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T-50 / Project 701 / PAK FA - Design

Although T-50 specifications remained classified, fragmentary data on its engines imply that this heavy-duty fighter will have a take-off weight of more than 30 metric tons and will be close in dimension to the well-known Sukhoi Su-27 Flanker. The new fighter's exterior was designed using Stealth technology, also known as LO technology (low observable technology).

Mikhail Strelets, the head developer at the Sukhoi United Aircraft Corporation, explained the key strong points of the cutting edge fifth generation Su-57 jet in comparison to its Western rivals, the F-22 and F-35 in an interview 11 November 2018with the Zvezda TV channel.

According to him, the F-22 lacks the capability to strike ground targets as opposed to the Su-57. Strelets explained that the F-22 was initially designed as an air superiority jet, while the Su-57 was created as a more versatile aircraft from the beginning. As a result, internal compartments of the F-22 were unable to hold munitions with significant payloads.

When comparing the F-35 and Su-57 aircraft, Sukhoi's chief developer stressed the increased manoeuvrability and acceleration of the latter. He also noted that both the F-22 and F-35 are less versatile in terms of fulfilling various combat tasks than the Russian plane.

The Russian Air Force T-50 reflects the latest scientific and technological achievements. This machine is the representative of the Russian military technology innovation, and its stealth technology, new materials technology and artificial intelligence techniques, so that the Russian air force into high-tech new level. The T-50 fuselage for the first time uses the latest composite materials, compared with the same hardness titanium or aluminum is 50% lighter than steel and lighter 20% -25%. On the T-50, 70% of the skin is made of this new material, T-50 weighs just a skin equivalent traditional materials used in aircraft skin 25%, the weight of these savings can be used to carry more weapons in on.

By weight of the empty aircraft composites are 25 percent. The advantage gained primarily by weight. In production, after working off the necessary technological processes, a significant reduction in the number of parts occurs. In comparison with the Su-27, the T-50 according to the airframe are four times less parts. Reducing the complexity and production time translates into a reduction in the price of the machine.

The PAK FA can carry either eight next-generation air-to-air R-77 missiles, or two large controllable anti-ship bombs weighing 1,500 kg each. The new jet can also carry two long-range missiles developed by the Novator Bureau which can hit targets within a 400 kilometer range. The jet can use a take-off strip of just 300-400 meters, and perform sustained supersonic flight at speeds over 2,000 km/h, including repeated in-flight refueling. The highly-maneuverable plane has a range of about 5,500 kilometers. The fifth-generation fighter is equipped with advanced avionics to combine an automatic flight control system and a radar locator with a phased array antenna.

In comparison with the fighters of the previous generations, the PAC[FA] possesses a number of unique special features, combining in itself the functions of attack aircraft and fighter. The fifth generation aircraft is equipped with the fundamentally new complex of avionics, that integrates the function "electronic pilot", and by a promising phased-array radar. This to a considerable degree reduces load on the pilot and makes it possible to be concentrated on the fulfillment of tactical missions. Onboard equipment of new aircraft permits implementation of the exchange of data in the regime of real time both with the ground-based systems for control and inside the air group. The application of composite materials and innovation technologies, the aerodynamic layout of aircraft, measure for reduction in distinctness of engine ensure the unprecedented low level of radar, optical and infrared distinctness. This makes it possible to considerably increase combat effectiveness in the work both along the air and ground targets, at any time twenty-four hours, in the simple and adverse weather conditions.

"This is the great success of Russian science and design thought. After this reaching stands the cooperation more than hundred subcontracting enterprises, our strategic partners. Program PAC[FA] derives Russian aircraft construction and adjacent branches to the qualitatively new technological level. These aircraft, together with the modernized aviation complexes of the fourth generation will determine the potential of Russian VVS during the next decades. Into the plans of company "Sukhoi" enters further development of program PAC[FA], at which we will work together with the Indian partners. I am confident, that our joint project will exceed western analogs on the criterion cost- effectiveness and will make it possible not only to strengthen the defense power VVS of Russia and India, but also will be occupied worthy place on the World Market", said the Director-General of joint stock company company "Sukhoi" Mikhail [Pogosyan], commenting on the beginning of flight tests.


