“Kaveri is a low bypass twin-spool turbofan jet engine which was slated to provide an 80 KN power pack and adequate ‘thrust to weight’ ratio required by a modern fighter jet configuration,” explained an aeronautical engineer

The indigenous Light Combat Aircraft (LCA) `TEJAS’, a 4.5 generation single-seat multirole fighter aircraft was conceptualized on the key factor of availability of indigenous `Kaveri’ jet engine which was being designed and developed by Defence Research and Development Organisation (DRDO). “Kaveri is a low bypass twin-spool turbofan jet engine which was slated to provide an 80 KN power pack and adequate ‘thrust to weight’ ratio required by a modern fighter jet configuration,” explained an aeronautical engineer.

TEJAS Prototype — How It All Started?

The government-sanctioned in 1983 the design, development and manufacture of the TEJAS over 8 to 10 years to evolve six flying prototypes and for both the TEJAS and Kaveri engine, DRDO had an Aeronautical Systems’ cluster. Aerial Delivery R&D Establishment (ADRDE), Aeronautical Development Establishment (ADE), and Centre for Airborne System (CABS), Gas Turbine Research Establishment (GTRE) and Centre for Military Airworthiness & Certification (CEMILAC) were part of the DRDO cluster four decades ago.

The TEJAS project under DRDO and state-owned Hindustan Aeronautics Limited (HAL) included complete development and integration of a jet engine, Airframe and multi-mode Radar, Flight control system, Digital Electronic Engine Control and integration of Kaveri engine, along with carbon fibre technology for Primary Structural Components. “This was no mean task for any nation since the technology required was cutting edge and not available within the country. Most importantly, at that stage itself, already other aircraft manufacturing nations had a jet engine advantage of more than three decades of their developmental life-cycle,” explained a former Indian Air Force officer.

What Was The Air Staff Requirements of IAF?

Indian Air Force (IAF), being the end-user for the TEJAS fighter jets, issued the Air Staff Requirement (ASR) in 1985 with a projected requirement for 220 Light Combat Aircrafts (including 20 trainer aircraft) to be inducted in the early 1990s. As per the ASR, TEJAS was to be built as a lightweight multi-mission fighter aircraft, having contemporary air combat and offensive air support capabilities with maintaining high manoeuvrability for close air combat (at low and medium altitudes). The purpose of the aircraft was to be able to provide extended Air Defence cover over the tactical battle area and forward bases.

In a recent interview to the Financial Express Online, the IAF Chief RK Bhadauria had said in response to a question that “order 83 MK IA is expected to be placed soon. And the deliveries of these aircraft will begin in three years.”

With the focus on indigenization and self-reliance the IAF will soon have 40+83 Tejas Mk I/IA and these will be around six squadrons of TEJAS Mk-II. And all these made in India fighters will be powered by the General Electric GE F414-INS6 of the US. This engine has been selected by Aeronautical Development Agency (ADA) to power the MKII version of the Tejas. The engine boasts a thrust to weight ratio of nine by one class and with a 98KN thrust class and similar class of engines are in use by many other aircrafts world over.

More About Kaveri

The Kaveri engine for the indigenous jet was undertaken by Gas Turbine Research Establishment (GTRE), however, the thrust to the weight ratio of Kaveri is below required figure for Tejas aircraft. Due to this, the DRDO was forced to steer the Kaveri engine away from the TEJAS program, after an investment of almost four decades of developmental effort.

And now the Kaveri engine is being justified for use in Unmanned Aerial Vehicles (UAVs), leaving a gap in the indigenous jet engine development. The halt in research on the jet engine at this juncture is critical for the future of indigenization effort, where demand for thousands of such jet engine is confirmed to be there in next few decades within India itself. Further, this may be a huge missed opportunity to call off aircraft jet engine development at this stage.

TEJAS Catch-Up With Technology

While TEJAS was facing various technological and other issues related to the sanctions imposed on India by the technologically advanced community, the military aircraft technology too was developing at a fast pace. “Apart from challenges pertaining to the jet engine and airframe, the avionics and sub-systems on board were under revised Air Staff Requirement by Air Headquarters so as to maintain an operational weapon edge of TEJAS. This package included air combat missiles, multi-mode Radar, Helmet Mounted Display etc. For example, Electronic Warfare capabilities were lacking in TEJAS Mark-I as were specified by IAF since the Self Protection Jammer was not fitted onboard due to space constraints etc. These changes necessitated design changes on the aircraft itself, requiring a revisit to the design board stage,” explained a former IAF officer who was associated with the program.

As a standard process, a fighter jet undergoes a strict Initial Operational Clearance (IOC) and a Final Operational Clearance (FOC) as part of airworthiness trials. TEJAS Mark-I, which achieved Initial Operational Clearance by December 2013 but had significant observations meeting the ASR specifications. These would have resulted in reduced operational capabilities and limiting its operational employability in an IAF squadron. Increased weight, reduced internal fuel capacity and reduced speed etc. shortcomings were expected to be overcome by the development of TEJAS Mark-II taken up by ADA. Meanwhile, the TEJAS trainer aircraft production by HAL too was delayed for being unable to clear the IOC/FOC mark. Hence, IAF had to commence TEJAS pilot training on a Mission Simulator.

Induction of Tejas

The first TEJAS squadron could be formed by IAF only by 2016 and that too, without the indigenous Kaveri engines. The TEJAS could not replace the ageing MiG-21s as was expected in1980’s and IAF continued to face depleting strength of fighter squadrons over the decades, leading to stressed manpower and aircrafts required to maintain the Air dominance over the Indian Air Space. As an adhoc measure, consequent up-gradation of MiG-21 Bis aircraft was undertaken to cover the shortfall gap in fighter aircraft. According to the former IAF officer who wished to remain anonymous “Unfortunately, dovetailing the operational IAF with research project affected the modernisation plans of the Service and this resulted in some awkward situations like a dogfight between a MIG-21 B with enemy’s superior F-16 aircraft in a real hostile Air dominance combat drill in 2019, a situation well representing the IAFs inability to replace its ageing fleet of aircraft.”

Further, to give a boost to the nation’s indigenization efforts, TEJAS Navy development was sanctioned to ADA in 2009 to initiate Design and Development activities. The aircraft is designed based on Ski-Jump Take-off but Arrested Recovery (STOBAR) concept and has successfully completed several trials. The Staff Requirements for Naval version of Tejas has been drawn out by the Indian Navy.

TEJAS-Kaveri Developmental Approach?

While Kaveri engine was in a developmental stage in the 1980s, Indian Space Research Organisation (ISRO) had just then launched its first experimental satellite launch vehicle SLV-3. The Space Agency has been evolving rapidly on its own and has successfully launched Chandrayaan and Mangalyaan missions. Though a comparison of the rocket engine to jet engine technology is not the focus the ISRO success highlights the advantages of a ‘User-developer’ paradigm.

In case of Tejas with a Kaveri engine, India is at a crucial juncture to achieve ‘Atmanirbhar’ status in the aerospace Industry with some path defining changes, while safeguarding country’s security.