AAIB BA38 B777 Initial Report Update 23 January 2008
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Could a 777 pilots perhaps comment on what amount of power would be needed to get the 777 to go 2nm from 600' in the landing config?
More thrust than they had available on the day!
Sensible......as has been stated on this and the other threads.....Jet pumps keep the water circulating and mixed in with the fuel at all stages of the flight.....as long as the fuel pumps are working. The water will then come out of suspension at 1ft per hour so as long as the pumps work there will be no pooling of fuel or contaminates at the bottom of the tanks.
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unless of course the water scavenge jet pumps are blocked by ice. If they are blocked on the suction side, the fuel jet will be undisturbed so there will be no indication that the water scavenge pumps are not working.
The Boeing manual states
So the only indication of the jet pumps not working is water accumulation.
Exectly that is the reason why those are jet pumps, and no impeller type pumps, if they fail they do not produce any secondary failure like blocking of an electric motor and setting of a circuit breaker or cause overheating etc.
The effect of those pumps is, that you don´t have a solid block of ice in the tank, but a slush of fine ice crystals.
The Boeing manual states
You should get a fuel sample from the sump drain valves
before and after you do the refuel procedure. A large
quantity of water in a fuel sample that you drain from
a tank before refueling is an indication of a blocked
water scavenge jet pump.
before and after you do the refuel procedure. A large
quantity of water in a fuel sample that you drain from
a tank before refueling is an indication of a blocked
water scavenge jet pump.
Exectly that is the reason why those are jet pumps, and no impeller type pumps, if they fail they do not produce any secondary failure like blocking of an electric motor and setting of a circuit breaker or cause overheating etc.
The effect of those pumps is, that you don´t have a solid block of ice in the tank, but a slush of fine ice crystals.
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Your questions incorrectly assume steady state. The final approach was not at constant IAS.
I know that this aircraft was not steady state. Still I do not believe that it would make the airport boundary if the engines were at idle. Steady state or not.
So again, my question: Can a 777 pilot possibly comment to roughly what power setting this aircraft had during its final phase.
Even if the answer is "more than flight idle" it would go some way towards knowing the facts.
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Interesting additional (speculative) information.
http://www.pilotsofamerica.com/forum...ad.php?t=19056
At about 700 ft AGL, the auto throttle commanded engine acceleration. One engine started to rollback during and the other engine started to accelerate then 8-10 seconds later began to roll back. Once the flight crew noticed, they pushed the throttles up and the engines' EECs responded but the engines did not. It appears that no fuel was getting to the engines.
The investigation continues to look broadly for a cause of the dual engine rollbacks. Fuel exhaustion is the only item that has been positively ruled out. Aspects that the FAA believes the investigation is concentrating on are:
• Ice in the fuel somehow limiting the fuel flow to the engines. A maintenance message indicating excessive water in the center tank was set during taxi on the two previous flight legs, although it cleared itself both times. The airplane was being operated in a high humidity, cold environment, conducive to ice formation.
• Small-sized contamination building up in the engine fuel systems somehow limited the fuel flow to engine. All the fuel samples have tested for contamination of larger particles (sizes outside the fuel specification). Testing has been started looking for small particles (greater than 5 microns).
• Engine hardware failures sending inaccurate data to the engine electronic control (EEC) causing the EEC to demand insufficient fuel. A preliminary review of the EEC data from the right engine shows erratic combustor inlet pressure (P30). A leaking P30 sense line could cause this, or the EEC receiving a higher than actual fuel flow parameter.
• Software coding problem in the EEC causing the EEC to demand insufficient fuel. British Airways installed a new engine EEC software revision in December 2007. The software was approved in May 2006. There were several changes to the software as part of the revision. Two items seem remotely related to the accident: improvements to low power stall recovery logic and fan keep out zones for ground maintenance. The first two items would be related to a part 25 compliance issue, while the last two items would be related to a part 33 compliance issue.
As stated yesterday in this briefing paper, the electrical system anomalies noted earlier have been resolved, as describe below, and the conclusion now is that the electrical buses were powered until impact and performing as expected.
