What caused this 767 diversion?

[JammedStab]

Airline de-identified.

"a B767-300 operated by XXXX Airlines was conducting flight 938 from the US to London Heathrow,UK (EGLL) with 11 crew and 178 passengers. While in cruise at FL350 and passing 58N and 050W the crew observed an EICAS "Low Fuel" caution message and noted a fuel imbalance. The EICAS message cleared but the imbalance remained. The crew consulted with both maintenance and dispatch, declared a MAYDAY and diverted to Keflavik Intl., Iceland (BIKFK). Ground maintenance checks found no fuel or fuel system issues. The aircraft was refueled and departed for destination after a several hour delay."

[DaveReidUK]

If it helps anyone with the search, flight was UAL938 KORD-EGLL on 24th March this year.

[Herod]

Seems like a sensible decision, but perhaps a "Mayday" was a bit of overkill? That depends on the fuel state of course.

[wiggy]

If nothing was found on the ground I'd suggest it was probably a transient Fuel Quantity Indication ( "gauge"/sensor) problem. Have had an instance of that, once v briefly, on descent. I suspect mid Atlantic it would get your attention. ..

[Landflap]

Excellent decision. Excellent Company back-up & support. Mate of mine had a similar case but not oceanic. Company nearly beat him to death for making, under similar circumstances, the very wise decision to make a cautionary diversion to a Company Maintenance Base. Indeed, the dysfunction Head of Training claimed that the decision was "appalling". Mate walked away changing his cowboy outfit for much more professional garb.

[vapilot2004]

It would be interesting to know if the imbalance came with the need for lateral trim.

[Fly26]

Sounds like a good decision to me, I wonder what ‘head of training’ thoughts would have been if you end up in the drink....

[CargoOne]

Seems like a sensible decision, but perhaps a "Mayday" was a bit of overkill? That depends on the fuel state of course.

Well if you remember Azores Glider story started basically almost like that: crew observed an EICAS "Low Fuel" caution message and noted a fuel imbalance.

[Herod]

Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.

[EDLB]

Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.

More important what you don’t know about the situation. Assume the worst for every unknown factor. With Mayday you get the attention of ATC and you don’t have to fiddle around with clearances if the situation went south quick.

[broompusher]

Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.


What you know and what the actual facts are could differ greatly..

https://en.wikipedia.org/wiki/Gimli_Glider

https://en.wikipedia.org/wiki/Air_Transat_Flight_236

[msbbarratt]

A well developed sense of self preservation is what caused this diversion. It's a good example of why us SLF types are very happy to have a couple of live human pilots up front.

[Herod]

I seem to have opened a can of worms with my comments. Again I say that I am not criticising the captain at all. I wasn't there, I don't have the information they had. I merely suggested the mayday might have been an overkill. However, again, if the captain decided it was warranted, then I'm the last one to argue with that.

[RAT 5]

Ref the diversion, not the Mayday.

A well developed sense of self preservation

"When in doubt there is not doubt." sometimes, especially in the middle of nowhere.

[OldLurker]

Excellent decision. Excellent Company back-up & support. Mate of mine had a similar case but not oceanic. Company nearly beat him to death for making, under similar circumstances, the very wise decision to make a cautionary diversion to a Company Maintenance Base. Indeed, the dysfunction Head of Training claimed that the decision was "appalling". Mate walked away changing his cowboy outfit for much more professional garb.In the case under discussion here (Incident: United B763 over Atlantic on Mar 25th 2018, fuel imbalance and fuel low indications (http://www.avherald.com/h?article=4b6a69aa)) the crew is reported to have taken the time to consult with maintenance and dispatch befose declaring MAYDAY and diverting: that consultation should have forestalled any criticism from United's Head of Training!

As Herod correctly says, we don't have the information that the crew (and maintenance and dispatch) had. We only have the AvHerald report. We don't know why the crew decided to call MAYDAY, which could have been for a perfectly valid reason.

[costalpilot]

"but the imbalance remained"

what does this mean? does it mean the individual tank indications indicated an imbalance?

who in their right mind would continue a flight under those circumstances? who would advocate it?

or, am i missing something?

[West Coast]

I don't have the information they had. I merely suggested the mayday might have been an overkill.

Then why did you feel it was ok to make any kind of judgement? Let the facts drive you towards your conclusion, not uninformed opinion.

[flash8]

Then why did you feel it was ok to make any kind of judgement? Let the facts drive you towards your conclusion, not uninformed opinion.

This is also a rumours (and that comes with speculation) forum :)

[JammedStab]

Thanks for the responses. It would be nice to have more info to see how the good decision making process was made. But of course, that is unlikely.

Keeping in mind that the original report may not be exactly correct, what does the QRH for the 767 say for a "Low Fuel" EICAS message. On my similar looking type, "FUEL QTY LOW" means that the fuel quantity is low in a main tank.

