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BA 777 Restriction Of Fuel Flow-AAIB Report  
User currently offlineCubastar From United States of America, joined Nov 2006, 410 posts, RR: 5
Posted (6 years 7 months 1 week 4 days 20 hours ago) and read 20266 times:

AAIB issues new report on BA 777 crash at LHR.
http://www.flightglobal.com/home/default.aspx

101 replies: All unread, showing first 25:
 
User currently offlineKaitak From Ireland, joined Aug 1999, 12593 posts, RR: 34
Reply 1, posted (6 years 7 months 1 week 4 days 20 hours ago) and read 20249 times:

The AAIB seems to have traced it to this: signs that the fuel pressure at the inlet to the engine high pressure (HP) fuel pumps had dropped because the pumps showed signs of “unusual and fresh cavitation damage”.

This would seem to exonerate the crew, which is good news. Hopefully Capt. Burkill and FO Coward can be returned to flight status asap.


User currently offlineIkramerica From United States of America, joined May 2005, 21582 posts, RR: 59
Reply 2, posted (6 years 7 months 1 week 4 days 20 hours ago) and read 20193 times:

So the fuel was waxy or frozen but not contaminated it would seem. As for exonerating the flight crew, lets wait and see. There were reported warning lights before the flight started, we don't know about warnings in the air or variations in flight procedures, and there is no part of this article that discusses how the final seconds of the flight were handled (other threads with pilot input indicate a lack of consensus on whether the PIC made the right or wrong choices in those seconds).


Of all the things to worry about... the Wookie has no pants.
User currently offlineLHR27C From United Kingdom, joined Aug 2004, 1279 posts, RR: 16
Reply 3, posted (6 years 7 months 1 week 4 days 20 hours ago) and read 20052 times:



Quoting Kaitak (Reply 1):
Hopefully Capt. Burkill and FO Coward can be returned to flight status

The FO is flying regularly for BA and has been for several months.



Once you have tasted flight, you will walk the earth with your eyes turned forever skyward
User currently offlineHotelmode From United Kingdom, joined Jan 2007, 460 posts, RR: 1
Reply 4, posted (6 years 7 months 1 week 4 days 18 hours ago) and read 19746 times:

The actual AAIB bulletin is here. Its a bit more expansive than the article and may save some pointless speculation.

http://www.aaib.dft.gov.uk/cms_resources/S3-2008%20G-YMMM.pdf

The fuel never got anywhere near its proven freezing point, and the flight was routine.

[Edited 2008-05-12 11:53:43]

User currently offlineGRIVely From United States of America, joined Dec 2006, 139 posts, RR: 0
Reply 5, posted (6 years 7 months 1 week 4 days 18 hours ago) and read 19604 times:

Having just flown back from LHR yesterday (11 May) to IAD onboard UA925, a 777, I have been following this matter closely and was interested to read the AAIB bulletin. Having done so carefully I realize we still don't know anything more than we did before the bulletin was issued. I am sure we would all like to know what sorts of "restrictions" occurred between the fuel tanks and the HP fuel pumps as well as the "unusual and fresh cavitation damage".

Perhaps one of these days we will actually learn what caused these vexing conditions.

Ta,

the GRIV


User currently offlineRbgso From United States of America, joined Jun 2006, 599 posts, RR: 0
Reply 6, posted (6 years 7 months 1 week 4 days 16 hours ago) and read 18483 times:



Quoting GRIVely (Reply 5):
"unusual and fresh cavitation damage".

What does this mean in laymen's terms?


User currently offlineLitz From United States of America, joined Dec 2003, 1788 posts, RR: 0
Reply 7, posted (6 years 7 months 1 week 4 days 16 hours ago) and read 18324 times:
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Cavitation happens when some kind of fluidic blade (ie: a propeller or impeller) tries to spin in a liquid and generates bubbles.

This can happen because the blades are moving faster than the fluid can be moved, or because there is insufficient fluid (e.g. low pressure), and the action of moving the fluid causes 'voids'.

Either way, you get areas of extreme differences in pressure which can cause damage to the blades.

This happens w/impellers in pumps when the fluid level is low, and in boats/ships/subs/etc when the propeller spins too fast.

