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AA 587 -- Vertical stabilizer & composites (thread#3)

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AA 587 -- Vertical stabilizer & composites (thread#3)

Old 20th Nov 2001, 03:58
  #21 (permalink)  
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Thanks for the NTSB reference. It is actually these pictures that are causing me to question the 'composite' theory.

I did study all of the pictures and became so confused it was necessary to break out the sketch pad and reconstruct the VS attachments on paper.

First, this picture seems to suggest a forward-starboard to aft-port removal of the VS.

Second, these look to be the two bottom forward brackets. These would be the bottom attachments which are constructed of metal.

From this second image, it appears that one of these bottom brackets failed. I believe it is the starboard bottom bracket which is bent up and back.

Hypothetically, IF the bottom bracket was the first point in the VS connection to fail, it is possible that all other failures (composite) were a direct result of the lost structural integrity (especially when combined with the resulting torque of 'rock and roll'). The fact that both forward top tonques are obviously broken, would be consistant with the above scenario. On the other hand, I cannot image a scenario where any of the broken tongues would cause the resulting failure of that bottom bracket.

After searching the internet, looking for some serious and informed discussion on the accident, I've landed here at pprune. Subsequently, I have a healthy disquiet related to the use of composite in airplanes. However, that one picture of the forward (bottom) brackets keeps sending me in a different direction on this particular case.
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Old 20th Nov 2001, 04:27
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Take it easy on the Spaniards.
The fin is and always has been designed and manufactured by the Germans (MBB/Deutsche Airbus/Daimler-Benz Aerospace Airbus/Daimler-Chrysler Aerospace Airbus/EADS Airbus/Airbus Germany or whatever).

The fin is pretty much a one shot process and there were some problems on a limited number of fins where rework /replacement was required due to disbonding.

For what it's worth my tuppence worth is that the aircraft experienced a divergent oscillatory vibration mode resulting in rudder control reversion subsequent to structural damage to the fin front spar attachment.

But I'll leave the speculation to the experts
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Old 20th Nov 2001, 04:27
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Samgop, the news reports that the vertical stab fractured above the attachment points was reported in both the New York Times and Washington Post. Given the dates these articles appeared, it would seem this information came from NTSB or FAA sources and not as part of a general press briefing. The NTSB and FAA were supposedly sending their top materials experts to examine the stab around November 14 and 15. (The last NTSB on-site press conference was on November 15, and given the publication dates, the info was probably 'released' on November 16 or 17, perhaps in conjunction with issuance of the inspection orders. As to the fracture point itself, the investigators have the good fortune of having a relatively 'pristine' vertical stab to examine; I suspect that the composite material around the attachment points and the empennage was largely destroyed by fire.

Trader Al, even the most rabid conspiracy theorists have yet to describe a single piece of evidence supporting the notion that AA597 was hit by a missile. TWA 800 suffered from a mid-air explosion (AA587 crashed largely intact and no evidence of an explosion); numerous witnesses said they saw an arc of light heading toward TWA 800 (witnesses of the entire flight of AA587 have not reported seeing any missile trail); the TWA 800 flight and data recorders stopped immediately (unlike AA 587 where the cockpit voice recorder worked until impact and there are no sounds of or pilot statements about an 'explosion'), and a large piece of AA587 has been found with an obvious failure point.
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Old 20th Nov 2001, 05:26
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In response to the TraderAl post speculating that a man-portable surface-to-air missile, such as a Stinger, might have brought down AA587:

The Stinger has a "small" fragmentation warhead that is designed to explode in close proximity to its target. It is a heat-seeking missile that aims for exhaust heat provided by the engine(s). Apparently, neither engine, nor for that matter the airframe itself, has been reported to have had fragmentation damage. The photos of the engine that landed at the gas station doesn't appear to have any fragmentation damage.

The targets that "China Lake" reports to have broken up in flight were probably either target drones or remote controlled fighter jets such as QF-4's. These are much smaller targets than an A300 and are generally flown at high subsonic or supersonic speeds to pose challenging targeting problems for the seeker to resolve.

That these targets would break up in flight when hit is expected. If the target drone or QF-4 lost flight path control when hit the resulting aerodynamic loads would likely cause major structural failure.

