Re: 727 engine config

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works
Date:         17 Nov 93 15:34:42 PST
References:   1 2
Followups:    1
Next article
View raw article
  or MIME structure

>The 727 is Boeing's only trijet, and is the only trijet I know of with
>all three engines at the tail.

There are a good number of other examples of this configuration.  Most
notable are perhaps the Hawker-Siddeley Trident (nee de Havilland 191)
(a number of people would claim the 727 is an American ripoff of the
Trident) and the Tupolev Tu-154 (a number of people would claim this
is a Soviet ripoff of the 727).

There are also several smaller Russian trijets of similar configuration
including the Yakovlev Yak-42 if I'm not mistaken, plus several other
Western aircraft in the business jet class.

>Anybody know why Boeing gave up on trijets after the 727

They didn't give up on them -- some proposals for the 757 and 767 were
for trijets, and there were at least two trijet 747-300 proposals.  I
do believe Boeing became a bit disenchanted with the trijet notion,
but I'll leave that for others who know more about the matter.

>why nobody else has built a trijet with three engines at the back?

Weight is an obvious problem, on any aircraft with rear-mounted
engines, not just a trijet, and the newer engines are making that
problem worse.  Wings do the lifting, so hanging a big heavy engine
from the wing gets the weight close to what's carrying it.  Putting
the engines in the back requires significantly greater structure in
the aft fuselage.  That structure adds weito the airframe.

A problem specific to a trijet is that the center engine duct is
expensive to re-size when new engines are applied, unlike a wing-
or fuselage-mounted nacelle.

--
Karl Swartz	|INet	kls@ditka.chicago.com		
1-415/854-3409	|UUCP	uunet!decwrl!ditka!kls
		|Snail	2144 Sand Hill Rd., Menlo Park CA 94025, USA
 Send sci.aeronautics.airliners submissions to airliners@chicago.com