HAL Tejas

Tejas
LCA Tejas
Role	Multirole fighter
National origin	India
Manufacturer	Hindustan Aeronautics Limited,
Designed by	Aeronautical Development Agency
First flight	4 January 2001
Introduction	2010 (December 2010 IOC) [1][2]
Status	In development
Primary users	Indian Air Force Indian Navy
Number built	6 prototypes 4 LSP aircraft
Program cost	US$1.2 billion[3]
Unit cost	US$21 million [4] US$31.09 million (Naval version)[5]

The HAL Tejas (Sanskrit: तेजस् "Radiant", Hindi pronunciation: [t̪edʒəs]( listen)) is a 4^th generation lightweight multirole jet fighter being developed by India. It is a tailless,^[6] compound delta wing design powered by a single engine. Originally known as the Light Combat Aircraft (LCA)—a designation which continues in popular usage—the aircraft was officially named "Tejas"^[7] by then Prime Minister Atal Bihari Vajpayee.^[8]

The IAF is reported to have a requirement for 200 single-seat and 20 two-seat conversion trainers, while the Indian Navy may order up to 40 single-seaters to replace its Sea Harrier FRS.51 and Harrier T.60.^[9] During its sea level flight trials off Goa, Tejas notched a speed of over 1,350 km per hour, thus becoming the second supersonic fighter being manufactured indigenously by Hindustan Aeronautics Limited after the HAL Marut.^[10]

Development

LCA programme

HAL Tejas at Aero India 2009.

In 1969, the Indian government accepted the recommendation by its Aeronautics Committee that HAL should design and develop an advanced technology fighter aircraft around a proven engine. Based on a 'Tactical Air Support Aircraft' ASR markedly similar to that for the Marut,^[11] HAL completed design studies in 1975, but the project fell through due to inability to procure the selected "proven engine" from a foreign manufacturer and the IAF's requirement for an air superiority fighter with secondary air support and interdiction capability remained unfulfilled.

The LCA programme was launched in 1983 for two primary purposes. The principal and most obvious goal was the development of a replacement aircraft for India's ageing MiG-21 fighters. The MiG-21 has been the mainstay of the Indian Air Force since the 1970s. The "Long Term Re-Equipment Plan 1981" noted that the MiG-21s would be approaching the end of their service lives by the mid-1990s, and that by 1995 the IAF would lack 40% of the aircraft needed to fill its projected force structure requirements.^[12]

The LCA programme's other main objective was to serve as the vehicle for an across-the-board advancement of India's domestic aerospace industry.^[13]The value of the aerospace "self-reliance" initiative is not simply the production of an aircraft, but also the building of a local industry capable of creating state-of-the-art products with commercial spin-offs for a global market. The LCA program was intended in part to further expand and advance India's indigenous aerospace capabilities.^[14]

To better accomplish these goals, the government chose to take a different management approach, and in 1984 established the Aeronautical Development Agency (ADA) to manage the LCA programme. Although the Tejas is most often described as a product of Hindustan Aeronautics Limited (HAL), responsibility for the development of the Tejas actually belongs to ADA, a national consortium of over 100 defence laboratories, industrial organisations, and academic institutions with HAL being the principal contractor.^[15]

The Indian government's "self-reliance" goals for the LCA include indigenous development of the three most sophisticated — and hence most challenging — systems: the fly-by-wire (FBW) flight control system (FCS), multi-mode pulse-doppler radar, and afterburning turbofan engine.^[16] Although India has had a policy of strictly limiting foreign participation in the LCA programme, these are the only major LCA systems on which the ADA has had to invite significant foreign technological assistance and consultancy. Moreover, the engine and radar are also the only major systems for which the ADA has seriously considered substituting foreign equipment.

The ambitiousness of the LCA programme in terms of pursuing self-reliance in aviation technologies is illustrated by the fact that out of a total of 35 major avionics components and line-replaceable units (LRUs), only three involve foreign systems. These are the multi-function displays (MFDs) by Sextant (France) and Elbit (Israel), the helmet-mounted display and sight (HMDS) cueing system by Elbit, and the laser pod supplied by Rafael (Israel). However, even among these three, when the LCA reaches the production stage, the MFDs are expected to be supplied by Indian companies. A few other important items of equipment (such as the Martin-Baker ejection seat) have been imported. As a consequence of the embargo imposed on India after its nuclear weapons tests in May 1998, many items originally planned to be imported were instead developed indigenously .

