BA038 (B777) Thread
There seems to be an assumption that the effective temperature within the wings is reasonably uniform and similar to or above the TAT.
Is this correct ? Are there no cold spots resulting from different aerodynamic conditions ?
Is this correct ? Are there no cold spots resulting from different aerodynamic conditions ?
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Tree and others, I didn't knew about the fact that such situations are actually practiced in certain companies and apologize for having said that is not so.
My information was based on the fact that in many many cases I've read on pprune that because is considered "negative training", dual engine failure is not part of the training. It's great news that not everyone thinks that way and thank you for correcting me.
My information was based on the fact that in many many cases I've read on pprune that because is considered "negative training", dual engine failure is not part of the training. It's great news that not everyone thinks that way and thank you for correcting me.
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Amount of water in the fueltanks on BA038
I have just read the latest report - interesting reading and thorough work, but many questions remain.
According the report (page 12): the estimated amount of water in the tanks at departure from PEK was max. 5 liters plus maybe some water left from the flight to PEK, but the aircraft was sumped before departure and on the day before, so I suppose that it will be safe to assume that the amount was rather small. (?)
The A/C had almost 100 000 liters of fuel at departure from PEK - and the 5 liters of water "was evenly spread throughout the fuel".
How could this extremely small amount of water have produced severe problems on just this flight and not on thousands of other flights in the past - the actual temperatures along the route were low, but not unusually low?
Which factor(s) made this flight so special? The report mentions some - but again 5 liters of water!?
I am looking forward to the final report.
I admire the crew for their excellent A/C handling.
According the report (page 12): the estimated amount of water in the tanks at departure from PEK was max. 5 liters plus maybe some water left from the flight to PEK, but the aircraft was sumped before departure and on the day before, so I suppose that it will be safe to assume that the amount was rather small. (?)
The A/C had almost 100 000 liters of fuel at departure from PEK - and the 5 liters of water "was evenly spread throughout the fuel".
How could this extremely small amount of water have produced severe problems on just this flight and not on thousands of other flights in the past - the actual temperatures along the route were low, but not unusually low?
Which factor(s) made this flight so special? The report mentions some - but again 5 liters of water!?
I am looking forward to the final report.
I admire the crew for their excellent A/C handling.
Last edited by grebllaw123d; 5th Sep 2008 at 11:58.
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El #
You say "What I know is that some real pilot did a real sim test and it seems like a normal landing could have been completed."
Well I personally know a real pilot who did a real test on a B777 full motion category A simulator. There is no way a normal landing could be made, ie reaching the runway.
Although many pilots practice total engine failures it is usually at a height that allows a glide approach to a runway. The BA038 was fully established on the ILS with flap 30 set. Airlines do not practice total engine failures at that stage as it is negative training as the plane will inevitably land short, ie crash. El # The pilots have been exonerated of blame in the latest AIB report. Please do not infer otherwise. Please accept the facts that it was impossible to reach the runway with the power available. A manual landing was achieved in which all the passengers survived.
You say "What I know is that some real pilot did a real sim test and it seems like a normal landing could have been completed."
Well I personally know a real pilot who did a real test on a B777 full motion category A simulator. There is no way a normal landing could be made, ie reaching the runway.
Although many pilots practice total engine failures it is usually at a height that allows a glide approach to a runway. The BA038 was fully established on the ILS with flap 30 set. Airlines do not practice total engine failures at that stage as it is negative training as the plane will inevitably land short, ie crash. El # The pilots have been exonerated of blame in the latest AIB report. Please do not infer otherwise. Please accept the facts that it was impossible to reach the runway with the power available. A manual landing was achieved in which all the passengers survived.
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If you want more pontification by people who think they know everything, check this thread out:
Comments on ?Ice in fuel caused Heathrow 777 crash? | The Register
Conspiracy theories are being spouted about now... :-)
S.
Comments on ?Ice in fuel caused Heathrow 777 crash? | The Register
Conspiracy theories are being spouted about now... :-)
S.
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Feathers :
I like cake!
On the assumption that a similar ice/fuel mixture was present, then the fuel flow that could pass the obstruction would be limited by the consistency of the ice and the throat area it is trying to pass. This will be the same in both engines (although perhaps there is a 'handedness' to the fuel piping, I do not know).
Not as much as me (I) !
The reproduceable result (IF I have read correctly) was a 95% reduction in the area before the valve. Somehow this occured in two separate systems at different times, but to the same effect. Somehow the UNKNOWN ice phenonomen managed to be dissimilar in the two systems enough to affect the valves at slightly different times, but to near-enough the same extent. (N.B. there is a possibility NOT NOTED IN THE REPORT that the 95% figure has a large margin of error - but ??????)
