Definition
An engine-driven mechanical pump that moves air through the aircraft's pneumatic system to drive air-powered gyroscopic instruments such as the attitude indicator and heading indicator. In most modern light aircraft it is a dry vacuum pump that draws air through the instrument cases, spinning their internal gyros; in some installations it is a pressure pump that pushes air through them instead.
Plain English
A pump turned by the engine that moves air through certain flight instruments to make their internal spinning wheels turn. Those spinning wheels are what allow the instruments to show the airplane's attitude and heading.
Context Anchor
Seen in vacuum and pressure instrument system diagrams, especially when studying how some attitude and heading instruments receive their power.
Derivation
“Pump” comes from older words for a device that moves fluid. In aviation, air counts as a fluid because it can flow, be pushed, and be pulled through lines and instruments.
Why Pilots Care
A failed air pump removes power from attitude and heading instruments, forcing reliance on partial-panel techniques or backup systems in instrument conditions.
Intuition Check
Do not picture a portable pump used to inflate a tire. In this context, an air pump is an installed aircraft component that supplies airflow for instruments.
Example Sentence 1
After takeoff the pilot checked the vacuum gauge to confirm the air pump was producing normal suction for the attitude and heading indicators.
Example Sentence 2
During preflight, the mechanic confirmed the air pump was producing proper vacuum for the instruments.