The subject of Tejas, the Indian effort to build a light fighter aircraft, is a hot potato. Rabidly defended by its advocates, lampooned by its opponents and a source of both pride and frustration for those within the programme — what exactly is going on with Tejas? We asked Jim Smith, a man had significant technical roles in the development of many of the UK’s leading military aviation programmes from ASRAAM to the Eurofighter Typhoon. 

“The Tejas is a most interesting project, being developed by India through a cooperative venture between Hindustan Aerospace Limited (HAL), several laboratories of the Defence Research and Development Organisation (DRDO), and a number of other companies and suppliers, under the management of the Aircraft Development Agency (ADA), which is an organisation within the Indian MoD. I describe the project as most interesting, because several facets of the programme are unusual, including the technical solution, the programme itself, and the evolving nature of both the requirement and the solution.
I should explain that this article represents an outsider’s perspective, and does not have the advantages of an insider’s view. Also, because it is based on my reading of open source information, it is, of course subject both to the limitations of that information, and my judgements and speculation in interpreting it. I’ll shamelessly admit my principal sources to be Wikipedia and Jane’s All the World’s Aircraft.
I’ll briefly discuss the programme, then look at the current design and the projected development of the aircraft, and finally make some comments on how the programme outcomes have, or have not, met expectations.

Programme Development
The Light Combat Aircraft programme was approved by the Indian government in 1983 with the intention of providing a replacement for the MiG-21. The MiG-21 had been produced in India under license by HAL, and a total of 657 were produced by that company. The aircraft entered service with India in 1964, and remains in service as an interceptor in some numbers. As a fighter aircraft, the MiG-21 was an outstanding success, more than 10,000 aircraft of all variants having been produced, with 60 or so countries having operated the aircraft.

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Key characteristics of the MiG-21 include its relatively small size, a single engine tailed-delta configuration, rapid rate of climb and supersonic performance at all levels and up to Mach 2.0 at altitude. Like many interceptors, internal fuel is limited, resulting in short range without external fuel tanks. The delta wing offers low wave drag and high rate of climb, but relatively high lift-dependent drag and poorer performance in turning flight.
The LCA programme has been extremely protracted, with the AF aircraft entering service in January 2015, and the Indian Navy variant currently in flight-test. The Final Operating Clearance of the Tejas 1 AF aircraft was issued in February 2019, 36 years after the initiation of the programme. Further development is ongoing, with the first flight of the substantially developed Mark 2 anticipated in 2023, and an interim standard Mark 1A also expected to fly in 2022.

Technology and Industry
The Tejas programme should not, however, be considered simply as a prolonged effort to develop a replacement for the MiG-21. It is, in addition, a vehicle to enable the development of the Indian military aerospace industry, with the intent of creating Indian ‘self-reliance’ in the critical technologies of advanced aerospace materials; military propulsion; cockpit displays; flight control systems and radar, and the integration of these technologies into advanced combat aircraft.

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Attempts have been made to advance national technology capability in all these areas with varying degrees of success. Perhaps the most successful areas are the development of glass cockpit display, composite aerospace materials and flight control systems, while efforts to develop the indigenous Kaveri engine and the radar for the aircraft appear to have been less successful, and the further development of the aircraft to Mk 1A and Mk 2 seeks to address these aspects, among others.
The programme is a complex one, with the involvement of both Government Research Agencies through the DRDO, Indian Industrial capability, and some assistance from different International partners as the programme has progressed. This is likely to have led to a complex project management and contractual environment, and progress has at times been further complicated by suspension of cooperation due to US concerns over the Indian nuclear programme.

What’s unusual about Tejas’ wing? Full story here

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Bearing in mind the desire to develop the Indian aerospace industry capability, there are some similarities with the joint Government and Industry efforts to exploit jet engine technology in the UK following World War II. At that time, many of the relevant technologies were immature, and the principal Government research establishments cooperated closely with Industry to develop, and to resolve the issues of aircraft being developed for both RAF and civil use.

A further complication has been the changing aerospace technology scene as the programme has progressed. The development of active electronically scanned array (AESA) radar systems; advances in digital flight control systems; electronic warfare; defensive aids; and the advent of stealth technologies have all resulted in an environment in which a lightweight, simple aircraft to replace the MiG-21 as an air defence fighter has perhaps become questionable. These changes in technology and the operational environment are additional drivers towards a Tejas Mk 2 capability.

