HazelNuts39
I don't see a value for "longitudinal" strength. Popping off the tail as the airframe comes to a complete stop is not a (planned for) dynamic load, and has no bearing on the above destructive testing by NTSB. While the action might happen in a fatal crash (Might), your "longitudinal" strength I take to be what The NTSB calls "Bending moment".
Longitudinal is not Lateral, for purposes of VS failure discussion vis a vis Machaca's images. As you bring it up, I would point out that it is not a design consideration, except collaterally as a result of the other three vectors. As an opinion I would venture to say this direction of failure is least likely in all but a rapid horizontal stop. The value of the velocity (horizontally) would be quite high, as you suggest. I think quoting a value of 66g is misleading, if what you mean is failure as described by BEA to wit: They claim a "Slight horizontal acceleration" and a "large vertical acceleration". They also claim an "En Ligne de Vol" so bias in heading can not be included. This brings up an apparent contradiction, as they (I believe) also claim a slight "rotation, left".
Longitudinal failure in the opposite direction, backward, though also unlikely, is quite possible. It would involve an inflight failure, however. The six joins resist the airstream (through drag) in respectively a tensile at #1 (pair), a tensile at #2(pair), and a compression at #3(pair). #2 works as a consonant fulcrum with #1. The system is basically an inverted "teeter".
That is with the Rudder centered, acting merely as additional "area" in the VS/R combination. If deflected, The Rudder introduces a Torsion, and additional tension at #1, with an additive tensile at #2. It also adds a "bending moment". Compression at #3 is comparably increased.
As with 587, if reversals occur, the self same failure could occur with 447. As I see it, the only addition to the antiquated design of the A300 in the A330 is the addition of what are termed "lateral rods". From the photographs, and aside from disagreeing with BEA re: the mode of failure, The rods look (demonstrably, qed) frankly inadequate; that is another discussion.
If my take on your post is incorrect, I am sorry, please do correct me.
I am extremely interested in your thoughts in disagreement with BEA relative to forward velocity at impact. I have not ever thought the a/c had time in her descent to lose enough energy to allow for the docile impact that is seemingly intimated by BEA. I think you are on to something, as is JD-EE. Next is evidence of damage to a/c not consistent with benign horizontal "acceleration".
bearfoil
Last edited by bearfoil; 30th Aug 2010 at 14:12.