Failed Avionics a Possible Cause of BA038 Crash 369
Muhammar writes "As you may have heard by now, both engines of the Boeing 777 aircraft flight BA038 suddenly cut off without warning at very low altitude and low speed during autopilot-assisted landing at Heathrow. A prompt reaction of the pilots prevented the stall and saved all lives aboard. The crash landing short of the runway tore off the landing gear on impact, and the fuselage plowed a long, deep gouge in the grass. With the investigation ongoing, the available information points to an electronic control problem as the most likely cause of the sudden engine power loss."
Software? (Score:3, Interesting)
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Re:Software? (Score:4, Funny)
That is not likely. More likely is they had a glitch from a strong RF field someplace. Knowing the timing, it is likely to be either a radar or other high power beam or a very near lower powered source such as a cell phone inside the farady cage. Very likely the radio source is from something like this; **RING** **RING** "Hi hon, we are landing now.. Oh no, somethings wrong.."
Re:Software? (Score:4, Interesting)
That said, my paranoia meter says this could have been caused by some nut near the airfield with a HERF Gun [slashdot.org].
Re:Software? (Score:5, Informative)
You're right that it's more likely than RF interference. But neither is likely at all.
A software glitch of this type (if that's what it was) has never happened in aviation history. Certainly not in the 10 year history of the 777, with more than 500 of them flying around the world, but not to any other type either.
Also, the engines didn't "fail". The engines were running both before and after the stall (and yes, the aircraft did stall, despite what the article summary says). "Failure" and "failure to respond" are two different things.
In some ways that's even more scary, because it rules out simple explanations like fuel exhaustion. It's one thing for engines to fail, quite another for them to simply ignore control inputs.
Re:Software? (Score:4, Informative)
Indeed. If I'm piloting a turbine engine aircraft, I much prefer for the engines to just fail then for them to ignore my commands. Fly-by-wire is pretty cool until the engines ignore your commands and you have no way to shut the fuel off to them.
Re:Software? (Score:4, Interesting)
It's certainly not without precedent. No case of air/fuel mixture explosion was found in 747's until TWA 800 [wikipedia.org] in 1996, and 1,396 of those were built since the 747 started flying commercially in 1970.
Re:Software? (Score:4, Informative)
You can only mathematically prove that software is bug free given some basic assumptions about hardware performance. If those assumptions fail, then your bug-free software is now buggy because the hardware is buggy and it can't sort out valid from invalid information.
TFA mentions another avionics glitch where a failed accelerometer caused a near accident on a 777 in Australia. The software inappropriately responded to the failure because the failure condition wasn't foreseen.
Most likely the root cause is hardware-related, not software-related. For example, maybe water-based corrosion on some contacts somewhere where the seal was damaged, or a short circuit on some sensor somewhere else. The issue is that this may have triggered failure conditions that were not previously foreseen in the software design.
The 777 has an impressive safety record. However incidents where, say, water gets into circuitry and causes problems, or some previously unforeseen failure situation arises, there will be problems.
As for the "first of its kind" remark-- this is not the first software initiated problem in the 777 if indeed that is the case. It *is* however, the first 777 crash ever. Which ought to make one a little less inclined to question previously unforeseen problems.
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IAAAE (I Am An Aeronautical Engineer) and to take serious issue with that statement.
According to the Times today [timesonline.co.uk], there have been at least 2 reported computer 'glitches' on 777s in the last 3 years. One lowered the airspeed from 270 to 158 knots along with putting the a/c in a
Re:Software? (Score:4, Informative)
As for fuel exhaustion - that was ruled out very quickly - plenty of fuel leaked from at least one breached fuel tank. It's the first thing the investigators would have done - look in the tanks and see if there was fuel. That doesn't rule out fuel STARVATION though - you can have plenty of fuel on board, but something stopping it from reaching the engines.
Re:Software? (Score:4, Informative)
Another data point to consider is that the failure was not transient. Normally if you introduce some noise into the channel then you lose some symbols here and there, or the clock even. But the higher level protocols take care of that. Pull the network cable, for example - your SSH session will stay alive for half a minute, until TCP timers run out. I am sure that in an airplane loss of a message will be first noticed and logged, then reported as a potential trouble, and if it continues then some other emergency action will be taken. But if the error ceases to be then the message gets through and you can continue using the controlled device.
