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

[SaturnV]

Having reached the 100 posts-per-thread cap, CaptPPrune has closed the two main previous threads on this accident. (Titles were new clues deepen AA 587 crash mystery ... and vertical stabilizer AA 587)

Uncertainties and skepticism were voiced on the previous threads about the ability to visually detect whether a composite has deteriorated because of age, stress, or from environmental factors. Might this not suggest the need to do some destructive testing of the composite area in the vertical stabilizer to see whether AA 587 was a one-of, or whether there are other incipient failures lurking in the fleet?

Are there any A-300's or A-310's parked in the desert or elsewhere whose vertical stab composite might be sacrificed to gauge whether the design strength still is present?

[Flight Safety]

This may be worth noting...

NTSB Identification: DCA99IA058

Scheduled 14 CFRPart 121 operation of Air Carrier AMERICAN AIRLINES
Incident occurred Tuesday, May 11, 1999 at MIAMI, FL
Aircraft:Airbus 300-600, registration: N7082A
Injuries: 129 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On Tuesday, May 11, 1999, at 1445 EDT, an American Airlines A300, flight 916, a scheduled passenger service from Bogota, Columbia, to Miami, Florida, landed successfully after the flightcrew experienced multiple rudder deflections that caused the airplane to yaw excessively from side to side while on final approach to runway 9R. There were no reported injuries to the 119 passengers or crew of 10.

Preliminary information from both the American Airlines engineering group and a Safety Board crew interview indicates that during the initial approach to runway 9R, as the crew configured the airplane for landing with flaps 40 degrees and the landing gear down, the airplane began to yaw left and right. The flightcrew stated in an interview that the rudder pedals in the cockpit did not move, though the rudder was deflecting and causing a yaw motion that was sufficient to prompt the captain to abandon the first landing. During the go around, and specifically, as the airplane was reconfigured with the landing gear up and flaps at 20 degrees for the go around, the yaw deviations increased and became extreme. The crew reconfigured the airplane twice during the go around and completed the landing with 20 degrees of flaps.

Initial information from American's FDR readout indicates that the rudder which is a single panel with three hydraulic actuators, deviated continuously but not rhythmically between 5 and 11 degrees each side of center during both approaches. The FDR has been transported to the Safety Board for additional readout.

[ 18 November 2001: Message edited by: Flight Safety ]

[NotMyJob]

Just scanned previous thread and saw that 1 post referred to loss of hydraulics with a departed vertical stab. Yes, the Blue and Yellow systems would have been immediately lost as the plumbing ripped away, but the Green system is protected from inflight collision scenarios by a hydraulic "fuse" that should shut in the event of excessive flow rate to protect remaining green fluid from loss. The location however of the fuse would in this case be critical. If it is located anywhere in the vert stab, or near its attach points, then it probably would have gone as well - and there goes your protection, as well as the remaining system, and all your primary flight controls (rudd, ail, elev). Don't have accurate enough documentation to determine exact location of this fuse, but suspect this may have been what happened. In this event, the aircraft would indeed have been extremely difficult to control, even if the crew had immediately resorted to a UAL Sioux City mode of control, which in the speed/power range they were in (climb out) they may not have been able to manage.

[widgeon]

There was a quote on previous thread that Boeing and Douglas do not use composite primary structure , got this form a google search :
Shorts awarded Boeing contract to produce Boeing 737 all-composite rudders. Shorts
offered for sale by the United Kingdom Government (1988) and acquired by bombardier .

also picked up story from flug revue:
http://www.flug-revue.rotor.com/FRHeft/FRH9807/FR9807b.htm

Composites were at first chosen mainly for weight savings, fatigue and corrosion resistance, but a major new criteria has appeared: manufacturing cost reduction. Initial employment of larger, more demanding primary composite structures at Airbus began in Germany with the single piece rudder for production model A300s and A310s as far back as 1983. The relatively straightfoward design utilized three carbon/epoxy skinned honeycomb sandwich panels assembled as a hollow triangle to form the rudder. About eight meters in lenght and varying from one to two meters in chord, weight of the composite version is 175 kilogramms. It could be directlysubstituted for the metal version without changes to the plane. Improvements over the original metal structure included weight savings of some 22 percent, component count reduced by nearly half plus reduction of details froom over 17000 down to only 4800.

Hardly two years later, the much larger, heavier and far more complex vertical stabilizer was converted from metal to composite. Essentially of carbon/epoxy laminate, with some glass and honeycomb core on the leading edges, and weighing 800 kilogramms, it was for several years the largest primary composite structure flying on a production model civil transport. As with the rudder, design and manufacture is by the German partner DASA Airbus, at its highly automated Stade plant south of Hamburg, a facility specializing in composite structures. The program entailed a running re-design and replacement of the original all-metal vertical stabilizer in all Airbus production models, beginning with the A300.

Two seperate manufacturing methods, matten and module, were investigated for this program, which the latter won. Module technology is a multi-step, semi-automated process whereby aluminium modules are wrapped with prepreg composite material to form integral skin stiffeners. They are then positioned by robot on the already laid up skin, where US strips are in turn placed on top of the modules to form spar caps. Most of the work at Stade except the actual module wrapping has been automated. Even prepreg is carried from the cutters to the layup area by robot vehicles employing carbon/epoxy containers or baskets made from scrap prepreg. The entire, single piece vertical stabilizer skin was then co-cured in a single step, in a large autoclave. The advantage: only one trip to the autoclave was necessary. the relatively massive attach fittings at the base of the fin are also of carbon/epoxy and integrated into the skin; only the pins and bushings are metal.

The original co-curing has since been modified to simplify the tooling, reduce manufacturing risk and cost, however more trips to the autoclave are required. Moreover the massive attach fittings, normally made up of hundreds of layers of prepreg, are being considered for manufacture by another method: Resin Transfer Molding RTM.

[Belgique]

DEJA VU- Thereby hangs a Tail

Reference this A320 series AD (below):
I would guess that a disbonding over a large area of the vertical stabilizer would make the fin and rudder much more prone to a destructive flutter-mode not encountered in pre-certification testing. After reviewing the comment regarding A330 (also) at the end of this AD, it must be said that there would seem to be few Airbus types unaffected.
____________________________________________
[4910-13-U]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39 [65 FR 37029 6/13/2000]

[Docket No. 2000-NM-139-AD; Amendment 39-11776; AD 2000-11-27]

RIN 2120-AA64

Airworthiness Directives; Airbus Model A319, A320, and A321
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

SUMMARY: This amendment adopts a new airworthiness directive (AD)
that is applicable to certain Airbus Model A319, A320, and A321
series airplanes. This action requires a one-time ultrasonic
inspection to detect disbonding of the skin attachments at the
stringers and spars of the vertical stabilizer, and repair, if
necessary. This action is necessary to detect and correct
disbonding of the vertical stabilizer structure, which could
result in reduced structural integrity of the spar boxes of the
vertical stabilizer.

DATES: Effective June 28, 2000.

The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal
Register as of June 28, 2000.

Comments for inclusion in the Rules Docket must be received on or
before July 13, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 2000-NM-139-AD, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056. Comments may be inspected at
this location between 9:00 a.m. and 3:00 p.m., Monday through
Friday, except Federal holidays. Comments may also be sent via
the Internet using the following address: 9-anm-
[email protected]. Comments sent via the Internet must contain
"Docket No. 2000-NM-139-AD" in the subject line and need not be
submitted in triplicate.

The service information referenced in this AD may be obtained
from Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707
Blagnac Cedex, France. This information may be examined at the
FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,
Renton, Washington; or at the Office of the Federal Register, 800
North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager,
International Branch, ANM-116, FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-2110; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION: The Direction Générale de l'Aviation
Civile (DGAC), which is the airworthiness authority for France,
notified the FAA that an unsafe condition may exist on certain
Airbus Model A319, A320, and A321 series airplanes. The DGAC
advises that localized disbonding has been detected on the skin
attachments at the stringers and spars of the spar boxes of the
vertical stabilizer. During the manufacturing process, pre-cured
parts (attachments of the stringers, spars, and ribs) are
installed on the skin panel before the final curing process. A
peel ply is used to protect the contact surfaces of the
attachment angles of the skin panels of the vertical stabilizer
until the pre-cured parts are ready for installation.
Investigation revealed that, after the peel ply was removed from
the attachment angles, a residue of polymer finish contaminated
the contact surfaces of some pre-cured parts. This contamination
reduced the adhesive strength of the bond and, in some cases,
caused debonding (disbonding) of the skin attachments. This
condition, if not detected and corrected, could result in reduced
structural integrity of the spar boxes of the vertical
stabilizer.

Explanation of Relevant Service Information

The manufacturer has issued Airbus Service Bulletin A320-55A1027,
dated May 12, 2000, which describes procedures for a one-time
ultrasonic inspection to detect disbonding of the skin
attachments at the stringers and spars of the vertical
stabilizer, left- and right-hand sides, and repair, if necessary.
If any disbonding (damage) is detected and the area of damage is
greater than 300 square millimeters (mm2), or if multiple damage
is detected on one specific component (stringer/spar attachment),
the repair involves installing additional fasteners in the
affected areas. The amount of damage determines the number of
additional fasteners to be installed in the affected area.

Additionally, Airbus Service Bulletin A320-55A1027 references
Airbus Service Bulletin A320-55-1026, Revision 01, dated May 20,
1999, which, for certain airplanes, describes procedures for
prior or concurrent modification of the vertical stabilizer to
ensure proper reinforcement of the structure/skin attachments.

The DGAC classified Airbus Service Bulletin A320-55-A1027 as
mandatory and issued French airworthiness directive T2000-208-
148(B) R1, dated May 17, 2000, in order to assure the continued
airworthiness of these airplanes in France.
_________________________________________
From an associate:

"You are aware that there was a big scandal in France when it was discovered that AI had the blank DGAC certification forms already signed and stamped in a drawer at their Toulouse headquarters. I believe some stuff was found to be dealing with "new material specification and certification".
"There was a serious problem at SR last year, when they discovered that their rudders in the brand new A 330 came apart by delamination..."

[GlueBall]

Belgique: Interesting Info. Reinforces my intent to avoid being a pax aboard any Bus until composite failures are understood and corrected. :(
Photos of separated vert stab attach fittings (http://www.ntsb.gov/Events/2001/AA587/tailcomp.htm) Click on individual photos to enlarge for full screen viewing!

[ 18 November 2001: Message edited by: GlueBall ]

[ 18 November 2001: Message edited by: GlueBall ]

[PETERJ]

Belgigue.....
Thanks for your outstanding informatory contributions on this page....much appreciated.....measured......non-biased and objective,,,,,Do you think we are looking at a Ford Pinto scenario here ???....

[SaturnV]

More information excerpted from the Nov. 18 Washington Post.

"..the fin sheared off above the brackets at its base, neither the brackets nor the bolts anchoring them to the plane's aluminum
fuselage appear to have failed. The joint itself survived; the break is in the composite above it.

"Engineers said this could mean that fatigue had weakened the polymer above the brackets, but it could also mean that catastrophic stress had simply snapped the fin. It seemed to rule out festering corrosion at the composite-aluminum joint as the cause of
the casualty.

"Airbus has been using composite tail fins for 16 years, said Roland Thevenin, the
company's certification specialist. The basic test procedure begins with the production of "sample" tail fins containing built-in delaminations and cracks.

"The sample is put through the equivalent of 120,000 "cycles" of a takeoff and landing to
test fatigue and damage tolerance. A "static test" measures composite strength at 1.5
times the maximum load the aircraft is expected to endure. Performance is measured at 70 percent humidity, and at minus 83 degrees Fahrenheit and 158 degrees Fahrenheit.

"When this is finished, the tail fin will not need to be tested again. "If we don't have any [subsequent] visible damage, the structure should be okay for life," Thevenin said. "The typical check is a visual inspection, and if there is something visual, you have to look more closely.""

Edited to add the following excerpts from the November 19 New York Times.

"The tail fin tore in places that investigators said were about two and a half inches thick, and consisted of layers a few thousandths of an inch thick. If a problem in this material is found to be the probable
cause of the crash — a determination is months away — it would be the first crash of a commercial airliner attributed to the failure of a piece of composite, crash investigators say.
....

"It turns out, though, that N14053 needed a repair to its composite tail fin even before it was delivered by the factory in Toulouse,
France, on July 12, 1988. The layers of the tail fin had begun to come apart from within one spot, where the tail connects to the
plane's fuselage.

"When the manufacturer delivered the plane, it said no further inspections of the part were required. The good news was that the
defect, called delaminating, was discovered. But the problem showed that composite can suffer from flaws in its fabrication. That
part of the tail that was fixed appeared to be intact when the tail was examined after the crash."

[ 19 November 2001: Message edited by: SaturnV ]

[RatherBeFlying]

Belgique, Thanks for the hint on seeing the enlarged NTSB photos. Yep, the forward attachment(s)? show obvious delaminations; the hard part will be distinguishing the fresh delaminations from the pre-existing delamination(s) -- same for the fractures which are typically at the bolt hole.
With metal, pre-accident fracture surfaces usually show some corrosion/oxydisation while the accident fracture surfaces are shiny. So, how do you determine fracture/delamination age in a particular composite?

Some composite and metal helicopter rotors have crack detection systems; for example, the hollow spaces in the rotor may be pressurised and a pressure drop shows damage somewhere.

