and Auxiliary Transfer Pump Noise. c. Insure tail Nav light is adequately grounded.

If boost pump noise is experienced in the audio sys-

tem, check the following. NOTE

a. Insure that wiring

is properly shielded. If it is determined the
noise is being radiated
b. Insure are properly grounded,
shields from the tail light, flash tube, the interference
c. Check loose wiring connections for looseness can be minimized by installing a strip of al-
and breaks. uminum metalized tape on top of the existing
white stripe painted on the glass and insuring
the aluminum strip is grounded to the metal
case of the light assembly.

Change 2
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-2C

AVIONICS COOLING BLOWER. FLIGHT PHONE.

An optional avionics cooling blower, if installed, is The flight phone system consists of an RT-18 trans-
located in the control pedestal. The blower system ceiver, an AT-460 antenna, a phone handset and
consists of a blower, filter, fuse holder, fuse and associated wiring and cables. The transceiver, and
electrical wiring. The blower is utilized to cool the antenna is located below the aft fuselage baggage
avionics equipment mounted on the radio panel of the compartment. The phone handset is normally lo-
instrument panel. cated under the aft RH passenger seat.

Removal of Avionics Cooling Blower. (See figure Removal and Installation of Flight Phone System.
15-1. ) (See figure 15-1A. )

a. Ensure electrical power is OFF. a. Open drawer assembly; remove phone from its
b. Remove access panel (2) from control pedestal base, tag wires and disconnect wire bundle (2).
(1). b. Remove phone mounting plate (3) from drawer
c. Identify and disconnect blower ground wire assembly by removing screws, washers and nuts.
(black) from structure; disconnect blower wire (blue) c. Remove nuts, washers and screws securing
at splice. drawer assembly to slide assembly (9); remove
d. Remove blower (7) from bracket (4) by removing drawer from seat base.
clamp (6). d. Remove slides from seat base by removing cap
nuts and bolts securing brackets (8) to seat base (7).
Installation of Avionics Cooling Blower. (See figure e. Remove carpet and aft floorboard as required
15-1.) to gain access to flight phone transceiver and an-
tenna.
a. Position clamp on blower and secure clamp to f. Disconnect wire bundle (2) and coax cable (12)
bracket with bolts, washers and nuts. from transceiver (14).
g. Remove transceiver from its mounting plate and
NOTE remove mounting plate from brackets (13) by remov-
ing attaching screws.
Clamp is to be positioned against stop block h. Disconnect coax cable (12) from antenna (11) and
(5). Install blower with flow arrow pointing remove antenna from aircraft by removing attaching
up. screws.
i. Install flight phone system by reversing removal
b. Identify and connect electrical wires of blower. procedures.

NOTE

Ensure ground wire is properly grounded.

c. Conduct operational check to ensure proper di-

rectional flow of air.
d. Install access panel of control pedestal.

Change 12
15-2D ELECTRONICS SYSTEMS 421 SERVICE MANUAL

o
a

Detail

51143027
Detail g A51141121
B51141120

1. Control Pedestal 3. Filter 6. Clamp

2. Access Panel 4. Bracket 7. Blower
5. Stop Block

Figure 15-1. Avionics Cooling Blower

Change 12
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-2E

Detail A
51143072
A51143049

Figure 15-1A. Flight Phone Installation (Sheet 1 of 2)

Change 12
15-2F ELECTRONICS SYSTEMS 421 SERVICE MANUAL

10

12

13

11

Detail

B51143073

1. Handset 6. Drawer Assembly 10. Doubler

2. Wire Bundle 7. Seat Base 11. Antenna
3. Mounting Plate 8. Bracket 12. Coax Cable
4. Magnetic Catch 9. Slide Assembly 13. Support
5. Latch Assembly 14. Transceiver

Figure 15-1A. Flight Phone Installation (Sheet 2)

Change 12
 421 SERVICE MANUAL ELECTRONICS SYSTEMs
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FURNISHED WITH YOUR AIRCRAFT.
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Figure 15-10. Cessna DME 800 (Sheet 1 of 4)

Change 1
15-12 mescreoNICS 421 SERVICE MANUAL
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FURNISHED WITH YOUR AIRCRAFT.

Figure 15-10. Cessna DME 800 (Sheet 2 of 4)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-12A/15-12B

NOTE
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APPLICABLE ELECTRONIC WIRlNG BOOK
FURNISHED WITH YOUR AIRCRA FT.

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Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15- 3

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ON AIRCRAFT 421B0001 AND ON CONSULT

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15-14 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

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Figure 15-11. Cessna Transponder 800

 421 SERVICE MANUAL ELECTRONICS SYSTEMS

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15-160 ELECTRONICS SYSTEMs 421 SERVICE MANUAL

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NOTE
*421A0090 TO 421B0001
ON AIRCRAFT 421B0001 AND ON CONSULT
APPLICABLE ELECTRONIC WIRING BOOK 421A0001 TO 421BOOO1
FURNISHED WITH YOUR AIRCRAFT.

Figure 15-13D. Cessna 800 Marker Beacon

Change 2
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-16

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APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT.

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Figure 15-131. Cessna 800 Antenna Interconnects

Change 1
15-16] ELECTRONICS SYSTEMS 421 SERVICE MANUAL

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NOTE
421A0129 TO 421BOOO1
ON AIRCRAFT 421BOOO1 AND ON CONSULT
APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRA FT.

Change 1 Figure 15-13J. Cessna 800 Transponder

 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-18A/15-188

Cl2BA24-Kifo
-
Moon /ww RS

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NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

100 /L tuAn RES
E LE CTRONIC WIRING BOOK
.

FROMT APPLICABLE
FURNISHED WITH YOUR AIRCRAFT.

] O CS\AZ4-Raut-I
UAtt-PA-A SEE FIGRE 19-3)

ST AosM SuvTCw
(mcu como SINGLE NAV/OMNI 800
421-0001 TO 421BOOO1

Figure 15-14. Cessna Nav-O-Matic 800 Autopilot (Sheet 3 of 5)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs15-20A

LOC-OFINIGROUND
ADAPTER PIN 2V2,D1-Oi

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YELLOW/WHITE(+UP [N)

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RED CA+)

cu
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NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
421-0001 TO 421B0001 FURNISHED WITH YOUR AIRCRAFT.

Figure 15-14A. 12310-1144 Ground Adapter

Change 1
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TB2
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GRN R GRN
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15-8

ROTOR. G=ROUND RV2iûAC.4 PESOLVER GROokD

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NOTE
2O3~OB2O REst3TOR

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT 421-0001 TO 421BOOO1

Figure 15-16. Cessna Nav/Com 500

Change 1
15-22. ELECTRONICS SYSTEMS 421 SERVICE MANUAL

3]e3D ESDYMAVERTEA

K€Y RV201A22

C,88c/U COMM

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NOTE

ON AIRCRAFT 421B0001 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
421-0001 TO 421B0001 FURNISHED WITH YOUR AIRCRAFT.

Figure 15-17. Cessna 500 Series Antenna Interconnects

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-23

27500 IwoicAmoet

ROUND -RD2AÛ 26-PGT 3¯'

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NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT. 421-0001 TO 421BOOO1

Figure 15-18. Cessna ADF 500 (Rotatable Loop)

Change 1
15-N ELECTRONICS SYSTEMs 421 SERVICE MANUAL

PIOA,1(o2tO CONN KIT

2.7 41O
IMPICATOA

GROUND A ----RD2f0Ct2 -947

13
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C -RožtSA12. -P67 (SEE. FIGURE li~IS) IS ANY
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NOTE
Autio

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
421-0001 TO 42180001 FURNISHED WITH YOUR AIRCRAFT.

Figure 15-19. Cessna Dual ADF 500 (Rotatable Loop)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-25

33fro) ¡¡ggimyÛ LooP ART.

GROt.IRD A A 6ROUMD
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AIRCRAFT CmROL)MD K RD2t4A24 -

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AUDIO AMPL
MATING COMM
--RD214A24 (SEE FIGUEE if-2
)

NOTE

ON AIRCRAFT 421B0001 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT.
421-0001 TO 421B0001

Figure 15-20. Cessna ADF 500 (Fixed Loop)

Change 1
15-26 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

28776 to 4

8943 COUW

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7826 C \\4 KlT

£7826 COMM KlT
2,4660 CONVERTER.
37£/0 INDICATOR

NOTE

421-0001 TO 421B0001 ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT.

Figure 15-21. Cessna Nav/Omni 500

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15 26

G_ AUDI
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ON AIRCRAFT 421B0001 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT.

COUPLED WITH RA-324C 38470-0000

Loor w my AÇCESSORY//2/7

Loo e IN 28

Hi0 IN I GnNIO 04T I

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SENJEAHT. ( -ROJSSA2#
421A0001 TO 421B0001

Figure 15-21E. Cessna 400 ADF

Change 1
15-26F ELECTRONICS SYSTEMS 421 SERVICE MANUAL

P377 P:u3
F-RA23Ÿ8.2,î---- G FLAG+
F---RA259A22---- S FLAG +
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NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
421-0001 TO 421B0001 FURNISHED WITH YOUR AIRCRAFT.

Figure 15-21F. Cessna Glideslope 400

Change 2
 421 SERVICE MANUAL ELECTRONICS SYSTEMS S-R Û

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CONN£CTOÑ
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2IP77G
.8/ f ,5X/29A24 /J Al
A2 f JX/JOA24 17 A2
A4 ( s×/3/A 21 20 A4
BI Ÿ JX/3>A 4 | Si
82 e sx/J34 2 4 5 B2
D Ef P JA/34A24 7 134
E C/ rÛ SX/JSA24 12 C/
C2 SX/JéA2A 16 C2
A
04 X ,SX/37A21 ---
19 CV
Di y .5x/JSA.34 4 of
D2 Y SA/39A24 4 D2
D4 J JX/404 i 10 D4
REP/Y MON/7OR C EX/4/424 /4 REPLY MOA//TOR
REPLY SQt/RCE S SA/42A22 /8 REPLY 504/RCE
LV RELAY . 13 sxid3A22 22 LV RELAY
34V -SM//TCH sx/44A22.
9 34V JWITCHED
SELF-TEST MuoE A F SA;4£A24 25 JELF-TEJT MODE /
SELF-TESJ MODEC R sk/4CA2f 27 S£LF-7EST MODE C
JENS Sw/TCH h EX/47A22 23 SENSE Gw;TCH
34V. SDURCE _h 34/423.¤. 2 34V SOURC£
GRD T SA/19A20 -- // GRO
IDENT E SX/SQA24 15 IDENT
GRD E
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39'750 00 Z 8
-

TEANSCE IV E R.

P 228
R45/-
P227
37443-0002 coNN x/T .
0002 CONN KIT

NOTE

ON AIRCRAFT 421B0001 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT- 421-0001 TO 421B0001

Figure 15-21G. Cessna Transponder 400

Change 1
15-2BHELECTRONICS SYSTEMS 421 SERVICE MANUAL

TABLE I 2T3lo-OO e
IN-16A IND
TERMINAL NO - - --
CWOSD -olo!

WJRE TDP LOOP BOTTOM LooP

COLOR TDP 90TTON1 TOP BOTTOM - ...

SENSE SENS£ STATORZ-ROTORC A WHT/BL 4

SENSE 5ENSE

L ---
WHT/BLK -----¾

RN J l 2 2 ROTOR RT/ Stx/DRN ROTOR H M WHT/ BLX/DAN I

PTR
HT 2 2 I i STATORX N WHT/8LX/BLU I
--
STATOR y WHT/BLR/YEL --I

424 D ND RMI OE)

424 2D IND RMI (BODE)
367 TERM

ST D - WHT/9L -
H Lg OLU
Y£L
--í

STATOR Z
WHij BLX -4

5/8 "O
I m)352920N - -- WBT/ StK --i

R
tic
WHT/BLX/DRN --í
PTR ROTOR H B NT/ BL /ORN - --
WHT/ BLK/ ORN --¶ STATORX
B
C VVNT/BLA,79LU M
TA HT BL TATORY WITT/ BLK/1EL ---i

NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
FURNISHED WITH YOUR AIRCRAFT.
36420 1 0 ANT-LODP

ND CN LD N LD

LDOP iB GONIO N 8

LOOP 2A 60 0 N PA

22803 CABLC ASSr

36380 00 CVR

/ \9 a
ANT
179M (X)00 CABLE
ASS

1)056 0000 CABLEAsst

(p.48TOF 38422 0028)
GENSE ANT JN

5 EL

29422 0028 CA8tl ^SS

I
5 1 7 TENM
RES 82 y Of IN Act] FUSE

A E 293zs 0003 (RE

ym m22 à
DDCSty OUT /

2f / / CAP 28 o LT

22 TUA.9070
C C
ROTORC
HASF

DJo UT 0 R

tLu F S I
28 Y Of LT

421-0001 TO 421B0001

Figure 15-21H. Cessna 400 ADF (Fixed Loop)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-29

AKITEMMA UMtT

Sut3ATA- TA..-T
TILT UP L O Up
TILT Dys/M M SAli4Ata i TR..T DWM
RG.SOt..V€W. S\ P SMIA2.L 1 2.esocVe.W. Si
RESOLVI-.R 52. SM2-All & W-CSOLV£9.. 31
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\\T VAC Mi DELAYER S ------ SMEG.A2.L

\\5 VAC.l..O DELAVE D -

SME/A2.1
SUPPLY GRO N SMLEALO
-50 VOUTE .) SM26,AE.

67-OkC.L -37.5 CO

RPilAl6 m V25A22 osc;«ox. es-a,- w.

J37

CB4e TW2A
PBS
°"° ---,a c°
0810 VZOAf0 \
1A0001 TO 421B0001
-SOVOLTS (To AhÃT) 20
ANTG-NMA GW.O 16
(tSVALk.O DELAWED 19
\\€VAC Mi DCLAVED 16

-Y T.« Votra A 597 33 '. 14V

04DlCATOR GW.O \7 'SMBAL l's SUPPLY GP.O
CalN CAkims ATE S Sk\¾A2A \L GrAtM CAt.ißW.ATG.

\\5 VA<.- Hi DLL.AVRO(00f)2C SkikOA2.2.- \3 \\SVAC.. M\ DE.LAVRO

its VAC. LO D LAVED(our 14 Sad\\ALl- 4 I\S VAC LO OCLAYEO

+asov It ss.itzA2.4 \s +z.sov

STANDTV et.LAY LO 12. SkatSAZ4 \¾ STAMDay RI LAY Lo

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41-6Voc To \MD 28 SMthA2.4 U, -4-Z¶$VOC..

M-OGT- Rit-AY LO tvaoN \ND'l T SMGA2.4- O OM-OWN RELAY Le

L. V. A\ SMTOA M 19
T'W.tGG 9... A2 Skt1\A - 7,1 TIL\GG-RSL.

itsVAC. L.O 4 --K2.1812. K2.3At2. B ikWVA¢. l..O

itSVAC. Mt 2 ---yz 1821 -KL\AL2.. 7 its VAC. N\

E.wvoc. + 7 -
skJte L2.

Oki-Off RELAY L $2ELAV) 6 -VT-4Al2.

PX 952.01-335-03 COMM

94

VELA
7Dit(2 LAY
30 JUMPER C

N2462. D\ODC(SEZ)

(3 21 JUMPER
°^'°
NOTE v2ta os
SC VA \MVEETIL

53 ON AIRCRAFT 421B0001 AND ON CONSULT

2°'
APPLICABLE ELECTRONIC WIRING BOOK 421-0001 TO 421BOOO1
FURNISHED WITH YOUR AIRCRAFT.

Figure 15-24. AVQ-55Weather Radar

Change 1
 15-30 ELECTRONICS SYSTEMs 421 SERVICE MANUAL

c""
Pi46 ' Oll U Ai luoros/o
045
us2cs/o eco Llt U T com

421A0001 TO 421BOOO1 t'

CRAb.kbdEt.thd> $6 RC 7ALL
R.ÆMOTe, t.oAOth.lG
IS RCiBA11.

2O RC I BAll. D
21 BCLOALL C.
A+ REMOTW. LDADIM -
43 RC BAtt H

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pc; RC3OA\G J (SEfflGURElf-À
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Aveto AMi3L

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FIGURE /6-2/
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007, 4
NigE RA?

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soo om more cotas
ORA

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COMMON TO COb.1TRQt-

V2

421-0001 TO 421BOOO1

COMTROL

i£/ O

co
Yat.ovi
ORANGE - -
NOTE

ON AIRCRAFT 421BOOO1 AND ON CONSULT

APPLICABLE ELECTRONIC WIRING BOOK
"°¯ " "'"°"

FURNISHED WITH YOUR AIRCRAFT.

Figure 15-25. T22RA HF Tra.nsceiver

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMS15-34A

RD209A16 ;
ADF RCVR 5 RD209B20

100G 5W
P75 RESISTOR
T. B. 10

RN219A14 ja
NAV/OMNI
RN219C20
RCVR

12 34 6
P58
bl RP17A20N

R- T UNIT
10 RV211C20
RP17B20
P125 RP18A20 BLOWER
r-----i MOTOR
10 RV103C20 13
XCVR RV103A14

P55 si RP19A20N 14
|9 v5 i FILTER
TO L - _1
o
-CB22 RP3A20 3 RP3B20
RP16A20
KEP17D11 RELAY \
TB6 (24V)
A40D717 FILTE
LOCATED ON LH SIDE
OF CONTROL PEDESTAL

Figure 15-30. Radio Cooling Blower

15-348 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

TB6

S1367-1-8
TERMINAL
SPEAKER
WIRE

RZ1A22 ,
6 NO. 360
WIRE -"
CODE FILTER

WHITE

38 ' 3 WHITE

17 GREEN -

18 GREEN --

BLACK ---

AUDIO AMPLIFIER TB9

MATING CONNECTOR CONNECTING 10-140 TERMINAL
WIRES TO BE STRIP
22 GAGE
(AS REQD.)

Figure 15-31. Audio Code Filter

 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15

Amp Reqd.

Cessna Idarker Beacon 300 . . . . . . . . . . . . . . 0.02

Cessna Nav/Com 400 . . . . . . . . . . . . . . . 1.5

Cessna Gilide Slope 400 . . . . . . . . . . . . . . . 0.45

Cessna Transponder 400 . . . . . . . . . . . . . . . 1.5

Cessna Transceiver 400 . . . . . . . . . . . . . . . 1.0

Cessna Nav/Onani400 . . . . . . . . . . . . . . . 0.5

Cessna Nav/Onani 500 . . . . . . . . . . . . . . . 6.7

Cessna ADF 500 . . . . . . . . . . . . . . . . 2.1

Cessna Nav/Com 500 . . . . . . . . . . . . . . . 2.6

Cessna Transceiver 500 . . . . . . . . . . . . . . 3.25

Cessna FPar Onani 800 (560 Channel) . . . . . . . . . . . . 2.0

Cessna Transceiver 800 . . . . . . . . . . . . . . 3.4

Cessna Transnaitter 800 . . . . . . . . . . . . . . 0.9

Cessna ADF 800 . . . . . . . . . . . . . . . . 2.1

Cessna Nav-O-hiatic 800 Autopilot . . . . . . . . . . . . 4.0

Cessna Nav-O-Matic 400 Autopilot . . . . . . . . . . . . 1. 2

Cessna RIJI 800 . . . . . . . . . . . . . . . . 3.1
Cessna DLIE 800 . . . . . . . . . . . . . . . . 2.75
Cessna 800 Audio Amp . . . . . . . . . . . . . . . 0.5
Cessna Transponder 800 . . . . . . . . . . . . . . 2.0
Cessna Gilide Slope 800 . . . . . . . . . . . . . . 0.7
Cessna Idarker Beacon 800 . . . . . . . . . . . . . . 0.38
T-22ILA H.F. Transceiver . . . . . . . . . . . .
. . . 2.0
Alli Slaved Directional Gyro . . . . . . . . . . . . . 0.08

AVQ 55Meather Radar . . . . . . . . . . . . . . 22.0

AVQ 45 TVeather Radar . . . . . . . . . . . .

. . 5.0
AVQ 46 TVeather Radar . . . . . . . . . . . . . . 5.0

Radio Cooling Blower . . . . . . . . . . . . . . . 0.74

PN 101 Systeni . . . . . . . . . . . . . . . . 8.0

Cessna Glidescope/Alarker Beacon 800 (Type KGT&690) . . . . . . . . .15

Cessna RTAI 800 CType SC-12 or SC-12A) . . . . . . . . . . 2.50

Cessna ADF 800 (Type R21B) . . . . . . . . . . . . . 2.80

Cessna Nav/Ornni800 (41A) . . . . . . . . . . . . . .075

Cessna Nav/Com 800 frype 131B) . . . . . . . . . . . . 1.50

Cessna Transponder 800 (Type 106) . . · · · · · · - - · ·

1.50

Figure 15-32. Electronic Continuous Load Chart

15-36 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

STA 43.0----
I

5013109 BAGGAGE
SHELF

I
STA 100.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 800 Transnaitter

26460-0028 Transnaitter 7.1
23400-0028 Dynaverter 3.5
30190-0028 Transnaitter (Export) 7.1

Cessna 800 Transceiver

19300-1028 Transceiver 13.8 Includes Afouni
20660 Adounting
27610-0028 Transceiver (Export) 13.8

Dynaverter (Transceiver 800)

22560-0028 Dynaverter 13.8 Includes liount
21455 DJounting

Cessna 800 Glide Slope

21420-0028 Gaide Slope Receiver 4.6
22510 Adounting 2.1
21790 Añounting 1.4

Cessna 800 D3dE

C582601-0101 Renaote Unit 8.4
071-4002-00 Rack Assenably .9

Cessna 800 b&arker Beacon

21430-0028 Receiver 3.7
22510 hiounting 2.1
21790 Adounting 1.4
22700 Mounting 3. O

TABLE OF ELECTRONIC EQUIPMENT LOADING

 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-9

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna RMI 800

28240 Converter 3.6
PN-101
28240 Converter 3.6
6781 Transformer
Cessna Nav/Omni 800
26410 Receiver 7. 0
27900 Converter 4. 5
22510 Mounting 2. 1

AVQ-55Weather Radar
MI-591003-2 Transceiver 27. 0
MI-591021 Shock Mount 2. 5
MGH 229-100 Inverter 13. 5

AVQ-45Weather Radar 14. O

MI-592021 Transceiver
MI-592032 Shock Mount

TABLE OF ELE CTRONIC EQUIPMENT LOADING

15-38 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

STA 69.00

5073110-3 BRACKET ASSY.

STA 56.00
I I
5073110-9 ANGLE

LBL 6.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 500 ADF

34660-0028 Dynaverter
21650 Mounting 2. 9

Cessna 300 Marker Beacon

,
31240-0028 Receiver 3. 7

Cessna 800 Marker Beacon

21430-0028 Receiver 3, 7

Cessna 800 RMI

29100 Dynaverter 3. 5

Cessna 800 ADF

24630-0028 Dynaverter
21650 Mounting 3. 5

PN-101
29100 Dynaverter 3. 5

TABLE OF ELECTRONIC EQUIPMENT LOADING

 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-U

5073110-4 CHAbHTEL

STA 56.30 ----

‡ o

5073110-5 CHANNEL

STA 48. 05 ---

LBL 6.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 800 Transnaitter

26460-0028 Transnaitter 7.7
23400-0028 Dynaverter 1.4

Cessna 800 baarker Beacon

21430-0028 Receiver 3.7
21790 Afount 1.4

Cessna 800 Transponder

34900-0028 Transceiver
29300-0000 Coder 3.5
22510 hiounting 2.1

Cessna 800 IdarkerBeacon

21430-0028 Receiver 3.7

Cessna Gdide Slope 800

21420-0028 Receiver 4.6

TABLE OF ELE CTRONIC EQUIPMENT LOADING

15-40 ELECTRONICS SYSTEMs 421 SERVICE MANUAL

STA 61.00---

5073113-2 SHELF ASSY.

STA 52.00 --·-

e
5073113-3 SHELF ASSY.

