Re: Soviet Aircraft

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works
Date:         06 Apr 93 04:59:34 PDT
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Jay Vassos-Libove writes:
>When I flew through Shannon airport recently, I noticed a Soviet
>plane ... the plane had four jet engines, all at the tail, attached
>with two on either side

That's an Ilyushin Il-62, the Soviet version of the Vickers VC-10 and
the backbone of Soviet long-range operations for many years, long
after the West had traded in the VC-10 and its contemporaris on new
equipment, mostly the 747, DC-10, and L-1011.  The VC-10 in BOAC
colours is one of my favorite aircraft, visually.

>What are the pros and cons of putting engines in pairs like
>this on the tail, versus putting them under the wing (as on
>the 747)?

The pros are that it permits a cleaner overall aerodynamic design
because it allows for a wing with fewer compromises, and it tends
to produce a quieter cabin since the engine noise is in the back.
It also reduces constraints on landing gear height which may be a
great advantage for smaller aircraft intended to service fields
with stairs instead of jetways and such.  Boeing had to work a lot
harder on the 737 than McDonnell-Douglas did on the DC-9 to get
the fuselage close to the ground, for example.

The biggest con is that those engines are heavy and when operating
produce some tremendous forces.  A lot more structure has to go
into a fuselage to suport aft-mounted engine(s) than into the wings
to handle wing-mounted engines, and that structure adds weight to
the airframe.  This is probably why all of the recent designs use
wing-mounted engines.  (The MD-90 isn't really new, being just a
reheated DC-9, and it would be pretty hard to put the #2 engine on
an MD-11 anywhere *but* the tail!)

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