Possible Causes of the Boeing 777 Crash Landing at Heathrow?

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A British Airways Boeing 777 crash-landed at Heathrow due to engine failure, with investigators noting that the engines did not respond to thrust demands from the Autothrottle shortly before landing. Thirteen passengers were injured during the emergency evacuation, and initial reports suggest the incident may involve a software or hardware malfunction rather than fuel starvation, as the aircraft had sufficient fuel reserves. The Air Accidents Investigation Branch is conducting an investigation, with assistance from the U.S. National Transportation Safety Board and Boeing. Concerns were raised about the suppression of warning signals below 600 feet, which may have delayed the pilots' awareness of the engine issues. The investigation will focus on potential causes, including avionics failures and the possibility of simultaneous engine issues.
  • #91
Question for Grant...Did your source say that the fuel flow rate went down or did it say that the same fuel rate was reported, but it had no effect?

I'm going with foreign matter or water in the fuel system. Not knowing the plumbing makes it tough to figure out, but I can not fathom a control system issue with what has been said. There is no way it's a FADEC problem either.
 
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  • #92
How much fuel would have been left? I wonder if toward the end of the flight, contaminants could have built up to the point where they mucked up the engine.

But wouldn't the fuel supply (in Beijing) have affected other aircraft? Why just that one?

I presume the fuel, the tanks and the engines will be thoroughly analzyed.
 
  • #93
Ohhhhhhh its from Beijing... UNLEADED FUEL ONLY.
 
  • #94
Question for Grant...Did your source say that the fuel flow rate went down or did it say that the same fuel rate was reported, but it had no effect?
It was a drop in fuel flow rate.

How much fuel would have been left? I wonder if toward the end of the flight, contaminants could have built up to the point where they mucked up the engine.

But wouldn't the fuel supply (in Beijing) have affected other aircraft? Why just that one?
I do not know how much fuel was on board. These are all very good questions and I have some of the same thoughts. Although the report that I saw is much more detailed than the press release by the UK AAIB, I am sure that it is a synopsis of an even more detailed report. There are obviously still a great deal of missing pieces to this puzzle.

Ohhhhhhh its from Beijing... UNLEADED FUEL ONLY.
I briefly had the same thought.:smile:

P.S. If I stop posting in the next 24 or so hours, it is probable because I got called to go fly a sequence.
 
  • #95
Astronuc said:
How much fuel would have been left? I wonder if toward the end of the flight, contaminants could have built up to the point where they mucked up the engine.
I seem to recall that most airlines require a specific amount of fuel to be in reserve for every flight to handle emergencies. It should not have been anywhere near empty. Even if it were, the protocols and requirements for proper fuel handling would prevent any large scale contamination that we would be looking at here.

Astronuc said:
But wouldn't the fuel supply (in Beijing) have affected other aircraft? Why just that one?
I'm thinking that there could have been an omission on the part of the airline to include an anti icing inhibitor, i.e. PRIST (FSII) into the fuel load the aircraft took on. It could be as simple as that. This does go back to my question to Grant in which he mentioned the fuel flow. I can't imagine a catastophic failure of something in the fuel system that would contaminate things to the point of clogging filters and reducing fuel flow to that point.

Astronuc said:
I presume the fuel, the tanks and the engines will be thoroughly analzyed.
Oh. You know it. They're going to do a ton of testing. As well as tearing apart the engine themselves. When any aircraft that is in this kind of accident that has our engines on it, they get sent back to us for disassembly and a thorough inspection.
 
  • #96
I'm thinking that there could have been an omission on the part of the airline to include an anti icing inhibitor, i.e. PRIST (FSII) into the fuel load the aircraft took on.
I don't know what type of fuel that they used but if it is Jet A1, then they shouldn't have to worry icing inhibitors because the presence of the icing inhibitor is what makes it Jet A1. However, if they used Jet A then the icing inhibitor will be absent as you mentioned.

The thing to remember here is that I only operate these airplanes (not design them). Therefore, there are many cases where you will know more than I do.
 
  • #97
This crash seems like a real 'who done it' With both engines operating on independent systems the only common denominator seems to be the fuel but even if it was contaminated what are the chances of both engines experiencing the identical effect within seconds of each other after taking off and flying 1000s of miles without a problem? Are there any other common denominators? Given that eyewitnesses said the engines were roaring as it passed them is it possible they did have the thrust but some part of the flight configuration was wrong regarding flaps or something?
 