STA 43.00---

RBL 6.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Dynaverter (Transceiver 800) (When using 114. 5 cu. It. oxygen

22560-0028 Dynaverter cylinder)
21455 Mounting 13. 8

Cessna 500 Transceiver

32380-0028 Dynaverter
24900 Mounting 4. 3

Cessna 500 ADF (Fixed Loop)

34660-0028 Dynaverter
21650 Mounting 2. 9

Cessna 800 ADF (Rotatable Loop)

24630-0028 Dynaverter
21650 Mounting 1, O
34850-0028 Receiver
21660 Mounting 7. 4
PN-101
101A1158-7 Inverter

TABLE OF ELECTRONIC EQUIPMENT LOADING

 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-41

STA 85.99 -

g
5073110-6
CHANNEL

STA 95.05- # A ,

5073110-7
CHANNEL
LBL 6. O

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 500 Transceiver

32380-0028 Dynaverter
24900 Mounting 4. 3

Cessna Glide Slope 800

21420-0028 Glide Slope Receiver
22700 Mounting 4. 6

Cessna 800 RMI

32210 Converter 3. 6

High Frequency Transceiver

T-22-RA Transceiver

Nav-O-Matic 800 Autopilot

0870069-1 Computer 9.90

Cessna DME 800

C582601-0101 Remote Unit 11. 4

TABLE OF ELECTRONIC EQUIPMENT LOADING

15-42 ELECTRONICS SYSTEMs 421 SERVICE MANUAL

STA 77. 84 ----

5073110-8 CHANNEL

5073110-2 CHANNEL

STA f>9.59 -

LBL 6. 00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 500 Nav/Omni

24660 Converter 3.7
31360-0028 Dynaverter
24900 Mounting 4. 3

Cessna 800 Nav/Omni (Single)

26410 Receiver 7. 0
27900 Converter 4. 5
22510 Mounting (Triple) 2, 1
23180 Mounting (Quad) 3. 9

5173100-5 SHELF

DTA 43.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna Glide Slope 800

21420-0028 Receiver 4. 6
21790 Mounting 1. 4

TABLE OF ELECTRONIC EQUIPMENT LOADING

 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-43

5173100-5 SHELF

STA 43.00
EQUIPMENT COMPONENT REMARKS
WEIGHT

Cessna 800 Transceiver

19300-1028 Transceiver
20770 Mounting 13. 8

Cessna 500 Nav/Omni Receiver

31360-0028 Dynaverter
24900 Mounting 3.7

Cessna 500 Nav/Com

31630-0028 Dynaverter
24900 Mounting 4. 3

5173100-6 SHELF

STA 43. 00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 800 Transceiver

22560-0028 Dynaverter
21455 Mounting 13. 8

Cessna 500 Nav/Com

24660 Converter
24900 Mounting 3. 7

TABLE OF ELECTRONIC EQUIPMENT LOADING

15-44 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

o
o O /

5013110-8 SHELF

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 400 Nav/Com

3660-0000 Accessory Unit 2. 2 Includes Mount
35540-0000 Mounting

Cessna 400 Transponder

34960-1000 Rec/Trans 4. 4

Cessna 400 Glide Slope

36440-0000 Receiv 2. 6
34650-0000 Mount 0. 3

Cessna ADF 400

34660-0028 Dynaverter
21650 Mount 2. 9 Includes Mount
35380-0000 Receiver Accessory 5.7 Includes Mount
35390-0000 Mounting

Cessna 800 Transponder 6. 5 Includes Mount

39210-0028 Transceiver
34980-0000 Mounting

Cessna 800 RMI

C582606-0101 Converter 5. 8 Includes Mount
C582606-0102 Converter 4. 6 Includes Mount
C582606-0103 Mounting

Cessna Marker Beacon 300

31243-0028 Receiver 3. 7

TABLE OF ELECTRONIC EQUIPMENT LOADING

 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-45

5013110-9 SHELF

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 400 Nav/Com

3660-0000 Accessory Unit 2. 2 Includes Mount
35540-0000 Mounting

Cessna 400 Transponder

34960-1000 Rec/Trans 4. 4

Cessna 400 Glide Slope

36440-0000 Receiver 2. 6
34650-0000 Mount

Cessna ADF 400

34660-0028 Dynaverter
21650 Mount 2. 9 Includes Mount

Cessna Marker Beacon 300

31243-0028 Receiver 3. 7

Cessna 800 Marker Beacon/Glide Slope

C582607-0101 Receiver 4. 2 Includes Mount
C582607-0103 Mounting

TABLE OF ELECTRONIC EQUIPMENT LOADING

15 48 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

LBL
6.00

A18

STA.
70.00
STA.
79.00

EQUIPMENT COMPONENT REMARKS

WEIGHT

Cessna 800 RMI

C582606-0101 Converter 5. 8 Includes Mount
C582606-0102 Converter 4. 6 Includes Mount
C582606-0103 Mounting

Cessna 800 Nav

37500-0000 Receiver 2. 7 Includes Mount
35950-0000 Converter 1.9 Includes Mount
36450-0000 Mounting

Cessna 800 Com

38500-0000 Accessory Unit 5, 6 Includes Mount
37260-0000 Transceiver 4. 1 Includes Mount
36280-0000 Mounting (Transceiver)
34980-0000 Mounting (Accessory Unit)

TABLE OF ELECTRONIC EQUIPMENT LOADTNG

 421 SERVICE MANUAL STRUCTURAL REPAIR l l

SECTION 16

STRUCTURAL REPAIR

Table of Contents

Page Page

GENERAL . . . . . . . .
16-1 REPAIR OF PLASTIC WINDOWS . . .
16-13
Type of Construction . . . . .
16-1 CONTROL SURFACE BALANCING
Ground Handling . . . . . .
16-1 PROCEDURES . . . . . .
16-17
Investigation of Damage . . . .
16-2 CHECKING WING TWIST AND LOCATION
Definition of Damage . . . . .
16-2 OF THRUST LINE . . . . .
16-20
Preparing Damaged Area for Repairs .
16-2 SEALING PROCEDURES . . . .
16-21
Control Surface Rebalancing Data . .
16-2 Application of Sealing Procedures . .
16-22
WING . . , . . . . .
16-2 Faying Surface Sealing . . . .
16-22
Access Openings . . . . . .
16-2 Hole Fitting . . . . . .
16-22
Wing Skin . . . . . . .
16-2 Injection Sealing . . . . .
16-22
Wing Ribs . . . . . . .
16-3 Fillet Sealing . . . . . .
16-23
Wing Spars . . . . . . .
16-3 Fastener Sealing . . . . .
16-23
Flaps and Ailerons . . . . .
16-3 Window Sealing . . . . .
16-23
TAIL GROUP . . . . . . .
16-3 Electrical Sealing . . . . .
16-24
Vertical Stabilizer and Dorsal . . .
16-3 ALIGNMENT AND SYMMETRY CHECK .
16-51
Rudder . . . . . .
16-4 FUEL CELL REPAIR . . . . .
16-53
Horizontal Stabilizer . . . . .
16-4 CABIN DOOR SEAL REPAIR . . . .
16-58
Elevators . . . . . .
16-4 REPAIR OF ICE PROTECTION PANELS .
16-58
FUSELAGE . . . . . .
16-5 R1VETS . . . . . . . .
16-59
BULKHEADS . . . . .
16-5 General . . . . . .
16-59
LANDING GEARS . . . .
16-6 Types . . . . . .
16-59
ENGINE NACELLE . . . . .
16-6 Substitution of Rivets . . . .
16-59
Engine Firewall . . . . . .
16-6A Diameters . . . . . . .
16-60
Engine Firewall Sealing . . . .
16-6A Lengths . . . . . . . .
16-60
Engine Mount . . . . . .
16-6A Removal of Solid Rivets . . . .
16-60
Engine Cowling . . . . . .
16-6A Riveting Installation . . . . .
16-60
FIBERGLASS PARTS . . . . .
16-6A Loose or WorkingRivets in Wing . .
16-62
REPAIR PROCEDURES FOR BONDED Loose or Working Rivets . . . .
16-62
HONEYCOMB . . . . . .
16-6A NOSE COMPARTMENT WATER SEALING .
16-64
RADOME REPAIR PROCEDURES . .
16-8 SEALANT MATERIALS .
. . . .
16-65
RAIN EROSION COATING APPLICATION PRESSURE DRAIN SEALS . . . .
16-66
(RADOME) . . . . . .
16-12

GENERAL. izer, and vertical stabilizer are built up around two

main spars, with formers,
ribs, and riveted skin
Type of Construction. forming the basic structure. Torsional stiffness of
this structure is afforded by the skin closure of areas
The Model 421 is an all-metal aircraft of semimono- between the spars forming enclosed "boxes. " Each
coque type construction with the skin carrying a por- movable surface consists of a hinge support spar
tion of all structural loads. The fuselage is com- with ribs, formers, and riveted outer covering skin.
prised of a nose section, cabin section and a tail-
cone. It is constructed of formed bulkhead rings, Ground Handling.
stringers, and stiffeners all of which are riveted to
the external skin. The cabin section is sealed to Leveling, jacking, and other ground handling details
form a pressure cell. The wing, horizontal stabil- are covered in Section 2.

Change 7
10-Ž STRUCTURAL REPAIR 421 SERVICE MANUAL

Investigation of Damage, d. Smooth out abrasions and dents.

e. Brush iridite all rough edges and scratches with
After a thorough cleaning of the damaged area, all an iridite solution diluted 1 oun,ce to 1 gallon of water
structuralparts should be carefully examined to de- and rinse thoroughly,
termine the extent of damage. Frequently the force f. Apply two coats of zinc chromate primer to all
causing;the damage is transmitted from one member internal surfaces and edges lapping one another.
to the next, causing strains and distortion. Abnor-
NOTE
mal stresses incurred by shock or impact forces
on a rib, bulkhead, or similar structure may be Damage adjacent to a previous repair requires
transmitted to the extremity of the structural mem- removal of the
old repair and inclusion of the
ber, resulting in secondary damage such as sheared entire area in the new repair. For repairs in
or stretched rivets, elongated bolt holes, canned the cabin section that would affect the pressure
skin plate or bulkheads. Points of attachment seal, see sealing procedures in this section.
should be examined particularly for distortion and
security of fastenings in the primary and secondary Control Surface Rebalancing Data,
damaged areas.
The control surfaces have been 100°/o
of the aircraft
Definition of Damage. statically balanced. After
each repair or painting of
the control surÏaces, they must be rebalanced. Cor-
Structural damage to the aircraft is divided into the rect balance is restored by the addition or removal
following classificationsi of lead ballast weights in the counterbalance sections
a. Negligible damage shall be considered damage of the surfaces. (See figure 16-8 and 16-9,)
that will not affect the airworthiness of the aircraft
and can be permitted to exist as is or can be cor-
rected with a simple repair such as removing dents, WING
burnishing scratches, and stop drilling cracks in
non-structural parts. The wings are all-metal, full cantilever, semimono-
coque type
construction, utilizing two main spars.
NOTE Each wing consists of a wing panel, aileron, flaps,
engine nacelle, wing tanks, wing tip fuel tank and
The cabin section from'fuselage station 100.00 main landing gear. The landing gear is attached to
to 273.94 is a pressurized cell and all skins gnd retracts into the wing.
between bulkheads must be considered as struc-
tural members including inspection openings. Access Openings.
(See Fuselage Repairs.)
Access openings with removable cover plates are
b. Damage repairable by patching will be consider- located in the underside of the wing between the root
ed damage that may be repaired by covering or rein- rib and the tip section. These openings afford access
forcing a portion of the aircraft. to the aileron bellcranks, flap bellcranks, electrical
c. Damage repairable by insertion will be consider- wiring, pulleys, cables, and inspection of internal
ed damage requiring replacement of a section with structure. When work is done on the trailing edge
the correct repair material, wing structure in the flap area, partial access can be
d. Damage necessitating replacement of parts will provided by lowering the flaps. Outboard of this area,
be considered as damage not repairable by patching the trailing edge wing structure can be made available
or insertion, but that may be repaired by installing for repair by removing the aileron.
a new or reconditioned part. If a part or:area of
an assembly is damaged to the extent that it requires Wing Skin,
replacement and a replacement cannot be made
because of tooling or jig requirements the entire All wing, aileron, and flap skin thickness and temper
assembly must be replaced, are listed in figure 16-19.

Preparing Damaged Area for Repairs. a. Negligible Damage:

To prepare an area for repair, examine and classify Any smooth dents the wing skin that are free from
in
the damage. Make a.thorough check before beginning cracks, abrásions, and sharp corners, which are
repairs. In some cases a damaged part may be clas- not stress wrinkles and do not interfere with any
sified as needing replacement when after removal, internal structure or mechanism, may be considered
closer inspection indicates the part may be repaired. as negligible damage, In areas of low stress inten-
Tafe more time for the damage estimate and save sity, cracks, deep scratches, or deep sharp dents,
iiian-hours on repairs. To prepare a damaged area after trimming or stop drillmg can be enclosed by a
for patch or inserting repairs: two-inch circle, can be considered negligible if the
a. Remove all ragged edges, dents, tears, cracks, damaged area is at least one diameter of the enclos-
punctures, and similar damages, ing circle away from all existing rivet lines. Stop
b. Leave edges, after removal of damaged area, drilling is considered a temporary repair,
parallel to any square or rectangular edges of the
unit. b. Repairable Damage:
e. Round all square corners.

Change 5
 421 SERVICE MANUAL STRUCTURAL REPAIR l6-3

Skin damage ahead of the front spar and also where to repair it. This should be considered carefully
the optimum in appearance is desired, should be re- prior to making any repair whether it be only a small
paired by the insertion method. Typical insertion part or a complete component.
repairs are illustrated in figure 16-29. Skin damage
aft of the front spar which exceeds the negligible
damage limit but it is not extensive enough to necessi- Wing Spars.
tate replacement of a skin panel can be repaired by
patching. Typical wing repairs are illustrated in the Repair of spar damage affecting the alignment of the
back of the section, wing spar should not be attempted in the field. Per-
missible spar repairs are illustrated in the back of
c. Damage Necessitating Replacement of Parts: the section.

In case the skin is extensively damaged, repairs

should be made by replacing an entire sheet panel Flaps and Ailerons.
from one structural member to the next. The repair
seams should be made to lie along stiffening members, a. Negligible Damage.
or bulkheads, and each seam should be made exactly
the same in regard to rivet size, spacing, and rivet Minor skin dents and nicks are considered negligible
pattern as the manufactured seam at the edges of the and can be worked out by burnishing.
original sheet. If the two manufactured seams are
different, the stronger one should be copied. b. Repairable Damage.

Skin damage exceeding that considered negligible

Wing Ribs. damage can be repaired by patching. Typical skin
repairs are illustrated in the back of the section.
All ribs except those exposed to the wheel well contain
flanged lightening holes. Flanged upper and lower c. Damage Necessitating Replacement of Parts.
edges of all ribs serve as cap-strips in addition to
providing rigidity to the rib. The skin riveted direct- Warped and cracked skin, ribs, hinge brackets and
ly to each rib flange provides the cellular strength torque tubes are replaceable items. Any damage
for each successive rib bay. The nose, center, and that covers more than half of the unit will require
trailing edge rib segments are riveted together through replacement of the entire unit.
the front and rear spars to form the basic airfoil
sections. Spanwise extruded stringers stiffen the NOTE
skin between ribs.
Flight control surfaces must be balanced in
a. Negligible Damage: accordance with balancing procedures after
repair or painting.
Any smooth dents in the wing rib that are free from
cracks, abrasions, and sharp corners, which are TAIL GROUP
not stress wrinkles and do not interfere with any
internal structure or mechanism, may be considered The all-metal tail group is a full cantilever design,
as negligible damage. In areas of low stress consisting of the conventional arrangement of verti-
intensity, cracks, deep scratches, or deep sharp cal fin and rudder, horizontal stabilizer and ele-
dents, which after trimming or stop drilling can be vators. The right elevator and rudder both contain
enclosed by a two-inch circle, can be considered flight adjustable trim tabs, actuated by a system of
negligible if the damaged area is at least one cables and pulleys controlled from the pilot's tab
diameter of the enclosing circle away from all control wheels.
existing rivet lines. Stop drilling is considered a
temporary repair.
Vertical Stabilizer and Dorsal Group.
b. Repairable Damage:
The vertical stabilizer and dorsal area are construct-
Repairs for wing rib webs and flanges are shown in ed jointly to form a single unit. Basically the unit
figures 16-36 and 16-37. Before repairing is attemp- consists of formed sheet metal spars and ribs to
ted, all cracks or deep scratches must be stop- which the outer skin is attached. The front spar is
drilled with a 3/32 inch drill, and all sharp corners reinforced at its root end and drilled to facilitate
and ragged edges must be trimmed and deburred. the installation of two attachment bolts. Stiffness to
the entire stabilizer and dorsal assembly is provided
c. Damage Necessitating Replacement of Parts. by the attachment of the skins and the forward leading
edge skin.
Parts such as stiffeners, small ribs, clips, and
brackets should be replaced if their damage exceeds a. Negligible Damage.
that specified as negligible. These parts due to their
size, are usually impractical to repair. In many in- Any smooth dents in the vertical stabilizer and dorsal
stances, the time required to replace the damaged group skin that are free from cracks, abrasions, and
part may be considerable less than the time required sharp corners, which are not stress wrinkles and do
16-4 STRUCTURAL REPAIR 421 SERVICE MANUAL

not interfere with any internal structure or mechan- ing rivet lines. Stop drilling is considered a tempor-
ism, may be considered as negligible damage. In ary repair,
areas of low stress intensity, cracks, deep scratches,
or deep sharp dents, which after trimming or stop b. Repairable Damage,
drilling can be enclosed by a two-inch circle, can be
considered negligible if the damaged area is at least Skin damage, exceeding that considered negligible
one diameter of the enclosing circle away from all damage, can be repaired by patching. Typical skin
existing rivet lines. Stop drilling is considered a repairs are illustrated in the back cf the section. Re-
temporary repair. paring or splicing of horizontal stabilizer spar caps
is not recommended. Access to the internal stabili-
b. Repairable Damage, zer structure may be gained by removing a portion of
the rivets along the rear spar and ribs and springing
Repair of the skins, ribs, and spars can be accom- back the skin. By using the proper bucking bars
plished as illustrated in the back of the section. Ac- through holes in spar web, the skins may be closed
cess to the internal stabilizer structure is best with a minimum of blind rivets.
gained by removing the skin attaching rivets on one
side of the rear spar and springing back the skin, c. Damage Necessitating Replacement of Parts,

c. Damage Necessitating Replacement of Parts. Extrusions, hinge brackets, stabilizer tab, spar, and
ribs should be replaced rather than repaired. In gen-
Extrusion, hinge brackets, and small ribs should be eral, where parts are available, the easiest and most
replaced rather than repaired. In general, where satisfactory repairs can be accomplished by replacing
parts are available, the easiest and most satisfactory the damaged parts,
repairs can be accomplished by replacing the
damaged parts.
Elevators.

Rudder, a. Negligible Damage

a. Negligible Damage. Any smooth dents in the elevator skin that are free
from cracks, abrasions, and sharp corners, which
Minor skin dents and nicks are considered negligible are not stress wrinkles and do not interfere with any
and will be worked out by burnishing. internal structure or mechanism, may be considered
as negligible damage. In areas of low stress intensity,
b. Repairable Damage. cracks, deep scratches, or deep sharp dents, which
after trimming or stop drilling can be enclosed by a
Skin damage, exceeding that considered negligible two-inch circle, can be considered negligible if the
damage, can be repaired by patching. Typical skin damaged area is at least one diameter of the enclos-
repairs are illustrated in the back of the section. ing circle away from all existing rivet lines. Stop
drilling is considered a temporary repair. The
c. Damage Necessitating Replacement of Parts, exception to negligible damage on the elevator sur-
faces is the front spar, a crack appearing in the
Warped and cracked skin, ribs, hinge brackets, and web at the hinge fittings or in the tip rib which sup-
torque tubes are replaceable items. Any damage ports the overhanging balance weight is not con-
that covers more than half of the rudder will require sidered negligible. Cracks in the overhanging tip
replacement of the rudder. rib, in the area at the front spar intersection with
the web of the rib, also cannot be considered neglig-
NOTE ible.

Flight control surfaces must be balanced b. Repairable Damage,

in accordance with balancing procedures
after repair or painting. Skin damage, exceeding that considered negligible
damage, can be repaired by patching. Typical skin
Horizontal Stabilizer. repairs are illustrated in the back of the section,

a. Negligible Damage. c. Damage Necessitating Replacement of Parts.

Any smooth dents in the horizontal stabilizer skin Warped and cracked
skin, ribs, hinge brackets, and
that are free from cracks, abrasions, and sharp torque tubes replaceable
are items. Any damage that
corners, which are not stress wrinkles and do not covers more than half of the elevator will require re-
interfere with any internal structure or mechanism, placement of the elevators.
may be consïdered as negligible damage. In areas
of low stress intensity, cracks, deep scratches, or NOTE
deep sharp dents, which after trimming or stop dril-
ling can be enclosed by a two-inch circle, can be con- Flight control surfaces must be balanced in
sidered negligible if the damaged area is at least one accordance with balancing procedures after
diameter of the enclosing circle away from all exist- repair or painting.
 421 SERVICE MANUAL STRUCTURAL REPAIR M-5
FUSELAGE wrinkle, which is hand removable, should be rein-
forced by a 1/2 x 1/2 x inch 2024-T42
.050
extruded
The fuselage is of semimonocoque construction con- angle. The angle should be inserted fore and aft
sisting of formed bulkheads, longitudinal stringers, across the center of the wrinkle and should extend to
reinforcing channels, and skin platings. The fuse- within 1/16 to 1/8 inch of the fuselage bulkheads
lage nose section consists of the fuselage structure comprising the ends of the bay. If the wrinkles can-
from the nose to fuselage station 100. 00. The cabin not be removed by hand, the damaged area should be
section consists of the fuselage structure from fuse- repaired. Typical methods of repair of skins,
lage station 100. 00 to fuselage station 273. 94, (421- bulkheads, stringers and channels are given in the
0001 to 421B0301) Fuselage Station 289-94 (421B0301 back of this section. Before repairing is attempted,
and On). The tail section consists of the structure all cracks or deep scratches must be stop drilled
from fuselage station 273. 94 to fuselage station with a #30 drill and all sharp corners and ragged
373. 56, (421-0001 to 421BO301) Fuselage Station edges must be trimmed and deburred.
289. 94 to 373. 56 (421B0301 and On). Formed bulk- c. Damage Necessitating Replacement of Parts.
heads, channels, and extrusions constitute frame
members of the cabin area. The cabin section is All forgings and castings of any material and struc-
pressurized to the skin from fuselage station 100. 00 tural parts made of steel must be replaced if dam-
to 273. 94, (421-0001 to 421B0301) Fuselage Station aged. Structural members of a complicated nature
100. 00 to 289. 94 (421-0301 and On). Drilling or any that have been distorted or wrenched should be
type of repairs of the pressurized cabin should be replaced. Major skin damage should be repaired
accomplished in a manner that will not change by replacing the entire damaged sheet.
structural integrity or pressurization capabilities of
The following instructions should be NOTE
the aircraft.
followed in repairing the cabin section: When replacing entire skin panels, duplication
of the forward edge on the original sheet is re-
1. Skin patches should be of same gage as the quired. In effect, this flange is a structural
original skin. Back up doublers should be of the
member, carrying specific loads across the
next heavier gage material.
two open areas.
2. All lap joints and skin patches should have
rows of rivets staggered. Spacing not to exceed BULKHEADS.
.75".

Bulkheads are composed of formed "U" channel sec-

3. Fay seal doublers and patches in accordance
of section to preserve
tions. The principle material of construction is
with sealing procedures 2024-0 alclad aluminum alloy, which after .forming
pressurization requirements°
All bulk-
is heat treated to a 2024-T42 condition.
4 All repair parts must be free of metal chips, the sheet
heads in the fuselage are of formed metal
burrs or scratches.
or the reinforced formed sheet metal type.
5. Rivets used should be of the same type and
size as used in the original structure. a. Cracked Bulkhead Web or Flanges.
6. Do not countersink deeper than 75°/o of the Acceptable methods of repairing various types of
material thickness. cracks occurring in service are shown in the back of
7. (421-0001 to 421B0301) The forward cabin the section. Small holes (3/32-inch) should be dril-
pressure bulkheadat Fuselage Station 100. 00 and aft led at the extreme ends of the cracks to prevent
cabin pressure bulkhead at fuselage station 273. 94 further spreading. Reinforcement should be added
are fabricated of honeycomb material. Standard to carry the stresses across the damaged portion
repairs may be made using honeycomb material of and stiffen the joints. The condition causing such
the same gage as the original part for insert patches cracks to develop at a particular point may be a
and 050 2024-T3
. backup doublers- stress concentration at that point, in conjunction with
8. (421B0301 and On) The forward cabin pressure a repetition of stress (such as produced by vibration
bulkhead at Fuselage Station 100. 00 and the aft cabin of the structure).
pressure bulkhead at Fuselage Station 289. 94 are
re_ NOTE
fabricated of 040 2024-T3
. materiaL Standard
pairs may be made using material of same gage heat An increase in sheet thickness alone is usually
treat and alloy. Backup doublers should be of next beneficial but does not necessarily remedy the
heavier gage materiaL conditions leading to cracking. Patch type re-
a. Negligible Damage. pairs are generally employed and are usually
satisfactory in restoring the original material
Any smooth dents in the fuselage skin that are free strength characteristics.
from cracks, abrasions, and sharp corners, which
d. Severly Bent, Kinked, or Torn Channels.
are not stress wrinkles and do not interfere with
any internal structure or mechanism, may be con- If practical, severaly bent, kinked, or torn portions
sidered as negligible damage. of bulkhead should be removed and a replacement
b. Repairable Damage. section installed and joined at the original splice joint.
If this is not justified, cutting away the damaged por-
Mild wrinkles occuring in the upper or lower skin tion and inserting a trimmed portion of the original
panels in the bay forward of the horizontal stabilizers section, adequately reinforced by splice plates or
and which extend through the corners (shoulder areas) doublers, will prove satisfactory. This is known as
may be repaired by the addition of a stringer. A an insertion type repair.

Change 6
18-8 STRUCTURAL REPAIR 421 SERVICE MANUAL

LANDING GEAR The landing gear assemblies are composed of parts

that are not regarded as repairable. Minor repairs
The main gears are carried by the wings and are are permissible on the doors but when they are re-
housed within the wing wheel wells when retracted, installed there must be no distortion that will prevent
The nose gear retracts into the fuselage nose wheel perfect operation.
well. Doors covering the wells are regarded as parts
of the landing gear assemblies but the wells are struc-
tural features of the wings and fuselage. ENGINE NACELLE.

a. Repairs of Landing Gear. The engine nacelle group, located in each wing, is
composed of the semicantilever bed-type mount, the

CRACK OR DAMAGED AREA

CLEAN DAMAGED AREA OU Y

SAND AND CLEAN SITRROUNDING AREA.

15°
APPROX.

FILL BACK SIDE WITH RESIN AS NECESSARY

TO OBTAIN ORIGINAL THICKNESS.

FIRST PATCH IS PLACED

OVER ENTIRE DAMAGED
AND CLEANED AREA.

SECOND PATCH SMALLER

IN DIAMETER IS PLACED SMOOTH THE PATCH AREA
OVER FIRST PATCH. WITH FINE SANDPAPER

THIRD PATCH SMALLER

IN DIAMETER IS PLACED
OVER SECOND PATCH ETC.

Figure 16-1. Typical Fiberglass Repair

 421 SERVICE MANUAL STRUCTURAL REPAIR l@~6A

stainless steel firewall, and the cowling group. The will be necessary on very porous material.
engine mount structure is made of 063 inch 2024-T4
. The sealant should be allowed to air dry 10
aluminum and 4130 cad-plated steeL The cowling is minutes between coats.
made up of three sections; the upper, the lower
which includes the left and right access doors, and d. Pro-seal #700 is the only sealant authorized for
the two piece nose section which fastens in the cen- the stainless steel firewall. If sealant other than
ter of the cowling. All sections fasten in place with pro-seal #700 has been used, it should be removed
Camloc quick fasteners. The nacelle firewall is from the firewall and resealed using only the recom-
made up of stainless steel sheet with a clad alumi- mended sealant.
num angle riveted around its contour.

a. Negligible Damage. Engine Mount.

Minor dents in the firewall and cowling, if straight- a. Engine Mount Repair,
ened, may be classified as negligible damage.
Scratches and dents should be burnished out. Replacement of mount is the only recommended re-
pair.
Engine Firewall,

a. Repair of Stainless Steel Firewall. Engine Cowling.

The firewall may be repaired by using the clear a. Repair of Skins.

structure-type patch, as shown in figure 16-53 of
this section, providing the patch is of the same Skins, if damaged extensively, should be replaced
thickness as the firewall and monel rivets are used, with a section of original manufacture. Small dam-
Maximum diameter on holes that can be patched is aged areas should be reinforced with a doubler in-
2 inches. The holes should be routed and repaired stalled on the inner side. Material selected should
in accordance with figure 16-53. Cracks should be be of the same thickness and characteristics as the
stop drilled and repaired in accordance with figure original part.
16-53. Parts having cracks extending to the edge
of the part must be replaced. Maximum allowable b. Repair of Cowling Reinforcement.
length of cracks to be repaired is 3 inches.
Cowl reinforcements, if damaged, should be replaced.
Due to their small size and complex angles they are
Engine Firewall Sealing easier to replace than to repair.
The engine firewall should be sealed with pro-seal
#700 (Coast Pro-Seal Company) using the following FIBERGLASS PARTS.
procedures:
The nose cone, empennage tips, fairings, heat ducts,
a. Clean area on surface to be sealed with solvent. and other parts of the aircraft are made of fiberglass.
b. Mix 1 part of Pro-seal #700 curing agent with
100 parts of Pro-seal #700 sealant. a. Repairable Damage.

