divemaster08
Topic Author
Posts: 168
Joined: Fri Jul 18, 2008 1:45 pm

B767 Etops Question

Wed Sep 04, 2013 3:58 am

Was reading this article on a Delta 767 that diverted due to a generator failing and it states the reason it had to was cause another generator failed on departure from BRU.

http://avherald.com/h?article=467e09e8&opt=0

Now not an expert but I would of thought that in this event, with a generator failing, your already onto your backup before you entered ETOPS airspace so wouldnt that require you to not even enter the ETOPs airspace and return to fix the problem?

Obviously I am only aware of 3 Gens on the 767 (engines and apu). Do the engines actually have 2 gens per engine which are automatically swapped out in the event of the prime gen failing?
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Max Q
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Joined: Wed May 09, 2001 12:40 pm

RE: B767 Etops Question

Wed Sep 04, 2013 4:59 am

Quoting divemaster08 (Thread starter):


Now not an expert but I would of thought that in this event, with a generator failing, your already onto your backup before you entered ETOPS airspace so wouldnt that require you to not even enter the ETOPs airspace and return to fix the problem?

No, for example you can dispatch on an ETOPS flight with a generator inop (although you may be restricted to a shorter time, e.g. 120 minutes)


So losing one is not that serious and you can certainly continue into ETOPS
Remember you have the APU generator as a back up that can power the entire electrical system if necessary.


Losing a second one, however is not good, you are now down to one with your only electrical redundancy on the 767 being the Hydraulic Motor Generator then the battery.


The HMG is really a last ditch back up that only powers select items and the battery even more so, also it only lasts for 30 minutes if you're lucky.


There are a total of three generators on the B767, one on each engine and one on the APU.
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XFSUgimpLB41X
Posts: 3961
Joined: Fri Aug 25, 2000 1:18 am

RE: B767 Etops Question

Wed Sep 04, 2013 5:59 am

Quoting Max Q (Reply 1):
the battery even more so, also it only lasts for 30 minutes if you're lucky.

Reminds me of that AA 757 about 6 years back that had some failure that put them on the battery. For whatever reason, they flew around for around an hour on battery only, and damaged the airplane on the landing. They were lucky it didn't end up much worse!
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roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: B767 Etops Question

Wed Sep 04, 2013 7:52 pm

The requirements for dispatch are different than the requirements for what would cause a diversion. For Non-ETOPS operations, one IDG may be inoperative if the APU is working and is powered up the entire flight. For 120 ETOPS operations, both IDGs must work. However loss of one IDG does not cause a diversion. 120 ETOPS may not be dispatched with an inperative generator, but once the airplane is in the air, the requirements change.

For a 767, if an IDG fails in flight, the procedure is to start the APU. If the APU starts, then it is ok to continue flight. If the APU fails, then the airplane is required to divert to the nearest suitable alternate. The diversion requirement is if the airplane has only one AC power source remaining. As stated earlier, there is still the hydraulic generator available as an emergency source of power.
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