Since the malfunction occurred quite far from the airport, and it did not fix itself after the aircraft moved away from a possible jammer location, then in my uneducated opinion the relevant controls just "wedged" somewhere, asking for a hard reset. It will take some Boeing engineers with the diagrams to find out where two independent engine control paths merge or at least get close to each other. And they still have the physical electronics of the airplane, most of it probably undamaged. On top of that they have every single bit from every single flight data recorder, and those are of improved type that record more parameters than usual.
In addition, if the two engines are identical (as they should be) and have the same firmware loaded into their controllers, then the same command sent to both engines could easily take them out at the same time. It could be a fairly complicated sequence, for example, but as long as both engines are operated by another computer (autopilot / autothrottle) then you can be fairly sure that the two engines would be as much in sync with each other as possible, and the "ping of death", so to say, would affect both.
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While already moderated funny, I'll just clarify that this is a myth. A more likely explanation for the cellphone ban on planes is due to the networks not being able to handle several hundred clients moving at 800km/h in view of tenths maybe hundreds of base stations.
Re:Software? (Score:5, Informative)
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For the plane to actually fail because of a software bug, the majority of the systems would need to have exactly the same bug at exactly the same time. Given their source code is checked ve
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Re:Software? (Score:4, Interesting)
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Re:Software? (Score:5, Informative)
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If the hardware weren't redundant then somebody has to be responsible for that and at least get a good kick in the ass. Probably at the economic department...
A software glitch may be triggered by borderline limits exceeded and started a default mode in which the engines were shut down or at least put to idle mode. Since this was at an unfortunate position this was triggering an accident. At a higher altitude there would have been ampl
Errrrr.. (Score:5, Insightful)
Airplane Operating Systems (Score:5, Funny)
Unless it was running on an OS like Windows for Aircraft, "now with fewer crashes".
Yes, I know it's all custom designed. But thinking about the infamous Windows for Warships [theregister.co.uk] I couldn't resist
Re:Airplane Operating Systems (Score:5, Informative)
Re:Airplane Operating Systems (Score:4, Funny)
But the idea of Windows for Airplanes is something that would strike fear into many a person's heart. Would you trust your aircraft to Windows for Airplanes?
Or your helicopter to Windows for Helicopters?
Re:Airplane Operating Systems (Score:5, Funny)
The Knowledge Base reports on Flight Simulator are scary enough [microsoft.com] as it is.....
the rest of the scenario writes itself
Re:Airplane Operating Systems (Score:5, Informative)
The 653 in the name is a reference ARINC-653, which is an industry standard that specifies the api that the OS exposes to the user. (Integrity also supports this same api)
I havent used VxWorks 653, but I am very familiar with both Integrity and Intregrity-178b, and there is no question that the latter is a LOT more reliable.
There may be a little bit of code reused in these platforms, but really the name is the same for marketing reasons. (kind of like how windows CE is completely different from the windows you run on your desktop)
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that explains the recent recruitment advert. i saw it first on theregister before christmas and thought it was a joke till i saw it on tv.
http://www.youtube.com/watch?v=aDHPCr5m4ko [youtube.com]
don't you feel safer knowing that they are using windows on expensive weapon platforms? you couldn't pay me to get on a sub with windows involved.
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http://www.adahome.com/articles/1998-07/nw_ghs.html [adahome.com]
"Written in Ada, RT Secure is a real-time, pre-emptive multitasking microkernel optimized for mission-critical applications that require true hard real-time response."
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a) The airplane drops below the glide path
b) The airplane flies at too high of an angle of attack
during landing.
Re:Errrrr.. (Score:5, Insightful)
I read a number of articles on it and:
1) Avionics resulted in a near miss relating to a 777 a few months ago operated by Malaysian Airlines. The problem was a combination of a software bug and a dead sensor (i.e. the software didn't properly handle sensor errors and a sensor went dead).
2) Despite this problem, the 777 still has an impressive safety record. Only one crash in the history of operating that aircraft and that didn't result in fatalities?
