India Weighs Su-57 Deal Su-57 Squadrons, Engines and Why ‘Perfect’ Stealth Is Elusive

Su-57: India is reported to be examining the purchase of two squadrons of Russia’s Su-57 fifth-generation fighter in fly-away condition, while exploring local assembly/production for another 3–5 squadrons under a Make-in-India arrangement. This move is being discussed as a way to quickly boost IAF fifth-generation capability while building local industry capacity over the next few years.

What the Su-57 offers

The Su-57 is Russia’s answer to a modern, multi-role, low-observable fighter: sensor fusion, internal weapons bays, advanced avionics and aircraft shaping that reduces radar returns compared with older fighters. For India, buying a small number of finished jets (fly-away) plus assembling others locally would give a faster operational edge while transferring manufacturing know-how.

Engines and why that matters for stealth

Two engines commonly discussed around the Su-57 are:

• AL-41F1 / Product 117 — the interim engine derived from the AL-31 family. It has powered early Su-57 prototypes and initial production jets but was always considered a stopgap.

• Izdeliye-30 / AL-51 (Product 30) — the next-generation “clean-sheet” engine being developed to replace the interim powerplant. It promises higher thrust, better fuel efficiency, lower maintenance and design features that reduce signatures.

Why the engine affects stealth in practice:

• Nozzle shape and materials: A round, exposed afterburner nozzle reflects radar and emits a strong infrared (IR) signature. Newer engine designs for stealth fighters use nozzle geometries and serrated/treated surfaces to lower radar returns and scatter heat — for example, recent Su-57 prototypes have been seen testing flatter, 2-D thrust-vectoring nozzles which improve stealth compared with older round nozzles.

• Heat and IR: Engines are the hottest part of a jet. Even if the airframe shape is low observable, a hot exhaust makes detection by IR sensors easier. New engine tech aims to manage exhaust temperature and flow to make the aircraft harder to spot with IR seekers.

Because the Su-57 initially flew with an interim engine, its early stealth performance has been considered less complete than Western fifth-generation jets that were designed from day-one around specific low-observable engines and exhaust treatments. That’s why Indian and other analysts describe some aspects of the Su-57 as “partially stealthy” rather than fully stealth-optimized yet.

Can India “fit” better engines or finish stealth upgrades locally?

In principle, yes — Russia’s development path for the Su-57 already plans the newer Izdeliye-30 engine as a drop-in replacement for production aircraft. A production/assembly arrangement with technology transfer could allow India to fit later-generation engines and nozzle treatments on locally assembled airframes as those upgrades mature. But there are real caveats:

• Technology and timelines: Product-30 development has had delays; full series production and mature reliability take time. India would need to coordinate delivery schedules and likely accept a phased introduction (interim jets first, upgraded engines later).

• Industrial readiness: Local assembly of a fifth-generation fighter requires deep industrial capability — not just final assembly but supply chains, composite manufacturing, precision systems and avionics integration. HAL and Indian industry know how to assemble complex aircraft, but full tech transfer for engines/nozzles is a separate, sensitive domain.

Why India might still find the Su-57 attractive

1. Faster squadron build-up: Buying a small number of finished jets gets capability into service faster than waiting for domestic AMCA to mature.

2. Make-in-India potential: A local assembly line for Su-57 components would boost domestic jobs and give HAL experience with 5th-gen manufacturing under license.

3. Operational pairing with S-400: India already operates the S-400 long-range surface-to-air missile system. The Su-57’s sensors and datalinks can benefit from integration with ground-based radars and command systems (shared situational awareness, queued targeting and layered defence). In simple terms: a long-range S-400 radar can see targets at very long ranges and share cues with fighters, helping them survive and operate more effectively in contested airspace. That networked approach is a practical force multiplier.

Straight talk: limitations and the tradeoffs

• Not “invisible” — even modern stealth fighters are not literally invisible; they reduce detection ranges and signatures in certain bands and angles. The Su-57’s early engine/nozzle choices meant compromises between raw maneuverability, thrust-vectoring and some aspects of low observability.

• Upgrade path matters: If India wants the most mature stealth performance, it will depend on timelines for engine upgrades (Izdeliye-30 / AL-51 family) and nose/skin/IR suppression technologies — and on how much of that technology Russia is willing to transfer.

India’s interest in two fly-away Su-57 squadrons plus local assembly of several more is a pragmatic mix: quick capability now, manufacturing buildup later. Engines and exhaust treatment are the key technical reasons the Su-57 today is not the “perfect” stealth jet — but planned engine upgrades (Izdeliye-30 / AL-51 family) and nozzle redesigns are intended to close that gap. Paired with India’s S-400 and Indian-built infrastructure, a Su-57 fleet (especially one that is upgraded over time) could be a meaningful addition to the IAF — provided timelines, technology transfer and local industry readiness line up.