An Enhanced Su-27 with Su-35 Avionics: How Capable is Russia’s Su-27SM3 Air Superiority Fighter?

Entering service in the Soviet Air Force and in the Soviet Air Defence Forces in 1984, the Su-27 Flanker was considered the most capable air superiority fighter developed during the Cold War era. After its unveiling caused significant concern in the Western world, the Flanker’s considerable advantages over rival fighters was subsequently confirmed during the 1990s after intensive testing in the United States against U.S. Air Force F-15s. Although the Soviet Armed Forces were scheduled to introduce enhanced variants of the Su-27 into service from the mid-1990s, including the improved Su-27M air superiority fighter, the Su-27PU interceptor, and the Su-27IB strike fighter, the state’s disintegration delayed the introduction of such aircraft by close to two decades. The events of the 1990s also ended the <a href="https://militarywatchmagazine.com/article/su57-half-price-ambitious-mig142" >MiG 1.42 program</a>, which was intended to operationalise the country’s first fifth generation fighters from 2001 as a direct successor to the Su-27, thus ensuring that the Russian Armed Forces would continue to rely heavily on the Flanker for decades longer than intended. Russian procurements of the Su-27 itself would decline sharply after 1991, with the bulk of remaining production being for export as the Chinese People’s Liberation Army Air Force <a href="https://militarywatchmagazine.com/article/final-gift-from-the-soviets-how-china-received-three-of-the-ussr-s-top-fighters-weeks-before-the-superpower-collapsed" >rapidly adopted</a> the Flanker as its new primary fighter. Although the Russian Defence Ministry funded upgrades for a portion of its Su-27 fleet to the Su-27SM fleet in the 2000s, the enhancements were highly conservative, and did little to reverse the fleet’s growing obsolescence.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/03/article_683e6246718d22_15488327.jpeg" title="Su-27 Fighter in Soviet Service">The Russian Aerospace Forces would begin procurements of enhanced Su-27 derivatives on a significant scale in the 2010s, namely the Su-30M2, Su-30SM, Su-34 and Su-35, allowing the service to gradually phase Soviet built Su-27s and other older fourth generation fighters out of service. As the service ordered the first Su-35s in 2009, it also placed an unexpected simultaneous order for 12 Su-27 fighters, which would be built to a new standard with capabilities far superior to those of the older Su-27SM. The decision to order Su-27s was taken due to the existence of surplus kits to build the fighters, which had been produced with the intention of delivering them to China for license production before the East Asian state cut its planned orders. With the fighters considered obsolete if built to the standard initially intended, development of a new variant of the Su-27 was considered necessary, the result of which was the Su-27SM3. The fighters integrated enhanced variants of the AL-31F engine, reportedly the AL-31F-M1, which provided improved power for onboard systems, higher levels of thrust, and reduced maintenance needs. This was paired with the integration of an avionics suite closely based on <a href="https://militarywatchmagazine.com/article/su35-vs-su27-ten-top-improvements" target="_blank">that of the Su-35</a>.&nbsp;<img src="https://militarywatchmagazine.com/m/articles/2025/06/03/article_683e6226c8b7f8_96991807.jpeg" title="Irbis-E Radar on Su-35 Fighter">A primary advantage which the Su-27SM3 retained over prior variants was the integration of the <a href="https://militarywatchmagazine.com/article/why-russia-s-air-force-loves-the-su-35-s-irbis-e-radar-a-detailed-look-at-the-sensor-suite-built-to-hunt-stealth-fighters">Irbis-E</a>&nbsp;X-band multi role passive phased antenna array radar, which was technologically decades ahead of the N001 mechanically scanned array radar used by the Su-27S and Su-27SM. As an electrically scanned array radar, the Irbis-E could simultaneously track and engage targets both in near space and a few metres off the ground, while being able to scan in fractions of the time and emitting a much lower signature to avoid revealing the fighter’s position. An outstanding feature of the radar is its two-step electro-hydraulic drive unit, which turns the antenna mechanically to 60° in azimuth and 120° in roll, while the the antenna device scans using an electronically controlled beam in azimuth and angle of elevation in sectors exceeding 60°, allowing the Su-27SM3 to scan across a particularly wide breadth of angles. Complementing the new radar, the Su-27SM3 integrated a fully glass cockpit based on that of the Su-35, as gained compatibility with a wide range of new munitions types, most significantly the R-77-1 active radar guided and the R-74 infrared guided air-to-air missiles.<img src="https://militarywatchmagazine.com/m/articles/2025/06/03/article_683e620424ad65_09588488.jpg" title="Russian Aerospace Forces Su-27SM2">The Su-27SM3 gained particular prominence in late November 2015, when the aircraft were deployed the <a href="https://militarywatchmagazine.com/article/repelling-israeli-turkish-su35-syria" target="_blank">Khmeimim Airbase in Syria</a> in response to the Turkish shootdown of a Su-24M strike fighter earlier that month. By that time the fighter program was considered a significant success, with a contract earlier that year having secured financing for the modernisation of ten Su-27S fighters to the same standard, with these aircraft designed Su-27SM2. Two Su-27s which had been modernised to test the upgrade package were also delivered, bringing the total number of enhanced fighters to 24. Modernisation of the Su-27 to the Su-27SM2/SM3 standard was far from isolated to the Russian Air Force, with the United States and China having implemented similar upgrades on much larger scales for their own older fourth generation fighters. These included the integration of the AN/APG-63 AESA radar onto Cold War era F-15s in the United States, and integration of a large AESA radar, likely the same as that from the J-16 fighter, onto J-11B fighters to bring them to the <a href="https://militarywatchmagazine.com/article/first-j-11bgh-fighters-with-aesa-radars-join-china-s-naval-aviation-how-capable-are-they" target="_blank">J-11BG standard</a>. Like the Su-27SM2, cockpit displays and weaponry were also modernised to complement the new radars. The Su-27SM3 upgrade package nevertheless stood out in that it brought a legacy fighter long since out of production back to assembly lines for a limited period, with Russia’s surplus of Su-27 airframe kits which stimulated interest in developing the upgrade package being a unique factor in the program.&nbsp;