HAL Tejas

The HAL Tejas (Sanskrit: : "Radiant") is a 4.5 generation lightweight multirole fighter aircraft being developed by India. It is a tailless, 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". by then Prime Minister Atal Bihari Vajpayee on 4 May 2003.

Limited series production of the Tejas commenced in 2007; it is currently projected to achieve limited initial operational clearance (IOC) with the Indian Air Force (IAF) by 2008, followed by full operational clearance (FOC) by the end of 2010. A two-seat trainer variant is also in development, as is a naval variant capable of operating from the Indian Navy's aircraft carriers. 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.

Through the use of modern design techniques, lightweight materials and composites, it is expected to become the lightest modern jet fighter in production.

Development

LCA programme

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Tejas in formation flight

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 Mikoyan-Gurevich MiG-21 (NATO reporting name 'Fishbed') fighters. The MiG-21 has been the mainstay of the Indian Air Force since the 1970s, but the initial examples were nearly 20 years old by 1983. The "Long Term Re-Equipment Plan 1981" noted that the MiG-21's 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.

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. Soon after gaining independence in 1947, Indian leaders established an ambitious national objective of attaining self-reliance in aviation and other strategic industries. 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 across the broadest range of modern aviation technologies.

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 principle contractor. The ADA formally falls under the auspices of the Indian Defence Ministry's Defence Research and Development Organisation (DRDO).

The Indian government's "self-reliance" goals for the LCA include indigenous development of the three most sophisticated — and hence most challenging — systems on fourth-generation fighter aircraft: the fly-by-wire (FBW) flight control system (FCS), multi-mode pulse-doppler radar, and afterburning turbofan engine. 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, albeit as an interim measure on the initial LCA aircraft where needed to allow more time for the full development of the indigenous versions — as has been the case with the LCA's Kaveri powerplant.

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 — like the landing gear — were instead developed indigenously .

Out 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 design and built a "completely indigenous" fighter, two have been entirely successful: the development and manufacture of advanced carbon-fibre composite (CFC) structures and skins (especially on the order of the size of a wing) 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 licenced to both Airbus and Infosys). 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, it is anticipated that, overall, about 70% of the LCA is to be manufactured in India itself.

Programme origins

In 1955, based on experience gained from the HT-2 programme and the manufacturing capabilities gained from licenced production of the de Havilland Vampire FB.52 and T.55, HAL took up the challenge of an Air Staff Requirement (ASR) that called for a multirole fighter aircraft suitable for both high-altitude interception and low-level ground attack. The ASR also required that the basic design be suitable for adaptation as an advanced trainer and for shipboard operation, options which would be later dropped. The result would be India's first domestically developed jet fighter, the subsonic HF-24 Marut, which first flew in June 1961. The Marut did not enter service with the IAF until 1967 due to problems obtaining or developing a suitable turbojet engine. In the meantime, HAL gained additional experience completing the development and testing of the Folland Gnat F.1, which it produced under licence from 1962-1974, and from which it later developed a much-modified variant, the Gnat Mk.II Ajeet, as well as the HJT-16 Kiran turbojet trainer, which entered service in 1968.

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, HAL completed design studies in 1975, but the project fell through due to inability to procure the selected "proven engine" from a foreign manufacturer. With production of the Ajeet attack aircraft underway, this left little design work for HAL's engineers, while the IAF's requirement for an air superiority fighter with secondary air support and interdiction capability remained unfulfilled.

In 1983, the DRDO obtained permission to initiate a programme to design and develop a Light Combat Aircraft, only this time, a different management approach would be taken. In 1984, the Aeronautical Development Agency was established to manage the LCA programme. The ADA is effectively a "national consortium" for which HAL is the principal partner. 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. 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 (ADE), which is responsible for developing the integrated fly-by-wire FCS itself. HAL and the Electronics and Radar Development Establishment (LRDE) are jointly developing the Tejas' Multi-Mode Radar (MMR). The Gas Turbine Research Establishment (GTRE) is responsible for the design and parallel development of the GTX-35VS Kaveri afterburning turbofan engine for the Tejas — which will be using the General Electric F404 turbofan as an interim powerplant until the Kaveri becomes available.