• The auxiliary power unit (APU) began its auto start sequence, even though the buses were still powered. In the days following the event, the flight crew has added additional details to their report. The crew now believes they turned the APU on prior to impact. There was sufficient time before the impact for the APU inlet door to open, but not for the APU fuel pump to turn on or the APU engine to start spooling up.
• The quick access recorder (QAR) saved data and shut down approximately 45 seconds prior to impact. The QAR saves data in batches. It is believed the QAR was working properly and was in the process of saving data when impact occurred, accounting for the “lost” 45 seconds of data.
• The fuel crossfeed valves were closed in flight according to the flight crew, but the switches were found in the open position and only one valve was open. In the days following the event, the flight crew has added additional details to their report. The crew now believes they opened the valves just prior to impact and the airplane lost power before both valves moved to the open position.
• The ram air turbine (RAT) was found deployed, even though the buses were still powered. It did not deploy until after the airplane came to a stop, as determined by the pristine condition of the turbine blades. The RAT either deployed due to electrical power loss during impact with a failed air/ground signal or the impact unlatched the RAT door.
Fuel system: Leads regarding water in the fuel and fuel contamination are continuing to be investigated. Fuel testing looking for small-sized contaminants (5 microns) is beginning. The tanks are still being drained and the team hopes to start evaluating the fuel system hardware tomorrow.
Engines: Component testing and teardown of the engine-driven fuel pumps and the fuel metering units is planned for later this week. The data from the electronic engine controls is still being analyzed. Rolls-Royce is planning an engine test, unscheduled as yet, to try and duplicate the rollbacks.
Crashworthiness: Cabin crew and passenger questionnaires indicate that the evacuation bell was faint, but the evacuation light was seen and the captain’s message to evacuate over the passenger address system was heard. Preliminary data indicates that the descent rate at impact was roughly 30 ft/sec. Dynamic seat requirements that became effective at the introduction of the Model 777 series airplanes require seats protect occupants for hard landing impact up to 35 ft/sec. The passenger with the broken leg was sitting next to the point where the right main landing gear punctured the fuselage and pushed into the cabin (pictured below).
Crashworthiness: There was only one serious injury, a compound fracture to the leg. The airplane landed on the main gear, bounced, came back down on the gear, then the gear failed, and the engines supported weight of the airplane. The descent rate at landing was 1500-1800 feet per minute. One of the main landing gear swung around and pushed slightly into the cabin. The other punctured the center fuel tank (empty) leaving a 1-by-2-foot hole. The report of a fuel leak is unconfirmed. All the slides deployed and the doors worked. Some passengers had to shuffle down the slides due to the slight angle. The flight deck door opened on its own during the landing. Some oxygen masks dropped.
The investigation continues to look broadly for a cause of the dual engine rollbacks. Fuel exhaustion is the only item that has been positively ruled out. Aspects that the FAA believes the investigation is concentrating on are:
• Ice in the fuel somehow limiting the fuel flow to the engines. A maintenance message indicating excessive water in the center tank was set during taxi on the two previous flight legs, although it cleared itself both times. The airplane was being operated in a high humidity, cold environment, conducive to ice formation.
• Small-sized contamination building up in the engine fuel systems somehow limited the fuel flow to engine. All the fuel samples have tested for contamination of larger particles (sizes outside the fuel specification). Testing has been started looking for small particles (greater than 5 microns).
• Engine hardware failures sending inaccurate data to the engine electronic control (EEC) causing the EEC to demand insufficient fuel. A preliminary review of the EEC data from the right engine shows erratic combustor inlet pressure (P30). A leaking P30 sense line could cause this, or the EEC receiving a higher than actual fuel flow parameter.
• Software coding problem in the EEC causing the EEC to demand insufficient fuel. British Airways installed a new engine EEC software revision in December 2007. The software was approved in May 2006. There were several changes to the software as part of the revision. Two items seem remotely related to the accident: improvements to low power stall recovery logic and fan keep out zones for ground maintenance. The first two items would be related to a part 25 compliance issue, while the last two items would be related to a part 33 compliance issue.
As stated yesterday in this briefing paper, the electrical system anomalies noted earlier have been resolved, as describe below, and the conclusion now is that the electrical buses were powered until impact and performing as expected.
