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Auxiliary Power Unit

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APU Panel

Usage

MASTER SW

Controls the APU operation and its start- and shutdown sequence.

  • ON:
    • Blue ON light comes.
    • APU system is powered and performs a power-up test is done.
    • APU Air intake flap opens.
    • Fuel valve opens.
    • APU fuel pump operates if fuel pumps are not in operation.
    • ECAM shows APU page
  • OFF:
    • Manual shutdown sequence.
    • ON light and the AVAIL light on the START pushbutton, go off.
    • The APU keeps running for a cooling period of 60 seconds, if the aircraft was using APU bleed air.
    • Air inlet flap closes at 7 %
  • FAULT Lt:
    • Amber light and ECAM warning message, if an automatic APU shutdown occurs. Possible causes:
      • Fire (on ground only)
      • Reverse flow
      • Air inlet flap not open
      • Low oil pressure
      • Overspeed
      • High oil temperature
      • No acceleration
      • No speed
      • DC power loss. (BAT OFF when aircraft on batteries only)
      • EGT over-temperature
      • ECB failure
      • No flame
      • Loss of overspeed protection
      • Under-speed
      • Oil system shutdown
      • Inlet overheat
      • Clogged oil filter
      • Loss of EGT thermocouples

START

  • ON:
    • Blue ON light.
    • Starter is energized when the flap is completely open.
    • Ignition activates 1.5 second after the starter is energized.
    • When N = 60 %. The APU starter is de-energized. The ignition is turned off.
    • 2 seconds after N reached 95%, or when N is above 99.5% the the ON light on START button goes out. The APU can now supply bleed air and electrical power to the aircraft.
    • APU page disappears from the ECAM display after >10sec.
  • AVAIL Lt:
    • Green light comes on when N is above 99.5 % or 2 seconds after N reaches 95%.

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Last update: August 28, 2021
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