Imposter Or the Real Deal?
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IMPOSTER OR THE REAL DEAL? The Sukhoi Su-57 ‘Felon’ was originally conceived in an effort to compete against Lockheed Martin’s F-22 and F-35. Initially known as the PAK-FA, its development has progressed at a relatively slow pace — but has it matured as a force to be reckoned with? REPORT Alexander Mladenov 96 April 2020 // www.Key.Aero The Su-57’s overall confi guration suggests that it has been designed to be stealthy in the forward hemisphere only, evidenced by well-exposed engines exhaust sections and nozzles. Vadim Savitskiy HE RUSSIAN MILITARY is However, initial tactical evaluations bouncing back from years and instructor training with the Russian of underinvestment and Aerospace Forces (VKS) start this year, slow progress. The military on what is the largest and most complex supremacy enjoyed by development e ort ever undertaken America both numerically in the post-Soviet aerospace industry Tand technologically can no longer be in Russia. taken for granted. Russia’s ‘Flanker’ The Su-57 is also known as the series may be old, but few doubt the PAK-FA (Perspektivnyi Aviatsionnyi capabilities of its latest variants. The Su- Kompleks Frontovoi Aviatsii — Future 57 ‘Felon’ — its o cial NATO reporting Air Complex of Tactical Aviation). It name announced in October 2019 — is incorporates a signi cant level of Russia’s rst stealth ghter, and is an cutting-edge technology including interesting comparison with products stealthy characteristics, aerodynamics, from the West, which has been in the powerplant design, system integration ‘ fth-generation’ ghter game for more and weapons. Most of the aircraft’s than two decades. features are highly classi ed and there Known as the T-50-1, the rst of this new are more questions than answers when it generation of Russian ghter aircraft made comes to its true operational capabilities its maiden ight on January 29, 2010, in and performance. It is di cult to Komsomolsk-on-Amur, in the capable evaluate just how successful Sukhoi’s hands of Sukhoi’s chief test pilot Sergey world-class designers have been in Bogdan. It marked the beginning of the solving serious challenges posed by an comprehensive ight-testing e ort, which all-new high-performance stealth ghter remains in progress. The intervening design, combining extremely high agility years have seen a series of technological and maneuverability with supersonic and budgetary issues, but the project cruise (supercruise), advanced sensors, has steadily progressed. Signi cantly, the sensor fusion and robust multi-role so-called rst stage of joint state ight- mission capabilities. This ghter has testing was declared complete in July been conceived to meet a complex VKS 2017, an important step towards low-rate requirement that includes the ability to serial production. The second stage of undertake deep penetration missions this complex e ort, undertaken by the to knock out well-defended, high-value Russian military with support from Sukhoi, targets, and command the air in high- commenced in early 2018 and is ongoing. threat scenarios. www.Key.Aero // April 2020 97 FEATURE ARTICLE // SU-57 ‘FELON’ The nozzles of the widely separated engines can be de ected in two planes, thereby providing e ective 3D thrust vectoring, with resultant control forces in pitch, roll and yaw axes — a design solution borrowed from the Su-30SM and Su-35 where the symmetric nozzle de ection is used for pitch control, while asymmetric de ection creates roll and yaw control forces. The 3D thrust-vectoring technology is considered to be a useful feature for retaining accurate control at slow speeds, when aerodynamic control surfaces are rendered ine ective. According to Sergey Bogdan, ight Evaluating the stealth It is also noteworthy that the Su-57’s performance is more or less similar to Sukhoi designers claim that the Su-57’s engines aren’t obscured by S-shaped inlet that of the Su-35. He reports a notable radar cross-section (RCS) is about 30 times ducts. The existing curvature appears di erence in supersonic acceleration smaller than that of a ‘Flanker’. Its fuselage insu cient to completely mask the engine — where he claims the Su-57 has no is distinctively angular and attened for compressors from incoming radar energy. equal. Bogdan has said that the Su-57’s RCS reduction, and there is extensive use However, the masking could be achieved acceleration is ‘raw and wild’. In addition, of radar-absorbing coatings plus enclosed by adding radar blockers in the inlets, Top: According he noted that the new ghter features weapons bays. but this aspect of the Su-57’s design still to Sukhoi, the good controlled spin characteristics, with Sukhoi designers aligned the leading remains highly classi ed. T-50-1 prototype rapid revolutions and a swift recovery. completed its edges of the wings, tailplanes and preliminary forward leading-edge extensions to