Cessna Nav-O-Matic 400A Service Letter

Brand: Cessna

Model: Nav-O-Matic 400A

Type: Service Letter

Cessna.

TAKE

YOUR

CESSNA

HOME

FOR

SERVICE

AT

THE SIGN

OF

THE

CESSNA

SHIELD"

SERVICE

LETTER

MARKETING

DIVISION

*

CESSNA

AIRCRAFT

COMPANY

WICHITA,

KANSAS

67201

·

CABLE

ADDRESS

/

CESSCO

WICHITA

August

18,

1972

SUBJECT:

400A

AUTOPILOT

MOISTURE

SUMP TNSTALLATION

AIRCRAFT

AFFECTED:

Those

below

which

are

equipped

with

400A

Autopilot

thru

310Q0463

thru

340-0051

thru

401B0215

402-0001

thru

402B0216

414-0001

thru

414-0262

421-0001

thru

42130232

REASON

FOR

LETTER:

A

moisture

sump

has

recently

been added

to

the

static

system

for the

400A

Autopilot

computer.

This

change

is

designed

to

prevent

moisture

from

accumulating

in

the

com-

puter

altitude

chamber

and

causing

erratic

altitude

hold

operation.

A

Service

Kit

(SK421-46)

has been

developed

for

incorporating

this

same

moisture

sump

on

earlier

in-service

aircraft.

ACTION

REQUIRED:

For

owners

who

have

experienced autopilot

pitch

stability

problems,

it

is

recommended

that

SK421-46

be

installed

at

the

next

convenient

inspection

period.

PARTS

INFORMATION:

SK421-46

can

be

obtained

through

the

Cessna

Dealer

Organization

at

a

suggested

list

price

of

$3.10

(A).

REMARKS:

While

the

above

change

is

a

beneficial

improvement,

proper

service

and

maintenance

continues

to

be

the

most important

means

of

insuring

maximum

performance

and

reli-

ability

of

the

autopilot

system.

As

an

additional

aid

to

service

personnel

in

maintaining

the

400A

Autopilot,

a

Troubleshooting

Guide

has

been

attached.

This.Guide

provides

up-dated

troubleshooting

and

servicing information

which

can

be

used

in

diagnosing

and

correcting

problems

in

the

field.

This

information

should

be

inserted

in

the

400A

Autopilot

Service/Parts

Manual

in

place

of

existing

corresponding

pages.

The

Service/Parts

Manual

will

also

reflect

these

changes

with

the

next

revision.

(Owner

Notification

System

-

No.

1)

ALL

PRICES

SUBJECT

TO

CHANGE

WITHOUT

NOTICE

**

*******

THE

CESSNA

AIRCRAFT

COMPANY

THERE

ARE

MORE

CESSNAS

FLYING

THAN ANY

OTHER

MAKE

310P0001

340-0001

401--0001

I

Section

V

|

SECTION

V

Maintenance

5-1.

MAINTENANCE.

5-2.

TEST

EQUIPMENT

AND

ACCESSORIES.

This

section

contains

maintenance

information

for

the

400A

Nav-O-Matic

autopilot.

Included

are

a

list

of

test

equipment,

system

performance

and

adjustment

procedures,

mechanical

inspection

pro-

cedures

and

removal

and

replacement

procedures.

The

following

test

equipment

is

available

from

the

Cessna

Dealers

Organization,

in

addition,

a

Ballan-

tine

Model

300H,

vtvm,

a

Hewlett-Packard

Model

412A

vtvm,

a

Triplett

Model

630

vom,

a

water

ma-

nometer,

and

a

well-regulated

14

or

28

Vdc

power

supply

rated

for

10

amperes,

minimum,

should

be

available

for

use.

Equivalent

equipment

may

be

substituted.

TABLE

5-1.

TEST

EQUIPMENT

Name

SK421-31

10182-045

or

10182-033

400A

Nav-O-Matic

Test

Unit

Assembly

Omni

Deviation

Simulator

Test

points

and

test

signal

inputs

and

interconnecting

cables.

