APU Flashcards
(38 cards)
How is the APU started?
- Aircraft batteries
- External power source
- Normal aircraft AC power
What is the main function of the Auxiliary Power Unit (APU)?
It is a self-contained unit that supplies the aircraft with:
PNEUMATIC and ELECTRICAL power
What does the APU provide during on-ground operations?
- supplies bleed air for starting the engines
- supplies air-conditioning
- supplies electrical power
What does the APU provide during takeoff?
- Supplies bleed air for air conditioning (for example, when optimum aircraft performance is required)
[APU bleed ON during takeoff]
*computation is packs OFF but PACK 1 and 2 pb still ON
What does the APU provide in-flight?
‐ It backs up the electrical system
- It backs up the air conditioning
- It can be used to start the engines
What is the basic element of an APU engine?
A SINGLE-SHAFT gas turbine that delivers mechanical shaft power for:
- Driving the accessory gearbox (electrical generator, starter, etc.)
- Produces bleed air (engine starting and pneumatic supply)
The basic element of an APU engine is a SINGLE-SHAFT gas turbine the delivers power for:
- Driving the accessory gearbox (electrical generator, starter, etc.)
- Produces bleed air (engine starting and pneumatic supply)
Is a full-authority digital electronic controller that performs the bulk of the APU system logic for all modes of engine operation:
Electronic Control Box (ECB)
What is an ECB?
Electronic Control Box
A full-authority digital electronic controller that performs the bulk of the APU system logic for all modes of engine operation
What does the Electronic Control Box (ECB) provide for the APU system?
Performs the bulk of the APU system logic for all modes of engine operation, such as:
- Sequences the start and monitors it
- Monitors speed and temperature
- Monitors bleed air
- Sequences the shutdown
- Controls the automatic shutdown
This allows external air to reach the compressor inlet of the APU:
APU air inlet flap
Where is the APU air intake flap located?
At the bottom of the tail cone, beneath the APU compartment
What controls the APU starter?
The ECB (Electronic Control Box)
When does the APU starter engage?
- When the APU MASTER switch and START pb is switched ON
and
- When the APU intake flap is FULLY OPEN
When the APU MASTER switch and START pb is switched on, what else is needed in order for the APU starter to engage?
APU air inlet flap fully open
Where is the APU located?
In the unpressurized tail cone
After the APU MASTER sw has been turned ON, the ECB will not allow an APU start until:
The APU air inlet flap is fully open
What are the two (2) things needed in order for the APU starter to engage?
- APU MASTER switch and START pb ON
- APU air inlet flap fully OPEN
When the APU MASTER switch and START pb is switched ON with the APU air inlet flap still fully closed, will the APU starter engage?
NO.
The APU air inlet flap MUST be FULLY OPEN
(Together with the APU MASTER switch and START pb ON)
The APU fuel system is normally supplied from?
The LEFT fuel feed line.
The required pressure is normally available from the tank pumps
What happens if the required pressure from the left fuel feed line is not available (batteries only or pumps off)?
The APU FUEL PUMP starts automatically
When does the APU FUEL PUMP turn ON?
Provided that the APU MASTER sw is ON:
It starts AUTOMATICALLY when the required pressure from the fuel feed line is not available.
The ECB controls the fuel flow.
When does the APU Fuel pump operate?
If no fuel tank pump is running
The APU bleed air system is fully automatic. True or False?
True
