View Full Version : jet engine specs!
Willit Run
4th Jul 2005, 02:43
there was a link a while back, about the various manufacturers engine models and their respective thrust outputs. Can anyone lead me that way? Specifically, the Pratt JT-9's and Rolls Royce RB-211's? Help,please, and i will buy you a beer, promise!
Engineer
4th Jul 2005, 03:03
Was it this (http://www.xplanefreeware.net/~morten/jpgs2/GasTurbines.pdf) you were looking for?
enicalyth
4th Jul 2005, 11:03
Beware beware. GE quote thrust specific fuel consumption on their lie-sheets for sea-level ISA takeoff conditions. Most everybody else will quote for a cruise Mach No and Flight Level.
Thus a GE lie-sheet might say 0.33lb/lb-hr whilst RR quote say 0.57 but if the actual reference conditions are omitted comparison is not only odious but as much use as a chocolate teapot.
If I had a dollar for every bean-counter (and sometimes a pilot) who says "Why don't we fit GE, they consume nearly half as much as a Roller?" I'd be a rich man.
The GE in good nick on my biggie just before I retired was doing 0.587lb/lb-hr at best cruise, opening out to 0.603lb/lb-hr when a tad "off-axis". I derived these figs from aerodynamic data gleaned over the years and courses in Seattle and working back from fuel flow figs.
When looking at figures it is a case of apples v. oranges and caveat emptor.
Best Rgds
The E
Willit Run
4th Jul 2005, 14:51
Engineer,
Thats exactly the link!
Thanks!
wondering
19th Jul 2005, 19:00
The requested URL........was not found on this server :confused:
Has it been moved?
Dixons Cider
20th Jul 2005, 17:14
enicalyth
I'm impressed. Enjoy the retirement ;)
DJohnsen
22nd Jul 2005, 11:18
Greetings Enicalyth… although it is true that measuring and comparing SFC at sea level vs. cruise is totally absurd, I have looked at several performance numbers for a B777-200 fitted with PW 4000, GE 90 and RR Trent 800 and although the RR has an advantage over the GE installation in the total weight of the propulsion system, the GE installation has a fuel burn advantage. If memory serves me right, the break over point was approximately four (4) hours of flight time. We are also seeing a significant improvement with the 3D compressor installation. Unfortunately the PW installation does not even come close…
To your other point, if I had a $ for every time some half-cocked bean counter ran off making decisions based on numbers they had no clue what meant… or if it even made sense, I would have been retired too… :p
And yes… enjoy your retirement
Dag