Re: 737 musings

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         19 Sep 94 01:28:39 
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>The NTSB has announced three preliminary scenarios for the crash ...

All of which have now been abandoned, or nearly so.  Looks like it'll
be a long time on this one.  (This one was pretty close for me, as I
used to live in Pittsburgh and an old friend from there was on 427.
Not as close as UA 232, though, which *I* was often on.)

>can an engine partially detach and stay in operation, much less
>remain attached to the wing ?

Depends on what exactly you mean by "partially detach" though for any
interesting definitions the answer is probably no.

>But wouldn't the engine lose its supply connections for fuel, hydraulics,
>and whatnot when the rear part breaks loose and it pivots ?

The usual design for a wing-mounted engine intentionally puts the weak
point in the mount at the rear of the engine.  This way, if something
happens that causes the mount to break, it'll break at the rear.  The
engine then rotates up around the front mount, breaking it too, and
the residual thrust carries the engine up, over the wing, and out of
harm's way.  (The trajectory is also designed to avoid the horizontal

This whole process will, of course, sever all the supplies.

>From what I have heard, both engines were running when it hit, but in 23
>seconds it may not have cooled enough if it quit to tell ...

There are lots of other clues beyond heat, which would have dissipated
by the time the NTSB started looking anyway.  For one thing, a turbine
engine operating at even a low power setting has tremendous rotational
energy, which should show up quite clearly in where the pieces fell
after the impact caused the breakup of the fan and other stages.

>They said all four (two per engine) locking actuators were found in
>the "stow" position.  They also said this means they were in the stow
>position.  Of course, they have also found three in the deploy position.

The actuators which were deployed were not locking actuators.  The
design apparently is such that if the locking actuators are stowed,
the reversers are stowed, without regard to the other actuators.

Karl Swartz	|INet
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