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AAIB BA38 B777 Initial Report Update 23 January 2008

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AAIB BA38 B777 Initial Report Update 23 January 2008

Old 29th Jan 2008, 22:50
  #181 (permalink)  
 
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The term "freezing point" for Jet-A1 is maybe somewhat misleading. It's basically the temperature below where the normally "transparent" fuel shows its first traces of "milkiness". Diesel guys refer to this as the Cloud Point. The flow is not impaired at this temperature.
Further... The Fuel Temp warning on the 777 has a triggerpoint 3degC higher than the temperature set by the crew (via the CDU).

This also increases the likelihood that freezing will be detected before it starts to cause a problem.
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Old 29th Jan 2008, 23:38
  #182 (permalink)  
 
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gonebutnotforgotten (post#185), the only thing you have not covered in your discussion of the descent from TOD to 600ft is the denouement.

Is it plausible that the 'plug of wax' (which you liken to an embolus) could affect both engines, when they are being fed from separate autonomous tanks? If not, there would have to be two plugs of wax evolving separately and independently.

Plausible enough, but is it likely that they would each migrate to the two engines and cause their separate failures at an interval of only 8 seconds?

You don't believe it either, do you?

Chris
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Old 30th Jan 2008, 04:06
  #183 (permalink)  
 
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Re-post

I first posted this ten days ago, but I just love repeating myself....

It will be fuel contamination

--------------------------------------------------------------------------------

China has a $2,000,000,0000 a year industry making fakes. Lest you think this is just the odd Rolex or Gucci bag for a laugh the China PLC inventory includes millions of fake car and truck parts not caring one whit how many people are killed thereby. More sinister is the the fake pharmaceuticals which often are not simply benign white chalk pills but random chemicals found out back in the garage, once again not caring one whit who or how many die.

In the case at hand the only other remotely possible explanations are a multiple bird strike of epic proportions or fuel exhaustion. Give credence to the former if you like, to the latter, well, you will need a lower opinion of BA aircrew than is common.

No, someone will have passed off a few million litres of doctored diesel fuel as jet fuel. This fake fuel of course is not tested for fuel freezing. Fuel freezing will then have occurred during the lengthy flight from China (not ice formation, but wax components of the fuel reverting to solid) and this slurry sank to the bottom of the tanks. On final with perhaps 4 tons or so sloshing around in near-as-empty tanks this fuel willl have been ingested.

Eh Voila

Have some faith in your hardware is what 10,000 hours on the 777 has taught me. There will be human skulduggery at root here somewhere
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Old 30th Jan 2008, 04:23
  #184 (permalink)  
 
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Ok then, why did no other China originating aircraft have problems ?
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Old 30th Jan 2008, 04:53
  #185 (permalink)  
 
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Of ALL the questions, in ALL the gin joints, you HAD to ask that one
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Old 30th Jan 2008, 05:59
  #186 (permalink)  
 
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Embolism?

Chris - I was just trying to make sense of the previous posts, and yes, it is pretty unlikely/unprecedented, but same fuel, same temperatures, and very nearly identical tanks (one hydraulic heat exchanger versus two) means that the independence may not be what it seems. As has been pointed out earlier, the fact that there was a small differnece in the reactions of the two engines means that the electronic explanations may be less likely than the 'mechanical' ones. In the end I'm as baffled as everyone else, this is a fascinating puzzle but it feels we may be zeroing in on the answer.
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Old 30th Jan 2008, 06:35
  #187 (permalink)  
 
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but it feels we may be zeroing in on the answer
to me it feels like you're tunneling in on the answer.

Hope to hear more soon (from the AAIB).
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Old 30th Jan 2008, 06:45
  #188 (permalink)  
 
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Gentlemen. The AAIB are zeroing in on the answers, probably a combination of several factors if history teaches us anything. You (the speculators rather than the sensible ' hang on a minute' ones) are waffling to pass an idle moment.

If by some bizarre coincidence one of you happens to be right, please don't expect me to place any trust in your opinion next time.
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Old 30th Jan 2008, 07:43
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Fitter 2: You (the speculators rather than the sensible ' hang on a minute' ones) are waffling to pass an idle moment.
Yes, its great, isn't it. But I tell you what.. irrespective of what the final outcome is, 1) it has raised the profile of aviation fuel quality, 2) it has raised awareness of the importance of managing unusual environmental conditions. Can raising awareness be a bad thing? Isn't that what PPrune is about?

NSEU: This also increases the likelihood that freezing will be detected before it starts to cause a problem.
Yes, but only if the fuel is on spec. If the fuel is off spec, how would you, or the machine know what that temperature relates to?

Stilton: Ok then, why did no other China originating aircraft have problems
Because no aircraft flew exactly the same route with exactly the same fuel at exactly the same time. If this flight had landed 5 minutes earlier, would it have in fact happened? Was it the same fuel in fact? Was it a bowser or a hydrant servicer? Could it have been a slug of water when tanks were switched?. Is there only one supplier to all aircraft? Was there maintenance done on the fuel system or the bowser? etc. etc. The AAIB will look into all this.

gonebutnotforgotten: Yes, thats about what I am supposing - but like anyone else, I have no idea really. I dont like the word "plug". I know that when I used to do the test in the lab, the wax crystals settled out. Maybe it was both ice and wax. Maybe it was water. Maybe it wasn't fuel at all. I just don't know. Its just one of a number of hypotheses. All I am saying is, the facts that we know argue more strongly for it than against it.

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Old 30th Jan 2008, 07:51
  #190 (permalink)  
 
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China has a $2,000,000,0000 a year industry making fakes. Lest you think this is just the odd Rolex or Gucci bag for a laugh the China PLC inventory includes millions of fake car and truck parts not caring one whit how many people are killed thereby. More sinister is the the fake pharmaceuticals which often are not simply benign white chalk pills but random chemicals found out back in the garage, once again not caring one whit who or how many die.