Of the five critical technologies the ADA identified at the beginning of the LCA programme as needing to be mastered for India to be able to design and build a "completely indigenous" fighter, two have been entirely successful: the development and manufacture of advanced carbon-fibre composite (CFC) structures and skins and a modern "glass cockpit." In fact, ADA has had a profitable commercial spin-off in its Autolay integrated automated software system for the design and development of 3-D laminated composite elements (which has been licensed to both Airbus and Infosys).^[16] These successes have gone mostly unnoticed in the shadow of the problems encountered with the other three key technology initiatives. Nonetheless, as a result of the accomplishments of India's domestic industries, presently about 70% of the components in LCA are manufactured in India and the dependence on imported components used would be progressively reduced in the coming years.^[17]

HAL serves as the prime contractor and has leading responsibility for LCA design, systems integration, airframe manufacturing, aircraft final assembly, flight testing, and service support.^[15] The ADA itself has primary responsibility for the design and development of the LCA's avionics suite and its integration with the flight controls, environmental controls, aircraft utilities systems management, stores management system, etc.

Of particular importance are the initiatives to develop an indigenous flight control system, radar, and engine for the LCA. The National Aeronautics Laboratory (NAL)—now called the National Aerospace Laboratories—was selected to lead the development of the flight control laws, supported by the [[Aeronautical Development Establishment| Aeronautical Development Establishment (ADE)]. HAL and the Electronics and Radar Development Establishment (LRDE)^[18] are jointly developing the Tejas' Multi-Mode Radar (MMR). The GTRE is responsible for the design and parallel development of the GTX-35VS Kaveri afterburning turbofan engine for the Tejas.

The IAF's Air Staff Requirement for the LCA were not finalised until October 1985. This delay rendered moot the original schedule which called for first flight in April 1990 and service entry in 1995; however, it also proved a boon as it it gave the ADA time to better marshal national R&D and industrial resources, recruit personnel, create infrastructure, and to gain a clearer perspective of which advanced technologies could be developed indigenously and which would need to be imported.

Project definition commenced in October 1987 and was completed in September 1988. Dassault Aviation of France was hired as a consultant to review the PD and provide advice based on its extensive aviation expertise. The PD phase is a critical early element in the aircraft design and development process because from this flow key elements of the detailed design, manufacturing approach, and maintenance requirements.

Development history

HAL Tejas parked next to F-16 and Eurofighter at Aero India.

The LCA design was finalised in 1990 as a small delta-winged machine with relaxed static stability(RSS) to enhance maneuverability performance. The sophisticated avionics and advanced composite structure specified caused some concern almost immediately, and the IAF expressed doubt that India possessed sufficient technological infrastructure to support such an ambitious project. A governmental review committee was formed in May 1989 which reported out a general view that Indian infrastructure, facilities and technology had advanced sufficiently in most areas to undertake the project. As a measure of prudence, though, it was decided that the full-scale engineering development (FSED) stage of the programme would proceed in two stages.

Phase 1 would focus on "proof of concept" and would comprise the design, development and testing (DDT) of two technology demonstrator aircraft (TD-1 and TD-2) and fabrication of a structural test specimen (STS) airframe; only after successful testing of the TD aircraft would the Indian government give its full support to the LCA design. This would be followed by the production of two prototype vehicles (PV-1 and PV-2), and creation of the necessary basic infrastructure and test facilities for the aircraft would begin.

Phase 2 would consist of the manufacturing of three more prototype vehicles (PV-3 as the production variant, PV-4 as the naval variant, and PV-5 as the trainer variant) and a fatigue test specimen, and the construction of further development and test facilities at various work centres.

Phase 1 commenced in 1990 and HAL started work on the technology demonstrators in mid-1991; however, a financial crunch resulted in full-scale funding not being authorized until April 1993, with significant work on FSED Phase 1 commencing in June. The first technology demonstrator, TD-1, was rolled out on 17 November 1995 and was followed by TD-2 in 1998, but they were kept grounded for several years due to structural concerns and trouble with the development of the flight control system.^[19]

One of the most ambitious requirements for the LCA was the specification that it would have "relaxed static stability" (RSS). Although Dassault had offered an analogue FCS system in 1988, the ADA recognised that digital flight control technology would soon supplant it.^[16] RSS technology was introduced in 1974 on the General Dynamics (now Lockheed Martin) YF-16, which was the world's first production aircraft to be slightly aerodynamically unstable by design. Most aircraft are designed with "positive" static stability, which means they have a natural tendency to return to level and controlled flight in the absence of control inputs; however, this quality tends to oppose the pilot's efforts to manoeuvre. An aircraft with "negative" static stability (i.e., RSS), on the other hand, will quickly depart from level and controlled flight unless the pilot constantly works to keep it in trim; while this enhances manoeuvrability, it is very wearing on a pilot relying on a mechanical flight control system.

