Top & bottom interspar skins & intermediate spars made of CFC
Main wing fuselage attachment brackets made of conventional and well proven A/ alloy
Heavily loaded components like pylon support brackets, slat track ribs made of Ti/Al alloy
Other machined & sheet metal components made from Al-Cu/Al-Li alloys
Most of the fatseners are Ti screws and stainless steel nuts/anchor nuts
Highly optimized wing, with appropriate variation of thickness, camber and twist along the span.
Cross sectional area distribution along the length, adjusted for good high speed characteristics
Leading edge slats, scheduled at higher AoA , for favorable aerodynamic behavior
Wing shielded bifurcated air intake duct, with diverters, suitably matched with engine to avoid buzz & to minimize distortion throughout the flight envelop
Safety Features employed in TejasTejas incorporates many world class systems to ensure the safety of pilots. Major systems are..........
An indigenous ‘on-board oxygen generating system’ designed for light combat aircraft (LCA) Tejas. With the development of ‘Integrated Life Support System-On Board Oxygen Generating System (ILSS-OBOGS)’ India joined the elite club of five countries who have established and mastered the technology in the field of ILSS for military flying. Developed by Debel, a DRDO lab focused on the development of bio‐medical and electro‐medical soldier support systems, the advanced ILSS‐OBOGS addresses the need for preventing in‐flight hypoxia (a particular problem during high-altitude flying and emergency escape) and gravity-induced loss of consciousness during high G-maneuvers.
The system uses the bleed air from the aircraft’s engine to produce oxygen, instead of the usual liquid oxygen based system. The technology consists of OBOGS that provides oxygen for breathing, a breathing regulator that supplies the breathing gas to the aircrew at desired flow and pressure, an Anti-G-Valve (AGV) that inflates the anti-gravity suit to apply desired counter pressure and an Electronic Controller Unit (ECU) to coordinate various functions. The system is helpful in long endurance flights. This system gets integrated within the confined space available in the aircraft. It replaces the Liquid Oxygen based system (LOX) by utilizing bleed air from the aircraft engine by separating oxygen from other components by a process based on Pressure Swing Adsorption (PSA) technology. This will prove to be beneficial as the LCA has lesser space to store the liquid oxygen. It also provides improved safety, reduced logistics and significantly lowered operational costs. The ILSS-OBOGS has the versatility to be customized to the needs of other fighter aircraft like MIG-29, Sukhoi-30 Mk1 and Mirage-2000.
A dedicated solid-state oxygen sensor to sense oxygen concentration in the breathing gas is an integral part of the system. In addition, many other subsystems that provide back‐up or redundancy and also impart life support during emergency escape are integral to the ILSS‐OBOGS.
The autopilot provides pilot relief functions. This helps the pilot to do more head down activities (especially mission critical activities) without being concerned about the aircraft departing from its flight path. The autopilot is also equipped with advanced features like auto level (which helps the pilot recover the aircraft if he gets disoriented and also during night flying), safe altitude recovery (which automatically pulls up the aircraft if it comes too close to the ground) and navigation modes (which steer the aircraft automatically along a pre-determined flight path).
3. Martin baker ejection seat
Tejas is using martin baker Mk 16LG ejection seat. Lightweight fighter aircraft, demand significant weight reduction for all their subsystems in order to achieve a lower aircraft total mass. The Mk16 ejection seat achieves its remarkably light weight by combining the twin catapult outer cylinder tubes as both propulsion system and as the seat's primary structure. The Mk16 ejection seat design optimizes pilot field of view, improves comfort and pilot efficiency. Reliability and maintainability have been key elements in the design, resulting in an escape system that has full component accessibility in the cockpit. Modular construction enables the seat to be safely removed or installed in minutes without removing the aircraft cockpit canopy.
