BA038 (B777) Thread
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Bunk-rest
If AAIB are that sinister, they certainly wouldn't need hints from the likes of PPRuNe. And if they're straight-up (obviously), conjecture doesn't hurt. What you seem to be suggesting isn't helpful, unless you're trying to be funny. Every venture undertaken by Human beings requires a little Faith.
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Smilin Ed, in respect of your last (1261), I think not.
"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?"
I'm not a fuel chemist, just a pure chemist of sorts and hope to be corrected if wrong by those in this thread more knowledgeable than me, but simply shortening the average alkane chain length in the fuel will be the basis of the lowering of the freezing point/waxing point temperatures, not the addition of non combustible additives.
Technically such changes will alter the Heats of Combustion a little but never so as to render the fuel non combustible. That the fuel was within spec is key.
The arguments for and against the effects of water scavenging additives (which are usually ether like molecules derived from ethoxyethane and inherently themselves very combustible) and / or fuel having become stratified, have been rehearsed at length in earlier posts on this thread.
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?"
I'm not a fuel chemist, just a pure chemist of sorts and hope to be corrected if wrong by those in this thread more knowledgeable than me, but simply shortening the average alkane chain length in the fuel will be the basis of the lowering of the freezing point/waxing point temperatures, not the addition of non combustible additives.
Technically such changes will alter the Heats of Combustion a little but never so as to render the fuel non combustible. That the fuel was within spec is key.
The arguments for and against the effects of water scavenging additives (which are usually ether like molecules derived from ethoxyethane and inherently themselves very combustible) and / or fuel having become stratified, have been rehearsed at length in earlier posts on this thread.
CW
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Stay the course BA 038
The BA 038 accident facts published to date make it one of the most significant events in aviation history. Those who respect aviation must keep the investigation front and center. Whether grey beard or shave tail, all of us must stay the course and do what must be done to bring this event to a conclusion which benefits each of us who dare to expand aviation.
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Smilin Ed, in respect of your last (1261), I think not.
"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?"
I'm not a fuel chemist, just a pure chemist of sorts and hope to be corrected if wrong by those in this thread more knowledgeable than me, but simply shortening the average alkane chain length in the fuel will be the basis of the lowering of the freezing point/waxing point temperatures, not the addition of non combustible additives.
Technically such changes will alter the Heats of Combustion a little but never so as to render the fuel non combustible. That the fuel was within spec is key.
The arguments for and against the effects of water scavenging additives (which are usually ether like molecules derived from ethoxyethane and inherently themselves very combustible) and / or fuel having become stratified, have been rehearsed at length in earlier posts on this thread.
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?"
I'm not a fuel chemist, just a pure chemist of sorts and hope to be corrected if wrong by those in this thread more knowledgeable than me, but simply shortening the average alkane chain length in the fuel will be the basis of the lowering of the freezing point/waxing point temperatures, not the addition of non combustible additives.
Technically such changes will alter the Heats of Combustion a little but never so as to render the fuel non combustible. That the fuel was within spec is key.
The arguments for and against the effects of water scavenging additives (which are usually ether like molecules derived from ethoxyethane and inherently themselves very combustible) and / or fuel having become stratified, have been rehearsed at length in earlier posts on this thread.
CW
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Some T7 operators sent out a bulletin stating that they had some EAI valve malfunctions lately and Boeing is working on it. In the mean time crews are requested to test the system in descent.
In view of my early posting (#75), i am just wondering if this is not some coincidence.
But the visor is set on fuel and i concurr with Bunk-Rest's post of the 30th.
In view of my early posting (#75), i am just wondering if this is not some coincidence.
But the visor is set on fuel and i concurr with Bunk-Rest's post of the 30th.
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Some T7 operators sent out a bulletin stating that they had some EAI valve malfunctions lately and Boeing is working on it. In the mean time crews are requested to test the system in descent.
In view of my early posting (#75), i am just wondering if this is not some coincidence
In view of my early posting (#75), i am just wondering if this is not some coincidence
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CONF iture
The bulletin does not say a lot more than what i posted.
