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

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: The Boeing Company
Date:         12 Jan 95 01:56:04 
References:   1 2 3 4
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In article <airliners.1994.1795@ohare.Chicago.COM>,
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.

Not so.  Engines will shear off in the aft direction in a ditching (or at
least, that is how we analyze it).

>Karl Swartz  wrote:
>
>>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.  (Especially for the water landing.)  Also, what is meant by
>"flipping" the aircraft when landing without gear?

An engine can shear off and depart the airplane by going over the wing
if it is still generating thrust and the rear emgine mount failed first,
as it is designed to do.

I think what Karl is referring to is when an airplane skids in and an 
engine hit some obstacle, like a berm at the end of the runway or 
something, causing the airplane to spin violently.  I think we'd rather
have the engine shear off.  It has the side benefit of absorbing (or
shedding, depending on your point of view) some of the aircraft's
energy.


-- 
Terry
drinkard@bcstec.ca.boeing.com
"Anyone who thinks they can hold the company responsible for what I say has
more lawyers than sense."