APU Flashcards
The APU is a self contained, single shaft, gas turbine engine with its own internal oil and fuel systems that provides the aircraft with….?
Pneumatic and electrical power
On the ground the APU supplies….?
Bleed Air for starting engines and air-conditioning, and
Electrical power
In flight the APU provides….?
- Back up to electrical system
- Back up to air conditioning
- Can be used to start engines
From where can the APU obtain power for starting?
- Aircraft batteries
- normal electrical system
- Ground service
Max altitude to assist engine start?
20 000ft
Max Altitude for air conditioning and pressurisation (single pack operation)?
a) YUD
B) all others
a) 22 500 ft (YUD)
b) 20 000 ft
Max Altitude for air conditioning (dual pack operation)
15 000ft
Is the use of APU bleed air for wing anti-ice permitted?
NO!
APU Battery Restart limit (Elec Emer Config)?
25 000ft
What is the APU operation and Normal restart envelope?
Can be operated and restarted throughout the aircrafts normal flight envelope.
Except starting APU on batteries (Elec Emer) limited to 25 000ft
Are the any limits on when the APU can supply electrical power?
No,
only limited to the aircrafts flight envelope
After 3 consecutive APU starts, Flight crew must wait ____mins before a new start attempt?
60mins
Max N speed
107%
Max EGT for starting?
a) YUD
b) others
a) YUD:
<35000ft -1090 deg C
>35000ft -1120 deg C
b) Others:
<25000ft -900 deg C
>25000ft -982 deg C
Max APU for running?
a) YUD
b) others
a) YUD:
675 deg C
b)
with 5 sec confirmation for shutdown: 682 deg C
for immediate shutdown:
700 - 742 deg C depending on ambient temperature
Is APU allowed to be start / shutdown during refuelling/defuelling?
Yes
If APU failed to start or following an automatic shutdown, during refuel / defuel. Is APU now allowed to be started?
No.
Do not start APU
What should be done with the APU if a fuel spill occurs?
Perform normal APU shutdown
The electronic control box (ECB)is a full authority digital electronic controller that performs the bulk of the APU system logic for all modes of engine operation, such as:
- Sequences Start and Shutdown
- Monitors Start, Temp, Speed and Bleed air
- Controls automatic shutdown
What controls the Electric starter?
The ECB.
Electronic Control Box
When will the starter engage?
When the:
- air intake is fully open, and
- MASTER SW and START pb are ON
Which fuel feed line supplies the APU?
Left side
Which fuel pumps normally provide required pressure for APU?
Tank pumps
When would the tank pumps not be available to provide pressure for APU?
Batteries only, or
Pumps OFF
How is fuel pressure supplied for APU if pressure from tank pumps is not available?
APU FUEL PUMP starts automatically
What controls the APU fuel flow?
ECB.
Electronic Control Box
What do the Inlet Guide Vanes )IGV’s control and what positions them?
IGV’s control bleed air flow
A fuel-pressure-powered actuator positions the IGV’s
Is the air bleed system fully automatic?
Yes
What is the APU speed for air contioning demand?
a) YUD?
b) others
a) temp -18 to 35 deg C -99%
other temps -100%
b) 100%
How is a routine APU shutdown performed?/
APU MSTR……OFF
on APU panel
How is an emergency shutdown performed?
Pilots: APU FIRE Handle, or
Ground crew: APU SHUT OFF on interphone panel
May the APU run without cockpit crew supervision on the ground?
Yes (FCOM)
What are the indications if APU Fire?
- APU fire warnings in cockpit
- Horn in nose gear bay
- AVAIL light goes out
- FAULT light in MSTR sw
- APU shuts down
- APU fire extinguisher discharges
The APU MSTR sw controls:
- Electric supply for operation
- Starting and shutdown sequences
When the APU MSTR is switched off and the APU was using APU bleed supply, for how long does the APU keep running?
For a cooling period of 60-120 sec
At what % does the air inlet flap close after APU shutdown?
7%
Does the APU ECAM page always display during APU start?
No, not in battery power.
Only if aircraft has ground power or main generator power
Other aircraft (Not YUD)
In the case of an automatic, non-emergency (emerg = fire) when does the air inlet flap close?
15mins after the APU speed is lower than 7%
Other Aircraft (Not YUD)
If an automatic non-emergency (not fire) shutdown happens on the ground when will the 15min countdown for the inlet flap to close, start?
after lift-off
What does the green AVAIL light mean?
The APU is started and can supply bleed air and electrical power to the aircraft systems
When does the AVAIL light come on?
a) YUD
b) other aircraft
a) when N is above 95%
b) when N is above 99.5%, or
2 sec after N reaches 95%
What components are attached to the accessory gearbox?
- Generator
- Starter
- Oil pump
APU bleed air valve position on ECAM APU page
a) crossline-Amber?
b) XX-amber?
a) APU bleed valve is closed and the APU bleed is ON
b) APU bleed valve / APU BLEED pb status info is not available
ECAM APU page:
Bleed air pressure shows amber XX
What does this mean?
ADIRS 1 or 2 is not available or selected OFF, or
the data from the ECB are invalid or not transmitted
ECAM APU page:
At what N speed does the indication become,
a) amber?
b) red?
a) amber - above 102%
b) red - above or equal to 107%
ECAM APU page:
When does EGT become
a) amber?
b) red?
a) amber: EGT >= EGT MAX-33
(inhibited during engine start)
b) red: EGT >= EGT MAX
(automatic shutdown begins)
What calculates EGT MAX?
The ECB and transmits it to ECAM
What is EGT MAX is a function of:
a) during start?
b) when APU is running?
a) Function of N during start
b) Function of ambient temperature when APU is running
When will the LOW OIL LEVEL advisory pulse green?
When aircraft is on the ground, and
APU not running
