P-factor

Not to be confused with the p-value.
This article is about the aerodynamic phenomenon. For the p factor of psychopathology, see p factor (psychopathology).
Propeller blade angle of attack (left) and propeller blade angle of attack change with aircraft pitch change, demonstrating asymmetrical load (right)

P‑factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller,[1] wherein the propeller's center of thrust moves off-center when the aircraft is at a high angle of attack. This shift in the location of the center of thrust will exert a yawing moment on the aircraft, causing it to yaw slightly to one side. A rudder input is required to counteract the yawing tendency.

  1. ^ Willits, Pat, ed. (2004) [1997]. Guided Flight Discovery: Private Pilot. Abbot, Mike Kailey, Liz. Jeppesen Sanderson, Inc. p. 3-49. ISBN 0-88487-333-1.)