Auto Pilot Flies Left Wing Low

[Bardample]

I have an RV7a, with Dynon servos. The plane flies wings level with usually no aileron trim needed, but some R rudder trim with a tab on rudder to keep ball centred.
When I turn on autopilot ( in simple mode) using HSI Track function, the left wing tends to drop (, ball stays in middle), and aileron trim is not adequate to keep wing level.If I switch off autopilot, the plane goes straight back to wings level. Otherwise the autopilot function in simple mode ok.

Can anyone help me with an explanation and how can I solve this issue? JeffR Australia.

 

[airguy]

Your ball is centered with the autopilot on and left wing low? If you need a little rudder trim, and don't have the ball centered with your feet off the rudders, then the AP will drop one wing to counter the rudder.

 

[Bardample]

Thanks for your reply. I shall have to go flying again, level wings on auto pilot and see if unloading the rudder keeps it level.

When I hand fly with ball centred, it’s not apparent to me that I need elevator to keep wings level. The stick seems vertical.

 

[jakej]

My method is to -
Center the 'ball' n flight at your normal cruise speed.
First step is that the plane should fly straight without your feet on the rudder pedals.
Add a rudder trim tab if necessary. Now you may have a 'heavy' wing so then adjust the rigging or add Aileron trim tab or raise or lower a flap a little.
What you should try to achieve is to get the plane to fly straight & level hands off without diverging - if you do that the autopilot will thank you for it .

 

[preid]

The plane flying straight without AP would tell me the plane is fine and to recalibrate the inflight autopilot.
I would do the full autopilot steps, including ground, and inflight calibration to assure that’s not the issue.
what firmware are you running?

 

[Bardample]

The latest Dynon. ( forgot the number). I’ll try your suggestion. Thsnks