New Clues deepen AA587 Crash Mystery
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NEW YORK (AP) - Neither turbulence from another jet nor pressure placed on the rudder by a desperate pilot should have been enough to snap off the tail of Flight 587, aviation experts said Friday - raising the prospect that something was wrong with the plane before it left the ground.
"I think there was a pre-existing structural problem with the tail,'' said Greg Feith, a former National Transportation Safety Board investigator. "It was going to fail regardless. It just so happened the conditions were right.''
The American Airlines Airbus A300 plunged into a New York neighborhood Monday, shortly after taking off from Kennedy Airport for the Dominican Republic. The crash killed all 260 people aboard and five more on the ground.
The cause of the crash has not been determined, but investigators have focused on the jetliner's tail assembly, which came off sometime before the crash.
The Federal Aviation Administration on Friday ordered airlines to immediately inspect the tail assemblies of their Airbus A300-600 and A310 planes. American and two cargo carriers, FedEx and United Parcel Service, have about 135 of the French-made jets in their fleets.
The FAA said no conclusions have been reached about whether the tail was related to the accident, but called the inspections a "prudent'' move.
Airbus A300 Tail Assembly diagram. Click Image For Larger View. (File Photo/National Transportation Safety Board).
NTSB Chairman Marion Blakey said the frantic efforts of the pilots aboard Flight 587 to save their plane also should provide clues to what went wrong.
"We do know, just from what we can see on the flight data recorder, that the pilots were trying to actively fly that plane out of the problem,'' Blakey told the Associated Press, cautioning that this does not imply pilot error. Investigators have already suggested the pilots wouldn't have known the tail fin was missing.
"It seems to me this was a very extraordinary crash. In fact, we don't have a parallel,'' Blakey said before she and other investigators left New York for Washington, where the inquiry will continue for months.
Investigators say Flight 587 shook violently from side to side after encountering two wakes generated by a Japan Air Lines 747 that took off about two minutes earlier from the same runway at Kennedy. Because of its size and weight, the four-engine 747 generates heavy turbulence.
While Flight 587 was more than four miles behind the JAL jumbo jet, as required by FAA regulations, NTSB spokesman Keith Holloway said the agency was looking at whether to suggest keeping planes farther apart, since wakes dissipate over distance.
Experts suggested more distance wasn't needed in this case.
"The wake vortex of a 747 should not bring down an aircraft,'' said Tom Ellis, a spokesman for the Nolan Law Group, a Chicago firm that represents victims of airline accidents.
"The A300 is designed to withstand forces of that nature. It should be well within its design tolerance. There's got to be something that interferes with the ability to recover.''
Based on information from the flight data recorder, investigators found that the plane's rudder moved sharply during the jetliner's three-minute flight.
Experts said the movement could have resulted from the pilot hitting the rudder pedal hard or from a jerk on the other end of the cable as the tail snapped off. But pilots of large planes don't usually use the rudder, except when they lose an engine or for help during landings.
"How did the pilots react?'' Blakey asked. "What did happen? Was it that reaction, or was it something mechanical?''
Examination of the two black boxes - the data recorder and the cockpit voice recorder - indicates the pilots were "working hard'' in the cockpit before the plane plummeted into the Rockaway Beach section of Queens, she said.
At one point, the pilots tried to use maximum power to regain control. But they were probably unaware the jetliner's tail had broken away, and the NTSB's George Black Jr. said calling for maximum power suggested they were in "recovery mode.''
"And they might be recovering from the wrong thing, because they don't know'' about the missing tail, he said.
Even if the pilots were rough with the rudder, that should not have caused the tail fin to fall off, said David Stempler, president of the Air Travelers Association, an advocacy group.
"Planes should be designed to withstand even abuse and still be able to maintain structural integrity,'' Stempler said. "The pilots may have done something but a plane has to be designed to even withstand harsh treatment by flight crews and not lose major structural elements.''
That has led several aviation experts to suggest that there was some unseen weakness in the tail assembly, which was made of carbon-reinforced plastic, a composite material that is lighter than aluminum.
The tail fin was held to the fuselage by six fittings. Maintenance records indicate that one of the fittings had to be repaired by the manufacturer before the plane was delivered to American Airlines in 1988.
