Sukhoi Su-57 / T-50 / PAK FA - flight testing and development Part II [2012-current]

There is a post from 2020 by Flateric claiming that the design study is from the late 1990s. Not entirely impossible as the F-22 was planned to have cheek arrays and the X-44 MANTA project would've been contemporary (even if the 602 looks very modern).
 

ПАКФА Т-50/Су-57 (часть 5) • Форум "Стелс машины"

Авиация, флот и космос - реальность и перспектива.
paralay.iboards.ru
A comprehensive read (in Russian) about Su-57 development history and issues.
From anniversary book mentioned above. Interesting that they are frank and open (for Russia) about problems that were encountered during development and testing.
 
flateric said:
No.
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Ah, interesting. I should have noted that the Sukhoi designs still have vertical stabilisers.

Was there a common influence? Is TsAGI still influential? I'm asking because of the highly swept wing combined with the small close-couple 'moustache' canards... it seems very similar in terms of aerodynamic approach.

P.S. If '602' looks like that - it'll be very interesting to see if E-721 ever gets declassified. I suppose '602' had between engine weapon bays like the PAK-FA/T-50?
 
flanker said:
"Spot 10 differences" in the attached pics... The last two are cleaned up by a friend of mine.
Click to expand...

Based on the text, it appears that this insider report from the 2015 timeframe was correct, particularly with the difficulties in applying aluminum-lithium alloys in the redesigned Second Stage air vehicle design, and the consequent weight increase.
 
Introduction

In 1996, the US Department of Defense announced a competition to develop a new family of aircraft that could replace several existing types and meet the diverse needs of the Air Force (the Joint Strike Fighter (JSF) program). Strike Fighter ). The competition, which involved leading American aerospace companies Boeing , Lockheed Martin and McDonnell Douglas , Lockheed 's X-35 prototype was selected in 2001 Martin . The key requirements for the aircraft were:

- ensuring survivability in combat conditions, as well as the introduction of onboard systems to obtain the minimum possible visibility of the aircraft in the radio and IR ranges;

- integration into a single system of onboard and ground sensors for controlling high-precision weapons; implementation of aircraft support systems throughout its life cycle;

- concentration of efforts on reducing the cost of development, production and operation of the aircraft throughout its entire life cycle. At the same time, the price was an independent variable in formulating the tactical and technical requirements for the aircraft.

During the same period, research began in Russia to determine the appearance of a promising light frontline fighter (LFI).

In November 2000, the Sukhoi Design Bureau submitted an Engineering Note with proposals for AK implementation options to the Russian Defense Ministry for consideration. The proposals were based on the results of research work in the direction of creating a new generation fighter obtained by the Sukhoi Design Bureau, including through participation in joint research projects with the Russian Defense Ministry institutes (2, 6, 30 Central Research Institutes).

Start of work

In 2000, work on creating a Russian fifth-generation aircraft received a new impetus. The forecast for the attrition of the domestic fleet of operational-tactical aviation, ensuring effective counteraction to new external threats, and resource constraints that arose led to a revision of the requirements and dimensions of the new-generation fighter.

The main tactical and technical requirements were:

- multifunctionality (ensuring air superiority and the ability to destroy ground and surface targets);

- low aircraft visibility (reduced visibility in the radar, infrared and optical ranges); high integration of onboard systems and complexes (combining the interaction and control of onboard complexes into a single information system based on advanced computers);

- long-term supersonic cruising flight;

- the possibility of using almost the entire range of aviation weapons. For the Sukhoi Design Bureau, the implementation of this program was part of the overall development strategy of the Design Bureau, adopted in 1999, aimed at continuous development and ensuring leading positions in the world market of the Su aircraft fleet at a level of 14...15%.

It should be noted that the starting conditions for the implementation of the program of the promising frontline aviation complex (PAK FA) were extremely difficult: there was no necessary funding, no mechanisms for implementing such large-scale projects in the new economic conditions, an outdated production base, a shortage of qualified personnel, etc.

All this set the Sukhoi Design Bureau the task of forming a new environment that would combine both technical and financial-organizational aspects. On the one hand, technical issues were addressed in forming the appearance of an aviation complex that would meet the requirements of the TOR (TECHNICAL ASSIGNMENT) and ensure superiority over similar complexes of a potential enemy, and on the other hand, issues of implementing the entire project were addressed. At the initial stages, the Sukhoi Design Bureau carried out work on the PAK FA project at its own expense. A comprehensive target program (CTP) was developed. In the absence of direct government funding, a mechanism of mixed funding (from three different sources) was proposed and implemented, and the issue of attracting funds from a foreign partner was worked out.

For the operational management and direction of work on the PAK FA project, a special structure was created under the leadership of the General Director of the Sukhoi Company M.A. Pogosyan - the program directorate, which in a short time was supposed to deploy work on the project, form cooperation, and approve the KCP.

In 2000, A.N. Davidenko, who had previously headed the design department of the Sukhoi Design Bureau, was appointed Chief Designer for the PAK FA project. From 2002 to 2014, A.N. Davidenko was the project manager in the position of Program Director and Chief Designer. The implementation of the PAK FA project at the Sukhoi Design Bureau was revolutionary in many ways. For the first time, the project was developed in a digital environment. All sketches, developments, and circuit design options were created using computer technology. The design bureau and the production plant were completely re-equipped for paperless design and production. For the first time in the country, a secure information technology facility was created that allowed for electronic design taking into account security measures. A unified information environment was formed, ensuring the joint work of the design bureau and the production plant, and an electronic model room was created.

For the first time, a single aircraft configuration implemented a comprehensive solution to the problem of radically reducing visibility and ensuring high flight performance characteristics.

The design and testing were carried out with the wide application of mathematical modeling methods, which allowed to reduce the amount of field work, the time frame and the cost of their implementation. The transition was made from a federal structure for the construction of the on-board equipment complex (OBE) to an integrated one with the allocation of an information and control system (ICS). For the first time, the developer of the ICS and the corresponding software was the developer of the aircraft.

A mixed financing mechanism was implemented. The project was implemented in parallel, for both external and internal markets.

For the first time, a prototype of the aircraft was built directly at a serial plant, and not at a pilot production facility. Large-scale modernization was carried out, modern equipment was purchased, a unified digital environment was formed, and new forms of production organization were introduced.

Preliminary project

On February 16, 2001, an order was signed by the Sukhoi Design Bureau to begin, from February 1, 2001, (RESEARCH AND DEVELOPMENT WORK) on the PAK FA and its export version (factory code - product T-50).

To ensure the necessary technical, technological and personnel development of the enterprise and its basic areas, subprograms were created for the KBO (COMPLEX OF ON-BOARD EQUIPMENT), ASP, new technologies and materials, operation, repair, training, flight- experimental work, quality, certification, information technology, information interaction and intellectual property. A manager was appointed to head each subprogram. At this stage, almost all design bureaus joined the work on the project.

As part of the preliminary design , the Sukhoi Design Bureau, together with the leading institutes of the Russian Ministry of Defense (30th and 2nd Central Research Institutes of the Russian Ministry of Defense) and industry ( GosNIIAS , TsAGI and TsIAM), conducted a comprehensive analysis of the choice of dimensions and appearance of the prospective AK FA for the Russian Air Force, taking into account the interests of potential foreign customers .

In cooperation with industrial institutes and the Ministry of Defense of the Russian Federation, 5 aerodynamic configurations were studied: tailless with a canard (basic version), an aircraft with a forward-swept wing, a normal configuration, a combined configuration with a lifting fuselage, a normal configuration with a lifting fuselage.

The comparison of the schemes was carried out at the level of aerodynamic and weight perfection, by the design and power scheme, technological face (features), by the expected labor costs for manufacturing and preparation of production, by adaptability for avionics (on-board radio-electronic equipment) and KAV. The visibility and modification suitability were assessed separately.

The following configuration options were considered: ZAM, ZB2, ZV, ZD, ZI, ZKOS (various wing options, with or without narrowing, and the organization of the extension), ZVKS and their modifications. On option 362, a deflectable compensated extension (analogous to the PGO (FRONT HORIZONTAL EMBLEM)) was used for the first time, resting on the fuselage. Taking into account the need to increase the efficiency of the VO, reduce aerodynamic losses and the RCS, on option 3B2 and, later, ZI, an ALL-MOVING VERTICAL EMBLEM (ALL-MOVING VERTICAL EMBLEM) was used. On options ZV, ZD, a "bearing" fuselage was used for the first time, composed of longitudinal aerodynamic profiles, as well as " semi-recessed " air intakes. Alternative layout options were also developed that were not included in the Avanproekt materials, in particular, with different air intakes. In the 3D-1 layout option with a "sector" air intake, a dimensional transverse chain was first linked for a profiled fuselage: air duct-OOSh-RMD (short-range missile), where the RMD (short-range missile) was located in the fuselage body at an angle, located outside the air intake, which served as a prototype of the technical solution subsequently used in the 3I layout. The OOSh retraction was implemented through an oblique spatial axis, with a wheel turn at the final section. This solution allowed the main landing gear to be retracted as compactly as possible. In order to improve the level of flight characteristics (flight performance characteristics) in supersonic flight modes, in version 3I, longitudinal profiling of the fuselage with low relative altitude profiles was used, and in order to maintain the solution of placing the short-range missile (short-range missile) in the fuselage with maximum offset relative to the air intake.

Based on the calculations of the characteristics of the configuration options presented at the Preliminary Design stage, the ZAM option was recognized as the best in terms of FLIGHT PERFORMANCE CHARACTERISTICS (Flight Performance Characteristics), with a slight lag behind the 3I option, which at the same time received a number of advantages: the maximum possible separation between the entrance to the engine air intake and the SRM (short-range missile) jet during launch was ensured, the best level of performance (taking into account additional measures).

One of the main criteria for selecting the main version of the Preliminary Project was the assessment of technical risks in the implementation of the layout scheme. Taking into account the applied main normal aerodynamic scheme, the set of obtained characteristics and results, the ZI option was selected. The future showed the correctness of the adopted layout solutions: subsequently, according to the results of the LI, in supersonic flight modes, results were obtained that were higher than expected in the calculated estimates. At the same time, controlled modes of supermaneuverability are ensured without restrictions on the use of SRM (SHORT-RANGE MISSILE).

