HAL Tejas

The HAL Tejas is an Indian single-engine, fourth-generation, multirole light fighter designed by the Aeronautical Development Agency (ADA) in collaboration with Aircraft Research and Design Centre (ARDC) of Hindustan Aeronautics Limited (HAL) for the Indian Air Force and Indian Navy. It came from the Light Combat Aircraft (LCA) programme, which began in the 1980s to replace India's ageing MiG-21 fighters. In 2003, the LCA was officially named "Tejas".
Tejas has a tail-less compound delta-wing configuration with a single vertical stabilizer. This provides better high-alpha performance characteristics than conventional wing designs. Its wing root leading edge has a sweep of 50 degrees, the outer wing leading edge has a sweep of 62.5 degrees, and trailing edge has a forward sweep of four degrees. It integrates technologies such as relaxed static stability, fly-by-wire flight control system, multi-mode radar, integrated digital avionics system and composite material structures. It is the smallest and lightest in its class of contemporary supersonic combat aircraft.
The Tejas is the second supersonic fighter developed by HAL after the HAL HF-24 Marut. Production of the Tejas Mark 1 for the Indian Air Force (IAF) began in 2016. The IAF plans to procure 324 aircraft in all three variants - MK1, MK1A and MK2. The first Tejas IAF unit, No. 45 Squadron IAF "Flying Daggers" was formed on 1 July 2016 with two aircraft. As of 2016 indigenous content in the Tejas was 59.7% by value and 75.5% by number of line replaceable units.
The first batch of 40 Mark 1 aircraft consists of 16 Initial Operational Clearance (IOC) standard that were delivered in early 2019. The delivery of the second batch of 16 Full Operational Clearance (FOC) standard aircraft commenced in late 2019 and led to the formation of the second Tejas squadron—No. 18 Squadron IAF "Flying Bullets"—in Sulur on 27 May 2020. The IAF will also receive eight Tejas twin-seat trainer aircraft. The next 83 aircraft on order are to be delivered in the upgraded Mark 1A standard. By the time these first 123 are delivered, the Tejas Mark 2 is expected to be ready for series production by 2025–26.
Development.
Origins.
In 1969, the Government of India accepted the recommendation by its Aeronautics Committee that Hindustan Aeronautics Limited (HAL) should design and develop a fighter aircraft around a proven engine. Based on a 'Tactical Air Support Aircraft' Air Staff Requirements 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 and the IAF's requirement for an air superiority fighter with secondary air support and interdiction capability remained unfulfilled.
In 1983, Government of India established the LCA project. The initial goal was to replace the ageing IAF fighters by early 1990s, especially the MiG-21 variants, which had been the mainstay of the IAF since the 1970s. The "Long Term Re-Equipment Plan 1981" noted that most of the IAF fighters were approaching the end of their service lives by the early-1990s, and that by 1995, the IAF would be 40 percent short of the aircraft needed to fill its projected force structure requirements.
In 1984, the Government of India established Aeronautical Development Agency (ADA) to manage the LCA programme. The ADA was entrusted with the design and development of LCA while HAL, a national consortium of over 100 defence laboratories, industrial organisations, and academic institutions, chosen as the principal contractor. The government's "self-reliance" goals for the LCA included the three most sophisticated and challenging systems: the Fly-by-wire (FBW) flight control system, multi-mode pulse-doppler radar, and afterburning turbofan engine.
The IAF's Air Staff Requirements for the LCA were not finalised until October 1985. This delay caused uncertainty in the original schedule which called for first flight in April 1990 and service entry in 1995; however, it also gave the ADA time to establish national R&D and industrial resources, recruit personnel, create infrastructure, and to identify which technologies could be developed locally and which would need to be imported.
Project definition commenced in October 1987 with France's Dassault-Breguet Aviation as consultant. Dassault-Breguet's expertise was mainly used in the design and system integration of the Tejas and this phase was completed in September 1988. In 1988, Dassault had offered an analogue flight control system for the LCA, but the ADA insisted on having quadruplex digital Fly-by-wire (FBW) flight control system. First flying in 1974, the General Dynamics F-16 was the first production aircraft to employ digital fly-by-wire flight control system to improve manoeuvrability.
LCA programme.
