Definition
The loss of suction produced by an engine-driven vacuum pump, which normally drives the gyroscopes inside certain flight instruments — typically the attitude indicator and heading indicator. When the pump fails, those instruments slowly become unreliable as their gyros spin down, even though the instruments may still appear to be working at first.
Plain English
The pump that spins the gyros inside some of your flight instruments has stopped working. The affected instruments will gradually give wrong readings as their internal spinning parts slow down.
Context Anchor
Seen in discussions of cockpit workload, abnormal situations, instrument indications, and task saturation during flight.
Derivation
Vacuum here means a region of lower pressure than the surrounding air. The pump creates that lower pressure to pull air through the instruments and spin their gyros. When pilots say 'vacuum pump,' they really mean a suction pump.
Why Pilots Care
It sharply increases workload and can trigger spatial disorientation or loss of control if the pilot does not immediately shift to partial-panel techniques.
Grounding Statement
A vacuum pump failure can turn a normal instrument scan into a high-workload problem because some familiar cockpit indications may no longer be dependable.
Intuition Check
Do not assume a vacuum pump failure means the engine has failed or the airplane has lost all electrical power. It means the pump serving certain air-driven instruments has failed, and those instruments may become unreliable.
Example Sentence 1
When the attitude indicator started leaning steadily to one side in level flight, the pilot suspected a vacuum pump failure and switched to the backup instruments.
Example Sentence 2
Task saturation quickly followed the vacuum pump failure in the clouds because the pilot had to cross-check the remaining instruments constantly.