One of the guys at our club just traded for a Sukhoi 40 by Midwest. I flies great except when he makes a sharp bank say 70 or 80 degrees. It gets about half way through the bank and then banks sharply the other way sometimes going all the way inverted. It does it every time. He changed the pushrods thinking they might be bending. All control surfaces are tight. He's a great pilot. We can't seem to figure it out. Anyone out there having similar problems???

Sounds like it could be a high speed stall.

Picture it this way. In a high speed turn, with a sharp bank angle, the lower wing will generate more lift than the high wing. If the high wing stalls at that point, the low wing is going to attempt to roll the plane to the right.

I wouldn't think the Sukhoi would do that though. Might want to check the wing and horzontal stab incidences.

Of course, I'm just guessing here. I could probably be more help if I saw it happen. :stupid:
Dennis-

Dennis,

I agree, the Sukhoi shouldn't do that. It appears to be a good building job. The wing is straight, the wing and stab are perfectly alligned and all control surfaces are straight and alligned.

Some additional info we found out today, it does the same thing when given full elavator without any other control. It usually goes right but sometimes goes left and very sharply.

Also, it looks like the wing had dihedral at one time and is now perfectly straight.

does he have a gyro on the aileron or rudder?

I'm pretty sure he doesn't have a gyro but I'll check. We're planning on flying tomorrow evening.

Sounds like a high speed stall. Backing off on the elevator throw would probably fix it.

It sounds like he is starting a snap in the turn, which is probably caused by excessive elevator movement, or a difference in the movement of each elevator half.

-DC