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Su-35BM (Bolshaya Modernizatsiya - Big Modernization)

What is new in the Su-35? First off, the fighter will get an improved airframe, which will dramatically increase its service life to 6,000 hours, 30 years of operation (the time before the first test and recondition and the between-repairs period has been increased to 1,500 hours, or 10 years of operation). Aerodynamically it is similar to the Su-27. But unlike the Su-30MKI it will feature no canard fins. All the three channels will have electrically signaled control without mechanical cabling. The use of a new integrated control system (developed by MNPK Avionika Moscow-based Research and Production Association) simultaneously performing functions of several systems - remote control, automatic control, limiting signals system, air signals system, chassis wheels braking system - will enhance the fighter's handling capability and maneuverability.

Among the Su-35 design features, worth of note is the absence of an overhead brake flap, a standard characteristic of the Su-27. Its functions are performed by an active rudder. The Su-35 chassis has been reinforced because of the increased takeoff and landing weight of the aircraft. For the same reason, the front bearing has two wheels. The improved radar stealth reduces the reflectance of the Su-35 in the X radio waveband and in the angle range of 60.

Radar Cross Section

Originally the Su-35 project did not contemplate the adoption of canards, however during the development of the aircraft at the beginning of the 1990s, the radar was installed then in development N-011M "Bars" in a prototype of the T-10 / Su-27. At the beginning it was noticed that the extreme weight of N-011M Bars affected the center of gravity of the aircraft, the radar was much heavier than the N-001 radar of the original Su-27. This compelled the designers of the aircraft to adopt some system that supported the frontal surface of the aircraft. The solution of canards appeared to reequilibrate the center of gravity of the aircraft. It was noticed in the flight of tests of the Su-35 that canards had improved the stability of the aircraft, improved the sustentation capacity, in closed maneuvers with very great angles of attack. This change made as much "success" that was adopted in other variants of the Su-27. The down side was that it increased the aerodinamico drag in supersonic regimen and even more increased the wing area of the aircraft, which resulted in an increase of the RCS of the aircraft.

Aiming at to reduce the RCS of the aircraft, the designers of the T-10 had opted to remove canards from the aircraft. But to make this was possible it would be necessary to reduce the weight of the embarked radar, with the purpose of re-equilibrating the center of gravity of aircraft without the use of canards. This was possible with the new radar that was in development and that will have substantially inferior weight to the N-011M, having had similar weight to the original N-001 of the Su-27. This minituarization of components and use of in the manufacture of the parts of lighter materials, allowed the center of gravity of the aircraft came back to be as the original Su-27, making possible withdrawal of canards of the aircraft.

Moreover, all the control surfaces of the aircraft were perfected and reduced in relation to the original T-10. The Su-35BM also reduced the area of empennage of the aircraft, better that the original Su-27. Another change in the structure of the aircraft, was the adoption of the same flight control system developed in the Su-47 Berkut, a quadruple flight control system. This allowed the engineers to substantially to reduce the size of the vertical empennage of the aircraft, to such point that it is smaller than the original Su-27. The aft part of the cabin of the Su-35 was also reduced. This is the part of the aircraft where a part of the avionics of the aircraft are installed. Initially, the very great size was necessary to increase the space of the fuselage to be able to install the avionics. But with the adoption of the new smaller and better avionics, this part of the fuselage was reduced, much smaller thnt the original Su-27. To increase the useful life of the body of the aircraft, the composition of the aluminum fuselage was substituted in part for titanium.

The main source of the Su-35's head-on RCS is the inlets. The straight duct provides direct visibility for the entire face of the engine compressor. While this may be good aerodynamics, Bill Sweetman noted that "the inlet might have been designed to advertise the fighter's presence at the greatest possible range." Part of the solution was a high-performance, ferro-magnetic RAM for the compressor face and duct walls. This model was carried through a work of radar signature reduction of approximately of 25db with the application of a process developed in experimental way with the Berkut and later perfected in the turbines of the new version for the Su-35. This goes beyond the application of a new type of absorbent material of high performance with bigger capacity of durability when subjected to the high temperatures emitted by the turbines. 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. Beyond these changes, radar absorbent material of greater durability allied with the structural changes, mean that it is expected that the RCS of the aircraft will be equivalent of a F-16, that is, around 1m (Reduced RCS (b/w F-16 (about 1m^2).

The maximum weight of the aircraft was reduced by 10% with the substitution of the composition of part of the components for lighter and resistant composite materials.

Armament

In addition to the armaments onboard the modern Su-30MK, it is planned to additionally arm the Su-35 with new types of air-to-air and air-to-surface guided missiles, including long-range types. The maximum ordnance load of the Su-35 is 8,000 kg. This is placed in 12 weapon stations.

For combat the Su-35BM will count for combat of short reach the R-74M (the missile is external identical to the R-73, but with processor of digital signals reprogrammable and new sensor more sensible multipursuing with 60 degrees of off-boresight, more good capacity of countermeasures and capable to acquire targets flying low.), for combat BVR incialmente the R-77M1 and after that the R-77-PD. The R-77M-PD will be equipped with engine ramjet of solid fuel Vympel KRLD-TT that functions for 50-70 seconds with reason weight: power of 7:1.

As weapon against targets of great strategic value as AEW/AWACS or bombers, the SU-35BM will count on the KS-172-1 with useful reach of 400km. Against ships it will have the PJ-10 and the Kh-59MK, and for the suppression of radars it will count on the Kh-31Pk and the R-27P. It will make use of the Kh-65 cruise missile of high precision with reach of up to 280km. And it will make use of new guided and un-guided bombs (KAB-500S, KAB-1500LG and LGB-250).

117S Engines

The Su-35BM is powered by a pair of the new AL-41 F1A turbofans, which provide 142 to 147 kN [36,000 pounds (approx)] of thrust each. The final production engine for the PAK-FA (T-50) will be the AL-41F1 fitted - when compared with the present A version - with a new core. Having installed in the nozzles the system of 3D vectored thrust, having useful life of 6,000 hours. The TVC possesss movement of deflection in the three axes of supersonic flow with amplitude of +-15e in the horizontal plan of +-8, with the made deflection being in a speed of 60/second. The movement is carried through through a mobile ring, which the supersonic nozzle is set in motion, and that is set in motion by three located hydraulical actuators around of the nozzle axle. In turn, the proper actuators are fixed in a "located fixed brace" around of the post-combustion chamber (to afterburner).

One important difference of the Su-35 from predecessors from the Su-27 family is the use, in its power plant, of new engines with an increased thrust. Those engines, known as 117S, have been developed by NPO Saturn Research and Production Association.

In terms of engineering, the engines are substantially modified AL-31F production engines employing fifth-generation technologies. They use a new fan, new high and low pressure turbines, and a new digital control system. A provision is made for using a vectored thrust nozzle. The modernization has increased the engine special mode thrust by 16%, up to 14,500 kgf. In the maximum burner-free mode it reaches 8,800 kgf. Compared to today's AL-31F engines, their capabilities will grow substantially, by 2 to 2.7 times. For instance, the between-repair period will grow from 500 to 1,000 hours (the operating period before the first overhaul is 1,500 hours). The designed period will vary between 1,500 and 4,000 hours.

The 117S engines will be co-produced by Ufa-based Motor Building Association and Rybinsk-based NPO Saturn Research and Production Association. The first production 117S engines were delivered to KnAAPO in early 2007 for testing on the first experimental Su-35 aircraft.




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