400A autopilot

[Pete Somers]

Loc mode is a switched output from the GNS unit which is connected to the A/Pilot, and as Dave says in LOC mode on the A/Pilot the glide slope is armed. However in Nav mode the glide slope is disabled.
The 400A is a very good system and like everything, maintained correctly will give you no problems, and they are easy to repair when they go wrong.

The main problems are-----

1 Pilots overriding the servos and either breaking the shear pin or damaging the clutch.
2. The follow up resistors in the servos go intermittant.

Apart from those, the system is fine, remember the 400A is installed into most Cessna twins until the 400B came out, but the 400B does not differ much from the 400A.

Hello Mr Underwood, all ok?

Regards
Pete