Russia’s Su-35 vs. Ukraine’s Su-27: How Overwhelming is the Advantage?

Following the sharp deterioration in Russian-Ukrainian relations from 2014, after the overthrow of the government in Kiev led to the installation of a more overtly pro-Western government and low-level hostilities with its neighbour, questions have increasingly been raised regarding the ability of the Ukrainian Air Force to tackle modern Russian combat aircraft should hostilities escalate. Ukraine has since 2014 sought to increase the number of combat aircraft in service, and although it's air force was one of the world’s five largest when the Soviet Union collapsed due to the share quantities of armaments inherited it deteriorated sharply in the aftermath. Even after investments in the fleet the air force today only feels an estimated 84 fighter jets, down from well over 1000 in the early 1990s. Fourteen of these are older variants of the Su-24M dedicated strike platform with very limited air-to-air capabilities, with the remainder being two battalions each of around 17 MiG-29 and Su-27 fighters the latter which was the Soviet Union's most capable fighter when it collapsed. The Su-27 is widely considered the most capable fighter fielded by any air force during the Cold War, and is a heavyweight air superiority aircraft with a very long range, high payload and strong sensor suite for its time which was then reserved for the Soviet Air Force exclusively. Following the Soviet collapse the aircraft were inherited by Russia, Ukraine, Belarus and Uzbekistan, but have since been retired by Belarus due to the high operational costs with relatively few remaining active in the Russian Air Force as they have been replaced by more modern designs. 

A common issue throughout the Ukrainian military is the lack of post-1980s hardware, which is particularly true in the air force where Soviet-built Su-27s armed with Soviet-era munitions remain by far its most capable assets. While the Russian Air Force was initially scheduled to field an entirely new post-Soviet aircraft as its primary air superiority fighter by the mid-2020s, namely the Su-57 stealth fighter, delays to the program largely due to strained budgets have forced it to rely on a heavily modernised derivative of the Su-27, the Su-35S, which entered service in 2014. Despite being based on the same Flanker design, the Su-35 remains an overwhelmingly more capable fighter in all areas of performance benefitting from close to 30 years of research and development after the Su-27 entered service. Its lighter more durable airframe makes much greater use of composite materials, of which practically none were used on the original Flanker, and has less than a third of the radar cross section while carrying more fuel for an increased range. Combined with its AL-41 engine, which puts out more thrust than that of any other fourth generation fighter and is the world's first to enter serial production with three dimensional thrust vectoring capabilities, the Su-35’s flight performance remains far superior to the original Flanker.

Perhaps the Su-35’s most significant advantages over the Su-27 are its avionics, with the older jet using a mechanically scanned array radar relatively easily jammed on 21st century battlefields while the newer one uses an electronically scanned array Irbis-E. Although formidable for the 1980s, the Su-27’s N001 radar has a detection range of just 80km against three square metre targets while the Irbis-E’s detection range against such targets is 400km - or 500 percent as long. The Su-35 is also notable for its main radar’s tremendous 120°maximum deflection angle, as well as for its integration of two additional L-band AESA radars further optimising it for electronic warfare and detection of stealth targets. Its OLS-35 infrared search and tracking system also has 180 percent the detection range of the Su-27’s OLS-27 at 90km as opposed to 50km. Thus it is no exaggeration to say that the Su-35 has superior situational awareness to a full half squadron of original Flankers. Improvements to avionics included a digital cockpit as opposed to the original Flanker’s analogue, as well as superior Khibny-M electronic warfare suite, the modern KSU-35 digital flight control system, and much more sophisticated data links and communications. 

The Su-35S’s other major area of improvements over the original Flanker is in armaments, most notably for air to ground and anti ship roles where it integrates a range of standoff weapons with precision guidance while the Su-27 had negligible air to ground capabilities. This reflects the general trend in the 1980s for high end air superiority fighters to be more specialised without versatile multirole capabilities. For air to air operations the Su-35 and Su-27 will primarily rely on the R-77 and R-27 missiles respectively, the former being active radar guided with modern electronic warfare countermeasures while the latter much older design uses semi active radar guidance. The fact that the R-27 was manufactured in both Ukraine and Russia means Ukrainian industry has likely been able to improve the design further that it could with other missile platforms. The Su-35’s most outstanding air to air missile the R-37M also has active radar guidance as well as more than triple the range of either the R-77 or R-27 complimenting that much greater power of the fighter's sensor suite. The aircraft is also compatible with the more sophisticated 200km range K-77M with active phased array antenna guidance although it has not been confirmed that any Su-35 units have received this weapon. Supplementing its thrust vectoring engines and superior flight performance, the K-74M2 infra red guided short range missiles provide the Su-35 with a very significant advantage in visual range engagements over the older R-60 and R-73 used by Ukrainian aircraft, against which Russia is expected to have effective countermeasures due to its familiarity with both designs which it formerly produced itself. 

The result of the Su-35’s much improved performance, designed with engagements against Western fifth generation fighters in mind in particularly the U.S. Air Force F-22 Raptor, is that the fighter will have a tremendous advantage in Ukrainian airspace. Even if significantly outnumbered it is highly unlikely to take losses in air to air combat. Large scale aerial battles between Russian and Ukrainian forces nevertheless remain unlikely, in part because neither side is likely to escalate but also because low availability rates in the Ukrainian Air Force mean aircraft are expected to be targeted on the ground in a conflict’s opening stages should it indeed break out. Neverthless the very comfortable superiority enjoyed by the Su-35 seriously limits the effectiveness of even the Ukrainian Air Force’s most capable units which, although world leading in their time, have increasingly become obsolete due to their age. With Ukraine’s Western partners unlikely to be able to offer upgrades compatible with the Su-27’s airframe, and the country highly unlikely to ever afford heavyweight fighters equivalent to the Su-27, this effectively diminishes chances for it to pose a serious threat to the Russian Air Force using its own combat aircraft which will likely lead to a greater reliance on ground based air defences. 

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