Auxiliary Power Unit
Description
The Auxiliary Power Unit (APU) is a small jet engine in the back of the A320neo which supplies the aircraft with pneumatic and electrical power.
Usage
MASTER SW
Controls the APU operation and its start- and shutdown sequence.
- ON:
- Blue ON light.
- APU system is powered (performs a power-up test after set to ON).
- 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: -Air inlet flap closed -Clogged oil filter -DC power lost (BAT OFF when aircraft on batteries only) -ECB failure -EGT overtemperature -Fire (on ground only) -High oil temperature -IGV failure -Inlet overheat -Loss of EGT thermocouples -Loss of overspeed protection -Low oil pressure -No acceleration -No flame -No speed -Oil system shutdown -Overcurrent -Overspeed -Reverse flow -Sensor failure -Slow start -Underspeed
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 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%.
Last update: September 18, 2021