New Clues deepen AA587 Crash Mystery

[gaunty]

This turned up on my Aviations Week email alert.
http://www.aviationnow.com/avnow/news/channel_maint.jsp?view=story&id=news/raa11114.xml

[newswatcher]

CNN reports that NTSB are now saying that JAL separation only 1 min 45 secs. Extract from CNN below:

"A Japan Airlines flight was cleared for takeoff about two minutes and 20 seconds before the American Airlines flight, but it actually took off one minute and 45 seconds ahead of Flight 587, National Transportation Safety Board Chairman Marion Blakey said Wednesday.

Blakey said preliminary analysis of the flight paths of both planes showed that the JAL flight was about four nautical miles out from the American Airlines flight and traveling 800 feet higher. Wind conditions at the time of Flight 587's takeoff, she said, were "consistent with a wake vortex encounter".

We do not know if this really contributed in any way to the actual accident, but we are looking at it very closely," Blakey said."

[SaturnV]

Below is a meld (didn't want to use the word 'composite') of articles in the Nov. 15 NYTimes and Washington Post. Investigators are zeroing in on a vertical stabilizer composite failure as setting in motion the accident sequence. A question to be answered is whether the composite section had a pre-existing condition that caused it to fail below, or even much below, design limits. I was intrigued by Belgique's post in the A-300 engines thread. American tended to use the A300 in the tropical environment of its Caribbean and Central American services.

"The vertical tail section of American Airlines Flight 587 cracked off when its modern reinforced plastic "composite" fittings failed, investigators said today, and the National Transportation Safety Board
announced that American will inspect the tail section of all its similar Airbus A300-600 widebody planes. The Federal Aviation Administration said it was dispatching its chief scientist to examine the composite materials as well.

"Safety Board Chairman Marion Blakey said there was no evidence of physical damage to the vertical tail fin, which was recovered from Jamaica Bay soon after the Airbus crashed into a Queens neighborhood Monday.

"But she presented radar data indicating that wake turbulence from a Japan Airlines 747 that took off just before Flight 587 could have hit the American widebody. The 747's path was to the west and about 800 feet higher than the A300's, she said, with the wind blowing from the northwest at about 12 mph.

"Because the swirling winds that flow from an aircraft's wingtips tend to move down slightly and drift with the wind, the aircrafts' paths "would be consistent with a wake vortex encounter," Blakey said.

"But board member George Black said he was unaware that any civilian aircraft had ever lost a vertical tail fin to wake turbulence.

"Investigators could not explain what outside force, combination of forces, human error or aerodynamic forces could have produced enough force to rip the vertical tail fin and rudder off the plane and rip both engines from the wing.

"The board last night released some preliminary data from the recovered flight
data recorder indicating that the vertical tail fin came off first. Both engines continued to operate normally for a short period after the crew said on the cockpit voice recorder that they had lost control.
Investigators at first believed the plane landed nose-down -- because of the lack of wider destruction that would have resulted had it hit the ground at a shallower angle. That did not explain, however, why they found so many intact or nearly intact bodies so quickly.

"Several sources now believe the explanation may be the speed of descent. The plane, they believe, having lost its heavy engines and vertical tail, made a relatively slow belly flop, nose tilted down and turning sideways. Its engines were found about 800 feet away --with the left and right engines exactly
opposite to where they would have been attached to the plane, indicating the plane might have been upside down or flopping around.

"Blakey announced American's planned inspection of all 24 of the tail fins on its Airbus A300-600 fleet.

"Officials with Airbus, the European manufacturer of large airplanes, were
discussing whether to advise other airlines to do the same.

"She [Blakey] also said the FAA was sending its chief scientist to the Flight 587 scene to study the possible relevance of composite materials. FAA spokeswoman Laura Brown said that if the scientist and other FAA officials find that more inspections or corrective actions are needed in other parts of the aircraft industry, "the FAA will mandate that immediately."

"Hans Weber, an airline engineering expert in San Diego, said most airliners still have metal tails. He also said that although the composite tails on Airbus planes are made with carbon fiber, the composition of that fiber has been constantly evolving as the plane maker tries to keep costs down.
Composite tail structures are five times more expensive than aluminum -- $1,500 a pound compared with $240 a pound.

"The tail was torn off, leaving the attachment points, which are made of the same composite, still bolted to the plane's
metal frame, investigators said. They have not found any evidence that an explosion or contact with another object in flight caused the damage.

"Among the questions for investigators are
whether the fin separated because of stresses that its design should have been able to handle or if the plane, in the air less than two minutes on a day with light winds and clear air, somehow encountered extreme air conditions.

"Airbus, far more than Boeing, its main rival, relies heavily on composite materials, to save weight and to avoid
corrosion. Experts say that composite materials are stronger per pound than aluminum, and are less prone to fatigue, in which repeated flexing weakens the material.

"But composite materials also can weaken. Sometimes the reinforcing carbon comes lose from the matrix that forms the bulk of the composite, or layers come apart, a process
called delamination.

"According to the maintenance log recovered from the crash site, there had been no major repairs recently, and no items awaited repair.

"The fittings that hold the fin to the fuselage are visually inspected every five years; the most recent inspection for the plane that crashed was in December 1999.

"Before the plane was delivered in 1988, the composite material in one of the six fittings holding the tail in place was found to be delaminating, meaning its layers were
coming apart. It was fixed by adding layers and inserting rivets, and the manufacturer decided that no extra inspections were required afterward.

"One new area for investigators is the composites, which are harder to read for clues than metal parts. They have been
used for years, but usually in doors or panels, not in the plane's skeleton. American Airlines will use a variety of
inspection techniques, including a tap test, in which technicians hit the part and listen for sounds that would indicate a void, said Thomas Haueter, the board's deputy chief of aviation safety.

"The carbon and plastic composites used by aircraft manufacturers tend to be extremely strong and resistant to cracking, and were strenuously tested, Robert T. Bocchieri
said. Dr. Bocchieri is an expert in assessing failures of composite materials and a senior engineer at Applied Research Associates, an engineering firm in Sunnyvale,
Calif.

"Cracks develop in metals or plastics as they age, but cracks tend to be stopped in these materials by the embedded fibers, he said. Still, "aircraft makers have tended to be extremely conservative in their use of
composites," he said.

"Because the materials, when proposed for airliners, were intended for a new domain in which hundreds of lives were at stake, they "were put through massive numbers of cycles of full-scale testing," Dr. Bocchieri said. "They had to simulate the entire life history of the aircraft."

"Airbus has made progressively greater use of composites. It plans to expand their use even further in its A380 superjumbo jet. According to Airbus, each A300 uses 14,600
pounds of composites, and by doing so, saves 3,300 pounds of weight.

"The fin of the A300 is almost all composite. Mr. Black said yesterday that when it was pulled from Jamaica Bay, the fin looked good.

""With the exception of the area where it separated, it is almost in new condition," he said.

"Both the fin and the rudder, the movable panel at the back of the fin, can float, he said. Aviation experts said that both could have traveled a significant distance from the
spot at which they separated from the plane. Thus, although they were found closer to the airport than the main wreckage, investigators are not certain that they were the first to come loose."

[gaunty]

I have seen a photograph somewhere taken by a construction worker on the airport of the aircraft.

It was a fair way away and a bit grainy but the aircraft appeared to be rolling to the left and going through the vertical with the left engine gone and the right at about a 45 degree angle to its normal plane, apparently about to separate. The horizontal stabiliser was still there but could not see the vertical stabiliser.

Has anybody else seen that photo as it seems to confirm the above.

[J-Class]

The possibility of a chain of events - weakened composite structure plus unusual, or extreme, wake turbulence seems to be emerging (and yes, this is all speculation, before anyone flames me!)

There is an interesting training manual for pilots and ATC published by the New Zealand CAA available on the web. It includes a couple of impressive pictures of wake effect of a CX 747-200 landing at Kai Tak. I can't copy these here, so follow this link (you will need Acrobat Reader, go to www.acrobat.com (http://www.acrobat.com) if your computer doesn't have this):

NZ CAA Wake Turbulence Manual (http://www.caa.govt.nz/fulltext/Safety_booklets/Wake%20Turbulence.pdf)

Edited to point out that I wouldn't bother with this link unless you have a broadband connection (and even then it's a big file).

[ 15 November 2001: Message edited by: J-Class ]

[SaturnV]

Gaunty, there are two videotapes that are apparently in NTSB possession. A construction worker at JFK airport filmed the takeoff and initial climb of AA 587, but had turned the camera off before the aircraft lost control. (He turned it back on once he saw the smoke from the crash.) The second is from a security camera on a bridge which supposedly shows the final moments of the flight, with both engines gone and flames from the wings.

I would be suspicious about another photograph suddenly surfacing, you remember the hoax about the guy atop the WTC with the jet coming toward him.

[ 15 November 2001: Message edited by: SaturnV ]

[Gulfer]

What do you think guys?
It must have been a Very light Jumbo and a very heavy A300 to be a vortex problem with one minute 45s separation.
The rotate point and subsequent climb gradient of a Jumbo compared to a big twin is generally chalk and cheese.

Perhaps another piece of terribly bad luck in a very sad, and I have to say worrying event.
" RIP & God bless to all concerned "

[Semaphore Sam]

Out of curiosity, didn't the consortium making up Airbus contract out various parts of its aircraft to different countries? Isn't/wasn't Spain responsible for the tail sections? And, responsible only for contruction, or also, quality control? Just curious.

[gofer]

J-Class, the warning is valid - some file even with broadband.

