Key point: Whereas Chinese defense commentary has been largely complimentary of the Su-57, their Russian counterparts have been much more tepid about the J-20. 

As the Su-57 enters serial production in much larger quantities than previously expected, Moscow is making a concerted effort to pitch the fifth-generation fighter to major arms importers including Turkey, India, and China.

Over the past several years, Chinese defense media has been particularly keen on following the Su-57’s development; their--mostly positive commentary--has long been taken as one bellwether of Chinese import interest.

But the question is rarely asked in reverse: namely, what does Russia think of China’s own J-20 fighter?

Whereas Chinese defense commentary has been largely complimentary of the Su-57, their Russian counterparts have been much more tepid about the J-20. In a recent article on the “mutual benefit” of a China Su-57 import deal, prominent Russian defense outlet RG concluded that the Su-57 is neither better nor worse than the J-20 but fulfills an altogether different operational purpose. The J-20 was designed as a stealth missile platform that can penetrate sophisticated air defenses in order to target critical infrastructure or military assets. The Su-57, on the other hand, excels as an air superiority platform that trades stealth and ground attack features for raw dog fighting potential. Thus, RG aptly characterizes the thrust of the Russian export argument: China’s air force should buy the Su-57 not as a replacement, but as a complement to the J-20.

Perhaps the most prevalent, if not contentious, aspect of Russian commentary on the J-20 is the recurring allegation that Chinese drew heavy inspiration from a Soviet fifth-generation fighter project that was tabled in 2000. Dmitry Drozdenko, deputy editor of the Russian military publication “Arsenal of the Fatherland,” told Sputnik that the J-20 “is based” on the ill-fated MiG 1.44: "In my opinion, the machine is based on the Russian MiG 1.44. That plane was created to compete with the PAK FA at the preliminary design stage, and made its maiden flight in 2000. The Chinese plane is very similar. Although it hasn't been announced officially, the J-20 uses our AL-31F engine, developed by Salut, which the Chinese bought for half a billion dollars." The article went on to cite a similarly-shaped canard configuration and tail section as examples of an allegedly uncanny resemblance between the two fighters.

TASS, Russia’s leading state news agency, echoed Sputnik in noting that a number of J-20’s currently run on the AL-31F engine and that the J-20 shares a distinctive “duck-like” aerodynamic design with the MiG-1.44, but stopped just short of claiming that the Chinese directly consulted the Russian fighter’s design in building the J-20.

Apropos of engine troubles, Russian defense commentators join their western counterparts in their skepticism about the status of the WS-15 engine that the J-20 was supposed to ship with. Performance and reliability issues with the WS-15’s  single-crystal turbine blades has led the Chinese to produce initial J-20 batches with older, inferior WS-10B’s as a stopgap measure. There was a brief spurt of speculation in 2018 that Chinese engineers had managed to fix the WS-15, but nothing has been confirmed as of the time of writing.

Although Moscow may have no intention of importing China’s flagship stealth fighter, their perception of it is relevant to their ongoing effort to sell China on the Su-57. Specifically, Rosoboronexport-- Russia’s arms export agency--will have to make a compelling case that the Su-57 has something that the Chinese need, and that the J-20 lacks. Likewise, their evaluation of the J-20 is strategically important within the context of the burgeoning Sino-Russian defense relationship in which neither side wants to be relegated to the role of junior partner.