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HAL Tejas

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The HAL Tejas (Sanskrit: "Radiance") is a compact supersonic multirole interceptor fighter aircraft being developed by India. ADA (Aeronautical Development Agency) of Department of Defence R&D is the nodal agency for the design & development of Tejas for the Indian Air Force (IAF). HAL (Hindustan Aeronautics Limited) is the principal partner in Tejas Programme with participation of DRDO & CSIR Laboratories, Public & private sector industries and academic institutions. The first test flight was conducted in 2001 and over 538 flights have been conducted since then. It is likely to enter IAF's mainstream in 2009-2010. Tejas is meant to replace the ageing MiG-21 aircraft, which currently form the backbone of the IAF.

Note: In aviation circles, the Tejas is more commonly known as the Light Combat Aircraft (LCA). Before it was christened Tejas, the project was known by this name. Also, throughout the article, the same aircraft will be referred by both names, depending on the origin of the information presented here.

The Tejas 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 Tejas design. The Tejas 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.

India's attempt of developing the LCA is often criticized as being anything but indigenous. On the contrary the LCA is the first aircraft in Asia to be developed completely from what is termed as "scratch". In contrast, Japan's Mitsubishi F-2 is an enhanced F-16, Taiwan's Ching-Kuo IDF (Indigenous Defense Fighter) has been developed by a combination of indigeneous Taiwanese aerospace research and also major consulting by US firms like Lockheed Martin, and China's J-10 is based on designs from Israel's cancelled Lavi fighter. Even China's FC-1 has substantial design consultancy from Mikoyan of Russia.

Out of a total of 35 major avionics components and LRUs, only 3 have foreign involvement notably, the Multi-function displays (Sextante), HMDS (cueing system from Elbit) and Laser Pod (Rafael). Of these, the MFDs of the production LCAs are expected to be from Indian private cos.

The radar and engine are also being developed indigenously, but foreign ones may be installed on the initial units, to allow time for the development of the local radar and engine.

Contents

History

In 1983, India commenced a programme to develop an aircraft to replace its aging Mikoyan-Gurevich MiG-21s as the Air Force's primary multi-role tactical fighter. The Aeronautical Development Agency (ADA) was established with the sole purpose of developing the Tejas. Initially simply dubbed the Light Combat Aircraft or LCA, the design was finalised in 1990 as a small, delta-winged machine. The sophisticated avionics and advanced composite structure specified caused some concern almost immediately, as a government commission expressed doubt that India possessed sufficient technological infrastructure to support such an ambitious project. Two technology demonstrators were ordered as proof of concept before full support was given to the design.

To avoid failures in the development of the final variant, it was decided that Full Scale Engineering Development would proceed in two phases. Phase 1 would consist of DDT (Design,Development,Test) of two aircraft that would be Technology Demonstrators (TD-1 and TD-2) and construction of a Structural Test Specimen. After the TD aircraft were to be tested extensively, construction of two Prototype Vehicles (PV1 and PV-2) would commence, and creation of infrastructure and test facilities for all the aircraft would take place. Phase 2 would consist of construction of three more Prototype Vehicles (PV-3 as the Production variant; PV-4 as the Naval variant and PV-5 as the trainer aircraft), construction of a Fatigue Test Specimen, and creation of facilities at various work centres. Cost of Phase I was Rs.2188 crores, and Phase II was estimated to cost Rs. 2,340 crores. Phase I commenced in 1990.

The two technology demonstrator (TD-1 and TD-2) aircraft were completed by 1995, but were kept grounded due to structural concerns, and trouble with the development of the flight control system. In 1992, the LCA National Control Law team was set up by NAL (National Aeronautics Laboratory), since no nation exports Fly-by-Wire technology to other nations. Since India did not possess advanced realtime ground simulators, eventually the US firm Lockheed Martin was brought in to consult on the latter of these difficulties. The team mathematicians made their control laws, which were tested on the F-16 Vista simulator in the US. But the involvement of Lockheed Martin was terminated in 1998 as part of a US response to India's second nuclear tests in 1998. The same US ban led General Electric to suspend delivery of the F404 engines that were to power the aircraft.

