FAA Aviation Mechanic Powerplant (AMP)PropellersMedium
A twin-engine aircraft experiences an engine failure in flight. Why does the pilot feather the propeller on the failed engine?
- ATo allow the propeller to windmill and assist in restarting the engine
- BTo lock the propeller shaft and prevent any rotation of the crankshaft
- CTo increase drag and help slow the aircraft for landing
- DTo align the blades approximately parallel to the airflow and minimize drag
Show answer & explanationAnswer & explanation
Correct answer: D. To align the blades approximately parallel to the airflow and minimize drag
Feathering rotates the blades to approximately 90 degrees (parallel to the airflow), which minimizes drag from the stopped propeller and prevents further engine damage from windmilling. This significantly reduces asymmetric drag on a twin-engine aircraft after an engine failure.
Why the other options are wrong
- A. Feathering stops windmilling; it does not encourage it.
- B. Feathering does not lock the crankshaft; it only changes blade angle.
- C. Feathering reduces, not increases, drag.
Propeller Feathering
Rotating propeller blades to approximately 90 degrees to the plane of rotation to minimize drag when an engine is shut down in flight.
- Blade angle set near 90° (parallel to airflow)
- Reduces drag and prevents windmilling damage
- Common on multi-engine and turboprop aircraft
Memory trick: Feather like a bird's wing edge-on to the wind to cut drag