sferrin wrote:They don't use the same core. Think of the F119 as the starting point. (Much like the B-1B's F101 was the starting point for the F110.)

Well.... it depends what you read.
PW BACKGROUND F135 wrote:The F135 evolved from Pratt & Whitney’s F119, the technologically advanced engine exclusively powering the U.S. Air Force’s F-22 Raptor. The common core of the F119 and F135 has more than 400,000 hours of operational use, offering proven dependability and unmatched single engine safety. The F119 recently achieved hot section full-life capability of 4,325 total accumulated cycles and depot inspection has validated the robustness and sustainability of this 5th generation engine. The F135 benefits from these F119 technologies and is designed to significantly lower lifecycle cost.
REF:
http://www.sanfordgrowth.com/uploads/fi ... ground.pdfOr...
Tom Johnson, Chief Engineer F119/F135 wrote:The F119 engine shares mature core components with the F135 engine, which provides tremendous benefits from a cost and durability standpoint. This will benefit the F-35 program with respect to engine maturity, single engine safety, and reduced sustainment costs.
REF:
http://www.prnewswire.com/news-releases ... 35871.htmlSo it boils down to being 'the core' or 'core components' which could be a specific % of the core.
GE has always said the F110/F101/F108/F118 are "based on the same core" (and it's how the USAF funds improvement and parts contracts) but it would almost always 'differ' somewhat; I'd venture to
guess the cores would be over 50% common between the engine versions, but not more than 90%, but I still feel as though you could say "these engines are based on the same core" - same basic design, layout, technology, airflow, build, maintenance, etc. No you can't take the core of the F110 and put it into the F108, but they are almost the same as far as jet engines go if you were to compare them with other GE engine lines.

In the end, the term is used rather loosely. I think it's safe to say either the F119 and F135 have "the same core", or "have similar cores", though they are most certainly not 'common' or interchangeable between the two engines. (Like GE has done with their line) The cores of each specific engine will always differ in minor aspects from one another but will look very much the same on paper. They will almost always share technology, funding, and improvements when it comes to USAF contracts with PW.
Keep 'em flyin'

TEG
[Airplanes are] near perfect, all they lack is the ability to forgive.
— Richard Collins