© KNAAPO Photos КнААПО
The Sukhoi Su-35 (formerly Su-27M)(NATO reporting name: Flanker-E) is a 4+ generation heavy class, long-range, multi-role fighter. Due to the similar features and components it contains, the Sukhoi Su-35 is considered to be a close cousin of the Sukhoi Su-30MKI, a specialized version of the Su-30 for India. It has been further developed into the Su-35BM. The Su-35 is in service in small numbers with the Russian Air Force with 12 in service as of 2008.
Su-35
Data from KNAAPO
General characteristics
Crew: 1
Length: 21.9 m (72.9 ft)
Wingspan: 15.3 m (50.2 ft)
Height: 5.90 m (19.4 ft)
Wing area: 62.0 m² (667 ft²)
Empty weight: 18,400 kg (40,500 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
Performance
Maximum speed: Mach 2.25[34] (2,410 km/h, 1,500 mph) at altitude
Range: 3,600 km (1,940 nmi) ; (1,580 km, 850 nmi near ground level)
Ferry range: 4,500 km (2,430 nmi) with 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)
Thrust/weight: 1.14
Armament
1 × 30 mm GSh-30 cannon with 150 rounds
2 × wingtip rails for R-73 (AA-11 "Archer") air-to-air missiles or ECM pods
12 × wing and fuselage stations for up to 8,000 kg (17,630 lb) of ordnance, including:
Air-to-Air Missiles
AA-12 Adder (R-77)
AA-11 Archer (R-73)
AA-10 Alamo (R-27)
Air-to-Surface Missiles
AS-17 Krypton (Kh-31)
AS-16 Kickback (Kh-15)
AS-10 Karen (Kh-25ML)
AS-14 Kedge (Kh-29)
AS-15 Kent (Kh-55)
AS-13 Kingbolt (Kh-59)
Bombs
KAB-500L
KAB-1500 laser/TV Guided Bomb
FAB-100/250/500/750/1000
Avionics
Passive phased antenna array.
Modernisation
Main article: Sukhoi Su-35BM
Sukhoi began modernising the Su-35 in the mid-2000s to provide a 4.5 type generation fighter making use of current technologies. The modernised Su-35 will be interim design until the fifth generation PAK FA (T-50) enters service. The first modernised Su-35 was recently presented at the MAKS-2007 air show in August 2007. The new Su-35 version first flew on 19 February 2008. The version is now in production with deliveries to customers to begin in 2009. The modernised Su-35 has been referred to as "Su-35BM" (Bolshaya Modernizatsiya - Big Modernization) by some sources, but Sukhoi simply refers to the fighter as "Su-35".
The new design has a reinforced airframe for longer service life and has a reduced radar signature from the front. The modernised Su-35's new nose holds an improved passive electronically scanned array radar and the aircraft featured many other upgrades to its avionics and electronic systems, including digital fly-by-wire and a rear-looking radar for firing Semi-Active Radar missiles. In the 1990s, a two-dimensional asymmetric thrust vectoring system was first tested on the Su-35 and served as a basis for further development of the Su-37. For the modernised Su-35, a new type of 2D thrust vectoring engine, the 117S, has been developed and replaces the current AL-31F or AL-35.[20] The modernised Su-35's Irbis-E radar has an average power output of 5 kW and a peak output of 20 kW. When the H035 radar was tested on Su-30MK No. 503, the detection range was as far as 290 kilometers with 1 kW power output.[20] The radar system can track up to 30 aerial targets and engage up to eight.[6] The radar has a diameter of 900mm and scans electronically to 60 degrees Azimuth and Elevation and mechanical scanning increases the Azimuth coverage to 120 degrees. It has an air to air detection range of 90 km against a stealth aircraft target RCS of 0.01 sqm, as compared to the 105 km range of the AIM-120C-5.[21]
Su-35BM at MAKS-2009
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Contrary to the designs of the original Su-35 and Sukhoi's other recent machines - the Su-30MKI and the Su-37 - the new Su-35 omits the canard and speedbrake. The canards were needed to increase/maintain maneuverability of the planes despite the addition of more modern, significantly heavier (than Su-27) hardware in the nose area. The disadvantages of the canards is that they significantly increase radar returns and drag, thus decreasing efficiency, speed, range, and weapons-carrying capacity. The Su-35 uses composite materials and newer on board electronic packages to make the insides of the aircraft significantly lighter, especially in the nose area. This allowed the designers at Sukhoi to do away with the Canards and their disadvantages while still keeping up high operational system characteristics. The lightness of the new design has actually allowed an increase in both fuel and weapons-carrying capacity as compared to earlier Su fighters. To maintain maneuverability equal to or greater than canard-equipped fighters, the Su-35 uses fully-rotating vectoring thrust nozzles on its new powerful Saturn engines.
