Whenever the subject of Indian aero-engines arises in public discourse, one name almost invariably dominates the conversation: Kaveri. For years, the GTX-35VS Kaveri has served as a convenient shorthand for the country’s struggles in high-performance propulsion. Commentators, defence analysts and even casual observers have repeatedly pointed to its long delays, shortfalls in thrust and eventual delinking from the Light Combat Aircraft programme as evidence that India remains incapable of mastering the “crown jewel” of aerospace technology.
This narrow focus has fostered a persistent sense of national underachievement. The narrative of failure has overshadowed a quieter, broader reality: India has been steadily building a diversified portfolio of aero-engines that now spans fighters, helicopters, unmanned systems, cruise missiles and smaller platforms. Far from a single stalled programme, the country is experiencing a genuine renaissance in propulsion technology, one that draws lessons from Kaveri’s difficulties while expanding capability across multiple thrust classes and applications.
The Kaveri story itself deserves accurate telling before the wider picture comes into view. In the mid-1980s, as India embarked on the ambitious Light Combat Aircraft project that would become the Tejas, planners recognised that true self-reliance demanded an indigenous powerplant. In 1986 the Defence Research and Development Organisation was tasked with the effort; formal sanction followed in 1989 with an initial budget of roughly ₹382 crore and a target completion date of 1996.
The Gas Turbine Research Establishment in Bengaluru was charged with designing a low-bypass afterburning turbofan capable of approximately 81 kN wet thrust. Early progress appeared promising. The Kabini core ran for the first time in 1995, and the first full prototype began ground testing the following year. By the late 1990s, several engines were under evaluation.
However, reality proved more stubborn. International sanctions on India after the 1998 nuclear tests restricted access to critical materials and testing facilities. Persistent problems with high-temperature metallurgy, turbine blade life and overall thrust-to-weight ratio slowed development. High-altitude trials in Russia in the 2000s revealed further shortfalls. By September 2008, the engine had been formally delinked from the Tejas programme so that the aircraft could proceed with the proven General Electric F404.
The original Kaveri engine never fully met its fighter-class performance targets, yet the programme was never simply abandoned. More than three thousand hours of testing, nine prototype engines and four cores generated invaluable design experience, manufacturing know-how and a cadre of specialists. That hard-won foundation has since been redirected into derivative and parallel efforts that are now yielding tangible results.
The Dry Kaveri and the Stealth Future
The most immediate descendants of the original Kaveri form a family of engines tailored to different operational needs. Rather than abandoning the core, the Defence Research and Development Organisation (DRDO) decoupled the engine from its afterburner section to create the ‘Dry Kaveri’. Generating approximately 46 kN of dry thrust, this engine has now resolved the legacy core issues and achieved stability.
Its destiny is no longer the Tejas, but the shadowy realm of uncrewed warfare. Optimised for unmanned platforms, it has been selected as the powerplant for the Ghatak stealth unmanned combat aerial vehicle. Because stealth drones prioritise internal payload, low radar cross-sections, and range over afterburning supersonic dashes, the Dry Kaveri’s specifications are a perfect fit. Godrej Aerospace has taken on series production, which delivered the first unit in 2025 and followed with additional engines for the certification campaign.
Parallel work continues on afterburning variants collectively referred to as Kaveri 2.0. An initial configuration using the existing afterburner is expected to deliver around 73 kN, while a new afterburner module and an uprated core aim for 80–85 kN or potentially higher wet thrust in the 90 kN class. Flight trials on a modified Tejas Limited Series Production airframe are planned, and the engine is being positioned as a possible future indigenous option for Tejas variants once certification is complete. Lightweighting measures, including titanium alloy blisks, and the progressive introduction of single-crystal turbine blades, are improving the thrust-to-weight ratio that earlier versions lacked.
A New Engine
While the Kaveri family continues to mature, India has launched a far more ambitious high-thrust programme for its fifth-generation fighter. The Advanced High Thrust Class Engine, targeting an initial 120 kN of thrust with growth potential to 140 kN, is intended primarily for the Advanced Medium Combat Aircraft (AMCA) Mark 2. The Gas Turbine Research Establishment retains design authority. An Expression of Interest has been issued for an Indian Development-cum-Production Partner that will manufacture and assemble the engines, with plans for eighteen development units over a decade.
