BA038 (B777) Thread
Controversial, moi?
Also Concorde comes to mind.
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The 747SP ... <snip as irrelevant> ... even completed a 54 hour flight
To celebrate the 50th anniversary of Pan Am, flight 50 as it was called flew a route from and to San Francisco that indeed took 54 hours, 7 minutes, and 12 seconds to complete but it was actually comprised of multiple sectors. Stopovers were at London Heathrow, Cape Town International, and Auckland Airports.
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Physics
Originally Posted by stickyb
Question from a non pilot.
When a liquid is compressed, temperature rises. When pressure reduced, temperature falls.
How is the flow of fuel controlled (physically, not logically) ?
Would it be possible for the 'valve' controlling the flow to form a point at which pressure was reduced, thus cooling the fuel even more and maybe causing ice to aggregate?
A small restriction could then, under some circumstances, become self perpetuating
When a liquid is compressed, temperature rises. When pressure reduced, temperature falls.
How is the flow of fuel controlled (physically, not logically) ?
Would it be possible for the 'valve' controlling the flow to form a point at which pressure was reduced, thus cooling the fuel even more and maybe causing ice to aggregate?
A small restriction could then, under some circumstances, become self perpetuating
Originally Posted by stickyb
I think you’ll find you can’t compress a liquid.
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I think you will find that you can compress a fluid although the visible effect is minute compared to gas/vapour. Indeed, a compressed fluid is less viscous than one which isn't compressed. That said, the values concerned are so small it is not worthy of any serious discussion.
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Posted by ChristiaanJ, ref. post #1782:
Please read the report(s) again.
AAIB interim report G-YMMM, Page 2, second column:
"The aircraft had previously operated a flight on 14 january 2008 from Heathrow to Shanghai, with the return flight arriving on 15 January 2008. The aircraft was on the ground at Heathrow for 20 hours before departure to Beijing on 16 January 2008."
AAIB interim report G-YMMM, Page 13, first and second column:
"G-YMMM was last sumped at Heathrow on 15 January 2008 prior to the flight to beijing. The aircraft had also been sumped at London heathrow whilst on maintenance, on 14 January 2008."
"Prior to the accident the operator had initiated a review of the effectiveness of their [water] sumping programme, . . . . . ., a number of aircraft were checked in a warm hangar where any ice in the fuel tanks would have melted and migrated to the drains. G-YMMM was sumped in this manner on 14 December 2007. The review established that whilst the free water does freeze and could occasionally block the tank drains, there was no evidence of any significant quantities of free water having accumulated in any of the 43 Boeing 777 aircraft."
AAIB Special Bulletin S1/2008, first column, Page 5:
"The aircraft's [G-YMMM] fuel tanks were last checked for water in the fuel on the 15t January 2008, this was prior to it's refuelling for the outboard sector to Beijing."
With the aircraft on the ground for 20 hours and a review programme in place, wouldn't it be logical that sumping on 15 january took place at a time it was estimated that any ice in the tanks had melted before sumping commenced? Especially with the aircraft on the ground for 20 hours and temperatures well above freezing (as records of those dates indicate) and sumping taking place before refuelling. The interim report does not mention how many hours after arrival from Shanghai water sumping was performed but to my knowledge this is done immediately prior to refuelling? Refuelling probably took place any time after the payload, flight planning and weather for the flight to Beijing were known, so this would have happened perhaps only a few hours (but still on 15 January?) before departure?
If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing.
After reading the report several times, although it is very informative, new questions regarding the aircraft systems and engines surfaced for me which i shall digest for a while.
The emphasis is now focussed on ice. 5 liters of water diluted in approx. 100.000 liters of fuel . . . . and a lot of data mining.
I'm sure they will find the facts, the evidence, and the reasons why in the near future. I hope they are not barking up the wrong tree.
The investigation, although very detailed and thorough, gives me the impression of trying to castrate a fly with boxing gloves on
Green-dot
Somebody, many hundreds of posts ago, suggested that, with water being heavier than fuel, under the circumstances a lot of water could already have drained from the aircraft by the time the fuel samples were taken.
Question: might there have been a lot more water than quoted in the AAIB report?
Question: might there have been a lot more water than quoted in the AAIB report?
AAIB interim report G-YMMM, Page 2, second column:
"The aircraft had previously operated a flight on 14 january 2008 from Heathrow to Shanghai, with the return flight arriving on 15 January 2008. The aircraft was on the ground at Heathrow for 20 hours before departure to Beijing on 16 January 2008."