Development of a FBW flight control system requires extensive knowledge of flight control laws and the expensive writing of a considerable amount of software code for the flight control computers, as well as its integration with the avionics and other electronic systems. When the LCA programme was launched, FBW was a state-of-the-art technology and such a sensitive one that India could find no nation willing to export it. Therefore, in 1992 the LCA National Control Law (CLAW) team was set up by the National Aeronautics Laboratory to develop India's own version. The CLAW team's scientists and mathematicians were successful in developing their control laws, but could not test them since India did not possess advanced real-time ground simulators at that time. Accordingly, British Aerospace (BAe) and Lockheed Martin were brought in to help in 1993, but the effort required for the Aeronautical Development Establishment to code the control laws into the FCS software proved a much larger job than originally anticipated.

Specific control law problems were tested on BAE's simulators (and on HAL's, once theirs became available). As it was being developed, progressive elements of the coding were checked out on the "Minibird" and "Ironbird" test rigs at the ADE and HAL, respectively. A second series of inflight simulation tests of the integrated flight control software were conducted on the F-16 VISTA (Variable In-flight Stability Test Aircraft) simulator in the U.S. in July 1996, with 33 test flights being carried out. However, Lockheed Martin's involvement was terminated in 1998 as part of an embargo enacted by the U.S. in response to India's second nuclear tests in May of that year.

The NAL's CLAW team eventually managed to successfully complete integration of the flight control laws indigenously, with the FCS software performing flawlessly for over 50 hours of pilot testing on TD-1, resulting in the aircraft being cleared for flight in early 2001. The LCA's maiden flight was made by TD-1 from National Flight Test Centre (NFTC), near Bangalore, on 4 January 2001, and its first successful supersonic flight followed on 1 August 2003. TD-2 made its first flight on 6 June 2002. The automatic flight control system (AFCS)of the Tejas has been highly praised by all of its test pilots, one of whom said that he found it easier to take off with the LCA than in a Mirage 2000.^[20]

Another critical technology area tackled for indigenous development by the ADA team is the Multi-Mode Radar (MMR). It was initially planned for the LCA to use the Ericsson Microwave Systems PS-05/A I/J-band multi-function radar,^[21] which was developed by Ericsson and Ferranti Defence Systems Integration for the Saab JAS-39 Gripen.^[22] However, after examining other radars in the early 1990s,^[23] the DRDO became confident that indigenous development was possible. HAL's Hyderabad division and the LRDE were selected to jointly lead the MMR program and the radar development effort began in 1997.^[24]

The DRDO's Centre for Airborne Studies (CABS) is responsible for running the test programme for the MMR. Between 1996 and 1997, CABS converted the surviving HAL/HS-748M Airborne Surveillance Post (ASP) testbed into a testbed for the avionics and radar of the LCA. Known as the 'Hack', the only major structural modification besides the removal of the rotodome assembly was the addition of the LCA's nose cone in order to accommodate the MMR.

By mid-2002, development of the MMR was reported to be experiencing major delays and cost escalations. By early 2005 only the air-to-air look-up and look-down modes — two very basic modes — were confirmed to have been successfully tested. In May 2006 it was revealed that the performance of several modes being tested still "fell short of expectations."^[25] As a result, the ADA was reduced to running weaponisation tests with a weapon delivery pod, which is not a primary sensor, leaving critical tests on hold. According to test reports, the crux of the problem is a serious compatibility issue between the radar and the advanced signal processor module (SPM) built by the LRDE. Acquisition of an "off-the-shelf" foreign radar is an interim option being seriously considered.^[24][26][27] The LSP-3 which flew on April 23, 2010 was flying with a hybrid version of Elta's EL/M-2032 pulse-doppler radar.^[28]

Engine and propulsion

Kaveri engine

Initially, it was decided to equip the prototype aircraft with the General Electric F404-GE-F2J3 afterburning turbofan engine. Simulataneously, in 1986, a parallel programme to develop an indigenous powerplant was also launched. Led by the Gas Turbine Research Establishment, the GTRE GTX-35VS, named "Kaveri", was expected to replace the F404 on all production aircraft. However, progress in the Kaveri development programme was slowed by technical difficulties. In mid-2004, the Kaveri failed its high-altitude tests in Russia, ending the last hopes of introducing it with the first production Tejas aircraft.^[29]

Continued development snags with the Kaveri resulted in the 2003 decision to procure the uprated F404-GE-IN20 engine for the eight pre-production LSP aircraft and two naval prototypes. The ADA awarded General Electric a US$105 million contract in 2004 for development engineering and production of 17 -IN20 engines, delivery of which began in 2006.

