'Permanent' trim up display

[FELX]

I have ony been able to conduct one flight to check out my newly installed AP (D100 + AP) - it seems to work OK in spite of a virtually permanent 'trim up' display in yellow.

I've not had chance to investigate fully but I'm convinced that every time I engaged the AP the aircraft had been correctly trimmed.

Naturally I would welcome feedback.

How does the AP detect this condition? Does it compare the servo positionin the air with the 'neutral' position set on the ground in the calibration process?? If so then perhaps all I need to do is to modify that??

My aircraft is a Sportcruiser which has an unbalanced elevator. On the ground it quite a heavy load - in fact too much for the servo. Is that a factor?? In the air the loading is quite light.

Finally I did find another thread on the forum where it was suggested that the 'servo trim detection' might be faulty. Plse don't suggest that I swap the servos to test - a good answer except that to remove the aileron servo is a major pain of a job!!!!!

Thanks in anticipation.

Terry

G-FELX

 

[dynonsupport]

The servo actually does measure the amount of external force that is being applied to the servo arm. So an unbalance elevator on the ground could certainly cause this behavior on the ground. In the air, though, if the air loads balance everything out, then, either there is still some residual force, or else there is something up with the servo. You might try trimming the airplane so that it wants to pitch up, and then engage the AP within its limits of control (no slip indicator) and then see if it asks for trim down. Do this VERY CAREFULLY and be aware that if if the servo slips, the airplane may pitch up abruptly. If it's still asking for trim up, that's a stronger indicator that it's the servo.

 

[FELX]

Many thanks for the comments - investigating!