AAIB interim report G-YMMM, Page 13, first and second column:
"G-YMMM was last sumped at Heathrow on 15 January 2008 prior to the flight to beijing. The aircraft had also been sumped at London heathrow whilst on maintenance, on 14 January 2008."
"Prior to the accident the operator had initiated a review of the effectiveness of their [water] sumping programme, . . . . . ., a number of aircraft were checked in a warm hangar where any ice in the fuel tanks would have melted and migrated to the drains. G-YMMM was sumped in this manner on 14 December 2007. The review established that whilst the free water does freeze and could occasionally block the tank drains, there was no evidence of any significant quantities of free water having accumulated in any of the 43 Boeing 777 aircraft."
AAIB Special Bulletin S1/2008, first column, Page 5:
"The aircraft's [G-YMMM] fuel tanks were last checked for water in the fuel on the 15t January 2008, this was prior to it's refuelling for the outboard sector to Beijing."
With the aircraft on the ground for 20 hours and a review programme in place, wouldn't it be logical that sumping on 15 january took place at a time it was estimated that any ice in the tanks had melted before sumping commenced? Especially with the aircraft on the ground for 20 hours and temperatures well above freezing (as records of those dates indicate) and sumping taking place before refuelling. The interim report does not mention how many hours after arrival from Shanghai water sumping was performed but to my knowledge this is done immediately prior to refuelling? Refuelling probably took place any time after the payload, flight planning and weather for the flight to Beijing were known, so this would have happened perhaps only a few hours (but still on 15 January?) before departure?
If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing.
After reading the report several times, although it is very informative, new questions regarding the aircraft systems and engines surfaced for me which i shall digest for a while.
The emphasis is now focussed on ice. 5 liters of water diluted in approx. 100.000 liters of fuel . . . . and a lot of data mining.
I'm sure they will find the facts, the evidence, and the reasons why in the near future. I hope they are not barking up the wrong tree.
The investigation, although very detailed and thorough, gives me the impression of trying to castrate a fly with boxing gloves on
Green-dot
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I am pretty sure at the beginning of the BA038 speculation threads, people were talking about the possibility of 100's of litres in not 100's of Kgs of water potentially being present, at least in the centre tank, as the norm? What's changed, or was this gross misinformation?
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What a fascinating interim report - illuminating and in plain English. I would like to highlight a few points which might be good to see addressed (or dismissed) in more detail in due course:
1. Cold soaked main tank fuel from previous sector
Figure 1 seems to indicate that just prior to the uplift of fuel in Beijing the temperature of the 4 tons or so of fuel in the left hand main tank which was left over from the previous sector was -20˚C. Even after the uplift of warmer 5˚C fuel in Beijing the left main tank temperature never appears to rise above -1˚C. If temperature is as relevant as suggested, then a body of fuel from the previous sector remaining at -20˚C seems noteworthy as a possible contributory factor leading to the potential subsistence and continued development of accretions of ice in at least those parts of the main tank fuel system which remained at or below 0˚C.
2. Prolonged fuel scavenge operation
The interim report currently seems relatively silent on a key design feature of the 200ER as compared to certain other Boeings - namely, the relative size of the centre tank and the prolonged operation of the fuel scavenge.
The data (in Figure 1) shows that the remaining 800kg of centre tank fuel to be scavenged once the main tanks contained less than 12.5 tons started a little under 3 hours before landing and was finished within 30 minutes.
Given the apparent ability of each of the two centre tank fuel scavenge pumps in G-YYYM to suction fuel at a rate of some 0.8 tons per hour into each main tank, could there be any unintended consequence (which would normally have no bearing on safe flight absent some of the other contributory factors present that day) as a result of them running “dry” for over 2 hours once the remaining 800 kg was indicated to have been scavenged (and similarly on previous sector)?
After remaining 800 kg of fuel was scavenged, would not the fuel scavenge pump, being a jet pump, scavenge air? What volume of air would be entrained/dissolved into fuel in each main tank over remaining 2.5 hours of flight given powerful nature of scavenge pump? The centre tank is open to the atmosphere so any air sucked out would be immediately replaced. Presumably entrained/dissolved air in main tank fuel would be subsequently released as part of dynamic process given low pressure at height? Could this entrained/dissolved air end up in the fuel manifold and be released in a manner which would cause the potential failure of the suction feed or the override/jettison pump valves to open? As the suction feed in the climb at least seems to have a known failure mode from vapour lock (see previous posts) arguably the interim report’s understandable assumptions as to the location of a restriction might need to be reconsidered slightly if it could be shown that the suction feed might be vapour locked and/or (even more speculatively but for a similar reason to the suction feed) air might not be drawn in from the centre tank. Fuel testing after the event would not be able to establish the existence (or absence I accept!) of any air saturation dynamic and any vapour lock would be long gone. NB: my point is limited to expanding the possible locations of the icing restriction as I note the comments about aeration not being the cause of the cavitation in the HP pump.
