31oct

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CHAPTER 1
AIRCRAFT STRUCTURE
1. INTRODUCTION -Fundamentals of aircraft design
The major structural component of a conventional aircraft includes the fuselage, wings,
empennage, control surfaces & landing gear. The empennage comprises of tail plane & fin. The
control surface comprises of ailerons, flaps, elevators & rudder.
The fuselage is main body mounting the operating crew, passengers, payloads & most of
aircraft system. The wings & empennage are attached to the fuselage. The ailerons & flaps are
attached to the wings. The elevators are attached to the tail plane & the rudder is attached to the
fin. The landing gear & power plant are accommodated in the wings & the fuselage depending
on the configuration. The wings provide the lift. The control surfaces are the means to control
the movement of aircraft in flight about the longitudinal and vertical axis. The landing gear
supports the aircraft on the ground. The power plant provides the thrust.
Aircraft are vehicles which are able to fly by being supported by the air, or in general, the
atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by
using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.
Rocket planes and cruise missiles are considered aircraft because they rely on lift from the air.
Another type of aircraft is the space-plane which is an aircraft designed to fly up to extreme
altitudes into space and land as a conventional aircraft.
1.1. FORCES ACTING ON AIRCRAFT
The miracle of flight exists because man has the technology to oppose natural forces that keep all
objects on the ground. Four forces affect an aircraft — two assist flight (thrust and lift), and two
resist flight (weight and drag). The important thing to note here is that when an aircraft is flying
straight and level, all four of these forces are balanced, or in equilibrium.
Fig 1.1 forces on aircraft
Thrust is created by the engines. As propeller blades push air through the engine (or as jet fuel is
combusted to accomplish the same end), the aircraft moves forward. As the wings cut through
the air in front of the aircraft, lift is created. This is the force that pushes an aircraft up into the
air.

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Principle of lift: principle of lift is based on The Bernoulli Effect .This creates a difference in
air pressure above and below. The pressure pushing up is greater than the downward pressure,
and lift is created. If you're banking, lift occurs in a slightly sideways direction. If you're
inverted, lift actually pulls you downward toward the ground. Note that lift occurs perpendicular
to a line drawn parallel to the centreline of the wing and occurs at a slightly backward angle.
Several factors determine how much lift is created. First, consider the angle at which the wing
hits the air. This is called the angle of attack, which is independent of the aircraft's flight path
vector. The steeper this angle, the more lift occurs. At angles steeper than 30° or so, however,
airflow is disrupted, and an aircraft stall occurs. During a stall, no lift is created. The aircraft falls
into a dive and can recover lift only after gaining air speed.
Fig 1.2 Diagram of lift
 If V1<V2 and P1>P2
 A resultant upward force called lift will equal to Pnet =P1-P2
Drag opposes thrust. Although it mainly occurs because of air resistance as air flows around the
wing, several different types of drag exist. Drag is mainly created by simple skin friction as air
molecules "stick" to the wing's surface. Smoother surfaces incur less drag, while bulky structures
create additional drag.
Weight is actually a force of acceleration on an object. The Earth exerts this natural force on all
objects. Being a constant force, it always acts in the same direction: downward. Thrust creates
lift to counteract gravity. In order for an aircraft to take off, enough lift must be created to
overcome the force of gravity pushing down on the aircraft. Related to gravity are G-forces—
artificially created forces that are measured in unit’s equivalent to the force of gravity.
1.2. AIRCRAFT FORWARD PRINCIPLE OF FLIGHT
When aircraft is at rest, its weight is supported by landing gear. As the engine are opened
up to full power, the aircraft starts to move forward on its wheel due to the ‘thrust’ created by the
reaction on the aircraft forced rearwards by propeller rotation. As the aircraft moves forward, the
various part of the aircraft offer resistance to the forward motion called ‘drag’. The drag is zero
at the commencement of the takeoff & builds up in proportion to the square of the forward
speed. The wings are specially shaped with an aero foil section. There is an area of low pressure
above the wings & area of high pressure below the wings. The net effect causes a vertical

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component called ‘lift’. Lift increases by increasing angle of attack and a stage is soon reached
when lift force is greater than the weight of the aircraft.
1.3. PARTS OF AN AIRCRAFT
The basic schematic of a traditional aircraft is as follows:
Figure 1.3 Parts of an aircraft
1.3.1. BASIC COMPONENTS
Fuselage: The fuselage is that portion of the aircraft that usually contains the crew and payload,
either passenger, cargo, or weapons. Most fuselages are long, cylindrical tubes or sometimes
rectangular box shapes. All of the other major components of the aircraft are attached to the
fuselage. Empennage is another term sometimes used to refer to the aft portion of the fuselage
plus the horizontal and vertical tails.
Tricycle under-carriage: The total load of the plane when standing on the ground is carried on
three wheels, two of which are provided in the fuselage or in the wings at the junction of wings
and fuselage, the third one is provided at the tail end of fuselage, thereby the nose of the plane is
pointing upward and the wings are at the greater angle of incidence.
Wings: The wing is the most important part of an aircraft since it produces the lift that allows a
plane to fly. The wing is made up of two halves, left and right, when viewed from behind. These
halves are connected to each other by means of the fuselage. A wing produces lift because of its
special shape, a shape called an air foil.
Engine: The other key component that makes an airplane go is its engine, or engines. Aircraft
use several different kinds of engines, but they can all be classified in two major categories.
Early aircraft from the Wright Flyer until World War II used propeller-driven piston engines,
and these are still common today on light general aviation planes. But most modern aircraft now
use some form of a jet engine. Many aircraft house the engine(s) within the fuselage itself.
Larger plane have their engines mounted in separate pods hanging below the wing or sometimes
attached to the fuselage. These pods are called nacelles.
The power developed in the engine is utilise to rotate the propeller in turn gives thrust to the
forward moving plane various types of engines are:
Gasoline Fed
Jet Propulsion
Turbo Jet Engine

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1.4. BASIC CONTROL SURFACES
In addition to the wing and tail surfaces, aircraft need some additional components that
give the pilot the ability to control the direction of the plane.
Different surfaces of air-craft: All control surfaces utilize the principle of lift, but they apply
lift forces in different directions. These forces act either independently or in conjunction with
one another to produce various maneuvers. Each manoeuvre is the net resultant force of all
individual forces. (A resultant force is the average force that results when two forces are
combined. For example, a pure vertical force and a pure horizontal force create an angled force.)
Fig 1.4 surfaces of aircraft
Elevator: The elevator is located on the horizontal stabilizer. It can be deflected up or down to
produce a change in the down force produced by the horizontal tail. The angle of deflection is
considered positive when the trailing edge of the elevator is deflected upward. Such a deflection
increases the down force produced by the horizontal tail causing the nose to pitch upward.
Rudder: Rudder is provided at the tail end of the fuselage. The function of a rudder is the same
as of the one provided in a boat i.e. to change the direction of the boat towards the left or right of
sailing direction. It is flap which is hinged to the vertical fin provided at the tail end of the
fuselage.
Aileron: Ailerons are so arranged that is the aileron on one side is raised up; the other aileron on
other side will go down. If the aileron is pulled down, it will increase the lift under the wing but
when pulled up, it reduces the lift on the part of the wing.
1.5. ADDITIONAL COMPONENT
Fig 1.5 Additional component of aircraft