NOTE Damaged fiberglass parts may be repaired by the

methods shown in figure 16-1. Cut and trim the area
Sealant should be mixed by weight. It is im- just beyond the noticeable damage. If the parts are
portant that accelerator be completely and painted, remove paint and sand clear an area at least
uniformly dispersed throughout the base com- two inches beyond the edge of the cutout. Prepare the
pound, necessary size and number of patches of glass cloth.
Mix a sufficient amount of resin in accordance with
c. Using a spatula, caulking gun, or flow gun, ap- the manufacturer's instructions.
ply a fillet of sealer along cracks, seams, joints and
rows of rivets. WARNING

NOTE Always follow the manufacturer's mixing in-

structions carefully as the mixing of peroxide
If the sealing is done before the parts are and cobalt together will result in a spontaneous
mated, use enough sealing compound to com- fire,
pletely fill the joint and wipe away the excess
after parts are mated. Be sure that your hands are free from oil, grease
and dirt. Apply an even coat of resin on the sanded
NOTE area. Impregnate all the glass cloth patches by lay-
ing them on a clear paper and working the resin
If the sealant is applied with a brush or a through the fabric with a small brush. Place the
brush flow gun, more than one coat of sealant larger patch over the cutout area, working out all air

Change 4
18-68 STRUCTURAL REPAIR 421 SERVICE MANUAL

bubbles and wrinkles. If the cutout is large enough to practical, rubber gloves shall be worn when
cause the patch to sag, place a suitable support be- performing solvent operations.
hind the repair area. Coat the support with auto-
mobile wax or wax paper to prevent the resin from c. Repair of Class 1 damage shall be as follows:
adhering to the support. Apply the second patch over 1. Class 1 damage resulting in a hole not exceed-
the first patch etc., working out all wrinkles and air ing 1-1/2 inches diameter, dents, scratches or
bubbles. After all the patches have been applied, scars of .030inch deep shall be repaired as follows:
brush the area with an even coat of resin and allow (a) Remove paint to bare metal using either 400
to cure. Smooth the patch area with fine sandpaper or 600 grit wet sandpaper,
until the desired finish is obtained. Repaint the fin- (b) Mask area adjacent to sanded area.
ished area with matching paint. (c) Mix thoroughly equal portions, by volume,
of Epon 828 and Versamid 125. Add alumi-
b. Damage Necessitating Replacement of Parts. num powder until a thick non-flowing paste
is obtained.
When the fiberglass parts are torn or cracked over
a large area or show signs of rigidity through the use NOTE
of too much pressure on the surface, then the parts
should be removed and replaced. Prepare only that quantity of material that will
be used in 30 minutes.

REPAIR PROCEDURES FOR BONDED HONEYCOMB. (d) Fill damaged area with mix and smooth with
(See figure 16-1A.) a putty knife or spatula.
(e) Allow the mix to cure at room temperature
a. The Model 421 engine cowling is fabricated until hard (approximately 4 hours),

l
using
a sandwich type honeycomb construction. Sometime (f) Wet sand the repaired area with 400 grit
during the life of the aircraft, damage may occur to wet sandpaper until smooth.
the skin and/or honeycomb which will require repairs. (g) Clean the repaired area with a clean cloth
In the event damage occurs to the bonded honeycomb moistened with Isopropyl Alcohol, Naphtha
the following repair procedures have been developed or Toluene. Allow to air dry,
with the objective of equaling, as nearly as possible (h) Brush a minimum of two coats of Zine
the strength of the original part with minimum loss of Chromate primer over the repaired area,
aerodynamic characteristics, electrical properties allowing each coat to dry.
and minimize increase in overall weight. (i) Refer to Section 2, and paint in accordance
b. Damages to sandwich honeycomb construction are with applicable finish specifications.
divided into.classes according to severity and pos _
2. Class 1 damage resulting in cracks shall be
sible effect upon the airframe structure. Damage repaired as follows:
classifications are as follows: (a) Stop drill crack at both ends with 3/16 inch
diameter holes.
Class 1. Dents, scars, scratches, cracks, etc., in (b) Prepare a circular external patch, which
the facings not accomplished by a puncture will extend one inch beyond damage area,
or a fracture. from 012 or 015 aluminum,
. .

(c) Remove all paint and primer around damage

Class 2. Punctures or fractures on one facing only, area by sanding with 400 or 600 grit wet
possibly accompanied by damage to the sandpaper.
honeycomb core but without damage to the
opposite facing. -

NOTE

Class 3. Holes or damage extending completely Sanded area must be approximately 1/2 inch
through the sandwich, affecting both facings wider than aluminum patch,
and the core.
(d) Lightly sand entire damage area with 400
Class 4. Adhesive voids between skin and honeycomb grit sandpaper until a satin finish is ob-
core. tained. Mask off around damage area.
(e) Wipe damage area with a clean cloth
WARNING moistened with Isopropyl Alcohol, Naphtha
or Toluene. Wipe dry with a clean cloth.
Solvents used must be stored in, transported (f) Mix thoroughly 100 parts (by weight) Epon VIII
in, and used from safety containers. Adequate Adhesive with 6 parts (by weight) of curing
ventilation must be provided in storage and agent "A".
usage areas. The solvents specified are flam-
mable and caution to prevent fires must be NOTE
taken. No smoking, sparks or open flames
shall be permitted in the immediate area where Prepare only that quantity of material that will
the solvents are being used. Storage and be used in two hours.
usage areas shall be free from excessive heat,
sparks, and open flames when possible and (g) Work some of the prepared adhesive in the
Change 8
 421 SERVICE MANUAL STRUCTURAL REPAIR G-¾

crack and drilled holes. Apply a thin film jacent skins and completely fills the
over sanded surface. damaged area.
(h) Prepare a one-ply No. 191 glass cloth or (d) Remove all paint and primer (approximately)
similar scrim cloth 1/8 inch wider than 1-1/2 inches larger in diameter than cut-out)
aluminum patch, from around damage area with either 400 or
(i) Apply a thin film of the adhesive on the al- 600 grit wet sandpaper.
uminum patch and assembly cloth between (e) Mask around sanded area and cut-out area.
patch and damaged assembly and apply suf- (f) Mix thoroughly 100 parts (by weight) Epon
ficient pressure to assure intimate contact. VIII adhesive with 6 parts (by weight) of
(j) Using mylar or cellophone over aluminum curing agent "A".
patch, place a clamping device on patch to
insure complete contact of all bonding sur- NOTE
faces.
(k) Remove excess adhesive with a clean cloth Prepare only that quantity of material that will
dampened with Naphtha or Toluene. be used in two hours.
150°
(1) Cure at to 200° F using heat lamps or
oven. (g) If balsa plug is being used, spread the ad-
(m) Remove clamps, pressure pads, etc., and hesive lightly over all surfaces. If alumi-
sand away remaining excessive adhesive, num plug is being used, brush or trowel
(n) Brush a minimum of two coats of Zine adhesive on the internal side of the existing
Chromate primer over the repaired area, skin and where the plug will make contact
allowing each coat to dry. with core.
(o) Refer to Section 2, and paint in accordance (h) Position balsa wood or aluminum plug into
with applicable finish specifications. place.
d. Repair of Class 2 damage shall be as follows: (i) Prepare a circular external patch, which
1. Class 2 damage to upper cowl resulting in will be one inch larger than plug hole, from
damages that extend completely through the aluminum .012 or .015 aluminum.
outer skin and into the aluminum honeycomb core but (j) Prepare a one-ply circular No. 191 glass
without damage to the inner skin; cloth or similar scrim cloth 1/8 inch larger
(a) Carefully trim out skin to a circular or oval than plug hole.
shape with a hole saw or fly cutter remov- (k) Apply a thin film of adhesive over sanded
ing honeycomb core completely to the oppo- surface and place the No. 191 glass cloth or
site skin, similar cloth over the plug.
(1) Clean the bond surface of aluminum patch
CAUTION and coat with adhesive.
(m) Assemble patch over glass cloth and plug and
Exterme care should be taken not to damage apply sufficient pressure to assure intimate
the inner skin. contact.

(b) Remove completely all the damaged honey- NOTE

comb core.
(c) Prepare either an aluminum honeycomb core Care should be taken to insure that plug and
or balsa wood replacement plug as follows: glass cloth remain in place.
(1) If balsa wood is used, fabricate plug
so that the grain will be perpendicular (n) Using mylar or cellophane over aluminum
to the skins. patch, place a clamping device on patch to
(2) Lightly sand balsa plug with 400 grit insure complete contact of all bonding sur-
sandpaper and wipe off dust with a clean faces.
cloth. (o) Remove excessive adhesive with a clean
cloth moistened with Naphtha or Toluene.
150°
NOTE (p) Cure at to 200° F using heat lamps or
oven.
Do not touch the bare surface with bare hands (q) Remove clamps, pressure pads, etc., and
after sanding. If the balsa wood is cut too sand away remaining excessive adhesive.
short, the distance between shall be shimmed (r) Brush a minimum of two coats of Zinc
up until intimate contact is made with all sur- Chromate primer over the repaired area,
faces. allowing each coat to dry.
(s) Refer to Section 2, and paint in accordance
(3) Wrap balsa plug in clean waxed paper with applicable finish specifications.
until ready for use. 2. Class 2 damage to upper cowl resulting in
(4) When aluminum honeycomb plug is damage which extends completely through the fiber-
used, the core shall be the approximate glass inner skin and into aluminum honeycomb Core
density of the original core. but without damage to the outer aluminum skin.
(5) Cut aluminum honeycomb plug so that (a) Carefully trim out skin to a circular or oval
the top edge will be even with the ad- shape with a hole saw or fly cutter removing

Change 8
16-6D STRUCTURAL REPAIR 421 SERVICE MANUAL

aluminum honeycomb core completely to (b) The skins shall be fabricated from either
opposite skin, Cordo's Pyropreg AC, U. S. Polymeric's
(b) Prepare a balsa wood or aluminum honey- Poly Preg 502, or Narmco's 506 (color black).
comb plug as stated in step 1(c) above. (c) The reinforcement shall be 181-150 Valan.
(c) Sand undamaged fiberglass skin lightly (d) Cure time for adhesives described in step
approximately 2 inches out from around the (a) above, will be a minimum of 5 hours.
hole, e. Repair of class 3 damage is as follows:
1. Class 3 damage to upper and side cowls result-
CAUTION ing in damage to both aluminum and fiberglass skins
having a minimum damage size of 1. O inch or maxi-
Do not sand through fiberglass skin, mum damage size of 4 inches.
(a) Prepare surfaces, plugs and patches as
(d) Prepare two No. 181 glass fabric patches, described in step d .

1/8 inch larger than hole diameter. (b) Fabricate a temporary mold or block to hold
(e) Mix thoroughly 100 parts (by weight) Epon the plug in place while aluminum outer skin
828 and 10 parts (by weight) Diethlenetria- is being repaired.
mine (DTA). (c) Repair outer aluminum skin in accordance
(f) Coat plugs with Epon 828 and DTA mix as with step d.
described in step 1. (g). (d) Remove temporary mold or block and repair
(g) Impregnate the two No. 181 glass patches fiberglass skin in accordance with step d.,
with mixture to the content of approximately and flare in patch with existing skin contour.
50°/o and assemble patches f. Repair of class 4 damage is as follows:
over plug.
1. Class 4 repairs are those repairs needed to fill
NOTE voids between aluminum core and skin surfaces.
(a) Drill sufficient 1/8 inch holes in the fiber-
Smooth out all wrinkles. glass inner skin adjacent to voids.
(b) Remove all burrs around drilled holes.
(h) Prepare one No. 181 glass fabric patch large (c) Mix thoroughly 100 parts (by weight) Epon
enough to cover sanded area and impregnate 828 with 10 parts (by weight) curing agent "D".
with mixutre.
(i) Assemble third patch over the two previous NOTE
layers and remove all wrinkles as before.
(j) Using mylar or cellophane, cover patches Prepare only that quantity that can be used in
and apply a clamping device. one hour.
150° 200°
(k) Cure assembly at to F for approxi-
mately 90 minutes. (d) Using a syringe or pressure gun, inject
(1) Remove clamps, pressure pads, etc., and resin mix into the aluminum honeycomb
sand smooth to original contour. cells until they become filled.
3. Class 2 damage to side cowl which extends com- (e) Wipe off excess resin with a cloth that has
pletely through aluminum skin and the aluminum been dampened with MIBK or MEK and cover
honeycomb core shall be repaired as follows: the holes with masking tape.
(a) Repair damage as described under step 1. (d) (f) Position the structure so that both skins will
except use Bloomingdale's HT-424 or be in intimate contact with resin.
Narmco's Metlbond 302 adhesives. (g) Cure adhesive for 2 hours at
150°
to 200° F.
(b) The cure time for adhesives described in (h) Remove masking tape and sand away excess
step (a) above, will be a minimum of 5 hours. resin.
4. Class 2 damage to side cowl which extends com-
pletely through fiberglass skin and aluminum honey-
comb Core shall be repaired as follows:
(a) Repair damage as described under step 2. (d),
except use either Bloomingdale's HT-424
or Narmco's Met1bond 302 adhesives.

Change 8
 421 SERVICE MANUAL STRUCTURAL REPAIR R

ALUMINUM PATCH
(.012 OR .015)

ALUMINUM PATCH
SS C1L
(. 012 OR 015)
.

GLASS CLOTH
(NO. 191, 1 PLY)
ALUMINUM HONEYCOMB
PLUG OR BALSA WOOD 3/16" HOLE

SANDED SURFACE SANDED SURFACE

(ALUMINUM SKIN)
(ALUMINUM SKIN)

ALUMINUM HONEYCOMB DAMAGED AREA

CORE
FIBERGLASS SKIN
CLASS 1: DAMAGE RESULTING IN CRACK
(UPPER COWL)

CLASS 2: DAMAGE THROUGH ALUMINUM OUTER SKIN

AND ALUMINUM HONEYCOMB CORE (UPPER COWL)
FABRICATED
PARTING BLOCK
MATERIAL
(MYLAR OR
CELLOPHANE)

ALUMINUM PATCH
(.012 OR .015)
. GLASS CLOTH
(NO. 191, 1 PLY)

GLASS CLOTH
(NO. 181, 1 PLY)
LUMINUM
ALUMINUM SKIN HONEYCOMB OR
(UPPER COWL) BALSA WOOD PLUG

GLASS CLOTH
(NO. 181, 1 PLY)

ALUMINUM HONEYCOMB
PLUG OR BALSA WOOD

FIBERGLASS SKIN
FIBERGLAS SKIN (UPPER COWL) ALUMINÛM
HONEYCOMB HONEYCOMB CORE
ALUMINUM
CORE
CLASS 3: DAMAGE THROUGH ALUMINUM
ALUMINUM SKIN HONEYCOMB CORE, ALUMINUM AND
FIBERGLAS SKINS

CLASS 2: DAMAGE THROUGH FIBERGLAS INNER

SKIN AND ALUMINUM HONEYCOMB CORE
(UPPER COWL)

Figure 16-1A. Bonded Honeycomb Repair

18-8 STRUCTURAL REPAIR 421 SERVICE MANUAL

Bench Life
RADOME REPAIR PROCEDURES.

a. Remove radome in accordance with Section 3. Approximately 30 minutes at room temperature.

Repair procedures are developed with the objective
of equaling as nearly as possible the electrical and (d) Over this coated surface, apply a sheet of
strength properties of the original part with a mini_ colored cellophane or polyvinyl alcohol film ex-
mum increase in weight. This can only be accomp, tending two or three inches beyond the surface.
lished by repairing damaged parts with approved ma- The cellophane or PVA prevents exposure to the
terials and working techniques. For convenience in air and will provide a smooth surface against
presentation and for clarity in designating repair pro- which the resin may cure.
cedures to be used, damages to solid laminate ra- (e) Tape cellophane or PVA in place and work out
domes in this procedure shall be divided into classes air bubbles and excessive resin with the hand or a
according to severity, as follows: rubber squeegee. Cure the resin as follows:
1. Class I Repair. Surface scratches, scars or (1) Gel resin at any surface temperature from
80°F 150°F.
erosion not penetrating through the first ply of fabric. up to a maximum of
2. Class II Repair. Punctures, delaminations, (2) After gelation the repaired area is cured
contaminates or fractures extending through the first at a surface temperature of 120 to 150°F for
ply down into the laminate but without damage to the 30 minutes. The surface temperature is then
opposite facing. raised to 200-230°F and maintained for 30 min-
3. Class III Repair. Damage extending completely utes. Heat may be obtained by heat lamps, glo
through the laminate affecting both facings. rods, etc.
4. Class IV Repair. Defect which does not exceed (f) After the resin has cured or set, remove the
an area 5 inch square and surface has not been
. cellophane or PVA from the cured resin and re-
broken and does not occur more than tWice in any 1 move any excessive resin by sanding lightly.
foot square area. 2. Class II Repair. Punctures, delaminations,
5. Class V Repair. Delamination in edge bond ex- contaminates or fractures extending through the first
tending up to 1/8 inch out from drilled holes; delami- ply down into the laminate but without damage to the
nations not extending more than 1/2 inch from trim- opposite facing.
med edges and approximately 1 inch in size.
Method I (Stepped Joint Method).
b. Repair Techniques.
(a) The preferred method of removing damaged
1. Class I Repair. Surface scratches, scars or plies in accomplishing a Class II Repair is by the
erosion not penetrating through the first ply shall be stepped joint method. For small damages the
repaired as follows: scarf method of repair may be used.
(a) Clean injured area thoroughly and carefully (b) Ascertain the extent of the damaged area by
using a clean cloth saturated with methyl-ethyl- visual inspection, using a strong light source,
ketone or another approved cleaning agent. prior to beginning repair. With aid of a straight
(b) Lightly sand the damaged area, using No. 280 edge or compass, outline the damaged area by
grit sandpaper, clean the sanded surface thorough- scribing a rectangle with rounded corners or circle
ly, using methyl-ethyl-ketone, Specification TT- that will necessitate removal of a minimum of
M-261. Moisture and solvents should be complete- sound material. Extend the sides of the circle a
ly removed to prevent their inhibiting the cure of distance in inches equal to the number of plies to
the resin. be removed less one inc'h. (Five inches if six
(c) Apply one or two coats (depending on severity plies are to be removed, four inches if five plies
of the abrasion) of the following resin mix to the are to be removed, etc.) Overlap should be at
abraded surface, least one inch per ply of glass cloth.
(c) With the aid of a straight edge, use a sharp
knife or other specially prepared cutter and cut
Composition along the lines scribed in the outermost ply. Use
extreme care not to cut or score the underlying
Resin Selectron 5003 100 parts by weight ply. A suggested method is to cut through the
(Alternate: Hetron 92) overlaying ply in a series of cuts rather than at-
Luperso1DDM 0. 5 to 1. 5 parts by tempt to cut through the ply in one cut.
weight (d) Remove the cut outermost ply by inserting the
Luperco ATC Paste . 95 to 1. 05 parts by knife blade under the corner and prying loose care-
weight fully. When this outermost ply is removed, scribe
Nuodex Cobalt 4 to 8 drops/lb. resin on the next exposed ply a similar outline except
reducing the dimensions one inch in all directions.
Refer to the end of this section for Vendor infor- (Overlaps shall be one inch each ply.) Repeat this
mation. procedure until all the damaged plies have been
Mixing Procedure removed. (See Figure 16-2.)
(e) Lightly sand exposed plies and clean surfaces
Dissolve ATC Paste in the resin and thoroughly using methyl-ethyl-ketone, Specification TT-M-261,
mix. Add Nuodex Cobalt and mix. Add DDM and and allow to dry thoroughly preparatory to com-
thoroughly mix. pleting repair buildup.
Change 5
 421 SERVICE MANUAL STRUCTURAL REPAIR l@$

WARNING skin irritation. Breathing of an excessive

The sanding operation on glass cloth reinforced amount of this dust may be injurious, therefore,
laminates gives off a fine dust that may cause precaution as to skin and respiratory protection
will be observed.

Figure 16-2. Removing Damaged Face Plies -

Step Joint Method

(f) Cut patches from the same type of fabric as until all air bubbles are swept past the edge of
was used in the original part. Cut the fabric the laminate. The working or wiping of the lami-
patches to the size of each hole. Impregnate the nate will be stopped when the plies of fabric are
cloth patches with the resin mix specified under firmly packed together. Further wiping will
Repair Method I, paragraph (c). Sandwich each create air or vapor voids observable as a whiten-
patch ply between two sheets of PVA or cellophane ing and a loss of transparency. Should the PVA
larger than the patch by at least two inches on all sheet be punctured during the void-free working
sides. (See Figure 16-3 and 16-4.) The im- or wiping process, the hole may be repaired with
pregnated glass cloth shall contain 45-50 percent transparent tape and the air which has penetrated
of catalyzed resin after cellophane has been re- the bag shall be worked from the laminate. Vacu-
moved. (Weight of resin equal to weight of dry um pressure shall be maintained during the com-
glass cloth comprises 50 percent resin content.) plete curing process.
Brush a coat of resin on the surface of the scarf- (i) Cure repaired area as described under Repair
ed plies. Method I, paragraph (c). After the resin has
(g) Fit the smallest patch in place taking care to cured, remove the PVA from the cured resin and
avoid entrapping air under the patch. Smooth out remove any excessive resin by sanding lightly,
all wrinkles and trim to fit. Add successive plies
in a like manner the warp direction of each patch Method II (Scarf Joint Method).
ply approximately the same as that of the original
ply. (a) The scarf joint method may be used when the
(h) Surround the patch with a bleeder and cover repair of a damaged area will require removal of
the entire area with polyvinyl alcohol film and an area less than three inches in diameter.
secure in an air tight seal with either double- (b) The scarf method consists of sanding out the
backed tape or extruded sealing tape or both. damaged plies to a circular or oval disc shape.
Evacuate the area under the PVA film. Sweep out (See Figure 16-5.) The damaged plies will be scar-
entrapped air and excess resin with the air of a fed back carefully to a distance of at least 50
rubber squeegee or a similar device. The motion times the total face ply thickness by using polisher-
of the squeegee shall be slow enough so that the sander Stock No. 5130-537-3394, or by hand sand-
air bubbles will be swept clear of the laminate by ing using No. 180 grit sandpaper. The scarfing
the wave, or motion of the excess resin. The air operation will be performed very accurately to
bubbles may be observed through the transparent provide a uniform taper and usually requires some
PVA sheeting and the wiping process will continue practice before acceptable scarfs are obtained.
16-10 STRUCTURAL REPAIR 421 SERVICE MANUAL

Figure 16-3. Suggested Method of Resin Impregnating Replacement Plies

Figure 16-4. Cutting Replacement Plies from Impregnated Glass Cloth

Sandwiched Between Sheet of Cellophane
 421 SERVICE MANUAL STRUCTURAL REPAIR

Figure 16-5. Damaged Face Plies Removed -

Scarf Method

OPPOSITE CUTOUT
2" LARGER

Figure 16-6. Completed Double Face Patch Repair

16-12 STRUCTURAL REPAIR 421 SERVICE MANUAL

(c) The glass cloth laminations for the facing re- Radome Repair Procedures (421B0501 and On)
pairs are prepared with the largest piece being
cut to the exact shape of the outside of the scarfed a. Remove radome in accordance with Chapter 3.
area. The smallest piece is cut so that it over- Repair procedures are developed with the objective
laps the scarfed area by its proportionate amount, of equaling as nearly as possible the electrical and
depending on the number of plies in the repair and strength properties of the original part with a mini-
the intermediate pieces are cut so as to have equal mum increase in weight. This can only be accom-
taper. plished by repairing damaged parts with approved
(d) Process the prepared area in accordance with materials and working techniques. For convenience
paragraphs (f), (g), (h) and (i) under Class II in presentation and for clarity in designating repair
Repairs, Method I. procedures to be used, damages to radomes in this
3. Class III Repair. Damage extending completely procedure shall be divided into classes according to
through the laminate affecting both facings· severity, as follows:
(a) Damages completely through the laminate 1. Class I Repair. Surface scratches, scars or
shall be repaired by removing and replacing the erosion not penetrating through the first ply of fabric.
damaged material as previously outlined under 2. Class II Repair. Punctures, delaminations, con-
Class II Repair. Never remove inner and outer taminates or fractures extending through the first ply.
radome face ply at the same time. One facing 3. Class III Repair. Damage extending completely
will be completed before repair is made on the through both face sheets.
opposite facing. On solid laminate radomes 1/2 b. Repair Techniques.
of the damaged face plies will be removed from 1. Class I Repair. Surface scratches, scars or
one side and the buildup repair completed, then erosion not penetrating through the first ply shall be
repeat removal and new ply buildup procedures repaired as follows:
on opposite side. (a) Clean damaged area thoroughly and carefully
(b) To accomplish Class III Repairs it is neces- using a clean cloth saturated with methyl-ethyl-
sary that the opposite side of the laminate be pro- ketone or another approved cleaning agent.
vided with a temporary mold or block to hold the (b) Lightly sand the damaged area, using No. 280
laminate in place during the first face ply buildup, grit sandpaper, clean the sanded surface thoroughly,
(c) The damaged facings shall be removed and re- using methyl-ethyl-ketone, Specification TT-M-261.
placed as previously outlined for removing and re- (c) Apply one or two coats (depending on severity
placing damaged plies for Class U Repair. Repeat of the abrasion) of the following material to the abrad-
repair procedures on the opposite facing except ed surface:
the cut out ply area will be larger by approximately Composition: Bostik 464-3-1 Surfacer, CA-142
two inches than the first ply cut out area on the op- Catalyst, TL-52 Thinner.
posite face repair. This will prevent the joints of Vendor: Bostik-Finch, Boston Street, Middleton,
the inner and outer repair area from being in the Mass.
same position. (See Figure 16-6.) Mixing Procedure: Mix in a ratio of 3 parts by
4. Class IV Repair. Defects which do not exceed volume 464-3-1 base to one part CA-142 catalyst.
an area 5 inch square and the surface has not been
. Surfacer may be thinned with TL-52 to approxi-
broken and does not occur more than twice in any 1 mately 25 seconds #2 Zahn cup.
foot square area. (d) Material may be applied by spray gun. The
(a) If surface is broken, sand smooth. coating will dry to sand in 3 hours at normal temper-
(b) Drill 2 to 3 No. 50 holes into the damaged skin atures. Sand with 320 grit paper and reapply paint.
spaced throughout the damaged area. Inject resin 2. Class II Repair. Punctures, delaminations
mix under Class I Repair, paragraph (c), with a extending through the outside face sheet.
hypodermic syringe and needle to insure contact (a) Punctures outside the radar window, not ex-
with all surfaces and to obtain a maximum possi- ceeding one inch in diameter.
ble "wetting up" of the fraëÏured skin. (1) Mix EA960F and apply to core area of
(c) Cure as described under Class I Repair, damage. Allow to harden, sand smooth
paragraph (e). and paint.
5. Class V Repair. Delamination in edge band ex- (b) Punctures inside the radar window, not ex-
tending up to 1/8 inch out from drilled holes; delami- ceeding 1/2 inch in diameter.
nations not extending more than 1/2 inch inward from (1) If face sheet and core are damaged beyond
trimmed edges and approximately 1 inch in size. use, fill core area with EA960F, allow to
(a) Work as much as possible resin mix under harden, sand smooth and paint.
Class I Repair, paragraph (c) into the discrepant (2) If face sheet and core are not damaged be-
area. Resin may be injected into the delaminated yond use, bond back together with the fol-
area along the panel edges with a hypodermic lowing adhesive mix:
syringe and needle through holes drilled with a Composition: EA9309 Adhesive Mix.
No. 50 drill bit. Extruded Sealing Tape placed Vendor: Hysol Division The Dexter Corporation,
-

around the needle and against the panel will force Olean, New York 14760.
the resin throughout the delaminated area.. Mixing Procedure: Combine 100 parts "A" with
(b) Apply pressure, if necessary, with C-clamps 23 parts "B" by weight and mix thoroughly.
or vacuum blanket. Cure per paragraph (3), under Bench Life: Approximately 40 minutes for one
Class I Repairs. pound mass at
75°
Fahrenheit.