A review committee was formed in May 1989 to study the feasibility of LCA programme, which reported that infrastructure facilities and technologies in India had advanced sufficiently in most areas and that the project could be undertaken. A two-stage full-scale engineering development (FSED) process was opted for the development of LCA. In 1990, the design was finalised, a small tailless delta wing design with relaxed static stability which incorporates "control configured vehicle" concept and digital Fly-by-wire flight control system for enhanced manoeuvrability. Kota Harinarayana was the original Programme Director and Chief Designer for the Tejas Programme. In 1992, the LCA National Control Law (CLAW) team was set up by the National Aeronautics Laboratory (now called National Aerospace Laboratories) to develop India's own state of the art fly-by-wire FCS for the Tejas and Lockheed Martin was selected as the consultant. In 1998, Lockheed Martin's involvement was terminated due to a US embargo in response to India's second nuclear tests in May of that year.
The Phase 1 of the LCA Programme was commenced in June 1993, which focused on "proof of concept" and comprised the design, development and testing of two technology demonstrator (TD) aircraft, named TD-1 and TD-2. This would be followed by the production of two prototypes (PV-1 and PV-2). The NAL's CLAW team completed the integration of the flight control laws with the FCS software performing flawlessly for over 50 hours of pilot testing on TD-1, resulting in the aircraft being cleared for first flight in January 2001 and TD-1 finally flew on 4 January 2001. The automatic flight control system (AFCS) on LCA Tejas has been praised by all the LCA test pilots. FSED Process Phase-I of LCA Programme was successfully completed in 2001 and Phase 2 of the programme was commenced in November 2001 which envisaged the manufacturing of three more prototypes - a production standard air force variant, a naval variant and a trainer variant, in addition to the replacement of imported Line-replaceable units (LRU) with indigenous LRUs.
Another critical technology needed for LCA was the multi-mode radar (MMR). Initially, the Ericsson/Ferranti PS-05/A I/J-band multi-function radar, also used on Saab's JAS 39 Gripen, was intended to be used. However, after examining other radars in the early 1990s, the Defence Research and Development Organisation (DRDO) became confident that local development was possible. HAL's Hyderabad division and the DRDO's Electronics and Radar Development Establishment (LRDE) laboratory were selected to jointly lead the MMR programme, and work commenced in 1997. The Centre for Airborne Systems (CABS) was responsible for the MMR's test programme. Between 1996 and 1997, CABS converted the surviving HAL/HS-748M Airborne Surveillance Post into a testbed for the LCA's avionics and radar.
By mid-2002, the MMR had reportedly suffered major delays and cost escalations. By early 2005, only the air-to-air look-up and look-down modes — two basic modes — were confirmed to have been successfully tested. In May 2006, it was revealed that the performance of several modes being tested "fell short of expectations." As a result, the ADA was restricted to weapon tests with a weapon delivery pod, which is not a primary sensor, leaving critical tests on hold. According to test reports, there was a serious compatibility issue between the LRDE/HAL multi mode radar and the LRDE's advanced signal processor module. Acquisition of an "off-the-shelf" foreign radar as an interim option being considered.
ADA met with success in the development of two of the five key technologies identified at the beginning of the LCA programme to develop an indigenous fighter aircraft. The successful endeavours were the development and manufacturing of carbon-fibre composite (CFC) structures and skins, and a modern glass cockpit. ADA has a profitable commercial spin-off in its Autolay integrated automated software for designing 3-D laminated composite elements (which has been licensed to both Airbus and Infosys). However, the development of the other two critical technologies (the propulsion system and the jet fuel starter) had lagged behind and the development of a multi-mode pulse-doppler radar, once delayed was completed as the AESA radar and is currently undergoing flight trials. Over the years the dependence on imported components for the Tejas has been reduced. As of 2016, the indigenous components in Tejas amount to 75% by number and 59% by value.
In October 2015, IAF Air Chief Marshal Arup Raha confirmed that the air force plans to order 123 (six squadrons) of Tejas Mark 1, triple the 40 aircraft it had previously committed to buying. Later it was declared that those 83 additional Tejas ordered would be the upgraded Mark 1A variant.
On 7 November 2016, Defence Minister Manohar Parrikar approved the procurement of 73 Tejas MK1A and 10 Tejas MK1 trainer aircraft for the IAF. HAL is setting up a second assembly line in collaboration with private industry to increase the production rate of the LCA from current eight to sixteen aircraft per year.
On 18 March 2020, the Defence Acquisition Council (DAC) provisionally cleared a procurement deal for 83 Tejas MK1A, including 73 single-seat fighters and 10 MK1 dual-seat trainers. HAL was to finalise the proposal, for review by the Cabinet Committee on Security (CCS). According to HAL, the first Tejas MK1A could fly by 2022 with serial production starting in 2023. The first squadron of Tejas MK1A could be delivered by 2025, and delivery of all 83 aircraft could be completed before 2029. The IAF also requested a strong aircraft maintenance package, and aircraft panel inter-changeability that can be carried out at squadron level, in a minimum amount of time using quick-release fasteners to reduce foreign object damage (FOD). Line-replaceable units (LRU)s are also expected to be pre-positioned.