• The auxiliary power unit (APU) began its auto start sequence, even though the buses were still powered. In the days following the event, the flight crew has added additional details to their report. The crew now believes they turned the APU on prior to impact. There was sufficient time before the impact for the APU inlet door to open, but not for the APU fuel pump to turn on or the APU engine to start spooling up.
• The quick access recorder (QAR) saved data and shut down approximately 45 seconds prior to impact. The QAR saves data in batches. It is believed the QAR was working properly and was in the process of saving data when impact occurred, accounting for the “lost” 45 seconds of data.
• The fuel crossfeed valves were closed in flight according to the flight crew, but the switches were found in the open position and only one valve was open. In the days following the event, the flight crew has added additional details to their report. The crew now believes they opened the valves just prior to impact and the airplane lost power before both valves moved to the open position.
• The ram air turbine (RAT) was found deployed, even though the buses were still powered. It did not deploy until after the airplane came to a stop, as determined by the pristine condition of the turbine blades. The RAT either deployed due to electrical power loss during impact with a failed air/ground signal or the impact unlatched the RAT door.
Fuel system: Leads regarding water in the fuel and fuel contamination are continuing to be investigated. Fuel testing looking for small-sized contaminants (5 microns) is beginning. The tanks are still being drained and the team hopes to start evaluating the fuel system hardware tomorrow.
Engines: Component testing and teardown of the engine-driven fuel pumps and the fuel metering units is planned for later this week. The data from the electronic engine controls is still being analyzed. Rolls-Royce is planning an engine test, unscheduled as yet, to try and duplicate the rollbacks.
Crashworthiness: Cabin crew and passenger questionnaires indicate that the evacuation bell was faint, but the evacuation light was seen and the captain’s message to evacuate over the passenger address system was heard. Preliminary data indicates that the descent rate at impact was roughly 30 ft/sec. Dynamic seat requirements that became effective at the introduction of the Model 777 series airplanes require seats protect occupants for hard landing impact up to 35 ft/sec. The passenger with the broken leg was sitting next to the point where the right main landing gear punctured the fuselage and pushed into the cabin (pictured below).
Crashworthiness: There was only one serious injury, a compound fracture to the leg. The airplane landed on the main gear, bounced, came back down on the gear, then the gear failed, and the engines supported weight of the airplane. The descent rate at landing was 1500-1800 feet per minute. One of the main landing gear swung around and pushed slightly into the cabin. The other punctured the center fuel tank (empty) leaving a 1-by-2-foot hole. The report of a fuel leak is unconfirmed. All the slides deployed and the doors worked. Some passengers had to shuffle down the slides due to the slight angle. The flight deck door opened on its own during the landing. Some oxygen masks dropped.
Keeping Danny in Sandwiches
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pilotsofamerica
seems to conflict with:
AAIB
The AAIB state clearly that both engines continued to produce thrust above flight idle so don't get carried away with the minutiae of the comments.
At about 700 ft AGL, the auto throttle commanded engine acceleration. One engine started to rollback during and the other engine started to accelerate then 8-10 seconds later began to roll back. Once the flight crew noticed, they pushed the throttles up and the engines' EECs responded but the engines did not. It appears that no fuel was getting to the engines.
AAIB
whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.
Last edited by sky9; 31st Jan 2008 at 15:58.
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Now....... Does "crossfeeds 1 out of 2 open" show the Captain had done the drill quick as he could after failure?
...OR, selected a little earlier as a precaution, whereupon ice or wax sludge got to both engines?
...OR,Were they both selected open for some considerable time for some reason , but one failed shut?
I detect that OATs were excessively low for along time...I`d like to know the history of fuel temp time line through the flight and any action taken, and the last logged fuel quantity and planned reserves
...Impact R.O.D. 1800fpm or more a helluva flare needed..(like my microlight dead stick,)and has to be perfect.
... Looking at the flight path not far off 600 or 700 fpm it may have actually stalled 2/3rds of a second, 120 feet, before touchdown Well done Frenchie
...OR, selected a little earlier as a precaution, whereupon ice or wax sludge got to both engines?
...OR,Were they both selected open for some considerable time for some reason , but one failed shut?
