Egypt Air 990

Date:         05 Nov 99 00:04:08 
From:         Joseph David Farrell <erisajd@erols.com>
Organization: Benefits Litigation Concepts
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OK - this is for the AE's out there.

Scenario -

Pilots distracted - i.e., one of them gets uop and goes potty after
they reach cruise.  One returns, while the other pilot is opeing the
door, there is upset from wake turbulence or some other unsteady air -

The elevator trim then goes uncommanded into a dive, say into a full
down deflection to govern an upset that was not that serious.  The
autopilot fights it until either the pilot is clicked off by a pilot
or the autpilot gives up and releases it.  At that point there is a
big negative G.  The pilots hands coming off the yoke if they were on
it at all when he was reaching back to open the door.  The pilot off
his feet smashes into the ceiling.  The pilot in his seat, hopefully
with his belt on, struggles to put his arms down and finally, after
whatever it takes, with redout problems, gets his hands on the the
yoke and pulls up.  At this point we have FULL nose down trim.

Cruise in a 763 is mach .84, with .86 the barber pole max IAS. This
a/c then exceeds the never exceed speed, and continues to accelerate.
At transsonic and even slower speeds there is the phenomenon of mach
tuckunder, where as the a/c speeds up the swept wing configuration
brings the nose down.  The nose down is now compounded by mack
tuckunder, and the on question is how fast did it get [i.e, supersonic
or merely transonic] and was the tail big enough at say mach .95 to
bring the nose up with full down trim? The second question is how much
time does it take to reach and unrecoverable airspeed, and the final
question is did the pilots simply pull the wings off when that
happened?

This type of scenario explains the entire observed issues, high rates
of descent, and the working transponder in a 20,000 fpm descent rate
until one of two things occurred, the a/c broke apart from the
overspeed or the pilots simply pulled too hard and pulled the wings
off from the G's - either of these explain the powered transponder and
the high rates of descent - the second one actually to fit the facts
better since it allows for the wings and stabilzers to shear off and
the airframe to remain powered until it completely breaks up from the
G forces.

I'd like to hear thoughts from anyone having aeronautical engineering
experience or education on the facts?  Anyone know the design specs of
the 767 enough to know what speed mach tuck under is not recoverable -
there is such a speed?

Joe