Su-57

SUKHOI Su-57

Piotr Butowski provides an update of Russia’s Su-57 new-generation fighter

slowed down?

Prototype Su-57, T-50-5, side number 055 painted with the latest camouflage scheme, seen in the spring of 2018.
All images by Piotr Butowski unless noted
A close-up shot of the forward fuselage of Su-57 prototype T-50- 11, side number 511, equipped with a production standard sensor suite

On August 22, 2018, Aleksey Krivoruchko, Deputy Minister of Defence of the Russian Federation and United Aircraft Corporation’s President Yuri Slyusar signed the irst contract for two Su-57 ighters to be delivered to the Russian Air Force. During the signing ceremony Krivoruchko said “the irst aircraft will enter service in 2019,” and within the coming years the service “intends to receive 15 production Su-57s”. Deinitely a disappointing declaration after earlier announcements of 60 production standard ighters by 2020 and plans for a further 150–160 by 2025.

So why is the Su-57 programme slowing down? The oicial reason given during a July 2018 TV interview by Yuri Borisov, Deputy Prime Minister of the Russian Federation focused on the Su-35. Borisov said: “The Su-35 is considered one of the best aircraft in the world. We therefore have no reason to go ahead with mass production of the fifthgeneration [Su-57] aircraft today. The Su-57 is our trump card, which we will be able to play when previous generation aircraft begin to lag behind similar aircraft operated by leading countries of the world.”

When Borisov served as Deputy Minister of Defence of the Russian Federation he spoke in a similar manner. As early as March 2015, during his visit to the Komsomolsk-on-Amur factory, he announced that fewer Su-57s may be purchased by 2020 in favour of lower-cost Su-30SM and Su-35 ighters. In August 2017, Borisov told Russian TV the Su-35 “is not inferior even to the irst-stage Su-57”.

However, the reason for a reduction in the number of Su-57s purchased can perhaps be found in the shortcomings of its current, irst version. Borisov’s words can be read two ways: if the Su-35 is not inferior to the Su-57, it means that the Su-57 is not better than the Su-35. In addition to the Su-57’s current capability, it is much more expensive than other ighters already in production, and the Russian Ministry of Defence is still unable to attract additional funding for the Su-57 programme from India.

Course of tests

Sukhoi’s Su-57 (designated T-50 inside the design bureau) is being developed under the PAK FA (Perspektivnyi Aviatsionnyi Kompleks Frontovoi Aviatsii or Future Air Complex of Tactical Aviation) programme that commenced around 1998. On April 26, 2002, Sukhoi’s T-50 proposal was chosen over the competing Mikoyan project. The T-50 aircraft features comparable capabilities to American fifth-generation ighters including super cruise and supersonic manoeuvrability, stealth, and sensor fusion. Major contributing features to the T-50’s reduced radar crosssection are an internal weapons bay and angular, faceted fuselage sides, wing and tail surface edges.

Nine years have passed since the T-50’s irst light on January 29, 2010, at Komsomolskon- Amur in Russia’s far east.

Ten prototypes are currently undergoing light testing: T-50-1, T-50-2, T-50-3, T-50-4, T-50-5, T-50-6, and T-50-8, T-50-9, T-50-10 and T-50-11. Aircraft T-50-7 is used for static tests of the modiied airframe.

Aircraft within the test light leet have completed around 2,000 test lights; test events required within the irst stage of the T-50’s state evaluation were completed at the end of 2017. A press release issued by Sukhoi at the time said: “Characteristics of stability and controllability at subsonic and supersonic speeds, at low and high altitudes, and at supercritical angles of attack are conirmed.” In Russian practice, the irst stage of state trials concludes with the acceptance of the aircraft as a lying vehicle. The second stage involves testing of mission systems and weapons; Sukhoi claims the second stage is scheduled for completion in 2019. Notably, the T-50 ighter was redesigned in the middle of the test programme.

As many as two-and-a-half years passed between the fifth aircraft 055 (irst light on October 27, 2013) and the upgraded sixth aircraft 056 (irst light on April 27, 2016), during which time signiicant design changes were introduced.

All ive aircraft made since 2016 difer from the earlier jets featuring a reinforced inner airframe structure and the airframe skin has been partially replaced with a new one made of composites. Other changes included lengthening of the aft fuselage section housing the electronic warfare equipment and modiications made to the circumferences of the aft lower fuselage, some doors, some hatches, and wingtips.