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  • #98
grant9076 said:
the presence of the icing inhibitor is what makes it Jet A1.
I can's say that I agree with that. Do you have any kind of reference I can look at that states that? I would appreciate it. The only difference I am aware of between Jet-A and A1 is that A1 has a slightly lower freezing point and is used extensively in Europe. It was decided to use Jet-A in the US because of the higher freezing point, a slightly larger percent could be manufactured in any given time.
 
  • #99
I guess I have to wonder why icing would be a problem just before landing. Why not at cruise altitude where the atmosphere is colder?

Given that eyewitnesses said the engines were roaring as it passed them is it possible they did have the thrust but some part of the flight configuration was wrong regarding flaps or something?
The flaps/pitch were probably OK, but the plane needs a certain amount of thrust.

I've been on flights where the engines power up a little just a few km from the end of the runway, while on others the plane just glides in gently, without additional power.
 
  • #100
FredGarvin said:
I can's say that I agree with that. Do you have any kind of reference I can look at that states that? I would appreciate it. The only difference I am aware of between Jet-A and A1 is that A1 has a slightly lower freezing point and is used extensively in Europe. It was decided to use Jet-A in the US because of the higher freezing point, a slightly larger percent could be manufactured in any given time.
You are exactly right. I was thinking of JP-8. Also, our minimum operating fuel temperatures for Jet A1 and Jet A are -43 degrees celsius and -37 degrees celsius respectively. So you are correct there too.
 
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  • #101
Given that eyewitnesses said the engines were roaring as it passed them is it possible they did have the thrust but some part of the flight configuration was wrong regarding flaps or something?

This is a very valid question. The likely reason is because the aircraft was well below glidepath and therefore much closer to the witnesses than it would normally be. The thing to remember is that these engines (even at low power settings) are loud enough to cause permanent hearing damage if you are close enough to them. So it is quite normal in this scenario for the people to hear them as being louder than normal.
 
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  • #102
But then again, there is also this passenger who seemed to have heart the engines roaring:

http://www.timesonline.co.uk/tol/news/uk/article3207393.ece

Antonio De Crescenzo, 52, from Naples, said there was little warning that the plane was in difficulty. “We were coming into land but the plane felt like it should have been taking off. The engines were roaring and then we landed and it was just banging.
 
  • #103
Andre said:
But then again, there is also this passenger who seemed to have heart the engines roaring:

http://www.timesonline.co.uk/tol/news/uk/article3207393.ece

That report also repeats the statement:
There appeared to have been a catastrophic loss of power affecting both engines. The cockpit electronics may also have failed, leaving only the battery-powered airspeed indicator and altimeter operating.

They lost avionics as well.

If that is so, say due to a power cut, would that have also affected the engine control systems?

If the engines were "roaring" on landing it indicates the problem may have been a temporary one and power came back on albeit too late.

The B-777 descent rate quoted in Andre's earlier post #38 would suggest the plane ought to have crashed onto houses before the airport perimeter, the fact that it didn't would be explained by the engines regaining power.

If they did come back at the last second, thus averting that disaster, their escape was closer than ever!

Garth
 
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  • #104
The (temporary?) loss of electrical power may have affected the fuel boost pumps temporarily. Just speculating.

In the same report quoting again:

Martin Green, another airport worker, told Sky News: “It came in at a very high angle and just dropped like a stone — I would estimate 200ft.

“It seemed to be flying fairly slow and it had a very high angle of attack. The nose was high up in the air, which is very unusual.”

Engines are installed so that the thrust vector passes underneath the centre of gravity that means by giving power, the torque causes the aircraft to pitch up. Also with many fast aircraft, Grant can confirm this for his category, under these conditions, slow speed and no significant thrust, the authority to pitch up to those very high angles of attack is simply not available without that engine torque in the aircraft I know. However if the engines 'roar' into max power, they also provide that required nose up torque to get there.

Just a thought. The investigators need to find out.
 
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  • #105
I guess I have to wonder why icing would be a problem just before landing. Why not at cruise altitude where the atmosphere is colder?
This is an excellent point.
It is possible that icing could have been a problem both in cruise and just before landing. It could be that the globules (or whatever form it may take) of frozen water did not migrate to the fuel boost pump intakes until during the descent. This is highly speculative but I have landed in warm climates and discovered (during the post flight walk around) frosting on the lower wing surfaces due to super cold fuel in the tanks. This indicates that the fuel temperature is well below zero degrees celsius and it is quite the norm after a long flight. FredGarvin is likely to know more about fuel icing than I do.