The IAF's Air Staff Requirement for the LCA would not be 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 would also prove a boon in that 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 (PD) 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. Moreover, this is the point at which overall programme costs are most effectively controlled. The costs to implement subsequent changes to design requirements, capabilities and features become increasingly expensive the further down the path of development they are introduced, and the more likely the program is to suffer schedule and cost overruns.

Development history

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Tejas nose cone radome being lightning tested at NAL's Lightning Test Facility in Bangalore

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.

Fly-by-wire control laws

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. RSS technology was introduced in 1974 on the General Dynamics (now Lockheed Martin) YF-16, which was the world's first 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 maneuver. 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 maneuverability, it is very wearing on a pilot relying on a mechanical flight control system. What made RSS practical on the YF-16 was a new technology — the "fly-by-wire" flight control system — which employs flight computers to electronically keep the aircraft's instability in check whenever it is not desired.

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 was scheduled to make its first flight in September 2001, but this was not achieved until 6 June 2002. The Tejas' automatic flight control system (AFCS) 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].

Multi-Mode Radar (MMR)

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The Tejas' Multi-Mode Radar

Another critical technology area tackled for indigenous development by the ADA team is the Tejas' 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, which was developed by Ericsson and Ferranti Defence Systems Integration for the Saab JAS-39 Gripen. However, after examining other radars in the early 1990s, the DRDO became confident that indigenous development was possible. HAL's Hyderabad division and the LRDE were selected to jointly lead the MMR program; it is unclear exactly when the design work was initiated, but the radar development effort began in 1997.

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." 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 like Elta's EL/M-2032 is an interim option being seriously considered.

Kaveri engine

Main article: GTRE GTX-35VS Kaveri

Although it had been decided early in the LCA programme to equip the prototype aircraft with the General Electric F404-GE-F2J3 afterburning turbofan engine, a parallel programme was also launched in 1986 to develop an indigenous powerplant. Being led by the Gas Turbine Research Establishment, the GTRE GTX-35VS, named "Kaveri", was expected to replace the F404 on all production aircraft. The GTRE's design envisions achieving a fan pressure ratio of 4:1 and an overall pressure ratio of 27:1, which it believes will permit the Tejas to "supercruise" (cruise supersonically without the use of the afterburner). A digital engine control system (Kaveri Digital Engine Control Unit- "KADECU")is also under development, as well as an axisymmetric thrust-vectoring nozzle to further enhance the LCA's agility. Plans are also already under way for derivatives of the Kaveri, including a non-afterburning version for an advanced jet trainer and a high-bypass-ratio turbofan based on the Kaveri core.

The original plans called for 17 prototype test engines to be built. The first test engine consisted of only the core module (named "Kabini"), while the third engine was the first example fitted with variable inlet guide vanes (IGV) on the first three compressor stages. Test runs of the first complete prototype Kaveri began in 1996 and all five ground-test examples were in testing by 1998; the initial flight tests were planned for the end of 1999, with its first test flight in an LCA prototype to follow the next year. However, progress in the Kaveri development programme was slowed by technical difficulties.

The 1998 sanctions forced General Electric to suspend delivery of the F404 engines that were to power the prototypes after only 11 F404's had been supplied. Alternative engines were considered — including the Rafale's SNECMA M88, the Eurofighter's Eurojet EJ200, and the MiG-29's Klimov RD-33 — but no decision had been made by the time sanctions were lifted in September 2001. In February 2002, the U.S. government agreed to supply an additional 40 F2J3 engines to permit flight testing of several previously engineless LCA prototypes to begin.

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 February 2004 for development engineering and production of 17 -IN20 engines, delivery of which is to begin in 2006. 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. According to GE press release in Feb 2007 Hindustan Aeronautics Limited (HAL) ordered an additional 24 F404-GE-IN20 afterburning engines to power the first operational squadron of Tejas fighter aircraft for the Indian Air Force. Before the subsequent order F404-GE-IN20 was trial-installed in Light Combat Aircraft (LCA) as part of final evaluations toward flight-testing, scheduled for mid-2007. The F404-IN-20 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 F404-GE-IN20 succeeds F404-F2J3 development engines used for nearly 600 flights, cumulatively covering eight engines. Also 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. The DRDO currently hopes to have the Kaveri engine ready for use on the Tejas by 2009-10.

