View Full Version : Electric Trim

Wayne Pearce
09-19-02, 05:19 PM
Good morning,
I was curious as to whether the electric trim actuator as used by the 400A autopilot is the same electric trim actuator as used by the yoke mounted elec trim.
Reason for the question is that I have the autopilot but not elec trim and I have toyed with the idea of fitting it, obviously it becomes very simple if they both use the same actuator, I guess

Hmmmmmm just a thought


09-20-02, 11:37 AM
Wayne... the trim and autopilot are two different things on the skymaster... the autopilot is mounted in the left boom for the elevator.. the trim in the right boom... so they are not the same sorry... if it were that easy... it would be easy...smile... but, if you look in the service manual or the parts manual you will see the location of the items. G.M> GMAs

Guy Paris
09-20-02, 06:03 PM
when the A/P trims the elevator, is it not using the electric trim motor? Guy....old72driver....

09-20-02, 06:36 PM
the trim on the elevator which is on the other side... right boom.. the elevator for the aP is using the elevator cable which is on the left side..boom... they are seperate things... and mounted in different locations... G.M> GMAs

Bob Cook
09-22-02, 12:01 AM

The electric trim (servo) and the the elevator servo are different. In the port boom there is a strain guage that detects tension in the elevator cable. The trim servo tries to neutralize the elevator tention by adjusting the trim thru the trim servo. The autopilot is continually adjusting trim to neutralize tension.

The electric trim switches operate when the autopilot is disengaged. There is a voltage applied to to the servo (regulated) that moves the trim up or down. The voltage regulator has an adjustment that controls the speed. The regulator is mounted up on the left side of the centre console in a small aluminum box near the pilots knees.

When the autopilot is enguaged, an inhibit circuit stops the trim switch on the control from functioning.

The elevator servo has a limited range before the forces on the servo override the clutch. The trim servo is mandatory and standard on any pilot that has altitude hold.



Pete Somers
09-24-02, 03:27 PM
See the message Autopilot trim for MY views regarding the electric trim problem.