FAA Aviation Mechanic Powerplant (AMP)PropellersMedium
A twin-engine aircraft has a hydromatic propeller system. The pilot activates the feather button, but engine oil pressure alone may be insufficient to fully feather the blades quickly. What component ensures rapid feathering under this condition?
- AA feathering accumulator that stores high-pressure oil for immediate use
- BThe synchrophaser control unit
- CThe propeller governor flyweights
- DThe blade counterweights alone
Show answer & explanationAnswer & explanation
Correct answer: A. A feathering accumulator that stores high-pressure oil for immediate use
A feathering accumulator stores oil under high pressure so that, when the feather button is pressed, a rapid surge of oil is available to drive the blades to the feathered position quickly, independent of engine-driven oil pump output which may be declining as the engine fails.
Why the other options are wrong
- B. Synchrophaser adjusts RPM synchronization, unrelated to feathering.
- C. Flyweights regulate normal governor operation, not feathering speed.
- D. Counterweights alone would feather too slowly without accumulator assistance in many designs.
Feathering Accumulator
A component in some hydromatic feathering systems that stores high-pressure oil to enable rapid propeller feathering.
- Stores oil under pressure for feathering
- Provides immediate high-pressure oil surge
- Works with feathering pump for a failed-engine's low oil pressure
Memory trick: Accumulator is the 'emergency oil tank' for fast feathering