The Kaveri Dry Engine (KDE), developed by the Gas Turbine Research Establishment (GTRE) in Bengaluru, has successfully completed high altitude and in flight trials in Russia. The 48.5 kN thrust demonstrated during these tests clears the path for powering India’s Ghatak stealth Unmanned Combat Aerial Vehicle (UCAV). The result marks a decisive turnaround for a programme that began in 1989 to power the Tejas fighter.
What Is the Kaveri Engine Project?
The Kaveri engine is India’s indigenous turbofan aero engine programme to power military jets and combat drones. The Gas Turbine Research Establishment (GTRE), a Bengaluru based laboratory of the Defence Research and Development Organisation (DRDO), leads its design and development. The engine is designated GTX-35VS Kaveri, named after the Kaveri river, and its core is called Kabini.
The DRDO was formed in 1958 and is headquartered in New Delhi. Within the DRDO, the GTRE holds the charter for gas turbine engines for military aircraft and unmanned systems. The GTRE operates from C V Raman Nagar in Bengaluru, and works closely with the Aeronautical Development Agency (ADA), the Aeronautical Development Establishment (ADE) and Hindustan Aeronautics Limited (HAL).
The Kaveri project was sanctioned in March 1989 at a cost of ₹382.81 crore with completion targeted for December 1996. The original goal was to power the Light Combat Aircraft (LCA) Tejas. The Kabini core ran for the first time in March 1995, and the first full Kaveri prototype began ground tests in 1996. By 2010 the programme had built eight full engines and four core engines and logged about 1,880 test hours, which later crossed 3,200 hours.
Why Did the Kaveri Engine Fail for Tejas?
The original Kaveri engine fell short of the strict demands of a single engine supersonic fighter, so it was delinked from the Tejas programme in September 2008. The Tejas then adopted the American GE F404-IN20 engine for production. The core issues were low thrust, excess weight and unstable afterburner performance at high altitude.
The Kaveri was sanctioned to produce 81 kN of thrust with afterburner. In tests the engine produced only 70 to 75 kN with afterburner and 49 to 51 kN of dry thrust. Its weight stayed around 1,180 to 1,236 kg, well above the 1,100 kg target, while the GE F404 weighs only 1,036 kg. The engine also faced turbine blade failures, problems with high temperature alloys and combustion instability in the afterburner, called screech.
High altitude trials in Russia in the mid 2000s confirmed the gap. India had no domestic high altitude test facility at that time, so prototypes weighing over a tonne each had to be flown to Russia. Post 1998 technology restrictions also slowed access to critical materials and test support. The project cost rose to over ₹1,892 crore by 2009 against the original estimate. The programme continued after 2008 as a technology demonstrator and was later refocused toward unmanned platforms where the thrust demand is lower.
What Is a Dry Engine and How Much Thrust Does Kaveri Produce?
The Kaveri Dry Engine (KDE), also called the Kaveri Derivative Engine, is the non afterburning version of the GTX-35VS Kaveri turbofan developed by GTRE for the Ghatak UCAV. It produces about 48.5 kN of dry thrust without an afterburner and is optimised for fuel efficiency, endurance and low heat signature.
A dry engine is a jet engine without an afterburner. An afterburner injects extra fuel into the hot exhaust to give a short burst of extra thrust for takeoff or combat. The burst comes at the cost of very high fuel use and a hotter, more visible exhaust. A UCAV needs long endurance and low visibility rather than supersonic bursts, so a dry engine suits it better.
The KDE achieved a peak dry thrust of 48.5 kN, against the Ghatak target of 46 kN. Ground runs showed stable output in the 49 to 52 kN band in recent configurations. The engine is a twin spool low bypass turbofan with a six stage high pressure compressor and a three stage low pressure compressor. Its bypass ratio is very low at about 0.17. The length is about 3,490 mm and diameter is about 909 mm.
