Definition
P-factor is the yawing tendency caused by the descending propeller blade producing more thrust than the ascending blade when the airplane is flown at a high angle of attack. On a typical single-engine airplane with a propeller rotating clockwise as viewed from the cockpit, the descending blade is on the right side, so the airplane yaws to the left. P-factor becomes most noticeable during high-power, high angle-of-attack flight conditions such as climbs, takeoffs, and slow flight.
Plain English
When the airplane's nose is pitched up and the engine is producing high power, one side of the propeller bites into the air harder than the other. This uneven pull tugs the nose of the airplane to one side, usually to the left.
Context Anchor
Encountered during takeoff and climb, especially when learning why right rudder is often needed in a single-engine airplane.
Derivation
The 'P' stands for propeller. The term is shorthand for 'propeller factor,' meaning a yawing effect caused specifically by the propeller's geometry when the airplane is flying at a high angle of attack.
Why Pilots Care
Unchecked P-factor produces unwanted left yaw that must be corrected with rudder to keep the airplane coordinated during high-power, high-angle-of-attack phases such as takeoff and climb.
Analogy
Picture a swimmer doing a freestyle stroke while leaning back. The hand pulling down through the water grabs more water than the hand reaching forward near the surface. That uneven pull twists the swimmer's body. The propeller does the same thing when the airplane's nose is pitched up.
Grounding Statement
Picture the airplane climbing steeply: the spinning propeller is not meeting the air evenly, so one side can pull harder than the other.
Intuition Check
P-factor is not the same thing as engine torque. Torque is a twisting effect from engine rotation; P-factor is uneven thrust from the propeller blades when the airplane is at a higher angle to the airflow.
Example Sentence 1
During the takeoff roll and initial climb, the student applied steady right rudder to counter P-factor and keep the airplane aligned with the runway centerline.
Example Sentence 2
P-factor becomes noticeable during a high-power climb and requires continuous rudder correction to maintain coordinated flight.