"Investigators at first believed the plane landed nose-down -- because of the lack of wider destruction that would have resulted had it hit the ground at a shallower angle. That did not explain, however, why they found so many intact or nearly intact bodies so quickly."
Washington Post article, Published Nov, 15, 2001, Page A18
And I thought this article was like reading a horror story-never have a read a more devastating rendition of the conditions of the cabin during a mechanical failure in flight. Horrendous.
I really believe that all mechanics and other personnel associated with maintenance and repair of aircraft need to be vetted-yesterday.
How easy this author makes it seem for someone to clip a few critical wires within an engine, making cuts that bring down an airliner without fail. I wonder how the delayed flight of this airliner fits into this scenario? It would be so nice to know exactly what caused the delay in lift-off since the critical time for the sabotage suggested by the author means that the engines needed to be running for only a certain time before failure would occur. IF it was a terrorist, he sure as heck did not want the engines to start leaking before the plane was airborne. Timing was everything in this event. And there must be plenty of leads. I sure hope they are looking at ground crews-big time.
The only problem with it is that I thought Al Queda would only do showy attacks that were against targets where there would be no ambiguity over whether it's terrorism or not. We're going to know for sure what happened only when all the data is analyzed; I don't think this is the sort of dramatic attack bin Laden specializes in. By the time we know what happened to Flight 587, it will have long since been overtaken by subsequent events.
I just don't think it fits the big egos of Al Queda.
D
I have two questions:
1) Wouldn't an indicator ("idiot light") illuminate on the flight deck during the pre-flight checks, indicating a loss of hydraulic pressure in the left thrust-reverser?
2) What evidence do you have to show that a thrust-reverser would gradually slip into the acuated position when pressure is lost in the hydraulic line?
"The board [NTSB] confirmed that Flight 593's thrust reversers were stowed, the flaps were apparently retracted, and the landing gear was up when the plane went down."
As I have also pointed out, there are a number of cases where these large airliners have been returned to landing after losing their vertical stabilizer--the fact the stab was gone would not be expected to have caused the airplane to fall out of the sky either.
"This is way beyond my expertise. But the statement about the B-2 fly-by-wire requiring no vertical tail doesn't prove a thing. There's nothing resembling that kind of special computer controls in an Airbus." Cicero, you are wrong. To the contrary, the Airbus is a pure fly by computer airplane. And in fact, that should not make any difference either--unless the pilots made serious errors which do not appear in the record, if they could have hand flown the airplane, loss of the vertical stab would not have kept them from returning to make a safe landing. The pilots were dependant on a computer driven control system to fly the airplane--although most of the new commercial airliners are fly by wire airplanes (electrical inputs to a computer run the control surfaces), the Airbus is the most dependant on the electrical computer system.
"I, too, thought that was a bit off the wall... the B1 and B2 will NOT fly without computer assistance because of their inherent instability." (From Swordmaker)
Sure but so what--there are other airplanes out there that also do not have vertical stabilizers and which have no computer or electrical servo driven flying systems either--the Bonanza V34 is one example. Loss of the vertical stab did not have anything to do with this event either.
The author here advances an analysis that would account for the accident--uncommanded deployment of the thrust reverser. He accounts for the event by sabotage. Well and good--that is a possibility. "How easy this author makes it seem for someone to clip a few critical wires within an engine, making cuts that bring down an airliner without fail. I wonder how the delayed flight of this airliner fits into this scenario?" (By Republic) No. His suggestion is a little more complicated than that--his sabotaur was not cutting wires, he was cutting hydraulic tubeing which is a little more difficult and requires a fair amount of knowledge because there are a number of metal tubes up there and if you cut the wrong one, the fan simply does not spin. But his thesis is possible although I think remote. Your point about the late departure is however relevant--by the time they were off the ground, they would have run out of the sabotaur's time line which makes the authors suggestion a little less likely.
For one thing, no reason an uncommanded thrust reverser event requires sabotage--it happens more often than the flying public wants to know for a whole host of reasons other than sabotage. One of the Boeing airplanes had a reputation for regular uncommanded deployments because of some glitch in the way the systems were wired.
The pilot is trained to recognize the problem and the usual remedy ought to have been to cut power to the engine. Even if the pilots screwed up and failed to recognize the problem, they still had to make a number of other mistakes to get this result--it is possible but in my view remote. Further, if it happened that way, the NTSB would have jumped on it because they could have said it happened by accident. So I tend to doubt the evidence will support this series of events.
My own view is that there is much more likely series of events that explains the crash and those events start with an incendary device in the checked baggage compartment. That explanation also deals with another piece of evidence which is the reliable eyewitness testimony to fire at the root of the wings on both sides of the airplane.
The thrust reverser is driven by an air motor powered with pneudraulic (air) pressure drawn from a bleed air duct off the compressor. Connection between the air motor and the reverser cowls is accomplished with the use of flexshafts (flexible drive shafts).
