HAL Internship Report

 

INDUSTRIAL TRAINING REPORT AT HINDUSTAN AERONAUTICS LIMITED HELICOPTER DIVISION BANGALORE

SUBMITTED BY: PREM BALAJI CHINNADURAI (17BME1020)

 

 

I am very grateful and would like to appreciate all the people who helped me to complete my training as the knowledge I gained during this period was immense. I also offer a very special thanks to “HAL, HELICOPTER DIVISION” for giving me such a golden opportunity of grateful stay in its industry as a trainee. I would like to express my deepest sense of respect to Mr. Thirupathi. R, Senior Manager, ALH Flight Hangar and Mr. Athavan. N Manager, ALH Flight Hangar for all their constant support, guidance, encouragement and advice during the training I hope that I can build upon the experience and knowledge that I have gained and make some valuable contributions to the society in the coming future  Prem Balaji Chinnadurai Vellore Institute of Technology, Chennai 

 

 

DECLARATION I, Prem Balaji Chinnadurai, student of fifth semester, Bachelors of Technology in Mechanical Engineering, Vellore Institute of Institute of Technology, Chennai, declare that the Industrial Training Report is submitted in partial fulfilment for the award of Bachelors of Technology in Mechanical Engineering in Vellore Institute of Technology, Chennai during the academic year 2019-2020.

NAME: SIGNATURE:

 

 

CONTENTS 1.  INTRODUCTION

1

2.  STRUCTURE OF ALH

5

3.  POWER TRANSMISSION IN ALH

11

  4. ALH ROTOR SYSTEM 5.  VIBRATIONS IN ALH 6.  FLIGHT CONTROL SYSTEM IN ALH 7.  HYDRAULICS IN ALH 8.  ENGINE PRESENTATION 9.  ALH FUEL SYSTEM

 

17 21 24 27 29 31

 

INTRODUCTION Hindustan Aeronautics Limited (HAL) is an Indian state-owned aerospace and

defence company headquartered in Bangalore, India. It is governed under the management of the Indian Ministry of Defence. The government-owned corporation is primarily involved in the operations of the aerospace and is currently involved in the design, fabrication and assembly of aircraft, jet engines, helicopters and their spare parts. It has several facilities spread across India including Nasik, Korwa, Kanpur, Koraput, Lucknow, Bangalore, Hyderabad and Kasaragod. There are 7 seven divisions of HAL in Bangalore, viz. Aircraft Division Helicopter Division Maintenance, Repair and Overhaul (MRO) Division HAL Aerospace Division HAL Engine Division Industrial and Marine Gas Turbine Division HAL Foundry and Forge Division

I was posted in ALH Flight Hangar of HAL, HELICOPTER DIVISION, BANGALORE. The HAL, HELICOPTER DIVISION in Bangalore basically manufactures helicopters for both civil and military purposes. There is also a HELICOPTER MRO DIVISION in the complex, which takes care of the maintenance, repair and overhaul of the helicopters. Various helicopters are manufactured in this division such as CHEETAL CHEETAH CHETAK. These helicopters have their repair and overhaul at Barrackpore, West Bengal  

 

The main focus is on manufacturing of ADVANCED LIGHT HELICOPTERS(ALH), MARK III and MARK IV versions of ALH are in production. MARK III, also called as ALH DHRUV, has Mission Integrated System is supplied to the Indian Army, Airforce, Navy and Coast guard, while MARK IV, better known as ALH RUDRA, has Machine Integrated System as well as Weapon Integrated System is supplied to the Indian Army and Airforce. The HAL Dhruv is a utility helicopter developed and manufactured by India's Hindustan Aeronautics Limited (HAL). The development of the Dhruv was first announced in November 1984. The helicopter first flew in 1992; however, its development was prolonged due to multiple factors including the Indian Army's requirement for design changes, budget restrictions, and sanctions placed on India following the 1998 Pokhran-II nuclear tests. The Dhruv entered service in 2002. It is designed to meet the requirement of both military and civil operators, with military variants of the helicopter being developed for the Indian Armed Forces, Fo rces, while a variant for civilian/comm civilian/commercial ercial use has also been developed.