In critical areas such as attachment lugs we may need damage detectors. For example narrow foil conductors between laminations would break in the case of a fracture and a structure integrity monitoring system could flag the change in resistance. A mechanism to detect delaminations is also needed. Threading it across layers will be quite a trick; the pre-preg would need a fine hole to enable the detector to traverse the laminations at an angle. The detectors would probably have to be placed before autoclaving.

[Belgique]

"..the fin sheared off above the brackets at its base, neither the brackets nor the bolts anchoring them to the plane's aluminum
fuselage appear to have failed. The joint itself survived; the break is in the composite above it."
Comment: Some are, some aren't (see photos below)
"Engineers said this could mean that fatigue had weakened the polymer above the brackets, but it could also mean that catastrophic stress had simply snapped the fin. It seemed to rule out festering corrosion at the composite-aluminum joint as the cause of
the casualty."
Comment: See remarks below "The Curse of Nylon Peel Ply" and the AD (partly reproduced above)
"When this is finished, the tail fin will not need to be tested again. "If we don't have any [subsequent] visible damage, the structure should be okay for life," Thevenin said. "The typical check is a visual inspection, and if there is something visual, you have to look more closely."
Comment: Statement would appear to be a bit cavalier in the light of what's emerging - but that may well have been the problem all along.

Quite a bit of Boeing's composite comes from Australia. We do the B777 vertical stab ("worlds largest composite component") at the old GAF factory and B737 elevators at the old HdeH - both are now Boeing subsidiaries. HdeH also does flaps for C130J.

We also have the Cooperative Research Centre for Aerospace Structures which develops design and m/f of composites. I've consulted for them - explaining the difficulties of certificating composites. Why we need to be so cautious!
Thanks for alerting me to this AD. Was not aware of it. Sadly keeping up to date gets increasingly difficult.

I'm guessing but this looks like the same problem that occurred during A320 structural testing. And yes, if not corrected, fault might precipitate fin/rudder flutter before it caused an overload failure.

I know of no similar problem being disclosed on the A300.

However the peel ply fault has been lurking for several years. McDD's guru on composites John Hart-Smith (now a Boeing employee and incidentally an Australian) has long preached against dangers of peel ply for the very reasons outlined in the AD.

An example paper by John in conjunction with Redmond and Davis of RAAF Amberley presented in March 1996 is titled "The Curse of Nylon Peel Ply". The abstract begins "A case is presented that most peel plies can be relied upon to ensure the creation of a surface on composite laminates on which it is NOT possible to produce a strong durable adhesive bond.........."

Yet until recently peel ply was industry norm. All manufacturers including McDD used it. I do not know to what extent it has been removed from current manufacturing.

If peel ply gets implicated in the A300 accident it will be real can of worms / chooks roosting time.

http://www.iasa-intl.com/images/AA587_09L.jpg

http://www.iasa-intl.com/images/AA587_10L.jpg

http://www.iasa-intl.com/images/AA587_03M.jpg

Anyone unfamiliar with the flutter phenomenon in composites can look here (http://www.iasa-intl.com/folders/Safety_Issues/others/violent_vibes.htm).

[Flight Safety]

In Belgique's last post, looking at the top picture, left side composite attachment point, isn't that a row of rivets running from left to right just above the retaining bolt?

Does it appear to anyone else that a fracture occurred at that rivet line? Is this possibly the location where the original delamination occurred at the factory on this fin, and was repaired with rivets and a doubler?

[Blacksheep]

From looking at all the pictures on the NTSB site the tears and fracture lines in the fin structure suggest that the right side let go first, with the fin tearing away to the left and the aft left attachment letting go last. In the two pictures of the left attachments shown above, there are clearly fasteners through the body of the Centre Left Fin Attachment. It appears therefore, that this is the area of repair mentioned. If that is the case, the final failure sequence seems not to have originated at the repaired attachment. Perhaps the repair was indeed strong enough for the design intent.

Much of the discussion so far has included learned opinions of a lack of knowledge about composite structures and their capabilities. If the state of knowledge is exactly as stated, our aircraft constructors and regulatory bodies are grossly negligent in allowing the use of composite materials in primary structure at all.

In fact, as I sarcastically pointed out on an earlier thread, aircraft manufacturers have built combat aircraft for a long time, using composite primary structures that remain intact at "G" loads far above anything experienced in a civil airliner. These highly loaded combat aircraft do not break apart with any regularity, so the whole problem isn't necessarily poor design or a lack of knowledge about the strength and load bearing capabilities of composite structures. More likely the problem lies in manufacturing techniques and process control. Faced with a delaminated attachment on a complete vertical stabiliser, was it wise to carry out a repair without giving due thought to the reason for the delamination? Was any thought given at all? Obvious delamination on one attachment might have thrown suspicion on the whole assembly. Composite structure is, as has been pointed out, notoriously difficlult to inspect. Did the cost of rejecting and scrapping an entire vertical stabliser drive the repair-and-fit decision? We may well wonder. The NTSB have the difficult task of digging into a foreign manufacturer's production records -but "decision trees" for such decisions are not committed to paper so the answer will be hard to find.

Some years ago, Boeing were building a nice new aircraft for our airline. Some of our Technicians on training courses were visiting the assembly building when one of them noticed a repair on the brand new rudder. Upon inquiry the repair was found to be beyond SRM limits for an in-service rudder - on a new assembly being fitted to a brand new aircraft no less! We asked for the rudder to be removed and replaced with a pristine one. I suspect that it was too expensive to scrap the original unit and I don't know what happened to it after we rejected it. I'd wager though, that it is flying today on an aircraft bought by a less fortunate or observant airline.

We must not lose sight of the real question here. Why was this vertical stabiliser repaired and installed? Is it yet another manifestation of the ever downward pressure on costs, in what has developed into just another low cost transport industry?

**********************************
Through difficulties to the cinema

[I. M. Esperto]

From AvFlash:
FLIGHT 587 -- WAKE TURBULENCE IDENTIFIED...
There were some new developments in the investigation of American
Airlines Flight 587, which crashed last Monday shortly after taking off
from New York's John F. Kennedy International Airport. Last Thursday,
NTSB officials announced that they had analyzed the data from the jet's
cockpit and flight data recorders, and investigators believe that the
A300-600 encountered two wake turbulence events caused by a Japan
Airlines Boeing 747-400. Even though standard separation was followed,
data showed sideward accelerations of the aircraft along with
considerable aileron and rudder movements.

...VERTICAL STABILIZER PUZZLES NTSB
The aircraft's vertical stabilizer was recovered from the waters of
Jamaica Bay and found to be largely intact with attachment bolts in
place at the main wreckage site. Wholesale failure of the structure
occurred above the attach points. Investigators are now almost certain
that the tail section was the first part to break off the plane, which
also lost both of its engines before impact. The FAA and French
authorities have ordered airlines to check Airbus A300-600s and A310s
for tail and rudder damage, lose fasteners, distorted surfaces and
cracks and corrosion, within a 15-day period.

NOTE: For more detail of recent findings, see AVweb's Newswire at
<http://avweb.com/n/?47a>.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Note that the fin's failure was ABOVE the attach points.

Composite failurs?

[El Grifo]

Belgique,
Help me out here. If what we are looking at in your pictures is the metal lugs which attach the stabiliser on to the fuselage and if, attached to the lugs are the parts of the stab that remained with the aircraft. How come we see a half rounded hole on the bottom of the stabiliser. Is it because there are four lugs used for the job and we are seeing only two?

Update 15.04
I have actually managed to answer my own question. I now understand that there is a row of lugs at each side of the vertical stab. On closer inspection it appears that one of them is badly damaged. could that be a front lug, if so is it possible that the flutter could have caused the failure of that lug with the subsequent events cascading from there.
http://www.ntsb.gov/events/2001/AA587/AA587_11.jpg

[ 19 November 2001: Message edited by: El Grifo ]

[ 19 November 2001: Message edited by: El Grifo ]

[Bubbette]

The FAA just put out an AD on these:

A safety warning affecting the tail section of Airbus A-300 jetliners was scheduled to take effect one day after the crash of American Airlines Flight 587, which plunged out of control Monday after its vertical tail apparently ripped off in flight.

The warning, known as an airworthiness directive, points out a serious safety problem that could leave the pilot without rudder control, making it difficult, if not impossible, to guide the airliner.

The American Airlines jet that crashed after takeoff in New York was an Airbus A-300 Model B4 manufactured in 1988. It was among those that the warning affects.

The U.S. Federal Aviation Authority first published the airworthiness directive on Oct. 29. It was scheduled to take effect Tuesday, forcing all A-300 operators to inspect key rudder-system components. http://www.airsafetyonline.com/cgi-bin/news.cgi?url==http://www.theglobeandmail.com/servlet/RTGAMArticleHTMLTemplate?tf= tgam/realtime/fullstory_print.html&cf=tgam/realtime/config-neutral&articleDate=20011117&slug=wxcras&date=20011117&archiv e=RTGAM&site=Front

[Belgique]

Likely to prove a red herring. That story in the Saturday Globe and mail by Peter Cheney can be read here (http://www.theglobeandmail.com/servlet/RTGAMArticleHTMLTemplate?tf=tgam/realtime/fullstory_print.html&cf=tgam/realt ime/config-neutral&articleDate=20011117&slug=wxcras&date=20011117&archive=RTGAM&site=Front)
http://av-info.faa.gov/ad/PublishedADs/012202.html - Airbus Model A300 B2 and B4 Series Airplanes (the rudder AD referred to below)
The A300-600 and A310 are advanced developments of the original A300- B2/B4


Even though this 18 Oct 01 rudder AD is applicable to the accident model Airbus, it's unlikely to have had anything to do with AA587's fate. The facts are slowly emerging that the well-known problem that the A320/A319/A321 model's vertical fin was having (disbonding of the skin from the stringers and spars) was later experienced on the A330 (their much newer product) and that is described here in this AD at this link (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebCurrentADFRMakeModel/7E9A6A336F2C021286256981 00479582?OpenDocument). Even though this AD does not apply to the A300-B4, the symptoms, as a preliminary to the style of accident AA587 had, were much as predicted in the language of that A320 series AD. The suspicion is that disbonding over a sufficient area can allow the early (gust-induced) initiation of a destructive flutter mode in the vertical fin. The disbonding is caused by polyester contamination introduced during the "peel process" in manufacture (which would be in Spain).

"DGAC advises that localized disbonding has been detected on the skin attachments at the stringers and spars of the spar boxes of the vertical stabilizer. During the manufacturing process, pre-cured parts (attachments of the stringers, spars, and ribs) are installed on the skin panel before the final curing process. A peel ply is used to protect the contact surfaces of the attachment angles of the skin panels of the vertical stabilizer until the pre-cured parts are ready for installation. Investigation revealed that, after the peel ply was removed from
the attachment angles, a residue of polymer finish contaminated the contact surfaces of some pre-cured parts. This contamination
reduced the adhesive strength of the bond and, in some cases, caused debonding (disbonding) of the skin attachments. This condition, if not detected and corrected, could result in reduced structural integrity of the spar boxes of the vertical stabilizer".


This particular rudder problem might lead to a directional controllability issue only if both rudder spring boxes were to seize up, but losing rudder control is nothing at all like having the vertical stabilizer depart the scene. I'd bet money on this one not having been the cause. The reason for the rudder evolutions on the accident aircraft is unlikely to have been pilot inputs and more likely to have been initially the system trying to counter the yaw and roll caused by the vertical fin rocking in a cross-wise fashion (as it fluttered toward detachment after the initial starboard side's "above attachment point" fracture). Latterly the rudder's recorded gyrations may have been due to pre-fin-departure stresses being placed upon the rudder actuator. i.e. As has been pointed out in this thread, the initial flutter mode failure would appear to have been above the attachment points on the starboard side. Once that permitted the flutter to increase in amplitude (laterally), the port side composite lugs, not being designed to cope with those type bending stresses would understandably have fractured through the composite lugs. It doesn't take much imagination to see that.

[RatherBeFlying]

At least two red herrings in the newspapers and picked up here: The two fractures in the left center and rear attachment lugs appear well above the bolts and have been seized upon as material defects. Keep in mind that the critical failure was in the forward attachment lugs -- both beginning at the bolt holes where stress would be concentrated (also the right center and rear attachment lugs may also have had pre-accident fractures in the area surrounding the bolts). Once the other four attachments had failed, the fin was coming off. That the failure occurred well above the attachment point testifies to the probable lack of pre-accident fractures in the vicinity of the bolts and an adequate engineering design in the absence of material defects. Speculation that pilot inputs took off the fin. I put my bets on the yaw damper combining with the flight control system. As the forward attachment(s) loosened, the fin leading edge would flex yawing the a/c and the rudder would act to correct the yaw such that the fin leading edge would then flex back and the rudder would then reverse .... resulting in a flutter couple between the structure and the rudder control.

[samgop]

There have been numerous references to a statement claiming that the VS fractured above the attachment points. Can somebody please reference the original source of this statement? It seems to have evolved into some authoritative claim covering ALL attachment points, and I would like to verify both the 'authoritative' and the 'ALL' presumptions. Furthermore, does this statement include the claim that NO failures occured below the attachment points?

As noted on other posts, a forward bottom attachment appears to have failed. If true, this would give a new perspective on the chain of events.