The final meeting to review the materials and select the basic version of the aircraft was held on September 13, 2001. Based on its results, the ZI version with two AL-41F-1 engines was determined to be the best.

All of this was presented in the materials of the preliminary design of the State Customer Commission, institutes of the Ministry of Defense of the Russian Federation and industry (10 positive conclusions were received from the Leading Institutes of the Ministry of Defense of the Russian Federation and industry).

The version proposed to the State Customer Commission was a fundamentally new aircraft with an integrated layout, because not only the airframe, but also almost all systems and complexes had fundamental differences from previous models:

- the aircraft's airframe was designed with internal compartments for accommodating the main armament, and its design made extensive use of large-sized composite panels (up to 70% of the aircraft's outer surface);

- the power plant, consisting of two AL-41F-1 turbojet engines (product 117), had a digital control system for the first time;

- the radar station was equipped with an active phased array (product Sh-121) and was combined with an electronic warfare and ELINT system integrated into the airframe design;

- a unified information and control system (ICS) was developed and implemented as part of the aircraft, combining the control of virtually all on-board systems and complexes in a single core;

- to ensure a significant reduction in the level of radar visibility, the development of a new system of radar-absorbing materials (RAM) began through joint efforts with the Institute of Theoretical and Applied Physics of the Russian Academy of Sciences, with the simultaneous design of a scheme for applying RAM to airframe units.

Commission for the Review of Preliminary Projects

On February 12, 2002, the Chairman of the VNK VVS, Chairman of the RF Ministry of Defense Commission for the competitive review of the PAK FA preliminary design , Major General S.A. Kolyadin , approved the Work Plan of the General Customer Commission (consisting of 313 people) for review of the T-50 preliminary design based on the Sukhoi Design Bureau. The composition of the commission was approved by order of the Commander-in-Chief of the RF Air Force.

The review of the T-50 preliminary design by the Sukhoi Design Bureau took place from 12 to 14 February 2002, and on 5 March the final plenary meeting of the commission for reviewing the I-21 preliminary designs was held with the participation of the Commander-in-Chief of the Russian Air Force. The final comprehensive comparative assessment of the preliminary designs of the T-50 (Sukhoi Design Bureau) and E-721 (RSC MiG) products was carried out according to the methodology approved by the Commander-in-Chief of the Air Force and the General Director of RAKA, agreed with the Institute of Applied Mathematics according to the following indicators:

- the degree of compliance of the declared characteristics of the aviation complex with the requirements of the BBC TTZ (TECHNICAL REQUIREMENTS);

-efficiency/cost;

- depth of project development;

- technical risk of implementing the declared characteristics;

- scientific, technical and financial and economic capabilities of the design bureau;

- production and financial-economic capabilities of serial enterprises.

An integrated comparative assessment of the quality and capabilities of the presented projects showed that the T-50 product is 43-47% superior to the E-721 product.

On April 26, 2002, a meeting of the Military-Industrial Commission under the Government of the Russian Federation was held under the chairmanship of the Chairman of the Government of the Russian Federation M.M. Kasyanov to review the results of the work of the tender committee of the Ministry of Defense of the Russian Federation. As a result of the discussion, it was decided: "... To approve the decision of the Ministry of Defense of the Russian Federation commission on the tender review of the PAK FA preliminary designs. The prime contractor for the PAK FA R&D project is to be the KnAAPO Design Bureau, the deadline for issuing the TOR (TECHNICAL REQUIREMENTS) for the R&D project is September, RSK MiG and the Sukhoi Design Bureau, the A.S. Lenin Prime Manufacturer is to be the A.S. Yakovlev to be designated as co-executors of the R&D, cooperation to be determined based on the results of competitions within the framework of the EP, to include the work in the state defense order from 2002, report to the President in May 2002. Within 3 months, submit for approval a comprehensive target program (CTP), provide the corresponding regulatory framework for attracting foreign partners to the work and extra-budgetary financing...". It was noted that "... the work was carried out in an organized manner." and "... complete the work on reviewing the preliminary designs and submit a report with the corresponding Government Resolution on the creation of the PAK FA for consideration at a meeting of the RF Government Commission on the State Defense Order...".

Working with co-executors

Fundamentally new approaches were applied not only in terms of technical implementation of the project, but also organizational measures.

More than 380 contracts were signed for the development of the SC, research, testing and development. Almost all leading technical and scientific institutes of industry and the Ministry of Defense of the Russian Federation took part in the work on the project.

Among the partners ("subcontractors"), it was the " engine specialists " who demonstrated a strategic vision of the prospects, from the point of view of the implementation of the entire program, they agreed with the concept of a two-stage implementation of the T-50 proposed by the Sukhoi Design Bureau. At the first stage, the engine should be a deeply modernized version of the AL-31FP. This significantly reduced the risks, timeframes and cost of the program. At the second stage, a new generation engine should be created.

The main figures of the “ engine specialists ” in those years were General Designer V.I. Chepkin , his deputy E.Yu. Marchukov, V.V. Kiryukhin and V.I. Fedyukin.

Another strategic partner was the Tikhomirov Research Institute of Instrument Design. The idea was not to create a radar, but a complex of 5 radars, ELINT, EW, IFF and air traffic control systems . The basis of this complex was to be the active phased array (APA) technology. Considering the high risks, cost and implementation time of the APAA, there was a great temptation to offer passive PAA technology at the first stage, which at that time was already well mastered in the Russian Federation. After these attempts were rejected, it was the NIIP management that created the ideology of what is now the basis of the Su-57, and the radar with passive PAA became the basis for the avionics (onboard radio-electronic equipment) of the Su-35.

Work on the creation of the Sh-121 complex at JSC Tikhomirov Research Institute of Instrument Design was entrusted to the chief designer of the complex V.G. Zagorodniy and was carried out with the active participation and support of the enterprise management represented by the general director Yu.I. Bely, his deputy for science, chief designer A.I. Sinani and many others.

Much work was done in the direction of developing and using polymer composite materials, which were among the most progressive and rapidly developing materials. Due to their specific properties, such as corrosion resistance, low density, high specific elastic-strength characteristics and high technological efficiency, these materials found wide application in the airframe design.

Thanks to the scientific and technical groundwork created during the implementation of the Su-47 project, new materials were used in the aircraft design - adhesive carbon and glass-reinforced plastics . A large number of design and technological solutions previously not used in domestic aircraft manufacturing were developed and implemented. Such a wide application of polymer composite materials was preceded by extensive experimental work on the manufacture and testing of research and design-like samples.

The main load-bearing elements made of PCM are the fuselage and wing skirt panels, which are also the walls of the fuel compartments. PCM is also used to make composite stabilizer, aileron and flaperon blocks , landing gear and cargo compartment doors, and various fairings (including radio-transparent ones).

In close cooperation with VIAM and JSC ONPP Tekhnologiya named after A.G. Romashin , which is a manufacturer of panels for experimental and production aircraft, more than 3,000 samples were manufactured and tested to refine the manufacturing technology and implement solutions in the airframe design.

At the stage of forming the appearance of the aviation complex under the PAK FA program, the Sukhoi Design Bureau, in close cooperation with the ITPE RAS, carried out extensive work on developing measures to drastically reduce radar visibility, during which the main conceptual solutions were laid down in terms of the airframe configuration, placement of electronic equipment elements, construction of the antenna-feeder system and algorithms for its application, and a system of radar-absorbing coatings and schemes for its application were developed. The work was carried out under the supervision of Academician of the Russian Academy of Sciences A.N. Lagarkov with the direct participation of Deputy Director of the ITPE RAS, Doctor of Sciences A.I. Fedorenko.

In developing the T-50, the scientific and technical groundwork was used, which was obtained during the development and testing of the Sukhoi Design Bureau aircraft - the Su-47 Berkut and the modernized 10M-8 aircraft (Svet R&D).

After the completion of the main flight test program of the Su-47 Berkut aircraft and the completion of the Svet research project, a whole range of advanced work was planned and carried out to flight evaluate various configurations of the internal cargo compartment on a flying laboratory based on the Su-47 Berkut.

The new directions formed in the Sukhoi Design Bureau, related to the research and development of technology for reducing radar visibility, including the production of low-visibility antennas, led to the creation of a section for the production of flexible printed circuit boards in the Sukhoi Design Bureau, which made it possible to abandon the expensive services of subcontractor enterprises and manufacture our own antennas and means of reducing radar visibility.

During the R&D, more than 200 contracts were concluded for the development of SC and complexes. Nothing "old" was used, everything was "new", the T-50 aircraft took off on its first flight with all new units and "its own" systems, the ideology of which was laid down by the developers in 2001.

The implementation of the T-50 project became possible largely due to the established team of like-minded people, not only from the Sukhoi Design Bureau and the Sukhoi Company, but also from the cooperative enterprises.

Results of the first period of formation and implementation of the program:

1. Thanks to the active position of the Sukhoi Design Bureau, the concept of the Russian Air Force for the PAK FA project was formed with significant differences from the LFI. As a result, work on the LFI and MFI was stopped, and work on the PAK FA was started. The TZ (TECHNICAL REQUIREMENTS) was adjusted.

components were formed systems (SC), including the power plant and locator.

3. The draft of the KTP for the development and production of PAK FA was formed and agreed upon.

4. The preliminary design of the T-50 product was successfully presented to the state customer and defended.

5. A decision was made on electronic design, information transfer, preparation of production and manufacture of the aircraft with the participation of an electronic model and electronic documentation. This required the creation, coordination and approval of regulatory documentation on the relationships of all participants in the process.

6. A general cooperation agreement was signed for many years, defining the relationship between the developers of the PAK FA and its systems.

By Protocol No. 3c of the Commission of the Government of the Russian Federation on Military-Industrial Issues dated April 26, 2002, the decision of the Commission of the Russian Ministry of Defense on the competitive review of preliminary designs for the fifth-generation aviation complex was approved, which determined the Sukhoi Design Bureau to be the prime contractor for the work, and instructed the prime contractor to issue the TOR (TECHNICAL REQUIREMENTS) for the R&D work.