The problems could have dated from 1994, when the jetliner was severely shaken by air turbulence, injuring 47 people. The plane was inspected following the incident.
"That's where the investigation really has to start,'' Feith said. "It may be the inspection was just a visible inspection. They're not going to be looking inside that fin area, they're going to be looking for obvious damage. Something could have happened that, although it didn't immediately fail the tail at that point, did set up a fail scenario.''
"I think there was a pre-existing structural problem with the tail,'' said Greg Feith, a former National Transportation Safety Board investigator. "It was going to fail regardless. It just so happened the conditions were right.''
The American Airlines Airbus A300 plunged into a New York neighborhood Monday, shortly after taking off from Kennedy Airport for the Dominican Republic. The crash killed all 260 people aboard and five more on the ground.
The cause of the crash has not been determined, but investigators have focused on the jetliner's tail assembly, which came off sometime before the crash.
The Federal Aviation Administration on Friday ordered airlines to immediately inspect the tail assemblies of their Airbus A300-600 and A310 planes. American and two cargo carriers, FedEx and United Parcel Service, have about 135 of the French-made jets in their fleets.
The FAA said no conclusions have been reached about whether the tail was related to the accident, but called the inspections a "prudent'' move.
Airbus A300 Tail Assembly diagram. Click Image For Larger View. (File Photo/National Transportation Safety Board).
NTSB Chairman Marion Blakey said the frantic efforts of the pilots aboard Flight 587 to save their plane also should provide clues to what went wrong.
"We do know, just from what we can see on the flight data recorder, that the pilots were trying to actively fly that plane out of the problem,'' Blakey told the Associated Press, cautioning that this does not imply pilot error. Investigators have already suggested the pilots wouldn't have known the tail fin was missing.
"It seems to me this was a very extraordinary crash. In fact, we don't have a parallel,'' Blakey said before she and other investigators left New York for Washington, where the inquiry will continue for months.
Investigators say Flight 587 shook violently from side to side after encountering two wakes generated by a Japan Air Lines 747 that took off about two minutes earlier from the same runway at Kennedy. Because of its size and weight, the four-engine 747 generates heavy turbulence.
While Flight 587 was more than four miles behind the JAL jumbo jet, as required by FAA regulations, NTSB spokesman Keith Holloway said the agency was looking at whether to suggest keeping planes farther apart, since wakes dissipate over distance.
Experts suggested more distance wasn't needed in this case.
"The wake vortex of a 747 should not bring down an aircraft,'' said Tom Ellis, a spokesman for the Nolan Law Group, a Chicago firm that represents victims of airline accidents.
"The A300 is designed to withstand forces of that nature. It should be well within its design tolerance. There's got to be something that interferes with the ability to recover.''
Based on information from the flight data recorder, investigators found that the plane's rudder moved sharply during the jetliner's three-minute flight.
Experts said the movement could have resulted from the pilot hitting the rudder pedal hard or from a jerk on the other end of the cable as the tail snapped off. But pilots of large planes don't usually use the rudder, except when they lose an engine or for help during landings.
"How did the pilots react?'' Blakey asked. "What did happen? Was it that reaction, or was it something mechanical?''
Examination of the two black boxes - the data recorder and the cockpit voice recorder - indicates the pilots were "working hard'' in the cockpit before the plane plummeted into the Rockaway Beach section of Queens, she said.
At one point, the pilots tried to use maximum power to regain control. But they were probably unaware the jetliner's tail had broken away, and the NTSB's George Black Jr. said calling for maximum power suggested they were in "recovery mode.''
"And they might be recovering from the wrong thing, because they don't know'' about the missing tail, he said.
Even if the pilots were rough with the rudder, that should not have caused the tail fin to fall off, said David Stempler, president of the Air Travelers Association, an advocacy group.
"Planes should be designed to withstand even abuse and still be able to maintain structural integrity,'' Stempler said. "The pilots may have done something but a plane has to be designed to even withstand harsh treatment by flight crews and not lose major structural elements.''
That has led several aviation experts to suggest that there was some unseen weakness in the tail assembly, which was made of carbon-reinforced plastic, a composite material that is lighter than aluminum.