[RatherBeFlying]

The best authority are the photos posted by the NTSB and noted previously in PPRUNE: http://www.ntsb.gov/events/2001/AA587/tailcomp.htm

Look for the three "forward attachment point" photos. The left and right forward lugs are shown along with the forward attachment brackets on the tailcone.

Look at all the photos.

[TraderAl]

Stinger?

Sorry to cross post this, but I thought I was posting this here when I initially posted it in the "Newspapers" thread.

OK Don't groan, and this is written by what can only charitably called a lay person.

When we were not at war and with no precedent like the WTC, TWA 800 was firmly believed by most to be a terrorist attack, even to the point that the FBI shouldered the NSTB out of the way for the first few weeks.

Now it is being played in exactly the opposite fashion, though we have precedent and the obvious presence of those with a will to do such a terrible deed.

Also, no one has explained in detail to the public why a hand held SAM type of weapon was not deployed in AA 587. Therefore many are suspecting some sort of cover-up. The lack of any clear definition of the cause of the crash or strongly held theories is also causing concern.

Seeking to dispel such thoughts, one hits the www to find out about Stinger hits on aircraft and is even more confused to find out that China Lake reports that Stinger hits usually do not result in a combustible explosion beyond that of a sharp bright white flash, and drop the target through causing break-up as key parts of the craft shear off which initiates a sharp sudden vertical fall. Of course this does sound like flight AA 587, with the sudden thrust/lurch to the right , the shearing of the tail, and then the dropping away of the engines prior to a large G-force vertical descent.

Could those on this board, especially the many with military flight training behind them, eliminate a SAM as a possible cause of AA 587?

While this may seem silly to request to those who already have such knowledge which seems obvious from their vantage point, it should be reminded that many of your passengers do not share your certainty. It would help if they started to share such certainty as a industrial/parts failure is something that can be understood while a Stinger strike would be a serious problem.

If you feel there is a possibility of a Stinger or similar weaponry strike, why do you think so?

If you can explain with certainty that it is impossible that a Stinger can be the cause, I would love to hear it so we can drive on.

Many thanks.

[samgop]

RatherBe-

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. http://www.ntsb.gov/events/2001/AA587/AA587_09.jpg

Second, these look to be the two bottom forward brackets. These would be the bottom attachments which are constructed of metal. http://www.ntsb.gov/events/2001/AA587/AA587_11.jpg

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.

[Plastique]

Belgique,

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 :)

[SaturnV]

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.

[gregga777]

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.

[RatherBeFlying]

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. :rolleyes:

[samgop]

RatherBe-

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!

[Shore Guy]

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.
ADVERTISEMENT

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
killed.

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
said.

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.

[pietenpohl]

An interesting article from today's NY Times concerning piloting techniques that may have contributed to the accident.
http://www.nytimes.com/2001/11/20/nyregion/20CRAS.html

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 (http://www.nytimes.com/2001/11/20/nyregion/20CRAS.html)

[TraderAl]

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.

:mad:

[Al Weaver]

TraderAL

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.

[Capt PPRuNe]

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.

[TraderAl]

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.

Cheers

[samgop]

TraderAl-

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…

[Lu Zuckerman]

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 ]

[LatviaCalling]

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.

Emil

[Tripper]

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

[gaunty]

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.

[UNCTUOUS]

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) ??

[Kubota]

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.

[sky9]

Latest info from the NTSB

http://www.ntsb.gov/Pressrel/2001/011120.htm

[Puzzled]

I am impressed by several of the posts re the curing and aging of the composites but I wonder if anyone has any detailed information re how the exterior of the aircraft are "washed". I raise this question because my first reaction to learning that the Tail was made of composite appears to have snapped off was that possibly some member of the maintainence crew could have sprayed the tail with a solvent during a routine inspection. I finally dismissed that as being probably not a practical method and would also be too obvious.

After thinking for a few days I rememberd an occasion when a plane I was about to take off in was being de-iced and they were spraying it with hoses. that led me to wonder how they normally "cleaned" the exteriors of grease, etc..

Anyway, as luck would have it I remembered I knew a guy who was in the Air Force Reserve at Travis and his job was maintainence of the C-13o and other aircraft stationed. When I asked him how they cleaned their planes and what they used he paused for a second and said he wasn't exactly sure because they
...use Outside Contractors. All he could say was that they used solvents of some kind and they had to use different solvents for different components depending upon what the materil was made of, and he had seen them masking off certain areas during the process.
I asked him if these solvents would be classified as Hazordous Materials and he said yes.
Now here's what I am puzzled about:

o Is there anyone out there who is aware of what solvents are used, how many kinds there are, their ingredients, are there any standards as to what can and cannot be used, etc.?

o Could the use of a solvent mixed to clean Aluminum being used on a Composite reduce its strength? Intentionally or un-intentionally.

o Could a specific solvent be mixed that would weaken the specific Composite used in this Tail?

o Do the Civilian Airlines also use Outside Contractors to clean their Aircraft.

o If so, are the solvents delivered in tanker trucks and applied to the aircraft from the trucks or put in holding tanks at the airport.

o When, where and by who was 587 cleaned, washed or de-iced?

o Has there been any effort at all to overhaul the screening, background checks and overall scrutiny of the Maintainence personnel and their associated sub-contractors. I haven't heard of much other than those who clean the interiors and deliver the food. The screeners at the gates have been getting pounded (deservedly so) and will be Federalized but that is, to some degree, locking the barn door after the horse is out. I would be encouraged to learn of a comparable scrutiny of maintainence personnel.

Now, I am not a conspiracy theorist or alarmist but I do recall that among the hundreds of people the FBI have rounded up there were several... 8, 10,or 12, who were Mid-Eastern and had applied for and/or received Hazardous Material drivers licenses.

The consensus of concern appeared to be possible use for truck bombs or biological material.

It's most likely a stretch on my part but could these aircraft cleaning solvents also been a reason? I hope not and I welcome intelligent refutation of my thoughts along these lines. I have actually deliberated posting here as I had , well, still have, a fear of looking ridiculous. But I finally concluded I would have been thought ridiculous if I had feared the scenario of 9/11 on 8/11.

But leaving sabotage out of the equation, what about these various cleaning solvents and their effect on composites?

[Blacksheep]

We wash them with detergents, just like your car only in bigger quantities. The bits that are masked off are the various orifices where we don't want water to go - like the static ports, outflow valves, and cooling system intakes etc. After washing is finished, specific parts such as the landing gears are re-lubricated. De-icing fluid is a special non-corrosive mixture developed and certified for the purpose.

While solvents are sometimes used for cleaning specific components, this is done only under controlled conditions. That is, they are cleaned at specific periods as part of the schedule of inspection. Chemicals used on aircraft are strictly controlled, may only be purchased from approved sources and the approved chemicals are listed in the Aircraft Maintenance Manual with the uses for which they are approved. The work is done by or under the supervision of licenced technicians and a release certificate is issued for the work.

I hope this satisfies your curiosity and eases some of your worries.

**********************************
Through difficulties to the cinema

[ 22 November 2001: Message edited by: Blacksheep ]

[Pom Pax]

Having been prompted by todays "Daily Telegraph" I have reread this incident report (http://www.aaib.dtlr.gov.uk/bulletin/feb01/n14065.htm)

The disturbance was accompanied by a loud bang which was noted by both the flight crew and some of the cabin attendants. They all reported the noise as being coincident with the disturbance.

Furthermore, there was nothing from the engineering investigation that could explain the loud noise reported

Could some as yet undetected delamination have occurred?

[Al Weaver]

>
The disturbance was accompanied by a loud bang which was noted by both the flight crew and some of the cabin attendants. They
all reported the noise as being coincident with the disturbance.<

Sounds like a recoverable engine surge. Quite often these are so quick that they will not be caught by DFDR sampling rates. Of course the quick ones don't do anything beyond a shake of the aircraft (no time for roll etc.)

[flufdriver]

Is there any truth to the rumour that this aircraft had experienced "severe turbulence" some time ago and was, (after return to service) "written up" several times for vibration in the "tail" and that a T/O (with this aircraft) was recently aborted in SanJuan for the same reason?

I hope not!

[John Farley]

lomapaseo

Sounds like a recoverable engine surge. Quite often these are so quick that they will not be caught by DFDR sampling rates. Of course the quick ones don't do anything beyond a shake of the aircraft (no time for roll etc.)

Very good point. How about a wake encounter causing the yaw and the yaw causing the self clearing "pop" surge.

[GlueBall]

When looking at the photos on page One of this thread, one may notice that at least two of the six hinge fittings showed parts of the vert stab composite attach points still attached, whereas the rest had a clean separation from the pins. Therefore it's conceivable that the vert stab may not have totally severed at once, but may have ripped off one side and then fluttered momentarily before tearing completely lose from the opposite attach points. This, in conjunction with a fluttering rudder may account for the "rattle" heard on the CVR. Also, it's interesting to note that the engines were severed at the wing rather than at the pylons, suggesting a severe airframe overload from lateral ocillation. :(

[Al Weaver]

> note that the engines were severed at the wing rather than at the pylons, suggesting a severe airframe overload from lateral ocillation. <

I doubt that you should infer anything from the separation point. The airframe manufacturer owns the loads no matter where generated and sizes the relative strengths of the joints.

The engine manufacturer must only show that his side of the joint does not deform under a full blade out test. Typically the airframe manufacturer provides margin way above the engine generated load so as to cover other things like gust loads etc.

[UNCTUOUS]

Reading this previous incident report at http://www.aaib.dtlr.gov.uk/bulletin/feb01/n14065.htm , you get the impression that it's almost as if it's the B737 rudder actuator problem in reverse (i.e. instead of seizing "hard-over", suffering instead from an excess of motility)

How much does the A300-600 rudder limiter system restrict rudder travel when enabled (gear and flaps up)?

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 250 knots - as the autopilot coped with the wake turbulence upset) ??

It's beginning to sound to me like a hydraulic hammer may be induced by the rudder limiter-valve cycling rapidly (much like audio feedback can cause a superheterodyne squeal). When they hit the 747 wake, the Flight Control System would have made a much larger than normal rudder input to correct the yaw and perhaps set up a hydraulic reverberation in the rudder limiter valve line that caused the rudder's large lateral oscillations, thereby setting up a destructive rudder-induced flutter in the vertical fin. We've all heard the very noisy hydraulic hammer that you can get in household water-pipe plumbing. If you didn't turn the tap off quickly, you'd swear the wall was going to fall down. Due to the corrective input being from the autopilot (and not the pilot's rudder pedals) that may be a factor in the destructive hydraulic hammer being aroused between the limiter valve and rudder actuator. The biggest factor in the reinforcing (or damping) harmonic of hydraulic hammer is the distance between the two "chattering" hydraulic line components and the feedback harmonic that can be set up. Some hydraulic systems necessarily have Quincke valves incorporated - coils that are designed to soak up these types of destructive hydraulic chatters. The initiator of this rudder-induced flutter may need to be an external force (such as wake turbulence) requiring a rapid autopilot input (i.e. to say that normal rudder pedal input and pilot reaction times would not create the conditions for hydraulic chatter).

[GlueBall]

During climb, unless there's an engine failure, there's no reason for any pilot to have his feet on the pedals. :p

[Shore Guy]

To all the engineering types-

Would one expect the design of the vertical stab attach points to be able to withstand the compromise of one of the attach points and retain strucural integrity?

How is the possibility of a lightning strike (not related to the AA accident) designed into a composite structure? I have read previously that some metal bonding is required on composite structures.How would one test to see if a lighting strike compromised the structure?

Thanks.

[Few Cloudy]

Beg to differ GlueBall,

Pilot flying should always be ready to take full control, including rudders (eng. failure, turbulence, control problems...)

[I. M. Esperto]

light 587 Observations From www.AviationNow.com (http://www.AviationNow.com) - Pieces I Cut Out

Aircraft Went Through All of This and Never Came Apart

In May 1997, the crew of an American A300-600 -- not N14053 -- stalled the
aircraft during a right turn to enter a holding pattern while on approach
to Miami. As the plane's nose pitched up 12 degrees and the bank angle exceeded 50 degrees, the first officer applied full left rudder to correct the roll, NTSB determined.

The bank angle hit 56 degrees and the angle of attack topped out at nearly 14 degrees before the A300-600's attitude changed dramatically. "The aircraft then pitched down, and entered a series of pitch, yaw, and roll maneuvers as the flight controls went through a period of oscillations for about 34 seconds," NTSB said in a report on the incident. The crew recovered the aircraft at about 13,00 feet, and landed without further incident. Several dozen people were injured.

Only 30 Degrees for Flight 587

After the three sudden movements, the plane banked sharply left and nosed
over about 30 degrees. The crew could not regain control and the aircraft
broke apart, with its vertical fin, rudder, and both engines separating
from
the fuselage.

NTSB Chairman Marion Blakey remains in contact with U.S. Federal Bureau of
Investigation Director Robert Mueller. But so far, NTSB has no evidence
that
points to foul play as a contributing factor to the accident.

