The aviation forums recently have been buzzing with discussion on the new Chinese "stealth fighter" recently spotted doing fast taxi runs.
In one of the discussions, the writer warned about the danger of "mirror-imaging", citing the incorrect evaluations of the Tu-22M "Backfire".
Now follows some slightly-educated guesses that may well be completely wrong.
I do not think, as Air Power Australia does, that J-20 is an F-35 rival. For five reasons:
1. It looks too large and too blocky for effective manoeuvrability in a situation where air-to-air combat is looking like going back into within-visual-range fights.
2. We still have no indication of the super-cruise capabilities of this thing, if it even has any.
3. Chinese missiles still aren't up to US standards. No-one is talking about any PLAAF missiles rivalling the AIM-9X/ASRAAM/IRIS-T weapons used by "Western" forces.
4. It doesn't really fit into believed and stated Chinese strategy. This talks about the defence of two "island chains", the second going out as far as Guam and the Northern Marianas.
5. There are plenty of capable Chinese SAM capabilities on the mainland and in their ships that will at least force F-35s to carry internal ordinance only. That's before we get to J-11 and J-15.
The classic scenario for a war involving China involves Taiwan. In this scenario, the defence of the Republic of China would be assisted by US carrier groups and air strikes from as far away as Guam, but more often from Japan or the Philippines.
It would be very useful for the PLA to attack land bases and the carriers directly. The propaganda potential of sinking a US carrier would be simply huge - and right now the Chinese lack the effective assets to do it.
DF-21D, which the US now evaluates as having achieved "Initial Operational Capability", lacks key elements in the "kill chain", such as the capability to locate a CVBG without being counter-detected and attacked. The US is rapidly improving AEGIS to cope with it as well.
The Chinese need an alternative strategy. Their other attack aircraft either have limited range (FB-7) and/or are vulnerable to AAM (Su-30/H-6).
Their planned carrier force will run into similar problems, particularly from the new US SSNs, as there is currently no "Chinese AEGIS" (or Russian one for that matter)
This is where the Chinese could do with a "stealth Backfire".
The Tu-22M "Backfire" turned out to be an aircraft designed for medium-range strikes with stand-off missiles against US carrier groups and land-based targets (e.g. Keflavik, which would play host to NATO maritime reconnaissance aircraft). Any "Backfire" raid against a US carrier group, though, would have had to get through the gauntlet of a rather capable CAP (Combat Air Patrol) made up of F-14s and F/A-18s. Even F-4s would have caused it severe problems. You either need luck a lot of "Backfires"; i.e. one hundred plus, or a fighter escort. It's a lot of resources involved.
However, with a stealth aircraft, you get a decent chance of avoiding said CAP and getting into sufficient range (say 20 kilometres) to launch a missile attack that is going to be difficult to defend against.
This also applies to strikes against land targets.
In conclusion, if this becomes operational, it will be a new and potent Chinese capability, but not because it can beat the F-35.