Also, there has apparently been no "foreign" debris found consistent with a missile. Recognizable pieces of the missile would probably be found if the airplane had been hit over land. Also, unlike TWA 800, there have been no reports of a missile plume streaking from the ground to hit the airplane.

Also, I recall reading a report of a business jet-sized airplane with twin tail-mounted engines, that had been hit by a Stinger-type, man-portable surface-to-air missile. The pilot successfully landed that airplane. It is possible for a large airplane to survive a Stinger hit.

Whatever, the cause of AA587's crash, it is highly unlikely that it had anything to do with a man portable surface-to-air missile.
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Old 20th Nov 2001, 07:46
  #25 (permalink)  
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Samgop, the twisted black piece of metal sticking up between the left and right forward attachment brackets is a black herring. It definitely obscures the other bracket, but what can be seen of the bracket behind looks sound.

PS. Our excellent host may prefer you post a URL rather than entire images as it beats up the bandwidth.
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Old 20th Nov 2001, 08:35
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DagDabIt! That explains why I couldn't match up the rivets (asymetrically don't ya know).

Obviously a composite failure then. Really blows a hole in my day, since I'll be a PAX on an A-300 in three weeks. Unlike most of us in the lower 48, I'd rather blame the 'evil doers' then the darned plane I'll be riding on next month. Playing the odds and all that...

I could always change my ticket, but then that would be giving in wouldn't it?

On third thought...the stinger thing sounds good, think I'll stick with that until my plane lands...

PS. bandwidth noted and understood.
PPS. 'black herring'...HA!
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Old 20th Nov 2001, 10:54
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Monday November 19, 6:35 pm Eastern Time
American Finds No Problems in Checks
By John Crawley

WASHINGTON (Reuters) - American Airlines said on Monday it had completed the
Airbus A300 tail and rudder inspections ordered by the government after last
week's crash of Flight 587 in New York and found no safety problems.

The Federal Aviation Administration ordered the checks of 34 American planes
and aircraft operated by other carriers on Friday after the ill-fated
jetliner, an A300-600, lost its vertical stabilizer, or tail fin, and rudder
before slamming into a residential neighborhood near John F. Kennedy
International Airport last Monday.

All 260 people aboard the aircraft and at least five on the ground were

The order to inspect the tail area and certain rudder parts also included
Airbus A300-series aircraft operated by major cargo carriers, United Parcel
Service Inc. (NYSE:UPS - news) and FedEx Corp. (NYSE:FDX - news)

Both of those companies said on Monday they were making good progress on
completing their checks and like American, which is an AMR Corp. (NYSE:AMR -
news) unit, had turned up no safety problems. FedEx flies 37 Airbus models
affected by the order, while UPS has 18.

While investigators do not yet know what caused the Flight 587 crash, they
focused heavily on the composite makeup of the tail section of the A300-600
series and extreme rudder movements just after the doomed aircraft passed
through a relatively common bout of turbulence from a bigger plane flying
several miles ahead.

The inspection order, which was duplicated by the French civil aviation
authority, DGAC, underscored concern there may have been a flaw with the
tail fin's composite materials that are becoming more widely used in
commercial aircraft construction.

The aircraft models singled out for inspection were not grounded.

Authorities required visual checks of the tail area for corrosion, cracks,
abrasions or other surface damage. The checks also covered any visible
imperfections in the composite structure of the fin.

Regulators also ordered carriers to be on the lookout for moisture damage on
aircraft that fly frequently over water or through very humid areas, like
the Caribbean.

The inspections also included hinges and other parts on the rudder that make
it move.

Some experts questioned whether visual inspections would be detailed enough,
especially for detecting flaws in composites, which are complex to analyze.

Nevertheless, Marion Blakey, the chairwoman of the National Transportation
Safety Board, said the inspection regimen was a good first step.

"These initial inspections will give us a good indication of what needs to
be done,'' Blakey told reporters at NTSB offices on Monday.

Blakey and other senior board officials said on Monday that investigators
had completed their initial review and transcription of the cockpit voice
recorder and found nothing from that analysis to change their belief that
the crash was an accident.

"We continue to not have anything that points to terrorism,'' Blakey said.
"But we are not ruling anything out at this time.''

She said the more detailed examination of the voice recorder also did not
change what investigators had already said about flight operations. "We
don't think anything is different in the cockpit. It initially was a normal
flight,'' Blakey said.