Prototypes

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LCA TD-1, TD-2 and PV-1 in echelon formation

The PV-series prototype air vehicles were meant to evolve progressively toward the actual production Tejas aircraft. The first prototype, PV-1, saw the initial attempt at achieving major weight reduction — resulting in a cut of 350 kg (770 lb) — and was intended to be representative of the production-standard airframe. Carbon-fibre composites are employed extensively in the fuselage, and PV-1's overall composite content was increased over that of the technology demonstrators to 45% by weight and 95% by surface area. The remaining structural material consists (by weight) of 43% aluminium alloys, 5% titanium alloys, 4.5% steels, and 2.5% other materials. The part count was reduced to 7,000 from TD-1's 10,000. The PV-1 first flew on 25 November 2003.

The second prototype, PV-2, was a significant step forward in the evolution to the production Tejas, especially in the fit of its Integrated Digital Avionics Suite (IDAS). This suite, developed by HAL, integrates the cockpit through an open architecture with the flight controls, environmental controls, aircraft utilities systems management, ADA-developed stores management system, etc. The production-standard cockpit has no standby electromechanical instruments; instead, it features three 5 in x 5 in multi-function active-matrix liquid crystal displays (AMLCD), two Smart Standby Display Units (SSDU), and the indigenous head-up display (HUD) developed by the Central Scientific Instruments Organisation (CSIO). An integral part of the cockpit avionics suite is the DASH helmet-mounted display and sight supplied by Elbit of Israel. PV-2 initially flew 1 December 2005, and is scheduled to be the first Tejas aircraft to be fitted with the indigenous Multi-Mode Radar, following completion of the radar's flight tests on a HAL HS 748 "Avro" testbed.

The technology demonstration phase was formally completed on 31 March 2004, but FSED Phase 2 was authorised in November 2001, shortly after international sanctions were lifted on 22 September 2001. Phase 2 also included a plan to order several "Limited Series Production" (LSP) aircraft. The ADA and HAL signed a memorandum of understanding (MoU) in 2001 for 8 LSP aircraft to be delivered by the end of 2006; the order was placed in June 2002, and production go-ahead was given in March 2003. The three Phase 2 PV-series prototypes are very similar to PV-2 and all are claimed to be full production-standard aircraft, but PV-3 is said to be the actual baseline production model. PV-3 made its maiden flight on 1 December 2006, reaching an altitude of 2.5 km and a top speed of Mach 0.8. PV-4 was originally planned to be a naval variant, but will actually be very similar to PV-3. PV-4 is anticipated to be the final baseline model for production aircraft, whereas PV-3 has effectively become the baseline for the pre-production LSP batch aircraft. Delivery of the PV-5, the two-seat operational trainer variant, and induction into service of the first LSP aircraft are also anticipated in 2006.

PV-4 has been replaced as the naval prototype by two prototypes designated NP-1 and NP-2; confusingly, these are respectively the two-seat and single-seat variants. A design permitting operation from a carrier deck with a 14º ski-jump was approved in early 1999, and development go-ahead was granted in mid-2002, although major funding was not released until early 2003. The naval prototypes have strengthened landing gear and other necessary modifications for service on an aircraft carrier. NP-1 is planned to achieve first flight in 2007, followed by NP-2 the next year.

Design

LSP-1 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. (It should also be noted that all equipments and technologies mentioned in this section were indigenously developed, unless noted otherwise.)

The tailless, compound-delta planform helps keep the Tejas small and lightweight — in fact, it is reputed to be the smallest and lightest supersonic combat jet in the world. 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 > 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 (317- or 211-US gallon; 264- or 176-Imp gallon) fuel tanks on the inboard and mid-board wing stations and the centreline fuselage station.

Airframe

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. 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.

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Frontal view of PV-3 prototype version

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. 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.

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. The Tejas trainer variant will have "aerodynamic commonality" with the two-seat naval aircraft design.

