Definition
A left-turning tendency that occurs when a propeller-driven airplane is flown at a high angle of attack. Because the propeller disc is tilted relative to the relative wind, the descending propeller blade (on the right side, with a typical clockwise-rotating engine viewed from the cockpit) meets the oncoming air at a higher angle of attack and at a higher relative velocity than the ascending blade on the left side. The descending blade therefore produces more thrust than the ascending blade, and this uneven thrust distribution across the propeller disc yaws the airplane to the left.
Plain English
When the airplane's nose is pitched up, one side of the spinning propeller bites into the air harder than the other side. That uneven pull tugs the nose sideways, usually to the left.
Context Anchor
Seen in discussions of takeoff, climb, slow flight, and other high-power, nose-high conditions where the airplane may need right rudder to stay aligned.
Derivation
Asymmetric comes from Greek roots meaning 'not the same on both sides.' The term describes the propeller producing unequal (asymmetric) thrust on its two sides. P-factor is shorthand for 'propeller factor,' a casual label for this specific cause of yaw.
Why Pilots Care
Produces noticeable left yaw that must be countered with right rudder to maintain directional control, especially at high power and high pitch attitudes.
Analogy
Think of two people rowing a boat, one on each side. If one person pulls harder than the other, the boat turns instead of going straight. P-factor is a similar uneven pull from the propeller.
Grounding Statement
Picture a full-power climb after takeoff: the airplane is nose-high, the propeller is pulling hard, and one side of the propeller is producing more thrust than the other.
Intuition Check
“Loading” does not mean the airplane is carrying more weight on one side. Here it means one side of the propeller is doing more work and making more thrust than the other.
Example Sentence 1
On the takeoff roll, the student added right rudder to counter P-factor as the tail came up and the nose rose into the climb attitude.
Example Sentence 2
At high power settings and steep climb angles the effect grows stronger, requiring more rudder input to keep the airplane straight.