"At the end it becomes clear they lost control of the aircraft,'' Blakey

Investigators are scrutinizing the last eight seconds of the flight data
recorder, which ended about 20 seconds before the cockpit recording
concluded, presumably at impact.

A key focus remains on turbulence from a Japan Airlines 747 flying in front
of the American plane.

Investigators believe that upset would not typically cause problems for a
plane the size of the Airbus A300, and initial indications showed the
ill-fated aircraft flew through the two waves of "wake turbulence'' without
a problem.

But three severe rudder movements after this were consistent with three
lateral jolts of the aircraft, which occurred seconds before the plane
spiraled into the ground.

Flight 587 was headed from New York to Santo Domingo, the capital of the
Dominican Republic.

Note: I work for one of the other A300 operators. As of this evening, about half of our fleet had been inspected with no major problems (some surface anomalies; "sanded out") I question whether visual inspection is adequate under the circumstances. I would have thought higher time/cycle aircraft would have been subject to VS removal and ultrasound/x-ray testing.
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Old 20th Nov 2001, 18:34
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An interesting article from today's NY Times concerning piloting techniques that may have contributed to the accident.

I seem to remember, from some years ago, being warned of fin-stall problems on the C130 should too much rudder be applied too rapidly.

NY Times Region: Inquiry Focus
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Old 20th Nov 2001, 19:08
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Gregga and Capt PPrune;

In North America, if one hears hoof beats behind you one assumes that it is likely a horse, not a zebra.

Dependent and independent variables and all that.

Gregga, the China Lake tests were carried out on a Tomcat on a tower with a full FBI team to develop forsenic patterns for future terrorist detection. As little as I can gleam, a stinger, in daytime, leaves little missile trail as it tavels at Mach 4, which would be maybe 1.5 seconds at 1500 to 2900 feet. There is little missile trail, if any. Also, again based on the little that I know, a stinger does not drop a plane with fragmentation or a large combustile explosion, but rather with a sharp hard explosion of about 2 pounds of some explosive which through shock waves "breaks" off pieces of the plane. While it is infra guided, it is not infra triggered, but depends on a rather complex program to allow explosion prior to blasting past a contail. At that attitude, traveling at Mach 4, it would not hit the engine, but seek proximity, likely blowing as it streaks by on a trajectory that woudl be 90 degrees, roughly, to the climbing plane. The blast, as the plane flies overhead, would be behind the engines and perhaps above the center line. The stinger would trigger at the point it felt it was about to pass the plane. The stinger explosion is white and very bright, which like a photo flash in daytime could be missed.

I cannot find any information regarding the actual forsenics - but I have been able to find that most assume, it seems incorrectly, that a stinger leaves shrapnel or foreign debris. My understanding is that there is little or any foreign debris remaining as the explosion self destructs the stinger body, and to prove a launch one must find the first stage and other material from the launch site. There is no shrapnel. In fact I think the nose and body of the stinger that encases the explosive is composite material.

My point is that there is a wierd desire these days, when it is more likely than any other time in history, to NOT suspect a MANPAD. But that desire is being denied without any specific facts to eliminate that possibility. Instead, because of the loons working on TWA 800 and other grassy hill folks, it is pigeon holed as conspiracy wonks and drive on. Folks, there is no conspiracy, but actuality during these times.

I think the possibility of a stinger can be eliminated easily with the forsenics the FBI has gathered on a stinger at China Lake. Or some with military background could easily provide some info. Shrapnel and drone talk, with respect Gregga, imply you are neither.

All I request is that such information be available so that we can move on past the first obvious concern. What reasonable man would not suspect a stinger during these times?

From a Washington Post article on TWA 800 (which ironically was not a terrorist action but pursued intially as if it were - the opposite of 587):

"Stingers carry infrared guidance systems that zero in on aircraft engines or other heat sources. Direct hits on military planes often have resulted not in the kind of fiery explosion seen when the TWA flight blew up, but rather in the noncombustive loss of an engine or wing, followed by the aircraft's free fall."

This sounds very familiar.

In anycase, as more and more confusion develops: the AA investigation of the the remaining A 300 planes turning up nothing, the discarding of the 747 wake and the GE engines as a cause; we could use some definitive disproof of a MANPAD so that when folks are set to chew over what will likely be a detailed and hotly debated dialogue over composite materials they do not have a underground of conspiracy chatter to eliminate focus.

