Re: ID'ing aircraft [Re: AA 777-200IGW]

Date:         17 Mar 99 01:24:41 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>Maybe a high-mounted wing on an airliner, like a Bae146 but larger?  I
>suspect that they haven't tried that for a reason.

There are several reasons.  One is that the high wing makes ditching
an even chancier event than it already is.  Another is that it makes
routine maintenance on the engines (assuming they're wing-mounted) and
the aerodynamic controls on the wings more difficult -- same reason why
the #2 engine location on the DC-10 (and MD-11) is less desireable than
the lower position afforded by the L-1011's S-duct.

>Also, the 757 originally had a T-tail like the 727, and I suppose this
>was redesigned for some specific reason, as well.

The T-tail introduces some tricky problems for stall recovery which must
be carefully avoided.  It also requires more structure in the tail to
handle the additional stresses.

>Another design I've wondered about would be a widebody airliner with a
>T-tail and rear-mounted engines (in fact I think there was such a plane
>proposed as a successor to the BAC-111).

Rear-mounted engines require more structural weight in the fuselage to
support them as compared to putting them on the wings which provide the
lift in flight and are close to the main landing gear when on the ground.
It costs a lot to lug that extra weight around.  The benefits are that
it keeps the engine noise away from most of the passengers (a lesser
problem with relatively quiet modern engines and airlines which care
more about efficiency) and it makes it simpler to design an efficient
wing (a problem which has been mitigated by experience and advances in
CFD and aerodynamic knowledge).

Karl Swartz	|Home
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