ALH DHRUV

 

 

The HAL Rudra, earlier known as Dhruv-WSI (Weapons Systems Integrated), is an attack variant designed for the Indian Army. It is to be armed with both anti-tank and anti-aircraft missiles, and a 20-mm turret-mounted cannon. The Dhruv-WSI is to be capable of conducting closed air support (CAS) and antisubmarine warfare (ASW) roles as well.[21] In addition to the Dhruv-WSI, HAL is also developing the Light Combat Helicopter (LCH) based on the Dhruv for the Indian Armed Forces. It is fitted with stub wings for carrying up to eight anti-armour missiles, four air-to-air missiles, missiles, or four pods loaded with either 70 mm or 68 mm rockets. The LCH will also have FLIR (Forward Looking Infrared), a CCD (Charge Coupled Device) camera, and a target acquisition a cquisition system with laser rangefinder and thermal vision.

ALH RUDRA

CHARACTERISTICS OF ALH MARK-III (DHRUV): Crew: Two pilots Capacity: 12 passengers (14 passengers in high density seating) Length: 15.87 m (52 ft 1 in) Width: 3.15 m (10 ft 4 in) Height: 4.98 m (16 ft 4 in)  

 

Gross weight: 4,445 kg (9,800 lb) Max take-off weight: 5,800 kg (12,787 lb) for Mk IV Fuel capacity: 1,055 kg (2,326 lb) Powerplant: 2 × HAL/Turbomeca Shakti turboshaft, 1,068 kW each Main rotor diameter: 13.2 m (43 ft 4 in) Main rotor area: 136.85 m2 (1, (1,473.0 473.0 sq. ft) Performance:

Never exceed speed: 295 km/h for Mk III Range: 590 km. Endurance: 3.5 hours Service ceiling: 6,100 m (20,000 ft) [16] Rate of climb: 10.33 m/s (2,033 ft/min)

 

 

STRUCTURE OF ALH

The ALH has the following structural assemblies:

RADOME: A radome is a structural, weatherproof enclosure that protects a radar antenna. The radome is constructed of material that minimally attenuates the electromagnetic signal transmitted or received by the antenna, effectively transparent to radio waves. Radomes protect the antenna from weather and conceal antenna electronic equipment from view. They also protect nearby personnel from being accidentally struck by quickly rotating antennas. ALH has a spherical radome.

 

 

COCKPIT ASSEMBLY: A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a pilot controls the aircraft. The cockpit of the ALH contains flight instruments on an instrument panel, and the controls that enable the pilot to fly the helicopter. In most airliners, a door separates the cockpit from the aircraft cabin. It is ergonomically designed to give all round visibility, ease of entry and exit from the crew, minimal reflections of illumi illuminations nations of reflected objects at night and accessibility controls. The cockpit is further divided into two parts – Outer shells and Inner frames. It is made of Kevlar and carbon prepregs with Nomex core. The windshield glass in the cockpit is 6mm, while the roof glasses and nose bottom glass are 2mm each. These glasses are made of Glass Reinforced Plastics. There are certain sealants coated to avoid water ingress. The pilot and co-pilot doors are hinged which is 7.113 kg each. There are electrical indicators present which indicates whether the doors are in open or closed position. The doors have two shells. The outer and inner shells are bonded using cold abrasives. The monolith is made of Kevlar prepregs. The bottom structure consists of machine floorboard for grin mounting. It is made of sheet metal in sandwiched position for attaching central controls and seat nails.

Cockpit assembly of ALH

 

 

CENTER FUSELAGE ASSEMBLY: It has the following sub-assembliesPrimary Assembly: It absorbs the load during flight and landing. It also

supports main power transmissions, engine landings, gears, aft structure and fuel tanks.

Shells: Consists of Cabin side shell, made of Aluminium face sheets and Nomex

core, which has sandwich construction. Inserts are provided for slide door attachments, fuel system and top cowlings. Transmission deck and Engine Deck Assembly: It supports the Main Gear Box

and Rotor System. It also isolates fuselage from vibrations caused by Main Gear Box and Rotor System. The Engine Deck Assembly carries engine and isolates other surrounding parts from the heat generated by the engine. Cabin roof assembly: Two slanting longitudinal beams running at the roof

structure of the helicopter between frames #3 and #4. They are connected through Aluminium alloy I structures. Bottom Structure beams and frames: Contour setup of fuselage is followed,

through top angles and webs. Stiffness holes are drilled for increase in stiffness and reduction in weight, covered by Kevlar and Carbon Composite with Flex core. Floor Boards: Aluminium face sheets and Aluminium core is2 floored between frames #3 and #6. It is designed to carry a load of 600 kg/m Fuel Bay: Prepared using foam and adhesives, so as to have smooth surface

bearing. The fuel tanks are fitted using Velcro-tapes. Centre Post: Provides roll over protection of crew. Accommodates control

rods, electronic and avionic looms. It is fitted with crash protection. Sliding door: Outer shell and inner frames of the doors are attached adhesives

by cold bonding. It is made of Kevlar prepregs and Nomex core. The Clamshell door is attached to frame #8 and #9, used to release the cargo during emergency period.  