To NOT prove that a stinger was NOT the cause prior to such a long argument and exploration, which will likely end without hard evidence, would only end with true conspiracy folks coming out fo the wood work and be very bad for the industry.

There is a large difference between proof and a brief, and now wierdly habitual, brushing aside so called "conspiracy theories", of which, after the WTC, considering a stinger strike is certainly NOT a conspiracy theorey.

So I ask for some info on the possibilities of a stinger hit with the reply not based on consideration of what my motives or vantage point as the main point of debate, but on physics and physicality of the situation.

As a frequent flier, trust me, I would be very relieved to know definitively that a stnger was NOT the cause. Composite material I can handle as I know the industry will immediately provide cure, stingers give me the willies as their use and misues does not fall under the domain of the FAA.

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Old 20th Nov 2001, 19:50
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Gregga is closer to target than yourself. You seem to dismiss Cons against a stinger based on what you have heard.

Once you get up close to the damage that a missile produces in a soft body structure such as a fuselage or engine tailpipe, you realize how distinctive it is compared to crash impact damage.

Today's on site investigators are not going to miss this, since some have been to China Lake and seen for themselves.
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Old 20th Nov 2001, 19:54
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Trader, this thread is for discussion of the vertical stabiliser and composites. Whilst you are welcome to start a debate on the possibility of a Stinger missile may I respectfully suggest you do so in either the Tech Log or Aircrew Notices forum.

Based on your reasoning
To NOT prove that a stinger was NOT the cause prior to such a long argument and exploration, which will likely end without hard evidence, would only end with true conspiracy folks coming out fo the wood work and be very bad for the industry.
it might be as well to try and prove that it was NOT a green alien was NOT the cause of the loss of control.

As the NTSB incestigators have said, they are not ruling terrorism out at this stage, we have progressed and are discussing what appears to be the most probable scenario based on what we have seen and and told by reasonably knowlegeble people on the subjects of composites, structures and aerodynamics. No need at this stage to introduce the scenario of terrorists running around New York suburbs armed with Stinger missiles, nor for that case Aliens messing with our air traffic.
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Old 20th Nov 2001, 21:16
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Well, it is your board Capt so I am away.

But last note: was it little green men who piloted the planes 9/11? Folks, the "little green men" are here.

That doesnt mean the "little green men" are the cause of 587, but they should be proven not to be the cause with information provided publicly prior to any other explanation is pursued unless a definitive and obvious reason is immediately forthcoming.

Otherwise the integrity of our public agencies and those in the industry (this board included) will be called into doubt. This is what one should expect when we are at war.

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Old 20th Nov 2001, 21:51
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Speaking as a fellow lay person (although my previous career could have been classified as Professional Passenger), I want to point out that the members of this forum have been most kind and considerate. I’m sure they wait for the day when I tire of this forum and find another hobby, but until then they seem to be willing to put up with me.

In the interest of keeping the theme of this thread while addressing the ‘stinger theory’, I just wanted to note that the vertical stabilizer appears to have ‘sheared’ off at the base and shows no evidence of trauma to the skin. Even a ‘kinetic’ type of SAM should leave some surface evidence. Furthermore, the attachment points of the fin appear to reside within the body of the fin, and are not accessible directly to an outer body experience unless the skin is first penetrated (or at the very least effected with some visible trauma).

So, it’s not my personal feeling that a stinger could have taken the vertical stabilizer out (not directly at least).

If there were evidence showing that the plane experienced some other severe trauma, causing loss of aerodynamics, yawing, and subsequent torque on the fin…still then, I believe the stabilizer is built to withstand extraordinary stress and would have only failed from torque if there were an inherent defect (this would mean terrorism PLUS defect – which I personally cannot deal with).

Actually, I really cannot understand why people are so sure mechanical failure would be a better scenario terrorism. If the composite connections are the true villain, we aren’t just talking about a few Airbus’. Aside from jumbo jets, it’s my understanding that composites are widely used in helicopters and smaller aircraft. And, I read somewhere that the 777 expanded Boeings use of composite.

Just my thoughts, as I try to muddle through the minutia of technical talk and industry interests.