Change 12
 421 SERVICE MANUAL STRUCTURAL REPAIR 16-12A/16-12B

(3) Sand, paint and gloss surface at least 1/2 RAIN EROSION COATING APPLICATION (RADOME)
inch around damaged area. Apply suffi-
cient adhesive to face sheet to rebond to Rain erosion resistant coatings shall be repaired if
core. Impregnate a patch of 181 or 1581 worn away,blistered, peeled or otherwise defective.
dry glass cloth with the 9309 adhesive mix. If the area is exposed to spilled or leaked oil, use
The patch should be 1/2 inch larger than only the expoxy enamel finish described later in this
the damaged area. Apply this patch to paragraph. Normal rain erosion coating specifica-
damaged area. Over this tape a sheet of tions are:
polyethylene until adhesive hardens. Re-
move, sand lightly and paint. MIL-C-7439, Coating Systems, Elastometerie,
(c) Delaminations in the edge bond. Delamination Rain Erosion Resistant and Rain Erosion Resis-
in the attachment edge bond may be bonded back to- tant with Anti-Static Treatment for Exterior
gether with EA9309 adhesive. If several plys of Aircraft and Missile Plastic Parts.
glass cloth are damaged, remove and replace with
equal number of 181 or 1581 glass. Impregnate the The repair materials are listed below, in order of
glass cloth with EA9309, apply and allow to harden. their application
Sand to shape or fit and repaint.
3. Class III Repair. Damage through both face Primer: Bostik No. 1007, made by B. B. Chem-
sheets. This damage covers 1/2 inch diameter in ical Co., Cambridge, Mass. Methyle-ethyl-
the radar window area and one inch outside the win- Ketone is a suitable thinner.
dow area. Damage beyond these limits should re- Rain Erosion Resistant Coating: consists of No.
quire replacement of the radome. 1801C Top Coat Cement and No. 983C Accelera-
(a) Remove damaged face sheet. Apply polyeth- tor. Both made by Goodyear Tire and Rubber
ylene sheet to core and backup with a thin sheet of Co., Akron, Ohio.
metal. Tape in place. Apply EA960F to fill core
flush. Allow to harden and remove sheet metal back- The above items (Primer, Top Coat Cement and Ac-
up. Apply EA9309 impregnated patches over damag- celerator) are included in Goodyear Kit No. 23-56
ed area overlapping by 1/2 inch all around. Tape a for brush application. For spraying, use Kit No. 23-
polyethylene sheet over impregnated patches and rub 56S which includes also:
polyethylene sheet to smooth the adhesive and remove
air from patch. Allow to harden, remove polyethyl- No. 1803C Diluting Solvent.
ene sheet and sand lightly.
Use Goodyear Kit No. 23-57 (brushing) or No. 23-575
(spraying, and including No. 1803 Diluting Solvent).
Both kits differ from Nos. 23-56 and 23-56S in that
they include:
Anti-Static Surfacer Cement No. 1804C. No.
983C Accelerator is used with this material.
EA9309
Made by Goodyear Tire and Rubber Co., Akron,
Ohio.
IMPREGNATED PATCH
GACO N-79 Rain Erosion Coating Kit may be used as
an alternate.

Components
1/2" OVERLAP TYPICAL
N-700-9 Top Coat Cement
N-300-9 Accelerator
+-1/2" IN WINDOW N-450-9 Thinner (MEK or Toluene may be used
1" OUTSIDE WINDOW as alternates)
N-81 Anti-Static, Gates Engineering P. O.
Box 1711, Wilmington, Deleware.

POLYETHYLENE
SHEET

TAPE THIN METAL

PLATE

Figure 16-6A. Typical Class III Radome Repair

Change 12
 421 SERVICE MANUAL STRUCTURAL REPAIR Î$ 13

REPAIR OF PLASTIC WINDOWS. with a circular motion, keeping the abrasive constantly
wet with clean water to prevent scratching the surface
NOTE further. Use minimum pressure and cover an area
large enough to prevent the formation of a "bull's eye"
No repairs of any kind are recommended on or other optical distortions,
highly stressed or compounded curves where
the repair would be likely to affect the pilot's CAUTION
or copilot's field of vision.
Do not use a coarse grade of abrasive; No.
a. When a crack appears in a panel, drill a hole 320 is the maximum coarseness permitted.
at each end of the crack to prevent further spreading.
The hole should be approximately 1/8 inch in diameter e. Continue the sanding operating, using progres-
depending on the length of the crack and the thickness sively finer grade abrasives.
of the material, f. When the scratches have been removed, wash the
b. temporary repair can be made on a curved sur-
A area thoroughly with clean water to remove all the
face by placing fabric patches over the affected areas, gritty particles. The entire sanded area will be
Secure the patches with airplane dope, Specification clouded with minute scratches which must be removed
No. MIL-D-5549; or Lacquer, Specification No. MIL. to restore transparency.
L-7178. Lacquer Thinner, Specification No. MIL-T- g. Apply fresh tallow and buffing compound to a
6094 can also be used to secure motor-driven buffing wheel. Hold the wheel against
the patch temporarily,
c. A temporary repair can be made by drilling the plastic surface, moving it constantly over the
small holes along sides of the crack 1/4 to 1/8 inch damaged area until the cloudy appearance disappears,
apart and lacing the edges together with soft wire. A 2000-foot-per-minute surface speed is recommen-
Small stranded antenna wire makes a good temporary ded to prevent heating, distortion or burns.
measure only, and as soon as facilities are available,
the panel should be replaced. NOTE

CAUTION Polishing can be accomplished by hand but it

will require a considerably longer period of
If temporary repairs are made, aircraft must time to attain the same result as produced by
be operated in unpressurized mode until re- buffing wheel.
placement of window can be made.
h. When buffing is finished, wash the area thoroughly
d. Scratches on transparent plastic surfaces can be and dry it with a soft flannel cloth. Allow the surface
removed by hand-sanding operations followed by buff- to cool and inspect the area to determine if full trans-
ing and polishing, provided subsequent instructions parency has been restored. Then apply a thin coat
are followed carefully. Wrap a piece of No. 320 (or of hard wax and polish the surface lightly with a
finer) sandpaper or abrasive cloth around a rubber clean flannel cloth.
pad or wood block. Rub the surface around the scratch

WOOD REINFORCEMENT
A B

WOOD
CUSHION OF RUBBER /
ALWAYS DRILL END OF CRACK
OR FABRIC
TO RELIEVE STRAIN

WR

RIGHT

SOFT WIRE CEMENTED

LACING FABRIC PATCH SANDING REPAIR

TEMPORARY REPAIR OF CRACKS

Figure 16-7. Plastic Window Repairs

16-14 STRUCTURAL REPAIR 421 SERVICE MANUAL

BALANCE POINT

? . 80 25. 80
15.00 INO. 30 (0.128)
8. 00 , HOLE
1.50 43.00 1.00
0.70 0.25
I __ 3. 00

12. 150. 0. 50
GREEN -
ALL SURFACES 50
14. 50 0. 50
BLUE -
ELEVATOR & RUDDER ONLY
18. 95 +-0. 50
YELLOW -
RUDDER ONLY 24.75 +0.50

BEAM 1. 0 x 1. 50 x 51. 60
WOOD
Detail g 3 16
EC
x 1-7/8
MFRER
DOWE L PIN
°
x 0. 03 EACH

1. 50
2. 00
DRLULEL3N/16 x 3/8

POSIT ON

5BE

0.12
S
CENTERLINE
BALANCE WEIGHT
MATL. CRS.
WEIGHT 4 OZ.
(ALL DIMENSIONS APPROX.) Detail B
TYPICAL DOWEL INSTALLATION

NO. 30 (. 128) HOLE THRU

2 REQD.
-.09R (TYP.)
.25

50 LH
. .

RH
1 REQD. 1 REQD,
ABJ 3 +-1.00-+

3.002. 35 / RIVETS
45°
CHAMFER .03 x (TYP.)

50 1. 00 ll
(
.
,

. 25R
T
.
25+ HANGER : 1. 50
'
HANGER
+ . 50 FABRICATION 1/8 INCH DIA STL ROD
+-. 75 PIN FABRICATION
MATL. .064
2024-T42 CLAD
+-1. 00 . 20 BEND RADIUS Detail D
Detail $
Figure 16-8. Balancing Fixture Fabrication. (Sheet 1 of 2)
Change 8
 421 SERVICE MANUAL STRUCTURAL REPAIR 645

45°
TYP.

.270

2.00-
4.00

. 010 MAX FLAT ON TOP

.25
1.50 SURFACE THIS AREA

1. 50R
.75
1.00R

3.25
2.30
MATL. COMMERCIAL STEEL
. 50

3. 50 i . 30
10191
FABRICATION OF BALANCE FIXTURE. b. Assemble the hanger using three MS20470AD3-5
rivets.

Beam. Pin.

a. Fabricate beam from wood (yellow pine) or a. Fabricate pin from 1/8 stl. rod per Detail D.
equivalent, one by one and one-half inch stock.
b. Locate center of beam. (Should be 25. 80 inches Balance Weight.
from end.)
c. Locate and drill 3/16 (. 1875) x 3/8 (. 375) holes a. Fabricate balance weight per Detail A.
.25 in from each end of beam.
d. (See Detail B.) Fabricate dowel and install in NOTE
beam using glue for security.
e. Measuring from the center point of beam or 25.80 If necessary, grind or file balance weight to
inch Station, locate and drill No. 30 (.128)diameter obtain four (4) ounce weight. Scribe center-
holes for aileron, elevator and rudder hanger loca- line after fabrication.
tions.
f. Mark off and paint the beam as indicated for Mandrel.
aileron, rudder and elevator positions.
a. Fabricate mandrel in accordance with Detail E.
Hanger.
NOTE
a. Fabricate right and left hanger halves per Detail
C. Mandrel may be fabricated from any suitable
material.

Figure 16-8. Balancing Fixture Fabrication. (Sheet 2 of 2)

Change 6
l6 -16

STRUCTURAL REPAIR 421 SERVICE MANUAL

LEFT HAND SIDE SURFACE DOWN

LOWER SURFACE DOWN

30. 65"
.1

AILERON:
Place balanced fixture (refer to balancing procedure)
on first rib line outboard of trim tab on the aileron
90°

RUDDER:
Place balanced fixture (refer to balancing procedures)
on first rib line above the trim tab on the rudder

40. 62" r-- -,

, FLAT SURFACE
90 |

TYPICAL BALANCED CONTROL

NOTE
LOWER SURFACE In a 100% static balanced condition
DOWN
dimensions x and y will be the same.
ELEVATOR:
Place balanced fixture (refer to balancing procedures)
on first rib line outboard of trim tab on the elevator

BALANCE
SURFACE TOLERANCE

AILERON +. 75 TO -.
75 in. lb. g
ELEVATOR +. 75 TO -2.
00 in. Ib.

RUDDER +.75 TO -3.75

in. lb.

Figure 16-9. Static Balancing Aileron, Rudder and Elevator (Sheet 1 of 4)

Change 6
 421 SERVICE MANUAL STRUCTURAL REPAIR S-Q
l

ADD WASHERS AS NECESSARY

TO BALANCE THE FIXTURE

FORWARD END OF BALANCE AFT END OF BALANCE

2 MAN EL
TOLERANCE RANGE AILERON, TOLERANCE RANGE
RUDDER AND ELEVATOR ELEVATOR AND RUDDER
AFT END OF BALANCE
TOLERANCE RANGE
AILERON

BALANCING PROCEDURES. NOTE

It is recommended that control surface balancing be Make sure rudder control surface has freedom
accomplished in a draft-free room/area using the of movement and does not drag on mandrels
balancing equipment fabricated from instructions con- and bonding wires do not interfere with move-
tained in figure 16-8. ment of control.

NOTE: d. Secure the trim tab in a streamlined po-

rudder
sition and install
associated hardware.
Be certain control surface weights are instal- e. Locate the position for balancing fixture on the
led, surfaces are clean, all foreign matter rudder and place balancing beam in position.
inside control surfaces removed, painted and
hinge bolts installed. Surfaces which have NOTE
trim tabs incorporated must have the tab se-
cured in a streamlined position and push-pull If balancing beam position falls on a rivet line,
rods, with attaching hardware on the trim tab, it will be necessary to move the beam to one
and installed before starting balancing proce- side to provide a flat surface for the balancing
dures. beam. The balancing beam must be perpen-
dicular to the hinge centerline and the trailing
edge of the rudder control surface must be
BALANCING FIXTURE. firmly seated in the cutout of the hanger.

a. Install hanger assembly in the appropriate posi-

f. If the rudder assumes position parallel with base
tion for the surface being balanced of mandrel and the balance weight is within the
b. Place mandrel on a table or other suitable flat Green, Blue and Yellow range, the rudder is stati-
surface and center balancing beam on mandrel at the cally balanced.
Centerline of bar- g. If rudder assumes a position of trailing edge up,
c. Add washers to dowel pins until a balanced con- when balance weight is on aft end of range, rudder
dition is obtained- is overbalanced and needs weight removed.

NOTE NOTE

When balancing fixture is in balance, it must Remove overbalance by using a 1/2 inch drill
assume a position parallel to the work surface· to remove some of the weight.

h. If rudder control surface assumes position of

RUDDER BALANCING PROCEDURE. trailing edge down, when balance weight is on for-
ward end of range, rudder surface is underbalanced
a. Remove rudder from aircraft in accordance with and needs more balance weight added.
Section 7. i. The approximate amount of weight needed for
b. Tape rotating beacon wire along the leading edge underbalance may be determined by placing small
of the rudder. amounts of loose weight in the balance weight area.
c. Insert hinge bolts in place and position rudder j. Additional balance weight may be added by pound-
on mandrels with bolts resting on the knife edge.

Figure 16-9. Static Balancing Aileron, Rudder and Elevator (Sheet 2 of 4)

Change 6
16-18 STRUCTURAL REPAin 421 SERVICE MANUAL

ing lead into existing holes of weight and staking. If NOTE

holes are not available to insert added weight, it will
be necessary to add 2 nutplates on each side of If balancing beam position falls on a rivet line,
lightening hole and add a lead bar weight secured by it will be necessary to move the beam to one
two bolts. side to provide a flat surface for the balancing
beam. The balancing beam must be perpen-
NOTE dicular to the hinge centerline and trailing
edge of the aileron control surface must be
The rudder tip and mounting screws must be firmly seated in the cutout of the hanger.
installed each time the rudder is checked for
balance- f. If the aileron assumes a position parallel with
base of mandrel and the balance weight is within
k. Install rudder in accordance with Section '7. Green range, the aileron is statically balanced.
g. If aileron assumes a position of trailing edge
up, when balance weight is on aft end of range, the
AILERON BALANCING PROCEDURE. aileron is overbalanced and needs weight removed.

a. Remove aileron from aircraft in accordance NOTE

with Section 5. (The outboard hinge is a pin.)
b. Balance the fixture for aileron control surface. Remove overbalance by removing weight
c. Insert hinge bolt in place and position aileron on as necessary,
the mandrels with bolt and pin resting on the knife
edge, h. If the aileron assumes position of trailing edge
down, when balance weight is on forward end of
CAUTION range, aileron is underbalanced and needs more
balance weight added.
Be sure bolt is inserted in correct hinge 10- i. The approximate amount of weight needed for
cation (upper hole). underbalance may be determined by placing small
amounts of loose weight in the balance weight area.
NOTE j. Addition of balance weight may be added by in-
serting lead into existing holes of the weight. If
Make sure aileron control surface has free- holes are not available additional weight may be
dom of movement, does not drag on man- added by removing existing screws and installing
drels and the bonding straps are free. longer screws to attach added weight.

d. Secure the trim tab on the left hand aileron in NOTE

a streamlined position and install associated hard-
ware. The aileron balance weight must be removed
e. Locate the position for balancing fixture on the from the aileron in order to remove excess
aileron and place balancing beam into position. weight.

IF ADDITIONAL WEIGHT MUST

BE ADDED BOLT TO RIB IN
THIS AREA

REMOVE WEIGHT
AS SHOWN WITH A
1/2" DRILL ADD WEIGHT BY FILLING
EXISTING HOLES REMOVE THESE SCREWS
AND NUTS TO REMOVE
BALANCE WEIGHT
RUDDER BALANCE WEIGHT

Figure 16-9. Static Balancing Aileron, Rudder and Elevator (Sheet 3 of 4)

Change 6
 421 SERVICE MANUAL STRUCTURAL REPAIR jg- 1

CAUTION f. If the elevator assumes a position parallel with

base of mandrel, and the balance weight is within
Make certain bolts securing weight in place the Green and Blue range, the elevator is statically
are tight before installing aileron on aircraft. balanced.
g. If the elevator assumes a position of trailing
k. Install aileron in accordance with Section 5. edge up, when balance weight is on aft end of range,
elevator is overbalanced and needs weight removed.

ELEVATOR BALANCING PROCEDURE. NOTE

a. Remove in accordance with Section 6.

elevator Remove overbalance by using a 1/2 inch
b. Balance the fixture for
elevator control surface. drill to remove some of the weight.
c. Insert hinge bolts in place and position elevator
on the mandrels with bolts resting on the knife edge. h. If the elevator assumes position of trailing edge
down, when balance weight is on forward end of
NOTE range, elevator is underbalanced and needs more
balance weight added.
Make sure elevator control surface has free- i. The approximate amount of weight needed for
dome of movement, does not drag on mandrels underbalance may be determined by placing small
and bonding straps are free. amounts of loose weight in the balance weight area.
j. Additional balance weight may be added by in-
d. Secure the elevator trim tab on right-hand eleve serting lead in existing holes of the weight. If holes
tor in a streamlined position and install associated are not available, additional weight may be added by
hardware. bolting a lead bar in the center of existing weight.
e. Locate the position for balancing fixture on the
elevator and place balancing beam into position.
NOTE
NOTE
Each time the elevator is checked for weight
If balancing beam position falls on a rivet and balance, the elevator tip must be installed
line it will be necessary to move the beam and elevator tip screws must be in the proper
to one side to provide a flat surface for the location (short screws toward aft end of ele-
balancing beam. The balancing beam must be vator).
perpendicular to the hinge centerline and
trailing edge of the aileron control surface k. Install elevator in accordance with Section 6.
must be firmly seated in the cutout of the
hanger.

ELEVATOR BALANCE WEIGHT

AILERON BALANCE WEIGHT

EXTRA WEIGHT MAY ALSO

BE ADDED BY BOLTING
WEIGHT TO EXISTING WEIGHT
IN THIS AREA

ADD WEIGHT BY
FILLING EXISTING
HOLES

REMOVE WEIGHT AS SHOWN

WITH A 1/2" DRILL

Figure 16-9. Static Balancing Aileron, Rudder and Elevator (Sheet 4 of 4)

Change 10
16-20 STRUCTURAL REPAIR 421 SERVICE MANUAL

CHECKING WING TWIST AND LOCATION OF 3. These two lines locate the wing datum plane, and
THRUST LINE. (See figure 16-10.) the three degrees of twist will be present if the lines
are parallel.
a. Remove wing in accordance with wing removal c. Locate the engine thrust line as follows:
procedures and place wing on suitable supports be- 1. Locate a plane which is 13. 50 inches above and
neath the root and tip ribs. parallel to the wing datum plane.
2. The thrust line, which lies in this plane, is per-
NOTE pendicular to the front spar, and 40.135 inches out-
board from the centerline of the bolt holes in the front
The wing tip tank must be removed during spar fittings.
check. d. Install wing tip tank on wing.
e. Install wing in accordance with wing installation
b. Locate wing datum plane as follows: procedures.
1. Locate a line at the root rib (wing station 46.89)
which is 4. 515 inches up from the lower surface of SEALING PROCEDURES
the front spar, and 3.99 inches up from the lower
surface of the rear spar. The cabin area of the fuselage extending from F. S.
2. Locate a line at the tip rib (wing station 217.66) 100.00 to F.,S. 273.94 has been carefully sealed in
which is 1. 44 inches up from the lower surface of the process of manufacture. During maintenance and
front spar, and 81 inch up from the lower surface of
.
repair, it is necessary to maintain a good cabin seal.
the rear spar. The following information is given to assist in the
maintenance and repair of the pressurized cabin
where sealing is required.

FRONT SPAR
I
90°
LEADING EDGE

WING STATION
44. 865
WING STATION THRUST LINE WING STATION
46. 89 217, 66
9. 00 WING DATUM PLANE
13 50

L CRANKSHAFT
40. 135

FRONT SPAR FITTINGS

WING DATUM PLANE

FRONT SPAR REAR SPAR FRONT SPAR REAR SPAR

1.44
3.99
4, 515 TIP RIB
ROOT RE

Figure 16-10. Wing Twist and Thrust Line Data

Change 12
 421 SERVICE MANUAL STRUCTURAL REPAIR l$-Îl

NOTES d. Polyethylene nozzles for sealant gun.

e. Polyethylene cartridges for sealant gun.
1. In rework or repair of faulty seal, the f. Rubber gloves,
sealant must be completely removed or
notched completely in the affected area to
produce a solid residual material. Cleaning.

2. Cutting tools should be made from mater- a. Clean the surface immediately prior to the appli-
ial not harder than 2024T-3 aluminum. cation of the sealing,compound to insure the surface is
Acrylic plastic is preferred. Steel cutting free of dirt, grease and chips.
tools should never be used. b. Metal cleaning should be done with a clean, soft,
lintless rag moistened with Methyl Ethyl Ketone
3. Sealant material should not be applied (MEK). The solvent should always be poured on the
when the temperature of the structure is cloth to refrain from contamination of the solvent.
60°F. The solvent should never be poured or sprayed on the
below
structure due to possibility of running between layers
WARNING of structure and creeping out again after cleaning,
bringing contamination to surface to which the seal-
Sealing compounds are highly inflammable• ant is to be applied.
Exercise precautions to prevent fire or c. Immediately dry the area thus cleaned with a
explosion. These materials are toxic and dry, clean, lintless rag before the solvent has eva-
should be applied in a well ventilated area• porated from the surface.
d. If primer is removed during cleaning, it should
Sealant Materials be touched up after all sealing operations are com-
plete.
The following sealants are recommended: e. Always clean an area wider than the width of the
a. Faying sealants. finally applied sealant.
1. EC1675 Class A Minnesota Mining and Manufac- f. Cleaned areas should be handled with care to pre-
turing Co. vent surface contamination.
2. Pro-Seal 890 Class A Coast Pro-Seal Manufac-
turing Co.
3. PR1422 Class A Products Research and Chemi- Application Sequence.
cal Corp.
b. Fillet sealant. In order to accomplish an adequate seal in an efficient
1. EC1675 Class B Minnesota Mining and Manufac- manner, the following sealant operations shall be
turing Co. accomplished in the following order:
2. Pro-Seal 890 Class B Coast Pro-Seal Manufac- a. Faying surface sealing as required on assembly.
turing Co. b. Fill holes and slots as required.
3. Class B Products
PR1422 Research and Chemi- c. Fill joggles and confined holes by injection as
cal Corp. required.
c. Hole filling compound. d. Fillet seal seams and joints as required.
1. Pro-Seal 567 Coast Pro-Seal Manufacturing Co. e. Seal fasteners as required.
d. Electrical connector and wire bundle sealing. f. Faying surface sealing of close-out panels as
1. Pro-Seal 727 Coast Pro-Seal Manufacturing Co. required.

NOTE
Mixing Two Part Sealants.
Class A -
Indicates brushable material.
Class B -
Indicates filleting or injection a. The base compound should be matched with the
material. appropriate batch numbered accelerator.
b. The two components must be weighed in pro-
Cleaning Materials. portions as marked on the container within a toler-
ance of ±2°/o.
The following cleaners are recommended: c. If the entire preweighed kit is to be used, it is
a. Electrical, not necessary to weigh out the accelerator and
1. Aliphetic Naptha (TT-N-95) Type IL base compound. Simply mix entire amounts of the
2. Mozels Cleaning Solvent #18 Mozell Chemical preweighed compounds in accordance with instruct-
Co. ions outlined.
b. Structural. d. The two components should be mixed thoroughly
1. Methyl Ethyl Ketone (MEK) Cleaning Solvent. so that the complete mixture is of uniform color.

Equipment· NOTE

a. Clean rags. Care should be exercised to preclude the

b. Stiff bristle brushes (not nylon). trapping of air in the sealing compound
c. Sealant gun (Pyle #950 or equivalent). Pyle Indus- during the mixing procedure.
tries Inc., Southfield, Michigan.

Change 8
18-22 STRUCTURAL REPAIR 421 SERVICE MANUAL

e. Mixed compound has a limited work life, so

only enough should be mixed to satisfythe immediate w =
. 50 max.
requirement.

Application of Sealing Procedures.

Faying surface sealing.

1 1/2w
0.1
a. Using sealant EC1675, Class A, apply to one
surface with a brush, spatula or roller. Spread '
evenly to approximately 1/32 inch thick over the en-
tire faying surface. The application should be ac-
complished with the sealing compound flowed on with I w 1 1/2w
a minimum of stroking so as to prevent formation of
PRESSURE SIDE
bubbles.
b. Avoid using excess amounts of sealing compound.
c. When the
surfaces are fastened together, any
extruded sealant should be faired out with a fairing
tool, leaving a smooth fillet along the joint. Figure 16-12. Hole Filling
d. All permanent fasteners must be installed within
the work life of the sealant. Sealant extruded through Hole Filling.
hole by rivet must be wiped from end of rivet before
bucking. If permanent fasteners cannot be installed, a. All tool and coordination holes through a pres-
use temporary fasteners and clamps as necessary to sure seal area should be plugged with soft rivets and
hold the parts firmly together until the sealant has overcoated with EC1675, Class A sealant.
cured. Remove individual temporary fasteners and b. Holes, gaps and other cavities that cannot be
replace immediately with permanent fatseners. filled with one application of sealant should be filled
Fresh sealant must be applied to the fastener. with a void filling compound. Pro-Seal 567 is pre-
ferred. The compound should then be overcoated
NOTE with sealant.

Any pressure testing required should not be

done before the sealing compound has com-
pletely cured.
SEALANT MUST
COMPLETELY
FILL SLOT

APPROXIMATELY
1/32 INCH THICK

EJECTION IS COMPLETE
WHEN SEALANT EMERGES
FROM THIS SIDE.

BEFORE ASSEMBLY

Figure 16-13. Injection Sealing

Injection Sealing.
a. Injection seal may be applied to provide continu-
ity of seals where fillet seals are interrupted by
holes, joggles or structure. Force EC1675, Class B
sealant into one end of the cavity or injection hole, if
AFTER ASSEMBLY provided, with a sealing gun until the sealant emer-
ges from a prescribed opening for continuity of seal.
b. When a seal is made at the bottom of a slot, the
sealant should be applied so as to fill and have a con-
Figure 16-11. Fay Surface Sealing tinuous contact with the bottom and sides of the slot.

