Trouble shooting electric rudder trim problem

[amekler]

When I'm flying with ball centered all of a sudden i'll feel the plane yaw and ball will go way out of center. I'll compesate with rudder pedals and readjust the rudder trim. After landing I noticed the rudder trim to be way to one side. I've checked the trim on the ground and it seems to move fine with the electrim trim both directions.
Any ideas of what is happening?
Alan

 

[Mike S]

Does it always go off center the same direction??

Could be a short in the wiring, the 5 wire cabling for the trim servo-----assuming you used the same wire I did----is easy to nick when striping, and it may be possible that you are getting an intermittent short circuit that is driving the servo.

What type of switch are you using for the trim?? Stick or panel mounted???

Give us more info, and photos if possible.

 

[amekler]

Mike,
I bought the plane so I don't know what wiring is used. The switch is a panel mount and has a right and left switch no center switch. Since it has only happened twice now i don't remember which way the ball went but it is quite abrupt yawing motion and goes way off to one side.
Alan

 

[Mike S]

but it is quite abrupt yawing motion and goes way off to one side.
Alan

Well, look on the bright side, at least the trim is effective.

I would contact the person who you bought it from, see if they can help------???

 

[PCHunt]

Yaw

Could it be that one of your gear leg fairings or wheel cover fairings (Spats) is shifting in flight, thus affecting the yaw trim?

How "sudden" is the shift of trim"? Faster than an electric trim motor running? Or fairly gradual, say over a period of 3-5 seconds? "Sudden" to me means "Right Now!", as in nearly instantaneous.

Any springs in your rudder system? Anything on the rudder cables that could hang up on one of the ferrules along the way? Etc.

(Just trying to think outside the box.)