The Sukhoi Su-57 (; NATO reporting name: Felon) is a twin-engine stealth multirole fighter aircraft developed by Sukhoi. It is the product of the PAK FA (, prospective aeronautical complex of front-line aviation) programme, which was initiated in 1999 as a more modern and affordable alternative to the MFI (Mikoyan Project 1.44/1.42). Sukhoi's internal designation for the aircraft is T-50. The Su-57 is the first aircraft in Russian military service designed with stealth technology and is intended to be the basis for a family of stealth combat aircraft.
A multirole fighter capable of aerial combat as well as ground and maritime strike, the Su-57 incorporates stealth, supermaneuverability, supercruise, integrated avionics and large payload capacity. According to the US, it will be nuclear-capable via a forthcoming missile similar to the Kinzhal. The aircraft is expected to succeed the MiG-29 and Su-27 in the Russian military service and has also been marketed for export. The first prototype aircraft flew in 2010, but the program experienced a protracted development due to various structural and technical issues that emerged during trials, including the destruction of the first production aircraft in a crash before its delivery.
In 2018, during the Russian intervention in the Syrian civil war, at least two Su-57 prototypes were first deployed and used in combat. After repeated delays, the first Su-57 entered service with the Russian Aerospace Forces (VKS)Russia established the Russian Aerospace Forces (VKS) as a new branch of its military on 1 August 2015 with the merging of the Russian Air Force (VVS) and the Russian Aerospace Defence Forces (VVKO). in December 2020. It has reportedly been sporadically used in Ukraine since the 2022 Russian invasion of Ukraine.
Development
Origins
In 1979, the Soviet Union outlined a need for next-generation fighter aircraft intended to enter service in the 1990s. The programme became the I-90 (, ) and required the fighter to be "multifunctional" (i.e. multirole) by having substantial ground attack capabilities, and would eventually replace the MiG-29 and Su-27 in frontline tactical aviation service. Two subsequent projects were designed to meet these requirements: the MFI (, ) and smaller LFI (, ), with conceptual work beginning in 1983. Mikoyan was selected for the MFI and began developing its MiG 1.44/1.42. Though not a participant in the MFI, Sukhoi started its own programme in 1983 to develop technologies for a next-generation fighter, eventually resulting in the forward-swept wing S-32 experimental aircraft, later redesignated S-37 and then Su-47.
Due to a lack of funds after the dissolution of the Soviet Union, the MFI was repeatedly delayed and the first flight of the MiG 1.44/1.42 prototype did not occur until 2000, nine years behind schedule. Owing to the high costs, the MFI and LFI were eventually cancelled while the Russian Ministry of Defence began work on a new next-generation fighter programme; in 1999, the ministry initiated the PAK FA or I-21 programme, with the competition announced in April 2001. Because of Russia's financial difficulties, the programme aimed to rein in costs by producing a single multirole fifth-generation fighter that would replace both the Su-27 and the MiG-29. Further cost-saving measures include an intended size in between that of the Su-27 and the MiG-29 and normal takeoff weight considerably smaller than the MiG MFI's and the Su-47's .Gordon 2021, pp. 95–96
Sukhoi's approach to the PAK FA competition differed fundamentally from Mikoyan's; whereas Mikoyan proposed for the three design bureaus (Mikoyan, Sukhoi, and Yakovlev) to cooperate as a consortium with the winning team leading the design effort, Sukhoi's proposal had itself as the lead designer from the beginning and included a joint work agreement that covered the entire development and production cycle, from propulsion and avionics suppliers to research facilities. Additionally, the two companies had differing design philosophies for the aircraft. Mikoyan's E-721 was smaller and more affordable, with normal takeoff weight of and powered by a pair of Klimov VK-10M engines with 10–11 tonnes (98.1–108 kN, 22,000–24,300 lbf) of thrust each. In contrast, Sukhoi's T-50 would be comparatively larger and more capable, with normal takeoff weight goal of and powered by a pair of Lyulka-Saturn AL-41F-1 engines each with maximum thrust in the 14.5-tonne (142 kN, 32,000 lbf) class.Gordon 2021, pp. 96–97
In April 2002, the Ministry of Defence selected Sukhoi over Mikoyan as the winner of the PAK FA competition and the lead design bureau of the new aircraft. In addition to the merits of the proposal, Sukhoi's experience in the 1990s was taken into account, with the successful development of various Su-27 derivatives and numerous exports ensuring its financial stability. According to the Russian Air Force Commander-in-Chief Vladimir Mikhaylov, flight tests were projected to begin in 2007. Mikoyan continued to develop its E-721 as the LMFS (, ) at its own expense.
