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Dynon Skyview roll oscillation in NAV mode

liuk

Active Member
Hello all, I purchased a RV-6A with all Dynon Skyview EFIS and autopilot installed. The autopilot has been working really nicely on long XCs until I decided to install the manual aileron trim kit from vans, hoping to lessen the roll force needed as I have a slightly heavy left wing.

After the manual aileron trim kit installed, the autopilot would constantly roll the aircraft between -2 to 2 degs on about 1 minute period. I included a foreflight track log picture which clearly shows the oscillation on the bank angle throughout the entire flight when AP is engaged. It seems it's only like this when in NAV mode.

Any suggestions on which direction I should look into? Thanks!
 

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Check for a broken shear pin in your roll servo. When my RV started oscillating in roll on AP, it turned out to be a broken shear pin. There was still enough friction it could (sloppily) control roll in smooth air.
 
Check for a broken shear pin in your roll servo. When my RV started oscillating in roll on AP, it turned out to be a broken shear pin. There was still enough friction it could (sloppily) control roll in smooth air.

Thanks! I just tried to locate the shear pin replacement kit but cannot find any. Finally I called Dynon support and left a message, they called back in 2 hours, gave the same diagnosis and offered to send me a replacement kit free of charge. That's very good service!
 
Follow-up

Hello all, after receiving the shear screw replacement kit from Dynon I removed the roll servo and found that the shear screw was actually intact in my case. Dynon support then suggested that I should try re-calibrate the AP by adjusting sensitivity and gain since there is a new component in the system (the manual aileron trim). I did several very long XCs and practically tried all possible sensitivity/gain adjustment combinations within the range. Different parameters certainly have an obvious change to the feeling of the AP, but nothing seemed to have any effect on this particular roll oscillation.

I then decided to temporarily remove the manual aileron trim and the roll oscillation disappeared. I suppose the combination of vans manual aileron trim and Dynon autopilot must be a very common, so I would like to ask if other people experienced similar issue and how it was fixed in the end? Thanks.
 
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