My friend has a sonic low wing which he powers with an LA 40. Although this plane is designed for (I think) a 25 engine, the LA 40 is a light and mild engine, and powers the sonic wonderfully. He used an old LA engine, and after lot of use, it finally wore out. He put in a new LA engine and we took it out to try it out. The engine flies the plane fine, except a strange problem has occured. The plane rolls fairly quickly to the right, but won't roll to the left. After he tried and tried, I also flew it, and it took horizon to horizon to make a roll to the left. We examined the ailerons, and the movement seems to be equal on both sides. We also tested for slop or weakness with our hands, and the airlerons seem to be very tight and strong. This is a complete mystery. We also looked for anything in the plane that could be restricting the movement of either aileraon rods, and found nothing. It's driving us crazy. Anyone out there ever have such a weird problem? This is a first for me, and I have been flying RC for many many years.

Never heard of such a thing. You could try to roll to the left at different throttle settings to try to determined if the problem is aerodynamic or electronic in nature.

could it be the latteral balance way off?

That is strange. I've always heard that prop driven planes roll left slightly better than right.

Sherman

Seems like a long shot, but perhaps the rudder is moving "right" when the ailerons are moving "left"? I have actually seen a fancy radio do things like this when it had a problem.

Sandy T

could the ailerons be blowing back in one direction more than the other.
could be that the ail servo is on the way out, may be a gear slipping in one direction only.
could be caused by a side mounted engine hampering the left roll.

piro may have something there. on those trainers, the ailerons use torque rods, they may have gouged out a space larger than they need and causing the aileron not to defect to the desired amount.

also, when you're up in the air, are the ailerons level? or at neutral are you having to compensate left aileron?