Definition
A mechanical pump mounted on and turned by the aircraft engine that creates suction (a partial vacuum) used to drive air-powered gyroscopic flight instruments such as the attitude indicator and heading indicator. The pump pulls air through the instruments at a regulated suction value, spinning their internal gyros at the speed needed for accurate operation.
Plain English
A pump bolted to the engine that sucks air through certain flight instruments to make them work. Without it, those instruments lose their power source.
Context Anchor
Seen in discussions of aircraft power sources, instrument systems, preflight checks, and vacuum-system failures.
Derivation
‘Vacuum’ comes from Latin vacuus meaning ‘empty.’ The pump doesn’t create a true empty space — it just lowers the air pressure enough to pull air through the instruments. ‘Engine-driven’ simply means the engine turns it, the same way it turns the alternator.
Why Pilots Care
Supplies the suction needed for reliable operation of primary attitude and directional gyros in most single-engine piston aircraft; loss of suction requires immediate transition to backup instruments.
Intuition Check
Do not think of “vacuum” here as outer-space emptiness. In this system, it means suction created by lower air pressure.
Example Sentence 1
During the runup, the pilot checked the suction gauge to confirm the engine-driven vacuum pump was producing the correct pressure.
Example Sentence 2
During the preflight inspection the pilot verified that the engine-driven vacuum pump produced suction within the green arc on the gauge.