Generating thrust

Special Report

Infusing new life into Kaveri engine

The process for the finalization of the contract for the acquisition of 126 combat aircraft under the MMRCA (Medium, Multirole Combat Aircraft) tender by sealing the deal with Dassault Aviation whose Rafale fighter had emerged a winner by overtaking the five other rivals seems to be acquiring “some speed” .

As it is, for more than two years now, the finalization of the deal has been affected from one uncertainty to another over the issues of technology transfer and life cycle cost.  And the Indian Air Force (IAF), which is now operating just 34 squadrons against an assessed requirement of 45 squadrons, is badly in need of medium class fighters. Under this deal, while 18 fighters will be made available in fly way condition, the state owned Hindustan Aeronautics Limited (HAL) will produce the remaining 108 fighters with the technology to be made available by the OEM (Original Equipment Manufacturer).

Aero engine

Beyond meeting the immediate needs of IAF, the MMRCA deal is expected to infuse new life into the home-grown Kaveri gas turbine engine whose development was taken up in late 1980s with a view to propel the indigenous fourth generation fighter aircraft, Tejas. However, with the Kaveri engine yet to reach the capability to generate the thrust considered sufficient enough to power the Tejas Light Combat Aircraft (LCA), the Mark-1 version of the fighter is being propelled with GE-F-404 engine and Mark-II version of the fighter with GE-F-414 engine. However, upgrading the Mark-1 version of Tejas to Mark-II standard would require the increase in length of the aircraft along with the redesigning of air intakes to accommodate GE-F-414 engine.

As things stand now, under MMRCA contract, India expects to get the latest genre aero engine technology from Snecma. For Snecma, which will be getting a massive order for the supply of Rafale engines under MMRCA deal, will have difficulties evading the commitment on the engine technology transfer to India on account of the huge amount it would be raking in.

For the offset clause forming part of the defence acquisition programme as well as the contractual obligation of technology transfer need to be honoured in letter and spirit.  Incidentally, each of the Rafale fighter is powered by two M-88-2 Snecma engines each of which generates a thrust of 75-kN. As it is, M-88-2 features the latest genre technologies including single piece bladed compressor disks, single crystal high pressure turbine blades, powder metallurgy disks, ceramic coating and composite materials.

Not long back, DRDO was in discussion with Snecma on how to take forward the development of Kaveri with the most advanced technological elements. However, the negotiations with the French engine major Snecma for co-developing Kaveri engine was called off in early 2013 after the state owned Defence Research and Development Organisaton (DRDO) came to the conclusion that Snecma instead agreeing to transfer latest genre engine technology to India had just offered the replacement of Kaveri’s Kabini core with Snecma Eco Core which is at the heart of M-88. Rightly, this was not acceptable to India which was keen on mastering the latest genre engine technologies.

Kaveri engine was originally envisaged to serve as the power plant for the home grown supersonic fighter jet Tejas LCA (Light Combat Aircraft) However, the Kaveri engine program  now stands delinked from the Tejas fighter aircraft project and it is planned to use an upgraded version of Kaveri to meet the needs of the Advanced Medium Combat Aircraft (AMCA) that is  now being developed as a follow up to Tejas by the Bangalore based Aeronautical Development Agency (ADA) of DRDO.

This implies that the Kaveri turbofan should be upgraded to generate 110-kN wet and 75-kN dry thrust. But then an engine of this capability will need to incorporate single crystal blade technology, integrated rotor disk and blades and super alloys of nickel and cobalt. Kaveri engine in its present form uses directionally solidified blade technology which is rather an old hat. The 20-tonne class AMCA designed for stealth features and super cruise capability is planned to be powered by two GTX Kaveri engines. Significantly, the Kaveri engine has been custom built to operate in the demanding Indian environment that ranges from the hot desert to the freezing mountain heights.

The Bangalore based GTRE (Gas Turbine Research Establishment) a constituent of DRDO, which is the lead agency for the development of Kaveri, is now hopeful of upgrading the Kaveri engine to meet the needs of AMCA in the context of the vastly improved industrial support base in the country that the aero engine development programme had helped create. The biggest challenge ahead of GTRE would be how to enhance the power of Kaveri without increasing its size and weight and through incorporating the single crystal turbine blade technology. But the reality is that GTRE is now nowhere close to developing single crystal blade technology. However efforts are now on to sharpen the expertise level in the country for developing the high performance nickel and cobalt super alloys for Kaveri.