In a plain like the 777 basically, you have three possibilities: human error, electronics failure, or mechanical failures. I think this case seems unlikely to be the result of other human or mechanical failures, so we are left with electronics issues and the primary suspect.
I am guessing that the real lesson here is that nothing is infallible, but that the 777 is pretty-darn good.
My suspicion is that we will eventually find that the 777 needs regular maintenance to portions of it which have not received as much attention in the past. It could be a similar issue to the MA failure-- a dead sensor sending information the software was not prepared to handle, it could be an electrical short circuit (for example, caused by water corrosian or even condensation) as we saw recently with the ISS. The point is that only now, thirteen years after the planes entered operation, we are running into these problems. I don't think that software alone could have caused the problem. More likely it is a combination ofhardware failure triggering bugs in software.
Re:Errrrr.. (Score:5, Insightful)
They experienced a catastrophic failure losing both engines at low altitude where the plane has all the flight worthiness of a brick and nobody died.
More complicated than that (Score:4, Informative)
You can prove that the software is bug free for any set of foreseen inputs. The question becomes whether there are unforeseen inputs which can cause problems. Suppose for example, that a sensor fails in an unexpected way-- for example shorting a circuit instead of breaking it, or by sending incorrect data to the computer. In essence you not only have to handle valid inputs from sensors, and normal sensor failures, but you also have to handle sensors which fail in unexpected ways, and you also have to handle every possible electrical fault as well. And then you *still* have to make some assumptions about the underlying communictions between the remaining components.
How, here is the real issue:
Software exists only to process information on underlying hardware. When you have failures in that hardware which cause the information to be corrupted, you cannot count on any results on the software. Hence you software can only be proven bug-free within a reasonably limited set of circumstances. Or, in simpler terms, garbage in? garbage out.
Good case to examine (Score:5, Insightful)
Re:Errrrr.. (Score:5, Informative)
- The autothrottle system commanded an increase in thrust from the engines which did not respond
- The autothrottle demanded further increases in thrust again with no results
- The PIC commanded an increase in thrust via movement of the throttles, with no result
- The aircraft slowed and subsequently lost height
http://www.aaib.dft.gov.uk/latest_news/accident__heathrow_17_january_2008___initial_report.cfm [dft.gov.uk]For both engines to have not responded to either the autothrottle or manual throttle movements, we are looking at a software issue in either the FADEC or the EMC.
BA are extremely happy about the crash (Score:5, Funny)
No, not the Avionics... (Score:5, Insightful)
The pilots then manually increased throttle - to no avail.
For both engines to malfunction like this at the same time greatly seems to point to a fuel delivery problem.
This does not necessarily mean "running out of gas" - as a plane like this has multiple tanks, valves and pumps, all of which can be configured multiple different ways - which change during the flight.
A simplistic example: they could have been running both engines off one tank - which went dry - though another was full - or both engines were being fed from a common fuel pump which failed, etc. These things *shouldn't* happen - but the investigation will tell...
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This does not necessarily mean "running out of gas" - as a plane like this has multiple tanks, valves and pumps, all of which can be configured multiple different ways - which change during the flight.
Re:No, not the Avionics... (Score:5, Informative)
The fact that the engines responded the same way, at the same time, strongly suggests a single point of failure in an electronic flight control system.
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Re:No, not the Avionics... (Score:4, Insightful)
Exactly why speculation as to the cause gets us nowhere. Pointing fingers and throwing blame about serves nothing, just like the guy above saying something about Iranians. We really should have something similar to a Godwin for Terrorist/Bush/Iranian bullshit that people post.
Re:No, not the Avionics... (Score:5, Insightful)
Just because the indicators in the cockpit show that the autothrusters were to provide more power doesn't mean the signal gets to the engines. There is a lot of wiring and other systems between the cockpit and the engine. On a "fly-by-wire" plane like the 777, even moving the throttle levers just sends a signal to a system that eventually gets to the engines. Bottom line is there are lots of lower level avionics systems that could have failed and the pilots would only see that the autothruster was supposed to provide more power and didn't.
The question is, which on the various boxes along the way had a BSOD?