Eventually, the integration of the flight control laws was done indigenously by the NAL team. It has been successful; one of the test pilots said that he found it easier to take off with LCA than Mirage. The LCA has been given Level 1 (top-most) rating by all its Test pilots.

A programme was launched to develop an indigenous powerplant (the GTRE GTX-35VS, christened 'Kaveri', whose development is under progress) to replace the F404 once the aircraft entered mass production. The first technology demonstrator flew with its American F404 engine on January 4 2001, the second technology demonstrator - on June 6 2002. The first prototype PV1 was flown on November 25 2003. The aircraft was first publicly displayed on June 24 2004.

Several prototypes of the Kaveri engine have been developed. India has sought external vendors for supply of some spare parts. Snecma, a French manufacturer supplies rotor blades and some turbine-related equipment. These are also being developed by GTRE since SNECMA does not give ToT of these parts (as they are critical trade secrets). Since India does not have bomber-aircraft, the high-altitude testing of Kaveri is contracted to Russia, which uses its Tu-13 bombers for the purpose.

The Kaveri has 13% higher thrust than the current GE-404 engines in use, and is also flat-rated. However, progress has been delayed by technical difficulties. In 2004, the Kaveri failed in high-altitude tests in Russia. In 2005, a government approval allowed GTRE to seek technical co-operation with foreign agencies in order to accelerate the project. SNECMA, that makes the engines that power the Mirage 2000, as well as Pratt and Whitney have expressed interest in rendering assitance to India in developing the engines. However, questions remain whether potential export customers would accept a relatively unproven engine, rather than the F404.

"We are ready to join in partnership with the Defence Research and Development Organisation to make Kaveri work," General William J. Begert of the world's leading aircraft engine manufacturers, Pratt and Whitney, told Press Trust of India (PTI). According to a report in PTI, American engine manufacturers had to pull out and fly in retired gas turbine experts as they too were initially "foxed" by the Indian Kaveri engine. But, like the DRDO officials, they refuse to say where the Indian engineers had got stuck merely commenting that the DRDO gas turbine technology is 'truly Indian and a very responsive effort' (PTI).

The aircraft is expected to enter full production by 2006 and service in 2010.

The LCA project is infamous for being slowed down due to many delays. According to Captain Kapil Bhargava, "To an extent the slow rate of development of the LCA was anticipated especially in view of US sanctions imposed on India after conducting nuclear tests in May 1998."

Airframe

Basics: The LCA is the smallest and lightest combat jet in the world. Confusion may arise with respect to the South Korean T-50, but it must be remembered that T-50 is primarily a hybrid trainer, that can assume fighter roles when necessary. The T-50 has a higher height and longer wingspan than the LCA, while its length is shorter by 22 cms. Thus, overall the LCA is the smallest combat jet in the world.

It is much smaller than even the JAS-39, which is ~1 m longer. An effort was made to reduce the number of individual composite parts to the minimum and hence keep the plane light.

Detailed description: The LCA is a tail-less compound delta planform with relaxed static stability. Extensive wind tunnel testing on scale models and complex computational fluid dynamic analyses have optimised the aerodynamic configuration of LCA, giving it minimum supersonic drag, low wing loading and high rates of roll & pitch. The tailless compound delta planform helps in keeping LCA small and light. It also means fewer control surfaces, wider choice of external stores and better close combat, high-speed and high-alpha characteristics.

The LCA has 45% composite frame, which make it light and strong at the same time as compared to other all-metal aircraft. The configuration is a delta wing, with no tailplanes or foreplanes, and a single vertical fin. The LCA is constructed of aluminium-lithium alloys, carbon-fibre composites, and titanium. The design incorporates "control-configured vehicle" concepts to enhance manoeuvrability, and quadruplex fly-by-wire controls.