Wang Yongqing, chief designer of China's Shenyang Aircraft Design Institute, wrote in Aerospace Knowledge magazine in February 2019 that while the Su-57's super-maneuverability and supercruise capabilities were impressive, these had been so emphasized at the expense of its stealth capabilities that it was questionable whether or not the jet could really be called "stealthy."

The new Russian fighter has significantly reduced the effective scattering surface (EPR) - the main characteristic of the aircraft visibility in the radar field. The average value of this indicator in the T-50 is 0.3-0.4 m. It must be borne in mind that these data are estimated, there is no official information on the EPR of the aircraft. The only official message is the phrase of the general designer of the aircraft, Alexander Davidenko, where he compared the PAK FA and F-22: "The F-22 aircraft has 0.3-0.4 m. We have similar requirements for visibility."

Sukhoi said, "T-50 fighter radar signature and infrared visibility at unprecedented low levels." Its overall radar reflector less than 0.5 square meters, and its predecessor, the Sukhoi-30MKI's radar reflector is close 20 square meters. This means that the radar can detect the Su-30MKI area of only about 1/40. Such a low radar reflective surface coupled with exceptional maneuverability Sukhoi champions, T-50 was found to be locked and the difficulty of attack greatly enhanced.

It was possible to achieve reduction in visibility due to the special geometry of the airframe, which in various angles reflects electromagnetic waves in the minimum number of directions and in the least dangerous sectors. Rocket-bomb armament is placed in the inner compartments, the inner and outer surfaces are covered with radio absorbing and composite materials, the joints and slots are filled with conductive sealants. There are no right angles in the geometry of the airframe. The front and rear edges of the bearing surfaces, air intakes, and hatch flaps are led to two or three different axial directions, which leads to the reverse reflection of electromagnetic waves to the same directions.

The sides of the fuselage in cross section and vertical aerodynamic surfaces are inclined in one direction from the vertical axis of the aircraft, which allows reducing the EPR in the side hemisphere due to the re-reflection of waves falling on the inclined surface of the airframe, away from the irradiation signal.

The reduction of the EPR in various sectors of the front hemisphere is provided by the use of S-shaped air inlet channels and their covering with radio absorbing materials. But, if you look closely at the schemes and photos available in the open access, you can conclude that the engine input unit (VNA), or more simply, the first stage of the compressor with blades, will be very clearly visible to enemy radar. The S-shaped channel provides a reduction in the ESR only in the axial directions, in order to reduce the visibility in other sectors of the front hemisphere, engineers of the Sukhoi Design Bureau applied VNA shielding.

A special device is installed in the air intake channel, partially blocking the VNA in the axial directions from electromagnetic waves. In addition to shielding, this design solution divides the air intake channel into several different cylindrical or flat cavities, and the surfaces of the flat cavities can be both parallel and intersecting. Such complex segmentation of the air intakes channels and covering the walls of the segments with radar absorbing materials reduces the power of electromagnetic waves reflected from the VNA and re-reflected onto the walls of the cavities, thus providing a reduction in the EPR in the forward hemisphere of the aircraft.

In all likelihood, the screen installed in the air intake channel is a construction of fine-mesh nets, in which the linear size of the cell is less than a quarter of the length of the electromagnetic wave that irradiates the aircraft. Thus, the fine meshed grid acts as a screen for electromagnetic waves from the radar and reduces the ESR of the entire aircraft.

