Wednesday, July 31, 2013

Sukhoi Su-35

Sukhoi Su-35

The Sukhoi Su-35 (Russian: Сухой Су-35; NATO reporting name: Flanker-E) is a designation for two separate heavily-upgraded derivatives of the Su-27 'Flanker'. They are single-seat, twin-engine supermaneuverable multirole fighters, designed by Sukhoi and built by Komsomolsk-on-Amur Aircraft Production Association (KnAAPO).
The first variant was designed during the 1980s, when Sukhoi was looking to upgrade its high-performance Su-27, and was initially known as the Su-27M. Later re-designated Su-35, this derivative incorporates aerodynamic refinements to increase manoeuvrability, enhanced avionics, longer range, and a more powerful engine. The first Su-35 prototype, converted from a Su-27, made its maiden flight in June 1988. More than a dozen of these were built with some used by the Russian Knights aerobatic demonstration team. The first Su-35 design was later modified into the Su-37 with thrust-vectoring engines and used as a technology demonstrator. A sole Su-35UB two-seat trainer was built in the late 1990s that, despite its name, shares a strong resemblance to the Su-30MK family.
In 2003, Sukhoi embarked on a second modernization of the Su-27 to produce what the company calls a 4++ generation fighter that would serve as an interim fighter prior to the arrival of the Sukhoi PAK FA. This derivative incorporates a reinforced airframe, improved avionics and radar, thrust-vectoring engines, and a reduced radar signature from the front, while omitting the canards and air brake. In 2008 the revamped variant, erroneously dubbed the Su-35BM by the media, started its flight test programme that involved four prototypes, one of which was lost in 2009.
The Russian Air Force has ordered 48 production units, designated Su-35S, of the newly-revamped Su-35. Both Su-35 models have been offered to many countries, including Brazil, China, India and South Korea, but so far have not attracted any export orders. Sukhoi originally projected that it would export more than 160 units of the second modernized Su-35 worldwide.



Design and development

Upgraded Su-27

A Russian Knights Su-35 in 2007
In the early 1980s, while the Su-27 was entering service with the Soviet Air Force, Sukhoi looked to develop a follow-on variant. This variant, originally designated "Su-27M" and known internally as the "T10-M", would be much more agile and feature greatly improved avionics compared to the aircraft considered to be the best contemporary fighter.[5] It was also to carry more armament to improve its capacity as an air-to-ground platform.[6]
The improved variant, the development of which began in the early 1980s,[7] featured a host of changes in aerodynamics, avionics, powerplants, and construction methods, as well as increasing payload capacity. High-strength composites and aluminium-lithium were used to reduce weight and boost internal fuel volume.[8][9] Distinguishing features are the canards, which improve airflow over the wings, eliminating buffeting and allowing the aircraft to fly at a very high angle of attack of 120°. The canards were governed by a new digital fly-by-wire flight-control system.[5] It was fitted with the Luylka AL-31FM turbofan engine which is larger, more reliable, and with a thrust of 125.52 kN (28,218 lbf) is more powerful.[5]
Also new was the fire-control system, at the heart of which is the more powerful N-011 Zhuk-27 pulse-Doppler radar. The radar can track 15 aerial targets simultaneously and guide six missiles towards them. To exploit the improved radar, two additional underwing pylons were added.[10] The tail "stinger" houses the Phazotron N-012 rear-facing radar for protection from attacks from behind.[9] The aircraft can carry a variety of bombs (including napalm, dumb and cluster bombs) and both air-to-air and air-to-surface missiles.[10] The cockpit was modernized, equipped with multi-function colour LCD screens, and was fitted with a K-36DM ejection seat inclined at 30° to improve pilot g-force tolerance.[10] Range was increased to 4,000 km (2,222 nmi) through additional fuel capacity;[11] with the fitting of an aerial refuelling probe, range can be further extended. The aircraft is characterized by its twin nose wheel – as a result of higher payload – and larger tail fins with carbon fibre square-topped tips.[9][12][13]