Very descriptive even though it was probably drilled into everybody to ever saw a King training VCR, but isn't it easy to under-estimate the consequences.

In various threads there are comments on and links to other previous wave, wake and vortex accidents. I think there is enough of a pattern over the loss of the vertical causing the engins to be bucked off, with the then inevitable consequences. If some of the more analytically and technically minded wanted to research.

Of course it is still conjecture and speculation at this time - but the investigators are good at finding all the needles in the haystack. Lets hope we can at least learn from the wreck. RIP

[OldAg84]

In light of the structural failure, regardless of cause- what types of non-destructive testing are available for carbon composites? I ask this specifically with regard to the potential damage from the A/C's previous encounter with severe turbulence.

[sky9]

It is not acceptable for the cause of this accident be put down to Wake Turbulence. We all encounter it 2 or 3 times a year in varying degrees.
As mention in another thread, it would only take a small amount of movement in the Vertical Stabiliser before the yaw damper would come into play possibly exacerbating the movement and breaking the structure of the VS. The noise of the FD would confirm the vibration.

Assuming that the VS then came off it would no doubt take the hydraulics with it. Does the A300 have quick shut off valves in the flight control hydraulic lines? If not the aircraft would rapidly lose all flight controls and become unflyable.
Even with hydraulics it would have been nigh on impossible to control with climb power on and no VS.
I presume that with high side loads on the engines and pylons that they exceeded their design loads for normal operation and came away.
Surely by now all A300's should be fully checked to ensure that nothing similar is occurring in other aircraft.

[Raas767]

Even though the investigation into this accident is ongoing, I must say that I agree with all of your postings regarding the probable tail seperation.
After AA lost a DC10 in ORD in 1979 the entire fleet was grounded worldwide to check engine pylon bolts. Given this catastrophe, with structural failure the probable cause, I think FAA and JAA should consider grounding all A300-600 and A310 aircraft until proper checks have been made.

[RatherBeFlying]

CBC Radio reported this morning that the fin came lose from its attachment fitting and that the attachment fitting was found still attached to the tailcone. Haven't seen this in print yet.

So how do you inspect for this?

It took decades and sadly, tragedies, to develop inspection procedures to catch deterioration in aluminum structures. I would like to think that this will be the last time we need to revise inspection procedures for composite structures.

[Kubota]

Not trying to do a 411A or a Guv here, but the statement that "board member George Black said he was unaware that any civilian aircraft had ever lost a vertical tail fin to wake turbulence" is completely untrue.

In the early or mid - 70's, a BOAC 707 lost it's vertical stab in an encounter with a rotor off Mount Fuji, Japan. It led to the inflight breakup of the machine, with the loss of all on board.

There are photos (somewhat grainy, but horrifying, nonetheless) in several publications of the machine during it's encounter and the subsequent breakup.

[PaperTiger]

A rotor or mountain wave is not 'wake turbulence', ie: caused by the passage of a preceeding aircraft.
Black is probably correct. Several GA and bizjets have crashed due to wake encounters, but I can't think of a transport-category event.
Here's a link to a description of the BOAC 707 breakup. http://pw1.netcom.com/~asapilot/911.html

[411A]

"Cannot think of a transport aircraft that crashed because of wake turbulence"..... well if you look far enough back you will find the DC-9 that crashed at the old Greater Southwest airport (Dallas) which followed an AA DC-10 on finals. Was a crew trainer I believe, all aboard died in the DC-9.

[slingsby]

Further to J-Class posting refereence top NZ CAA wake turb. manual. Those having difficulty downloading may want to try to download DAP sofware (free at mom), this takes care of slow non broadband transmissions. My download took 2 mins.

God rest their souls.

[McGinty]

On the CBC (Canadian Broadcasting Corporation) morning radio newscasts today there was an item on the AA587 crash which mentioned that this particular Airbus had experienced severe turbulence some years ago in which some 40 passengers/crew had been injured.

The news reporter went on to mention that the tail of the plane had been repaired as a result of that incident.

I have looked and looked at the various web news sites this morning, and none seem to be reporting that there were repairs to the plane's tail. For example, here is all that the NY Times had to say on this matter:

"The investigators have many areas of inquiry still open. One is that seven years ago, the plane hit turbulence in flight and 47 people on board were injured. Whether this could have produced structural damage that went undetected was not clear, although the plane itself was designed to withstand a degree of turbulence that could result in injuries or deaths."

Maybe I misheard what the CBC Radio reporter said about repairs to the tail of this A300, but if there were any such repairs made following the violent turbulence then this crash may be a repeat of the JAL 747 crash where its tail eventually failed after botched repairs carried out years before.

If the reporter was incorrect, and the tail was not repaired, then there remains the possibility that the tail failed because of undetected fatigue in the composite materials which was initially stimulated by the violent turbulence experienced by this airframe years ago.

[PaperTiger]

Thanks 411A, that one had escaped the grey matter. Non-standard separation though ? http://dnausers.d-n-a.net/dnetGOjg/300572.txt

[PaperTiger]

McGinty
I think that reporter was combining two separate incidents, both of which have been mentioned here.
Prior to delivery to AA, Airbus fixed part of the fin which had delaminated.
Then in 1994 this aircraft encountered CAT over the Caribbean. FAA classified the damage as 'minor' and I've seen no reference to repairs to the fin resulting from this.

[moggie]

Why is it that any accident involving a european built airliner results in calls of "ground them" when Boeings, apparently, should just fly on?

I am thinking of the two hull losses caused by rudder hard overs on B737, a near hull loss caused by structural failure on an Aloha 737 and two hull losses caused by fuel pumps catching fire (TWA 800 747 and a Thai 737). And if anyone syas "but Boeing say the rudder hardover does not exist" I know that BA had at least one and Boeing also chose to redesign it for the NG model. So why redesign if it is OK?

These are just a few which come to mind - but this is (as best I can tell) the first airbus crash in which structural failure MAY have contributed - the majority of the rest are "operator error".

So lets get it straight guys - if the FAA are happy to let Boeing operators risk pax lives while they have a long slow think about rudder hardover and fuel pumps, why the call to ground the Airbus? protectionism that's why. And I don't care if it's non-PC to say so, it's true.

[basil fawlty]

With ref to the BOAC 707 crash, my father was flight engineer on the previous sector (San Francisco - Honolulu). He recalls that they went thru some serious CAT, "nodding pods", autopilot out and flown attitude etc etc.
The astonishing thing is that he was never called to give any evidence at the board of enquiry!

[allianceair]

Gaunty:

Where did you see this photograph and what newspaper do you write for??

[Shore Guy]

Bob Francis, former NTSB investigator, in an interview said that wake encounter was possibly influenced by the fact that the AA aircraft turned inside the arc of the JAL 747, thereby reducing the already reduced separation (? believe aircraft took off with slightly less than two minute separation ?). This also puts the AA aircraft entering the wake/vortice at an angle, increasing loads/stresses.

[brain fade]

Surely the question of whether or not there was a wake turbulence encounter is irrelevant? The Airbus should be strong enough to survive easily.
What i think we are seeing here is the first instance of structural failure of Carbon fibre composites when used as primary load bearing structure on a composite (ie alloy+CFC) airframe. We all know this material is good for doors, flaps, fairings etc, but these are all either hinged or non load bearing. We also know that it makes great all plastic aircraft.But when you make an aluminium aeroplane with a bolt on Plastic tail, you need to spend a lot of time making a joint which allows all the loads to pass but is good for the different materials on both sides. Perhaps we have a bit of the learning curve still in front of us here. I suppose this amounts to idle speculation, but it was a most unusual accident.

[Wino]

Moggie
My what a short memory you have. The FAA grounded all DC-10's for a very long time after the engine seperation and crash in chicago.

In the case of the 737 rudder hard overs, a fix was immediately implemented. The aircraft speeds were changed to require flying faster than crossover speed so that a hard over rudder could be overcome by the ailerons. That required adding 10 knots or more to approach speeds.

For those of you who are not into aerodymanics, crossover speed refers to a specific angle of attack. An angle of attack lower than crossover will have the ailerons stronger than the rudder and a greater angle of attack would make the rudder stronger. So to reduce angle of attack you either unload (reduce G) or increase speed. The 737 is now flown faster so that a rudder hardover, while exciting, isn't fatal, like an engine failure or other problem we are trained to deal with.

As to the aloha aircraft, much of ALoha's fleet and several other aircraft of similar vintage were immediately grounded. Others were life limited as a result of the ageing aircraft program that followed the initial grounding. (60000 cycle inspection became too expensive)

So, no it is not a plot against airbus, you are free to keep thinking that however. In the meantime there is another similar accident in Africa from about 2 years ago on the A300/310 that is also unsolved. 2 aircraft out of 400 or so vs 2 out of 3500 737s sure doesn't look favorable for airbus.

But go ahead and falsly scream protectionism if it helps you sleep better.

Cheers
Wino

[SaturnV]

The NTSB has a set of pictures of the vertical stabilizer and the empennage attachment points at:
http://www.ntsb.gov/Events/2001/AA587/tailcomp.htm

From the presswires:
NEW YORK (AP) - American Airlines Flight 587 twice ran into turbulence left by a jumbo jet, including a blast of air that sent it
careening sideways seconds before it crashed, investigators said Thursday.

The doomed plane's flight data recorder indicates the Airbus A300 had two turbulent "wake encounters'' during its three-minute
flight, said Marion Blakey, chairwoman of the National Transportation Safety Board.
"The second was similar in intensity to the first,'' she said.

