HAL Tejas
The HAL Tejas is an Indian single-engine, 4.5 generation, delta wing, multirole combat aircraft designed by the Aeronautical Development Agency and manufactured by Hindustan Aeronautics Limited for the Indian Air Force and the Indian Navy. The aircraft made its first flight in 2001 and entered into service with the IAF in 2015. It is the smallest and lightest of the supersonic fighter jets of its generation.
The aircraft was officially named as Tejas in 2003. The name means 'radiance' or 'brilliance' in Sanskrit, and continued an Indian tradition of choosing Sanskrit-language names for both domestically produced and imported combat aircraft.
Tejas is the second jet powered combat aircraft developed by HAL, after the HF-24 Marut. It has two production combat variants - Mark 1 and Mark 1A apart from trainers. In 2016, the Mark 1 aircraft had an indigenous content of 59.7% by value and 75.5% by the number of line replaceable units, which was increased in the 1A variant.
, the IAF has about 30 Mark 1 aircraft and six trainers in its inventory across two squadrons. The first squadron, No. 45 Squadron IAF became operational in 2016 and is based at Sulur in the southern state of Tamil Nadu. The second squadron, No. 18 Squadron IAF is based at Naliya in Gujarat in Western India. The IAF has 141 combat aircraft of the Mark 1A type on order, in addition to 41 trainers. The IAF plans to procure at least 324 aircraft or 18 squadrons of Tejas in all variants, including the heavier Tejas Mark 2 which is currently being developed.
Development
LCA programme
In the 1980s, the Indian Air Force had been operating ageing fighter aircraft such as the MiG-21. The MiG-21 had been the mainstay of the IAF since 1963, and the IAF had operated 874 of these aircraft in the past. The Long Term Re-Equipment Plan of 1981 of the Ministry of Defence noted that most of these fighter aircraft 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 1983, the Government of India established the Light Combat Aircraft programme with the initial goal of developing a new light combat aircraft to replace the ageing fleet of the IAF. In 1984, the government established the Aeronautical Development Agency under the aegis of the Defence Research and Development Organisation to manage the LCA programme. The ADA was entrusted with the design and development of LCA while Hindustan Aeronautics Limited was chosen as the principal contractor. The government's requirements for the aircraft included the following: fly-by-wire flight control system, multi-mode pulse-doppler radar, and afterburning turbofan engine.
The project definition phase commenced in October 1986. French company Dassault-Breguet acted as a consultant for the design and system integration of the planned aircraft. Kota Harinarayana was appointed as the director and chief designer of the LCA programme. While the project was initially conceived to replace the MiG-21 aircraft, the Minister of Defence told the Indian Parliament in 2021 that the aircraft is no longer considered as a replacement for the MiG-21, and is part of a general IAF fleet modernisation programme.
Design
The design of the LCA was finalised in 1990 as a small tailless compound delta wing design with relaxed static stability. To provide enhanced manoeuvrability, it was planned to be a control configured vehicle incorporating a digital fly by wire flight control system. Dassault-Breguet offered a hybrid fly by wire flight control system for the project, consisting of three digital channels and one analog channel, with a redundant analog channel as a back up. However, the ADA favored a quadruplex digital channel flight control system. In 1992, a dedicated National Control Law team was set up by the National Aerospace Laboratories to develop an indigenous fly by wire flight control system for the aircraft. While initially Lockheed Martin was proposed as a partner, it did not materialise following a United States led embargo in response to India's second nuclear tests in 1998. This delayed the programme partly by about 18 months.The quadruplex digital fly-by-wire flight control system was developed in house for the LCA. The CLAW team completed the design and integration of the flight control laws with the flight control system software, with the aid of an Iron Bird test rig. The flight control system conducted over 50 hours of pilot testing on the test rig. Aerodynamic characterization research was conducted at NAL's tri-sonic wind tunnel facility.
For the multi-mode radar, the team intended to use the Ericsson-Ferranti PS-05/A I/J-band multi-function radar used on Saab JAS 39 Gripen. However, DRDO later decided to develop an indigenous radar for the aircraft. DRDO's Electronics and Radar Development Establishment laboratory and HAL were jointly assigned the MMR development programme, and with the work commencing in 1997. The Centre for Airborne Systems was responsible for the MMR's test programme, and a HS-748 airborne surveillance aircraft was re-fitted for the purpose. By 2005, only two radar modes-the air-to-air look-up and look-down were successfully tested, and the performance of other modes that had been tested were rated as sub-optimal. The problem was attributed to the lack of compatibility between the radar and the LRDE's signal processor module.
The development of MMR was later abandoned in favour of using a foreign developed radar as an interim option. The Israeli Elta EL/M-2032 multi-mode and EL/M-2052 Active electronically scanned array radar units were selected for the Mk1 and initial Mk 1A aircraft respectively. In 2012, the DRDO started development of the Uttam AESA Radar, which was undergoing trails as of 2024.