And What About This?
>
> Several witnesses reported seeing fire, smoke, and debris coming from the
> side of the aircraft. Reports conflicted over whether it was the right
side
> or the left side. One witness at JFK reported seeing the aircraft headed
for
> the ground at a severe nose-down angle, followed seconds later by a plume
of
> smoke.
>
> The Associated Press reported that U.S. Federal Bureau of Investigation
> officials were looking into the possibility that there was an explosion
> onboard Flight 587. It was not clear whether they considered the explosion
> to be from a bomb or some other non-aviation source, or if they were
> considering something mechanical, such as an engine failure.
>
> In perhaps the most perplexing development Tuesday, the A300-600's
vertical
> stabilizer and rudder were pulled from Jamaica Bay -- about a half-mile
from
> the main debris site -- and both pieces "appear to be complete," Black
said.
> Television images of the tail showed no marks, holes, or other structural
> damage that would indicate that the tail was knocked off by debris -- such
> as from a disintegrating engine.
>
> And Why Wouldn’t He Talk About It?
>
> While no sounds pointing to explosions have been picked up from the CVR
> analysis sessions, Black said investigators noted "noises" on an air
traffic
> control tower tape of communications between controllers and Flight 587.
The
> noises -- which Black did not describe in detail -- were heard at about
the
> time crew lost control. He did not say what the sounds indicated.
>
> Both Engines Came Off?
>
> The plane's No. 1 engine ended up in a gas station parking lot about 700
> feet from the crater, while the No. 2 engine came down in about 800 feet
> from the main crater. All of the debris is "more or less in a line," Black
> said.
>
> Interesting
>
> All communications with the cockpit were normal prior to the crash," White
> House spokesman Ari Fleischer told reporters. Asked if that meant
officials
> were ruling out terrorism as the cause of crash, Fleischer said not yet.
>
> Ridge then convened a conference call with other cabinet members,
including
> representatives from the U.S. Department of Transportation, Federal
Aviation
> Administration, and FBI to assess potential homeland security threats. New
> York City and state officials were also involved in the talks.
>
> Wake Turbulence
>
> Neither encounter was particularly severe, investigators said, and were
> certainly not violent enough to rip an airworthy A300-600's tail off.
>
> Checking the Tail
>
> Inspections of Airbus A300-600 and A310 tail sections haven't turned up
any
> significant clues that would explain why an American Airlines A300-600's
> tail ripped away shortly before the aircraft crashed into a New York City
> suburb last week.

[Right Way Up]

Haven't seen any mention of this in the news but this incident must ask a few questions!
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20011128X02309&key=1

[Dagger Dirk]

FAA has called for visual inspection of plastic A300/A310 tails. NTSB recommended NDT testing of composites after an MD-11 turbulence event in 1995. Fast forward to 2001 -- we kill a bunch of people and the FAA still says visual inspections are adequate.
Queries
a. Does anyone recall the details of that MD-11 incident or have a URL?

b. Anyone any idea how much composite structure is in an MD-11?

[baranfin]

I read in the paper that the tail and rudder have been sent to NASA for them to inspect.

[SaturnV]

Rudder problems on another AA A-300 as reported by CNN. (See below) The vertical stab from AA587 has been sent to NASA's Langley Research Center (Norfolk VA area, and a lead NASA Center for aeronautics) for detailed study.

"LOS ANGELES (CNN) -- An American Airlines Airbus jetliner departing Lima, Peru, Wednesday evening experienced severe rudder problems during takeoff, forcing it to return to the airport, CNN learned Friday.

"The aircraft, an Airbus A300-600, is the same model aircraft as American Airlines
Flight 587.

"In Wednesday's incident in Peru, the pilots reported "fish tailing" soon after takeoff.

"An aviation source told CNN the aircraft experienced severe rudder fluctuations. A
preliminary NTSB report said the plane landed safely and its flight recorders have
been pulled for further investigation.

"CNN has previously reported on yet another incident involving an American Airlines
Airbus A300-600. That plane, on a flight from Colombia to Miami, Florida in 1999,
had to abort its final approach after the pilots experienced what they called severe
rudder deflection problems.

"NTSB spokeswoman Lauren Peduzzi, reached late Friday, said she had no information on any incident in Peru and would not know anything until Monday.

"American Airlines told CNN the plane remains in Peru but the flight recorders have been sent to the NTSB in Washington. An airline spokesman said no previous problems with the jet had been reported.

After the crash of Flight 587 the FAA ordered airlines flying the A300-600 to
visually examine the tail sections for signs of possible stress cracks. But critics said
that more sophisticated tests are needed to detect any problems with the vertical fin
and rudder which, on the Airbus, are made of composite plastic materials and not metal."

[Flight Safety]

This is from the Aviation Week website, regarding the Miami incident in 1999...

In May 1999, another American A300-600 experienced multiple rudder deflections while on final approach to Miami, but landed without incident. A probe revealed that the autopilot's wiring had been cross-connected by American mechanics in Tulsa.

I wonder if a cross-connected autopilot had anything to do with the most recent Peru incident?

[bblank]

Dagger Dirk wrote " ... after an MD-11 turbulence event in 1995 ... Does anyone recall the details of that MD-11 incident or have a URL?"

Maybe you are thinking of this one: In 1992 China Airlines Flight C1-012, an MD-11 delivered earlier that year, encountered turbulence (described as "moderate") at FL330. Control of the plane was lost and parts of the left and right elevators separated. According to reports, before the captain regained control both roll and pitch exceeded 30 degrees and the plane stalled 4 times. I recall the reported length of time that the plane was out of control but it strains belief. The NTSB report is listed as AAR-94-02 but it came out before they
began web-posting. Not sure but I think that this same MD-11 was destroyed in 1999 after a landing at Hong Kong that was somewhat similar to the 1997 Fedex MD-11 accident in Newark.

[InitRef]

Brian B,
You can find that CI MD11 Turb Report here:
AAR94-02.pdf (http://amelia.db.erau.edu/reports/ntsb/aar/AAR94-02.pdf)

[bblank]

Thanks InitRef. The NTSB recommendation (A-94-38) concerning inspection of composite structures seems very limited in extent:

"Require inspection using nondestructive ultrasound "A" scan inspection techniques of composite elevators on MD-11 airplanes that are known to have been operated outside the design buffet boundary."

I presume that the NTSB regards their other recommendations as sufficient to prevent the *first* operation of the a/c outside the design buffet boundary.

The NTSB report of this 1992 incident describes a very similar one (pitch and roll oscillations with elevator skin loss following turbulence) that happened to an Alitalia MD-11 on 26 Aug 93.

[UNCTUOUS]

It's clutching at straws perhaps, but when you look for an initiator for that destructive flutter mode of AA587's fin and this AA rudder fish-tail (out of Lima PE on 28 Nov), you can only come up with three obvious common denominator type factors:

a. It can logically only start with the rudder (and the rudder's prime-mover is the hydraulic system) and thereafter potentially graduate to a rudder-induced flutter (catastrophically perhaps - as in the case of the AA587 fin separation).

b. It's occurring in the transition from lower towards higher speeds or vice versa (i.e. take-off into the climb or on approach as in the earlier AA Airbus A300-600 incident. That plane, on a flight from Colombia to Miami, Florida in 1999, had to abort its final approach after the pilots experienced what they called severe rudder deflection problems.)

c. It possibly needs an external initiator like wake turbulence (or is greatly excitated by the prime mover being an external force - such as turbulence-induced yaw).

The speed transition may be the clue as the rudder-limiter functions to limit rudder travel at the higher speeds (and conversely to de-inhibit it when the aircraft slows to approach type speeds). If there were to be set up a hydraulic hammering between the rudder actuator and the limiter valve that caused rudder fluctuations, it might plausibly explain how fin flutter could be thus "excitated".
But if so, how come it wouldn't be a more common occurrence? Well I guess the answer must be roughly the same reason why hydraulic hammer doesn't always happen in my house's plumbing. It depends which tap (faucet) you turn on (and how fast) and how long you run the water. It may also depend upon the water pressure. The airplane equivalent might be whether the rudder is being deflected by the autopilot, pilot's rudder pedals or the yaw damper - or perhaps the turbulence that you just flew through.

It may also be the case that something as simple as a (recent) FCS software patch could change the rate at which the yaw-damper or rudder responds, via the autopilot, to an externally applied yawing moment. That rate-change might be sufficient to set up that feedback "echo" between the rudder actuator and the limiter valve (or other hydraulic system component). Sometimes when you turn on a faucet in my house, the hammering is so bad you just have to turn it off and slowly back on - because that hammering has an ever-increasing amplitude and it sounds as if the walls are coming down. At other times it rattles away and then cancels itself out. In the airplane case, at 3000 psi a hydraulic hammer flinging the rudder left and right could be enough to set up that destructive aerodynamic fin-flutter. I'm not sure what (if any) trim, balance or servo tabs are on the rudder, or indeed how many actuators it has (but I presume three). The deflection of any secondary surfaces may be in that equation somewhere (also). AUW, CofG (and consequently the horizontal stabilizer's setting) could also be a factor.

It used to be the case that flutter was guarded against (damped) by aerodynamic (horns) and mass balancing ahead of a control surface's hinge-line. I believe that it's now done more scientifically by software control. It wouldn't be the first time that aviation has come up against unintended consequences of innocent or innovative modifications.

READ ALSO: http://www.aaib.dtlr.gov.uk/bulletin/feb01/n14065.htm Airbus A300B4- 605R, N14065 severe rudder yawing (27 Jun 2000)

"The loud bang reported by the crew could have been directly associated with the cause of the upset or could have been a secondary result of the movement of the aircraft". (I wonder if they would have carefully checked the engine pylon-to-wing attachments for cracks?)
The UKAAIB Conclusion: "The disturbance experienced by the aircraft could be attributed to a localised severe turbulence event."
(very facile IMHO - almost as good as a "miswired autopilot").

[Dagger Dirk]

It may be more than straws because, so far, it looks like we have five A300 'uncommanded rudder' ..... incidents including this latest AA 587.

Note the lack of NTSB concern here in these - as evidenced by 'preliminary' reports still open or no apparent investigations at all. You would think these kind of incidents would be of real concern since they have no conclusions as to how this may have happened - repeatedly. One wonders if, like the four electrical failure modes known in the 737 'hard overs' that the answer may be simply "wiring" induced and perhaps merely to the rudder limiter system rendered to the 'ground mode' (or shorting intermittently). In the absence of an internal component failure, Hydraulics may just be the 'muscle' but Electricity can be the 'brains'.

Survey Of 4 Yaw Incidents BEFORE AA Flight 587.


Summaries: See referenced pages (below) here (http://www.iasa-intl.com/PDF/AA587yawSurvey.rtf) for more complete text and sources/URLs. [It's a downloadable file in rich text format].

With the exception the 5/11/99 incident, which is still 'preliminary', None of the other three (including the 10/3/99 incident said to have been investigated by the NTSB) are listed at the NTSB Monthly Accident and Incident database (http://www.ntsb.gov/NTSB/month.asp).

6/27/00. Airbus A300B4- 605R, Reg. N14065. As the aircraft was approaching FL220, at a reported airspeed of 325 KIAS, the aircraft experienced an abrupt disturbance which was perceived by the flight crew to be a disturbance in yaw with no attendant lateral motion evident in the resulting manoeuvre. They believed that the yawing motion had been caused by an uncommanded rudder input. The disturbance was accompanied by a loud bang which was noted by both the flight crew and some of the cabin attendants. They all reported the noise as being coincident with the disturbance. At the time of the event the aircraft was configured as follows: flaps and slats 'IN', landing gear 'UP', auto pilot 'OFF', pitch trim (systems 1 and 2) 'ON' and yaw damper (systems 1 and 2) 'ON'. The aircraft was clear of cloud and there were no other aircraft reported in the vicinity. Following the disturbance the aircraft appeared to behave normally. However, the commander decided to return to London (Heathrow) rather than commence a transatlantic flight following a suspected uncommanded flight control input. An uneventful, overweight landing on Runway 09L was completed at 1624 hrs. Ref. AAIB Bulletin No: 2/2001, ref EW/C2000/6/10. No cause attributed. See page 2.


10/3/99. A-300. American Airlines. During cruise flight, pilots experienced an uncommanded movement of the aircraft described as a "rudder jolt." Rudder system investigated by the NTSB. See page 5.


5/11/99. A-300. American Airlines. Flt 916 experienced multiple rudder deflections that caused the airplane to yaw excessively from side to side while on final approach to Miami. Ref. NTSB Monthly Report DCA99IA058 and NTSB AVIATION ACCIDENT/INCIDENT DATABASE REPORT. Report Number: DCA99IA058. See page 6.
This is still a PRELIMINARY Report in this NTSB database.

9/?/96. A-300. Near Luis Munoz Marin Int'L, PR. Aircraft started to shake and yaw with rudder pedal movement shortly after leveling at FL 310. The aircraft was slowed down and the flight characteristics returned to normal. An emergency was declared and the flight made an overweight landing at SJU. Ref. Aviation Safety Reporting System Report Number: 347914. See page 7.

[Raas767]

I havn't read all the posts on this so forgive me if this is redundant, but I have heard that FedEx has grounded some of their A310's because they found a few that showed signs of delamination on the vertical stab. Any truth to this?

[Flight Safety]

Dagger Dirk, if you add this incident (already posted elsewhere) then we may be looking at 6 total incidents of this type.

"LOS ANGELES (CNN) -- An American Airlines Airbus jetliner departing Lima, Peru, Wednesday evening experienced severe rudder problems during takeoff, forcing it to return to the airport, CNN learned Friday.

"The aircraft, an Airbus A300-600, is the same model aircraft as American Airlines
Flight 587.

"In Wednesday's incident in Peru, the pilots reported "fish tailing" soon after takeoff.

"An aviation source told CNN the aircraft experienced severe rudder fluctuations. A
preliminary NTSB report said the plane landed safely and its flight recorders have
been pulled for further investigation.