Super maneuverability ground and fl ight Supercruising capability make them parallel to each other. This all The Su-57 can perform ‘Flanker’ type trials campaign The ability to cruise in dry power and by early March points to a reasonably stealthy forward post-stall maneuvers, indicating a high 2011, with the lone supersonic speed (supercruise) is hemisphere that o ers tactical advantages level of agility for close-in ghting. prototype having considered vital in modern ghter design in head-on air-to-air and air-to-surface Its blended-body aerodynamic amassed 36 and this is achieved in the Su-57 via sorties. Sukhoi engagements. However, there is little con guration features a lift-generating two principal design features. For the evidence of RCS reduction measures in body, fuselage extensions for improving Above left: The ‘Felon’ it’s a combination of low drag for the rear hemisphere, with well-exposed aerodynamic performance at high angles Su-57’s K-36D-5 a high lift-to-drag ratio in supersonic ejection seat engine nozzles. In fact, this approach is of attack and wings liberally endowed is the same as cruise, combined with a high thrust-to- likely attributed to the Russian concept with high-lift devices. There are no fewer that used on the weight ratio. The Su-57’s wide engine for low observable design — there’s little than 12 ight-control surfaces, grouped Su-35, featuring installation accommodates rather large so-called ‘smart inclination to trade overall performance in six symmetrical pairs, augmented control’ of the and deep weapons bays, a ording a with RCS reduction. Instead, Sukhoi has by moving engine nozzles for thrust ejection sequence ‘clean’ con guration in all mission modes, tended to rely on the use of an advanced vectoring control. The six pairs of to increase the with increased-thrust engines and a chances of multi-spectral sensor suite. This approach aerodynamic surfaces include all-moving pilot survival lightweight airframe using composite was conceived to a ord better detection horizontal stabilizers, all-moving vertical in complex materials. The aircraft can optionally carry capability to counter the potential tails, ailerons, wing leading-edge aps, situations such as external stores if required. low-level inverted advantage of other low-observable (LO) aperons and wing moving leading-edge fl ight. Alexander The Su-57, in its initial con guration, platforms such as the F-22. extensions. Mladenov is powered by a pair of AL-41F-1 98 April 2020 // www.Key.Aero active electronic scanning array (AESA) radar. This is augmented by a second module, also working in the X-band, which employs a pair of side-looking antennas just aft of the nose antenna, designed to expand the system’s angular coverage in azimuth. The third element is a pair of L-band phased-array antennas built into the wing leading-edge extensions, intended to endow the Su-57 with enhanced detection performance against stealth aircraft, as well as for identification friend or foe (IFF) purposes. Stealth technologies fielded in Western fighters are mostly tailored to counter airborne and ground-based radars operating in the X-band; as a consequence, LO characteristics are afterburning turbofans — an evolution supersonic and subsonic regimes of flight, deemed less effective when pitted against of the AL-31 series of engines powering Above: The T-50-3 hitting Mach 2.0 and above. L-band airborne radars. This could be also prototype is being the Su-27/30 family, developed by NPO used for manned- regarded as an attempt to compensate Saturn-Lyul’ka and designated as the unmanned Sensor fusion for the Su-57’s apparently higher RCS so-called ‘Phase 1’ powerplant. Its design teaming trials The Su-57 features the brand new NIIP compared with that of the F-22 and F-35, with the S-70 is based on the izdeliye 117S engine of the Okhotnik Tikhomirov N036 Byelka modular multi- which would facilitate extended-range Su-35, with a dry rating of 20,938lb (93kN) (‘Hunter’) band radar system, also known as Sh121. detection of these fighters. thrust while the full afterburner rating is jet-powered This integrates three principal modules The infrared search-and-track (IRST) stealth-design 33,060lb (147kN) thrust. unmanned aerial — one being the nose-mounted X-band sensor suite is integrated with the Su-57’s The definitive Su-57 engine, dubbed vehicle. Alexander izdeliye 30, began flight-testing in Mladenov December 2017 on the T-50-2 prototype. Right: The This is the so-called ‘Phase 2 engine’, with T-50-1 prototype full-authority digital control, expected to approaching the factory airfield be rated at about 24,220lb (107kN) dry and in Komsomolsk- 37,468lb (166.77kN) at full afterburner. The on-Amur on new engine — expected to be installed completion of its maiden flight on on production-standard Su-57s by 2022 at January 29, 2010, the earliest — is lighter, more powerful and in the capable includes a reduced number of components.