ORIGINAL: polikarpov i16
if your airplain is rolling to the right witch is diferent than a snap it has to do with the propeller
you do not notice it on a 40 size because you have a small prop
the gyroscopic forces of a 15 inch prop are huge
enough to roll your airplain over
Gyroscopic procession should produce a *yaw* to the right and not a roll. However, if your plane has a lot of yaw-roll coupling then this will manifest itself as a rolling movement.
The way to check this is to suddenly apply *down* elevator -- the plane should then yaw/roll to the left if gyroscopic procession is the cause.