July 20, 2011:
Last year, China revealed that it was replacing the engines in its J-10 fighter, installing Chinese made WS-10A in place of the Russian made AL-31FN. Despite that, China just ordered another 123 AL-31FNs, to be delivered over the next two years.
The Chinese claim the WS-10A is superior to the AL-31 series (AL-31, AL-31F, AL-31FN etc), even though the WS-10A copied a lot of the Russian technology. But the Chinese say they have improved on that. For example, as delivered from Russia, the AL-31 is good for 900 hours of operation. Chinese engineers figured out how to tweak the design of the engine so that it would last for 1,500 hours. This may be true, and it may also be the case that the Chinese cannot produce enough WS-10As for all the new airframes they are building.
China believes it will be free from dependence on Russia for military jet engines within the next five years, which implies that Chinese engine manufacturers still have a way to go. For years, China has imported two Russian engines, the $3.5 million AL-31, and the $2.5 million RD-93 (a version of the MiG-29's RD-33) for the JF-17 (a F-16 type aircraft developed in cooperation with Pakistan.) But in the meantime, Chinese engineers have managed to master the manufacturing techniques needed to make a Chinese copy of the Russian AL-31 engine. This Chinese copy, the WS-10A, is part of a program that has also developed the WS-13, to replace the RD-93 as well. While the Chinese have been able to build engines that are durable, they are still having problems with reliability. That's probably another reason for the new AL-31FN order.
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 encountered many of the same problems the Russians did in the beginning, Developing the necessary engine design and construction skills is difficult. But China has several advantages. First, they knew of the mistakes the Russians had made, and so were able to avoid many of them. Then there was the fact that China had better access to Western manufacturing technology (both legally and illegally). Finally, China was, unlike the Soviets, able to develop their engine manufacturing capabilities in a market economy. This was much more efficient than the command economy that the Soviets were saddled with for seven decades.
An example of this in action occurred with the J-10 fighter, which began development in 1988 and first flew in 1996. The J-10 is based on the abandoned Israeli Lavi (an improved F-16) project. The J-10 initially used a Russian engine (the AL-31F, the same one used in the Su-27), and was to have used Israeli electronics. But the United States leaned on the Israelis to back off making the Chinese air force too lethal, given the probability of American pilots possibly having to fight the Chinese air force some day. The Chinese developed their own avionics, based on Russian equipment. But this did not work out well. Some J-10s, using the Chinese copy of the Russian AL-31F engine, suffered from poor engine reliability. This appears to have been the cause of several accidents. At least three J-10 crashes are known, and there may be more. These accidents are rarely reported in state-controlled media.
The Chinese consider the J-10 and WS-10A part of the learning process, and they do learn from their mistakes.