Sukhoi Su-57

• 1. Introduction

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  The Sukhoi Su-57 landed at the Russian Khmeimim air base in Syria on the 21st of February 2018, and nobody was supposed to notice. Two prototypes of Russia's first stealth fighter slipped into a war zone while the aircraft had not yet even entered formal service. Within days, the Russian Defence Ministry confirmed the jets had flown combat missions and fired cruise missiles. A program that had spent nearly two decades fighting technical failures, cost overruns, and a collapsed partnership with India had just announced itself to the world from the skies over Syria.

  This is the story of the PAK FA programme and the aircraft it produced, designated internally as the T-50 and later named the Su-57, assigned the NATO reporting name Felon. It is a story that begins in 1979, when Soviet planners first set down a requirement for a next-generation fighter, and it is a story that is still unfolding today. The questions that drive it are: how does a nation rebuild a fifth-generation fighter programme from the ruins of a collapsed superpower? What does it actually mean for an aircraft to be stealthy when the production quality is visible to anyone with a smartphone? And what does this jet's turbulent journey reveal about Russian military aviation's ambitions and limits?

• 2. Soviet Roots and the PAK FA Contest

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  In 1979, the Soviet Union put to paper a requirement for fighters intended to enter service in the 1990s, and the programme that emerged was called the I-90. It demanded a multirole aircraft to replace both the MiG-29 and the Su-27. Two design tracks ran in parallel: the heavier MFI, assigned to Mikoyan, and a smaller LFI, with conceptual work beginning in 1983. Sukhoi, though excluded from the MFI competition, started its own internal next-generation research that year, eventually producing the forward-swept wing S-32 experimental aircraft, later redesignated S-37 and then Su-47.

  The dissolution of the Soviet Union gutted the funding. The MiG 1.44/1.42 MFI prototype did not fly until 2000, nine years behind schedule. Both the MFI and LFI programmes were eventually cancelled, and in 1999 the Russian Ministry of Defence launched a replacement effort, the PAK FA programme, with a competition announced in April 2001. The ministry wanted a single aircraft to do what two programmes had failed to deliver at half the cost: a multirole fifth-generation fighter that could supplant both the Su-27 and the MiG-29.

  Sukhoi and Mikoyan competed under sharply different visions. Mikoyan's E-721 was smaller and cheaper, with a normal takeoff weight of 16-17 tonnes and powered by a pair of Klimov VK-10M engines producing 10-11 tonnes of thrust each. Sukhoi's T-50 was the more ambitious design: a normal takeoff weight goal of 22-23 tonnes and a pair of Lyulka-Saturn AL-41F-1 engines each in the 14.5-tonne thrust class. Sukhoi also proposed itself as lead designer from the outset, with a joint work agreement covering the entire cycle from propulsion suppliers to research facilities. Mikoyan had favoured a consortium of equals.

  In April 2002, the Ministry of Defence selected Sukhoi. The decision weighed not only the merits of the designs but Sukhoi's financial track record in the 1990s, sustained by successful Su-27 derivatives and export sales. The research and development programme was given the code name Stolitsa, and Alexander Davidenko was selected as the T-50's chief designer at Sukhoi in 2002.

• 3. A Difficult Birth

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  On the 24th of December 2009, the T-50's first taxi test was completed successfully at KnAAPO's Dzemgi Airport in the Russian Far East. The maiden flight followed on the 29th of January 2010, piloted by Sukhoi test pilot Sergey Bogdan. The aircraft flew for 47 minutes. Russia had its first fifth-generation prototype in the air, years behind the schedule that Air Force Commander-in-Chief Alexander Zelin had publicly projected in 2007.

  The problems that emerged during testing were severe. When the first two prototypes were shown publicly at the MAKS-2011 airshow, the airframes cracked despite flying under a restrictive five-g limit. Both aircraft had to be grounded and structurally reinforced for over a year. The initial prototypes did not have adequate fatigue life, with early structural cracks forming throughout the airframe. The programme responded with a full structural redesign: increased composite material usage, a reinforced airframe, an elongated tail sting, and a slightly greater wingspan. The sixth flying prototype was the first of the redesigned second-stage aircraft.

  The accident record worsened the timetable further. On the 10th of June 2014, the fifth flying prototype, T-50-5, was severely damaged by an engine fire after landing. The pilot escaped unharmed, but the aircraft was written off, its salvageable parts cannibalized to complete the sixth first-stage prototype. Then on the 24th of December 2019, the first serial production Su-57 crashed 110-120 km from Dzyomgi Airport in Khabarovsk Krai during the final stage of its factory trials. A control system malfunction sent the aircraft into a rapid spiral descent from 8,000 m; the pilot ejected at 2,000 m and was recovered by helicopter.

  The compressor stall that forced a Su-57 to abort takeoff at MAKS-2011 was not an isolated engine incident. In June 2014, the Indian Air Force openly questioned the reliability and performance of the AL-41F-1, expressing concern about its lack of supercruise ability, a defining feature of other fifth-generation fighters. By 2019, the first production aircraft had been destroyed before delivery, and the entry into service date had slipped from 2015 to 2020.

