FAA Sport Pilot Airplane (SPA)Aircraft Performance and SystemsEasy
During takeoff at a high angle of attack and low airspeed, a propeller-driven airplane tends to yaw to the left. This tendency is primarily caused by which factor?
- AP-factor (asymmetric propeller loading)
- BTorque reaction
- CSpiraling slipstream
- DGyroscopic precession
Show answer & explanationAnswer & explanation
Correct answer: A. P-factor (asymmetric propeller loading)
At high angles of attack, the descending propeller blade (on the right side, viewed from the pilot's seat) takes a larger bite of air than the ascending blade, producing more thrust on the right side and yawing the nose left. This is called P-factor.
Why the other options are wrong
- B. Torque reaction causes a rolling tendency, not primarily yaw.
- C. Spiraling slipstream affects the tail, but P-factor dominates at high AOA/low airspeed.
- D. Gyroscopic precession results from a force applied to a spinning propeller, not high AOA alone.
P-Factor
Asymmetric propeller thrust caused by the descending blade producing more thrust than the ascending blade at high angles of attack.
- Most pronounced at high AOA and low airspeed
- Causes left-yawing tendency in U.S.-built engines/props
- One of four left-turning tendencies
Memory trick: P-factor pushes the nose left when the nose is high.