On September 27th China announced that its J-20 stealth fighter had officially entered service. Earlier in 2017 Chinese officials admitted that at least a dozen J-20s had been delivered to the Chinese air force as part of a new fighter squadron. This information was apparently released to help with export sales because the recent official announcement comes at the same time that a recent Chinese press release about China-Pakistan relations seemed to confirm that Pakistan had agreed to buy J-20s. Numbers were not announced and there are still questions about how effective the J-20 actually is. Pakistani interest in the J-20 may have more to do with the fact that China is the only major-power ally they have, their main supplier of weapons and, best of all, a neighbor.
While China began offering its 18 ton J-31 stealth fighter to export customers in 2014 (as the FC-31), it was not until recently that efforts were made to export the more advanced J20. The manufacturer of the J20 (CAC. Chengdu Aircraft Company) also produces the JF-17 and J-10. The JF-17 is a joint effort with Pakistan and Pakistan is the main customer.
The J-20 made its first flight in 2011, and many more since then. Before mass production began in late 2015 eight prototypes were built. There were 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. Since then several more prototypes have been built along with at least twenty production models.
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 twin engine J-20 first appeared to be about the same weight class as the 30 ton F-15C but the production model was closer in weight to the F-22. 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.
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 older, non-stealthy American F-15C. In other words, the J-20 is 20.4 meters (67 feet) long, with a wing span of 13.5 meters (44 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 soon made it clear 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. Based on recent Chinese warplane development projects (J-11 in particular) it was believed that the J-20 had a long development road ahead of it. There were some obvious changes between the first and the later prototypes, but nothing all that drastic.
The J-20 is only the fifth stealth warplane to fly, the others being the American 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. 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. A more powerful and reliable version of the WS-15 for J20 is now believed possible by 2020.
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. It may be that the J-20 is not meant to be a fighter but a stealthy strike aircraft, like the first American “stealth fighter” the F-117. This innovative aircraft was actually a stealthy light bomber that first flew in 1981 and entered service a few years later. It was very successful as a strike fighter and the Chinese may have noted that such an aircraft would also make an excellent interceptor. That would also explain Pakistani interest as they still use fighters armed with nuclear weapons and the main foe here is India, a country that has been improving its air defense systems a lot lately.
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 was 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.
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.