The next morning about an hour after the jet engines were started, the hydraulic fluid now under pressure would drip from the cut line until none was left in the line and the thrust reverser would simply slowly drift into the full on condition while in flight and a catastrophic crash would occur only seconds later.
Hydraulic fluid under pressure wouldn't drip from a cut or severed line. It would fly out of there, rather like a severed artery. Any falling onto the hot section would cause a massive amount of smoke to come from the engine, enough that the ground start crew would stop the startup procedure. If it leaked out overnight, then it would have leaked through the cowling as well, and left a puddle on the ground.
With regards to the thrust reverser cowl "simply slowly" drifting into the full on condition. It would have to be driven into position by the flexshafts. At full power, depending on the model, the CF6 puts out between 40,000 and 72,000 pounds of thrust. Reverser cowls are driven into place and held there...because that much thrust will just blow them open.
Now we move into the realm of science fiction, or even fantasy. Suppose that there is a teleportation device, carried back to us by time travelers, to inject these mysterious occurrences into our everyday lives, at a time in history where there was great turmoil about bacteriological agents, and terrorist attacks using airliners. A small piece of a structural part on the tail surface of the airliner was teleported away, so it looked like a stress failure, and a small quantity of anthrax spores were teleported into the woman's nasal passages.
But of course there shall be developed much more rational explanations, for each of these seemingly unrelated events. Just keep in mind, that not all the frontiers have yet been explored, or even defined very well so far.
Cutting hydraulic lines before the engine is started guarantees a hydraulic fluid gusher that would be easily discerned before takeoff - it would take just a few seconds to gush ALL aircraft hydraulic fluid onto the runway - it works at 3000 psi.
All thrust reversers are manufactured and fitted with a system of locks and feedback mechanisms. Lock failures show up on the cockpit instruments, and having a red light on will prevent the flight from occurring. The feedback mechanism detects a thrust reverser starting to deploy, and then sends the hydraulic fluid to stow the reverser before it can deploy. If they can't fix the T/R system on the ground, then they put a pin in the reverser structure to prevent commanded or uncommanded deployment.
After the Air Lauda crash in Thailand, caused by a T/R inadvertently deploying, all aircraft makers had to declare their aircraft either reliable or controllable. The big twins like the A300 are not controllable with a T/R deployed, so they had to go the reliability route and install a better safety system with 3 redundant locks. There was a deadline to do it, which has passed, I think. Therefore, it's highly likely that this aircraft had the redundant system installed.
The author is correct that an in-flight T/R deployment would cause the aircraft to fly approximately the way it did. It was the first comment in my office after the crash - it may be a T/R deployment. But the statements from the NTSB make it clear that the T/R's were not the cause.
I've previously offered two probable causes to this crash - a rudder partially breaking loose from the vertical tail, causing high static and dynamic loads before it departs the aircraft; or a latent structural defect in the vertical tail skins that was excited by either the wake turbulence or anomalous rudder operations.
As I've stated before, I am an aerospace engineer at a company that makes engine nacelles, including thrust reversers.
From witnesses on the ground indicate the aircraft was experiencing a compressor surge in one of the engines. The popping sound and flames are the trademarks. A compressor surge used to be common with older engine but rare by today's standards with the digital engine controls. The compressor surges, putting out the flame within the engine, the engine loads up with unburnt fuel and when the engine goes into automatic restart, it produces a loud bang and lots of flames. Most engines are made to withstand these backfires but last year; an Alaska 757 had a serious compressor surge that blew off the front cowl of the engine, damaging the engine and wing which forced an emergency landing. They can be quite violent. Witnesses stated that the engine made popping sound and flame could be seen between the wing and body. They also state that parts of the wing left the aircraft and hit the tail. The one report indicates that the flaps were fully retracted as indicated by the black box but have all the panels been accounted for on the ground? I am curious as to what else was they had dredged from the bay.
The flat spin does account for the break up of the aircraft and lost of vertical surfaces but the cause still seems to be engine failure with possible damage to flight surfaces. The full thrust of one engine without rudder control would put it into flat spin. The popping sounds heard would indicate that one engine was not working properly. Fuel delivery seemed to be intermittent or low. The rumblings may be key.
My theory is a main tire exploded after stowing (first rumble), causing damage to fuel feed line and pumps within the wheel well. This downed a 727 in Mexico in the 70s which caused the segregation and protection of hydraulics and fuel lines running within the wheel wells. This lesson has been lost on modern aircraft designers which routinely run hydraulics and fuel lines through the wheel wells without any shrapnel protection. The second rumble was the engine starting to miss from lack of fuel and going into a series of compressor surges that loosen something that hit the tail causing lost of rudder control (three violent full swings were recorded).
The crash and fire usually make analysis of wheel failure impossible to determine but I would start looking there.
I guess I fall in the sabateur column on this one, but believe explosives started the mechanical failures. I also think it happened in NY to rub salt in wounds not healed yet. And that it crashed into Rockaway is simply chilling.
Whatever happened-this discussion has been remarkable. And it reflects what many of us hunger for when we drop into our FR world-top notch debate of issues and ideas. This thread is a TEN in my book!