Supply

VOR/LOC

and

GS

error

sig-

nal

for

bench

test.

Gyro

Test

Table

Position

attitude

gyro.

Measure

actuator

clutch

torque.

28953

SK402-22

Adapter

(Torque)

Connector

Kit

5-3.

PERFORMANCE

TEST

AND

ADJUSTMENT

PROCEDURES.

Generally,

the

400A

Nav-O-Matic

units

are

ready

for

installation

if

all

the

adjustments

outlined

in

Preinstallation

Adjustments,

paragraph

2-1,

can

be

accomplished

In

the

event

that

operation

in

the

air-

craft

is

unsatisfactory,

the

best

method

for

trouble-

shooting

is

by

substitution

of

units.

When

trouble-

shooting

the

system

or

individual

units

on

the

bench,

the

information

in

Table

5-2

may

be

used

as

a guide

Couple

torqometer

to

actuator

clutch.

Permits

computer

amplifier

assem-

bly

to

be

extended

from

mounting

to

cabin

area

for

adjusting.

for

locating

the

trouble.

Possible

causes

are

not

limited

to

those

outlined

in

the

table

and

in

most

cases

the

aircraft

wiring

or

rigging

may

be

included

in the

list

of

possible

causes.

Bench

tests

may

be

accomplished

with

the

use

of

the

test

equipment

listed

above

when

interconnected

as

shown

in

Figure

2-1.

Location

of

computer

ampli-

fier

electrical

adjustments

are

shown

in

Figures

6-3

through

6-8.

5-1

Qty

Part

No.

1

1

1

Use

10182-041

Snap

On

TQ

1

1

Torqometer

Cessna

400A

Nav-O-Matic

Autopilot

TABLE

5-2.

TROUBLESHOOTING

GUIDE

PROBABLE

CAUSE

CORRECTION

GENERAL

ALL

SERVOS

DEAD

AUTOPILOT

WILL

NOT

ENGAGE.

NOTHING

HAPPENS

WHEN

EN-

GAGE

SWITCH

IS

ACTUATED

AIRCRAFT

WILL

NOT HOLD

STRAIGHT

AND

LEVEL

WITH

AUTOPILOT.

ERRATIC

PITCH

AND

ROLL OPERATION,

AUTO-

PILOT

ENGAGED

AND

ON

BASIC

GYRO MODE.

AIRCRAFT

SLOWLY

ROLLS

OR

PITCHES

-

DOES NOT

HAVE

ATTITUDE

REFERENCE

AUTOPILOT

ENGAGE

SWITCH

WILL

NOT

ENGAGE

-

ROLL

AXIS

ENGAGES

AND

PITCH

SYNCHRONIZES

AND

ENGAGES

K-4

relay

in

computer

defec-

tive.

Faulty

switch

or

circuitry

in

control

unit.

Gyro

switch

on

back

of

control

unit

positioned

wrong.

Defective

attitude

gyro.

Autopilot

disengage

switch

on

pilot's

control

wheel

or

asso-

ciated

wiring

is

defective.

Refer

to

Figure

6-1,

A-2

relay

module,

replace

K-4

relay

or

A-2

relay

module.

Refer

to

Figure

6-5

and

6-6.

Re-

pair

or

replace

control

unit.

Position

switch

on

back

of

control

unit

to

"IN".

Replace

attitude

gyro.

Refer

to

applicable

aircraft

ser-

vice

manual

and

verify

the

dis-

connect

and

its

associated

wiring

is

good.

±6

Volt

monitoring

circuit

in

autopilot

control

unit

is

mal-

functioning.

Refer

to

Figure

6-6,

A-7

power

supply

and

troubleshoot

or

re-

place

autopilot

control

unit.