Western analysts often cited the poor cosmetics and crude surface finishes of Soviet weapon components as an example of the poor quality of Soviet workmanship. In fact, the lack of polish on Soviet machine surfaces was a deliberate trade-off to increase producibility of parts. Tight tolerances and high-grade surface finishes were generally restricted to areas where they are functionally required, but for stealth aircraft, these tolorances are required on all external surfaces. The Soviet state standards for machine tools generally specified a lower level of accuracy to be built into their machines than are built into their Western counterparts, which resulted in a lower tolerance capability on the factory floor.


The new fighter's control systems, avionics and cockpit will be designed on the basis of the Su-35BM's systems, but not the radar. The N035 Irbis radar, a passive electronic scanning design derived from the Bars radar on the Su-30MKI, is being developed by the Tikhomirov Niip institute for the Su-35. The Tikhomirov Institute of Instrument Design, which developed the Irbis radar for the Su-35BM Flanker, has been working on the T-50 radar, which will feature an active antenna system, including three X-band radars (forward and side-looking), in addition to a ventral Ku-band radar including IFF and electronic warfare subsystems. The technical design was approved in December 2005, so that the radar will probably be ready before series production gets under way.

The aircraft of the fifth generation is equipped with the fundamentally new complex of avionics, that integrates the function "electronic pilot", and by promising phased-array radar. This to a considerable degree reduces load on the pilot and makes it possible to be concentrated on the fulfillment of tactical missions. Onboard equipment of new aircraft permits implementation of the exchange of data in the regime of real time both with the ground-based systems for control and inside the air group. The application of composite materials and innovation technologies, the aerodynamic layout of aircraft, measure for reduction in distinctness of engine ensure the unprecedented low level of radar, optical and infrared distinctness. This makes it possible to considerably increase combat effectiveness in the work both along the air and ground targets, at any time twenty-four hours, in the simple and adverse weather conditions.

The most important element of the on-board electronic equipment of the Su-57 - the radar - is unique. It is radically different from the airborne airborne radar in the traditional sense. The X-band AFAR (Active Phased Antenna Array) radar element is located not only in the front of the fuselage, but on the sides of the aircraft and even on the deflected wing socks. True, there is an L-band AFAR. It allows you to see space, both air and ground, for many hundreds of kilometers. There is no such radar on any fifth-generation multi-functional fighter - neither on the F-22, nor on the F-35, nor on the J-20. And the law of air combat is known: the first to see - the first to shoot, the first winner.

The angle of the T-50's active phased array is installed on an incline. Because of this, the aircraft's rcs is reduced. Going with this design, which also makes possible a reduction in power usage during operation, was made possible thanks to the excellent characteristics of the N036 Belka radar, developed to replace the N035 Irbis passive phased array antenna system.

The N036 is more effective than the N035, but even the earlier system remains very convincing when compared with the US AN/APG-77 radar. The Russian system finds targets with an rcs of 1 square meter at distances up to 300 km. The American radar, meanwhile, does the same up to 225 km. For targets with an rcs of 0.01 square meters, the Russian radars range is 90 km. For the US system these figures are not available.

Altogether, the T-50 has six radars onboard including one on the planes nose, two on its sides, two on the wings and one in the aft section. They are capable of monitoring up to 60 targets at once, and targeting up to 15. In addition to the radar-based visibility, the T-50 features the OLS-50M optic-electronic sensor system, which includes a thermal scanner using a QWIP-matrix with unique resolution and range characteristics. In this area, Russia is considered to be a absolute world leader. A similar system, which enables the pilot to detect targets which have their radar systems turned off, is fitted on the F-35, albeit the US design has a smaller range. The F-22 does not have this technology.

The pilot will perform all tasks as intended due to the integrated provision of information. This was made possible through the use of a different architecture of aviation systems. On aircraft of the previous generation, the so-called federal system of the aviation complex was used, now - integrated. Previously, each system had its own individual controls, indicators. Now the control of the systems is displayed on the ENG (aircraft control knob) and throttle control (engine control lever), and the display is displayed on two monitors.