Flight 587 began banking hard with its left wing down within eight seconds of the second wake encounter, said Tom Haueter, the NTSB's deputy director of aviation. The flight data recorder cut off at that point.

"Obviously, the whole time we're talking about is the last eight seconds,'' he said. "We have eight seconds we're going to be
looking at in extreme detail.''

Earlier, NTSB investigator George Black Jr. said investigators were almost certain the tail broke off before the jetliner's twin
engines. While cautioning that investigators are not ready to rule out sabotage, he said the tail "doesn't appear to have been sabotaged in any way.''

Black also said the pilots of Flight 587 were probably unaware its tail fin had broken off as they struggled to control the plane.

"They don't have a rearview mirror,'' he told The Associated Press. "They have no idea they've lost a tail.''

In Washington, the Federal Aviation Asministration was preparing to order inspections of Airbus A300s, focusing on the tail. The order would cover 90 of the European-built planes used by three U.S. airlines - American, FedEx and United Parcel Service. American has already agreed to do voluntary inspections of its 34 remaining A300s."

[Cisco Kid]

Wino, By a "Fix" do you mean merely increasing approach speeds or was the Yaw Damper system modified?,I don´t know & am just curious.As you may know a similar "Fix" has been applied to A319/320 A/C. After a "landing".. when a low go around had been commanded,A/C remained in landing flare...software problems!,so until it´s really corrected add 10 kts,& use a reduced flap setting for ldg. in gusty conditions.Real "fixes" would be nice,I don´t believe in conspiracies either;Cisco.

[Willie Everlearn]

I was wondering if this latest FAA inspection mandate for the A300 in the US shouldn't include the A310, A330 and A340.
Do they all not have the same or very similar Vertical Stab including attachment design???

[boofhead]

Of course I dunno the facts but it seems unlikely that the Airbus was going fast enough, so soon after takeoff, for it to break up in any sort of turbulence, or pio.
But I was told by an old and boldy when I first flew the classic 747 that if I was to over-react to an engine failure by using too much rudder, too quickly, engine pods would start breaking away, especially in cruise flight. The inference was that one should not jam in full control at high speed. If this airplane had some existing vert stab damage, it might have been susceptible to failure if the crew did use full rudder, even at 250 knots.

[ 16 November 2001: Message edited by: boofhead ]

[TechFly]

I suppose a combination of "fatigue/aeroelasticity/cycles/construction type" together with the aerodynamic flow encounter (i.e. high energy vortex) may give an overall answer or contribution to the disaster.

We will remember all of them forever.

Thanks to everybody around the world for contributing and detailing.

Cheers

[chillpill]

If we are talking about fatigue of the vertical stabilizer, irrespective of its construction being composite or conventional, has anyone ever noted the considerable vertical movement of the B757 horizontal stabilizer when take off power is applied and felt by this control surface. The more eagle eyed may have noted that the larger exhaust cone exit of the RB211 efflux causes considerable more movement to the stabilizer surface than the alternative engine CFM with a multi cone exit. Has Mr B noted this in the B757 fatigue test bed airframe?

[pigboat]

What are the Dutch roll characteristics of an aircraft that has just lost it's vertical stab? Sounds to me that after the loss of the fin, any Dutch roll may have progressed to the point where the aircraft may have actually snap rolled. That'd explian why both engines were pulled off the pylons. In that scenario, wake turbulence would indeed have exacerbated the initial rolling action.

[Deaf]

Boofhead

Don't forget the 250kts, if that was the speed, would be close to the IAS and that is essentially the IAS (and associated forces) of cruise at altiude.

[Charlie O]

A composite or honeycomb structure may have its strength reduced by the actions of high altitude to low altitude operation. Any space, no matter how small, in which air might be enter, will eventually lead to material separation. This can include microscopic cracks created by prior operational stresses, which might be easily overlooked by inspectors.

When an A/C changes from low temperature, high altitude operation (cruise) to a low level, low altitude condition (landing), the low pressure inside the composite material with microscopic cracking will draw in air, which will accumulate water inside due to condensation created by the cold interior. With a return to high altitude, low temperature operation, the water will freeze inside and NOT be expelled on landing.

With repeated cycles of low pressure, low temperature operation to areas of high humidity and high pressure, water can accumulate inside a composite material which has spaces in which air can enter. Eventually water will accumulate in these spaces until its freezing will can cause separation of the composite material.

Enough of these microscopic (internal and unseen) seperations and operational cycles may lead to complete failure of the composite assembly during "normal" operation. The same process has already caused the failure of many (vented) honeycomb structures in the past. No proof for the present accident, just another theory based on physical facts.

[moggie]

Wino- The rudder PFCU on the B737 was not "Fixed" but flight techniques were developed which reduced the risks inherent in the poor design. Note however, that the NG version has been fixed, although no changes to the classics took place.

It was not just 2 out of 3500 aircraft - there have been others (as I said in my last post, at least 1 at BA and other "unexplained" problems have occurred at toher operators.

Still no explanation as to why B737 and 747 fuel pumps have not been sorted - none of them were grounded - just asked to fly with a bit of uel in the tanks to keep the pumps cool. Now that sounds like a good idea to me - much cheaper than actually fixing the problem.

If you read my post it is not about how the FAA react but the outcry form the anti-European lobby every time a european built aircraft has a problem. I do remember the FAA grounding DC10s, but I don't recall the pro-Boeing lobby asking for B737 and 747 to be grounded when they hit a problem. Who called for the MD 80/83 etc. series of aeroplanes to be grounded after the Alaska crash? No-one west of Shannon, that's who!

[SaturnV]

A-310's are to be inspected as well. It does seem the authorities and experts are still deciding how best to inspect for voids or delamination in the composite structure.

Excerpted from the Nov 16 New York Times:
"American Airlines said on Wednesday that it would inspect its 34 surviving Airbuses. John L. Hotard, a spokesman for the airline, said yesterday that it was still planning how to carry out the inspections. The part to be inspected most carefully is a section at the base of the tail fin that was torn apart.

"The [FAA] order is expected to cover the 91 A300's registered in this country and another 46 A310's, which are similar but shorter planes. It will give the operators about 10 days to inspect the tails.

"The shaking incident evidently followed the encounter with the wake, but the connection is not yet clear. Airplanes leave two wakes behind them, disturbances in the air that resemble horizontal tornadoes, one trailing each wingtip. The plane that crashed bumped over the first one about 28 seconds before the flight data recorder stopped working, and the second one about 8 seconds before the data ended.

"In the first seconds after clearing the second wake, "the airplane appears to be consistent with flight control inputs," said Thomas Haueter, the board's deputy director of aviation safety, meaning that the plane's performance still matched the pilot's working of the controls.

"But shortly after that second encounter with a wake vortex, the plane was shaken laterally, changing its direction suddenly and forcefully. Forces on the plane are measured in G's, with one G being equal to the normal force of gravity.

"In mere seconds, passengers felt a sudden powerful swing in one direction, and then another slightly more forceful one in the same direction. They were being hit with forces 30 or 40 percent as strong as the normal force of gravity. (In contrast, the bumps from the wake vortices were equal to only 10 percent of the force of gravity, Mr. Haueter said; he said that the 10 percent was
"the type that sloshes your drink."

"Investigators said the plane's rudder moved in concert with the swings, apparently causing the sideways movements, but Mr. Haueter said investigators were looking into whether the rudder had moved on its own or the pilots had manipulated it. Then, in the last 2.5 seconds or so that the data recorder was still working, the plane lurched wildly to the side, its left wing lowered and its nose pitched forward. The drop to the ground had begun.

"Despite witness accounts to the contrary, Mr. Haueter also said that there was no evidence of any fire in the engines before impact."

Excerpted from the Nov 16 Washington Post:

"According to information released by Blakey today, this was what happened during the last seconds before the flight data recorder stopped working:

"• The American Airlines plane moved abruptly in a way consistent with hitting wake turbulence, but was not affected in any significant way. A similar movement occurred seconds later. Again, the plane was not significantly affected. The force of the encounters were about 10 percent of the force of gravity, certainly enough for passengers to notice but not particularly
dangerous.

"• About one second after the second wake turbulence encounter, and eight seconds before the recorder cut off, the plane made a violent movement to the right, jerking passengers sideways at about 30 percent of the force of gravity. It then made an even more abrupt move to the right, affecting
passengers with about 40 percent of the force of gravity. Then it moved left at about 30 percent the force of gravity. The data show that the rudder moved abruptly at the time of each movement. "This was a very significant lateral acceleration," Blakey said.

"The board said the rudder pedals in the cockpit moved in tandem with the rudder itself. That would almost always mean that the pilots induced the movements by pushing the rudder pedals. At this point, however, investigators cannot rule out some other explanation, including an autopilot malfunction or, perhaps, events that may never have happened before. The rudder -- the movable flat plate at the rear of the vertical tail fin -- is seldom used in flight
except when an engine fails, or to keep the plane from fishtailing in turbulence or when coming out of turns.

"• At 2.5 seconds before the end of the tape, rudder data on the recorder became "unreliable," possibly because the rudder had cracked off.

"• Side pressure increased to 80 percent of the force of gravity, and the plane rolled left to 25 degrees left-wing down as the nose pitched down 30 degrees. Passengers were pushed down into their seats at twice the force of gravity. The recorder cut off at that point.

"According to accident and incident records, at least two other A300-600s have
experienced serious in-flight emergencies, one apparently crew-induced and one
caused by an autopilot malfunction.

