Su-27S Flanker: How Ukraine's Top Fighter Went From the Very Best in Europe to an Obsolete Mess

The Ukrainian Air Force is one of very few in Europe to have seen extensive combat operations on its own soil since the end of the Second World War, with the service continuing to fly combat sorties longer than most analysts expected but still suffering extreme losses to its airfields and fleet under Russian bombardment. While Ukraine fielded well over 1000 fighter jets in the early 1990s, sharp economic decline over the following three decades collapsed the size if its fleet to just 84 by 2022 all of which were 1980s designs inherited from the Soviet Union. Alongside 14 Su-24M dedicated strike fighters, this included approximately 35 each of the MiG-29 and Su-27 which both entered service in the 1980s and were intended as complementary medium and heavyweight aircraft to serve in the Soviet fleet. The Su-27 saw significant action in the first two weeks of the Russian-Ukrainian conflict that began in February 24, and having been considered the most capable fighter fielded by any air force during the Cold War it represented Ukraine’s most outstanding aerial warfare asset. Ukraine fielded the world’s second largest Su-27 fleet after the Soviet Union collapsed, inheriting a large portion of the Soviet inventory with the remainder going to Russia, Belarus and Uzbekistan, although Ukraine's fleet is today much smaller due to a high number of accidents and high operational costs.

When the Su-27 entered service in 1985 it was intended to provide the Soviet Air Force with a fighter which could comfortably outperform the U.S. Air Force’s elite the F-15C Eagle. The aircraft was far more manoeuvrable and benefited from high off boresight capable short ranged air to air missiles paired with helmet mounted sights - something no non-Soviet fighter had which ensured an overwhelming advantage at short ranges. The fighter’s R-27ER air to air missile with a 130km range was also seen to be the most capable in the world carried by fighter sized aircraft. The fighter used a blended body-fuselage layout allowing it to generate greater lift with a smaller wing area, and had a fuselage cross section between 20 and 25 percent less than top end American fighters. The aircraft’s AL-31 engine was the most powerful integrated onto any fighter in the world, and its endurance was wholly unrivalled at 4000km on internal fuel alone, with 50 percent more of the airframe allocation to fuel carriage than the F-15. 

When the Soviet Union collapsed Ukraine fielded the most capable fighter in Europe - one that very likely outperformed any in the United States Air Force - although neglect for the fleet and very low pilot training hours compared to the Soviet era meant that operationally it was far less capable than the fighter’s actual potential. This was true for both Russia and Ukraine at a time of internal turmoil in the 1990s. Where Russia in the 2000s gradually began a recovery from its extreme post Soviet economic crisis, and initiated conservative modernisation efforts for its Su-27 fleet while continuing to produce advanced derivatives of the airframe for export, Ukraine’s Su-27s have continued to perform almost identically to when they were first built for the Soviet Air Force with negligible upgrades since the USSR’s collapse. Thus while the fighters retain excellent flight performances, in terms of avionics, sensors and armaments they are entirely obsolete. Russian Su-27 derivatives which entered service in the 2010s have almost triple the air to air engagement range at 400km using new R-37M missiles as opposed to 130km using the R-27, as well as five times the detection range against enemy aircraft at 400km as opposed to 80km. Use of active rather than semi active radar guidance on missiles, thrust/weight ratio, endurance, electronic warfare systems and countermeasures, cockpit displays, and perhaps most importantly data links for network centric warfare, all provide modern Russian Su-27 derivatives with a tremendous advantage and show how far behind Ukraine’s Su-27s had fallen. While the airframes had strong potential to incorporate much needed avionics upgrades, the necessary investments were not made. 

The Su-27 saw action from the opening hours of conflict in Ukraine, taking significant losses to friendly fire, seeing one land in neighbouring Romania as its pilot fled, and another reportedly shot down near Kiev by a Russian S-400 unit stationed in Belarus. Four Su-27s were reportedly shot down on March 5 near the city of Zhytomir in Western Ukraine, with Russian Air Force Su-35 fighters located in Belarus suspected of being responsible. Against the Su-35 there was little doubt that the Su-27 would be overwhelmingly outmatched, with both being based on the Flanker design but the Ukrainian operated jet being technologically close to three decades behind while Ukrainian pilots suffered from greater limits on the number of hours training in the air. The Su-27’s high maintenance requirements and need for relatively large airfields meant they are less well suited to Ukraine’s situation where its fleet had little room to operate, with the MiG-29 having been designed to operate near frontlines with airfields under attack and thus being easier to operate. The future of the Ukrainian Su-27 fleet, including under a possible future Russian-aligned government after hostilities cease, remains highly uncertain, but the airframes do have significant potential to be modernised as demonstrated by the Russian Air Force’s own enhancement of its jets with Su-35 avionics, sensors and weapons under the Su-27SM2 program. 

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