By order of the Government of the Russian Federation of December 4, 2002 No. 1699-rs, the KTP for the creation of the PAK FA was approved, the state customer of the work (the Russian Ministry of Defense) and the prime contractor of the KTP (OAO Sukhoi Company) and the prime contractor of the R&D (OAO Sukhoi Design Bureau) were determined, the deadlines for completion and the amounts of funding for the main stages of the work were determined.

In pursuance of the Government Order of July 21, 2003, the Russian Ministry of Defense concluded a state contract with the Sukhoi Design Bureau to carry out experimental design work on the development of the PAK FA (designation code "Stolitsa-1"), and on August 14, 2003, an agreement was concluded between the Sukhoi Design Bureau and the Sukhoi Company.

By the protocol of the meeting of the Commission of the Government of the Russian Federation on military-industrial issues of November 28, 2003 No. 5c, the program was defined as a pilot project implementing new approaches and principles for the creation of weapons and military equipment models for the Russian Ministry of Defense; the complex itself was classified as a priority weapons and military equipment model.

Development

At the stage of the Preliminary Design, the leader of the topic was not officially appointed, but de facto, it was M. Yu. Strelets. By September 2004, all technical materials and books of the EP were developed. The only layout option based on the layout of the 3I Avanproekt was presented for the EP defense. However, at the EP stage, a number of significant changes were made to the layout. For the first time, instead of a compensated one, an uncompensated deflectable influx (analogous to a deflectable nose) was used. This feature made it possible to make the PCH a more functional element, allowing not only to provide a reserve of the diving moment at high angles of attack, but also to be included in the work together with the wing, creating a common carrier system operating at various flight angles, similar to a rotating nose, increasing the load-bearing properties of the aerodynamic configuration. Ensuring increased requirements for the FLIGHT AND TECHNICAL CHARACTERISTICS (FLYING AND TECHNICAL CHARACTERISTICS) at supersonic speeds, taking into account the gradual increase in the mass of the airframe and systems from stage to stage of the R&D, required, when moving from the AP to the EP, the use of an additional decrease in relative heights when setting the longitudinal profile of the fuselage. This led to the fact that the use of a "semi-recessed" engine air intake practically degenerated into an "extended" air intake, and, taking into account the limitations on the clearance of the layout, the need for under-fuselage placement of suspension points for weapons, it was decided to develop a new air intake. Low clearance was due to the need to ensure an operational approach to almost all ground handling points without the use of additional means and, what turned out to be more important, to minimize the overall dimensions of the landing gear themselves in order to minimize the volume they occupied in the layout. When developing a new air intake, it was necessary to solve the problems of ensuring a performance level not worse than the "semi-recessed" one, improve the LTH (flight performance characteristics) and weight return when integrated into the layout, while ensuring its regulation. As a result, an air intake of the so-called "parallelogram" type with an "oblique" regulation system was developed for the first time. This design, as it turned out, was used for the first time not only on a domestic device, but also in world practice for devices of this class. As a result, a geometric scheme for setting the theoretical contours of a parallelogram air intake was developed, which formed the basis for the TP stage. In parallel, the improvement of the aerodynamic scheme and the development of local aerodynamics of the airframe continued.

Starting from the AP stage, the layout of the compartments and the variant as a whole were laid down with maximum density. The solution to this problem seemed extremely important, since it was necessary to compensate for the increase in the geometric and weight dimensions of the scheme in the presence of cargo compartments, as well as the increased, relative to foreign analogues, dimensions of the ASP placed inside the fuselage. Work on increasing the density of the layout was continued at the EP and TP stages.

Technical project

At the TP stage, individual changes were made to the layout, the main ones being: organizing the upward deflection of the PCH; changing the direction of the POSH retraction; increasing the length of the rear fairing of the TsKhB.

Starting from the draft design, with deep elaboration at the TP stage, the appearance of the PAK FA R&D MC was fully formed. Thus, together with the design division of the Sukhoi Design Bureau, a multi-antenna AFAR in a low-profile configuration was developed at the JSC NIIP, effectively fitting into the aerodynamic contours of the airframe. Together with other related companies, fundamental design solutions were agreed upon and designs of multifunctional antenna systems and complexes were developed. At the same time, their maximum integration with the design and contours of the airframe was ensured. The tasks that the PAK FA onboard equipment complex had to solve were significantly expanded compared to the tactical aircraft of the previous generation. In deep integration with the onboard equipment complex, a unique appearance of the information and control system (ICS) was developed, which is the central computing and logical core of all processes and has absorbed the intellectual functions of the so-called "second pilot".

According to the memoirs of A.N. Davidenko:

"In April 2006, the TP was presented to the State Customer Commission. It contained 23 volumes of explanatory notes, 16 volumes of additional materials, 20 volumes of technical documentation, lists, etc., 30 conclusions. The commission's work period was scheduled from 19 to 28.04.2006. The commission itself was approved by the Deputy Minister of Defense of the Russian Federation and consisted of 187 people, only 9 of whom were representatives of the developer - the Sukhoi Design Bureau. The chairman of the commission was A.N. Zelin - Deputy Commander-in-Chief of the Air Force. In addition to the technical project, the commission reviewed the created electronic model of the aircraft, its operating system based on the same EM, a cockpit model and all additional materials."

At this time, other issues were also being resolved:

- reorganization of the management system of both the program and the company, which ended with the creation of the T-50 Directorate;

- in the interests of future pages of the T-50 R&D, work was carried out on structural, professional and quantitative issues at the Sukhoi Design Bureau.

All this took place against the backdrop of the formation of a new State Defense Policy until 2015.

The Comprehensive Target Program for the Implementation of the PAK FA (CTP), approved by the government, played a huge role in the implementation of the program, ensuring the unification and solution of problems in the interests of creating the PAK FA.

In 2005, the KCP was seriously adjusted in terms of the financing model and terms. This was the subject of a meeting of the RF Government's Military-Industrial Commission in November 2005 and a report by the Director General of RACA, Yu.N. Koptev.

A decision was made to finance the program with budget funds through the Ministry of Industry and Energy (MIE) within the framework of a separate State contract for the implementation of the R&D project “I-21 Technologies”, within the framework of a state defense order outside the state armament program; subsequently, the Ministry of Industry and Trade of Russia becomes the legal successor to the R&D project “I-21 Technologies ” .

This was also an innovation, before that the Ministry of Industry and Energy of the Russian Federation concluded contracts for research and development (R&D) with a deadline of no more than a year, and here funding was allocated for three years and had a technological focus. On January 13, 2006, an agreed decision was made by the State Customer to adjust the terms of the program, specifying the funding volumes for the next three years (three-year funding). Submission of the technical design was scheduled for March 30, 2006, RKD - June 30, 2007, preparation for production and manufacture of the OO - December 10, 2010, testing stages until December 10, 2015, the first flight in the 1st quarter of 2009, the start of manufacturing the UP aircraft - December 10, 2014.

RKD

The stage of development of working design documentation (WDD) began in 2005. One of the most important areas of work carried out under the leadership of the Deputy Director General for the KBO (ON-BOARD EQUIPMENT COMPLEX) V.B. Polyakov was the transition from a federal system for constructing the KBO (ON-BOARD EQUIPMENT COMPLEX) to an integrated one. A distinctive feature of this version of the KBO (ON-BOARD EQUIPMENT COMPLEX) is the allocation of an information control system in which secondary processing of signals from all KBO (ON-BOARD EQUIPMENT COMPLEX) systems is performed, and aircraft systems and combat use are controlled. The developer of the IUS and the corresponding software was the developer of the aircraft.

All “systemic” mathematics, data exchange via multiplex channels, management and control of general aircraft equipment were taken over by the created structural divisions of the Sukhoi Design Bureau, united into the scientific and technical center (NTC) of the IUS.

Center of the IUS, under the leadership of Chief Designer D.I. Gribov, was assigned the function of not only developing system software and linking the functional software of the aircraft components and systems, but also manufacturing, testing and delivery to the customer of experimental, and subsequently serial samples of the IUS.

Sukhoi Design Bureau acquired and successfully developed a fundamentally new competence. The main advantages of the integrated on-board equipment complex (OBORUDOVANNYE EQUIPMENT COMPLEX) include:

- expansion of the list of tasks performed by the aircraft and their complication;

- improving the quality of tasks being solved;

-increasing the degree of automation of control and indication,

All this made it possible to reduce the workload on the pilot and significantly simplify maintenance and pre-flight preparation.

To ensure the implementation of the program, the following were created for the first time:

KNS (complex ground test facility) is a full-scale, but non-flying aircraft, equipped with all systems and complexes, which made it possible to conduct ground testing of the aircraft's systems and complexes in a single information field under the control of the IUS;

a PNM (semi-naturalistic modeling) stand using an anechoic chamber and an IUS stand for testing and debugging the IUS software and components of the on-board equipment complex (OBC) and aircraft systems.

The T-50-0 aircraft was built to conduct static tests.

During the work carried out at stand 27 (testing of the KSAP) at the testing ground in Tomilino, a full range of work was completed to ensure the safe ejection of the pilot.

Despite the need to solve a large complex of diverse tasks (from air combat to reconnaissance and destruction of ground and surface targets), the T-50 aircraft was initially designed with one pilot. The second pilot was designed as a virtual one. This is a complex of "intellectual support of the crew". The designers of the Sukhoi Design Bureau, in cooperation with the enterprises - co-executors, managed to implement a set of measures to create an intelligent cabin.

The first aircraft had a simplified composition, and this was of great help in mastering the documentation and meeting the set deadlines for construction and development of the OO. The logic was simple: the first aircraft in production was an aircraft for static (strength) tests (T50-0) - this is the airframe, canopy and chassis - this is priority No. 1. The second - KNS (T-50-KNS) - an aircraft for ground development and testing - working systems are added to the first group, but the fact that it is not flying creates some opportunity for iterations. The first and second flight (T-50-1, T-50-2) - aircraft for testing and development of flight-technical and maneuvering characteristics, strength, gas dynamics and everything connected with this. T-50-3, 4 and 5 - these aircraft were intended for testing the ASP KBO (ON-BOARD EQUIPMENT COMPLEX) systems and continuing work on the airframe, aerodynamics, OSO and SU. Of course, there were some overlaps. Communication, navigation and IUS should work on all aircraft, starting with the first one. But in general, this logic determined that first of all we need the KD and everything that concerns the airframe, SU, OSO and the KBO (ON-BOARD EQUIPMENT COMPLEX) that is needed to start testing. Secondly, everything else. This logic became the basis for technical solutions and schedules for the transfer of documentation to the plant.