Still dissatisfied.
Well, the latter statement is quite correct, and you will see that AAIB are saying that an urgent investigation into precisely that condition is needed, it clearly isn't just a Trent issue it's just that the one instance so far happened to be on a Trent-powered airframe.
As for the reproducibility, yes, so far they have shown that a problem is seen in circumstances not that alike to the real fuel system. More work is to be carried out to improve the test to mimic reality better. They may not succeed, but they have to try.
The ultimate mimic though would be a 12 hour flight from China in similar TAT conditions and flight profile with the same approach clearances, descent rates, power profiles. If they are lucky they get to see it happen again, but maybe this time with a 777 embedded in Hatton Cross tube station.
The other thing to note, they state quite clearly that very little is known about the precise effects of ice in fuel under varying circumstances. So a major research task would be called for to understand it better, that will take time.
Do you feel that it wasn't ice? Because there surely are precious few other culprits lurking.
I still see no reason why ALL 777s aren't affected by the AAIB report.
I am dissatisfied because the report is NOT stating anything firm (both icing scenarios proposed are left dangling) - they are merely grasping the reproduceability of the 95% blockage causing cavitation. They have got a "one" and a "one" and made "ten" because the other eight parts of the puzzle are still to be found.
.
I like cake!
On the assumption that a similar ice/fuel mixture was present, then the fuel flow that could pass the obstruction would be limited by the consistency of the ice and the throat area it is trying to pass. This will be the same in both engines (although perhaps there is a 'handedness' to the fuel piping, I do not know).
Not as much as me (I) !
The reproduceable result (IF I have read correctly) was a 95% reduction in the area before the valve. Somehow this occured in two separate systems at different times, but to the same effect. Somehow the UNKNOWN ice phenonomen managed to be dissimilar in the two systems enough to affect the valves at slightly different times, but to near-enough the same extent. (N.B. there is a possibility NOT NOTED IN THE REPORT that the 95% figure has a large margin of error - but ??????)
Still dissatisfied.
Well, the latter statement is quite correct, and you will see that AAIB are saying that an urgent investigation into precisely that condition is needed, it clearly isn't just a Trent issue it's just that the one instance so far happened to be on a Trent-powered airframe.
As for the reproducibility, yes, so far they have shown that a problem is seen in circumstances not that alike to the real fuel system. More work is to be carried out to improve the test to mimic reality better. They may not succeed, but they have to try.
The ultimate mimic though would be a 12 hour flight from China in similar TAT conditions and flight profile with the same approach clearances, descent rates, power profiles. If they are lucky they get to see it happen again, but maybe this time with a 777 embedded in Hatton Cross tube station.
The other thing to note, they state quite clearly that very little is known about the precise effects of ice in fuel under varying circumstances. So a major research task would be called for to understand it better, that will take time.
Do you feel that it wasn't ice? Because there surely are precious few other culprits lurking.
I still see no reason why ALL 777s aren't affected by the AAIB report.
I am dissatisfied because the report is NOT stating anything firm (both icing scenarios proposed are left dangling) - they are merely grasping the reproduceability of the 95% blockage causing cavitation. They have got a "one" and a "one" and made "ten" because the other eight parts of the puzzle are still to be found.
.
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Difference in rollback times
The AAIB report records, but does not comment on, that the fuel flows to the left engine were generally lower than those to the right engine, whilst the EPR of the right engine reduced first and to a value slightly higher than that of the left engine.
If, as is hinted, the engines (or rather some of their pumps) were separately sucking fuel from the pipework downstream of blockages at similar points in the two sets of pipework, it seems reasonable that the less thirsty engine could run for a few seconds longer. The extra pipework leading to the APU could possibly give the left side system a little more volume to suck from - but this would depend on the position of the constriction.
However, whilst possibly explaining the time difference between the rollbacks, I might expect that with similar restrictions the less thirsty engine might develop the larger, rather than smaller, EPR.
On a different theme, a couple of questions that physical chemists may be able to answer with a definite NO: does the presence of dissolved water alter the increase the temperature at which some waxing compoents solidify; and do the variations in composition of the Chinese fuel from normal Jet A1 modify the response to the previous question?
And finally: would it not be possible to provide the QAR with enough battery or even capacitor backup energy to enable it to write the volatile memory to non-volatile memory on failure of external power?
If, as is hinted, the engines (or rather some of their pumps) were separately sucking fuel from the pipework downstream of blockages at similar points in the two sets of pipework, it seems reasonable that the less thirsty engine could run for a few seconds longer. The extra pipework leading to the APU could possibly give the left side system a little more volume to suck from - but this would depend on the position of the constriction.
