The civil one and military one can be the same one, with some minor changes for sure, as long as the requirements specs are the same.Question for aviation experts - why can't these same engines be used for civilian aircrafts? I understand design is different, but is it more economical to design a totally new engine for civilian aircrafts?
The military one safety standard usually can be a bit lower, versus civilian safety standard is quite high.
If Y-20 engine has 99.9% reliability, which means one of the four engines of Y-20 may stop working in 1,000 taking off and landing. It's totally acceptable.
C-919 engine may need 99.999%+ reliability. Do the math, if you are operating 1000 c-919 daily in China, and each of them make 2 taking off and landing per day. In one year, you have 700,000 landing and taking off.
99.999% reliability means 7 times of engine stop working per year. C-919 has only 2 engines, one engine stop working can be handled by design, but still dangerous. 7 times of engine stop working per year means the civilian jet failed in the market. No one dare to take it.