BA038 (B777) Thread
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BA038
I understand that the engines were idling when a command to increase thrust produced a brief increase followed by reduction in both engines.
Has it been reported if the engines were reduced to idle followed by a successful command for increased thrust at any earlier point in the descent? Or was each thrust reduction to a low level without in intervening idle period?
Has it been reported if the engines were reduced to idle followed by a successful command for increased thrust at any earlier point in the descent? Or was each thrust reduction to a low level without in intervening idle period?
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Thanks, pinkman!
Nothing to add to your insightful post, except that if someone wants to eyeball the actual chromatograms for some varieties of fuels, including raw crudes, as well as Jet-A, JP-5, Diesel #1 gasoline, AV-Gas, etc. then this little 6 page PDF has them displayed (caution - link is directly to a PDF file).
http://www.image-train.net/products/.../CM1_alimi.pdf
General method of analyzing kerosene w/GC (from NIOSH):
http://www.osha.gov/dts/sltc/methods...39/pv2139.html
This caution caught my eye: "Different kerosenes may have similar constituents but not have similar concentrations of these constituents..."
and it seems to reinforce the likelihood that we are probably looking at a very subtle issue, that until all the swiss cheese lined up for BA038, might have manifested itself only in ways far below overt detection/specific identification. Once the chain of cause and effect is determined with finality (and unlike some, I feel it will be), I'll bet there will be an opportunity to look back at some 'oddities' in past, and finally go "Ah HA! there you are, you little son of a gun!"
Nothing to add to your insightful post, except that if someone wants to eyeball the actual chromatograms for some varieties of fuels, including raw crudes, as well as Jet-A, JP-5, Diesel #1 gasoline, AV-Gas, etc. then this little 6 page PDF has them displayed (caution - link is directly to a PDF file).
http://www.image-train.net/products/.../CM1_alimi.pdf
General method of analyzing kerosene w/GC (from NIOSH):
http://www.osha.gov/dts/sltc/methods...39/pv2139.html
This caution caught my eye: "Different kerosenes may have similar constituents but not have similar concentrations of these constituents..."
and it seems to reinforce the likelihood that we are probably looking at a very subtle issue, that until all the swiss cheese lined up for BA038, might have manifested itself only in ways far below overt detection/specific identification. Once the chain of cause and effect is determined with finality (and unlike some, I feel it will be), I'll bet there will be an opportunity to look back at some 'oddities' in past, and finally go "Ah HA! there you are, you little son of a gun!"
Pinkman Re your post:
' a couple of us have repeated endlessly our prediction that it was due to fuel stratification caused by unusual temperatures leading to.....'
If this were so, the problem would have shown up long ago. There is no need to reproduce the accident flight profile, as it has been flown many times without incident already. There is some other factor which will emerge in due course....
' a couple of us have repeated endlessly our prediction that it was due to fuel stratification caused by unusual temperatures leading to.....'
If this were so, the problem would have shown up long ago. There is no need to reproduce the accident flight profile, as it has been flown many times without incident already. There is some other factor which will emerge in due course....
gerryfoley,
Not quite. According to the AAIB, BA38 had complied with BA stabilised approach criteria, i.e. it was in the landing config. by 1,000'AAL with approach power set. As there was some wind that day, the power would have been varying around the normal datum during gusts and lulls; at around 700' one engine stopped responding to commands and ran down to a low EPR, followed seven seconds later by the other one.
Following the normal LHR speed control involves staged reductions from 220Kts-->180Kts-->160Kts-->Vapp. The last two or three reductions usually occur after being established on the GS and for a 777 on an average day you need to have the engines at idle plus some drag from gear or speedbrake to make the change happen. I don't think the actual thrust levels during the intermediate/final approach have been reported but I would be surprised if the engines weren't at flight idle for a significant time before the power came up prior to the 1,000' approach 'gate'.
777fly,
Without incident, defined as a discovered anomaly, yes. What we don't know is how many times there has been a restriction in the fuel supply system that has gone unnoticed because it has not been severe enough to affect the engines.
If it was, in fact, quite common, how would we know about it? Imagine a blockage forming that only became evident over 90% of rated power: how often do we use full TOGA power after starting the descent? Not very often, IMHO. If the restriction reduced the delivery capacity of the fuel system from 200% of maximum to 110% it would remain undiscoverable by normal means but still exist...
I understand that the engines were idling when a command to increase thrust produced a brief increase followed by reduction in both engines.
Has it been reported if the engines were reduced to idle followed by a successful command for increased thrust at any earlier point in the descent? Or was each thrust reduction to a low level without in intervening idle period?