 

Stretcher Assembly: Each assembly has two stretchers each. This assembly is

held by eight points in helicopter, between frame #4 and #5 Cargo Release Assembly: There are semi-automatic cargo release for carrying

loads in suspension beneath the helicopter. It secures the suspended load beneath the helicopter.

Fuselage Assembly

TAIL BOOM AND EMPENNAGE: Forward Tail Boom: Present between frame #9 and inclined frame #10. It has

two shells- top shell and bottom shell, which is of sandwich construction. The shells are made of Aluminium Aluminium face sheets and Aluminium flex core. The top and bottom shells are riveted. Empennage: It comprises of vertical fin, horizontal stabiliser and end plates. 





 

 

Vertical Fins: Consists of spar made of carbon prepregs. The intermediate and top ribs are made of monolithic sections. It has totally

seven ribs, two at Intermediate Gear Box, two at Tail Gear Box and one at the top made of aluminium alloy   Horizontal Stabilisers: Consists of shell, single spar, intermediate and end ribs. The shells are made of Kevlar prepregs, outer face sheets and Nomex core. The web is made of sandwich construction and Nomex core. It is attached by two forehand fitting spar.   End plates: Made up of Kevlar face sheets and Nomex core.

 

Tail Boom and Empennage

COWLINGS AND FAIRINGS: There are five cowlings:     

         

Control Cowling Equipment Cowling Engine Cowling Centre Cowling After Cowling

They are fixed through Camlock studs. Meant for covering the respective equipment from dust, water, etc. It also gives aerodynamic shape to the helicopter. Fairings: There are three fairing assemblies:   

 

  Tail drive shaft fairing assembly.   Intermediate Gear Box fairing assembly.   Tail Gearing Box fairing assembly.

 

Cowling assembly Emergency Floatation Gear:

There are four stowable floats. The four pressure vessels are charged with N2 at 4500 psig. It also has an electrical system for initiation of Pressure Vessels. Nitrogen is used in the pressure vessel because it is not advisable to store air containing O2 at high pressure (4500 psig) from fire safety point of view. The floats are present at forward skid cross tubes and rear slid cross tubes

Emergency Floating Gear  

 

POWER TRANSMISSION SYSTEM

ASSEMBLY OF A TRANSMISSION SYSTEM:   Main Gearbox   Auxiliary Gearbox   Intermediate Gearbox   Tail Gearbox

  Tail Drive Shaft

MAIN GEARBOX It has the following functions:   Transmission of power and reduction of rotational ro tational speed between

engine and rotor.   Transmission of reaction torque from main rotor to structure.   Provision of fixed anchoring of flight servo controls.   Drive hydraulic pumps, alternators, cooler fans, AC component units, etc.

 

 

The components involved are:   Main Bolt   Upper Hub plate   Lower Hub plate

  Stub shaft

  Lift rod   Titanium Centre Piece   Hydraulic Pump

  Alternator

  MGB housing   Freewheel housing

  Actuators

  Gear Input

The assembly of Main Gear Box consists of the following sub-assemblies.  

Collector Gear Subassembly

  Actuating Freewheel Subassembly   Oil Filter Subassembly   Accessory Housing Subassembly

Power Train of the Main Gear Box consists of two stage reduction system between engine and rotor shaft. The primary power train is made up of spiral bevel input stage followed by spiral bevel collector gear. It has the following advantages. 

 

  Low weight of the Main Gear Box, including accessory drives   Ease of arrangements of tail rotor power take-off and accessory drives.   Spiral bevel gears are used to redirect the shaft from the horizontal gas turbine engine to the vertical rotor.