In the case at hand the only other remotely possible explanations are a multiple bird strike of epic proportions or fuel exhaustion. Give credence to the former if you like, to the latter, well, you will need a lower opinion of BA aircrew than is common.
I dislike these "False Choice" arguments. We don't know the cause at this stage.

I can think of all sorts of other reasons the engines might not have responded, for example, differential expansion of fuel control componentry which was apparently at the root of the B737 rudder problem.

Could we please wait and see?
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Old 30th Jan 2008, 08:06
  #191 (permalink)  

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Ok then, why did no other China originating aircraft have problems ?
Now who has failed to grasp the significance of the nonlinear system.....

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Old 30th Jan 2008, 08:53
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I found the following elsewhere:

http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=comm...


http://preview.tinyurl.com/2p2tgy
"Sources close to the investigation also tell The DAILY that British
Airways engineers have been collecting fuel samples from every flight
emanating from China. The sample collection, plus comments from the
AAIB indicating the aircraft had "adequate" fuel remaining on board at
the time of the crash, is believed to point toward suspicions of a
heavier-than-fuel contaminant being present. Theories propounded by
crew include the possible presence of water in the tanks that, having
become frozen during the intense cold-soak period of the flight,
partially melted and formed a slush that could have partially blocked
the fuel lines.

Sources also tell The DAILY that upper air temperatures over Russia
and northern Europe were extremely cold on the day of the accident.
Information from other crews coming from Asia on Jan. 17 encountered
extremely low temperatures in the -70 to -75 degrees C. range,
resulting in fuel temperatures dipping into the -40s. European upper
air temperatures also indicate the last 6.5 hours of the inbound China
flight would have been flown at an outside air temperature of -60 deg.
C. or lower. Although this would have resulted in fuel temperatures on
approach in the -35 degrees C range, this would not normally
constitute a problem unless, potentially, contaminants were present."

And it's been said (not by me) that "Sources close to the investigation" means a leak from the AAIB investigation. True? Likely? Or just yet more speculation & rumour-mongering?
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Old 30th Jan 2008, 09:07
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In Journalist-speak, "sources close to the investigation" can also mean anybody the AAIB has had any dealings with including the mini cab driver who overheard some gossip driving the investigator to LHR.

"Sources WITHIN the investigation" might be slightly more interesting as weasel words...but that's not the case here.

Bobbsy
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Old 30th Jan 2008, 09:22
  #194 (permalink)  
 
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British Airways engineers have been collecting fuel samples from every flight emanating from China.
Why would they do that? Why dont they just test the retention sample from BA038 on that day? Unless there isnt one; or unless they have ongoing concerns; and does "emanating from China" mean "after its arrived" or "before it takes off"?
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Old 30th Jan 2008, 09:27
  #195 (permalink)  
 
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Low temperature operation

Speaking as a non driver (at least for the last 50 years), but who spent many years trying to make various bits of A/C equipment work at -60 and beyond. May I ask what other equipment is in the fuel lines, apart from filters. Are there turbine type flowmeters for example. and rotational type valves. What has to happen to increase fuel flow.
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Old 30th Jan 2008, 10:42
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Isn't it just deliciously ironic that Boeing brought out a Service Letter reference worldwide Fuel Specifications on the 18/01/08?
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Old 30th Jan 2008, 11:24
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Originally Posted by Bobbsy
In Journalist-speak, "sources close to the investigation" can also mean anybody the AAIB has had any dealings with including the mini cab driver who overheard some gossip driving the investigator to LHR.

"Sources WITHIN the investigation" might be slightly more interesting as weasel words...but that's not the case here.

Bobbsy
Thanks, you've confirmed my suspicion that rather too much was probably being read into the Aviation Week report.
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Old 30th Jan 2008, 12:36
  #198 (permalink)  
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PROJECT MECH
Isn't it just deliciously ironic that Boeing brought out a Service Letter reference worldwide Fuel Specifications on the 18/01/08?
Do you mean when a major event took place only the previous day? As you will understand, an important Service Letter would have been prepared carefully over many days and it was purely coincidental that such an unfortunate incident took place the previous day. Boeing and all it's staff are working assiduously ... etcetera.
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Old 30th Jan 2008, 14:55
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Why did no other China operating aircraft have problems?

There's a simple solution you've all missed. Sure China is notorious for counterfeits. But why just the fuel? Take a very close look at that B777. Can you be sure it hasn't been replaced with an ALMOST PERFECT REPLICA while on the ground in China? And if it hadn't been for that pesky fuel system they'd have gotten away with it too...
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Old 30th Jan 2008, 17:33
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Glide performance of 777?

So as to avoid any speculation on a probable cause, I'd like to find out more about the glide performance of the 777.

Can a 777 pilot please comment...

Most machines I've flown (737 the biggest) have glide ratios of between 2 and 3 nm per 1000 ft in the clean configuration.
Fully configured this normally halves.

Argument: When the engines failed to respond (or thrust decreased) the aircraft was at 600' and 2nm.

If the glide performance of a configured 777 is say 1.5nm per 1000' (Im guessing!) the aircraft would have flown another 0.9nm (and obviously not made it)

Above assumes that the aircraft was already at glide speed and any extra speed would obviously send it farther (but I doubt all the way to the airfield).

We do however know that the engines were turning and it seems obvious that they were producing some amount of thrust till touchdown.

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?

I understand that knowing a rough power setting is not really relevant to the incident, but it will certainly help pass the time while we wait on the AAIB

PP
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