Sorry for the ref to my post, it was on a early but different thread about BA38.
Here is what I wrote. (I have to put it in the right timely context though: It was only three days after the accident, well before the AAIB report this thread refers to.)
The bulletin does not say a lot more than what i posted.
Sorry for the ref to my post, it was on a early but different thread about BA38.
Here is what I wrote. (I have to put it in the right timely context though: It was only three days after the accident, well before the AAIB report this thread refers to.)
If i go about the RR Trents on the T7, there is a possibility of no malfunction but still having the effect described. The engine anti-ice is mostly switched to "AUTO". I have witnessed its reluctance to go to "ON" more than once. Lets assume the inlet PT probe was iced up, apparently a ice warning was out that day and prolonged holding in the FL80 to 120 is a ice prone region. As the EEC uses EPR as parameter for thrust setting, in conjunction with the thrust lever angle, a demand either by the auto throttle or the pilots might have been ignored by the EEC, simply because with a PT inlet iced up and PT outlet not, the difference would fake "differential pressure", thus thrust, to the EEC. It would say "I am already giving you what you're asking for", not increasing FF and the result would be the low thrust setting persisting with a functioning and happy EEC.
Far fetched?
Far fetched?
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Ok GMDS, but this doesn't fit with AAIB Bulletin S3/2008 SPECIAL
The reduction in thrust on both engines was the result of a reduced fuel flow and all engine parameters after the thrust reduction were consistent with this. Parameters recorded on the Quick Access Recorder, Flight Data Recorder and non-volatile memory from the Electronic Engine Controller (EEC) indicate that the engine control system detected the reduced fuel flow and commanded the fuel metering valve to open fully. The fuel metering valve responded to this command and opened fully but with no appreciable change in the fuel flow to either engine.
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CONF iture:
Absolutely, that's why I backed off with my suspicion (I mentioned that my theory was very early in the debate). In my re-contribution just above I also clearly stated " ... I wonder ... ", as apparently ice was not involved. However, i still wonder ..... but backing off a second time.
airfoilmold:
in a situation as i described, it would make no difference if with A/T or in manual. In both cases the command to the EEC would be the same -> "gimme more diff press" and in both the EEC would say "you already have max".
Absolutely, that's why I backed off with my suspicion (I mentioned that my theory was very early in the debate). In my re-contribution just above I also clearly stated " ... I wonder ... ", as apparently ice was not involved. However, i still wonder ..... but backing off a second time.
airfoilmold:
in a situation as i described, it would make no difference if with A/T or in manual. In both cases the command to the EEC would be the same -> "gimme more diff press" and in both the EEC would say "you already have max".
GDMS,
When referring to the "engine anti-ice system", most pilots would call this the cowl hot air, that stops ice building up in the inlet then coming off in big chunks and going through the engine. AFAIK the various probes are electrically heated (like the main pitots) and I suspect would be on all the time, thus unlikely to block unless the icing was incredibly severe. Standing by to be corrected...
When referring to the "engine anti-ice system", most pilots would call this the cowl hot air, that stops ice building up in the inlet then coming off in big chunks and going through the engine. AFAIK the various probes are electrically heated (like the main pitots) and I suspect would be on all the time, thus unlikely to block unless the icing was incredibly severe. Standing by to be corrected...
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GMDS, Don't go anywhere just yet. Backing off isn't necessary either. I'm a trifle gun-shy on this thread, but the worst that can happen is, well, never mind. I can see a Pressure Probe (electronic) but a PITOT? My 777 architecture is insufficient it would seem. My engineering is osmotic and unreliable, but relying on an aperture signal rather than a sensor seems way archaic. Do go on.
Airfoil
Airfoil
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FADEC
As an old one, I still have to think about Full Authority....... I keep thinking it has to do with a Beatnik's sound system. My manual throttle inputs need to filter through an EM spectrum sensor to have any effect? My God I so prefer Pistons. Excommunicate me if you must, but I'm all ears. Again.
