FAA Powerplant Written Practice Test

How does a constant-speed propeller achieve maximum efficiency?

1. By maintaining a constant blade pitch during flight.

2. By adjusting blade angle for varied flight conditions.

3. By rotating at a fixed speed regardless of flight conditions.

4. Through the use of a hydraulic control mechanism.

The correct answer is: By adjusting blade angle for varied flight conditions.

A constant-speed propeller achieves maximum efficiency by adjusting the blade angle for varied flight conditions. This ability to change the blade pitch allows the propeller to maintain an optimal angle for the current flight dynamics, which can include variations in airspeed, engine power, and altitude. When the blade angle is adjusted, it changes the amount of lift and drag the propeller generates, enabling the engine to operate at its most efficient RPM. For example, during takeoff, a finer pitch can be set to provide more thrust, while at cruise, a coarser pitch is selected to enhance fuel efficiency and performance at higher speeds. The adjustment mechanism may utilize a hydraulic control system to facilitate quick and precise changes in blade angle, allowing for continuous optimization of performance based on the demands placed on the aircraft. This adaptability is key to achieving the most efficient performance throughout different phases of flight, making the choice of dynamic blade angle adjustment critical for maximized operational efficacy.