Why do Russia’s Su-75 Checkmate and Su-57 have visible screws and rivets?

A screen grab from a video of RT news. Screws are visible on the airframe of Su-57 without any surface treatment. Source RT news.

In 1990, the Russian aviation industry was divided into four agencies: Ministry of Aviation Industry, Ministry of Industries, State Committee of Defense Industries and Ministry of Defense Industries. The latest change occurred in May 1997 when the Ministry of Defense Industries that was responsible for the military-industrial complex and civil aviation was dissolved and incorporated into the Ministry of Economy in the form of a Department of Aerospace Industry and Shipbuilding. On 21 August 1997, the reorganization of airspace and defense industry was formally announced to enable it to have a more equitable share of foreign arms sales. By the end of 1997, just five airliners plus seven helicopters were delivered to Russian airlines and about the same to foreign customers.

In early September 1997 after heated debates at the Ministry of Economics the plan entitled “Concept of Restructuring the Russian Aviation Industry Complex” was finally made public. Essentially the plan presupposed vertically integrated structures and large-scale merges and consolidation among aerospace organizations and research institutions. Four core enterprise groups were to emerge to promote 5-6 families of Russian aircraft within the country and in the world market: MiG-MAPO complex (military-industrial group); the Sukhoi group; the Tupolev group, and the Ilyushin group.

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The Russian government also looked to reorganize and revitalize Russia’s aircraft industry in the context of a larger restructuring plan for Russia’s defense industry. Specifically, large-scale consolidation of the aircraft industry took place with the government creation of the Unified Aircraft Corporation. Government officials have suggested using proceeds from Russia’s Stabilization Fund to support this new corporation.

Su-75 inherited the same problem of Su-57. Screws and rivets are visible on the surface of the Checkmate.

Russia remains a country with tremendous market potential for aerospace and defense industry services. After decades of restrictions on traveling abroad during the Soviet period, many Russians are now using the opportunity to travel extensively on business, study aboard and learn new technology. In order to cater to skilled manpower demand, the Russian aerospace and defense industry needs to overcome the current crisis and develop an improved aviation infrastructure.

As the Russian aerospace and defense industry consolidates, it is integrating more and more into the world market. The most important factors are:

  • Dramatic decrease in domestic defense orders
  • Decrease in acquisition potential of the Russian air force following the collapse of Soviet Union
  • Absence of a well-organized and transparent democratic system
  • Significant reduction in state investments into research and development
  • Highly dependent on foreign exports to sustain defense industries
  • Develop and produce composite wings for the Russian aircraft
  • Develop, design and manufacturing competency for composite airframe components
  • Lack of design and manufacturing framework for making composite structural components
  • Lack of skilled manpower to support industries

Aerospace Industries Under Russian Federation

 After the collapse of the USSR, this massive ministry was separated into four main holding companies: Unified Aircraft-Building Corporation (OAK), United Engine-Building Corporation (ODK), Russian Helicopters and the Tactical Missiles Corporation (KRTV). The idea was that four streams of design and development activity as opposed to forcing all of this activity through one single administrative structure would create certain synergies that would produce better and more advanced systems at a lower cost.

During the August 2019 MAKS Moscow Air Show, the head of the “aerospace cluster” within Rostec (Chalet J31), Anatoliy Serdyukov, gave a briefing to Russia’s RIA Novosti in the extensive plans for reforming the entirety of the industry. Rostec is the Russian state defense-industrial conglomerate that controls Rosoboronexport (ROE), the state-controlled arms export monopoly. Serdyukov himself was the Russian defense minister from 2007–2012 until being replaced by the current defense minister, Sergei Shoigu.

Debt Problem and Su-57

What appears to be the main point of contention in this proposed arrangement is that while Russia’s Su-57 is fiscally sound and has a healthy book, OAK has significant debt obligations.  Executives of the helicopter holding company have voiced concerns that they may be lumped in with the fixed-wing OAK to balance the financial books between the two.

Serdyukov’s response is that debt obligations accrued by OAK “were formed in the course of solving state problems. Therefore, the problem of their expansion requires a comprehensive solution with the participation of the state.” This seems to suggest that somehow a bailout of OAK might be forthcoming, either as a write-off of those debts or a flush of state orders.

Russian industry analysts have told AIN that in 2020 the next round of the Russian State Defence Orders (RosOboronZakaz) would be initiated and would keep Russia’s combat aircraft production lines running at a high level for the next two years, which could theoretically address part of the debt dilemma.

One of the most expensive programs in the stable of OAK’s new projects is the Sukhoi Su-57 fighter, which has so far been built in limited numbers. The program suffered a small setback on 24 December 2019 when an aircraft that had recently been rolled off the Komosomolsk-na-Amure factory production line was lost after conducting acceptance flights in an effort to complete product targets before year-end.

