Definition
A hydraulic pump that is mechanically driven by the airplane's engine and serves as the sole source of hydraulic pressure for systems such as landing gear, flaps, brakes, or flight controls. If the engine stops, the pump stops, and any hydraulic system relying on it loses its normal pressure source.
Plain English
A pump that creates hydraulic pressure by being turned by the engine. There is only one of them, and it only works while the engine is running.
Context Anchor
Encountered in engine-failure and emergency-procedure discussions for aircraft that use engine-powered hydraulic pressure for items such as landing gear, flaps, brakes, or some flight controls.
Derivation
"Hydraulic" comes from the Greek hydor (water) — originally describing systems powered by liquid under pressure. "Engine-driven" simply means the pump is turned by the engine itself, the way an alternator or vacuum pump is. "Single" tells you there is no backup pump of the same kind.
Why Pilots Care
Loss of this pump during engine failure disables hydraulic systems, requiring emergency procedures or alternate power sources to maintain control.
Grounding Statement
If the engine that turns the pump stops, the pump stops making hydraulic pressure.
Intuition Check
“Single-engine-driven” does not mean the airplane has only one engine. It means this particular pump is powered by one engine, so losing that engine can also mean losing that pump.
Example Sentence 1
Because the airplane has a single engine-driven hydraulic pump, the checklist requires the pilot to use the hand pump to extend the landing gear after an engine failure.
Example Sentence 2
The pilot confirmed which systems depended on the single-engine-driven hydraulic pump before practicing engine-out procedures.