Most recently, we've seen a set of 3 photos coming out of CFTE testing center at Yanliang. The test aircraft in question were J-20 prototype No 2012, Y-20 prototype No. 783 and Y-8FQ (ASW variant) prototype No. 731. All 3 of these projects are obviously very important, but J-20 has the special distinction as China's first 5th gen fighter jet project. This entry just provides a quick look at where China is with its 5th generation project.
Earlier this year, J-20's Prototype No. 2011 came out with significant changes from the earlier prototypes. It was quite clear at that time J-20 project has advanced from the demonstrator stage to pre-production prototypes. When prototype No. 2012 came out in July, PLA followers compared the new prototype to No. 2011. As expected from previous analysis, not much has changed from No. 2011 to No. 2012. As this projects continue to progress, it's likely that no further major changes will be made before certification unless problems are detected in flight tests. I would expect some changes to be made at the rear when domestic 5th generation engine becomes available for testing, but we are a couple of years away from that. No. 2012 had its maiden flight on July 26th and was delivered to CFTE recently for PLA flight tests. At the time No. 2012 appeared, there were a lot of rumors online that 2 more prototypes (No. 2013 and 2014) are likely to come out before the end of the year for flight testing. I would also expect there to be a couple of more prototypes built for static testing. Based on J-10 project where 4 pre-production prototypes (No. 1013 to 1016), this might be all the prototypes that are needed to complete the flight tests. Of course, J-10 had more initial prototypes, but CAC at that time probably needed more time and prototypes to settle on the final design. After these pre-production flight test prototypes are delivered, CAC will probably start producing initial production variant and then deliver them to FTTC for developing combat tactics, flight techniques, training programs for new aircraft and conducting certification of J-20. Further prototypes for the J-20 project will be delivered to CFTE if any major changes are made to the aircraft or when new engine (like WS-15) becomes ready.
More recently, we have seen a bunch of flight testing photos of prototype No. 31001 posted online. This led to a lot of speculations online surrounding the status of the project. I've even read online that some Chinese military expert proclaimed serial production will start within five years for this project. Now, I personally think that's complete nonsense. At this point, this project still seems to be at demonstrator phase. It looks like a model of this aircraft might appear at Zhuhai air show for export interest. I do expect PLAAF to pick up this project to create a high-lo combination with J-20. While it will most likely be given the designation of J-31, I try not to settle on that name yet in case it gets a different designation in the end. The problem with this project is that the lack of available engine options. We know J-20's final production variant will be using WS-15. Even though that engine is not ready, it has been worked for a while and should become available for flight testing in a few years. Until then, upgraded variants of WS-10 engine could be used in the first batch of J-20s. For J-31, there is no current domestic option for flight testing, since WS-13 is not certified yet. The development for this next generation engine in its class began more recently and is not given the same level of importance as WS-15. Even if PLAAF picks up this project in the next year, all of the initial testing would be done using an engine whose power and propulsion will be quite different from the eventual engine. So, I always thought that this project will go into service probably 5 years after J-20 does.