According to Paul Schwartz, China is "still heavily reliant" on Russian turbofan engines:
Beijing is still heavily reliant on Russian aircraft engines, however, due to the great difficulty of reverse engineering advanced turbofan engines. Thus, additional purchases in this area remain likely as well. [...] The purchase of additional Russian turbofan engines will allow China to continue building out its military transport fleet, while keeping its J-10 fighters and H-6K medium-range bombers operational. The J-10 is an important component of China’s air force, while the H-6K allows China to conduct cruise missile strikes out to the second island chain.
Source: Paul N. Schwartz, The changing nature and implications of Russian military transfers to China, CSIS, June 21, 2021.
Why is China "still heavily reliant" on Russian turbofan engines? Why is reverse-engineering advanced turbofan engines so difficult? Is it due to lack of expertise on
materials and metallurgy?
precision machining technology?
China is an industrial powerhouse. Naively, one would expect China to be ahead of Russia on all fronts, but that is not the case, which piqued my curiosity. I know that, in recent years, COMAC faced difficulties but it is alleged that those were of a structural nature, not quite turbofan-related.