The Quixotic State of Affairs Surrounding the Propulsion Conundrum of India's Advanced Medium Combat Aircraft

Chandigarh: For decades, India’s military aviation establishment has been burdened by a critical and enduring existential handicap: it could design a combat aircraft, but not develop its engine.

Yet, rather remarkably, in recent months, it has begun to confront the opposite conundrum: a potential embarrassment of “engine riches” for its most ambitious indigenous 5^th-generation Advanced Medium Combat Aircraft (AMCA) programme, being jointly pursued by the Aeronautical Development Agency (ADA), the Defence Research and Development Organisation (DRDO) and Hindustan Aeronautics Limited (HAL).

This apparent engine abundance, however, comes with a paradoxical caveat: the more propulsion options emerge, the less certain the AMCA’s actual powerplant appears. In reality, only one of these alternatives is currently a functioning engine, and even that remains clouded by uncertainty over its price, technology transfer and local manufacture. The other three exist variously as proposals, negotiations or distant possibilities.

F414, despite its selection, remains far from a settled proposition

The curious – and potentially absurd – part is how India’s military-aerospace establishment has arrived at this quixotic state of affairs.

At the heart of the AMCA’s propulsion conundrum is the US General Electric (GE) F414-IN-S6 engine, already selected for the fifth-generation fighter’s Mk1 prototypes and, potentially, the first two squadrons or even possibly more of its initial Mk1 production variant. Yet the F414, despite its selection, remains far from a settled proposition, with its eventual place in the AMCA programme still uncertain, bedevilled by cost, intellectual-property issues and related issues.

This uncertainty is further exacerbated by parallel negotiations over the F414 itself

One strand involves HAL and GE working towards local manufacture of the engine under the much-publicised June 2023 understanding announced during prime minister Narendra Modi’s US visit. The other involves the ADA and DRDO seeking imported F414s for the AMCA prototypes and limited series models. The latter has become particularly contentious, with reports that the engine’s estimated price has risen from around Rs 70-80 crore to more than Rs 200 crore apiece – almost three times the earlier figure – while the broader arrangements for local F-414 production remain under discussion.

Consequently, there is considerable speculation within the military aviation and aerospace community over whether the F414 arrangement will ultimately be resolved on terms acceptable to India, or whether the AMCA programme will eventually have to look elsewhere. More troublingly, there appears to be no clear strategic thinking yet on what the propulsion pathway should be, if the F414 negotiations fail to produce an acceptable outcome.

Alongside this dilemma are two competing proposals for new high-thrust engines: one from the recently announced UK Rolls-Royce–Reliance Industries partnership and another being pursued by France’s Safran Aircraft Engines with the DRDO. And, bringing up the rear is a possible fourth option, Kaveri 2.0, a proposed successor to the Kaveri engine programme launched by the DRDO’s Gas Turbine Research Establishment (GTRE) in 1989 to power the Tejas light combat aircraft (LCA), but which failed to deliver the required thrust and was eventually decoupled from the indigenous fighter project.

The Rolls-Royce–Reliance proposition acquired greater substance on August 14, when the two companies announced their strategic intent to jointly develop and manufacture a “sovereign indigenous combat engine” specifically for the AMCA. The proposed partnership envisages an Aerospace Gas Turbine Complex in India covering the engine’s design, development, testing, manufacture and through-life support. The proposed engine is in the 120-kN (kilonewton) class, but it remains a proposal, not a government-selected replacement for the F414.

Simultaneously, Safran is pursuing a broadly similar proposition, but for the AMCA’s more powerful future variants. In partnership with the DRDO, it is working towards a new high-thrust powerplant in the 120-kN class, with a pathway to around 140 kN. Safran has offered extensive technology transfer, including critical hot-section technologies, with the stated objective of developing and manufacturing the engine in India. Unlike the F414 and much like the Reliance-Rolls Royce venture, it has proposed a new propulsion programme, aimed at giving  India access to fighter engine technologies it has struggled for decades to master.