The tail fin was held to the fuselage by six fittings. Maintenance records indicate that one of the fittings had to be repaired by the manufacturer before the plane was delivered to American Airlines in 1988.
The problems could have dated from 1994, when the jetliner was severely shaken by air turbulence, injuring 47 people. The plane was inspected following the incident.
"That's where the investigation really has to start,'' Feith said. "It may be the inspection was just a visible inspection. They're not going to be looking inside that fin area, they're going to be looking for obvious damage. Something could have happened that, although it didn't immediately fail the tail at that point, did set up a fail scenario.''
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Late in the day, and I have only scanned all the above, but....
composites, or more correctly plastic polymer composites, do degrade with age - they constantly release fumes (smell plastic boats, etc.) i.e lose molecules so that the resin that glues it all together changes. Some polymer resins do this more quickly than others - it's the same in all plastics. Many such products have an expiry date, others rely on obselescence or changing fashion.
Do we have a polymer expert in the house?
....this in addition to the other aspects like wake, A/C handling, etc.
WE (NOT an expert!)
composites, or more correctly plastic polymer composites, do degrade with age - they constantly release fumes (smell plastic boats, etc.) i.e lose molecules so that the resin that glues it all together changes. Some polymer resins do this more quickly than others - it's the same in all plastics. Many such products have an expiry date, others rely on obselescence or changing fashion.
Do we have a polymer expert in the house?
....this in addition to the other aspects like wake, A/C handling, etc.
WE (NOT an expert!)
ex-Tanker
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Caveman,
Somewhere in your post it mentions that there has never been a similar case. There has actually, strangely enough to a JAL 747, where the vertical stab was lost following a depressurisation through the rear pressure dome into the fin structure.
Those gallant guys managed to keep the ship airborne for over 40 minutes before coming to the same conclusion that they had no chance. There was one survivor, who still appears on TV from time to time.
Somewhere in your post it mentions that there has never been a similar case. There has actually, strangely enough to a JAL 747, where the vertical stab was lost following a depressurisation through the rear pressure dome into the fin structure.
Those gallant guys managed to keep the ship airborne for over 40 minutes before coming to the same conclusion that they had no chance. There was one survivor, who still appears on TV from time to time.
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I would have thought a couple of camera's covering giving a external view of the aircraft would be a help, instrumentation is fine but sometimes a analog view can save a lot of confusion.
It seems crazy that in some circumstances the crew have to come into the cabin and look out a port to see what the problem is.
It probably wouldn't have helped in this case,, but at least they would have known the tail was gone.
It seems crazy that in some circumstances the crew have to come into the cabin and look out a port to see what the problem is.
It probably wouldn't have helped in this case,, but at least they would have known the tail was gone.
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The only time I have had a bit of the aeroplane fall off it was a section of the leading edge slats. Examination of the remaining sections revealed a honeycomb structure behind the shiny leading edge.
That was a 757 which would have been about 14 years old at the time.
That was a 757 which would have been about 14 years old at the time.
Keeping Danny in Sandwiches
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Surely
1. If the VS and Rudder become detached they take the hydraulic fluid and therefore power with them unless there are rapid shut off valves in the lines. If there was no hydraulic power to the flight controls and no rudder to provide yawing stability whatever the crew do after that is of little consequence.
2. On a Boeing Rudder Ratio ensures that full rudder cannot be put on at high speed, I would not expect Airbus to be any different. There really cannot be anyway that gross mishandling could even be considered as a cause.
1. If the VS and Rudder become detached they take the hydraulic fluid and therefore power with them unless there are rapid shut off valves in the lines. If there was no hydraulic power to the flight controls and no rudder to provide yawing stability whatever the crew do after that is of little consequence.
2. On a Boeing Rudder Ratio ensures that full rudder cannot be put on at high speed, I would not expect Airbus to be any different. There really cannot be anyway that gross mishandling could even be considered as a cause.
