The reasons FC-31 fans deny J-20 for the carrier-borne fighter aircraft competition are:
- J-20 is difficult to take off and land in an aircraft carrier with canards.
- J-20 is too large for the Chinese aircraft carriers.
- CAC can't produce sufficient J-20s needed for the Navy because the orders from the Air Force has taken up its production capacity for the next 20 years.
Is that for real and reasonable?
As far as we can see, French Navy has been operating Rafales for 15 years, they never complained on the canard layout of Rafales even when they were operating in a carrier with smaller deck.
J-15 is longer, wider-spanned and higher than J-20, but PLAN-AF never complained on their size and weight. And the upcoming 018 and future vessles will be even larger than Liaoning and Shandong.
CAC is not a private company, and its contract with the Air Force is not tied by commercial terms that are irrevocable, but determined by the Central Military Commission. There is no reason for the CMC to deny the navy orders for J-20.
So why the cannards, size, weight and production capacity could be the obstacles that J-20 cannot pass to be a carrier-borne fighter? Even the Air Force variant of J-20 just entered service in 2018. Maybe the PLAN is waiting for the new WS15 and the new CATOBAR carriers to enter service.
On the other hand, the performance of FC-31 has been modified by fans magically. The WS-19 engineer, being a upgrade product of WS-13 the localization solution of RD-93, was bragged to have 12 tons thrust (means thrust-to-weight ratio 12!). The MTOW of FC-31 was bragged to 29 tons. With such MTOW, it will still keep a significantly smaller dimensions of 20-ton fighter. That's not science, it's creating miracles.
Unlike the Air Force facing different level opponents, the PLAN-AF will defnitely confront the F-35s of US Navy, JASDF and RoKAF. So would they accept a mediocre medium weight, medium range fighter? I don't think so.