See Hunt for Red October for good examples about cavitating propeller blades and their effects.

- litz


User currently offlineSEPilot From United States of America, joined Dec 2006, 7116 posts, RR: 46
Reply 8, posted (6 years 7 months 1 week 4 days 16 hours ago) and read 18281 times:



Quoting Rbgso (Reply 6):

What does this mean in laymen's terms?

It means that the pump was turning but not as much liquid was reaching it as it wanted, which caused the fuel that did reach it to essentially boil, and the gas bubbles that formed left visible damage on the pump parts. This happens on boat propellers that turn too fast, or are partially out of the water when turning fast.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineZANL188 From United States of America, joined Oct 2006, 3588 posts, RR: 0
Reply 9, posted (6 years 7 months 1 week 4 days 15 hours ago) and read 18190 times:
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Quoting Rbgso (Reply 6):
What does this mean in laymen's terms?

The pumps were starved of fuel and began to cavitate.

Cavitation from Wiki:

"Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure.Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial cavitation. Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Such cavitation often occurs in pumps, propellers, impellers, and in the vascular tissues of plants. Non-inertial cavitation is the process where a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers etc."



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User currently offlineRivet42 From United Kingdom, joined Aug 2005, 818 posts, RR: 1
Reply 10, posted (6 years 7 months 1 week 4 days 14 hours ago) and read 17392 times:



Quoting Hotelmode (Reply 4):
The fuel never got anywhere near its proven freezing point

I don't see how you can make that assumption - all we know is that samples of the fuel froze in tests at -57'c, the lowest recorded temperature during the flight was -45'c, but the Met Office reported atmospheric tempuratures down to -76'c. It is therefore perfectly plausible that portions of the fuel may well have reached 'near-freezing', and it wouldn't have to actually freeze for the density and fluidity to change - imagine a tank of fuel with semi-solid 'lumps' swimming around inside it, and then consider how this might affect - at random - the flow of fuel towards the engines. I'm not speculating on anything here, I'm just trying to show that your 'conclusion' is in itself speculation not born out by the evidence.

Riv'



I travel, therefore I am.
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9810 posts, RR: 52
Reply 11, posted (6 years 7 months 1 week 4 days 14 hours ago) and read 16942 times:

Each wing tank has a forward and aft boost pump. Inlets are on the forward and aft side of the tanks for the pumps. There are three pick up points in each wing tank. The fuel is then sent to the engines from there. It can go from either tank to either engine.

It amazes me that the pumps could all cavitate. That pretty much means that there was no fuel or restricted flow in those lines. What could have caused it for all the lines? It will be interesting to see. At least we know there was fuel in the tanks and it was of an acceptable quality now.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineAwthompson From United Kingdom, joined May 2005, 498 posts, RR: 0
Reply 12, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16670 times:

I just watched the TV review of tomorrow's newspapers and one major newspaper is reporting "fuel freeze" as the cause of this crash. Views?

User currently offlineIkramerica From United States of America, joined May 2005, 21582 posts, RR: 59
Reply 13, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16535 times:



Quoting Awthompson (Reply 12):
I just watched the TV review of tomorrow's newspapers and one major newspaper is reporting "fuel freeze" as the cause of this crash. Views?

Not an expert, but sounded like it from the start, or the after effects of such a freeze, including uneven expansion and separation after unfreeze and damage to the systems from the "lumps". What caused the freeze was the question for me, the cold temps (one of the coldest winters ever known in the region the plane flew), contaminated fuel (what I thought would end up being a contributing factor), the wrong flight path chosen in light of conditions, error on the part of the crew when dealing with warnings, etc.

but also, what lead to the crash that occurred vs. a worse crash vs. not having a crash at all? Again, we don't know yet, but to say the pilots were not in any way at fault, it's too soon to say. Maybe they did such a good job they averted death to all. Maybe they made a critical mistake that led to a crash instead of a skin of the teeth landing. We don't know yet.