Gears manufactured for aerospace applications use high quality materials and are manufactured to tight tolerances. Special manufacturing machine tools and computer numerically controlled coordinate measurement systems have enabled rotorcraft drive system manufacturers to produce extremely highquality gears during their normal production.

 

 

Gear alignment in Main Gear Box

Gear Parameters in MGB

 

 

AUXILIARY GEARBOX: It consists of spur gear drive train to increase the tail drive shaft speed from 4163 rpm to 15120 rpm. It runs the oil cooler fan and auxiliary hydraulic pump of retractable wheel version of ALH Components Involved:  

Pump bearing housing

  Transfer ring

  Oil Transfer tube

  Bearing Housing

  Transfer ring pump   Pressure Reduction Valve

The lubricating oil in the MGB gets heated to a temperature of around 1000 C, in order to reduce the temperature of oil, so that the lubricating capacity of the oil is intact, AGB is provided which is used to cool the MGB oil and re-circulate the cooled oil to the MGB. It is also used to drive various auxiliary equipment and to transmit power to IGB.

Auxiliary Gear Box

 

 

TAIL DRIVE SHAFT Tail drive shafts are used to transmit the motion from Auxiliary gearbox to Tail gearbox through Intermediate gearbox. Sliding spline connection is provided between the IGB and the TGB (i.e. Shaft between the IGB and TGB). This accommodates mounting tolerances and differential thermal expansion of tail rotor drive shaft and tail boom structure. There are six tail drive shafts of four different sizes. It is made of hollow Aluminium alloy with the tubing of Titanium Alloy fitted with rivets BECAUSE:    

       

Lighter weight solution with Aluminium Alloy tube segments. Better damage tolerances Avoid winding up of single long shafting Testing is easier when done one by one segments.

Tail Drive Shaft Between MGB and AGB Between AGB and Bearing I Between Bearing I and Bearing II Between Bearing II and Bearing III Between Bearing III and IGB Between IGB and TGB

Length in mm 783.1

Speed IN RPM 4163.41

1114.5

4163.41

1177.55

4163.41

1177.55

4163.41

1136.85

4163.41

1114.5

4033

Intermediate Gearbox: Intermediate gearbox is mounted on the tail boom at its intersection with the canted vertical fin. It has one stage of spiral bevel gearing which serves to redirect the driveline upward to the tail gearbox through a 125° angle. It has a small speed reduction (i.e. the speed reduction ratio is (4163/4033). The estimated dry weight of the IGB assembly is 15 kg. It involves splash type lubrication.  

 

Intermediate Gearbox  Tail Gearbox The main purpose of the Tail gearbox is to drive the tail rotor blade by receiving the power from the IGB by means of a tail drive shaft. The basic purpose of the tail rotor blade is to give a force in a direction opposite to the force generated by the main gear box by virtue of friction which tries to rotate the whole of the helicopter with it, such that the whole of the helicopter is in a stable position during the course of the flight. It also involves splash type lubrication.

TAIL GEARBOX  

 

ALH ROTOR SYSTEM It is the most complex system of the helicopter. Agility, human comfort, structural integrity, performance and community acceptance depends on an efficient rotor system. The main rotor blades of ALH uses flexible fibre reinforced plastics (composites), which eliminates eliminates the need of hinges, hence the main rotor blade is hinge less. The pitch change bearing is replaced by elastomeric bearing, thereby removing the need of lubrication. Hinge Less Main Rotor & Bearing Less Tail Rotor

The technological advancement in material science especially composites, has led to the elimination of physical hinges in the rotor system. The main rotor blades of Dhruv (ALH -Advanced Light Helicopter), uses the flexibility of fibre reinforced composites in order to eliminate the need for hinges. The flap and lead-lag articulations are provided by the flexing of the soft neck area of the rotor blades. This type rotor without mechanical hinges is called Hinge less Rotor. The pitch change bearings have been replaced by elastomeric bearings which do not need any lubrication. In tail rotor of Dhruv, all the three articulations (flap, lead-lag and pitch) are obtained through flexing and twisting of flex beam. Such rotors are called Bearing less Rotors.