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FLAP: Flaps are usually located along the trailing edge of both the left and right wing, typically
inboard of the ailerons and close to the fuselage. Flaps are similar to ailerons in that they affect
the amount of lift created by the wings. However, flaps only deflect downward to increase the
lift produced by both wings simultaneously. Flaps are most often used during takeoff and landing
to increase the lift the wings generate at a given speed. This effect allows a plane to takeoff or
land at a slower speed than would possible without the flaps. In addition to flaps on the trailing
edge of a wing, a second major category is flaps on the leading edge. These leading-edge flaps,
more often called slats, are also used to increase lift.
CABIN & COCKPIT: Sometimes these two terms are used synonymously, but most of the time
the term cockpit is applied to a compartment at the front of the fuselage where the pilots and
flight crew sit. This compartment contains the control yolks (or sticks) and equipment the crew
use to send commands to the control surfaces and engines as well as to monitor the operation of
the vehicle. Meanwhile, a cabin is typically a compartment within the fuselage where passengers
are seated.
NOSE & MAIN GEAR: The landing gear is used during takeoff, landing, and to taxi on the
ground. Most planes today use what is called a tricycle landing gear arrangement. This system
has two large main gear units located near the middle of the plane and a single smaller nose gear
unit near the nose of the aircraft.
PROPELLER
It consists of two or more blades which are provided on the nose of plane or the wings of the
aircraft.
1.6. MOVEMENT OF AIRCRAFT
Corresponding to these three axes there are three basic movement in aircraft known as pitching
rolling and yawing movement.
Rolling motion: The motion of aircraft about fuselage datum line i.e. x-axis is called rolling
motion.
Pitching motion: The motion of aircraft about y-axis is called pitching motion.
Yawning motion: The motion of aircraft about z-axis is called yawning motion.
Fig 1.6 Basic Movements in Aircraft

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Pitching motion: Pitch is the up and down movement of the aircraft's nose around an axis line
drawn from wingtip to wingtip. When you apply pitch by pulling back on the stick, you angle the
aircraft's elevators up, causing the nose to rise.
Yawing motion: Yaw is the side-to-side rotation of the aircraft's nose around a vertical axis
through the centre of the aircraft. It changes the direction of horizontal flight, but does not affect
altitude. You use the rudder to angle the aircraft's rudder left or right, which creates yaw.
Rolling motion: Roll is the tipping of the wings up or down. The aircraft maintains its current
direction of flight, but the wings spin around an imaginary line drawn from the nose through the
tail. Roll occurs when you push the stick left or right, causing one aileron to angle down and the
other to angle up. These increases lift under one wingtip while decreasing lift under the other,
creating roll.
Fig 1.8 rolling motion in aircraft
1.7. TYPES OF AIRCRAFT
The general aircrafts are divided into two types.
Lighter than air: - It also known as aerostat includes airships, balloons etc. Aerostats use
buoyancy to float in the air in much the same way that ships float on the water. They are
characterized by one or more large gasbags or canopies, filled with a relatively low density gas
such as helium, hydrogen or hot air, which is less dense than the surrounding air. When the
Fig 1.7 Yawing motion in aircraft

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weight of this is added to the weight of the aircraft structure, it adds up to the same weight as the
air that the craft displaces e.g. Balloons & air chips.
Heavier than air: Heavier-than-air aircraft must find some way to push air or gas downwards,
so that a reaction occurs (by Newton's laws of motion) to push the aircraft upwards. This
dynamic movement through the air is the origin of the term aerodyne. There are two ways to
produce dynamic up-thrust: aerodynamic lift, and powered lift in the form of engine thrust.
Aerodynamic lift involving wings is the most common, with fixed-wing aircraft being kept in the
air by the forward movement of wings, and rotorcraft by spinning wing-shaped rotors sometimes
called rotary wings. A wing is a flat, horizontal surface, usually shaped in cross-section as an
aerofoil. To fly, air must flow over the wing and generate lift. A flexible wing is a wing made of
fabric or thin sheet material, often stretched over a rigid frame e.g. Glider, helicopter and
aeroplanes they can be also divided into three groups with different event consideration that are
as following.
LAND PLANES (which take off from and can land on ground).
SEA PLANES (which can takeoff from and can land on sea).
AMPHIBIANS (which can take off from and can land on ground and sea both).
ON THE BASIS OF WINGS:-
Mono- planes (one wing on each side).
Biplane (two wings on each side).
ON THE OF NUMBER OF ENGINES
Single engines
Multiple engines
ON THE BASIS OF TYPE OF ENGINE
Propeller driver
Jet planes
ON THE BASIS OF SPEED
Sonic
Sub-sonic
Super-sonic

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CHAPTER 2
COMPANY PROFILE
2.1. INTRODUCTION OF HAL
Figure 2.1 Company logo and owner of HAL
TRANSPORT AIRCRAFT DIVISIONS OF HINDUSTAN AERONAUTICS LIMITED
2.1.1. HISTORY:
The history and growth of the Hindustan Aeronautics Limited is synonymous with
the growth of Aeronautical industry in India over the past 70 years. The Company which had
its origin as the Hindustan Aircraft Company was incorporated on 23 Dec 1940 at Bangalore
by Shri Walchand Hirachand a farsighted visionary in association with the Government of
Mysore with an Authorized Capital of Rs.4 carores (Paid up capital Rs.40 lakh) and with the
aim of manufacturing aircraft in India. In March 1941, the Government of India became one
of the shareholders in the Company holding 1/3 of its paid-up capital and subsequently took
over its management in 1942. In collaboration with the Inter Continental Aircraft Company
of USA, Hindustan Aircraft Company commenced its business of manufacturing of Harlow
Trainer, Curtiss Hawk Fighter and Vultee Bomber Aircraft.
In Dec 1945, the company was placed under the administrative control of Min. of
Industry & Supply. In January 1951, Hindustan Aircraft Private Limited was placed under the
Administrative control of Ministry of Defence. The Company had built aircraft and engines
of foreign design under licence, such as Prentice, Vampire and Gnat aircraft. It also
undertook the design and development of aircraft indigenously. In August 1951, the HT-2
Trainer aircraft, designed and produced by the company under the able leadership of Dr.
V.M. Ghatge flew for the first time. Nearly 200 Trainers were manufactured and supplied to
the Indian Air Force and other customers. With the gradual building up of its design
capability, the company successfully designed and developed four other aircraft i.e. two