- Seat firing handle pulled, centrale initiates Rigid Hermetic Transmission Chain (RHTC)
- Command firing initiated
- Harness power retraction unit retracts shoulder straps
- Canopy fractured by canopy pyrotechnic cutting system
- Primary cartridge fires, bottom latches engage, top latches disengage seat rises up rails
- Aircraft services disconnected
- Emergency oxygen supplied to aircrew
- Legs and arms restrained
- IFF tripped
- Secondary cartridges fire as seat rises
- Multi-purpose initiators fire
- Mechanical Mode Selector (MMS), Barostatic Time-Release Unit (BTRU) and Drogue Deployment Unit Timer (DDUT) sears tripped
- Underseat and lateral rocket motors fire
- Leg restraint lines become taut and rivets shear, freeing lines from floor brackets
- Aerodynamic surfaces deploy
- Drogue deployment unit fires after delay
- Time delays initiated for MMS and BTRU
- Manual Override (MOR) lock disengaged
- MMS senses mode, fires primary circuit
- Drogue canister deployed, pulls bridle clear
- Upper and lower bridle locks released
- MMS inhibited above 7500ft (2286m)
- Drogue stabilises and decelerates seat
- MMS inhibited above 260 KEAS or 4 G
- Drogue stabilises and decelerates seat
- BTRU runs out firing primary circuit
- Drogue stabilises and decelerates seat
- Emergency oxygen supply continued
- Drogue releases at barostate altitude of 16400ft (5000m)
- Headbox deployment initiated
- Upper harness locks release
- Man portion PEC release
- Arm and leg restraint lines cut
- Lower harness locks release after delay
- Parachute inflates
- Auxiliary drogue pulls headbox clear
- Personal locator beacon activated
- Personal Survival Pack (PSP) retained
- Aircrew descends on parachute
- PSP automatically lowered after delay
- Liferaft automatically inflates
Protection from Lightning
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 Electro – magnetic Interference, Aluminum foils cover bolt heads while the fuel tank is taken care of with isolation and grounding.
Canopy Severance system
Canopy Severance system (CSS) is the state of the art technology developed first time in India at ARDE for Tejas. The main aim of CSS system is to rescue the pilot in a shortest possible time during emergency of military aircraft.
CSS has got two independent systems:-
In flight Egress system (IES) - to rescue the pilot in case of emergencies when the aircraft is in flight.
Ground Egress system (GES) - TO rescue the pilot case of ground emergencies without initiating the ejection seat
The main principle behind this system is the “controlled propagation of detonation wave”
Recovery parachute system
It is mandatory for a combat aircraft to demonstrate its spin recovery capability during flight test programme. The purpose of this system is to provide emergency recovery of aircraft from an inadvertent spin in case the aircraft controls are ineffective and are unable to pull it out of spin. The recovery is achieved by deployment of a parachute, which applies an anti-moment force at the rear of the out of control aircraft bringing its nose down further. This brings the aircraft into a controlled stabilized dive and helps it to come out of spin/deep stall.
Fire Extinguisher Bottle
Fire Extinguisher Bottle is used to store and discharge fire extinguishant on initiation of cartridge by Push-button selection or automatically by a crash warning switch located in the airframe. Production Centers are M/s GTTC, Bangalore and M/s Veekay Industries, Mumbai.
Major Mechanical Systems
Major Mechanical System includes Microprocessor Controlled Brake Management System, Environment Control System, Fuel System, Nose Wheel Steering System, Landing Gear System, Hydraulic System, Secondary Power System, Life Support System, and Escape System. Major LRUs developed by ADA are Aircraft Mounted Accessories Gear Box, Filters, Up Locks, QDCs, NRV’s, Depressurization Cock, Gimble joints, ten different types of Heat Exchangers.
Major LRUs Developed by ADA are
~Aircraft Mounted Accessories Gear Box (AMAGB)
AMAGB is a gearbox that forms part of a gas turbine engine. Although not part of the engine's core, it drives the accessories, fuel pumps etc. that are otherwise essential for the operation of the engine or the aircraft on which it is mounted. Accessory drives on large engines handle between 400–500 hp.
An Aircraft-Mounted Accessories Gearbox (AMAGB) has been designed and developed for Tejas. It is a lightweight, single-input, multi-output gearbox, which takes its input drive from engine through a power take off shaft at a rated speed of 16810 rpm. AMAGB has a high power-to-weight ratio and a self-contained lubrication system. It carries four aircraft accessories on its output pads, viz., two hydraulic pumps (60 kW @ 6000 rpm each), one generator (40 kW @ 7950 rpm), and one starter unit. Together, these cater to a major part of hydraulic and electrical power requirements of the Tejas and hence forms a crucial part of its secondary power system.
The design of AMAGB included: (i) installation study, (ii) preliminary design, and (iii) detail design for prototype fabrication. All these were subjected to critical project reviews at each stage. Installation studies were carried out and cleared in consultation with HAL. The software used for gear train optimization, gear size selection, stress analysis of gear teeth and its webs, shafts stress critical speed analysis, and spline stress analysis has been developed indigenously.
