Cessna Nav-O-Matic 400A 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