The first J-20 squadron expected to be fully delivered by year's end, the China Flight Testing Evaluation regiment will being developing operating procedures, tactics and technical proficiency to bring the J-20 to combat readiness. At this pace, it is expected that in 2017-2018, the Chinese Air Force will have its first operational stealth fighter squadron.
The J-20 currently relies on Russian AL-31 series turbofan engines (the powerful domestic WS-15 engine will enter service in 2019-2021), everything else on the J-20 is Chinese; its stealth coating, infrared sensor, powerful AESA radar, are all domestically made.
Development of the WS-15 began in the 1990s. The thrust target was reported as 180 kilonewtons (40,000 lbf) in 2012. In 2009, it was known that the prototype was able to achieve 160 kilonewtons (36,000 lbf).
China has about a ten year lead on building and using domestically developed stealth fighters versus other Asian rivals (domestic Indian, Japanese and Korean stealth fighters are not expected to enter service until after 2027). In addition to J-20 and the soon to follow in production J-31 stealth fighter, Chinese plans also call for stealthy drones, bombers and advanced cruise missiles.
SOURCE - Popular Science