Negotiations with France’s Safran have advanced significantly. This month the joint-venture proposal, promising complete technology transfer including the critical hot section and full Indian intellectual-property ownership, reached the Cabinet Committee on Security. Alternative offers from Rolls-Royce have also been received. Supporting infrastructure is expanding: a 130 kN twin-cell test bed near Bengaluru is under construction, and plans exist for high-altitude facilities and flying test beds converted from Su-30MKI airframes. The programme represents a deliberate shift from pure indigenous development of the most complex classes toward structured collaboration that still keeps strategic control in Indian hands.
Beyond the fighter-class efforts, a range of smaller but operationally vital made-in-India engines has reached advanced stages.
HTFE-25: The Versatile Workhorse
Hindustan Aeronautics Limited has pursued its own complementary programmes through its Aero Engine Research and Design Centre. The HTFE-25 is a 25 kN-class low-bypass turbofan suitable for basic and advanced trainers, small business jets and large unmanned aerial vehicles. Two core engines and a technology demonstrator have already been built. The core had reached 99.5 per cent of design speed during acceleration trials earlier this year. Certification is targeted within the next four to five years, with potential application on the Intermediate Jet Trainer.
Crucially, HAL did not stop at dry thrust for HTFE-25. By integrating a basic afterburner, the HTFE-25 is projected to reach approximately 40 kN of maximum thrust. This unlocks a massive strategic possibility: re-engining the Indian Air Force’s ageing SEPECAT Jaguar strike fleet. Long considered underpowered by its original Rolls-Royce Adour Mk.811 engines, the Jaguar fleet could gain a lethal new lease on life with twin afterburning HTFE-25s, bypassing the exorbitant costs of stalled foreign upgrade proposals.
The HTFE-25 project began in 2013–14 as an internally funded initiative by HAL, with an initial goal of completion within approximately six years. The core engine achieved its first successful run on 14 December 2015, witnessed by then-Defence Minister Manohar Parrikar. en.wikipedia.org
By 2019, two core engines had been produced and collectively completed 339 test runs. These tests demonstrated cold starts at 14°C using spark igniters and 100% maximum core speed both with and without inlet guide vane (IGV) modulation. Work on a basic afterburner configuration was also initiated.
Progress faced delays due to issues such as testing infrastructure, procurement challenges, component manufacturing including intermediate gearboxes, and technology gaps. A full technology demonstrator later completed initial runs, with acceleration trials reaching about 55% of design speed by mid-2024. A new design and test facility at AERDC, inaugurated in 2023, helped accelerate efforts.
The HTFE-25 prioritises a compact size, competitive thrust-to-weight ratio, and efficiency suitable for subsonic and transonic regimes typical of trainers and UAVs. Its modular core supports potential growth, including an afterburning variant that could approach higher thrust levels of around 40 kN for light combat or unmanned combat applications.
The HTFE-25 engine is targeted for advanced military trainers such as the HAL HJT-36 / IJT-36 Yashas. It is also suited to large UAVs (including concepts in the Combat Air Teaming System or CATS family), small business jets, and other light aircraft. In single-engine form, it suits aircraft in the roughly 5-tonne class, while twin-engine installations extend to the 9-tonne class. This versatility positions it for both military and potential civil/export markets where India currently lacks a fully indigenous option in this thrust class.
Development of the program has built indigenous expertise in compressor aerodynamics, combustor design, hot-section materials and cooling, precision manufacturing, and advanced testing—foundational capabilities for more ambitious future engines. The HTFE-25 is not India’s final destination in aero-engine development, but it is a critical proving ground—building the design, manufacturing, and testing foundations needed for future fighter and advanced unmanned platforms.
HTSE-1200: Securing the Vertical Lift
Perhaps the most consequential of HAL’s indigenous programmes is the Hindustan Turbo Shaft Engine (HTSE-1200). Developed by Hindustan Aeronautics Limited through its Aero Engine Research and Design Centre in Bengaluru, the Hindustan Turbo Shaft Engine-1200 is a 1200 kW-class powerplant designed specifically for helicopters in the three-to-six-tonne weight category. While larger fighter-engine programmes often capture public attention, the HTSE-1200 addresses a more immediate and widespread operational need. India operates and plans to operate large fleets of light and medium helicopters across the Army, Air Force, Navy and civil sectors. Ensuring that these platforms are not permanently dependent on foreign engines has become a strategic priority, and the HTSE-1200 is central to that goal.