I detect that OATs were excessively low for along time...I`d like to know the history of fuel temp time line through the flight and any action taken, and the last logged fuel quantity and planned reserves
...Impact R.O.D. 1800fpm or more a helluva flare needed..(like my microlight dead stick,)and has to be perfect.
... Looking at the flight path not far off 600 or 700 fpm it may have actually stalled 2/3rds of a second, 120 feet, before touchdown Well done Frenchie
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Well, I'm guessing that the pilotsofamerica poster's friend has been to his last accident site... The chap in that photo will know who took it, and you can bet your bottom $ that he (and his bosses) won't be happy.
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Fuel waxing etc....
This incident is still puzzling everybody
I still have great diffuculty in believing the talk about about possible fuel waxing, because the presence of wax would imply that the flight deck crew had FAILED to adhere to the proper and straigtforward procedures for flight in low OATs.
And I have no reason to mistrust the professionalism of the involded BA crew in this respect.
Also, I do not believe in the theory concerning water/ice contamination of the fuel for the reasons already put forward by several earlier posts.
I will just repeat one of the arguments: even if tiny ice crystals were present in the fuel, how could they "survive" their travel through 2 fuel pumps, the fuel/oil cooler and a filter and still have a potential of almost shutting an engine down?
And on both engines at almost the same time!
I believe that the cause(s) to this incident will turn up to be problems in the hardware/software parts of systems controlling the engines (FADEC, EEC, AUTOTHRUST etc..).
But there is of course a weak point, i.e. how can 2 engines, running independently, show problems at almost the same time, unless the problems are in some way connected?
In theory it may be possible!
By the way: A great WELL DONE to the crew!
(This is my first post - I am a retired captain, the last 10 years in my career were on B-767 and A340).
I still have great diffuculty in believing the talk about about possible fuel waxing, because the presence of wax would imply that the flight deck crew had FAILED to adhere to the proper and straigtforward procedures for flight in low OATs.
And I have no reason to mistrust the professionalism of the involded BA crew in this respect.
Also, I do not believe in the theory concerning water/ice contamination of the fuel for the reasons already put forward by several earlier posts.
I will just repeat one of the arguments: even if tiny ice crystals were present in the fuel, how could they "survive" their travel through 2 fuel pumps, the fuel/oil cooler and a filter and still have a potential of almost shutting an engine down?
And on both engines at almost the same time!
I believe that the cause(s) to this incident will turn up to be problems in the hardware/software parts of systems controlling the engines (FADEC, EEC, AUTOTHRUST etc..).
But there is of course a weak point, i.e. how can 2 engines, running independently, show problems at almost the same time, unless the problems are in some way connected?
In theory it may be possible!
By the way: A great WELL DONE to the crew!
(This is my first post - I am a retired captain, the last 10 years in my career were on B-767 and A340).
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Where Was the Aircraft When Fuelled?
In the discussion about possible fuel contamination, whether from heavier fuel components (e.g. diesel), or water, no-one seems to have raised what to me is one of the biggest unknowns, at least by the arm-chair investigators:
Where at PEK was the aircraft when it was re-fuelled prior to the PEK-LHR sector?
If the aircraft was on a much-used stand, and other long-haul aircraft had been fuelled before it, and were fuelled subsequent to it, then it seems unlikely that BA038 would have been the only aircraft to have received off-spec fuel, and the other aircraft might (but only might), have experienced difficulties, notwithstanding that BA038 possibly had the longest and coldest soak, and notwithstanding that if ‘it’ had all happened three minutes later, then the aircraft would have been safely on the ground.
But if the aircraft was on a more remote stand, perhaps one fed by a ‘dead leg’ of the hydrant system, or if the aircraft was on a stand where the hydrant system was, or had been, under maintenance, or if the aircraft was fuelled by bowsers (more than one, I imagine, for a long haul), then the chances that it received suspicious fuel must be higher.
Part of the Quality Assurance system for Jet is that not only are samples taken and tested at the refinery whence the fuel originated, but that samples are taken and tested from the tank farm at the airfield, and samples are taken and tested from the hydrant systems and bowsers. All these samples have to be retained for specified periods (basically, until it can be certain that all the batch of fuel has been consumed, plus quite bit more), AND the laboratory where these tests are done also is regularly checked to ensure that the correct testing methods (for Jet, normally ASTM, or IP), are used, and the results that any particular laboratory obtains are correlated with other laboratories in ‘round robins’ to ensure consistency within the statistically determined accuracy of the methods.
