Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Posted (3 years 11 months 3 days 2 hours ago) and read 3395 times:
Off the Wiki, the Garrett TFE731 introduced on Learjets and Falcon in 1972 was a Geared Turbofan design. My question is why was it the only one? Or was this first GTF implementation much less attractive/efficient than what PW is proposing with their PW1000G? It seems strange that the benefits of GTF were already available 37 years ago but were only adopted on one (very highly successful) engine...
I'm not sure why it didn't show up on other biz-jet engines. Small jets tend to have lower bypass ratios, where the GTF advantage isn't as large, so it's easier for a non-GTF to compete with a GTF. It's the diameter mismatch between the fan and the turbine that causes the fundamental problem that the GTF is trying to resolve. On a biz jet engine, that mismatch isn't near so bad.
Quoting Faro (Thread starter): Or was this first GTF implementation much less attractive/efficient than what PW is proposing with their PW1000G?
I would hope the efficiency is better on the PW1000G because of the higher bypass. However, the major achievement of what Pratt has done is the scale up. Gearboxes at the biz jet size aren't really any more challenging that gearboxes on turboprops, which have been around for a very long time. It's the scale-up to the power levels required for modern turbofans that's been the challenge, and has consumed decades of research at Pratt.
Trex8 From United States of America, joined Nov 2002, 3970 posts, RR: 14 Reply 2, posted (3 years 11 months 2 days 18 hours ago) and read 3293 times:
Quoting Faro (Thread starter): Off the Wiki, the Garrett TFE731 introduced on Learjets and Falcon in 1972 was a Geared Turbofan design. My question is why was it the only one? Or was this first GTF implementation much less attractive/efficient than what PW is proposing with their PW1000G? It seems strange that the benefits of GTF were already available 37 years ago but were only adopted on one (very highly successful) engine...
I'm no engineer but everything I have ever read about the history of GTFs says it was all about getting the gearboxes reliable enough
Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Reply 4, posted (3 years 11 months 2 days 3 hours ago) and read 3162 times:
Quoting Tdscanuck (Reply 1): I'm not sure why it didn't show up on other biz-jet engines. Small jets tend to have lower bypass ratios, where the GTF advantage isn't as large, so it's easier for a non-GTF to compete with a GTF. It's the diameter mismatch between the fan and the turbine that causes the fundamental problem that the GTF is trying to resolve. On a biz jet engine, that mismatch isn't near so bad.
Thanx for the input; I guess Garrett -now Honeywell- should be commended for their foresight and enterprising design. Given the range of aircraft on which the TFE731 was fitted, I doubt that it was unreliable, too heavy or explosive. Just an innovative, fuel-efficient small fan engine.
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