The limit of Soviet aviation's legacy: is Russia really making progress in fifth-generation fighter jets?
There is currently much discussion about a possible direct confrontation between Russia and NATO forces. Some believe that Russia has surged ahead thanks to its combat experience and the development of unmanned systems in the war against Ukraine.
However, as we have seen in Iran, NATO forces are capable of quickly establishing air superiority and then systematically destroying depots, launch sites and concentrations of forces over a wide area.
It is clear that any potential clash between Russia and NATO would largely be determined by air warfare at tactical aircraft level. On paper, both sides possess fifth-generation aircraft, but the reality is far more complex.
Can Russia's flagship Su-57 offer any real challenge to NATO aircraft, and is Russia truly making progress in fifth-generation fighter jets?
The legacy of the Soviet school
To understand where Russia's tactical aviation stands today, it is worth going back five decades, to the design bureau of Pavel Sukhoi. In the late 1960s, work began there on a fighter that would become one of the symbols of the Soviet aviation school.
The Su-27, which made its first test flight in 1977, was a truly formidable aircraft for its time: highly manoeuvrable, with a powerful engine, large take-off weight and long range.
Over the following four decades, the Russian aviation industry focused mainly on deep modernisation of the Su-27's basic design – producing the Su-30, Su-35, Su-34 and other variants. In essence, these are different versions of the same platform. Each new modification received more advanced avionics, a more powerful radar and updated weapons systems.
This approach ensured a certain level of progress, kept the design bureau active, and made it possible to report on "cutting-edge developments". Nonetheless, a genuinely new next-generation aircraft did not appear for a long time.
Only in the early 2000s, with the United States advancing its stealth fighter F-22 Raptor, did the advantage of the Sukhoi platform begin to fade.
Response to Western fighters
The nature of aerial warfare changed. The West was no longer building highly manoeuvrable fourth-generation fighters – it was developing stealth aircraft based on a fundamentally different concept of long-range combat. Stealth capabilities, supersonic flight without afterburner (engine boost) and deep sensor integration to enhance situational awareness became the core pillars of this new approach. The Soviet school effectively had no ready answer to any of these.
Russia's PAK FA project – the Advanced Frontline Tactical Fighter – was launched as this experimental response. The technical specification was issued in 2002, and the first flight of the T-50 (the prototype of the future Su-57) took place in 2010. However, even at that stage, the concept contained a fundamental ideological flaw.
The Soviet – and now Russian – aviation schools were psychologically unable to abandon super-manoeuvrability. Thrust vectoring, the ability to perform widely publicised advanced aerobatic manoeuvres, and extreme agility at low speeds were, in a sense, a cult – almost part of the Sukhoi's DNA.
As a result, when drafting the requirements for the Su-57, the priority remained super-manoeuvrability rather than the development of new experimental engines, the creation of infrastructure for data exchange with other systems, or even more technologically advanced weaponry.
It was precisely this approach that undermined the aircraft's stealth capabilities as early as the design stage. The Su-57's engines are spaced relatively far apart to improve thrust vectoring and stability, creating a radar profile that is clearly visible from multiple angles.
The air intakes are not designed with S-shaped ducts. In the F-22 and F-35, such ducts conceal the compressor blades from the front – one of the main sources of radar reflection.
This issue stems from the fact that the Su-57's new main engine, the Izdeliye 30, with a circular exhaust nozzle, is expected to produce thrust of around 171 kN. It is not possible to design a fighter with S-shaped air intakes or rectangular exhaust nozzles without engines powerful enough to compensate for the energy losses caused by such design solutions. The rear sections of the Su-57's nozzles lack stealth coatings or specialised reflective geometry, making both its infrared and radar signature in the rear hemisphere poorly suited to stealth requirements.
By comparison, other fifth-generation fighters such as the F-22 are designed to be low-observable from all angles. The F-35, despite criticism of its manoeuvrability, has a very low radar cross-section (RCS).
The RCS is a parameter that indicates how large an aircraft appears to enemy radar. The smaller the RCS, the harder it is to detect and track the aircraft. From the frontal aspect, the F-35's RCS is estimated at 0.001–0.005 m². There is no official data for the Su-57, but according to a patent, its frontal RCS is around 0.1 m² – significantly worse than its American counterparts. This places it closer to a well-modernised fourth-generation aircraft than to a truly low-observable fifth-generation fighter.