Cheers,
Dave
From various articles on the incident (Score:3, Interesting)
Now the root fault may be due to some sensor or processing system failing and causing a cascade failure to other portions of the system. This sort of thing *has* happened in other 777's (an accelerometer failing in a way as to cause a cascade error into fl
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The design of a typical jet's fuel system means that you just cannot have engines running from the same tank. Each engine has it's own tank (in the case of a twin such as the 777 this is the entire wing tank). Fuel can be fed from other tanks int
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On February 7, 2005, a Virgin Atlantic Airbus 340, flying from Hong Kong to Heathrow, was passing through Dutch airspace when, without warning, one of its four engines - the outer engine on the port wing - went dead.
The crew quickly established from the Airbus's sophisticated displays that the amount of fuel contained in the inner tank, from which the engine was feeding, registered as "0". What they did not realise was that the automatic transfer system between the tanks had failed.
The oute
Re:No, not the Avionics... (Score:5, Informative)
Re:No, not the Avionics... (Score:5, Informative)
They probably do. This is the time to whip out An experimental evaluation of the assumption of independence in multiversion programming [google.co.uk] by Knight and Leveson. It's a 47-page paper, but here's the summary:
Of course, one would think there would be two types of redundancy: The software would be N-version programmed and there would be separate systems for each engine. The chances of two independent N-version-programmed programs failing at the same instant seems particularly low.
It's easy to jump to the it-must-be-the-computers conclusion because PCs are unreliable in everyday use compared to washing machines, cars or compact disk players. But until the accident investigators' report comes out there really isn't much evidence to base speculations upon; the problem could have been anything.
Just my $0.02
Made by Diebold? (Score:4, Funny)
Re:No, not the Avionics... (Score:5, Insightful)
Re:No, not the Avionics... (Score:4, Insightful)
Ah, no, they don't glide THAT well (Score:5, Informative)
Damnit! (Score:4, Funny)
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Re:Damnit! (Score:4, Funny)
I read it was actually MIX machine code converted directly to Java byte code by a drunken leprechaun.
Wikipedia is an awesome source.
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Possible autothrottle problem (Score:5, Interesting)
What I've read is that the pilots observed a relatively gradual loss of power symmetrically on both engines. This tells me that I can rule out engine problems with FADEC and fuel. It all points to the auto-throttle. Autopilot tells where it wants the plane to go and autothrottle calculates how much throttle is needed. It then commands both engines FADECs via the bus system which is doubly redundant. What I'm thinking is that auto-throttle is supposed to be backed up, bypassed by a manual direct control to the engine FADECs from the cockpit throttle control?
Any B777 avionics mechanics around - I only know military jets...
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Re:Possible autothrottle problem (Score:5, Insightful)
What I've read is that the pilots observed a relatively gradual loss of power symmetrically on both engines.
Interesting. Do you have a link to the source for that? Not that I doubt you, just curious to parse it myself.
This tells me that I can rule out engine problems with FADEC and fuel.
FADEC, possibly, but fuel? It's quite possible there was either water or crud in the fuel, especially since the aircraft almost certainly took on fuel in China, and China seems to have had problems of late with products being adulterated in some form. The crud could cause blockages in the filters from the tank(s). The water would cause an increasingly-diluted fuel mixture to enter the engines as the level dropped which might also cause the gradual loss of power.
The two most-likely culprits I would examine first are the discrete devices at either end of the control path that send the data and receive it at the other end, and the cables and connectors used to transmit the data.
The next point I'd check would be the power supply that powers the electrical actuators that physically move the actual throttles in each engine. This supply would be separate from the power used for the electronics, as it would be a relatively high-current source. This might also be caused by cabling/connector problems.
Aircraft tend to have many problems with cabling due to high vibration and multiple pinch-points and stress and vibration/abrasion at support points, as well as contact problems at connectors.
Another very major problem is human error. In many cases the turn-to-lock type connectors are in very tight spaces, sometimes so much so that it may only be visible by a small mirror and flashlight held by the tech while he may be laying on his back or nearly standing on his head. I had a whole set of strange-looking pliers of different lengths and weird angles with curved padded jaws for just this purpose in my tool box, along with small hand-held extend-able flexible-tubing-mounted inspection mirrors and flashlights with the head on flexible tubing as well.
