India’s Gas Turbine Research Establishment (GTRE), part of the Defence Research and Development Organisation (DRDO), has announced that the Kaveri engine has been cleared for inflight testing, marking a significant development in India’s indigenous aero-engine development program, according to latest reports.
The non-afterburning Kaveri engine, developed to power India’s first stealth, unmanned combat aerial vehicle (UCAV), Ghatak, has been cleared for inflight testing, GTRE announced on December 23.
The engine is now ready for real-world performance evaluations aboard a specialized flying test bed (FTB). In this phase of testing, the dry-Kaveri engine will be mounted on an FTB to evaluate its response to various flight conditions, its integration with aircraft systems, and its overall reliability in a dynamic and challenging environment. The engine’s endurance and efficiency in extended flight will also be tested.
Earlier, it was reported that the FTB for inflight testing of the dry-Kaveri engine is a modified Ilyushin (II)-76 fixed-wing, four-engine turbofan aircraft. During the trials, the Kaveri Dry engine will replace one of the Il-76’s four engines. The testing location would be Gromov Flight Research Institute, located near Moscow, Russia, where the modified IL-76 is based.
The clearance for inflight testing follows extensive and rigorous evaluations, including high-altitude simulations conducted in Russia and extensive ground trials in India.
The high-altitude tests were conducted successfully last year at the Central Institute of Aviation Motors (CIAM) in Russia, simulating an altitude of 13,000 m (42,651 ft). During these trials, the dry-Kaveri engine also managed to generate 48.5kN of thrust, much more than the benchmark target of 46kN that it had to demonstrate for UAV applications.
These high-altitude simulator tests in Russia and extensive ground trials in India demonstrated promising results in reliability, thrust output, and operational stability, meeting the required performance metrics for inflight testing.
GTRE hopes to complete all tests by 2024-25 and commence limited series production by 2025-26.
Engine Specifications & Applications
The dry version of the Kaveri engine delivers approximately 49-51 kN of thrust. During high-altitude simulations conducted in Russia last year, the engine generated 48.5kN of thrust, making it well-suited for UAV applications, particularly the 13-ton Ghatak, India’s advanced stealth Unmanned Combat Aerial Vehicle (UCAV) program.
Going forward, DRDO plans to integrate an afterburner to increase the engine’s thrust to 73-75Kn for more demanding scenarios.
In 2018, the Kaveri engine successfully passed a Safran audit, which certified it had attained a maturity level suitable for aircraft integration—albeit on a limited scale. The next testing phase involves integrating the engine onto an FTB to evaluate its performance, endurance, efficiency, reliability, and compatibility with aircraft systems under dynamic conditions.
India’s Tryst With Fighter Jet Engine
India’s Kaveri engine project has a long history, albeit with many disappointments and failures and few successes. The project began in the late 1980s, with DRDO authorized to launch a program to develop an indigenous jet engine to power the Light Combat Aircraft (LCA) Tejas.
In the 1990s, when India was pursuing economic reforms, opening up its markets, conducting nuclear tests, diversifying its defense partnerships after the collapse of the Soviet Union, and raising its international profile, New Delhi also decided to revive its long-cherished dream of developing a domestic fighter-jet engine.
Notably, HAL’s earlier efforts to develop a reheated version of the 21.6 kN Orpheus 703 engine used in the indigenously developed HF-24 Marut fighter jet had ended in failure.
Thus, the Indian defense establishment began work on a homegrown military jet engine: the Kaveri, named after a river in the country’s south.
However, producing advanced fighter jet engines is extremely complex, requiring real-world experience built up over decades.
To date, only five countries — incidentally, all of them current permanent members of the UN Security Council — know how to build them: the US, UK, France, Russia, and China. Even among them, China is only a recent entrant.
The Kaveri project, which received US$53 million in funding, planned to develop 17 prototypes of Kaveri engines. However, the first bid could only achieve the core module, called ‘Kabini.’ The third prototype was the first to get variable inlet guide vanes on the first three compressor stages and had its first run in 1995.
The first entire run of the Kaveri engine took place in 1996, and all five ground-test prototypes were tested in 1998. The initial flight tests were planned for 1999, and the test on Tejas was to happen in 2000. However, the crippling sanctions that followed the 1998 Pokhran nuclear tests resulted in the Kaveri project slowing down due to technology acquisition difficulties.
The Kaveri project continued in spurts until mid-2004, when a failure during a high-altitude test in Russia ended all hopes for its introduction with the first production batch of Tejas fighter jets.
The Kaveri engine was sent to Russia again in 2008 for its second high-altitude test, though in 2007, GTRE decided to bifurcate the project into two separate programs. The K9+ program was a proof of concept in complete design and for experience in integration and flight trials, and the K10 program was the final production variant through foreign collaboration.
One of the Kaveri prototypes (K-9) was successfully flight-tested at the Gromov Flight Research Institute in Moscow on November 4, 2010. The test results were promising, but the 2011 CAG report came as a rude shock. It highlighted the program’s cost overruns, with only two out of the six milestones having been met.
The CAG report stated that the engine was overweight than the design specifications, being 1,235 kg (2,723 lb) against 1,100 kg (2,400 lb), and there was no significant progress toward developing the compressors, turbines, and engine-control systems.
A 2010 Ministry of Defense report identified technological complexities, the lack of critical equipment, the denial of technologies by technologically advanced countries, the lack of test facilities in the country, and the non-availability of skilled manpower as key reasons for the repeated delays in the Kaveri project.
DRDO virtually abandoned the project by 2014, but it was revived in 2016 when India announced a collaboration with Safran to make Kaveri engines worthy of the Tejas fighter jet.
However, DRDO later shifted its focus to develop a dry version of the Kaveri engine to power India’s indigenous unmanned combat aerial vehicles. This version has now received clearance for inflight testing.
Design Enhancements
To improve performance for UAV applications like the Ghatak, GTRE has focused on enhancing the dry thrust and designing a new fan with high inlet pressure distortion tolerance. The updated design features a 3.4:1 pressure ratio and supports 78 kg/s mass flow across three stages.
These modifications aim to enable compatibility with future stealth aircraft featuring serpentine air intakes, which are known to cause higher pressure distortions at the fan inlet. GTRE first showcased a model of the serpentine-compatible Kaveri engine during Aero India 2019, underlining its potential for future stealth aircraft programs.
Looking Ahead
With inflight testing now approved, GTRE is set to evaluate the Kaveri engine’s capabilities in real-world conditions. Success in this phase will allow for refining the afterburner design for Kaveri 2.0 and achieving higher thrust outputs required for advanced fighter jets and other aerial platforms.
This development represents a critical step forward in India’s pursuit of self-reliance in defense technology and indigenous aero-engine development. The successful inflight testing of the Kaveri engine will also reduce India’s dependence on foreign suppliers, which is crucial for India’s self-reliance (Atmanirbharta) goals in critical defense technologies.
- Sumit Ahlawat has over a decade of experience in news media. He has worked with Press Trust of India, Times Now, Zee News, Economic Times, and Microsoft News. He holds a Master’s Degree in International Media and Modern History from The University of Sheffield, UK. He is interested in studying Geopolitics from a historical perspective.
- He can be reached at ahlawat.sumit85 (at) gmail.com
