APU Flashcards
What does the APU ECU do?
Responsible for the automatic start and shutdown of the APU
Provides all APU protections
With engine start selector to Ground, the ECU ensures 21 psi (preventing hot start)
How many batteries are needed to start the APU?
- APU battery and main ship battery
What systems are on the main battery?
Fire detection
APU Fuel Valve
DC Fuel Pump
Where is fuel for the APU normally provided from?
Forward Left AC Fuel Pump
How is the APU started and stopped?
Automatic. Controlled by the EEC
What must happen for APU to power buses?
External power must be selected off
What must happen for APU to power buses?
External power must be selected off
With the APU running and powering system, does external power still power anything?
Ground Handling bus
Shutting down the APU, after running loaded, what happens?
APU bleed valve closes, allows APU to cool down, APU fuel valve closes, APU shuts down.
Other than APU fire, what other horns can be heard from the ground APU panel?
Ground call
External power disconnected
E&E compartment overheat
What powers the APU inlet door?
Main battery
When does the APU Run light come/remain on?
95% and remains on until fuel cutoff/shutdown
On the ground, without the engines started, if the battery is selected OFF, what happens to the APU?
Shuts down. No fire detection available
In flight if the battery switch is turn off, what happens to the APU?
Will NOT shut down. Left main DC bus powering battery bus. No effect on fire detection.
What is the Start sequence?
Off > On > Start > Springs to On > Fault light blinks once > run light blinks twice > fuel introduced > ignition > 95% > Run light on steady.