Of all the things to worry about... the Wookie has no pants.
User currently offlineBaw716 From United States of America, joined Nov 2003, 2028 posts, RR: 27
Reply 14, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16535 times:



Quoting Rivet42 (Reply 10):
imagine a tank of fuel with semi-solid 'lumps' swimming around inside it, and then consider how this might affect - at random - the flow of fuel towards the engines. I'm not speculating on anything here, I'm just trying to show that your 'conclusion' is in itself speculation not born out by the evidence.

Question:
Are the HP pumps in the actual tank itself or are they outside the tank with lines leading from the tank to the pumps?

I have a theory, but I don't want to share it until I get this question answered.
thanks
baw716



David L. Lamb, fmr Area Mgr Alitalia SFO 1998-2002, fmr Regional Analyst SFO-UAL 1992-1998
User currently offlineBristolFlyer From United Kingdom, joined May 2004, 2312 posts, RR: 0
Reply 15, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16509 times:



Quoting Awthompson (Reply 12):
one major newspaper is reporting "fuel freeze"

Which newspaper was this? I read an article in the Scum (sorry, Sun) from a journalist that was encouraging people to boycott BA 'cos he suspected the crash was caused by fuel running out. T*sser. I was on a BA flight the next day.



Fortune favours the brave
User currently offlineBAW716 From United States of America, joined Nov 2003, 2028 posts, RR: 27
Reply 16, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16405 times:



Quoting BristolFlyer (Reply 15):
Which newspaper was this? I read an article in the Scum (sorry, Sun) from a journalist that was encouraging people to boycott BA 'cos he suspected the crash was caused by fuel running out. T*sser. I was on a BA flight the next day.

Ah, jounalistic expertise at it's finest (eh, um)...

That's about as silly a notion as I've ever heard...perhaps the journalist would like to observe a 777 engine operating up close?

baw716



David L. Lamb, fmr Area Mgr Alitalia SFO 1998-2002, fmr Regional Analyst SFO-UAL 1992-1998
User currently offlinePellegrine From United States of America, joined Mar 2007, 2494 posts, RR: 8
Reply 17, posted (6 years 7 months 1 week 4 days 13 hours ago) and read 16391 times:



Quoting Rivet42 (Reply 10):
It is therefore perfectly plausible that portions of the fuel may well have reached 'near-freezing', and it wouldn't have to actually freeze for the density and fluidity to change - imagine a tank of fuel with semi-solid 'lumps' swimming around inside it, and then consider how this might affect - at random - the flow of fuel towards the engines.

The properties of the refined hydrocarbon at question here, Jet A-1, don't really reflect that from the information I've read. "Freeze point" isn't the temperature at which the fuel freezes solid, it's the temperature at which the last solid crystal melts AFTER the fuel has already been frozen. When they conduct a spot test, they drop the temp of the sample down to -100-120*C, let it warm up, and mark the temperature as the last solid disappears. The pour point, under which the fuel does not flow appreciably as a liquid, is a few degrees below freeze point. The fuel tested with an even wider margin than required. I can't really see how fuel icing could have been a problem, especially since the lack of thrust happened on approach not during cruise or TOD (top of descent). By that point the fuel temp could have gone up a degree or two (input from one of the long-haul pilots on here would be welcome).

see: http://www.boeing.com/commercial/aeromagazine/aero_16/polar_story.html



oh boy!!!
User currently offlineCrjfixer From United States of America, joined Mar 2008, 172 posts, RR: 0
Reply 18, posted (6 years 7 months 1 week 4 days 11 hours ago) and read 15664 times:

Also aircraft fuel is heated by a fuel/oil heat exchanger ( cools the engine oil while warming the fuel ). so i highly doubt freezing fuel could have been a factor.

User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 19, posted (6 years 7 months 1 week 4 days 11 hours ago) and read 15572 times:

Quoting Baw716 (Reply 14):
Are the HP pumps in the actual tank itself or are they outside the tank with lines leading from the tank to the pumps?

The fuel tanks have electrically powered boost pumps ( usually centrifugal impellers ) which deliver fuel to the engine driven fuel pump. The engine driven fuel pump is mechanically driven off the accesory gearbox, and has two stages, a low pressure stage ( usually a centrifugal impeller ), and a high pressure stage ( usually a gear type pump ).

