Which statement describes a constant-speed propeller?

• A. A fixed-pitch propeller.
• B. A constant rpm maintained by manual control.
• C. A controllable-pitch propeller whose pitch is automatically varied by a governor to maintain a constant rpm.
• D. A feathering propeller.

Answer: (C)

A constant-speed propeller operates as a controllable-pitch system that automatically varies blade pitch to hold the engine RPM at a selected value. The pilot sets the desired RPM with the propeller control, and a governor senses the actual RPM and adjusts blade pitch via oil pressure to absorb more or less power as flight conditions change. If the load on the propeller increases, the governor increases pitch to absorb extra power and keep RPM from dropping; if the load decreases, it reduces pitch to prevent RPM from overshooting. This automatic pitch adjustment is what keeps engine speed steady across different airspeeds and power settings, improving efficiency. A fixed-pitch propeller has a single blade angle and cannot maintain a constant RPM as conditions change. A feathering propeller is designed to reduce drag when the engine is failed or not producing power, not to maintain a constant RPM. A statement about maintaining constant RPM by manual control ignores the automatic pitch adjustment that characterizes constant-speed props.