Which term describes yaw to the left caused by unequal thrust from the propeller blades during a climb?

• A. P-factor
• B. PFD
• C. Phugoid oscillations
• D. PIREP

Answer: (A)

P-factor explains this yaw. When the airplane climbs, the propeller operates at a higher angle of attack, and the blade moving downward through the air encounters a steeper incidence than the blade moving upward. That downward blade tends to produce more thrust, and because the thrust is applied off the aircraft’s centerline, it creates a yaw moment. In a typical light, single-engine airplane with a standard propeller rotation, this asymmetric thrust tends to yaw the nose to the left during a climb. P-factor is most noticeable at high power and high angles of attack and diminishes as speed increases or the aircraft moves toward level flight.

The other terms relate to different concepts: PFD is the primary flight display, phugoid oscillations are a long-period pitch/airspeed oscillation, and PIREP is a pilot weather report.