In order to give quickening impetus to the development of Kaveri engine, DRDO should look at setting up a high altitude test facility in the country. This would help obviate the dependence on the Russian facility for carrying out the high altitude tests of the engine in Russia. As it is, Indian Space Research Organisation (ISRO) was able to successfully qualify the home grown cryogenic engine constituting the upper stage of the three stage Geosynchronous Satellite Launch Vehicle (GSLV) after a high altitude test facility was set up at Mahendragiri complex near to Kanyakumari.

Of course, the design, development and qualification of an aero engine is a costly, complex and time consuming process and as such very few  countries have succeeded in mastering the technology of gas turbine engines. India’s Ministry of Defence has identified five problem areas for the delay in the developmental schedule of Kaveri. They are: ab initio development of state of the art gas turbine technologies, technical/technological complexities, lack of availability of critical equipment and materials and denial of technologies by advanced countries as well as the lack of availability of skilled manpower.

Optimal utilization

Meanwhile, India has decided to use the variants of Kaveri engine in its present format as the power plants for its Unmanned Strike Air Vehicle (USAV) and the Unmanned Combat Air Vehicle (UCAV) now under development. This will help India obviate the restrictions of MTCR (Missile Technology Control Regime) which prevents foreign suppliers from selling India engines that helps provide the unmanned attack vehicles a range greater than 300-km. While USAV is a 10-tonne class aerial vehicle designed to deliver unguided bombs to designated targets and return to the base, UCAV is a stealth vehicle in 15-tonne class designed for carrying precision guided munitions and missiles.

Indian Navy too has snapped up the marine version of Kaveri engine for powering the growing fleet of its warships. Over the next fifteen years, Indian Navy might need as many as 40 Kaveri marine gas turbines. Not surprisingly then, the Indian Navy has agreed to fund 25% of the cost of the project. GTRE developed the marine Kaveri by modifying the aero engine with a shaft through which power can be delivered to the propellers.

The mastery of aero engine technology cannot but be a win-win development for India. For according to one estimate, India’s aero engine market, both civilian and defence, could amount to around US$15-billion over the next one decade.

The aero engine has been a vital missing link in India’s military aviation. A 2011 survey by GTRE had revealed that in this decade alone India could spend Rs 180,000 crore to buy engine plus another Rs 400,000-core for their upkeep. Clearly and apparently, developing and producing aero engines indigenously could imply a big leap forward for the Indian aerospace sector that would in addition free India from its costly and continued dependence on global engine majors.

Moreover, the Indian industry can stand to benefit enormously by engineering civilian products from out of the spin offs generated by the home grown aero engine technology. In particular, the power generation sector of the country would stand to benefit substantially from this development.

China on its part is making all out efforts to realize a range of advanced power plants to propel its military aircraft. The demands placed on an engine of a military aircraft are far more complex and challenging in comparison to the engine of a commercial aircraft. High strength materials and super alloys along with composites are used in the power plants deployed on board combat aircraft so that they can easily withstand high temperature ranges in addition to meeting the needs for speed and manoeuvre. Future fighter aircraft are expected to feature an advanced type of power plant, a variable cycle turbine that can operate in two specific modes-one for higher speed and one for fuel efficiency.

In a development that could speed up the progress of home grown aero engine technologies, the state owned  Indian aeronautical giant Hindustan Aeronautics Limited (HAL) has come out with a proposal to join hands with the public sector enterprise BHEL (Bharat Heavy Electricals Limited) and DRDO. The idea is set up a joint venture to design, develop and manufacture gas turbines for a variety of civilian and military applications. It is also planned to involve private industrial enterprises with experience in developing engines in the venture.

Both HAL and BHEL have expertise in licence producing gas turbines of a variety of specifications and fusing their expertise with the experience that DRDO has acquired while developing Kaveri engine could be a veritable “force multiplier” to move ahead with the development of advanced aero engine technologies.

In a development of significance, HAL has received responses from eight international engine manufacturers for its Request for Proposal (RFP) for the power plant that would go into the proposed Regional Transport Aircraft (RTA) to be built by a consortium led by HAL and NAL. For, the design of the aircraft can be frozen only after finalizing the engine that would be fuel efficient and affordable to maintain. The vendor finally chosen to supply the engine will be required to transfer the critical technologies to India to help the country create a manufacturing base for aero engines. However advanced countries do not easily part with the critical engine technology. Only a large and alluring commercial deal could nudge them to transfer the technology.

