Mechanical & Propulsion Systems

                      Aircraft-Mounted Accessories Gearbox

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.


Salient Features

Power plant :            GE-F404-F2J3/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)
 

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 pressurisation. 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.


Salient Features

Hot Air Side
Nominal mass flow :  34 kg/min
Temperature drop :   130 șC
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 -31°C and mass flow rate of 33 kg/min.


Salient Features
Hot Air Side
Mass flow rate :      35 kg/min
Temperature drop : 25 șC
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.


Salient Features

Hot Air Side
Nominal mass flow : 35 kg/min
Temperature drop :  25 șC
Pressure drop :        150 mbar
Cold Air Side
Nominal mass flow : 5 kg/min
Pressure drop :        150 mbar

Reheater
 

Reheater Heat Exchanger is a cross-flow plate fin heat exchanger made of Al alloy. It performs the function of cooling the hot air before it enters the condenser and reheat the hot air before it enters the turbine of cold air unit. It cools charge air from 75 șC at a flow rate of 35 kg/min to less than 63 șC for cold air at 38 șC at a flow rate of 34.5 kg/min.
 

Salient Features
Hot Air Side
Mass flow rate :      35 kg/min
Temperature drop : 20 șC
Pressure drop :       60 mbar
Cold Air Side
Mass flow rate :     34.5 kg/min
Pressure drop :      80 mbar
 
Gimbal Joints
 

Gimbal Joints are used to provide angular movement of + 6o (cone angle 12o) through 360o caused due to engine manoeuvring or thermal expansion of ECS bleed pipes. The components of these parts are fabricated with high temperature resistant INCONEL 625/718 material. ADA has designed and developed f63, f50, and f32 mm Gimbal Joints for Tejas. The technology has been transferred to M/s Metallic Bellows, Chennai.
 

Salient Features
Gimbal Joint                                       Ф63 mm             Ф32 mm             Ф50 mm
Operating pressure (bar)                          7                          7                         37
Operating temperature (șC)                     650                      650                     650
Angle of deflection (degree)                     ±6                       ±6                       ±6
Life (cycles)                                         100000                100000               100000
 
Secondary Power System Heat Exchanger (HE-1)
 

The hydraulic oil–IDG oil-fuel cooler is a part of secondary power system of Tejas. It is in fact a combination of two separate heat exchange sections in series. Section one is hydraulic oil-fuel section, while section two is IDG oil-fuel section. Fuel from the aircraft's fuel supply tank enters section one first, cooling the hydraulic oil. Heated fuel then enters section two, where it is further heated up by heat transfer from IDG oil.

Salient Features
Heat load
Hydraulic oil :            9 kW
IDG oil :                    14 kW
Temperature (max.) : 135 oC
Pressure (max) :         35 bar
 
Secondary Power System Heat Exchanger (HE-2)
 

The gearbox oil–hydraulic oil-fuel cooler is a part of secondary power system of Tejas. It is also a combination of two separate heat exchange sections in series. Section one is gearbox oil-fuel section, while section two is hydraulic oil-fuel section. Fuel from the aircraft's fuel supply tank enters section one first cooling the gearbox oil. Heated fuel then enters section two, where it is further heated up by heat transfer from hydraulic oil.

  
Salient Features
Heat load
Hydraulic oil :            11 kW
Gearbox oil :              6.5 kW
Temperature (max.) : 135 oC
Pressure (max.) :       35 bar
 
 
Liquid-to-Air Heat Exchanger
 
 

Liquid-to-Air Heat Exchanger is a cross-flow plate fin heat exchanger made of Al alloy. The outlet on air side has two connections, one for cabin cooling and other for avionics cooling. It performs the functions of cooling the coolanol R25 coming from radar by using cold air coming from the low pressure side of the condenser.

Salient Features
Liquid
Nominal flow :              15 L/min
Heat removal capacity : 3 kW
Pressure drop :             500 mbar
Air
Nominal mass flow :     33 kg/min
Pressure drop :            200 mbar
 
Fire Extinguisher Bottle

Fire Extinguisher Bottle is used for storing Halon-1301. It discharges the same through the outlet by explosion of a hermetically sealed cartridge. The operation is selected by pilot/automatically by a crash warning switch.


Salient Features
Volume :                        1 L
Weight :                         2.8 kg
Working pressure :         40 bar
Burst pressure :              502 bar
Operating temperature : -54 oC to 120 oC
 
 
Carbon-Carbon Brake Discs
 
 

Carbon-Carbon Brake Discs have been designed and developed by DRDO especially for Tejas. These discs provide drag, absorb kinetic energy of the aircraft by converting it into heat and hold the aircraft stationary against engine thrust.
 

Salient Features
Heat sink loading : 1140 kJ/kg
Disc area loading : 2510 J/cm2
Area loading rate : 96 W/cm2
 

Cold Air Unit
 


Cold Air Unit (CAU) has been designed and developed by Lucknow Division of HAL for Tejas. Design optimisation of rotating elements and shaft has been done by use of 3-D modelling, dynamic and stress analysis software for reduction in weight with the safe margin for shaft critical speed and element’s resonance frequency as well as reduction in vibration and noise levels. Rotating assembly of CAU is dynamically balanced to G2.5 (ISO 1940) to incorporate reduction in unbalanced mass, reduction in vibration and noise levels, and reduction in loads on bearing.
 

Salient Features
Type :                                 Turbo compressor
Medium :                            Air
Speed :                               69000 rpm
Flow rate :                          34 kg/min
Turbine PR :                        9
Compressor PR :                1.8
Min. Turbine outlet temp :   - 30 oC
Weight :                              6.5 kg
 
 
Jet Fuel Starter
 
 

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 optimisation 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.

Salient Features
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