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Interesting article with pics on ANN Aero-News network for 11/16/01
http://www.aero-news.net/indexnews1.htm
Also, the FAA Airworthiness Directives:
http://av-info.faa.gov/ad/PublishedADs/011609.html
[ 17 November 2001: Message edited by: JudyTTexas ]
http://www.aero-news.net/indexnews1.htm
Also, the FAA Airworthiness Directives:
http://av-info.faa.gov/ad/PublishedADs/011609.html
[ 17 November 2001: Message edited by: JudyTTexas ]
quidquid excusatio prandium pro
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Few Cloudy,
The JAL 747 you refer to did lose portions of its vertical stab, but the primary problem caused by the aft pressure bulkhead blowing was the rupture of the hydraulic lines of all four systems and subsequent total fluid loss. The aircraft did remain airborne for over 30 minutes, the crew had differential thrust for roll control and alternate flap extension for pitch control. For some reason they were not able to steer it away from mountainous terrain. It is a difficult business, but most crews after some practice in the sim are able to bring it home. This unfortunate crew, I believe, were the first to encounter it.
There were 24 survivors of that accident, there should have been many more. In a remarkably shameful display of bureaucratic bungling, the Japanese authorities decided that a crash into mountains is simply not survivable, and so went home to bed. The aircraft impacted the mountain side at approximately 6:30 pm, the first rescue teams arrived at around six the next morning. All the survivors were in reasonably good condition, they would have had to be in order to survive the night.
The JAL 747 you refer to did lose portions of its vertical stab, but the primary problem caused by the aft pressure bulkhead blowing was the rupture of the hydraulic lines of all four systems and subsequent total fluid loss. The aircraft did remain airborne for over 30 minutes, the crew had differential thrust for roll control and alternate flap extension for pitch control. For some reason they were not able to steer it away from mountainous terrain. It is a difficult business, but most crews after some practice in the sim are able to bring it home. This unfortunate crew, I believe, were the first to encounter it.
There were 24 survivors of that accident, there should have been many more. In a remarkably shameful display of bureaucratic bungling, the Japanese authorities decided that a crash into mountains is simply not survivable, and so went home to bed. The aircraft impacted the mountain side at approximately 6:30 pm, the first rescue teams arrived at around six the next morning. All the survivors were in reasonably good condition, they would have had to be in order to survive the night.
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Wangeye , the smell in boats is Polyester resin . There is no place , even in tertiary structure , that polyester is used. Most primary and secondary stucture composites are made from Epoxy resin cured at either 120 or 170 deg c ususally in an autoclave at up to 100 psi. Boats on the other hand are usually made from chopped mat impregnated with polyester resin and cured at room temp with no pressure.
The main cause of degradation of Epoxy resins is exposure to UV light which is why it is important to ensure the paint is not damaged. Part of the qualification process for a new composite material involves long term exposure to extreme temperatures and levels of humidity. In the early 70's I worked on a program at Westlands to qualify several Ciba resin systems , this involved sending test coupons to Australia and Central America for long term exposure testing . The results of these test are used in determining the margins of safety used in design of composite structures. That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure . The hardest thing in the design of any composite part is attatching it to anything , the ratio of bearing strength to ultimate strength is far lower in composite materials when compared to metals , which is why attatch lugs on composite assemblies have to be much larger in relation to a similar metal structure with similar loads . Sorry to ramble on !!!.
The main cause of degradation of Epoxy resins is exposure to UV light which is why it is important to ensure the paint is not damaged. Part of the qualification process for a new composite material involves long term exposure to extreme temperatures and levels of humidity. In the early 70's I worked on a program at Westlands to qualify several Ciba resin systems , this involved sending test coupons to Australia and Central America for long term exposure testing . The results of these test are used in determining the margins of safety used in design of composite structures. That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure . The hardest thing in the design of any composite part is attatching it to anything , the ratio of bearing strength to ultimate strength is far lower in composite materials when compared to metals , which is why attatch lugs on composite assemblies have to be much larger in relation to a similar metal structure with similar loads . Sorry to ramble on !!!.
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Thanks again to everybody contributing and detailing with interesting infos.
Do you think we can resume that for any particular reason the tail composite section has lost its full aeroelastic strength and so the associated resonance frequency was perturbated till the separation?
Let's hope our aviation world will begin soon to move up again...
Do you think we can resume that for any particular reason the tail composite section has lost its full aeroelastic strength and so the associated resonance frequency was perturbated till the separation?
