In 2003, Sukhoi Design Bureau embarked on the second-most modernization of the Su-27 fighter to create the Su-35 aircraft. The characteristics achieved in the modernization process make it possible to call it a 4 ++ generation fighter, which means the maximum approach of capabilities to the fifth-generation PAK FA aircraft.
Development background
In the early 1980s, while the Su-27 was still being mastered by the Soviet Air Force, its general designer Pavel Sukhoi was already planning the development of a modernized version. Originally designated as the Su-27M, it was equipped with significantly improved avionics, which gave reason to consider it the best fighter of those years. It was also equipped with a more diverse set of weapons, which allowed the Su-27M (see photo below) to carry out missions and ground targets.
The modernized version was characterized by many changes in aerodynamics, avionics, design of power plants, and also had an increased load capacity. High-strength composite materials and aluminum-lithium alloys have been used to reduce weight and increase fuel supply.
The Su-27M aircraft was equipped with a 125 kN turbojet engine, more powerful than the Su-27. The program of modernization of the Su-27 was designated "Su-35BM", where the letters meant "great modernization." A lot of what was done at that time was also incorporated by the modern Su-35 aircraft, the technical characteristics of which significantly exceed its original prototype Su-27M.
Further upgrade
In 2003, a fighter production project was launched to bridge the gap between the upgraded versions of the Su-27M and Su-30MK and the fifth-generation PAK FA combat vehicle. The aim of the project was the second modernization of the airframe of the Su-27 aircraft (hence its classification as a 4 ++ generation fighter) so that the Su-35 performance corresponded to the level realized at the PAK FA. In addition, the aircraft was supposed to be an alternative to the Su-30 family in export deliveries.
The development of the aircraft continued until 2007, when it became available for sale. Somewhat later, the Sukhoi Design Bureau reported that the Su-35 creation program was launched because of fears that the PAK FA project might run into a lack of funding.
Update horizontal plumage
The characteristic of the Su-35 regarding the design of its airframe includes numerous differences from the Su-27M, although the aircraft externally retains a strong external resemblance to its predecessor.
One of the distinguishing features of the design of the Su-27M airframe was the aerodynamic design of duck-type controls, which allows the aircraft to fly at maximum angles of attack of up to 120 °. With this scheme, the horizontal tail of the aircraft — stabilizers with elevators — is located in front of its wings.
However, with this arrangement of the horizontal tail, the radar signal reflected from the surface of the aircraft turns out to be larger than with the traditional pattern behind the wings. This facilitates the detection of the aircraft. Therefore, modern aircraft, inconspicuous for radars (F-22 Raptor, PAK FA, and also Su-35) have a traditional horizontal tail arrangement - behind the wings. To preserve the advantages of using the front horizontal plumage, they, along with the main plumage behind the wings, also have rotary sections of the influx on the wings.
What new was introduced by these changes in the appearance of the Su-35? The characteristics (the photo below shows the differences in its appearance from the Su-27M) of the fighter turned out to be as close as possible to the 5th generation aircraft, with the exception of its greater radar visibility and the absence of an active airborne radar.
Other glider improvements
The characteristic of the Su-35 in terms of its braking method differs from the Su-27M in the absence of an air brake (shield). The braking method of the Su-35 is that its rudders located in the rear of two vertical keels deviate in different directions when landing, which creates a braking force. Other aerodynamic improvements include reducing the height of the vertical stabilizers, a smaller protrusion of the cockpit lantern and covering it with conductive spraying to mask when the aircraft is radiated.
Strengthening the strength of the airframe was achieved due to the wide use of titanium alloys, which increased its service life to about 30 years of operation while increasing the maximum take-off weight to 34.5 tons. The internal fuel supply was increased by more than 20% to 11.5 tons and can be raised to 14.5 tons due to additional tanks.
Advanced Avionics
Sukhoi Design Bureau did everything so that the performance of the Su-35 in terms of avionics was only excellent. The work of all units and devices of the aircraft is controlled by an information management system equipped with two on-board computers. It collects and processes data from various tactical and flight control systems and presents relevant information to the pilot through two primary multifunction displays (MFD), which together with three secondary MFDs form the cockpit glass. The aircraft has many other updates for its avionics and electronic systems, including a digital wireless flight control system, and the pilot is equipped with a helmet-mounted information screen and night vision goggles.
Radar and Aiming System
In this part, the characteristics of the Su-35 include the presence of the Irbis radar with a passive phased antenna array, which is an important component of the aircraft’s fire control system. The radar is capable of detecting an air target of 3 square meters. m at a distance of 400 km and can give target designation for 30 air targets, with eight of them being conducted.
