Overview
This lesson explains why airplanes exhibit a left turning tendency under certain flight conditions and the aerodynamic forces responsible for it.
Left Turning Tendencies
- Airplanes tend to turn left at high angles of attack, high power settings, and low airspeeds.
- Right rudder pressure is required during takeoff and under these conditions to counteract the left turn.
Torque Effect
- Torque reaction is caused by Newton's third law; as the propeller turns one way, the airplane tends to roll left.
- Torque effect increases with higher power and is strongest at low airspeeds and high angles of attack.
- Older airplanes may compensate for torque at cruise speed but not at low speeds.
- Newer airplanes may offset the engine to help reduce torque effect at low airspeeds, but not eliminate it.
P-Factor
- P-Factor occurs when the downward-moving propeller blade (right side) has a higher angle of attack during nose-up flight.
- This causes more thrust on the downward blade, yawing the airplane to the left.
- P-Factor is strongest at high angles of attack.
Corkscrew Effect (Spiraling Slipstream)
- The propeller creates a spiraling airflow (slipstream) that strikes the left side of the vertical fin at low speeds and high power.
- This impact causes the airplane to yaw left.
- As airspeed increases, the slipstream extends and may no longer affect the fin.
Gyroscopic Precession
- The spinning propeller acts as a gyroscope, experiencing precession 90 degrees ahead of any applied force.
- When the airplane's nose pitches up or down, precession creates additional yaw moments.
- Particularly significant in tailwheel airplanes during takeoff as they pitch down to lift the tail.
Key Terms & Definitions
- Torque Effect — Left-rolling tendency of the airplane from propeller/engine rotation.
- P-Factor — Asymmetric thrust caused by differing angles of attack on propeller blades during high nose-up attitude.
- Spiraling Slipstream/Corkscrew Effect — Spiraling air from the propeller hitting the vertical fin, causing left yaw.
- Gyroscopic Precession — Resultant force acting 90 degrees ahead of applied force on a spinning object, affecting airplane yaw.
Action Items / Next Steps
- Review left turning tendencies: torque effect, P-factor, and corkscrew effect.
- Pay attention to when these forces are strongest (high power, low speed, high angle of attack).