Oh, and TraderAl – you might want to refocus on ground sabotage. A small explosive, placed within the fuselage at the point of (or close to the point of) one of the forward attachments might work. Of course, then you have to explain the lack of ‘explosive’ noise, but ya know…if it’s projected up and back… the characteristics of sound waves might support this one…
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Old 20th Nov 2001, 22:48
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Composites are a bit tricky in revealing defects that occur where the damage is not evident and in others where the repair can’t be verified.

My son was the senior coordinator on the B-747 / 767 production floor. He told me about an incident where a bridge crane operator was moving a large production jig and he made contact with the vertical fin of a 767 which was of composite construction. He indicated to production that it was just a very small contact, which was verified by visual inspection. Inspection of the outside skin showed minor contact with attendant abrasion of a localized surface. Since there were many composite structures on Boeing aircraft they had a team to repair composite materials in the event of production related damage. The senior tech inspected the abrasion and suggested that they inspect the interior of the vertical fin. They sent in an inspection team and they found that stringers and interior stiffeners had been broken away from the structural skin. These elements had been dislodged 6-12” away from their bonded position. What appeared to be minor damage on the outside was found to be major damage on the inside. The fin was removed and subsequently repaired and a new fin installed so as to not slow the production.

When I worked on the V-22 program the Navy instructed Boeing on how to repair composite structure (mainly skins). They specified the method of repair and the specification of the patching material. In order to verify the efficacy of the repair they had to use X-ray equipment. When Boeing did this they found out that the Navy specified patching material was opaque to X-rays and as such the repair could not be verified as complete and structurally sound. I left the program and the argument between Boeing and the US Navy was still going on.

I have a thought on why the tail was in such good shape and that is the structural integrity of the tail assembly may have been greater than that of the attaching structure. If the loads were great enough no matter how they were generated the tail being the stronger part of the structural assembly broke away from the weaker attaching structure. If this has been mentioned previously I’m sorry, as I did not read through the complete thread.

[ 20 November 2001: Message edited by: Lu Zuckerman ]
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Old 21st Nov 2001, 00:05
  #35 (permalink)  

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Glue Ball,

You say that as and SLF you're not going to fly on an Airbus until this thing is resolved. Those may be facts down the road, but right now I believe they are your emotions talking.

I've sweated out two 320 flights in the past week and I can honestly say that I wished I was on a 737. Again, pure fear and emotion.

But what do flight crews have to say about this whole incident? Airbus, itself, has remained strangely quiet, except to acknowledge that it will cooperate with the investigation in all ways.

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Old 21st Nov 2001, 04:50
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While discussing the failure of the compsoites, can anyone explain the failure of three independant parts due to wake turbulence? I can understand that the stabilzer failed due to structural defect but how does the vortex blow out the two engines separately?
I think that there is more to it than just wake turbulence
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Old 21st Nov 2001, 05:31
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Lu Z

Hi, towards the end of the last thread I made an observation about flutter mode and asked a question re multiple load paths and "fail safe" concepts, pointing out that IMVHO the only attachment in this scenario that could be 'allowed' to fail would be the middle one.

The attach system is reminiscent of 'old technology' that does not seem to provide alternative load paths?? Am I out of touch on this, or have we rationalised it out of our system altogether in the name of economics.???
I would very much appreciate your usual expert thoughts.
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Old 21st Nov 2001, 05:37
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Got any idea how much the rudder limiter system retricts rudder travel when enabled (gear and flaps up).

I recall the DC-8s had about 7 degrees with gear and flaps up...15 degrees with both down.

Perhaps the rudder limiter system faulted permitting the greater travel at 280 knots (as the F/O coped with the wake turbulence upset) ??
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Old 21st Nov 2001, 07:15
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Could the aircraft have been going that fast already? The distance from JFK to Rockaway Point (debris field) is only 8nm. Assuming the separation happened at about 5nm after T/O, they would not have been that fast, nor does the dreaded "250 knots UFA" allow you to accelerate, unless specifically cleared to do so. Also, this would hardly have been likely since the JAL machine was less than 4 miles ahead, somewhat slower to accelerate and the separation was something that the ATC would want to maintain.
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Old 21st Nov 2001, 18:28
  #40 (permalink)  

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Latest info from the NTSB

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