FAA Ground School Practice Test

What causes the left turning tendency in an airplane due to P-factor?

1. The propeller blade descending on the left produces more thrust

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

3. Both blades produce equal thrust, neutralizing yaw

4. Increased drag on the left wing results in yaw

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

The correct answer pertains to how the propeller's rotation affects the thrust produced by its blades, particularly in a conventional propeller-driven aircraft. P-factor, short for asymmetric propeller loading, is the phenomenon where the angle of attack of the ascending and descending blades differs due to the airplane's forward motion. As the aircraft moves forward, the blade on the right side of the propeller is ascending and thus has a lower angle of attack and generates less thrust. In contrast, the blade on the left side is descending and has a higher angle of attack, which results in more thrust being produced on that side. This unequal thrust causes the airplane to yaw to the left, creating a left turning tendency. Understanding this concept is essential for pilots, as managing this yaw tendency is crucial during operations such as takeoff and climb, where the effects of P-factor are most pronounced. Recognizing how the orientation and action of propeller blades impact thrust allows a pilot to apply appropriate control inputs to maintain the desired flight path.