View Full Version : One Gen Failure and APU Gen Failure

21st Jan 2010, 13:23
Hi folks,

Want to get your opinion what would you declare in this situation.

Type of acft B733,

You just reached your cruising altitude,one of the Generators goes off, Apu Gen isn't working either.
So you left with one primary source of AC.
Would you declare emergency(Mayday,Pan) or would you ask for priority handling.Crew returned back but didn't declare anything( just electrical problem).


21st Jan 2010, 13:34
In this situation a pan is appropriate in my view. If you were unlucky enough to lose the last remaining generator then a mayday is required.


21st Jan 2010, 14:01
From the Boeing QRH:

There are some situations where the flight crew must land at the nearest suitable
airport. These situations include, but are not limited to, conditions where:
• the non–normal checklist includes the item “Plan to land at the nearest
suitable airport.”
• fire or smoke continues
• only one AC power source remains (engine or APU generator)
• only one hydraulic system remains (the standby system is considered a
hydraulic system)
• any other situation determined by the flight crew to have a significant
adverse effect on safety if the flight is continued.

Requesting priority handling without declaring an emergency is not contemplated in the ICAO rules and in general airline OPS regulations and does not ensure you will be assigned priority.

So, to comply with the Boeing rules, to my understanding, a PAN call would be applicable, upgradable to MAYDAY if conditions warrant.

21st Jan 2010, 17:22
I once had this situation, had a dual IDG failure (don't ask lol) and only had the APU supplying AC power. We declared a PAN. The linechecker (yes it WAS a line check when this happened lol) agreed with us as well.

21st Jan 2010, 18:10
My oppinion is:

PAN call for double generator failure and MAYDAY call for triple generator failure.

21st Jan 2010, 22:03
I wish you the best of luck trying to explain what PAN is if you are outside of the UK.

21st Jan 2010, 23:13
easy, something you cook food in....:ugh:

21st Jan 2010, 23:34
PAN call - I have a problem which requires that I have priority handling in order to get on the ground as soon as possible.
Mayday call - I have a problem and need priority handling as above, also the outcome is uncertain. I may also need ambulance and hospital support.

In this case - full AC and DC is available, albeit from one source. Land at the nearest suitable - but do you really need to "skip the cue" or have special handling (like a long straight final, only left hand turns etc etc)? Would you want to go in front of a medical emergency?

I would be happy without a Pan call, certainly in daylight, provided I was happy that the failures weren't linked (i.e. I am satisfied that the remaining source only has the usual (small) chance of failure.)

I certainly wouldn't hassle anyone who did give a pan call.

22nd Jan 2010, 11:08
I would be happy without a Pan call, certainly in daylight, provided I was happy that the failures weren't linked (i.e. I am satisfied that the remaining source only has the usual (small) chance of failure.)

maybe they had same thinking, but in their case,they were number 2. So still would you like with such technical problems not to have priority?
Luckily they weren't subjected to speed reduction or long vectoring?

Thanks for replies all.

22nd Jan 2010, 12:26
The point I was trying to make, is that it wouldn't bother me if I was number ten. :ok:

Everything still works with one generator - the approach would be completely normal. I would put in a pan call if the last gen failed, placing the aircraft on standby power, of course, but saving 5 minutes or so doesn't change the situation that much.

underread east
22nd Jan 2010, 13:18
I have also experienced a similar situation. Single AC remaining caused other load sheds - incl equip cooling on my type - and getting back to the nearest suitable was certainly desirable. As things heated up, other failures started to creep in - including signs of CRTs failing. PAN declared. Normal landing in my case, but had we taken any longer, we would have been onto SBY instruments. Doable, yes, desirable, no.

On the face of it, these things look like they might not be worth declaring an urgency/emergency for, but there certainly isn't any harm in declaring and finding things did work out OK after all, rather than truck around at no.10 and find things deteriorating further while you wait you're turn.

Kirks gusset
22nd Jan 2010, 13:19
Its a Pan call.. " Plan to land at the nearest SUITABLE airport", bearing in mind there is no ILS on the failed side, crew workload will be higher than normal and I would not "assume" the battery will operate as it should. I certainly wouldn;t want to be in a holding stack or dithering around in this situation. As one comment stated, the situation at night would be even worse. General rule in BA was, anytime you're down to one of anything its a PAN. BOAC? care to comment

22nd Jan 2010, 19:28
anytime you're down to one of anything its a PAN

Fully agree with the guys posting above stating they'd call a PAN. So would I. I recall a couple of incidents in my previous employer.

However, while I was in flight school, one day I had an alternator failure. I remember I told my CFI that since we were down to the Batt, shouldn't we call for urgency? He said "well, that's not going to do much for us right now."

How does one reacts to an alternator failure in a single engine?

Best regards

capt. solipsist
20th Feb 2010, 10:10
I agree with the PAN guys. The entire commercial aviation philosophy rests on redundancy (that's why there are always 2 badly-paid guys in the cockpit).

As well, for a lazy bastard like me, I'd much rather declare PAN and get land priority, rather than be coy then have the remaining GEN conk out. That would just be one too many procedures to perform before getting on the ground. :ugh:

21st Feb 2010, 17:35
The concept of aviation safety is based on F.A.R. 25 and has been for a long, long time.