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Accueil >> Forum >> BA 777 lands short of runway at LHR Forum Aviation civile
BA 777 lands short of runway at LHR
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Message de Cathay Pacific - Envoyé le 17 Jan 16:33 |
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Message de speedbird9468 - Envoyé le 17 Jan 17:31 |
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Let the speculation begin. Ive seen many reports and theories on this. But if it is complete power failure as people are saying and the CPT had to glide in he deserves a medal a T7 can't be easy to glide and all the lifes he has saved in doing so well done CPT and crew
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Message de Cathay Pacific - Envoyé le 17 Jan 18:20 |
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Message de shuttle6m - Envoyé le 17 Jan 19:08 |
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Message de Luton Spotter - Envoyé le 17 Jan 21:04 |
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Message de dan - Envoyé le 17 Jan 21:13 |
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Message de flylinefrontier - Envoyé le 18 Jan 2:31 |
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Message de citation - Envoyé le 18 Jan 3:58 |
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Message de FLX - Envoyé le 18 Jan 5:38 |
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Fm the photos and the early reports, the engines are completely devastated and the wing structures are bended out of shape. Although we can't see the underbelly, it's easy to imagine the kinda of stress incurred to the remains of the landing gear structure+attachments and the rest of the airframe. Let alone all the expensive & fragile avionics. My gut feeling is that this aircraft is beyond economic repair and BA may be better off salvage some usable spare parts to benefit their large 772 fleet.
It's amazing there was no serious injuries(Cabin must hv dropped 2-3m when the landing gears collapse) and the impact was on soft grass just inside the airport perimeter only meters away fm the motorway+dense urban area surrounding LHR.
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Message de captain bill - Envoyé le 18 Jan 16:53 |
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Talking with some of my colleagues I'm told we should know on Saturday the preliminary findings of the investigators. Full power failure seems unlikely and many knowledgeable speculators are going for wind sheer. I don't know so I will not speculate but I do know that a bad wind sheer is a very dangerous thing.
My one and only experience was many years ago on approach to EDI on a Trident 3 and we had to go around twice before we could land. The increase in speed and the momentary loss of control is frightening.
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Message de aaa - Envoyé le 18 Jan 22:39 |
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Accident to Boeing 777-236, G-YMMM at London Heathrow Airport on 17 January 2008 - Initial Report
The flight crew were interviewed on the evening of the event by an AAIB Operations Inspector and the Flight Data Recorder (FDR), Cockpit Voice Recorder (CVR) and Quick Access Recorder (QAR) were removed for replay. The CVR and FDR have been successfully downloaded at the AAIB laboratories at Farnborough and both records cover the critical final stages of the flight. The QAR was downloaded with the assistance of British Airways and the equipment manufacturer. All of the downloaded information is now the subject of detailed analysis.
Examination of the aircraft systems and engines is ongoing.
Initial indications from the interviews and Flight Recorder analyses show the flight and approach to have progressed normally until the aircraft was established on late finals for Runway 27L. At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond. The aircraft speed reduced and the aircraft descended onto the grass short of the paved runway surface.
The investigation is now focussed on more detailed analysis of the Flight Recorder information, collecting further recorded information from various system modules and examining the range of aircraft systems that could influence engine operation.
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Message de JohnMorris - Envoyé le 19 Jan 23:33 |
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First I would like to add my praise for all concerned in the actions taken and safe although unconventional landing of this aircraft at Heathrow. During the news bulletin on T.V. one expert put forward a theory for the cause of this accident which may have some truth in it was that the instruments were giving a false reading of how much fuel was on board and maybe giving some reason why both engines seemed to fail at the same time and that was when asked for more power they did not respond due to fuel starvation? Does anyone think this may be possible, after all it was a long flight. I could not tell if there was a lot of fuel spillage at the crash site and certainly landing on the grass although heavy would have reduced the risk of sparks igniting any fuel leading to a fire plus of course the fast response time of the emergency services. All in all it will be a mystery untill the official report, meantime WELL DONE to all concerned.
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Message de Werkur737 - Envoyé le 19 Jan 1:28 |
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Message de speedbird9468 - Envoyé le 19 Jan 2:09 |
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Message de flylinefrontier - Envoyé le 20 Jan 23:07 |
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I think I am going to agree that something is wrong with the engine, or the plane's eletricty and stuff. Because after looking at the crash area, the plane used less than a half of a normal runway. That could show that the plane is coming down slowly.