The gears are made of electro slag refined 3.5 per cent Ni-Cr case hardening alloy steel. The gears are case carburized and ground to DIN 5 class of accuracy. Many gears are designed integral with the shafts for minimum weight consideration. ISO standard splines, precision gear grinding and cylindrical grinding have been successfully developed adhering to appropriate quality standards requirements. The shaft ends have been suitably designed to act as inner race of the bearings eliminating the inner race.
Two modules of external gear type lube pumps have been developed and assembled at the rear side of AMAGB casing. The pumps are driven by AMAGB gear train itself and provide sufficient flow and pressure requirement (20 lpm, 10 bar at 6000 rpm) to AMAGB lubricating system. Other items of AMAGB, such as drive pads, static deaerator, gravity die cast aluminium alloy components, lubrication jets and static oil seals have been developed successfully utilizing manufacturing facilities available locally.
The casing for AMAGB is made of thin walled magnesium alloy (RZ-5) with integral reservoir and built-in mini cored oil passages. Solid/surface models of the casing were made on the IBM 3020 computer using CATIA software and stress analyzed using ELFINI software.
The thin walled magnesium alloy casting with in-built lubrication passages and integral reservoir for proto type production has been developed and inspected as per MIL-STD 2175 class 1 using Mini Core technology. Seven prototypes of AMAGB have been built. These assemblies were carried out in a specially designed dust free assembly cubicles. Number of special assembly/dis-assembly tools were designed, manufactured and used during assembly of prototypes.
Power plant : GE-F404 / Kaveri
Power transmission : 185 kW (250 hp)
Speed : 16810 rpm
Weight : 34.4 kg
Overall dimension : 720 mm (L) x 450 mm (H) x 120 mm (W)
AMAGB is designed and developed by CVRDE, Chennai and production center is HAL - Engine Divsion, Bangalore.
To lock the undercarriage (U/C) and its doors on retraction in the up position. Locking is mechanical and unlocking is controlled hydraulically. M/s Turbo Tech India Pvt Ltd., Bangalore is the Production Center.
~Carbon-Carbon Composites for Aircraft Brakes
Carbon-Carbon Brakes are developed by ASL, Hyderabad and Production Center Graphite India Ltd, Bangalore
- Provide drag
- Absorb Kinetic Energy by converting into heat
- Hold Aircraft stationary against Engine thrust
Hydraulic systems are used on aircraft to move and actuate landing gear, flaps and brakes. Larger aircraft use these systems also on flight controls, spoilers, thrust reversers and what not. The reason to use hydraulics is because they are able to transmit a very high pressure or force with a small volume of fluid (hydraulic oil). Hydraulic system liquids are used primarily to transmit and distribute forces to various units to be actuated. Liquids are able to do this because they are almost incompressible.
Tejas employs a high performance 4000psi rated hydraulic system with the fluid conforming to MIL H5606/DTD 585/AMG-2 standards, at a rated flow of 1101 pm for each system. All hydraulic pumps including the 35 lpm and 130lpm pumps as well as the system filters
Flight controls consists of four elevons , six slat and two air brake actuators besides the single rudder actuator , for driving the control surfaces. The dual hydraulic, quadruplex electric elevon and rudder actuator have direct drive valves and develop a 10 and 5 ton class stall force respectively. The single hydraulic, duplex leading edge slat and airbrake actuators have electro hydraulic servo control and are designed for 2 ton and 5 ton class stall force respectively.
Tejas hydraulic system is fitted with filters having mesh sizes in the range of 10 to 25 micron. Filters are used in pressure, return and drain lines, to ensure supply of clean oil to the system components for their reliable operations as per NAS (class-1) cleanliness level these filters have a higher filtration rating (β≥100) and operate at -54 C to 135 C temperature conditions. Filters have been provided with unique by-pass valve & automatic shut-off valve arrangement, visual clogging indicator with manual reset and excellent resistance to flow fatigue. Filters developed are qualified for aircraft applications, in conformity with requirements of MIL-F-8815D standard
~Hydraulic and Lube Filters
Filters provide adequate control of the contamination problem during all normal hydraulic system operations. LCA Hydraulic system is fitted with 9 filters of 6 types to control the particulate contamination in the system. Filter element is developed by M/s Mikro Flo Filters, Hyderbad. Production Center is M/s CTTC, Bhuvaneshwar. The high performance hydraulic filters are qualified to meet requirements of MIL-F-8815D.
