The HAL Tejas is a lightweight multirole jet fighter developed by India. It is a tailless,compound delta wing design powered by a single engine. It came from the Light Combat Aircraft (LCA) programme, which was begun in the 1980s to replace India's aging MiG21 fighters. Later the LCA was officially named "Tejas" by then PM ,AB bajpayee.
The Indian Light Combat Aircraft (LCA -- sometimes called Last Chance Aircraft) is the world's smallest, light weight, multi-role combat aircraft. The LCA is designed to meet the requirements of Indian Air Force as its frontline multi-mission single-seat tactical aircraft to replace the MiG-21 series of aircraft. The delta wing configuration, with no tailplanes or foreplanes, features a single vertical fin. The LCA is constructed of aluminium-lithium alloys, carbon-fibre composites, and titanium. LCA integrates modern design concepts and the state-of-art technologies such as relaxed static stability, flyby-wire Flight Control System, Advanced Digital Cockpit, Multi-Mode Radar, Integrated Digital Avionics System, Advanced Composite Material Structures and a Flat Rated Engine.
The LCA program was launched in 1985. The development effort for the LCA is spearheaded by the Aeronautical Development Agency (ADA) under the Department of Defence Research & Development. ADA’s responsibilities include project design, project monitoring and promoting the development of advanced aeronautic technologies of relevance to the LCA.
The LCA design has been configured to match the demands of modern combat scenario such as speed, acceleration, maneuverability and agility. Short takeoff and landing, excellent flight performance, safety, reliability and maintainability, are salient features of LCA design. The LCA integrates modern design concepts like static instability, digital fly-by-wire flight control system, integrated avionics, glass cockpit, primary composite structure, multi-mode radar, microprocessor based utility and brake management systems.
The avionics system enhances the role of Light Combat Aircraft as an effective weapon platform. The glass cockpit and hands on throttle and stick (HOTAS) controls reduce pilot workload. Accurate navigation and weapon aiming information on the head up display helps the pilot achieve his mission effectively. The multifunction displays provide information on engine, hydraulics, electrical, flight control and environmental control system on a need-to-know basis along with basic flight and tactical information. Dual redundant display processors (DP) generate 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. A state-of-the-art multi-mode radar (MMR), laser designator pod (LDP), forward looking infra-red (FLIR) and other opto-electronic sensors 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. An advanced electronic warfare (EW) suite enhances the aircraft survivability during deep penetration and combat. Secure and jam-resistant communication systems, such as IFF, VHF/UHF and air-to-air/air-to-ground data link are provided as a part of the avionics suite. All these systems are integrated on three 1553B buses by a centralised 32-bit mission computer (MC) with high throughput which performs weapon computations and flight management, and reconfiguration/redundancy management. Reversionary mission functions are provided by a control and coding unit (CCU). Most of these subsystems have been developed indigenously.
The digital FBW system of the LCA is built around a quadruplex redundant architecture to give it a fail op-fail op-fail safe capability. It employs a powerful digital flight control computer (DFCC) comprising four computing channels, each powered by an independent power supply and all housed in a single line replaceable unit (LRU). The system is designed to meet a probability of loss of control of better than 1x10-7 per flight hour. The DFCC channels are built around 32-bit microprocessors and use a safe subset of Ada language for the implementation of software. The DFCC receives signals from quad rate, acceleration sensors, pilot control stick, rudder pedal, triplex air data system, dual air flow angle sensors, etc. The DFCC channels excite and control the elevon, rudder and leading edge slat hydraulic actuators. The computer interfaces with pilot display elements like multifunction displays through MIL-STD-1553B avionics bus and RS 422 serial link. The digital FBW system of the LCA is built around a quadruplex redundant architecture to give it a fail op-fail op-fail safe capability. It employs a powerful digital flight control computer (DFCC) comprising four computing channels, each powered by an independent power supply and all housed in a single line replaceable unit (LRU). The system is designed to meet a probability of loss of control of better than 1x107 per flight hour. The DFCC channels are built around 32-bit microprocessors and use a safe subset of Ada language for the implementation of software. The DFCC receives signals from quad rate, acceleration sensors, pilot control stick, rudder pedal, triplex air data system, dual air flow angle sensors, etc. The DFCC channels excite and control the elevon, rudder and leading edge slat hydraulic actuators. The computer interfaces with pilot display elements like multifunction displays through MIL-STD-1553B avionics bus and RS 422 serial link.