In 2021, the Cabinet Committee on Security, approved the 2015 agreement to procure 73 Tejas MK1A, and an additional 10 Tejas MK1 Trainer aircraft, at a cost of , along with of supporting infrastructure, as part of a order.
Prototypes and testing.
In March 2005, the IAF placed an order for 20 aircraft, with a similar purchase of another 20 aircraft to follow. All 40 were to be equipped with the F404-GE-IN20 engine. In December 2006, the Indian Air Force formed an "LCA Induction Team" to manage the aircraft's service introduction.
On 25 April 2007, the first Limited Series Production (LSP-1) Tejas performed its maiden flight, achieving a speed of . Weapon trials began in the same year, by test firing an R-73 close combat missile. Test flying with the Litening targeting pod was also carried out in the same year.
On 16 June 2008 LSP-2 made its first flight followed by the first flight of the trainer variant in November 2009. The Tejas completed its crucial high altitude trials at Leh, early in 2008, using the LSP-2 and PV-3 prototypes. In December 2009, the government authorized ₹8,000 crores to begin the production for the Indian Air Force and Indian Navy. The IAF ordered 20 additional Tejas fighters after the defence acquisition council cleared the plan.
On 23 April 2010, LSP-3 flew with a hybrid version of the Israeli Elta EL/M-2032 multi-mode radar; in June 2010, LSP-4 made its maiden flight in an IAF IOC configuration. By June 2010, the Tejas had completed the second phase of hot weather trials in an IOC configuration, with the weapons system and sensors integrated to check the performance of the systems in high temperature operational conditions up to . Sea trials were also carried out in the same year to asses radar performance in the air-to-air and air-to-sea modes, at various altitudes. Flutter vibration tests were also carried out in different configurations at high AoA to assess the structural integrity across the flight envelope. LSP-5 with IOC standard equipment started flight trials on 19 November 2010.
Tejas completed its air to ground weapon trials in 3 phases - unguided munition trials in 2009 and advanced weapon trials involving precision guided munitions in 2012 and 2014.
On 9 March 2012, LSP-7 was first flown. In the later half of 2012, the Tejas was grounded for over three months due to a serious safety issue which arose with the introduction of a new pilots' helmet, which protruded above the ejection seat. There was concern that, during an ejection, the helmet would strike the canopy before the canopy was jettisoned. Flight tests resumed in November 2012 after the ejection system had been modified.
LSP 8 had a successful maiden test flight on 31 March 2013. In the same year Tejas also conducted an inflight engine relight test at high altitude to asses engine response on flameout, a critical parameter for IOC-II clearence. By 27 November 2013 Tejas programme had completed 2,418 test flights. On 8 November 2014, PV-6 (KH-T2010), a trainer variant, completed its first test flight.
Out of a total of 35 major avionics components and line-replaceable units (LRUs), only two involve foreign systems. These are helmet-mounted display and sight (HMDS) cueing system by Elbit, and the laser pod supplied by Rafael (Israel). A few 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 locally; these sanctions also contributed to the prolonged delays suffered by the LCA programme.
After the successful completion of laboratory trials, Tejas MK1 platform will start flight trials with DRDO developed on-board oxygen generation system (OBOGS) in 2020.
Operational clearance.
On 10 January 2011, IOC-I, allowing IAF pilots to fly the Tejas, was awarded by Defence Minister A K Antony to Chief of Air Staff Air Chief Marshal P V Naik. The IAF raised the first squadron in Bangalore to iron out issues with ADA and HAL, and eventually based these fighters at Sulur Air Force Station, Coimbatore in the southern state of Tamil Nadu. The No. 45 Squadron IAF "Flying Daggers" was the first to get their MiG-21s replaced by Tejas aircraft at the base. Tejas' FOC was repeatedly delayed since 2011.
To ease up the process of FOC, an interim IOC-II was issued to Tejas on 17 January 2015, which allowed the aircraft to be flown by regular IAF pilots and begin squadron service. The IOC-II also permits the aircraft to carry payload close to three tons, including laser-guided 500 kg bombs and R-73 missile close combat missiles, withstand turns up to +7 g (which was limited to +6g in IOC-I), reach angle of attack of 24 degrees (from 17 degrees initially, in IOC-I), and have an operational radius of 400–500 km.
