APU PANEL

Question 0

DESCRIBE THE START/STOP SWITCH-LIGHT.

Answer 0

When pressed in the APU start motor engages and:
Start light illuminates
APU START status message appears
Fuel and Ignition introduced at 4%
At 50% start motor de-energized, APU START message and light extinguish
At 99% ignition is de-energized
4 Seconds later AVAIL is illuminated indicating the APU is ready for pneumatic loading
When pressed out:
APU ECU generates a false overspeed signal and starts an auto shutdown, APU SOV closes.
When RPM drops below 50% the ECU commands the APU door closed.

Question 1

DESCRIBE THE PWR/FUEL SWITCH-LIGHT.

Answer 1

When selected in, the APU ECU is powered and:
APU door opens
APU ECU starts the IN BITE self test
APU gauges appear on the Status Page
APU fuel SOV opens
Crossflow/APU fuel pump is energized
PUMP FAIL – Crossflow/APU fuel pump has failed.
SOV FAIL – Indicates the APU fuel feed SOV has failed.

Question 2

WHAT HAPPENS WHEN THE PWR/FUEL SWITCH-LIGHT IS PRESSED AGAIN?

Answer 2

When selected out:
Deactivates the Crossflow/APU fuel pump
60 Second BITE test is preformed
After 60 seconds, APU RPM & EGT gauges are removed
NOTE: The primary purpose of the APU is electrical and the secondary is pneumatics.

Question 3

WHEN DOES THE APU DOOR MOVE AND WHAT CONTROLS ITS POSITION?

Answer 3

THE POSITION IN A FUNCTION OF AIRSPEED AND ALTITUDE.