Multi-mode radar (MMR), the primary mission sensor of the LCA in its air defence role, will be a key determinant of the operational effectiveness of the fighter. This is an X-band, pulse Doppler radar with air-to-air, air-to-ground and air-to-sea modes. Its track-while-scan capability caters to radar functions under multiple target environment. The antenna is a light weight (< 5 kg), low profile slotted waveguide array with a multilayer feed network for broad band operation. The salient technical features are: two plane monopulse signals, low side lobe levels and integrated IFF, and GUARD and BITE channels. The heart of MMR is the signal processor, which is built around VLSI-ASICs and i960 processors to meet the functional needs of MMR in different modes of its operation. Its role is to process the radar receiver output, detect and locate targets, create ground map, and provide contour map when selected. Post-detection processor resolves range and Doppler ambiguities and forms plots for subsequent data processor. The special feature of signal processor is its real-time configurability to adapt to requirements depending on selected mode of operation.
Seven weapon stations provided on LCA offer flexibility in the choice of weapons LCA can carry in various mission roles. Provision of drop tanks and inflight refueling probe ensure extended range and flight endurance of demanding missions. Provisions for the growth of hardware and software in the avionics and flight control system, available in LCA, ensure to maintain its effectiveness and advantages as a frontline fighter throughout its service life. For maintenance the aircraft has more than five hundred Line Replaceable Units (LRSs), each tested for performance and capability to meet the severe operational conditions to be encountered.
Hindustan Aeronautics Limited (HAL) is the Principal Partner in the design and fabrication of LCA and its integration leading to flight testing. The LCA has been designed and developed by a consortium of five aircraft research, design, production and product support organizations pooled by the Bangalore-based Aeronautical Development Agency (ADA), under Department of Defense Research and Development Organization (DRDO). Various international aircraft and system manufacturers are also participating in the program with supply of specific equipment, design consultancy and support. For example, GE Aircraft Engines provides the propulsion.
The Ministry had stated, in December 1994, that the LCA was expected to enter into squadron services with Initial Operational Clearance by 2002 and with Final Operational Clearance by 2005 provided Government approved Phase-II of FSED in 1995 and accorded clearance for production in 1997. Since proposal for approval of Phase-II of FSED was yet to be submitted to the Government, the chances of meeting the induction schedule of LCA by 2002/2005 were remote.
The first prototype of LCA rolled out on 17 November 1995. Two aircraft technology demonstrators were powered by single GE F404/F2J3 augmented turbofan engines. Regular flights with the state-of-the-art "Kaveri" engine, being developed by the Gas Turbine Research Establishment (GTRE) in Bangalore, were planned for 2002, although by mid-1999 the Kaveri engine had yet to achieve the required thrust-to-weight ratio.
The LCA is India's second attempt at an indigenous jet fighter design, following the somewhat unsatisfactory HF-24 Marut Ground Attack Fighter built in limited numbers by Hindustan Aeronautics Limited in the 1950s. Conceived in 1983, the LCA will serve as the Indian air force's frontline tactical plane through the year 2020.
Following India's nuclear weapons tests in early 1998, the United States placed an embargo on the sale of General Electric 404 jet engines which are to power the LCA. The US also denied the fly-by-wire system for the aircraft sold by the US firm Lockheed-Martin. As of June 1998 the first flight of the LCA had been delayed due to systems integration tests. The first flight awaits completion of the Digital Flight Control Systems, being developed by the Aeronautical Development Establishment (ADE).
The Ministry explained, in February 1999, that delay in conducting first flight of first technology demonstrator was the main reason for not seeking sanction for Phase-II of FSED. However, clearance for an interim Phase-II from the Government was underway and Phase-II would be concurrently undertaken with the last two years of Phase-I. With this arrangement, Initial Operational Clearance in 2003 and Final Operational Clearance in 2005 would be realised.
The LCA can be inducted into the Indian Air Force (IAF) in limited numbers starting in 2008, though 'full-scale' induction won't happen anytime before 2010. Further delays are expected. Most critics put the date of induction between 2012 and 2015, if it is inducted at all. Apart from the MiG-21, LCA will also replace MiG-23 and MiG-27, also in service with the IAF.
The IAF had placed an order for 20 Tejas lightweight multi-role planes, and may increase the number to 40.
Naval Variant Tejas Light Combat Aircraft (LCA)
Having resolved the issue of sourcing material for the landing gear of the naval variant of the Tejas Light Combat Aircraft (LCA), the Aeronautical Development Agency (ADA) slated the inaugural flight for late 2009. The naval fighter aircraft is a twin-seater variant with the nomenclature NP1 (naval prototype one). It would look similar to PV-5 (prototype vehicle five) of the LCA being developed for the Indian Air Force (IAF), though the naval aircraft will be powered by a more powerful engine. It will be a replacement for the British-made Sea Harrier jump jets currently used by the Navy. The Navy has placed intent to procure 40 aircraft.
(source:HAL/www.globalsecurity.org/livefist.blogspot.com)
