This may not necessarily be the case. It all depends on how much you are willing to spend in RCS reduction measures. RCS depends on 3 major factors; size, reflectivity and directivity.
Size, well it is not a large aircraft and hence will have a small RCS. Reflectivity is stealth shaping which is adequate on all 3 airframes, J-31, J-20 and PAKFA.
However what you haven't considered at all is probably the most important of the three. This is what makes the F-22 the king of the hill while the others are only trying to catch up. This is Directivity or the materials that go into making the airframe and the radar absorbent materials including paints. F-35 uses a jacket made of carbon nanotubes and covered with RAM. PAKFA, currently unknown, what we have seen is only the outer shell. J-20 may be doing well with what it already has today.
So, you see just looking at an airframe and claiming it is as stealthy as fully funded programs is not enough. As a matter of fact there is nobody on the planet who can claim the aircraft has this and this RCS just by eyeballing the airframe, especially if you are comparing two different airframes.
The reason I came to this opinion of mine is not because of size or reflectivity. It is because of directivity. Considering SAC built the frame for export out of their own pocket, how much would they be able to spend on materials if aircraft like J-20, PAKFA and F-22 require Billions just to get prototypes flying in the air. Sukhoi/Russia alone have been speculated to have spent $2Billion on the 3 PAKFA prototypes. Would SAC spend Billions for an export customer they may never get?
Even getting JF-17 to fly cost $500Million, all that money on just an airframe, FCS and engine.
As of today we cannot say whether SAC has been involved in a govt funded stealth program like CAC to claim they have been researching materials since sometime. All we know is they had a design as a competitor to J-20. There is no information if actual prototypes were built, like the YF-22 and YF-23 or whether they were flight tested. Perhaps it was a direct jump to the J-20 prototype after a paper competition. If SAC is able to use these expensive materials and built their own prototype after spending Billions all on their own funding, then be my guest, believe anything you want.
It's primary role may be air superiority.
Only if there is confirmation that it is a state funded project and not a company funded project.
Your oldest J-10As will be old enough for replacement, nearing 20 years by the time J-31 or equivalent is ready. Your newest J-10Bs don't have to be replaced at the same time. As J-31s or equivalent's production continues the older J-10s will be subsequently replaced. Or are you suggesting the J-10As will receive service life extension programs to keep it relevant. Unless of course China is not able to manufacture the jets fast enough to replace older ones.
You' seem to be over-looking two things:
1. AVIC, like any other company in the world would not invest billions of dollars into developing a stealth aircraft without concrete agreements with potential customers. You're basically sugesting that they developed this jet in the faith that a customer would come up somewhere.
Even when developing the JF17, AVIC was assured of a substantial order from the PAF. The only customer AVIC can look to, to order this aircraft in numbers high enough to make a profit is the PLA(whether its the PLAN or PLAAF). No export customers could order any substantial numbers(even Pakistan could probably only afford 2 squadrons), so you cant designate this fighter an export jet in the same way as the JF17. They would never embark on such a venture without concrete assurance of large orders from the PLA..
2. AVIC is an ENORMOUS corporation, of which Chengdu and 601 institute are just fractions of. It's revenues have already crossed 300 billion CNY (ie $47.5 billion) this year. It can easily afford a project that at most would cost $500 million a year, for not a very long period of time (this project is said to have started in 2008).
And considering that both Chengdu and Shengyang are arms of AVIC, the RAM on the J20 could easily be used as input in designing the J31's RAM, there's no need to re-invent the wheel within the same corporation on products that are separated by 6 years. Same as on the F22 and F35. The improvement offered by the F35's nanotube jacket RAM over the F22's is in terms of durability of the RAM, which is pretty maintenance intensive on the F22. Two projects give the advantage of benig able to correct weaknesses on the first design when working on the second as technologies mature.
Considering that its been officially leaked(it was obviously a purposeful leak by the CCP), it should not be discounted that maybe PLA funding has already been approved.
This IS the medium weight compliment to the J20. It would be erroneous to assume that China will produce yet another stealth, A2A airframe, which would be an enormous waste as this airframe, considering its stealth shaping could easily fulfill the medium weight fighter requirement and the export fighter requirement (just as the PAK FA is essentially an export fighter). The only other manned stealth airframe we can look towards seeing coming out of China in the foreseeable future would have to be Xian's bomber prototype, not another medium weight fighter(unless its STOVL).
PS. The J10 is there to replace the J7 of which there are hundreds of examples.. Even the first J10's are no where near 20 years old. remember that they entered service in only in circa 2004 2005. Add to that the J10B and they wont need replacing until the 2030's.