The system can continue to operate if the electric boost pumps fail, as there is sufficient suction in the low pressure side of the engine driven fuel pump, which combined with gravity, will still allow fuel to reach the engine.

Regards, JetMech

[Edited 2008-05-12 18:57:31]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 20, posted (6 years 7 months 1 week 4 days 9 hours ago) and read 15010 times:



Quoting GRIVely (Reply 5):
Having done so carefully I realize we still don't know anything more than we did before the bulletin was issued.

Sure we do. We know it wasn't contaminated fuel, an aircraft or engine malfunction, or water in the fuel. That's a lot of potential causes that have been eliminated.

Quoting Rivet42 (Reply 10):
It is therefore perfectly plausible that portions of the fuel may well have reached 'near-freezing', and it wouldn't have to actually freeze for the density and fluidity to change - imagine a tank of fuel with semi-solid 'lumps' swimming around inside it

Pellegrine beat me to it in Reply 17...if you've got semi-solid "lumps" swimming around in the fuel tank, you're already way below the freeze point. Freeze point on jet fuel is when you *first* start getting solids (or when the last solid melts, if going the other direction), not when it goes solid.

Quoting Roseflyer (Reply 11):
Each wing tank has a forward and aft boost pump. Inlets are on the forward and aft side of the tanks for the pumps. There are three pick up points in each wing tank. The fuel is then sent to the engines from there. It can go from either tank to either engine.

It amazes me that the pumps could all cavitate.

As I read it, the cavitation was on the HP pumps, not the boost pumps. There are only two HP pumps, one on each engine, and the fuel from all boost pumps is co-mingled long before it gets to the HP pump.

Quoting Baw716 (Reply 14):
Are the HP pumps in the actual tank itself or are they outside the tank with lines leading from the tank to the pumps?

They're on the engine.

Quoting Crjfixer (Reply 18):
Also aircraft fuel is heated by a fuel/oil heat exchanger ( cools the engine oil while warming the fuel ). so i highly doubt freezing fuel could have been a factor.

The fuel *on the engine* is heated by a heat exchanger. On a 777, no hot fuel goes from the engine back to the fuel tanks. There is a hydraulic oil cooler in the fuel tanks but it's there to cool the hydraulic oil...the heat input, relative to the fuel thermal mass, is incredibly tiny. There are, functionally, no heaters in the fuel tanks.

Tom.


User currently offlineMax Q From United States of America, joined May 2001, 4779 posts, RR: 19
Reply 21, posted (6 years 7 months 1 week 4 days 9 hours ago) and read 14823 times:

There is no indication that the Pilots did anything but an exemplary job.

It is typical of you 'IKRAMERICA' to cast doubt in this respect as you have never been able to disguise your contempt for Flight crew.

The aircraft was operated within all company and Boeing limitations for the entire flight, we deal with cold and sub-freezing fuel all the time.In their case they did not allow the fuel to go any colder than allowed.

Indeed the Captains last minute flap adjustment probably allowed the aircraft to make it onto the airport, thus saving lives.

As you said IK, you are not an expert not even close ! in fact your personal grudges seem to eliminate any consideration of facts and logic.



The best contribution to safety is a competent Pilot.
User currently offlinePlanesNTrains From United States of America, joined Feb 2005, 5792 posts, RR: 28
Reply 22, posted (6 years 7 months 1 week 4 days 7 hours ago) and read 14256 times:



Quoting Max Q (Reply 21):
There is no indication that the Pilots did anything but an exemplary job.

It is typical of you 'IKRAMERICA' to cast doubt in this respect as you have never been able to disguise your contempt for Flight crew.

All he said was that the jury is still out. Considering we don't have a final report, I would say that that is a fair assumption. If you could point out where he places the blame on them, or implies that they are likely at fault, I'd be happy to alter my post.

-Dave



Next Trip: SEA-ABQ-SEA on Alaska
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 23, posted (6 years 7 months 1 week 4 days 7 hours ago) and read 14170 times:



Quoting JetMech (Reply 19):
The system can continue to operate if the electric boost pumps fail, as there is sufficient suction in the low pressure side of the engine driven fuel pump, which combined with gravity, will still allow fuel to reach the engine.