Bringing up the rear is Kaveri 2.0, an adjunct to the nearly four-decade-old GTRE engine programme that has never quite been allowed to die, surviving miraculously instead on a bureaucratic lifeline. Its proposed Mk 2 successor now seeks to draw on the technology and experience accumulated over decades to revive the indigenous fighter-engine effort – its prospects, like those of its Mk1 predecessor, periodically viewed with the optimism normally reserved for miracles.

Entangled in a technological and commercial standoff

So there it is: a profusion of engine promises – one functioning US engine, but entangled in a technological and commercial standoff; two competing proposals with foreign original equipment manufacturers (OEMs) to develop entirely new powerplants; and a fourth, indigenous option that remains largely aspirational.

But this proliferation is not without operational consequences.

Military aviation industry officials are agreed that the AMCA cannot afford to drift while its propulsion options multiply. With the first prototype targeted for around 2027 and series production envisaged from 2035 onwards, the programme has a relatively narrow window in which to settle the powerplant, integrate it into the fighter and complete the testing and certification that follow.

Once an engine is selected and a fighter designed around it, changing course is not simply a matter of choosing another supplier as it entails revisiting fundamental elements of the airframe, with knock-on effects for development costs, testing and production schedules. India therefore needs to decide what engine it wants the AMCA to fly with and then stay the course, rather than continually adding new engines to an already crowded menu.

The immutable reality is that a fighter, like most complex aerospace platforms, is designed around one engine and not an assortment of competing powerplants.

Besides propulsion, an engine determines the fighter platform’s dimensions, weight and thrust, as well as its airflow requirements, fuel consumption, heat generation and power extraction. These in turn shape its intakes, centre of gravity and maintenance architecture, while also influencing weapons payload, operational range and overall performance, while in a stealth fighter, the engine can even affect critical aspects of its physical and thermal signature. The fighter engine is, therefore, far more than a component that can be casually substituted, when another proposition appears on the horizon, without potentially triggering an extensive redesign.

That aspect is particularly crucial for the AMCA, which has already been designed around the GE F414 for its Mk1 prototypes and initial production aircraft. Changing this powerplant at this stage would require the aircraft to be re-engineered around the new choice, with substantial implications for structural and systems integration, flight-control parameters and the wider development programme.

In short, replacing the F414 would impose humungous  cost, delay and technical risk to the AMCA.

More strikingly, such a consequence not merely triggers military complexity but also commercial uncertainty. OEMs like Safran or Roll Royce, considering joint ventures with Indian entities, local manufacturing or technology partnerships have to commit capital, technology and industrial capacity but without always knowing whether the proposition they are pursuing will ultimately translate into a firm requirement or order. The outcome, industry officials argued, can be a difficult commercial calculation for the OEMs: why invest heavily in a partnership or establish production capacity when the eventual choice – or even whether the requirement itself will survive—remains uncertain?

Speculation over acquiring two or more Su-57 squadrons

Meanwhile, the potential acquisition of Russia’s Sukhoi Su-57 5^th generation fighters as an ‘interim measure’ by the Indian Air Force (IAF) further aggravates this problem starkly. In recent months there has been mounting speculation with the IAF and influential veterans over acquiring two or more Su-57 squadrons, while the AMCA remains under development.

But former Air Chief Marshal R.K.S. Bhadauria categorically warned on India Today television on August 15 that such an eventuality could end up effectively “killing” the AMCA programme. He reasoned that such a procurement, intended to plug an immediate capability gap, could dilute the urgency, political commitment and resources required to bring the AMCA to fruition, turning an interim solution into a substitute for the programme itself.

In conclusion, the stakes surrounding the AMCA are critical – and they extend well beyond the aircraft itself. They concern whether India can indigenously restore some of the air-power balance being steadily eroded by Beijing’s rapidly expanding J-20 fleet and Pakistan’s move towards acquiring the J-35, another Chinese 5th-generation fighter. The IAF presently has just 29 fighter squadrons against an authorised 42, while China is already producing J-20s in substantial numbers.

The AMCA therefore cannot afford another prolonged development saga centred on its propulsion: it needs one credible powerplant now, another that follows on time – and, above all, a propulsion policy that knows when to stop exploring alternatives and start building the fighter.

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