"On May 12, 1997, an American Airlines aircraft went through a series of violent maneuvers somewhat similar to Flight 587's as it prepared to land in Miami. The safety board determined that the crew first had inadvertently allowed the plane to stall, then mishandled the plane's recovery. The aircraft landed safely at West Palm Beach, Fla., but seven passengers and crew members
were injured.

"On May 17, 1999, an American Airlines plane experienced uncommanded rudder movements. The crew was unable to move the rudder with the foot pedals but used other controls to make the landing. The problem was caused by the autopilot."

[ 16 November 2001: Message edited by: SaturnV ]

[moggie]

Coincidentally, there are two post on "tech Log" about Boeing fuel pumps/wiring and B737 rudder PFCUs. Now, if the FAA has just decided that B737 rudders DO actually need to be fixed properly, why have they been happy to let them fly for the last 5 years in an unsafe state? If it needs fixing, it needs fixing NOW and not over the NEXT 5 YEARS as proposed.

Concorde was grounded and fixed straigh away - after the Air France crash (and I agree that it needed doing) but more people have died in the TWA 800 and the B737 hardover accidednts (not mentioning Alaskan MDs) than in the Concorde/A300 crashes.

I think consistency is what we need.

[gaunty]

allianceair

I think it was on one of the news sites if not an aviation news site.

I do not write for any newspaper. PERIOD. end of story.

I will for my own peace of mind go see if I can find it again, sorry to disappoint you but I am not in the habit of imagining these things either.

[gaunty]

In any event there has always been controversy surrounding all composite main structures.
Beech tried with their ill fated all composite Starship. They were an outstanding failure insofar as the market was concerned and if my memory serves me correctly a presurisation fuselage test article failed catastrophically without any/or the sort of warning you get with impending failure in metal.
Failure prediction in composites as far as I am aware is not an exact science, unless it has become so in recent times.
Boeing and other large manufacturers take a much more conservative approach in there use.
I dont work for Boeing or any of the others either.

I think Pandoras box has just been opened.

[SaturnV]

Moggie, I have neither heard nor read where the FAA or the NTSB has called for a grounding of A300's because of the vertical stab coming off. Yet in your earlier post, you stated:
"Why is it that any accident involving a european built airliner results in calls of "ground them" when Boeings, apparently, should just fly on? .... So lets get it straight guys - if the FAA are happy to let Boeing operators risk pax lives while they have a long slow think about rudder hardover and fuel pumps, why the call to ground the Airbus? protectionism that's why. And I don't care if it's non-PC to say so, it's true."

Please enlighten us as to who in the United States Government has called for grounding these aircraft. Otherwise, chimerical visions set out simply to generate more Boeing v. 'Bus controversy detracts from a sober discussion of a tragic event which may have profound consequences for aircraft design.

BTW, I believe the Lockheed Electra L-188 was either grounded, or severely restricted with respect to flight regime, around 1960. This was after the wing came off on two aircraft during cruise. Severe CAT was a contributing factor in one accident, and undampened prop whirl was the main factor in the second.

[ 16 November 2001: Message edited by: SaturnV ]

[moggie]

Saturn V - read my posts carefully and also look at "Tech Log". I did not say that the FAA or NTSB called "ground 'em" I was referring to the "popular" opinion on this site (not necessarily on this particular thread).

However, I do stand by my amazement that the FAA did not order immediata grounding/inspection/rectification of B737 after rudder hardovers or MDs after the Alaskan accident.

The popular opinion from west of Shannon is that any Airbus is unsafe - this is boll*cks. They are no better no worse than Boeing (OK in my opinion they are in fact better!) but there is always a cry from the Boeing boys that any european built airliner crash requires immediate grounding and a Boeing accident is just bad luck.

[Eff Oh]

Moggie:- Just wondering, which models of Airbus and Boeing have you flown??

[Beanbag]

I have some sympathy for Moggie's point in general, but less so in this case where most coverage I've seen has been reasonably fair. It certainly seems that there is a discussion to be had about composite materials, and no-one's interests are served by deflecting this into Airbus v Boeing

Incidentally this prejudice (pre-judgement of Airbus) isn't confined to West of Shannon - the BBC website is just as guilty, since after every Airbus incident (e.g. Gulf Air) it wheels out a list of prior Airbus incidents, but for US aircraft the list they use includes all manufacturers.

[ShotOne]

What a pity that what started as a very interesting thread has degenerated into another tedious airbus v boeing whine.

To come back to AA587, is the broken fin supposed to hve followed on from an engine failure -and where does the fact that the wing, or part of it, detached come in??

[Belgique]

Overall timeline

T = start of AA 587 takeoff roll.

T-105 seconds (approx.): The JAL 747-400 begins its takeoff roll. Throughout the flight of AA 587, the horizontal distance between the two planes was somewhere between 4 and 4.3 miles. The JAL flight was about 800 feet higher than the AA flight generally speaking.
T-0: AA 587 begins its takeoff roll.
T+96 seconds: The flight data recorder indicates first encounter with wake turbulence. “Airplane attitudes did not change much.” Widened wake-funnel has significant cross-track vector components (think of as a sudden burst of cross-wind)
T+107: An airframe rattling noise is heard on the cockpit voice recorder. the faulty (repaired) attachment point has taken the brunt of the first (likely athwartwise) wake encounter and sheared. Structural integrity of the tail has now been lost (see later) and it is vulnerable to any further such side-blows.
T+114: The captain makes a comment about wake encounter.
T+116: Flight data recorder begins to show aircraft movement “consistent with wake encounter.” It is “similar in intensity” to the first wake encounter. The plane "responds normally" at first. Then come the three side acceleration excursions.
T+121: A second airframe rattling sound is heard on the CVR. (Tail has torn off?) No, loosened fin is now into a lengthy L/R rocking across its attachment base, having suffered an initial fracture at one or more of its attachment point composite upper lugs (on the gustwards side). This rocking process is a destructive flutter-failure mode. Its death-rattle is transmitted via the "sounding board" of the fuselage.
T+121.5: Rudder position data becomes “unreliable.” (Rudder has begun to depart along with tail?) AGREE, in that the rudder is beginning to be activated [by the flight control system] to counter L/R yawing motions induced because the base of the fin has become semi-detached on one side and is "rocking quickly left and right). At about this point, the plane begins to undergo the “side acceleration excursions.” Caused by the rocking (tip of fin moving through as much as a metre) First there’s a .3 G excursion in one direction, then a .4 G excursion in the same direction, then a .3 G excursion in the opposite direction. This is “coincident with rudder deflections.” (Tail has ripped off but the pilots don't know it?) DISAGREE, Tail is shaking lose - vertical fin is pivoting crooss-ship to and fro (i.e. L/R relative to the direction of flight) around its base due to one side's composite upper brackets being mostly sheared. "coincident with rudder deflections" simply means that the flight control system is feeding in compensatory rudder inputs which are unfortunately out-of-phase with fin oscillation - and tend to accelerate the fin's breakaway. ) BREAKAWAY itself would be clean and indicated by a cessation of the drumming, suddenly ineffectual rudder pedals and a CofG change nose-drop. Over the next couple of seconds, the plane undergoes dramatic course changes: Its heading changes at a rate of about 10 deg/second, the bank angle increases through 25 degrees with the left wing down. Pitch drops to 30 deg nose down. Standard spiral dive entry due to loss of directional stability - as a function of the yaw resulting from the differential thrust outputs of the engines at "max power" Vertical force increases to 2 G’s. N.B.: NTSB description of eyewitness reports: “The general observation that the witness seemed to -- remarkably similar observations have been that they saw the aircraft "wobble," is the word used. "Wobble" aptly describes the L/R yaw/roll oscillations (fin movements and with rudder countering, yet reinforcing the destructive process) over the few seconds that it took for the fin to wholly detach - after being compromised on one side's brackets. And they saw pieces come from it. (fin and fairings/fillets, later the engines) And then it went into a steep spiraling dive into the ground.”
T+124: The FDR stops recording. (Electrical system goes out?) The plane is at an altitude of about 2,900 feet. If the FDR is in the tail area, possibility is that the fin detachment caused some disruption to the electrics thereabouts because of cables being pulled out/through and the resulting generator trips. The 2g max recorded would be insufficient to detach the engines - so they would have started detaching at about the centripetal forces equivalent to 5g (T+137 say) once the thrusted spiral dive had almost reached its terminal velocity (about 1000ft agl).
T+125: The copilot calls for max power. [N.B: CVR continues to work because it is powered by batteries.] Still think this "max power" call might have been precipitated by the nose-drop resulting from the sudden C of G change as the fin and rudder departed.
T+127: There are several comments suggesting loss of control of the aircraft. By this stage the aircraft would have entered the spiral dive (about quarter-way into first turn)
T+144: The cockpit voice recording ends.

Layout of the wreckage:
"If you look at the locations of the fin and the rudder, first in line in direction the airplane was traveling, the fin was first. Then at about -- then came the rudder about 200 yards later (rudder/fin flailing after detachment would have quickly caused hinge-line fracture) . And then all of this is within a -- one-half nautical mile of the crash site. So it's a fairly tight cluster, relatively speaking, of the wreckage. Spiral would have been tight - about a half-mile radius event . Engine detachments may have been almost coincident (pylon attachments being similarly stressed by the same centripetal forces)

Power plants, it is the left engine, the number one engine, in case you're interested, that is at the gas station. That's on 129th Street. That's about 700 feet from the Crater. The right engine, number two, is next to the boat behind the house. It's on 128th Street. And that's about 800 feet from the crater. But again, if you center all of this wreckage, it's more or less in a line.

