Possible cause of AA flight 587 crash...a new thought

Vanity | 11/15/01 | Agent Smith

[Agent Smith]

Up until now, my best guess as to the cause of the 587 crash was defective/substandard bolts used in attaching the vertical stabilizer to the tail and a failure to detect the problem through inspections.

However, I heard on the news last night that the vertical stabilizer was not fabricated from aluminium, but from a carbon fiber composite. This material is very strong and light but can fail catastrophically if a stress fracture/crack develops. Based on the photos of the recovered stabilizer showing that it was cleanly severed from the tail, I now believe that this is the most likely cause of the accident.

The turbulence from the JAL 747 was the straw that broke the camel's back.

[eno_]

Can't do the math in my head but I'd betcha the load from the rudder while making that tight turn was several times the max theoretical load that could have been produced by turbulence when the plane was flying straight after completing the turn. Let's see if NAMMARINE and the chorus line of 12 Frogbus engineers still say the vert stab was hanging by a thread until it hit turbulence. It never would have finished the turn. The vert stab was not the initiating event. Something put the plane sideways at 300kts. THAT would be enough to snap off the vert stab. And the engines.

[jaz.357]

...aaaHHH, ZORDAS...I TRUST THIS GUY!

[David]

"The TV depictions show the Airbus in the wake event because it was flying through the airspace where the 747 had been (a minute and a half earlier)--one of the many problems with that analysis is that the wake would no longer have been there by the time the Airbus got there because the wind tends to move whatever vortex it does not disipate. Wake turbulance just didn't have anything to do with this event."

However, wake turbulence sinks. And it is blown by the wind. The wind was from 320 at 11 knots. Thus, by turning inside the JAL 747 and by flying 400-800' below the track of the 747, AA 587 would have entered the area where the 747's wake was sinking/drifting.

The wind you cite is the reported surface observation. At 2500 feet, the wind would have been somewhat stronger and more westerly (as a general proposition; I have not looked for the winds aloft reports). I have not done any calculations that would yield a precise scientific answer as to where the vortex might be expected but based on my 38 years driving airplanes, my opinion is that any turbulance to be expected from the wake of the 747 would be well behind and below the Airbus--a long way behind and below. And that is if there was much left which there probably was not.

I just saw the lady from the NTSB on CNN and they are backing away from wake turbulance as a significant contributor--any experienced pilot who looks at this is going to think the wake turbulance explanation is a joke.

[Tony in Hawaii]

Thanks, I'll check it out.

[WFTR]

I saw an article yesterday that said that this specific plane had been involved in a severe turbulence event in 1994. The event was severe enough to injure 46 passengers (or some large number). A possibility that we haven't mentioned so far on this thread is that the plane suffered damage during that incident but that the damage was not detected during subsequent inspections. As a very rough rule of thumb, 90% of fatigue life on a metal piece is the initiation of a crack. The other 10% is propagation of that crack through the part. I'm certain that this idea does not translate to composites exactly, but previous damage could have caused cracks which would accelerate fatigue.

I didn't give this crash much thought originally, but one of the guys at work mentioned that coincidental, simultaneous, failure of multiple components is rare. One of the previous posts describes how failure of the vertical stabilizer could cause forces that would put tremendous stresses on the wings and therefore engine mounts. If that is the case, then the root cause failure is the loss of the vertical stabilizer and all other failures resulted from that one. If the failure of the vertical stabilizer didn't cause forces that led to the loss of both engines, then this plane suffered coincidental failure of the vertical stabilizer and both engine mounting assemblies. Maybe all three areas had hidden damage from the previous turbulence incident, but I am skeptical that three different parts of the plane suffered fatigue fracture in the same fifteen second interval.

For the record, I'm not a pilot and have no experience in composites. On the other hand, I have bachelor's and master's degrees in materials engineering. My main focus has been corrosion, but I have done extensive failure analysis including many failures caused solely by mechanical forces.

WFTR
Bill

[Tony in Hawaii]

Some great pictures at this NTSB site Click the pictures for large versions.

[Fixit]

Bump for a good read.

(I am smiling thinking about what they do to that media whore reporter that insists on coming along for the test ride...)

[RaceBannon]

I saw an article yesterday that said that this specific plane had been involved in a severe turbulence event in 1994.

Sounds like you confirmed an explosion that threw the aircraft to the side at 6 G's in an instant. If there was a crack in the vertical spar in the tail section due to the previous severe turbulence event, the load due to the bomb force pushing the aircraft 10 to 20 feet sideways could overload the tail section due to the combined loads applied; Flight loads, bomb force, wake turbulence, all mixed up with a previously cracked vertical spar.

Now all we need to hear is wind shear, that could also be a force assumed to debunk the bomb theory.

[MassLengthTime]

AA 587 registration N14053 was A300B4-605R s/n 420. As such, the rudder debonding airworthiness directive I mentioned previously does not apply.

[WFTR]

I certainly didn't intend to confirm anything about a bomb. My first point was that this plane had been exposed to some severe forces in the past. These forces could have produced damage that was not found by inspection. My second point was that coincidental fatigue failure of several components is very unusual. Therefore, I don't immediately dismiss the idea of sabotage or other intentional acts to destroy this plane. Maybe the evidence will confirm that the whole thing was just turbulence or wind shear, but I'm not as dismissive of other ideas as I was at first.

[Thud]

As a trial attorney who sometimes sees other attorney's aircrash files, it sounds to me like there may be some until-now unknown long-term factors at work. I wonder if there are any testing protocols for this sort of composite deterioration.

[Thud]

Just reading the posts to No. 81 makes me suspect Airbus design and delamination problems.

[MassLengthTime]

Vertical Stabilizer and components of aircraft recovered from the water

Vert Stab attachment point. To my very untrained eye, there appears to be a lot of wear in the area where the bolt/flange/fuselage bracket assembly attaches.

More pics here.

[Thud]

Airbus has to be shitting bricks right now. Their certification is at risk if the cause turns out to be composite deterioration over time.

[Thud]

Re bad forming from the start:

"When you eliminate the impossible, whatever remains, however improbable, must be the truth." Arthur Conan Doyle through his Sherlock Holmes character.

[Thud]

If the original repair job created different and unanticipated stresses which eventually caused a failure, Airbus will breathe a lot easier. That is a one of kind matter as opposed to anything inherent in the design of that type of aircraft.

[Thud]

Your post in the other thread does seem to explain how the crash happened. Thanks.

To: John Jamieson

I'm with you. Plane hit one side of vortex, then the other. (up then down, and/or right then left) Resulting torque forces jar stabiliser loose. (musta been weak already) Pilots apply power to gain altitude (as plane noses over) Plane departs controlled flight. Plane begins flat spin as differntial lift (swept wings) aggravated by yaw forces kicks in. Extreme cross wind stalls compressor on upwind engine, accounting for reported 'pop pop pop'. Rotational forces later sling motors off mounts. Wing shears at root, fuel catches fire. Debris scatters. Plane hits ground. All this in the space of about 15 - 30 seconds near the end.

It could have happened. But to believe this, I think the airframe had to be near death to begin with.

31 posted on 11/15/01 2:53 PM Pacific by Blueflag

[185JHP]

CAT can be a real stress inducer. I was on a "commuter" airline flying to a southern airport and I was amazed at how the 16-passenger turboprop bounced around in CAT. Easy to drive the distances they fly - and wait 'til you have a G5 lease...

[185JHP]

Do you know what Vne is for this airbus?