Setup / Trim Question
 

I have a QQ Yak 102 that I am puzzled with. On the pullup for a 1/2 reverse cuban eight: I pull 45, climb, then right half roll but after the right half roll it comes out 20 degrees pointing left.

I am happy with the CG, thrust angles, lateral balance, adjusted aileron throws with aileron differential for axial rolls on a 45, mixed out coupling in knife edge and have a down elevator mix for downlines. But, I'm puzzled with this change of direction. What could be the possible causes? Twist in wing or stab? Myself pushing in down elevator too early? Maybe I need even more aileron differential?

The Yak was pulling left (toward canopy) during a left half roll into knife edge, but I continued to work the aileron throws until it rolls axial now. I've tried that on this right half roll, but it does not seem to have an impact. I've tested the 45 degree climb with rolls and they are axial with no wandering both directions.


Thx in advance for any insight, Bob...

RE: Setup / Trim Question
 

Bob,
sorry but I don't understand.

You say that ail differentials are ok since you get axial rolls, but after an half roll you're plane is completely out of heading???

I would suggest to follow a systematic setup process, since before ail differentials IMHO it is important to fix other variables, otherwise you can't find the real source of the problem.

RE: Setup / Trim Question
 

bmac

I had this happening to me and it was the differential ailerons.

RE: Setup / Trim Question
 

Thanks for the replies. Got some more trim time in today and it was a aileron differential problem. Bob...