UNIDENTIFIED MALE: How far from the crater?

BLACK: Number one engine 700 feet. Number two engine 800 feet. And these are rough measurements."

The lesson is obviously this: Composite structures (unlike fairings, fillets and other non load-bearing components) get their integrity and strength by being born of a singular process. A mixture of resins during in situ repairs just create weak-points that are always going to be vulnerabilities (as in this case). A glue sitting atop a glue will never make a good bond. When you incorporate a doubler and make that attachment point dissimilar and perhaps even sitting proud by a few mm, the likelihood is that it will be taking a disproportionately higher load (as well as being inherently weaker). That is not good. Thereafter whacking a few rivets through (as a salve to safety and QC) is really just a concession to your realisation and admission that it is otherwise a weaker proposition than the other attachment points. The six attachment points have to be both equally strong and share the loads equally, otherwise you have created a path for progressive failure. Structural composites have to be 100% as born from their process - or ditched and replaced. Repairs, in situ or otherwise, remain a bad idea. One has to wonder how many other "repairs" are out there.

[ironbutt57]

Rewinding the brain back to 1978, one remembers the grounding of the dc-10's over the o'hare engine separation..apparently caused by engine/pylon installation practices in place at continental and united,excerbated by a shim installed by douglas during manufacturing to correct production line.."discrepancies".(REF NTSB REPORT)..so now where do we go from here...apparently this a-300-600 was breaking up 3 mins after take-off....what was the operational history of this aircraft...any recent encounters with severe CAT? american did have one recently in an a-300....casting aspersions at manufacturers and airlines resolves nothing...let's find out why.... :confused: :confused: :confused:

[forget]

NTSB photographs of fin attachments at;
http://www.ntsb.gov/Events/2001/AA587/tailcomp.htm

[anawanahuanana]

Moggie:

I think you`ll find that all the 737s in BA (can`t say for other airlines `cos I don`t know!) have a rudder pressure reducer valve fitted, to reduce hydraulic px to the pcu, and therefore authority.They have also all had their yaw damper couplers upgraded. So don`t say nothing was done. It`s clearly just not true.......

[sky9]

Belgique

The only thing missing from your breakdown is that the yawdamper would have been attempting to correct the deviation of the VS,causing the vibration.

[RatherBeFlying]

It may be hard to tell between the yaw damper and the flight control system inputs on the Airbus. I believe centered rudder pedals on the Airbus command the flight control system to automatically do what's necessary to point the nose straight ahead, effectively a yaw damper.

Looking at the NTSB photos of the forward attachment points on the fuselage, they seem to be the same size as the center and rear attachment points. As we have just seen, the forward attachment points are more critical and perhaps more vulnerable to aerodynamic forces. Damage at the center or rear attachment points MIGHT have been survivable, but once a forward attachment point fails, its mate takes on the entire load in that area and in this case could not shoulder the added burden. Corrective rudder inputs in response to forward fin flexing add a substantial extra burden to the remaining forward fitting at the worst possible time.

Given the criticality of the forward attachment, why is it apparently the same size as the center and rear attachments?

We also see a fat composite lug fitted into a substantially smaller metal fitting and not much contact surface in the area surrounding the pin.

[MarkD]

chillpill [page 3] what 757 CFM alternative are you thinking of? Mr. Boeing's website only lists RB211 and PW20xx alternatives...

All this talk about load-bearing composites is all very well, but considering no analysis has yet been done on likely g-forces at point of failure it seems a bit previous.

The tail wouldn't have fallen off if wake vortex hadn't occurred, unless the tail was faulty already. Mr. Airbus only has to build them to tolerances involving normal flight conditions - he can't account for incorrect separation, otherwise we wouldn't need separation.

Sure we'd all like to fly in scramjet-powered steel boxes but that's not gonna happen anytime soon...

[PETIGRAM]

Composite materials are not all honeycomb – was any or a substantial amount of this rudder attachment point – the portion in the vertical fin that apparently failed – made of honeycomb composite?

Why was there a repair done, during manufacture, to the attachment point and was it accomplished at the forward attachment point? (damaged during installation, misalignment noticed in subsequent inspection after installation?)

[Belgique]

There was a repair carried out during airplane manufacture (assembly build), supposedly due to damage/delamination (may have occurred during shipment possibly). Someone said they thought the tails were a Spanish job (CASA?). Not sure which attachment point was involved but there was a doubler and rivets applied in situ.

http://www.iasa.com.au/images/vertfin.gif

[PaperTiger]

Tracks of the two flights (don't know how long the graphic will stay on site):
http://a799.ms.akamai.net/3/799/388/c7dc34088ebe59/www.msnbc.com/news/1264795.gif

[iflyboeing747]

Interesting information from you Belgique..

One cannot help thinking that maybe a tailfin shouldn't just be attached as shown at the image you supplied above..

One would rather suggest a more substantial and solid attachment via some sort of heavy metal beam coming from within the body of the fuselage - like the wings are attached - and then going all the way up to the top of the fin along the front edge - do you get the picture..

I'm not an engineer, but the attachment points, I've seen from the photos and the sketch, seems very fragile to support such a crucial stabilizing part of the aircraft..?!

[samgop]

From NTSB pic's, it looks like the VS ripped off from forward starboard to aft port. Supporting pictures show the forward starboard bottom bracket (METAL) bent in an up/rearward direction. And, the aft port bottom bracket in tact, with 'ripped' composite top bracket showing direction and force of detachement.

It sure would be nice to get a better picture of that forward bottom bracket!

[Roc]

Moggie,

You may think what you want concerning some American/Boeing conspiracy to somehow stain the reputation of Airbus by calling for a grounding. But your theory falls on its face in light of the facts. Fact one, probably the biggest customers of Airbus jets are US airlines. I know for a fact UPS's order for up to 120 A-300's was the only thing that kept that production line from shutting down, also United and USAirways have substantial orders for A-320 series, as well as Fed-Ex for A-300/380. So if Boeing and the US gov were in cohoots I'm sure these orders would have gone to Boeing. As far as to why there is no similar outcry for groundings when a Boeing product crashes, others have pointed out when US jets were grounded in the past, and I believe that over the past 80, thats EIGHTY years, Boeing has a relatively PROVEN TRACK-RECORD whereas Airbus doesn't. Also Airbus prides itself on being the "cutting edge" of airliner technology, hence some of these newer technologies/processes are looked upon suspiciously ie composite tails. And finally how many times in your life have you seen the pictures of B-17's and 29's that brought their crews safely home after absorbing huge amounts of damage. The picture of the B-52 that lost its tail after an encounter with turbulance comes to mind. These are some of my reasons why you may not here a similar outcry. Maybe someone in Pprune-land can scan the famous picture of the B-52. Theres a reason why some say "if it ain't Boeing I aint going...there may be some truth to this phrase. PS UPS flies DC-8's and they are said to be built like a tank..and there are a few incidents of eights encountering turbulance and losing engines and portions of their wings and still flying home. I think the A-300 design is sound, I feel that particular plane had some defect that went unnoticed.

[Out Of Trim]

Firstly my condolences to the passengers and crew aboard this flight.. but, I had a couple of questions to ask that I hadn't heard covered yet.

Does anyone know if AA587 had any "Trim Tank" fuel in the tail for "Take-Off Trim" or not?

Also is the Trim tank actually in the tail fin (vertical stabiliser )that became detached or located within the tail fuselage?

[PETIGRAM]

“One would rather suggest a more substantial and solid attachment via some sort of heavy metal beam”
As someone else suggested – not only does this bring into question the integrity of the material used but the ability to detect the continued integrity of the material. Composite designed brackets may have twice the strength of a similarly sized metal fitting – but if they don’t show deterioration in strength as does metal were we can identify crystallization or other forms of weakness – they won’t do the job in the long run.
Any thoughts on this subject from the engineers – which I am clearly not?

[Budgie69]

During a thirty year airline career from 748s to 747s I cannot recall any dramatic wake turbulence encounter after t/off - sure, a few bumps etc. but that is all.
Has anybody had a severe wake turbulence encounter after t/off in a large a/c?

[allianceair]

Gaunty:

Did you find the article, I am waiting :rolleyes: you know the one about the construction worker and the grainy photo of the engine falling off :D

[sky9]

URL of FAA AD for the A300

http://www.faa.gov/apa/emerad.htm

[lame]

Out Of Trim,

The tank is located wholly within the horizontal stabiliser.

Best regards,

"lame"

[PETIGRAM]

I’ve had 2 “interesting” encounters with wake turbulence in 737’s – both approaching in the terminal area. One encounter was along the track of the vortices and caused about a 30 degree bank with a significant amount of opposite aileron along with some rudder input. The other was 90 degrees to the vortices – and caused 2 very abrupt bumps in otherwise calm air. Neither of these prompted a change in draws afterwards but they definitely caught my attention. Of course the 737 doesn’t have the mass of an Airbus 300 but given other structural problems I could see how the event could start the ball rolling.

[Covenant]

A number of people appear to be beginning to question the design choices of the Airbus engineers, apparently on the basis of looking at a few small pictures on the internet.

For the same reason that we would hesitate to start shouting "pilot error" so soon after an accident, let's not start a witch hunt for the engineers until we know a lot more of the facts.

It may turn out that it is down to a design flaw, or something to do with the little known effects of temperature/pressure cycles on composite materials over long periods. One thing is fairly certain: I doubt they would have made such an obvious error as to have made the attachment lugs too small or weak. :eek: In the meantime, a little bit less of the hyperbole please - you don't like it when people do it to you!

