.Chinese engineers thought they had managed to master the manufacturing techniques needed to make a Chinese copy of the Russian AL31F engine. This Chinese copy, the WS10A, was meant for the Chinese J-10 fighter, which entered service two years ago. But the Chinese Air Force was not satisfied with the reliability or performance of the WS10A, and have ordered another hundred AL31Fs from Russia, in order to continue building J-10s.
China has long copied foreign technology, not always successfully. But in the last decade, China has poured much money into developing a jet engine manufacturing capability. The Chinese have encountered many of the same problems the Russians ran into when developing their engine design and construction skills. Russia has yet to match the quality of Western engines, but has been closing the gap more quickly since the end of the Cold War, which made it possible for Western suppliers to provide Russian manufacturers with the best components and manufacturing technology.
China only publicly announced the J-10s status in January, 2007. What was not mentioned in the press releases was that only one J-10 squadron was stationed where it might encounter Taiwanese F-16s or Mirage jet fighters. That squadron is sitting at a base just out of range (560 kilometers) of the F-16s and Mirages. The Taiwanese believe that their pilots are much better trained than their Chinese counterparts. Moreover, the word out of China is that the J-10 is a maintenance nightmare, and that the Chinese are having a hard time keeping the aircraft operational in reasonable numbers.
The J-10 is the first modern jet fighter designed and built in China. The aircraft is an attempt to create a modern fighter-bomber that could compete with foreign designs. The experiment was not completely successful. Work on the J-10 began over twenty years ago, in an attempt to develop an aircraft that could compete with the Russian MiG-29s and Su-27s, and the American F-16. But the first prototype did not fly until 1998. There were problems, and it wasn't until 2000 that the basic design flaws were fixed. By 2002, nine prototypes had been built, and flight testing was going forward to find, and fix, hundreds of smaller problems. It was a great learning experience for Chinese engineers, but it was becoming apparent that the J10 was not going to be competitive with the Su-27s/30s China was buying from Russia.
The J-10 looks something like the American F-16, and weighs about the same (19 tons). Like the F-16, and unlike the Su-27, the J-10 has only one engine. Originally, the J-10 used a Russian AL-31FN engine, but China has been working for a decade to manufacture their own version of this, the WS10A. The WS10A is something of an acid test for them, as it is a powerful military engine, and a complex piece of work. Russia refused to license China to produce the AL-31FN, so the Chinese stole as much of the technology as they could and designed the WS10A. This engine has been tested, and officially approved for production, but apparently still has quality control and performance problems.
It's no accident that the J-10 resembles the F-16, because Israel apparently sold them technology for the Israeli Lavi jet fighter. Israel abandoned the Lavi project, because of the high cost and availability of cheaper alternatives (buying F-16s and F-15s from the United States.) But the Lavi was meant to be a super F-16, and incorporated a lot of design ideas from the F-16 (which the Israelis were very familiar with, as they used them, and had developed new components for them.)