777fly,
...There is no need to reproduce the accident flight profile, as it has been flown many times without incident already.
If it was, in fact, quite common, how would we know about it? Imagine a blockage forming that only became evident over 90% of rated power: how often do we use full TOGA power after starting the descent? Not very often, IMHO. If the restriction reduced the delivery capacity of the fuel system from 200% of maximum to 110% it would remain undiscoverable by normal means but still exist...
Last edited by FullWings; 27th May 2008 at 10:01.
Pp:
Cavitation bubbles are full of low pressure gas or vacuum, and they occur as the fluid is torn apart by suction. The vacuum filled bubbles collapse implosively when pressure is restored and the shock waves cause local damage. This happens in a very localised area as the fluid passes from the low pressure side of a pump to the high pressure side.
Used as a hydraulic fluid under pressure, cavitation bubbles would not be present.
Fuel full of cavitation bubbles isn't likely to work very well as a hydraulic fluid.
Used as a hydraulic fluid under pressure, cavitation bubbles would not be present.
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Wow. Well, we finally hit the wall -- it's been a couple of days with NO new posts on this thread.
I do not want to post in order to prattle on and just hear myself talk, but I will make one observation, which others can respond to or not. I know I previously mentioned the idea of using GC/MS to test/characterize the Chinese fuel, and it was properly pointed out that such a test may be far from definitive, and that other test measures may be better. Fair enough, and point well taken.
But let's review an article that gives on overview of the observations to date, as well as the latest tack the inquiry is taking:
[Looking at restrictions in piping]
...engine test cell... altered to enable... calibrated restrictions at various locations in the engine and aircraft fuel feed...
[looking at environment]
...primary challenge... to create the environmental conditions experienced... to test a representation of the aircraft fuel system... replicating the fuel system performance experienced on the day...
[reviewing/re-accomplishing system design characterization]
... developing a more complete understanding of the dynamics of the fuel as it flows from the fuel tank to the engine...
[flight data review]
...a data analysis team... reviewing and analyzing recorded data from a large sample of flights on similar aircraft.... concentrating on... abnormal combinations of parameters...
[recap]
"Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the Autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust... work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles," the second AAIB report stated.
http://www.aviationtoday.com/asw/cat...ial/22017.html
IMHO, the ONE potentially relevant factor that this article, and the AAIB updates themselves are completely silent on is the MATERIAL, i.e. the fuel itself, whether it be chemical composition, or physical properties, or additives, or other attributes.
The only data presented so far on the physical material responsible for combusting and being converted to the required energy was that it's freezing point 'far exceeded' the spec. for that parameter.
Super.
However, I find the lack of ANY further information on that front, even if it is just to close off the fuel itself as possibly being a contributor (with evidence to back it up), to be very odd.
Am I off in the weeds here?
I do not want to post in order to prattle on and just hear myself talk, but I will make one observation, which others can respond to or not. I know I previously mentioned the idea of using GC/MS to test/characterize the Chinese fuel, and it was properly pointed out that such a test may be far from definitive, and that other test measures may be better. Fair enough, and point well taken.
But let's review an article that gives on overview of the observations to date, as well as the latest tack the inquiry is taking:
[Looking at restrictions in piping]
...engine test cell... altered to enable... calibrated restrictions at various locations in the engine and aircraft fuel feed...
[looking at environment]
...primary challenge... to create the environmental conditions experienced... to test a representation of the aircraft fuel system... replicating the fuel system performance experienced on the day...
[reviewing/re-accomplishing system design characterization]
... developing a more complete understanding of the dynamics of the fuel as it flows from the fuel tank to the engine...
[flight data review]
...a data analysis team... reviewing and analyzing recorded data from a large sample of flights on similar aircraft.... concentrating on... abnormal combinations of parameters...
[recap]
"Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the Autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust... work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles," the second AAIB report stated.
IMHO, the ONE potentially relevant factor that this article, and the AAIB updates themselves are completely silent on is the MATERIAL, i.e. the fuel itself, whether it be chemical composition, or physical properties, or additives, or other attributes.
The only data presented so far on the physical material responsible for combusting and being converted to the required energy was that it's freezing point 'far exceeded' the spec. for that parameter.
Super.
However, I find the lack of ANY further information on that front, even if it is just to close off the fuel itself as possibly being a contributor (with evidence to back it up), to be very odd.
Am I off in the weeds here?
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However, I find the lack of ANY further information on that front, even if it is just to close off the fuel itself as possibly being a contributor (with evidence to back it up), to be very odd.
The AAIB states: "The spar valves and the aircraft boost pumps were serviceable and operated correctly during the flight."