This landing shot of prototype Su-57, T-50-8, shows how slender the main fuselage is.

Wingspan and fuselage length are estimated to have increased from 14.0m (45ft 11in) to 14.1m (46ft 3in), and 19.7m (64ft 7in) to 20.1m (66ft) respectively.

The latest aircraft to fly was T-50-10 (side number 510), which made its first flight on December 23, 2017. Aircraft T-50-11 (side number 511) flew earlier, on August 6, 2017. Not one aircraft was produced in 2018.

Sensor fusion

All of the Su-57’s systems and sensors are coupled and controlled by a central computing system. Sukhoi’s design bureau is responsible for systems integration, which is in fact a novelty with Russian fighter aircraft. In the past, fire-control and flight navigation systems were integrated by instrument companies; on Sukhoi fighters, this work was usually entrusted to RPKB of Ramenskoye.

The sensor suite includes the Sh121 radio-electronic suite and 101KS electrooptical system. Developed by the Tikhomirov NIIP institute at Zhukovsky, the Sh121 suite comprises the N036 radar and the L402 electronic countermeasures suite.

The NIIP N036 Byelka (squirrel) radar has five active electronically scanned arrays, three X-band (30mm wavelength) and two L-band (decametre wavelength), that together search air space within a 270o angle of regard, +/- 135° from the aircraft’s axis.

Use of L-band radar in air-to-air mode is the T-50’s main means of dealing with stealth targets, which are detected (but not targeted) by radio waves longer than the X-band for which the radar-cross section’s reduction is typically optimised. Head of NIIP Yuri Belyi said the last two prototypes, T-50-10 and T-50-11, are fitted with radars made by the GRPZ serial production facility at Ryazan; the previous fighters are equipped with radars made by NIIP’s experimental workshops.

Developed by the KNIRTI institute in Zhukov near Kaluga and manufactured by the Signal factory in Stavropol, the L402 Gimalai (Himalaya) electronic intelligence and electronic countermeasures suite has its own arrays, but when operating within range of the same frequencies used by the radar it utilises the N036 radar’s arrays.

The 101KS Atoll electro-optical suite produced by UOMZ in Yekaterinburg is intended to provide full control of the airspace around the aircraft within optical range and self-defence against missile attack. Atoll comprises the forward 101KSV infrared search-and-track sight, four ultraviolet missile approach warning sensors that cover the whole sphere around the fighter, and two 101KS-O sensors, which UOMZ claims to be directional infrared countermeasures.

Another 101KS-P device comprises a small imaging infrared sensor to aid low-level flying and landing. Furthermore, the 101KSN navigation and targeting pod is under development. The Su-57’s pilot now uses the new Elektroavomatika NSTsI-50 helmetmounted sight and display.

Both T-50-10 (side number 510) and T-50-11 (side number 511) are fitted with a production standard sensor suite configuration; other prototypes are fitted with either mock-ups or only some of the suite’s sensors.

Weapons

The Su-57 carries its basic weapon payload in two tandem internal bays that occupy the entire length of the fuselage ventral surface. Typical loads include up to four mediumrange K-77M or long-range izdeliye 810 air-to-air missiles, Kh-58UShK anti-radiation missiles and Kh-38M or KAB-250 electrooptically guided air-to-ground munitions.

Additionally, one K-74M2 close range airto- air missile can be loaded in each of two oblong underwing bays. In missions not requiring stealth capability, more weapons and stores can be carried on external pylons. The fighter has a fixed 30mm single-barrel cannon.

Progress of the Su-57 weapon tests is only known in part. There are lots of photographs showing the Su-57 loaded with typical Russian R-73 and R-77 air-to-air missiles and Kh-31 air-to-surface missiles carried externally. Internal weapons carriage, a very important capability for a stealth fighter, has only been seen once.

The author’s graphic showing the location of the Su-57’s various sensors.
A part-pixel camouflage scheme applied to T-50-9, side number 509, seen at Zhukovsky.
Still frames from an oicial Russian Ministry of Defence video showing a Su-57 launching a Kh- 59MK2 stand-of missile.
Russian MoD

At a meeting of a board of Russia’s Ministry of Defence on May 25, 2018, Sergey Shoygu, Defence Minister of the Russian Federation, declared: “For an assessment in combat conditions of the declared capabilities of developed military equipment, in February of this year, practical launches of prospective theatre- and tactical-level cruise missiles from the Su-57 ighter were carried out.” Low-quality footage showed the release of large, more than 4m-long (13ft) missile from the aft internal weapon bay of a Su-57. After one or two seconds of freefall light, the missile’s wings extended and its motor ignited for powered light. Among known Russian airborne missiles, the one launched from the Su-57 is most similar to the Raduga Kh-59MK2, though Shoygu did not specify the missile type.