The programme was formally launched in December 2015 when then Defence Minister Manohar Parrikar inaugurated the design and development effort alongside the parallel HTFE-25 turbofan project. HAL undertook the work with internal resources, drawing on decades of experience gained through licensed production and co-development of engines such as the Artouste, TM333 and, most significantly, the Shakti (Ardiden 1H1) developed jointly with Safran. The first run of a technology demonstrator core took place on 12 February 2018, achieving 76 per cent of design speed. Since then the engine has accumulated hundreds of test hours, progressively climbing the performance ladder.
Technically, the HTSE-1200 is a free-power-turbine turboshaft optimised for shaft power delivery rather than pure thrust. It features a two-stage centrifugal compressor delivering a pressure ratio of approximately 11.2 and a mass flow of around 4.25 kg/s. An effusion-cooled annular combustor manages high turbine entry temperatures, reported in the region of 1493 K. The gas-generator turbine and free power turbine extract energy to drive the output shaft at approximately 6000 rpm. Physical dimensions of the engine are compact: length of 1.30 metres, diameter of 0.55 metres and a dry weight of about 235 kg.
Maximum power output is rated at 1200 kW (roughly 1 600 shaft horsepower) at sea level, with the ability to operate across ambient temperatures from –50 °C to +55 °C and up to altitudes of around seven kilometres. These figures place it in the same performance band as contemporary engines such as the LHTEC CTS800, MTR390 or Safran Arrano, making it suitable for both single-engine installations on lighter platforms and twin-engine configurations on heavier ones.
Development has proceeded through distinct jet-mode and power-mode prototypes. The jet-mode engine has been used primarily for core validation and component testing, while the power-mode configuration incorporates the free turbine and reduction elements required for helicopter drive trains. Additive manufacturing has been employed for several critical parts, including the radial straightener, diffuser and rear bearing support, which have been evaluated under operational conditions. Directionally solidified and single-crystal turbine blades, developed with support from the Defence Metallurgical Research Laboratory, have been incorporated to improve high-temperature capability and component life. High-altitude trials have already been completed in both cold-weather and hot-weather conditions at Leh, South Pullu and Khardung La, confirming starting and running behaviour in the thin air of the Himalayas, an essential requirement for Indian operations.
By 2024 the core had achieved 100 per cent design speed, and sea-level trials were successfully concluded. After that fabrication of an initial batch of five near-production-standard engines was launched. The engine is planned to be installed on older Dhruv prototypes for in-flight evaluation before full certification, currently targeted for completion in 2026.
A particularly significant recent development is the commencement of an indigenous Full Authority Digital Engine Control system for the HTSE-1200. Until now, engines in this class have typically relied on FADEC units supplied by established Western manufacturers. Developing the digital control system in-house closes one of the last major technology gaps. FADEC provides precise management of fuel flow, acceleration schedules, temperature limits and protective functions across the entire flight envelope. For a helicopter engine that must handle rapid power demands during manoeuvring, high-altitude starts and emergency conditions, an indigenous FADEC not only improves performance and reliability but also removes a potential source of export-control restrictions. The system is being developed in parallel with the mechanical maturation of the engine so that both can be certified together.
The engine will power HAL’s existing and future helicopter families. In single-engine configuration, the HTSE-1200 is suited to the 3.5-tonne Light Utility Helicopter. In twin-engine layout it can equip the five-to-eight-tonne Advanced Light Helicopter Dhruv, the Light Combat Helicopter Prachand, and potentially future derivatives or the Indian Multi-Role Helicopter once that programme matures. There has also been discussion of adapting the core into a turboprop configuration for fixed-wing trainers such as the HTT-40, offering a route to replace the currently imported Honeywell TPE331. The modular nature of the gas generator makes such a conversion technically feasible with the addition of a suitable reduction gearbox and propeller accessories.
The strategic value of the HTSE-1200 extends beyond any single platform. India faces projected demand for several thousand helicopter engines over the coming decades. Continued reliance on foreign sources creates both cost and supply-chain vulnerabilities. By developing an indigenous alternative, HAL gains the ability to control production rates, implement upgrades without external approval, and offer life-cycle support from Indian facilities.
