MajTom's P-factor explanation was dead on -- simple really



Proverse roll is pretty simple to understand -- the aircraft rolls in the direction of rudder input (note rudder, not aileron). The roll will subsequently cause the AC to turn. This is what you would normally expect to see -- it is a sort of naturally occurring self-coordinating turn mechanism. Model trainers almost always exhibit this behaviour -- right rudder, for example, results in a right yaw & a near-simultaneous right roll, giving a nicely coordinated turn without even touching the ailerons. Causitive factors include, but are not limited to; dihedral, swept back wings, & substantial upward vertical displacement of the aerodynamic center from the vertical C-of-G (high-wing pendulum effect).

Adverse roll is just the opposite -- the aircraft rolls away from the direction of rudder input. Right rudder produces a right yaw, but a LEFT roll. This is counterintuitive & it gives inexperienced pilots a very bad time. The turn must be coordinated by using both rudder and aileron together (in the same direction). Causitive factors include; forward swept wings, low wings, and anhedral (or simply insufficient dihedral).


I'm going to use proverse roll to down-play the Major's claimed effects of P-factor in explaining roll-neutral aircraft at power-on near-stall conditions