APU shutdown-NG

[alexban]

HY
Selecting the APU switch to off will start the shutdown process of the APU. On NG ,unlike the classic,this will allow for 1min cooling before automatic shutdown,after you select switch to off.
My question is: if,after you select APU off,during this minute,before apu close,you select the switch again to on,will this cancel the shutdown process or not?
Is there any danger in doing this?
Brgds Alex

[B73567AMT]

Yes, you can place the switch back into the ON position and the shutdown will be cancelled. I've done it before on tha airplane.
I don't see any danger in doing this. The APU stays at 100 % RPM during it's cool-down (some APU shutdown cooldowns have the APU lower it's RPM, the B767-400 and B777 come to mind)

[BobbyR]

APU shutdown cooling period is basically there to allow the APU internal temperatures to stablise in an unloaded condition. This reduces the amount of thermal shock on components hence reducing the amount of wear and increasing the life of the engine.