An RFP inviting companies for further development of Kaveri was issued. In February 2006, the ADA awarded a contract to the French aircraft engine company Snecma for technical assistance in working out the Kaveri's problems.^[9] The Kaveri engine based on Snecma’s new core, an uprated derivative of the M88-2 engine that powers the French Rafale fighter, providing 83-85 Kilonewtons (KN) of maximum thrust is being considered a third option by DRDO leading the IAF to object that since Snecma has already developed the core of the engine it is offering the DRDO will not participate in any “joint development” but merely provide Snecma with an indigenous stamp.^[30]

In 2007, HAL ordered an additional 24 F404-IN20 afterburning engines to power the first operational squadron of Tejas fighter aircraft for the Indian Air Force.^[31] Before the subsequent order, F404-GE-IN20 was trial-installed in the Tejas as part of final evaluations toward flight-testing, scheduled for mid-2007. The F404-GE-IN20 engine generated more than 19,000 pounds (85 kN) uninstalled thrust and completed 330 hours of Accelerated Mission testing, equivalent of 1,000 hours of flight operation.

The Eurojet EJ200 propulsion offer has thrust-vectoring.

In 2008, it was announced that the Kaveri would not be ready in time for the Tejas, and that an in-production powerplant would have to be selected^[32]in the 95 to 100 kilonewton (kN) (21,000–23,000 lbf) range. The contenders are likely to be the Eurojet EJ200 and the General Electric F414.The single crystal turbine blade technology, originally denied to Indian scientists, has also been offered to India by Eurojet via the EJ200 engine.^[33]

The current F404 engine does not produce enough thrust to enable the aircraft to carry out combat maneuvers with optimal weapons load. Eurojet Turbo and General Electric will be competing to supply 100 engines for the LCA. The Eurojet EJ200 and the GE F414 engines meet the IAF's requirement as they generate a thrust of 95–100 kilonewtons. It has also been said by IAF sources that the airframe will have to be redesigned in order to accommodate the heavier engine which is expected to take up to three-four years. The initial batch of Tejas aircraft will be powered by the F404 engine.^[34]

It was reported that Eurojet was offering two variants of the EJ200, which through a software change would also be able to meet the requirements of the Naval variant of the LCA. Eurojet also offered to help India in the development of the Kaveri engine^[35]

Status

Tejas trainer under construction.

In March 2005, the IAF placed a 2,000 crore (US$ 454 million) order for 20 aircraft, with a similar purchase of another 20 aircraft to follow. All 40 will be equipped with the F404-GE-IN20 engine.^[36] The Tejas is presently undergoing flight testing. It will be inducted into the IAF when it has received Initial Operating Clearance (IOC) which is expected to be in December 2010.^[1][2] Consequently, the IAF has created a 14 member "LCA Induction Team" stationed in Bangalore that is composed of IAF pilots and officers and headed by an Air Vice Marshal. The team's objectives are to reportedly oversee the induction of the LCA, help solve any challenges that may arise, assist HAL in customizing the Tejas for operational use, and to create doctrines, training and maintenance programs and finally to assist the IAF in ensuring a smooth introduction of 'Tejas' into operational service.^[37][38]

HAL Tejas high-altitude trials at Leh successfully completed by December 2008.

The first production variant of the 'Tejas' (LSP-1) flew on June 2008. Tejas completed 1000 Test Flights by January, 2009 with more than 530 hours of in-flight testing.^[39] By February 2009 officials of the Aeronautical Development Agency stated that the Tejas had started flying with weapons and integration of radars would be completed by March 2009. In addition, they stated that nearly all system development activity would be completed by that time.^[40] On April 2010, the third production aircraft (LSP-3) flew with a hybrid version of the Elta EL/M-2032 multi-mode radar and ^[28][41] by June 2010, the fourth production aircraft took flight in the configuration it would be delivered to the Indian Air Force in.^[42] By June 2010, Tejas had also completed the second phase of hot weather trials. The objective of the hot weather trials was to prove that the aircraft was in an IOC configuration with the weapon system and sensors integrated.^[43]

The trainer variant prototype took to the skies in November 2009.^[44] In December 2009, the Indian government sanctioned 8,000 crore (US$ 1.82 billion) to begin production of the fighter jet for the Indian Air Force and Indian Navy.^[45] The Indian Navy has a requirement of 50 Tejas and the first protoype, NP-1 was rolled out in July 2010.^[46] IAF had ordered 20 additional Tejas fighter jets and the defence acquisition council had cleared the plan.^[47]

Design

PV-3 in Indian Air Force grey camouflage pattern.

The Tejas is single-engined multirole fighter which features a tailless, compound delta-wing planform and is designed with "relaxed static stability" for enhanced maneuverability. Originally intended to serve as an air superiority aircraft with a secondary "dumb bomb" ground-attack role, the flexibility of this design approach has permitted a variety of guided air-to-surface and anti-shipping weapons to be integrated for more well-rounded multirole and multimission capabilities.