They lost avionics as well.

If that is so, say due to a power cut, would that have also affected the engine control systems?
I did not remember reading about any loss of avionics. That news report using the term "may" indicates that they probably got it from a passenger because the pilots would know for sure whether or not they lost avionics. If it is from a passenger or flight attendant, then the normal load shedding feature will explain it. All of the boeing aircraft that I have flown are designed to remove power from non-essential equipment (passenger seat lighting, galley power, etc.) if there is a risk of overloading the generators (engine problems, etc). This will leave passengers nervous and in the dark, but the pilots will have all of the electrical equipment that they need.

Each electronic engine control (EEC) has its own separate generator which is operational even at extremely low RPM's (windmilling), and the engines would not have time to spool down to this low of an RPM. In other words, the EEC's are designed to still be working long after the main generators have lost their exciter fields. Besides, the data records showed that the EEC's were fully functional throughout the event. However, it is possible that the engines may have quit and restarted. The more modern boeing aircraft have a feature where the EEC for a particular engine will energize both ignition systems for that engine if it senses an uncommanded drop below idle N2 RPM (or N3 if it's a triple spool engine). The net result is that if an engine quits without the pilot shutting it down, the EEC for that engine will automatically keep trying to restart it.

If the engines did actually fail and then restart, this would be further evidence that the EEC's were functional.
 
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  • #106
Just to get the facts right as far as we know at present.

The United Kingdom's Air Accident Investigation Board (AAIB) report copied from the Professional Aviation Maintenance Association.

Initial Report Update 23 January 2008

Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18th January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.

The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.

As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust.

All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways

This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.

Further factual information will be released as and when available.

So not a complete engine shutdown, but loss of thrust at a crucial time, and affecting both engines, but not exactly simultaneously.

And dated 26 Jan 08

Investigators in 777 Crash Looking at Fuel Systems

By Dominic Gates
Seattle Times aerospace reporter

Investigators studying last week's crash landing of a British Airways Boeing 777 said Wednesday they are looking closely at the possibility that the accident was caused by an interruption in the flow of jet fuel to the engines.

The cause of the Jan. 17 crash at London's Heathrow airport has not been established. Even if it is a fuel-flow interruption, that doesn't necessarily exonerate Boeing.

But this focus of the investigation seems to increase the possibility of an external cause such as contamination of jet fuel loaded before the 777 took off from Beijing.
http://seattletimes.nwsource.com/html/nationworld/2004144384_777crash25.html

Garth
 
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  • #107
I was just coming into Heathrow yesterday and I noticed they had fitted some new runaway lights...http://www.outpost.pwp.blueyonder.co.uk/Z-Private/runway.gif

Garth
 
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  • #108
Garth said:
I was just coming into Heathrow yesterday and I noticed they had fitted some new runaway lights...

Garth
Clever! :smile: Good think I had just swallowed the coffee.
 
  • #109
Latest on the crash,

No engine defect on crash plane
The engines of a jet that crash-landed at Heathrow Airport had no mechanical defects, investigators have said.

The Air Accidents Investigation Branch (AAIB) added the black box data recorder showed nothing wrong with the major aircraft systems.

But there was some damage to the fuel pumps, and some small items of debris were found in the fuel tanks.

All 136 passengers and 16 crew on the British Airways flight from Beijing survived the incident on 17 January.

Not giving any cause of the accident, the AAIB said it was carrying out a full examination and analysis of the entire Boeing 777 aircraft and engine fuel system.
http://news.bbc.co.uk/2/hi/uk_news/england/london/7251435.stm

The focus now is on the fuel pumps but don't these work independently pumping from separate tanks? If so what are the chances of both sets failing within seconds of each other?
 
  • #110
Art said:
the fuel pumps but don't these work independently pumping from separate tanks? If so what are the chances of both sets failing within seconds of each other?
If it was a random failure of a component in the pump then very low - if it was a failure of a control system common to both of them then it is higher.

It's like the argument for allowing twin engine aircraft, like the 777, to fly over water - the chance of a random fault happening on both engines within a short time is very low. A failure of a common system that took out both engines is just as likely to happen on a 4 engine aircraft so having 4 engines is no advantage.
 
  • #111
It's impossible to design in redundancy in the fuel you carry. That is one of the few "components" on an aircraft that doesn't have a back up. If it goes bad, things get ugly.

BTW..Thanks for the update, Art. I was just wondering about this.
 