~Gimbal Assembly with Venturi
Gimbal Assy. With venturi is designed for Max. Operating Temp: 650ºC, with Max. Operating Pressure: 37bar’g’ and Movement: ±10mm (Three axes). M/s Metallic Bellows, Chennai and M/s Veekay Industries, Mumbai are the Production Centers.
A heat exchanger is a piece of a machine built for resourceful heat transfer from one medium to another. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Heat exchangers are commonly used to cool hydraulics, RAM air, auxiliary power units, gearboxes, and many other components that consist of an aircraft. Although temperature is a feature associated with liquid cooling, when heat exchanger services are used at high altitudes air density and pressure are additional features considered. For sufficient airflow, heat exchanger’s fan must be carefully selected based on the ambient pressure. At high altitudes, the density of air is drastically lower. So it takes more airflow to remove the same amount of heat since the same volume of air has fewer air molecules for absorption of heat. The two most commonly use heat exchanged in aviation are the flat tube and the plate-fin heat exchangers.
Successfully designed, developed by BHEL-HPVP (Formerly BHPV) and flight qualified 10 types of compact plate-fin heat exchangers for LCA TEJAS aircraft.
~Secondary Heat Exchanger
Secondary Heat Exchanger is a cross-counter flow plate fin heat exchanger made of Al alloy with a single pass for the cold stream (ram air) and a double pass for hot stream (charge air). A part of the heat exchanger is also used for cooling air supply for fuel tank and gearbox pressurization. It cools charge air at 230 C and mass flow rate of 34 kg/min to less than 102 C for ram air at 91 C and mass flow rate of 224 kg/min.
Hot Air Side
Nominal mass flow : 34 kg/min
Temperature drop : 130 C
Pressure drop : 350 mbar
Cold Air Side
Nominal mass flow : 285 kg/min
Pressure drop : 260 mbar
~Condenser Heat Exchanger
Condenser Heat Exchanger is a cross-flow plate fin heat exchanger made of Al alloy. It performs the function of cooling the hot air coming from reheater before entry to water separator using cold air from turbine inlet. It cools charge air from 63 C at a flow rate of 35 kg/min to less than 38 C for cold air at -31C and mass flow rate of 33 kg/min.
Hot Air Side
Mass flow rate : 35 kg/min
Temperature drop : 25 C
Pressure drop : 130 mbar
Cold Air Side
Mass flow rate : 33 kg/min
Pressure drop : 100 mbar
~Regenerative Heat Exchanger
Regenerative Heat Exchanger is a cross-flow plate fin heat exchanger made of Al alloy. It performs the function of cooling charge air coming from secondary heat exchanger (SHE) by using a part of ram air tapped from SHE ram air inlet duct and water drained from the water separator. It includes a mixing chamber with water injected at ram air inlet end. It cools charge air at 102 C and flow rate of 35 kg/min to less than 75 C by using mixture of ram air at 91 C and water with a mass flow rate of 5.2 kg/min.
Hot Air Side
Nominal mass flow : 35 kg/min
Temperature drop : 25 C
Pressure drop : 150 mbar
Cold Air Side
Nominal mass flow : 5 kg/min
Pressure drop : 150 mbar
~GTSU-127 (Jet fuel starter)
A jet fuel starter (JFS) is a small turbo-shaft engine designed to drive a jet engine to its self-accelerating RPM. Rather than supplying bleed air to a starter motor in the manner of an APU, a JFS output shaft is mechanically connected to an engine. As soon as the JFS begins to turn, the engine turns; unlike Auxiliary Power Units, these starters are not designed to produce electrical power when engines are not running.
A Jet Fuel Starter has been designed and developed by Engine Division of HAL, Bangalore, especially to start the engine of Tejas on ground and in the air. Design optimization of rotating elements and shaft has been achieved by use of 3-D modelling, dynamic and stress analysis software to reduce weight of the JFS with the safe margin for shaft critical speed and element's resonance frequency as well as to reduce vibration and noise levels.
Also, dynamic balancing of entire rotating assembly to G2.5 as per the ISO 1940/1-1986 (E) has been carried out for reduction in unbalanced mass and vibration and noise level and to improve turbine volumetric efficiency through the controlled radial clearance between rotor and stator.