AUTOPILOT

ENGAGE

SWITCH

WILL

NOT ENGAGE

-

ROLL

AXIS

ENGAGES

-

PITCH

AXIS

WILL

NOT

ATTEMPT

TO

SYNCHRONI

Z

E

AUTOPILOT

WILL

NOT

DISEN-

GAGE

WHEN

DISENGAGE

SWITCH

ON

PILOT'S

CONTROL

WHEEL

IS

ACTUATED

ERRATIC

PITCH

AND

ROLL

OPERATION. AIRCRAFT

ROLLS

RIGHT

AND

PITCHES

DOWN

ABRUPTLY

10

Volt

AC

power

supply

in

computer

is

malfunctioning.

±6

Volt

power

supply

in

com-

puter

is

malfunctioning.

Defective

disengage

switch

or

circuit.

Faulty

disengage

circuit

in

control

unit.

Defective

pot

in

computer

amplifier

power

supply

±6

volt

circuit.

Refer

to

Figure

6-1,

A-7

power

supply

module.

Troubleshoot

and

repair

or

replace

A-7

power

supply

module.

Refer

to

Figure

6-1,

A-7

power

supply.

Troubleshoot

and

re-

pair

or

replace

A-7

power

sup-

ply

module.

Refer

to

applicable

aircraft

wir-

ing

diagrams

and

repair

switch

or

associated

wiring.

Refer

to

Figure

6-5

and

repair

or

replace

control

unit.

Refer

to

Figure

6-1,

A-7

power

supply.

Replace

defective

pot

or

repair

and

replace

A-7

power

supply

module

card.

TROUBLE

COMMON

TO

ACTUATORS

TORQUE

NOT CONSTANT

WHEN

AUTOPILOT

IS

BEING

OVERRIDDEN

Clutch

washers

dirty

or

worn.

Clutch

faces

dirty.

Clean

and

adjust,

refer

to

Section

2.

Clean

with

Trichlorethylene,

refer

to

Section

2.

Clutch

spring

defective.

Overhaul

or

replace

actuator,

refer

to

Section

2.

TROUBLE

5-2

TROUBLE

FUNCTION

WILL

NOT

ENGAGE

AND/OR

NULL

OUT

PROPERLY

PROBABLE

CAUSE

CORRECTION

TROUBLE

COMMON

TO

ROLL

CHANNEL

Defective

roll

actuator.

Overhaul

Roll

actuator

follow

up

pot

out

Defective

control

unit.

Attitude

gyro

defective.

Refer

to

computer

amplifier

out

of

ad-

channel

adjustment

procedures

Check

null

voltages

as

necessary.

Repair

or

replace

control

unit.

Replace

altitude

gyro.

ROLL

MODES

FUNCTION,

BUT

ARE

SLUGGISH

OR

ERRATIC.

EXCESSIVE

ROLL

OSCILLATION

WHILE

FLYING

BASIC

GYRO

OR

HEADING

MODES.

(AIRCRAFT

REQUIRES

MORE

THAN

5

SEC-

ONDS

TO

ROLL

LEVEL

FROM

A

25"

ROLL

COMMAND.)

Low

Roll

actuator

slipping

at

low

torque

Refer

to

applicable

aircraft

vice

manual

and

adjust

cable

for

proper

tension

Refer

to

Table

2-1

and

proper

roll

actuator

clutch

torque

setting.

Refer

to

Section

2,

alignment

procedures

and

align

Defective

rol

1

Check

A-3

and

A-1

ROLL

MODES

FUNCTIONING,

BUT

AIRCRAFT

BANKS

MORE

OR

LESS

THAN

25

°

WHEN

TURN

COMMAND

KNOB

IS

FULL

LEFT

OR

RIGHT

OR

TO

INTERCEPT

A

NEW

HEADING

IN

HEADING

MODE"

ROLL

COMMAND

INOPERATIVE

HEADING

MODE

INOPERATIVE

Def

Heading

engage

switch

or

cir

ruitry

in

control

unit

inopera-

tiv

e.

Refer

to

Section

2

and

perform

in

-flight

adjustmentof

bank

angles.

Repair

replace

Control

unit

Repair

or

replace

control

unit.

Defective,

dir

ectional

gyro.