Among the most significant breakthrough is the use of advance carbon composites for upto 45% of the LCA air frame, including wings, materials fin and fuselage. This percentage of composites is one of the highest as compared to other contemporary aircraft of its class. Apart from making it much lighter, there are less joints or rivets making the aeroplane more reliable. Fatigue strength LCA studies on computer models optimise performance. National Aerospace Laboratory (NAL) has played a lead role. Materials include Aluminium-Lithium alloys, Titanium alloy and Carbon composites. Composites for wing (skin, spars and ribs), fuselage (doors and skins), elevons, fin, rudder, airbrakes and landing gear doors.

Special mention: The skin of the LCA measures 3 mm at its thickest with the average thickness varying between 2.4 to 2.7 mm. BAe was consulted. The fin for the LCA is a monolithic honeycomb piece. No other manufacturer is known to have made fins out of a single piece. The cost of manufacture is reduced by 80% from Rs 2.5 million in this process. This is contrary to a subtractive or deductive method normally adopted in advanced countries, when the shaft is carved out of a block of titanium alloy by a computerized numerically controlled machine. A 'nose' for the rudder is added by 'squeeze' riveting.

The use of composites results in a 40% reduction in the total number of parts (if the LCA were built using a metallic frame): for instance, 3,000 parts in a metallic design would come down to 1,800 parts in a composite design. The number of fasteners has been reduced to half in the composite structure from 10,000 in the metallic frame. The composite design helped to avoid about 2,000 holes being drilled into the airframe. Though the weight comes down by 21%, the most interesting prediction is the time it will take to assemble the LCA -- the airframe that takes 11 months to build can be done in seven months using composites.

Flight Envelope:

According to defence analyst B. Harry, the Naval LCA shall feature with LEVCONs or (Leading Edge Vortex Controllers). This shall require development of new control laws for it. These LEVCONs shall be control surfaces that extend from wing-root leading edge and thus afford better low-speed handling of the LCA which otherwise is slightly hampered due to increased drag that results from its delta-wing design. It shall also increase controllability at high AoA. At high speeds though, the delta-winged design offers better manoueverability than conventional winged-designs.

According to him, such a feature (as in the Naval LCA), has not been implemented on any other combat aircraft.

Stealth:It is expected that being the smallest combat jet, and coupled with a highly composite airframe (that do not reflect radar waves) and RAM (RadarAbsorbent Material) coating, the LCA shall exhibit a very low RCS to radar detections from airborne enemy aircraft and AWACs. The Y-duct intake shields the engine compressor from radar waves.

LCA is expected to be highly maneuverable by virtue of its double delta wing and relaxed static unstability of its Fly-By-Wire system. Provisions for the growth of hardware and software in the avionics and flight control system, available in Tejas, 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.

Lightning tests: When lightning strikes the LCA, four metal longerons stretching from end to end, afford protection. In addition, all the panels are provided with copper mesh. One out of five is 'bonding' bolt with gaskets to handle Electromagnetic interference. Aluminum foils cover bolt heads while the fuel tank is taken care of with isolation and grounding.

Air intakes: The wing shielded side mounted bifurcated Y-duct air intake with optimised diverter configuration ensures buzz free air supply to the engine, at acceptable distortion levels.

Weapon stations :Seven weapon stations provided on Tejas offer flexibility in the choice of weapons Tejas can carry in various mission roles. Provision of drop tanks and inflight refueling probe ensure extended range and flight endurance of demanding missions.

Cockpit: The LCA has a glass cockpit with two Multi Function Displays, Head-Up Display , Multi Function Keyboard and Get-You-Home Panel.