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seater 'Pushpak' suitable for flying clubs, 'Krishak' for Air Observatory Post(AOP) role, HF-
24 Jet Fighter '(Marut)' and the HJT-16 Basic Jet Trainer '(Kiran)'.
Meanwhile, in August 1963, Aeronautics India Limited (AIL) was incorporated as a
Company wholly owned by the Government of India to undertake the manufacture
of the MiG-21 aircraft under licence. In June 1964, the Aircraft Manufacturing Depot
which was set up in 1960 as an Air Force unit to produce the Airframe for the HS-748
transport aircraft was transferred to AIL. Soon thereafter, the Government decided to
amalgamate Hindustan Aircraft Limited, with AIL so as to conserve resources in the field of
aviation where the technical talent in the country was limited and to enable the activities of
all the aircraft manufacturing units to be planned and co-ordinated in the most efficient and
economical manner. Amalgamation of the two companies i.e. Hindustan Aircraft Limited and
Aeronautics India Limited was brought about on 1st Oct 1964 by an Amalgamation order
issued by the Government of India and the Company after the amalgamation was named as
"Hindustan Aeronautics Limited (HAL)" with its principal business being design,
development, manufacture, repair and overhaul of aircraft, helicopter, engines and related
systems like avionics, instruments and accessories.
2.1.2. HAL TODAY:
HAL is a fully owned Government of India undertaking under the administrative
control of Ministry of Defence, Department of Defence Production. The Authorized Capital
of HAL is Rs.600 Carore consisting of 600000000 equity shares having face value of Rs.10
each. The current programs under progress at HAL are production of SU-30 MKI, Hawk-
AJT, Light Combat Aircraft (LCA), DO-228 Aircraft, Dhruv-ALH and Cheetal Helicopters,
Repair Overhaul of Jaguar, Kiran MKI/IA/II, Mirage, HS-748, AN-32, MIG 21, Su-30MKI,
DO-228 aircraft and ALH, Cheetah / Chetak helicopters.
The Company takes up maintenance and overhaul services to cover the life cycle
requirement of all the old and new products. Presently, 13 types of aircraft/ helicopters and
17 types of engines are being overhauled. In addition, facilities exist for repair/ overhaul of
various accessories and avionics Sifted on aircraft of Russian, Western and Indigenous
designs.HAL is currently meeting the requirements of structures for aerospace launch
vehicles and satellites of ISRO through its dedicated Aerospace Division. Infrastructure has
also been set up to undertake completed assembly of the strap-on L-40 stage booster.
Structures for GSLVMk.III have been productionised. HAL has also contributed to Mars
HAL Today
•Navratna Company
•36th among Global Aerospace Companies
•20 Production Division
•10 R& D Centers
•33,000 employes
•ISO-9001,AS-9100,NADCAP

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mission by supplying riveted structural assemblies and welded propellant tankages for the
Polar Satellite Launch Vehicle (PSLV-C25).Industrial and Marine Gas Turbine: The LM-
2500 marine gas turbine engine, a 20 MW aero derivative, is being produced and overhauled
from the production line in the Industrial and Marine Gas Turbine Division, Bangalore.
The Division also undertakes Repair and overhaul of Industrial Avon and Allison
engines. The Company has an impressive product track record. 15 types of
aircrafts/Helicopters manufactured with in-house R & D and 14 types produced under
license. HAL has manufactured over 3646 Aircrafts/Helicopters, 4096 engines and
overhauled over 9447 aircraft and 29886 engines. HAL has been successful in numerous R &
D programs developed for both Defence and Civil Aviation sector.
2.2. DIVISIONS OF HAL
HAL has 20 divisions and 10 R&D centres. These 20 divisions are divided into 4 complexes.
Fig: 2.2. DIVISIONS OF HAL
2.2.1. BANGLORE COMPLEX
 AIRCRAFT DIVISION
Aircraft Division was established in the year 1940. Since inception, the Division has
manufactured a variety of Aircraft both under licence as well as indigenously designed and
developed. The division also exports high sub-assemblies to renewed aircraft manufactures
like – AIR BUS, BOEING FOKKER and DORNIER.
 ENGINE DIVISION
Engine division is presently engaged in manufacture of Adour MK 871, Adour MK 811,
Garrett TPE 331-5, and Artouste III B&PTAE-7 engines.
Banglore
Complex
•Aircraft Division
•Engine Division
• Foundary and Forge
Division
• Aerospace Division
• Overhal Division
• Indusrty and Marine gas
Turbine Division
• Facalities Management
Division
• Airport Service Division
Helicopter
Complex
•Helicopter
Manfacturing
Division Banglore
•Helicopter MRO
Division Banglore
•Overhaul division
•Composite
Manufacturing
Division Banglore
Accesories
Complex
•Accesories division
Lucknow
•Avionics division
Korwa
•Avionics division
Hyderabad
•TransportAircraft
Division(TAD),
Kanpur
MIG Complex
•Aircraft Manfacturing
Division Nasik
•Aircraft Overhal
Division Nasik
•EngineDivision
Korapur
•Sukhoi

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Service facilities in HAL Engine Division:
Repair and Overhaul of Engines
Spectro Photo-metric Oil Analysis (SOAP test)
Electron Beam Welding
Robotic Plasma Spray Facility
Sermetal Coating (High Temperature Corrosion Resistance Painting)
Chemical Milling
Turn Key Basis - Design and Construction of Engine Test Beds
 OVERHAUL DIVISION
For over seven decades, Overhaul Division has been a leading Military Aircraft Maintenance,
Repair and Overhaul organization in India. The present activities of overhaul division
includes Major servicing of Kiran MK I/IA, Kiran MK II, Jaguar strike & Trainer and major
inspection of Mirage 2000 Fighter & Trainer, overhaul & repair of Lycoming engines( HPT-
32 & Islander) overhaul & repair/ servicing of accessories. Overhaul Division provides
maintenance support to Military aircraft at various Customer bases of IAF and also the Kiran
and Sea Harrier Aircraft at Goa Naval base.
 AEROSPACE DIVISION
Aerospace Division is engaged in the manufacture of Aluminium alloy riveted structures and
welded tankages of conical, cylindrical and other shapes with different types of detailed parts
such as sheets, rings, brackets, stiffeners, bulkheads, panel bolts, nuts, rivets etc. Some of the
important structures manufactured are Heat Shield Assembly, Nose Cone Assembly and Tank
and Shrouds used in Satellites. Products of aerospace division are PSLV: (Polar satellite
launch vehicle), GSLV: (GEO-GEO-synchronous satellite launch vehicle) MK II, GSLV:
(GEO-synchronous satellite launch vehicle) MK III, Indian remote sensing satellite, Indian
national satellite.
 FOUNDARY & FORGE DIVISION
The Foundry & Forge Division was established in 1953. The Division's facility, set up on a
lush expanse of 32 acres, manufactures Castings, Forgings, Rolled Rings, Shape Memory
Alloy Ferrules, Brake pads and Rubber Products for critical applications for the Aeronautics,
Space, Defence, Locomotive, Earth mover and other industries. Advanced Technology,
Quality and Reliability and a highly skilled workforce have enabled the Division to turn out
fail safe components for vital applications in war and peace, meeting the exacting needs of
every customer.
 IMGT DIVISION
IMGT Division, HAL, Bangalore, India provides the most comprehensive service by offering
support in areas of Inspection, Spare Parts, Maintenance, Equipment Overhauls & Assembly
for Industrial & Marine Gas Turbines under license from reputed manufacturers. The IMGT