Heading

selector

inoperative.

Defective

computer.

Check

heading signal

fr

om

direc-

tional

gyro.

Repair

of

replace

as

necessary.

Check heading

selector

and

associated

wiring.

Check

A-2,

A-3

and

A-1

module

cards.

Repair

or

replace

as

necessary.

HEADING

BRACKETING;

AUTO-

PILOT

CAUSES

THE

AIRCRAFT

HEADING

TO

VARY

±2

OR

3

DEGREES

FROM

THE

SELECTED

HEADING

Computer

out

of

alignment.

Realign

heading

demod

and

head-

ing omni

circuit

in

the

computer.

5-3

I

Cessna

400A

Nav

O-Matic

Autopilot

PROBABLE

CAUSE

CORRECTION

TROUBLES

COMMON

TO

PITCH

CHANNEL

AUTOPILOT

PITCH

AXIS

WILL

NOT

ENGAGE

-

ROLL

AXIS

EN-

GAGES

AND

PITCH

AXIS

AT-

TEMPTS

TO

SYNCHRONIZE,

BUT

COMMAND

WHEEL

RUNS

TO

UP

OR

DOWN

STOP

Pitch

actuator

is

not

centered

properly.

Pitch

actuator

follow

up

pot

is

malfunctioning.

Refer

to

pitch

actuator

-

center-

ing

adjustment

procedures

and

center

actuator.

Repair

or

replace

follow

up

pot

index

(96)

Figure

7-1.

Computer

is

malfunctioning.

Refer

to

Figure

6-1,

A-4 pitch

module

card

and

repair

or

replace.

PITCH

MODES

FUNCTION,

BUT

ARE

SLUGGISH

AND/OR

ERRAT-

IC.

PITCH

OSCILLATIONS

ARE

SLOW

TO

DAMPEN

OR ARE

EASY TO

INDUCE

WHILE

FLY-

ING

IN

THE

BASIC

OR

GYRO

MODE

PITCH

MODES

FUNCTION,

BUT

ARE

SLUGGISH

AND/OR

ERRAT-

IC.

ABRUPT

PITCH

CHANGES

INITIATED

BY

AUTOPILOT

TRIM

(PITCH

TRIM

WHEEL

STARTS

MOVING

SIMULTANE-

OUSI.Y

WITH

AIRCRAFT

Pitch

gyro

out

of

adjustment.

Incorrect

trim

sensor

time

delay

in

either

or

both

directions.

Pitch

actuator

clutch

torque

low.

Refer

to

Section

2

and

adjust

gyro

sensitivity

on

the

bench.

Refer

to

Section

2,

check

trim

sensor

time

delay

-

adjust

or

replace

pitch

trim

sensor

as

necessary.

Refer

to

Section

2,

Table

2-1,

and

adjust

actuator

for

proper

torque.

Pitch

actuator cable

tension

set

too

low.

Refer

to

applicable

aircraft

ser

vice

manual

and

adjust

cable

tension.

PITCH

MODES

FUNCTION,

BUT

ARE

SLUGGISH

AND/OR

ERRAT-

IC,

ABRUPT

PITCH

CHANGES

INITIATED

BY

THE

PITCH

ACTUATOR

(PITCH

TRIM

WHEEL

DOES

NOT MOVE

UNTIL

AFTER

THE

AIRCRAFT

ATTITUDE

STARTS

TO

CHANGE)

ALTITUDE

HOLD

MODE

ERRAT-

IC.

ABRUPT

PITCH

CHANGES

INITIATED

BY

THE

PITCH

ACTUATOR

(PITCH

WHEEL

DOES

NOT MOVE

UNTIL

AFTER

THE

AIRCRAFT

ATTITUDE

STARTS

TO

CHANGE)

PITCH

MODES

FUNCTION,

NOR-

MAL

EXCEPT,

AUTOPILOT

DOES

NOT

CORRECT

PROPERLY

FOR

AIRCRAFT

ATTITUDE

CHANGES

WITH

FLAP

OPERA-

TION

Defective

actuator

follow

up

pot

or

associated

wiring.