However, whilst possibly explaining the time difference between the rollbacks, I might expect that with similar restrictions the less thirsty engine might develop the larger, rather than smaller, EPR.
On a different theme, a couple of questions that physical chemists may be able to answer with a definite NO: does the presence of dissolved water alter the increase the temperature at which some waxing compoents solidify; and do the variations in composition of the Chinese fuel from normal Jet A1 modify the response to the previous question?
And finally: would it not be possible to provide the QAR with enough battery or even capacitor backup energy to enable it to write the volatile memory to non-volatile memory on failure of external power?
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Warning: I'm non-professional; not crew, not engineer - just scientist guest and thanks.
A more detailed reading of the AAIB interim report leads me to the following conclusions:
1) The AAIB strongly suspects that an unknown (or possibly forgotten - reference the mentioning of B52 operations) fuel condition led to a blockage (partial) in the fuel delivery system.
2) The AAIB does not understand the details of how the blockage occurred.
3) The AAIB does not think any other organisation has a current understanding of how very cold fuel behaves.
4) The AAIB strongly suspects that aircraft type, operator, manufacturer (airframe and engines) are irrelevant to the root cause of this accident, i.e. the accident could, and may, happen to any aircraft using that fuel type in similar operating conditions.
5) Given point 4 then this incident is extremely important to the industry, not only for those now manufacturing or operating, but also for the future design and operation of aircraft. Put another way, this incident, and the avoidance of recurrence, will be very expensive.
There seems a strong possibility that a rigorous research programme will be initiated, probably involving multiple organisations not directly related to commercial concerns, to study very cold fuel.
I wouldn't be surprised if a flying test rig was involved maybe operated by an outfit like NASA.
Following on from the AAIB reference to B-52s and FSII, I wonder if some poor souls are not already deep into the RAF and USAF/SAC archive records looking for those papers that covered their 1950-60s tests on cold weather flying.
What has been written, and the quick response from the NTSB, suggests that the AAIB has already had detailed discussions with all the interested parties, that there is common agreement on interim measures and, hopefully, agreement on a research programme to find the eventual cause. The final AAIB report is years away.
I still think the fuel within the main tanks stratified in some form and that a pulse of "gloop" entered the delivery systems and partially blocked them.
But, I'm intrigued by the some of the hints in the AAIB's report about low maximum fuel flow rates from the main tanks and two flights in very cold circumstances separated by a cold stop in Beijing. Are the AAIB thinking that ice built up over two flights in the fuel lines/systems emanating from the main tanks and that a new operating procedure of some kind should be considered to 'purge' the lines under similar circumstances? Time will tell.
Regards, Tanimbar
A more detailed reading of the AAIB interim report leads me to the following conclusions:
1) The AAIB strongly suspects that an unknown (or possibly forgotten - reference the mentioning of B52 operations) fuel condition led to a blockage (partial) in the fuel delivery system.
2) The AAIB does not understand the details of how the blockage occurred.
3) The AAIB does not think any other organisation has a current understanding of how very cold fuel behaves.
4) The AAIB strongly suspects that aircraft type, operator, manufacturer (airframe and engines) are irrelevant to the root cause of this accident, i.e. the accident could, and may, happen to any aircraft using that fuel type in similar operating conditions.
5) Given point 4 then this incident is extremely important to the industry, not only for those now manufacturing or operating, but also for the future design and operation of aircraft. Put another way, this incident, and the avoidance of recurrence, will be very expensive.
There seems a strong possibility that a rigorous research programme will be initiated, probably involving multiple organisations not directly related to commercial concerns, to study very cold fuel.
I wouldn't be surprised if a flying test rig was involved maybe operated by an outfit like NASA.
Following on from the AAIB reference to B-52s and FSII, I wonder if some poor souls are not already deep into the RAF and USAF/SAC archive records looking for those papers that covered their 1950-60s tests on cold weather flying.
What has been written, and the quick response from the NTSB, suggests that the AAIB has already had detailed discussions with all the interested parties, that there is common agreement on interim measures and, hopefully, agreement on a research programme to find the eventual cause. The final AAIB report is years away.
I still think the fuel within the main tanks stratified in some form and that a pulse of "gloop" entered the delivery systems and partially blocked them.
But, I'm intrigued by the some of the hints in the AAIB's report about low maximum fuel flow rates from the main tanks and two flights in very cold circumstances separated by a cold stop in Beijing. Are the AAIB thinking that ice built up over two flights in the fuel lines/systems emanating from the main tanks and that a new operating procedure of some kind should be considered to 'purge' the lines under similar circumstances? Time will tell.
