I have been having an issue with my AP74 on a D180 for over a year and cannot resolve the issue. The AP holds ALT perfectly for hours at a time but the HDG, TRK and NAV modes all have a similar issue. The AP holds direction perfectly for a while, from a few minutes to half an hour and the suddenly the compas tape on the D180 veers off to the right and the AP tries to follow it. If I dont disengage the AC keeps turning tighter and tighter till over a 60deg bank. Once it starts doing this, I cannot use any of those modes for the balance of the flight. So far Ive updated all software, replaced the shear screw, recalibrated the compass and recalibrated the Ap and swapped out the D10A. The issue still remains. I sent the AP to Dynon who tested it for quite a while and found no issue.
Any other ideas would be very welcome.
Any other ideas would be very welcome.