You say tomato, I say tom-ah-to, let’s call the whole thing off … as the song goes.

And so goes the relationship between Russia and China, when it comes to their precious fifth-generation stealth fighters.

It has nothing to do with which fighter is more strategically important, within the contest of the burgeoning Sino-Russian defense relationship.

In effect, it is about neither side wanting to be relegated to the role of junior partner.

And so, as Russia’s Su-57 enters serial production in 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, China’s 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?

According to a report by Michael Peck in The National Interest, 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.

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. Credit: Handout.

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.

Russia’s leading state news agency, TASS, 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.

Meanwhile, according to Yahoo News, in terms of overall kinematic performance, the Su-57 is likely a superior performer compared to the Chinese J-20.

With its three-dimensional thrust-vectoring capability and ample thrust, the Su-57 is likely to have excellent low speed high angle of attack maneuverability even with the current Saturn AL-41F1 afterburning turbofans, which are rated at 32,500 lbs thrust each.

The Russian jet should also have very good supersonic performance — with some degree of supersonic cruise capability even with the current AL-41F1 engines. However, once the Su-57 receives its second stage Saturn izdeliye 30 engines, which are expected to deliver roughly 28,000 lbs of dry thrust and 42,000lbs of afterburning thrust, the PAK-FA should be able to achieve kinematic performance — including supersonic cruise and maneuverability — roughly on par with the Lockheed Martin F-22 Raptor.

Indeed, as one now retired military official with extensive fifth-generation fighter experience had told me sometime ago: “Performance-wise it certainly looks to compete with the Raptor.”