As regards the 800 kg remaining shallow layer of fuel in the centre tank, is there any temperature or other information as to potential stratification in the 5 hours or so that it sat in a largely empty, cold still tank after OJ pumps selected OFF? Does the 0.14 max litres of water from condensation reflect turnover (if any) of atmosphere in the centre tank as a result of the operation of the fuel scavenge pumps in the last 3 hours of the flight (or the earlier sector)? Might there be any concentrations of water from accreted ice melting in the later stages of flight? Would slugs of water scavenged from centre tank be more likely to result in any particular form or size of ice crystal more susceptible to accretion when swept into main tanks? If ice had also previously accumulated and not melted on previous sector into Beijing could this be a contributory factor? The AAIB’s comment re unknown fluid dynamics seems spot on and not easily resolved given the complexities of the many different variables (eg Jet A1, ice, temperature, pressure, airframe, geometry, timing etc). Testing showing only 40ppm of water makes explaining the degree of icing sufficient to cause a restriction (sorry two restrictions), but not subsisting in any quantity in the main tank fuel, the mother of all tortuous theories though.
One relatively simple precautionary safety recommendation might be (eg as per certain other Boeings) to require the motive flow to the centre tank fuel scavenge pumps in 200ERs to be cut off after 30/40 minutes of renewed operation. Continued scavenging is unnecessary and might be a necessary contributory factor in lining up the holes in the two swiss cheeses (two cheeses, given must be at least one restriction on each side of the fuel system).
Alternatively, the fuel system test rig should perhaps also attempt to take account of what effect each fuel scavenge pump might have on fuel in the main tanks and the fuel supply system leading out of them?
3. Statistical significance of duplicated restriction in two independent fuel systems
The comment on page 19 of the interim report that "This is the first such event in 6.5 million flight hours and places the failure as being 'remote' as defined in EASA CS 25.1309" perhaps does not do justice to the statistical significance of what happened. While the statement may be correct, it could be seen as overstating the remoteness of the "event" - in particular, given the sharpened awareness from the data-mining that the particular environmental factors relevant to this event have occurred in but a few of those many flight hours and the fact that the current strawman is dependent on there being two separate duplicated events, i.e. one restriction in each independent fuel system, with assumed common contributory factors.
Also, if I may quibble with what may have been unintentionally implied by the word “remote” in the context of EASA CS 25.1309, when is a double engine rollback on a twin engine aircraft at very low altitude over a highly populated area caused by a restriction to the fuel supply to each engine limiting effective supply to about 15% or so of the certified maximum just a “major failure condition” for which “remote” is the relevant test, rather than a “hazardous failure condition” or a “catastrophic failure condition” which have to meet stricter standards? It would seem extraordinary to play down the significance of this demonstrated and duplicated failure condition, even if the improbability of its recurrence is in question.
4. Indications, annunciations and corrective actions
Also in the context of that same EASA CS 25.1309, which states in paragraph (c) (just read it at http://www.aaib.gov.uk/sites/aaib/cm...pendix%20B.pdf) that:
“Information concerning unsafe system operating conditions must be provided to the
crew to enable them to take appropriate corrective action. A warning indication must
be provided if immediate corrective action is required. Systems and controls, including
indications and annunciations must be designed to minimise crew errors, which could
create additional hazards.”
would it not be helpful and practical (and perhaps necessary) to introduce an immediate warning and annunciation of the discrepancy between the Actual EPR and the Commanded EPR as soon as the more normal 2-3 second lag becomes a clear discrepancy as at about second 154[95] (in figure 2), rather than requiring crew to observe the discrepancy and establish if it is “just” a glide slope, autothrottle or other issue – even more so by second 160[95] when both engines are rolling back.
Needless to say, the crew did the most remarkable job – and this seems more apparent as the background unfolds and you look at how little time and room they had to act.