The FOC campaign began in December 2013, with deadline set to 2014, but this and subsequent deadlines were missed. In February 2016, Tejas (LSP-7) test-fired a Derby beyond visual range air to air missile on Ballistic Non-Guided (BNG) mode in Jamnagar as part part of the FOC mandate. The aircraft was also scheduled to fire a Python-5 Close Combat Missile (CCM) as part of the FOC trials. On 12 May 2017, Tejas successfully test fired a Derby Air-to-Air BVR missile in radar guided mode scoring a direct hit on the maneuvering target. The missile launch was performed in lock-on after launch mode. By 19 November 2017, HAL had delivered five Tejas in IOC-II standard to the IAF and have flown more than 600 sorties. In February 2018, as part of the FOC campaign Tejas carried out a "hot refuelling" - refuelling with engine running, which shorten the turnaround time between sorties. In September 2018, Tejas successfully completed mid-air refuelling trials required for the aircraft to obtain FOC. In January 2019, HAL received permission from CEMILAC to start production of FOC standard Tejas.
On 20 February 2019, during the Aero India 2019 show, FOC was formally awarded to the Tejas. After the release of the Drawing Applicability List (DAL) and SOPs by the Centre for Military Airworthiness and Certification (CEMILAC), the first series production aircraft in FOC standard (SP-21) took 12 months to complete production and flown on 17 March 2020. The Tejas MK1 in FOC standard comes with aerial refuelling probe compatible with both NATO and Russian tankers that will allow flights of over 8 hours, an additional centre line drop tank with pressurised refuelling, an improvement over the existing and external fuel tanks that come with the Tejas IOC variants, cleared for 28 degree angle of attack and +8 g limit, capability to fire Derby BVR missile, Python-5 close combat missile and a GSh-23 twin-barrelled gun. Delivery of the next 15 Tejas FOC aircraft after SP-21 will be completed by financial year 2020–21, due to improvements in manufacturing process and feedback from the Tejas IOC program. The second IAF Tejas squadron No.18 "Flying Bullets" was formed at Sulur Air Force Station on 27 May 2020 with the first four serial production FOC aircraft.
Shortcomings and upgrades.
In May 2015, the Mark 1 aircraft was criticised by the Comptroller and Auditor General of India (CAG) for not meeting IAF requirements, such as a lack of a capable tandem-seated trainer aircraft, electronic warfare capabilities, performance shortcomings of radar warning receiver or missile approach warning system, weight and cost increases, limited internal fuel capacity, non-compliance of fuel system protection, inadequate forward-facing pilot protection, and performance shortfalls due to under-powered engine. Most of these issues are to be addressed in the upcoming interim upgrade called Mark 1A and subsequent advanced version called Mark 2 or MWF.
It was reported that IAF agreed to accept 40 aircraft to keep the programme going, even though the CAG had found serious operational shortfalls. IAF had initially ruled out further acquisition of Tejas MK 1 until MK 2 was ready. In 2015, the ADA, DRDO and HAL proposed a more advanced Tejas MK 1A variant; as an improved stop-gap to keep production running as Mark 2 was delayed. Following an approval from Defence Acquisition Council for 83 Tejas Mk 1A, HAL invited global bids for AESA radar and ECM pods in December 2016. On 20 December 2017, IAF initiated a tender to buy 83 Mark 1A worth 33,200 crores from HAL. However, with HAL quoting a price of per unit, substantially higher than the Mark 1, the Defence Minister Nirmala Sitharaman announced in July 2018 that a committee to look into the cost of the Mark 1A, along with other products manufactured by defence Public Sector Undertakings. In December 2018, it was reported that HAL had selected Elta's EL/M-2052 AESA radar and EL/L-8222 ECM pod. In 2019, DRDO unveiled a fully functional AESA radar prototype named 'Uttam' at Aero India expo, the radar prototype was mounted inside the glass nose of a Tejas prototype. As of 2021, 3 prototypes built and the radar has accumulated 230 hours of airborne testing onboard two Tejas fighter jets (LSP2 and LSP3) beside an executive jet; presumed to be DRDO's Dornier 228 "Nabhratna" used as a flying test bed by LRDE. It is expected that 51% of the Tejas MK1A could be equipped with indigenous Uttam AESA radar.