The tailless, compound-delta planform is designed to keep the Tejas small and lightweight.^[48] The use of this planform also minimises the control surfaces needed (no tailplanes or foreplanes, just a single vertical tailfin), permits carriage of a wider range of external stores, and confers better close-combat, high-speed, and high-alpha performance characteristics than comparable cruciform-wing designs. Extensive wind tunnel testing on scale models and complex computational fluid dynamics analyses have optimised the aerodynamic configuration of the LCA, giving it minimum supersonic drag, a low wing-loading, and high rates of roll and pitch.

All weapons are carried on one or more of seven hardpoints with total capacity of greater than 4,000 kg: three stations under each wing and one on the under-fuselage centreline. There is also an eighth, offset station beneath the port-side intake trunk which can carry a variety of pods (FLIR, IRST, laser rangefinder/designator, or reconnaissance), as can the centreline under-fuselage station and inboard pairs of wing stations.

The Tejas has integral internal fuel tanks to carry 3,000 kg of fuel in the fuselage and wing, and a fixed inflight refuelling probe on the starboard side of the forward fuselage. Externally, there are "wet" hardpoint provisions for up to three 1,200- or five 800-litre (320- or 210-US gallon; 260- or 180-Imp gallon) fuel tanks on the inboard and mid-board wing stations and the centreline fuselage station.

Airframe

Composites in the LCA

The LCA is constructed of aluminium-lithium alloys, carbon-fibre composites (C-FC), and titanium-alloy steels. The Tejas employs C-FC materials for up to 45% of its airframe by weight, including in the fuselage (doors and skins), wings (skin, spars and ribs), elevons, tailfin, rudder, air brakes and landing gear doors. Composites are used to make an aircraft both lighter and stronger at the same time compared to an all-metal design, and the LCA's percentage employment of C-FCs is one of the highest among contemporary aircraft of its class.^[49] Apart from making the plane much lighter, there are also fewer joints or rivets, which increases the aircraft's reliability and lowers its susceptibility to structural fatigue cracks.

The tailfin for the LCA is a monolithic honeycomb piece, an approach which reduced its manufacturing cost by 80% compared to the customary "subtractive" or "deductive" method, whereby the shaft is carved out of a block of titanium alloy by a computerized numerically controlled machine. No other manufacturer is known to have made fins out of a single piece.^[50] A 'nose' for the rudder is added by 'squeeze' riveting.

The use of composites in the LCA resulted in a 40% reduction in the total number of parts compared to using a metallic frame. Furthermore, the number of fasteners has been reduced by half in the composite structure from the 10,000 that would have been required in a metallic frame design. The composite design also helped to avoid about 2,000 holes being drilled into the airframe. Overall, the aircraft's weight is lowered by 21%. While each of these factors can reduce production costs, an additional benefit — and significant cost savings — is realised in the shorter time required to assemble the aircraft — seven months for the LCA as opposed to 11 months using an all-metal airframe.^[51]

Tejas at Aero-India 09

The airframe of the naval variant of the Tejas will be modified with a nose droop to provide improved view during landing approach, and wing leading edge vortex controllers (LEVCON) to increase lift during approach. The LEVCONs are control surfaces that extend from the wing-root leading edge and thus afford better low-speed handling for the LCA, which would otherwise be slightly hampered due to the increased drag that results from its delta-wing design. As an added benefit, the LEVCONs will also increase controllability at high angles of attack (AoA).

The naval Tejas will also have a strengthened spine, a longer and stronger undercarriage, and powered nose wheel steering for deck manoeuvrability.^[52][53] The Tejas trainer variant will have "aerodynamic commonality" with the two-seat naval aircraft design.^[54]

Landing gear

Hydraulically retractable tricycle-type landing gear.

The Tejas has a hydraulically retractable tricycle-type landing gear with a pair of single inward-retracting mainwheels and a steerable, twin-wheel forward-retracting nose gear. The landing gear was originally to have been imported, but following the imposition of trade sanctions, HAL developed the entire system independently.

India's Nuclear Fuel Complex (NFC) led the team that developed the titanium half-alloy tubes that are used for hydraulic power transmission and they are critical components in the LCA.This technology also has space applications.^[55]

Flight controls

The HAL Tejas conducting an inverted pass shown here is an example of Fly-by-wire control.

