The Sukhoi Su-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 super maneuverable 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 seeking to upgrade its high-performance Su-27, and was initially known as the Su-27M. Later re-designated Su-35, this derivative incorporated aerodynamic refinements to increase maneuverability, 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, some of which were used by the Russian Knights aerobatic demonstration team. The first Su-35 design was later modified into the Su-37, which possessed thrust-vectoring engines and was used as a technology demonstrator. A sole Su-35UB two-seat trainer was built in the late 1990s that strongly resembled 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, while omitting the canards and air brake, incorporates a reinforced airframe, improved avionics and radar, thrust-vectoring engines, and a reduced frontal radar signature. In 2008 the revamped variant, erroneously named the Su-35BM in the media, began its flight test programme that would involve 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 marketed to many countries, including Brazil, China, India, Indonesia, 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.
In the early 1980s, while the Su-27 was entering service with the Soviet Air Force, Sukhoi looked to develop a follow-on variant. Originally designated "Su-27M" and known internally as the "T10-M", it would be much more agile and feature greatly improved avionics compared to the aircraft considered to be the best contemporary fighter. It was also to carry more armament to improve its air-to-ground capabilities.
The improved variant, the development of which began in the early 1980s, 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. One of the distinguishing features of this early design were the canards, which improved airflow over the wings, eliminating buffeting and allowing the aircraft to fly at an angle of attack of 120°. These canards were governed by a new digital fly-by-wire flight-control system. The aircraft was fitted with the Luylka AL-31FM turbofan engine which is larger, more reliable and, with a thrust of 125 kN (28,200 lbf), is more powerful than those found on the Su-27.
Also new was the fire-control system, at the heart of which is the N011 pulse-Doppler radar. The radar could track up to 15 aerial targets simultaneously, as well as guiding up to six missiles in the same instance. The tail "stinger" houses the Phazotron N-012 rear-facing radar. The aircraft could carry various bombs (including napalm, dumb and cluster bombs) and both air-to-air and air-to-surface missiles; and had two additional underwing pylons. The cockpit was modernized, equipped with multi-function colour LCD screens, and fitted with a K-36DM ejection seat inclined at 30° to improve pilot g-force tolerance. Range was increased to 4,000 km (2,222 nmi), the adoption of an aerial refueling probe enables further range extension. The aircraft was characterized by its twin nose wheel – as a result of higher payload – and larger tail fins with carbon fibre square-topped tips.
Testing and demonstration
The Su-27M (T-10S-70) prototype first flew on 28 June 1988 piloted by Sukhoi chief test pilot Oleg Tsoi. 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. 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). They differed slightly, as four were converted from Su-27s, and the others were new-builds. The second prototype started flying in January 1989, while the third followed in mid-1992. The prototypes were used to validate the canards and new flight-control system.
In 1990, the first prototype was displayed to Ministry of Defence officials at Kubinka Air Base.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. The third prototype, T10M-3, appeared at the Dubai Airshow in 1993, by which time Sukhoi had re-designated its fighter the "Su-35". 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. The Su-35 performed at numerous air shows during the following years, including at the 1993 and 1995 MAKS Airshows and the 1994 ILA Berlin Air Show. In addition to Su-27 conversions, three production Su-35s were completed in 1996 and delivered to Russian Air Force (VVS) for testing.
Throughout 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. A second Su-35 was modified into an Su-37 in the late 1990s. In 2001, AL-31F engines with fixed nozzles, an upgraded fly-by-wire controls, and improved cockpit systems were fitted to a Su-37 for testing.
In total, 15 airworthy Su-35s (Su-27M) were produced, including an Su-35UB two-seat prototype, along with two static test prototypes. 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. The original Su-35 never entered serial production due to a lack of funding, 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. One of the Su-35s, T10M-10, served as a testbed for the Saturn 117 (AL-41F1) engine intended for Russia's upcoming fifth-generation jet fighter.