The fault of the crash appears to have been linked to the aircraft’s engine, which is still the same Saturn A-41F-series powerplant that powers the Su-35.  Serdyukov had been asked during his interview about the progress on the new, fifth-generation engine for the Su-57 and had not been able to provide a date for its availability to insert into the Su-57 program.

“The creation of the second-stage engine for the Su-57 aircraft is planned to be completed within the time agreed upon with the customer,” he stated, which in this case would be the Russian Aerospace Forces. “At the moment, prototypes of the engine are being tested…and special types of tests are being conducted.  Installation on production aircraft will be possible after the completion of the prototype validation process.”

Thus far neither Serdyukov nor ODK have given a date for the completion of this engine’s validation trials.  Industry insiders suggest that this would not be before the fourth quarter of 2021 or later, meaning that the Su-57 could remain at a low rate of production until then.

Sukhoi Su-75 Checkmate, a technological challenge for Russia

Sources in Moscow point out that the VKS desperately needs affordable fighters that can be built in large numbers, but the force’s leadership may not support Su-75’s production. It would also be problematic to sell this aircraft to export customers without it being a program of record in Russia.  Also, if there are no more than a handful of export sales, the numbers do not reach the required economies of scale to support a production run.

Su-75 inherited the same problem of Su-57. Screws and rivets are visible on the surface of the Checkmate.

A carrier variant of the Su-75 would almost certainly be proposed for the Indian Navy as a replacement for the MiG-29K carrier-capable fighter the force currently operates. The design team has also been evaluating the possibility of a two-seat variant, as well as an unmanned version, but there are no prospective buyers that have expressed interest in either of these options.

The big question mark is whether Moscow’s industry can carry through with this design concept to turn out a fully functional aircraft. The defense industrial base has suffered considerable contractions in its capacity and overall size since 2017. Critical personnel have also died in the last year due to the COVID pandemic, including the general designer of the NIIP radar design bureau, Yuri Beliy.

Su-57 canopy has bubbles which means the molding of the glass canopy was built with poor quality.

While the Sukhoi designers have proven they can turn out an actual prototype of this new aircraft, the non-ferrous/composite materials used in its construction may still be a question mark. In his presentation, Slyusar stated that it would take at least a year to complete the static “shake and bake” tests of the aircraft’s structure. This will be a real test of Russia’s composite materials industry, which is not nearly as well-developed as it is in the US or Europe.

Those materials are key to the aircraft’s low RCS. Not only would they have to be produced to extreme tolerances and the sections joined together without so much as a micron between them, but they would also have to have their radar-absorbing properties “baked-in” at the kiln for the aircraft to be a low-maintenance platform as advertised. But Russia’s approach to stealth in the past has been the opposite — a heavy reliance on coatings and appliques that are labour-intensive and require top-to-bottom refurbishing after every flight.

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The other factor is that what makes a modern fighter aircraft effective in combat are its onboard systems, which in the past have been the proverbial “long pole in the tent” of Russian fighter designs. The izdeliye 30 engine is not in series production yet and is still completing flight tests. Also, according to industry sources, Russia still has not designed a cost-effective AESA radar set and has problems with the technology required to manufacture the radar’s transmit/receive modules.

The MC-21 exposed lack of composites industries in Russia

UAC’s product range development strategy has not formally changed during the past year. Along with its target of boosting sales of the SSJ100, the company’s main emphasis is on completing the development of the advanced MC-21 medium-haul narrow-body airliner and, in the more distant perspective, to also succeed with the joint Russo-Chinese wide-body programme dubbed CR929. However, a stiffening of western economic sanctions is forcibly transforming the first two programmes from the once-popular format of wide international cooperation into smaller local projects.

In order to ring-fence the independence of Russia’s MC-21 aircraft programme from the uncertain availability of foreign-manufactured items, the Russian aerospace industry has successfully designed its own replacement parts for the advanced narrow-body aircraft’s composite centre-wing and wing box sections, Russia’s vice-premier Yury Borisov has revealed to Kommersant business daily.

Those parts were originally constructed from imported composite materials, deliveries of which were stopped after the USA imposed sanctions against Russian company Aerocomposite.

With the Russian industry designing its own replacement components, the foreign-made parts will gradually be phased out from the MC-21 project (Irkut).

Siemens helped Aerocomposites with its Digital Industries Software. Several factors led to the selection of Fibersim, including comprehensive functionality, multi-platform features, a unified digital thread from design to manufacturing and compliance with the software standards of United Aircraft Corporation (UAC).

NPK Khimprominzhiniring, JSC (a brand of UMATEX Group), a management company comprising an R&D centre and enterprises manufacturing high-strength and high-modulus carbon fibres (CF) and CF fabrics, was set up to form a market of composite materials in Russia.

The honeycomb core made of aluminium foil is referred to the category of composite materials that are very firm and light at the same time developed with the help from Germany.

Siemens is helping Russia develop a composites industry. photo by Siemens.