Avionics

The avionics system enhances the role of Light Combat Aircraft as an effective weapons 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 multi-function 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 Tejas 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 1×10-7 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 multi-function displays through MIL-STD-1553B avionics bus and RS 422 serial link.

Multi-mode radar (MMR), the primary mission sensor of the Tejas 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 broadband 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.

Following are the important avionics components:

Mission Computer (MC): MC performs the central processing functions apart from performing as Bus Controller and is the central core of the Avionics system. The hardware architecture is based on a dual 80386 based computer with dual port RAM for interprocessor communication. There are three dual redundant communication channels meeting with MIL-STD-1553B data bus specifications. The hardware unit development was done by ASIEO, Bangalore and software design & development by ADA.

HUD: The Head-up-Display of the LCA is a unit developed by the state-owned CSIO, Chandigarh. The HUD is claimed to be superior to similar systems in the international market. According to Mr. CV M L Narasimham, head of CSIO's Applied Optics division, compared to Israel's HUD, the CSIO equipment is noiseless, silent, and offers a better field of view. It is compact, reliable, non-reflective and designed for high-performance aircraft. It was first put on the PV-2 version of the LCA.

Control & Coding Unit (CCU): In the normal mode, CCU provides real time I/O access which are essentially pilot's controls and power on controls for certain equipment. In the reversionary mode, when MC fails, CCU performs the central processing functions of MC. The CCU also generates voice warning signals. The main processor is Intel 80386 microprocessor. The hardware is developed by RCI, Hyderabad and software by ADA.

Display Processors (DP): DP is one of the mission critical software intensive LRUs of LCA. The DP drives two types of display surfaces viz. a monochrome Head Up display (HUD) and two colour multifunction displays (MFDs). The equipment is based on four Intel 80960 microprocessors. There are two DPs provided (one normal and one backup) in LCA. These units are developed by ADE, Bangalore.

Mission Preparation & Data Retrieval Unit (MPRU): MPRU is a data entry and retrieval unit of LCA Avionics architecture. The unit performs mission preparation and data retrieval functions. In the preparation mode, it transfers mission data prepared on Data Preparation Cartridge (DPC) with the help of ground compliment, to various Avionics equipment. In the second function, the MPRU receives data from various equipment during the Operational Flight Program (OFP) and stores data on Resident Cartridge Card (RCC). This unit is developed by LRDE, Bangalore.

USMS Electronic Units: The following processor based digital Electronics Units (EU) are used for control and monitoring, data logging for fault diagnosis and maintenance: Environment Control System Controller (ECSC), Engine and Electrical Monitoring System Electronics Unit (EEMS-EU), Digital Fuel Monitoring System Electronics Unit (DFM-EU) and Digital Hydraulics and Brake Management System Electronics Unit (DH-EU)

Changes in PV-2: The production standard cockpit has no electro mechanical standby instruments. The cockpit is dominated by three 5”x 5” AMLCD MFD’s, two Smart Standby Display Units (SSDU) and the indigenous HUD. The HUD has an Up Front Control Panel (UFCP) which is a significant man machine interface (MMI) enhancement which allows the pilot to program, initialize the avionics and enter mission and system critical data through an interactive soft touch keyboard. Although the FOV of this HUD is slightly less than that of contemporary units on other aircraft of this generation it is not considered significant because the ELBIT, Israel furnished DASH helmet mounted display and sight (HMDS) will form an integral part of the avionics suite.

The four utilities system monitoring LRUs have been reduced to two dual redundant units. These units perform the control, monitoring, data logging for fault diagnosis and maintenance functions.

A HAL Korwa developed Flight data recorder will be fitted after the initial flights.

The PV2 is a much lighter aircraft and possesses advanced software technology, unlike the Test Demonstrator I, II and PV1. There is an advancement in the build standard of PV2, which is a software intensive fourth generation combat aircraft built to production standard. Besides having a high percentage of composite materials in its airframe structure, it incorporates a state-of-the-art, integrated, modular avionics system with open architecture concepts to facilitate easy hardware and software upgrades and re-usability.

