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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 8th Feb 2008, 23:24
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close the thread

this thread has run its course...we simply must wait for new, factual information and analysis by the British authority.

I hope the webmaster closes this thread...promising to restart as a brand new thread when new information is released.
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Old 8th Feb 2008, 23:29
  #322 (permalink)  
 
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I suspect (educated guess...) that the FADEC senses IEPR on a Roller.
On an RB211, it does sense integrated EPR. The 777 Trent seems to be simplified, however. It only measures fan inlet pressure (P2.0) and the low pressure/hot turbine exhaust pressure (P5.0).

This seems unusual to me as most of the thrust comes from the fan exhaust, not the core.

P2.0 probes are heated. Failure of heating would be evident on the flight deck (but failures like this simply don't happen at the same time... and even if both heaters failed, the crew would still be able to power up the engines)
Probe heat is monitored by both channels of the EEC. On the 777, probe heat is activated at 5% N1 (rather than 50% N3 on the RB211)

Rgds.
NSEU
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Old 8th Feb 2008, 23:36
  #323 (permalink)  
 
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greekdalek

Compressor stalling occurs when air flow across some blade/blades reach their maximum angle of attack/alpha. This usually results in an avalanche of successive blade stalls which produces that unwelcome bang. The blades are loaded up to their maximum just prestall.

Any bleeds from the core compressor will unload the compressor and take it further from a stall. Disturbed intake air can initiate a stall when the compressor is heavily loaded.

The lower the RPM/n the further away the compressor is from a stall.

Don't know how close the bi-pass compressor blades get close to stalling except that their designer/s will have taken care to avoid like the plague.
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Old 9th Feb 2008, 08:58
  #324 (permalink)  
 
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Gassss Mannn!

Somehow, we are all supposed to believe that all the theories of various conditions proferred by posters result in no warning to the crew that something is awry with the donks which are helping them to remain aloft.
Yeah. Right.
Boeing built a heap of junk which gives no impending warning of any condition which might have an effect on engine performance. Sure they did.
Jet jock Jacks and Jills, they're gonna have to come up with a better excuse than that.
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Old 9th Feb 2008, 13:53
  #325 (permalink)  
 
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Sorry Milt, I've got to go with greekdalek about low-rpm compressor stalls.

IF the bleeds were closed at idle, and/or IF variable stators too open, the engine is very likely to burp when an accel is requested. It's the result of the HPC aft stages being unable to pump away all the air delivered by fwd stages, which then find themselves overloaded and stall-prone.

But the chance of simultaneous independent failures on multiple donks is - well, just about zero...
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Old 9th Feb 2008, 15:53
  #326 (permalink)  
 
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Question for those in the know...

The EEC's have an input of Altitude and Mach number. Is this data calculated seperately or is the data input to each engine's EEC from a single source?
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Old 9th Feb 2008, 16:16
  #327 (permalink)  
 
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woodpecker,
Somebody already described the 777 as two airplanes in close formation.
The EECs would run off separate air data systems, and I mean separate.

The fact that the two engines behaved similarly but not identically should already have removed a lot of 'common fault' theories, i.e., those faults that would have affected both engines identically at the same time.
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Old 10th Feb 2008, 03:58
  #328 (permalink)  
 
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2 airplanes in close formation, so whats common here. Same Fuel source, same Crew fingers.
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Old 10th Feb 2008, 04:42
  #329 (permalink)  
 
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Sunday Times,UK
February 10, 2008
Crash blamed on ice blockage