• 4. The India Partnership and Its End

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  On the 18th of October 2007, Russia and India signed a contract for Sukhoi and Hindustan Aeronautics Limited to jointly develop a derivative of the PAK FA called the Fifth Generation Fighter Aircraft, or FGFA. The ambition was enormous: India had originally planned to buy 166 single-seat and 48 two-seat fighters, a figure later revised to 214 single-seat aircraft and then reduced again to 144 by 2012. In September 2010, both countries agreed on a preliminary design contract with each investing $6 billion; a memorandum of understanding was signed in December 2010, and the development was expected to take 8-10 years.

  The FGFA was to differ from the base PAK FA in 43 specific ways, with improvements to stealth, supercruise, sensors, networking, and combat avionics. Yet Mikhail Pogosyan, the head of United Aircraft Corporation, stated in 2013 that the PAK FA and the FGFA would use "identical onboard systems and avionics", a position that directly contradicted India's detailed list of required improvements.

  By 2014, the Indian Air Force had begun voicing its concerns clearly: the stealth characteristics were limited to a frontal 60-degree arc, the supercruise capability was absent, and the workshare and technology transfer arrangements were unsatisfactory. India found the aircraft did not meet its requirements and formally withdrew from the partnership in April 2018. Indian Air Force Air Chief Marshal Birender Singh Dhanoa stated that the Su-57 was not being considered for service, though it could be evaluated once it entered Russian service.

  The rupture cost Russia more than a customer. The export orders for 250-300 FGFA that had been expected to begin in 2017 evaporated entirely. By October 2019, Indian Air Force Chief of Air Staff RKS Bhadauria confirmed that India would not import stealth fighters like the Su-57 and would focus on indigenous programmes such as the HAL AMCA. As of early 2025, Rosoboronexport had unofficially offered the Su-57E for the Indian Air Force at the Aero India show, with manufacturing proposed at HAL's Nashik plant under 100% technology transfer, though the plan remained at a preliminary stage.

• 5. What the Felon Is Built From

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  The Su-57's airframe reflects a series of deliberate trade-offs. Sukhoi cited the Lockheed Martin F-22 as the baseline for a supermaneuverable stealth fighter, but designed the T-50 specifically to address what the bureau considered the F-22's shortcomings: its inability to use thrust vectoring to induce roll and yaw moments, insufficient payload resulting from limited space for weapons bays between the engines, and complications for post-stall recovery if thrust vectoring fails.

  The structural materials lean heavily on aluminum alloys, which comprise 40.5-44.5% of the total, with titanium alloys at 18.6%. Composite materials account for 22-26% of the structural weight but cover approximately 70% of the outer surface. The normal takeoff weight grew from the original 22-23 tonne goal to approximately 26.7 tonnes after the second-stage structural redesign was completed.

  Two tandem main weapons bays, each approximately 4.4 m long and 0.9 m wide, sit in the large ventral volume between the widely spaced engine nacelles. These bays use two types of ejection launchers: the UVKU-50L for missiles weighing up to 300 kg and the UVKU-50U for ordnance up to 700 kg. Smaller side bays near the wing root use VPU-50 launch rails and carry short-range infrared-homing missiles. For missions that do not require stealth, six external hardpoints are available. The aircraft also carries a 30 mm autocannon with 150 cartridges mounted internally near the right leading-edge vortex controller root.

  The integrated avionics suite, called IMA BK, runs on over 4 million lines of code and uses fibre optic channels throughout. The main radar system, the N036 Byelka, comprises a nose-mounted X-band active electronically scanned array with 1,514 transmit-receive modules and two side-looking X-band AESA radars embedded in the forward fuselage cheeks, each with 404 T/R modules. The wing leading edge flaps carry L-band transceivers used for both identification friend-or-foe functions and electronic warfare. The Su-57 was also the first fighter to mount a directional infrared countermeasures system, with one turret mounted behind the canopy and another under the cockpit.

• 6. Stealth's Real Limits

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  Sukhoi's own patent for the T-50 stealth features cites an intention to reduce average radar cross-section to approximately 0.1 to 1 m2, compared to the Su-27's RCS of approximately 10 to 15 m2. The combined effect of airframe shaping and radar absorbent material coatings on the production aircraft is estimated to have reduced the aircraft's RCS to a value thirty times smaller than that of the Su-27. The canopy is coated with 70-90 nm thick metal oxide layers that reduce the cockpit's radar return by 30%.

  However, on the 4th of November 2024, the fourth Su-57 prototype, T-50-4, made a fuel stop at Taiyuan city while en route to China's Zhuhai Airshow, and a member of the public photographed the aircraft up close. The images and video uploaded to social media showed screws and rivets clearly visible and not flush with the panels, sections described as poorly aligned with visible gaps between parts of the fuselage, and the weapons bay door unable to fully close. Observers noted the tail used different types of bolts, including single-slotted, Phillips, and hexagonal hex head variants. By comparison, the F-35 has a reported RCS of around 0.005 m2 and the F-22 around 0.0005 m2.

