Autopilot and trim

[paxhia]

I'm testing my installation, Murphy Moose with capstain drive servo's. When the AP is disconnected I go a pitch down. The procedure used is trim airplane with AP off and then engage AP for straight and level. The AP slips and calls for trim and I trim until no slip and trim request. When the AP is disconnected pitch down is a 2000+fpm decent. Why is AP calling for trim when airplane was in trim to begin with?

 

[DBRV10]

Your servo needs to go back to Dynon to have the trim sensing calibration re-done.

Did you happen to pull the stepper motor and servo case apart by any chance?

 

[dynonsupport]

Please get in touch with our tech support staff at 425-402-0433 or support at dynonavionics dot com for further help with this.

 

[paxhia]

The servo has not been taken apart. I will give support a call.

 

[paxhia]

Wow, great support, the new servo came in noon UPS delivery. I had a little trouble getting the arm off the servo to mount the capstain, but after getting it wired and installed did a test flight.
The AP calls for trim but less than before and when disconnecting the airplane pitches up and then does several oscillations and ended up at 150 to 200 feet per minute climb. This is very acceptable, more testing to go.