APU Flashcards
What does the APU system provide power for?
Starting the engines and operating the Environmental Control System (ECS)
The APU incorporates a generator for ground and emergency in-flight electrical operations.
What is the APU?
A gas turbine engine
What is the fuel consumption rate of the APU at rated power?
150 pounds per hour.
Is the APU intended for routine in-flight use?
No.
What are acceptable in-flight uses for the APU?
- Emergency procedures
- Single engine training
- Practice autorotations
- Powering the ECS during extreme temperature operations.
What is the purpose of the prime/boost pump?
To prime the engine or APU fuel lines and provide fuel under pressure during starting and operations.
What is the minimum accumulator pressure required for starting the APU?
Approximately 2,650 psi.
How can the hydraulic accumulator be recharged?
Using the accumulator hand pump or by the backup hydraulic pump when AC power is available.
What happens when the APU CTRL switch is turned ON?
It opens the APU airframe fuel shutoff valve and sends a start signal to the APU Digital Electronic Sequence Unit (DESU).
What does the DESU do?
Controls and monitors the APU.
What indicates an APU failure?
The APU FAIL indicator.
What does TEMP HI indicate?
The APU has reached the maximum oil temperature for continuous operation.
What is the function of the FUEL PUMP switch in the APU BOOST position?
Supplies pressurized fuel from the left fuel tank to the APU.
What happens when the accumulator pressure drops below 2,650 psi?
The APU ACCUM LOW advisory and ACCUM LO caution light appear.
What does the APU ACCUM LOW advisory indicate? Possible delete
That the accumulator pressure is low.