JetMech - dealing with Australian refined products you may know the answer to this. Is there a special problem if there is a small contamination from waxy molecules?

Some years ago when Bass Strait oils were first fed to refineries there were problems with tractors on the Highlands of E Aus where large crystals of waxes inhibited feed to the oil pumps.

This was fixed by a dramatic lowering of acceptable levels of waxy HCs in refinery output. Could something similar have happened here but in the main fuel system. As I understand it, the waxes crystallize according to their own scheme of things and not according to the average for the whole liquid.

Is it possible that some of the Chinese fuels have problematic amounts of waxes that could have crystallized during the flight, inhibiting feed to the fuel pumps? The more I read that FI article, the more I think WAXes. Presumably with crude supply the way it is, refineries may well have to change feed and that could lead to variations in the product chemistry.


User currently offlineScbriml From United Kingdom, joined Jul 2003, 12876 posts, RR: 46
Reply 24, posted (6 years 7 months 1 week 4 days 5 hours ago) and read 13790 times:
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Quoting Max Q (Reply 21):
There is no indication that the Pilots did anything but an exemplary job.

There's no doubt the crew did well to avert a potentially serious loss of life at the end this flight. However "heroic" their actions at that point, it is also entirely possible that something they did earlier in the flight contributed to the situation they found themselves in on short final. At this point in time, we simply don't know.

Quoting PlanesNTrains (Reply 22):
All he said was that the jury is still out. Considering we don't have a final report, I would say that that is a fair assumption.

