APU Flashcards
What kind of APU is on the aircraft?
Sundstrand APS 2300
Describe the APU
- Constant speed
- Single-stage smeller with a 2-stage axial-flow turbine
What is the voltage and kVA of the APU?
115VAC, 40 kVA
What monitors and controls the APU?
Its own dedicated FADEC
What battery is used for the APU start?
- BATT 2 powers the starter
- BATT 1 powers the FADEC and EICAS for monitoring
What is the fuel source for the APU when the engines are running?
Right fuel tank (ejector pump)
What fuel pump is used for APU start?
- When BATTs on only: DC fuel pump
- AC power on: AC fuel pump
- DC power only: DC fuel pump
What normally provides fuel to the APU when the engine is not running?
- # 2 fuel tank
- AC power: AC fuel pump
- DC power only: DC fuel pump
When does APU electrical and pneumatic loading become available?
3 seconds after the APU speed has reached 95%
Describe the APU start sequence during a ground start
Starter engagement, ignition at 6%, fuel after 0.5 secs and starter cutout at 50%
Describe the APU start sequence during an in-flight start
Starter engagement, ignition at 7-17%, fuel after 0.5 secs and starter cutout at 50%
Will the APU shutdown automatically if speed and acceleration rate isn’t reached in starting cycle time?
Yes
What indication would you have of an APU auto-shutdown?
An APU FAIL EICAS message
What does moving the APU start switch to OFF do?
- Initiates normal shutdown
- 1 min cool down
- Pneumatics removed immediately and electrical power is removed after the 1 minute cool down
What happens when you rotate the APU master switch to ON?
Powers the FADEC and opens the APU shutoff valve
Can the APU shutdown be cancelled?
Yes, by moving the START switch back to ON before the 1 min cool down is over
Can the APU pneumatics be used during the cool down period?
No
Can the APU electrical power be used during the cool down period?
Yes
How is the APU shutdown immediately?
- APU EMER STOP button
- No 1 min cool down
What is indicated by an illuminated red bar in the upper half of the EMER STOP button?
An APU fire
What BUS provides APU fire protection>
DC ESS BUS 2
What BUS provides APU fire detection?
DC ESS 1 and 2 (Using MAU 1 and 2). I think it may just be DC ESS BUS 1
What happens when the APU EMERGENCY STOP button is pushed?
The APU fuel shutoff valve closes and the APU still shut down with no cooling period. A white stripe displays on the switch
Selecting the APU control MASTER selector knob from On to OFF initiates a normal APU shutdown, monitored and controlled by?
FADEC
How is the APU monitored and controlled?
FADEC
What will happen if batteries are turned OFF during the 1-minute cool down period?
APU will shut down immediately
When will automatic shutdown of the APU occur?
- Ground: overspeed, underspeed, FADEC critical fault, fire, EGT overtime, sensor failure, high oil temp, low oil pressure
- Flight: Overspeed, underspeed, FADEC critical fault
The APU can be used for pneumatics to a max of what altitude?
15,000 feet
What is the max altitude for operation of the APU electrical?
33,000 feet
What is the max altitude for APU start?
30,000 feet
Up to what altitude may the APU assist in engine start?
21,000 feet
On which display would the crew find info regarding the operational status of the APU?
EICAS
Where would you find the APU RPM and EGT indications?
On EICAS
If both engine bleed and APU bleed is available which one has priority?
Engine bleed
During APU start where does the fuel come from and what pump does it use when only DC power is available?
Right fuel pump and DC pump until AC power is available, then AC pump takes over
With the right engine running and the APU running where does the fuel come from?
Engine ejector pump?
The AMS controls the APU and engine bleeds. During an engine start what happens to the bleed valves?
The APU bleed valve opens which supplies the bleed air for the start. After the start the engine bleed valve opens and the APU bleed valve closes
Do you get the APU cool down period when you press the APU emergency stop button?
No
If you need the APU 50 secs into shutdown is there a way to get it back?
Yes, turn the APU master switch back to ON
How would you operate the APU while using from from Tank 1?
Select XFEED selector to LOW 2
In normal operations on the ground with APU running it would be normal to see the fuel imbalanced with less fuel in which tank?
Right tank
Can the APU be started after a critical fault?
No
Will the APU auto-shutdown inflight for an APU fire?
No
What is the APU starter duty cycle?
- 1st and 2nd attempt: 60 secs on/60 seconds off
3rd: 60 secs ON/5 mins off
