FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightEasy
A student pilot asks why, during a high-power, low-airspeed climb, the propeller's slipstream creates a corkscrew-shaped airflow pattern that strikes the left side of the vertical stabilizer and rudder, causing a left-yawing tendency. What is this effect called?
- AP-factor
- BSpiraling slipstream
- CAdverse yaw
- DGyroscopic precession
Show answer & explanationAnswer & explanation
Correct answer: B. Spiraling slipstream
The spiraling slipstream is the corkscrew-shaped flow of air behind a rotating propeller. At high power and low airspeed (such as during climb), this slipstream wraps around the fuselage and strikes the left side of the vertical stabilizer, pushing the tail right and yawing the nose left.
Why the other options are wrong
- A. P-factor is caused by asymmetric propeller blade angle of attack, not by slipstream shape striking the tail.
- C. Adverse yaw results from differential aileron drag during a turn, unrelated to propeller slipstream.
- D. Gyroscopic precession results from forces applied to a spinning propeller disc, not airflow striking the tail.
Spiraling Slipstream
The corkscrew-shaped airflow behind a rotating propeller that wraps around the fuselage and strikes the left side of the vertical stabilizer, producing a left-yawing tendency, most pronounced at high power/low airspeed.
- One of four left-turning tendencies
- Most noticeable at high power and low airspeed (e.g., climb)
- Requires right rudder correction in most single-engine airplanes
Memory trick: The slipstream corkscrews and slaps the tail's left cheek