While China is offering its 18 ton J-31 stealth fighter to export customers as the FC-31, it will not export its more advanced J20, made by CAC (Chengdu Aircraft Company). CAC also produced the JF-17 and J-10. The J-20 made its first flight in 2011, and many more since then. There are at least two original J-20 prototypes, and in 2013 a new prototype appeared that had several modifications and is estimated to have a max weight of 36 tons. While the J-20 looks like the American F-22 when viewed head on, it's overall shape, weight, and engine power is closer to the American F-15C. In other words, it's about 20 meters (62 feet) long, with a wing span of 13.3 meters (42 feet). The J-20 has about the same wing area as the F-15C, which is about 25 percent less than the F-22 (which is a few percent larger than the F-15 in terms of length and wingspan). Worse, for the J-20, is the fact that its engine power is about the same as the F-15C, while the F-22 has 65 percent more power. With the afterburner turned on, the J-20 has more power than the F-15C and nearly as much as the F-22. But because the afterburner consumes so much fuel you can't use more than a few minutes at a time. The new J-20 model appears to be able to supercruise, joining the F-22, Eurofighter, and the Gripen as aircraft that can supercruise (go faster than the speed of sound without using the afterburner).
The J-20 has some stealthiness when it's coming at you head on. But from any other aspect, the J-20 will light up the radar screen. For this reason the J-20 appeared to be a developmental aircraft, not the prototype of a new model headed for mass production. China now indicates that the J-20 is the basis for a new fighter and will go through as many design and shape changes are needed to become combat ready. As such, J-20 is only the fifth stealth fighter to fly, the others being the U.S. F-22 and F-35, plus the Russian T-50. The older U.S. F-117 was actually a light bomber and the B-2 was obviously a heavy bomber. Based on recent Chinese warplane development projects (J-11 in particular), the J-20 has a long development road ahead of it.
While the shape of the J-20 confers a degree of stealthiness (invisibility to radar), even more electronic invisibility comes from special materials covering the aircraft. It's not known how far along the Chinese are in creating, or stealing, these materials or the needed engines. China would most likely use the J-20 singly, or in small groups, to seek out and attack American carriers. To make this possible F-22 class engines are needed and that is still in development. Over the last few years China has admitted it has been developing the WS-15 engine (since the 1990s), a more powerful beast well suited for the J-20. No date was given as to when the WS-15 would be available for use or whether it would have the same vectoring (ability to move the hot jet exhaust in different directions in order to make the fighter more maneuverable) the F-22 uses.
For the J-20 to be a superior fighter, it would need electronics (including radars and defense systems) on a par with the F-35 and F-22. So far, the Chinese have not caught up with stuff used by current American fighters. But the gap is being closed, faster than it was during the Cold War when the Russians were creating, or stealing, their way to military tech equivalence with the West. The Russians never made it but the Chinese believe they can succeed.
Work on the J-20 began in the late 1990s, and the Chinese knew that it could be 25 years or more before they had a competitive stealth fighter-bomber. The J-20 is being tested in central China. The twin engine J-20 appears to be about the same weight class as the 30 ton F-15C. The F-35A is a 31 ton, single engine fighter, while the twin-engine F-22 is slightly larger at 38 tons. The Russian T-50 weighed in at 37 tons.
China is also developing other support technologies, like the AESA radar, highly efficient cockpit, stealth, and software to tie everything together. Developing, or even copying, this tech is not easy. But the Chinese already know that, having decades of experience adapting stolen technology to their needs. Thus, it appears that China is planning on having the J-20, in some form, ready for service by the end of the decade. The key factor is their ability to develop or steal the needed technology by then. The J-20 appears to be a fighter-bomber, as this kind of aircraft would be most useful dealing with the U.S. Navy and key targets in Taiwan or Japan. In any event, the J-20 is an attempt to develop some kind of 5th generation aircraft, complete with stealth.
Pakistan has expressed some interest in the FC-31, but then Pakistan is the largest export customer for Chinese weapons. Pakistan might want to wait a bit because it is unclear how ready the J-31 is for active service. Since 2012 China has been testing the J-31 “Falcon Eagle” (from an inscription on the tail). While it looks like the American F-22, it’s also smaller than China’s other stealth fighter (the 35 ton J-20, which has been around longer). The J-31 was built by the Shenyang Aircraft Corporation (which makes the J-11, the illegal Chinese copy of the Russian Su-27). The J-31 has some characteristics of the F-35 as well and appears to be something of an “F-35” to the earlier J-20s effort to match the American F-22. The J-31 flew for the first time in October 2012 and at that point there were at least two prototypes. The designer has talked of the J-31 being able to operate off an aircraft carrier (like the U.S. F-35 and the Chinese J-15, a J-11 variant).
One advantage the J-31 is that it has two engines, compared to one for the 31 ton F-35. In theory this means the J-31 could carry more weapons, but this is less crucial with all the guided weapons available. Moreover the J-31 is seen using Chinese engines, which are less powerful and reliable, even when two are used, compared to the single engine in the F-35C. The lack of a suitably powerful and reliable engine is not only a major problem for the Chinese stealth designs but also the Russian T-50.
The J-31 and J-20 are further evidence that China is determined to develop its own high tech military gear. While China is eager to develop advanced military technology locally, it recognizes that this takes time and more effort than nations new to this expect. Thus, China is trying to avoid the mistakes Russia made in this area. That means having competing designs and developing necessary supporting industries as part of that. All this takes a lot of time and involves lots of little (and some major) failures. The Chinese are doing it right and are willing to wait until they get military tech that is truly world class.