English name: Radiant

TYPE: Multirole fighter.

PROGRAMME: Development, as Light Combat Aircraft (LCA), approved by Indian government in 1983 as MiG-21 replacement; project definition begun second quarter 1987, completed late 1988, with first flight then predicted for April 1990 and service entry in about 1995. However, due to early slippages, basic design not finalised until 1990; construction by HAL started mid-1991. First aircraft (TD1: technology demonstrator; serial number KH2001) was nine months behind revised schedule at roll-out on 17 November 1995; several subsequent postponements of new (June 1996) target date for first flight, which eventually took place on 4 January 2001; completed first phase of flight tests with 12th flight on 2 June 2001, reaching 8,000 m (26,250 ft) altitude, 18^o AoA and M0.71 speed. First supersonic flight targeted for January 2002, but eventually achieved on 1 August 2003.
TD2 (KH2002) rolled out on 14 August 1998 and scheduled to fly in September 2001, but did not do so until 6 June 2002. This has marginally lighter empty weight, increased usable fuel and Indian-developed HUD compared with TD1. Both aircraft powered by F404-GE-F2J3 afterburning turbofan, ground runs of which began on 9 April 1998; indigenous Kaveri engine being developed by Gas Turbine Research Establishment (GTRE) Bangalore and will undertake flight trials in Russia in Tu-16 testbed. Bench trials of this engine had reportedly totalled some 1,200 hours by early 2003 (of 8,000 required), but flight trials still not started by that time. SNECMA and Eurojet reported to have offered technological assistance in developing Kaveri engine, which now considered unlikely to be ready until 2007. Meanwhile, to offset delays in Kaveri programme, prototypes PV1 to PV5 and at least first eight production aircraft will be fitted with F404 engine, further 40 of which received US export approval in 2002. TD1 and TD2 had made about 50 flights by February 2003; aircraft named Tejas (pronounced thay' jus) by Indian Prime Minister on 4 May 2003, at which time aircraft made its first public appearance (TD1 and TD2 flying) and third aircraft rolled out. Four of the PVs to be single-seaters (including one in naval configuration); the fifth will be a two-seat operational trainer having commonality with the naval variant of LCA.
Programme delays further exacerbated by May 1998 US embargo on supplies and assistance following India's refusal to abandon nuclear weapons testing, necessitating all-Indian completion of development of integration of digital AFCS and some other systems (aircraft is inherently unstable and thus unable to fly without AFCS). However, sanctions lifted on 22 September 2001 and deliveries of air data and initial sensors by BAE Systems Controls (ex-Lockheed Martin) due to resume in mid-2003. Development of the indigenously developed radar is said to be on schedule; this is to be flight tested initially in a HAL HS 748 and first installed in the PV1. Work on PV1 and PV2 was under way in late 1998; additional US$125 million released in May 1999 to accelerate remaining development.
Mid-2002 estimate indicated third (PV1) prototype due to fly in 2002 (not achieved; subsequently expected in second half of 2003); fourth and fifth (PV2 and 3) in 2003; two-seater (PV5) in 2004; IOC now expected in 2006 and final operational clearance by 2008.

CURRENT VERSIONS: Tejas: Single-seat version for Indian Air Force. As described.
Tejas Trainer: Tandem two-seat operational trainer; under development.
Tejas Navy: Single-seat carrierborne version; drooped nose, arrester hook, long-stroke landing gear, retractable canards and movable vortex controls at the wingroot. Design approved early 1999; development approved by Indian government in mid-2002. First flight (PV4) targeted for 2004, service entry for 2006.

CUSTOMERS: Indian Air Force (requirement for 200 single-seat and 20 trainers); Indian Navy may order up to 40 single-seaters. First eight for IAF approved in MoU March 2002; production by HAL at Bangalore.

COSTS: Phase 1 (TD1 and TD2) costs, including engine, estimated at approximately Rs30 billion (US$675 million) by late 2000. Estimated unit cost, based on 220 production total, US$17 million to US$20 million (2001).

DESIGN FEATURES: Tail-less delta planform with relaxed static stability; shoulder-mounted delta wings with compound sweep on leading-edges; large twist from inboard to outboard leading-edges; wing-shielded, side-mounted, fixed-geometry Y-duct air intakes. Advanced materials for minimum structural weight; fly-by-wire and HOTAS controls; high agility; supersonic at all altitudes; wide range of external stores.