The engine as the main constraint
The first production Su-57s rolled off the production line equipped with the AL-41F-1 (Izdeliye 117) engine – a deeply modernised version of the AL-31, originally designed in the late 1970s. Officially, the use of the Su-35 engine was presented as a temporary "first-stage" solution. In reality, however, this "temporary" measure has dragged on for years. According to various estimates, the Russian Aerospace Forces have received only about a third of the aircraft planned under the 2019 contract: 10 aircraft in 2022 and another 11 in 2023.
The new Izdeliye 30 (AL-51F1) engine first flew on a prototype back in December 2017. However, as it turned out, years of work separated the first test flight from mass production. The programme progressed slowly and unevenly, with flight tests continuing until 2025.
Only in early 2026 did the parent corporation officially announce that new Su-57s are now being delivered with the Izdeliye 30 engine. Meanwhile, all previously produced aircraft remain equipped with the older AL-41F1 engines. As a result, the Russian Aerospace Forces now operate a heterogeneous fleet, with aircraft capabilities varying significantly depending on the production batch.
Why does this matter? The key requirement for a fifth-generation fighter engine is the ability to sustain supersonic flight without an afterburner – that is, in so-called supercruise mode. An afterburner is a system which works in emergency high-thrust mode in which additional fuel is injected into the engine. It provides rapid acceleration but significantly increases the aircraft's thermal signature, making it far more visible to infrared systems, and greatly raises fuel consumption.
By comparison, the F-22 has been capable of sustained supersonic cruise flight without afterburner for more than twenty years. New Su-57s equipped with the Izdeliye 30 engine can reportedly maintain a cruising speed of around Mach 1.3–1.5 (Mach 1 equals the speed of sound).
Older engines lack this capability, while the new ones have effectively appeared only "yesterday" and still need to prove themselves in full-scale mass production.
The problem of sensor scarcity
On paper, the Su-57's radar suite is genuinely impressive. The aircraft carries five antenna systems: the primary N036 Belka radar in the nose with 1,514 X-band transmit-receive modules; two N036B side-looking radars with 404 modules each; and two additional L-band arrays mounted along the wing leading edges for identification friend or foe (IFF) and electronic warfare functions. In theory, this provides full angular coverage, something most fourth-generation fighters equipped with a single nose-mounted radar do not possess.
However, it is important to distinguish between the number of sensors installed and what the pilot actually sees in the cockpit. The defining principle of fifth-generation aircraft is that all sensors – radars, infrared systems, and passive receivers – are automatically merged into a single operational picture without pilot involvement. This is known as sensor fusion. It is precisely this capability that has made the F-35 what it is: the pilot does not manually switch between systems but instead sees a ready-made situational picture. The Su-57 does have a suite of radars and passive detection systems, yet the level of their integration into a unified picture remains inferior to that of the F-35, where the AN/APG-81/85 radar, the Distributed Aperture System and the electro-optical targeting system are combined into a single data stream.
A key issue nevertheless remains the electronic domain, which is directly dependent on the level of development of the semiconductor industry. Since the Su-35 features a synthetic aperture radar (SAR) mode whose resolution roughly corresponds to that of the mechanically scanned radar of an F-15E from 20 years ago, this clearly illustrates the central limitation of Russian radar systems – namely their restricted operating frequency bands.
Because of these narrow frequency bands, it is not possible to achieve genuinely effective low-probability-of-intercept (LPI) characteristics – that is, radar emission modes designed to be difficult for an adversary to detect through the use of various counter-detection mechanisms and algorithms, such as frequency hopping, focusing signals on selected sectors, and similar techniques.
The same limitations also hinder the use of narrow, directional line-of-sight data links, which can operate in low-probability-of-intercept (LPI) modes. As a result, Russian systems are forced to rely on omnidirectional communications channels at lower frequencies. These transmit signals in all directions, which reduces the aircraft's stealth characteristics while simultaneously imposing constraints on data transmission speeds.
In modern aviation, low observability is determined not only by the shape of the airframe. On-board electronics also play a major role. Without the ability to maintain strict control over electromagnetic emissions, the pilot must either fly almost "blind", avoiding the use of radar and communications altogether, or activate these systems and lose the element of surprise that a stealth aircraft is theoretically meant to provide.
Behind this lies a more fundamental technological problem. Full real-time fusion of data from multiple radars and sensors requires extremely powerful onboard computing systems based on advanced microchips. These processors must handle large volumes of information and generate a unified situational picture for the pilot. Since 2022, sanctions have significantly complicated Russia's access to Western microelectronics, which had previously been used in many elements of the avionics of its combat aircraft.
