China appears to have solved some of its key problems with building high-performance military jet engines. It’s WS-10C engine is now in mass production with factories equipped to build it operating in multiple shifts to deal with the backlog. The WS-10 family of engines was designed to replace jet engines China had to import from Russia plus China’s inability to obtain the latest version of the Al-31F engine, the AL-41F1, used in the Russian Su-57 stealth fighter. The WS-10C is an improved, and reliable, WS-10 that makes the J-20 more effective but not equal to the F119 engines that power the F-22 and F-35. Russia and China are both trying to build an engine that will match the performance American F119. With the F119 the F-22 is capable of very agile maneuvering as well as supercruise (efficient supersonic speed without using the afterburner). Getting the WS-10 and more powerful WS-10C into production replaces the Russian AF-31 engines used in most modern Chinese fighters. The WS-10C makes the twin engine J-20 more effective, but not as effective as the F-22 with two F119 engines. The F-35 is powered by one F-135 engine, which is a variant of the F119. The Chinese version of the F119 is the WS-15, which is still trying to overcome reliability problems. Despite that China has been closing in on Russian engine performance and reliability and beginning to surpass the Russians in some categories. Currently, China is seen more likely to match F119 performance before Russia does.
Engines, more than anything else, determine when a new aircraft is ready. In mid-2020 China revealed that its J20 stealth fighter had officially entered mass production. This was not the original J20 prematurely declared ready in 2017, but a much-improved J20B. This came two years after China admitted that production of the J20 was stalled and the manufacturer confirmed the reasons why. The details were explained on state run television, in part to help recruit the skilled workers needed to produce the J20. There is a labor shortage in China, largely because of the decades of low birth rates mandated by the “one child” policy. The Chinese aircraft manufacturing industry, for both military and commercial aircraft, is booming and workers able to fabricate and assemble components are in short supply. Building the J20 requires a disproportionate number of skilled workers. Parts of the fuselage are made of alloys that are particularly time-consuming to mold and then fabricate into complex structures. Many of the components come from Chinese suppliers who are still developing and perfecting their production capabilities. In general, the J20 requires a lot of exotic components and supplies are tight. China also revealed that development of the J20 has cost $4.4 billion as of 2018, and that the construction cost for each aircraft is $110 million. In addition to the manufacturing difficulties, there were performance problems with the prototypes and six production models turned over to the Chinese Air Force by 2018.
At that time, it was known that there were several potential problems with the J20 production but the main ones had to do with stealth and the delicate materials added to the airframe that make radar detection less effective, and engines. The most obvious problem was the engines. In 2018 the WS-10 engines installed were a stopgap and not efficient enough to support supercruise.
China has been developing the more powerful (and supercruise ready) WS-15 engine since the 1990s, for a larger aircraft like the J20. Despite a lot of effort, the WS-15 was still not able to work reliably enough for service (rather than a prototype) aircraft. Officials also confirmed rumors that a WS-15 exploded during a 2015 static (on the ground) test. That failure had been a secret, but when an engine this important fails by blowing up, the incident is difficult to hide. It also turned out that the WS-15 design and manufacturing problems were less difficult to fix than those encountered with other components and the skilled labor shortage.
In 2018 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 American F-22 uses. At first, a more powerful and reliable version of the WS-15 for J20 was believed possible by 2020, but changes in the shape and weight of the WS-15 would require modifications to the shape of the J20 which would require a lot of testing to ensure that stealth was not compromised. The factory would have to install new or modified manufacturing equipment and suppliers would have to do the same to produce the new airframe components. Apparently, the claim was that most of those problems were solved by mid-2020. This included the WS-15 reliability problems. The claim turned out to be premature. The WS-15 saga was one of repeated disappointments and there may be more of that. Some high-performance jet engines are more reliable than others. Western engine manufacturers have been through this for decades as each new generation of engines was developed. China knows of that history and is resigned to repeating it.
The J20 made its first flight in 2011, a year before the rival J31. Before the originally scheduled mass production could begin in late 2015, eight prototypes were built. There were at least two original J20 prototypes, and in 2013 a new prototype appeared that had several modifications and is estimated to have a max weight of 37 tons. By 2018 several more prototypes have been built along with at least six production models plus over a dozen stalled on the assembly line. All of these were built with the understanding that some major (and time-consuming) refurbishing might be needed once the WS-15 engine was ready for service.
Work on the J20 began in the late 1990s, and the Chinese went forward on the assumption that it could be 25 years or more before they had a competitive stealth fighter-bomber in service. The twin-engine J20 first appeared to be about the same weight class as the non-stealthy American 30-ton F-15C, but the production model was closer in weight to the F22. By comparison, the U.S. F-35A stealth fighter-bomber is a 31-ton, single engine fighter, while the twin-engine F-22 is slightly larger at 38 tons. The Russian Su-57 weighed in at 37 tons and its production is also stalled over technical issues. The Russians can make more powerful (and reliable) engines than the Chinese but are still having problems with their other techs, like stealth coatings and electronics. Russia has officially put production of its Su-57 stealth fighter on hold as it suffers from some of the same production problems as the Chinese.
While the J20 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 J20 is 20.4 meters (67 feet) long, with a wing span of 13.5 meters (44 feet). The J20 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 J20, 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 J20 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 afterburner also generates a lot more heat which makes an aircraft more visible to heat sensors. The J20B appears able to supercruise with a powerful enough engine, joining the F-22, Eurofighter, and Swedish Gripen as aircraft that can supercruise. The J20B appears capable of doing lots of engine-dependent things during tests or in theory that it has not been able to sustain in regular service.
The J20 has some stealthiness when it's coming at you head on. But from any other aspect, the J20 will light up the radar screen unless it has effective radar absorbing material on the exterior. For this reason, the J20 initially appeared to be a developmental aircraft, not the prototype of a new model headed for mass production. China soon made it clear that the J20 was indeed the basis for a new fighter and would go through as many design and shape changes needed to become combat ready. Based on recent Chinese warplane development projects (J-11 in particular) it was believed that the J20 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. Thus, it was surprising when the J20 was declared ready for service in 2017 but not so surprising when production was quietly halted because of unspecified problems. Yet the Chinese have been competent and relentless in developing complex technologies and there was no reason to believe they won’t get the J20 working. That has apparently happened but that won’t be confirmed until J20Bs show up in an operational J20 fighter squadron.
The J20 is only the fourth stealth warplane to fly, the others being the American F-22 and F-35, plus the Russian Su-57. The older U.S. F-117 was a light bomber and the B-2 was obviously a heavy bomber. While the shape of the J20 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 data on, these materials. China would most likely use the J20 singly, or in small groups, to seek out and attack American carriers. For the J20 to be a superior fighter capable of that, it would need electronics (including radars and defense systems) on a par with the F-35 and F-22 as well as powerful and reliable engines and effective radar absorbing materials.
The J31 and J20 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 the military tech that is truly world class.