No reference has been given as to how the AAIB came to that conclusion. Logically this would mean recorded data is available, at least that is the perception when reading the report . . . . .
Perhaps the final report will explain how the AAIB came to this conclusion.
Also, i wonder when approach idle was activated over minimum idle.
Was this activated by engine anti-ice or during landing flap selection?
If it was activated during landing flap selection, the thrust increase from minimum idle to approach idle (if the aircraft was indeed following a CDA profile at minumum idle) must have occurred during intermediate/final approach, sometime before the final thrust increase and rollback?
If it was activated by engine anti ice, there would have been a cycling between minimum- and approach idle several times, each time engine anti ice activated and de-activated, before landing flap was selected. In both cases, with landing flaps selected, the engines would have been in approach idle when the problems started.
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Originally Posted by soem dood
Am I off in the weeds here?
"Ice collecting in or near an engine component has emerged as a prime suspect."
It's "a prime suspect", but until more testing is done, it cannot be listed as the "probable cause", and the AAIB has not yet done so.
IMHO, the ONE potentially relevant factor that this article, and the AAIB updates themselves are completely silent on is the MATERIAL, i.e. the fuel itself, whether it be chemical composition, or physical properties, or additives, or other attributes.
Special bulletin 3/2008
The fuel has been tested extensively; it is of good quality, in many respects exceeding the appropriate specification, and shows no evidence of contamination or excessive water.
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The Fuel
With a fully open mind, the Fuel will attract attention, however.
Reading a release of information can be subject to premature conclusions, especially when very little further data is supplied. Nothing of what has been said by AAIB totally eliminates its consideration, obviously, since AAIB have Not provided a causal chain.
"Exceeding" the appropriate specification is a troubling statement. In what way? A Spec is a range of points that contain a compliant sample in all respects. Is a freezing point of -57 "better" than -49? Perhaps, but in what way; what about the Asian Fuel causes the odd (Though lower) temp? What about its composition makes it "different"?
BA038 flew at much higher altitude than other A/C in a similar profile. The 777 has but one Fuel Temp sensor, and it is located in the Port wing, which basked in the sun for much of the flight. Was 38C an accurate reading? Was the Sensor tested for performance? What of the Temp. elsewhere?
Was there some attribute of the Chinese Fuel related to its lower FP that ennabled it to contain water in solution as well as in emulsion?
In Soem Dood's defense (not that it is necessary), Fuel (Lack) is the proximate cause of loss of Thrust; Saying the Fuel played no part in a result that has remained publicly unexamined (completely) is very premature, very. Fuel temperature is a Fuel attribute. To be blunt, the Fuel on Board BA038 came from a supply that is not widely used in similar flights elsewhere, drawing attention simply by virtue of its "rarity".
Airfoil
Reading a release of information can be subject to premature conclusions, especially when very little further data is supplied. Nothing of what has been said by AAIB totally eliminates its consideration, obviously, since AAIB have Not provided a causal chain.
"Exceeding" the appropriate specification is a troubling statement. In what way? A Spec is a range of points that contain a compliant sample in all respects. Is a freezing point of -57 "better" than -49? Perhaps, but in what way; what about the Asian Fuel causes the odd (Though lower) temp? What about its composition makes it "different"?
BA038 flew at much higher altitude than other A/C in a similar profile. The 777 has but one Fuel Temp sensor, and it is located in the Port wing, which basked in the sun for much of the flight. Was 38C an accurate reading? Was the Sensor tested for performance? What of the Temp. elsewhere?
Was there some attribute of the Chinese Fuel related to its lower FP that ennabled it to contain water in solution as well as in emulsion?
In Soem Dood's defense (not that it is necessary), Fuel (Lack) is the proximate cause of loss of Thrust; Saying the Fuel played no part in a result that has remained publicly unexamined (completely) is very premature, very. Fuel temperature is a Fuel attribute. To be blunt, the Fuel on Board BA038 came from a supply that is not widely used in similar flights elsewhere, drawing attention simply by virtue of its "rarity".
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Maybe very stupid, but,
Can the AAIB issue a full report with no conclusions, i.e. "this is all we've done, here are the things we've ruled out, but we don't know what actually caused the accident" ?
And would Boeing and Rolls-Royce have to "sign-off" on that ?
.
Can the AAIB issue a full report with no conclusions, i.e. "this is all we've done, here are the things we've ruled out, but we don't know what actually caused the accident" ?
And would Boeing and Rolls-Royce have to "sign-off" on that ?
.
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Phil Gollin ...
I suspect the AAIB will be thinking, "let's not take our fences until we have to".