Moisture

or

water

in

static

line

to

computer.

Altitude

sensor

malfunctioning.

Autopilot

computer

not

receiving

correct

voltage

from

the

pot

on

the

flap

actuator.

Repair

or

replace

pitch

command

pot

-

refer

to

Figure

6-5.

Disconnect

static

line

at

computer

and

sump

and

blow

out

static

line

in

accordance

with

applicable ser

vice

manual.

Replace

altitude

sensor.

Refer

to

Section

2.

Check

voltage

from

the

flap

actuator

pot,

adjust

or

replace

pot

as

necessary.

5-4

TROUBLE

--

PROBABLE

CAUSE

CORRECTION

PITCH

MODES

FUNCTION

BUT

ARE

SLUGGISH

AND/OR

ERRAT-

IC.

PITCH

TRIM

ACTUATOR

RUNS,

BUT

ELEVATOR

TRIM

WHEEL

DOES

NOT

MOVE

(MAY

CAUSE

AN

ABRUPT

PITCH

CHANGE

WHEN

THE

AUTO-

PILOT

IS

DISENGAGED

PITCH

MODES

FUNCTION

BUT

ARE

SLUGGISH

AND/OR

ERRAT-

IC.

AUTOPILOT

PITCH

TRIM

ACTUATOR

OPERATES

IN

ONE

DIRECTION

FROM

ZERO

ONLY

PITCH

COMMAND

INOPERA-

TIVE

(NO

UP

OR

DOWN

AUTHORITY)

Low

trim

actuator

cable

tension

causing

slippage

on

cable

drum.

Faulty

trim

sensor.

Defective

command

pot

in

control

unit.

Defective

pitch

actuator.

Refer

to

applicable

aircraft

ser-

vice

manual

and

adjust

cable

ten-

sion.

Repair

or

replace

trim

sensor.

Repair

or

replace

control

unit.

Overhaul

or

replace

pitch

actua-

tor.

Defective

A-1

module

card.

Defective

A-4

pitch

module

in

computer

card.

Check

A-1

module.

Repair

or

replace

as

necessary.

Check

A-4

module

card.

Repair

or

replace

as

necessary.

PITCH

MODE

FUNCTIONS,

BUT

IS

SLUGGISH

AND/OR

ERRATIC.

AUTOPILOT

PITCH

TRIM

AC-

TUATOR

DOES

NOT

RUN

ALTITUDE

HOLD MODE

WILL

NOT

ENGAGE

-

AIRCRAFT

CHANGES

PITCH

ATTITUDE

WHILE

THE

ALTITUDE

SWITCH

IS

HELD

ENGAGED

MANUALLY

ALTITUDE

HOLD

MODE

WILL

NOT

ENGAGE

MANUALLY

-

HOLDING

CAUSES

NO

CHANGE

IN

AIRCRAFT

PITCH

ATTITUDE

ALTITUDE

HOLD

POOR;

AIR-

CRAFT

PORPOISES

OR

TAKES

EXCESSIVE

TIME

TO

REACH

SELECTED

ALTITUDE

Trim

sensor

inoperative

or

elec-

trical

connector

not

connected.

Defective

trim

actuator.

Defective

altitude

sensor

in

computer.

Pitch

synchronization

in

com-

puter

needs

alignment

on

bench.

Defective

computer.

Defective

engage

switch

or

cir-

cuitry

in

control

unit.

Altitude

gain

control

out

of

adjustment.

Defective

A-4

pitch

module

card

in

computer.

Check

trim

sensor

electrical

connection

for

proper

connection.

Overhaul

or

replace

trim

actua-

tor

PA520A.

Replace

sensor.

Refer

to

Section

2,

pitch

synchro-

nization

and

align

on

bench.

Check

K-6

relay,

A-i,

A-4

and

A-6

modules

in

computer.

Re-

pair

or

replace

as

necessary.

Repair

or

replace

control

unit.

