Prototype No. 2011 of the J-20 project had its maiden flight last weekend. As previously discussed, No. 2011 has significant changes to the previous J-20 prototypes that we've seen in flight testing (No. 2001 and No. 2002).
There were probably 2 more prototypes similar to 2001/2002 for the purpose of static and RCS testing. It seems like 2001/2002 are more like the demonstrator prototypes whereas 2011 is the first pre-production prototype.
It's likely that the production version of J-20 will not see any major differences unless major problems are found in testing. The pictures below show prototype 2001 vs prototype 2011 from different view point with Chinese labels on parts that changed in the first 2 pictures.
Generally speaking, CAC appears to have taken much greater care for the LO properties of No. 2011 compared to 2001/2002. Quite a bit of type elapsed from 2002 to 2011 and it looks like they really tried to address a lot of issues from RCS testing. The workmanship and fit/finishing of 2011 all appear to be better. Some of the more obvious changes include
- Clipped corners on canard/v-tails
- Redesign slender intakes with bump larger or protruding more
- F-22-style light-grey colour scheme
- Larger weapon bay and smaller wing actuators
- Straightened leading edge
- Inner canopy frame like F-35
- Redesigned front landing gear door
- New EOTS-like sensor and holographic HUD display
- Redesigned rear fuselage around the engines and nozzles moved further in with longer tail sting.
It seems like more care is put into all-aspect stealth as the clipped canards has decreased returns from some angles and the ventral fins now seem to completely block engine nozzles from the sides. Looking at the inner edge of the canard, they are modified to conform nicely around intake so as to not create gaps.
Here is a good side view of the front part of the prototype.
Comparing to other 5th generation projects, I think PLAAF had a higher LO design requirement for J-20 than PAK-FA, while still trailing F-22/35. Compared to PAK-FA, it looks like everything conform to the body a lot better leaving fewer gaps and deflecting surfaces all around.
Compared to F-22, it still has some areas like engine nozzle (which is covered by thrust vectoring plates on F-22) that are just not as well shielded even after the treatments. This is all from my extremely untrained eyes, so feel free to give me additional insights.
Project 310, China's other next-gen project, at this point still has not received official PLAAF designation. It looks to be in the flight demonstration stage and would probably need to become an offical PLAAF program before proceeding further to where J-20 is right now.