Re: A330/340 vs. B777

Date:         01 Jan 97 20:59:23 
From: (Chilukuri)
Organization: Rohr
References:   1 2 3
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In article <airliners.1996.3095@ohare.Chicago.COM>, kls@ohare.Chicago.COM

>Another alternative might be to get Pratt (and GE) to push the thrust
>of the 62K engine up a bit, without going to the larger fan of the
>A330's 65K-68K engines.  Physically, this is essentially the same
>engine as the 56K version used on the 747-400, and maybe also the 52K
>version used on the A310, so 62k is probably already close to the
>Upsizing the 62K engine's fan just a little -- enough to get a bit
>more thrust without resorting to the potentially substantial air-
>frame mods needed to accomodate A330-class engines -- probably is
>not an economically viable option for the engine manufacturers.

Variable geometry, for example a variable nozzle, is a "last gasp" option
that allows the engine manufacturer to boost thrust at critical climb
segments without having to increase fan diameter. However, as Karl rightly
points out, this is a relatively expensive modification, with substantial
weight impact.

I believe that the A320/V2500 engine has been ground-tested with a variable
nozzle in order to overcome thrust limitations.