According to Borisov – after a recent visit to Aerocomposite, at which he was able to see for himself the specific structural elements consisting of the centre-wing and wing box assemblies being created without the need for US-made materials: “Our confidence [in the programme’s future] lies in real prototypes which have confirmed their performance parameters.”

The first problems with the deliveries of composites occurred in September 2018, when the USA imposed sanctions against Russian producers, namely Aerocomposite (part of UAC) and ONPP Tekhnologiya (part of Rostec), an action that prevented the USA’s Hexcel and Japan’s Toray from supplying composite material for the MC-21.

The timetable for the phasing out of all imported components will continue until the end of 2020 and will proceed in parallel with the certification of the base version of the MC-21.

European Union Cut-off Composite Supplies

Although the consequences of western sanctions for international cooperation in aircraft production have been widely discussed in Russia for quite some time now, the symbolic point-of-no-return was passed in the autumn of 2018, when the sanctions reached Aerocomposite and Technologiya, two of UAC’s subsidiaries that manufacture composite aircraft parts, thereby cutting off access to western supplies of composite materials. The resultant need to find locally resourced substitutes for western composites pushed back the MC-21’s certification schedule by a further six months to the end of 2020, and its service entry is now set for early 2021.

This is yet another delay for the MC-21 programme from its initial timeline but is not critical for the existing sales backlog, which has remained unchanged for several years at 175 firm orders, mainly from state leasing companies. Aeroflot is set to become the launch customer, with a firm order for 50 aircraft and options for a further 35. But the composite materials hiatus has revealed the technological vulnerability of the Russian aerospace industry, which remains heavily exposed to political risks. It has affected not just the MC-21 programme, but also the SSJ100 towards wider localization and import phase-out. On the one hand, this spells good news for domestic suppliers for whom the situation opens new windows of opportunity to take on leading roles in significant projects. For example, it has forced the acceleration of the PD-14 engine development, Russia’s first all-new commercial engine that is being adopted for the MC-21. In turn, this engine programme may grow into a platform for a family of engines.

Russia lacks machining, baked-in and molding technology

The “naked” skin of the F-35 is very stealthy without regard to any externally applied “coatings”.

The skin comprises a sophisticated CYCOM bismaleimide resin and very proprietary geometric laminations of carbon nanotube matte. The skin itself has different RCS mitigation capabilities at different depths and orientations of the matte and resin. It must resist flex, twist, thermal expansion and contraction, retain shape and stability under very high poly-axial physical loads, as well as retain those properties for several decades in the full spectrum of global environmental conditions.

The F-35 has a small opening which uses air traveling past the aircraft to cool down the fuel inside the aircraft. This is important because the F-35 uses fuel to cool many aircraft systems, including the exhaust nozzle, to make it less detectable on infrared and also so that things like the radar can use more power without overheating.

The F-35’s skin is highly effective at mitigating X-band and upper S-band radars, as well as having a useful degree of mitigation vs VHF-frequency radars.

An artist impression of naval variant of Su-57. Actual photo of clunky Su-57 aft and forward section. Look carefully, there are two big holes on the vertical stabilizers.

The F-35’s skin is so hard that it requires diamond-edged machine tools to drill, mill, cut etc. It is harder and stronger than steel, as well as being a superior microwave mitigation material. That is before any coating is externally applied.

The F-35 airframe is composite, not metallic. Lockheed-Martin has found a way to incorporate much of the radar adsorbing qualities into the skin of the aeroplane that previously had to be applied after it was finished. This has been described as a “conductive layer…where the magic happens” and a “fibre mat” that was the most extensive technical breakthrough of the entire program.

Final steps, once the composite skins are molded, trimmed and inspected, they are ready for attachment to constituent airframe structures.

What Russia does in their aircraft — airframe structure is accomplished with fasteners drilled through the skin and into the frame at predetermined locations. The process involves evaluation of drills, drilling tool geometry, tool efficiency, tool life, hole-drilling time, cost per hole drilled and other variables; hence the Sukhoi Su-75 and Su-57 have screws and drill holes. Thanks to poor quality, screws are exposed to heat and weather conditions detrimental to the integrity of the aircraft’s airframe.

The Su-57 is not overly doomed to failure; it might just be a stepping stone for Russia’s aerospace industries. The Russians think it is a good aeroplane, fit in Russia’s defensive doctrine, but they aren’t going to mass produce it if they can’t find a buyer. The plane is not a 5th generation fighter, so it is not quite as stealthy as it is touted. It may be manoeuvrable, and having few exposed screws and a clunky airframe wouldn’t stop it from fighting close combat.

Suppose Su-57 fights stealthy F-35 or even a 4.5 generation Gripen in a BVR combat; F-35 and Gripen will see the Su-57 first and shot first, making it harder for Su-57 engage in a close combat. The aerial battle for Su-57 and Su-75 will be finished against any American and European fighters before it starts.

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