FAA Private Pilot Airplane (PAR)Aerodynamics and Aircraft SystemsMedium
During takeoff roll in a single-engine airplane with a clockwise-rotating propeller (as viewed from the cockpit), the pilot must apply right rudder pressure to keep the nose tracking straight down the runway centerline, with the need for correction increasing as the tail rises and the airplane accelerates at high power and low airspeed. Which left-turning tendency is primarily responsible for this yaw during the initial climb at a high angle of attack?
- ATorque reaction from the engine and propeller
- BSpiraling slipstream wrapping around the fuselage
- CGyroscopic precession from the propeller
- DP-factor from asymmetric propeller thrust
Show answer & explanationAnswer & explanation
Correct answer: D. P-factor from asymmetric propeller thrust
P-factor (asymmetric thrust) occurs when the airplane is flown at a high angle of attack, causing the descending propeller blade (on the right side, for a clockwise-turning prop) to have a greater angle of attack and produce more thrust than the ascending blade on the left. This creates a yawing moment to the left, most pronounced during climb at low airspeed and high power.
Why the other options are wrong
- A. Torque reaction is present throughout flight but does not specifically increase with angle of attack.
- B. Spiraling slipstream causes yaw regardless of angle of attack and is most pronounced at low airspeed but is not attributed to blade thrust asymmetry.
- C. Gyroscopic precession is caused by pitch changes acting on the spinning propeller disk, not a high angle of attack.
P-Factor (Asymmetric Thrust)
A left-turning tendency caused by the descending propeller blade producing more thrust than the ascending blade when the airplane is at a high angle of attack.
- Most pronounced at high power, low airspeed, high angle of attack
- Descending blade has greater AOA and thrust than ascending blade
- One of four left-turning tendencies along with torque, slipstream, and gyroscopic precession
Memory trick: P-factor points the nose left when the nose points up.