APU Flashcards
When does the maximum fuel valve opens during the APU start sequence? For what purpose?
When speed reaches 90% and after a time delay of 1.5 seconds, the maximum fuel valve opens. It allows a governor to control the fuel flow. The APU ON capsule on the upper console and the legends on the pilot’s and copilot’s inboard MFDs will then go on.
How does the ESU determine the speed of the APU?
A speed sensor on the accessory drive assembly provides a pulse signal to the ESU. The ESU converts the pulses to an RPM signal which is used to operate the main fuel and maximum fuel valves.
Where can the procedures for the APU Fuel Line Prime be found?
WP1481
What components are mounted to the APU accessory gear box?
The gear box provides the mount for the hydraulic starter, fuel pump, and accelerator
What does 100% on the tape position indicator represent? What does 0% represent?
When the tape position indicator is at 100% (full left), the pressure chamber is fully charged. When the tape position indicator is at 0%, the accumulator is empty and needs recharging.
List three things that occur when the APU-T handle is pull?
Pulling the T-handle:
· Arms the fire extinguisher
· Removes 28 vdc from the APU control switch
· Cuts fuel, thus shutting down the APU.
Sends signal to ESU
Arms fire ext
Changes directional control valve to APU
Shuts off prime boost pump
De-energizes APU fuel shutoff valve
What fault is represented by (white, white, black, white, black) BITE indication? What is its BITE NO.?
Main Fuel Valve Failure.
BITE NO. 28
What are the major components of the APU?
The APU consists of a gas turbine power section, reduction gear drive, and appropriate controls and accessories.
What are the two modes the ESU monitors during APU use?
Start sequence mode and the operational mode.
What must you not turn off if you have an APU start sequence failure?
The #1 & #2 battery switches.
What does the accumulator pressure gauge indicate?
The pressure gage will indicate how much pressure the hydraulic charge has placed on the nitrogen pre-charge.
