APU Flashcards
What is APU ?
Auxiliary power unit is a self-contained unit that supplies a/c with pneumatic and electrical power.APU is a single-shaft gas turbine which deliver power to drive the accessory gear box
What is the power source for APU start ?
- Battery
- Normal electrical system
- Ground service
What are the component of APU ?
- APU engine
- ECB
- Air intake system
- Starter
- Fuel system
- Oil system
- Inlet guide vanes
- Airbleed system
What is ECB ?
Electronic control box
Like FADEC of engine, ECB monitor and control all APU operation
What kind of stater does APU have ?
Electric starter
When will starter engage ?
When air intake fully open and MASTER SW and START pb ON
Which fuel line feed the APU ?
the left side
How does APU fuel pump work ?
Normally,tank pump will supply pressure. APU pump start automatically when pressure not avail.
What is the function of inlet guide vane ?
aka IGV
Control bleed air flow
a fuel-pressure-powerd actuator position the IGV
ECB control the actuator
What is APU speed for operation ?
ECB set APU speed 100% except for air conditioning demand if temp is btw -18°C and 35°C
How to perform an emergency shut down ?
- Push APU FIRE pb
- APU SHUT OFF pb on the interphone panel under nose fuselage
What will happen when APU fire on ground ?
- APU fire waring in cockpit
- A horn in the nose gear bay
- AVAIL light go out
- FAULT light in MASTER SW lights up
- APU auto shut down
- APU fire extinguisher discharges
What is APU manual shut down sequence ?
- ON light on MASTER SW and AVAIL light go out
- If APU bleed was used, APU will keep running for cooling period of 60s to 120s
- At 7% air inlet flap close
When will AVAIL light lights up ?
N>99.5% or 2s after N >95%
