[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

[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.