  The design deliberately prioritises frontal stealth, with RCS-reducing features concentrated in the forward hemisphere. The aft fuselage shaping is less optimised compared to American stealth designs, a trade-off attributed to cost reduction and to Russian doctrine, which anticipates operating the aircraft within the coverage of friendly integrated air defence systems. The Su-57's stealth measures are also primarily effective against super-high-frequency radars in the 3-30 GHz range, the kind typically carried by aircraft. Low-frequency early-warning radars can detect the aircraft more readily due to Rayleigh scattering effects, though such radars are also large, susceptible to clutter, and less precise.

  The inlet ducts are partially serpentine and coated with RAM to obscure the engines' compressor faces; a slanted blocker grid placed 0.7-1.2 times the duct diameter in front of the inlet guide-vanes covers the remaining exposed engine face, similar in principle to the arrangement on the Boeing F/A-18E/F.

• 7. Procurement, Production, and Ukraine

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  Russia's original procurement plans called for 52 Su-57s by 2020 and 150-160 more by 2025, alongside export orders for 250-300 FGFA beginning in 2017. By 2015, those plans had collapsed under the combined weight of technical setbacks, India's uncertain commitment, international sanctions following the annexation of Crimea, and falling oil prices. Deputy Minister of Defence Yury Borisov announced that the Russian Air Force would slow production and reduce its initial order to 12 fighters.

  The reversal came in May 2019 when President Vladimir Putin announced a purchase of 76 aircraft to be delivered by 2028, following negotiations that reduced the Su-57's price by 20%. The formal contract was signed on the 27th of June 2019 at the International Military-Technical Forum ARMY-2019. Serial production began in July 2019. After the crash of the first production aircraft in December 2019, the Russian Aerospace Forces took delivery of the second Su-57 as its first aircraft in December 2020. By the end of 2023-12 aircraft had been delivered in total, and according to Yuri Slyusar, another 20 were expected to be built in 2024.

  The Su-57's combat record in Ukraine is murky by design. In May 2022, Russian sources claimed the aircraft had been used two or three weeks after the start of the invasion, striking targets with missiles from outside Ukrainian air defence coverage. In June 2022, four Su-57s working in a network were reportedly used in a suppression of enemy air defences role. General Sergey Surovikin claimed in October 2022 that the aircraft had scored kills in both air-to-air and air-to-ground roles, and some Russian sources attributed the shoot-down of a Ukrainian Su-27 and a Su-24 to R-37 missiles fired by Su-57s. No independent hard evidence for the kill claims has surfaced.

  On the 9th of June 2024, Ukraine's Main Directorate of Intelligence claimed to have damaged or destroyed two Su-57s using drones during a strike on the Akhtubinsk air base in Astrakhan Oblast. Satellite imagery from Maxar Technologies showed a crater next to a Su-57 at the base. Several Russian Telegram channels affiliated with the military confirmed the attack and that at least one aircraft was damaged by shrapnel, while criticising the absence of protective hangars. On the 5th of October 2024, a Su-57 used an air-to-air missile to deliberately shoot down an out-of-control Russian Sukhoi S-70 Okhotnik-B drone that had drifted approximately 10 miles behind Ukrainian lines.

• 8. The Path Forward

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  The upgraded Su-57M variant is being developed under the programme name Megapolis, incorporating improved mission systems, reliability enhancements, electromechanical flight control actuators, and a new engine from NPO Saturn designated the AL-51F-1 or izdeliye 30. The AL-51F-1 is designed for an estimated 11 tonnes of dry thrust and 16.5 tonnes in afterburner, and its glass-fibre plastic inlet guide vanes and serrated nozzle flaps are also intended to reduce the aircraft's radar and infrared signatures. The engine has had a sluggish testing pace and developmental difficulties.

  As a fallback, Rostec unveiled a new engine at the 2025 Dubai Air Show designated the izdeliye 177, combining technologies from both the AL-41F-1 and AL-51F-1. Producing 11 tonnes dry and 16 tonnes in afterburner, it made its first flight in December 2025. A non-axisymmetric flat nozzle option for the engine began flight testing in late 2024. In July 2021, Russian state media announced a two-seat variant designated the Su-57D, intended for pilot training and control of the Sukhui S-70 Okhotnik UCAV; it first flew on the 19th of May 2026.

  Algeria became the export launch customer, signing a contract for 14 aircraft in December 2019 and receiving its first two Su-57s by November 2025. The export variant, Su-57E, was officially unveiled at the MAKS-2019 air show on the 28th of August 2019. At the same time, international sanctions have made it significantly harder for Russia to source the Western avionics and microelectronics that have been essential to advanced Russian fighter cockpits, and the war in Ukraine has further constrained the programme's development capacity.

  At the 2021 Moscow Air Show, Sukhoi also revealed a mockup of a lighter, single-engine affordable fighter designated the LTS and named Checkmate, which shares radar, main weapons bay, vertical stabilisers, and wings with the Su-57, demonstrating how much Sukhoi intends the Felon's technology to anchor an entire family of future combat aircraft.