greg47

[greg47]

What's the gen on APU shutdown. Previously on larger types we offloaded the air for 2 mins and gen for 1 minute. Some had an auto shutdown sequence similar and the air could be up to 3 mins ?depending on ambient . Now flying a F50 and the procedure we are told is to shut it down with no cooling cycle . Their argument is one thermal shock.
Which procedure is correct

[Valmont]

Depends on the APU. What does your FCOM says about it ?

For example on the A320, there's different kind of APUs. Some will shut down within 120 seconds after the last use of APU bleed, some of them are 90 seconds and some others 60.

I'd say, if there's no autoshutdown on the F50, look up in the FCOM what's the correct procedure.

[Natstrackalpha]

A320
Shut off the APU start button pb. NOT the master - yet. The APU will slow down and cool down too for an indetermined time (minutes, not months!) to . . . cool down.

This is also why you must keep batts on until APU cooldown . . .sequence has completed (or you will mess it up basically and it wont cool properly),

also, this process (sequence) includes flap closure.

When, all this has been done by the APU shut down program then you can turn off the main APU Switch pb and the light will go out.

The system has cooled itself down. The flap has closed and you have now finally switched it off.

Just to bore you absolutely fartless; When switching the whole thing on again - first start with the Master sw. APU page comes up and in a few mins, the flap is open and it will then be ready for the start sw pb to be pushed (button below the master APU pb.), at this point in time the APU will, start up (providing the flap is open) warm up and get going and will only shutdown again for one or more of 14 failures plus you turning it off - as above.