Trình bày quá trình STARTING APU

When you put the MASTER SW pushbutton switch in the ON position:

-       The ECB starts the power-up test.

-       The APU fuel pump system is energized

-       The APU air inlet door opens approximately 25s.

When you put the START pushbutton switch in the ON position:

-       The ECB energizes the back-up start contactor and the start contactor.

-       The contactors energize the starter motor and the APU starter motor starts to turn.

-       The de-oil valve opens (if oil temp is below 6.6 deg C or fuel temp below  -12.2 deg C or altitude above 20,000 ft ).

At 7% speed, the ECB:

-       The ECB energizes the ignition system

-       Opens the fuel shutoff solenoid valve.

-       Controls the fuel flow to the APU with the start acceleration control logic.

-       The IGVs close.

At 50% speed, the ECB:

-       De-energizes the start contactor (above 20,000 ft at 58%) which switches off the starter motor and the ECB accelerates the APU automatically.

-       De-energizes the back-up start contactor 10KA, after 5 seconds.

At 60% speed, the ECB:

-       De-energizes the ignition unit

-       De-energizes the de-oil solenoid (if opened).

At 95 % + 2 s of the nominal APU speed:

-       The ECB controls and monitors the APU automatically.

-       The green AVAIL legend in the START pushbutton switch comes on.

-       The blue ON legend in the START pushbutton switch goes off.

-       The APU bleed valve is ready for operation.

-       The APU generator is ready for operation.