Here's the NTSB preliminary report...

NTSB Identification: DCA02WA011

Scheduled 14 CFRPart 121 operation of Air Carrier AMERICAN AIRLINES INC
Incident occurred Wednesday, November 28, 2001 at Lima PE
Aircraft:Airbus Industrie A300-600, registration: N7055A

American Airlines A300-600 flight reported "fish tailing" soon after takeoff from Lima, Peru, on November 28, 2001. The flight returned to land at Lima without injuries. The flight recorders were pulled pending possible readout.

[boofhead]

According to the NY Post sunday, there were at least two witnesses to the initial loss of control of the A300, both of whom said they had a clear view and both were dissmissed, they say, by investigators. One was a police officer. Their story is that they clearly saw the initial explosion, and heard a sharp noise. The intitial explosion was alongside the fuselage, at the right side, and they said they saw the right engine come off after the airplane pitched down, followed by the vertical stab separation. But they say the stab did not seem, to them, to have initiated the chain of events. OK, they are not aviation trained, but maybe there is something in their stories.

[ATC Watcher]

I was once explained by a psy on an accident ivestigation that the memory can switch chain of events in case of psychological shock, such as witnessing an accident.
The "flames"and "explosions "or the noise of the explosion are generally what struck the memory brain and in re-collecting the events later, one would have the tendency to attribute this "shock "as the first event in the chain. This can be even collectively experienced by a group of witnesses, who saw an accident.
This is for this reason, that generally investigators do not consider eye witnesses reports as factual, and generally they are contradicted by the "hard "evidence such as FDR.
If, as you said, the NTSB diregarded the 2 eye witness accounts , that could mean that the chain of event is already well established by the FDR readings..
But all this is speculation of course...

[SaturnV]

This is the New York Post article, written by a columnist, and not carried as a news story. Again shows that what witnesses actually saw and what they think they saw often can be quite different. In AA587, the wreckage pattern and the flight data recorder contradict the two observations below.

"December 2, 2001 -- LITTLE wonder the National Transportation Safety Board has bleated for help from NASA to help them out in the tragic crash of American Airlines Flight 587. The NTSB has shown in the past that it is run by a bunch of bumbling bureaucrats who couldn't find a needle in a thimble.

"Here they were with 265 dead, and God knows how many mourners, giving us this claptrap that the tail fell off mysteriously.

""No tail fell off, not before the explosion. I swear to that," said retired firefighter Tom Lynch, who was doing his
exercise march along Rockaway Beach Boulevard on Nov. 12.

""I had my head up taking in that beautiful, clear day and was staring straight at the plane.

""It made a bank turn and suddenly there was an explosion, orange and black, on the righthand side of the fuselage. It was a small explosion, about half the size of a car.

""The plane kept on going straight for about two or three seconds as if nothing had happened, then ‘vwoof' - the second, big explosion on the right wing, orange and black.

""It was only then that the plane fell apart. It was after the explosion and I'm telling you, the tail was there until the
second explosion."

"Lynch, who lives near the crash site in Belle Harbor, claims he has 13 people who saw the plane on fire before the breakup. Until the explosion the tail was intact.

"He contacted the FBI, NTSB, Rep. Anthony Weiner, and Sens. Chuck Schumer and Hillary Clinton.

""I got no response from anyone," said Lynch, "Sabotage? That's for other people to decide. At first, we hear there were seagulls in the engine, the plane was caught in a jet stream and the tail fell off. No damn tail fell off until after the second explosion."

"Jim Conrad, who retired last month as a police lieutenant after 34 years, accidentally met Lynch in a dentist's office
one week after the crash.

""I saw exactly what Tom saw. I was near a stop light at the Marine Parkway Bridge. First, the small explosion. The plane kept on going, tail intact, then the big explosion and the plane nose-dived. The first thing I said was: ‘The bastards
did it again.'"

"For the NTSB to seriously speculate that the bloody tail fell off in the face of so much evidence that it didn't happen is
arrogant and treating us all like a bunch of morons.

"But NTSB spokesman Ted Lopatkiewicz said: "We don't have any evidence of an explosion [after searching] the wreckage or from the cockpit recorder. It doesn't mean it
didn't happen.""

[TraderAl]

Hate to be a "conspiracy nut", but as more and more detail produces more and more bafflement - seems there was a sharp hard explosion on one side of the plane leading to break-up.

Stinger, or some variation of MANPADS. I assume a bomb would have been noticed attached to the plane.

I am perplexed why this is not a very reasonable possibility which should be accepted until proven not to be the case. I mean, we are at war, arent we?

As far as I am aware the FBI is still involved.

[RatherBeFlying]

Once the leading edge of the fin reached a certain point in its excursions, the resulting yaw may have been too much for the engine pylons; so, they could possibly come off first severing fuel, hydraulic, pneumatic and electric lines giving off both fuel and sparks including from all the breaking metal. Hydraulic fluid is petroleum based, i.e. flammable, and likely has a flash point considerably below jet fuel; its ignition could lead to ignition of the jet fuel.

As with the Sibir shoot-down by missile, a bomb or missile explosion would show abundant evidence of blast particles.

[Wino]

Trader AL, When a main spar in a wing, tail or Pylon breaks, the resulting release of energy looks and sounds very much like a bomb.

Go find the films of the test of the 777 Wing SPar to destruction. When the SPar lets go it looks and sounds like someone exploded a bomb in the Boeing factory.

As a science experiment of your own, find a big dry stick and crack it, makes a lot of noise and releases a lot of energy into your hand. Now imagine a big I beam steel girder breaking (which is pretty much what the spar of a wing is, only bigger.)

Wino

[SaturnV]

Aviation Week has an article and pictures (not the best quality) taken from an NSTB video of the vertical stabilizer. According to the Aviation Week article, different failure modes are seen in the lug attach points for the vertical stabilizer, including a skin delamination at the aft left attach point.
http://www.AviationNow.com/content/publication/awst/20011203/avi_air.htm
________________________________________
Trader, if you want to pursue conspiracy theories, the far better candidate is ascertaining who prepared and mailed the anthrax letters, --as it now seems spores of that quality and purified concentration were previously made only in U.S. Department of Defense biological-warfare laboratories. And as it seems no other country or group has ever achieved that level of capability.

[Dagger Dirk]

From the article at http://www.aviationnow.com/content/publication/awst/20011203/avi_air.htm

The A300 has a yaw damper that can move the rudder at a rate of up to 39 deg. per sec. Maximum throw is limited to ±10 deg. at speeds below 165 kt., reducing to 2 deg. at maximum operating speed. The two-channel yaw damper actuator is separate from the autopilot yaw actuator, and yaw damper inputs are not felt at the pedals

The A300 has a rudder limiter that places variable stops on the actuator input, depending upon airspeed. Two computers electrically drive the stops. Full 30-deg. travel is allowed up to 165 kt., then it is cut back to 3.5 deg. at 395 kt.

...the rudder position measurement became unreliable 2.5 sec. before the FDR stopped. Lateral acceleration increased to 0.8g, an extreme value for forces in that direction. Based on radar data, the airspeed was about 250 kt. at that point.

From the NTSB Factual
Based on radar data, flight 587 took off approximately 105 seconds behind Japan Airlines flight 47, a Boeing 747. The FDR indicates that flight 587 encountered two wake vortices generated by JAL flight 47. The second wake encounter occurs about 8 seconds before the end of the FDR data. For the first few seconds after the second wake encounter, the aircraft responded to flight control inputs. Both wake encounters averaged about 0.1 G lateral (side to side) movement. During the last 8 seconds of FDR data, the plane experienced three stronger lateral movements, two to the right of 0.3 and 0.4 Gs, and then one to the left of 0.3 Gs. These lateral forces corresponded in time with rudder movements. The NTSB continues to investigate the cause of the rudder movements.

The Electronics are the brains, the Hydraulic actuators are the muscle, but the electrical inputs to those actuators are the messages that convey flight control system commands. Just wondering here if there may not be a wiring-related dimension to AA587 and the five other instances of A300 uncommanded yaw. Rudder pedal inputs, autopilot outputs, the yaw damper's signals and the rudder limiter's variable stops all depend upon wiring transmitting commands to the hydraulic actuators - and wiring can fail. It can fail intermittently. As per my earlier theory about hydraulic hammer, it is equally possible that the computer-selected rudder limiter's variable stop positions, which are electrically driven, could have been driven to distraction (or out of the equation) by a wiring fault.

Without a doubt the hydraulic system is capable of driving the rudder at a high rate to high deflections (circa 30 degrees), and if those variable stops were out of position, the forces on the fin as a result of a rapidly applied rudder "throw" would be destructive (fin flutter mode entered or not). Indeed the FAA had criticised American Airlines SOP's for unusual attitude recovery as being too reliant upon the rudder. They were concerned that this might cause fin overstress. So what would you need to look for by way of a fault? I would look for a rudder-related wiring bundle traversing a corner down there in the empennage, a metal edge upon which it could rub or chafe - and short or arc or interact inductively with another circuit. That bundle would possibly carry both the rudder limiter and autopilot-controlled FCS inputs to the rudder actuators (perhaps even the yaw-damper signals as well). I would look in all of the A300 aircraft (six to date) that have experienced this phenomenon.

But why would this have happened to AA587 during a wake encounter? Think of the rudder as being "normally neutrally dormant". That is to say that unless you have an engine failure or are recovering from an unusual attitude or carrying out a croswind landing, normally the rudder sits peaceably in trail and any yaw imbalance is compensated for by a combination of having symmetrically balanced engine power and via the autopilot-controlled rudder trim. The significance is this. If there were to be an electrical wiring "ticking" fault down around the tail it too could lie latently dormant until such time as the FCs (flight control system) had a need to make a significant input to the rudder actuator - during a rudder deflection or aircraft yaw induced by a wake encounter for instance. The FCS would call for a corrective rudder deflection but because of the wiring fault the rudder limiter's variable stops are absent - and so the FCS computer's very reasonable request (in percentage throw perhaps?) becomes a gross rudder deflection.

What happens next? This is where you need some systems knowledge and imagination (to be sure). Two things could happen next. Firstly the FCS computer would react to a massive yaw (that it hadn't ordered) by treating it just as it had treated the original gust response requirement - it would feed in a correction of an appropriate amplitude. Because this would be towards the NULL position of the rudder, an overthrow would be less/not likely. However the next lateral gust of the continuing wake encounter would bring about a repeat of the first massive yaw input. If you then get a little out-of-phase with the required inputs and the rudder exceeding max throw for that speed, well you might stall the vertical fin or it might enter a fin flutter mode. In the former case any stall would be momentary because the FCS corrective inputs would tend to immediately unstall the fin. But in the latter case, you could have a harmonic set up between the FCS computer calling for minor corrections and it becoming out-of-kilter with the rudder's over-travel. Because of the limiting stops being mispositioned the rudder travels further and because of that there is no longer any logical relationship between rudder response and the magnitude and periodicity of the FCS computer's commanded corrections. In simple terms it might then be zigging instead of zagging and amplifying the rudder/fin interaction (leading to the perplexing "rattle" heard on the CVR). An out-of-phase computer frantically driving an overthrowing rudder? I am trying to think of an analogy. Automotive understeer/oversteer? That unfortunately doesn't convey the correct imagery. Perhaps a temp datum system or prop control "hunting" around a mean? But in the case of a destructive rudder throw and an always lagging and out-of-phase FCS computer, the better simile might be the roller-coaster ride of a divergent phugoid - but around the vertical axis.

What about the incidents that weren't wake encounter initiated? Perhaps it's just one of those phantom ticking faults where the short (or ticking fault arc) makes and breaks as the fuselage flexes during the rudder-induced yaw and/or with the directional changes of the yaw. The thing to remember about wires in a wiring bundle interacting is that the manifestation can be in either or both associated systems. That is the phenomena unique to wiring-fault induced systems outages. It can be very perplexing, particularly if it's an intermittency. One manifestation can be a single rudder jolt, the other can be the compromise of the limiter's variable stops positioning. A third could be an uncommanded yaw-damper actuation.

If you examine the six incidents (see this rtf file (http://www.iasa-intl.com/PDF/AA587yawSurvey.rtf)) you will note that they are all "unresolved" - however they all have the smell of an intermittent electrical fault.

[FFFlyer]

Any system when it becomes unstable reacts in an unpredictable and totally random manner. Traffic flow is a good example. The reason that busy traffic on the motorway slows down and speeds up for no apparent reason is because the traffic flow rate exceeds the capabilities of the road network and the rate of traffic movement becomes unstable.
If for whatever reason, hydraulic or electrical, the system had become unstable then the effects would be totally unpredictable.

[TraderAl]

I challenge the more learned readers of this forum to explain how a stinger or MANPADS could (not an automatic could not) have caused 587 with the results noted and documented to date.

Can it be done?

I think it behooves the people in the industry to try and prove is was a MANPADS first and then move on to other reasons if it can not be done.

Why? Simply because we are at war and those professionally involved in the industry are obligated to approach the crash in this fashion.

It seems most here have only cursory knowledge about MANPADS and retort with either a bias to purposefully ignore such avenues of approach (denial, fear, not chic in times prior to current war) by simply labeling it as "conspiracy theory" or alarmist etc etc etc ; or provide commonly held wisdom such as shrapnel or missile trails.

