The Chengdu J-20 is a Stealth, twin-engine fifth-generation fighter aircraft prototype being developed by Chengdu Aircraft Industry Group for the Chinese People's Liberation Army Air Force (PLAAF). The J-20 has the potential to rival the F-22A Raptor in performance once appropriate engines become available
If J20 tests are successful this year, small numbers of J-20 fighters can go into production for frontline units of the PLA Air Force, a military expert told Duowei. Knowledgeable sources have said the sensors and cyber warfare capability of the J-20 are as good as Lockheed Martin's F-35.
A Pentagon report predicted the J-20 may enter service in 2018 and the PLA could have its first squadron of 24 of the aircraft by 2020.
One of the greatest obstacles China still faces is its inability to build a sufficiently powerful and reliable engine for the fighter. The Russian-built AL-31F engine has been used for the test flights of the prototypes but it is believed that China will need to complete the design of its domestically built WS-15 engine before the J-20 is ready for high volume production.
The WS-15 is a Chinese turbofan engine designed by the Shenyang Aeroengine Research Institute and manufactured by Xi'an Aero-Engine Corporation. It is intended to power the Chengdu J-20 fighter
SOURCES - Wikipedia, china Defense blog, wantchina times