Re: Engines CAN jettison (Was Rear engined aircraft. (727 DC9 MD80) )

From:         olesen@metronet.com (Eric Olesen)
Organization: Texas Metronet, Internet for the Individual  214-705-2901 (info)
Date:         03 Jan 95 01:40:40 
References:   1
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Clemens Emanuel Tillier (ctillier@leland.Stanford.EDU) wrote:
: >>(1) They are designed in a ditching situation to shear off and flip over
: >>    the top of the wing rather than dig into the water & pull the wing off.

: >This is also for landings on runways without landing gear, but I think
: >the concern is more to keep the aircraft from flipping than it is for
: >tearing off the wings.

: How can an engine shear off and go *over* wing?  In situations such as
: described above, I would expect the engine wreckage to go *under* the
: wing.

On most aircraft with underwing engines (except for the 737-100 & 200), 
the engine nacelles project slightly forward of the leading edge of the 
wing. Assuming that the impact would be on a slight flare (nose up), it 
appears (I'm not an engineer...) that the nacelles would be deflected 
upward, and hopefully, over the wing. If the engine was hung directly 
below, it would be deflected upward, and immediately downward by the wing 
surface.

: Also, what is meant by "flipping" the aircraft when landing without gear?

Obtain a copy of the UA232 crash at Sioux City to see an airframe flip 
and cartwheel....... Although the UA232 flip was not caused by the engine, 
the flip can occur when debris deflects a wing upward, which will cause 
the other wing to strike the ground... The other wing will slow down 
either from friction or become imbedded in the ground, allowing the 
remaining intertia to carry of the rest of the airframe into a flip and 
cartwheel. 

This can also happen on any airframe -- CO flipped a DC9 back at DEN back 
in '87 I believe -- one wing was loaded with ice, and hit the runway on a 
takeoff roll... Flip.... Skid.... Oops...

I'd guess that most of the casualties of the UA232 crash resulted from 
the cartwheel, and not the initial impact.


E