1. Cold soaked main tank fuel from previous sector
Figure 1 seems to indicate that just prior to the uplift of fuel in Beijing the temperature of the 4 tons or so of fuel in the left hand main tank which was left over from the previous sector was -20˚C. Even after the uplift of warmer 5˚C fuel in Beijing the left main tank temperature never appears to rise above -1˚C. If temperature is as relevant as suggested, then a body of fuel from the previous sector remaining at -20˚C seems noteworthy as a possible contributory factor leading to the potential subsistence and continued development of accretions of ice in at least those parts of the main tank fuel system which remained at or below 0˚C.
2. Prolonged fuel scavenge operation
The interim report currently seems relatively silent on a key design feature of the 200ER as compared to certain other Boeings - namely, the relative size of the centre tank and the prolonged operation of the fuel scavenge.
The data (in Figure 1) shows that the remaining 800kg of centre tank fuel to be scavenged once the main tanks contained less than 12.5 tons started a little under 3 hours before landing and was finished within 30 minutes.
Given the apparent ability of each of the two centre tank fuel scavenge pumps in G-YYYM to suction fuel at a rate of some 0.8 tons per hour into each main tank, could there be any unintended consequence (which would normally have no bearing on safe flight absent some of the other contributory factors present that day) as a result of them running “dry” for over 2 hours once the remaining 800 kg was indicated to have been scavenged (and similarly on previous sector)?
After remaining 800 kg of fuel was scavenged, would not the fuel scavenge pump, being a jet pump, scavenge air? What volume of air would be entrained/dissolved into fuel in each main tank over remaining 2.5 hours of flight given powerful nature of scavenge pump? The centre tank is open to the atmosphere so any air sucked out would be immediately replaced. Presumably entrained/dissolved air in main tank fuel would be subsequently released as part of dynamic process given low pressure at height? Could this entrained/dissolved air end up in the fuel manifold and be released in a manner which would cause the potential failure of the suction feed or the override/jettison pump valves to open? As the suction feed in the climb at least seems to have a known failure mode from vapour lock (see previous posts) arguably the interim report’s understandable assumptions as to the location of a restriction might need to be reconsidered slightly if it could be shown that the suction feed might be vapour locked and/or (even more speculatively but for a similar reason to the suction feed) air might not be drawn in from the centre tank. Fuel testing after the event would not be able to establish the existence (or absence I accept!) of any air saturation dynamic and any vapour lock would be long gone. NB: my point is limited to expanding the possible locations of the icing restriction as I note the comments about aeration not being the cause of the cavitation in the HP pump.
As regards the 800 kg remaining shallow layer of fuel in the centre tank, is there any temperature or other information as to potential stratification in the 5 hours or so that it sat in a largely empty, cold still tank after OJ pumps selected OFF? Does the 0.14 max litres of water from condensation reflect turnover (if any) of atmosphere in the centre tank as a result of the operation of the fuel scavenge pumps in the last 3 hours of the flight (or the earlier sector)? Might there be any concentrations of water from accreted ice melting in the later stages of flight? Would slugs of water scavenged from centre tank be more likely to result in any particular form or size of ice crystal more susceptible to accretion when swept into main tanks? If ice had also previously accumulated and not melted on previous sector into Beijing could this be a contributory factor? The AAIB’s comment re unknown fluid dynamics seems spot on and not easily resolved given the complexities of the many different variables (eg Jet A1, ice, temperature, pressure, airframe, geometry, timing etc). Testing showing only 40ppm of water makes explaining the degree of icing sufficient to cause a restriction (sorry two restrictions), but not subsisting in any quantity in the main tank fuel, the mother of all tortuous theories though.
One relatively simple precautionary safety recommendation might be (eg as per certain other Boeings) to require the motive flow to the centre tank fuel scavenge pumps in 200ERs to be cut off after 30/40 minutes of renewed operation. Continued scavenging is unnecessary and might be a necessary contributory factor in lining up the holes in the two swiss cheeses (two cheeses, given must be at least one restriction on each side of the fuel system).
Alternatively, the fuel system test rig should perhaps also attempt to take account of what effect each fuel scavenge pump might have on fuel in the main tanks and the fuel supply system leading out of them?
