China is somehow unimpressed with Russia’s Su-57. However, there are some technologies that Beijing may still want to own.
China’s WS-15 engine has a problem
The WS-15, says Topwar, as it turns out, is the unresolved problem of a sharp drop in the thrust of the WS-15 engine when the temperature of the turbine of the power plant approaches the operating parameters. When the temperature exceeds 1,350 degrees Celsius, the engine loses its thrust, and initially the loss reached 25 percent, which, for obvious reasons, is unacceptable for fighters claiming high maneuverability.
In addition, the unstable engine operation can also cause the pilot to lose control of the aircraft in some situations. Chinese aeronautical engineers tried to overcome this shortcoming of the WS-15 in the next version, but the engine’s performance still decreased by up to 18% when the temperature was too high.

According to Topwar, China has not been able to completely solve the technical problems of the WS-15, which is the biggest reason why the J-20 plan to equip this engine model has not been implemented yet.
The Su-57’s Izdeliye 30 engine
As for China, the technology that Russia will use on the Izdeliye 30 is what it needs to fix the technical problems of the WS-15. However, it will not be easy for Russians to sell the Izdeliye 30 privately to any other country.
The only way China can get the Izdeliye 30 is to order a limited quantity of the Su-57 from Russia as it did with the Sukhoi Su-35 with the Saturn AL-41 engine. This can be seen as an effective solution for Beijing to accelerate its domestic engine development program.
The Chinese media continue to discuss the situation that arose after the fall of the fifth-generation Russian fighter at the time of the acceptance tests. However, Chinese military experts still appreciate the combat qualities of Russia’s Su-57 fifth generation fighter.
Xu Guangyu, a spokesman for the Chinese Association for Arms Control and Disarmament, suggests that China’s purchase of the latest Russian fighters is likely. Earlier it was reported about the possible purchase of a limited batch by China – “for study”.
The Izdeliye 30 engine designated AL-51F, produces dry thrust of 44,110 lb, 196.3kN and burns7,510lb/hour, sans afterburner, according to designer Evgeny Marchukov.
The F22’s PW119 produces 26,000lb and burns 5,00lb/hr.
The Russian engine is a huge advance.