Production

The lead contractor for the construction of prototypes of the T-50 products was determined to be the serial plant "KNAAPO named after Yu. A. Gagarin" in the city of Komsomolsk-on-Amur under the leadership of General Director A. I. Pekarsh.

A technical council was created for the "Launch of Production of T-50 Prototypes" consisting of representatives of the Sukhoi Company, Sukhoi Design Bureau, KnAAPO, and NAPO to organize work on technical re-equipment and organization of production, on technological support for the development of design documentation, on preparation of production, on information technology, on the development and mastering of new materials and technologies, on the analysis of the economic efficiency of design and technological solutions and production.

In mid-November 2006, a meeting was held at the KnAAPO named after Yu. A. Gagarin in Komsomolsk-on-Amur with the participation of all potential participants in the aircraft construction process. For the first time, they were all informed of the following: information about the T-50, proposals on the timing, the order of work, the composition of the production cooperation, etc.

In June 2007, the plant received all the design documentation for the T-50-0, 1 and the first stage of construction of the KNS. Active work began on the construction of these aircraft, design and technological testing was carried out, and these activities provided additional material for refining the design documentation itself.

The production of 3 aircraft was launched: T-50-0, T-50-KNS, T-50-1. 2007 and 2008 were spent on preparation of production, technological development and correction of documentation, production of parts and assembly of units, their joining and development of some systems. This required increasing participation of specialists from the plant and the design bureau, many issues required solutions on site.

During this period, the Komsomolsk-on-Amur Branch of the Design Bureau under the leadership of I.V. Gusev carried out a huge amount of work. The designers and engineers of the branch became a strong link between the Moscow site and the plant, and provided almost round-the-clock design support for the work.

A separate major problem of the plant is the test objects (TO) for the bench development of the Sukhoi Design Bureau on the T-50 theme. Among them were three head parts with a canopy, an air intake with an air channel of the Su, three wing boxes, a tail section. 18 objects for bench tests were manufactured to conduct tests on the operability and initial service life of the systems and units of the T-50 product of the 1st stage.

In the end, all of this was done and tested, including what needed to be done for the first flight, despite the fact that the rocket stand was lost during one of the first tests due to a malfunction of the braking system. It and the warhead (the test object) had to be restored.

The creation of large-sized KM panels, skylight glazing, mechanization, etc. required large and complex tooling, which had to be manufactured at the factory.

High-precision equipment was purchased for the manufacture of mechanical parts, which allowed to improve the quality and reduce the manufacturing time of parts several times. The production of welded tail booms of the product was mastered on a modern electron-beam welding unit. To improve the quality of assembly inside the tank assemblies of the middle part of the fuselage, a rotary stand was designed and manufactured, allowing for the installation of the pipeline in a vertical position. A chamber for applying a radar-absorbing coating was built and equipped. Given the closed nature and uniqueness of the T-50 product design, protected assembly areas for the T-50 aircraft were formed in the unit-assembly shops.

The construction of prototypes at a serial plant subsequently made it possible to significantly reduce the time and financial costs of mastering serial production of aircraft.

On January 29, 2010, the first flight of the first prototype of the T-50 aircraft took place at the airfield of the KnAPO named after Yu. A. Gagarin in Komsomolsk-on-Amur. The aircraft was piloted by test pilot S. L. Bogdan. By decision of M. A. Pogosyan, in order to reduce the time frame, the fundamentally new combat aircraft was first launched not at the Gromov Flight Research Institute in Zhukovsky, but at a serial plant.

This was preceded by many months of intense work by a complex team of specialists from the Sukhoi Design Bureau, the Design Bureau branch, plant workers and related specialists. A complete testing of the systems and complexes that ensure flight was carried out. More than 50 engine races were carried out to test the power plant, auxiliary power plant, fuel system and control system. In order to ensure the regime events, the races were held mainly at night.

To perform the first flight of the new aircraft, with new engines and systems, it was necessary not only to obtain conclusions from specialized institutes on almost every system, but also to hold a Methodological Council at the Gromov Flight Research Institute. This most important section of work was assigned to the first deputy chief designer M.Yu. Strelets.

The first flight summed up the results of the great work done, confirmed the correctness of the technical decisions taken, and opened the way for the aircraft to the sky. On the other hand, it was the first step in implementing the test program. It was necessary to perform about 6,000 test flights, teach the aircraft not only to fly, but also to fight, i.e. to make it a full-fledged combat aviation complex.

First tests

The initial stage of testing was carried out at the Sukhoi Design Bureau Flight Research Institute base at the Gromov Flight Research Institute airfield in Zhukovsky.

Before the tests began in Zhukovsky and Akhtubinsk, the laboratory and testing base was modernized and equipped at the LiiDB base. Two protected information facilities (PIF) for processing and analyzing flight information were created and put into operation.

On April 8, 2010, the An-124 Ruslan transport aircraft delivered the T-50-1 and KNS aircraft to Zhukovsky, and on April 29, the T-50 aircraft, piloted by S. L. Bogdan, made its first flight at the Moscow site. Preliminary flight tests of the aircraft began.

Between April 2010 and August 2011, a team of testers led by aircraft leader M.V. Lakhtin completed more than 100 flights.

Preliminary tests of the first stage (PI-1) were conducted from 2010 to 2014. The main characteristics of the aircraft and its components were brought to a level that ensured the solution of the tasks of the first stage of testing. General aircraft systems, power plant, navigation system, communications system, and onboard equipment complex were tested.

In addition to the T-50-1, the T-50-2, T-50-3, T-50-4 and T-50-5 experimental aircraft, built in 2011-2013, took part in PI-1 and were connected as they were ready.

In 2014, the second stage of preliminary tests (PI-2) began.

Simultaneously with the flight tests of the T-50-1 aircraft, ground tests of the T-50-KNS were conducted, which made it possible to test the systems and units of the T-50 aircraft without distracting the flight models.

One of the main requirements specified in the TTZ (Technical Assignment) for the T-50 aircraft was low radar signature. Therefore, in 2011, a decision was made, agreed with the Russian Ministry of Defense, to apply a radar-absorbing coating to the T-50-KNS object. For this purpose, the object was relocated to LAZ named after V.P. Voronin (Lukhovitsy ) , where the radar-absorbing coating (RAC) was applied in the paint booth.

To assess the radar visibility level, the T-50-KNS was relocated to the VUNTS VVS VVA testing ground to conduct measurements. Based on the results of these works, a report was prepared, the conclusion of which confirmed the main requirements in terms of the radar signature specified in the technical requirements for the T-50 aircraft.

In addition to flight tests of the T-50 objects, the OKB conducted a huge volume of ground rig tests. Some of the rigs were located on the territory of the OKB in Moscow, some of the rigs and equipment were at the Flight Research and Design Bureau in Zhukovsky, some of the rigs and laboratory facilities were at the FKP "SC NIPAS named after L.K. Safronov" in Faustovo , and some were at co-executor enterprises.

The evaluation of the characteristics of the power plant with the 117 engine, in order to reduce the testing time and improve the safety of test flights, was carried out on the Su-35 (10M-10) aircraft, lead engineer Yu. A. Pronin. The tests were carried out with the participation of specialists from the A. Lyulka Design Bureau, chief designer V. V. Kiryukhin and the head of flight tests E. V. Balukov .

In total, more than 190 flights of the power plant were performed between January 2010 and March 2017. Thanks to the results obtained, it was possible to significantly reduce the volume of flight tests in terms of Product 117 and VSU-117 on T-50 experimental aircraft.

On January 17, 2013, S. L. Bogdan made his first solo flight from Komsomolsk-on-Amur to Zhukovsky on a T-50-4 aircraft, making three stops in Chita, Kansk and Chelyabinsk. After that, all experimental aircraft "arrived" at the Sukhoi Design Bureau's Flight Testing and Design Bureau base in Zhukovsky only "under their own power."

There were also some problems during the work, which affected the timing of the work on the R&D project “Stolitsa-1”.

On June 10, 2014, during a test flight on the T-50-5 aircraft, the left engine failed. Pilot R.V. Kondratyev turned off the engine and landed. After leaving the runway, a fire broke out and the aircraft was damaged.

In 2013, Chief Designer A.N. Davidenko fell seriously ill and the management of the project was taken over by First Deputy Chief Designer M.Yu. Strelets. It was he who had to solve the most difficult task of transforming the aircraft from a prototype into a combat aviation complex.

Second stage

By the beginning of 2011, based on the results of static tests and computational studies of the airframe structures, insufficient strength and rigidity of the middle fuselage section (MCF), in the center section area, and the tail fuselage (TF). Insufficient rigidity of the TF affected the efficiency of the VO and GO controls and led to the impossibility of the aircraft reaching maximum speeds when flying near the ground. In addition, based on the results of ground tests of the airframe components, it became clear that some design solutions implemented in the frame required adjustment. As a result, the chief designer decided to prepare proposals for the creation of second-stage prototypes devoid of the identified deficiencies.

Several options were prepared: starting from the maximum localization of changes in the center section area between the main cargo compartments and ending with changes throughout the entire volume of the fuselage, allowing for the maximum improvement of the entire set of airframe characteristics. But the option with the maximum modification of the frame led to a change in the planned wing projection, to a decrease in its sweep, and affected the design of the center section, starting from the main wing section and ending with the main wing section.

As a result, all the developed variants of the T-50 modifications were submitted for approval to the chief designer A.N. Davidenko and the executive director of the design bureau, based on the results of which a decision was made to implement a limited amount of changes to the center section design. The layout scheme with the greatest modification of the frame was not accepted, since it would have required a complete redesign of the wing panel frame assembly and an additional volume of ground and flight tests of the T-50.