Let's hope our aviation world will begin soon to move up again...
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Folks,
I was over in Blighty when I heard of AA's latest 'trouble'. As is usually the case, "experts"-particularly terrorism experts-were wheeled out to speculate their best(wild) guesses on us.
As heartbreaking as the subject is, I have to say that this is one of the best threads (which for the most part has stayed on topic) I've recently come across. Ppruners should be commended for their mostly wait and see attitude.
Belgique, and others, your insight and comments is enlightening.
Some FYI..
A few years ago AA adopted slightly different unusual attitude recovery techniques. One of the main points was that pilots weren't always using enough rudder during recovery. Several simulator unusual attitude recovery scenarios now call for "unloading" the wing by applying forward yoke pressure and using (coordinated) rudder inputs to level the wings.
As terrible as this incident (coupled with events on September 11th) is, the point should not be lost that despite being issued challenges that were insurmountable, these proffessional pilots did their ABSOLUTE BEST, as they were trained to.
It may well be that none of the five recent hull losses can be blamed on the ubiquitous "pilot error" caveat. That would be the only silver lining.
God bless them all,
Cheers,dd.
I was over in Blighty when I heard of AA's latest 'trouble'. As is usually the case, "experts"-particularly terrorism experts-were wheeled out to speculate their best(wild) guesses on us.
As heartbreaking as the subject is, I have to say that this is one of the best threads (which for the most part has stayed on topic) I've recently come across. Ppruners should be commended for their mostly wait and see attitude.
Belgique, and others, your insight and comments is enlightening.
Some FYI..
A few years ago AA adopted slightly different unusual attitude recovery techniques. One of the main points was that pilots weren't always using enough rudder during recovery. Several simulator unusual attitude recovery scenarios now call for "unloading" the wing by applying forward yoke pressure and using (coordinated) rudder inputs to level the wings.
As terrible as this incident (coupled with events on September 11th) is, the point should not be lost that despite being issued challenges that were insurmountable, these proffessional pilots did their ABSOLUTE BEST, as they were trained to.
It may well be that none of the five recent hull losses can be blamed on the ubiquitous "pilot error" caveat. That would be the only silver lining.
God bless them all,
Cheers,dd.
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Assuming the cause of the AA accident was the failure of the vertical stabiser, I wonder what the long term implications are for all Airbus aircraft that use this type of material. Indeed what are the legal implications for Airbus if this involves faulty manufacturing. Looking back at two 707 accidents during its early days of introduction, (Braniff and a PANAM freighter) where uncontrollable Dutch rolls threw off a number of engines, I can only assume that failure of the vertical stabiliser would cause an immediate and agressive Dutch roll which would throw off the engine pods. It would appear that both engines of the AA Airbus were detached from the aircraft before it hit the ground.
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I'll freely admit my total ignorance of aircraft composites, but according to other posts, the vertical stabilizer was repaired during manufacture by attaching a doubler onto the base of the stabilizer, along with some rivets. I know that in the case of ordinary fiberglass, you have to be *very* careful with fitting anything where it isn't designed to be fitted, because you are putting a hole in something that depends on not having holes for a large portion of its strength. Also, rivets provide a channel for moisture ingress into the core of the structure, which can cause later delamination. Could the manufacturing repair be the root cause of this accident?
Sympathies to all those affected by this dreadful accident.
Sympathies to all those affected by this dreadful accident.
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posted by Satrun V (pg 1) quoting news source
"The vertical tail section of American Airlines Flight 587 cracked off when its modern reinforced plastic "composite" fittings failed, investigators said today...
"Before the plane was delivered in 1988, the composite material in one of the six fittings holding the tail in place was found to be delaminating, meaning its layers were coming apart. It was fixed by adding layers and inserting rivets, and the manufacturer decided that no extra inspections were required afterward.
posted by widgeon (pg 6)
.... That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure ...
"The vertical tail section of American Airlines Flight 587 cracked off when its modern reinforced plastic "composite" fittings failed, investigators said today...