The ARDC of HAL had completed the structural design for Tejas Mark 1A which is now awaiting clearance from Centre for Military Airworthiness and Certification (CEMILAC), Directorate General of Aeronautical Quality Assurance (DGAQA) and Aircraft and Systems Testing Establishment (ASTE) while system design works are in progress which will be completed by February 2021. A total of 200 flight trials will be conducted with upgraded systems on two limited series production (LSP) aircraft, while final configuration for Tejas Mark 1A will be ready for production by 2022–23. The major improvements on Tejas Mark 1A are in operational roles and increasing the combat ability by addition of active electronically scanned array (AESA) radar, DARE Unified Electronic Warfare Suite (UEWS), self protection jammer (SPJ), integration of Astra Mark 1, ASRAAM, digital 2D and 3D moving maps with perspective view for pilot, integration of GNSS augmentation like GAGAN and additional GLONASS, NavIC satellite navigation systems and higher maintainability. To increase turn around time and ease of long term maintainability, new set of cables will be incorporated in Tejas Mark 1A to add space inside aircraft while a technique called panel-in-panel will increase visibility of components and reduce daily inspection time.
Future development.
To meet air staff qualitative requirements (ASQR) of the Indian Air Force (IAF), ADA had to make substantial changes to the basic Mark1 and Mark 1A air-frame to improve payload and performance in the more advanced upgrade called Tejas Mark 2. Initially they had planned to simply elongate the Mark 1 with a 0.5 m fuselage plug to hold more fuel, while fitting a more powerful General Electric F414-GE-INS6 engine with 64–98 kN of thrust.
To be renamed eventually, the Mark 2, which is now classified as a medium-weight fighter, is also to feature an indigenous integrated life support system-onboard oxygen generation system (ILSS-OBOGS) which uses pressure swing adsorption technique and a built-in integrated electro-optic electronic warfare suite among other improvements to avionics. The oxygen generation system is developed by Defence Bioengineering and Electromedical Laboratory (DEBEL). Tejas MK2 will have an infrared search and track (IRST) system and a missile approach warning system (MAWS). An increase in payload capacity to , and an increase in number of weapons stations from 8 to 11, will allow the MWF to carry more weapons. Defence Institute of Advanced Technology (DIAT) is developing aircraft health and usage monitoring system (HUMS) to integrate various sensors onboard Tejas Mark 2. In May 2021, OBOGS developed for Tejas has been adapted to alleviate severe Oxygen crisis faced by the country due to the Second wave of COVID-19 pandemic in India
Naval variant.
The LCA navy programme was commenced in 2003, after the successful initial flight testing of the air force variant. LCA Navy Programme was envisaged to complete in two phases - Phase 1 and Phase 2. Under Phase 1 two technology demonstrators were developed - NP1 and NP2 based on Tejas MK1 design to carryout carrier suitability certification and weapon integration. Under Phase 2, two single-seat prototypes were planned to be built, based on the Tejas MK2 design, with further design optimisation and integration of a more powerful General Electric F414 INS6 engine. The Indian Navy has a requirement for 50 Tejas aircraft and the first prototype, NP-1 was rolled out in July 2010. The naval LCA made its first flight almost two years after being rolled out, on 27 April 2012. In December 2012, the Indian Navy expressed interest in procuring eight Tejas aircraft.
In December 2014, the LCA Navy successfully conducted ski-jump trials at SBTF, INS Hansa. The navy variant has a special flight control law mode. It controls a hands-free take-off, which reduces the pilot workload, as the ramp launches the aircraft on an upward flight path.
In December 2016, the Indian Navy (IN) announced that the naval variant of the fighter is overweight, and they will look for other alternatives. The Indian Navy eventually issued an RFI for 57 naval multirole fighters. However, despite rejecting the Tejas initially for being overweight, the Navy restarted testing with the NP-2 (Naval Prototype 2) in August 2018. The naval variant of the Tejas conducted its first "taxi-in" test of its capability to land on an aircraft carrier. The Indian Defence Minister, Nirmala Sitharaman's backing of the Tejas programme allowed the restarting of tests and gave its naval variant a fresh lease on life.
A two-seater naval variant of Tejas successfully completed its first arrested landing on 13 September 2019 at the Shore Based Test Facility (SBTF) in Goa. On 12 November 2019, a Tejas navy prototype successfully carried out a night arrested landing at the SBTF in Goa. On 11 January 2020, the Naval LCA Tejas successfully carried out its first arrested landing on the aircraft-carrier INS "Vikramaditya". On 12 January 2020, the Tejas performed its first ski-jump assisted take-off from the aircraft-carrier. Technology for hands free automatic take-off and landing system had already been proven on Naval Tejas prototypes and will be carried over for further development on TEDBF and AMCA.