Let us hope that the retained samples for the fuel supplied to this particular aircraft were correctly taken, were correctly identified and retained, and that any further testing has been done in an accredited laboratory under the supervision of a third party inspector.
One other thought… accidents are very rarely the result of a single cock-up, but the consequence of a chain of events that lead to an improbable, but sadly unforeseen, event. It seems unlikely that BA038’s slightly premature arrival on 27L was the result of a single factor.
Where at PEK was the aircraft when it was re-fuelled prior to the PEK-LHR sector?
If the aircraft was on a much-used stand, and other long-haul aircraft had been fuelled before it, and were fuelled subsequent to it, then it seems unlikely that BA038 would have been the only aircraft to have received off-spec fuel, and the other aircraft might (but only might), have experienced difficulties, notwithstanding that BA038 possibly had the longest and coldest soak, and notwithstanding that if ‘it’ had all happened three minutes later, then the aircraft would have been safely on the ground.
But if the aircraft was on a more remote stand, perhaps one fed by a ‘dead leg’ of the hydrant system, or if the aircraft was on a stand where the hydrant system was, or had been, under maintenance, or if the aircraft was fuelled by bowsers (more than one, I imagine, for a long haul), then the chances that it received suspicious fuel must be higher.
Part of the Quality Assurance system for Jet is that not only are samples taken and tested at the refinery whence the fuel originated, but that samples are taken and tested from the tank farm at the airfield, and samples are taken and tested from the hydrant systems and bowsers. All these samples have to be retained for specified periods (basically, until it can be certain that all the batch of fuel has been consumed, plus quite bit more), AND the laboratory where these tests are done also is regularly checked to ensure that the correct testing methods (for Jet, normally ASTM, or IP), are used, and the results that any particular laboratory obtains are correlated with other laboratories in ‘round robins’ to ensure consistency within the statistically determined accuracy of the methods.
Let us hope that the retained samples for the fuel supplied to this particular aircraft were correctly taken, were correctly identified and retained, and that any further testing has been done in an accredited laboratory under the supervision of a third party inspector.
One other thought… accidents are very rarely the result of a single cock-up, but the consequence of a chain of events that lead to an improbable, but sadly unforeseen, event. It seems unlikely that BA038’s slightly premature arrival on 27L was the result of a single factor.
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sccutler
That was supposedly written as an update on 30th January. Are pilots in the USA incapable of reading AAIB reports? Maybe they don't know where to look for them. The initial report states very clearly:
and the update:
Perhaps you would care to point them in the direction of these reports which can be found here.
The report of a fuel leak is unconfirmed. All the slides deployed and the doors worked.
A significant amount of fuel leaked from the aircraft but there was no fire
Recorded data indicates that an adequate fuel quantity was on board the aircraft
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Does anyone really think that, with the help of Boeing, the investigation will manage to avoid blaming the pilots?
The great job that they did in making the accident survivable will not help them too much if there was the possibility they could have made a normal landing.
The great job that they did in making the accident survivable will not help them too much if there was the possibility they could have made a normal landing.
Hi Guys,
This thread seems to have concentrated almost exclusively on fuel waxing.
It seems to me that any fuel low temperature issues will have been eliminated as the aircraft descended into warmer air. As has been correctly mentioned, Jet A-1 freezes at -47 deg centigrade. This temperature is found at around 26,000 feet on a day in UK winter, (say ISA -10). But from experience, even during flight over Greenland at FL 400, where the SAT can reach -73 deg centigrade; it still takes a couple of hours to reduce the outer wing tank (non-warmed fuel) to reduce to -47 deg centigrade. An aircraft in-bound to the UK from Japan/China would have passed below flight level 260 well north of LHR. By the time it was on short finals, the wing tank fuel would have warmed well above -47 deg centigrade, and in any case, the inner wing tank fuel (which feeds the engines) is warmed anyway, so fuel waxing would surely not have been an issue; the fuel in the BA 777 wing tanks would have been above waxing temperature.