Adjust

gain

A1R37

in

accordance

with

adjustment

procedures

on

the

bench.

Repair

or

replace

A-4

pitch

module

card.

Defective

A-8

altitude

sensor

in

computer.

Defective

A-1

module

card

in

computer.

Basic

pitch

gain

control

impro-

perly

adjusted.

Replace

A-8

altitude

altitude

sensor.

Repair

or

replace

A-1

module

card.

Adjust

A1R34

in

accordance

with

adjustment

procedures.

5-4A

TROUBLE

Section

V

Cessna

400A

Nav-O-Matic

Autopilot

PROBABLE

CAUSE

CORRECTION

TROUBLE

WITH

VOR/ILS

COUPLER

SHALLOW

BANK

ANGLES

ON

VOR/ILS

INTERCEPT

Heading

bank

angle

adjustment

Check bank

angles

in

heading

mode;

adjust

A3R6

and

A3R8

as

required.

VOR/ILS

intercept

bank

angles

should

be

10°

less

than

maximum

heading

bank

angle.

Incorrect

signal

from

navigation

set.

A-5

roll

radio

card

in

computer.

Defective

A-1

module

card

in

computer.

K-5

relay

in

computer

amplifier

inoperative.

Check

signal

from

NAV;

should

be

30

millivolts

per

dot.

Repair

or

replace

A-5

roll

radio

card.

Repair

or

replace

A-1

module

card.

Replace

K-5

relay.

NAV

MODE

DOES

NOT

INTER-

CEPT

A

VOR

RADIAL

PROPER-

LY

OR

FAILS

TO

CORRECT

FOR

CROSSWIND

WHILE

IN

TRACK

MODE

(MAXIMUM

CRAB

ANGLE

AVAILABLE

IS

APPROX-

IMATELY

15°).

WITH

FULL

SCALE

OBI

DEFLECTION

AND

A

HEADING

CHANGE

BETWEEN

60°

AND

110°,

THE

INTERCEPT

ANGLE

IS NOT

THE

REQUIRED

45

±2

DEGREES

FAILS

TO

CAPTURE

AND

TRACK

VOR

RADIAL

Right

and

left

intercept

adjust-

ment

pots

in

computer

out

of

adjustment.

Incorrect

heading

source

voltage

to

computer.

Refer

to

Section

2,

and

adjust

intercept

angle.

Verify

heading

source

voltage

is

158

millivolts

per

degree.

Add

or

delete

resistance

in

RJB1

to

obtain

proper

voltage.

Repair

or

replace

A-5

roll

radio

module.

Defective

A-5

roll

radio

module

in

computer.

Defective

A-1

module

card

in

computer.

K-5

realy

in

computer

amplifier

defective.

Defective

NAV

engage

switch

on

control

unit.

Repair

or

replace

A-1

module

card.

Replace

K-5

relay.

Replace switch.

EXCESSIVE

BANK

ANGLE

ON

STATION

PASSAGE

FAILS

TO

CAPTURE

AND

TRACK

LOCALIZER

Defective

roll

radio

module

in

computer.

Improper

NAV

input

signal.

Repair

or

replace

A-5

roll

radio

module.

Verify

that

output

signal

from

NAV

set

is

30

millivolts

per

dot.

Defective

A-5

roll

radio

module

in

computer.

Defective

A-1

module

card

in

computer.

Repair

or

replace

A-5

roll

radio

module.

Repair

or

replace

A-1

module

card.

TROUBLE

5-4B

PROBABLE

CAUSE

CORRECTION

FAILS

TO

CAPTURE

AND

TRACK

GLIDESLOPE

Improper

NAV

input

signal.

Verify that

output

signal

from

NAV

set

is

30

millivolts

per

lot

Defective

A-6

pitch

radio

module

card

in

computer.

Defective

K-1

or

K-3

relay

in

computer

amplifier.

Defective

A-5

roll

radio

module

card

in

computer.

Repair

or

replace

A-6

pitch

radio

module

card.

