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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 26th Jan 2008, 20:02
  #101 (permalink)  
 
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Pinkman,
Just looked up Aeroshell, Jet A-1 freezes at -47deg C. We don't know how G-YMMM was refuelled, could have been supplied from more than one bowser/refuelling point. Fuel samples should have been retained and can be tested and probably has been.
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Old 26th Jan 2008, 20:04
  #102 (permalink)  
 
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Can the theories about fuel waxing etc. be divorced from the GE90 AD issue - while I'm prepared to entertain a fuel temp scenario for this accident, as mentioned above the GE issue was freezing in PNEUMATIC lines, not fuel lines. A very different phenomon, basically. So the mechanism by which fuel waxing, if it occurred, would cause a thrust loss/engine abnormality isn't clear. Well, not to me.
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Old 26th Jan 2008, 20:09
  #103 (permalink)  
 
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Fly380

For you to endorse anything from today's article in the Daily Mail suggests your post should be moved to the WAGS, where similar idiotic posts have already gone!
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Old 26th Jan 2008, 20:34
  #104 (permalink)  
 
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The Ps3 (or P30) air line is a primary means of determining the limits to fuel flow (max & min) that the engine can instantaneously tolerate. The fuel flow must stay between these limits: Too much fuel, and a surge or overtemp may occur; and too little flow, a lean blowout (flameout) is likely.

Thus you can see a blocked air line causes the control to think the engine is at a lower-than-actual setting, and may thus deliver less fuel than the engine needs to stay alive.

Think of it as maintaining the fuel/air ratio within safe bounds.
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Old 26th Jan 2008, 21:02
  #105 (permalink)  
 
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Oldlae,

RP-3 (Jet fuel No3, the Chinese version of Jet A-1) actually freezes much lower than conventional A-1 (-52 C or so). This is the only thing that makes me question the fuel hypothesis. But as the Boeing article points out, pour point is actually the more relevant characteristic.

The plot, or maybe the fuel, thickens!
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Old 26th Jan 2008, 21:07
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Don't the fuel lines contain filters? Could these have become progressively clogged with wax/ice during flight?
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Old 26th Jan 2008, 21:44
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Time Tables

Does anybody know of a site that can do an historic analysis of flights leaving from Beiging on the same day as BA38?
You could look at the OAG timetables for that. We have a complete database of all flights that have operated in and around North American Airspace for the last several years. I could have a look in that. I would think that a flight out from Beijing to the Canadian East coast would be similar in duration and OATs experienced but I would have to check with our weather lab to confirm that.
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Old 26th Jan 2008, 21:46
  #108 (permalink)  
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Filter failure and clogging is a known issue since long before airplanes took off. I would be very surprised if any single failure tolerant designed airliner today doesn't have a filter bypass and warning system in place in all key areas of fluid transfer.
 
Old 26th Jan 2008, 22:18
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About same route and time outbounds PEK on 17/01



Full list:
http://www.flightstats.com/go/Flight...ate=2008-01-17
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Old 26th Jan 2008, 23:19
  #110 (permalink)  
 
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I understand, from a close connection, that the focus of the investigation is on the quality and composition of the fuel uplifted in Beijing.
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Old 26th Jan 2008, 23:21
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May I ask please?

As I understand it, fuel in the wing and centre tanks is kept unpressurised.

"Commencement of waxing" occurs at a certain minus temperature!

Does the pressurizing of the fuel between the first series fuel pumps/oil heat exchangers and the engine actually change the characteristics at which waxing would commence/diminish?

As an example, water boils at 100 degree Celsius at sea level IIRC.

By raising the pressure, the temperature of when water boils also rises.

Does pressurizing of the fuel change any "waxing conditions/characteristics?"

Regards

Mike McInerney
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Old 26th Jan 2008, 23:55
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I'm grimly amused to see that BA 38 is shown with status 'Landed'.
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Old 27th Jan 2008, 01:11
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Let me preface this with the following:
1. I am not a pilot.
2. I am not an engineer.
3. I am not an expert.
4. I happen to work with solvents and other Kerosene related products.

