Private Pilot License (PPL) Aerodynamics Practice Exam

The left turning tendency in an airplane caused by P-factor results from:

1. The propeller blade ascending on the right producing more thrust

2. The propeller blade descending on the right producing more thrust

3. The left wing producing more lift

4. Increased drag on the left side of the airframe

The correct answer is: The propeller blade descending on the right producing more thrust

P-factor refers to the asymmetrical thrust produced by a propeller, particularly in a multi-blade propeller system during a climb or when the airplane is at a high angle of attack. This phenomenon occurs because of the difference in the angle of attack between the ascending and descending blades of the propeller. When the propeller rotates, the blade that is ascending (typically the right side of a clockwise rotating propeller) has a lower angle of attack and thus generates less lift and thrust compared to the descending blade (the left blade in this case), which has a higher angle of attack. This results in more thrust being produced by the descending blade on the left side. As a result, the greater thrust on the left side causes the airplane to yaw to the left, leading to the left-turning tendency. Therefore, the correct choice accurately reflects that the propeller blade descending on the right produces more thrust, contributing to the overall left turning tendency experienced by the aircraft. This understanding of P-factor is critical for pilots, especially during takeoff and climb, as it influences handling characteristics and necessitates appropriate control inputs to maintain the desired flight path.