The Russian Su-57 Felon frequently dominates discussions regarding fifth-generation combat aircraft.
Analysts routinely measure its stealth capabilities against the American F-22 Raptor, the F-35 Lightning II, and the Chinese J-20. Yet, these direct comparisons often miss a crucial point: the fundamental design philosophy behind the Su-57 was entirely different from the approach taken by Western aerospace engineers.
Rather than focusing solely on invisibility to radar, Russia's Sukhoi design bureau opted for a well-rounded strategy. They blended moderate radar evasion with exceptional agility, sustained supersonic speeds, rapid interception abilities, and versatile multirole functions.
Although this strategy yielded a formidable fighter, it also clarifies why the Indian Air Force (IAF) eventually decided that the jet fell short of the specific goals set for the cancelled Fifth Generation Fighter Aircraft (FGFA) joint project.
The engine air intakes of the Su-57 remain a major point of technical debate.
Stealth fighters like the F-22, F-35, and J-20 utilise curved, S-shaped ducts to completely hide the engine's compressor blades from enemy radar waves.
In contrast, the Su-57 features shallower, straighter intakes equipped with radar-blocking structures. While these blockers help reduce the aircraft's radar cross-section, they are not as effective as serpentine ducts.
Because exposed engine blades reflect radar strongly, this design is a calculated trade-off that sacrifices some stealth in favour of better airflow and superior aerodynamic handling.
The placement of the aircraft's optical sensors highlights another clear divergence in design.
The Su-57 mounts its 101KS-V Infrared Search and Track (IRST) system openly in front of the cockpit, alongside external 101KS-O Directional Infrared Countermeasure (DIRCM) turrets.
While these advanced systems offer outstanding situational awareness and strong missile defence, they protrude from the airframe.
Conversely, jets built strictly for very-low-observable (VLO) stealth typically integrate these sensors seamlessly into the aircraft's skin to prevent radar detection.
The tail section of the Russian fighter also draws scrutiny from aviation experts. The Su-57 utilises traditional round engine exhaust nozzles equipped with thrust vectoring, which allows the aircraft to perform incredible aerial manoeuvres.
However, these round nozzles are less successful at masking the jet's heat and radar profile from behind, especially when compared to the flattened or shielded exhausts seen on other stealth platforms.
It is evident that Sukhoi chose to maintain unmatched physical agility and three-dimensional thrust control rather than compromising flight performance purely for the sake of stealth.
Ultimately, these structural decisions mirror the overarching strategic vision that guided the entire Su-57 development effort.
While Western jets like the F-22 and F-35 were built from the ground up with maximum stealth as their absolute priority, the Su-57 was envisioned differently.
It was crafted as a versatile combat aircraft that merges moderate stealth with outstanding flight dynamics, long operational range, high speeds, and top-tier dogfighting capabilities.
Russian engineers maintain that remaining unseen is merely one aspect of survival, arguing that a fighter must also rely on electronic warfare, integrated sensors, and sheer speed and agility.
This mindset sharply contrasts with the prevailing doctrines in the United States and China, where minimising the aircraft's radar cross-section remains the primary objective driving modern fighter design.
These fundamental philosophical differences proved to be a critical stumbling block during India's involvement in the joint FGFA initiative.
During the development phase, the Indian Air Force consistently raised alarms over multiple facets of the joint venture. Key concerns included the jet's inadequate stealth parameters, ballooning financial costs, and the lack of equitable workshare for Indian engineers.
Furthermore, New Delhi was dissatisfied with Russia's reluctance to transfer critical aerospace technologies. Although both nations kept the exact negotiation details classified, it was clear that they had vastly different visions regarding the fighter's final capabilities and India's manufacturing role.
From the Indian perspective, the FGFA project was meant to be much more than a simple purchase of foreign hardware.
The objective was to secure deep access to next-generation aviation technology, allowing domestic Indian industries to play a major part in designing and building the aircraft.
As talks dragged on over the years, these core expectations were never satisfactorily met.
Open-source records indicate that India had already invested nearly $295 million in the preliminary design phase before officially halting its participation in 2018 to avoid further financial risks and capability compromises.
In addition to these technical and industrial disagreements, the geopolitical and strategic landscape has changed dramatically since the FGFA was initially proposed.
China’s rapid deployment of its own J-20 stealth fighters and its continuous investments in advanced air-defence networks have altered regional threat perceptions.
These aggressive modernisation efforts by the People’s Liberation Army Air Force have forced the IAF to prioritise extreme stealth and survivability.
In a modern airspace saturated with long-range radars, networked missile systems, and robust anti-aircraft defences, India requires an aircraft that can operate undetected.
Driven by these new combat realities, New Delhi has heavily pivoted towards its own indigenous Advanced Medium Combat Aircraft (AMCA) programme.
Unlike the Su-57, the AMCA is being engineered with very-low observability as a foundational requirement. It will also be equipped with home-grown sensors, modern electronic warfare suites, and the architecture necessary to accommodate advanced engine upgrades in the future.
To reinforce this strategic shift, the Indian government’s Cabinet Committee on Security (CCS) officially cleared the AMCA project in early 2024, sanctioning substantial funds for prototype development and underscoring a commitment to self-reliance in aerospace defence.
Despite India's withdrawal from the partnership, the inherent combat value of the Su-57 cannot be understated.
The Russian platform boasts a formidable array of features, including the ability to fly at supersonic speeds without afterburners (supercruise), internal payload bays, cutting-edge sensors, and thrust vectoring for supreme dogfighting dominance.
By blending selective stealth technologies with networked combat systems and modern avionics, the Su-57 rightfully earns its classification as a fifth-generation fighter.
Nonetheless, it embodies a distinctly alternative vision of modern aerial warfare. Instead of sacrificing everything to achieve an invisible radar signature, the Su-57 aims to strike a harmonious balance between aerodynamic superiority, sheer kinetic power, and moderate stealth.
For India, however, this specific balance of capabilities simply did not match the stringent long-term demands established by the IAF.
Preparing for potential future conflicts against highly equipped adversaries and complex air-defence umbrellas, India has firmly decided that maximum stealth, technological self-reliance, and absolute control over future aircraft upgrades are the only paths forward to ensure true survivability.