The radar can also reproduce a map of the earth using various modes, including the aperture synthesis mode. Radar "Irbis" is complemented by an optical-electronic aiming system, which uses the functionality of a laser rangefinder, TV, infrared target detector.
Armament aircraft
What weapons can a Su-35 fighter carry? The characteristics of its weapons systems involve the use of a variety of long-range and short-range air-to-air missiles, accurate and uncontrolled air-to-ground weapons, which include missiles, air-blast bombs and conventional bombs. The maximum useful weapon load is 8 tons, which can be carried at fourteen points of suspension. The fighter can use rockets with a range of up to 300 km.
Fighter engines
Su-35 is equipped with a pair of turbojet engines, the thrust vector of which is controlled in one plane. This engine is a simplified version of the power plant type "Saturn-117" fifth-generation fighter PAK FA. Its thrust is estimated at 145 kN, which is 20 kN more than the Su-27M. It has a lifespan of 4000 hours. A pair of aircraft engines has the ability to control the resulting thrust vector. Each of the nozzle thrust vectors has its own axis of rotation inclined to the vertical plane. In this case, the deviation of the thrust vector of each nozzle can be represented as a result of the deviation of the nozzle itself in the down-in and up-out directions. If the thrust vectors of both nozzles deviate synchronously, then the position of the aircraft can only be controlled by the pitch angle, but with different deviations of the thrust vectors of the nozzles, yaw and roll angles can also be controlled. A similar control system is also implemented on the PAK FA fighter.
The engine allows the Su-35 to achieve a stable supersonic speed without the use of afterburner. A radar absorbing coating is used for engine parts to reduce the radar signal reflected from the aircraft.
Comparative characteristics of the Su-35 and F-22
To date, the only 5th generation fighter adopted in the world is the American F-22 Raptor. As you know, the basis of the Stealth technology, implemented in its design and providing stealth aircraft radar, are two principles:
- giving the aircraft glider a specially designed geometric shape, which provides reflection of the radar signal in the direction opposite to the direction of its arrival;
- the scattering (absorption) of energy of the radar signal in the materials that make up the surface of the aircraft in order to attenuate it to such a level that detection of the reflected signal becomes unlikely.
According to American data, the reflectivity of an F-22 fighter is equivalent to a golf ball, according to Russian data, it is 0.3-0.4 m 2 . For comparison: in the MiG-29 it is 5 m 2 , and in the Su-27 - 12 m 2 . Is it possible, at least partially, to achieve the performance of the Raptor on the Su-35? The characteristics (a comparison of them with the F-22 is given below) of the Russian aircraft allow us to express cautious optimism in this matter.
Russian designers and scientists have developed materials and methods that significantly reduced the reflectivity of the Su-35. Russian scientists have created mathematical tools to calculate the scattering of electromagnetic waves by bodies of complex configuration, such as the Su-35, breaking them into small faces and adding the effects of edge waves and surface currents. Antennas are modeled separately and then added to the entire calculation model.
A new radar absorbing material has been developed that covers aircraft engines. It does not interfere with the operation of deicing systems and withstands high-speed air flows and temperatures up to 200 ° C. A radar absorbing layer 0.7-1.4 mm thick is applied to the surface of the engines and to the front stages of the low pressure compressor using a robotic spraying system.
The Su-35 also has a machined cabin light that reflects radar waves, reducing the contribution to the image intensifier from the metal components of the cabin. Russian technologists have developed a process for plasma deposition of alternating layers of metallic and polymeric materials. In this way, a coating is created that blocks the electromagnetic waves of the radio frequency range, is resistant to cracking and does not trap solar heat in the cabin.
Of course, all these events only bring the characteristics of the Su-35 closer to the capabilities of the F-22 Raptor, but do not make them identical. Real parity (and possibly superiority) will be achieved after the adoption of the Russian fifth-generation fighter PAK FA.
As for the other flight characteristics, their comparison for the Su-35 and F-22 gives the following picture. The Russian aircraft is four meters longer (21.9 m versus 18.9 m) and almost a meter taller (5.9 m versus 5.09 m) of an American one with a larger wingspan (14.75 m versus 13.6 m). At the same time, the mass of the Su-35 (empty) is almost equal to the mass of the F-22 (19,500 kg versus 19,700 kg), but the maximum mass of the “American” is two and a half tons more (34,500 kg against 38,000 kg). The maximum speed for both aircraft is almost the same - about 2400-2500 km / h, as well as the practical lift ceiling - 20 000 m.
But the flight range of the Su-35 with two hanging tanks is higher (4600 km versus 2960 km), without tanks the “drying” will also fly further than the Raptor (3600 km versus 3220 km).