3. Statistical significance of duplicated restriction in two independent fuel systems
The comment on page 19 of the interim report that "This is the first such event in 6.5 million flight hours and places the failure as being 'remote' as defined in EASA CS 25.1309" perhaps does not do justice to the statistical significance of what happened. While the statement may be correct, it could be seen as overstating the remoteness of the "event" - in particular, given the sharpened awareness from the data-mining that the particular environmental factors relevant to this event have occurred in but a few of those many flight hours and the fact that the current strawman is dependent on there being two separate duplicated events, i.e. one restriction in each independent fuel system, with assumed common contributory factors.
Also, if I may quibble with what may have been unintentionally implied by the word “remote” in the context of EASA CS 25.1309, when is a double engine rollback on a twin engine aircraft at very low altitude over a highly populated area caused by a restriction to the fuel supply to each engine limiting effective supply to about 15% or so of the certified maximum just a “major failure condition” for which “remote” is the relevant test, rather than a “hazardous failure condition” or a “catastrophic failure condition” which have to meet stricter standards? It would seem extraordinary to play down the significance of this demonstrated and duplicated failure condition, even if the improbability of its recurrence is in question.
4. Indications, annunciations and corrective actions
Also in the context of that same EASA CS 25.1309, which states in paragraph (c) (just read it at http://www.aaib.gov.uk/sites/aaib/cm...pendix%20B.pdf) that:
“Information concerning unsafe system operating conditions must be provided to the
crew to enable them to take appropriate corrective action. A warning indication must
be provided if immediate corrective action is required. Systems and controls, including
indications and annunciations must be designed to minimise crew errors, which could
create additional hazards.”
would it not be helpful and practical (and perhaps necessary) to introduce an immediate warning and annunciation of the discrepancy between the Actual EPR and the Commanded EPR as soon as the more normal 2-3 second lag becomes a clear discrepancy as at about second 154[95] (in figure 2), rather than requiring crew to observe the discrepancy and establish if it is “just” a glide slope, autothrottle or other issue – even more so by second 160[95] when both engines are rolling back.
Needless to say, the crew did the most remarkable job – and this seems more apparent as the background unfolds and you look at how little time and room they had to act.
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Pardon me if this has already been discussed (I just joined), but glancing through the previous posts as best I could looking for remarks on what the pilots did in the final moments, I couldn't find what I was looking for.
What are the thoughts of those pilots on here about the Captain (I believe it was) REDUCING the flap setting after realizing their problem of maybe not making the runway? Seems to me this aggravated the problem by INCREASING the stall speed, therby requiring the F/O to lower the nose, thereby making it impossible to reach the runway.
What are the thoughts of those pilots on here about the Captain (I believe it was) REDUCING the flap setting after realizing their problem of maybe not making the runway? Seems to me this aggravated the problem by INCREASING the stall speed, therby requiring the F/O to lower the nose, thereby making it impossible to reach the runway.
What are the thoughts of those pilots on here about the Captain (I believe it was) REDUCING the flap setting after realizing their problem of maybe not making the runway?
The last stage of flap is almost all drag with little contribution to CL (coefficient of lift) so he immediately got rid of some drag.
The go-around procedure on, e.g., the B747 is - max thrust, flap 20 (jus' like that!) and you don't drop out of the sky but transition instantly to a high energy situation partly by getting rid of drag which has permitted you to keep the engines spooled up just for that eventuality.
The Restriction Was Upstream of the FMV
Would it be possible for the 'valve' controlling the flow to form a point at which pressure was reduced, thus cooling the fuel even more and maybe causing ice to aggregate?
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Green-dot (post #1805),
Many thanks for taking the AAIB report apart more carefully than I did.
However, how effective is sumping? The report quotes no figures, just the conclusion from the review: "there was no evidence of any significant quantities of free water having accumulated..."
And also "If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing."
All this is qualitative, not quantitative, which made me wonder whether we were talking about 5 ltrs, 20 ltrs or 100 ltrs being "significant" or "virtually free of water"..
But, going back to the report, the amount of water estimated in the Bejing fuel upload was in the order of 40 ppm (the 5 ltr quoted). The samples taken after the crash were in the same order.
So, for the moment, it looks as if I'm barking up the wrong tree.
Bedankt, Green-dot!
CJ
Many thanks for taking the AAIB report apart more carefully than I did.
However, how effective is sumping? The report quotes no figures, just the conclusion from the review: "there was no evidence of any significant quantities of free water having accumulated..."
And also "If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing."
All this is qualitative, not quantitative, which made me wonder whether we were talking about 5 ltrs, 20 ltrs or 100 ltrs being "significant" or "virtually free of water"..
