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To: r9etb

Composite material that is fatigued will appear to be normal with no stress, however, it does not have elasticity, when it is stressed, it stays opened, it shaters, it shards.

The pictures they showed of the fuselage section showed either the bolts sheared off or snapped off (same thing really), but NO FATIGUE failure, no sharding, no shredded composite material.

If the tail section fatigued off, the area where the bolt went through would have remained with the bolt, those bolts are most likely 3/4 hard, and that is about 250,000 Lb shear force failure for EACH bolt, and that tail had I think 8 bolts securing it.

NONE had the portion of the tail that actually held the bolt to the tail, it only had the portion of the fuselage where the bolt went through.

That means all sections of the tail that had a bolt through it failed at the same time! Something that would not happen during a fatigue failure that would go unnoticed for a couple years after a supposed hard landing.

One or two sections of the tail that had a bolt through it would have remained attached to the fuselage while the rest would have been ripped away in the failure. Those parts that were strongest would have to fail suddenly, SNAP off, not shard, or splinter like a fatigue failure.

NONE showed a splintered, sharded, sharp edged composite material failure, and that means this was catastrophic, not fatigue.

Also, I didn't see any bolts attached, either, and that tells me the bolts sheared off, not the tail mountings!


88 posted on 06/03/2004 9:28:18 AM PDT by RaceBannon (VOTE DEMOCRAT AND LEARN ARABIC FREE!!)
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To: RaceBannon
those bolts are most likely 3/4 hard, and that is about 250,000 Lb shear force failure for EACH bolt

Is that stress or load? 250ksi seems right.

Also, didn't the AA aircraft fail at the lugs..not the bolt? I don't remeber.

Bottom line though, I agree with you, this looks like a simple overstress.

90 posted on 06/03/2004 9:32:44 AM PDT by Dead Dog (Expose the Media to Light, Expose the Media to Market Forces.)
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To: RaceBannon
That means all sections of the tail that had a bolt through it failed at the same time! Something that would not happen during a fatigue failure that would go unnoticed for a couple years after a supposed hard landing.

Not "at the same time," so much as "after the first one broke." It would be a cascading effect -- the first one breaks, and sets up a rotational oscillation that begins to weaken and break the others. A few good twists and I can see them all popping, in a matter of a few seconds.

91 posted on 06/03/2004 9:33:10 AM PDT by r9etb
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To: RaceBannon
If the tail section fatigued off, the area where the bolt went through would have remained with the bolt, those bolts are most likely 3/4 hard, and that is about 250,000 Lb shear force failure for EACH bolt, and that tail had I think 8 bolts securing it.

You mean, it would have looked like this?

The fact is, the pictures show something a lot different from what you're describing. The bolts are in all cases still there. The pieces of the tail fin appear to have broken off at the attach point:


95 posted on 06/03/2004 9:41:12 AM PDT by r9etb
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To: RaceBannon; r9etb

Thanks r9etb,

Race, does this look like composite fatigue? I have no idea, I deal with sheet metal.


Vertical Stab attachment from AA587

http://www.ntsb.gov/events/2001/AA587/AA587_01.jpg


96 posted on 06/03/2004 9:43:17 AM PDT by Dead Dog (Expose the Media to Light, Expose the Media to Market Forces.)
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