 checkmark 



Time flies like an arrow, but fruit flies like a banana! #44cHAMpion
25 JetMech : I'm not too sure Baroque! I really never had too much to do with fuel quality except doing water checks each time I filled up an aircraft. I would im
26 BAW716 : FIrst, JetMech...thanks for the explanation. I am no expert, but what I do believe is that a series of events led to this crash (much like any other
27 Post contains links BMIFlyer : I'm surprised nobody linked to the BBC article. Anyway.... http://news.bbc.co.uk/1/hi/england/london/7396899.stm
28 OA260 : Yes I was just reading that myself.
29 David L : Unless there's new evidence of which warnings were displayed, I suggest we remember the earlier contributions from our real expert colleagues that th
30 SEPilot : And if I remember correctly, the warnings had to do with water, and water seems to have been ruled out as a cause. So we really are no closer to know
31 Rivet42 : ... in addition to the analysis, the AAIB report states that the aircraft is damaged beyond economic repair, which may seem rather obvious to most, bu
32 Tdscanuck : It's true that the wax has a different freezing point than the whole liquid, but this is true of all the fractions in a hydrocarbon like jet fuel. Th
33 Rivet42 : Does this criteria also cover viscosity? Whilst the fuel may not cantain any solids at the 'melt' point, does that mean that it has returned to its '
34 Tdscanuck : I don't believe the freezing point test covers viscosity, though I'm not positive. If it's partly frozen, it's certainly not homogenous. However, the
35 Baroque : Thanks Tom. Presumably those specs would prevent that problem, but I just have a residual wonder because there is a fair chance that the refineries w
36 Awthompson : I have not bought the paper but I am led to believe that it is in today's Daily Telegraph. I thought that it was one of the more serious ones, but we
37 Tdscanuck : This is one of the problems with a specification based fuel like Jet-A...it presumes you have normal hydrocarbon feedstock. The Jet-A tests are not e
38 EarlyNFF : Don´t mix up temperatures: -76°C "atmospheric temperature" is measured as SAT or "static air temperature". Lowest recorded (fuel-)temperature was -
39 Tdscanuck : I totally agree about not mixing up temperatures, but it's not correct that the fuel temperature is measured as TAT. The fuel temperature is measured
40 Rivet42 : I certainly wasn't intending to do so. My point is simply that there is a difference of up to 30' between the temperature of the air-mass that the wi
41 Nomadd22 : Hope I didn't miss this in all these posts, but were the engines at idle during the descent, and could the fuel flow being reduced to bare minimum hav
42 Max Q : No, an exhaustive investigation has already taken place. With the extensive data available from numerous sources on the aircraft quite apart from the
43 Cubsrule : Most freezing point tests don't (it's a practical concern; I can't, off the top of my head, think of a single technique to assess freezing/melting an
44 Okie : My thoughts have always been the other direction. -57C seems like a very wide cut fuel, or for lack of a better term seems to have contained considera
45 Bond007 : No it hasn't. If it was 'exhaustive', by definition, it wouldn't be continuing! Well, that's your opinion only, as you correctly said. Until we have
46 Cubsrule : ...and, of course, we may not even know then.
47 Tdscanuck : The thermal mass of the fuel should be a lot higher than the thermal mass of the piping (fuel piping is *really* thin). Since even at flight idle the
48 Max Q : Well Mr Bond.. Since when does exhaustive mean finished ? I did not say that ! Perhaps we may never know the reason.. Yes it is my opinion this crew's
49 PlanesNTrains : What is your deal? No one is anxious to blame someone. We're just waiting for the final report. I admit from the start that I am not knowledgable, so
50 Bond007 : Look up the word, and get back to me if you think an 'exhaustive investigation' means anything but that. In fact, Merriam Websters even uses the exac
51 BA777ER236 : Gentlemen. I think that there are a few statements in the report that are worth noting: 'The flight from Beijing to London (Heathrow) was uneventful'
52 Post contains links Aviationbuff : http://www.washingtonpost.com/wp-dyn...le/2008/05/12/AR2008051202728.html Found this article by Del Quentin Wilber on Washingtonpost
53 Baroque : Hmmm, getting commercial grade products is not my field. But in general terms, I think I would rather start simple and work to the complex (as in the
54 Bond007 : Well, that's your interpretation of an ongoing investigation. An educated interpretation perhaps, but nothing more. What you might 'think' does not n
55 TristarSteve : On a B777 maintenance messages are generated from Status Messages and EICAS Warnings. This centre tank water message is lower status than this. It is
56 BAW716 : This may sound like a dumb question, but why would this be a factor? That late in the flight, wouldn't the aircraft be operating out of the wing tank
57 TristarSteve : Not a dumb question at all. Your statement is correct. I was just responding to Post 51. I do not think water was involved. All modern aircraft take
58 BA777ER236 : Well, my 'interpretation' is based on several thousand hours of flying the aircraft and having spoken to the guy involved and read the interim report
59 Bond007 : I thought I made that clear ... and that's the reason I try not to say that pilots involved in serious accidents were either 'heroes' or 'incompetent
60 BA777ER236 : I haven't used either of these phrases either. All I have said is that the focus of the investigation is elsewhere and that the report effectively st
61 Rivet42 : I'm very interested to hear from a pilot in this discussion, because it enables me to ask a very pertinent question - do you know how many pilots hav
62 JetMech : G'day Steve, Would it be possible for you to elaborate on how the water detection system works? Is it something to do with the densitometer and / or