None of the above matters really, just don't want to set myself up for a fall.
I DO NOT believe these fuel theories, for one reason and one reason alone... I cannot believe that in the 10 (or 12) years that the 777 has been in the air that this is the first occasion that this has happened.
Look, flying from Beijing to London may be a cold route, but can somebody tell me if it is the coldest? Surely the Boeing engineers over-engineered the fuel system to take account and over-compensate for these situations?
I think fuel is an easy speculation (one which was being bandied about by people who have since ended up in the WAGs thread), c'mon people, tax those expert brains of yours!
Lacking the necessary expertise in this area, I more inclined to think it was an electromechanical failure of some sort.
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Old 27th Jan 2008, 01:27
  #114 (permalink)  
 
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You gotta give em credit for landing on time!
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Old 27th Jan 2008, 01:53
  #115 (permalink)  
 
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"I DO NOT believe these fuel theories, for one reason and one reason alone... I cannot believe that in the 10 (or 12) years that the 777 has been in the air that this is the first occasion that this has happened."


I was flying a 747 that morning across Russia and Germany, landing in LHR at 0500am from the Far East. I have never had to decend to a lower FL in order to increase my fuel temperatue in 25 years of jet flying. That particular morning I had to go down for the last hour of cruise to FL250 before my fuel temp began to warm up. Every other jet in my vicinity that day also decended for the same reasons and some were unable to decend as low as requested. IE Qantas, Malasian and Thai Air) There was an unusually cold air mass over S Russia and Germany that day so it could well have been the cause of the 777s problems.
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Old 27th Jan 2008, 02:15
  #116 (permalink)  
 
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Thanks, Chambudzi, finally something resembling hard data.
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Old 27th Jan 2008, 02:20
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Chambudzi, I have had to do that in a -400 (although not as low, 'cause we still had a long way to go - N of Nikolayevsk), and speed up and cycle the speedbrakes to increase hot hyd fluid flow through the fuel/hyd tank cooler. Didn't seem to have much effect later on over China, though.
I'm sure fuel low temp is stored in the hard memory of the 777.

A question for the kerosene expert above: does increased flow rate in cold-soaked fuel cause a greater propensity for any water particles in suspension to form ice crystals upon hitting the face of a filter or pump casing? ie: if the EEC's commanded more thrust and hence increased fuel flow, could this cause instantaneous increase in ice crystal formation?

I have had it explained to me once that a filter face can cause a multitude of microscopic points of decreased pressure perpendicular to the direction of flow, much as we all learned during fluid dynamics with a varying pipe diameter.
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Old 27th Jan 2008, 04:11
  #118 (permalink)  
 
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An interesting quote from the link posted by go-si :

http://www.boeing.com/commercial/aer...lar_story.html

A review of the service history of transport airplane operations worldwide for the past 40 years does not show a single reported incident of restricted fuel flow because of low fuel tank temperatures.
Doesn't prove it didn't happen.
There always has to be a first time.
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Old 27th Jan 2008, 06:10
  #119 (permalink)  
 
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Don't the fuel lines contain filters? Could these have become progressively clogged with wax/ice during flight?
Fuel filters have differential pressure sensors which generate "impending bypass" alerts in the cockpit.
If the blockage is large enough, the filters are bypassed, but note that these pressure sensors should give a warning well in advance of the actual (bypass) event.
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Old 27th Jan 2008, 06:47
  #120 (permalink)  
 
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Dunno if it was mentioned before but out of curiosity......... Bearing in mind Heathrow usually has 20 or 30 knots on or near the nose at a thousand feet for that end, it's a pity it wasn't an Airbus instead. Groundspeed mini would have thrown on more than a few knots at a thousand feet through into late finals and an Airbus suffering similar fate might have made it to the runway.

Don't think the 777 has and Vapp additive does it?
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