HINGE LESS MAIN ROTOR

 

 

Specifications of main rotor: -

Rotor type: - Hinge less, Fibre-elastomeric Number of blades: - 4 (composite material) Rotor speed: -314 rpm. Direction of rotation: - Clockwise (as seen from top) Rotor diameter: - 13.2 m (43.3 feet) Blade plan form: - Rectangular with Parabolic tip. Blade chord: - 0.5 m up to 0.9242R, 0.167 m at the tip Aerofoil: - DMH 4 up to 0.8R (STA 5280) DMH3 from 0.9242R (STA 6100) to 1R (STA 6600) Advantages of main rotor system: -

1. Reduced number of parts 2. Ease of maintenance (No greasing points) 3. High Fatigue life for rotor hub and blades. 4. Fast control response suitable for superior nap of earth flying and manoeuvres. Special features of main rotor: -

1. Glass and carbon composite rotor blades. 2. Carbon composite rotor hub. 3. Upper controls located inside the main gearbox and stub shaft. 4. Rotor blade attachment to the hub through radial and conical bearings. Materials used for the manufacture of main rotor blade: -

1. Carbon fibres 2. Glass fibres 3. Copper mesh 4. Epoxy resin  

 

5. Foam for the core 6. Lead mass 7. Stainless steel tube for trim chamber 8. Stainless steel sheet and nickel shield for erosion protection 9. Teflon film at the spoon 10.Paint (polyurethane based) INTEGRATED DYNAMIC SYSTEM:

Integrated Dynamic System (IDS) is the advanced adv anced system in ALH, which combines several key rotor control functions into a single module carrying the engine power to the rotors.

Integrated Dynamic System in ALH

 

 

Main Rotor Hub:  It has the following components: Hub plates: Two plates made of Carbon composite. It is light in weight, can handle high load capacity and takes care of stiffness Titanium centre Piece: They house the radial elastomeric bearings subjected to lead lag and flapping load from the blades. Radial Elastomeric Bearings: Concentric Cylindrical metallic shims separated by elastomers and are bounded to housings. It also provides the feathering axis. It is maintenance free as there is no lubrication required. Main Bolt: Titanium bolts are attached so that the rotor blades are mated to the hub plates through the conical bearing. Anti-rotation pin: Prevents rotation of the conical bearing about axis of main bolt Bearing stop: Prevents linear motion of the radial bearings. Bracket and Scissor: It is attached to the lower hub plate through a pair of rotating scissors. Stub shaft: Thin-walled Titanium alloy fitted which supports rotor head and houses the upper control. Swash-plate mast: Mounted on the Main Gearbox with axis coincident on the rotor axis. It provides vertical axis for sliding motion of swash plate mechanism. Swash plate moves up and down depending on input given by collective. Swash plate: A swashplate is a device that translates input via the helicopter flight controls into motion of the main rotor blades. Because the main rotor blades are spinning, the swashplate is used to transmit three of the pilot's commands from the non-rotating fuselage to the rotating rotor hub and main blades.

 

 

Swash Plate

VIBRATIONS IN ALH Causes of Vibration:

1.  Mass Imbalance: When centre of rotation does not fall on centre of gravity. Maybe due to:    

         

Manufacturing defect

           

Compression

Installation error Propeller Damage Corrosion

Maintenance/Paint/Repair 2.  Aerodynamic Imbalance: Due to misshape in Blades 3.  When complication such as: 

      

 

Spark Fuel flow Worn Wearing Intake and Exhaust Variances Gear box

  Aerodynamic interactions occur

 

Effects    

       

Bearing wear Sliding wear Cowling cracks Exhaust cracks

VIBRATION DAMPERS PRESENT IN ALH: Anti-Resonance Vibration Isolation System (ARIS)

The Anti-Resonance Isolation System (ARIS) is a six-degree of freedom vibration isolation system. ARIS isolates the fuselage from the rotor-induced ro tor-induced vibrations. Four units of ARIS are installed between the main gearbox (MGB) and fuselage. It is placed at ± 45°position to the fuselage centreline. This results in each unit being subjected to reaction forces generated by main rotor forces. An ARIS unit consists of a spring mass system and it transmits low frequency loads due to flight conditions and absorbs high frequency loads due to vibration caused by rotation of the main rotor. The ARIS units, each of 2 degree of freedom, which are interposed between rotor and fuselage system, isolate vibratory loads pertaining to 3 forces and 3 moments arising from the rotor and hence ARIS is effective in all 6 degree of freedom. Function and capabilities of ARIS:

1. It reduces the transmissibility of 4/rev contents of all rotor hub forces and moments from the rotor/gearbox unit to the fuselage. 2. In case of the total failure of the spring of ARIS the system ensures transfer of static loads to the fuselage. 3. It is functional in manoeuvres at typical load factors. 4. It significantly reduces the vibration in the continuous power-on at an rpm range of 98-102%, Where 100% is 32.88 rad / sec.