2. looking at the gear that it had been broken free, that must be because of the hard landing and the grass...
I think that might be some kind of evidence that the plane is coming without any power...
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Message de citation - Envoyé le 20 Jan 2:36 |
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Message de FLX - Envoyé le 21 Jan 5:24 |
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I don't really understand the theory of fuel contamination applied to this case.
Are we saying the engines had no problem and transmit no warning to the crew re abnormal/declining performance caused by burning contaminated fuel during all phases of this flight:
1. Engine start in PEK
2. Taxi
3. Take-off
4. Climb
5. Cruise
6. Descend
And only decide to fail @ final approach?
Or the contaminated fuel is a small portion of all fuel in that tank and it can somehow partition itself and not mixing with the rest and can also somehow 'escape' fm being burnt earlier and timed to wait till the last moment to feed/strike the engines?
Sorry, I just don't get how this theory works.
I always thought if the contaminated fuel is 'clean' enough for engine start, U'll get a steady decline in performance or a series of engine 'hiccups' over the entire flight, NOT a sudden/abrupt lost of power in a matter of seconds during final with no prior signs/warnings. How exactly can U burn pure clean fuel in 1 min and switch into dirty fuel the nex???
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Message de captain bill - Envoyé le 21 Jan 8:59 |
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Yes FLX you are right and how so called experts came up with this one is strange. Also being out of fuel seems to be a no go and also a number of 777 people are saying that how all power failed at the one time seems to be in dispute.
One expert talked about a bird strike but to have any effect on the engines it would need to be a flock of big birds to stop both engines and this would have shown up on the radar and the crew would have called bird strike also as I reported earlier some were talking about wind sheer but again you would have expected the crew to have identified a high level glide slope sheer and have called the tower and requested a go around to take full control of the kite so until all the details are known we will just have to wait.
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Message de FLX - Envoyé le 21 Jan 15:14 |
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captain bill:
I just read further about water as the culprit re the fuel contamination theory:
http://www.flightglobal.com/articles/2008/01/18/220942/what-pilots-are-saying-about-the-ba-777-accident.html
The explanation sounds plausible @ 1st. On the ground/during climb, amount of liquid H2O in the tank must be tiny relative to fuel so that they couldn't affect the engines. At cruise, they froze and couldn't be mixed with the remaining fuel @ that stage. At/near final approach, they melted and mixed with the small amount of remaining fuel @ that stage and the concentration of water were then high enough to cause engine failure.
However, the ice must remain solid during the entire descend +most of the final approach and then need to melt & mix with the fuel pretty fast(Perhaps within a min or less) in order for it to cause sudden/abrupt engine problem just 3km fm Rwy threshold. I understand it's not impossible but how likely can the conditions be perfectly set for that to happen?
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Message de FLX - Envoyé le 21 Jan 15:26 |
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Also, I don't think temparture @ LHR was high enough for that kinda rapid warming to occur......it wasn't exactly steep landing/short-finaling in a tropical island or hot desert.
A crazy idea: How about sabotage? Perhaps a time/altitude dependent device to overide throttle control?
Yes, I just had a few beer before I wrote this msg....
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Message de JohnMorris - Envoyé le 22 Jan 23:36 |
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Just a further thought about the fuel contamination theory FLX and captain bill but admitedly I'm no expert on how the fuel is supplied to the engines on a plane during flight I assume its pumped similar to fuel injection on a car but more complicated no doubt but what I'm getting at was when the fuel was loaded onto the plane at Beijing I assume it was from a tanker therefore if there was contamination with water the tanker would have to transfer all of its load ie fuel and water to the plane. Why I say this is because fuel and water quickly separate into two distinct layers in a container and the same could have happened on board in the fuel tanks unless they were continually aggitated this could account for the guages showing plenty of fuel but in theory perhaps the fuel got used up and then there would have been a sudden influx of water to the engines giving rise to the sudden power loss? Like I say I'm no expert and it probably shows so just a thought!
John.
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Message de shuttle6m - Envoyé le 22 Jan 1:58 |
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Having read various accounts and the AAIB report, YMMM had a fairly straight forward descent rarely being asked to descend and maintain a flight level but rather being given clearances prior to reaching the previous Issued clearance. When the aircraft was short finals it required an increase in thrust to maintain speed and height, the autothrottle commanded an increase in thrust but the engines did not respond, bare in mind the 777 is FBW so the throttles are no more then computer inputs, when the A/T was overidden by the handling pilot again the commanded input did not respond.