I am appealing for someone who knows MANPADS unequivocally to supply some information, not parrot belief systems. I am asking, not challenging. Begging really. And I would actually prefer the outcome of such scrutiny to arrive at the conclusion that most on this forum wish to immediately leap towards.

As I have mentioned before, one such "expert" I am in touch with on first hand, who use to deploy MANPADS for elite military squads in a past life (Stinger used by SOPs) says all he has seen of 587 is consistent with what he knows a Stinger does. This man was a soldier on the ground, not a pilot. He looked up, not down.

Are there other "experts" who can also provide information to such a view? This "expert" I know claims Stingers do not provide shrapnel debris or fire damge, but produces a massive air blast which rips appendages from the main body of an AC. From this person's point of view, he would not at all find a "pristine" tail assembly to disprove a Stinger hit, but would expect that sort of damage.

That is the full limit of my info from an expert in MANPADS.

I also know a bit about composites, enough to risk making a fool out of myself in front of such readership as this forum, having worked with them on large sailing crafts in spars and hulls. I do know that they are 100% reliable and better than metal over the life of the craft provided they do not "blow-up" almost immediately with any sort of trial at sea. They do not blow up after being used for 10 years or so. I also know that at sea, a tried and true composite hull/spar is something I would find much more comfort in than metal. Personally, I would prefer a woven 6 or 7 layered fiberglass hull to an aluminum hull in the midst of a storm. I also would not have any doubts over my carbon fiber mast provided it had already gone through such a storm. If the boat had not had such sea-test,I would prefer metal and wood. Obviously this is an analogy considering 587 was a well "sea-tested" craft.

What I find alarming is that previously held conceptions developed from, mainly, TWA 800 investigations are being used towards 587 without thought to the current context. I personally found that the idea of a missile was far fetched for TWA 800.

But.

May I remind this readership that we are at war with an enemy who already has achieved the fantastic. Ask yourself, if I described the potential for the WTC last year, would you have laughed and scolded me out of this forum? Would it be considered mere "conspiracy theory" and suggest I was the worst kind of nut, a lay person nut? Would Capt Pprune shut me down immediately?

I think it is sober and pragmatic to ask those who know, not those who think they know, for solid evidence that a MANPADS was a possibility in regards to 587. If such evidence cannot be provided, or if affirmation of the damage is ocnsistent with a Stinger can not be provided, then we shoudl move on to non-war scenarios. To date I have had contact only with one such "expert", someone who has actually fired the things, and I am disturbed with his thoughts.

In North America, if one hears hoof beats behind you, chances are it is a horse, not a zebra. We are at war.

If such a possibility of a MANPADS causing 587 can be easily eliminated, not from surmise but rather as it can not be shown to fit the cause by an expert, that a reasonable scenario cannot be made for this agent causing 587, then we move on to NASA and mystery. There is no mysterious conspiracy out there, there is a conspiracy! What more than WTC and Ridge declaring an "alert" is required to show the seriousness of the situation?

[arcniz]

FFFlyer: I disagree with your statement that electronic or mechanical 'systems' typically become totally unpredictable and random when they enter "unstable" territory. It is very hard to get real things to behave randomly. Closer to the mark is to say that they will behave in an 'uncharacterized' manner which may be counterintuitive at first brush. An inherent problem with the complex control processes that result when pilots and aircraft combine with digital and analog electronics, mechanical actuators, and sensors is that they can have unwelcome behaviors in boundary conditions. The #1 principle of designing and making control systems is: if a function, mode, condition, etc. hasn't been specifically simulated or tested, one cannot know with any confidence what will really happen in that case.

DAGGERDIRK: IMHO, your suspicion re a non-obvious fault mechanism in the controls warrants exploration. You assume that the rudder travel stops are mechanical or quasi-mechanical, but is that really the case? If they are being changed in complex ways in real-time, it would make sone sense to put those interlocks into one or another level of software (or electronic hard-wired) loop. At a minimum, some secondary process controls the stops, n'est ce pas?

A complex set of sensors, manual controls, actuators, electronics and computer programs interact with aerodynamics and crew commands to determine the actual rudder movement in real time. Surely the control process has n-many operational 'modes', each with its own behavior plan, priority, and inherent speeds, delays, and damping factors. Somewhere in there may be an unexamined sensitivity to, say, climb attitude, sudden lateral acceleration from wake, noisy or intermitent sensor response, pilot/autopilot rudder input, and fuselage resonances - the sensor responses to the second, etc, reflections of the sharp wake bumps as they bounce around the airframe / engine mechanical matrix. In short, there could be a 'bug' in the time-dimension responses of the control system.

Whatever the cause of this tragic accident, I strongly believe that future aircraft designs should include secondary FDR's -plus aditional sensors- that are easily and routinely offloaded after each flight - with the full envelope of flight data for each individual bird captured and stored for the entire service life of the aircraft fleet - and beyond. SOP copies to the factory, every bit of data automatically analyzed there and used to confirm and refine design engineering and maintenance assumptions. Faults usually manifest in small ways before the big one. Better to have the aircraft tell us what they're up to while still in one piece.

Ditto on composites. I have seen published practical methods to fabricate sensors into aircraft composite structures and elements so they can me monitored in real-time through their entire operating life.

Maybe new aircraft should use more of the technology that is readily available to do more/better self-diagnosis. Diagnostic systems are unobtrusive and not inherently very expensive, next to the cost of insurance settlements, nor do they significantly compromise aircraft design, weight or safety. They do improve the ability to find design and wear problems, to track operating results, and to find the 'glitches' before destiny does.

[ 05 December 2001: Message edited by: systemsguy ]

[SaturnV]

Trader Al, you persist in seeking to have someone, anyone, prove a negative to you. For whatever reason, you seem to have convinced yourself that this plane crashed as a result of a terrorist act because the United States is at "war"; and, ipso facto, all plane crashes that occur during wartime must first be shown as not having been the result of eneny action before other causes can be investigated.

In applying your wartime postulate to AA587, you choose to ignore every bit of evidence to the contrary, and drag in a so-called 'expert' who was not there, who has not seen the wreckage, who has not reviewed the data recorders, yet who posits that the crash is apparently similar to what he has observed after supposedly firing a MANPADS at an airplane.

Your last post declared: "This "expert" I know claims Stingers do not provide shrapnel debris or fire damge, but produces a massive air blast which rips appendages from the main body of an AC. From this person's point of view, he would not at all find a "pristine" tail assembly to disprove a Stinger hit, but would expect that sort of damage."

The Stinger has a 2.2 lb. penetrating high explosive warhead. (Stingers use a passive infrared system to home in on targets.) A penetrating warhead uses impact and explosive self-destruction to destroy the target, and it is not a proximity airburst weapon.

Thus, one should expect to find evidence of impact and explosion in the wreckage of AA587, including on the vertical stabilizer and rudder as these parts departed the aircraft first. Presumably, to fit your hypothesis, this is where the missile would have hit. (You may wish to review the NTSB preliminary examination of the FDR and the physical examination of both engines and note that both engines were operating normally up to the point they separated, which would seem to indicate that neither engine was hit by a hypothetical missile.

BTW, I'm sure NASA has yet to prove to a few souls out there that the manned lunar landing was not staged on a Hollywood backlot. After all, Hollywood subsequently went on to make a movie, Capricorn One, on just such a premise.

[GeofJ]

Heres a question for all of the conspiracy theorists and the "eyewitnesses" - If there was an explosion and an engine fell off and then the tail came off how did the tail wind up in the water and both engines come off further along the flight path over land? Unless I am missing something here it seems that the eyewitness reports do not match physical evidence.

As to the question of stingers or other ground launched missiles - unlike Afghanistan it would be extremely difficult to obtain or import one into the US. In addition all of these ground launched missiles usually create a huge exhaust plume when the back blast of the missile motors igniting stir up all the cr@p in the immediate vicinity of the launcher - this would be hard to hide as well.

[Dagger Dirk]

AD/AB3/107 Rudder Trim Control Switch 9/97


Applicability: All models A300-600.

Requirement: Replace control switches P/N 097-023-00 with new switches P/N 097-023-01 in accordance with Airbus Industrie Service Bulletin A300-27-6037.
Note 1. AD/AB3/90 is cancelled.
Note 2. DGAC AD 97-111-219(B) refers.
Compliance: Unless previously accomplished prior to 14 January 1998.
This airworthiness directive becomes effective on 14 August 1997.
Background: The actions required by this AD are to prevent any interference between the 408VU panel and the rudder trim control knob, which could prevent the self recentering of the switch to the neutral position when released, thus causing a rudder movement up to the maximum deflection, and which could lead to critical flight situations. AD/AB3/90 required an ongoing compliance whenever the switch was replaced. This AD supersedes AD/AB3/90 and constitutes terminating action for that AD
http://www.casa.gov.au/avreg/aircraft/ad/OVER/AB3/AB3-107.HTM

[TraderAl]

This is why I am looking for someone who knows, as the following quote is a good illustration of the current dismissive cant:

"The Stinger has a 2.2 lb. penetrating high explosive warhead. (Stingers use a passive infrared system to home in on targets.) A penetrating warhead uses impact and explosive self-destruction to destroy the target, and it is not a proximity airburst weapon."

That I know is not true, they work on a proximity airburst. That I do know. Their guidance system is infrared but also has sophisticated software which prevents the missile, as it moves so much faster than the plane, especially at only a few thousand feet in take -off, to bypass the target so they allow for the proximity burst. he software also serves so the missile does not strike at the engine or heat source but in proximity.

This is why I am concerned as to date all we hear are cant, brief condescending dismissive gestures and disinformation. I am not out to promote a thesis but to shed the thesis. It seems by even mentioning the topic one is branded a "conspiracy nut". But the thesis cannot be shed with simple pitying glances and disdain for the unwashed ones who pose the question. Answers to date in regards to MANPADS are cant, not analysis. The above quote is from someone who does not work with Stingers or know their ordance, but someone like me who has simply lifted data to suite their objective from the web.

I have a fear this will play opposite from TWA 800, where the FBI panicked and instantly jumped to the view that there was a bomb, then as the facts bcame apparent they had already done the damage and to this date have a pack of conspiracy folks chewing over TWA 800. This time there does exist a deadly and unprecedented conspiracy. But rather than deal with/in that context, the NSTB immediately stepped in with what seemed to be a pre-arranged strategy and precluded the FBI. But the FBI now keeps in contact just as the NSTB did in the first phase of TWA 800. Beyond firm dismissive sentence with no analysis, except that terrorists were not heard in the cockpit and no sign of any on board bomb, I have heard nothing definitive in regards to MANPADS. I really really wish I could hear something.

[SaturnV]

http://twa800.com/images/imp.jpg

TraderAl, this is a picture of a Stinger missile hitting an F-14 on a static stand. Note the smoke trail and the bright flash. No witness to AA587 has reported a similar bright flash nor any smoke trail from burning propellant. (Given the altitude and the visibility that day, a smoke trail would have been visible from the launch site up to impact point)

A Stinger's 2.2 lb. warhead is puny. The weight is about five times that of the explosive charge in an ordinary concussion grenade. A 2.2lb warhead detonating in a proximity airburst would likely not be lethal to an aircraft the size of an A-300. By way of comparison, the SA-5 surface to air missile that struck the Sibir Airlines Tupolov over the Black Sea several months ago carries a 450 pound HE warhead. The SA-5 explodes in a proximity airburst. As I recall, the Sibir pilots were aware they had been hit and had communication with ATC to that effect.

You stated that you know that a Stinger uses a proximity airburst to destroy its target (rather than an impact and warhead explosion mode). Can you please give a factual source for this knowledge. If you cannot, I suggest this prolonged sidetrack to an otherwise informative discussion thread be put to rest.

[Mirkin About]

Trader Al, Janes lists all variants of the Stinger as having a 1KG HE blast smooth case fragmentation head with a time delay CONTACT fuse . Is that clear enough , can we please get back to the "merits" of composite construction as the posts so far have been fascinating.

[ 06 December 2001: Message edited by: Mirkin About ]

[Evo7]

Mirkin About

I've tried quoting Janes already... :( :rolleyes:

[FFFlyer]

SystemsGuy - surely if there was lose or damaged wiring making intermittent contact then this scenario would not have been specifically simulated or tested.

'If a function, mode, condition, etc. hasn't been specifically simulated or tested, one cannot know with any confidence what will really happen in that case.'
Isn't this then unpredictable and random behaviour?

[rubecula]

FYI (http://www.scoop.co.nz/mason/stories/HL0112/S00027.htm)

[ 06 December 2001: Message edited by: rubecula ]

[Dagger Dirk]

I've reproduced some facts between the lines in order to make it easier to refer to the data.

A learned aerodynamicist said: "I can see how a wiring fault could change persistent state settings, such as rudder travel limitations, but I do not see how a wiring fault could generate oscillatory commands."