The Kh-59MK2 (an export designation, the Russian designation is not known) is a counterpart to the MBDA Storm Shadow intended to destroy small, hardened targets of known coordinates. For this purpose, it has a guidance system borrowed from a strategic cruise missile that includes strap-down inertial navigation corrected by GPS/GLONASS for the cruise phase, and an electro-optical digital scene-matching area correlation system for use close to the target. The missile features a square-section box-shaped airframe with dimensions that it the Su-57’s 4.2m-long (13ft 9in), 400mm-wide and high (16in) weapon bay. Two missiles can be carried side by side in each weapon bay. A deployable 2.45m (8ft) wing is itted to the top of the box missile’s airframe. Powered with a Saturn izdeliye 37-04 motor, the missile lies to the target at high subsonic speed. The export version has a declared range of 157 nautical miles (290km), but the range of the Russian version may well be much greater.

Deployment to Syria

Shoygu spoke about the missile launch in the context of Russian operations in Syria, but refrained from explicitly saying that the practical launches were performed in Syria. The low-quality footage presented by Shoygu featured a red missile, which is peculiar for an experimental missile undergoing range tests and therefore arouses doubt.

Two Su-57s were deployed to Syria for two days in February, 2018, a fact only publicised by the Russian Ministry of Defence in November, when it released video footage showing two aircraft taking of and landing at Hmeimim Air Base in Syria. Both aircraft’s tactical numbers were painted over, but their camoulage schemes indicated the aircraft to be side numbers 509 and 511 (T-50-9 and T-50-11). Commentary on the video stated:

“The aircraft’s technical characteristics, intellectual data management and indication system, activity of all onboard systems, including the weapons, were checked in real conditions with higher temperatures, complex terrain and other factors. The Su-57 crews performed more than ten lights in Syria.”

One fact the footage did conirm was that two Su-57s lew there without corner relectors itted, which enabled any surveillance system operating in the skies over Syria to discover the aircraft’s radar signature.

Block 2

When signing the contract for the irst two production Su-57s, Aleksey Krivoruchko stated that the Russian Ministry of Defence expects deliveries of second-stage Su-57s by 2023. Second stage Su-57’s primary feature will be its power plants, new Saturn izdeliye 30 engines.

Currently, all Su-57s are powered by Saturn AL-41F-1 (izdeliye 117) engines, which is a highly upgraded version of the AL-31F engine used by the Flanker family of ighters. The izdeliye 30 is a clean-sheet design intended to ofer increased thrust, lighter weight, a smaller number of elements and lower operating costs. The developer claims the new izdeliye 30 engine will be “17 to 18% more efective”. If that percentage gain refers to the full thrust, the new engine should provide 37,500lb (166.8kN), compared to the AL-41F-1’s 32,000lb (142.3kN).

The izdeliye 30 engine’s cold section has a three-stage compressor (instead of four in the current AL-41F-1) and a single-stage turbine; the hot section (the engine core) has a ivestage compressor (instead of a nine-stage one) and a single-stage turbine. The izdeliye 30’s dry weight is estimated at 1,450kg (3,197lb), compared to 1,600kg (3,527lb) for the AL-41F-1. Thanks to glass-ibre plastic inlet guide vanes, the izdeliye 30 engine fan will have a much smaller radar cross-section in front view.

The first izdeliye 30 demonstrator engine was run on a ground test-bed on November 11, 2016. On December 5, 2017, the T-50- 2LL (Letayushchaya Laboratoriya, lying testbed) started light tests with an izdeliye 30 prototype installed on the port side. After the irst light, Yuri Borisov said with the new engines the characteristics of Su-57 will improve signiicantly.

UAC President Yuri Slyusar declared the Su- 57 will become the basis of a whole family of aircraft, just as the Su-27 became the basis for a family of modern fighters in demand around the world.

Su-57 T-50-9 was one of two deployed to Syria in February 2018; the aircraft is seen taxying at Hmeimim Air Base without corner relectors itted.
Russian MoD