Re: TWA 800 wingtip separation

Date:         17 Dec 97 03:41:24 
From:         Patrick McConnell <patrickmc@sprynet.com>
Organization: Sprynet News Service
References:   1
Followups:    1
Next article
View raw article
  or MIME structure

Wayne Dohnal wrote:
> During the Monday night TWA 800 NTSB hearings, the "sequencing team"
> reported that both wingtips separated from the inner portions of the
> wings fairly early in the breakup sequence.  The man giving the report
> tried to explain the logic of this, and the panelists shook their heads
> like they understood what he was saying, but I still can't understand!
>
> Can anyone explain how it make any sense for the wingtips to separate
> when they weren't anywhere close to the explosion or structural breakup
> area?  After watching the load test and breakup of the 777 wing on TV,
> I concluded that there was no possible way for a wing to break up in
> flight.  (I realize these are different aircraft, but I'm assuming
> Boeing would have similar wing strength across the product lines).

My guess would be that, after the nose separated from the aircraft, the aft
section pitched up violently because the center of gravity move way, way
aft. The pitch-up caused the wings to reach an angle of attack far beyond
that which could be achieve by the intact aircraft at the airspeed they
were travelling. The resulting lift loads could quite conceivably have
failed the wings.

The wing will fail at it's weakest point, which could well be just outboard
of the fuel tanks. Fuel in the wings relieves the wing bending moment (at
least compared to an equivalent weight carried in the fuselage), so the
fuel tank termination could be the failure point. Or, the outboard engine
attachment point, where the engine point load is introduced, could be it.
Certainly the failure point is known to the investigators from the full
scale static test.