Since the Tejas is a relaxed static stability design, it is equipped with a quadruplex digital fly-by-wire flight control system to ease handling by the pilot.^[56] The Tejas' aerodynamic configuration is based on a pure delta-wing layout with shoulder-mounted wings. Its control surfaces are all hydraulically actuated. The wing's outer leading edge incorporates three-section slats, while the inboard sections have additional slats to generate vortex lift over the inner wing and high-energy air-flow along the tail fin to enhance high-AoA stability and prevent departure from controlled flight. The wing trailing edge is occupied by two-segment elevons to provide pitch and yaw control. The only empennage-mounted control surfaces are the single-piece rudder and two airbrakes located in the upper rear part of the fuselage, one each on either side of the fin.

The digital FBW system of the Tejas employs a powerful digital flight control computer (DFCC) comprising four computing channels, each with its own independent power supply and all housed in a single LRU. The DFCC receives signals from a variety of sensors and pilot control stick inputs, and processes these through the appropriate channels to excite and control the elevons, rudder and leading edge slat hydraulic actuators. The DFCC channels are built around 32-bit microprocessors and use a subset of the Ada language for software implementation. The computer interfaces with pilot display elements like the MFDs through MIL-STD-1553B multiplex avionics data buses and RS-422 serial links.

Propulsion

General Electric F404-IN20 engine for the eight pre-production LSP aircraft and two naval prototypes.

The wing-shielded, side-mounted bifurcated, fixed-geometry Y-duct air intakes have an optimised diverter configuration to ensure buzz-free air supply to the engine at acceptable distortion levels, even at high AoA.

The original plan was for the LCA prototype aircraft to be equipped with the General Electric F404-GE-F2J3 afterburning turbofan engine, while the production aircraft would be fitted with the indigenous GTRE GTX-35VS Kaveri turbofan being developed in a parallel. Continued development snags with the Kaveri resulted in a 2003 decision to procure the uprated F404-GE-IN20 engine for the eight pre-production LSP aircraft and two naval prototypes and after accelerated trials an order was placed for 24 more IN20 engines for installation on the first 20 production aircraft.

The Kaveri is a low-bypass-ratio (BPR) afterburning turbofan engine featuring a six-stage core high-pressure (HP) compressor with variable inlet guide vanes (IGVs), a three-stage low-pressure (LP) compressor with transonic blading, an annular combustion chamber, and cooled single-stage HP and LP turbines. The development model is fitted with an advanced convergent-divergent ("con-di") variable nozzle, but the GTRE hopes to fit production Tejas aircraft with a multi-axis thrust-vectoring version. The Defence Avionics Research Establishment (DARE) developed an indigenous Full-Authority Digital Engine Control (FADEC) unit for the Kaveri (KADECU). The DRDO's Central Vehicle Research and Development Establishment (CVRDE) was responsible for the design and development of the Tejas' aircraft-mounted accessory gear box (AMAGB) and the power take-off (PTO) shaft.

Avionics

The Tejas has a night vision goggles (NVG)-compatible "glass cockpit" that is dominated by an indigenous head-up display (HUD), three 5 in x 5 in multi-function displays, two Smart Standby Display Units (SSDU), and a "get-you-home" panel (providing the pilot with essential flight information in case of an emergency^[57]). The CSIO-developed HUD, Elbit-furnished DASH helmet-mounted display and sight (HMDS), and hands-on-throttle-and-stick (HOTAS) controls reduce pilot workload and increase situation awareness by allowing the pilot to access navigation and weapon-aiming information with minimal need to spend time "head down" in the cockpit.

The MFDs provide information on the engine, hydraulics, electrical, flight control, and environmental control systems on a need-to-know basis, along with basic flight and tactical information. Dual redundant display processors produce computer-generated imagery on these displays. The pilot interacts with the complex avionics systems through a simple multifunction keyboard and function and sensor selection panels.

Target acquisition is accomplished through a state-of-the-art radar — potentially supplemented by a laser designator pod, forward-looking infra-red (FLIR) or other opto-electronic sensors — to provide accurate target information to enhance kill probabilities. A ring laser gyro (RLG)-based inertial navigation system (INS) provides accurate navigation guidance to the pilot. The LCA also has secure and jam-resistant communication systems such as the IFF transponder/interrogator, VHF/UHF radios, and air-to-air/air-to-ground datalinks. The ADA Systems Directorate's Integrated Digital Avionics Suite (IDAS) integrates the flight controls, environmental controls, aircraft utilities systems management, stores management system (SMS), etc. on three 1553B buses by a centralised 32-bit, high-throughput mission computer.

