OFF: Normal shutdown is initiated. Pneumatic power is removed immediately, electric power is removed at the end of a 1-minute cooldown. Rotating the knob back to ON during shutdown cancels the shutdown sequence.

ON: Normal position when running.

START (Momentary position): Initiates the APU start cycle.

Note: APU electrical and pneumatic are available 3 seconds after reaching 95% rpm.


PUSH IN: Closes the APU shutoff valve, shutting the APU down without a cool down period. White bar illuminates in the lower half of the button.

PUSH OUT: Normal Position.

Red striped bar in the top half of the button illuminates in the event of an APU fire. When pushed in a white striped bar illuminates and the APU FIRE EXTINGUISHER button illuminates.

APU Fuel Supply:

  • DC power only the DC fuel pump provides fuel to the APU.

  • AC power available with engines off, the fuel is provided by the AC fuel pump 2.

  • Right engine running fuel is supplied by the ejector fuel pump from the right wing tank.

  • Fuel normally supplied from the right or left fuel tank through the crossfeed valve.

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