The question and answer session [below at bottom] was probably not quite clear enough (in its basic premise) - so I'll try and re-state the proposition:

[b]a. Ockham's Razor tells me that the second wake encounter was the initiator. What did it initiate? A significant yaw around the vertical axis. What did the FCS think of that? It quickly decided that that yaw had to be corrected and fed in a restorative yawing moment via a rudder displacement signal. In a serviceable airplane that would have been the end of that i.e. the aircraft's natural directional stability plus the rudder movement would have dampened down that yaw quite quickly with little or no oscillation. But what if the rudder limiter's variable stops were not where they should have been? The FCS computer software would be saying "a yaw of that magnitude requires 15% of the presently allowable rudder deflection (at this speed)" and so it applies that. However (see the limiter's variability directly below), instead of applying 15% of the (say) 20 degrees of travel allowed by the variable stops at 250kts it applies 15% of the full 30 degree travel (to the hard stops). The result is an overcompensation (which the FCS understandably misreads as another externally inspired yaw) and so the FCS feeds in another restorative rudder correction which begets yet another overtravel. So instead of a dampening you have an excitation process underway. By this time we have set up a destructive harmonic (the CVR "rattle") and a fin-rudder interaction that has the fin into an out-of-phase flexure (an FCS-induced flutter mode if you will). Perhaps we should see it as the mirror image of aerodynamically-inspired flutter. If the software thinks in percentages of available travel, then the theory is sound.

b. Now why would/could this be? If a wiring fault existed, which caused the variable (computer-driven) stops to be reset to the hard stops, would the computer know? i.e. is there some feedback mechanism that would indicate that this was the case? Possibly/probably not....why should there be? Few systems make provision for wiring flaws. Why wouldn't pilot pedal-inputs be excessive also? Normally a rudder sits quiescently and neutrally in trail. Large rudder displacements are only used in (say) low speed landing or take-offs in crosswinds, low-speed (practise) asymmetric work (and most of that in the simulator) or, at higher IAS, unusual attitude recoveries (wake or CAT - both quite rare). At the lower speeds the variable limiter stops are not in play. Minor disturbances or out-of-trim/unbalanced minor asymmetric thrust situations are usually soaked up quickly by the FCS running the rudder-trim to softly bias the rudder. It is only when a wake upset hits with a large lateral gust that the FCS would be stimulated to respond with a rapid corrective and restorative rudder movement of any magnitude. The latent flaw needs to be "kick-started".

c. So whether any wiring (or software) induced flaw in the rudder limiter's variable stops was permanent or intermittent, I doubt whether there is an FCS BITE function to ascertain its existence. It would simply lurk and await its (yawing) moment. Its moment for AA587 may have been a lateral gust sufficiently great to have kick-started a process that was self-sustaining and divergent (i.e. one that exceeded the dampening capabilities of the airplane's inherent directional stability at that speed). Liken it to the 737's "cross-over" speed.

d. If you examine the other five incidents in light of this, you may also be able to identify that they may have luckily been in a speed regime where the inherent directional damping was sufficient to cause the overall process NOT to be divergent, and/or without a sufficiently strong lateral gust to get the process "kick-started". (other five: http://www.iasa-intl.com/PDF/AA587yawSurvey.rtf )

I hope that's clear and comprehensible. I don't have the facts on the A300 nor AA587 to say more than that I think it's an analysis worthy of follow-up - simply because it fits the bill and accords with a logical dissection of the scenario. There's no doubt that postulating a divergent phugoid around the vertical axis might inspire some scoffing in academic quarters - but Airbus have managed some amazing things with their designs.

I retreat to the notion that a computer is a computer, and the supposition that an FCS can handle an unknown loss of a major variable is likely wishful thinking. Garbage, in, garbage out.

Consider all the modal problems we've seen with FBW and near-FBW aircraft as they encounter unexpected flight conditions. The A320 with spoilers stuck out after a maintenance check, F-100 with a locked air/ground sensor, the A320 Warsaw crash (another air/ground modality). etc etc (you know of many more).
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +
The A300 has a rudder limiter that places variable stops on the actuator input, depending upon airspeed. Two computers electrically drive the stops. Full 30-deg. travel is allowed up to 165 kt., then it is cut back to only 3.5 deg. at 395 kt.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +

Quest: What makes the rudder move? Answer: hydraulics (in response to electrical signals from the electronics (the FCS computers) or pilots' pedals or yaw-damper signals or gusts)

Quest: What would cause fin-destructive rudder movement? Answer: Excessive throw (in spite of or beyond the rudder limiter's variable stops) or a flutter-inducing excessive rate

Quest: Why would you get excessive rate? Answer: an FCS failure (hydraulic chatter caused by either hyd-valve cross-talk or an electrical wiring glitch)

Quest: Why would you get excessive rudder-throw? Answer: If the variable stops on the rudder limiter were inappropriately set for the speed. FCS calls for a % of what should be available, but gets instead a % of what is available.

Quest: How could the variable stops become mis-set? Answer: Software patch fault / intermittent or permanent wiring fault / latent software anomaly

Quest: Why would this fault turn up infrequently? Answer: Unique combination of circumstances required:
a. Aircraft at higher IAS with limiter inop (or variable stops mis-set) and rudder able to be deflected beyond its design stops for that IAS (but would ONLY do so if stimulated by a requirement to counter yaw)
b. What would cause the rudder to need to counter yaw to the extent that it might exceed the (now absent) limit of the missing rudder limiter stops? Answer: A wake turbulence encounter (i.e. an external stimuli of some significant magnitude). Usually the rudder sits peaceably in trail with no real task. Slight out-of-trim is usually constantly and continually accommodated by a rudder-trim imposed rudder-bias.

Quest: So what would happen after a rudder moves excessively in response to an FCS signal? Answer: The FCS would identify a need to again immediately deflect the rudder (simply because the resultant yaw would have been far in excess of the reaction to the initial yaw that it directed - and expected). => react/over-react/react/over-react => divergent phugoid

Quest: If this confusion continues (between the FCS reasonable request and the rudder's resultant excessive travel), what might happen? Answer: The "rattle" heard on the AA587 CVR may have been that rapido argument between the FCS and the rudder, manifested initially by a chattering of hyd valves, latterly (or simultaneously) by a flailing rudder-induced fin-flutter.

[TraderAl]

Heh, about to give up.

My knowledge of the proximity burst comes from an ex-US Ranger who was in charge of deploying stingers in various overseas conditions for several years. As far as using stingers and being on the ground he is an expert. If you are an American your tax dollars spent mucho on his education. If you read the content from China Lake that comes with the pic of the stinger strike, you will find it destroys aircraft by detaching appendages and that rarely is a large explosion seen as the white fireball in daytime is not easily detectable. The white flash goes off like a photog flash bulb. In fact that si why the China Lake test was done at dusk, as in daylight the stinger strike is hard to discern. Reports of using stingers in Afghanistan in the 80s states that what is discerned from the ground during daylight is no explosion, but a wing or tail falls off and then the aircraft drops. The trail is not easily seen due to the speed and the effieciency of the stinger. The destruction of aircraft by dettachment of appendages is done through a proximity blast, not contact. The 2.2 pounds is more than enough to detach a wing or a tail in proximity. Larger amounts of explosive is required if you depend on contact or penetration. I do not know what "smooth casement fragmentation" means. Does it mean that shotgun like pattern would be seen on AC surface or does it mean it is only containing and shaping the burst? The above is all I know for sure.

I can read Janes. I can do "China Lake" in Google. I can read all the wild TWA 800 stuff. What I am appealing for is a qualified response from someone reading this who has first hand knowledge about MANPADS forensics. NOt those who have already made up their mind and then start hitting Google.Com. Why is the thesis of a stinger, known to be in the possesion of those who dropped the WTC and considering all of the above, not a very calm and non-emotional consideration? Why does it bring up hysteria and disdain and even anger?

If I were a pilot, I would prefer to know that the approaches are not vulnerable to such an attack, which the first step would be to ascertain whether such an attack took place with AA 587.

It is easy to see the "stretch" being made with flutter, hydraulic lock chatter, composite material - all looking internal in the AC. Why not calcualte the load required to sheer the tail off of a healthy AC and then look for something that provides such a load? Why not first assume the AC was healthy (which years of operation would suggest) and the load was extraordinary.

Obviously this was what was first considered in terms of the wake consideration. In that context, this is the most pragmatic posting in regards to the question of the topic heading.

I find it far more likely that some extraordinary load sheered off a healthy tail rather than consider the total gutting of the second largest airplane manufacturer due to a flawed core design approach, the use of composites. This might be the case, but why not consider the simple answer first?

[Few Cloudy]

Well Trader Al, I guess that one reason some people don't like the missile theory, apart from not having detected missile damage so far, is that it is out of sync. with the modus operandi on 11.September.

Hallmarks then were,

No import of weapons - use of what was around and improvisation (in this case aircraft full of fuel and plastic knives)

Suicide method in order to get right to the objective (the WTT and Pentagon)

No military hardware and no random crash site.

The AA crash, if caused by missile, would be a new tactic for bin Ladin.

[sky9]

Trader Al

Listen very carefully I'll say his only once:
Foxtrot Oscar :mad:

and start your own thread somewhere else: Better still start your own BB.

[arcniz]

FFFlyer - re Surely... not tested. Where I come from, as a designer you test it IF IT COULD happen. That's what separates the beginners from the finishers in the technology game - and the folks who design airframe control systems are surely not lightweights or careless. Prudent care would require testing critical control system behavior for every failure imaginable before releasing the design. That this was done should be ascertainable as a matter of record. How do you say subpoena in French?

Probably the structural flaw in the system, if one exists, is that the most careful top to bottom system-level scrutiny occurs once at original design time and is not repeated with anything resembling such intensity when changes are made, despite the acknowledged propensity of software 'fixes' for causing unintended consequences. Removing this long-term management problem is the rationale behind my suggestion of 'perpetual re-simulation' during the airframe product life.

From the POV of a computer looking at the universe in slices of a few millionths or billionths of a second, everything is lumpy. An ordinary gold-plated aircraft toggle switch, for example, has to be checked over a long span of time - say a few milliseconds, to see if it is really open or closed, because the contacts bounce a little when the switch reassuringly thunks into position, and instantaneous sample checks during the bounce interval may say open, may say closed. Electronic and especially digital controls have to be designed to tolerate ambiguity and noise as normal qualities of the universe. But intermittent shorts or opens and other non-characteristic noise may be interpreted in ways different from what one would want. One typical effect of noise on sense lines is that decisions may be deferred - or at least greatly delayed, while waiting for it to go away.

With appropriate software design, any/all events of observed transients on signal and sensor and control wires can and should be recorded as abnormal events for maintenance review. This provides red-flags before hard failure. How many aircraft have this type of diagnostic recordkeeping for the wiring web?


Difference between 'unpredictable and random' vs 'not tested' in this case is (sadly) that you can reconstruct the facts AFTER the event when the process is deterministic instead of random -- just as you could have constructed them BEFORE the event, if sufficient analysis were applied.

If events are truly random, even luck will not help you much in prediction or reconstruction.

[arcniz]

DaggerDirk - It is interesting, in passing, that Ozzies and others of the British persuasion fall back to the logical Mr. Occam, while Yanks tend to cite the darkly capricious Mr. Murphy.

A thought for your learned aerodynamicist: Electronic, digital, and human control processes all take information from one or more events happening in the past and use that to determine events or processes happening in the future. The control decision is basically: Where, how hard, and for how long?

Time delay and the potential for oscillation are inherent in control sytems. Mass and velocity retard the effects of control, so intended time spans for issued control actions in heavy jet aircraft may be quite long. The trend for modern control systems is to make them heuristic - able to learn from the environment and from consequences of control actions. So, just like a pilot who kicks the pedal harder when he thinks or knows it's jammed, 'smart' control systems will naturally tend to amplify the intensity of their actions if the measured results from control actions are less than expected. Very abnormal outside stimulus (wake) at just the wrong time might conceivably provoke this kind of behavior - on a bad day - but it would probably take a series of precursor events to predispose the control system to excercise very aggressive control authority. In normal and exceptional circumstances, the control systems should have the same objective as the pilot - to push the airframe back into an acceptable envelope.

We do not have sufficient detail or knowledge for any other than armchair analysis, but I strongly concurr with the idea that there is merit in reviewing the class of possibilities suggested by your logic and neatly clarified explanations: the concept that the automatic controls reacting improperly to an uncommon set of circumstances could have scuttled the aircraft by overcontrolling the tail enough to rip it off. Your dialectic of queries is an entirely appropriate way to move the topic forward. Ta.

[Ignition Override]

Do people really believe that a missile caused the AA 587 tragedy? I'm surprised. Now as for TWA 800, several witnesses saw a smoke/flame trail before the plane exploded. That is quite different.

Dagger Dirk has an interesting AD link, which concerns the A-300 tail.

Good topic guys/gals. I plan to read the whole thing when my days off begin after two trips on a 30 year-old plane.

[TraderAl]

Regarding missile strike: it is not an issue of believe or not believe, nor whether there is a "conspiracy" afoot. [Perhaps what is obviously a pre-arranged deal between the FBI and the NTSB to have the NTSB take over the investigation is a "conspiracy", but that does make sense in light of the possible panic and considering the screw-up of TWA-800.]

What is strange and alarming, though, is the the uncritical view of almost all, especially it seems professionals and those who usually leap into a dispute, to consider an extraneous force being present large enough to sheer a sound tail. This was the first view most people pursued, which shows how reasonable this approach is, when considring the wake vortex - but as people figured out that could not be enough of a force we are immediately plunging into surmise.

