Definition
A friction device fitted to a turboprop or turboshaft engine that stops the propeller from rotating while the engine's gas generator section continues to run. It allows the engine to operate on the ground without the propeller turning, typically to power onboard systems or provide bleed air.
Plain English
A brake that holds the propeller still while the engine itself keeps running, so the engine can be used as a power source on the ground without the blades spinning.
Context Anchor
You may see this term in turboprop systems, engine shutdown procedures, ground operation procedures, or maintenance descriptions.
Derivation
Propeller comes from a Latin root meaning “to drive forward.” Brake comes from older words connected with stopping or slowing motion. Together, the term means a device that slows or stops the part that normally drives the airplane forward.
Why Pilots Care
It prevents damage to the propeller, gearbox, and engine from unintended wind-driven rotation while the aircraft is parked.
Intuition Check
Do not read this as a brake that slows the airplane like a wheel brake. A propeller brake acts on the propeller system itself, stopping or holding the propeller from turning.
Example Sentence 1
With the propeller brake engaged, the crew ran the engine to provide electrical power to the aircraft systems on the ramp.
Example Sentence 2
Strong winds made engaging the propeller brake necessary before leaving the aircraft.