This suggests a major computer failure.
The theory of fuel contamination in my opinion is a no go, if contamination was a problem it would be a massive coincidence for it to affect both engines at the same time.
Nor would I go with the wind shear theory, from what we have been told so far, the aircraft has been shown to have lost speed and height in a consistent manner, no sudden drop off of height or speed as would be expected if it encountered wind shear.
All of this is theory, we all await the AAIB report, but I will say again the crew did a damn fine job getting it down in the fashion they did.
AIRFLEETS.NET STAFF
PHOTO SCREENER
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Message de FLX - Envoyé le 22 Jan 6:13 |
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JohnMorris:
Fyi, all Int'l flights operate fm T2(Terminal2) of PEK. Like almost all major Int'l terminals in the world, it has vast underground fuel storage+refueling facility accessible directly fm the tarmac @ each gate. No fuel tanker truck is needed for refueling.
For this reason, contaminated fuel in the undergound facility should hv affected other aircrafts refueling @ T2 gates particularly those parked adjacent to BA38. However, there seems to be no other reports of contaminated fuel re PEK. I hv been to PEK 4 times and by my experience, T2 has been operating at or beyond its design capacity most of the time(That's why they're building T3 which will be significantly larger than all LHR terminals combined when it opens nex mth). It's extremely unlikely no other aircrafts were parked near BA38 when it was @ T2.
The only possibility was contamination caused by human error/equipement failure during refuel prep process when fuel hose was hooked fm the tarmac to the fuel pump truck and then onto BA38. But then again, why BA38 only? The same could hv occurred to other aircrafts nearby.....
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Message de captain bill - Envoyé le 22 Jan 8:28 |
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What gives me a problem with the contaminated fuel syndrome is the fact that both engines stopped at the same time. This just would not happen or has things changed so much since I was an Aero Engineer. It would look as if there was a massive engine management system failure and when I say massive I mean massive.
Was there a double engine stall due to some sort of maneuver by the crew ?
Was there a wind sheer and the crew were going for a go around hence the reason for the acute nose up attitude of the airliner ? If this were so you would not yoke it upwards without power and if you did then it would stall.
In the words of the song There are more questions than answers so we will just have to wait and see what the outcome of the investigation is.
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Message de JohnMorris - Envoyé le 22 Jan 18:41 |
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FLX:
Well from what you have said I think you are right it is very unlikely that BA38 could have been affected this way without the same problem occuring with nearby a/c. We all like to have a stab at possible causes and like captain bill says we will have to wait for the official verdict to get the answer. Fortunately we can speculate about this case as other than a major inconveience to all concerned no overall harm was done to anybody. I hope they do find a specific reason because there is nothing worse than there being some doubt about the findings and always that nagging feeling would remain.
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Message de Werkur737 - Envoyé le 21 Feb 5:58 |
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Message de 23left - Envoyé le 09 Feb 13:00 |
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It's very interesting to re-read this thread in the light of today's publication of the Air Accidents Investigation Branch final report into this incident. It was due to ice build up in the fuel system, the water forming this ice being natural in the fuel.
The speculation two years ago among contributors to this thread very nearly got it right - not bad for amateur air accident investigators!
Fuel contamination was an early speculation, followed by the thought that the contaminant might be water and even that the water might be ice. What seemed to fox everyone was that both engines failed at exactly the same time.
It appears that the engines were starved of fuel by ice build up at their Fuel Oil Heat Exchangers leading to reduction in thrust. In fact the left engine lost power seven seconds after the right (not long in the context of a flight from China to the UK, but clearly a critical happening at 43 seconds before touchdown). Had the left engine not lost power when it did but sometime in the subsequent 36 seconds the aircraft might have made it to the runway threshold.
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Message de speedbird9468 - Envoyé le 09 Feb 17:55 |
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Message de 23left - Envoyé le 09 Feb 19:51 |
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Reading between the lines of the report it seems that ice build up in the fuel system may be the norm. It seems that normally the ice would be freed by the increased flow of fuel associated with the use of more engine power during the cruise, perhaps when climbing to a higher level as fuel burn reduces the overall weight. Apparently on this flight there was no need to increase thrust until the approach into Heathrow.
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