 

 

Components of ARIS: -

The hardware of ARIS, mainly consists of casing ring, support tube, R glass spring, composite diaphragm, composite pendulum and the elastomeric bearings.

Active Vibration Control System (AVCS)

Dhruv (ALH) helicopter incorporates a highly advanced hinge less main rotor. This rotor configuration induces high dynamic loads on the airframe, particularly at the blade passing frequency 4/rev (21 Hz), which is equal to the number of blades 4 multiplied by the rotor speed of 314 rpm. The 4/rev main rotor vibration is a cause of discomfort for passengers and crew, reduces fatigue life, cause damage to on-board sensitive equipment and increase maintenance cost. The AVCS along with ARIS will enhance the crew and passenger comfort and attenuate the 4/rev main rotor vibration to acceptable levels.

 

 

VIBRATION MONTORING SYSTEM: It consists of MSPU (Modern Signal Processing Unit) and accelerometers at Main Gearbox and Tail Gearbox for 1/rev and separate accelerometer at Main Gearbox. This accelerometer works on the principle of Piezo-Electric effect. The vibrational output is provided to the MSPU, which process the data and provide warning signals to DMC (Display and Mission Computer). The DMC provides the warnings to the pilot if any vibrations are beyond the critical limit. The MSPU also stores the data of the values of vibration of 1W and 4W, which can also be downloaded on a diagnostic laptop for processing and analysis. The software in the diagnostic laptop provides the required solution such as mass correction and tracking link correction to lower the vibrations with required values.

Vibrations are measured in the units of ips (inches per second) or G-force(m/s). The vibration is measured by accelerometer in terms of acceleration, which is plotted in a graph by the computer against time in the X-axis and ips in Y-axis. The peak value of vibration is taken for correction.

 

 

FLIGHT CONTROL SYSTEM IN ALH An AUTOMATIC FLIGHT CONTROL SYSTEM (AFCS) is a system which augments the stability, improves handling and provides automatic flying thus relieving the pilot’s workload and also freeing him for other mission related activity by providing auto pilot functions such as velocity, hold, altitude hold, heading hold etc. Control system comprises of: 1. Collective control (using collective stick): for controlling the movement of

helicopter in up and down motion. (PITCH MOTION) 2. Cyclic longitudinal control (using cyclic stick): for controlling the movement

of helicopter in forward and backward direction. (ROLL MOTION) 3. Cyclic lateral control (using cyclic stick): for controlling the movement of helicopter in lateral direction 4. Directional controls or Tail Rotor Control (using rudder pedals): for turning

of the helicopter in left and right direction. (YAW MOTION) 5. Control rod Vibration Isolation System 6. Force Feel and Trim System (FFS) 7. Push Pull rods and Bell cranks

Need for AFCS:   Achieve adequate stability. (Stability augmentation)

  Achieve required level of controllability and manoeuvrability. (Control

augmentation)   Provide good gust response.   Provide auto pilot modes.

  Reduce pilot workload

 

 

 

 

Cyclic blade control Cyclic controls are used to change a helicopter's roll and pitch. Push rods or hydraulic actuators tilt the outer swashplate in response to the pilot's commands. The swashplate moves in the intuitively expected direction, tilting forwards to respond to a forward input, for instance. However, "pitch links" on the blades transmit the pitch information way ahead of the blade's actual position, giving the blades time to "fly up" or "fly down" to reach the desired position. That is, to tilt the helicopter forward, the difference of lift around the blades should be maximum along the left-right plane, creating a torque that, due to the gyroscopic effect, will tilt the rotor disc forward and not sideways.

Collective blade control

To control the collective pitch of the main rotor blades, the entire swashplate must be moved up or down along its axis without changing the orientation of the cyclic controls. Conventionally, the entire swashplate is moved along the main shaft by a separate actuator. However, some newer model helicopters remove this mechanically complex separation of functionalities by using three interdependent actuators that can each move the entire swashplate. This is called cyclic/collective pitch mixing.

