AMP - Aviation Maintenance Technician Powerplant Practice Exam

How does a constant-speed propeller maintain its performance?

1. By rotating at a fixed angle

2. By adjusting blade angle to maintain selected RPM

3. By decreasing engine power output

4. By varying the amount of fuel used

The correct answer is: By adjusting blade angle to maintain selected RPM

A constant-speed propeller maintains its performance by adjusting the blade angle to maintain a selected RPM. This mechanism allows the propeller to adapt to varying flight conditions and engine power settings effectively. As the load on the propeller changes—such as during climbs, descents, or level cruising—the system automatically alters the blade pitch. When the engine RPM increases beyond the set point, the blade angle decreases (often referred to as "feathering"), allowing for less drag and thus stabilizing the rotational speed. Conversely, if the RPM drops below the desired threshold, the blade angle is increased to generate more lift and increase the resistance of the propeller, which brings the RPM back up to the selected value. This adaptive capability enhances efficiency and performance across different phases of flight, ensuring that the engine operates within optimal parameters while providing the pilot with precise control over the aircraft's speed and power output.