Later, at a meeting with the General Director of the Sukhoi Design Bureau M.A. Pogosyan, a report was made on the considered options for upgrading the second-stage T-50 prototypes, indicating the areas of change in the frame and aircraft systems design. The General Director approved the choice made in favor of introducing a limited amount of changes to the airframe. By Decree of the Government of the Russian Federation of December 23, 2011 No. 1116-36, the aircraft of the pilot batch were introduced into the Stolitsa-1 R&D project as second-stage prototypes for the purpose of introducing new technological solutions and design changes.

On March 30, 2013, together with the Ministry of Defense of the Russian Federation, a Decision was drawn up “On the procedure for manufacturing and connecting to testing of prototypes of the T-50 of the second stage.”

Production of the first samples of the second stage

The design documentation for the second-stage prototypes (T-50-6 and later), in terms of the airframe and communications (pipelines and harnesses), was completely reissued . The changes also affected the design documentation for the aircraft systems, but to a lesser extent.

During the re-release of the design documentation for the airframe structure, measures were introduced to retain the mass of the frame. Within the framework of these measures, a new aluminum-lithium alloy 1461 was used, developed by the VIAM team, which had 30-40% better specific characteristics, which in the future allowed to reduce the mass of the T-50 airframe structure by 100-120 kg. The results of strength tests of both the simplest samples and complex parts (in particular, the under-canopy rigidity) gave confidence in the correctness and success of the implementation of this material.

Work on introducing the new alloy into production lasted for a year and encountered a large number of problems: when heated in various ways, including during milling, the material released toxic substances, but their concentration level did not exceed the standards prohibiting the use of this material in production. As a result, additional measures were developed to protect personnel in production.

At the initial stages of manufacturing parts, there were occasional cases when, when cutting semi-finished products, cracks appeared in the material, or parts warped during thermal or mechanical processing with a strong deviation of their shape from the theoretical contour. These features in the behavior of the material led to the introduction of semi-finished product checks at intermediate stages of processing and the search for additional methods for securing large parts.

Difficulties with alloy 1461 also arose at the stage of assembling structures: the material turned out to be very sensitive to impact effects, which almost completely excluded the possibility of using impact riveting. A list of measures for assembling structures from alloy 1461 was developed and implemented, as a result, the KnAAZ plant named after Yu.A. Gagarin carried out a commission assembly of the air intake. Which proved the technical feasibility of not only working with parts from this alloy, but also the production of complex prefabricated structures from alloy 1461 without cracks and deviations from the theoretical contour. Later, parts of the new aluminum-lithium alloy were used in the production of the first prototypes of the second stage.

In parallel with the development of alloy 1461 at the experimental production of the Sukhoi Design Bureau, together with NIAT and VIAM, research was conducted to develop measures for working with structures made of this material and to find the reasons for such behavior of the material itself. Gradually, they came to an understanding of the features of this material. Later it turned out that the material supplied by VIAM for the manufacture of the first simple test samples and under-canopy rigidity was not from the average sample, but specially selected with high characteristics, and semi-finished products from it underwent additional mechanical processing (forging) before being sent to the Design Bureau. Re-melting of the entire supplied batch of material and additional forging in the conditions of a serial aircraft plant turned out to be impossible.

The decisive factor in the issue of introducing the new aluminum-lithium alloy 1461 was the test of the static sample T-50-7, during which a fan-shaped destruction of the power frames in the middle part of the fuselage, as well as individual walls and belts, occurred upon reaching half of the calculated loading case. The results of the static tests were stunning: the airframe structure was destroyed not in one place or several local zones, as often happens, but on a large scale, and the main reason for such destruction was the absence of a zone of plastic deformation of the material before destruction. "The airframe structure behaved like an old dry stump," which finally convinced the chief designer M. Yu. Strelets (since 2013) to abandon the use of this material in serial T-50s and switch to parts made of "classic" alloys. The abandonment of alloy 1461 in the design of prototypes occurred gradually and step by step, since prototypes T-50-8, -9, -10 had already been laid down on the stocks by that time). With each subsequent prototype T-50 released, the share of alloy 1461 steadily decreased (primarily in highly loaded parts) and by the time of the creation of T-50-11 the material was almost completely replaced, with the exception of several local places in unloaded parts of the frame.

The results of the strength tests of the restored and modified T-50-7 static machine (excluding alloy 1461) were positive: the design of the second stage airframe began to behave differently compared to the design of the first stage: due to the implemented changes, the distribution of loads on the airframe became more uniform, which made it possible to obtain a full strength pass in static tests.

The exclusion of alloy 1461 and the introduction of the second stage measures led to an increase in the weight of the airframe, but made it possible to meet the overload requirements, moreover, with a reserve that was confirmed by the results of flight tests at the State Flight Test Center.

Unfortunately, the introduction of the new aluminum-lithium alloy 1461 led to a delay in the production of the second-stage T-50 prototypes and their delivery. Only by 2016-2017 were 6 T-50 second-stage aircraft manufactured and connected to testing: 5 flight and 1 static.

It was on the prototypes of the second stage that the bulk of the work and testing was carried out to transform the T-50 aircraft into a combat aviation complex.

From prototypes to combat aviation complex

In 2014, the first stage of testing was completed and the T-50-2, T-50-3 and T-50-4 aircraft were relocated to the 929th State Flight Test Center of the Ministry of Defense of the Russian Federation in Akhtubinsk for submission to the State Joint Tests.

The second stage of testing began.

Later, aircraft of the first and second stages were connected to the GSI, with tasks divided by objects. The largest number of tasks were solved by aircraft of the second stage.

For the T-50, the period of implementing ideological decisions incorporated into the basic platform has begun, bringing the characteristics up to those specified in the TTS (TECHNICAL REQUIREMENTS) for the complex, and confirming them with the Russian Ministry of Defense.

At that time, a team of designers, technologists and production workers was formed and gained experience in the Sukhoi Design Bureau and related organizations. A team was formed from specialists who had started designing the T-50 and gained experience, and young people. Much credit for this goes to the company's youth policy, specially organized under the leadership of M.A. Pogosyan and M.Yu. Strelets, back in the late 1990s. Thanks to a single team that combined experience and youth, it was possible to accomplish a difficult task - not only to teach the aircraft to fly in all required modes, but also to use weapons and solve the most complex issues.

In the process of bringing the T-50 to the appearance of the Su-57, while maintaining the external appearance, the aircraft changed significantly in terms of systems and equipment. Preserving the external appearance made it possible to continue flight tests in terms of aerodynamics, stability and controllability, individual systems and a set of onboard equipment on the experimental aircraft of the first stage (T-50-1, -2, -3, -4 and -5). And in the future, they will be carried out more intensively on the aircraft of the second stage (T-50-6, -8, -9, -10 and -11).

In the period from 2017 to 2019, the company's management, represented by I.Ya. Ozar and M.Yu. Strelets, organized work to solve key problems, in the volume necessary to obtain a Preliminary Conclusion and launch production of the pilot batch of aircraft.

A major contribution to solving key issues and problems was made by Deputy Chief Designers in the following areas: in terms of flight tests Yu.F. Serov, in terms of the onboard equipment complex, aviation weapons and their tests V.M. Knyazev and V.B. Murzin. Throughout the T-50 project, a key role in organizing the work was played by First Deputy Director of the program B.M. Savelyev. Great credit for solving the most difficult issues goes to First Deputy Chief Designer V.A. Runishev .

One of the main areas was to expand the range of altitudes and flight speeds of the T-50 to those required in the TTZ (TECHNICAL ASSIGNMENT). This area required a comprehensive approach and solutions to many related issues related to the aircraft's internal systems. To solve them, since the beginning of 2017, M.Yu. Strelets organized a special Working Group on a permanent basis. On the part of PJSC "UAC", the work was under the control of General Designer S.S. Korotkov and First Deputy General Designer N.F. Nikitin. At this stage, the main causes of the factors that formed restrictions for further advancement in flight speed and altitude were identified. The importance of high-precision calculations in conjunction with a properly organized flight experiment became clear. Flight tests were organized with high intensity (85-90 flights per aircraft per year) while ensuring high efficiency.

A large set of works was carried out to ensure acceleration and range characteristics, measures were developed that allowed achieving record values of ferry flight range for operational-tactical aviation. As part of these works, a large-volume external fuel tank with reduced aerodynamic drag was developed and implemented with the possibility of placement on the existing airframe structure. Also, the volume of fuel on board was significantly increased, using insert fuel tanks, which made it possible to meet the requirements of the TZ (TECHNICAL ASSIGNMENT) for ferry range.

Using high-precision calculations on "supercomputers" and specialized flight experiments, Sukhoi Design Bureau specialists managed to push the restrictions to the required right boundaries in less than six months. The issues of ensuring the loads on the tail section of the fuselage, horizontal tail unit incorporated into the airframe design and control system were resolved, flutter phenomena on the vertical tail unit and wing mechanization were eliminated during flight at maximum airspeed pressure, including near the ground. Stable operation of engine air intakes at maximum Mach numbers was ensured, the operation of the air conditioning system at maximum flight altitudes was ensured, and other issues were addressed. Due to the fact that the T-50 has a large number of control surfaces and a reconfigurable integrated control system, it was possible to adapt the aerodynamic configuration using specialized algorithms and redistribute the loads on the airframe structures.

At that time, special attention began to be paid to the direction of high-precision calculations on a supercomputer. The Sukhoi Design Bureau acquired its own supercomputer, but many works were carried out in close cooperation with the RFNC VNIIEF. The specialists of this organization developed mathematical software products and separate modules for them directly for the tasks of the Sukhoi Design Bureau, allowing for quick and, as was later repeatedly confirmed, accurate solution of a complex of complex interdisciplinary problems.

One of them since 2015 has been the task of teaching the T-50 to use weapons. This was complicated by the fact that the entire modern range of Russian weapons was incorporated into the aircraft concept, most of which were used from internal compartments. The first, most difficult and atypical challenge was the use of products with an active start, the engine of which is turned on even before separation from the carrier.

