Definition
A propeller design in which the blades cannot be rotated to an edge-on (feathered) position aligned with the relative wind. The blade pitch range is limited to normal operating angles and does not extend to the streamlined position used to stop a failed engine's propeller from windmilling.
Plain English
A propeller that cannot turn its blades sideways into the wind to stop them spinning if the engine fails. Its blades only move within the normal range used in flight.
Context Anchor
Seen in propeller system discussions, especially when comparing single-engine and multiengine airplanes after an engine failure.
Derivation
Feather' comes from the idea of turning the blade so its edge slices the air like a feather laid flat into the wind. 'Non-feathering' simply means the propeller lacks this capability.
Why Pilots Care
On a failed engine, non-feathering propellers produce high drag that reduces climb performance and increases the risk of loss of control.
Analogy
It is like trying to move a flat hand through water instead of turning your hand edge-first. If you cannot turn it edge-first, the water pushes back much harder.
Intuition Check
Do not read non-feathering as a small naming detail. It means the pilot cannot place the propeller blades in the low-drag feathered position.
Example Sentence 1
Most training airplanes use a non-feathering propeller, so after an engine failure the blades continue to windmill and add drag during the glide.
Example Sentence 2
Pilots flying behind non-feathering propellers practice immediate engine restarts to avoid sustained high-drag conditions.