In the context of India’s aero-engine efforts, the HTSE-1200 occupies a pragmatic middle ground. It is less glamorous than a 120 kN fighter engine, yet far more immediately relevant to the large numbers of helicopters already in service and on order.
Aravalli: Powerplant for Next-Gen Helicopters
The Aravalli engine is a new-generation high-power turboshaft being jointly designed and developed by SAFHAL Helicopter Engines Private Limited, a joint venture between Hindustan Aeronautics Limited and Safran Helicopter Engines of France. Named after the majestic Aravalli mountain range that stretches across western and northern India, the engine symbolises the nation’s determination to achieve Aatmanirbharta in critical aero-engine technologies.
In August 2024, HAL signed an airframer contract with SAFHAL to commence the joint design, development, manufacture, supply and support of this advanced engine. It has been specifically selected to power the Indian Multi-Role Helicopter, a 13-tonne medium-lift platform under development by HAL for the Indian Armed Forces, as well as the Deck-Based Multi-Role Helicopter, a 12.5-tonne naval variant intended for the Indian Navy. Both helicopters are expected to operate in highly demanding environments ranging from the scorching deserts of Rajasthan to the high-altitude regions of Ladakh and the challenging conditions of maritime operations.
The Aravalli is designed to deliver between 3,500 and 4,000 shaft horsepower, placing it among the most powerful engines Safran has developed to date. Leveraging the combined expertise of HAL and Safran, the engine will incorporate cutting-edge technologies to ensure superior performance, reliability, fuel efficiency and operational flexibility. Initial prototypes of the IMRH may fly with existing Safran engines while the Aravalli completes its development cycle, with full integration planned for later production batches. Entry into service is targeted for the early 2030s.
This programme builds upon a long and successful partnership between HAL and Safran that began with the Artouste engines powering the Chetak and Cheetah helicopters and continued with the Shakti family of engines for the Advanced Light Helicopter, Light Combat Helicopter and Light Utility Helicopter. The Aravalli marks a significant elevation of this collaboration, moving from licensed production and co-development of earlier engines to true joint design of a next-generation powerplant.
Beyond military applications, the engine holds promise for future civil roles such as offshore operations, utility services and VVIP transport, along with associated maintenance, repair and overhaul activities. By mastering the design and production of a high-power turboshaft of this class, India is taking a decisive step towards reducing dependence on foreign suppliers for medium-lift helicopter propulsion and strengthening its overall aerospace and defence industrial base. The Aravalli thus stands as both a technological milestone and a strategic enabler for India’s growing indigenous helicopter fleet.
Manik: Homegrown Power for Missiles
The Manik engine, formally known as the Small Turbofan Engine or STFE, is an indigenous small turbofan developed by the Gas Turbine Research Establishment under the Defence Research and Development Organisation in Bengaluru. Designed as a compact, efficient propulsion system delivering around 4.5 kilonewtons of thrust, it serves primarily as the powerplant for India’s subsonic cruise missiles and holds promise for various unmanned aerial vehicles.
This twin-spool bypass turbofan, developed without an afterburner, was created to replace imported engines that earlier powered platforms such as the Nirbhay series. It incorporates advanced features including a full-authority digital engine control system, a wide-chord fan, a mixed-flow compressor, and the capability for mid-air starting using pyro devices. Weighing approximately 100 kilograms, the engine is optimised for reliable low-altitude, long-endurance flight at subsonic speeds, making it well suited for precision strike and loitering missions.
The Manik has already demonstrated its performance in several successful flight tests of the Indigenous Technology Cruise Missile and the Long Range Land Attack Cruise Missile. BrahMos Aerospace has undertaken limited series production, delivering batches of engines for trials and integration, while plans are advancing for larger-scale manufacturing involving both public sector units and private industry partners. This expansion aims to meet the growing demand for cruise missiles across the Indian Armed Forces and to support potential applications in medium-weight unmanned combat aerial vehicles.
An uprated 10 kN variant has been proposed for larger unmanned systems such as medium-altitude long-endurance drones and collaborative combat aircraft. In parallel, GTRE designed a 350 kg thrust-class expendable turbojet specifically for one-time-use applications. The first production unit, manufactured by Hyderabad-based Azad Engineering, was delivered in July 2026. Intended for cruise missiles, jet-powered loitering munitions, target drones and tactical unmanned aerial vehicles, the engine marks a significant industrial milestone: a complete indigenous jet engine built by a private firm to a government design.