The flat rated design is a key strength. The GTRE designed the Kaveri core to give steady thrust even in hot and humid Indian conditions. The GE F404, by contrast, can lose close to 8 to 10 percent thrust in such heat, which brings its effective thrust down from about 84 kN toward 77 kN. This trait makes the indigenous core valuable for desert and high altitude bases.
| Parameter | KDE Dry Configuration | Original Kaveri Target |
|---|---|---|
| Type | Non afterburning turbofan | Afterburning turbofan |
| Dry thrust | 48.5 kN demonstrated | About 52 kN |
| Wet thrust with afterburner | Not applicable | 81 kN |
| Weight | 1,180 to 1,236 kg | 1,100 kg |
| Intended platform | Ghatak UCAV | Tejas fighter |
Latest Update: Kaveri Dry Engine Test in Russia
The GTRE completed the crucial Russian test campaign in September 2026, covering both high altitude simulation and in flight evaluation. The tests were conducted at the Baranov Central Institute of Aviation Motor Development (CIAM) and the Gromov Flight Research Institute (GFRI) near Moscow. The campaign used a modified Ilyushin Il-76 flying testbed, in which the Kaveri engine replaced one of the four standard engines to measure real airborne behaviour.
The altitude rig simulated conditions up to 13,000 metres (about 43,000 feet). The flying testbed evaluated the engine up to 12 km altitude and 0.7 Mach forward speed across different pressure and throttle settings. Engineers checked thrust delivery, relight, control response and thermal stability. The cumulative effort involved 70 hours of ground runs at GTRE Bengaluru and 75 hours of altitude testing in Russia, with a final block of about 25 hours of in flight tests to close the certification data pack.
The first production standard engine, designated D1, was delivered by Godrej Aerospace in September 2025. Godrej Aerospace then moved to assemble D2 and D3 engines in the first half of 2026 for endurance and reliability trials. Serial production is planned with Hindustan Aeronautics Limited (HAL), which is headquartered in Bengaluru and was established in 1940 as Hindustan Aircraft.
Certification now rests with the Centre for Military Airworthiness and Certification (CEMILAC) in Bengaluru. CEMILAC functions as the airworthiness authority for military airborne stores developed by DRDO laboratories and defence firms, working through Regional Centres for Military Airworthiness (RCMAs). The Ministry of Defence has directed the GTRE to secure full certification of the dry engine by late 2026. Only after this clearance can the engine be formally integrated into the Ghatak airframe for prototype flight tests.
Ghatak UCAV: The Stealth Platform Powered by Kaveri
The Ghatak UCAV is India’s planned stealth unmanned combat aerial vehicle for deep strike missions inside heavily defended airspace. The Aeronautical Development Establishment (ADE) leads its development, with design support from the Aeronautical Development Agency (ADA). The programme began as Project AURA (Autonomous Unmanned Research Aircraft) and is now pursued as the Remotely Piloted Strike Aircraft (RPSA).
A UCAV is an unmanned aircraft built to fight, unlike a basic surveillance drone. It can carry weapons, fly pre programmed combat missions and respond to commands through secure data links. Ghatak uses a tailless flying wing shape with no vertical tail. This shape deflects radar waves away from the source and gives the aircraft a low radar signature. The airframe will use 80 to 90 percent carbon fibre composites, with infrared suppressing coatings near the exhaust to cut heat visibility.
Ghatak is sized in the 13.5 to 15 tonne maximum takeoff class and is expected to carry 1,000 to 2,000 kg of weapons in an internal weapons bay. Internal carriage keeps the outer surface smooth and stealthy. The system is designed to cruise near 0.9 Mach at altitudes up to 40,000 feet, with a range beyond 1,000 km. Planned roles include suppression and destruction of enemy air defences, precision strike and intelligence, surveillance and reconnaissance in contested zones. It is also meant to operate as a loyal wingman alongside manned fighters such as the Advanced Medium Combat Aircraft (AMCA) and Tejas Mk2.
The Defence Acquisition Council (DAC), chaired by the Defence Minister, cleared the procurement of 60 Remotely Piloted Strike Aircraft on 27 March 2026. The decision followed clearance by the Defence Procurement Board on 3 March 2026. The RPSA plan is estimated at ₹39,000 crore, including six prototypes at about ₹10,000 crore, to be executed with a Development cum Production Partner.
How the SWIFT Demonstrator Paved the Way
The Stealth Wing Flying Testbed (SWiFT), also called the Autonomous Flying Wing Technology Demonstrator, is the scaled down prototype for Ghatak. The project was sanctioned in 2016 at a cost of ₹70 crore. The ADE built two prototypes and started ground trials in June 2021. The demonstrator completed its maiden flight on 1 July 2022.
SWiFT proved control of the unstable flying wing shape at high subsonic speeds, along with indigenous flight controls, undercarriage and avionics. Early SWiFT flights used a small Russian NPO Saturn 36MT engine. The full scale Ghatak will switch to the 46 to 50 kN class Kaveri dry engine. This step by step approach lowered risk before committing the larger stealth airframe to flight.