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. India is one of only six nations which have developed this technology, which also has space applications.

Flight controls

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. 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

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 effort by the Gas Turbine Research Establishment. 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. After accelerated trials of F404-GE-IN20 engine 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

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LCA Tejas cockpit mockup

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. 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 "identify friend or foe" (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 LCA's coherent pulse-Doppler Multi-Mode Radar is designed to keep track of a maximum of 10 targets and allows simultaneous multiple-target engagement. Jointly developed by the LRDE and HAL Hyderabad, the MMR will be fitted in production Tejas aircraft, supplanting the flight test instrumentation carried in the prototype aircraft. The MMR performs 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. Developmental delays, however, have resulted in consideration being given to procuring foreign "off-the-shelf" radars for early production examples of the Tejas.

Due to delay in development of MMR, government have come out with the collaboration with IAI for development of Radar the sensor for the new radar is supposed to be Aesa 2052 and the remaining item and software will be combination of MMR and IAI developed products.

Self-protection

An advanced electronic warfare suite enhances the Tejas' survivability during deep penetration and combat. The LCA's EW suite is being developed by the Defence Avionics Research Establishment (DARE) — which was known as the Advanced Systems Integration and Evaluation Organisation (ASIEO) until June 2001 — with support from the Defence Electronics Research Laboratory (DLRL). This EW suite, known as "Mayavi" (Sanskrit: "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 have been purchased from Israel's Elisra for the LCA prototypes.

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 ejection seat is slated to be replaced with an indigenous ejection seat 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. This system, which is the first of its kind, can be operated from outside the aircraft, an important consideration when the pilot is trapped or unconscious.

Mission Simulator

Indian Light Combat Aircraft "Tejas" Real Time Simulator (RTS) has been developed. The simulator has been developed by Aeronautical Development Establishment (ADE), Bangalore. It was inaugurated by deputy chief of air staff of Indian Air Force. It's a giant leap from simple fixed base simulator developed during early nineties which was envisaged to provide design support during the initial phase of LCA development has been fully developed in to a dome based mission simulator which can be used for handling quality evaluation as well as for planning and practicing mission profiles. The simulator is set up inside a 9 meter dia. dome. The visual cues are generated using 6 synchronized high performance Image Generators (COTS based) and projected on the inner surface of the dome with 6 – Channel projection system giving a seamless out-the-window view for the pilot with a FoV of 180° (Azimuth) x 80° (Elevation). The cockpit is close to the PV2 standard aircraft with actual pilot controls, synthetic instrument panels and various avionics displays like MFDs and SSDUs based on COTS components. The high fidelity flight model runs at 80 Hz frame rate on a dual processor machine under Linux and RTLinux operating subsystem. The audio cues generated include the simulation of aircraft engine noise, tyre screech sound, landing gear thud, etc.

This simulator also provides facility for using a Digital Control Loading Unit (DCLU) for simulating the different force feel characteristics of the pilot control stick. An Instructor monitoring station is used for complete control of the simulator. A touch sensitive monitor located close to the cockpit allows for initiation, running of various configured versions of CLAW, Real Time plots, Insertion of faults etc.

Costs

Development costs

The LCA was originally expected to fly in 1993, and in May 1989 the program was projected by the government's review committee to cost Rs. 5,600 crores (56 billion rupees or about US$1.2 billion at the time). FSED Phases 1 and 2 were projected to cost, respectively, Rs. 2,188 crores (US$467 million) and Rs. 2,340 crores (US$499 million). According to the 1999 Comptroller and Auditor General (CAG) report, the first phase of the project had by the end of 1998 consumed Rs. 2,500 crores; by the end of 2000, the total Phase 1 cost had risen to about Rs. 3,000 crores. The delays have also led to further indirect costs. For instance, the unavailability of the Tejas compelled the Indian Air Force to upgrade its MiG-21bis aircraft at a cost of Rs. 2,135 crores.

When FSED Phase 2 was launched in November 2001, it was authorised under a budget of Rs. 3,302 crores (about US$704 million). This financing covered not only the manufacture of the five prototypes (PV-1 to PV-5), but also eight limited series production (LSP) planes. In July 2001 it was reported that beyond the FSED, HAL would require a further Rs. 400-600 crores to set up facilities for the manufacture of 12 to 14 LCAs a year.