In addition, India has, of course, selected the Dassault Rafale as an air superiority and strike aircraft, in addition to fielding a very substantial fleet of Su-30MKI and MiG-29s. Some might question the need for a significantly less capable air defence aircraft as well as this fleet of air superiority aircraft, not to mention the multi-role Mirage 2000 and the MiG-21, which remains in service. While not commenting on operational matters, I would simply observe that the availability of a complementary air defence aircraft may provide additional freedom in tasking the air superiority assets. In addition, there are some advantages in operating a largely locally-produced aircraft, not overly reliant on third-party support arrangements.

Tejas Mk 1

Tejas Mk 1 is a small, single-engine aircraft, featuring a shoulder mounted wing of near-delta configuration, powered by the General Electric F404-GE-IN20 turbofan engine. Compared to the MiG-21, which it is to replace in Indian AF service, the Tejas is ~1.5m shorter, has 60% greater wing area, and features relaxed stability. These features suggest that the Tejas should have significantly better instantaneous turn rate than the MiG-21, although the short fuselage may contribute to a common problem for interceptors – low combat persistence and range due to the relatively low internal fuel.
The aircraft has considerable flexibility to operate in other roles, with the provision of three wet stations for external fuel tanks, out of a total of 7 hardpoints for stores, plus provision for a targeting pod. Naturally, external stores carriage will impact performance, and it is likely that in combat scenarios external fuel tanks would be jettisoned to enhance supersonic performance.

The Tejas maximum Mach number of 1.8* is less than the Mach 2.0 achieved by both the MiG-21 and the more contemporary Gripen. Given the similar installed thrust, it seems likely that this is due to higher wave drag from the relatively large wing and relatively short fuselage. It is also probable that the MiG, with its variable area intake, may better exploit engine performance when supersonic. These factors will reduce the transonic acceleration, climb rate, maximum Mach number and energy manoeuvrability of the Tejas Mk1.

*This figure may actually only currently be M1.6.

Looking at the key technologies being developed for, and by, the Tejas programme, the advanced composite structure, advanced flight control system and modern glass cockpit goals appear to have been largely met, although some concerns have been expressed about the aircraft weight. The desire to develop an indigenous engine and radar for the aircraft, however, has been less successful, and the Mk1 Tejas is fitted with the GE F404 engine, and a hybrid ELTA/M2032 multi-mode radar.
In parallel with the development of the Mk1 AF fighter Tejas, a two-seat trainer and a naval variant are also in development and flight test. The naval variant has a number of significant differences, including a modified structure suitable for arrested landings, an arrester hook, a drooped nose to improve visibility on approach, and inboard leading-edge vortex controllers, to improve low-speed performance and handling. The naval variant has recently conducted its first land-based arrested landing trials.

Tejas Mk 2 (AF)
Given the long development programme of the Tejas, it is unsurprising that aerospace technology has moved on during the programme, and that the Mk 1 product does not fully meet the expectations of today’s Indian AF or Navy. In addition, as noted above some technologies have not matured as expected, and alternatives are required.
From the AF perspective, the following main issues and proposed solutions have been identified:
Reduced endurance due to insufficient internal fuel – greater volume to be found through both a lengthening and a widening of the fuselage.

Lack of sufficient thrust – GE F414 engine to be substituted for the F404 in the Mk 1

Poor transonic acceleration – close-coupled canards to refine wing aerodynamics

1.25m increase in fuselage length, re-profiled canopy, re-designed stores pylons

Inadequate radar performance – Uttam AESA radar to be fitted

Inadequate EW capability – new missile approach warning system, provision of EW pods

Insufficient payload – 11 external pylons to be fitted.
As a consequence of all these changes, the Tejas Mk 2 has been referred to as the Medium Weight Fighter (MWF), and is essentially a new design. With a new engine, and the change in aerodynamics from the introduction of canards, a new set of Flight Control Laws will be required. The introduction of an EW capability and IRST will also impact the man-machine interface and cockpit displays. First flight of this new design is planned for 2023, and the achievement (or not) of this date will be a good indicator of how Indian aerospace capability is progressing.

