APU Start

Flight Preparation (APU start)

The aircraft has now DC power from the batteries. To get AC power to the aircraft, either a ground power cart must be attached, or the APU must be started. Note that the APU will need to be started, irrespective of ground power, in order to get APU bleed air available for engine start later.

The APU start controls are located on the overhead panel at the front in between the light switches. The control panel consists of an APU Master button and an APU start push button.

Prior to APU start, the aircraft walk around would have checked for APU flap position, APU extinguisher bottle pressure plug, APU exhaust exit not blocked etc.

In addition the APU fire test push button may be pressed to test the APU fire system. The button is located on the APU Fire panel on the left hand side of the overhead panel.

First, press the APU master button in. This will illuminate the ON/R light in blue.

The APU can be started on APU battery, using external power or using the aircraft electrical power.

Next push in the momentary APU start button which will illuminate the ON light indicating that the APU is starting.

If there is already external power to the aircraft the system display will show the APU system page.

There will be a delay of some seconds for the APU flap to open before the APU N1 begins to increase.

When the APU is running ( APU N1 > 95%) the AVAIL light is illuminated and the ON light extinguished.

The APU is now ready to supply the aircraft with electrical power.

On the electrical overhead panel press in the APU generator push button. All the displays will now function and the APU AVAIL indication will be shown on the EWD.

The APU generator takes over the electrical power for the left side of the aircraft ( if EXT A had been used ) or the whole of the aircraft power if no external source had been used.

Selecting the APU bleed on the pnumatics panel will provide air conditioning to the aircraft and the EWD will show APU BLEED instead of APU AVAIL.