If necessary, the pilot can control various systems with the help of sensors on the monitor panels, to which information on piloting, navigation, weapons use and the state of the systems is displayed. All information is called by the pilot as necessary, and does not loom in front of him constantly and does not distract attention. Work is underway to create a promising system that allows you to display information on the glass of a pilot's protective headset. The T-50 provides intelligent crew support. The board is computerized. The existing information system allows you to solve all the problems in the complex. It simultaneously processes all information, controls the systems, gives the pilot the necessary visual and audible indication. He can make changes to the program and receive messages in a sequence more convenient for him.


The creation of a fifth generation jet with stealth technology, the Su-57, began in early 2001 and it is planned to be commissioned in 2019, while models with advanced engines are scheduled to arrive by 2025. The Russian Air Force is planning to acquire the first batch of 12 jets in 2019.

Prototypes and initial production aircraft will feature many elements from the Su-35. The aircraft will be equipped with the same engines -- two AL41F1s, an improved version of the AL-41F on the Su-27, delivering 142kN (vs 123kN). The future engine would not be ready until 2017, at least three years later than the initial 2015 deadline. The combat aircraft is fitted with 117S (upgraded AL-31) turbofan engines from the Russian aircraft engine manufacturer Saturn.

By 2019, nine of the 10 existing versions of the Su-57 make use of the aging Saturn AL-41F1S engine, which can't provide the plane with the thrust or fuel efficiency it needs, nor the low-observable and thrust vectoring capabilities of newer engines like Saturn's Izdeliye 30, which is still under development. Models with advanced engines are scheduled to arrive by 2025.

The designers are working on a new fifth generation engine, Izdeliye-30 [Product-30], in order for the fighter to meet all the challenges of the new era. Flight tests of the new engine would start at the end of 2017, or in early 2018. It will take the designers another two or three years to finalize the project before the aircraft goes into series production and into service with the Russian Air Force.

The new engine will make it possible for aircraft to maintain cruising speeds during supersonic flights, with a speed of Mach 1.6, (about 1,200 mph), depending on the location over which the plane flies. The engine will also significantly improve the PAK FA's stealth capacity and cloak it from enemy radar thanks to new composite materials. Development of the engine stalled in the 1990s and early 2000s due to the collapse of the country. Scientific and technical research programs were either closed or curtailed. Hence, designers have to catch up in a short period of time.

Sukhoi Su-57 fighter jet, known during its development as PAK FA and T-50, on 20 February 2018 performed its maiden flight with a new engine, designed specifically for the cutting-edge military plane. The test flight was successfully performed on Tuesday and lasted some 17 minutes, according to the Russian Industry and Trade Ministrys press service. A Su-57 aircraft, fitted with new engines known as Product 30, was piloted by a chief pilot of the Sukhoi company, Sergey Bogdan.

The new Izdeliye 30 engines increase the Su-57 thrust to 11,000 kg without afterburner and 19,000 kg in afterburner according to reports. The successful test flight of the plane with the new engines proved that Russian aircraft builders are capable of creating cutting-edge advanced systems, the press service said, citing Minister Denis Manturov. While little is known about the specifications of the new Product 30, the engine-building company that designed it said earlier this year that it is an entirely new device, fully suitable for the fifth-generation planes.

After testing is completed the new engine will enable the Su-57 to accelerate in non-afterburner mode to supersonic speed, and maintain this velocity for its entire flight. I think the speed will be 1.6 Mach, about 2,000 km/h, depending on where it will be flying. The engine will also improve the Su-57s stealth capacity thanks to new composite materials, said Pavel Bulat, avionics expert and director of Kupol. According to the expert, the upgrade will be fully integrated by 2020. The Sukhoi Corporation, which builds the jets, is also planning to improve its radar system. Bulat believes the aircraft is the most advanced 5th generation jet in the world.

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Page last modified: 08-08-2019 12:40:13 ZULU