APU System Flashcards
When does the APU inlet door open and close?
Prior to engine start and remains open until after shutdown.
The APU can be started on the ground and left running up to______.
20,000’
Can you start the APU in the air?
No
Where can you find the APU operating status? Things like EGT, N1, N2, Oil quantity.
STATUS page
How many APU generators?
2
Is the APU capable of supplying the entire electrical load of the aircraft?
Yes, only on the ground.
Can the APU provide any electricity in flight?
No
On the ground, the APU can run ____packs, except for during_____.
All (3) packs ; except during engine start.
In flight, the APU can run ____ pack(s) up to _____.
1 pack ; up to 15,000’
APU fuel is normally supplied from____.
Main tank 2
When AC power is available, the APU normally gets fuel from which pump?
Main pump 2 aft.
If main pump 2 aft supplies fuel to the APU, why does main pump 3 aft also run?
To prevent tank to tank transfer and also to be a backup if main 2 aft fails.
What supplies fuel to the APU when AC power is unavailable?
A dedicated DC pump.
Where is the DC fuel pump located?
Main tank 2
How many fire detection loops are in the APU compartment? How many loops required to trigger a fire warning?
2 (dual loop)
Only 1 is required to set off the warning.
If a fire is detected in the APU compartment, what happens?
-It sets off the warning
-It shuts off the APU
ON GROUND: It also discharges the fire bottle
Where is the APU ground control fire protection panel?
In the right body gear well.
What does the APU ground control fire protection panel provide?
-APU fire horn
-APU fire light
-A shut down Switch
-A shut down/arm lever
-A fire extinguisher discharge switch
Do you need both batteries to start the APU?
Yes
What components related to the APU are powered by the main battery (Main hot battery bus and main battery bus) ?
-APU fire extinguisher
-APU fuel valve
-Standby APU controller
What components related to the APU are powered by the APU battery? (APU Hot Battery bus and the APU battery bus as a whole)
-DC starter and DC fuel pump
-APU inlet door and APU controller
-APU fire detection system
What is the APU START SOURCE switch on the overhead MX panel that has 2 positions, TR and APU BATTERY for?
It is the start source for the APU.
TR: APU starter powered by a TR whenever utility bus 4 is powered.
APU BATTERY: APU starter powered by the batteries
What does the OFF position do on the APU start selector?
-Closes the APU bleed air valve
-Initiates the normal shutdown
-Resets auto shutdown fault logic, except if the shutdown due to an APU bleed duct leak
What does the ON position do on the APU start selector?
-Opens fuel valve and inlet door
-Arms APU bleed isolation valve
-Activates DC fuel pump or 2 AC fuel pumps as appropriate. (Main tank pump 2 and 3 aft)
What does the START position do on the APU start selector?
INITIATES AUTOMATIC START SEQUENCE.
Initiates the start by:
-Opens APU fuel valve
-Opens inlet door
-Engages starter after inlet door opens
-Engages ignition
When does the EICAS memo message APU RUNNING display?
When the APU start selector is in the ON position an APU RPM is 95% or more.
After you start the APU, what is a good indication that air and electrical are available from the APU?
The memo message APU RUNNING
After selecting OFF, the bleed air is cutoff from the APU. How long does the APU keep running for its cooldown?
60 seconds
If the battery is positioned OFF prior to APU cooldown being complete, what happens?
The APU shuts down immediately
Wait at least ____ minutes before placing the battery switch to OFF after the APU is selected OFF.
2