In the first quarter of 2003, the Indian Government approved the equivalent of US$210 million (nearly Rs. 1,000 crores) for a programme to develop a carrier-capable variant of the LCA for the Indian Navy. The cost covers development and testing of two prototypes, the two-seat NP-1 and single-seat NP-2. NP-1 is expected to achieve clearance for carrier operation in 2007, followed a year later by NP-2, with service entry no later than 2010.

In July 2006, the Times of India revealed that the overall cost of the LCA project could well eventually reach Rs. 10,000 crores (about US$2.26 billion). By that date, the government had authorised a total of Rs. 5,489.78 crores (over US$1.24 billion) for the program through the production of the eight LSP pre-production aircraft (but excluding costs for the separate Kaveri program).

Development of the Kaveri engine was projected in 1989 to cost Rs. 382.81 crores (nearly US$82 million). In December 2004, it was revealed that the GTRE had spent over Rs. 1,300 crores (around US$295 million) on developing the Kaveri. Furthermore, the Cabinet Committee on Security judged that the Kaveri would not be installed on the LCA before 2012, and revised its estimate for the projected total development cost to Rs. 2,839 crores (more than US$640 million). The DRDO, however, currently hopes to have the Kaveri engine ready for use on the Tejas by 2009-10.

Unit costs

In December 1996, A. P. J. Abdul Kalam, the then Scientific Adviser, calculated unit costs of US$21 million.

At the end of 2001, Dr. Kota Harinarayana, director of the ADA and of the LCA programme, estimated the unit cost for the LCA (for an expected order of 220 aircraft) to be between US$17-20 million, and once production ramped up, that could drop to US$15 million.

However, by 2001 others were indicating that the LCA would cost US$24 million (in excess of Rs. 100 crores per aircraft). Considering cost escalations, some aviation experts feel that when the aircraft comes out, it could cost upwards of US$35 million apiece.

A Rs. 2,000 crores (over US$450 million) order for 20 Tejas aircraft would represent a unit procurement cost of US$22.6 million for each, which would be consistent with Abdul Kalam's estimates. At a price tag of around Rs. 100-110 crores, the Tejas will be much cheaper than other contemporary fighters.

By comparison, the Times of India quoted the costs for the Swedish JAS-39 Gripen and French Rafale as Rs. 150 crores (US$34 million) and Rs. 270 crores (US$61 million)

Operational history

File:Pv3 tip.jpg

Tejas PV3

• As of 16 May 2008, the LCA had completed 872 successful test flights in all (TD1-233,TD2-275,PV1-166,PV2-94,PV3-77,LSP1-27).

• On 13 May 2006 the PV-2 went supersonic for the first time and on 14 May 2006 it did so again, but this time in a weaponised state (i.e., carrying weapons such as missiles and an internal gun).

• On 1 December 2006, the PV-3 flew for the first time for 27 minutes at an altitude of 2.5 km and at a speed of Mach 0.8. According to LCA Programme Director P.S. Subramanyam, this flight-test was meant for "product enhancement" and clearing the Indian Air Force's Initial Operational Clearance envelope. He said that the PV-3 is equipped with a more advanced pilot interface, refined avionics and higher control law capabilities compared with the previous versions. LCA has flown at speeds of Mach 1.4.

• On 25 April 2007, the first Limited Series Production LCA (LSP-1) made its first flight and it reached a speed of Mach 1.1.

File:Tejas R-73.jpg

Tejas PV-1 firing an R-73 missile during weapons trials in Goa

• PV-2 and PV-3 underwent sea-level trails at INS Rajali Naval Air Station, Arakkonam to study the effects of flying at sea-level, as all earlier trials have been conducted at Bangalore which is 3,000 feet above sea-level. The reliability of the LCA systems under the hot and humid conditions, as well as low level flight characteristics was tested. It is due to this intense flight testing schedule that the LCA was not able to fly at the Paris air show-2007, as was originally planned.