Change 2
 421 SERVICE MANUAL STRUCTURAL REPAIR 6- 3

d
d

.: FAIRING TOOL

d =
. 08 minimum
w =
. 12 to 25 .

t = 02 to 10 except
.Ÿ.I|.Íi
.::lli.
. .

t 0 when b
=
15 or more
=
.

a =
. 04 to 15 except .

a 0 when b
= 15 or more
=
.

Figure 16-14. Fillet Sealing

Fillet Sealing. Window Sealing.

a. Apply masking tape to window and outside mating
a. Fillet sealing should be done with EC1675, Class
skin or fairing. If window is already masked, or
B sealant, using a sealing gun for application. The
otherwise protected,
main- peel off the protective coating
nozzle tip should be pointed into the seam and in areas to be in contact with the sealant,
tained nearly perpendicular to the line of travel. A
b. Clean both surfaces thoroughly. Acrylic mater-
bead of sealant will be forced ahead of the nozzle ials should be cleaned with Aliphatic Naptha (TT-
tip• N-95, Type H) and a clean lint-free cloth,
b. Fillets may be worked into the surface with
fairing tools or gun tip. NOTE
c. Fillet shapes and dimensions should conform to
dimensions given in figure 16-14 as near as possible. Do not use ketone or any cleaner that may
cause crazing of the acrylic type glass.
O.05 THICK (MIN)

SE T

PRESSURE SIDE

ROX

0. 06 THICK (MIN) MASKING TAPE

0.05 THICK (MIN)

CLOTH WRAP WINDOW

PRESSURE SIDE
BEFORE ASSEMBLY

DAB SEALANT
IN SCREW HOLE

0. 06 THICK (MIN)

Figure 16-15. Fastener Sealing

SEALANT
Fastener Sealing.

a. Fastenersinstalled through a faying surface with-

in life of the sealant
the work need no further sealing.
b. Fasteners installed through a faying plane
where no faying surface sealant is used should be
sealed by one of the following methods: AFTER ASSEMBLY

\
1. Apply EC1675, Class A sealant to the fastener
or hole on installation.
2. Brush the fastener with sealant after installation. Figure 16-16. Window Sealing

Change 2
16-Ž4 STRUCTURAL REPAIR 421 SERVICE MANUAL

CAUTION life (freshly mixed) to obtain a good flow throughout

I
the and between the wires leaving no voids.
fitting
Windows are of acrylic materials and must be i. sealant using a sealant gun at a pressure
Inject
sealed only with EC1675, Class B sealant with of approximately 100 psi until the sealant, without
NONCRAZING accelerator. visible evidence of entrapped air, emerges from
both notches in the outer periphery of the seal
c. Apply sealant to surfaces as required, consistent assembly mounting flanges.
with the type of sealing. j. Remove excess sealant which extrudes from
d. Assemble mating surfaces allowing the sealant to the seal assembly mounting flanges.
extrude out the edge of the skin or fairing. Complete k. Remove the masking tape after the sealant has
assembly using the appropriate fasteners and dabbing cured.
sealant into the dimpled or countersunk hole,
e. Fair extruded sealant over cloth wrap and over
edge of masking tape. . Pre-Pack Method.
f. After sealant is cured, remove masking tape.
a. Accomplish steps a through d of injection method.
b. Place seal fitting halves around the wire bundle
Electrical Sealing. on the pressure side of the bulkhead.
c. Wrap several turns of masking tape around the
When the wire bundles are continuous and pass through seal assembly on the far end only to center the
a pressurized bulkhead, they should be sealed in ac- bundle and retain the sealant when applied.
cordance with one of the following alternate methods d. Hold the seal assembly in a vertical position
using the S45 nylon seal fitting. with the open end up and inject sealant in around the
wires. Remove and reinject the nozzle at several
Injection Method, locations within and around the bundle to fill all
the voids between the wires and around the wires
a. Clean the metal area where the seal fitting will and the seal assembly,
seat. Clean the wires and seal fittings with Mozel e. Wrap the open end of the seal assembly with
solvent #18. masking tape to center the bundle and retain the
b. Pass the wire bundle through the bulkhead cutout sealant.
and secure, leaving approximately two inches of f. Lay a heavy bead of sealant within the flange
slack. of the fitting so that when placed against the bulk-
c. Bundle ties must not be placed within six inches head, some would be extruded between the fitting and
of the seal assembly to facilitate penetration of bulkhead.
sealant around individual wires. g. Position fitting in the cutout and secure with
d. Place the seal halves around the wire bundle on the required fasteners.
the pressure side and position in bulkhead cutout, h. Remove any excessive sealant which extrudes
e. Wrap several turns of masking tape around the from the seal assembly mounting flanges,
seal assembly ends and the wire bundle to center the
bundle and retain the sealant when applied.
f. Secure the seal assembly to the bulkhead with Adding Additional Wires to Continuous Bundle.
the required fasteners.
g. Puncture the tape over the injection hole in the When additional wires need to be added to a bundle
fitting. which has been installed and sealed, one of the
h. Injection sealant should be Pro-seal 727 and following procedures may be used:
should be used toward the beginning of its work

SEALANT
INJECTION
HOLE
SEALANT --WIRE BUNDLE
INJECTION
HOLE
S45 NYLON
SEAL FITTING

INJECT SEALANT
FITTING HALVES MASKING TAPE UNTIL VISIBLE
(APPLY BOTH ENDS) HERE

Figure 16-17. Electrical Sealing

Change 2
 421 SERVICE MANUA.L STRUCTURAL REPAIR 18-25

a. Filler rods may have been added during manu- d. Retie any remaining filler rods to the wire bun-
facture to accommodate future wire installations. If dle on each side of the seal fitting approximately 1
so, remove as many filler rods as necessary to in- . inch from the end of the rods.
stall the required wires. Several wires can be e. When there are no filler rods, it is necessary
added through the same hole, but room must be to remove the seal assembly from the structure by
retained to inject sealant around the wires. Remove prying loose at the seal assembly mounting flanges.
the filler rods by pulling straight from the hole with f. Remove and discard the old seal fitting and
pliers, remove all the original sealing material from the
b. Route and connect the wires prior to sealing. wires and structure. Care must be taken to avoid
c. Seal each cavity by injecting Pro-seal 727 seal- damage to the wire insulation.
ing compound completely around the wires in the g. Assemble and reseal the assembly in accordance
cavity, with the appropriate methods.
16- Û STRUCTURAL REPAIR 421 SERVICE MANUAL

1 13 5 10 5 10 10 10 6 - 8 8

FUSELAGE LEFT SIDE

2 1 10 10 5 3

2 L « 6 10 5 b 5 10 13 7 1

FUSELAGE RIGHT SIDE

7

STABILIZER & ELEVATOR TOP VIEW g

1. FIBERGLASS 4
2. .020 T2024 T3 ALCLAD 2
3. .020 T2024 T42 ALCLAD
4. .025 T2024 T3 ALCLAD 12
5. .032 T2024 T3 ALCLAD
6. .040 T2024 T42 ALCLAD 3
7. .025 T2024 T42 ALCLAD
8. T2024
.016 T3 ALCLAD
9. .040 T2024 T3 ALCLAD
10. .032 T2024 T42 ALCLAD
11. .040 T2024 T42 ALCLAD
12. .016 T2024 T42 ALCLAD 2 7 5 3
13. Polycarbonate FIN & RUDDER LEFT SIDE
(421A0001 AND ON)

Figure 16-18. Fuselage and Empennage Skin

 421 SERVICE MANUAL STRUCTURAL REPAIR 16-

4 *
5

11
11

8 11 1
.--

TOP VIEW LEFT WING

4
11

3 --•
7
9
11 1. . FIBERGLASS
2. .025 T2024 T3 ALCLAD
3. . 032 T2024 T42 ALCLAD
BOTTOM VIEW LEFT WING 4. . 032 T2024 T3 ALCLAD
5. . 040 T2024 T42 ALCLAD
6. .050 T2024 T42 ALCLAD
421BOOO1 AND ON 7. . 040 T2024 T3 ALCLAD
8. .020 T2024 T42 ALCLAD
9. .016 T2024 T3 ALCLAD
10. .090 T2024 T42 ALCLAD
11. .025 T2024 T42 ALCLAD

Figure 16-19. Wing Skin

16-Ž$ STRUCTURAL REPAIR 421 SERVICE MANUAL

DOUBLER

EXISTING SKIN

EDGE DISTANCE
2 D. MIN.

SPACINGL 4-6 D

.50 R. MIN.
TYPICAL

APPLY SEALANT IN
CONTACT AREA
SPREAD EVENLY
APPROX. 1/32" THICK

PATCH

DOUBLER DOUBLER

ORIGINAL PARTS

REPAIR PARTS

REPAIR PARTS IN CROSS SECTION

NAS1097AD4 RIVETS --
PATCH

Figure 16-20. Over Structure Repair of Pressure Cabin

 421 SERVICE MANUAL STRUCTURAL REPAIR

NAS1097AD4 l..........,,..,...!
ORIGINAL PARTS
RIVETS
E A REPAIR PARTS
15°
REPAIR PARTS IN CROSS SECTION

4 D TYPICAL

O -C1H
00000 oo
-N- "
O O O O h

O ,
O
DOUBLER
OO OO
FAY SEAL BETWEEN PARTS
O O
O O

3" DIA. HOLE

PATCH REPAIR FOR 3 INCH DIAMETER HOLE

22-1/2°-+
4 D TYPICAL
NAS1097AD4
RIVETS PATCH

OO --
-i"

Ö OO

OO OO
OO OO
DOUBLER

FAY SEAL BETWEEN PARTS

2" DIA. HOLE
PATCH REPAIR FOR 2 INCH DIAMETER HOLE

45° 4 D TYPICAL
1" DIA. HOLE

PATCH
1/2"

O 10 OO
O

DOUBLER

NAS1097AD3 FAY SEAL BETWEEN PARTS

RIVETS

PATCH REPAIR FOR 1 INCH DIAMETER HOLE

Figure 16-21. Typical Circular Hole Skin Repair in Pressure Cabin

18-30 STRUCTURAL REPAIR 421 SERVICE MANUAL

EDGE MARGIN = 2 X RIVET DIA.

1/2" RADIUS o e
e o PATCH 2024T3 ALCIAD
--

(SAME GAGE AS SKIN)

XGREMET
CLEAN OUT
D ETER
DAMAGED AREA

SKIN

RIVET SPACING =

A 4-6 X RIVET DIA.

DOUBLER 2024T3 ALCIAD

-
EDGE MARGIN =

(SAME GAGE AS SKIN) 2 X RIVET DIA.

EDGE MARGIN =

2 X RIVET DIA.

1/2" RADIUS

1/2" RADIUS

SPREAD SEAIANT
EVENLY APPROX.
1/32" THICK NAS1097AD4 RIVETS

1/ B

ORIGINAL PARTS

REPAIR PARTS
+ 1/2 B+
REPAIR PARTS IN CROSS SE CTION
SECTION THRU ASSEMBLED PATCH

Figure 16-22. Typical Insert Patch in Pressure Cabin

 421 SERVICE MANUAL sTRucTunAL REPAi -M

ADD .063 2024ST3

DOUBLER

CUT OFF DAMAGED SECTION HERE

DOUBLER OF SAME GAUGE
AND MATERIAL AS BULKHEAD

ADD
MS20470 AD4
RIVETS

EXISTING STRUCTURE

CLEAN OUT OLD SEALER

AND RESEAL

DAMAGED SECTION REPLACEMENT

TYPICAL REPLACEMENT OF BULKHEAD SECTION

A -A
EXISTING
FASTENERS

FLATTEN T.TGHTENING
" HOLE AS REQUIRED
B

MS20470AD4 "
RIVET o
4. 25"

DEFECT

U B-B
ADD 063 2024T42
.

ANGLES 2 REQ'D
B.R. .19

TYPICAL REPAIR OF CRACKED MULKHEAD I

ORIGINAL PARTS

REPAIR PARTS
REPAIR PARTS IN
CROSS SECTION

Figure 16-23. Typical Cabin Bulkhead Repair (Sheet 1 of 2)

18-32 STRUCTURAL REPAIR 421 SERVICE MANUAL

ADD NAS 1097AD4 RIVETS

DEFECT

ADD
MS20470 AD4 'e
RIVETS

ADD BULKHEAD SEGMENT- LENGTH

TO EXTEND TO ADJACENT STRINGERS
OR APPROXIMATELY 7" EACH SIDE
OF DEFECT

T I 1

ORIGINAL PARTS

REPAIR PARTS
-REPAIR PARTS IN
CROSS SECTION

TYPICAL CABIN BULKHEAD REPAIR

Figure 16-23. Typical Cabin Bulkhead Repair (Sheet 2 of 2)

 421 SERVICE MANUAL STRUCTURAL REPAIR

A A-

B
APPLY SEALANT IN CONTACT
AREA-SPREAD EVENLY APPROX
THICK
.03"

NAS1097AD4 RIVET

0"

CLEAN OUT DAMAGED AREA

IGN
.040 1 "

"
B

2. 50"
NAS1097AD4 RIVET
ORIGINAL PARTS

REPAIR PARTS
ASIRPcARTOSNIN

. 50"
APPLY SEALANT IN CONTACT
AREA-SPREAD EVENLY APPROX
.03" THICK

Figure 16-24. Typical Cabin Skin Crack Repair

16-34 STRUCTURAL REPAIR 421 SERVICE MANUAL

NEW SECTION 2024T3

--

ALCLAD (GAGE AND DIMENSIONS

BUTT NEW SECTION SAME AS ORIGINAL STRINGER)
TO ORIGINAL SECTION
o

CLEAN OUT OLD

SEALER AND RESEAL
ANGLE 2024T3 ALCLAD
(GAGE AND DIMENSIONS SAME 6

AS EXTRUSION)
ORIGINAL SE CTION

0
0
1/4" EDGE MARGIN
0

-ANGLE 2024T3 ALCLAD

o (GAGE AND DIMENSIONS SAME
AS EXTRUSION)

MS20470AD4 RIVETS
5 RIVETS EACH SIDE OF
SPLICE

NAS1097AD4 RIVETS

ORIGINAL PARTS

REPAIR PARTS IN CROSS SECTION

REPAIR PARTS

Figure 16-25. Typical Cabin Section Stringer Splice

 421 SERVICE MANUAL STRUCTURAL REPAIR $•

1/4 B - B

1/2 B

SECTION THRU ASSEMBLED PATCH

EDGE MARGIN 2X
¯A RIVET DIAMETER
=

,
o PATCH--2024 T3 ALCLAD
(SAME GAGE AS SKIN)

1/2 " RADIUS

CLEAN OUT ,
DAMAGED AREA EDGE MARGIN = 2X
RIVET DIA.

1/2" RADIUS

RIVET SPACING =

6 X RIVET DIA.

1/2" RADIUS

EDGE MARGIN 2 X RIVET DIA.

DOUBLER--2024 T3 ALCLAD
(SAME GAGE AS SKIN)
RIVET TOBLE
SKIN GAGE RIVET DIA.

.020 3/32

.025 1/8

.032
1/8

ORIGINAL PARTS .040 1/8

REPAIR PARTS .051 5/32

RE PAIR PARTS IN CROSS SECTION

Figure 16-26. Typical Clear of Structure Skin Repair

18-30 STRUCTURAL REPAIR 421 SERVICE MANUAL

FILLER--2024 T3 (SAME GAGE

AND DIMENSIONS AS ORIGINAL)

A-A

' e CLEAN OUT DAMAGE:D AREA

HAT SECTION

1/4" EDGE MARGIN

DOUBLERS--2024 T3
(SAME GAGE AND
DIMENSION AS ORIGINAL)

3/4" RIVET SPACING

---
NAS1398D4 RIVETS

ORIGINAL PARTS
REPAIR PARTS
REPAIR PARTS IN CROSS SECTION

Figure 16- 27. Typical Pressure Bulkhead Hat Section Repair

 421 SERVICE MANUAL sTRucTURAL REPAIR Û'

MS20470AD4 RIVETS
24 REQ.

O ! O
4.o605DOIAD
oo ° oo PATCH
Oi V \O
O i IO O
O\
O O''-OO O EXISTING
7.50 DIA

o o SKIN
SECTION THRU PATCH

3. 00 DIA. HOLE

PATCH REPAIR FOR 3 INCH DIAMETER HOLE

MS20470AD4 RIVETS
16 REQ. 1/2°
22
-5.00 DIA.

3.00 DIA
PATCH
O/ \O
O ¿ O
O OO EXISTING 4. 00 DIA.
SKIN
2.00 DIA. HOLE
SECTION THRU PATCH

PATCH REPAIR FOR 2 INCH DIAMETER HOLE

MS20470AD4 RIVETS
8 REQ• +
45° 2. 50 DIA.
EXISTING
PATCH
SKIN
Of
'
O .
·

1. 75
1. 00 DIA. HOLE DIA.

SECTION THRU PATCH

PATCH REPAIR FOR 1 INCH DIAMETER HOLE

Figure 16- 28. Typical Patch Repair of Circular Holes

18-38 STRUCTURAL REPAIR 421 SERVICE MANUAL

E I TING SKIN

DOUBLE
. 025 1/8
SECTION THRU ASSEMBLED PATCH
. 032 1/8
A-A
. 040 1/8

. 051 5/32

1/2" RADIUS EDGE MARGIN = 2 X RIVET DIA.

PATCH--2024 T3 ALCLAD
(SAME GAGE AS SKIN)

EDGE MARGIN =.-

2 X RIVET DIAMETER
CLEAN OUT
e o DAMAGED AREA

e SKIN
o
1/2 RADIUS
o
o RIVET SPACING =

6 X RIVET DIA.

DOUBLER-- 2024 T3 ALCLAD-

(SAME GAGE AS SKIN)
EDGE MARGIN =

e o 2 X RIVET DIA.

o 1/2" RADIUS
1/2" RADIUS o o

ORIGINAL PARTS

RE PAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-29. Typical Insert Patch

 421 SERVICE MANUAL STRUCTURAL REPAIR 649

1/4"EDGE MARGIN STRINGER--2024--T3 ALCLAD

(GAGE AND DIMENSIONS SAME
AS ORIGINAL STRINGER)

6 RIVETS EACH SIDE RIVET SPACING TO MATCH

OF DAMAGED AREA e PATTERN IN SKIN

CLEAN OUT
DAMAGED AREA
'
e STRINGER

A¯A FILLER--2024--T3 ALCLAD

(GAGE AND DIMENSIONS SAME
AS ORIGINAL STRINGER)

MS20470AD4 RIVETS

ORIGINAL PARTS

RE PAIR PARTS

REPAIR PARTS IN CROSS SECTION SKIN

Figure 16-30. Typical Wing L. E. Stringer Repair

lß-40 STRUCTURAL REPAIR 421 SERVICE MANUAL

BAD RIVET HOLE OR DAMAGED STRINGER

FILLERS SAME THICKNESS AS STRINGER

DOUBLER -.051
2024 T3 ALCLAD

BULKHEAD

SKIN

BULKHEAD

RIVE TS SAME TY PE AND

DIAMETER AS ORIGINAL

A- A STRINGER

SKIN

ORIGINAL PARTS
REPAIR PARTS
REPAIR PARTS IN CROSS SECTION

Figure 16-31. Typical Stringer to Bulkhead Repair

 421 SERVICE MANUAL STRUCTURAL REPAIR 16-41

FILLER 2024 T3 ALCLAD

-

(GAGE AND DIMENSION SAME

AS EXTRUDED ANGLE.)

A-A
STRIP -
2024 T3 ALCLAD (SAME
GAGE AS EXTRUDED ANGLE)
1/4" EDGE MARG

CLEAN OU
DAMAGED AREA

R E ADO I E
A

ANGLE 2024 T3 ALCLAD

-
t
(GAGE AND DIMENSIONS SAME
'
AS EXTRUDED ANGLE) e
3/4" RIVET SPACING

PICK UP EXISTING SKIN RIVETS

STRINGER

MS20470AD4 RIVETS ON

SKIN

ORIGINAL PARTS
RE PAIR PARTS

RE PAIR PARTS IN CROSS SECTION

Figure 16-32. Typical Stringer Repair

18-42 STRUCTURAL REPAIR 421 SERVICE MANUAL

FILLER T3 ALC·LAD
--2024

(SAME GAGE AS CHANNEL)

PLATE--2024 T3 ALCLAD
(SAME GAGE AS CHANNEL)

A-A

CLEAN OUT DAMAGED AREA ec

eRADIUS

2 ROWS OF RIVETS
OUTBOARD OF
LIGHTENING HOLE

CHANNEL

A
3/4" RIVE T
SPACING
MS20470AD4 RIVETS
1/4" EDGE
MARGIN
e

DOUBLER--2024 T3 ALCLAD
(SAME GAGE AS CHANNE L)

ORIGINAL PARTS
RE PAIR PARTS
REPAIR PARTS IN CROSS SECTION

Figure 16-33. Typical Channel Flange Repair

 421 SERVICE MANUAL STRUCTURAL REPAIR 18-43

ORIGINAL PARTS
REPAIR PARTS
REPAIR PARTS IN CROSS
SECTION

STOP DRILL CRACK

A-A °
.
e
0 e
e

CHANNEL e

3/4 " RIVET e

SPACING e

2 ROWS RIVETS
e I OUTBOARD OF
DOUBLER--2024--T3 ALCLAD e o LIGHTENING HOLE
(SAME GAGE AS CHANNEL)
1/4" EDGE MARGIN

SKIN

o A

MS20470AD4 RIVETS

SKIN

Figure 16-34. Typical Channel Repair

18-44 STRUCTURAL REPAIR 421 SERVICE MANUAL

THICK-
SAME CONTOUR AND
NESS AS DAMAGED RIB.

STUB OF DAMAGED RIB

JOGGLE BOTH FLANGES

TO FIT INSIDE THE
CLEANED-UP STUB OF
THE DAMAGED RIB.

NUMBER OF ROWS OF RIVETS

IN WEB DEPENDS ON AREA
4D AVAILABLE. SEE MINIMUM
4D MIN SPACING. MAXIMUM SPACING
MIN .38 MIN IS ONE INCH. RIVETS IN
FLANGES MUST BE AS SHOWN.

5D MIN

FOR RIB THICKNESS OF 032 OR

.

5D MIN LESS USE AD-3 RIVETS AND FOR

THICKER MATERIAL USE AD-4.

6D MIN- +

.38 TYPICAL

ORIGINAL PARTS

REPAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-35. Typical Repair of Control Surface Rib

 421 SERVICE MANUAL STRUCTURAL REPAIR

STOP DRILL CRACK IF CRACK DOES

NOT EXTEND TO EDGE OF PART
DOUBLER- .032 2024 T3 ALCLAD

1/4" EDGE
MARGIN

RIB

RIVET TABLE
SKIN GAGE RIVET DIA.
.020 3/32

.025 1/8

.032
1/8

. 040 1/8

.051 5/32

ORIGINAL PARTS A
REPAIR PARTS
REPAIR PARTS IN CROSS SECTION

Figure 16-36. Typical Rib Web Repair

18-46 STRUCTURAL REPAIR 421 SERVICE MANUAL

FILLER--2024 T3 ALCLAD
(SAME GAGE AS RIB)

DOUBLER--2024 T3 ALCLAD
(SAME GAGE AS RIB)

CLEAN OUT DAMAGED AREA

-1/4"
EDGE MARGIN

R IVGE
T

ANGLE--2024 T3 OR T4 ONE ROW OF RIVETS

(SAME GAGE AS RIB) AROUND DAMAGED AREA
RIB

MS20470AD4 RIVETS

ORIGINAL PARTS
A- A
RE PAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-37. TypicaLRib Flange Repair

 421 SERVICE MANUAL STRUCTURAL REPAIR ÎÛ-47

NOTE
DOUBLER--.032 2024 T3 ALCLAD
TO ACCOMPLISH THIS SPLICE A
REPLACEMENT SPAR MUST BE
RN CRUED TA LFLAUCS
TORRA
A D I TED

RIB ATT CHMENT ANGLES

CAP SPLICE-- 7075 T6

ANGLES X.750 .750

(SAME THICKNESS AS
SPAR CAP IN REPAIR
AREA)

REPLACEMENT SPAR 'O

ALL RIVETS THROUGH UPPER AND LOWER

c/ CAP SPLICE ARE MS20470ADS REMAINING
-

RIVETS ARE MS20470AD4 RIVETS

A-A B-B

ORIGINAL PARTS

1 RE PAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-38. Typical Rear Spar Repair (Section 128. 86 and Outboard)
16-48 STRUCTURAL REPAiR 421 SERVICE MANUAL

CAP SPLICE--.064 2024 T3 ALCLAD- WEB SPLICE--.040 2024 T3 ALCLAD

FORWARD FITTING -

.050 2024 T3 ALC D

REPLACEMENT CAP--
.064 2024 T3 ALCLAD

AFT FITTING--
.050 2024 T4 ALCLAD

DOUBLER--.032 2024 T3 ALCLAD

OUTBOARD
HINGE HALF
REPLACEMENT WEB--.032 2024 T3 ALCLAD e

OUTBOARD HINGE BRACKET

o\

ALL RIVETS THROUGH UPPER AND

LOWER CAP SPLICES ARE MS20470AD5
REMAINING RIVETS ARE MS20470AD4 RIVETS

ORIGINAL PARTS
REPAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-39. Typical Rear Spar Repair (Station 206.94 and Outboard)
 421 SERVICE MANUAL STRUCTURAL REPAIR 16- A

RIB ATTACHING ANGLE

DOUBLER--.032 2024 T3 ALCLAD

CAP SPLICE--7075 T6 ANGLES 1.00 X 1.00

(SAME THICKNESS AS SPAR IN REPAIR AREA)

DOUBLER--.032
2024 T3 ALCLAD

SPACER--SAME MATERIAL AND '

THICKNESS AS CAP SPLICE

CAP SPLICE--7075 T6 ANGLES

e. 1.00 X 1.00 SAME THICKNESS
d. AS SPAR CAP IN REPAIR AREA

A- A
A TOTAL OF 20 MS20470AD5 RIVETS
SHOULD BE USED THROUGH THE
UPPER AND LOWER CAP SPLICES
REMAINING RIVETS ARE MS20470AD4

ORIGINAL PARTS
REPAIR PARTS

REPAIR PARTS IN CROSS SECTION

Figure 16-40. Typical Front Spar Repair (Station 186. 49 and Outboard)
18-50 STRUCTURAL REPAIR 421 SERVICE MANUAL

CRACK OR HOLE

PATCH

--MECHANICALLY EXPANDED RIVET

RIVET PART NUMBER

3/32 NAS 1398

(Blind)

l ORIGINAL PART

I REPAIR PART
REPAIR PART IN CROSS SECTION

Figure 16-41. Typical Repair of Trailing Edge of a Control Surface

Change 2
 421 SERVICE MANUAL STRUCTURAL REPAIR 1E51

ALIGNMENT AND SYMMETRY CHECK. (See figure with Section 2. Figure 16-42 provides the measure-
16-42. ) ments and shows the relative elevation points to be
measured during the alignment symmetry check.
Before making an alignment and symmetry check, the Measurements are made with a steel tape projected
aircraftshould be defueled and leveled in accordance between alignment points.

