APU Flashcards
What is the function of the APU surve control valve (SCV)?
Reduces APU surge potential
APU bleed air is controlled by modulating what?
APU LCV
When is the surge control valve commanded open (SCV)?
When the APU is supplying electrical loads above 17,000 feet
Under high demand what takes APU priority?
APU electrical loads over pneumatic loads
Max APU operating altitude
41,000 feet
Max starting altitude
37,000 feet
Main engine and ECS operation limited to what altitude?
25,000 feet
What controls and monitors all facets of the APU operation?
APU electronic control unit (ECU)
APU door position speed
220 KIAS if door is open and APU not operating
How is the APU door operated?
Electrically by the ECU
Where is the APU door position displayed?
EICAS status page
Where does the APU receive fuel from?
Left collector tank
When will the APU starter disengage
Between 46-60% rpm, dependent on altitude
Battery voltage required for an APU start?
22 volts in both batteries
At what RPM will the ECS inhibit start?
7% RPM on ground
12% RPM inflight
What is the purpose of the internal bypass valve?
Allows the APU to continue to run if the APU pump fails
When will the APU AVAIL light illuminate?
99% RPM plus 2 seconds
APU OVERSPEED warning is displayed when?
When RPM exceeds 106%
Max permissible load on the APU generator?
40 KVA
What does the main battery power during an APU start?
APU ECU
What does the APU battery power during a start?
The 28v DC electric start motor
When does the APU ignition turn off during a start?
95% rpm
What happens when the PWR FUEL switchlight is pressed?
- ECU is powered
- APU IN BITE
- APU fuel pump activates
- APU gauges appear
- Fuel SOV opens
- APU air inlet door opens
Can the APU supply bleed air for anti-icing?
No
Can the APU bleed air and another source of bleed air be used at the same time?
No
How many squibs does the APU fire bottle have?
1