FLYING CONTROLS: Hydraulically actuated two-segment trailing-edge elevons and three-section leading-edge slats; vortex-shedding inboard leading-edges with inboard slats to form vortices over wingroot and fin; airbrake in top of fuselage each side of vertical fin; these and rudder also actuated hydraulically.

STRUCTURE: Advanced materials to include aluminium-lithium alloy, carbon composites and titanium alloys; CFRP wings (including elevons), fin and rudder; Kevlar radome. Wings manufactured with one-piece CFRP top and bottom skins, bolted on to wing box; majority of spars and ribs in composites. Fin, rudder, elevons, airbrakes and landing gear doors embody co-cured, co-bonded techniques. Carbon fibre composites to be increased from 30 per cent of airframe weight in TD1/2 to 45 per cent in PVs, with corresponding reduction of aluminium alloys from 57 to 43 per cent.
Hindustan Aeronautics (HAL) responsible for fuselage, communications system, electrical system, mechanical system LRUs and utility systems management; Aeronautical Development Establishment (ADE) flight control system, cockpit displays and display processors; National Aerospace Laboratories (NAL) responsible for development of fin and fabrication of rudder.

LANDING GEAR: Hydraulically retractable tricycle type. Single inward-retracting mainwheels; twin-wheel forward-retracting and steerable nose unit. DRDL carbon disc brakes; computer-controlled brake management system. ADRDE brake-chute in fairing at base of rudder.

POWER PLANT: One 80.1 kN (18,000 lb st) General Electric F404-GE-F2J3 afterburning turbofan in TD1 and TD2, prototypes PV1 to PV5 and initial production batch; Indian GTRE GTX-35VS Kaveri turbofan (52.0 kN; 11,700 lb st dry, 80.5 kN; 18,100 lb st with afterburning), with digital engine control unit (KADECU), under development for later production aircraft. Multi-axis thrust vectoring nozzle planned.
Internal fuel in wing and fuselage integral tanks. Fixed in-flight refuelling probe on starboard side of front fuselage. Provision for up to three 1,200 or five 800 litre (317 or 211 US gallon; 264 or 176 Imp gallon) external fuel tanks on wing inboard, mid-board and underfuselage stations.

ACCOMMODATION: Pilot only, on Martin-Baker zero/zero ejection seat. Canopy opens sideways to starboard. Development will include two-seat training version.

SYSTEMS: Hydraulic system (by HAL) for powered flying controls, brakes and landing gear; electrical system for fly-by-wire and avionics power supply; Spectrum Infotech environmental control system for cockpit, radar and fuel tanks; lox system; HAL GTSU-110 gas turbine starter unit; aircraft-mounted accessory gearbox; USMS for aircraft utilities systems management.

AVIONICS (production version): Comms: HAL V/UHF (with built-in ECCM) and standby UHF radios and audio management unit; HAL air-to-air/air-to-ground secure datalink; HAL IFF transponder/interrogator.
Radar: Electronics Research and Development Establishment (ERDE)/HAL multimode radar with multitarget search and track-while-scan and ground mapping functions; coherent pulse Doppler system, with look-up/look-down modes, Doppler beam-sharpening and moving target indication.
Flight: Quadruplex digital fly-by-wire AFCS. RLG-based INS; provision for GPS/INS; HAL RAM 1701A rado altimeter.
Instrumentation: NVG-compatible 'glass cockpit'; two Bharat Electronics active matrix, reconfigurable colour LCD MFDs; CSIO (India) collimated HUD; dedicated LCD 'get-you-home' panel; LCD multifunction keyboard.
Mission: Three multiplexed MIL-STD-1553B digital databusses; 32-bit mission computer operating in Ada, backed up by a second, equally powerful computer; IRST; laser range-finder/designator pod. Provision for reconnaissance, EW or other sensor pods. Helmet-mounted display/sight.
Self-defence: EW suite, by Advanced Systems Integration and Evaluation Organisation (ASIEO), includes radar warning receiver, self-protection jammer, laser warning system, missile approach waming system, countermeasures dispensing system and chaff/flare dispenser.

ARMAMENT: GSh-23 twin-barrel 23 mm gun with 220 rounds in blister beneath starboard engine intake trunk. Eight external stores stations (three under each wing, one on fuselage centreline and one beneath port intake trunk) for wide range of short/medium-range air-to-air missiles, PGMs, air-to-surface (including anti-ship) missiles, targeting or ECM pod, unguided rockets, conventional and retarded bombs, and cluster bomb dispensers. Indigenous Astra active radar-guided ASM under development by DRDL. All except outboard underwing stations are wet for carriage of drop tanks.