"Before the plane was delivered in 1988, the composite material in one of the six fittings holding the tail in place was found to be delaminating, meaning its layers were coming apart. It was fixed by adding layers and inserting rivets, and the manufacturer decided that no extra inspections were required afterward.
posted by widgeon (pg 6)
.... That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure ...
assembly was identified as defective at a high stress point - then repaired, not replaced? I am sure the manufacturer avoided a costly replacement with that procedure. Might make sense if reliable inspection procedures existed to identify deterioration as it aged. Hey, it held for 11 years! Too bad that is not the lifetime of the aircraft.
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The FAA has issued an AD to inspect A300/A310 vertical stabilisers:
http://av-info.faa.gov/ad/PublishedADs/012351.pdf
http://av-info.faa.gov/ad/PublishedADs/012351.pdf
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How does the vertical stabiliser of the A300B series compare with the -600? If time-related degradation of the composite is a factor, those guys should be running on empty...
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RTFI
bad taste plain & simple. are you implying that airbus would conciously put pax at risk to save remanufacturing a part? idiot.
I'm not saying Airbus did this either, but there are precedents where large corporations - US automobile manufacturers have been caught out here - have made safety based decisions based purely upon cost. Who had to pay out loadsamoney when a memo was found saying it was cheaper to pay the lawsuits resulting from a bad design than fix the design itself? Business decided not to to recall the cars.
Same with seats in exit rows, putting water sprinklers in the cabin to suppress smoke, 737 rudder design, the list goes on....
Cost ALWAYS comes into the picture.
So what would have been the procedure for repairing and approving this part? It's an expensive part, certainly.
I had a chat last night with an engineer who works for a large company who manufactures these composites for aircraft - non structural only. I asked him what statistical methods were used to make sure a composite (which apparently can only confidently be said to be in good shape after you have destroyed it
) was OK to fly. The guy laughed at me and said those sort of statistics didn't really exist in aerospace. He implied that when they put an expensive part in the autoclave for curing, they will put a little test piece in there with it. They destructively test the small piece, if it passes, the large part passes too!
If they have put [i]two[/] large and expensive parts in the autoclave, and the test part fails, they destroy one of the large expensive parts. If that passes, the other large expensive part passes.
So where the hell is the science in that? Will somebody please say that's not true, or at least we shouldn't worry.
bad taste plain & simple. are you implying that airbus would conciously put pax at risk to save remanufacturing a part? idiot.
I'm not saying Airbus did this either, but there are precedents where large corporations - US automobile manufacturers have been caught out here - have made safety based decisions based purely upon cost. Who had to pay out loadsamoney when a memo was found saying it was cheaper to pay the lawsuits resulting from a bad design than fix the design itself? Business decided not to to recall the cars.
Same with seats in exit rows, putting water sprinklers in the cabin to suppress smoke, 737 rudder design, the list goes on....
Cost ALWAYS comes into the picture.
So what would have been the procedure for repairing and approving this part? It's an expensive part, certainly.
I had a chat last night with an engineer who works for a large company who manufactures these composites for aircraft - non structural only. I asked him what statistical methods were used to make sure a composite (which apparently can only confidently be said to be in good shape after you have destroyed it
) was OK to fly. The guy laughed at me and said those sort of statistics didn't really exist in aerospace. He implied that when they put an expensive part in the autoclave for curing, they will put a little test piece in there with it. They destructively test the small piece, if it passes, the large part passes too!If they have put [i]two[/] large and expensive parts in the autoclave, and the test part fails, they destroy one of the large expensive parts. If that passes, the other large expensive part passes.
So where the hell is the science in that? Will somebody please say that's not true, or at least we shouldn't worry.
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Just by looking at the engine size and its location from the body of A300, doesn't it appear to be way in front of the leading edge of the wing? Wouldn't this produce a huge torque when the plane encounters a severe side force such as when it first enters a wake turbulence?
I haven't read all the posts and reports on the accident, but has this possibility been discussed before to explain the engine loss?
[ 17 November 2001: Message edited by: 747dreamer ]
[ 17 November 2001: Message edited by: 747dreamer ]
I haven't read all the posts and reports on the accident, but has this possibility been discussed before to explain the engine loss?
[ 17 November 2001: Message edited by: 747dreamer ]
[ 17 November 2001: Message edited by: 747dreamer ]