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Does engine technology in commercial airliners translate to Chinese military aircraft as well?

Beijing Bureau Chief Bradley Perrett answers:

It does, but only as far as China can apply it. However, Western engines for Chinese commercial aircraft programs are supplied complete. CFM International proposed to assemble the Leap 1C in China for the Comac C919, but the deal was scuppered when the authorities demanded more technical information about the design.

Unavoidably, something about propulsion technology is learned when a Chinese airframe company works with a foreign engine company on integrating their products. The engine itself cannot be kept secret: China can strip down and examine any powerplants imported for commercial use, including, for example, the latest Rolls-Royce Trent XWBs on Airbus A350s.

Whatever is learned about high-bypass turbofans can go into Chinese programs for such engines in military use—and indeed for civil use, subject to patents. Technology from the core is relevant to low-bypass engines.