Domestic semiconductor production in Russia operates on process nodes of roughly 90-60 nm (and more recently closer to 28 nm), whereas modern combat avionics typically rely on chips at the 7-5 nm level and below. This difference is not merely numerical. With older process nodes, it becomes far more difficult to achieve the required computing performance within the same physical dimensions without a noticeable increase in equipment mass and power consumption.
Baptism of fire: long-range strikes and avoidance of direct contact for the sake of reputation
Russia's full-scale invasion of Ukraine became the first serious combat test for the Su-57. The results of this test are revealing not so much in terms of what the aircraft does, but rather what it avoids doing.
From the first months after the invasion in 2022, the Su-57 has been used exclusively for long-range strikes, remaining outside the engagement zone of Ukrainian air defence systems. At present, its primary weapons are the Kh-69 cruise missile, designed with reduced radar visibility thanks to its internal carriage within the fuselage bays, and the R-37M air-to-air missile with a range exceeding 300 km, which the Su-57 has used to engage Ukrainian aircraft without even entering their detection zone. There have been no confirmed encounters with Ukrainian air defence at low altitudes.
By mid-2025, the tactics had become more sophisticated: Su-57 aircraft began operating either in full formations or in coordination with lower-class fighters. A typical configuration involves one aircraft providing cover with R-77M air-to-air missiles while another pair conducts strikes using Kh-69 cruise missiles or guided bombs. In effect, this represents an attempt to develop a fully fledged strike package in which the Su-57 simultaneously performs both escort and strike roles.
The loss of an aircraft is something Russia seeks to avoid at all costs. As of October 2025, the operational fleet of Su-57 aircraft numbered no more than 25. Given such limited numbers, each aircraft carries significant political and reputational value, and command therefore employs them with extreme caution and primarily at relatively safe stand-off distances.
For comparison, the US has produced approximately 200 F-22 aircraft and continues to expand its F-35 fleet on a large scale, with more than 1,300 units already built in various variants. At such production rates, each Su-57 effectively remains a bespoke platform with unique modifications.
The end of an era: why the future no longer belongs to the Sukhois
The paradox of the Su-57 is that it is simultaneously the most ambitious project of Russia's aviation industry and its technological limit.
While Russia is still attempting to bring a fifth-generation fighter fully into mass production, the rest of the world is already moving towards the sixth generation. In essence, the concept of next-generation fighters – and to some extent even that of the fifth generation – is no longer about building a single extremely capable aircraft, but about turning the aircraft into a command centre for an entire swarm of autonomous drones, sensors and weapons, each performing specialised roles ranging from reconnaissance to interception and electronic warfare.
Russia is attempting to move in the same direction with the S-70 Okhotnik unmanned aircraft. The programme envisages the Su-57 controlling up to four such drones simultaneously as a command node. The first joint flight took place as early as September 2019. However, there is a significant gap between a demonstration flight and a functioning combat network. The October 2024 incident in which a Su-57 shot down its own Okhotnik following a malfunction clearly demonstrated that a reliable digital link between the platforms most likely still does not exist.
Once again, the problem ultimately comes down to microelectronics. Controlling a swarm of drones in a real combat environment requires artificial intelligence algorithms capable of processing data streams and making tactical decisions within milliseconds. This, in turn, demands modern chips able to handle such processing onboard the fighter itself.
It increasingly appears that the Su-57 is not a springboard into the future but rather the final stage in the evolution of ideas first formulated in Soviet design bureaux back in the 1980s. Super-manoeuvrability has proved unnecessary in an era of missiles with ranges of 300 km. Analogue stealth is losing out to digital approaches. And a production base weakened by decades of incremental modernisation instead of new development – and further constrained by sanctions – is unable to deliver the required scale.
For Ukraine, however, this is little consolation. Even fourth-generation aircraft continue to inflict real losses and will go on doing so as long as the war continues. The Su-57 does not need to be a technological revolution to remain effective in this war.
But when looking further ahead – towards a full-scale confrontation with NATO systems, their networks, satellite communications, and fully integrated fifth-generation aircraft – the limitations rooted in Soviet-era design assumptions will become a serious constraint.
New aircraft will still be assembled somewhere in Russia's Komsomolsk-on-Amur. Yet in the air warfare of the future, where networks, data, and autonomous systems will be decisive, the Su-57 is today chasing a train that has already long since departed.
Arkadii Dotsenko
Translated by Myroslava Zavadska and Anna Kybukevych
Edited by Susan McDonald