Private Pilot License (PPL) Aerodynamics Practice Exam

When does P-factor cause the airplane to yaw to the left?

1. When at high speeds

2. When at high angles of attack

3. When in a steep turn

4. When cruising at low altitude

The correct answer is: When at high angles of attack

P-factor refers to the asymmetrical thrust produced by a propeller, particularly in airplanes with propellers that rotate clockwise when viewed from the cockpit. This phenomenon typically occurs during flight at high angles of attack, such as when climbing or during slow flight. When the aircraft is at a high angle of attack, the downward-moving blade on the right side of the propeller has a higher angle of attack than the upward-moving blade on the left side due to the relative airflow and the inclination of the aircraft. This results in greater lift and thrust on the right side, causing a yawing moment to the left. Consequently, the airplane tends to yaw to the left during these conditions because the thrust vector is not acting symmetrically relative to the aircraft's centerline. This yaw can require corrective action by the pilot, typically using right rudder input, to maintain coordinated flight. Understanding this dynamic is critical for pilots, particularly during climbs or maneuvers where high angles of attack are prevalent.