Type : Free turbine type
Power output : 110 kW
Max. Speed : 50500 rpm
Compressor PR : 3.5
Turbine inlet temp : 1150 K
Weight : 50 kg
Fuel : JET A-1/DERD 2494/F-35/IS 1571-85 or JP-5
- Twin spool
- Centrifugal compressor
- Reverse flow compressor
- Axial gas generator turbine
- Axial free power turbine
- Digital electronic fuel control
- Engine air mass flow : 1.27Kg/Sec
- Compressor pressure ratio : 3.7
- Gas generator speed : 50500 rpm
- Power turbine speed : 40000 rpm
- Output shaft speed : 9750 rpm
- Output power : 127 KW
- Length : 655mm
- Diameter : 290mm
- Height : 360mm
- Weight : 54Kg
Utility systems management systems (USMS) and ECSFour LRUs are featured on Tejas , the environment control system controller (ECSC), Hydraulics, Engine and Electrical Monitoring System Electronics Unit (HEEMS-EU), Digital Fuel Monitoring System Electronics Unit(DFM - EU), and the Digital hydraulics and Brake Management system electronics unit (DH-EU), are combined into a dual redundant USMS. USMS caters to control and monitoring, data logging for fault diagnosis and maintenance.
Tejas Environment control and Fuel Management Electronic Unit (ECFM-EU) and a dual lane digital controller with resident software code, interfaces with the aircrafts ECS and manages the aircraft environment in terms of cooling and pressurization, the oxygen system, bleed air cooling pack temperature, ant icing, cabin temperature control as well as the cooling and pressurization of avionics bay, radar and sensors, engine bay ventilation, cabin sealing and wind screen demisting.
Bleed air is rounded from the 7th stage of the engine compressor at a maximum of 600c and 37 bars, following which , six heat exchangers and a cold air unit (CAU) reduce the temperature and pressure for use in the ECS. The entire system is designed for performance under the extremes of IAF operating conditions including tropical conditions. The controller LRU also operates and manages the fuel system and refueling operations.
The HEEMS EU , based on a 64 bit power PC-750 processor , operating at 500 MHz , manages and controls all hydraulic, engine and electrical systems as well as the secondary power system, starting system, and fire detection system . Other functions include engine accessory bay and under carriage system management, adaptive wheel brake management during takeoff and landing, and nose wheel steering management control.
Engine & fuel systemThe LCA is provided a total internal fuel capacity of 2486Kg with 1200Kg of fuel being stored in the wing tanks, 800Kg in the centre fuselage tank and around 486 Kg in the front tank, pressure at the wing tank being 49kpa. Two or three external fuel drop tanks of 800 or 1200 liters capacity, pressure 70 Kpa, may be carried under the wet hard points of the wing and the centre line to take the maximum fuel capacity up to 5297 liters. Fuel temperature is maintained between -54 d & 80 dC, maximum flow rate to engine at 6.4Kg/s
The F404-GE-IN20 engine is an enhanced production version of the F404, which is successfully powering India’s Light Combat Aircraft MKI. The highest thrust variant of the F404 family, the F404-GE-IN20 incorporates GE’s latest hot section materials and technologies, as well as a FADEC for reliable power and outstanding operational characteristics.
Dimensions\t\t: Diameter 890 mm, Length 3.9 m
Weights\t\t: Max Weight 1,035 kg (2,282 lb)
Engines Performance\t: Thrust 9,163 kg (20,200 lb)
GTRE GTX-35VS Kaveri
The GTRE GTX-35VS Kaveri is an afterburning turbofan project developed by the Gas Turbine Research Establishment (GTRE), a lab under the DRDO in Bangalore, India. An Indian design, the Kaveri was originally intended to power Tejas .Kaveri programme failed to satisfy the necessary technical requirements or keep up with its envisaged timelines and was officially delinked from the Tejas programme in September 2008.Decayed performance at high altitude, insufficient thrust, and excessive weight. Some of the problems the DRDO have reported on its Kaveri turbofan engine.
French company Safran agreed to help India revive its Kaveri combat jet engine project. Snecma, as part of the offsets deal for the 36 Rafale jets India bought for its air force, would handhold the Gas turbine and research establishment (GTRE), which has designed Kaveri, to fix gaps in its performance, address safety concerns, certify and fly it on a Tejas light combat aircraft. The Rs 600 odd crore expenses for Snecma, which powers the Rafale jets, would be adjusted against the 50 per cent offsets that it is mandated to spend in India.