It can be very hard to tell, given the above circumstances, if the locking sleeve on these aircraft instrumentation connectors had been twisted far enough to complete the lock. It doesn't take much imagination to see what could happen given time, vibration, and G-forces.
Of course, these are just my rough guesses, and I don't have enough information to really make any informed statements.
Cheers!
Strat
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The article describes the EPR (Engine Pressure Ratio, a measure of the power output) as slowly decreasing in both engines at the same time. If thats true it doesn't sound like fuel starvation. One: the EPR would simply drop to zero, not tail off, and two: the engines are unlikely to both stop at the same time.
There was a 767 that ran out of fuel over the Atlantic some time
Are the pilots heros? (Score:2, Interesting)
Re:Are the pilots heros? (Score:5, Insightful)
The word "hero" is thrown around a lot these days...
I believe what they meant, was that the pilots realized that things were going wrong, and the "normal" reaction would be to add thrust. When they realized that they couldn't add thrust, that this would result in loosing airspeed, entering a stall, and crashing
So they realized that an alternative was to lower their angle-of-attack, preventing the stall, and maintaining a bit of airspeed. This would have the unfortunate side affect of landing well-short of the runway (and perhaps airport) and destroying the aircraft - but given the information available - was a bad - but the best alternative
So they implicitly decided the best course of action was to glide the airplane and ditch it in a field - not a decision that would have exactly won them any praise had they read the situation wrong - but it saved everyone
Re:Are the pilots heros? (Score:5, Insightful)
In principle, the airplane could have been landed on the runway without damage, if the right variables had come together -- but low and slow, in a big heavy airplane, with full flaps and no power, you're pretty well boxed in. I don't think they could have done better.
rj
Re:Are the pilots heros? (Score:4, Funny)
Yes, but it doesn't make for as a striking newspaper headline as Coward the Hero!.
Re:Are the pilots heros? (Score:5, Insightful)
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It seems you didn't RTFM. Here's some help...
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As for the number of 777s in service, that's between 600-700, according to reports on Sky news. Another report said that Boeing reports they have around 300 pending orders for 777s over the next few years. A remarkably safe and capable plane. And this accident investigation will likely only make them safer.
Patience (Score:5, Insightful)
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Seriously though, this is the place to come for some two-bit speculation...
Had to fix that for you. Go back and read any /. article about NASA problems and just see the posts from folks who "know better" than the rocket scientists.
I think I had too much coffee this morning. I'm feeling a bit cranky.
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Typical (Score:5, Funny)
It's uncanny how they made the flight control system sound just like my wife.
That's a feature that is sadly lacking, though.
uniforms (Score:2)
Pointless story (Score:2)
The facts that we know so far are those in the interim AAIB report.
The AAIB will publish their full report in due course, at which point we can expect to know what happened.
That's it, basically.
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I'll bet just everyone is just dying to have you at their parties....
Are cables safer? (Score:2)
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I found the bug (Score:3, Funny)
Not avionics, it was another problem... (Score:2, Funny)
have released what actually caused the accident. The evidence is clearly visible
in these pictures:
http://www.heathrowpictures.com/pictures/images/picturegallery_baw_b772_gymmm20.jpg [heathrowpictures.com]
The cause for the engine problems is massive ingestion of dirt. The manuals clearly
specify that the engines need to be run on air, not dirt. Even small quantities
of dirt can cause loss of power.
Pointless speculation by we who know nothing (Score:5, Insightful)
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Re:Pointless speculation by we who know nothing (Score:5, Informative)
In case people are confused by people talking about a BA772 or a 773, these are standard designations. a Boeing 777-200 is referred to as a 772, the 777-300 is a 773, etc. Other common ones you'll find are things like 742 and 744 which designate 747-200s and 747-400s, respectively. Airbus planes also have similar designations.
Re:That Is Brilliant! (Score:4, Informative)
In this case, then, the quote needs to be properly attributed and sourced, which I neglected to do. Apologies. The quote comes from this thread, [airliners.net] post #6 by a user named IADCA [airliners.net].
