FAA Commercial Pilot Airplane (CAX)Aircraft SystemsEasy
A constant-speed propeller governor uses flyweights sensitive to engine RPM to control the oil pressure directed to the propeller hub. What is the primary purpose of this system?
- ATo automatically adjust the propeller blade angle to maintain a pilot-selected RPM
- BTo control fuel flow to the injector nozzles
- CTo feather the propeller during normal cruise flight
- DTo vary manifold pressure independent of the throttle setting
Show answer & explanationAnswer & explanation
Correct answer: A. To automatically adjust the propeller blade angle to maintain a pilot-selected RPM
The governor senses RPM through flyweights and meters oil pressure to change propeller blade angle, holding RPM constant at the value selected by the pilot regardless of airspeed or power changes.
Why the other options are wrong
- B. Fuel flow is controlled by the fuel injection system, unrelated to the propeller governor.
- C. Feathering only occurs on multiengine or specially equipped aircraft, not during normal single-engine cruise.
- D. Manifold pressure is controlled by the throttle (and turbocharger), not the propeller governor.
Constant-Speed Propeller Governor
A flyweight-actuated device that meters engine oil pressure to the propeller hub to automatically change blade pitch and hold a selected RPM.
- Flyweights sense RPM changes
- Oil pressure changes blade angle
- Maintains selected RPM despite airspeed/power changes
Memory trick: Governor guards the RPM gauge like a thermostat guards temperature.