While India has managed to create a fourth-generation jet fighter, it is yet to perfect a low-bypass turbofan (LBTF) engine that can power an aircraft of this class. Indeed, without mastering contemporary jet engine technology, India’s objective of becoming a true aerospace power will remain unfulfilled.
As such, after years of domestic effort by the Defence Research and Development Organisation’s (DRDO) Gas Turbine Research Establishment (GTRE) to develop the Kaveri LBTF engine on its own, India is now turning towards foreign handholding to modify the existing design in order to make it flightworthy.
While the current collaborative effort is limited in scope, a much bigger programme is needed to bring India up to speed in jet engine technology. It must be noted that China is investing very heavily in this domain and will likely steal a march over India if the latter does not do the same.
After some Rs 2,133 crores in expenditure and a couple of decades of development, GTRE’s Kaveri has not yet met its design goals in their entirety. As opposed to a targeted wet thrust level of 81 kilo newtons (KN), the current standard of preparation (SoP) prototypes manage 7-8% less than that figure.
SoP prototypes have achieved dry thrust goals though having demonstrated about 52 KN without afterburner. However, current Kaveri SoP prototypes are not flight capable given their tendency to stall in certain regimes, besides other reliability issues. It has been clear for a while now that foreign expertise is needed to modify the existing SoP level design to make it flightworthy.
This is precisely why the DRDO has engaged France’s Safran Aircraft Engines (Snecma) to perform a design audit on the Kaveri. At the moment, Snecma is preparing a detailed report outlining the design changes needed to create flightworthy Kaveri prototypes.
Once Snecma’s report is ready, GTRE expects to get the go-ahead for the next phase of work that will involve modifying existing SoP prototypes and testing them, with a view to creating new prototypes that can be integrated with an actual flight capable airframe. Snecma will also be a consultant for aircraft integration activities.
As it turns out, GTRE is yet to access some Rs 500 crore in funds that were approved years ago by New Delhi for aircraft integration work as part of the overall outlay for the Kaveri programme. Now that GTRE is looking to actually fly a Tejas test vehicle using a Kaveri engine, it is likely to write to the Centre to disburse this sum.
It seems GTRE will first incorporate Snecma’s recommended design changes onto three existing SoP Kaveri prototypes called K6, K8 and K9. These will be tested both on GTRE’s testbed and on a flying testbed at the Gromov Flight Research Institute in Russia.
After which, a few refined prototypes will be built that are likely to meet the Centre for Military Airworthiness and Certification’s (CEMILAC) reliability standards and receive certification for a limited number of flights on board a Tejas class aircraft.
One of these engines post-CEMILAC clearance will be integrated with a Tejas prototype and some 30-40 sorties will be conducted to demonstrate India’s ability to build a LBTF in the 70-80 KN class. GTRE expects to accomplish all this by Aero India 2019.
Greater thrust needed
However, an engine with this level of thrust is inadequate to power even current combat capable Tejas variants, not to mention future ones. Indeed, the Tejas MK-2 design, given its much greater maximum take-off weight will need a jet engine in the 90 KN wet thrust class.
It is felt that the work done on the Kaveri programme should be taken forward by enlisting Snecma’s help to create a Kaveri-derived engine in the 90 KN category that would be compatible with the Tejas. To be compatible with the Tejas, this engine would have to retain the dimensions of the existing Kaveri design with compressor and turbine sizes remaining unchanged.
So, the chief way in which a similar sized derivative can be uprated to 90 KN would be by having an engine core that can withstand much higher turbine entry temperatures. This, in turn, would require the core to be made up of different materials, such as next generation titanium alloys, from what make up the current Kaveri engine core called Kabini.
This undertaking will not prove cheap though. Dr K Tamilmani, former Director General of DRDO’s Aeronautics cluster, estimates that this effort may cost Rs 10,000 crores and take a decade to complete if work began now.
However, given that India is likely to import engines worth several multiples of that figure in the next 15 years or so, the expense could well be worth it, since the expertise gained could allow India to indigenise several classes of jet engines, besides delivering an indigenous LBTF for the Indian Air Force’s Tejas fleet.
Incidentally, the Chinese have already understood the critical importance of being able to design and build modern jet engines and have apparently engaged thousands of technical personnel in a multi-billion dollar effort to achieve the same.
(The writer is a New Delhi-based commentator on security and energy issues)