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. Additionally, the aircraft was to be an alternative to the Su-30 family on the export market. The design phase was to take place until 2007, when it would be available for sale. It was later reported that the programme was launched due to concerns that the PAK FA project would encounter funding shortages. Although the in-house designation for the project is T-10BM (Bolshaya Modernizatsiya, "Big Modernization"), the aircraft is marketed as the Su-35.
While maintaining a strong superficial resemblance to the Su-27, the Su-35 has been thoroughly overhauled in terms of the airframe, avionics, and propulsion and weapons systems. Technological advancements have produced more compact and lighter hardware, such as the radar, shifting the centre of gravity to the aircraft's rear. These improvements removed the need for canards and saw the abandonment of the "tandem triplane" featured on several Su-27 derivatives. Also omitted was the Su-27's dorsal airbrake, which was replaced by differential deflection of the vertical stabilizers. Other aerodynamic refinements include a height reduction of the vertical stabilizers, a smaller aft-cockpit hump, and shorter rearward-projecting "sting".
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. Internal fuel capacity was increased by more than 20% to 11.5 tonnes, and could be raised to 14.5 tonnes with the addition of drop tanks; in-flight refueling can also be used to extend missions.
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 data from various 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 the glass cockpit. The aircraft features many other upgrades to its avionics and electronic systems, including digital fly-by-wire flight-control system, and the pilot is equipped with a head-up display and night-vision goggles.
The Su-35 employs 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-square-metre (32 sq. ft.) aerial target at a distance of 400 km (250 mi), and can track 30 airborne targets and engage eight of them at the same time. 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. 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 can be carried on the fourteen hardpoints.
The Su-35 is powered by a pair of Product 117S (AL-41F1S) turbofan engines. Developed jointly by Sukhoi, NPO Saturn and UMPO, the engine is a heavily upgraded AL-31F variant, and draws on the design of the fifth-generation PAK FA's AL-41F1 engines. Its thrust output is estimated at 142 kN (31,900 lbf), 20 kN (4,500 lbf) more than the Su-27M's AL-31F. It has a service life of 4,000 hours, compared to the AL-31F's 1,500; to compensate for the loss of canards the engines feature a fully rotating thrust-vectoring capability. The Su-35S has substantial supercruise capability, or sustained supersonic speed without the use of afterburners. Radar-absorbent material is applied to the engine inlets and the front stages of the engine compressor to half the Su-35's frontal radar cross-section (RCS); the canopy was also modified to reflect radar waves.
Production and flight testing
Design work on the Su-35 had been completed by 2007, paving the way for KnAAPO to construct the first prototype in the summer of 2007. Upon completion, Su-35-1 was ferried to the Gromov Flight Research Institute in Zhukovsky Airfield before being placed on static display at that year's MAKS air show. At the time, Sukhoi General Designer Mikhail Pogosyan commented that the aircraft was in great demand abroad, saying Russia was negotiating with several prospective customers and that there were plans to export the aircraft starting in 2010.
Preparations began for the aircraft's maiden flight immediately following the air show. Particular efforts were made to debug the flight-control system and test the engine. By mid-February 2008, Su-35-1 had been rolled out to conduct taxiing tests. On 19 February, Sukhoi test pilot Sergey Bogdan took the aircraft aloft for its first flight from Zhukovsky, accompanied by an Su-30MK2 acting as a chase plane. During the 55-minute flight, the Su-35 reached a height of 5,000 metres (16,000 ft), and tests were carried out on its stability, controllability and engines. The prototype was put on static display for President Vladimir Putin and Prime Minister Dmitry Medvedev the following day.
Approximately 40 flights were conducted before the second prototype took to the air on 2 October from KnAAPO's Dzemgi Airport, again piloted by Sergey Bogdan. The Su-35 had earlier in July made its first demonstration flight in front of Defence Ministry and foreign officials. At the time, Sukhoi estimated that a total of 160 Su-35s would be supplied to customers worldwide, in particular those in Latin America, Southeast Asia and the Middle East. Domestically, the VVS Commander-in-Chief Colonel General Alexander Zelin stated that the service was seeking enough aircraft, estimated to be 24–36 units, to equip "at least two to three regiments".
