FAA Commercial Pilot Airplane (CAX)Aircraft SystemsEasy
A pilot flying a constant-speed propeller airplane in cruise moves the propeller control lever forward, commanding an increase in RPM. As the governor responds, what happens to the propeller blade angle?
- AIt increases toward a coarser pitch
- BIt moves to the full feather position
- CIt remains unchanged until throttle is adjusted
- DIt decreases toward a flatter (finer) pitch
Show answer & explanationAnswer & explanation
Correct answer: D. It decreases toward a flatter (finer) pitch
Increasing commanded RPM causes the governor to reduce oil pressure to the propeller dome (or route oil away, depending on design), allowing the blades to move toward a flatter, lower pitch angle, which reduces resistance and lets the engine spin faster for the same power. A coarser pitch would slow RPM, and feathering only occurs during shutdown/engine failure.
Why the other options are wrong
- A. Coarser pitch would decrease RPM, the opposite of what's commanded.
- B. Feathering is a shutdown/emergency function, not a normal cruise adjustment.
- C. The blade angle changes immediately as the governor responds to the new RPM setting.
Blade Angle vs RPM
Constant-speed propellers change blade angle to maintain selected RPM: flat/fine pitch for high RPM, coarse pitch for low RPM.
- Fine pitch = low blade angle = high RPM (takeoff/climb)
- Coarse pitch = high blade angle = low RPM (cruise)
- Governor automatically adjusts blade angle to hold selected RPM
Memory trick: Flat and fast, coarse and calm.