• On 7 September 2007, Tejas Prototype Vehicle (PV-1) made a successful maiden flight with two 800 litre drop tanks.

• On 25 October 2007, Tejas PV-1 fired a Vympel R-73 missile for first time. The trials were conducted off the Goa coast at INS Hansa Naval Air Station.

• On 11 December 2007, LITENING Pod was successfully tested on Tejas PV-2.

• On 7 February 2008, Tejas Prototype Vehicle (PV-1) made a successful flight powered by fuel from two 800 litre drop tanks. It made a one hour and 24 minute long sortie. On internal fuel LCA can perform a 40-minute sortie.

The Tejas was scheduled to fly at the Paris Air Show-2007 and Singapore Air Show-2008. However, these were cancelled due to test schedules. The Tejas is scheduled to be unveiled to an international audience for the first time at the Berlin Air Show, ILA-2008, to be held from May 27 to June 1 2008. Along with the LCA, HAL will also be showcasing the HAL HJT-36 trainer aircraft and the HAL Dhruv Helicopter.

Status

Tejas trainer under construction.

The Tejas is presently undergoing flight testing. It will be inducted into the IAF in limited numbers once Initial Operating Clearance (IOC) is achieved. Full scale induction will commence once Final Operating Clearance (FOC) is achieved. IOC testing is expected to be completed by 2010, and FOC by 2012. Independent analysts and officials in the IAF expect that deliveries of operational Tejas fighters are likely to begin in 2010, with combat service entry around 2012.

The IAF has created a 14 member "LCA Induction Team", composed of IAF pilots and officers and headed by Air Vice Marshal BC Nanjappa. This team's objectives are to oversee the induction of the LCA, help to solve any challenges that may arise, help the developers customize the Tejas for operational use, as well as help create doctrine, training programs, maintenance programs and help prepare the IAF to speedily ready the Tejas for operational service. This reveals the IAF's desire to be more involved in the LCA development as well as its urgency to induct new aircraft. The team is stationed in Bangalore.

Senior HAL officials had said in March 2005 that the IAF would place a Rs. 2,000 crores (over US$450 million) order for 20 Tejas aircraft, with a similar purchase of another 20 aircraft to follow. All 40 will be equipped with the F404-GE-IN20 engine. So far, Rs. 4806.312 cr have been spent on development of various versions of Light Combat Aircraft.

Delay

In a May 2006 interview, HAL chairman Ashok Baweja had said that the fifth prototype vehicle (PV-5), the trainer prototype, and the first of the eight LSP aircraft would be delivered before the end of 2006. These aircraft will help accelerate the initial operational clearance for the LCA. It was expected to be inducted into the IAF by the end of 2006, with the LCA's System Design & Development (SDD) phase finally being completed in 2010. A trainer version is under development and the design of the Naval version is complete, and are expected to fly in 2008. However LSP-1 made its first flight only in April 2007, while the Trainer prototype is yet to be delivered.

In 2007, it was reported that the Tejas in its present form may not be able to meet the IAF's Air Staff Requirements (ASRs). Reportedly, it's performance in terms of thrust and airframe qualities was still unsatisfactory. To complete the project at the earliest, a top level review is conducted by the Chief of Air Staff once every quarter and a monthly review by the Deputy Chief of Air Staff.

Despite the delays, there are no plans to cancel the LCA program or any part of it, including the Kaveri engine.

Variants

File:LCATrainerModel.jpg

Model of Tejas Naval version

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Prototypes

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) - 1 November 2003
• PV-2 (KH2004) - 2 December 2005
• PV-3 (KH2005) - 2 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 - Two-seat Trainer variant aircraft.

Naval Prototypes (NP)

• NP-1 - Two-seat Naval variant for carrier operations.
• NP-2 - Single-seat Naval variant for carrier operations.

Limited Series Production (LSP) aircraft

Currently, 8 LSP series aircraft are on order.

• LSP-1 (KH2011) - 25 April 2007
• LSP-2 - Will be the first aircraft to have a radar integrated and will have GE-404 IN20 engine with higher thrust than the GE-404-GE-F2J3.
• LSP-3 - Will be the first aircraft to have the MMR and will be close to the IOC standard.
• LSP-4 to LSP-8 - Planned to fly by late 2008.

