It's always interesting for me to look back 10 years to see where things were to see how much have changed. I often do this with surface combatants because 10 years ago China did not have a fleet of 054/As or 052C/D or Type 071s or Type 056 that now form the backbone of their navy. It's less apparent when we look at the air force because China still has many J-7/8s around and still severely lacks strategic transport, tankers, large AEWC&C and helicopters.
Recently, I have been looking at J-20 progress and wondering about whether or not it is ahead of PAK-FA. I also have been talking with some people on India's participation in the PAK-FA program. Looking back now, was it possible for China to join the PAK-FA project with Russia instead of India (India would go for F-35 + MCA)? This is important question because India's participation in PAK-FA program means that China would probably not be able to buy PAK-FA until a much later point if at all.
Looking back on things, it's hard to see how things could have turned out differently. At the time, India was still buying most of its weapons from Russia, since it was not yet getting access to the most advanced US hardware. Russia also trusted India more than China, so was willing to give access to more advanced systems. In this case, it offered the co-development opportunity to India, which happily took up the offer. China at the time had just welcomed J-10 into service after 18 years of development and was in the process of indigenizing flankers. Although China had already started working on the 5th generation R&D, it was unclear just how long it would take them to finish. These efforts were given the designation J-XX and speculations ran wild on SAC's work on them. There were speculations on Chinese sites that this project would be ready by 2015. All of that were wild speculations that by now have been invalidated. Given the amount of R&D required to develop a 5th generation aircraft, it was unclear if China would be able to have something in service before 2025. For someone like me that was outside of the situation, I would've recommended to China to co-develop with Russia as well as work on its own program if the former was offered. That way, China has something that is reasonable capable if the domestic program does not progress on schedule. It would also have to divert resource, so would only have one domestic program focusing on a medium sized design. One of CAC or SAC will license produce the co-development and the other one produce the indigenous fighter jet. Even though China could afford to fund two such projects, this kind of investment would certainly divert money from improving domestic industry at a time when it was growing without Russian help.
We know that the Russian cooperation with China since 1992 have been very beneficial to China. China at that time already knew Western companies were very good at guarding its secrets and unlikely to assist China's modernization efforts. Russian companies simply lacked that expertise, so it sold a lot of technology to China quite cheaply. By early 2000, China had already obtained most of the non-strategic and matured weapon that it wanted from Russia. As Russia would see later on, China was also very good at copying the stuff that it liked. At this time, Russia had to offer China weapon system that was still in development stage to China. In the case of Su-30MKK, the project was delivered very quickly by KNAAPO, because China was looking for something that was rather mature. So while the avionics were not very impressive, China did get something that was able to carry a lot of payload and have long range. China has since used its experience with this platform to develop J-16. While some of the weapons that came with Su-30MKK were mature and got delivered at the same time, other subsystems were still to be delivered and came way behind schedule like SAPSAN-E. Similarly, while Russians were able to deliver things they already developed very quickly and cheaply, the development of new subsystems were late more often than not. Even though J-10s have been getting AL-31FN engines on time for years, the 99M project that China funded have lagged behind 117S development to the point that China has been considering Su-35 purchase just to access 117S. At the same time, PLAAF must have had a lot of confidence in the continued improvement of AVIC1 and the progress of their R&D to believe that they will be able to complete the projects in a reasonable manner.
Back a year ago at this point, it looked like the PAK-FA was quite ahead of J-20, since it had 5 vs 2 flying prototypes. Since then, we found out that China was planning some major changes that moved J-20 off the demonstration phase and produced 4 J-20 prototypes this year in what looks to be LRIP. PAK-FA's T-50-5 prototype suffered fire problems in a demonstration in front Indian representatives in June and that may have slowed down the program somewhat. Even so, I would imagine PAK-FA program have had far more test flights than J-20. However, there is speculation that a 2nd stage of PAK-FA development is coming with some major changes in store. I guess these changes are to address deficiencies found in the flight tests of the first prototypes. It would be interesting to see if the level of changes will be the same as we saw on No. 2011, but the new PAK-FA prototypes should be more cleaned up that are closer to production version. Since J-20 prototypes are already at that point now, it could be the case that J-20's airframe is now further ahead in development than PAK-FA. As far as the subsystems, I think J-20's engine solution is a bigger issue now than PAK-FA, because it's probably using AL-31FN Series 3 which would have less thrust (13.5 ton) than Type 117. Even further iterations of AL-31FN series is likely to have less power than Type 117, which is probably why China is trying to get Type 117S. This effort also points to uncertainty to the improved variant of FWS-10 engine. For the long run, it appears China's WS-15 project will probably be ready for mass production at around the same time as Russia's Izdeliye 30 project. I think out of everything, J-20's avionics subsystems are probably further ahead than that of Russia. The AESA radar, modern MMI and the integrated electronic system for the modern network centric warfare will be tested on J-10 series first. While it's hard to predict what level all of this will be, J-20's subsystems will not be China or CAC's first kick at the can. For example, J-20's radar will most likely use GaN T/R modules rather than GaA T/R modules. Russia is still in the process of bringing down the cost of producing GaA T/R modules and PAK-FA will be their first fighter jet to use AESA radar. We should get a better idea of the progress of the two project by this point next year, since the 2nd stage prototypes of PAK-FA should come out by then. With the appearance of FC-31 project, it certainly seems like China is better off going alone even if it had been offered co-development of PAK-FA. At this point, J-20 looks slightly closer to joining service than PAK-FA (albeit with underpowered engine) and also looks to be far more stealthy than PAK-FA.