Is the Kaveri Engine Ready?
The Kaveri dry engine is flight test proven but not yet certified for operational UCAV use, with CEMILAC clearance targeted for late 2026. It has cleared Russian high altitude and Il-76 flying testbed trials at 48.5 kN thrust. Full readiness still needs airworthiness approval, Ghatak integration and prototype flight tests.
Readiness has different layers. The Russian campaign proved that the dry core can deliver rated thrust and remain stable across altitude, speed and pressure changes. That answers the basic propulsion question for Ghatak. The next layer is formal airworthiness certification, which audits every test record, safety margin and structural limit.
The final layer is platform integration. The certified engine must be fitted inside the stealth fuselage with shielded intake and exhaust, linked to the UCAV flight controls and fuel system, and flown on the actual Ghatak prototype. The Cabinet Committee on Security clearance for full scale Ghatak prototyping is tied to this engine milestone. So the engine is successful as a UCAV powerplant demonstrator, while its journey to an operational combat engine is still in progress.
Kaveri 2.0 Engine and Comparison with GE F404
The Kaveri 2.0 engine is the planned higher thrust upgrade aimed at fighter class performance. The GTRE targets 55 to 59 kN of dry thrust and 90 to 100 kN of wet thrust with afterburner for this version. That would place it close to the American engines that power the Tejas fleet and open the door for mid life upgrades in the 2030s.
The Tejas Mk1A flies with the GE F404-IN20, which gives about 54 kN dry thrust and 84 to 85 kN with afterburner. The Tejas Mk2 will use the more powerful GE F414, rated at about 58 kN dry and 98 kN with afterburner. The current KDE at about 49 kN dry cannot replace these fighter engines. Kaveri 2.0 is designed to close that gap with a new core, redesigned high pressure compressor, single piece blisks in titanium alloy and single crystal turbine blades that tolerate higher temperatures.
BrahMos Aerospace is already building a new afterburner section for the dry core to add about 29.4 kN and reach 78.4 kN combined thrust. Defence Minister Rajnath Singh witnessed a full afterburner test of this line of development at the GTRE in February 2026. The GTRE also plans to fly an afterburning Kaveri of about 73 kN on an older Tejas Limited Series Production aircraft around 2030 as a flying testbed, before moving to an 84 to 85 kN unit. A separate heavier engine of 120 kN class for the AMCA is being pursued with French company Safran.
| Engine | Dry Thrust | Wet Thrust | Weight |
|---|---|---|---|
| Kaveri Dry Engine | 48.5 kN tested | No afterburner | 1,180 kg |
| Kaveri 2.0 planned | 55 to 59 kN | 90 to 100 kN | About 1,200 kg |
| GE F404-IN20 in Tejas Mk1A | 54 kN | 84 to 85 kN | 1,036 kg |
| GE F414 in Tejas Mk2 | 58 kN | 98 kN | About 1,200 kg |
The Way Forward
The immediate task is to convert Russian test data into Indian certification. The GTRE must submit the full flight and altitude record to CEMILAC and close endurance, control and safety checks on the D2 and D3 engines. Once CEMILAC grants clearance, HAL can move toward limited series production and the ADE can begin mating the engine with the full scale Ghatak prototype.
The larger test will be sustained funding and industrial depth. Single crystal blades, high pressure compressor work and reliable afterburners need steady orders for firms like Godrej Aerospace and PTC Industries. If the dry engine enters Ghatak service on schedule, it will free the combat drone from imported propulsion and build the base for Kaveri 2.0. That path, from UCAV engine today to fighter engine in the next decade, is now the central measure of success for the programme.
Key Takeaways
- The Kaveri Dry Engine developed by GTRE Bengaluru cleared Russian trials in September 2026 with 48.5 kN dry thrust against a 46 kN target.
- Trials were held at CIAM and Gromov Institute in Russia on an Il-76 flying testbed up to 12 km altitude and 0.7 Mach.
- The Kaveri project was sanctioned in March 1989 for ₹382.81 crore to power Tejas and was delinked in September 2008.
- Certification rests with CEMILAC Bengaluru, with full clearance targeted for late 2026 before Ghatak integration by HAL.
- The Ghatak UCAV, earlier called Project AURA, is a 13.5 to 15 tonne flying wing stealth aircraft cleared for 60 units on 27 March 2026.
- The planned Kaveri 2.0 targets 55 to 59 kN dry and 90 to 100 kN wet thrust to match the GE F404 class.