Steven Swinford and Paul Eddy


INVESTIGATORS believe the crash-landing of a British Airways Boeing 777 at Heathrow last month may have been caused by ice clogging its fuel supply, according to a leaked memo to US regulators.
The Air Accidents Investigation Branch is examining whether water leaked into fuel tanks and froze on the 10½hour flight from Beijing.
The discovery, if borne out by laboratory tests, may force airports and airlines to review safeguards and checks on fuel before long-haul flights, when planes on some routes are exposed to temperatures as low as -75C. Pilots say, however, that heating systems and friction from air passing over the wings should keep the fuel warm.
The BA jet landed 1,000ft short of the runway after both engines failed. There were no obvious computer malfunctions or problems with the engines, and tests on fuel recovered from the jet and other planes that refuelled in Beijing in the same period show that it met specifications.
Boeing said: “The 777 has been in service for 12 years and has flown around 3.6m flight hours, during which there have been no fatalities. It would be inappropriate to comment at this stage.”
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Old 10th Feb 2008, 17:21
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Just another ancient engineer here.
Remember Concorde? Mach 2? Total temperature up to +127°C and structure temperature up to 100°C + ? And yet...
I dived into the fuel system of the Concorde not too long ago.
(Somebody asked me. I'm not a fuel system engineer but I can read system diagrams - thank you.)
Even Concorde had arrangements to keep residual water mixed in with the fuel, rather than letting it settle in "inaccessible" places.

So I AM following this with interest... hoping there will be an answer.
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Old 11th Feb 2008, 01:39
  #331 (permalink)  
 
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There is a lot of speculation regarding the fuel uplifted in PEK. BA38 would probably have uplifted it's fuel from the hydrant system at terminal 2. PEK shifts a lot of fuel, it nearly has as many movements as JFK these days. A lot of other aircraft would have also uplifted fuel from the same system, including the 8 flights my company operates each day to PEK. There are no reports of other problems, and my company is not concerned about substandard fuel at PEK.

Regarding cold soak, it may be significant that while the aircraft was on the ground at PEK, the temperatures were sub zero. This means the aicraft would have been cold soaked for a period in excess of 24 hours.

One thing that is not always known is that jet fuel supplied in China is not always Jet A or Jet A1. It's known as RP-3 (or No. 3 Jet Fuel) and is compatiable and aligned with Jet A1. It has a freezing point 2 degrees lower than Jet A1.
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Old 11th Feb 2008, 04:28
  #332 (permalink)  
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Just another Muppet.

The FAA has released a statement stating that fuel exhaustion is the only item that has been removed as a possible cause
the umpteent time fuel starvation has been wrongly cited
"Exhaustion" and "Starvation" are two different things.

One means it is all gone, the other means that not enough fuel is being supplied to sustain the engines at the requested power settings.

Billings, fuel starvation at the moment is the NUMBER ONE theoretical cause of the crash.
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Old 11th Feb 2008, 13:48
  #333 (permalink)  
 
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I just read in the dutch media, that the b777 is the 1st W/O. appologies if it's reported somewhere in the few hunderd posts.
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Old 11th Feb 2008, 14:04
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What does W/O stand for?
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Old 11th Feb 2008, 14:11
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What does W/O stand for?

It means "write off" - i.e. it will not fly again, although I presume they may use parts of it for other aircraft
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Old 11th Feb 2008, 17:50
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W/O = Written Off
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Old 11th Feb 2008, 17:51
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Aircraft is confirmed as written off, the insurers had paid out.

http://www.investegate.co.uk/Article...2010700330296N
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Old 12th Feb 2008, 10:53
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that is quick, i never knew that an insurance company would agree to pay in full just 8 days after the accident. seems a rather quick statement to me.
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Old 12th Feb 2008, 11:16
  #339 (permalink)  
 
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It is actually quite standard for insurers to pay out on aircraft damaged beyond repair in short order, especially where the case is quite apparent to the assessor. The extent of the damage is self-evident, the insurance contract is straightforward for both parties, the hull value is immediately calculable, that's it.

Completely different to insurance on persons and overall "liability" where the opposite applies.
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Old 12th Feb 2008, 11:33
  #340 (permalink)  
 
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This thread is turning into a load of waffle.

Until more officially released information becomes available there is no point trying to second guess what the failure (or series of failures) that caused the accident.

I appreciate that its an interesting topic, but nothing new has been posted and its covering old ground repeatedly.

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