On 26 April 2009, the fourth Su-35 prototype was destroyed at Dzemgi Airport during a taxi run. The aircraft crashed into a barrier at the end of the runway, burned, and was written off. The pilot, Yevgeny Frolov, ejected and was taken to hospital with burns and other injuries. The aircraft was expected to be the third flying prototype, with its first flight scheduled on 24 April, but which was rescheduled for 27 April. A commission was opened to investigate the crash, but several sources initially speculated that the incident had been the result of a brake failure or a faulty fuel pump.
During the 2009 MAKS air show, the Russian Defence Ministry signed a US$2.5 billion contract for 64 jet fighters, which consisted of a 48-aircraft launch order for the Su-35S ("Serial"). The Russian government promised to provide Sukhoi an additional US$100 million in capital, with additional financial assistance from Sberbank and Vnesheconombank, the latter of which was contracted to provide US$109 million to start the production programme. The Su-35S's estimated price was $40 million each, and the 64-aircraft contract was the largest aircraft order after the collapse of the Soviet Union. All are expected to be delivered by 2015.
In November 2009, KnAAPO started manufacturing the first serial aircraft; Sukhoi estimated that 24 to 30 aircraft would be produced each year from 2010 to 2020. On 11 October 2010, the first production Su-35S had completed general assembly; at this point the preliminary flight test programme had logged 350 flight hours across 270 flights using the two remaining flying prototypes. Sukhoi confirmed that the aircraft had fully met all specifications and parameters, including maximum speed, height, radar detection range and manoeuvrability. The first Su-35S took its maiden flight in May 2011.
Following preliminary tests, the Defence Ministry was expected to initiate state joint tests involving six Su-35s to further scrutinize systems such as weapons. In early 2012, two aircraft were reportedly planned for delivery in 2011, eight in 2012, twelve in 2013 and 2014, and fourteen in 2015; in 2014, the first delivery was now expected to take place that year.
Two-seat trainer. Features taller vertical stabilizers and a forward fuselage similar to the Su-30.
Single-seat fighter with upgraded avionics and various modifications to the airframe. Su-35BM is informal name.
Designation of production Su-35BM version for the Russian Air Force.
Russian Air Force – 34 Su-35S in inventory as of February 2014
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) at 50% internal fuel
Max. takeoff weight: 34,500 kg (76,060 lb)
Powerplant: 2 × Saturn 117S (AL-41F1S) 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: 11,500 kg (25,400 lb) internally
Maximum speed: Mach 2.25 (2,390 km/h, 1,490 mph) at altitude
High altitude: 3,600 km (1,940 nmi)
Ground level: 1,580 km (850 nmi)
Ferry range: 4,500 km (2,430 nmi) with 2 external fuel tanks
Service ceiling: 18,000 m (59,100 ft)
Rate of climb: >280 m/s (>55,100 ft/min)
Wing loading: 408 kg/m² (84.9 lb/ft²)
Maximum g-load: +9 g
Guns: 1× 30 mm GSh-30 internal cannon with 150 rounds
Hardpoints: 14 hardpoints, consting of 2 wingtip rails, and 12 wing and fuselage stations with a capacity of 8,000 kg (17,630 lb) of ordnance, and provisions to carry combinations of:
S-25L laser-guided rocket
S-25 unguided rocket
B-8 unguided S-8 rocket pods
B-13 unguided S-13 rocket pods
Vympel R-77 – the proposed R-77M, R-77T
Vympel R-73E/M, and R-74M
FAB-250 250-kilogram (550 lb) unguided bombs
FAB-500 500-kilogram (1,100 lb) unguided bombs
KAB-500L laser-guided bomb
KAB-1500 laser-guided bomb
buddy refueling pod
Irbis-E passive phased array radar
KNIRTI SAP 14 jamming pod (centreline pylon
KNIRTI SAP 518 jamming pod (one each on both wingtips)
OLS-35 infra-red search and track system
Khibiny-M electronic warfare suite