Well if Western companies are 30 yrs ahead and afraid of being copied and don't to share the the latest, then China can attempt to purchase of transfer of something about 10 yrs behind. It's a bit old but Not too OLD like 50 yrs old.
Actually tech from the 80s aren't too bad. B2 and Raptors came to the scene in the 80s. And that's 30 yrs ago already.
The problem for the Chinese is and always will be as long as they are behind, economic efficency.
I will give you and example.
Modern Rolls Royce engines are not pure british, contrary to what people think, Rolls Royce has suppliers.
GE is the same.
GE gets designers or suppliers from several countries to help, same is RR.
If China wants to compete needs internationalize its programs.
Why? first is risk partners, GE works with the German MTU in the GExn engine which is the engine used on B-787.
German engineers are working in the program, same is Boeing Russia, which used Russian engineers to design some parts of the B-787 and GE Mexico, where mexican engineers design engine components for GExn engines.
Today aviation is an international venture, where the best companies are the ones globalizing better, Embraer is an example.
Military is the same, Today India builds the Al-31 with thrust vectoring with full license in India, for Russia, India is a reliable partner, in the same way Japan is for the US in F-100 engines for F-15s.
China has a very bad reputation, at least in what respects intelectual property protection, Russia was worried AL-31 was going to be cloned without any respect for Lyulka Saturn, so no license was granted.
So China in order to catch up needs to re-invent the wheel, in this case the jet engine, this takes time and money and you might end up with an engine which is basicly still behind and economically is still inefficient.
Why J-20, Y-20 and J-31 have russian engines? the answer is reliability and the fact the opossition already improved their engines.
Too much talk was said about China improving their AL-31s, when in Russia they did the same and fly much better versions.
To get tech transfers you need to pay a lot of money an you always get old technology.
To be risk partner you need to respect your partner rights, otherwise you get not partner, Russia is the only nation willing to share important military engine tech, but they are not going to do it as long as China does not stick to international agreements and threat the economic interests of Russian firms
China is trying to force western firms to share their secrets, but they only do if large amount of money is paid and some technology is restricted, that is the case of Embraer or Airbus in China.
. Not Germany, not Japan, and not Russia.