[slim_slag]

Not being an engineer myself, though finding this a very interesting subject, I had a chat with a mate of mine the other night over a bottle of wine or three. This guy is responsible for the final approval of the turbine disks in lots of the planes you guys fly, so knows his metallurgy, he doesn't claim to be an expert on composites, but this is what he emailed me today.... What do you say to this Belgique?

"I agree structural composites are a bad idea because repairs are difficult and the lack of toughness of composite materials. I have never seen a repair scheme for a structural composite, because it is not wise and there are few structural composite parts out there. Typically, to manufacture a composite there is the fabric, honeycomb, resin and tooling. The process requires vacuum bagging and a moderate temperature cure cycle with ventilation and plumbing to maintain the vacuum as the bagged composite assembly outgasses - not possible for an in-situ repair. Beyond that composites lack toughness. They have strength to weight ratios greater then metal, but they do not yield. Composites support a load, with little elongation, until failure, which is usually catastrophic - I am not sure what their response to fatigue loading is or their crack propagation characteristics. Because metals are loaded to a fraction of their 0.2% yield strength, they are somewhat easier to design with.

I suspect the tail was composite as a last resort to save weight. The inspection practice for the tail, probably ultrasonic, was insufficient to pickup material degradation. Ultrasonic inspection will pickup voids, but if you have delamination without a void, the sound will pass through the assembly without an echo, and the part will pass the inspection. Other inspection techniques, eddy current or fluorescent penetrant inspection, also require a void of some sort, near surface crack tip or inclusion, or porosity open to the surface.

I believe Airbus have incorporated many technologies to save weight and cost including structural composites and structural casting. But for this there is some risk. Most likely Airbus will have to reevaluate the risk associated with its business model as a result of the accident."

[whizzjet]

As a Metallurgist who became a pilot I can concur with all above.

The bottom line is that although composites have been around for many years they are still relatively new. We simply do not have enough data on the "real" ageing properties of composites. I put that in quote marks because all age data so far is obtained by methods used to prematurely age a material (increasing operating temperature in aluminium being an example). I have a bad feeling that we may now be getting the real data. I hope to god I am wrong and this can be traced to a manufacturing flaw.

16 years ago a professor in this field stated that his opinion was that a composite would lose 50% of its structural integrity over 10 years. Just an opinion but a sobering one.

Another point was that a composite could be stressed repeatedly to 60% of it ultimate tensile strength before suffering fatigue cracking, a metal is typically 30-40% of UTS. In a composite panel a hole(eg a bullet hole) reduces the strengh to 60-70%, in a metal panel this reduces to 90%, a point to ponder in your carbon fibre winged AV8B/Harrier.

My personal feeling is that we are about to see a lot of ageing research carried out on genuinely aged composites.

[ 16 November 2001: Message edited by: whizzjet ]

[Belgique]

Slim-Slag
Couldn't have put it better myself -so I won't. There is a lot more one could say but there's not much point posting it all here. I've written about eight pages on the subject in the last four hours. Data is plentiful, knowledge is not. But enough has been said that I think everyone has the general idea. The AD, if you read it, gives adequate insight into the paucity of inspection and test technologies. It requires you to gaze peerlessly at the areas in question, utilising a strong light if necessary. That sounds like wishful thinking where composite's are concerned but adequately demonstrates that it's an area where the FAA's brightest need more than just a strong light and a magnifying glass. They too will need to call in some fractography experts and buy a machine or two. An extract from a letter to Farley Esq below:

".. (glass-fibre sets exothermically, while carbon-fibre is an endothermic process). When the aviation industry got into the thermo-plasticand thermoset game, they were very cautious inasmuch as it was doors, hatches, fillets and fairings only - for quite a while. They gained experience in laying up composites and the black art of setting the angle of weave of each layer of the cloth matrix became a science. There was a great selection of resins. However when they then crossed the Rubicon into structures they only had that sort of passive panel experience and designing for load-bearing was a suck it and see over-design/over-build process (with lotsa testing to destruction as a confidence builder). Those tests were with aged, as in cured, (but not aging) resins and composites. I owned a Messerschmidt Boelkow Bloehm Phoebus C (VH-GYA) designed by the famed Dr Eppler. It had a mighty balsa substrate with glass overlay and weighed a ton. That airplane came out in 1965 and is still going strong at Cunderdin WA. I reglassed it myself after a number of bingles (never mine) and I was always happier that it was a true hybrid composite. The wing fittings were embedded metal and the all-flying tail's likewise. I could easily live with that but I freely admit that I have great pause for thought when I consider metal brackets hugging composite lugs in the manner shown here and the piccies below. Methinks they have since maybe gotten a little overconfident and that AA587 may just be the proof of that."

I don't endorse the whimsical notion that you'll find now on the front page of aero-news: http://www.aero-news.net/
They are suggesting that there's a mystically strange empennage destructive flutter mode that's peculiar to the A300 and excitated by wake turbulence. I think that the answer's much simpler (as per what has been said already and in particular in the last two posts (by slimslag and whizzjet).

[The Truth]

Whilst not qualified to comment on the pro's and con's of the use of composites in aircraft primary structures, I think it is worth pointing out to the anti-airbus brigade that the Boeing 777 also has CFRP primary structure. The vertical stab. primary torsion boxes are CFRP as are the ones in the horizontal stab. If this does prove to be a composite failure, then it is of great concern not only to Airbus but the whole aviation industry. :eek:

[Out Of Trim]

Lame - Thanks for your info - I didn't Know that! Gooday to you!

[widgeon]

Belgique : glass sets exothermically wheras carbon endothermically ?. It is the resin that cures and in most cases a simlar epoxy resin is used for Carbon fibre and glass fibre. As far as I know all epoxies require heat to cure and will generate exothermic heat as the cross linking process goes on ( in thick laminates care has to be taken with the heat up rate to avoid run away exothermic reaction ). Can you expand a bit on the statement.

[bugg smasher]

Some years ago I took off behind an MD-11, I was flying a fully loaded DC-8 freighter. Separation was not more than a minute. At about 800 feet, the aircraft began to roll starboard, full control wheel throw in the opposite direction didn’t stop it, merely slowed it down somewhat. At 40 degrees of bank, we exited the vortex and recovered.

[sammym]

Just wondering, do all Airbus models have composite tals like the A300? :rolleyes:

[gaunty]

I reckon Belgique is on the right track, there resides in the fair place in which he (or at least his aircraft anyway) resides being the home of a fair bit if research in this area.

Having said that and looking at the attach diagram, what appears to be missing are multiple load paths to the main structure, ie the absence of a "fail safe" mechanism.
OK OK there are three brackets but the descriptions of the failure mode I have heard so far seem to suggest that the loss of any bracket but the middle one would tend to accelerate the separation. This seems to me to be a bit dodgy.
There does not appear to be (and I am not an engineer) an alternative load path from the VS to the main structure beyond those three brackets??
Belt and braces, sure, but I thought that was what the certification process had evolved towards and is this still a requirement.
This is not a criticism of the product or the magnificent technology, but when the Governments, therefore certifying authority and manufacturers are the same people and national pride is involved the pressure towards pushing the boundaries has to be higher.
IMHO the entire raison d'etre of the Airbus philosophy is towards maximising modern lightweight composite technology which awards better operating economics against the higher order of technical difficulties in manufacture and repair. A more conservative approach might produce weight penalties that nullify those benefits.
This must inevitably lead to a sort of technical hubris.

I noticed some one talking about composite primary structure in the B777, I would be interested to know if they also provide an alternative load path around it and/or what are the consequences of it failing?

And no I don't work for Boeing.

allianceair

No I have not found the photo yet but would appreciate some help. I did ask if anyone else had seen it.

[ 17 November 2001: Message edited by: gaunty ]

[Blacksheep]

Since the aeronautical engineering world allegedly knows b*gger-all about structural composites, perhaps its time for all those Harrier/AV8 and certain other military pilots to ease up on the aerobatics. I mean, pulling +9G/-3Gs they're more likely to have the wings fall off rather than getting them shot off by anti-aircraft fire.

Or aren't they?

Thank goodness aeroplanes aren't designed in bars over a few pints... :rolleyes:

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

[samgop]

Not an engineer, mechanic, pilot, anything... BUT, I'm tellin ya...too much attention to composite removes the visual clues. Aft left attachment seems to indicate a forward right to aft left removal, leading one to look at the forward right attachments. It's a fuzzy picture, but the BOTTOM forward right bracket seems to be bent up and back. Leads me to think it was that bracket, a metal bracket, which failed and caused the 'rocking' so well described by Belgique - leading to failure of top composite brackets.
http://www.ntsb.gov/events/2001/AA587/AA587_11.jpg

Going crazy, thinking I'm crazy. Somebody (vastly more knowledgable then I) please give some technical advise on why the attached picture doesn't show what I think it shows.

...not trying to defend Airbus or composites...

[BOING]

Unfortunately, due to lax statements by NTSB reps. and the usual ignorant press reporters the pilots are already being blamed for this accident in the US press. Along the lines of "actions of the pilots caused the rudder to fail".
I would welcome opinions on my thoughts. Following a couple of loss of control events our company started, quite rightly, to train recovers from upsets. At some point the use of rudder became a PRIMARY recovery aid to be used in all circumstances where roll enhancement is needed. I have always felt that the rudder should be used with extreme caution because of the danger of overstress. Unfortunately, because we have never had a rudder break off during simulator training we are, I believe, encouraging pilots to take actions which could lead to rudder overstress during flight. I sat in on simulator training recently where FULL rudder was applied at 300 + knots!
What do other airlines teach?