6L
6R

POINT "A"
1L
1R
POINT "A"
5LL

(2R TO 5R) (2L TO 5L)

(2R TO PA L TO PA)

0 0

2R 2L
3R 3L

(1R TO 3R) (1L TO 3L)

6R 6L
(4R TO 6R) (4L TO 6L)

4R 4L
(2R TO 6R) . (2L TO 6L)

3R 3L
BR 5L

1R 1L

Figure 16-42. Alignment and Symmetry Check (Sheet 1 of 2)

18-52

STRUCTURAL REPAIR 421 SERVICE MANUAL

4L
AFT RIVET LINE 6L e

SKIN TRIM LINE

TOP VIEW STABILI2 ER

POINT "A"

SKIN TRIM LINE

1R

i BOLT

TOP VIEW LH WING

2L

ALIGNMENT AND SYMMETRY CHECK

421-0001 TO 421B0001 g
421B0001 AND ON
Details of Check Points: POINTS DISTANCE DISTANCE

A. Center line aft tail skid bolt. 1L TO 3L

20'1. 00 ±1. 25" 21'1. 00" ±1. 25"
1. Center line of bolt at gear strut and drag 1R TO 3R
brace attachment. Center line head of
bolt RH side and shank of bolt LH side. 2L TO 5L
20'11. 00" ±2. 00" 21'6. 00" ±2. 00"
2. Skin trim line and inboard edge of tip 2R TO 5R
fairing at front spar.
Same as 2 except bottom of wing. 2L TO PA
3. 25'8. 00" ±1. 50" 26'5. 00" ±1. 50"
2R TO PA
4. Center line aft rivet line of rear stabi-
lizer at outboard edge of stabilizer.
4L TO 6L 9'5. 50"
5. Same as 4 except bottom of stabilizer. . 4R TO 6R 9'4. 00" ±1. 00" ±1. 00"
6. Skin trim line at forward fin spar and
lower edge of tip cap• 2L TO 6L
26'2. 00" ±2. 00" 26'11. 00" ±2. 00"
2R TO 6R

Figure 16-42. Alignment and Symmetry Check (Sheet 2 of 2)

Change 8
 421 SERVICE MANUAL sTRuctuR^' REPAIR 18-53

Figure 16-43. Buffing with Air Drill Figure 16-44. Fabrication of Patch

FUEL CELL REPAIR. table and natural contours maintained if pos-

sible. Prevent cell from contact with sharp
The fuel cells installed in the wings are a bladder- edges, corners, dirty floors or other sur-
type, known as Construction BTC-39, manufactured faces.
by Goodyear Tire and Rubber Company. The follow-
ing cold patch repair procedures are approved repair WARNING
practices of Vithane BTC-39 fuel cells. These pro-
cedures apply only to BTC-39 fuel cells and devia- Repair area must be well ventilated and no
tions from these procedures should not be permitted. open flame or smoking in area of cell repair.

CAUTION b. Repair Limitations.

1. FT-160 repair fabric is for repair of simple
Repair of the BTC-39 Vithane fuel cells is
restricted to authorized personnel, and/or
those certified or approved by factory trained
schools.lowing

a. equipment will be needed to make

the cold patch repair.
1. Repair Kit, Dwg #2F1-3-35342, available from
the Cessna Service Parts Center, consisting of the
following:
(a) 2331 Repair Cement (1/2 pint cans, 173 cc in
each can).
(b) 2328C Cross-linker (1 Oz. bottle, 28 cc in
each bottle).
(c) Methyl Ethyl Ketone (1 pint cans).
(d) FT-160 Repair Fabric (sheet 12" x 12").
(e) Cellophane (sheet 12" x 24").
(f) Foam rubber, cloth back (sheet 12" x 12").
2. Paintbrush, 1-inch.
3. Roller, 1-inch diameter x 3/4" flat, or equiva-
lent.

NOTE

The repair should be made on a well lighted Figure 16-45. Centering Patch Over Injury

I
18-54 STRUCTURAL REPAIR 421 SERVICE MANUAL

5. Tape a piece of cellophane inside ceu over in-

6ry
When all the above preparatory work has been
completed, and all has been positioned for patch
application on repair table, mix the 2331C cement
(173 ce) with the cross-linker 2328C (28 ce), and stir
mixture thoroughly.
7. Brush one even coat of mixed repair cement on
the cell wall around injury and on the contact side of
--
repair patch. Allow to dry for twenty minutes.
ti .
8. Repeat a second mixing of repair cement and
brush on a second coat.
O
CAUTION

DO NOT USE FIRST CAN OF MIXED CEMENT

FOR THIS COAT.

9. Allow cement to dry approximately ten minutes

and then center patch over injury as shown in figure
16-45.
Figure 16-46. Use of Roller Stitcher 10. (See figure 16-46.) Lay repair patch by roll-
ing down on surface from center of edge without
trapping air. Hold the unrolled portion of repair
contours only. Patches referred to in these proce- patch off the cemented surface until roller contact
dures are of this material. insures an air-free union. At this time repair patch
2. Inside patches are to lap defect edges two- may be moved by hand on wet surface to improve
inches (2") in each direction. lap. Do not lift repair patch, slide it.
3. Outside patches are to lap two and one-quarter
inches (2-1/4") in each direction. CAUTION
4. Outside patches are to be applied and cured
prior to applying an inside patch. Make sure cellophane inside cell over injury
5. Blisters between interliner and fabric larger remains in place, because any cement will
than 1/4" in diameter, require an outside and an
inside patch.
6. Separations between outer plies larger than
one-inch (1") in diameter require an outside and in-
side patch. Holes and punctures require an outside
and inside patch.
7. Slits and tears, up to three-inches (3") maxi-
mum length, require an outside and inside patch.
8. External abraided or scuffed areas, without
fabric damage, require an outside patch only.
9. A loose lap may be trimmed, provided that a
one-inch (1") effective bond remains.
10. Air cure repair patches are to remain clamped
and undisturbed for 72 hours at room temperature of
75°F.
approximatelý
c. Repair Patch.
1. Prepare exterior cell wall and exterior patch
first. Cut repair patch from FT-160 material to
size required (see figure 16-44) to insure proper lap
over injury in all directions in accordance with Re-
pair Limitations. Hole shears at an angle to produce --

a beveled edge (feather) on patch when cutting patch.

Round corners of patch. Dull side or gum contact
face of repair patch should be the largest surface
after beveling.
2. Wash one square foot of cell wall surrounding
injury, and repair patch contact side with a clean
cloth soaked with Methyl Ethyl Ketone solvent.
3. Abraid cell wall surface about injury and con-
tact side of patch with fine emery cloth or emery
buffer wheel (see figure 16-43) to remove shine.
4. Repeat Methyl Ethyl Ketone washings two more
times. A total of three washings each surface. Figure 16-47. Repair of Blisters
 421 SERVICE MANUAL STRucTURAL REPAla
B-55

stick cell walls together without it as a sepa- fuel cell wall. Be careful not to pull cell lap open
rator. while peeling accessory off. Pull from blind side of
cell lap toward the exposed edge.
11. Cover one smooth surface each of two alumi- 5. Buff the cell surface under accessory with
num plates (plates must be larger than patch, with emery cloth or emery buffer wheel (see figure 16-43)
1/4" fabric-backed airfoam, fabric side out. Tape to smooth roughness and prepare for cement.
airfoam in place. Foam must cover edges of plate
for protection. NOTE
12. Fold cell adjacent to patch and place prepared
plates, one over repair patch, and one on opposite Removal of accessory may leave an uneven
side. cavity and surface. The surface under ac-
13. Secure the assembly with a "C" clamp, tighten cessory should be buffed even and smooth.
by hand. Check cement flow to determine pressure.
6. Prepare replacement accessory by buffing and
CAUTION washing contact surface. Also wash cell surface
(see Repair Patch paragraph).
Make sure that cell fold is not clamped be- 7. Apply mixed 2331C repair cement to both sur-
tween plates. This would cause a hard faces.
permanent crease. Also, be sure patch does 8. Roll new accessory into place as with a repair
not move when clamp is tightened. patch and place suitable padded plates in position to
insure adequate pressure when clamped. Use cello-
14. Inside patch is applied in the same manner as phane separator to prevent cement sticking in wrong
the outside patch. See Repair Limitations paragraph places.
for size of inside patch, after outside patch has been 9. Cure as with repair patch procedure cure
cured. method.
f. Defects Repair.
CAUTION 1. Blisters (see figure 16-4'7).
(a) Remove loose material by buffing or trim-
Success of applying both an outside and inside ming. Apply an outside and inside patch.
repair simultaneously is doubtful and not 2. Holes, punctures, cuts, tears and deep
recommended, abraided areas.
(a) Trim away any ragged material and apply an
d. Metal Fitting Sealing Surfaces.
-
outside and inside repair patch.
1. Rub off roughness of affected area with a fine 3. Loose seams.
file, emery cloth or emery wheel as shown in figure (a) Buff loose edge and contact surface. Wash
16-43. three times with MEK. Apply 2331C mixed
2. Clean metal surfaces using a clean cloth dipped cement, two coats, as with repair patch.
in Methyl Ethyl Ketone. Moisten cleaned surface Clamp and cure. Loose seams may be trim-
with clean cloth dipped in water. Apply Alodine 1200 med if minimum lap remains.
solution, undiluted, to the affected area with a small 4. Loose fitting flange -

Inside.
nylon brush. Allow solution to dry until a light gold- (a) Buff edge of flange and contact surface under
en color appears. When coating has been formed, flange.
remove excess solution by wiping with a clean water- (b) Apply 2331C mixed repair cement, cellophane
moistened cloth. Wipe dry. padded plates and clamp.
(c) Follow procedure.as outlined for repair patch
WARNING except patch itself.
5. Missing coat.
Do not allow solution to come in contact with (a) Buff surface.
hands, eyes or clothing. (b) Wash three times with MEK.
(c) Apply 2331C mixed cement two coats as with
e. Accessory Replacement. repair patch.
1. Obtain cured repair accessory from manufac- (d) Clamp and cure.
turer. 6. Looseness against metal.
2. Mark location of old accessory and preserve (a) Prepare metal as per metal fitting-sealing
marking for guide lines to locate new part. surface.
3. Remove old accessory by gradually loosening (b) Apply 2331C mixed cement and cure.
an edge with a blunt probe-like instrument. g. Testing.
4. When an edge is loose, grasp accessory by 1. Attach test plates to all fittings.
loose edge with pliers and gently pull accessory off 2. Inflate the cell with air to a pressure of 1/4
PSI maximum.
3. Apply soap suds to patched area and check for
leaks.
18-58 STRUCTURAL REPAIR 421 SERVICE MANUAL

B
I

CL DOOR FRAME SEAL--

LOWER DOOR
C SEAL

( LOWER DOOR
SEAL

SEAL
RETAINER
I

NOTE
FWD EXISTING
ENLARGE CUTOUT
AIR HOLES
WHEN AND AS
ON SIDE OF
REQUIRED TO
SEALS
I CLEAR SEAL.

FWD

Detail A SECTION A -
A

Figure 16-48. Cabin Door Seal Repair (Sheet 1 of 2)

 421 SERVICE MANUAL STRUCTURAL REPAIR 6-57

I
L-- ------...--J
l I | |
SPONGE RUBBER
(WHEN REQD.)

DETAIL A

HOLE
OR GAP
TO BE
REPAIRED
->

. 50 +- -+
. 50 +-

END OF r ¯'UT
-,,--

C'ABIN
- -
DOOR
REPAIR MATERIAL
SEAL

Detail B
CM507 MATERIAL
DACRON FABRIC
(AS REQD )

SMALL
C CLAMPS
-

(REF.)

EXTRUSION
(RUBBER MOLD)
METAL PLATES (AS REQD.)
(4 PLACES)

Detan (

Figure 16-48. Cabin Door Seal Repair (Sheet 2 of 2)

16•58 STRUCTURAL REPAIR 421 SERVICE MANUAL

CABIN DOOR SEAL REPAIR. NOTE

When repairing the cabin door seal the work area Fabricate (4) four metal plates 0.06 thick-
must be clean and dirt free. The cabin door seal ness same length and width as rubber mold.
need not be removed from the cabin door, only re-
move enough seal in the damaged area to allow in- h. Clean the entire surface area to be repaired
stallation of rubber mold. with alcohol and let dry.
i. Remove cellophane lines from cut piece of CM507
NOTE material Dacron Fabric.
-

j. .Apply a coat of Silastic Silicone Rubber 140 Adhe-

Seals with damaged area of holes or gaps in sive approximately 0. 005 thick to cleaned surface
excess of six inches in length should not be of seal and to cut piece of fabric spatula.
repaired. The seal should be replaced. k. Allow applied Silastic Silicone Rubber 140 Adhe-
sive to dry until tacky, but no longer, transfer to the
a. The following equipment will be necessary before knuckles when touched, (usually between 5 and 30
attempting to repair the cabin door seal. minutes).
1. SK421-2A available from Cessna Service Parts
Center. NOTE
2. 3 each small "C" clamps.
3. Blunt plaster tool (for removing and installing Use the back of the knuckle to touch the ad-
seal in cabin door retainer). hesive surface instead of finger tips to mini-
4. Spatula. mize contamination.
b. (Refer to Figure 16- 48 ) Mark seal and seal re-
tainer to insure proper reinstallation of seal in seal 1. Install CM507 material Dacron Fabric
-
Patch
retainer. on seal with the adhesive surface mating and posi-
c. Remove damaged seal from retainer. tioned over hole or gap per dimensions as shown
in Figure 16-48, Detail B.
CAUTION m. Insure that seal retains its symmetrical size
and shape and that no wrinkles exist in patch or seal.
Use extreme care in removing seal from seal n. Apply a thin coat of parting agent (soap stone or
retainer, use only plastic tools with blunt ends talcum powder) to extrusion rubber mold to prevent
to prevent additional damage to seal. seal sticking to rubber mold.
o. Place extrusion rubber mold over installed fabric
d. (See figure 16-43 ) Using buffing wheel or other patch as shown in Figure 16-48, Detail C.
suitable means, buff seal area to be repaired slightly p. Apply light pressure to fabric patch during cur-
and as required to obtain a smooth repairable sur- ing of adhesive, using fabricated metal plates and
face. small "C" clamps as shown in Figure 16-48 Detail C.
e. If a large hole or gap exists in the seal, fill the
void with a piece of foam rubber as shown in Detail B NOTE
to help support the repair material.
When seal is only partially removed from re-
NOTE tainer to make repair, support the seal and
clamped rubber mold to prevent distortion of
Make sure the sponge rubber extends at least cabin door seal.
0. 50 inch beyond ends of hole or gap and
trimmed to mate inside surface of damaged q. Allow adhesive to cure a minimum of 24 hours
area of seal. under pressure clamp before removing from rubber
mold.
NOTE r. Remove seal from rubber mold.
s. Position seal on seal retainer with marks aligned
Insure only enough sponge rubber (R411N and reinstall seal, using a blunt tool and talcum
closed cell rubber) is used to support the powder or water as required to facilitate installation.
seal material, for each applicable repair.
Excess sponge rubber results in cabin door NOTE
being difficult to close.
Insure that door frame seal is installed with
f. Cut a piece of CM507 material Dacron Fabric
-

existing air holes in seal toward door opening

(included in SK421-2A) the width to extend 0. 50 inch and lower door seal with holes toward the top
beyond ends of hole or gap in seal and long enough to of door. Pressurized air from inside cabin
wrap around seal as shown in Figure 16-48, Detail enters the holes, inflating the seal to form a
B. pressurized seal.
g. Cut a piece of extrusion rubber mold (included in
SK421-2A) long enough to cover and overlap ends of REPAIR OF ICE PROTECTION PANELS.
CM507 material Dacron Fabric
-

Patch as shown
in Figure 16-48, Detail C. The following repair procedures should be used for
repairing the polycarbonate type ice protection
panels. See figure 16-49 and 16-50 for types of
 421 SERVICE MANUAL STRUCTURAL REPAla 6-59

1. Ice Protection Panel 2. Rivet 3. Crack 1. Crack 3. Rivet

2. Stop Drill 4. Ice Protection Panel
Figure 16-49. Repairing Crack in
Ice Protection Panel Figure 16-50. Repairing Combination of Cracks
in Ice Protection Panel

cracks and method of repair. Figure 16-49 is an ex- ally fabricated from aluminum alloys. In special
ample of the cracks starting at a rivet hole propagat- cases, monel, corrosion-resistant steel, mild steel,
ing to the outer edge of the panel. copper and iron rivets are used.
a. See figure 16-49, rout the crack using router
bit. Rout material approximately 1/32 wide and 1/2 Types,
the depth of the panel thickness. a. Standard solid shank rivets are those generally
b. Clean routed crack with isopropyl or ethyl used in aircraft construction. They are fabricated in
alcohoL the following head types: roundhead, flathead,
c. Fill crack with epibond 1331 in accordance with countersunk-head, and brazier-head. Roundhead
manufacturer's instructions, rivets are generally used in the interior of aircraft
NOTE except where clearance is required for adjacent
members. Flathead rivets are generally used in the
Epibond 1331 may be procurred from Furane interior of the aircraft where head clearance .is re-
Plastics quired. Countersunk-head rivets are used on the ex-
4514 Brazil Street, Los Angeles,
California 90039. terior surfaces of the aircraft to minimize turbulent
airflow. Brazier-head rivets are used on the exteri-
d. Figure 16-50 illustrates a combination of cracks or surfaces of the aircraft where strength require-
which may occur. Cracks which do not extend to the ments necessitate a stronger rivet head than that of
outer edge of the ice protection panel, shall be drill- the countersunk-head rivet. Both the brazier-head
ed through the ice protection panel with a #40 drill. and the countersunk-head rivets are used on the ex-
e. Fill the stop drilled hole with Epibond 1331 as terior of the aircraft where head clearance is re-
per manufacturer's instructions. quired.
NOTE b. Hi-shear rivets are special patented rivets hav-
ing a high shear strength equivalent to that of the
Bondite or Ditzler DX-666 may be used as standard AN bolts. They are used in special cases
an alternate for Epibond 1333. in locations where high shear loads are present,
such as spars, wings and heavy bulkhead ribs. The
f. Normal finishing, priming and painting shall be rivet consists of a cadmium plated pin of alloy steel
accomplished following the repair, and a collar of aluminum alloy. The installed rivet
can be readily identified by the presence of the at-
NOTE tached collar in place of the formed head on stan-
dard rivets.
Refer to section 2 for painting Polycarbonate. c. Blind rivets are used where strength require-
ments permit when one side of the structure is inac-
RIVETS cessible making it impossible or impractical to drive
standard solid shank rivets.
General.
Substitution of Rivets.
The following rivets are commonly used in aircraft
structures: standard solid shank, hi-shear, and blind. a. Standard solid shank rivets.
Rivets used in aircraft construction are most gener- 1. In the replacement of rivets in installations
16-60 STRUCTURAL REPAIR 421 SERVICE MANUAL

which require the raised head rivets, it is desirable of the repair. Should too long a rivet be used, the
to use whichever of the rivets that correspond to the formed head will be too large, or the rivet may bend
type of rivet removed. or be forced between the sheets being riveted.
2. Countersunk head rivets are to be replaced by Should too short a rivet be used the formed head will
rivets of the same type and degree of countersink. be too small or the riveted material will be damaged.
3. When rivet holes become.enlarged, deformed, b. If proper length rivets are not available, longer
or otherwise damaged use the next larger size as rivets may be cut off to equal the proper length (not
replacement. grip).
4. Replacements shall not be made with rivets of c. The rivet length is based on the grip.
lower strength material unless they are larger than
those removed. Removal of Solid Rivets. (See figure 16-51. )
5. In the absence of aluminum rivets, stainless,
monel, or iron rivets may be used with generous ap- a. When it becomes necessary to replace rivets,
plication of zine chromate primer only to permit nec- great care should be taken in their removal so that
essary flights of aircraft. The proper replacement the rivet hole will retain its original size and not
shall be made as soon as facilities are available. acquire replacement with a larger size rivet.
b. Hi-shear rivets. When hi-shear rivets are not b. To remove a rivet, file a flat surface on the
available, replacement of sized 3/16 or greater shall manufactured head. It is always perferable to work
be made with bolts of equal or greater strength than on the original head rather than on the one that is
the rivet being replaced and with self-locking nuts of bucking over, since the former will always be more
the same diameter. The flush-type hi-shear rivet symmetrical about the shank. Indent the flat surface
may be temporarily replaced by like diameter flush- with a counter-punch so the drill may be correctly
type steel screws of equal or greater strength and centered. A drill slightly less in diameter than the
self-locking nuts provided the threaded part of screw rivet shank should be used to drill and weaken the
does not extend into material being fastened together. head. Take care that rivet shank does not turn with
This latter procedure is temporary only and replace- the drill and cause a tear. If the other end of the
ment with the hi-shear flush-type rivet must be ac- rivet is supported, the head may be sheared off with
complished as soon as they become available. a sharp chisel. This cutting should always be done
c. Blind rivets. Blind rivets have higher deflection along the direction of the plate edge. If shank is un-
rates in shear than standard solid rivets. For this duly tight after removal of the head, the rivet should
reason, it is not advisable to replace any consider- be drilled out completely. It may be forced out with
able number of solid rivets in a given joint by blind a counter-punch of a smaller diameter than the rivet,
rivets in as much as this may result in over- provided the sheet is properly supported from the op-
stressing the remaining solid rivets. The following posite side; however, there is greater danger of dam-
specific instructions apply, aging the sheet and enlarging the hole when using this
1. The hollow blind rivet shall not be used. method. This procedure will also apply to flush
2. The blind rivet used shall be of the same or rivets.
greater strength and one size larger than the rivet it
replaces, except that blind rivets may be replaced Riveting Installation.
size for size.
3. In cases of dimpled assembly, the rivet holes a. Riveting procedure. A large percentage of the
shall be drilled after the sheets are dimpled. riveting of aircraft structures is done on thin gage
4. When possible, the exposed end of each clipped aluminum alloy and the work must be so accom-
plug shall be coated with a 10 percent chromic acid plished that the material is not distorted by hammer
solution or with zine chromate primer. blows or injured with riveting tools. All aircraft
5. Blind rivets shall not be used in hulls, floats, power riveting is done by upsetting or heading rivets
or tanks except in cases of absolute necessity. against a bucking bar instead of striking the shank
6. If blind fasteners other than blind rivets are en- with a hammer,
countered, it is recommended that replacements be 1. To prevent deforming of its head a rivet set
made by either of these fasteners or by standard must be selected to fit each type. The depth of this
rivets. set must be such that it does not touch the material
being riveted.
Diameters. 2. Parts which are to be heat-treated should be
heat-treated before riveting since heat treating after
a. Rivet diameters range from 3/32 inch to 3/8 inch. this process causes warping. This is also necessary
The 1/8, 5/32 and 3/32 inch sizes are the most fre- when assemblies are heated in a salt bath as the salt
quently used, cannot be entirely washed out of the cracks.
b. Since smaller rivets lack the proper structural 3. Rivets of a diameter smaller than three thirty-
qualities and larger rivets may dangerously reduce seconds inch must not be used for any structural
the splice or patch area, care must be exercised be- parts, control parts, wing covering, cowling, or
fore substituting other than the specified sizes of similar sections of aircraft except where there are
rivet diameter. actual replacements.
4. Rivets through hollow tubes, which are loaded
Lengths. only in shear, should be hammered just enough to
form a small head. No attempt should be made to
a. The proper length of rivet is an important part form the standard round head as the amount of ham-
 421 SERVICE MANUAL STRUCTURAL REPAIR

1. FILE A FLAT ON THE 2. CENTER PUNCH 3. DRILL THROUGH HEAD

MANUFACTURED HEAD THE FLAT USING DRILL ONE SIZE
SMALLER THAN RIVET
SHANK

I I

4. DRILL THROUGH DIMPLE COUNTER-

SUNK OR COUNTERSUNK HEAD USING
DRILL ONE SIZE SMALLER THAN
RIVET SHANK

5. REMOVE WEAKENER HEAD

WITH SHARP CHISEL 6. PUNCH OUT RIVET WITH
MACHINE PUNCH

Figure 16-51. Removal of Rivets

DISTANCE "E" SHOULD EQUAL

TWICE THE RIVET DIAMETER
RESULTANT CRACK
SECTION A-A
E- E

D -

D A
A

SAFE
INCORRECT TOO
-
CORRECT
C LOSE TO EDGE E 2D=

Figure 16-52. Rivet Edge Distance

16•62 STRUCTURAL REPAIR 421 SERVICE MANUAL

mering required often causes the rivet to buckle in- 4. An average spacing or pitch of rivets in the
side the tube, with resultant injury to the member. cover or skin of most structures, except at highly
5. Aluminum alloy rivets must never be used in stressed joints, will be from 6 to 12 diameters of
tension for structural, control, or other critical the rivet.
parts of aircraft. Whenever such an installation is 5. The best practice in repair jobs is to make the
required, bolts should be used. pitch of the rivets equal to those in the original
6. The use of hollow rivets in joining highly stress- structure.
ed parts is not permitted. When rivets cannot be
driven because of the inaccessibility of the end for Loose or Working Rivets in Outboard Section of Wing.
bucking or driving, the next size self-plugging
cherry rivet may be used. Loose or working rivets attaching skin to upper and
7. The selection of the proper rivet and proper lower front spar cap may be repaired by adding
number of rivets is very important. MS20470AD4 or equivalent rivets midway between
8. The rivets must be of the proper length for the and in line with existing working rivets and four
total thickness of the pieces being riveted. Ordin- rivets beyond the last loose rivet, starting repair at
arily, from 1-1/2 to 2 times the diameter of the wing tip and working inboard. This repair is limited
rivet is about the right amount for the rivet shank to the area between the nacelle and tip tank fitting.
to protrude through the material to form the head.
For heavy material such as plates or fittings, from NOTE
2 to 2-1/2 diameters may be used.
9. The rivet should not be too loose in the hole as Care must be taken to avoid damage to fuel
this condition will cause it to bend over while being tanks and wiring,
headed, and the shank will not be sufficiently ex-
panded to completely fill the hole. A drill from Loose or Working Rivets.
0.002 to 0.004 inch larger than the rivet should be
used for sheet and plate riveting. a. Rivets which appear to be loose shall be checked
10. Pieces should be held firmly together by by the use of a 0. 002 feeler gage by inserting the
clamps, screws or bolts while they are being drilled gage around the head of the rivet in question. If the
and riveted. feeler gage can be inserted to the shank of the rivet,
11. Where rivets are headed on the inside of the it shall be classified as a loose rivet and must be
structure, the bucking bar is held against the end of replaced.
the rivet shank. Care must be exercised doing this b. If the feeler gage can be inserted approximately
operation to prevent unseating the rivet by the appli- half-way to the shank for 30°/oof the circumference
cation of too much pressure. For the first few blows of the rivet head, it shall not be classified as a loose
the bucking bar should be held lightly against the rivet.
rivet shank so that it will receive the impact of the c. The feeler gage shall be used to check the shear
blow through the rivet. The bucking bar must be section between the riveted members, such as skin
held square with rivet to avoid turning it over. to spar or different sections of skin in a similar
12. Only a sufficient number of blows should be manner to that used around the rivet head,
struck to properly upset a rivet. The blows must be d. If the skin around the brazier head or counter-
as uniform as possible. sunk rivet can be moved by depressing the skin with
b. Sparing and diameter of rivets. There are no finger pressure around the rivet, the rivet shall be
specific rules which are applicable to every case or replaced.
type of riveting. There are, however, certain gen- e. If rivets are found to turn by applying a rotating
eral rules which should be understood and followed. load to the head of the rivet, they should be replaced.
1. The edge distance of rivets should not be less f. In areas where exterior paint has been applied to
than two diameters of the rivet measured from the rivet heads, the paint may harden due to aging pro-
edge of the sheet or plate to the center of the rivet cesses and show hairline cracks around the edge of
hole. (See figure 16-52-) the rivet heads. This should not be used as a basis
2. The spacing between rivets, when in rows, de- for determining whether the rivet is loose or not,
pends upon several factors, principally the thickness The hardened paint may crack at times and collect
of the sheet, the diameter of the rivets and the man- dirt or exhaust fumes which will appear as discolor-
ner in which the sheet will be stressed. This spac- ation. It is not possible to detect loose rivets
ing is seldom less than four diameters of the rivet, visually.
measured between the centers of the rivet holes. g. When replacing rivets, it is desirable to replace
Rivets spaced four diameters apart are found in cer- them with like size and type. In some instances, it
tain seams of monocoque and semimonocoque fuse- will be necessary to go to the next size larger di-
lages, webs of built-up spars, various plates or fit- ameter. For general repair practices, the spacing
tings, and floats or hulls, between the centerlines of adjacent rivet holes shall
3. Where there are two rows of rivets, they are be four diameters or greater. In areas where the
usually staggered. The transverse pitch or distance spacing between rivets prohibits the use of the next
between rows should be slightly less than the pitch of size larger rivets, special repair instructions and
75°/o the
the rivets, of rivet pitäh being usual practice. procedures shall be utilized.