Would it be normal at this point in a flight for a main tank(I am assuming that this is one of two wing tanks) to have low fuel quantity in a 767? Sort of sounds like an actual it could be a real leak if a main tank quantity is low in mid-cruise. But there was no fault found. So how would a main tank quantity become low.

As you can see, no direct knowledge of the 767 on my part so the questions may not make sense.

[Airbubba]

With a normal fuel load and no malfunction a scenario where you might get a LOW FUEL with an imbalance is leaving the crossfeed valves open.

Over time one side inevitably has more boost pump pressure than the other and an imbalance occurs much faster than with the crossfeeds closed (or so I'm told ;)). However, you should get a FUEL CONFIG when the imbalance reaches 2200 pounds, normally well before you get a LOW FUEL when the useable fuel drops below 2200 pounds in either main tank.

One time where weird stuff seems to happen with the 767 fuel system is when somebody decides to balance the fuel. United demoed a double engine 'roll back' out of Maui in 2001 and got to check the RAT auto-deploy feature at sunset as they limped into Kona for an overweight landing. Somehow all of the main tank pumps were switched off after fuel balancing on climbout. The DEN ground school lesson on suction feed has now been updated. The star-crossed plane was N666UA but fortunately Captain Luck was in command. :ok:

The fuel gauges on the '76 are on some odd ground service bus that I think is used to run 400 Hz vacuum cleaners. I had a jumpseat rider come up to the cockpit and plug his cheap knockoff computer charger into one of the covered AC service outlets without telling me. We were about to go feet wet for a crossing. The fuel quantity gauges went to dashes and half of the landing gear lights started flashing. As I pondered my own overweight landing options, the goofball sitting behind me said 'Look, it quits when I unplug my computer!' :ugh:

I don't know if it was the fake Dell adapter or maybe the tight plug pushed wires together behind the panel.

There is also a microswitch in the fueling panel door out on the wing that sometimes can cause problems with the fuel indication. There is some trivia question about that on the oral but it's been a long time since I got the rating.

[JammedStab]

With a normal fuel load and no malfunction a scenario where you might get a LOW FUEL with an imbalance is leaving the crossfeed valves open.

Over time one side inevitably has more boost pump pressure than the other and an imbalance occurs much faster than with the crossfeeds closed (or so I'm told ;)). However, you should get a FUEL CONFIG when the imbalance reaches 2200 pounds, normally well before you get a LOW FUEL when the useable fuel drops below 2200 pounds in either main tank.

Interesting...thanks.

[cooperplace]

Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.
it's off topic, but I'd be happy to hear the story about those 3 occasions.
As SLF I'm happy with the captain's decision to issue a mayday if he/she thinks it's warranted.

[JammedStab]

Originally Posted by Herod
Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.

it's off topic, but I'd be happy to hear the story about those 3 occasions.
As SLF I'm happy with the captain's decision to issue a mayday if he/she thinks it's warranted.

I suspect each MAYDAY occasion occurred in quick succession with a half second between each occasion.

Occasion 1: MAYDAY
Occasion 2: MAYDAY
Occasion 3: MAYDAY

As heard by ATC: MAYDAY, MAYDAY, MAYDAY (also known as putting out three MAYDAYS).

[KelvinD]

By a coincidence, I watched the same aircraft abandon an approach to Heathrow on April 5th. It seemed to start to go around about a mile from touch down. Nothing special about that, except various "spotters" noted the wheels remained down. And they remained down throughout the entire circuit back to making a successful landing.
As I was taking photos at the time, I compared the "before & after" pictures and it seems there was a difference in the setting of the inboard flaps, almost as if they had not fully deployed when the decision to go around was taken.

[Herod]

Originally Posted by Herod
Like I said, it depends on fuel state. What you KNOW about the situation. I wasn't there, and I'd be the last person to criticise a captain's decision, having put out three maydays myself.



I suspect each MAYDAY occasion occurred in quick succession with a half second between each occasion.

Occasion 1: MAYDAY
Occasion 2: MAYDAY
Occasion 3: MAYDAY

As heard by ATC: MAYDAY, MAYDAY, MAYDAY (also known as putting out three MAYDAYS).

Thanks for your patronising comment, JammedStab.
One. Generator fell off its perch and severed an engine oil line. Low oil pressure warning, shutdown, mayday.
Two. Severe icing day. Very bad engine vibration, checklist called for shutdown, mayday. No fault found, and it was assumed a big chunk of ice separated from the wing and went into the (rear-mounted) engine.
Three. Structural failure of the rudder, resulting in hard-over situation. resultant sideslip caused an engine to fail due fuel starvation. mayday.

Since my original comment has set rats among the corn, this will be my last post on this thread. I say again, there was no criticism of the captain's decision.

[KelvinD]

Don't give up Herod. It was immediately obvious to me what you meant. Idiotic responses are to be expected from idiots! :ok:

[slowjet]

Old Lurker : LF refers to a "mate" of his. I know Lf and his mate referred to as well. In that case, he did have a time limited discussion with both Flt Ops & Maintenance Control as he sped by. He also displayed much airmanship by reducing speed in order to talk to the guys before heading from VHF to HF territory. It was just of interest that a similar incident resulted in vilification rather than support. Oh to have been in United !