Regards, Tanimbar
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'Which factor(s) made this flight so special?'
Doesn't the answer come from page 17?:
Analysis of fuel flow from the 13,000 flights shows that 10% had fuel flows less than 10,000 pph during step climbs (the accident flight did not exceed 8,896 pph), and 10% had had fuel flows greater than 10,000 pph during the approach phase (the accident flight was greater than 12,000 pph). Although these were not unique, they were at the edge of family for the data analysed. However, when analysed in conjunction with the fuel temperature data above, all of these factors make this flight unusual within the 13,000 flights analysed.
Maybe we should infer that the absence of high fuel flows in the cruise (gentle cruise climbs) promotes ice formation while the high flow on descent encourages any slug that has formed to move; take away either and you break the chain. Since, as others have said, it isn't obvious that there is anything special about the RR engine in all this, maybe this analysis will be continued to the other 128000 PW and GE powered 777 flights. If BA38 is still ' unusual' in the bigger data set, that would be more than interesting.
Analysis of fuel flow from the 13,000 flights shows that 10% had fuel flows less than 10,000 pph during step climbs (the accident flight did not exceed 8,896 pph), and 10% had had fuel flows greater than 10,000 pph during the approach phase (the accident flight was greater than 12,000 pph). Although these were not unique, they were at the edge of family for the data analysed. However, when analysed in conjunction with the fuel temperature data above, all of these factors make this flight unusual within the 13,000 flights analysed.
Maybe we should infer that the absence of high fuel flows in the cruise (gentle cruise climbs) promotes ice formation while the high flow on descent encourages any slug that has formed to move; take away either and you break the chain. Since, as others have said, it isn't obvious that there is anything special about the RR engine in all this, maybe this analysis will be continued to the other 128000 PW and GE powered 777 flights. If BA38 is still ' unusual' in the bigger data set, that would be more than interesting.
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No comment on the probable cause, but the proposed revised operating procedures remind of my Tiger Moth days (1961); "when descending with throttle closed, regularly open throttle to rev engine". Trouble is, you guys no longer train on Tigers. 
Second Law
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Sun in my eyes 176p.
Sir,
(i)
Disagreed, if you read the whole thread and like many others I have, there are current 777 pilots out there and for whom I have great respect having read their postings over time, who claim to have made it to the runway in the sim using the data as published.
(ii) Agreed, this interim report confirms magnificent, intuitive and effective flying by the pilots in "less than a minute". Although we need to wait for the final report, this report should at least now stop any poisonous whispers to the contrary.
(iii) For the record I have been proven wrong by this report as I have speculated here that it was low Molecular Mass fuel components (hydrocarbon or the friends of ethoxy ethane as addditives) that caused the HP pump cavitation.
I have unequivocal respect for the AAIB and I need to think through the water ice explanation at the ppm level in fuel that is within spec.
The magic bullet flying oxygen cylinder retracing its steps as it exited the Quantas 747 and now this, reminds me not only to respect those slices of cheese but to show a little more humility.
CW
Sir,
(i)
There is no way a normal landing could be made, ie reaching the runway.
(ii) Agreed, this interim report confirms magnificent, intuitive and effective flying by the pilots in "less than a minute". Although we need to wait for the final report, this report should at least now stop any poisonous whispers to the contrary.
(iii) For the record I have been proven wrong by this report as I have speculated here that it was low Molecular Mass fuel components (hydrocarbon or the friends of ethoxy ethane as addditives) that caused the HP pump cavitation.
I have unequivocal respect for the AAIB and I need to think through the water ice explanation at the ppm level in fuel that is within spec.
The magic bullet flying oxygen cylinder retracing its steps as it exited the Quantas 747 and now this, reminds me not only to respect those slices of cheese but to show a little more humility.
CW
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Tanimbar:
Having read the report twice now I concur with your analysis and in particular I'm drawn to the last conclusion. Ice accretion inside the wing fuel pipes over the two flights separating when the high fuel flow was demanded and causing the restriction. Where the restriction is is not clear but the face of the FOHE looks like a good bet.
They say that formation of the ice there was unlikely but don't comment on this being the collection point for ice formed upstream.
I'm sure we will see requirements for fuel feed line purging by high thrust demands coming to an AFM near you pretty soon.
Having read the report twice now I concur with your analysis and in particular I'm drawn to the last conclusion. Ice accretion inside the wing fuel pipes over the two flights separating when the high fuel flow was demanded and causing the restriction. Where the restriction is is not clear but the face of the FOHE looks like a good bet.
