APU inoperative

[busy]

Hello, everyone!
a day ago we encountered the following case in the Oceanic area control zone:
the crew asked rerouting due to inoperative auxillary power unit. It was neither emergency nor urgency situation, just rerouting request.
So the questions are:
how does inop APU affect flight in the Oceanic airspace and why did the flight need change of route?
Thanks in advance.

[cessna157]

I'm not familiar with overwater/ETOPS procedures, but here's my 1.5 cents:

If the APU were running during the flight (which is sounds like it was, or else no reason for reroute), it would have been running for a reason.  On my airplane, 1 main generator can be deferred.  If that is the case, the APU must be kept running for the duration of the flight for electrical redundancy (1 generator can handle the entire airplane just fine, you just don't want to be reliant on only 1 generator).

So, what may have happened is the APU shut down for some reason during flight.

Once again, that is pure speculation.  But if that were the aircraft that I fly, and we had a generator deferred and the APU shutdown mid-flight, we are required to land at nearest suitable airport.

[busy]

but they didn't say they were going to land, neither they reported any engine problems. Is there a possibility that the generators were ok, APU failed and they made decision to change their route slightly just to be closer to the continent, for example. Just to be on safe side?

[cessna157]

Well, to say "to be on the safe side" may very well be true, but it may have just been the result.  Something would have forced them to change tracks. 

The only reason I'm guessing it was elecrtical is APUs usually cannot/do not serve as pressurization sources while airborne, especially at altitude.

What type of aircraft was it?

[busy]

It was triple 7

[busy]

Do crews always report about generator problems or is it not always necessary?
 If they had told it there would be no any other questions. But they didn't. They just said that "AUP needed for backup on polar route is inoperative"

[busy]

Is polar route of any importance here or does their position make no difference?

[cessna157]

Do crews always report about generator problems or is it not always necessary?
 If they had told it there would be no any other questions. But they didn't. They just said that "AUP needed for backup on polar route is inoperative"

If I remember correctly, I think the only systems failures that we have to report are problems with communications or navigation equipment that would affect the progress of the flight.

Ha, if we were to tell ATC about every little thing that happens in flight, there'd be no air time left for instructions.

[dave]

...Ha, if we were to tell ATC about every little thing that happens in flight, there'd be no air time left for instructions.

That would make for a great ATC comedy tape!