  • #112
If one engine fails to power up as expected, would the flight control system back off on the other one to keep trim?
 
  • #113
Garth said:
I was just coming into Heathrow yesterday and I noticed they had fitted some new runaway lights...


http://www.outpost.pwp.blueyonder.co.uk/Z-Private/runway.gif

Garth

:smile: Good idea! :smile: :smile:
 
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  • #114
russ_watters said:
If one engine fails to power up as expected, would the flight control system back off on the other one to keep trim?

Why would it do that? It could just give it more rudder. The entire point of fly by wire is that if one thing fails, you can use all the other flight surfaces to compensate and fly as normal.
 
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  • #115
FredGarvin said:
It's impossible to design in redundancy in the fuel you carry. That is one of the few "components" on an aircraft that doesn't have a back up. If it goes bad, things get ugly.
It's amazing that it happened toward the end of the flight and not sooner. Those folks are lucky that it happened just at the airport as opposed to over a populated area.

I supposed that as the fuel is consumed, the density/concentration of crud/contaminants builds up.

Fred's right. The fuel is common to all the tanks. The only recourse would be to carry extra onboard fuel from a different source, which means carrying extra mass.

Now they have to figure out where the fuel came from. Is it one source, or more than one, and was it a one time event. The same source of fuel could affect other aircraft.

On the plane side, it would seem that a more robust filter system is needed.
 
  • #116
Cyrus said:
Why would it do that? It could just give it more rudder. The entire point of fly by wire is that if one thing fails, you can use all the other flight surfaces to compensate and fly as normal.
Dunno, just speculating.
 
  • #117
Astronuc said:
Now they have to figure out where the fuel came from.


The jet flew direct from Beijing, China, where it had last refueled.

Maybe the fuel had melamine in it.
 
  • #118
Astronuc said:
It's amazing that it happened toward the end of the flight and not sooner. Those folks are lucky that it happened just at the airport as opposed to over a populated area.
Indeed. I was thinking the same thing myself. Someone was watching over them that's for sure.

Astronuc said:
Now they have to figure out where the fuel came from. Is it one source, or more than one, and was it a one time event. The same source of fuel could affect other aircraft.
The chain of custody shouldn't be too difficult to follow. Most major airports have large pipeline systems direct from a terminal. I am going to guess that the terminal and pipeline system will be ok. If it weren't then there would have been a lot of reports of aircraft with bad fuel. There are a lot of precautions taken in the US and Europe regarding the proper handling of fuel. My guess is that there was a serious breech of procedure in this area. There are a lot of things that could go wrong between offload from the pipeline to the offload to the aircraft. The items that most quickly come to mind are improper amounts or improper fuel additives, an exceptionally large amount of water in the truck carrying the fuel and all out contamination of the truck by some other chemical. I don't want this to turn into another China bashing thread, but we all know that the Chinese are notorious for cutting corners.

Astronuc said:
On the plane side, it would seem that a more robust filter system is needed.
I'm not so sure about that. Aircraft fuel systems are usually pretty well filtered and strained. 10 micron filters are standard on engines and strainers are usually used quite a bit. I am guessing that this was something a filer could not have prevented.
 
  • #119
FredGarvin said:
The chain of custody shouldn't be too difficult to follow. Most major airports have large pipeline systems direct from a terminal. I am going to guess that the terminal and pipeline system will be ok. If it weren't then there would have been a lot of reports of aircraft with bad fuel. There are a lot of precautions taken in the US and Europe regarding the proper handling of fuel. My guess is that there was a serious breech of procedure in this area. There are a lot of things that could go wrong between offload from the pipeline to the offload to the aircraft. The items that most quickly come to mind are improper amounts or improper fuel additives, an exceptionally large amount of water in the truck carrying the fuel and all out contamination of the truck by some other chemical. I don't want this to turn into another China bashing thread, but we all know that the Chinese are notorious for cutting corners.
One other possibility could be a microbial contamination in the fuel storage systems, especially if there is build up of moisture. I could be inadequate procedures, or not following procedures, or cutting corners on quality of fuel.
 
  • #120
I find it difficult to believe the fuel could be the source of the problem. It would take an incredible coincidence for both fuel pumps, having worked perfectly for several thousand miles and several hours pumping this fuel, to both suddenly pack up within a few seconds of each other through fuel contamination.

edit One report speaks now of unexpected air in the roller bearing casings of the fuel pumps causing cavitation, could this be due to contaminated fuel?