They say that formation of the ice there was unlikely but don't comment on this being the collection point for ice formed upstream.
I'm sure we will see requirements for fuel feed line purging by high thrust demands coming to an AFM near you pretty soon.
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I think the previous posts questioning the temperatures reached within the pylon pipework may be significant.
In the refining and petro-chem industries, pipework which is subject to icing, waxing or similar problems is often trace heated. This is usually by steam or electrical heaters, but I guess a warm air bleed would also work.
Does anyone know if anything similar has ever been applied in aviation.
In the refining and petro-chem industries, pipework which is subject to icing, waxing or similar problems is often trace heated. This is usually by steam or electrical heaters, but I guess a warm air bleed would also work.
Does anyone know if anything similar has ever been applied in aviation.
occasional,
From the latest Interim report:
One of the difficult to find and, I think, generically interesting pieces of information to emerge from this investigation.
There seems to be an assumption that the effective temperature within the wings is reasonably uniform and similar to or above the TAT.
On long flights the temperature of the fuel in the main wing tanks will tend towards the temperature of the boundary layer around the wing, which can be up to 3°C lower than TAT
Junior trash
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On long flights the temperature of the fuel in the main wing tanks will tend towards the temperature of the boundary layer around the wing, which can be up to 3°C lower than TAT
One of the difficult to find and, I think, generically interesting pieces of information to emerge from this investigation.
One of the difficult to find and, I think, generically interesting pieces of information to emerge from this investigation.
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chris weston: "there are current 777 pilots out there and for whom I have great respect having read their postings over time, who claim to have made it to the runway in the sim using the data as published."
No simulator has true airport environs and runway fidelity.
It's not an argument. Just a statement of fact.
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Try try and try again?
It would be interesting to hear whether they reached past the grass on the
first attempt, or after a few tries.
Given the available energy, I find it hard to believe a crew being able to
make it to the concrete. However, details of how different strategies played
out might be interesting. I don't remember reading such a post.
If they set up the sim just to try BA038, then they were in a much better
position than the real crew: they knew the exact problem to expect, had
seen the true outcome, and no lives were on the line. A true test would be to
spring BA038 rollback on crews when their configuration and energy
matched in the simulator, and see how they did first time, building up
data slowly.
For what my view's worth: getting BA038 over the fence, stopped
and evacuated with only a single serious injury onboard and none on the
ground - for real - deserves much respect.
first attempt, or after a few tries.
Given the available energy, I find it hard to believe a crew being able to
make it to the concrete. However, details of how different strategies played
out might be interesting. I don't remember reading such a post.
If they set up the sim just to try BA038, then they were in a much better
position than the real crew: they knew the exact problem to expect, had
seen the true outcome, and no lives were on the line. A true test would be to
spring BA038 rollback on crews when their configuration and energy
matched in the simulator, and see how they did first time, building up
data slowly.
For what my view's worth: getting BA038 over the fence, stopped
and evacuated with only a single serious injury onboard and none on the
ground - for real - deserves much respect.
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Training & Value
El #
From posts since mine your claim from "not-easy-to-dismiss" sources" appears to have been dismissed.
And please don't be so dismissive of me. I have read all post & also the one you suggested.
Your statement re: dead stick landings also appears to be incorrect. "sheer luck" Well I dont think so. Ok I'm just SLF but my view was reflected by suninmyeyes in post 1765.
My trust in flying has not been decreased by this, in fact has been increased. I trust the people I fly with. I also trust the AAIB to get to the bottom of this no matter however much speculation there might be on this site.
My bottom line was reflected by suninmyeyes. "A manual landing was achieved in which all the passengers survived" For that I thank & respect the crew. I'd rather have been on BA038 than the Madrid flight.
From posts since mine your claim from "not-easy-to-dismiss" sources" appears to have been dismissed.
And please don't be so dismissive of me. I have read all post & also the one you suggested.
Your statement re: dead stick landings also appears to be incorrect. "sheer luck" Well I dont think so. Ok I'm just SLF but my view was reflected by suninmyeyes in post 1765.
My trust in flying has not been decreased by this, in fact has been increased. I trust the people I fly with. I also trust the AAIB to get to the bottom of this no matter however much speculation there might be on this site.
My bottom line was reflected by suninmyeyes. "A manual landing was achieved in which all the passengers survived" For that I thank & respect the crew. I'd rather have been on BA038 than the Madrid flight.
Controversial, moi?
It would be interesting to hear whether they reached past the grass on the first attempt, or after a few tries.
http://www.pprune.org/rumours-news/3...ml#post4322326