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Division undertakes the Overhaul and Repair of Industrial Avon Engines and Allison 501K
Engines.
 AIRPORT SERVICES CENTRE
Presently Airport services centre is providing the technical services of Air Traffic Control,
maintenance of runway and navigation/ landing aid and various ailed services of airport.
 FACILITIES MANAGEMENT DIVISION
Dedicated management units have been set to handle series production. That provides better
work environment etc.
2.2.2. MIG COMPLEX
 AIRCRAFT DIVISION NASIK
The division manufactured other MIG variants; via MiG-21M, MiG-21 BIS, MiG-27 M and
the state-of-the-art aircraft i.e. Su-30 MKI. Along with manufacturing, the division also
carries out overhaul of the MIG series aircraft and started ROH of Su-30 MKI.
 AIRCRAFT OVERHAUL DIVISION NASIK
The division is engaged in repair/ overhaul and upgraded of MiG-2 aircraft variants/MiG-
27M aircraft and their aggregates & rotables.
 ENGINE DIVISION KORAPUT
Present activities of koraput division include manufacture of RD33 engines for MiG-29
aircraft and overhaul of R-11/R25 engines for MIC series aircraft, R-29B engines for MiG-
27M aircraft and RD-33 engines for MiG29 aircraft. The division also had undertaken
development & manufacture of forgings & castings for aeronautical & industrial applications.
Co-located gas turbine R&D centre deals with design improvement of Russian engines.
 SUKHOI ENGINE DIVISION KORAPUT
A separate division has been set up for manufacture an overhaul of AL 31FP engine for SU-
30MKI aircraft
2.2.3. ACCESSORIES COMPLEX
 TAD-KANPUR DIVISION
Currently, the activities of TAD-Kanpur Division include manufacturing and overhauling of
DO-228 aircraft in addition to overhaul of HS-748 and HPT-32 aircrafts and their rotables
and manufacturing of HJT-36. HAL detachment Agra, attached to TAD-Kanpur, is involved
in servicing of the AN-32.

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 ACCESSORIES DIVISION LUCKNOW
The division undertakes manufacturing of hydraulic system, Wheel & Brake system,
environmental control system, engine fuel control system, Flight control system, panel
instruments- Gyroscopic, Barometric & Electro-Mechanical, Electrical systems, Fuel
Management system & Oxygen system for the various aircraft & helicopters of indigenous,
western & Russian origin.
 AVIONICS DIVISION HYDERABAD
Presently, the product profile of the division includes Communication. To begin with, the
Division's dedicated design team took up the task of indigenizing, the following critical
avionics.
Identification of Friend or Foe
UHF Communication set
V/UHF Communication System
Automatic Direction Finder (ADF)
Radio Altimeter
 AVIONICS DIVISION KORWA
This Division undertakes the repair and overhaul of the airborne avionic systems of Jaguar,
MiG-27 and Mirage-2000 aircraft throughout the lifecycle of the product. Currently Korwa
Division is manufacturing the Navigation, Ranging, Display and Attack Systems for both
jaguar and MiG-27 aircraft.
2.2.4. HELICOPTER COMPLEX
 HELICOPTER DIVISION BANGALORE
The division undertakes production of Advanced Light Helicopter.
Dhruv
Chetak
Cheetah
Lancer
Cheetal
 HELICOPTER MRO DIVISION BANGALORE
A dedicated MRO Division has been created to address product support, spares, maintenance
& services for Dhruv helicopter.

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 OVERHAUL DIVISION WEST BENGAL
The division undertakes manufacture & overhaul of cheetah (SA-315 Lama), Chetak, Lancer,
Cheetal and Chetan helicopters.
 COMPOSITE MANUFACTURING DIVISION
A dedicated division has been created for manufacture of composite structures of aircraft &
helicopters (like ALH & LCA), apart from export programmes.
RESEARCH AND DESIGN CENTRES
HAL has successfully completed many system updates and integration tasks. HAL has 10
research & design centres engaged in the design and development of combat aircraft,
helicopters, aero engines, gas turbines, engine test beds, aircraft communication and
navigation system and mechanical system accessories. The company is backed by high
profile, highly skilled manpower with an impressive track record of more than five decades
of rich experience in all discipline of aeronautics.
 Aircraft R&D Centre
 Engine & test bed R&D Centre
 Strategic electronics R&D Centre
 Aerospace system and equipment R&D Centre
 Central materials and processes R&D Centre
 Rotary wing R&D Centre
 Aircraft upgrade R&D Centre
 Transport aircraft R&D Centre
 Gas turbine R&D Centre
 Mission & Combat system R&D Centre
2.3. TRANSPORT AIRCRAFT DIVISION, KANPUR
Transport Aircraft Division of HAL was set up in 1960 to manufacture the HS-748, a
medium haul turbo-prop passenger transport aircraft. Over the years, it has vastly developed
its infrastructure and capabilities and undertaken the manufacture of agriculture aircraft (HA-
31), basic trainer aircraft (HPT-32), 15-19 seater multirole utility aircraft (Dornier-228) and
variety of aerospace structural assemblies and components for both domestic and
international market.
Transport aircraft R&D centre located in the division carries out production updating, role
modification and other R&D activities. Concurrent with the manufacturing activities,
Transport aircraft R&D centre located in the division carries out production updating, role
modifications and other R&D activities. Transport Aircraft Division has developed extensive
facilities for repair, overhaul and modification of these aircraft as well as for about 400 types

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of rotables fitted on these aircraft. Apart from the above, Division is doing Depot Level
Maintenance of Engines and Hydraulic Systems of Unmanned Air Vehicles (UAV). Searcher
- I , Searcher - II and Heron since JAN'2004 under Transfer of Technology Agreement with
Malat division of Israel Aircraft Industries and Servicing of AN-32 & Canberra aircraft at its
detachment workplace at Agra from 2000 onwards.
2.3.1. VARIOUS DEPRTMENT OF HAL-TAD KANPUR
Production Department
Design Department
Manufacturing Department
Quality & Control Department
Service & Over hall Department
Customer Service & Marketing Department
Integrated Material Management
Outsourcing Department
Lean Management
Finance Department
Personal & Administration
Transport Aircraft R & D Centre located in the Division carries out product updating, role
modifications and other R & D activities.
2.3.2. UPGRADATION OF AIRCRAFT AND ROLE EQUIPMENT INTEGRATION
The Transport Aircraft R & D Centre is involved in carrying out aircraft upgrades,
modifications and role equipment integration. Our major projects in the past include:
Mid-life upgrade of HS-748 Nav. & Comm. system
Integrally machined wing fuel tank of HPT-32 aircraft replacing rubber flexible fuel tank
Integration of TCAS, MOD ’S’, EGPWS on Boeing, HS-748, DO-228 and AN-32 aircraft
Integration of maritime radar Elta and Supermarec Radar on DO-228 aircraft
Integration of Search Light Pod, Gun Pod and IR/UV Scanner on DO-228 aircraft
Modification on DO-228 Aircraft for high altitude operation & Para dropping / Para jumping.
2.3.3. AIRCRAFT OVERHAUL, REPAIR AND MODIFICATION
1. Extensive facilities and expertise are available for the overhaul, repair, maintenance and
modification of
HS-748 medium capacity aircraft
DO-228 light transport aircraft
Servicing of AN-32

