A FLIGHT SEEN AROUND THE WORLD Two J-20s make the public debut of China's first stealth fighter, coming low over the Zhuhai runway. dafeng cao (@xinfengcao) With its J-20 heavy fighter, China became the second nation in the world (after the USA) to field a fleet of stealthy fifth generation fighters. But until recently, there has been a key limitation for the J-20 heavy fighter, and Chinese aerospace in general: a reliance on foreign engines. That's looks to be changing, quickly. Images that just surfaced online show a new-built J-20 with stealthy WS-10 turbofan engines, which are developed and manufactured in China. These engines are distinguished by their serrated afterburner nozzles and interior flaps for manipulating the exhaust flow. Once these new J-20s enter service, China will have comprehensively mastered the major parts of fighter technology, including radars, stealthy fuselage, missiles, computers, and engines. WS-10A The WS-10A, which powers the J-11 heavy fighters, is China's first operational low bypass, afterburning turbofan engines. Errymath Both prototype and production models of the J-20 fighter currently rely on an advanced variant of the Russian Al-31 turbofan engine. Using this tech since the fighter's first flight in 2011 has put China at the mercy of a single, foreign supplier. But not for much longer, it seems. Photos of the new Chinese J-20, production number "2021," reveal turbofan engines that clearly belong to the WS-10 Taihang (built by Shenyang Liming). Among the shared features are the semicircle of small flaps, vanes for controlling exhaust flows, on the inner nozzle, and wider afterburning, variable geometry petals. The Russian Salyut AL-31 does not have those features. Additionally, the WS-10X (possibly officially designated WS-10G or WS-10IPE) has sawtoothed serrations on the edges of its afterburning nozzles, like the F-35's F119 engine. The sawtooth edges provide a gain in stealthiness, as they redirect radar waves away from the nozzles. (The straight edges on non-stealthy engines like the AL-31 are major contributors to the radar cross section of a fighter). In addition to the gains in stealth, the WS-10X is believed to provide about 14-15 tons of thrust. This may be enough power to allow the J-20 to engage in low supersonic supercruise at Mach 1-1.2 speeds. The Eurofighter Typhoon has a similar low supercruise capability, which means it can hit supersonic speeds without using fuel-thirsty afterburners. The gains in engine connect to broader news in materials. The Chengdu Aerospace Superalloy Technology Company, a privately held corporation, made a major breakthrough in superalloy research. CASTC, according to the Global Times and People's Daily, is producing world class single crystal turbine blades from rhenium-nickel superalloys; adding rhenium to nickel increases the superalloy's melting point, allowing for a hotter and more efficient engine. High rhenium content superalloys are used in light weight, high thrust engines like the F-22 Raptor's F109 turbofan. Previously, the development of Chinese engines like the WS-10 were delayed as they suffered from quality control issues regarding single crystal turbine blades. China's mastery of the rhenium superalloy (and by the private sector, no less) won't just help China build current fighter engines, but also quickly research more capable, higher tech models.