The experience gained in testing the naval prototype will help in the development of Twin Engine Deck Based Fighter (TEDBF) aircraft. The HAL TEDBF will be powered by two General Electric F414 engines and will have increased payload and range. Labelled as the Omni-Role Combat Aircraft it is to sport two engines, elongated fuselage and an expanded wing-span, Diverterless supersonic inlets, Conformal Fuel Tanks etc.
Design.
Overview.
The Tejas is a single-engine multirole fighter which features a tailless, compound delta wing design which confers better close-combat, high-speed, and high-alpha performance characteristics than comparable cruciform-wing designs. Tejas is designed with "relaxed static stability" for enhanced manoeuvrability and agility. Originally intended to serve as an air superiority aircraft with a secondary ground-attack role, its flexibility permits a variety of guided air-to-surface and anti-shipping weapons to be integrated for multirole and multimission capabilities. The tailless, compound-delta planform is designed to be small and lightweight. This also minimises the control surfaces needed (no tail-planes or fore-planes, just a single vertical tail-fin). Extensive wind tunnel testing on scale models and complex computational fluid dynamics analysis have optimised the aerodynamic configuration for minimum supersonic drag, a low wing-loading, and high rates of roll and pitch.
The maximum payload capability of Tejas is . All weapons are carried on one or more of seven hardpoints with total capacity of greater than 5,000 kg: three stations under each wing and one on the under-fuselage centreline. An eighth offset station beneath the port-side intake trunk can carry a variety of pods like FLIR, IRST, laser rangefinder/designator, as can the centre line under-fuselage station and inboard pairs of wing stations. Auxiliary fuel tanks of 725, 800 and 1,200 litres can be carried under the fuselage to extend range. An aerial refuelling probe on the starboard side of the forward fuselage can further extend range and endurance. RAFAEL's I-Derby ER fire-and-forget missile will serve as the Tejas' initial beyond visual range air-to-air missile. The BrahMos NG supersonic cruise missile is being developed for the Tejas.
Stealth features have been designed into Tejas. Being small provides an inherent degree of visual stealth, a Y-duct inlet which shields the engine compressor blades from probing radar waves reduces the frontal radar cross section (RCS), the airframe's high usage of composites and the application of radar-absorbent material (RAM) coatings are intended to minimise its susceptibility to detection and tracking.
Tejas uses Martin-Baker 16LG zero-zero ejection seat. DRDO integrated an indigenous canopy severance system (CSS) in the Tejas which allows the pilot to eject safely.
Airframe.
Tejas is constructed of aluminium-lithium alloys, carbon-fibre composites, and titanium alloys. Composite materials make up 45% of the airframe by weight and 90% by surface area. Upper and lower wing skins are manufactured from a single piece of carbon-fibre reinforced polymer. Wing spars and ribs are also made out of carbon composites. The construction of elevons, tailfin, rudder, air brakes and landing gear doors use co-cured and co-bonded manufacturing techniques. The radome is made out of Kevlar, while the fin tip is made out of glass-fibre reinforced plastic. Composite materials are used to make an aircraft lighter and to reduce radar cross section (RCS) compared to an all-metal design, and the LCA's percentage employment of carbon-fibre composites 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. The wing and fin of the compound-delta aircraft are of carbon-fibre-reinforced polymer, and were designed to provide a minimum weight structure and to serve as integral fuel tanks. The tailfin is a monolithic honeycomb structure piece, reducing the manufacturing cost by 80% compared to the "subtractive" or "deductive" method, involving the carving 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.
The naval variant have nose droop to provide improved view for carrier landings, 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 Navy, which would otherwise be compromised by the increased drag that results from its delta-wing design. The LEVCONs should also increase controllability at high angles of attack (AoA). The naval Tejas also has 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.
Avionics.
The Tejas has a night vision goggles (NVG)-compatible "glass cockpit", domestically-developed head-up display (HUD) by Central Scientific Instruments Organization (CSIO), three 5 in x 5 in multi-function displays, two Smart Standby Display Units (SSDU), and a "get-you-home" panel with fail-operational/fail-safe air data computer (ADC) manufactured by Bharat Electronics Limited (BEL) that uses computational intelligence based autoland system to provide the pilot with essential flight information in case of an emergency and is connected with IAF ground station network to take over emergency controls of the unstable aircraft. The displays provide information on key flight systems and controls on a need-to-know basis, along with basic flight and tactical data. The pilot interacts with onboard systems through a multi-functional keyboard and several selection panels. The CSIO-developed HUD, Elbit-furnished DASH IV Helmet mounted display and sight (HMDS) with night-vision goggles compatible glass cockpit, and hands-on-throttle-and-stick (HOTAS) controls reduce pilot workload and increase situation awareness by allowing access to navigation and weapon cueing information with minimal need to spend time "head down" in the cockpit.