For a composite airframe, it is not an easy task to withstand the load from such a product. The efforts of Sukhoi Design Bureau specialists have carried out complex experimental ground work to find and test measures to reduce the impact of the torch to the required value, as well as additional special protection of individual sections of the structure. These experimental works were carried out with the launch of the product both from the stand and from the ground-based T-50-KNS aircraft-stand. For the first time in Russia, RFNC VNIIEF created a software module that allows calculating with high accuracy the combustion of a torch of a solid-fuel rocket engine of a complex shape. It was on the basis of these calculations that the search and optimization of design solutions was carried out, and on March 16, 2016, the product was launched for the first time from the cargo compartment of the T-50 aircraft in flight.

As part of the work on the cargo compartments, the issues of reducing aeroacoustic loading and eliminating the buffeting of the launch device were successfully resolved. Based on the results of the work, an original design of the weapons compartment and launch device was proposed and implemented.

Also, with the help of multiple optimization using supercomputers in 2018-19, issues of using products with a catapult launch method, which has an unstable configuration, from the weapons compartments were resolved.

Since 2014, as the weapons themselves were ready, practically all types of ASP listed in the TTZ (TECHNICAL REQUIREMENTS) were systematically integrated onto the T-50, their use and interaction of the aviation weapons system with the components of the onboard equipment system were tested, and thousands of flights were conducted to ensure the integration of weapons and onboard equipment, including the radar station.

The cannon mount stands apart in the aircraft armament complex: due to the need to ensure low visibility on a 5th generation aircraft, it is integrated into the airframe design, which is made with extensive use of composite materials. Based on the results of the first ground tests of the cannon rig in 2014, it became clear that the implementation of explosion safety requirements and filling of links inside the compact cannon compartment requires a special approach. In combination with testing solutions on rigs, a supercomputer came to the rescue again. A gun compartment purge system was developed and optimized. Also, based on the results of calculating the trajectory of the links inside the compartment, the design of the link collector was changed . For the first time, gas flow calculations in the internal compartment of an aircraft were carried out with the same care and accuracy as is done for engine air intakes. And this yielded results - the problem was solved. It was verified both in ground and flight tests. The first use of the NNPU in flight was carried out on April 5, 2017.

Computational studies using supercomputer technologies have played an invaluable role

role in such a seemingly simple and comprehensively studied issue as the development of a canopy design. For the first time, in addition to the standard requirements for weight, heat resistance, bird resistance and safety during ejection, the canopy was required to have low radar signature. The introduction of a triplex design made of silicate materials required transparency, homogeneity and the application of special coatings. There were questions both about bird resistance: sealing the canopy glazing into the frame (too rigid sealing is not always good), and about the structure and number of layers in the triplex. Thanks to a large number of mathematical calculations, all this was successfully solved with a minimum amount of ground testing.

In parallel with the introduction of silicate glass, polycarbonate glass was developed together with JSC ONPP Tekhnologiya im. A.G. Ro -Mashina, the complexity of the application of which was associated with the formation and source of the material. As a result, a design of the sliding part of the lantern with polycarbonate glass was developed and successfully passed all tests. Today, there are developments in creating a PCHF with polycarbonate glass and built-in heating.

The design of the T-50 glazing with the frame, front and sliding parts of the canopy turned out to be unique and possessed properties that are not available to other canopies: bird resistance, high heat resistance and low radar visibility. The integrated emergency escape system allows safe ejection in the entire range of altitudes and flight speeds of the T-50 aircraft. It proved its operability in real conditions in one of the test flights.

One of the main properties of the 5th generation aircraft is low radar signature. Despite the conceptual solutions incorporated into the design and equipment of the T-50, almost the entire 2018 was spent on reworking design solutions, conducting research work on stands and implementing measures in the design of experimental and serial objects. Subsequently, at the end of 2018, as part of an inter-service flight and technical experiment, the required characteristics of the technical specifications for the level of radar signature were confirmed. For the first time in Russia, an aviation complex with the possibility of covert use was developed, built and tested.

Considerable efforts were also required to meet the requirements of the technical specifications in terms of a shortened landing run. Active work in this direction was carried out at the stage of flight tests of prototypes starting in 2016. Pilots S.L. Bogdan and R.F. Suleimanov participated in the flight tests.

At the first stage, they tried to solve the problem using instrumental means. The short landing was supposed to be carried out at increased angles of attack, and the limited visibility of the runway was to be compensated for by displaying images from additional cameras on the standard MFI in the cockpit. Landing at increased angles of attack increased the risk of the aircraft touching the runway. In order to ensure the required level of safety, the T-50-4 prototype was equipped with a whole system of cameras and backup devices determining the altitude parameters relative to the ground during landing as part of the short landing work.

The first flights with simulated landing at a certain altitude level or cloud showed that the picture on the MFI was displayed at a scale that distorted the pilot's understanding of the actual distance to the runway. And creating a picture at a scale of 1:1 led to the emergence of an "embrasure" effect with severely limited visibility. Moreover, landing speeds were still high, which did not provide the landing distance specified in the TOR (TECHNICAL ASSIGNMENT).

At the next stage, the technique of performing a shortened landing was adjusted: it was prescribed to perform landing at slightly lower angles of attack (at the limit of visibility of the runway from the cockpit) with the introduction of forced opening and release of the brake parachute before touching the runway. The calculation results showed that the inherent strength of the tail section of the fuselage allows it to withstand the loads from the brake parachute released before touching the runway. This method of approaching the landing made it possible to significantly reduce (aerodynamically) the landing speed of the aircraft at the moment of touching the runway, which significantly shortened the ground braking section. In order to ensure the release of the brake parachute at a strictly defined moment in time, additional audio prompts to the pilot and light information on the instrument panel were introduced, the inclusion of which was carried out automatically. It was possible to implement an automated release of the brake parachute, but landing is one of the most critical stages of the flight, in which the pilot must fully control the situation, so this idea was abandoned. In addition to releasing the brake parachute before touchdown, the wheel braking algorithms were modified to ensure a shortened landing. As a result of the work carried out, the T-50 aircraft began to fully meet the requirements of the TOR (TECHNICAL ASSIGNMENT) for a shortened landing distance, which was demonstrated by S. L. Bogdan at the MAKS 2019 exhibition. Thanks to the systematic work of the Sukhoi Design Bureau team, significant progress was made in all components of the onboard equipment complex, which made it possible to give recommendations for the production of an installation batch and further serial production.

But one area was especially difficult - the communication equipment and antenna-feeder devices. Starting in 2018, the Sukhoi Design Bureau specialists, with the support of specialists from NPP Polet and VNIIRA, redesigned the antenna-feeder system in a low-profile design to suit the capabilities of a digital communication equipment complex, taking into account the solutions to the problems identified during flight tests. Thanks to this, today the Su-57 is an aircraft with the maximum number of communication types, made in a low-profile design. During the design, issues of electromagnetic compatibility and integration of antennas into the airframe design were resolved, as well as their adaptation to the new generation communication equipment complex. Starting in 2018, a lot of work has been done on software and hardware changes and fine-tuning of the communication equipment complex itself.

With the increase in the intensity of flight tests, individual minor "diseases" began to appear, which were systematically cured. For example, during tests at speeds of about 500 km/h near the ground, increased noise-whistle in the pilot's cabin was detected. Based on the results of calculation studies and the development of various types of design, the source of the noise was localized; it was associated with the resonant exhaust of the air cooling system in the canopy design. Measures were promptly introduced on all aircraft to completely eliminate this effect.

By 2018, cases of engine damage by foreign objects entering the engine air intake channel had become more frequent on the T-50. To find and eliminate the causes, systematic work was organized to drastically reduce the likelihood of foreign objects entering the air intake channels. Based on the results of calculations on the simplest particles and experimental testing on the ground using special catcher nets, a set of special measures was selected and, starting in 2019, implemented.

Based on the results of the T-50 platform development in conditions close to real combat operations, the aircraft received new lighting equipment, in addition to energy-efficient landing lights: the cabin lighting was improved, new lighting equipment was introduced to ensure group flights at night. This made it possible to solve the problem of ensuring two conflicting requirements: stealth and safety.

At the same time, based on the results of the refueling system development, the Sukhoi Design Bureau team had to work on increasing the efficiency of docking with the tanker. This was done by improving the lighting technology of the refueling system, design changes to the kinematics of the refueling boom, and the formation of algorithms for approaching the refueling cone. To this end, the aerodynamics department, together with test pilots, carried out a large amount of work on flight stands and in flight tests.

In July 2017, the first stage of preliminary tests was completed, with the corresponding Act being issued, and a Preliminary Conclusion on the first stage of GSI was issued based on the achieved results. Further work within the GSI program allowed in May 2018 to issue the GSI-1 Act with recommendations on the launch of serial production of aircraft. In July 2019, based on the results of the preliminary flight test program, the PI-2 Act was issued, and on November 15, 2019, the set of design documentation was assigned the letter "O".

At the second stage (GSI-2), the most complex tests were completed on the prototypes of the second stage in terms of assessing the strength characteristics, flutter characteristics, stability and controllability characteristics, maneuverability characteristics were determined and super-maneuverability characteristics were confirmed. The main machines for this assessment were the T-50-8 (lead engineer E.V. Gorbunov) and T-50-11 (lead engineer - M.V. Lakhtin).

These tests allowed us to finalize the integrated control system - KSU-50, which allows for a high degree of safety in piloting the T-50 aircraft in any flight conditions. Additionally, an assessment was made and recommendations were prepared for the aircraft RLE in terms of interrupted and continued takeoffs in the event of an engine failure during takeoff. The specified characteristics of shortened takeoff and shortened landing were assessed and confirmed. The results of the work on assessing the strength characteristics, flutter upon reaching maximum values of overloads and flight speeds of the aircraft confirmed the readiness of the airframe, control systems, and power plant for serial production. In addition, a large amount of work was performed on the interfacing and combat use of almost the entire specified range of aircraft weapons. Positive recommendations were received for the combat use of both serial and new ASP samples developed for the Su-57 aircraft.

In June 2022, to test the characteristics with installed insert and external fuel tanks, test pilot A.V. Shendrik flew a T-50-9 aircraft from Komsomolsk-on-Amur to the Gromov Flight Research Institute airfield in Zhukovsky, with one landing in Novosibirsk.