[IcePack]

Boing don't airbuseses have rudder ratio thingy's to ensure structural integrity!

[Shore Guy]

I just don't get it. The FAA Airworthiness Directive seems terribly inadequate. All the posts on this and other forums on composite structures tell of the difficulty in adequately (non-destructive) testing of composite material. How is a cursive visual inspection (literaly "lights" and "mirrors") going to determine the structural integrity of the vertical stab?

I would have thought that perhaps the newer aircraft in the fleet could initially be subject to less scrutiny, but the older higher time/cycle aircraft be inspected more thouroughly.

Comments from some engineering types?

[VBO]

NEW YORK (AP) - Neither turbulence from another jet nor pressure placed on the rudder by a desperate pilot should have been enough to snap off the tail of Flight 587, aviation experts said Friday - raising the prospect that something was wrong with the plane before it left the ground.
"I think there was a pre-existing structural problem with the tail,'' said Greg Feith, a former National Transportation Safety Board investigator. "It was going to fail regardless. It just so happened the conditions were right.''

The American Airlines Airbus A300 plunged into a New York neighborhood Monday, shortly after taking off from Kennedy Airport for the Dominican Republic. The crash killed all 260 people aboard and five more on the ground.

The cause of the crash has not been determined, but investigators have focused on the jetliner's tail assembly, which came off sometime before the crash.

The Federal Aviation Administration on Friday ordered airlines to immediately inspect the tail assemblies of their Airbus A300-600 and A310 planes. American and two cargo carriers, FedEx and United Parcel Service, have about 135 of the French-made jets in their fleets.

The FAA said no conclusions have been reached about whether the tail was related to the accident, but called the inspections a "prudent'' move.


Airbus A300 Tail Assembly diagram. Click Image For Larger View. (File Photo/National Transportation Safety Board).
NTSB Chairman Marion Blakey said the frantic efforts of the pilots aboard Flight 587 to save their plane also should provide clues to what went wrong.

"We do know, just from what we can see on the flight data recorder, that the pilots were trying to actively fly that plane out of the problem,'' Blakey told the Associated Press, cautioning that this does not imply pilot error. Investigators have already suggested the pilots wouldn't have known the tail fin was missing.

"It seems to me this was a very extraordinary crash. In fact, we don't have a parallel,'' Blakey said before she and other investigators left New York for Washington, where the inquiry will continue for months.

Investigators say Flight 587 shook violently from side to side after encountering two wakes generated by a Japan Air Lines 747 that took off about two minutes earlier from the same runway at Kennedy. Because of its size and weight, the four-engine 747 generates heavy turbulence.

While Flight 587 was more than four miles behind the JAL jumbo jet, as required by FAA regulations, NTSB spokesman Keith Holloway said the agency was looking at whether to suggest keeping planes farther apart, since wakes dissipate over distance.

Experts suggested more distance wasn't needed in this case.

"The wake vortex of a 747 should not bring down an aircraft,'' said Tom Ellis, a spokesman for the Nolan Law Group, a Chicago firm that represents victims of airline accidents.

"The A300 is designed to withstand forces of that nature. It should be well within its design tolerance. There's got to be something that interferes with the ability to recover.''

Based on information from the flight data recorder, investigators found that the plane's rudder moved sharply during the jetliner's three-minute flight.

Experts said the movement could have resulted from the pilot hitting the rudder pedal hard or from a jerk on the other end of the cable as the tail snapped off. But pilots of large planes don't usually use the rudder, except when they lose an engine or for help during landings.

"How did the pilots react?'' Blakey asked. "What did happen? Was it that reaction, or was it something mechanical?''

Examination of the two black boxes - the data recorder and the cockpit voice recorder - indicates the pilots were "working hard'' in the cockpit before the plane plummeted into the Rockaway Beach section of Queens, she said.

At one point, the pilots tried to use maximum power to regain control. But they were probably unaware the jetliner's tail had broken away, and the NTSB's George Black Jr. said calling for maximum power suggested they were in "recovery mode.''

"And they might be recovering from the wrong thing, because they don't know'' about the missing tail, he said.

Even if the pilots were rough with the rudder, that should not have caused the tail fin to fall off, said David Stempler, president of the Air Travelers Association, an advocacy group.

"Planes should be designed to withstand even abuse and still be able to maintain structural integrity,'' Stempler said. "The pilots may have done something but a plane has to be designed to even withstand harsh treatment by flight crews and not lose major structural elements.''

That has led several aviation experts to suggest that there was some unseen weakness in the tail assembly, which was made of carbon-reinforced plastic, a composite material that is lighter than aluminum.

The tail fin was held to the fuselage by six fittings. Maintenance records indicate that one of the fittings had to be repaired by the manufacturer before the plane was delivered to American Airlines in 1988.

The problems could have dated from 1994, when the jetliner was severely shaken by air turbulence, injuring 47 people. The plane was inspected following the incident.

"That's where the investigation really has to start,'' Feith said. "It may be the inspection was just a visible inspection. They're not going to be looking inside that fin area, they're going to be looking for obvious damage. Something could have happened that, although it didn't immediately fail the tail at that point, did set up a fail scenario.''

[WangEye]

Late in the day, and I have only scanned all the above, but....

composites, or more correctly plastic polymer composites, do degrade with age - they constantly release fumes (smell plastic boats, etc.) i.e lose molecules so that the resin that glues it all together changes. Some polymer resins do this more quickly than others - it's the same in all plastics. Many such products have an expiry date, others rely on obselescence or changing fashion.

Do we have a polymer expert in the house?

....this in addition to the other aspects like wake, A/C handling, etc.

WE (NOT an expert!)

[Few Cloudy]

Caveman,

Somewhere in your post it mentions that there has never been a similar case. There has actually, strangely enough to a JAL 747, where the vertical stab was lost following a depressurisation through the rear pressure dome into the fin structure.

Those gallant guys managed to keep the ship airborne for over 40 minutes before coming to the same conclusion that they had no chance. There was one survivor, who still appears on TV from time to time.

[tony draper]

I would have thought a couple of camera's covering giving a external view of the aircraft would be a help, instrumentation is fine but sometimes a analog view can save a lot of confusion.
It seems crazy that in some circumstances the crew have to come into the cabin and look out a port to see what the problem is.
It probably wouldn't have helped in this case,, but at least they would have known the tail was gone.

[mallard]

The only time I have had a bit of the aeroplane fall off it was a section of the leading edge slats. Examination of the remaining sections revealed a honeycomb structure behind the shiny leading edge.
That was a 757 which would have been about 14 years old at the time.

[sky9]

Surely
1. If the VS and Rudder become detached they take the hydraulic fluid and therefore power with them unless there are rapid shut off valves in the lines. If there was no hydraulic power to the flight controls and no rudder to provide yawing stability whatever the crew do after that is of little consequence.
2. On a Boeing Rudder Ratio ensures that full rudder cannot be put on at high speed, I would not expect Airbus to be any different. There really cannot be anyway that gross mishandling could even be considered as a cause.

[JudyTTexas]

Interesting article with pics on ANN Aero-News network for 11/16/01
http://www.aero-news.net/indexnews1.htm

Also, the FAA Airworthiness Directives:
http://av-info.faa.gov/ad/PublishedADs/011609.html

[ 17 November 2001: Message edited by: JudyTTexas ]

[bugg smasher]

Few Cloudy,

The JAL 747 you refer to did lose portions of its vertical stab, but the primary problem caused by the aft pressure bulkhead blowing was the rupture of the hydraulic lines of all four systems and subsequent total fluid loss. The aircraft did remain airborne for over 30 minutes, the crew had differential thrust for roll control and alternate flap extension for pitch control. For some reason they were not able to steer it away from mountainous terrain. It is a difficult business, but most crews after some practice in the sim are able to bring it home. This unfortunate crew, I believe, were the first to encounter it.

There were 24 survivors of that accident, there should have been many more. In a remarkably shameful display of bureaucratic bungling, the Japanese authorities decided that a crash into mountains is simply not survivable, and so went home to bed. The aircraft impacted the mountain side at approximately 6:30 pm, the first rescue teams arrived at around six the next morning. All the survivors were in reasonably good condition, they would have had to be in order to survive the night.

[widgeon]

Wangeye , the smell in boats is Polyester resin . There is no place , even in tertiary structure , that polyester is used. Most primary and secondary stucture composites are made from Epoxy resin cured at either 120 or 170 deg c ususally in an autoclave at up to 100 psi. Boats on the other hand are usually made from chopped mat impregnated with polyester resin and cured at room temp with no pressure.
The main cause of degradation of Epoxy resins is exposure to UV light which is why it is important to ensure the paint is not damaged. Part of the qualification process for a new composite material involves long term exposure to extreme temperatures and levels of humidity. In the early 70's I worked on a program at Westlands to qualify several Ciba resin systems , this involved sending test coupons to Australia and Central America for long term exposure testing . The results of these test are used in determining the margins of safety used in design of composite structures. That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure . The hardest thing in the design of any composite part is attatching it to anything , the ratio of bearing strength to ultimate strength is far lower in composite materials when compared to metals , which is why attatch lugs on composite assemblies have to be much larger in relation to a similar metal structure with similar loads . Sorry to ramble on !!!.

[TechFly]

Thanks again to everybody contributing and detailing with interesting infos.

Do you think we can resume that for any particular reason the tail composite section has lost its full aeroelastic strength and so the associated resonance frequency was perturbated till the separation?