By mastering the design, development and production of this engine, India has taken a significant step towards self-reliance in critical defence propulsion technology. The Manik not only reduces dependence on foreign suppliers but also strengthens the foundation for future indigenous engines that can power more advanced missiles and drones, thereby enhancing the nation’s strategic capabilities under the Atmanirbhar Bharat initiative.
PTAE-W: Upgraded Turbojet for CATS Warrior UCAV
The PTAE-W is an upgraded indigenous turbojet engine developed by Hindustan Aeronautics Limited through its Aero Engine Research and Development Centre in Bengaluru. It represents a refined evolution of the earlier PTAE-7, originally designed as the Pilotless Target Aircraft Engine to power the DRDO Lakshya series of unmanned target drones.
The original PTAE-7 was conceived in the early 1980s as India’s first fully indigenous small turbojet and completed its development by the mid-1980s, with successful remote-controlled trials announced in 2001. It featured a four-stage axial-flow compressor with a transonic first stage and a single-stage turbine, delivering reliable performance for short-duration target practice missions. Building upon this proven foundation, the PTAE-W incorporates substantial modifications to meet the more demanding requirements of modern unmanned combat aerial vehicles. In its current form, the PTAE-W is a single-shaft lightweight turbojet measuring 1.27 metres in length and 330 millimetres in diameter while weighing approximately 65 kilograms. Its core comprises a four-stage transonic axial compressor, a single-stage turbine, an annular flow combustion chamber fitted with sixteen fuel burners, and an advanced Full Authority Digital Engine Control system.
These enhancements have raised the thrust output to 380 kilogram-force, or roughly 3.7 kilonewtons, with a specific fuel consumption of 1.15 kilograms per kilogram-force per hour. The time between overhauls has also been extended to one thousand hours, significantly improving operational endurance and reliability.
The engine is primarily intended to power the HAL CATS Warrior, an indigenous loyal-wingman unmanned combat aerial vehicle designed for reconnaissance, electronic warfare and precision strike roles alongside manned fighters. In a twin-engine configuration, the PTAE-W provides the necessary redundancy and balanced thrust for a platform with a maximum take-off weight of around 2.1 tonnes.
Notably, a loyal wingman is an unmanned combat aerial vehicle designed to operate in close coordination with manned fighter aircraft, functioning as a semi-autonomous or fully autonomous teammate that extends the capabilities of the pilot. These drones can perform high-risk missions such as reconnaissance, electronic warfare, suppression of enemy air defences, or precision strikes, while remaining under the supervisory control of the manned aircraft. By absorbing threats and sharing sensor data in real time, the loyal wingman enhances situational awareness, multiplies combat power and reduces risk to human pilots, representing a key element of modern manned-unmanned teaming concepts being pursued by several air forces worldwide, including India’s Combat Air Teaming System.
The first successful ground run of the twin PTAE-W installation took place on 21 November 2024 at HAL’s Bengaluru facility, lasting approximately fifteen minutes and validating performance, fuel systems and integration. Subsequent testing has included extensive fault-free endurance runs exceeding two hundred hours, confirming the engine’s robustness for the intended mission profiles.
By adapting a decades-old indigenous design into a modern, digitally controlled powerplant suitable for combat drones, HAL has demonstrated incremental yet meaningful progress in aero-engine technology. The PTAE-W not only reduces dependence on imported propulsion systems for unmanned platforms but also strengthens India’s overall capability in the rapidly expanding domain of autonomous aerial combat systems under the broader vision of Aatmanirbharta.
Thus, despite the well-discussed setback in the Kaveri engine program, HAL and DRDO continue to build the foundational pillars of India’s heavy aerospace propulsion, from stealth UCAVs and rotary fleets to the fifth-generation AMCA fighter engine.
This article is Part 1 of a three-part series on aero engine programs in India, exploring the public sector workhorses, private startup disruptions, and extreme metallurgical breakthroughs shaping the future of Indian aerospace propulsion. In Part 2 of this series, we turn our attention to the agile, heavily capitalised private sector, where homegrown start-ups and precision manufacturing giants are unveiling indigenous turbofans, diesel-capable micro-jets, and cruise missile engines that are rapidly rewriting the rules of Indian defence technology.