One article FUD, the other reasonable (Score:3, Informative)
The simple "running out of fuel" hypothesis is very unlikely. All aircraft are supposed to carry reserves to divert to another airport (not far in this case) plus ninety minutes flying. While cheapo airlines might short-cut on this, I cannot imagine BA doing so. There is no indication that the aircraft had been "stacked" for any length of time, so it shoudl have landed with two hours worth of fuel on board. There have been cases of aircraft being misfueled, but on a regular run between two sophisticated endpoints, this seems unlikely.
Some facts about the 777 Electronic Engine Control (Score:4, Informative)
Engine flameout protection is provided for an auto-relight and rain/hail ingestion. The auto-relight function is activated whenever an engine is at or below idle with the FUEL CONTROL switch in RUN. When the EEC detects an engine flameout, the respective engine ignitors are activated.
Fuel is supplied by fuel pumps located in the fuel tanks. The fuel flows through a spar fuel valve located in the main tank. It then passes through the first stage engine fuel pump where additional pressure is added. It flows through a fuel/oil heat exchanger where it is preheated. A fuel filter removes contaminants. If the filter becomes clogged, the filter will be bypassed, passing fuel directly to the engine. In that case, a Advisory EICAS message "ENG FUEL FILTER L/R" will be displayed.
When main tank fuel pump pressure is low, each engine can draw fuel from its corresponding main tank through a suction feed line that bypasses the pumps.
Re:terrists? (Score:4, Funny)
Your skepticism about such things is justified. (Score:2)
In that case, it was difficult to control perceptions because too many people knew that the runway had just been re-surfaced, and had been put back in service before the non-skid grooves had been cut.
Too often, the "news" is not an honest attempt to unde
Re:terrists? (Score:4, Interesting)
First, there were MANY credible witnesses that swore they saw a missile shoot into the sky before the explosion. Of course, it turned out to be the different trajectories of the airplane pieces, but that was only figured out after a detailed analysis of radar records.
Second, prior to Flight 800 the terrorist explanation WAS more likely - I don't think a modern airliner had EVER exploded by itself before that, but there had been a few that did it with outside help.
Finally, the intelligence and police agencies were careful NOT to peg it on terrorists as the only theory. It was the news media that ran with the "Arabs and Stingers and Bombs Oh My" stories incessantly. Yeah, the government floated the idea - because it was a definite possibility. What are they going to say? "We have some eyewitness acounts of what looks like a missile launch, but we have definitely ruled out terrorist involvement."
As an aside, where are the Flight 800 "Truthers"? Why isn't anyone blathering about the conspiracy to hide the REAL reason Flight 800 blew up?
Re:terrists? (Score:5, Informative)
a) no, they were not credible, and
b) they by and large didn't claim they saw "a missile".
What they claimed is that they saw a "streak of light" or some variation thereof. Only a few people claimed they saw "a missile", and those people by and large are the people that made it onto the news. So it probably seemed like there were more of them than there were. The news outlets chose the most radical, attention whoring witnesses to put on the air.
But if you read the NTSB report, they break down the witness statements. Out of something like 2,000 witnesses, only a relatively small percentage (I'm remembering it being something like 25%) saw a "streak of light". Of that percentage, about half saw the light going up, half saw it going down. Some saw it going to the left, some going to the right. In other words, none of them had any idea what they were looking at.
This is pretty normal for witnesses to an airliner crash. Nobody's expecting to see what they're seeing, so their mind initially doesn't record things correctly. What the NTSB has to do is filter out the crud and see if there's anything that everybody agrees on. If there is, then they investigate that. In this case, a large enough percentage of people indicated they saw a flash of light, and that ended up supporting the mid-air explosion theory.
But the NTSB never gave any real credence to it being a missile. Neither did the FBI, for that matter. There was just never any evidence. The FBI had pretty much ruled out terrorism within 2 days of the accident.
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I'l let the boys at the AAIB know about the cause - that'll save a shit load of time and money - and I'll have a word with Boeing and see if they know about this 'redundancy' thing of whuch you speak.
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Re:Summary Correction (Score:5, Informative)
There are a set of interlocks involving both weight being present of the landing gear and the wheels rotating to prevent the reversers deploying.
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