Radar

The coherent pulse-Doppler Multi-Mode Radar in development is designed to keep track of a maximum of 10 targets and allowing simultaneous multiple-target engagement. Jointly developed by the LRDE and HAL Hyderabad, the MMR is being designed to perform multi-target search, track-while-scan (TWS), and ground-mapping functions. It features look-up/look-down modes, low-/medium-/high-pulse repetition frequencies (PRF), platform motion compensation, doppler beam-sharpening, moving target indication (MTI), Doppler filtering, constant false-alarm rate (CFAR) detection, range-Doppler ambiguity resolution, scan conversion, and online diagnostics to identify faulty processor modules. While originally planned to be fitted on production aircraft, delays in the development of MMR prompted the DRDO to co-operate with Israel Aerospace Industries to integrate a Hybrid version of the EL/M-2032 radar for use with Tejas.^[28][41] The EL/M-2032 radar used in LSP-3 has a detection and tracking range of up to 150 km in air-to-air mode, the air-to-ground mode generates high resolution radar imagery of locations at up to 150 km, and air-to-sea mode can detect and classify naval targets at ranges of up to 300 km.^[58]

The development of an AESA radar for the Tejas is expected to begin pending the selection of an developmental partner.The contenders for the contract are the European Consortium EADS and the Israeli company Elta.The initial contract will see the co-development of 10 prototypes.^[59]

Self-protection

The electronic warfare suite is designed to enhance the Tejas' survivability during deep penetration and combat. The LCA's EW suite is developed by the Defence Avionics Research Establishment (DARE) with support from the Defence Electronics Research Laboratory (DLRL).^[18] This EW suite, known as "Mayavi"(Illusionist), includes a radar warning receiver (RWR), self-protection jammer, laser warning system, missile approach warning system, and chaff/flare dispenser. In the interim, the Indian Defence Ministry has revealed that an unspecified number of EW suites had been purchased from Israel's Elisra for the LCA prototypes.^[60]

The ADA claims that a degree of "stealth" has been designed into the Tejas. Being very small, there is an inherent degree of "visual stealth", but the airframe's use of a high degree of composites (which do not themselves reflect radar waves), a Y-duct inlet which shields the engine compressor face from probing radar waves, and the application of radar-absorbent material (RAM) coatings are intended to minimise its susceptibility to detection and tracking by the radars of enemy fighters, airborne early warning and control (AEW&C) aircraft, active-radar air-to-air missiles (AAM), and surface-to-air missile (SAM) defence systems.

Escape systems

Although two-seat variants of the LCA are planned, the examples built to date are crewed by a single pilot on a Martin-Baker zero-zero ejection seat. The British Martin-Baker ejection seat is planned to be replaced with a locally-developed alternative.^[61] To improve pilot safety during ejection, the Armament Research and Development Establishment (ARDE), Pune, India created a new line-charged canopy severance system, which has been certified by Martin-Baker.

Flight simulator

To support the aircraft a dome-based Mission Simulator has been developed by the Aeronautical Development Establishment (ADE), Bangalore. It was inaugurated by deputy chief of air staff of Indian Air Force. It has been used to provide design support during the initial phase of LCA development in particular handling quality evaluation and planning and practicing mission profiles.

Variants

Prototypes

Model of Tejas Naval version

Conceptual drawing of the Naval LCA

LCA Trainer

Aircraft already built and projected models to be built. Model designations, tail numbers and dates of first flight are shown.

Technology Demonstrators (TD)

• TD-1 (KH2001) - 4 Jan 2001
• TD-2 (KH2002) - 6 June 2002

Prototype Vehicles (PV)

• PV-1 (KH2003) - 25 November 2003
• PV-2 (KH2004) - 1 December 2005
• PV-3 (KH2005) - 1 December 2006 - This is the production variant.
• PV-4 - Originally planned to be a Naval variant for carrier operations, but now a second production variant.
• PV-5 (KH-T2009) - 26 November 2009 - Fighter/Trainer Variant

Naval Prototypes (NP)

• NP-1 - Two-seat Naval variant for carrier operations.Rolled out on July, 2010.^[62]
• NP-2 - Single-seat Naval variant for carrier operations.

Limited Series Production (LSP) aircraft

Currently, 28 LSP series aircraft plus 20 aircraft are on order.

• LSP-1 (KH2011) - 25 April 2007
• LSP-2 (KH2012) - 16 June 2008 This is the first LCA fitted with GE-404 IN20 engine.
• LSP-3 23 April 2010 The first aircraft to have the Hybrid MMR radar^[28][41] and will be close to the IOC standard.
• LSP-4 (KH2014) - 2 June 2010 The first aircraft that was flown in the configuration that will be delivered to the Indian Air Force^[42] In addition to the Hybrid MMR, the aircraft also flew with a functioning Countermeasure Dispensing System ^[63]
• LSP-5 - Planned to fly by June 2010. In addition to all the systems fitted in LSP-4, it will have night lighting within the cockpit, and an auto-pilot.^[63]
• LSP-6 to LSP-28 - Planned to fly by late 2010.

