One way to make sense of this is to presume that the engine core the 624th institute tested and handed off to the 606th institute was ultimately rejected by the 606th, and the 606th started from scratch, which might make sense given some of the rumors we’ve heard about the 606 and 624 institutes having disputes over the engine core. However, that would mean the 606th institute also canned a second design and started a third design sometime between 2008 and 2018, with enough time get the third design ready for flight testing at the end of this year. I’m not sure how believable that is. It might fit with the fact that supposedly they had started building a full prototype in 2014 and we still haven’t seen any flight tests. Maybe it’s because between now and 2014 they pushed the reset button, or maybe that reset happened between 2014 and 2018. If they did push the reset button, it’s plausible that design and development the second and third times around were much faster by simple accumulation of experience and knowledge, and the reuse of research and other elements from their previous tries. It might also explain why we were hearing that the codename for the engine was E’mei for years, only to more recently hear it is actually Zhufeng (Everest).
That said, if I can piece together the tidbits of information we’ve gotten through the years to make these supposed leaks sound plausible, someone else can use the same bits of information to manufacture stories that fit the same fact patterns. What makes me *most* suspicious of this leak is the variable cycle engine claims. While resetting the engine’s design twice doesn’t sound too unlikely, going all the way to a VCE design sounds like a massively risky undertaking for a project that is already on a tight deadline and was already anticipated to be behind schedule, and for an industrial base that is still trying to catch up in expertise and experience compared to their competition, who themselves haven’t put a VCE design into production yet. Furthermore, how would anyone outside the US defense establishment know what the F119’s thrust at 10,000 ft is to know that the supposed VCE WS-15 could generate 30% more thrust in the same condition? Specificity can often be useful to distinguish between what’s real and what isn’t when we’re trying to sort out rumors, but specificity can also be faked, and we should be careful not to bite onto details too assuredly if we don’t have ways of vetting those details.