BA 777 Update

Particle Contaminated fuel can clog fuel nozzles as I recall.

Does this make any sense? I hear that there are tolerances how long particle contaminated fuel can work in newer jet engines..............
 
I think if it were a fuel contamination problem there would have been other instances of this occurring out of PEK that day. On the 744 if we get low fuel temps we have to resolve the issue as quickly as possible. We can usually accomplish this by speeding up and/or descending.

I encountered outside temps of -75C a few weeks ago over northern Canada. We sped up and descended. This kept the fuel temp at roughly -36C until we came out of that cold air. Initially we sped up from .83 to .87 and that started to do the trick. Keep in mind, we were fueled in DFW with Jet A not A1. Our procedure is that we must have been fueled three sectors with A1 before we can use that -47C as a freeze point.

Could be that the aircraft had been fueled with Jet A at some point in the past couple days and a bit of it was still in the tanks? Not sure what MMO is on the 777 but they may not have been able to speed up enough to get above -40C. Having been fueled with Jet A1 out of Beijing, they may not have been concerned with it. It would be interesting to see where that aircraft had been over the previous few days.
 
rjmore said:
I think if it were a fuel contamination problem there would have been other instances of this occurring out of PEK that day. On the 744 if we get low fuel temps we have to resolve the issue as quickly as possible. We can usually accomplish this by speeding up and/or descending.

I encountered outside temps of -75C a few weeks ago over northern Canada. We sped up and descended. This kept the fuel temp at roughly -36C until we came out of that cold air. Initially we sped up from .83 to .87 and that started to do the trick. Keep in mind, we were fueled in DFW with Jet A not A1. Our procedure is that we must have been fueled three sectors with A1 before we can use that -47C as a freeze point.

Could be that the aircraft had been fueled with Jet A at some point in the past couple days and a bit of it was still in the tanks? Not sure what MMO is on the 777 but they may not have been able to speed up enough to get above -40C. Having been fueled with Jet A1 out of Beijing, they may not have been concerned with it. It would be interesting to see where that aircraft had been over the previous few days.
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True, although it would have mixed, and the pour point temp would have been inbetween the two, somewhere. Recall that -40 is the max temp for JetA, and that it can be colder. LAX JetA, for example, averages closer to -50c. To my knowledge, only NWA actually tests the fuel and uplinks the actual temp to the International flights, after departure.
 
I'd be surprised if it was fuel. Like rjmore said, there should have been problems experienced by other flights as well. If fuel was a cause, I would have expected the problem to manifest more gradually and asymmetrically: one engine goes to a reduced thrust, recovers, declines, then the other has trouble later.

Also, the engines were producing thrust above flight idle, but did not respond to commanded changes.
 
Minuteman said:
Also, the engines were producing thrust above flight idle, but did not respond to commanded changes.
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Which is exactly how my engine behaved after a long cold-soak.

Different engines, different fuel system, but the kinds of temperatures they were subjected to on their flight were definitely toward the edge of the envelope. Not routinely experienced and certainly a possible factor.

It's almost never just one thing. If it is a fuel contamination issue, it could be that if they had operated at more "normal" temperatures that nothing would have happened. It's all conjecture for now, but given that several of these airplanes will be configuring for approach today and the crews will be watching to see if the thrust comes up as commanded, conjecture is inevitable.
 
seagull said:
To my knowledge, only NWA actually tests the fuel and uplinks the actual temp to the International flights, after departure.
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Now that would be cool. The only airport we get a report on the temp is PANC. Everywhere else we use the most conservative, which is why we get an amber fuel low temp at -37C. We can somewhat ignore it as long as we know for sure what we have on board.

I'm not sure where they were but terrain along the Asia-Europe/UK routes wouldn't probably allow them to descend low enough to make a difference, especially if they were on Y1. Anyone know MMO on the 777?
 
rjmore said:
Now that would be cool. The only airport we get a report on the temp is PANC. Everywhere else we use the most conservative, which is why we get an amber fuel low temp at -37C. We can somewhat ignore it as long as we know for sure what we have on board.