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Servicing of Canberra aircraft
Depot level maintenance of Un-manned Air Vehicles (UAV-Searcher-I, Searcher-II and
Heron)
3. Services offered include major overhauls, scheduled and unscheduled maintenance,
repairs, embodiment of SB's, cabin refurbishing etc
4.Runway adjacent hangars
5.Full range of facilities for quality control, inspection and testing
6. Site repair and retrieval of damaged aircraft
6.3.1. AIRCRAFT PAINTING
Exclusive Paint hangar with dust-free and controlled environment can accommodate aircraft
up to 50 seater capacity. Expertise is available for various types of aircraft painting systems
like Poly-urethane, Epoxy, Cellulose, etc. Full range of facilities for testing of paint, paint
thickness measurement.
6.3.2. ROTABLES OVERHAUL AND REPAIR
Extensive facilities for over 400 types of Rotables of different aircraft including HS-748, DO
-228, HPT-32 and other medium category aircraft. Rich experience of overhauling more than
50,000 Rotables in the past. Competent and qualified workforce to meet the exacting
requirement of the Aviation industry. Shops built to clean room specifications and equipped
with the complete range of Test Equipment.
Table 2.1: Total numbers of aircraft delivered
Product Period Quantity
HS-748 Aircraft 1960-83 89
Gliders 1963-86 164
Basant Aircraft(HA-31) 1975-78 19
HPT-32 Aircraft 1983-98 142
Dornier-228 Aircraft 1985 onwards 83
ATP tail plane(for export) 1987-95 24

Page | 17
Ranges of rotables which can be overhauled and repaired include the following:
Mechanical items like propellers, landing gears, actuators, wheel-brake assembly, hydraulics,
fuel and de-icing systems and accessories
Instrument items like flight instruments, fuel quantity and fuel flow system, pressurisation
system instruments, Autopilot and all types of pressure switches and gauges
Electrical items like alternators, invertors, motors, regulators, control and protection units,
booster pumps, actuators, fans, batteries and voltage regulators
Avionic items pertaining to communication, navigation, and intercom systems, weather radar
and antenna
6.4. MISSION & VALUES OF HAL
MISSION
To fulfil the fresh mandate of the present days and to meet the challenges of the open market
economy of recent times the Mission of the Company has been redefined as,
"To become a globally competitive aerospace industry while working as instrument for
achieving self-reliance in design, manufacture and maintenance of aerospace, defence
equipment and diversifying to related areas, managing the business on commercial lines in a
climate of growing professional competence"
VALUES
We are committed to these values to guide us in all our activities…..
i. Customer satisfaction
We are dedicated to building a relationship with our customers where we become partners to
building a relationship with our customers where we become partners to building a
relationship with our customers where we become partners in fulfilling their mission. We
strive to understand our customer’s needs and to deliver products and services that fulfil and
exceed all their requirements.
ii. Commitment and total quality
We are committed to continuous improvement of all our activities. We will supply products
and services that conform to highest standard of design, manufacture, reliability,
maintainability & fitness for uses as desired by our customers.
iii. Cost and time consciousness
We believe that our success depends on our ability to continually reduce the cost and shorten
the delivery period of our products and services. We will achieve this by eliminating waste in
all activities and continuously improving all processes in every area of our work.

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iv. Innovation and creativity
We believe in striving for improvement in every activity involved in our business by pursuing
and encouraging risk- taking, experimentation and learning at all levels within the company
with a view to achieving excellence and competitiveness.
v. Trust and team spirit
We believe in achieving harmony in work-life through mutual trust, transparency,
cooperation and a sense of belonging. We will strive for building empowered teams to work
towards achieving organizational goals.
vi. Respect for the individual
We value our people. We will treat each other with dignity and respect and strive for
individual growth and realization of everyone’s full potential.
vii. Integrity
We believe in a commitment to be honest, trustworthy and fair in all our dealings. We
commit to be loyal and devoted to our organization. We will practice self-discipline and own
responsibility for our action.
6.5. CUSTOMER PROFILE
DOMESTIC CUSTOMER INTERNATIONALCUSTOMER
Indian Air Force Government of Mauritius
Indian Coast Guard British aerospace U.K.
Indian Navy Dornier Germany
Indian Air Lines Druk airways Bhutan
Border Security Force Necon air-Nepal
Oil and Natural Gas Commission Everest air Nepal
Air Port Authority of India South Korea
Private Air Lines

Page | 19
CHAPTER 3
AVIONICS LAB
7. INTRODUCTION
The word “Avionics” is a combination of aviation and electronics. Avionics deal with
all communication and navigation part of the aircraft Avionics are the electronic systems used
on aircraft, artificial satellites and spacecraft.
Avionic systems include communications, navigation, the display and management of
multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles.
These can be as simple as a searchlight for a police helicopter or as complicated as the tactical
system for an airborne early warning platform.
The cockpit of an aircraft is a typical location for avionic equipment, including control,
monitoring, communication, navigation, weather, and anti-collision systems. The majority of
aircraft power their avionics using 14 or 28 volt DC electrical systems; however, larger, more
sophisticated aircraft (such as airliners or military combat aircraft) have AC systems operating at
400 Hz, 115 volts AC.
International standards for avionics equipment are prepared by the Airlines Electronic
Engineering Committee (AEEC).
3.1. ELECTRICAL SYSTEM
STATIC INVERTERS :
Fig: 3.1 Static Inverter
In many applications where continuous dc voltage must be converted to alternating voltage,
static inverters are used in place of rotary inverters or motor generator sets. The use of static
inverters in small aircraft also has increased rapidly in the last few years, and the technology
has advanced to the point that static inverters are available for any requirement filled by rotary
inverters. A block diagram of a typical regulated sine wave static inverter is shown in figure
below. This inverter converts a low dc voltage into higher ac voltage. Output taps are normally
provided to permit selection of various voltages; for example, taps may be provided for a 105,
115, and 125 volt ac outputs.