Let's hope our aviation world will begin soon to move up again...

[dallas dude]

Folks,

I was over in Blighty when I heard of AA's latest 'trouble'. As is usually the case, "experts"-particularly terrorism experts-were wheeled out to speculate their best(wild) guesses on us.

As heartbreaking as the subject is, I have to say that this is one of the best threads (which for the most part has stayed on topic) I've recently come across. Ppruners should be commended for their mostly wait and see attitude.

Belgique, and others, your insight and comments is enlightening.

Some FYI..
A few years ago AA adopted slightly different unusual attitude recovery techniques. One of the main points was that pilots weren't always using enough rudder during recovery. Several simulator unusual attitude recovery scenarios now call for "unloading" the wing by applying forward yoke pressure and using (coordinated) rudder inputs to level the wings.

As terrible as this incident (coupled with events on September 11th) is, the point should not be lost that despite being issued challenges that were insurmountable, these proffessional pilots did their ABSOLUTE BEST, as they were trained to.

It may well be that none of the five recent hull losses can be blamed on the ubiquitous "pilot error" caveat. That would be the only silver lining.

God bless them all,

Cheers,dd.

[Nightflyer]

Assuming the cause of the AA accident was the failure of the vertical stabiser, I wonder what the long term implications are for all Airbus aircraft that use this type of material. Indeed what are the legal implications for Airbus if this involves faulty manufacturing. Looking back at two 707 accidents during its early days of introduction, (Braniff and a PANAM freighter) where uncontrollable Dutch rolls threw off a number of engines, I can only assume that failure of the vertical stabiliser would cause an immediate and agressive Dutch roll which would throw off the engine pods. It would appear that both engines of the AA Airbus were detached from the aircraft before it hit the ground.

[alanbur]

I'll freely admit my total ignorance of aircraft composites, but according to other posts, the vertical stabilizer was repaired during manufacture by attaching a doubler onto the base of the stabilizer, along with some rivets. I know that in the case of ordinary fiberglass, you have to be *very* careful with fitting anything where it isn't designed to be fitted, because you are putting a hole in something that depends on not having holes for a large portion of its strength. Also, rivets provide a channel for moisture ingress into the core of the structure, which can cause later delamination. Could the manufacturing repair be the root cause of this accident?

Sympathies to all those affected by this dreadful accident.

[SLB]

posted by Satrun V (pg 1) quoting news source
"The vertical tail section of American Airlines Flight 587 cracked off when its modern reinforced plastic "composite" fittings failed, investigators said today...
"Before the plane was delivered in 1988, the composite material in one of the six fittings holding the tail in place was found to be delaminating, meaning its layers were coming apart. It was fixed by adding layers and inserting rivets, and the manufacturer decided that no extra inspections were required afterward.

posted by widgeon (pg 6)
.... That beeing said the largest variation can be caused by processing , which is why there are stringent in process controls at all stages of lay up and cure ...Hmm, prior to placement in service the original
assembly was identified as defective at a high stress point - then repaired, not replaced? I am sure the manufacturer avoided a costly replacement with that procedure. Might make sense if reliable inspection procedures existed to identify deterioration as it aged. Hey, it held for 11 years! Too bad that is not the lifetime of the aircraft.

[RogerTangoFoxtrotIndigo]

SLB

bad taste plain & simple. are you implying that airbus would conciously put pax at risk to save remanufacturing a part? idiot.

[320DRIVER]

The FAA has issued an AD to inspect A300/A310 vertical stabilisers:
http://av-info.faa.gov/ad/PublishedADs/012351.pdf

[MarkD]

How does the vertical stabiliser of the A300B series compare with the -600? If time-related degradation of the composite is a factor, those guys should be running on empty...

[DoctorA300]

MarkD,
The OLDBUS B2/B4 has an all Alu Tail.
Brgds
Doc

[slim_slag]

RTFI

bad taste plain & simple. are you implying that airbus would conciously put pax at risk to save remanufacturing a part? idiot.

I'm not saying Airbus did this either, but there are precedents where large corporations - US automobile manufacturers have been caught out here - have made safety based decisions based purely upon cost. Who had to pay out loadsamoney when a memo was found saying it was cheaper to pay the lawsuits resulting from a bad design than fix the design itself? Business decided not to to recall the cars.

Same with seats in exit rows, putting water sprinklers in the cabin to suppress smoke, 737 rudder design, the list goes on....

Cost ALWAYS comes into the picture.

So what would have been the procedure for repairing and approving this part? It's an expensive part, certainly.

I had a chat last night with an engineer who works for a large company who manufactures these composites for aircraft - non structural only. I asked him what statistical methods were used to make sure a composite (which apparently can only confidently be said to be in good shape after you have destroyed it :mad: ) was OK to fly. The guy laughed at me and said those sort of statistics didn't really exist in aerospace. He implied that when they put an expensive part in the autoclave for curing, they will put a little test piece in there with it. They destructively test the small piece, if it passes, the large part passes too!

If they have put [i]two[/] large and expensive parts in the autoclave, and the test part fails, they destroy one of the large expensive parts. If that passes, the other large expensive part passes.

So where the hell is the science in that? Will somebody please say that's not true, or at least we shouldn't worry.

[747dreamer]

Just by looking at the engine size and its location from the body of A300, doesn't it appear to be way in front of the leading edge of the wing? Wouldn't this produce a huge torque when the plane encounters a severe side force such as when it first enters a wake turbulence?

I haven't read all the posts and reports on the accident, but has this possibility been discussed before to explain the engine loss?

http://www.cruisinaltitude.com/images/a300/repfra300hcdgl.jpg

[ 17 November 2001: Message edited by: 747dreamer ]

[ 17 November 2001: Message edited by: 747dreamer ]

[gaunty]

I have not so far seen any discussion of flutter in this accident, a mode that seems to absorb a fair bit of attention in the design and test of airframes.
The following email was forwarded to me which seems to resonate, so to speak, with the sequence of events.

Howdy,

Re: the New York 11-12-2001 Airbus crash.

I found this photo of the vertical stabilizer's failed composite
Attachment blades or webs. The bolts that attached the composite vertical stabilizer to the fuselage, remain properly attached. Clearly, the failure is a delamination of the composite vertical tail above the points of attachment to the fuselage.

There are reasons (despite the weight savings) why Douglas Aircraft and Boeing have never used composites this way - and you're looking at one. As the delamination of the composite progressed, the entire 37-ft. tall vertical tail would have fluttered briefly & violently. That would explain why both engines were literally shaken off the airplane. (This is particularly remarkable, because unlike Douglas and Boeing, Airbus has bragged of purposely designing their engine mounting pylons to keep the engines in place no matter what!) One wing tip was found several blocks away from the main wreckage.

BTW, you'll be hearing a lot about an encounter with wake turbulence. That is a red herring. Wake turbulence can make it difficult - maybe even impossible to control the airplane - but no amount of wake turbulence can remove the vertical tail at such low flight speeds unless there is a pre-existing structural fault.

What is flutter? This morning, I got an email from a friend who is the Director of Structural Engineering of a major American aircraft maker. He described a chilling picture: "Flutter modes often have an explosively quick onset, rising from nothing to catastrophic in the blink of an eye.
Furthermore, the shaking can happen so fast that, despite the large (huge) deflections involved, an observer on the ground might not see it. It's just a blur. The people in the back of the airplane would have been shaken senseless and worse as the seats tore lose and everything was homogenized back there; but it was all over a few seconds later."

The design weakness can and will be fixed on other Airbuses. If not, there are plenty of nice Boeing jetliners mothballed in the Mojave Desert, that can trade places with the Airbuses. In the meantime, I'm not riding Airbus.



The email might sound a little US v European product but IMHO does raise an interesting point which should not be lost in that argument.
BTW I am Australian so I don't have any commercial or national agenda beyond riding safely in whoevers product.

Blacksheep
Hi long time no seeum.
Don't think the Harrier/AV8 has any problems, it's had the best from both worlds methinks.

Which is the way it should be with passenger airframes.

[SLB]

SLB
bad taste plain & simple. are you implying that airbus would conciously put pax at risk to save remanufacturing a part? idiot.The implication was your interpretation, not mine. I would not suggest that anyone made a conscious decision to risk pax lives. I am suggesting their is a paucity of reliable knowledge related to repairing manufacturing defects in load bearing composite structures. If the decision to repair rather than replace was unrelated to costs, then it most certainly should have been replaced?
I'm not saying Airbus did this either, but there are precedents where large corporations - US automobile manufacturers have been caught out here - have made safety based decisions based purely upon cost.You don't need to look any further than this Forum to find that supposition put forward as it relates to Airbus and its sub contracting process. HOW SAFE IS THE AIRPLANE YOU DRIVE? (http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=1&t=014143)

[I. M. Esperto]

These composite materials DO deteriorate with age. Whyy would an engineering firm liek Airbus Consortium not realise this? They must have.

I had no idea these things were made of this material. The particular aircraft was 13 years old.

This bears watching, and thanks for the info GG - I never saw this in anything published. I forewarded it to severl chemichal engineers of my aquaintance for their opinions.

[Capt PPRuNe]

Thankfully this thread has sorted itself out into a reasonably mature discussion on the issues of concern and the few who try to deflect it with conspiracy theories or "sounds good questions" of little substance have been ignored.

Unfortunately, due to the constraints we have with the server this thread has reached its limit of 100 replies and must be closed. Please feel free to continue the debate in a new thread and you can of course reference this thread.

I would like to suggest that technical discussion take place in the Tech log forum.