Re: 757 highest thrust to weight ratio ?

From:         cid@athena.mit.edu (Derek H Cedillo)
Organization: Massachusetts Institute of Technology
Date:         11 Dec 92 00:38:19 PST
References:   1 2 3
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In article <airliners.1992.132@ohare.Chicago.COM> greg@saltydog.dpsi.com (Gregory R. Travis) writes:
[good outline of engine loading]


>However, I am confused by Karl's statement that Lufthansa chose the A340
>over the A330 because of concerns that the twin-engined A330 would place more
>stress on its two engines whereas the A340 would enjoy higher engine
>reliability as its four engines loafed along.
>
>Since a twin engine jet is nominally overpowered compared to a four engine
>jet, it should be able to operate, on aggregate, at a lower thrust setting
>during takeoff or be operated at high thrust for a shorter overall climb.
>
>Since a four-engine jet has all four operating closer to the margin, in
>normal operation, the engines should suffer from higher demands all around.

I think the thing here, is that you are imagining two different engines
entirely.  This isnt exactly the case.  I dont have thrust data handy,
so I cant compare the A330 engine performance with the A340, but as a quick
example, I'd like to point out that the A340, A320 and A321 all have
the same GE engine spec (CFM56-5) while the A340 is a four engine plane
and the A320 and 21 are two engine planes.
Althought the 340 is definately bigger than the 320/1, I dont think the
engine loading would be twice as much.  (can someone come up with stats 
to prove or disprove please)

Another look is the 767-200ER/300/300ER, MD-11 and 747-200/300/400 which 
can choose the GE CF6-80C2.
All are relatively large planes, and they gradually increase
in size, but is it huge enough to say the 747 is Twice as heavy/aero dyn
loaded, etc, to require twice the thrust as the 767?
Note that they have 2,3,4 engines respectively
Again, I would appreciate any airframe data to support the 
weight/thrust/loading claim, or shoot me out of the sky as seen fit.


Can someone help?
Thanks,


Derek

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