Testing and demonstration

The Su-27M (T-10S-70) prototype first flew on 28 June 1988 piloted by Sukhoi chief test pilot Oleg Tsoi.[10][14] The first prototype differed slightly from later examples in: retaining standard Su-27 vertical stabilizers without the cropped top; lacking a fire-control system; having a three-tone grey/blue camouflage scheme, along with minor differences.[10] Designated T10M-1 to T10M-10, the first ten prototypes were built by Komsomolsk-on-Amur Aircraft Production Association (KnAAPO) in conjunction with Sukhoi (as the Soviet military-industrial structure separated the aircraft designer and manufacturer).[10] They slightly differed from another; four were converted Su-27s and the others being new-builds.[15][16] The second prototype started flying in January 1989, while the third followed in mid-1992.[10][17] The prototypes were used to validate the canards and new flight-control system.[9]
In 1990, the first prototype was displayed to Ministry of Defence officials at Kubinka Air Base.[10] The aircraft first aerial demonstration occurred on 13 February 1992, in front of CIS leaders in Machulishi, Minsk, before making its public debut at that year's Farnborough Airshow.[10][18] The third prototype, T10M-3, appeared at the Dubai Airshow in 1993, by which time Sukhoi had re-designated its fighter the Su-35.[15][19] T10M-3 demonstrated its dogfight manoeuvres, including the Pugachev's Cobra, to potential export customers. Viktor Pugachyov subsequently piloted the prototype in a mock fight with an Su-30MK.[15] The Su-35 performed at numerous air shows during the following years, including the 1993 and 1995 MAKS Airshows and the 1994 ILA Berlin Air Show.[15] In addition to Su-27 conversions, three production Su-35s were completed in 1996 and delivered to Russian Air Force (VVS) for testing.[20]
The sole Su-35UB (Bort 801) twin-seat trainer, which first flew on 7 August 2000,[17] in flight alongside another Sukhoi demonstrator, the Su-47
During the Su-35's flight test programme, active controls during manoeuvres such as the Pugachev's Cobra and tailslide could not be maintained. The eleventh Su-27M (T10M-11) was built by KnAAPO and delivered in 1995 for the installation of exclusive systems to give it thrust-vectoring capabilities. The resultant Su-37 technology demonstrator made its first flight in April 1996.[21][22] A second Su-35 was modified into an Su-37 in the late 1990s.[23]
In total, 15 airworthy Su-35s (Su-27M) were produced, including an Su-35UB two-seat prototype, along with two static test prototypes.[1][24] The Su-35UB, powered by two modified AL-32FPs with thrust-vectoring nozzles, made its first flight on 7 August 2000. It was demonstrated to South Korea during that country's F-X replacement fighter tender, before becoming an avionics testbed.[25] The original Su-35 never entered serial production due to a lack of funding,[20] and the VVS continued to use its Su-27 fleet. The Su-35's automatic control of canards and the Su-37's thrust-vectoring technology were applied to the Sukhoi Su-30MKI.[26] One of the Su-35s, T10M-10, served as a testbed for the AL-41F1A engine intended for Russia's upcoming fifth-generation jet fighter.[27]