By all means, Kaveri is a technologically complex power plant. It is a two spool, bypass turbofan engine having three stages of transonic low pressure compressor driven by a single stage low pressure turbine. The core engine consists of a six stage transonic compressor driven by single stage cooled high pressure turbine. The engine is provided with a complete annular combustor with air blast atomiser. The aero-thermo dynamics and mechanical designs of engine components were evolved using many in house and commercially developed software for solid and fluid mechanics. Its three stage transonic fan, designed for good stall margin handles an air mass flow of 78 kg and develops a pressure combustion chamber line ratio of 3:4. Kaveri engine has been designed to achieve a fan pressure ratio of 4:1 and overall pressure ratio of 27:1. These pressure parameters are claimed to be good enough to support the super cruise manoeuvres of an advanced combat aircraft.


The last significant milestone in the Kaveri project was the 2011 flight test fitted on the IL-76 transport aircraft in Russia which identified “some problems”, despite completion of the 90% of the flight envelope. At its current stage of development, the engine has been able to produce a thrust of 70-75-kN while IAF has projected a need for  around 90-95 kN of thrust  Of course, a high performance fighters like AMCA need engines that generates thrust around 100-kN. If the idea of transforming the currently under performing Kaveri engine into power plant robust enough to propel the AMCA with stealth and super cruise features is to materialize, no time should be lost in pushing ahead with the up-gradation of the engine with advanced technological elements.

HAL along with the British engine maker Rolls-Royce has set up a joint venture facility named International Aerospace Manufacturing Private Ltd (IAMPL) at Bangalore for the production of civil aircraft engines and subsystems. HAL has been building Rolls-Royce engines under licence for India’s Jaguar fighter and the Hawk Advanced jet trainer fleet. Rolls-Royce whose engines propel Airbus and Boeing civilian jets has been sourcing ring forgings from HAL for its civilian engines since 2003. “The state of the art facility in Bangalore will produce components for the technologically advanced Trent family of civil aero engines as well as for a number of marine and energy gas turbines.

On another front, HAL and Honeywell have signed an agreement under which HAL will manufacture Honeywell TPE 331 engine components and kits. The TPE-331 engine family represents the most fuel efficient and reliable turboprop engine and will be the first aerospace engine to be manufactured in India for the world wide market. TPE 331 powers the Dornier transport aircraft being manufactured by HAL. The engine division of HAL undertakes repair and overhaul of various aero engines operated by defence forces, coast guard, civilian enterprises and government organisations. The engine division of HAL is also involved in the development and certification of Kaveri engine.

According to K.Tamilamani, Director General (Aeronautical Systems) of DRDO, there is a need for the creation of an autonomous body for design, development, testing and production of aero engines of varying specifications. The amalgamation of the expertise and competence available in both the public and private sectors of the country should be fused to create a high tech platform for developing aero engines. Indeed resources available in private companies such as Kirloskar, L&T and Godrej could be harnessed for giving a quickening impetus to build a vibrant technological base for realizing aero engines of varying thrust ranges.

Indeed to be able to move out of the syndrome of “dependence and import”, India should demonstrate its technological excellence by producing at least one engine with enough parameters of thrust to weight capabilities. Around this engine, India must create a variety of platforms custom made to meet the requirements of IAF. Kaveri with its present level of 70-kN thrust could be a starting point for the development of a range of high performance engines.

Mastering complex technologies involved in high performance aero engines will provide India a solid spring board for developing engine of different thrust ranges meant for use in ships, missiles, UAVs, armoured vehicles, aircraft and helicopters. Moreover, the engine technology has a massive application in the civilian areas and has the potential to boost the power plant industry.

Foremost of India’s mission should be to revive the indigenous Kaveri engine with the thrust to weight ratio sufficient enough to propel Tejas. Significantly, the vision document related to the indigenous aero engine development focuses on the facilities and infrastructure available in the country with suggestions on the initiatives for up-gradation with a view to match the development and service phase of the aero engine cycle.

In the ultimate analysis the plan for developing aero engines in India should take into account the potentials of future technologies so that aero engine built in the country remains contemporary and state of the art.