I would, in time of war, eliminate a missile with 100% certainty and provide proof of that certainty. But to even consider it brings such loathing and panic that clear heads do not prevail - just read previous responds to my questions, they are all emotional and those that offer facts are only shallow and based basically on what are popular tenets easily dredged up on the web. Yet people will go into great detail about composite failure on a AC with over a decade of good performance history. (By the way, a MANPAD would fill both Murphy and Occum's law)

If you consider the record to date on the AA 587 investigation, you will find not one attempt to address this issue, with NTSB allowing surface and flippant considerations to grow and dominate this possible thesis. NTSB has almost categorily eliminated the possibility of a bomb, or knife wielding terorists able to claw their way into the cockpit during take-off, but has been studied in not mentioning a missile. Yet with even far thinner evidence, weeks were spent to prove TWA-800 was a missile. Go figure. The NTSB has not mentioned nor examined the possibility of a MANPAD.

I am sure, with such easily available evidence in the wreckage, a MANPAD thesis can be easily refuted or considered with certainty. Why have no qualified experts eliminated this thesis?

Is it conspiracy or being "nuts" to ask a government agency to release such proof during wartime, after our enemy dropped 3 planes and destroyed the WTC and has suffered us to decale another general threat warning?

[I. M. Esperto]

New York Post

NTSB BIRDBRAINS STICKING HEADS IN ROCKAWAY SAND

By STEVE DUNLEAVY


December 2, 2001 -- LITTLE wonder the National Transportation Safety Board
has bleated for help from NASA to help them out in the tragic crash of
American Airlines Flight 587. The NTSB has shown in the past that it is run
by a bunch of bumbling bureaucrats who couldn't find a needle in a thimble.

Here they were with 265 dead, and God knows how many mourners, giving us
this claptrap that the tail fell off mysteriously.

"No tail fell off, not before the explosion. I swear to that," said retired
firefighter Tom Lynch, who was doing his exercise march along Rockaway
Beach
Boulevard on Nov. 12.

"I had my head up taking in that beautiful, clear day and was staring
straight at the plane.

"It made a bank turn and suddenly there was an explosion, orange and black,
on the righthand side of the fuselage. It was a small explosion, about half
the size of a car.

"The plane kept on going straight for about two or three seconds as if
nothing had happened, then 'vwoof' - the second, big explosion on the right
wing, orange and black.

"It was only then that the plane fell apart. It was after the explosion and
I'm telling you, the tail was there until the second explosion."

Lynch, who lives near the crash site in Belle Harbor, claims he has 13
people who saw the plane on fire before the breakup. Until the explosion
the
tail was intact.

He contacted the FBI, NTSB, Rep. Anthony Weiner, and Sens. Chuck Schumer
and
Hillary Clinton.

"I got no response from anyone," said Lynch, "Sabotage? That's for other
people to decide. At first, we hear there were seagulls in the engine, the
plane was caught in a jet stream and the tail fell off. No damn tail fell
off until after the second explosion."

Jim Conrad, who retired last month as a police lieutenant after 34 years,
accidentally met Lynch in a dentist's office one week after the crash.

"I saw exactly what Tom saw. I was near a stop light at the Marine Parkway
Bridge. First, the small explosion. The plane kept on going, tail intact,
then the big explosion and the plane nose-dived. The first thing I said
was:
'The bastards did it again.'"

For the NTSB to seriously speculate that the bloody tail fell off in the
face of so much evidence that it didn't happen is arrogant and treating us
all like a bunch of morons.

But NTSB spokesman Ted Lopatkiewicz said: "We don't have any evidence of an
explosion [after searching] the wreckage or from the cockpit recorder. It
doesn't mean it didn't happen."

[END]

[innuendo]

The Dec 10 issue of Time magazine carried an article stating that the FAA and Airbus, (I believe it was those two bodies, lost the copy), had written to American Airlines to express their concern about the companies procedures on use of rudder during turbulence. Other than obviously harsh use of the system I can't imagine how you would misuse the rudder during turbulence. Most yaw dampers do the job unless it is extreme.
Any one from AA know what they are talking about?

[stuartbaker]

I've been trying to follow up on a Letter in last week's (4-10 Dec) Flight International which talks about "Aircraft-Pilot Coupling" where pilot inputs in-phase with the aircraft yaw movements upset the stability of the control system. In the example given, of an S3 Viking on test flights out of Pax river, the sideslip forces generated were large enough to break off the vertical stabilizer.

I've found a Master's thesis (http://scholar.lib.vt.edu/theses/available/etd-062199-123258) on the subject but does anybody know anything more about this particular event or have a simplified explanation of the phenomenon? (Preferably one that doesn't include the words Nyquist or Bode 0r any 3 dimensional diagrams)

null (http://null)

[Dagger Dirk]

Possibilities and Plausibilities

1. A software bug in the frequency-time-domain of yaw-axis control response?

2. Rudder-trim switch fouling its panel and able to drive rudder to full throw (3 AD's = a number of goes to get it right => a possible choice [for mis-installation] of two wrong switches)[see previous post this thread]. "interference between the 408VU panel and the rudder trim control knob, which could prevent the self-recentering of the switch to the neutral position when released, thus causing a rudder movement up to the maximum deflection, and which could lead to critical flight situations."
There is actually another almost identical AD covering the aileron trim switch (which sits alongside on that same 408VU panel). Anyone want to theorize whether someone managed to "Murphy" an aileron-trim switch into the rudder-trim switch position? Above the panel they look identical. Below the panel the wiring has been modified for the lengthier rudder-trim switch #3.

3. and now we add PIO's (Pilot Induced Oscillations)

I've reviewed the PIO academic paper (URL in Technobabble's post) and dismiss that as irrelevant. It is EASILY possible to induce PIO's by changing that F14 pilot's stick to stabilator ratio and simulating a hyd-fail with a low-pressure rate-limited actuator. I severely doubt that that is what happened to AA587. There is a world of difference between plugging into a tanker's refuel basket with a crippled FCS and simply riding out a wake turbulence encounter. One is a precision task requiring maximum concentration / fine control technique / many rapid inputs (and is thereby prone to overcontrol) and the other is simply NOT. My money is on there having been an external stimuli (the wake encounter) excitating a latent flaw in an unserviceable system (the rudder limiter - as per my previous post on this thread). Just as perversely, you could rationally theorise about it having been an undetected FCS software glitch - as Systemsguy has put forward. But a fleet-common glitch would perhaps have been more likely to announce its presence over the long history of the early non-FBW Airbusses - than would a latterly developed hard-flaw in a wiring bundle. If NASA could manage to mix British Imperial and metric in a Mars Mission, then it's perhaps possible that a flight control system could contain some flawed logic - the type that doesn't readily accommodate another failure (the rudder limiter) within the same system. It may not seem as silly as an Imperial versus metric fiasco, but Percentage travels can be a rough game -if unintentionally misapplied inside a malfunctioning closed system.

There's no doubt that it is possible to set up a rudder/fin interaction (courtesy of a flawed FCS input) that could lead to fin flutter, composite failure and fin departure. Stepping ahead a little here, I think that the real challenge is in detecting that flight control system failure mode, not in working out more esoteric inspection methods for composites.

PIO expertise: http://www.piofree.com/white_papers_and_essays.htm

[pelican larry]

Any Thoughts ???
From: http://www.newsmax.com/archives/articles/2001/12/17/200515.shtml

Sabotage Explains Flight 587 Crash, Says Expert
Dave Eberhart, NewsMax.com
Tuesday, Dec. 18, 2001
Federal investigators still have no evidence indicating that a benign structural failure played a role in the tail breaking off of Flight 587 last month, sending the plane tumbling into Queens, N.Y., according to AviationNow.com.
But as National Transportation Safety Board and other safety experts wrestle to solve the mystery of the powerful forces that ripped the plane’s fin off and then cast the engines from their mountings, one aviation expert said sabotage of the aircraft’s left engine while still on the ground could explain what shook the aircraft to pieces.

Expert Marshall Smith opined, "A single point failure, the in-flight actuation of the left engine thrust reverser, can account for all three observed phenomena of the clean breaking off of the tail and the failure of both pylons holding the engines.

"If the left engine thrust reverser had either partially or completely actuated during flight, it would cause the plane to go into a flat spin to the left. The airplane would spin something like a flat Frisbee with the right engine pushing forward and the left engine pushing backwards,” Marshall explained.

"Within a second of the flat spin occurring, the sideways windblast would rip off the tail assembly, since it was never designed to take such a side blast of air.

"As soon as the tail assembly broke off, there is now very little wind resistance to the flat spin. At this point the engines would cause the aircraft to spin even faster with the g-forces away from the center of the spin becoming so great that both engines would be violently ripped off the wings and thrown outward away from the plane,” Marshall said.

Marshall’s opinion is that the spin accounted for why the engines were found so far away from the crash site and why the tail came off first.

Terrorist Scenario

The mechanical engineer, aviation ground school instructor and former NASA adviser painted this scenario:


During the night, a terrorist saboteur disguised as a ground crew mechanic reached up in the back of the left jet engine of the American Airlines Airbus and cut the hydraulic line going to the thrust reverser actuator and the control safety sensor lines.

The next morning after the jet engines were started, the hydraulic fluid began dripping from the cut line.

When the aircraft was about 3,000 feet in the air, the sound of an "airframe rattle” was heard in the cockpit voice recorder (CVR) record. Cause: the tampered-with left thrust reverser had started to close, causing the plane to turn to the left.

The pilot compensated by applying right rudder to bring the nose back to straight flight by turning to the right.

The aircraft commenced a "side slip.” During this condition, the burbling air flowing over the extended control surfaces made the plane shake, rattle and roll, accounting for the airframe rattle noise heard on the CVR at 107 seconds into the flight.

The pilot thought he had overcompensated, worried about losing too much airspeed, and returned the controls to normal. The rattling momentarily stopped as indicated on the CVR.

The plane continued to turn back to the left.

Seven seconds later, one of the flight crew commented about "air turbulence.”

The pilot again tried to compensate for the plane's strong drift to the left caused by the partially closing thrust reverser by again applying right rudder and opposite aileron. The same rattling sound is heard at 121 seconds into the flight.

Four seconds later, at 125 seconds into the flight, the first officer calls for "full power,” presumably to compensate for the side slip, which had slowed the plane down to dangerously low speed.

As soon as the power went to full, the spinning effect caused by the partially or fully actuated thrust reverser caused the plane to spin out of control in a flat spin.

Two seconds later, at 127 seconds, the CVR indicated the flight crew making a comment about being out of control. No more comments are made after that, and the recording ends 17 seconds later when the plane hits the ground.

Fighting to control the aircraft, the pilot held full right rudder and hard left aileron just as the left thrust reverser came into the full-on position. The application of full power greatly increased the turn to the left, created a huge side force on the tail and rudder assembly, and snapped them off cleanly.

Within another second, without the vertical tail assembly to slow the spin, the plane spun violently to the left about the center of gravity of the airplane. The plane spun horizontally with the full power from both engines increasing the spin faster and faster until both engines broke off.

The flight crew at the front was thrown violently forward with such g-force they were instantly rendered unconscious or killed, explaining why no more comments from the flight crew are heard after applying full power.

With the plane completely out of control and the engines still running at full power, the engines broke away ripping the fuel tanks in both wings and igniting the plane.
Wake Turbulence Discounted

Marshall created his saboteur scenario because he concluded early on that it is not possible for any type of wake turbulence from a preceding jet to rip off the tail of an airplane. Furthermore, he concluded, even with the vertical stabilizer gone, Flight 587 would not have gone out of control in such a way that both engines would also fall off.

He pointed to a 1985 incident where a Japanese Boeing 747 with the vertical tail assembly completely torn away continued to fly in large circles for over half an hour before hitting a mountain.

According to Marshall, Flight 587, an Airbus A300, used a modern "fly-by-wire” computer system and could fly quite easily with complete loss of the vertical fin and rudder.

"Most air accident investigators would easily conclude that the chances of three simultaneous airframe failures all occurring at the same time is not probable. It must be one or the other but not all three. It would be much easier to conclude that something else actually caused all three failures,” Marshall said.

Marshall pointed to a statement by New York City Mayor Rudolph Guiliani at a news conference Nov. 14 that the rescue workers recovered 262 bodies including "a man still holding a baby.”

"Certainly no man can be strong enough to hold on to a baby through that force, unless instead the plane was in a flat spin. For the passengers in the center of the plane, the force would have been downward [not forward] as the plane hit the ground, and the baby would be simply forced deeper into the man’s lap as he sat in the passenger seat.

Further clues pointing to his theory, said Marshall: news videos of the crash scene as firemen put out the flames. A large section of the central part of the plane is lying on the ground almost intact but in flames.

[Midnight Blue]

Quote Marshall:
He pointed to a 1985 incident where a Japanese Boeing 747 with the vertical tail assembly completely torn away continued to fly in large circles for over half an hour before hitting a mountain.
End Quote.

He better doesn´t call himself an "expert".
The vertical tail assembly of the Japanese 747 never was torn away!
They lost control, because they had no more hydraulic pressure to move the control surfaces due to rupture of hydraulic system in the tailsection. (Source http://aviation-safety.net/database/type/index.htm)

And he should calculate how much "rpm" of the A300 would be necessary, to create a force, which could kill the cockpitcrew in an instant (I doubt this). Must have been several rotations in less than 2 minutes???
Why didn`t anybody mention a "frisbeeing" airplane...

[PaperTiger]

The vertical tail assembly of the Japanese 747 never was torn away!

Sure looks like it was to me.
http://www.airdisaster.com/special/special-jal123.shtml

[Capt PPRuNe]

Sorry but 100 posts and this is going to be closed. I strongly advise any continuation of this thread takes place in the Tech Log forum for the time being.