Planned production variants

• Tejas Trainer – Two-seat operational conversion trainer for the Indian Air Force.
• Tejas Navy – Twin- and single-seat carrier-capable variants for the Indian Navy.
• Tejas Mark 2- Featuring more powerful engine and refined aerodynamics.

The Tejas Mark-2 expected to be developed due to the inability of the Mark-1 to meet the Indian Air Staff requirements,will have a more powerful engine, refined aerodynamics and replacing other parts to reduce obsolescence according to an IAF spokesman.^[36]

The LCA's naval variant would be ready for carrier trials by 2013 and is slated for deployment on the INS Vikramaditya as well as the Vikrant class aircraft carrier.^[64]

Some of features of "Naval LCA Version":

• Aircraft carrier operation with ski-jump and arrested landing
• Nose drooped for better cockpit vision
• Additional aerodynamic features like LEVCON and fore plane to reduce carrier landing speed
• Maximum take off weight from carrier—12.5 tons
• External store carrying capacity from carrier—3.5 tons
• Strengthened fuselage
• Stronger undercarriage due to higher sink rate
• Arrestor hook for deck recovery
• Fuel dump system

Operators

 India

• Indian Air Force
• Indian Navy- Signed an order for six Naval LCAs at an approximate cost of US$31.09 million per aircraft.^[65]

Specifications (HAL Tejas)

Data from Indian-military.org

General characteristics

• Crew: 1
• Length: 13.20 m (43 ft 4 in)
• Wingspan: 8.20 m (26 ft 11 in)
• Height: 4.40 m (14 ft 9 in)
• Wing area: 38.4 m² (413 ft²)
• Empty weight: 5,680kg (12,522 lb)
• Loaded weight: 9,500 kg (20,945 lb)
• Max takeoff weight: 13,500 kg (31,967 lb)
• Powerplant: 1× General Electric F404-GE-IN20 turbofan
  • Dry thrust: 53.9 kN (11,250 lbf)
  • Thrust with afterburner: 85 kN (19,100 lbf)
• Internal fuel capacity: 3000 liters
• External fuel capacity: 5×800 liter tanks or 3×1,200 liter tanks, totaling 4,000/3,600 liters

Performance

• Maximum speed: Mach 2+ (2,376+ km/h at high altitude) at 15,000 m
• Range: 3000 km (1,840 mi (without refueling))
• Service ceiling: 16,500 m (54,000 ft (engine re-igniter safely capable))
• Wing loading: 221.4 kg/m² (45.35 lb/ft²)
• Thrust/weight: .91

Armament

• Guns: 1× mounted 23 mm twin-barrel GSh-23 cannon with 220 rounds of ammunition.
• Hardpoints: 8 total: 1× beneath the port-side intake trunk, 6× under-wing, and 1× under-fuselage with a capacity of >4000 kg external fuel and ordnance
• Missiles:
  

HAL Tejas carrying R-73 missile and Drop Tank.

• Air-to-air missiles:
  • Python 5
  • Derby
  • Astra BVRAAM
  • Vympel R-77 (NATO reporting name: AA-12 Adder)
  • Vympel R-73 (NATO reporting name: AA-11 Archer)
• Air-to-surface missiles:
  • Kh-59ME TV guided standoff Missile
  • Kh-59MK Laser guided standoff Missile
  • Anti-ship missile
  • Kh-35
  • Kh-31
• Bombs:
  
• KAB-1500L laser guided bombs
• FAB-500T dumb bombs
• OFAB-250-270 dumb bombs
• OFAB-100-120 dumb bombs
• RBK-500 cluster bombs
• Others:
• Drop tanks for ferry flight/extended range/loitering time.
• LITENING targeting pod ^{[66][67] [68]}

Avionics
Hybrid MMR radar (Israeli EL/M-2032 back end processor with Indian inputs)^[28][41]

See also

• HAL Tejas timeline
  

Related development

• Medium Combat Aircraft
  

Related lists

• List of fighter aircraft
  

References

External links

• Tejas specifications on Aeronautical Development Agency website

Features and analysis:

• "Flying into the unknown" — A feature by The Hindu on the Tejas test pilots.
• "LCA and Economics" by Sunil Sainis and George Joseph
• "The Light Combat Aircraft Story", by Air Marshal MSD Wollen (Retd).
• The case to support the indigenous LCA programme, by Ashok Parthasarathi and Raman Puri.

Technical:

• An Approach to High AoA Testing of the LCA
• Development Flight Testing of the Tejas Light Combat Aircraft
• LCA Avionics And Weapon System Mission Computer Software Development: A Case Study

General:

• "Tejas / Light Combat Aircraft (LCA)", Fighter-planes.com
• Unofficial Website of LCA-Tejas