In 2010-2018, during the flight tests, more than 4,500 test flights were performed, the flight and technical characteristics were confirmed for compliance with the specified requirements in the entire range of altitudes and flight speeds, which allows solving combat missions for the main purpose of the aircraft and ensures the use of aviation weapons against air and ground targets, conducting covert actions, day and night, in simple and difficult weather conditions, individually and in a group in conditions of enemy fire and electronic countermeasures, in addition, combat use was carried out with positive results, and this finally confirmed the readiness of the aircraft for operation and combat use.

In order to control the testing and timely decision-making on emerging problematic issues, the prime contractor and the cooperation enterprises formed a State Commission. Deputy Minister of Defense Yuri Ivanovich Borisov was appointed Chairman of the Commission. The Commission included representatives of the Russian Ministry of Defense and the enterprises participating in the cooperation for the creation of the PAK FA aircraft.

The decisions and recommendations of the State Commission helped to promptly resolve complex technical and organizational problems, which significantly reduced the time required to make decisions.

On December 5, 2017, in accordance with the requirements laid down in the TTZ (TECHNICAL ASSIGNMENT) for the aircraft, with the aim of further expanding its capabilities and increasing the level of combat effectiveness, the T-50-2 prototype made its first flight with the second stage engine (product "30"). The aircraft was controlled by test pilot S.L. Bogdan, the flight duration was 20 minutes, the flight task was fully completed.

The lead developer of the promising engine was determined to be JSC "UEC", the chief designer of the product was A.S. Zinoviev, under the leadership of the General Designer of "UEC" - Yu.N. Shmotin . Work on the creation of the promising engine was mainly carried out on the basis of the A.M. Lyulka Design Bureau, headed by the General Designer - E.Yu. Marchukov .

On July 3, 2017, by the decision of the Commander-in-Chief of the Aerospace Forces V.N. Bondarev, the T-50 products delivered to the operating organizations of the Russian Ministry of Defense were assigned the index Su-57. The completed volume of tests and the achieved results provided the State Customer with the opportunity to conclude contracts in 2018 and 2019 for the manufacture of aircraft of the pilot batch (for connection to tests) and serial aircraft (for delivery to operating organizations of the Russian Ministry of Defense). Taking into account the state of tests and readiness of the equipment, a decision was made to participate in the T-50 prototypes in a special military operation in the SAR in order to assess the aircraft's capabilities in solving problems in a real combat situation. The aircraft gained invaluable experience of operation in combat conditions with the combat use of new ASP.

On December 24, 2019, a flight accident occurred with the first aircraft of the Cy-57 installation batch.

The aircraft was performing a flight according to the acceptance test program, during which there was a sharp increase in the angles of attack and pitch with a drop in flight speed. After which the aircraft went into a flat spin and began to lose altitude. After reporting to the dispatcher, the pilot turned off automatic control and, changing the operating modes of the control system, tried to regain control of the machine, but it was not possible to stop the rotation and loss of altitude. At an altitude of less than 2 km, the pilot ejected.

After studying the data from the objective control system, it was established that the cause was a failure of the fly-by-wire control system, which resulted in an uncontrolled movement of the left stabilizer to the extreme pitch-up position.

Based on the results of the investigation, the commission determined that the cause of the accident was a combination of unintentional actions by the ground crew and features of the control system setup procedure that coincided with a single failure in the stabilizer control path.

As a result of the accident, additional measures were introduced for the Su-57 aircraft to increase the reliability of the control system and improve training procedures in order to completely eliminate the recurrence of similar incidents in the future.

As part of the experimental design work on the creation of the Su-57 aircraft, new advanced equipment for the flight crew was designed. The equipment mock-ups prepared and tested at the PI level are currently the most advanced in terms of the achieved characteristics: long-term transfer of maximum overloads, ease of operation for pilots, minimum weight of equipment. In the future, these prototypes should be included in the serial set of flight equipment used on all types of aircraft in the OTA.

In 2021, serial production of the Su-57 aircraft began at the Gagarin KnAAZ . Despite the need to manufacture serial Su-57 aircraft before the full completion of tests, the introduction of design changes and modifications required based on the test results, the team of the Komsomolsk-on-Amur plant ensured the delivery of serial Su-57 aircraft to the operating organizations of the Russian Ministry of Defense in 2021-2023. Every year, PJSC UAC fulfills all obligations to the Ministry of Defense for the delivery of 5th generation systems to the troops. This was preceded by extensive organizational and technical work together with related organizations to ensure the pace of production of components and their cost parameters.

The first serial Su-57 aircraft entered service in 2021 and were immediately included in plans for the training and retraining of technical and flight personnel of the units.

In 2018, the Su-57s gained their first combat experience in the Syrian Arab Republic, and the combat capabilities of the Su-57s were tested twice with new types of air-to-air weapons. Since 2022, the Su-57s have also been taking part in special military operation missions.

Thanks to the stealth properties of the system and its large range without in-flight refueling, the Su-57 aircraft has become a universal means for both performing combat missions of keeping watch in the air and for striking remote ground and sea targets.

Work is being carried out on a broad front to further improve the qualities of the Su-57 aircraft, give it new properties, and integrate new weapons. These decisions will allow us to make a confident step in the formation of the next generation combat system in the near future, where the Su-57 can become its central link.

Since 2013, the aircraft has been presented to the general public by participating in the International Aviation and Space Salon (MAKS) in Zhukovsky and the Army exhibition in the Patriot Park. Sukhoi test pilots demonstrated the aircraft's capabilities in solo and group aerobatics. On May 9, 2018, prototypes of the T-50-4 (pilot - T.A. Artsebarsky ) and T-50-5 (pilot - A.V. Shendrik ) aircraft took part in the Victory Parade on Red Square for the first time. Since 2019, prototypes of the T-50 aircraft have been taking part in the air part of the Victory Parade, flying in formation over Red Square in Moscow.

Development of PMI

In 2002, in accordance with the order of the President of the Russian Federation, it was proposed to involve foreign partners , primarily India, in cooperation in the creation of an export version of the PAK FA aircraft, renamed for this purpose as a promising multi-role fighter (PMI).

Beginning in November 2002, a series of rounds of negotiations with India were held on this issue, and a presentation of the PMI was held, during which the Indian side was presented with materials on the appearance and characteristics of the PMI and proposals were made on India's participation in the program. In October 2007, within the framework of international economic cooperation, an Agreement on Cooperation in the Field of Development and Production of a Prospective Multifunctional Fighter was concluded between the Government of the Republic of India and the Government of the Russian Federation. The main area of interaction between the parties under the General Contract was the joint development and certification of the PMI. In order to implement this area, a contract was signed in which the parties determined the order of work and its distribution at all stages of development, technical specifications and other issues.

M.Yu. Strelets was appointed chief designer of the promising multi-role fighter.

In 2009, a representative Indian delegation from the Ministry of Defense and the Hindustan Aircraft Corporation visited Moscow. Aeronautics Ltd. (HAL). During the visit, the parties discussed organizational and production issues of the project, and the Indian delegation also visited the aircraft plant in Komsomolsk-on-Amur.

In March 2010, the Russian Ministry of Defense and the Indian Ministry of Defense approved the tactical and technical assignment (T TZ (TECHNICAL ASSIGNMENT)) for the PMI. And already in December, as part of fulfilling the obligations of the 2007 Intergovernmental Agreement, a contract was signed for the development of the preliminary technical design of the prospective multifunctional fighter (ETP PMI) - as the first stage of joint work.

In February 2011, the parties completed the necessary formalities and confirmed the entry into force of the contract. The work under the contract was carried out in a constructive and friendly atmosphere. In August, the parties carried out a preliminary acceptance of the ETP materials and signed an act on the preliminary acceptance of the ETP materials and a protocol containing minor comments on the ETP materials, as well as proposals for improving the documentation. The elimination of the comments was completed in 2012, and in early 2013, the ETP documentation was delivered to India.

Megapolis

In 2016, as part of the work agreed with the Russian Ministry of Defense, the Sukhoi Design Bureau prepared an engineering note with proposals for further enhancing the functional capabilities of the 5th generation aviation complex. Based on this work, in 2017 the Russian Ministry of Defense issued a Tactical and Technical Assignment for the implementation of the second stage of the PAK FA development - the Megapolis R&D project.

In 2018, together with the Russian Ministry of Defense, a draft of the TOR (Technical Assignment) was developed, which was approved in 2018 and a state contract was signed for the implementation of the R&D work. M.Yu. Strelets was appointed as the head of the topic.

To effectively solve the tasks set, about 90 contracts were concluded with related enterprises. At present, flight tests of several prototypes are underway.
 
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QuadroFX said:

ПАКФА Т-50/Су-57 (часть 5) • Форум "Стелс машины"

Авиация, флот и космос - реальность и перспектива.
paralay.iboards.ru

ПАКФА Т-50/Су-57 (часть 5) • Форум "Стелс машины"

Авиация, флот и космос - реальность и перспектива.
paralay.iboards.ru
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This is awesome thanks! So they tested a short landing system with automatic parachute release; that’s really cool
 
So from reading the translation I could gather that the su-57 has an adaptive flight control system; the breaking system includes algorithms to improve breaking distance; they tested a high aoa landing approach and automatic parachute deployment coupled with cockpit displays for landing, that the aircraft antennas are made to be stealthy, that there were difficulties with the alloys and airframe strength, that there is an internal fuel thank that can be carried inside the weapons bay? I think this a very cool read; I wish we could get this kind of stuff from other programs.
 
Avimimus said:
Ah, interesting. I should have noted that the Sukhoi designs still have vertical stabilisers.

Was there a common influence? Is TsAGI still influential? I'm asking because of the highly swept wing combined with the small close-couple 'moustache' canards... it seems very similar in terms of aerodynamic approach.

P.S. If '602' looks like that - it'll be very interesting to see if E-721 ever gets declassified. I suppose '602' had between engine weapon bays like the PAK-FA/T-50?
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It's possible.
 

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paralay said:
Later it turned out that the material supplied by VIAM for the manufacture of the first simple test samples and under-canopy rigidity was not from the average sample, but specially selected with high characteristics, and semi-finished products from it underwent additional mechanical processing (forging) before being sent to the Design Bureau. Re-melting of the entire supplied batch of material and additional forging in the conditions of a serial aircraft plant turned out to be impossible.
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It sounds like the book and Sukhoi is blaming VIAM for essentially falsifying data on 1461 Al-Li alloy with cherry-picked samples and caused years of delay.