The ADA was successful in the development and manufacturing of carbon fibre composite structures and skins, and a glass cockpit for the aircraft. The Autolay computer-aided design software developed as part of the LCA programme was later licensed to Airbus for its A380 wide-body aircraft project. The government's self-reliance goal oriented development considerably increased the sourcing of indigenous components for the programme and contributed to the expansion of the aviation industry. For the LCA programme, Amphenol provided loom assemblies, Lakshmi Machine Works produced air intakes, and Tata Advanced Systems manufactured the composite parts.
Prototypes and testing
On 4 January 2001, the first technology demonstrator successfully achieved flight. The second such aircraft began testing in 2003. The first production variant made its maiden flight in 2003. The first trainer variant was rolled out in 2009 and made its first flight on 26 November 2009. A total of two trainer prototypes were built and designated PV-5 and PV-06. The first naval prototype, designated NP-1, made its first flight on 27 April 2012. It was a twin-seater aircraft, while the second naval prototype, designated as NP-2, was a single seater. Both naval prototypes were used extensively for various aircraft carrier-related trials at the Shore Based Test Facility in Goa. NP-2 was used in the actual carrier trials, where it made an arrested recovery and ski-jump assisted take-off from the aircraft carrier in January 2020.The first Limited Series Production aircraft performed its maiden flight on 25 April 2007. A total of seven limited series production aircraft were built. The LSPs were extensively used for developmental trials such as weapon testing – involving test firing of the R-73 and Python-5 close combat missiles, the I-Derby ER beyond visual range air-to-air missile and guided–unguided munition releases. The LSPs were also used for sensor trials involving integration and testing of the Israeli Elta EL/M-2032 multi-mode radar, and EL/M-2052 AESA radar, and the Indian Uttam AESA Radar and Rafael Litening targeting pod. The Uttam radar was integrated on the Tejas LSP-2 and LSP-3, and logged about 30 hours of flight testing on the Tejas alone. The high altitude trials and hot weather trials were carried out with the LSPs and the PV-3 prototype, in IOC and FOC configurations. These trials were mainly focused on assessing the performance of the various sensors and avionics on board, at temperatures ranging from below -10 degree Celsius to more than +45 degrees Celsius.
Sea trials to assess the radar performance in air-to-air and air-to-sea modes at various altitudes were carried out in 2010. Flutter vibration tests were also carried out in different configurations at high angle of attack to assess the structural integrity across the flight envelope. LSP-4 completed the successful trial of BDL developed Counter Measure Dispensing System with R-73 missile on 2 December 2010. It worked well Open Architecture Mission Computer and Digital Stores Management System.
In the second half of 2012, the Tejas fleet was grounded for over three months and the ejection system had to be modified to resume flight tests by the end of 2012. In 2013, Tejas conducted an inflight engine relight test at high altitude to assess the engine response on flameout, a critical parameter for operational clearance. The inflight engine relight test is crucial for single engine combat aircraft. On 15 April 2023, HAL received a flight clearance certificate for the Aircraft Mounted Accessory Gear Box bearings and power take-off shaft. The Centre for Military Airworthiness and Certification also gave clearance for the pre-production of landing gear seals developed by the Combat Vehicles Research and Development Establishment and Fluoro Carbon Seals Limited.
Operational clearance
In December 2006, the IAF announced that it would form an "LCA Induction Team" to manage the aircraft's service introduction. The Tejas was awarded initial operational clearance-I in January 2011. To ease up the process of FOC, an interim IOC-II was issued to Tejas in December 2013. The IOC-II expanded the g-limit, angle of attack and allowed the aircraft to carry precision guided munitions and close combat missiles. The IOC-II Tejas have an operational radius of. The first squadron, consisting of Tejas in IOC-II configuration, became operational in 2016. The No. 45 Squadron IAF based at Sulur Air Force Station, Coimbatore was the first to have their MiG-21s replaced by Tejas aircraft at the base.The FOC campaign began in December 2014. Two critical parameters set by IAF for FOC clearance was expansion of angle of attack from 24 degree in IOC-II to 28 degree in FOC and inflight refueling capability. In February 2018, as part of the FOC campaign, the Tejas carried out a "hot refuelling" - refuelling with engine running, which shortens the turnaround time by 30% and doubles the sortie rate. In September 2018, the Tejas successfully completed its mid-air refuelling trials required for the aircraft to obtain its FOC. In January 2019, HAL received permission from CEMILAC to start production of the FOC standard Tejas.
On 20 February 2019, during the Aero India 2019 show, FOC was formally awarded to the Tejas. The HAL handed over the FOC certificate to the then Air Chief Marshal BS Dhanoa at the Yelahanka Air Force base. After the formal ceremoney, ACM Dhanoa stated that Tejas was "ready" and "behaved like a true fighter". The second 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.
A full mission simulator phase-1 was commissioned at Sulur Air Force Station on 23 October 2021. Phase 1 of the FMS features training in aircraft handling and full envelope flying. Phase 2 will further augment the training with focus on weapons system and advance sensors onboard Tejas.