Su-35BM
Russian stealth researchers have developed materials and techniques that can reduce the head-on radar cross-section (RCS) of a Sukhoi Su-35 fighter by an order of magnitude, halving the range at which hostile radars can detect it. The research group - working with Sukhoi, but based at the Institute for Theoretical and Applied Electromagnetics (ITAE) at the Russian Academy of Sciences in Moscow - has performed more than 100 hours of testing on a reduced-RCS Su-35 and has also experimented with the use of plasmas - ionized gases - to reduce RCS.
US and European aircraft manufacturers have used specially developed materials to reduce the RCS of basically non-stealthy aircraft for many years. Notable examples include the Have Glass and Have Glass II modifications to the F-16. However, Russian work in this area was undisclosed until ITAE researchers presented a paper to a conference on stealth in London in late October 2003, which was organized by the International Quality and Productivity Centre.
According to the ITAE presentation, Russian researchers have developed mathematical tools that can calculate scattering from complex configurations, such as an Su-35 carrying a full external missile load, by breaking them down into small facets and adding the effects of edge waves and surface currents. The antennas are modelled separately and then are added to the entire RCS picture.
"A problem of huge size" is how the researchers describe the Su-35 inlet, with a straight duct that provides direct visibility to the entire face of the engine compressor. The basic solution has been to apply ferro-magnetic radar absorbent material (RAM) to the compressor face and to the inlet duct walls, but this involves challenges. The researchers note: the material cannot be allowed to constrict airflow or impede the operation of anti-icing systems and must withstand high-speed airflows and temperatures up to 200°C. The ITAE team has developed and tested coating materials that meet these standards. A layer of RAM between 0.7mm and 1.4mm thick is applied to the ducts and a 0.5mm coating is applied to the front stages of the low-pressure compressor, using a robotic spray system. The result is a 10-15dB reduction in the RCS contribution from the inlets.
The modified Su-35 also has a treated cockpit canopy which reflects radar waves, concealing the high RCS contribution from metal components in the cockpit. ITAE has developed a plasma-deposition process to deposit alternating layers of metallic and polymer materials, creating a coating that blocks radio-frequency waves, is resistant to cracking and crazing and does not trap solar heat in the cockpit. The plasma-coating process is then carried out robotically in a 22 m3 vacuum chamber.
ITAE and its partners have also developed plasma-type technology for applying ceramic coatings to the exhaust and afterburner. The conference video also showed the use of hand-held sprays to apply RAM to R-27 air-to-air missiles.
ITAE has studied at least three techniques for reducing the RCS contribution of the radar antenna, in addition to the simplest method of deflecting the antenna upwards and treating or shrouding other components. One of these is to design a radome that can be switched from RF-transparent to RF-reflective. The interior of the radome would be coated with a cadmium sulphide or cadmium selenide thin-film semiconductor material which changes conductivity when illuminated with visible or ultra-violet light. However, the problem of making such a film has not been solved.
A second technique that is also described in Western literature is to place a frequency selective surface screen in front of the antenna. This is a foil-like metal screen etched with small apertures which allow RF energy to pass within a narrow waveband, corresponding to the radar's own operating frequency. This reduces RCS, according to ITAE, but at the expense of radar performance.
However, ITAE has flight-tested a more exotic technology: the use of a low-temperature plasma screen in front of the radar antenna. The screen hardware is mounted in front of the antenna and is transparent to the radar when switched off. When activated, the screen absorbs some incoming radar energy and reflects the rest in safe directions over all RF bands lower than the frequency of the plasma cloud. It switches on and off in tens of microseconds, according to ITAE.
In principle, this is the same as the 'plasma stealth system that was reportedly developed by the Keldysh Scientific Research Center (also part of the Academy) in 1999.
At the time, it was claimed that the system, using a 100kg generator, could reduce the RCS of any aircraft by two orders of magnitude, or 20dB. ITAE has not attempted to develop a whole-aircraft system, but researchers expressed the view that it would be difficult to apply except to a high-altitude, low-airspeed aircraft because the airstream would dissipate the plasma faster than it could be generated.
The ITAE paper also gave some indications of the direction of stealth technology for future stealth aircraft. Test facilities include large compact indoor RCS ranges for large-scale models and outdoor ground-level ranges with short pylons that can be used to test full-size aircraft (rather than the models used for US pylon tests).
In future designs, one emphasis is on large, complex skin panels, reducing the number of gaps and mechanical fasteners in the skin.