MMR: The Multi Mode Radar (MMR) jointly developed by LRDE and HAL Hyderabad will be fitted in the nose after redistributing the FTI carried in the first three aircraft. The MMR features LPRF, MPRF and HPRF modes, platform motion compensation, MTI and Doppler filtering, CFAR detection, range-Doppler ambiguity resolution, scan conversion, display of target and ground map data on MFDs and on line diagnostics to identify faulty processor modules.

The aircraft has the ADA developed Stores Management System (SMS) which will provide fully integrated control of weapon systems, external stores and fuel tanks. The SMS is based on a 32 bit, single chip micro controller with dual redundant architecture. Its main components include the single Stores Interface Box (SIB) and multiple pylon interface boxes (PIB) for each hard point.

EW suite: A state of the art EW suite will be integrated and tested later in the program. Primary responsibility for development of the EW suite is that of the Defence Avionics Research Establishment (DARE), Bangalore.

Weapons

Internally mounted: GSh-23 mm twin barrel gun with 220 rounds of ammunition. Seven external hardpoints. Can carry air-to-air missiles, air-to-surface missiles, anti-ship missiles, rocket launchers and ECM pods.

Miscellaneous

Ejection Seat: Pune-based premier Armament Research and Development Establishment has developed an innovative high-tech line-charged Canopy Severance System for the Light Combat Aircraft, for safe ejection of the pilot.

Since testing laboratories and facilities are not present in India, the certification was done by Martin Baker AIC Co London. After nearly 40 test trials, Martin Baker,--the certifying authority-- has certified commercial production of the canopy severance system.

Dr. Sudharshan Kumar Salwan, director of ARDE, said in an interview to rediff.com, "While in the conventional system, the entire canopy flies off and can result in an injury to the pilot, in the newly indigenously developed system, only a certain portion of the canopy which is line-charged, gets severed. This absolutely minimises injury to the pilot."

He stressed in the same interview, that no aircraft in the world had this kind of live system which could be operated from outside the aircraft, especially when the pilot was unconscious due to some injuries or in the event of crash-landing.

Software: The ADA developed a software called 'Autolay' as part of the LCA project. Autolay is used in the design of integrated virtual manufacturing capability for laminated composite components. It is due to it that the LCA uses 45% composites in its airframe.

Autolay enables parellel processing of composite design activities viz..,details design studies,laminate engineering and generationof design and manufacturing drawings ,thus providing concurrrent engineering benifits in a project environment. The resulting data is accessible for tool design ,lay-up process (both manual and automatic),and generation of substructure drawings,without any loss of geometric information and thereby help in striving towards the concept for paperless design office . Development of Autolay is the result of more than 300 man-years effort over the last 13 years.

Airbus Industries purchased Autolay for their 600-seater A380 project from ADA for $3.2 milion in 2001.

Titanium tubes : Nuclear Fuel Complex (NFC) has developed titanium half alloy tubes, critical components in the LCA. It is a key component for the LCA, as the tubes were used for hydraulic power transmission.

Status

The PV-2 was first test-flown in December 2005. As of 17 July 2006, the LCA has completed 548 test flights in all. On 13 May 2006 the PV-2 went supersonic for the first time and on 14 May 2006 it did so again in a weaponised state (ie. carrying a load of weapons such as missiles and an internal gun).

According to HAL chairman Ashok Baweja, interviewed in May 2006, the fifth prototype vehicle, trainer and the first of the eight Limited Series Production (LSP) will join the programme before the end of 2006. These aircraft will help accelerate the initial operational clearance for the LCA. The first Limited-series-production LCA shall be inducted into the IAF by the end of 2006.

Variants

Specifications (HAL Tejas)

Other equipment:

External links

News:

Technical:

http://rapidshare.de/files/9986319/tejas.pdf.html

General:

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