Research and development The research and development programme of the PAK FA was called Stolitsa (). In 2002, Alexander Davidenko selected as the T-50's chief designer at Sukhoi. The Novosibirsk Aircraft Production Association (NAPO) and Komsomolsk-on-Amur Aircraft Production Association (KnAAZ) would manufacture the new multi-role fighter, with KnAAZ performing final assembly at Komsomol'sk-on-Amur. Following a competition held in 2003, the Tekhnokompleks Scientific and Production Center, Ramenskoye Instrument Building Design Bureau, the Tikhomirov Scientific Research Institute of Instrument Design (NIIP), the Ural Optical and Mechanical Plant (UOMZ) in Yekaterinburg, the Polet firm in Nizhny Novgorod and the Central Scientific Research Radio Engineering Institute in Moscow were selected for the development of the PAK FA's avionics suite. In April 2004, NPO Lyulka-Saturn (now NPO Saturn) was signed as the contractor for the AL-41F-1 engines with the development designation izdeliye 117.The Russian term , translit. izdeliye literally means "manufactured article" or "product".
Sukhoi used existing airframes as testbeds for various subsystems and concepts; the Su-47 tested internal weapon bays, and Su-27M prototypes served as testbeds for the flight control system and engines. To reduce developmental risk and spread out associated costs, as well as to bridge the gap with extant fourth generation fighters, Sukhoi implemented some of the T-50's technology and features, such as propulsion and certain avionics, in an advanced derivative of the Su-27 called the T-10BM (, ), which was eventually procured by the Russian Ministry of Defence in 2009 and entered service as the Su-35S in 2014.
In December 2004, the T-50's conceptual design and shape was complete and approved by the Ministry of Defence; government funding of the programme began in 2005 and drastically increased in 2006 when detailed design was underway. On 8 August 2007, Russian Air Force Commander-in-Chief Alexander Zelin was quoted by Russian news agencies that the programme's development stage was complete and construction of the first aircraft for flight testing would begin, with three flyable T-50 prototypes planned to be built by 2009. In 2009, the aircraft's design was officially approved. The T-50 was named Su-57 in July 2017.
Since the early stages of the PAK FA programme, Russia sought after foreign partnerships on the project to increase funding for its development and also secure large export orders. On 18 October 2007, Russia and India signed a contract for Sukhoi and Hindustan Aeronautics Limited (HAL) to jointly develop a derivative of the PAK FA called the Fifth Generation Fighter Aircraft (FGFA). In September 2010, India and Russia agreed on a preliminary design contract where each country was to invest $6 billion; a memorandum of understanding for the preliminary design was signed in December 2010, and the development of the FGFA was expected to take 8–10 years. By 2014, however, the Indian Air Force began voicing concerns over performance, cost, and workshare. India found that the aircraft does not meet its requirements and eventually left the partnership in 2018. The concerns over the aircraft included the limited stealth characteristics up to the frontal 60° arc, limiting its advantage over fourth-generation fighters, and the lack of supercruise ability – a distinction of other fifth-generation fighters. Nevertheless, Sukhoi continued to develop and promote the Su-57 for prospective export customers and marketed the aircraft during the 2019 Langkawi International Maritime and Aerospace Exhibition. The export variant, designated Su-57E, was officially unveiled at the MAKS-2019 air show on 28 August 2019.
Prototyping
The T-50's maiden flight was repeatedly postponed from early 2007 after encountering unspecified technical problems. In August 2009, Alexander Zelin acknowledged that problems with the engine and in technical research remained unsolved. On 28 February 2009, Sukhoi general director Mikhail Pogosyan announced that the airframe was almost finished and that the first prototype should be ready by August 2009. On 20 August 2009, Pogosyan said that the first flight would be by year's end. Konstantin Makiyenko, deputy head of the Moscow-based Centre for Analysis of Strategies and Technologies said that "even with delays", the aircraft would likely make its first flight by January or February, adding that it would take five to ten years for commercial production.
Flight testing was further delayed when Deputy Prime Minister Sergei Ivanov announced in December 2009 that the first trials would begin in 2010. The first taxi test was successfully completed on 24 December 2009, and the maiden flight of the first prototype aircraft, T-50-1, occurred on 29 January 2010. Piloted by Sukhoi test pilot Sergei Bogdan, the aircraft's 47-minute maiden flight took place at KnAAPO's Dzemgi Airport in the Russian Far East. Construction of the prototypes would progress slower than initially planned; by the end of October 2013, the test programme had amassed more than 450 flights across five aircraft.
A total of ten flying and three non-flying T-50 prototypes would be built for preliminary flight tests and state trials. Initially, the program was planned to have up to six prototypes before the start of serial production; however testing would reveal that the initial prototypes did not have adequate fatigue life, with early structural cracks forming in the airframe.