The first 40 production Tejas MK1 are equipped with a hybrid version of the EL/M-2032 radar. It features look-up/look-down/shoot-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. The first batch of 20 Tejas Mark 1A will be equipped with improved version of EL/M-2052 AESA radar developed jointly by Elta Systems and HAL. The remaining 63 fighter aircraft will come equipped with domestically developed Uttam AESA radar from Electronics and Radar Development Establishment (LRDE).
The electronic warfare suite is designed to enhance combat survivability during deep penetration. The EW suite is developed by the Defence Avionics Research Establishment (DARE) with support from the Defence Electronics Research Laboratory (DLRL). This EW suite, known as "Mayavi", includes a radar warning receiver (RWR), Missile Approach Warning (MAW) system and a Laser warning receiver (LWR) system, Infrared & Ultraviolet Missile warning sensors, self-protection jammer, chaff, jaff and flares dispenser, an electronic countermeasures (ECM) suite and a towed radar decoy (TRD). In the interim, the Indian Ministry of Defence has revealed that an unspecified number of EW suites had been purchased from Israel's Elisra for the LCA prototypes.
Tejas is also to be equippable with an infrared search and track (IRST) sensor, which can detect and track thermal energy emissions, VHF to UHF radio communication with in-built counter-countermeasure system that supports air-to-air and air-to-ground mode connected via secure datalink network. This system shall be pod-based, additional sensor pods are to include FLIR targeting pod, ECM pods, Flares/Infrared decoys dispenser pod and chaff pod, EO/IR sensor pod, LITENING targeting pods, and a laser designator/laser rangefinder, which can be used in various capacities, including reconnaissance, training, or attack. The identification friend or foe (IFF) system on Tejas is developed by Centre for Airborne Systems (CABS). Tejas comes with flight utility system and management system (USMS) to monitor various parameters from sensors like ADA developed hybrid environmental monitoring and control system (EMCS), engine and electrical/electronics monitoring system (EEMS), digital fuel monitoring system (DFMS), digital hydraulics and brake management system (DHMS), MIL-STD-1760C stores management system and aircraft weapon management system (AWMS). Tejas uses various form of onboard navigation instruments like tactical air navigation (TACAN) system, terrain referenced navigation system (TERPROM), VHF omnidirectional range–instrument landing system (VOR–ILS), DARE developed enhanced ground proximity warning system (EGPWS) and ring laser gyroscope based inertial navigation system integrated with satellite guidance from Research Centre Imarat (RCI).
Flight control system.
Since the Tejas is a relaxed static stability design, it is equipped with Aeronautical Development Establishment developed full authority quadruplex fly-by-wire digital automatic flight control system (DAFCS) with fail-operational/fail-safe safety feature for automatic manoeuvre limiting and to ease pilot handling. The Tejas flight control system is operated with dual redundant modular MIL-STD-1553B standard databus and open architecture Digital Flight Control Computer (DFCC) developed by Defence Avionics Research Establishment (DARE). The mission computer uses a 32-bit processor based on Power ISA developed by Solid State Physics Laboratory (SSPL). The Tejas aerodynamic configuration is based on a pure delta-wing layout with shoulder-mounted wings. Its advanced flight control surfaces actuators are all hydraulically actuated with dual redundant hydraulic system powered by quad redundant electrical power supply. 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 roll 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.
Propulsion.
Early on, it was decided to equip prototype aircraft with the General Electric F404-GE-F2J3 afterburning turbofan engine while a program to develop a domestic powerplant led by the Gas Turbine Research Establishment (GTRE) was launched. In 1998, after Indian nuclear tests, US sanctions blocked sales of the F404, leading to a greater emphasis on the domestic "Kaveri". In 2004, General Electric was awarded a US$105 million contract for 17 uprated F404-GE-IN20 engines to power the eight pre-production LSP aircraft and two naval prototypes; deliveries began in 2006. In 2007, a follow-on order for 24 F404-IN20 engines to power the first operational Tejas squadron was issued.