This does not rule out fuel contamination, but a more likely scenario in my view must be the engine FADECS or the authothrust system. I wonder if a passenger, seeing they were just about to land decided to illegally switch on their mobile 'phone before landing and engine shut down, in order to pick up "vital" messages as soon as they were on the ground. Could the burst of digitally coded RF from such a 'phone have got into the engine FADECs and confused them into commanding idle thrust ?
Notwithstanding why the engines failed, I would like to record my respect for the Captain and F/O for getting the aircraft into the airport in severly testing circumstances. We practice many engine failure scenarios in the SIM every 6 months, but double engine failure when 600' above the ground has got to be the 'Daddy' of them all !! One is left with very few options in such a situatuion, the only one really available being trading speed for height, and I take my hat off to both the pilots for a really successful outcome.
PS What was all that nonsense in the gutter press about the pilot's lifestyle, holidays, and salary ?? How exactly was that relevant ?
This thread seems to have concentrated almost exclusively on fuel waxing.
It seems to me that any fuel low temperature issues will have been eliminated as the aircraft descended into warmer air. As has been correctly mentioned, Jet A-1 freezes at -47 deg centigrade. This temperature is found at around 26,000 feet on a day in UK winter, (say ISA -10). But from experience, even during flight over Greenland at FL 400, where the SAT can reach -73 deg centigrade; it still takes a couple of hours to reduce the outer wing tank (non-warmed fuel) to reduce to -47 deg centigrade. An aircraft in-bound to the UK from Japan/China would have passed below flight level 260 well north of LHR. By the time it was on short finals, the wing tank fuel would have warmed well above -47 deg centigrade, and in any case, the inner wing tank fuel (which feeds the engines) is warmed anyway, so fuel waxing would surely not have been an issue; the fuel in the BA 777 wing tanks would have been above waxing temperature.
This does not rule out fuel contamination, but a more likely scenario in my view must be the engine FADECS or the authothrust system. I wonder if a passenger, seeing they were just about to land decided to illegally switch on their mobile 'phone before landing and engine shut down, in order to pick up "vital" messages as soon as they were on the ground. Could the burst of digitally coded RF from such a 'phone have got into the engine FADECs and confused them into commanding idle thrust ?
Notwithstanding why the engines failed, I would like to record my respect for the Captain and F/O for getting the aircraft into the airport in severly testing circumstances. We practice many engine failure scenarios in the SIM every 6 months, but double engine failure when 600' above the ground has got to be the 'Daddy' of them all !! One is left with very few options in such a situatuion, the only one really available being trading speed for height, and I take my hat off to both the pilots for a really successful outcome.
PS What was all that nonsense in the gutter press about the pilot's lifestyle, holidays, and salary ?? How exactly was that relevant ?
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autoflight
The AAIB report will not "blame" anyone or anything, but hopefully establish the "cause".
And do you really think the a/c had enough energy for a "normal landing"?
TP
Does anyone really think that, with the help of Boeing, the investigation will manage to avoid blaming the pilots?
And do you really think the a/c had enough energy for a "normal landing"?
TP
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Fuel Management and RF Interference
The fuel sensors in the 777 are ultrasonic and bounce a signal off the top of the fuel to measure the tank capacity. If there was waxing in the tank I am sure it would have given some very strange readings very early on and the management system would have moved the fuel if a problem was seen. I imaging this will have been part of the design.
RF interference on the FADEC is possible but very very unlikely. They are designed to withstand massive RF loads, lightning strikes and have triple fall over. Indepentant systems are making calculations then checking themselves against each other and if they don’t agree they alert. A digital coincidence in the form of a misinterpreted signal is statistically possible but then so is time travel. My guess would be a set of complex and rare and unforeseen circumstances and a software fault. But that’s just a guess.
RF interference on the FADEC is possible but very very unlikely. They are designed to withstand massive RF loads, lightning strikes and have triple fall over. Indepentant systems are making calculations then checking themselves against each other and if they don’t agree they alert. A digital coincidence in the form of a misinterpreted signal is statistically possible but then so is time travel. My guess would be a set of complex and rare and unforeseen circumstances and a software fault. But that’s just a guess.