Planned production variants

• Tejas – Single-seat fighter for the Indian Air Force.
• 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.

Operators

The Tejas is currently undergoing flight testing. Eight pre-production aircraft are on order, with deliveries having begun in mid 2007. In late 2006 the IAF placed an order for 20 production-standard Tejas fighters, and ordered another 20 in 2007. IOC is presently anticipated for late-2008, with FOC following a couple of years thereafter.

Early on IAF was reported to have a requirement for 200 single-seat and 20 two-seat conversion trainers, while the Indian Navy was also looking to order up to 40 single-seaters to replace its Sea Harrier FRS.51 and Harrier T.60 fighters.. [2]

• India
  • Indian Air Force- Two Squadrons
  • Indian Navy - Naval version being built

Specifications (Tejas)

Three view of the Tejas

Three view of the Tejas

General characteristics

• Crew: OneInternal fuel capacity: 3000 liters
• External fuel capacity: 5×800 liter tanks or 3×1,200 liter tanks, totaling 4,000/3,600 liters

Performance

• Thrust/weight: 1.07

Armament

• 1 × 23 mm GSh-23 cannon internally mounted twin-barrel cannon with 220 rounds of ammunition.
• Eight external stations: three hardpoints under each wing, one fuselage centreline hardpoint, and one station beneath the port-side intake trunk for a pod (FLIR, IRST, laser designator, or reconnaissance).
• Maximum external payload: >4000 kg.
• Air-to-air missiles include Astra BVRAAM, Vympel R-77 (NATO reporting name: AA-12 Adder), and Vympel R-73 (NATO reporting name: AA-11 Archer).
• Air-to-surface munitions include anti-ship missiles, laser-guided bombs, unguided bombs, cluster bombs, and unguided air-to-surface rockets.

See also

• HAL HF-24 Marut
• Medium Combat Aircraft

Aircraft of comparable role, configuration, and era

• Dassault Mirage 2000
• F-16 Fighting Falcon
• JF-17 Thunder
• Mitsubishi F-2
• Chengdu J-10

External links

• Aeronautical Development Agency home page
• Tejas specifications on Aeronautical Development Agency website

News reports:

• Aeronautical Development Agency – More Current News
• ARDE develops safe ejector system for LCA
• India's fighter engine will be world class: US
• Indigenous titanium tubes for LCA
• Light Combat Aircraft-Tejas Testing
• No Takeoff in sight
• Unique head-up display developed for LCA

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
• PCs in Flight Simulation Research – the LCA (Navy) Experience

General:

• Aeronautics - A DRDO perspective — A February 2007 speech by Dr. M. Natrajan, the head of the DRDO, at an aeronautics seminar during the Aero India-2007 aerospace trade show.
• "Aircraft: LCA", Space Transport
• "Air Force Readies For Net Centric Warfare Capability In The Future" by Ranjit B. Rai (via India Defence)
• Fighter Aircraft - 1960-2002
• "Hindustan (HAL) Light Combat Aircraft (LCA) Light Multi-Role Fighter", Aerospaceweb.org
• "LCA and its Features", ADA's LCA website
• The LCA Puzzle, Frontline, 16 July 2005.
• "Tejas / Light Combat Aircraft (LCA)", Fighter-planes.com
• Unofficial Website of LCA-Tejas

Photo links:

• Bharat-Rakshak.com Aero India-2005, Photo gallery: Tejas in flight.
• Bharat-Rakshak.com Aero India-2007, Photo gallery: Static display - Tejas
• Bharat-Rakshak.com Aero India-2007, Photo gallery: Tejas in flight

Video links:

• An Excellent Doordarshan Video about the LCA
• Formation flying of 2 Tejas aircraft
• HAL Tejas - courtesy National Geographic Channel
• LCA Flying Display at Aero India-2005
• LCA Tejas fires R-73 missile
• LCA Tejas PV-1 Test Flies with Drop Tanks
• Tejas LCA at Aero India 2007
• Three LCAs in formation flight
• Video of First flight of the LCA - 4 January 2001