Tejas Mk 2 (IN)

The IN has expressed the view that Tejas Mk 1 is too heavy for shipboard operations. Loosely translated, I suspect this means that the approach speed is too high, as the aircraft is much lighter than many naval aircraft. Of course, a high approach speed is a significant issue as reducing the approach speed generally calls for an aerodynamic redesign. As an example, compare the T-45 Goshawk with a Hawk T1. The T1 is unable to meet mandatory approach speed requirements for the US Navy, and a slatted wing design had to be introduced for the Goshawk.
In the case of Tejas, while the AF is pursuing a Mk 2 solution using canards, the Navy is examining an option with an aft tail fitted, presumably to trim out the aircraft with high lift devices for the wing. This takes the Navy Mk 2 off onto a completely different development path to that of the AF aircraft, and will require the development of yet another set of control laws.
It is not clear which of the other AF modifications would carry across to the Navy aircraft.

Tejas Mk1A
Given the changes in design being considered for both the AF and IN Mk 2 aircraft, the Indian MoD has decided to procure an interim aircraft, the Tejas Mk 1A, which will go some way towards remediating the deficiencies of the Mk 1, without the additional complexities introduced by some of the features of the Tejas Mk 2.
The changes envisaged are:

—Introduction of the Elta/HAL EL/M-2052 AESA radar
— Carriage of Elta EL L-8222 ECM pod
— Weight, drag and RCS reduction programmes aimed at reducing weight by some hundreds of kg, drag by 6%, and RCS through the use of coatings and RAM

— Reduction in maintenance requirements.
At this point, I would just observe that some of these aspirations are easier said than done, particularly when there is an intention to simultaneously reduce weight by 10 to 15%. The first flight of the Mk 1A is apparently expected in 2022.
Has the Tejas programme achieved its objectives?

I suspect that even in India, one could get different answers to this question, depending on whether you were talking to the Air Force, the Navy, the ADA, Industry, the DRDO or the MoD.
The service perception will, of course, be coloured by operational needs, and it is clear from the discussion above that neither the AF nor the IN regard Tejas Mk 1 as the fully developed solution to their needs. Indeed, both services are looking to rather different directions as they identify what a Tejas Mk 2 should be. The trends in aerospace design and capability over the development of the aircraft have tended to take operational requirements away from the simple MiG-21 replacement that was perhaps envisaged in 1983, and both services are looking to a more flexible and multi-role aircraft, better protected and with better sensors and weapons than were available at programme initiation. Inevitably this is likely to be delivered in a larger package, leading to the perception that what is needed is less of a Light Combat Aircraft, and more of a Medium Weight Fighter.

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ADA, Industry and the DRDO have delivered some of the capability they planned at the start of the programme. Yes, the engine and radar are off-the-shelf products, but the aircraft is in service, and is reported to be delivering good handling qualities. The performance is, perhaps, a little disappointing in some respects. Compared to the MiG-21, Tejas probably under-delivers in supersonic performance, but should be more agile, and has demonstrated the ability to launch BVR-capable weapons. From a technology perspective the Tejas Mk 2 programme offers more opportunities for innovation – but also some more integration challenges.

From an MoD perspective, should they just have gone out and procured the Gripen E/F? From a pure cost and Defence capability perspective, it is tempting to say ‘yes’. But to do so would be likely to close off the development of the industrial capability with which India hopes to develop its own ‘next generation’ fighter aircraft. Is this a realistic aspiration? Well, it may or may not be, but without attempting something like the Tejas programme, a leap to the ‘next generation’ would certainly be unrealistic.

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There are some warning signs. Everything has taken far too long. There is no propulsion system design capability for the advanced engines that are likely to be required by future combat aircraft, and the radar development programme appears to have struggled. But progress has been made in systems and systems integration, and in structural and aerodynamic design, and there is already a strong weapons capability in place.
Having moved from the UK to Australia, it is clear that there is a vast difference in capability between an Industry that is capable of assembling other people’s designs, and an Industry that can deliver its own designs to meet local requirements and conditions, without being dependent on third parties for support.
Australia crossed that capability gap in one direction a long time ago. India is trying to progress in the opposite direction. Tejas Mk 1 is a step down the path, and the development of Tejas Mk 2, if successful, will be a significant further step.”

What’s unusual about Tejas’ wing? Full story here

 Jim Smith,  had significant technical roles in the development of many of the UK’s leading military aviation programmes from ASRAAM and Nimrod, to the JSF and Eurofighter Typhoon. He was also Britain’s technical liaison to the British Embassy in Washington, covering several projects including the Advanced Tactical Fighter contest. His latest book is available here.

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