But to be fair Al-Li has always been a tricky material to work with, the T-50/Su-57 being mostly aluminum meant that Al-Li with better strength-to-weight ratio on paper seemed very attractive but it didn’t work out in the end.
 
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From OKB Sukhoi in 2018, some wing spars and nacelle area.
file.php
 
LMFS said:
And again, without even deploying flaps...
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The body layout is pretty close to an Delta wing, with the big Elevators sinking into the main wings and body.
Anyway, it should have plenty of lift surface, so take-off with the need for downfacing Flaps is something of the past.
You see the FCS do put the elevators with a nose down authority for a brief moment, which seems to me, it helps create additional lift upon final rotation and getting airborne.
Ofc you have the extended LEVCONS in the front too, they face down thus help create more lift.

A ridiculous short take-off.
 
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Looks like the aircraft is primarily made from aluminum with titanium primary load bearing/load path bulkheads/structure. One thing that does not work well is a metal structure and trying to adapt composite skins and it does not look like the SU-57 design does this. The GD/McAir A-12 as an example tried that and it was a disaster, lesson learned. The Russians have seemed not to embrace composites for their aircraft and the Su-75 will probably be constructed like the SU-57. If you are going to go composites, you have to go all in or nothing. Historically, it seems the Russians thought stealth had no value plus you have to do the R&D. The F-117 was basically a treated, rubber coated airplane which did work and the slab treatments were heavy but that was and is 1st gen LO. The Su-57 is not an LO fighter, cool design and very nimble but not LO.
 
The number of carbon fiber plastics in the structure Su-57 22 - 26 %, for F-22 - 24%

You probably don't know, but the Russians tested radio-absorbing materials back in 1976, but not on airplanes, but on ships. In the second half of the eighties, ships with such a coating were in mass production. The purpose of using these materials is not to make the ship invisible, which is obviously unattainable. And redirect an enemy cruise missile to a less significant place of the ship, for example, into the exhaust pipe
 

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Hydroman said:
Historically, it seems the Russians thought stealth had no value plus you have to do the R&D. The F-117 was basically a treated, rubber coated airplane which did work and the slab treatments were heavy but that was and is 1st gen LO. The Su-57 is not an LO fighter, cool design and very nimble but not LO.
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Like, su-57 has proper stealth geometry and a long list of costly rnd programs to make it work. It may be a more achievable LO level with different operational concerns (function of different military needs of a military power on back foot), but it is very obviously LO.

Before that there were kh-101/102 - one-way, but still factually LO "planes".
After that - S-70(VLO? Also, very high composite %), Kh-69.
In making - PAK-Da(VLO?), Su-75 (LO without visible su-57 compromises).

Also, Russians were in the end the only ones who actually killed a flying pre-LO canard delta program in favor of a LO reboot.

Your write-up just doesn't match that Russia does.

VKS clearly invested into stealth more than anyone other than US and PRC - i.e. those whom Russia just can't outspend.
 
Ainen said:
Like, su-57 has proper stealth geometry and a long list of costly rnd programs to make it work. It may be a more achievable LO level with different operational concerns (function of different military needs of a military power on back foot), but it is very obviously LO.

Before that there were kh-101/102 - one-way, but still factually LO "planes".
After that - S-70(VLO? Also, very high composite %), Kh-69.
In making - PAK-Da(VLO?), Su-75 (LO without visible su-57 compromises).

Also, Russians were in the end the only ones who actually killed a flying pre-LO canard delta program in favor of a LO reboot.

Your write-up just doesn't match that Russia does.

VKS clearly invested into stealth more than anyone other than US and PRC - i.e. those whom Russia just can't outspend.
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Like, su-57 has proper stealth geometry and a long list of costly rnd programs to make it work. It may be a more achievable LO level with different operational concerns (function of different military needs of a military power on back foot), but it is very obviously LO.

Looking at it's design, it seems they have focused more on the aero-performance efficiency rather than the LO aspect and that's OK but this is not in the class of an F-22 in regards to LO and not with those leading edge flaps not unless they get locked out for BVR.

Before that there were kh-101/102 - one-way, but still factually LO "planes".

Some very minor LO on the nose. Did they intend on only frontal minimal LO, probably?

After that - S-70(VLO? Also, very high composite %), Kh-69.

S-70, getting better but not there yet due to other features. KH-69, frontal aspect only.

In making - PAK-DA(VLO?), Su-75 (LO without visible su-57 compromises).

PAK-DA maybe real but don't know. SU-75, probably going to be built like the SU-57.

All I am saying the Russians seem to put more emphasis in aero than LO and again, that's OK. Russia including the rest of the world (and China) had and have a huge deficit in LO tech evolution, Northrop and Lockheed began their real LO work (with substantial company investments) in the "1950s!" also exploring work with composites and non-metallics especially in regards to Northrop R&D. The B-2s in the Balkans conflict could not be picked up or tracked even with low-frequency radar so we know at least US LO works. Not trying to start an argument, just pointing out some of the obvious.
 
Well composite skin tho is the only way i think if Russians wants a "maintenance free" Absorbers. I think Pogosyan's paper back in 2003 already suggested that. That's what i see from Su-57 construction, and i made speculation on the composition with.
 
Its much different operational requirements , they operate within own SAM umbrella mostly on own borders while US was historically attacking countries far away and overcoming AD was always of prime importance ,so US LO requirements will always be higher than either Russian on even European designs for that matter

Composite airframes will mature on UAVs , so far the orthodoxy of aircraft manufacturing treats composites like a lighter stiffer skin material that still held together with bolts same as metal skin ,only smaller parts like moving control surfaces actually see composites applied in the way composites will eventually be used
 
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paralay said:
The number of carbon fiber plastics in the structure Su-57 22 - 26 %, for F-22 - 24%

You probably don't know, but the Russians tested radio-absorbing materials back in 1976, but not on airplanes, but on ships. In the second half of the eighties, ships with such a coating were in mass production. The purpose of using these materials is not to make the ship invisible, which is obviously unattainable. And redirect an enemy cruise missile to a less significant place of the ship, for example, into the exhaust pipe
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Not just we know, but we all know about it

For a certain period of time (80s) the Kirov was rumored to be painted with RAM, making it's RCS looks like a 2,000 ton vessel. So do Udaloy and Sovremenny classes.

And, are you sure you want the funnels of your vessel to be the target?

God I feel old when typing these......
 
Honestly I think there are pratical limits to stealth. The fact is when we take the radar equation, and order it for detection range, range will scale according to the fourth square root of the RCS.
If we run the following thought experiment, plugging in reasonable values:
Let's say we have a radar which can detect an 1m2 target at 200km. (this is the upper bound I got for the F-15EX's APG-82 radar, which establishes a reasonable upper bound).
For the lower bound, I got 5m2 at 150km
Against an F-35, which is said to have an RCS of 1cm2 or 0.0001 m2, this gives a detection range of 10-20km.

For the Su-57, lets assume its RCS is 10x-100x that of the F-35,
this would give detection ranges of 17-35km in the 10x case, and 31.5 to 63km in the 100x case.

But, we must also consider that modern fighters have an impressive suite of others sensors (IRST etc.) which make getting close to them undetected practically impossible. *How* close is up to debate, but I think it's safe to say that 30km is well within the detection range and 60km maybe pushing the upper bounds (if we assume the SU-57s IRST is as good as the Eurofighters PIRATE, which is a claim I've definitely seen, it's possible, even from the front).

What does this tell us?

Even if we consider the most US-favoring scenario outlined here (Su-57 RCS 100x that of F-35, most optimistic parameters for F15EX radar (which afaik is better than the F-35s)), the F-35 just barely manages to have a real-world advantage in detection range, due to passive sensors on the Su-57.

If we run with more favorable (or middle of the ground parameters), the F-35 has no real world advantage.

And please consider that, it's not out of the question that the real world RCS advantage of the F-35 is less than 10x as my most optimistic estimate for the Su-57 was somewhat conservative as to not torpedo my own argument.

Also, I'd like to add a small opinion of my own: Americans like to assume that stealth technology is the crown jewel of fighter tech, and requires unparalleled sophistication, but I'm rather skeptical about the argument - adversaries had decades to catch up, the math behind it has been public since the 70s, the amount of computer power used to design aircraft such as the B-2 an F-22 is trivially available nowadays (or a decade ago) to anyone etc.
 
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paralay said:
The exhaust pipe of a Soviet ship is an empty fenced-in space, let a cruise missile fly there rather than into the Main Command Post
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So do every vessel design, an empty fenced-in space mostly, however are you sure you know what's beneath/connected with the exhaust right?
 
Elysium said:
For the Su-57, lets assume its RCS is 10x-100x that of the F-35, ...
If we run with more favorable (or middle of the ground parameters), the F-35 has no real world advantage.
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The F-35 will still have a practical advantage, particularly when it comes to EW. The Su-57 will need 10-100x the wattage to prevent burn through at any given range. Or the F-35 needs less wattage to produce the same effect.
IRST is miles better than where it's come from, but it is still relatively limited. The wavelengths mean you're going to get attenuation through weather (not like Europe ever has that), and detection doesn't mean identification or a target solution.



Overall, the questions you raise are valid and under-asked. How much is "enough"? In view of cost and availability, how much is "too much"?

I actually think the Su-57 reflects that balance pretty well. " Good enough" without the price tag and concerns about exotic materials and maintenance, etc. They don't have trillions to dump down a black hole to come out the other side with thousands of F-35's at reasonable prices. Water under the bridge, because we already spent that money and have a F-35 to order, but I wonder if we wouldn't be better off in light of recapitalization concerns having taken a more limited and affordable approach that we could produce in great number cheaply with mature technologies (and could have done it much more quickly).
 
Willythekid said:
The Size of Things: Human vs. Su-57

View attachment 749718

:rolleyes:
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I think it’s very kind of the Su-57 to pet his friend on the head. You never see this in the west... we need more kind 5th generation aircraft

also: the perspective on this picture is quite blown out, so it’s kind of difficult to discern proper scale here
 
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