63 Nomadd22 : Did they ever get the timing of the crossfeed switches being opened figured out? It may have been just more idiot reporting, but I remember early repo
64 Max Q : As a matter of idle curiosity, how many hours do our readers think IK and Bond7 have operating 777's ? Not sitting in the back playing with the PTV. N
65 Bond007 : First, it's irrelevant. The AAIB are investigating the accident ... not a.net pilots, and they haven't finished their investigations. Second ... what
66 Traindoc : I was in India when the BA flight went down. On the way back, DEL to EWR, (Jan 26) we flew almost a polar route, going east of Moscow, then north of S
67 Atpcliff : Hi! We were talking about this accident in recurrent class (yearly technical ground training) the last few days. It is a HIGHLY unusual accident, and
68 FXramper : Bingo. Another rubbish excuse. I've got 2-3 email forwards detailing the equipment used in G. Brown's envoy.
69 Max Q : Wrong mr bond.. Hours in the aircraft type are extremely relevant.They allow an individual to make reasonable conclusions. You cast aspersions on the
70 BA777ER236 : I haven't done it myself, but a few of my training mates have. From what has been said, no one has made the threshold of the runway in the sim. This
71 Tdscanuck : Most FQIS systems have a compensator (gussied up capacitor) and a densitometer at the tank low points. You can pick up water by the increase in densi
72 Nomadd22 : Capacitive probes are subject to degradation and can give inaccurate readings. Ultrasonics, like the 777 uses for water detection, can fail or lose th
73 TristarSteve : The water detection probes on the B777 are similar in design to the fuel quantity probes, but they are fitted upside down. For fuel quantity an ultra
74 AustrianZRH : Maybe a dumb question but I ask it nevertheless and hope for input from the experts! All I read in this thread is about the JetA freezing out, with a
75 Nomadd22 : Admitting my ignorance of 777s again. I was pretty sure that the timing of the signal for the sonic water probes changed because of the density differ
76 Cubsrule : So the system really generates the water in tank message based on a time difference between the fuel signal and the water signal (for with no water i
77 JetMech : Perhaps this is why it is proving hard to find the actually cause of the accident. Maybe all the "slushiness" melted before investigators could get f
78 Baroque : If it was there, it would disappear like the dew of the morn! However, it could easily be reproduced by taking the fuel down through possible tempera
79 AirNZ : Here are just another two examples of which I am curious about. Despite the fact that you repeatedly don't claim to know what happened why do you, al
80 SEPilot : It's not as simple as that. You really do not know exactly what temperature the fuel was at various point, and small variations in fuel composition a
81 JetMech : Yes, I could imagine that such a comprehensive set of tests would reveal any anomalies, but perhaps there was a specific one off anomaly that has not
82 Baroque : There could indeed be some special effects. For there to have been segregation, that would mean that a sold phase had separated at some stage. While
83 TristarSteve : The water detectors are ultrasonic probes. They are very short, only a few inches long and sit at the bottom of the tank so that they are usually imm
84 ChrisNH : It's interesting that Boeing has been tasked with trying to 'replicate' the conditions with another 777. That means going up over Siberia when it's a
85 Nomadd22 : All you need to do is put a fuel system with the same pumps and lines and flow rates in a cold vacuum chamber. "With another 777" might just be a com
86 OldAeroGuy : From what I understand, this is exactly what Boeing is doing except I don't think it's in a vacuum chamber. They are also using a large tank that can
87 Nomadd22 : I just guessed. Since they don't seem to a good idea of what happened I'd expect them to reproduce all the conditions at all stages of the flight, ev
88 OldAeroGuy : Nah, they wouldn't been able to see the gremlin in the wing tank.
89 JetMech : Most certainly. But to me, this is the crux of the situation. I know it is a very remote possibility, but to me at least, it seems that some sort of
90 TristarSteve : In some of the wing tank probes there are targets built in. The FQPU knows the distance of these targets and measures the time. It then knows the Vel
91 Bond007 : Wrong! In fact exactly the opposite. Read what I said. You are the one 'casting aspersions on the crew's performance'. I said we don't what happened
92 JetMech : But but but......what if one or both of the targets happens to be covered over with a certain level of water ! Regards, JetMech
93 Max Q : Yes, go ahead 'mr bond' Exactly how much experience do you have as a Pilot on large jet transports and what would they be. You say you have the experi
94 Bond007 : LOL .... it's totally irrelevant in terms of my comments. Let's stick to the topic. .... moving on. If you want to discuss my comments in relation to
95 TristarSteve : But these are in probes further out in the tank. There will be no free water there.
96 Tdscanuck : Jet-A has a freezing point defined by a test...at the temperature labeled "freezing point" the vast majority of the substance is liquid. The "freezin
97 Ikramerica : If you choose to read it that way, that is your mistake to make. I can't stop you. I clearly stated that we do not have enough evidence to know wheth
98 Max Q : I would say without reservation that the two BA pilots that morning showed their professionalism and dedication to a degree encompassing heroism. 'mr
99 Bond007 : It's obvious from this post that you haven't read a word that I wrote, so please stop this childish nonsense. You are getting rather tiring Jimbo
100 SEPilot : From everything I have read, there is absolutely no evidence that the flight crew did anything wrong. The fact that other pilots tried in the simulat
101 Max Q : Very well said SEPilot.
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