Vacuum Pump

An engine-driven pump that creates suction to spin the gyroscopic rotors inside the attitude indicator and heading indicator. A typical vacuum system maintains 4.5 to 5.5 inches of mercury of suction, monitored on the suction gauge in the cockpit. If the vacuum pump fails, the attitude indicator and heading indicator will slowly spool down and become unreliable, which is especially dangerous in instrument conditions. Pilots should include the suction gauge in their instrument scan and know how to fly using partial-panel techniques (turn coordinator, magnetic compass, and airspeed indicator) in case of vacuum failure.