Can India master relaxed static stability design for advanced fighters?

Roughly eight nations can design a fighter that flies while trying to fall out of the sky. India is one of them.

Relaxed static stability, or RSS, deliberately places an aircraft's centre of gravity behind its aerodynamic centre. This makes the machine naturally unstable — eager to pitch and change course — which is exactly the point. That instability buys exceptional manoeuvrability. The cost is that the aircraft cannot fly at all without a computer correcting its attitude many times a second. Get the correction wrong and it crashes; Sweden's early Gripen fell in 1989 to a fly-by-wire control-law fault, and needed outside software fixes to recover.

India crossed this threshold with the HAL Tejas. Its design was finalised in 1990 as a tailless compound delta-wing aircraft — no tail planes, no foreplanes — a configuration that reduces control surfaces and leans entirely on RSS for agility. To keep it in the air, the National Aerospace Laboratories set up a dedicated Control Law team in 1992 to build an indigenous fly-by-wire flight control system. The result is a quadruplex, four-channel digital system: four redundant paths so a single failure is survivable.

The status today is fielded, not experimental. No. 45 Squadron became operational with RSS-equipped Tejas in July 2016; No. 18 Squadron followed in May 2020 with Final Operational Clearance aircraft, that clearance itself validated in February 2019. HAL now builds the Mk1A, with 83 aircraft ordered in February 2021 for delivery through 2032. The Mk1A has demonstrated a 50-degree carefree angle-of-attack while cutting pilot workload by 40 per cent — a direct dividend of mature control laws.

The hard part was never the airframe alone; it was the software beneath it. India's import dependence remains high specifically on fly-by-wire control-law development, and each RSS aircraft demands its own control laws tailored to its aerodynamics. The engine remains imported — the Tejas uses the GE F404 — so the capability is currently semi-dependent, proven on a single-engine design. Indigenous content sits at 59.7 per cent by value.

What it would take is now visible in the next step. In October 2025, ADA confirmed a quadruplex digital fly-by-wire system cleared for the Advanced Medium Combat Aircraft, an inherently unstable design. Carrying validated control-law expertise from a fielded jet to a more demanding airframe — while closing the engine gap beneath it — is how a demonstrated capability becomes an independent one. India has climbed the first face. The steeper pitch is above.