Which of the following describes 'P Factor'?

The concept of 'P Factor,' which stands for "propeller factor," refers to the asymmetrical thrust produced by a propeller that results from its angle of attack and rotational motion during an aircraft’s climb. In simpler terms, this phenomenon happens primarily during ascent when the aircraft's nose is pitched up. The downward blade of the propeller creates more lift than the upward blade due to the differing angles of attack; this discrepancy causes the aircraft to yaw to the left (for aircraft with clockwise rotating propellers).

Understanding this concept is crucial for pilots, as they need to be aware of how P Factor can affect their control of the aircraft during takeoff and climb. This is particularly significant at lower speeds when the aircraft is more susceptible to variations in thrust and directional stability.

The other options, while related to different aerodynamic concepts, do not encapsulate the essence of P Factor. Stability during descent relates to how an aircraft maintains its path while descending, drag produced by landing gear deals with resistance as the aircraft rolls on the ground, and friction between tires and the runway concerns ground handling rather than propeller dynamics. Thus, these options do not accurately define or describe P Factor.