Hazy recall of the fab 767 but I seem to remember basic thinking ; "Low Fuel" in any tank required placing all pumps on & X-feed open. In tank to engine, fuel imbalance was another drill & a sometimes the result of the low fuel drill. There was an imbalance limitation too. Get down to that limit with Xfeed open suggested you were feeding the leak so the Xfeed was closed. You now had a possible leak, identified & out of balance & with refined drills after the Airbus (I think) incident suggesting the Xfeed should be closed. Sim Tripper-uppers loved that scenario ,


On thread though, the question asked was why did he divert. Obvious to the pros here. I concur. Excellent decision because he was faced with a worrying problem, over the ocean with time consuming drills & analasys which might have led to very low fuel and lovely Kef floating away at 8 miles a minute.


Landflap's "mate" had a lovely discussion with a top train driver comparing lifestyles,pay, opportunities etc . Traindriver reckoned we were not worth the money we got because we were not doing anything (mid Atlantic & when FD visits were permitted). "Mate" responded ; " Well, at the moment, we are five miles above the planet earth & we doing eight miles a minute........and........if anything goes wrong, WE can't stop."


Enviable support from the Crew's employer as well.

[Long Haul]

It wouldn’t surprise me if the MAYDAY was requested by ATC in order to facilitate the diversion. The North Atlantic is very busy most nights, and they won’t just clear all the other traffic out of the way without a good reason.

[JammedStab]

Thanks for your patronising comment, JammedStab.
One. Generator fell off its perch and severed an engine oil line. Low oil pressure warning, shutdown, mayday.
Two. Severe icing day. Very bad engine vibration, checklist called for shutdown, mayday. No fault found, and it was assumed a big chunk of ice separated from the wing and went into the (rear-mounted) engine.
Three. Structural failure of the rudder, resulting in hard-over situation. resultant sideslip caused an engine to fail due fuel starvation. mayday.

Since my original comment has set rats among the corn, this will be my last post on this thread. I say again, there was no criticism of the captain's decision.

Sorry to have hurt your feelings. I misunderstood your post because the post went through my mind as either three fuel-related emergencies(highly unlikely) or three MAYDAY statements. I honestly thought that was what you meant and that it had been mis-interpreted by the other poster. Obviously, I was wrong. Apologies once again and I would hope you wouldn't leave a thread for such a minor misunderstanding by myself.

[Herod]

Thanks, JammedStab. No, not fuel related, but in my company an engine failure/shutdown on a twin was an automatic "mayday".

[tdracer]

Hazy recall of the fab 767 but I seem to remember basic thinking ; "Low Fuel" in any tank required placing all pumps on & X-feed open. In tank to engine, fuel imbalance was another drill & a sometimes the result of the low fuel drill. There was an imbalance limitation too. Get down to that limit with Xfeed open suggested you were feeding the leak so the Xfeed was closed. You now had a possible leak, identified & out of balance & with refined drills after the Airbus (I think) incident suggesting the Xfeed should be closed. Sim Tripper-uppers loved that scenario ,

The FAA mandated a new EICAS message in response to the Airbus Azores' glider, basically to indicated a major fuel leak. I wasn't directly involved and don't know details, but basically it compares fuel used according to the engine fuel flow sensors with the fuel remaining based on the FQIS. If there is a large discrepancy (my memory says 7% but I wouldn't swear to that) it pops up an EICAS message (sorry, I don't remember the text).

[wiggy]

...... but basically it compares fuel used according to the engine fuel flow sensors with the fuel remaining based on the FQIS. If there is a large discrepancy (my memory says 7% but I wouldn't swear to that) it pops up an EICAS message (sorry, I don't remember the text).

Sounds like the trigger for the EICAS message “Fuel Disagree” on the T7 and if I recall it correctly the 744......

[tdracer]

Sounds like the trigger for the EICAS message “Fuel Disagree” on the T7 and if I recall it correctly the 744......
As noted, it was an FAA requirement. Timing of the implementation would have been different (updating EICAS s/w is a big deal), but the requirement was the same. So yes, 747-400/-8, 757, 767, 777, and 787 got more or less the same change - even that old antique 737 got something (even though it doesn't have an EICAS as such)...

[slowjet]

Herod, glad you are staying with it. Your experience & posts highly admired by most of us. You are also correct in the knowledge that an engine failure in a twin is a "Mayday". Actually, reference is to " a 50% loss of power". Two donks gone on a four-holer would also be an automatic Mayday.

[Fbwdude]

Hi ,
The 767 QRH states that if o FUEL IMBALANCE EICAS msg is shown ,the first suspicius is a fuel leak and then you will deal with the imbalance
later( after being sure there is no leak ).
Fly safe!