Change 7
 421 SERVICE MANUAL STRUCTURAL REPAin W•·¾

1/4 B : B MONEL RIVETS MONEL SEAL PER

RIVETS CES2602
SEAL PER CES2602 CLASS I
- .. CLASS I, TYPE 1, 2 .
TYPE 1, 2

1/2 B i

SECTION THRU ASSEMBLED PATCH

SECTION THRU ASSEMBLED PATCH
B- B
EDGE MARGIN = 2X
RIVET DIAMETER

1/2" RADIUS
.. PATCH STAINLESS STEEL
--

(SAME GAGE AS FIREWALL)

CLEAN OUT
DAMAGED AREA EDGE MARGIN 2X =

RIVET DIAMETER

1/2" RADIUS
RIVET SPACING =

6X RIVET DIAMETER

DOUBLER STAINLESS--

STEEL
(SAME GAGE AS FIREWALL)
1/2" RADIUS 1/2" R

EDGE MARGIN 2X
STAINLESS RIVET DIAMETER
STEEL GAGE RIVET P/N
HOLE REPAIR METHOD
. 016 3/32 MS20435M
MS20427M
(BLIND) NAS1398M
PATCH STAINLESS
--

STEEL
(SAME GAGE AS FIREWALL)

1/2" RADIUS

B
STOP DRILL
HOLE DIAMETER . 0937"

RIVET SPACING =

PARTS 6X RIVET DIAMETER

ORIGINAL

REPAIR PARTS

REPAIR PARTS IN CROSS SECTION

CRACK REPAIR METHOD

Figure 16-53. Repair of Firewall

Change 2
16-64 STRUCTURAL REPAIR 421 SERVICE MANUAL

NOSE COMPARTMENT WATER SEALING. (See CAUTION

figure 16-54.)
All surface cleaning and all sealing must be
When access panels have been removed or when re- done in a clean, well ventilated area. Take ·

pairs have been made in the nose section or water precautions to guard against sparks or open
has entered the nose compartment, it will be neces- flame in the vicinity of the aircraft at all
sary to seal the nose section in accordance with the times. Observe all safety precautions and
following instructions. regulations.

a. Seal all skin joints, rivets and stringersin nose

baggage and radio compartment by brushing the joints WARNING
with PR1422, Class A2 sealant, using a small paint
brush. Avoid excessive skin contact and prolonged
b. Remove nose access panel and seal with No. breathing of vapors of any solvent or seal-
5550 sealer. ant. Wash hands thoroughly after using
c. Detach nose cone or radome and seal all voids sealants or solvents before smoking or eating.
between nose cone or radome assembly, aircraft
skin and nose bulkhead using 576-1'sealer (Prestite- e. EC612 fillet sealant is applied along cracks,
Permagum). seams and joints, where sealant is applicable, using
d. Seal around pitot tube using No. 5120C sealant. a spatula or pressure extruder.
e. Seal around rivets and voids of cabin heater inlet f. Allow EC612 sealant to air dry until quite tacky
and nose section skin using PR810 sealant. to the back of the knuckles (15 to 30 minutes) and
f. Seal any opening, all voids in nose wheel well, then apply a coat of PR810 sealant over the entire
which might have water leakage possibilities using fillet of EC612 sealant, using a spatula or extrusion
PR1422 or PR810 sealant. gun.
g. Seal entire perimeter of all access panels using g. Apply PR810 sealant using a spatula, calking
No. 5550 sealer. gun, flow gun or brush along cracks, seams, joints
h. Seal voids around baggage doors, lower latch and rows of screws or rivets as specified.
assemblies, between lower doorframe channel and 1. When sealing is done before parts are mated,
aircraft skin with 576-1 sealer (Prestite-Permagum) use enough PR810 sealant to completely fill the joint
or PR810 sealant. and wipe away the excess after the parts are joined.
i. If baggage doorframe seal is replaced, use 2. Joints shall not be flexed until sealant has cured
ECß80 cement for sealant. to tack-free condition. Fillet seals shall overlap the
edges of all materials thinner than 20 and may or
.

may not overlap materials over 20 inch.

.

Preparations, Application and Procedures for Seal-

ants, Cements and Surfaces.
NOTE
a. All surfaces shall be free of dirt, grease, mois-
ture or chips at the time of application of sealants or PR810 sealant cures by solvent release.
cements. Length of cure period depends on air circu-
b. Metal surfaces shall be thoroughly cleaned with lation and temperature. Parts may be hand-
solvents such as Trichlorethylene, Stoddard Super led or installed after sealant has become tack-
Solvent or Methyl Ethyl Ketone (MEK). This is very free. The tack-free condition can be deter-
important for sealant and cement adhesion. mined by placing the knuckles firmly against
the sealant. When the sealant doesn't adhere
to the knuckles, the sealant is tack-free
NOTE (approximately 2 hours).

Do not use any of the above solvents on trans- h. PR1422, Class 2A sealing compound shall be
parent plastic surfaces. mixed per manufacturer's instructions on container.

c. Use a lint-free cloth for application of solvent

and another for wiping surfaces dry. Do not allow NOTE
the solvent to evaporate; the area must be wiped dry.
Blow faying surfaces free of solvent using filtered Mix PR1422 sealing compound in a wax-free
air. container and insure the two components are
d. Transparent plastic surfaces (windshield, win- mixed thoroughly so that the mixture is uni-
dows) shall be cleaned by wiping lightly with a cloth form in color. Care should be taken in mix-
or small paint brush saturated with Aliphatic Naph- ing to avoid incorporation of air by too rapid
tha (TT-N-95, Type II) or equivalent, and dry with stirring or folding action.
a clean cotton-flannel cloth.

Change 2
 421 SERVICE MANUAL STRUCTURAL REPAIR |-6

NOTE until quite tacky, but no longer transfers to the

knuckles when touched, (usually between 5 and 30
Mixed compound has a limited work life, mix minutes). Porous surfaces may require two coats.
only quantity of PR1422 sealing compound re-
quired to accomplish each sealing operation. NOTE

L Mixing temperatures for PRi422, Class A2 Use the back of the knuckle to touch the ad-
75°
sealant is to 40°F. hesive surface instead of fingertips to mini-
2. Sealant shall not be applied at temperatures be- mize contamination.
60°F 60°F.
low or to structure that is below
1. Place the two surfaces in contact and press
NOTE firmly together to insure intimate contact. If less
strength is required, only one surface need be coated
PR1422, Class A2 tack-free condition can be (the less porous), in which case, the drying period
determined by placing the knuckles firmly will be from 5 to 8 minutes.
against the sealant. When sealant no longer 2. One hour should be allowed before the part is
adheres to the knuckles, (approximately 30 handled. Very good bond strength is obtained if
hours), the sealant is tack-free. Final curing parts are allowed to set for at least 24 hours.
time of sealant is approximately two and one-
half times the tack-free curing time. All
clean up must be done before sealant cures. NOTE

i. No. 5120C sealer is furnished in extruded beads Rubber seal materials shall be prepared by
or ribbons and can be cut to size and placed by hand abraiding or roughening the surface to be
in area indicated. bonded to remove the surface gloss, then
j. No. 5550 sealer is furnished in cartridges, use solyent cleaned,
cartridge to apply sealer.

NOTE Sealant Materials.

If No. 5120C or No. 5550 sealers flow out a. PR1422, Class A2 sealant, PR810 sealant,
after joints are mated, wipe off the excess Products Research Company.
material. b. No. 5550 sealer, No. 5120C sealer, Schnee-
Moorhead Chemicals, Inc.
k. EC880 cement shall be applied in a thin even c. 576-1 sealer, Prestite Engineering Company.
coat to each surface to be bonded and allowed to dry d. EC880 cement, 3M Company.

SEAL ENTIRE PERIMETER

OF ACCESS PANELS
USING NO. 5550
SEALER

RH FORWARD AND > -

AFT ACCESS PANEL

NOSE ACCESS
PANEL

NOSE CONE (OR RADOME

PITOT TUBE AND CABIN BAGGAGE DOOR
HEATER INLET DUCT LATCH ASSEMBLY

Figure 16-54. Nose Compartment Water Sealing

Change 2
16 -66
STRUCTURAL REPAIR 421 SERVICE MANUAL

Pressure Drain Seals.

The pressure drain seals, located on the lower skin

of the fuselage, provide a drain should moisture ac-
cumulate between the lower skin and floorboards.
When the pressure cabin is in the unpressurized
mode, the seals will allow moisture to drain.

Removal of Pressure Seals. (See figure 16-55.)

Removal of the pressure seals is not recommended s

-

unless the seal has been punctured or the seal has

been damaged rendering it inoperative.
a. Using the proper size drill, remove rivets,
b. Remove seal and discard.

2
Installation of Pressure Seals. (See figure 16-55.)
3
a. Position seal in place.
b. Secure with proper rivets using good shop
practice.

CAUTION 1. Belly Skin 2. Retainer 3. Pressure Seal

Never insert a sharp object in drain hole, Figure 16-55. Pressure Drain Seals
this will puncture the seal.

Resin Selectron 5003 Comparable to MIL-R-7575

- -

Vendor: PPG Industries, Inc. , One Gateway Center,

Pittsburg, Penn. Attention: International
,
Dept.
a. Alternate: Hetron 92 Comparable to MIL-R-
-

7575 Vendor: Hooker Electrochemical

-
Co. ,
Niagra Falls, N. Y.

Luperson DDM -
No MIL specification -

Vendor:
Lucidol Division, Wallace and Tiernan, Inc. ,

Buffalo, N. Y.

Luperco ATC. Paste No MIL specification

- -

Vendor: Lucidol Division, Wallace and Tiernan,

Inc. Buffalo, N. Y,
,

Nuodex Cobalt Federal-

Standard TT-D-643 -

Manufacturer: Nuodex Canada Lmt. 34 Industrial ,

St., Toronto 352, Ontario, Canada.

Change 5
 421 SERVICE MANUAL STRUCTURAL REPAIR 16-67/16-68

DOUBLER

STOP DRILL
NAS1738B4-1 RIVET (TYP)
SKIN
CRA CK

. 25 (TYP)
RADIUS , 06 (TYP)

RL VO
ST FROM
WHERE CRACK MAY
OCCUR (TYP BOTH ENDS)

RIB

DOUBLER TO BE 016 x 1, 25 x LENGTH

.

AS REQUIRED 2024T3 ALCLAD

QQ-A-250/5. DOUBLER MAY BE
INSTA LLED INSIDE OR OUTSIDE OF SKIN

STOP DRILL BOTH ENDS OF CRACK WITH

, 098 DIA. DRILL (THRU SKIN ONLY) RIB
---SPAR

SECTION A-A
51342001

Figure 16-56. Typical Elevator Skin Repair

g
Change 12
 421SERVICE MANUAL ELECTRICAL SYSTEMs 14-31

Part Number Nomenclature

15 1. RV6NAYSD25A Volume Control -

Stereo
2. RV6NAYSD25A Volume Control -
Stereo
3. RV6NAYSD25A Volume Control -
Stereo
10 14 4. RV6NAYSD25A Volume Control -
Stereo
5. 060880-02TWA Transducer -
Dual
18 19 6. 55-4 Speaker
7. 060880-02TWA Transducer -
Dual
eeraeker&
00. 00 17D11 Aft PA System
10. AS-830H Stereo Tape Player
11. 7063 Sw Stereo Select
20 22 -

12. MOR-15-10 Resistor

13. 55-4 Speaker
14. 060880-02TWA Transducer Dual -

¯ 15. 55-4 Speaker

\¾Toc o ¢ M R A. 09T)
16. RV6NAYSD25A Volume Control Stereo -

17. RV6NAYSD25A Volume Control Stereo -

18. RV6NAYSD25A Volume Control Stereo -

19. RV6NAYSD25A Volume Control Stereo -

20. S-1232-10 Ckt Bkr Cab Fan

-

21. DS04-27-25S Recp Nose Bhd

-

22. IN3313 Diode (Zener)

23. 7777K1 Recp 100 V. AC
-

24. S-1102-1 Mike Jack Intercom -

25. VM911M-4 Intercom Call Lt

26, 470 r, 1 watt Resistor Intercom -

5 KO SYSTEMDr
F.S. 100.00 13
21
10
20 22

421 08421A

8
23

I i

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14-86 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

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Change 9
5-34 ausevnoNICS SYSTEMs 421 SERVICE MANUAL

264A18-P202-7 J28V DC (See Fig. 15-21A)

15-21G) RV264A18-P202-7 (See Fig. 15-5B) RD358C24 RD29A22-P95D {See Fig. 15-7)
(See Fig. RC30A16-P141-45 +28V DC (See Fig. 15-25)
' RP11A16-CB25- (See Fig. 15-7) RD29B22-P96D RD23A22-P94E (See Fig. 15-7)
RV1A16-P23-A +28V DC (See Fig. 15-2)
e8e FDig.
RV239A22-ANT RELAY K18-5 (See Fig. 15-7) RD25A22-P98E RD9A22-P931 (See Fig. 15-7)
15-15)
RV521A18-P343AA $(See Figure 15-13G) RD353A20 RD358A24 (See Fig. 15-21E)
RNB93A18 )(See Figure 15-29) (See Fig. 15-12) TN28A24-P91M
RA139A20 )(See Figure 15-10)
RN133A14-K PWR )+28V DC (See Fig. 15-4) (See Fig. 15-8) RD127B22-P102C RD127A22-P101A---(See Fig. 15-8)
RV46A14-P32-A )+28V DC (See Fig. 15-1)
(See Fig. 15-5B)---RD365A24 RD365B24 (See Fig. 15-5B)
RP12A16-CB24--- -RV253A18-P201-7 $+28V DC (See Fig. 15-21C)
RV227A14 $(See Figure 15-16)
RV239A22 $(See Figure 15-17)
28V DC(See Sec. 14, Sht. 8) < RV253A18-P201-7 §(See Fig. 15-21G)
SX128A18 (See Figure 15-13C)
RA102A20-J4-15 428V DC (See Fig. 15-10)
RP14A16-CB23--- ---SX119A18-P118-8 +28V DC (See Fig. 15-11)
SX128A18-P227-K (See Fig. 15-8) RD128B22-P102B RD128A22-P101B (See Fig. 15-8)
+28V DC (See Fig. 15-21G)
(ŠeeFig. 15-13C) P-373 (See Fig. 15-5B)---RD366A24 RD366B24 (See Fig. 15-5B)

RP15A16-CB17 RD120A16-P100-1 (See Fig. 15-8)

RD367A24 RD131A22-P101F·
C130A20-K16 311A16-P106-18 (See Fig. 15-19) RD131B22-P102-A RD117A22-P99S (See Fig. 15-8)
C55A18-P36-57 RD352A20-P69-I +28V-DC (See Fig. 15-6) Il RD126A16N RD118A22-P104J
28V DC(See Fig. 15-14) C68A20-K5 RD211A16-P76-18 +28V DC (See Fig. 15-20) RD119A16-P100-C RD367B24N 4|I

C133A20-P47-Z F100B18-P122-C RD367C24 (See Fig. 15-5B)

(See Fig. 15-13) F25B20-P49-K 25 F100C18-P123-B +2BV DC (See Fig. 15-26)
(See Fig. 15-14A) C298A24 F116A24-P121-U NOTE
(See Figure 15-5B) RD211A16 120000 1W
ON AIRCRAFT 421B0001 AND ON CONSULT
5 TN1A14 C250A20 (See Fig. 15-14C)
(See Figure 15-12) APPLICABLE ELECTRONIC WIRING BOOK
$ F17B20 TN56A18-PB812 f(See Fig. 15-12) FURNISHED WITH YOUR AIRCRAFT.
C200A18 (See Fig. 15-14C)
C200D20
RD27B22-P96C RD27A22-P95A See Fig. 15-7) RD364C24
RD129B22-P102D ---RD129A22-P101D
(See Fig. 15-7)
RD125A22-P104E RD123A22-P100E
( RD356B24 RD356A24 (See Fig. 15-21E)
(See Fig 15-12 i TN30A24-P91A RD364A24 RD109A22-P991

----C136A24-P121-B Sel HD6 Error Output

TN29A24-P91N (See Fig. 15-12) (See Fig. 15-26)
RD28A22-P95-B (See Fig. (See Fig. 15-26) 6209 1W
15-7)
(See Fig. 15-7) RD28B22-P96B.-...-- Bootstrap XMTR 26V400
"' 35 -----C51B24-P121-V
RD357Ii24 (See Fig. 15-26)
RD357A24 (See Fig. 15-21E) (See Fig. 15-26) ( C51A24-P36-52
10000 1/2 W (See Fig. 15-13)
311B24-RJB1-12-
C66B24-K16 Back Course
C125A24-Kl6--~
(See Fig. 15-14
RD31B22-P96A RD17A22-P93-S C11C24-Kl6
(See Fig. 15-7)( (See Fig. 15-7) .

5009 1/2 W (See Fig. 15-13)

Il RD26A16N RD18A22-P98-J (See Fig. 15-7) 39
il RD214B24N RD214A24-P74-K A/C Ground (See Fig. 15-18) CRS Sel Rotor Crd
il RD353B20N-------- ----RD353A20-P69-C A/C Ground (See Fig. 15-6) (See Fig. 15-26) F134A24-P123-38-(See
M820O 1W Fig. 15-26)
(See Fig. 15-7)§ RD19A16-P94 RD353A20-P69-C A/C Ground (See Fig. 15-6) ---F140A24-P121-c---- Nav. Rsve Rotor
(See Figure 15-21E)$ RD370A24 RD31A22-P95F (See Fig. 15-7) (See Fig. 15-26)
II RD353B20N 421-0001 TO 421BOOO1
RD353A20 (See Fig. 15-21E)

Figure 15-29. Radio Junction Box Terminations (Sheet 2 of 2)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-7

(See Fig. 15-1 C121B24-K16 ,C87A24-K8

G. S. Lockout Back Course (See Fig. 15-14)
(See Fig. 15-21C) RN36A22-P204-13 15-29) C121A24-P36-4 x C114A24
( (See
-

RN898A24 Figure
gRNB99B24-P337-14 -(See Fig. 15-139) BACK COURSE SWITCH
(See Fig. 15-13F) RN899B24-P337-1 \
' C29A24-P36-30 /C88A24-K8 '
C246A22 FF135C24-P123-35- + Right (See Fig. 15-15)
(See Fig. 15-14C) F135D24-P121-i- Sw. G.S. Int1k. Back Course C29B24-K16 -(See Fíg. 15-14)
C246A22-K22 (See Fig. 15-26) C-115A24
'
-

C100A24-K6 1 --RN201A24-P59-6 BACK COURSE SWITCH

C104B24-P47-H RN201B24-P58-A-
·

Dev Indt Right (See Fi 15-21

(See Fig. 15-14) + Right
C113A24-K8 RN1A24-P4-A -·---i

RN1B24-P13-16-AVert + Right (See Sec. 14, Sht. 8)

-

C75A24-K6 Pomter C89A24-K8 Right (See Fig. 15-14)

(See Fig. 15-14) + Right y +
(See Figure 15-29) RN898B24-P338-2 C244A22 (See Figure 15-14C) (See Fig. 15-14) LOC/VOR C11A24-P36-12 12
C11B24-RJB1-36---§÷ Right (See Fig. 15-14)

Vent Pointer + Left C12B24-K16 )4 Left (See Fig. 15-14)

(See Fig. 15-21)
' RN37A22-P204-13 RN898B24-P338-2-§ (See Fig. 15-13$ (See Fig. 15-14) LOC/VOR C12A24-P36-1
CC110051A2244--K467-D 33 P11 + C86A24-K8 + Right (See Fig. 15-14)
15-14) Left 4 Dev Indt Left (See Fig. 15-21)
(See Fig. +
% C112A24-KB C RN202A24-P59-7---g(See Fig. 15-4)
(See Fig. 15-14) + Left C76A24-K6 RN202B24-P58-B--JVert Pointer + Left
C248A22 RN2A24-P4-B (See Fig. 15-21C)
(See Fig. 15-14C) ÷ Left
( RN2B24-P13-17 ert Pointer + Left
C245A22 ---

RN898A24 $(See Figure 15-29)

(See Fig. 15-21A) +Left RN36A22-P204-12 -RN101A24-P7-A---\(See Fig. 15-4)

(See Fig. 15-14) + Right C102A24-K6 Q ---RN101B24-P20-16-JVert Pointer + Right rRV264A18-P202-7928V DC (See Fig. 15-21A)
(See Fig. 15-14) + Right C77A24-K6 RN203A24-P77-6--p(See Fig. 15-16) (See Figure 15-21G) RV264A18-P202- ----

16
(See Fig. 15-14C) ÷ Right C247A22-K22 RN203B24-P78-A---JDev Ind + Right
RN898B24-P338-2 C248A22 §(See Fig. 15-14C)
(See Fig. 15-13F) + Left
(See Fig. 15-14) ÷ Left C103A24-K6
(See Fig. 15-14) + Left ----C77A24-K€ Os rRN898B24-P338-2-
Vert PT + Left (See Fig. 15-13F)
(See Fig. 15-14C) + Left-----C249A22-K22 - -RN102A24-P7-B
-RN102B24-P20-17 (See Fig. 15-16) RV264A18-P202-7928V DC (See Fig. 15-21A)
(See Figure 15-14C) C249A22 (See Fig. 15-21G)' RV264A18-P202-7
(See Figure 15-29) RNB98A24 LRN204A24-P77-7 Dev Ind + Left RV46A14-P32-A $28V DC (See Fig. 15-1)
See Section 14 Sheet 8 RP1A14-CB20--
Vert Pointer + Left (See Fig. 15-131¶·RN37A22-P204-13 RN204B24-P78-B--&Vert Pointer Left
-

+
15-13F) RV101A14-P54-17--·§28V DC (See Fig. 15-15)
(See Fig. 15-14) Sw.(---C46A24-P36-47 (See Fig.
LOC/VOR 28V DC Sig. (See Fig. 15-13H)! RA201A20 RN218A14-P60-13--Í28V DC (See Fig. 15-21)
---C46B24-NAV SEL SW
(See Fig. 15-26)
-RN558A24-P123-5 4LOC Relay See Section 14 Sheet 8 RP2A16-CB19 RN33A14-K PWR---128V DC (See Fig. 15-3)
---C106A24-K6
-

(See Fig. 15-14) LOC Relay C11201A24-2P59-11

RR 24-P205 5e4vDevd
Ind + Downee(SFeeLFil5-2115-21F)
(See Fig. 15-21F)----RA210A20-P209-BB RV253A18-P201-7428V DC (See Fig. 15-21C)
(See Fi 15-13H)
RA259A22 RA3B24-P121-a-i + Down G. S. (See Fig. 15-26) (See Figure 15-29) RNB93A18 RN749A18 )(See Figure 15-13E)
(See Fig. 15-14)
Out 5 C99A24-P47-Y Q RA3A22-P97-3 (See Fig. 15-5) NOTE
Glideslope + Down -

(See Fig. 15-14) Glideslope i C127A24-P36-11 RA3B22-P4-C Horiz Pointer + Down

(See Fig. 15-21F)RRA210B22-P209-J RN645A24 $(See Figure 15-26) ON AIRCRAFT 421B0001 AND ON CONSULT
(See Fig. 15-13B) RA210A22 / APPLICABLE ELECTRONIC WIRING BOOK
(See Fig. 15-14) rRA4B24-P121-rd + Up G. S. (See Fig. 15-26) FURNISHED WITH YOUR AIRCRAFT.
Glideslope + Up Out -
C98A24-P47-Q Os rRA4A24-P97-4
)-Horiz
C126A24-P36-10 ---RA4B22-P4-D Pointer + Up (See Fig. 15-5)
(See Fig. 15-14) Glideslope 7 -

-----RA209A22 RN206B24 i Dev Ind + Up (See Fig. 15-21)

(See Fig. 15-13H) -RA260A22
RN644A24
RA15A24-P97-15 RP5A16-CB16 RD20A16-P94-I
RA15B24-P121-s--- Horiz Flag + See Section 14 -
Sheet 8 $(See Fig. 15-7)
(See Fig. 15-26) + G. S. Mask (See Fig. 15·-5) TN1A14-P89-C F17B20-P48-K
RA204A22 RA15B22-P4-G $28V DC (See Fig. 15-13)
(See Fig. 15-13H)( RA261A22 / (See Fig. 15-12) 28V DC --TN53A18 NAV SEL SW-
-

(See Figure 15-26){ RN643A24 | 10000 1 W $(See Fig. 15-5) TN56A18-P88-12---? RD352A20-P69-I---928V DC (See Fig. 15-6)
'-RA16A24-P97-16-- Horiz Flag (See Fig. 15-5B) RD211A16 RD211A16-P76-18 28V DC (See Fig. 15-20)
RA16B24-P121-t-
-

(See Fig. 15-26) -

G. S. Mask ·28V DC
----RA205A22 RA16B22-P4-H (See Fig. 15-5)
(Se e F ig. 15-13H)
---RA262A22 / LRN642A24 §(See Fig. 15-26)
421-0001 TO 421BOOO1

Figure 15-29. Radio Junction Box Terminations (Sheet 1 of 2)

Change 1
 421 SERVICE MANUAL ELECTRICAL SYSTEMS ÎA"ÎÎÎ
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14-118 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

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Change 11
14-116 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

REVIIIONS
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 421 SERVICE MANUAL ELECTRONICS SYSTEMS -$

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15-10 ELECYRONICS SYSTEMS 421 SERVICE MANUAL

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 421 SERVICE MANUAL ELECTRONICS SYSTEMS 15-15

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GROUND C

+LV A ----RD32AA2Z -PL9 6-

MV I B -RD330A24-Pt.9 3-
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MODULATOR ON-Cff D -RD332A24 -P71 C-
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BAND \ F --RD3%4AE4-P72 D-
SAND IL G - -ROS35A2A- P72 f.-
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-RO33f..A24.-P72 B-
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e GOADO 1NPUT28
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t. \OO CPS PLNT E M RO341 A24 - PG.9 F -
D GROUND
+ 100 CPS PLAT£ N RD342Ato-PG9 0-
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PLATE O , RD343A12-P71 A-
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LOOP ŸOBYTiON 4 RO3MA14 -PT 4 - CONIO 00TPUT \
LOOP RELAY R RDS%At4 -P7t F- 8 CONtO QUTPUT 2
GROUNO S RDS¾A24-P7D C- C SHIELD

--FD364A2.4 P700 Rosavcta-P<=9 13v100cest •

e \MS CONN -RO3¾A24 P23

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3 R 3/o7À2A PfDC -RD34 C GROUND
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RD354^24N H AIRERAMEGRouWo
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A
BAND 12 B -RO3¾A14-P73 H -
O
BAND SEL c
COM ---Ro34/oß24-P7O C-
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uuN 35979 COMM
BANDT D -RD334A24-PY3 F-
BAND E E ---RD335A24-PT3 G-
24(.30 18 DYNAW.RTER

2,818-0005 cow.

