Originally Posted by
KRviator
Were there any meaningful differences in the CF6 that "made it" more reliable than the Pratt or Rolls offerings? Interesting to see the note GE out-sold both PW& Rolls put together!
GE's big advantage with the CF6 is that it was a major derivative - not an all-new engine. Normally, a clean sheet new engine gives better fuel burn - but generally at the price of reliability early on until the bugs get ironed out. However in this case, GE pretty much matched the fuel burn of the PW4000/94" and had outstanding reliability at EIS. Worse, Pratt had issues performance retention - a brand new PW4000 had marginally better fuel burn than a CF6-80C2, but the Pratt rapidly deteriorated such that after 1,000 hours the CF6 had the fuel burn advantage. Pratt finally addressed that with the Ring Case Compressor upgrade, but that didn't come for another 15 years - too little, too late.
The RB211-524G/H was a good, reliable engine (aside from the previously mentioned engine control issues) and had very good performance retention (big advantage of the 3 spool design - less bending moments that rub seals) but was heavier than the other two and was a bit worse on fuel burn.
In short, GE really nailed the design of the CF6-80C2 - even though it was a derivative it gave nothing away to the 'state of the art' PW4000 and was more reliable to boot. Ironically, Boeing thought the PW4000 would have the dominate market share and the CF6 wasn't going to be a big seller. As a result, Boeing elected not to invest in developing the engine nacelle for the CF6-80C2, instead buying the nacelle from GE (at a much higher price than an in-house design would have cost). An expensive mistake.