Second modernization

In 2003, even as Russia was looking to export the Su-27M, Sukhoi launched a project to produce a fighter that would bridge the gap between the upgraded variants of the Su-27 and Su-30MK, and Russia's fifth-generation Sukhoi PAK FA. The project's aim was to undertake a second modernization of the Su-27 airframe (hence its classification as a "4++ generation fighter") by incorporating several characteristics that would be implemented on the PAK FA.[28][29] Additionally, the aircraft was to be an alternative to the Su-30 family on the export market.[30] The design phase was to take place until 2007, when it would be available for sale.[28] It was later reported that the programme was launched due to concerns that the PAK FA project would encounter funding shortages.[31] Although the in-house designation for the project is T-10BM (Bolshaya Modernizatsiya, "Big Modernization"), the aircraft is marketed as the Su-35.[28][32][N 1]
Compared with the Su-27M, the new aircraft has undergone a thorough overhaul in terms of airframe, avionics, and propulsion and weapons systems, with a strong superficial resemblance to the Su-27. Indeed, technological advancements have resulted in lighter and smaller hardware, particularly the radar, shifting the centre of gravity to the rear of the aircraft. This allowed for the elimination of the canards and the abandonment of the "tandem triplane" design found on many derivatives of the Su-27.[28][30] Also omitted was the Su-27's dorsal airbrake, the functions of which were replaced by differentially deflecting the vertical stabilizers.[17] Other less obvious aerodynamic refinements saw the reduction in size of the vertical stabilizers, aft-cockpit hump, and rearward-projecting "sting".[28]
The Su-35 incorporated numerous differences to the Su-27M, including a shorter rearward-projecting "sting", the omission of the dorsal air brake, and the use of thrust-vectoring engines
The reinforced airframe sees extensive use of titanium alloys, increasing its durability to some 30 years or 6,000 service hours, and raising the maximum take-off weight to 34.5 tonnes (76,000 lb). At the same time, the empty weight is comparable to that of Su-27's 16.5 tonnes (36,000 lb).[17][N 2] Internal fuel was increased by more than 20% to 11.5 tonnes (25,000 lb) which can further be increased with external fuel tanks to 14.5 tonnes (32,000 lb); the aircraft also has in-flight refueling capability.[17][30]
Sukhoi has overhauled the avionics suite, at the heart of which is the information management system that greatly enhances man-machine interaction. The system, which has two digital computers, collects and processes information from several other tactical and flight-control systems and presents the relevant information to the pilot through the two main multi-function displays, which, together with three secondary MFDs, form a part of the glass cockpit.[33][34] The aircraft featured many other upgrades to its avionics and electronic systems, including digital fly-by-wire flight-control system, and the pilot is equipped by a head-up display and night-vision goggles.[35]
The Su-35 employs an Irbis-E passive electronically scanned array radar that constitutes an essential component of the aircraft's fire-control system. The radar is capable of detecting a 3 m2 (32 sq ft) aerial target at a distance of 400 kilometres (250 mi); and can track 30 airborne targets and engage eight of them at the same time.[34] The radar can also map the ground using a variety of modes, including the synthetic aperture mode. The Irbis-E is complemented by an OLS-35 optoelectronic targeting system that provides laser ranging and TV and infrared detection.[34] The Su-35 is compatible with a multitude of long- and short-range air-to-air missiles, precision and unguided air-to-ground weaponry that include missiles, fuel-air bombs and rockets. A maximum weapon payload of 8 tonnes (18,000 lb) can be carried on the fourteen hardpoints.[36]
Thrust vectoring nozzles on a Sukhoi Su-35S
The most profound design alterations of the Su-35 are related to the engine. The aircraft is powered by two Product 117S (AL-41F1A) turbofan engines developed jointly by Sukhoi, NPO Saturn and UMPO. The engine is a heavily upgraded variant of the AL-31F that draws on the design of the AL-41FA intended for the fifth-generation PAK FA. The 117S's output is estimated at 142 kN (31,900 lbf), 20 kN (4,500 lbf) more than the AL-31F used on the Su-27M.[28] It has a service life of 4,000 hours, compared to the AL-31F's 1,500, and to compensate for the loss of canards, has fully rotating thrust-vectoring capability.[17][37] The Su-35S is the first non-US aircraft to have substantial supercruise ability (sustained cruising at supersonic speed without the use of afterburners), which gives it a crucial energy advantage against non-supercruising opponents.[38][39] A layer of radar-absorbent material has been applied to the engine inlets and the front stages of the engine compressor, halving the Su-35's frontal radar cross-section (RCS). Other RCS-reducing measures include modifications to the canopy to reflect radar waves.[40]



Variants

Su-27M/Su-35 
Single-seat fighter.
Su-35UB 
Two-seat trainer. Features taller vertical stabilizers and a forward fuselage similar to the Su-30.
Su-35BM 
Single-seat fighter with upgraded avionics and various modifications to the airframe. Su-35BM is informal name.[56][58]
Su-35S 
Designation of the modernized Su-35 variant of the Russian Air Force.[56][58]
Su-37 
Thrust-vectoring demonstrator.


Specifications (Su-35S)

The Irbis-E radar for the modernized Su-35 at MAKS Airshow 2009
GSh-301 cannon in starboard wing root, Su-35, Paris Airshow 2013
Data from KnAAPO,[127][128] Su-27 books,[11][129] Jane's,[130] Airforce-technology.com[8]
General characteristics
  • Crew: 1
  • Length: 21.9 m (72.9 ft)
  • Wingspan: 15.3 m (50.2 ft) (with wingtip pods)
  • Height: 5.90 m (19.4 ft)
  • Wing area: 62.0 m² (667 ft²)
  • Empty weight: 18,400 kg (40,570 lb)
  • Loaded weight: 25,300 kg (56,660 lb)
  • Max. takeoff weight: 34,500 kg (76,060 lb)
  • Powerplant: 2 × Saturn 117S with TVC nozzle turbofan
    • Dry thrust: 8,800 kgf (86.3 kN, 19,400 lbf) each
    • Thrust with afterburner: 14,500 kgf (142 kN, 31,900 lbf) each
  • Fuel capacity: 14,350 litres (3,790 US gal)
Performance
Armament
Avionics








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