APU master sw FAULT
AUTO SHUTDOWN has occurred
APU AVAIL
The APU is running above 99.5% or 2 seconds after reaching 95%, and the APU can accept an electric or pneumatic load.
What condition in the APU system would cause an external horn to sound on the ground?
APU FIRE
With both APU and EXT AVAIL lights on, which is powering the aircraft?
the APU
If possible, how would the APU be used if it has already started the cool down cycle?
APU master back ON
Why is it important to wait 2 minutes after the APU AVAIL light goes out before switching off the batteries?
Battery power is required for 2 minutes for the APU flap to close.
* Not waiting may cause smoke in the cabin during the next flight.
Auto Shutdown
Some reasons for an auto shutdown are…
Fire (on the ground)
Flap closed
Overspeed
No acceleration
No light off
DC power lost during start
low oil pressure
high oil temperature
If one generator fails, what is the maximum altitude that you can start the APU?
FL 410
If the aircraft is in the emergency electrical configuration, what is the maximum altitude to start the APU?
FL 250
What does APU BLEED FAULT illumination indicate?
APU bleed leak
Can the APU bleed be used for wing anti-ice?
nope
Max altitude to use APU bleed for single pack operation
22,500’ for the Honeywell and
20,000’ for the Hamilton Standard
If a mechanic pressed the APU AUTO EXTING TEST push button, what would happen?
The APU would shutdown