Page | 20
An inverter is used in some aircraft systems to convert a portion of the aircraft's dc power to ac.
This ac is used mainly for instruments, radio, radar, lighting, and other accessories. These
inverters are usually built to supply current at a frequency of 400 cps, but some are designed to
provide more than one voltage; for example, 26 volt ac in one winding and 115 volts in another.
The inverters are selected on or off by two switches on the cockpit overhead panel. Air Manitoba
procedure was to select the switches on at the start of a series of flights and leave them on until
the end of the last flight for that crew. A transfer switch for each inverter enables, through a
transfer relay, the transfer of all electrical services from a failed or de-selected inverter to the
operating inverter. Either inverter is capable of supplying the total AC electrical power
requirements of the aircraft. Single voltmeter and frequency gauges display the output from one
inverter at a time, whichever one is selected to display.
Since static inverters use solid state components, they are considerably smaller, more compact,
and much lighter in weight than rotary inverters. Depending on the output power rating
required, static inverters that are no larger than a typical airspeed indicator can be used in
aircraft systems. Some of the features of static inverters are:
1) High-efficiency
2) Low maintenance
3) long life
4) No warm-up period required
5) Capable of starting under load
6) Extremely quiet operation
7) Fast response to load changes
Static inverters are commonly used to provide power for such frequency sensitive instruments
as the attitude gyro and directional gyro. They also provide power for autosyn and magnesyn
indicators and transmitters, rate gyros, radar, and other airborne applications.
Technical Description
To test and overhaul these static inverters, there is a “Static Inverter test bench” which
provides each and every required instrument and excitation for checking the system.
Typically, a static inverter is 12” in length, 8.5” in width and 4.09” in height and weighs
about 12.5 Lbs. It can operate over a temperature range of -55° to 71°C and up to an altitude
of 55000 feet. It has an integrated fan for its cooling purpose.
Fig: 3.2

Page | 21
The input voltage ranges from 18V to 36V, but, is typically 28V at 2.47A in case of
Do-228 aircraft. It provides an output of 115V A.C. RMS at 400 Hz (±1.5%) or can further
step down the output to 26V A.C. RMS at 400 Hz at a lag ranging from 0.8 to 0.9. Its output
is analyzed using distortion meter and Signal Oscilloscope (30 MHz).
3.2. COMMUNICATION SYSTEM
Communications connect the flight deck to the ground and the flight deck to the passengers.
On-board communications are provided by public address systems and aircraft intercoms.
The VHF aviation communication system works on the air band of 118.000 MHz to
136.975 MHz. Each channel is spaced from the adjacent ones by 8.33 KHz. VHF are also used
for line of sight communication such as aircraft-to-aircraft and aircraft-to- ATC. Amplitude
modulation (AM) is used, and the conversation is performed in simplex mode. Aircraft
communication can also take place using HF (especially for trans- oceanic flights) or satellite
communication.
System’s which are used for having communication between ground to air & air to air and vice
versa.
 Internal communication system.
 External communication system.
3.2.1. INTERNAL COMMUNICATION
Inter phone/Intercom/Passenger address are landline communication systems which are used for
communication between Crews, Pilot & C0-Pilot during flight.
Interphone/Intercom/Passenger Address (PA): This system is used for landline
communication. This system consists of following LRU’s (Line Replacement Unit):-
1. Junction box.
2. Audio selector.
3. IC Amplifier.
4. Headset
Junction Box: It collects various audios of different systems and feed it to audio selector
unit. Since the level or output of each is different, so to make this audio constant to a required
constant level a junction box is required.
Audio selector: This is one type of switch board containing VHF/UHF and HF
transmitter switching on switch. In this system there are two lines used for transmission
purpose, one line for transmission and another for receiving for collecting audios of NAV,
ADF, altimeter, etc.
Headset: This is the assembly which contains two ear pieces and one carbon mike
by which audio from certain distance can be converted to electrical signal.

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3.2.2. EXTERNAL COMMUNICATION
There are two types of external communication system:
Long range communication’s which are carried out by I.L.F. communication system
Short range communication’s which are carried out by V.H.F. system.
HF (high frequency) system
Operating frequency of HF system is 2MHz to 30MHz. Using HF system long distance
communication can be achieved even throughout the whole global provider power output of
transmitter is sufficient.
In aviation, HF system is employed for gathering information such as status of airport
and condition of atmosphere outside the plane. This plane is also used for collecting information
about storm or obstacle i.e. referred to as met warning the drawback with HF system is that these
systems do not have secrecy.
In HF system various LRU’s are used which as follows:
a) IF control unit.
b) HF power amplifier.
c) HF super receiver exciter.
d) HF antenna tuning unit (ATU).
e) HF antenna assembly.
HF antenna can be further classified into:
a) Open end antenna.
b) Grounded antenna.
Fig: 3.3

Page | 23
In Open-end antenna, minimum length of antenna is 10m or in other words quarter lambda of
the operating frequency. Whereas in grounded antenna, antenna length is less than 10m are used
in AVRO and Dornier aircrafts. In grounded antenna, there is loss of powering transfer of
information whereas in open end antenna there is no power loss. Antenna length can be
increased or decreased electrically by ATU which contains assembly of wire and capacitors
using which frequency can be selected to match the impedance.
3.3. COMUNICATION EQUIPMENT
3.3.1. AUDIO SELECTOR UNIT
Audio selector unit and Intercom system
This system serves the purpose of intercommunication between the crew, radio telephone
communication as well as monitoring call and warning signals.
GENERAL DESCRIPTION
ASI unit is designed as a mono-block unit and intended for installation in the operating
consoles of aircraft.
The ASI unit features the following plug-in modules:
- 2 mike amplifiers modules (1 module for emergency operation only).
- 1 speaker amplifier module (for emergency operation only used instead of headphone amplifier).
- 1 HOT MIKE module.
- And 1 identifier module for AS-3100 only.
Fig: 3.4

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Fig: 3.5 Audio Selector Units
Audio Selector and Intercom unit features the following plug-in modules – 2 mike amplifier
modules (1 for emergency only), 1 speaker amplifier module (for emergency only), and 1 hot
mike mode. The audio selector and Intercom unit permits the following mode of operation:
1. IC/Hot MIKE operation, threshold controlled aircraft intercommunication without
operating an element in position 1-4 Passenger Address (P.A.) of transmitter selector
switch.
2. IC operation aircraft intercommunication with IC key in all possible positions of the
transmitter selector switch. In position IC, IC operation is also possible with PTT key.
3. Drive of the connected transceiver (maximum 4 transceivers) in the position 1 to 4 of
the transmitter selector switch by means of the PTT key with simultaneous IC muting
(priority transmission).
4. Receiver interception monitoring the connected receivers by means of pushbutton
switches.
5. Drive of a remote public address amplifier in position P.A. of the transmitter selector
switch with the PTT key
6. Emergency operation by means of EMER push button switch in the event of failure of
supply voltage or a part of the normal operation circuit in unit.
In addition, call and warning signals can be monitored via three fixed inputs and two
expander inputs. The Audio Selector and Intercom unit is designed for connection of headsets
with standard mikes of 160 ohms and headphones of 8 Ω or 300 Ω.
In Do-228, AS-3100 from Becker Avionics is used. Some technical details are enlisted below
for mike of AS-3100.
3.3.2. VHF/UHF TRANSCEIVER MODEL VUC-201A
The VUC-201A is a VHF/UHF trans-receiver for air-to-ground and air-to-air communication.
Homing and radio relay facilities are available. The equipment covers 100 to 155.975 MHz with
2,240 channels and 225 to 399.975 MHz with 7,000 channels. Channel spacing is 25 kHz, and
there are 19 pre-set channels plus one manual channel which can also be used as a pre-set. A
guard channel is tuneable from 238 to 248 MHz and the trans-receiver has BITE. Power output is
10 W nominal (VHF) and 20 W nominal (UHF). The receiver part has a sensitivity of 2 µV.
Operating between -55 to +55°C and at altitudes of up to 21.3 km, the VUC-201A is powered

