Auto Pilot (420A)

[SkyMac]

Hi everyone

Just sorting through my last remaining bug after the extensive rebuild, and it is proving to be a troublesome little thing. Hard to believe it has been 2 years since it returned to the skies and 103hrs later, yes I'm still smiling!

Need some help, I have been methodically working through the entire autopilot system and struggling to rectify the pitch control.

On the ground the entire auto pilot works fine in every function through every test following the manual for post installation and the pilots guide for pre-operations check prior to flight.

Now once in the air and in level flight, turning on the autopilot it tracks following the heading bug without issue, however within 3 to 4 seconds the pitch will automatically engage and climb the aircraft and continue to pull the yoke backwards, if I apply pressure to the yoke and push forward after some resitsance the autopilot will go into down pitch and continue to push the yoke forward.

Now I have checked all wiring, actuators, reset actuators as per the post installation checks, and as mentioned completed all on ground checks.

Any thoughts? (besides buying an new system) as I want to keep it original.

The other issue is limited experience left in Australia to work on these systems, one last remaining thing to check is the pitch sensors in the A/H (G519A). This is where I need some more help, I will be in the USA in two weeks, is there an avionics shop that can test these pitch sensors I can send it to whilst there?

To wrap this up, I have been 2 years without it as the plane once trimmed is very stable. But it would be nice to have it fully operational.

Let me share a recent photo of some flying over a bit of our high country.