RDL53BloN tsD35tA24-P7o 8 AO v 100 CPS

SEEFIGL/REIS RB353A20-Pé9 C RD32AA22-P78 A- 6 +LV
ROSS2.A2D-PG9 I RDSE3A20----RIBl18- C GROUND
-RD337A24-P731 0349At4---P71 hA-- O POWER RELAY
--RDh37624-P71 E E 13v 100 CPS/N
.SE£FtGURE 15-37) ÑL Zd41f p-72
A
--RÐ35]C14 -970
A -Ros*\A14 -P73 M--- F I CRS PLATE
100
A-F PLATE A RD343A22-P73 O"-- ROS41A24---P73 4-
2699/-0500 UNIT- G + lOOCPS PLATE
CONIROL A-F GRID RD353At2-P73
B E RD350A24---P'N R--- M 43V ¡OOCPS
*

MODULATOR OM-OFF C RD 33tA24-P76 D- ly-¿7) RD352A20-RJBi 21---

(SEEF/GL/ÑE fi'Z3 A12--P73 Q I +LV
870 OM-OFF D RD340A24-P73 L 80330A24-P73
-
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13V IOOCPS¿.9° E fÑ3fdA2†--Pl.9 N -
/ ggg-diA24----P/3 C- W MV2
LOOPRY.LAN RD345A24-P-/3 R- AUDIOAMPMAI\NG CONM'
F u SO34M24-P71 P--- L PRASF.2 ON-OFF
+ LV LMAP R ÑL20f79 -PRE A -

GROUNO J RD ½roC24-P7o C-
R-F SENS K - li'Olif422 Pf3
- R-
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L
POVIER RELAN M -RO34GN24-PG9 D
421-0001 TO
-

Loon oosmos s esa e "a

-
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PHASE 2 DN-OFE P RD344A24 PG9 L-

13v 100 CPSLI_BO°
R -- Æ0777A2†-pm t¯-
og nn n
421A0001
UneUU U
@---soaswzo---os9 c-2 --RD353A20--PfiC-i
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(5EE DEti-2.?) g---Ro352Ato-m9 1- --RD352ATO--P69IB

(seersomys-a-, FL20AZ4----P72 AM
RL20A24 -P72A (
421-0001 TO 421BOOO1 (SEEFIGul2E ti-Z7) ÑZ3c2fZWP73 a-?
RD339A2di-P73J -4

coweicT vowES AS SMOWN

NOTE FOR NO. 2 AOF talSTL NMMUAMPhwT10GCOMM

CONNEL7
MigdAs
/ Skolux REN..2 Aermcrt
ON AIRCRAFT 421BOOO1 AND ON CONSULT
APPLICABLE ELECTRONIC WIRING BOOK
mmse
MF.
ËÛ
421A0001 TO 421BOOO1
FURNISHED WITH YOUR AIRCRAFT.

Figure 15-6. Cessna ADF 800 (Fixed Loop)

Change 1
15-8 ELECTRONICS SYSTEMS 421 SERVICE MANUAL

E7.340 1MO

---RO3tSEE-Raßt 28
GROUND
STATOR X B ---Reasar.I WAS\ 27
C -RO27621 RJO\ 26
gygyž;g, y
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--RD3tAZ2-PDEF- RO3tA22-RJ3128- F
RD26AiCM RDI7ALT-PD35-
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RDE9972-PSG D RDE9Att-PSED
--RD25A22-998E RO23Al2-PDA
-

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FIG.15-3f --RozoAm-pse i -

(SEE
CT
17985-- 0000 CABLE 455Y

-18000 Loop may,

(SE.E FIGn. 15-27) RLSA22- 997 A, Li90°

,-Ro3oA22- P95 E 4O V toc cPS
--RDI A22-PS3 A- a 41-V
\9A\G-9.JØl28- C GRD
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-RO23A12 R30\29- E 13V 100CPS LO"
-RDGA22-PS3 0- F Ì 100 CPS PLATE
(6EE- FIG- 15-11) RE29 P93 J, ,-ROT2At2-PS3M- \OO CPS PLME_ 2 30-0028 OYNAVERTER
G
RDERN21-PsS a N 13 V 100 CPS l. tro
-
-

JA AuOiO AMP MATMC Couw RD2DN<.-RJOi 2\ I *LY

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PHASE Ž ON-OFF

AF PLATV. A GROt4A22-PS3 o 994 \(./42 COMM

GROŒAtt-PB37..
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MODULNTbt OM-OFF C -RO4AIT.-PS3D ----

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SFO ON-OR
Lo•
D -

-RD26Az2-RJS\29
993 6 --

NOTE
ISV 10ccPS E
RO)&Ktt- 753 R
LOOP RELAY F -

L w -

ON AIRCRAFT 421BOOO1 AND ON CONSULT >••^

R-F SEMBE \0N22-PS3K APPLICABLE ELECTRONIC WIRING BOOK s,,,..,_,_,o ness-oooo SENSE ARTENNA
o ce TERM QABLE As%Y
POWE.R RELAY 2 FURNISHED WITH YOUR AIRCRAFT.
LOOP POSIT\ON u -Rosatt-Pos a -- Uce2.90 U LooP
26904--E00 CONTROL PWASE 2 ON-OFW P -RO22A12-P94 L ----
CONN LODP
/3 v too ces stro• R Ror4kt2-Por w
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Pas 175ta-ootoco

ROIAZZ-PPAS- (LV
RO2At2-POR J- B HVI
RLSatt-Ÿ98 M -RO3At2-PSA K- C HVE
+ LV LAMP A 9-L SA22-1 Ronzz- P98 c -
o MODLII.ATOR ON-OFT
BAND 1IE D -RDGAl2-993 w RorAt2-P980-- E /kF ORD
BAND SE-L COM f. -RDtBS12-POS J RO(.A22-PS7 D -- F SAND I
BAÑO Î. O --ROGA7.t-PB3 RD7A22-PS7 E- - G BAND TI
BAhlD E E -RO7At2-PD3a--- ,7 RosAzz. Por a --
e SAWom
20480-0028
RDSAtt-R334 29 i 13 Y 100 GPS L O* RCVR
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997 278tB-ooor CAM RaioAt7.-posa K RV SENSF.
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-
' -R.Ot2AZ2-PD4
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&
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M
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26891-7528
- -
-Ru3Att-PDA F U i 100 CPS PLATE.
coNTROL A---- AF PLATE
-ggggyz-pge
O
P
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F R LOOP
-RD AZZ-RJBt 28 S GaoumD
I
993 4G\\¶ COMM

421-0001 TO 421BOOO1

Figure 15-7. Cessna ADF 800 (Rotatable Loop)

Change 1
 421 SERVICE MANUAL ELECTRONICS SYSTEMs 15-18A

INDICAToA :Lt47e-oooo
AdBI
$-1347-1-10 TERM 4.gg
4 gg
ADF 1 i AoT IL Hi 6 --AD358C24 oToac
UG-290/ucen i JTAToA ( C ---RD354824
E A RD37eA24
I JTAToA y o --RD357014 A B---RD3545A4
i STAfoA 7. A--RD37eA24 No
y C-RD357BA4
7984- 2
00 CABLE ASSy
1 STATDA X N ----ROJ45824 F- RD3kk6
To J -RD3dfeB2
78 -O c5 C NM

SA o I-------- D ---RD334A24
SANPžr-
Lv LAMP- A (, RE3DA22
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RECEivER 8 -
RDIEBC24
34850- oxa N M--RD358CA4
X C--RD35(.824
I Ro3t.oß24N 766 1 L---RP37eA24
Y 0-RDIS7014
2TBIS-Oo q COM L A-AD370A14 K #---80336024
- i Y P--RD357824

UCRD340A14- AMPICS-
I GRO N
LV LAMP -
N -AL2ûß24 --

kF PLATE- I .2-

A-YGRID----- 8-PSTITI27

Moc oN-OFF- C-??"?I.M

BFO ON-OFF D--RD340A24
LooÞ RELAY- r ":3 fi 424. D RM
R-F K I E
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c Ro 35461#
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---

2 oN-OFF- P-80549A24 Y D--Roasys2‡

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--
L
f3V foo~Ágo'- W
RD358B24
13V foo LD*--- E RO337A24 Î
+LV e - i;JE .

WV I J ---RD330A24 C
HV2 x -RD55tA14 Q CATpA 310
F- LIII?21 AD370A2.4
±100 PLATE
L- G --RD342A24 STAToR RD35GO24
40V ioov /_to" -
A -RD371A24 RDSETB24
GROUNo- c-RD363AIGW | R070A H AD350c24
+Lv Soonce I o

1449:coNN

-12D20Alto

I RD355620N- -RO353A20
) CABLE ASSy
-RD354A24 --- --

-RD35M24 ----

( ACC UNif
3t»B20-oDOO
TABLE I TERM. CORÑS. FOR Acy
-RD358A24-
WIRE TCP LOOP SoTToMLooP
COLOR TOP 30T Top ger
RJS I BODY TCR SENSE SENSE SEN3E SEN35
3v 1004 I GY BLK 18 16 l9 ¡q
40 V içQ. SAN SLK 19 19 Ig ¡g
ROTOR C RED BLK 22 23 23 22
BRia BLK 23 22 22 23

OTOR y

LoDP AN 39

GRO HD - ---
D D

NOTE 421A0001 TO 421B0001

32803 CAŠLE ASSY -¯~

ON AIRCRAFT 421B0001 AND ON CONSULT

-

APPLICABLE ELECTRONIC WIRING BOOK

COUPLED WITH RA-21C. FURNISHED WITH YOUR AIRCRAFT.

-i i miimimiiii- IIII I-IIII I I----

Figure 15-13A. Cessna 800 ADF

Change 1
 \
5-188 ELECTRONICS SYSTEMS 421 SERVICE MANUAL
. I

S-1367-1-IO TEÑTi
414-( M
RDOI 4M-20 GY S-ts&7-t-lo TEûM

C A RD37aA24 --AD358C24
I AoTOA Hi US-290/uf.ONN
e B-.-RD558c14
t STATon y C--Ro354024
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JTATom Y o WITH RA-21C.
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i -Romf7824 COUPLED
o coi e 7ez'4 COUPLED WITH RA-21B• 57984- OO CAOLE ASSy
c F----Ro3<.7C24 F--RD364C24
RotoA. Hi
N H --"

1 STAToA x N ---Ro]Cro24
2 STATOA Y J --A0346824 7904- 78tB-
--RDWAGOli CABLE AssY 5 Conn

278ID-ooosconN oNynã¯umt

AMPff,f-ifrCoAIN
--
SENSE ANT 26991-m28

cournot¯ünt l(el15 CoNN

S'--RD33&A24 SA.ND JIr SANP2r E Typ

BAND
D -RD334A24 r ßAND I Lv LAMP---- A
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BAND 27 E -Ro335A14 6 BAtto 2E BAND SEL.co -
C
RL20A14 R23oA22 0 TEL RECEivER
roa. 17310-00 EpL 34650-00&&
2 M RD3&oß2‡¾-
RDISBC24 ÑdBI O D Con ---
D o 4 I TSC
--

RD370A2.4 2Tois-
c -- Ro35G 624 STAroR RD 56814
- --Â RECETVER 00/4 CONN
34e350-0028
----Ro36ooz4N
AeroA NO N -40560A24-

AMPIGS-loX -

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A-F A-F PLATE floD ON.f ry
PLATE A
A-& GRin A-E GRID B¶D ON-OFF
11
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I BFo oN-OFF R-F enn.

GFD OH-0WW
LOOP RELAY I LOOP RELAY Loop ,

o ATo
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R-y SE.yg f3V foo ¿p' R -RD3 7824 RD359A24N
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3--RG365 24 13V IDOrvla -RÞ&37024 RD359A24H- f2 ON-GFF- P-RD549A24
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5 GROUND
POVER AELAY-- M-RD34GA24-
903f.fe61# 13V 10com
C --
N--RD356024
D-AD3fsAC.24 jó1 0N-OFF RD349A34----
P---RD357824 0340A24-
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16742 CONN
ARCIB39t.
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OWER RFLAY c f3V 100 •-
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2 ON•OFF L e /
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IIV IDow k RD3{,4814 + LV B -RD329A22
lŠV Ico/v E -8033TA14 I A3V10 IVA "Vi 'SUS
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Hvi a -Ro35oA24 i loo

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F --QDI4'B.1
PLATE
HV2 K--RD33IA24 HV2. L- G-RD342A24
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fr
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roturrR X B-RossusA4 40V Joorvli ' ^ -R 3elA14 +LvSoonce- I
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y C-RD357BA# GRouHO D
SproAR D-RD358C14 +LV SouRCE I--RD2llAI(, -

)t E--RD3f.5624 60Nio:NPUT1
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y RD3i.4614
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ToAC & ,.-- 33786-00,0 CASLF ASFY -RD35feA24

-RO357AP-4 ----
ACC UNJT
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IG74J COWN -Ro358A24--
GONio OUTE
CONH -/5 GOWlO OUT I
icob RJSI

TABLEI ENWS
TERM.COWNS.FOR ADFI
TABLETE TERMCONNS. FOR ADF2 EcT I 5 13v

WIRE TCPLDOP 60TTotatooP 42/A000tjeu

WIRE TOP LooP SoTTOMLooP 403a2Ato
SOCOLOR ToP coy Top ger AOLOR yep 8 MA0TO
R
ggg ggy 24
SENSE SENSE
SrNSE SENSE BODY TCA SENSEj SENSE SENSE NSE M3;fi ( 10 XSTA

GRN
GRN stK 16 e6 ir - RCHOU.! li Y STATON
RE
GY BLK $7 gy 78 rypwrrgig ggyATÖR LOOPAN 43
2 3 2 2
SRT* OLK 23 22 22 23

o A A SHIELD
LooP IA B B G ** IN lA LOOP 2A
LDOR28 C GONIOIN28 L-‡OS
GROUND D D SNIELD I
NOTE 'oop , e r ses,o ts se a2eos cAúLE ASSY - --

I LOOP2A F GoNJ©lN24
DL -
o _e
-
421A0001 TO 421A0050 ON AIRCRAFT 421BOOO1 AND ON CONSULT azeos cAßLF ASSY
APPLICABLE ELECTRONIC WIRING BOOK ADF 2 ADF 1
421A0051 TO 421BOOO1 FURNISHED WITH YOUR AIRCRAFT.

Figure 15-13B. Cessna 800 Dual ADF

Change 2
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-Ñl

RED RED I

2 1 Part Number Nomenclature

WH/TE h///lTE
I 1. 1820 Lt -
Seat Belt Sign
2. 1820 Lt -
Seat Belt Sign
3. 1820 Lt -
Oxygen Sign
-

4. 1820 Lt -
QKygen Sign
SPI 5. MST-205N Sw -
Seat Belt Sign
6. MST-205N Sw -
OKygen Sign

ELAC BBC y \D\¾¾ASLE \WIER\oR. LTSf

4 3
L 6R2O WHITE WH/

SP/

LS35/120 L5tBAZO

¯¯¯1
- - -
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No
-

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c C c C I Ne o i
--

I_ ____-_.a L528B20

LS2;A20 LS28B20
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ES3/4A20
Ce O

SPi
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sPI 2 1
WH/T£ RITE
WHTE
LS35A2D
w/4/7£
REF STD VV1RIN6 DIA6RAM
DIMMABLE (NTEKlOR LTS ) 421BOOO1AND ON
Ft)K OPT PlfléUP POINT 3LACK ---SLACK
CONTRACT NO. IN
MILITA Y D VistoN

DATE C - WlCHITA.KANSAso1201

TITLE:
DRAWN WIII TAJAN -··

•·°ue
Au skßf OXYGEN¢ SEATSBELT LTS .-

esses
y WIRINGDIAGRAM --

STRESS (OPT) SEATS -

S E Co70E IDE o. DRAWlNG Not

oTHER I 84 5 5 i
scALE: gdjVS REF SHEET / Ûf /
14-92 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

Part Number Nomenclature

1. 7277-2-5 Transfer Pump LH Ckt Bkr -

2. 7277-2-5 Transfer Pump RH Ckt Bkr - -

3. 7277-2-5 Eng Gage LH Ckt Bkr -

4. 7277-2-7. 5 Radio Lts Ckt Bkr -

5. 7277-2-5 Copilots Lts Ckt Bkr -

6. 7277-2-5 Prop Synchro- Ckt Bkr

exu 7277-2-7.5
40 42 7. Gyro INvr 1 CktBkr
39 41
-

i , sana 8. 7277-2-7.5 Gyro Pwr 2- CktBkr

--

9. 7277-2-7.5 GyroPwr3 CktBkr -

10. 7277-2-5 Turn& Bada 1 CktBkr -

11. 7277-2-5 Turn& Bank 2 CktBkr -

12. 7277-2-15 Cabin Fan Ckt Bkr -

43 44 45 46 13. 7297-2-15 Air Cond Ckt Bkr -

14. 7277-2-5 Trim Pwr Ckt Bkr -

15. 7277-2-5 Stereot- Ckt Bkr

16. 7277-2-15 Elec SèatLH Ckt Bkr -

17. 7277-2-15 Elec Seat RH Ckt Bkr -

1 2 3 47 48 49 18. 7277-2-10 Conan 1 CktBkr -

-esr.o

19. 7277-2-10 Comm 2 Ckt Bkr -

20. 7277-2-10 Corun 3 CktBkr -

21. 7277-2-7.5 Nav 1 Ckt Bkr

-

' 7277-2-7. 5
4 5 50 --ss
,, ___
22. Nav 2 Ckt Bkr
-

23. 7277-2-5 Audio Amp CktBkr -

24. 7277-2-5 Mkr Ben Ckt Bkr -

25. 7277-2-5 ADF 1 CktBkr -

7 8 9 10 ll 26. 7277-2-5 ADF 2 Ckt Bkr -

a6°6 a = - , 27. 7277-2-5 Glideslope 1 Ckt Bkr -

o o' 28. 7277-2-5 Glideslope 2 CktBkr -

29. 7277-2-7. 5 Autopilot Ckt Bkr -

12 13 14 15 16 30. 7277-2-5 DAIE Ckt Bkr

17 -

es,oe asio9 e sano e i 31. 7277-2-5 Troasponder Cki EBO: -

32. 7277-2-5 IUJI1 CktBkr

-

33. 7277-2-5 Raßar CktBkr

-

34. 109-230-101 Av0 Lav 1 CktBkr -

18 19 20 21 22 23 I 35. 109-230-101 100 hiv 2 CktBkr -

s s s 36. 7277-2-5 Radio Alt Ckt Bkr -

37. 7277-2-5 Shaver Inv- Ckt Enn:

38. 7277-2-7.5 Cigar Lighter Chi Bkr -

24 25 27 39· 112-205-101 Strobe Lt- Ckt Bkr

26 28
°s
40. 112-205-101 Anti-Co11Ben- CktBkr
41. 112-205-101 Nav Lts -

Ckt Bkr
42. 112-205-101 Taxi Lts- CktBkr
i 43. 112-205-101 Stal & Vent1Ieat Ckt Bkr
29
-

i 30 31 32 33 44. 112-205-101 Deice Lt- Ckt Bkr

45. 112-215-101 Prop Anti-Ice Ckt Bkr -

46. 112-205-101 \VindshieklAnti-Ice Ckt Bkr -

i 47. 112-215-101 Cabin Heat- Ckt Bkr

34 35 36 3 48. 112-507-101 PitotHeat1 CktBkr -

49. 112-507-101 PitotHeat2 -

CktBkr
50. 7277-2-10 Ldg Lt LH -

Ckt Bkr 421BOOO1 A10D ON

L

, SIDE CONSOLE (oPT)

cooK iornt. No. onAwmo No

-pg D 71379 SI IS4 5 ta

m=L MONE nar wari y 1
 421 SERVICE MANUAL ELECTRICAL SYSTEMS l("$Î

TB
nry merzrast, Part Number Nomenclature
RE 35 A22 3 TD W/2/MG D/4GRR/1
Dio y Doo 1. DD-505 Audio Amp Connector
L.MPEOESTAL- 2. 55-4 Speaker Aft P.A. & Stereo
-

43B2 3. 55-4 Speaker Aft P. A. & Stereo

-

--RasseAza----ci BLK 4. IN2482 Diode Boom Mike

-

4 RED
7 5. IN2482 Diode Audio-

EF £7Amo 6. IN2482 Diode Audio-

ei 7. C596503-0102 Boom Mike

5 WMNIlió
a 0422
8. 5-13-B Boom Mike Jack -

9. 4709 1 Watt Resistor Intercomm -

10. S-1102-1 Mike Jack Intercomm Passenger

11. 17-1030 Recept Annunciator
-

12. 17-20370 Plug Annunciator

-

13. 5618009-1 Annunciator Assy

R2532A22 e 14. 5072422-1 Booster Amp
15. 126-222 Plug Booster
-

Amp (P. A. )
16. F8WP Speaker Fwd P. A. -

BOOM MIKE 17. C596506-0101 Speaker Aft P. A. -

RE53/C 22. REGI4-A21N

----RES3/B22 RF5/7A22 N j i

AFT P. A.

TB
1
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INTERCOMM
AFT P. A. (OPTIONAL)

421BOOO1 AND ON
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8 RT547820 ----
36 DATE

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EXT RA., /A/TERCOMM AFT P.A
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F

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D 71379 : 5\l8452
,15

EXTERNAL P. A. scate. SHEET

.

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REF jQ¶

Change 4
14-88 ELECTRICAL SYSTEMS 421 SERVICE MANUAL

sT42 Part Number Nomenclature

RED--LEO3BEC
no -
1. 9910077-9 El Pnl -

Aft CB Cons
2. 9910077-11 El Pnl -

CB Cons
1 2 3 4
¯

18 19 20 22 23 3. 9910077-12 El Pnl SW CB Pnl

21 -

4. 9910077-10 El Pnl -

Upper Sw Pnl
L- 5. 1-203739-6 Recept Fwd Side Cons
-

6. 1-203735-5 Plug -
Fwd Side Cons
7. 9910077-13 El Pnl -

LH Fuel Select

9910077-15 El Pnl -

LH Aux Fuel Select

8, 9910077-14 El Pnl -

RH Fuel Select
\ or
9910077-16 El Pnl -

RH Aux Fuel Select

27 RH PE ESTAL TERM AL SitRP(REL 9. 9910066-17 El Pnl -

Manual Gear Ext

r-
24 17 or
87 18 El Prn1 Wing Locker Fuel
10.
11. 1625R12 Recpt
ELO
12. 9910077-19 El Pnl Manifold Prews Chart
-

7 8 9 13. CM2990-2 Post Lt Press Rate Control -

"°3
14. CM2990-2 Post Lt Vacuum Gage -

15. CM2990-2 Post Lt Cabin Rate of Change-

16. CM2990-2 Post Lt Differential Press

-

EL 3 L 4 EL 7 15 17. CM2990-2 El Pnl Radio -

18. 9910077-5 El Pnl Master Sw Pnl

-

(0 MABLE 3TA
EL 5 ELl EL S
REF STD uhRING PNL L78)
19. 9910077-4 El Pnl Cabin Press-

2' 20. 9910077-1 E1 Pnl Ldg Gear Sw

-

-- 21. 9910077-7 El Pnl Flap Indicator

-

sovAeo RED
11 ¯ 22. 9910077-8 El Pnl Indicator -
Guard
10 12 23. 9910077-3 El Pnl CabinHeat -

24. 20416 Recpt

25. 20416 Recpt
26. RC42GF182K Resistor
oc sanzo 27. RC42GF272K Resistor
28. 5118486-1 Lt Assy Voltmeter -

L502A2D REF STO ÐlbkABLE

EMS. lA)4TR. LiaWT3

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Change 4
14 -110
ELECTRICAL SYSTEMs 421 SERVICE MANUAL

INo
ZONE LTR O DATE APrnovEu

OPT Avio c4 Su c .T nos

L.fi/EL PVMP
LTS
24 66 18 158 13 - -
RADAR R. FUEL PUMF F P

21

CD LDT L. AUX PUMP L S ELS BEACON

AC R
IN VERTR (OFT) I
SS fl 68 4
6820 ßbt6 68 11
NVERACUR EIGA CLABN
NAV LT
UM A ICE

6 0 66
1

LDT ELEC L.LANDING

L FUEL ST TA I LT.

FL LLM/DING
EL
- ŸlAAI
STEffD
EA

ßß21 [5615
REF ScotBIDL

REF SMS4(.1 55C.\ psast,to

5.4 E C.DMSOLE S E. C31 SOLE > N 10

REF LWR TRri. ßbâRO
suaso,oO-psssc.2o CRs en

PS5A20 -
7 P55820
PlFI4
ccA
c ucysa sa LT ss PS
rate =we
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REF LHT ô0 PIElO
8830

PIGIO -- -- -

PTO\C4

REF 5(.,\bt.04

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PicA p as
EEF 187 5.00
REC

P D+ PIBG -5

REF SHT LOD

AIRCRAFT
MtLtYA a TWI DIVISION

g co- wicuiva.nAnsAsevao!

OWER DIS7RIBUTION SUS

WIRING DIAGRAM
BIEE CODE IDEMr. NO. DRAWING No.

D 71379 : 5 I \ 8 4 2 O
scALI. No Nr ner sneer 6.00 OF 15.00
c....4,.........,

Change 6
 421 SERVICE MANUAL ELECTRICAL SYSTEMS 14-109

. - AWMTFIX

SLDE OLTMun Moa>iyOR

CONSOLE.
2o P4 11 Paw-
-Reo- MTi
PbtMD PS7AL
Ato e Pi thron 3A

po arc. JPT -
a ¯

Assy
R4 OtSTRIBulloM s
-----
210
1
FotB2o- PS

ANN N TOR
4 15
LE
D CONN. Y D
ND
42f Bogo AWD ON
LRT Eu ALT
LP

5AI

tierna 5610- -P Ato - -

3Cs ric

CS LD 28It
F LD

P4
REF 5118438
HERY BA
:
EL 5 LD 5 CH

Di rov CLE

av FL
ELA1