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Autopilot automatic trim

Ron B.

Well Known Member
Trying to solve an issue in a friend’s RV-14 .
He claims the Garmin auto pilot trims the ailerons all the way to the right, but if he disconnects the autopilot he needs to remove some trim to fly straight wings level.
Anyone ever experience the autopilot over trim the ailerons?
Thanks Ron
 
Trim Motor reversed in the autopilot settings? Its more exciting when you do it on pitch....

The servo should be easily able to overpower the aileron trim. At least it can on my -10, so it would look like that.


Derek
 

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No , we have been through all that before first flight. It is going in the correct direction but appears to trim too much.
 
I rarely hook up roll trim, a spring bias trim system is not very effective with autotrim in my experience
If you just keep the fuel balanced, there really is no need for aileron trim IMO.
 
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I had the same issue but it would keep trimming all the way to the left.
I just unhooked mine. I didn’t like the spring mechanism anyway. Seems to fly fine without so far although I haven’t done long trips. Can always add it back.
 
G3X Touch FDL

Trying to solve an issue in a friend’s RV-14 .
He claims the Garmin auto pilot trims the ailerons all the way to the right, but if he disconnects the autopilot he needs to remove some trim to fly straight wings level.
Anyone ever experience the autopilot over trim the ailerons?
Thanks Ron

Morning Ron,

If you have a Flight Data Log from this flight, email it to us and we can help unpack what is going on using the autopilot torque and command values logged in the file. Send the FDL to [email protected] and we can get to work on it.

Thanks,

Justin
 
I have developed several auto-trim controlllers, and here is what I have found. This is based on Dynon’s algorithm, I can’t judge what Garmin does.

If you consistently use the autopilot to fly a programmed course, the roll trim will adjust to remove the crosswind component. When you land, you will see this bias in the system. Theoretically, this will also happen with pitch trim if fly in ascending or descending air.

Using heading hold will minimize (but not eliminate) the roll trim bias…. but your ground track will not following your heading due to the crosswind.

Simply put, using the AP to fly a course can cause your aircraft to crab into the wind, using the trim system. As others have said, load imbalance and airframe imbalances are at play, too.

VV
 
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