Page | 25
from 27.5 V DC. Dimensions are 155 × 160 × 357 mm and weight, with shock mount, is 13 kg
.VUC-201A is an airborne V/UHF communication transceiver. It belongs to new generation state
technology. It employ modular construction for ease in maintenance equipment covered by this
specification shall provide radio frequency reception & transmission of AM signal on any of
2240 channel in the 100 to 155.975MHZ of very high frequency band and 7000 channel in the
225 to 399.975MHZ of ultra high frequency band in 25KHZ increment.
Main function of equipment is to provide simplex two way communication of AM, Radio
telephony A3. Additional the equipment shall provide the capabilities for the following:-
Continuous monitoring of the UHF AM in the guard band, by incorporation of a
separate fixed tuned receiver in the frequency range of 238 to 248 MHZ in 25KHZ
increment.
Reception of V/UHF automatic direction finder signal on any selected channel to
provide necessary input to ADF for further processing.
Automatic relaying in V/UHF band.
Technical Features:
Frequency Range : 100-155.975MHZ(2240 channel), 225-399.975MHZ
(7000 channel)
Present Channel : 25KHZ
Present Channel : 19+1 manual channel, which can also be used as present
channel
Modulation : A2 &A3
Guard Channel : 238-248MHZ (for 243 MHZ)
Power Supply : 27.5V DC
Power output : VHF 10 watt UHF 20 watt
Power Consumption : 100 watt during receiver, 550 watt during transmit
Main receiver audio output : 50mw
Guard receiver audio output : 50mw
Intercom output : 50mw
Main receiver sensitivity to
obtain s+nn of 2microvolt
: 2 micro volt ,10db min(closed circuit)
Main receiver sensitivity to
obtain s+nn of 2microvolt
: 4. micro volt ,10db min(closed circuit)
Main receiver sensitivity : Not less than 20khz at 6db & not more than 70khz at 60db
Main receiver sensitivity : Not less than 40khz at 6db & not more than 120khz at
60db
Frequency stability : +_ 5ppm max
Antenna impedance : 52ohm
Microphone : low level, EM type J150ohm
Duty cycle : 1 minute transmit 5min receive
21.3KMS

Page | 26
3.3.3. SELCAL
SELCAL is a selective-calling radio system that can alert an aircraft's crew that a ground
radio station wishes to communicate with the aircraft. SELCAL uses a ground-based encoder
and radio transmitter to broadcast an audio signal that is picked up by a decoder and radio
receiver on an aircraft. The use of SELCAL allows an aircraft crew to be notified of incoming
communications even when the aircraft's radio has been muted. Thus, crewmembers need not
devote their attention to continuous radio listening.
OPERATION
SELCAL operates on the high frequency (HF) or very high frequency (VHF) radio
frequency bands used for aircraft communications. HF radio often has extremely high levels of
background noise and can be difficult or distracting to listen to for long periods of time. As a
result, it is common practice for crews to keep the radio volume low unless the radio is
immediately needed. A SELCAL notification activates a signal to the crew that they are about to
receive a voice transmission, so that the crew has time to raise the volume.
An individual aircraft has its own assigned SELCAL code. To initiate a SELCAL transmission, a
ground station radio operator enters an aircraft's SELCAL code into a SELCAL encoder. The
encoder converts the four-letter code into four designated audio tones. The radio operator's
transmitter then broadcasts the audio tones on the aircraft's company radio frequency channel in
sequence: the first pair of tones is transmitted simultaneously, lasting about one second; a silence
of about 0.2 seconds; followed by the second pair of tones, lasting about one second.
A SELCAL decoder is connected to each aircraft's radio receiver. When a SELCAL
decoder on an aircraft receives a signal containing its own assigned SELCAL code, it alerts the
aircraft's crew by sounding a chime, activating a light, or both.
3.3.4. WARNING CAUTION PANEL/ ANNUCIATOR PANNEL
An annunciator panel is a group of lights used as a central indicator of status of
equipment or systems in an aircraft, industrial process, building or other installation. Usually, the
annunciator panel includes a main warning lamp or audible signal to draw the attention of
operating personnel to the annunciator panel for abnormal events or conditions
Range : air to ground& air to air two way communication can be
had for a distance of 350KM over radio horizon ranges
Figure 3.6. : Warning caution panel

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In the aircraft industry, annunciator panels are groupings of annunciator lights that indicate status
of the aircraft's subsystems. The lights are usually accompanied with a test switch, which when
pressed illuminates all the lights to confirm they are in working order. More advanced modern
aircraft replaces these with the integrated electronic Engine Indicating and Crew Alerting
System or Electronic Centralized Aircraft Monitor.
An aviation annunciator panel will have a test switch to check for burned out lamps.
Indicator lights are grouped together by their associated systems into various panels of lights.
Lamp colours are normally given the following meanings:
 Red: Warning, this systems condition is critical and requires immediate attention (such as an
engine fire, hydraulic pump failure)
 Orange/yellow: Caution, this system requires timely attention or may do so in the future (ice
detected, fuel imbalance)
 Green: Advisory/Indication, a system is in use or ready for operation (such as landing gear down
and locked, APU operating)
 White/blue: Advisory/Indication, a system is in use (seatbelt signs on, anti-ice system in-
use, landing lights on).
The annunciator panel may display warnings or cautions that are not necessarily
indicative of a problem; for example, a DO-228 on its after-landing roll will often flicker the
"Volts" warning simply due to the idle throttle position and therefore the lower voltage output of
the alternator to the aircraft's electrical system.
3.4. NAVIGATION SYSTEM
Navigation is the determination of position and direction on or above the surface of the Earth.
Avionics can use satellite-based systems (such as GPS), ground-based systems (such as VOR),
or any combination thereof. Navigation systems calculate the position automatically and display
it to the flight crew on moving map displays. Older avionics required a pilot or navigator to plot
the intersection of signals on a paper map to determine an aircraft's location; modern systems
calculate the position automatically and display it to the flight crew on moving map displays.
Figure 3.7: Navigation Operation