 

 

HYDRAULICS IN ALH Hydraulic fluid power is widely used in airborne applications specifically to operate the flight controls and landing-gear systems due to its compact size, high response rates, high load holding capabilities and excellent power to weight ratio. Modern helicopters are no exceptions in this regard due to the adaptation of advanced rotor systems calling for higher control loads, fast response requirements and use of retractable landing gear systems. There are three hydraulic systems involved in the helicopter, in which two are involved in flight control system, and one is used for utility services like landing gear, wheel brake, rescue hoist, harpoon and small winch.

SELECTION OF HYDRAULIC FLUIDS: Suitable hydraulic fluid is selected considering functional requirements, operating andfor limitations. Careful consideration hasenvironment to be imparted fooperating r the fluidtemperature properties like viscosity, pour point, lubrication ability, oxidation resistance, rust & corrosion protection etc. Mil-H-5606 is a mineral based hydraulic fluid which is very much suitable for hydraulic systems working under operating temperature range -40 to +107°C with a maximum temperature temperature range of -54 to +135°C.

Each hydraulic system has three modules:   HYDRAULIC PUMP

  HYDRAULIC PACKAGE   HYDRAULIC ACTUATOR

HYDRAULIC PUMP:

The most popular hydraulic pumps in the aerospace applications are the variable delivery axial piston pumps due to their simple construction, smaller size and low weight against a defined hydraulic power output. The power drain is absolutely minimum in these pumps due to the existence of automatic outlet pressure compensator as a part of this pump. These pumps have minimum  

 

internal fluid leakage and collected back to the reservoir through pump case drain.

HYDRAULIC PACKAGE:

In conventional helicopters, like Cheetah and Chetak, the reservoir unit and control valves were separate leading to more maintenance. To avoid this, in modern helicopters like ALH all control valves and reservoirs are clubbed into single units called as hydraulic package. It is also called as bootstrap reservoir incorporating all the control valves. There are two hydraulic packages used in ALH 1.  To control the main rotor and the tail rotor 2.  To operate accessories such as landing gear, harpoon system, wheel brake system of ALH ALH uses 2.75l hydraulic packages

HYDRAULIC ACTUATORS:

Duplex type of hydraulic servo actuators is used in ALH during the main and tail rotor controls. All the main rotor actuators in ALH for control channels collective, pitch, roll is identical in design except for actuator stroke. The weight of each main rotor is 8.75 kg. All the three main rotor actuators are installed on MGB of ALH with hydraulic interface through specially designed hydraulic manifold. Other Hydraulic Equipments: High pressure relief valve is used as a safety equipment to off-load fluid from

high pressure line to reservoir in case of increase in the fluid pressure beyond 125% of nominal system operating pressure. Check Valve is used to avoid control the fluid flow in a defined direction. For example, if no check valve is provided in the pump pressure line, the pump

may function as a motor during the system interface with ground hydraulic power source during system checks.

 

 

Solenoid Valve can be used in each of the subsystem in multi-system

configuration to isolate defined sub-system. Reservoir Low Fluid Indicator, is a part of reservoir to indicate low fluid level

when falls below a predetermined volume. Pressure Transducer is used to continuously measure the system pressure and

indicate the same in the cockpit. Pressure Switch is used to provide a low-pressure warning in the cockpit when

the system pressure drops below a defined level. Temperature Switch can be used to check the temperature of fluid returning

to reservoir & provide a high temperature warning in the cockpit when the fluid temperature goes above a defined level. Quick Disconnect Couplings are used in places where fluid connections are

disturbed frequently and to isolate certain sub-systems. This will avoid air ingress to the system during servicing and eliminates use of any tools for connection

 

 

ENGINE PRESENTATION The engines used in ALH are twin-spool Shakti Engine, which is of 1065 KW class. It is of free turbine type. Main Gearbox is connected to free turbine at the cold end. Power is taken from the free turbine shaft. It has a two-stage centrifugal compressor . There is no mechanical connection between the gas generator turbine and power turbine. Shakti Engine consists of the following systems.   FUEL SYSTEM: Supplies fuel into combustion chamber under all

operating conditions. Engine fuel system is divided into: 1.  Low Pressure fuel system 2.  High Pressure fuel system 3.  Fuel injection system 4.  Inlet Guide Vane actuating system.   OIL SYSTEM: Lubricates and cools the mating and rubbing parts and measures engine torque. This system is fully integrated with engine. Operation of oil is divided into three parts: 1.  Supply system 2.  Scavenge system 3.  Breathing system There are many devices such as electro-magnetic detector, pressure and temperature indicator to monitor the oil system.   STARTING AND IGNITION SYSTEM: Starter generator starts the engine

