quote:to confirm. if this twin engined plane was running in the an airless situation - is the angular momentum build up the same as if the position of the plane was contrained by a sort of bar through the yaw axis?
Correct. It seems a bit un-intuitve, but its the way things are.
Think of the problem this way. Subtract from both engines the power produced by the under-performing engine. So that now, you only have to consider the effect of the over-performing engine. Since the power produced by this engine is not balanced it generates a moment about the yaw axis of the aircraft. The effect is to generate a yaw motion. If left unchecked this yaw induces a roll with the wing carring the under-powered engine dropping (since the wing carrying the over-powered wing is travelling at a higher speed during the yaw). The aircraft will enter a spiral dive. The effect of a slight under-powered engine on a twin (mutli-) engined aircraft can be compensated for by trim in the yaw axis. If the yaw effect is significant a large amount of opposite rudder must be maintained to counter the yaw.
Alternatively, by keeping a neutral rudder but applying opposite roll through the ailerons, the over-powered engine can propel the aircraft through a flat turn. This would look like a smooth circular arc flown with level wings. It''s a basic skill learned when learning to fly. It can be produced in single engine aircraft by applying rudder and opposite aileron.
I hope this helps you to visualise what is happening to the aircraft in your problem and thus helps you understand the physics of the problem.