Cost overruns and delays were encountered in the Kaveri's development. In mid-2004, the "Kaveri" failed high-altitude tests in Russia, ruling out it powering the first production Tejas aircraft. In February 2006, the ADA awarded a contract to French engine company Snecma for technical assistance on the Kaveri. Using Snecma's new core, an uprated derivative of the Dassault Rafale's M88-2 engine, providing 83–85 kilonewtons (kN) of maximum thrust was being considered by DRDO. The IAF objected that since Snecma already developed the core of the engine, the DRDO will not be participating in any joint development but merely providing Snecma with an 'Indian-made' stamp. In November 2014, the DRDO was submitting documents to cancel development of Kaveri.
In 2008, it was announced that an in-production powerplant would have to be selected; this was required to be in the 95 to 100 kilonewton (kN) (21,000–23,000 lbf) range to execute combat manoeuvres with optimal weapons load. After evaluation and acceptance of technical offers for both the Eurojet EJ200 and the General Electric F414, the commercial quotes were compared in detail and GE's F414 was declared as the lowest bidder. The deal covered the purchase of 99 GE F414 engines, an initial batch will be supplied directly by GE and the remainder to be manufactured in India under a technology transfer arrangement. According to the IAF, adopting the new powerplant required a three-to-four years of redesign work.
Operational history.
The formation of the first Tejas-equipped squadron started in July 2011. The Tejas entered service with No. 45 Squadron IAF "(Flying Daggers)" based at the Aircraft and Systems Testing Establishment at HAL, Bangalore on 1 July 2016 before being moved to Sulur Air Force Station in Coimbatore. The squadron initially had four aircraft. The IAF's Aircraft & Systems Testing Establishment was to receive four aircraft already built including two development aircraft. The Tejas made its international debut on 21 January 2016, at the 4th edition of Bahrain International Air Show. 
In June 2017, HAL stated that it expects to have delivered 123 Tejas aircraft to the Indian Air Force by 2024–25. HAL outlined a three–pronged approach to accelerate aircraft production—it would build an additional assembly line, reuse the Hawk assembly line, and outsource major components to the private sector.
The Tejas has participated in several military exercises, most recent being Gagan Shakti 2018 and Vayu Shakti 2019, after which the Indian Air Force Air Marshal Birender Singh Dhanoa commended its reliability and precision of air-to-ground payload delivery. The 45 Squadron of LCA Tejas has successfully flown over 1,500 sorties during trials. During Exercise Gagan Shakti 2018, the eight Tejas deployed each flew six sorties per day. Group Captain Samrath Dhankhar of the Indian Air Force, the commanding officer of No. 45 Squadron "Flying Daggers" which flies Tejas, claimed that DASH IV HMDS on Tejas enables the fighter pilot to exploit full potential of HOBS close combat missiles just by looking at the target. The second Tejas squadron, Squadron 18, was formed at Sulur on 27 May 2020.
On 27 April 2021, Tejas successfully test fired Python-5 high off-boresight (HOBS) close combat missile and further validated enhanced capability of Derby BVR missile. Both missiles scored direct hits on targets during the trial.
Potential operators.
On 21 November 2016, the Indian Ministry of Defence proposed exporting the Tejas, with preliminary talks taking place with several friendly countries. It was reported in March 2020 that HAL planned to set up logistic facilities in Indonesia, Malaysia, Sri Lanka and Vietnam as part of potentially exporting the Tejas.
Malaysia.
In January 2019, the Royal Malaysian Air Force issued a request for information to HAL regarding the Tejas for their light combat aircraft requirement.HAL Tejas is one of the contenders participating in Malaysia's Light Combat Aircraft (LCA)/Lead-In Fighter Trainer (LIFT) competition along with China/Pakistan joint venture Jf-17 and South Korea's KA-50.
Sri Lanka.
It has been reported that Sri Lanka has shown interest in purchasing Tejas to replace its aging fleets of IAI Kfir and Chengdu J-7 aircraft. The programme is for acquisition of 8 to 12 aircraft and is to be pursued through a government-government basic agreement. In 2021, it was decided to overhaul Kfirs instead of buying new aircraft which would cost around $40 million per unit compared to $49 million for overhauling the five kfirs 
United Arab Emirates.
The Tejas has solicited interest from United Arab Emirates (UAE) with some discussions made during a visit by UAE Minister of State and Defence Mohammed Ahmed Al Bowardi Al Falacy during a state visit in October 2018 as part of growing defence relations between India and UAE.
United States.
In December 2020, in response to the US Navy’s request for information (RFI) for its Undergraduate Jet Training System (UJTS), HAL offered its Tejas-LiFT as a contender to replace US Navy's T-45 Goshawks.
Variants.
Prototypes.
Aircraft already built and projected models to be built. Model designations, tail numbers and dates of first flight are shown.
External links.
Features and analysis:
Technical:
General: