Sorry, but what sounds fine in theory is simply not in return correct.
I have to admit that I have no official source, but from all we know, Saturn was asked to develop especially for the J-10 a new version .... As such the FN was especially designed as a J-10-tailored version for CAC. In the same way You can't fit a GE F110 used in the F-14B to a F-15 or F-15S it's also here: You can't fit a FN into a Flanker or a F into a J-10.
I am hardly surprised, not many folks have lateral thinking or think outside of the box. Although I must expressed my disappointment with you on this particular case. I always imagine you to be an adept when it comes to China War Flying Machines then how could you missed all these out. Any experienced China Military Watchers who are figuring out the final puzzle will work on the available data and info to perform some wild guesswork, extrapolate some numbers, etc instead of blindly resorting to the usual stereotype… Where is your source?
So in other words if no reliable or official source is available hence the J-10 never existed. We don’t bother ourselves with useless sources anyway because we know they are all rumors, hearsays many based on alleged insider information. FYI China never officially confirmed the presence of its J-10 projects for many years and had even denied its existence until many years later. CW just follow their instincts based on the events and their dates made available.
EXAMPLE:
1. The first prototype J-10 01 was rolled out in November 1997 and first flown on 23 March 1998 in a twenty-minute flight. So what engine did China fitted to this aircraft. WS-10A was not ready yet.
2. According to Salyut website, AL-31FN project only commenced only in 2002.
3. Wiki reads: The AL-31FN is based in the AL-31F which is designed for a twin engine aircraft such as SU-27 and to fit the smaller J10 the engine parts have been moved and re-designed to fit the smaller engine bay in the J-10. Meaning engine may rotate 180% around so that the gearbox is below with mounting realigned, etc etc.
4. Although the first picture of the J-10 appeared in the internet in 2005, the plane has flown much earlier on.
5. China signed an order for AL-31FN in 2005 which is strictly based on PLAAF requirement. Salyut do not have another customer for the AL-31FN.
6. All this indicated to us that China aviation engineers had most probably modified spare AL31F engine supplied around with the SU-27 to fit the smaller engine bay of the J-10 then later submit their requirement and specification to the manufacturer.
It won't be easy to prove me wrong or you right in this case.
Yes. Mine may be a theory but it is a plausible one. The accepted theory is filled with many unexplanable holes as well.