But, going back to the report, the amount of water estimated in the Bejing fuel upload was in the order of 40 ppm (the 5 ltr quoted). The samples taken after the crash were in the same order.
So, for the moment, it looks as if I'm barking up the wrong tree.
Bedankt, Green-dot!
CJ
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And also "If so, and water sumping was done correctly, there would be very little water in the tanks. This, together with sumping on 14 january during maintenance should imply the tanks were virtually free of water as G-YMMM departed to Beijing."
All this is qualitative, not quantitative, which made me wonder whether we were talking about 5 ltrs, 20 ltrs or 100 ltrs being "significant" or "virtually free of water"..
All this is qualitative, not quantitative, which made me wonder whether we were talking about 5 ltrs, 20 ltrs or 100 ltrs being "significant" or "virtually free of water"..
I also work in Sweden, we do not sump tanks when the OAT is below zero. Bit silly really, but ice will not come out!!
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I don't know if anyone else caught this little gem in the letters page of today's Telegraph;
Letters to the Telegraph
6 September 2008
De-icing aeroplanes
SIR – As a frequent flier with smaller aircraft, I know that it is common knowledge among pilots that condensation builds up in fuel tanks. This water sinks to the bottom of the tank and must be periodically drained to avoid it being drawn into the engine.
One would assume that ice forming in the fuel lines of a big jet (report, September 5) indicates that there’s too much water around and that someone hasn’t been doing their job properly.
Roger West, Appenzell, Switzerland
Why the hell didn't anyone else think of that......
Letters to the Telegraph
6 September 2008
De-icing aeroplanes
SIR – As a frequent flier with smaller aircraft, I know that it is common knowledge among pilots that condensation builds up in fuel tanks. This water sinks to the bottom of the tank and must be periodically drained to avoid it being drawn into the engine.
One would assume that ice forming in the fuel lines of a big jet (report, September 5) indicates that there’s too much water around and that someone hasn’t been doing their job properly.
Roger West, Appenzell, Switzerland
Why the hell didn't anyone else think of that......
#1796
Nigel on Draft " Absolutely - the crew were faced with a totally new experience and did their best, magnificently. I'm not sure I would have had the courage to even touch the flaps at that stage, and just thankful that I was never placed in that situation.
To the guy who suggested that draining a thimble full of fuel out of something like a Cessna 152 bears any relation to what might have happened .............. !! Why do I even bother to respond !!
Nigel on Draft " Absolutely - the crew were faced with a totally new experience and did their best, magnificently. I'm not sure I would have had the courage to even touch the flaps at that stage, and just thankful that I was never placed in that situation.
To the guy who suggested that draining a thimble full of fuel out of something like a Cessna 152 bears any relation to what might have happened .............. !! Why do I even bother to respond !!
Paxing All Over The World
Non-pilot speaking.
Since the new interim report, a couple of people have asked "5 liters of water diluted in approx. 100.000 liters of fuel" and how that could cause the failure.
As I have understood it - that is not what is being suggested. The failure may have occurred because of ice and other particles resulting from the low temperatures. There has been much talk (in PPRuNE) about stratification of the fuel and that a 'dollop' of fuel thickened but not frozen.
Unless I much mistake, no one is saying that a small amount of pure iced water caused the loss of thrust. I sit to be corrected.
Since the new interim report, a couple of people have asked "5 liters of water diluted in approx. 100.000 liters of fuel" and how that could cause the failure.
As I have understood it - that is not what is being suggested. The failure may have occurred because of ice and other particles resulting from the low temperatures. There has been much talk (in PPRuNE) about stratification of the fuel and that a 'dollop' of fuel thickened but not frozen.
Unless I much mistake, no one is saying that a small amount of pure iced water caused the loss of thrust. I sit to be corrected.
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Basil -
"The go-around procedure on, e.g., the B747 is - max thrust, flap 20 (jus' like that!) and you don't drop out of the sky but transition instantly to a high energy situation partly by getting rid of drag which has permitted you to keep the engines spooled up just for that eventuality."
Similar with all jet transports. But.....you have the engines spooled up. In this case they were basically without power. Not sure I'd want to touch anything.
"The go-around procedure on, e.g., the B747 is - max thrust, flap 20 (jus' like that!) and you don't drop out of the sky but transition instantly to a high energy situation partly by getting rid of drag which has permitted you to keep the engines spooled up just for that eventuality."
Similar with all jet transports. But.....you have the engines spooled up. In this case they were basically without power. Not sure I'd want to touch anything.