Repair

or

replace

K-1

and/or

K-3

relays

in

computer

amplifier.

Repair

or

replace

A-5

roll

radio

module

card.

-3A.

POWER

SUPPLY.

NOTE

If

voltage

or

frequency

checks

are

in

toler-

ance,

do

not

adjust

or

peak

up

Step

1.

Turn

A/P

on.

TP-20

shall

be

28.

0

V

DC

11%.

If

not,

adjust

power

source

for

pro-

per

voltage.

Step

2.

Wait

ten

(10)

minutes.

TP-18

should

read

10.

0

V

RMS

±2%.

If

not,

adjust

A7R12

for

proper

reading.

Frequency

should

be

400

±5Hz.

If

not,

adjust

A7R2

for

proper

fre-

quency.

Step

3.

Check

at

TP-19

for

+6

V

DC

±l%.

If

pro-

per

reading

is

not

obtained,

adjust

A7R30

for

correct

value.

Step

4.

Check

at

TP-9

for

-6

V

DC

±1%. If

proper

reading

is

not

obtained,

adjust

A7R30

for

correct

value.

NOTE

If

any

power

supply

adjustments

are

made,

all

null

voltages

should

be

checked.

NOTE

Adjustment

callouts

in

parentheses

are

for

computers

with

serial

numbers

shown

in

Figure

6-1,

Sheet

1.

e.

ull Adjustments

Disconnect

attitude

gyro

and

heading

gyro.

Set

the

calizer

enable

switch

to

"OUT,

"

and

set

the

glide

lope

disable

to

"OUT.

"

push

in

the

heading

knob

and

djust

the

roll

trim

until

(TP-15)

is

less

than

±5

mV

Heading

Demod:

(Refer to

Figure

6

1.

Sheet

2

for,

Computer

Serialization.

)

Adjust

A3R48

until

(TP

21)

is

less

than

±10

mV

DC.

Heading

Amplifier:

Adjust

A3R10

(A3R2)

until

TP-22

is

less

than

±10

mV

DC.

Roll

Amplifier:

Disconnect

plug

P6 and

adjust

A3R24

(A3R11)

until

TP-17

(Pin

8

of

A3-IC2)

is

less

than

±10

mV DC.

Roll Follow-up: Reconnect

plug

P6

and

adjust

A3R30

(A3R19)

until

TP-16

is

less

than

±10

mV DC.

Pitch

Command:

With

the flap input

to

the

"OUT"

position,

adjust

the

pitch

command

wheel

until

TP-

5

is

less

than

t5

mV

DC.

Altitude

Hold

Amplifier:

Remove

plug

J4

from

the

altitude

sensor

and

ground

contact

J4F.

Adjust

A4R9

(A4R61)

until

TP-24

is less

than

-5

mV DC.

Altitude

Sensor:

Reconnect

plug

J4.

TP-24

shall

be

less

than

±100

mV

DC.

Pitch

Amplifier:

Remove

plug

P7

and

adjust

A4R24

(A4R13)

until

the

voltage

at

TP-7

(Pin

8

of

A4-

IC21

is

less

than

±10

mV

DC.

Pitch

Follow-up:

Reconnect

plug

P7 and

adjust

A4R30

(A4R24)

until

TP-6

is

less

than

±10

mV

DC

Pitch

Radio:

With

the

omni

simulator

OFF.

engage

the

NAV

switch

and

adjust

A6R16

until

TP-2

is

less

than

±15 mV

DC.

Pitch

Radio

Demodulator:

Adjust

A6R4

until

the

voltage

at

TP-1 (across

A6-C1)

is

less

than

±5 mV

DC.

NOTE

Repeat

Pitch

Radio

and

Pitch

Radio

Demodu-

lator

steps

until

both

are

within

specifications.

5-4C/5-4D

TROUBLE

1
2
3
4
5
6
7
8

Cessna Nav-O-Matic 400A Service Letter

Brand: Cessna

Model: Nav-O-Matic 400A

Type: Service Letter

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