Meaning, there is a long way to go before a FINAL report is issued - possibly years. And during that time the AAIB and others will seek the answer to the riddle. And they know they must find the answer/cause.
Meanwhile other bulletins will probably be issued which will include operational changes to high altitude, low temperature flights. Expect the next before the northern hemisphere Winter.
Regards, Tanimbar
Meaning, there is a long way to go before a FINAL report is issued - possibly years. And during that time the AAIB and others will seek the answer to the riddle. And they know they must find the answer/cause.
Meanwhile other bulletins will probably be issued which will include operational changes to high altitude, low temperature flights. Expect the next before the northern hemisphere Winter.
Regards, Tanimbar
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The Fuel
As airfoilmod suggests, the exact physics of the fuel must surely be where the best minds are concentrated.
A friend of mine joined me and the kids at the weekend for a Chinese 'cook-in'. You know, root ginger, garlic, chillis stir fried, sweet and sour sauce from scratch ... superb smells from the kitchen and the kids just loved getting involved right from the initial shop we all did together at WalMart, to individually coating the chicken and prawns for deep fry, and then scoffing the lot
WalMart were right out of cornflower. My friend said potato flower worked just as good, and so it did.
But as the kids were coating the prawns and chicken in the water/flower mix, some of the physics emerged...I still find what we saw quite astounding all these years after I first saw the starch experiment at school.
One moment you are mixing the water and flower and saying "Its not quite right, shall we add some more? It's too runny"
Next you are saying well it fries good.
Then you return to the bowl and put your finger in and say "Wow, lookey here - it's gone hard!"
And you stir your finger and it becomes runny again before anyone can see what you meant.
And if you play further with it, and let it settle again, and remove just a tiny amount of the surface water, you can prize out the mixture in one bowl shaped solid, with the consistency of those bbq firelighters ... but you ain't gonna light no fires with it ...
A friend of mine joined me and the kids at the weekend for a Chinese 'cook-in'. You know, root ginger, garlic, chillis stir fried, sweet and sour sauce from scratch ... superb smells from the kitchen and the kids just loved getting involved right from the initial shop we all did together at WalMart, to individually coating the chicken and prawns for deep fry, and then scoffing the lot
WalMart were right out of cornflower. My friend said potato flower worked just as good, and so it did.
But as the kids were coating the prawns and chicken in the water/flower mix, some of the physics emerged...I still find what we saw quite astounding all these years after I first saw the starch experiment at school.
One moment you are mixing the water and flower and saying "Its not quite right, shall we add some more? It's too runny"
Next you are saying well it fries good.
Then you return to the bowl and put your finger in and say "Wow, lookey here - it's gone hard!"
And you stir your finger and it becomes runny again before anyone can see what you meant.
And if you play further with it, and let it settle again, and remove just a tiny amount of the surface water, you can prize out the mixture in one bowl shaped solid, with the consistency of those bbq firelighters ... but you ain't gonna light no fires with it ...
Of course the fuel is the source of on-going investigation, I neither stated nor implied it wasn't, and nor do the AAIB. I was merely pointing out that those assuming that GCMS/FTIR or whatever had not been undertaken were probably mistaken. Rest assured, the properties of that fuel are being thoroughly evaluated. (I investigate contaminations in jet fuel for a living by the way )
)
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Thixotropy
Slip and turn nicely describes the thixotropic (http://en.wikipedia.org/wiki/Thixotropy) behaviour of his starch/water/oil (?) cooking mixture in a mouthwatering way in 1256 but I doubt that the likely BA038 fuel problem lies in this direction.
I am pretty sure that the kind of molecules (yes I know about the ionics that may or may not be there too!) you need for this sort of thixotropic behaviour, will show up big time on the standard battery of NMR/MS/IR analytical weaponry available to AAIB.
We'll see!
CW
I am pretty sure that the kind of molecules (yes I know about the ionics that may or may not be there too!) you need for this sort of thixotropic behaviour, will show up big time on the standard battery of NMR/MS/IR analytical weaponry available to AAIB.
We'll see!
CW
Last edited by chris weston; 30th May 2008 at 19:26. Reason: punctuation
Second Law
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Thixotropy again
The plot thickens......
Sorry.
Seriously, in my view if it was one or more thixotropes at work, truly the mother of all Sinoadditives, the fuel would have been out of spec and we would have heard by now.
CW
Sorry.
Seriously, in my view if it was one or more thixotropes at work, truly the mother of all Sinoadditives, the fuel would have been out of spec and we would have heard by now.
CW
Do I interpret this discussion correctly? Is it being said that whatever caused the freezing point of the fuel to be much lower than typical caused the fuel to not be properly combustible?