Definition
The intake or line that supplies air pressure to a pneumatic instrument or system. In light aircraft, the primary pressure source is typically an engine-driven vacuum or pressure pump that drives gyroscopic instruments such as the attitude indicator and heading indicator. For pitot-static instruments, the pressure sources are the pitot tube (ram air pressure) and the static port (ambient pressure).
Plain English
Where an instrument gets the air it needs to work. If that supply is blocked, broken, or switched off, the instrument can give wrong readings or stop working entirely.
Context Anchor
Seen in pneumatic system failure discussions, especially when a pilot is checking why pressure- or vacuum-powered instruments are not working normally.
Derivation
Pressure comes from a Latin word meaning “to press.” Source means “where something comes from.” Together, pressure source means the place or device the needed air force comes from.
Why Pilots Care
Loss of the pressure source stops the gyros, removing attitude and heading information essential for instrument flight.
Intuition Check
Do not read pressure source as just any place where pressure exists. In this context, it means the device or supply that creates the pressure or suction for the system.
Example Sentence 1
When the vacuum pump failed, the attitude indicator lost its pressure source and slowly began to lean and tumble.
Example Sentence 2
After the pressure source was restored on the ground, the attitude indicator returned to normal operation.