<P> P - factor, also known as asymmetric blade effect and asymmetric disc effect, is an aerodynamic phenomenon experienced by a moving propeller, that is responsible for the asymmetrical relocation of the propeller's center of thrust when an 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 . </P> <P> When an aircraft is in straight and level flight at cruise speed, the propeller disc is perpendicular to the relative airflow . Each of the propeller blades will contact the air at the same angle and speed and thus the thrust produced is evenly centered across the propeller . As the aircraft's angle of attack increases and the propeller disc rotates toward the horizontal, the airflow will meet the propeller disc at an increasing angle . The propeller blades moving down and forward (for clockwise rotation, from the one o'clock to the six o'clock position when viewed from the front) will have a greater relative wind velocity and therefore will produce greater thrust, while propeller blades moving up and back (from the seven o'clock through 12 o'clock position) will have a decreased relative wind velocity and therefore decreased thrust . This asymmetry displaces the center of thrust of the propeller disc towards the blade with increased thrust . In an aircraft with two or more propeller engines, P - Factor is what determines which engine is the critical engine . </P>

When does p factor cause the airplane to yaw to the left