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The Trent P2/T2 probe is electrically heated all the time the engine is running.
The Trent EAI only heats the nose cowl inlet lip and the air (HP 3) is cooled prior to entering the nose cowl, this air is then vented overboard.
The Trent EAI only heats the nose cowl inlet lip and the air (HP 3) is cooled prior to entering the nose cowl, this air is then vented overboard.
The Trent P2/T2 probe is electrically heated all the time the engine is running.
The Trent EAI only heats the nose cowl inlet lip and the air (HP 3) is cooled prior to entering the nose cowl, this air is then vented overboard.
The Trent EAI only heats the nose cowl inlet lip and the air (HP 3) is cooled prior to entering the nose cowl, this air is then vented overboard.
I wonder if it is annuciated (recorded) when it does
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And
We are still stuck with a philosophical foundation to the engineering. How do TWO separate, isolated and independently controlled systems exhibit virtually identical (Failure) behaviour simultaneously.
Last edited by airfoilmod; 3rd Jun 2008 at 21:43.
Airfoilmod,
We still have pitots on the 777, according to Boeing. Managed to get a "HEAT PITOT LEFT" the other day.
The engine PT2/TT2 probe heater systems will generate "ENG EEC MODE (L/R)" status messages on failure.
P.S. Have you been at the duty-free?
We still have pitots on the 777, according to Boeing. Managed to get a "HEAT PITOT LEFT" the other day.
The engine PT2/TT2 probe heater systems will generate "ENG EEC MODE (L/R)" status messages on failure.
P.S. Have you been at the duty-free?
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I wonder what would be found on other operators a/c if they carried out a random inspection of in service pumps i.e signs of cavitation wear etc?
similiar to the ba a/c with similiar hours/cycles?
just a thought......
similiar to the ba a/c with similiar hours/cycles?
just a thought......
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Airfoilmod: We are still stuck with a philosophical foundation to the engineering. How do TWO separate, isolated and independently controlled systems exhibit virtually identical (Failure) behaviour simultaneously.
Why do you assume FAILURE?
It is quite possible that no FAULT (i.e. DEFECT) occurred in the homologated imstalation. Just that operating parameters (possibly even STANDARDS) were (are) inadequately specified.
I suspect that fuel QUALITY is a "Black Art" and to a large extent relies on standardised manufacturing process to control various aspects of quality.
Since the initial AAIB report I have been concerned regarding the low fuel freezing point on the sample taken from BA038. It sticks out like a sore thumb!
Maybe some of you guys can provide DATA on what the expected RANGE of this parameter is. If, as I suspect, the range is normally in the order of +/- 5 degC from whatever is the agreed "norm" is, then what made this fuel have such a spectacularly different freezing point?? OR is this very low freezing point understood, and simply a red herring?
The fuel may be "in spec" but something was unusual IMHO about the sample(s?) measured.
Whether this unusually low freezing point was due to something linked to the original fuel processing / additives or whether it was the result of some strange in flight stratification process remains IMHO an OPEN question.
Even if the low freezing point itself is not an issue maybe it highlights (indicates) a fuel with a greater propensity to cause cavitation or whatever.,
A reason exists for this near disaster! With all the data that exists I find it almost incredible to accept that a (potential) cause / sequence of events has not been identified.
OK it may take time to CONFIRM any such potential sequence of events but although we are struggling with inadequate data I'm convinced that this cannot be the case for the investigators.
However, the part of this that I don't understand is why no activity has occurred to put in place more rigorous procedures at least till the sequence of events is published. e.g. Tightening of fuel min temp or whatever.
So maybe the cause is understood and since the RISK of a repeat event is considered LOW there is no need to rush out a further report especially if this is POLITICALLY SENSITIVE in someway.
All will become clear in the fullness of time!
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This has Min (-78F), Max (-42F) and Average (-53F) for 19 jet fuels in the USA in 2005...
http://pps.ms.northropgrumman.com/aviation.htm
http://pps.ms.northropgrumman.com/aviation.htm