Definition
A propeller whose blades can be rotated to a position where their leading edges face directly into the relative wind, producing minimum drag and stopping rotation when an engine is shut down in flight. Feathering propellers are found primarily on multi-engine airplanes and turboprops, where the ability to streamline a stopped propeller is essential to maintaining controllable flight after an engine failure.
Plain English
A propeller whose blades can be turned edge-on to the airflow so they slice through the air instead of pushing against it. This stops the propeller from spinning and dramatically reduces drag when an engine has failed or been shut down.
Context Anchor
Seen during before-takeoff checks on airplanes equipped with propellers that can change blade angle, especially two-engine airplanes.
Derivation
From the image of a bird's feather lying flat against the wind. A feather offers almost no resistance when its edge faces the airflow. A feathered propeller does the same — the blades turn until their thin edges meet the wind, so the air flows past rather than spinning the blades.
Why Pilots Care
On multi-engine aircraft, feathering prevents a windmilling propeller from producing severe drag that can cause loss of directional control or performance after an engine failure.
Analogy
It is like turning a flat paddle edgewise as you move it through water. Flat against the water it resists strongly; edgewise it slips through with much less resistance.
Intuition Check
Feathering does not mean making the propeller lighter or softer. It means rotating the propeller blades so their thin edges face the oncoming air.
Example Sentence 1
After the left engine failed, the pilot identified, verified, and feathered the propeller before continuing to the nearest airport.
Example Sentence 2
After the right engine failed the pilot feathered the propeller to keep the airplane flying straight.