with 24V DC external source. After self-sustaining speed, the starter acts as a generator. Used for 1.  Cranking 2.  Fuel Supply 3.  Ignition 4.  Air purging   INDICATING SYSTEM: These are the engine instruments located at the instrument panel. Both pilot and co-pilot can monitor the system. Instruments that are provided are: 1.  Gas Generator Turbine speed 2.  Power turbine speed 3.  Turbine gas generator 4.  Engine torque  

 

5.  Engine oil pressure 6.  Engine oil temperature 7.  Engine limit indicator 8.  Fuel flow display unit   ELECTRICAL SYSTEM: There are three electrical systems involved: 1.  From engine to FADEC and accessories 2.  From cockpit to FADEC and FADEC to cockpit 3.  From engine to cockpit and cockpit to engine.   CONTROL SYSTEM: Regulates fuel consumed to the engine based different load requirement and conditions. The control systems involved are: 1.  Fully Authorised Digital Electronic Control (FADEC) 2.  Engine Electronic Control Unit.

SHAKTI ENGINE

General characteristics:

Type: Turboshaft Length: 1,250 mm (49 inches) Dry weight: 205 kg (452 lb) Components:

Compressor: Two centrifugal compressor stages, coupled to a single-stage high-pressure turbine, reverse annular flow combustion chamber, Gas generator and Power turbines.  

 

ALH FUEL SYSTEM It ensures continuous supply of fuel to both the engines while the flight is in operation mode. The fuel tanks are made of hycalite material as they are light in weight and fully flexible. The fuel tanks are mounted in the cabin. Different tanks present in ALH and their capacities: 1.  2. 3. 4. 5. 6.

 

Front Main Tank Middle Main Tank Supply Tank I Supply Tank II Rear Main Tank Auxiliary Tank (additional)

525 litres 252 litres 102 litres 102 litres 160 litres Either 200 or 500 litres

 

OBJECTIVES OF TRAINING This full training was oriented towards a big positive on the exposure to the works carried out in an aviation industry and hence learnt a good deal from them. It was a major step towards the practical things going outside our syllabus, which was like a really different world and the environment we usually get in our college under the umbrella of our university syllabus. The base aim of the training was to know about how and in how many stages a helicopter blade is manufactured. It was also towards the learning of how complicated a helicopter’s working mechanism can be and what are the ways our engineers have found to bring it of simplest mechani mechanism, sm, better safety and more efficiency. The advancement in helicopter since it was first built in any Indian industry to presently an armed ALH has been a great gr eat example of advancement and of premier example set upon for me and all the upcoming engineers in future.

 

 

METHODOLOGY My training consisted of three sessions; In first session I did attain an industrial environment where I observed the process and procedure going on in the industry about how machines are used and how to use the the instruments w with ith comprehensive e explanations. xplanations. In this I observed the working of all the staff and how they operated the machines taking all the possible precautions. In second session we were given a manual about the instruments which included all the details about the parts to be manufactured and how to use all these instruments under the guidance of my seniors in industry. In the last session, I observed all the product produced on day and observed the final assembly obtained from that whole day.

 

 

BENEFIT OF THE TRAINING As the training was fully concentrated towards our approach in any industry, I hope this would help me solve real-life problems in the field of engineering. This training will work up as a boost for me in future, when I step up in the shoes of an engineer in coming years. This training will also be helpful to me in future at the time of my project along with all the theoretical knowledge I gain in my college, as now I can be more confident with my approach towards the machining, stressing, stretching stretching and other processes going on any of the materials I have worked on in my short stay with the industry. This short stay at HAL HELICOPTER DIVISION was of uttermost utility at the time when I will be supposed to put my visual experience along with my imagination, as said: “Invention is the place where poetry and engineering come together”.

 

 

BIBLIOGRAPHY www.safran-helicopter-engines.com HAL/Turbomeca hal-india.co.in Helicopter Hydraulics www.danubewings.co hydraulic pump in helicopter - Google Search HAL Rudra - Wikipedia intermediate gearbox OF Helicopter - Google Search swash plate - Google Search www.google.com