I'm not sure where they were but terrain along the Asia-Europe/UK routes wouldn't probably allow them to descend low enough to make a difference, especially if they were on Y1. Anyone know MMO on the 777?
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Most of the World, outside the U.S., use Jet A1. Look on your fuel ticket (or ask, if you don't get a copy of it with your paperwork). On the -11, we just enter the fuel type in the FMS and it adjusts the temp in the system for the fuel system controller.
 
I know that the rest of the world uses A1. I should have clarified, the only place we get an adjusted temp for Jet A is PANC. The -400 doesn't have the capability to adjust the bells and whistles in the FMS, at least not ours.
 
Nick said:
In looking up "prist" after reading this, here is a page I found that might be of interest to anyone curious about the basics of this subject:

http://www.csdinc.org/prist/prod_info.htm#Why

I always heard corporate pilots saying "with prist" on some fuel orders. I know little about it -- does it get mixed into the airport fuel supplies at places like Beijing and the rest of the world's airline hubs?
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At my FBO we use DICE (yet we still call it PRIST, which is just another trade name... I think the military calls it "FIZZY"... but I digress...). It is stored in bottles on our fuel trucks, and we inject it into the fuel when requested at a ratio of around 1 gallon of Prist/1,000 gallons of Jet-A. I believe fuel can be delivered to the airport premixed as well, but we don't do that here. I'll see if I can take some pictures of it and post them later.
 
JaceTheAce said:
Throttles?
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Are you mocking the use of the term 'throttles' with respect to a jet engine? That it should be 'PCL' or something of the like?

taildragger173 said:
Whats the difference between Jet A and Jet A1?
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From Wiki:

Jet A is similar to Jet-A1, except for its higher freezing point of −40 °C (vs −47 ° Jet A-1). Like Jet A-1, Jet A has a fairly high flash point of 38 °C, with an autoignition temperature of 410 °F (210 °C).
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seagull said:
More problematic is fuel cooling to the point it is like jello on long haul ops. It can be thick enough so the fuel pumps won't pull it in. I would not imagine that would be true in this case, as it should have warmed on the way down, and the fuel low temp sensors would have alerted the crew well before their approach.
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After a long-haul, high-altitude flight where the fuel has cold soaked, you won't have significant warming in the relatively short time period of the descent. The air is warmer, but it has a much lower thermal coefficient than the fuel (kind of like why you thaw a turkey in water instead of air--heat moves less efficiently in air).


rjmore said:
I think if it were a fuel contamination problem there would have been other instances of this occurring out of PEK that day.
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But how many other flights flew that high, for that long? We don't know. And other flights may have had problems, but to a lesser degree, and they could have easily gone unnoticed or at least unreported.


Minuteman said:
If fuel was a cause, I would have expected the problem to manifest more gradually and asymmetrically: one engine goes to a reduced thrust, recovers, declines, then the other has trouble later.
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I'm not sure why you would expect that. Both engines would have been feeding from the same tank. If gelled fuel went into the fuel lines, the reaction from both engines would have been virtually simultaneous.

Actually, to me, the gelled fuel scenario seems the most likely, especially given the unusually low temps that day and the long flight time of the sortie.
 
Fly4Pay said:
But how many other flights flew that high, for that long? We don't know. And other flights may have had problems, but to a lesser degree, and they could have easily gone unnoticed or at least unreported.
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Very true, but I was thinking more along the lines of fuel mixing and maybe that aircraft had been to the US in the past couple days. But what you are saying is also plausible since any airplane going to Europe out of there would go the same way.
 
Fly4Pay said:
I'm not sure why you would expect that. Both engines would have been feeding from the same tank. If gelled fuel went into the fuel lines, the reaction from both engines would have been virtually simultaneous.

Actually, to me, the gelled fuel scenario seems the most likely, especially given the unusually low temps that day and the long flight time of the sortie.
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Good post, just wondering about the fuel feed. I'm not familiar with the 777 fuel system. Are there two wing tanks a center tank, so they were feeding off the center tank? Why wouldn't it be "tank to engine"?
 
seagull said:
Good post, just wondering about the fuel feed. I'm not familiar with the 777 fuel system. Are there two wing tanks a center tank, so they were feeding off the center tank? Why wouldn't it be "tank to engine"?
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One would think it would be 'tank-to-engine' at that late of a flight. Most airliners with 3 tanks will burn the center tank first so I'd imagine they were on 'tank-to-engine' by that point.
 
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