Definition
An automatic propeller feathering system on multiengine turboprop airplanes that, when armed and triggered by a sensed loss of engine power (typically below a set torque threshold during takeoff or initial climb), automatically rotates the propeller blades of the failed engine to a streamlined, edge-on position to minimize drag without pilot action.
Plain English
A system that, if an engine quits during takeoff, automatically turns the dead engine's propeller blades sideways to the airflow so they don't drag the airplane down while the pilot is busy flying.
Context Anchor
Seen in multiengine airplane training, especially when discussing engine failure, minimum control speed, and how much drag the failed engine creates.
Derivation
A combination of 'auto' (Greek 'autos', meaning self or by itself) and 'feather'. In aviation, to 'feather' a propeller means to turn its blades parallel to the airflow, like a feather lying flat in a breeze, so the blade slices through the air rather than catching it. 'Autofeather' simply means the airplane does this for the pilot automatically.
Why Pilots Care
Reduces asymmetric drag after engine failure, lowering VMC and giving the pilot better directional control at slower speeds.
Intuition Check
Autofeather does not mean the engine fixes itself or restarts itself. It means the failed engine’s propeller is automatically moved to a low-drag position.
Example Sentence 1
Before takeoff, the crew confirmed the autofeather system was armed as part of the checklist.
Example Sentence 2
Aircraft equipped with autofeather demonstrate a lower VMC because the failed propeller creates less yaw force.