Re: Engine Design

From:         torresa@pwfire.pweh.utc.com ( 0 Torres_Alfred x6514 B-195 )
Date:         22 Mar 95 02:34:21 
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>: >Surprisingly, the Trent 800 is the lightest engine for the B777 (but
>: >it has the highest specific fuel consumption).  R-R claims that the
>: >Trent is at least 3,000 lb lighter than the competitor (i.e., 6,000
>: >lb per aircraft)!!!
> 
>: I assume you're reading the same ad I saw in AW&ST.  Like any sort of
>: advertising, read carefully:
> 
>No, please read on.
> 
>:     "The Trent 800 is also the lightest engine for the new Boeing,
>:     weighing UP TO 6,500lb less PER AIRCRAFT than its competitors."
>:              ^^^^^              ^^^^^^^^^^^^


Considering that the engines (GE, RR, PW) all weigh in the area of
#8,000 to #10,000 (I'm not sure on the exact figures for each of the
manufacturers) I think the figures floating around here must figure in
the delta fuel burn between the different engine designs. I'm sure that
BRAND X would find the best combination of altitude, weight, and range
in order to CLAIM that their engine can save XXX pounds per airframe. 
It simply isn't possible for two engines in the same thrust class to be 
30% lighter than its competition. 

_____________________________________________________________________________

Al Torres
Pratt & Whitney 
Mid-Thrust HPC Component Center Engineering
M/S 169-04
Phone: (203) 565-6514, Fax: (203) 565-2914, Profs ID: torresa
e-mail: torresa@pwfire.pweh.utc.com