APU Flashcards
Pressurized fuel is supplied to the APU by the:
APU fuel pump.
The APU ECU Controls the APU during:
All phases of operation.
Max Altitude for starting?
37,000 ft
Max Altitude for APU bleed air extraction?
25,000ft
The battery master is ON and the PWR FUEL switchlight is pressed, what then occurs?
- The ECU is powered
- APU IN BITE
- APU Fuel pump activates
- APU RPM and EGT gauges appear
- Fuel SOV opens
- APU air inlet door opens
Max speed with APU door open?
220 kias if APU not running, otherwise no restriction
What batter voltage is required before starting the APU?
22 volts on both batteries
What does the main battery power during an APU start?
APU ECU
What does the APU battery power during an APU start?
The 28 vDC electric start motor
When will the AVAIL switchlight illuminate?
99% rpm + 2 seconds
What is the purpose of the internal bypass valve?
Allows APU to continue to run if APU pump fails
APU Bleed Air is controlled by modulating
APU LCV (Load Control Valve)
APU bleed pressure readout can be monitored on?
EICAS “ECS” synoptic page
The APU gauges(RPM and EGT) appear on EICAS when:
APU POWER / FUEL switch light is pressed in
“APU OVERSPEED” warning message is displayed when RPM exceeds:
106%
When does APU ignition turn off during a start?
95% rpm
When does the APU starter motor disengage?
46% rpm when on ground
60% RPM when in flight
Can the APU be used for Anti Ice Bleed Air?
No
Can APU bleed air and another source of bleed air be used at the same time?
No
What valve opens when the APU is providing electrical power above 17,000 ft?
The Surge Control Valve (SCV). The opening of this valve helps to reduce the chance of APU surges when operating in an unloaded bleed air condition.
How many squibs does the APU fire bottle have?
1
When will the APU ECU inhibit a start due to APU RPM?
The APU ECU will inhibit a start while on the ground if the RPM exceeds 5% or in flight if the RPM exceeds 12%
Max permissible load on the APU generator?
40 KVA
Max Altitude for APU operation?
41,000ft