Page | 28
To meet the navigational requirements of military aviation by providing the user receiver
position of the aircraft and the ground station in latitude and longitude. It also gives the
information relating to navigational management, flight plan navigation and other operating
frequencies of the ground station.
System’s which provides facilities to the flying aircraft to make the flying easy.
 V.O.R. (Very High Omni Range).
 I.L.S. (Instrument landing system).
 G.P.S. (Global Positioning System).
 A.D.F. (Automatic Direction Finder).
3.4.1. COLLINS VIR-32 RADIO NAVIGATION SYSTEM
The VIR-32 Radio Navigation System provides VOR, localizer, glide slope and marker
beacon output and VOR/ADF display for general aviation aircraft. The system has 200
VOR/LOC operating channels and 40 glide slope channels.
The system is compatible with standard 2-out-of-5 control unit and provides a full
complement of navigation outputs to interface with pictorial navigation system and conventional
flight control system.
PURPOSE OF EQUIPMENT: The VIR-30 Radio Navigation System supplies either
automatic/manual or manual information; localizer and glide slope deviation outputs; high and
low-level flag signals; to/from information; marker beacon lamp signals and VOR; localizer and
marker beacon audio output.
PRICIPLE OF OPERATION:
The VIR-30 Radio Navigation System receives and displays automatic VOR
information and provides signal to display ILS and manual VOR data transmitted from VOR and
ILS ground stations for enroute and terminal navigation. When VOR mode is selected, the
navigation system receives and displays bearing and relative bearing on the RMI-30 Radio
Magnetic Indicator and detects course deviation and to-from data for depiction by the flight
director. When ILS mode is selected, the RMI bearing Pointer Park in a horizontal position
indicating 90 degrees relative bearing. ILS data (localizer, marker beacon and glide slope) is
received and processed to provide inputs to the flight director and the marker beacon lamp panel.
It divided into two parts:
I. V.O.R
II. I.L.S
3.4.1.1. V.O.R (VHF omnidirectional radio range)
VOR, short for VHF omnidirectional radio range, is a type of short-range radio
navigation system for aircraft, enabling aircraft to determine their position and stay on course by
receiving radio signals transmitted by a network of fixed ground radio beacons, with a receiver
unit. It uses radio frequencies in the very high frequency (VHF) band from 108 to 117.95 MHz

Page | 29
the reception of VHF signals is a line of sight situation. You must be on the minimum altitude of
1000 feet (AGL) above ground level in order to pick up an Omni signals service range.
Figure 3.8: VOR
A: Rotating Course Card is calibrated from 0 to 360 degrees, which indicates the VOR
bearing chosen as the reference to fly by pilot.
B: Omni Bearing Selector or OBS knob, used to manually rotate the course card to where the
point to fly to.
C: TO-FROM indicator. The triangle arrow will point UP when flying to the VOR station.
The arrow will point DOWN when flying away from the VOR station. A red flag replaces
these TO-FROM arrows when the VOR is beyond reception range or the station is out.
D: Course Deviation Indicator (CDI). This needle moves left or right indicating the direction
to turn the aircraft to return to course.
DOT: The horizontal dots at centre are representing the aircraft away from the course. Each
dot represents 2 degrees deviate from desired course.
Principle of operation:
The received signal from a VOR station consist of a carrier frequency (108 to 117.95
MHz) and a sub-carrier frequency (9960 Hz), both modulated by 30Hz signals. One 30Hz signal
is the variable phase signal and the other 30Hz signal is the reference phase signal. The 30Hz
reference phase is the frequency modulated component of 9960Hz frequency-modulated sub-
carrier. The sub-carrier frequency varies from 9480 to 10440Hz at 30Hz rate.
The 30Hz variable phase signal is an amplitude modulated component of VOR station
reference carrier. This signal is generated by rotating the transmitting antenna, either
mechanically or electronically, at 1800 revolutions per minute (30 revolution per second). The
station identification code and voice transmission are also amplitude modulated components of
the selected VOR frequency.
The VOR navigation receiver separates the reference and variable signal. The phase of
the variable signal is then compared to the phase of refernce signal. The phase difference is
proportional to the radial angle from VOR station.
The to from information is determined from the phase difference between reference
signal and the variable signal shifted by 90 degree in phase.
Reception Range vs. Altitude of VORs
VOR Class Range
nm
within Altitude
feet

Page | 30
Terminal (T) 25 1000 – 12,000
Low Altitude (L) 40 1000 – 18,000
High Altitude (H) 40
100
130
1000 – 14,500
14,500 – 60,000,
18,000 – 45,000
Tabel 3.1: Reception Range vs. Altitude of VORs
3.4.1.2. I.L.S (Instrument Landing System)
An instrument landing system (ILS) is a based instrument approach system that
provides precision guidance to an aircraft approaching and landing on ground- a runway, using a
combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe
landing during instrument meteorological conditions (IMC), such as low ceilings or reduced
visibility due to fog, rain, or blowing snow.
System employed at the time of landing of aircraft is referred to as instrument landing
system. They are broadly classified into three main categories:
LOCALIZER
This system provides central line of the runway. Modern localizer antennas are
highly directional. However, usage of older, less directional antennas allows a runway to have a
non-precision approach called a localizer back course. This lets aircraft land using the signal
transmitted from the back of the localizer array. A pilot may have to fly opposite the needle
indication, due to reverse sensing. This would occur when using a basic VOR indicator.
The localizer provides horizontal guidance to the centre line of the runway when making
an approach. The received signal from localizer ground station transmitter consists of a carrier
(108.10 MHz to 111.95 MHz) modulated by 90 Hz and 150 Hz. The localizer signal is radiated
to produce two intersection lobes, one predominantly 150 Hz. When on the centre line of the
runway, equal amplitude of 90Hz and 150Hz are received and the localizer needle is centred. If
the aircraft is to the left of the centre line, 90Hz modulation predominates and localizer needle is
to the right of centre. If an aircraft is to the right of the centre line, 150Hz modulation
predominates and localizer needle is to the left of centre.
Fig: 3.9: Instrument Landing System)

Page | 31
Figure 3.10: Localizer and Glide slope aerial
GLIDE SLOPE
This system provides gliding angle (2 to 6 degrees) which is the safest angle so hat
aircraft is not damaged. A glide slope (GS) or glide path (GP) antenna array is sited to one side
of the runway touchdown zone. The GP signal is transmitted on a carrier frequency between
328.6 and 335.4 MHz using a technique similar to that of the localizer. The centre line of the
glide slope signal is arranged to define a glide slope of approximately 3° above horizontal
(ground level). The beam is 1.4° deep; 0.7° below the glide slope centreline and 0.7° above the
glide slope centreline.
These signals are displayed on an indicator in the instrument panel. This instrument is
generally called the Omni-bearing indicator or NAV indicator. The pilot controls the aircraft so
that the indications on the instrument (i.e., the course deviation indicator) remain centred on the
display. This ensures the aircraft is following the ILS centreline (i.e., it provides lateral
guidance). Vertical guidance, shown on the instrument by the glide slope indicator, aids the pilot
in reaching the runway at the proper touchdown point.
The glide slope provides a glide path for vertical guidance making an approach to the
runway. If the aircraft is on the glide path (glide slope centre line) equal amplitude both 90Hz
and 150Hz are received and the glide slope deviation bar is centred. If the aircraft is above the
glide path, 90Hz predominates and the deviation bar moves downward. If below the glide path,
150H predominates and deviation bar moves upward.
MARKER BEACON
At the time of landing of the aircraft this system provides line indication to pilot. The
marker system provides visual and audio indication of geographical points, and the distance of

Page | 32
the aircraft from the approach end of the runway. Its carrier frequency is 75 MHz three types of
beacons are used on airport approaches: outer marker, middle marker and inner marker.
Each marker beacon transmits a cone shaped pattern at a frequency of 75MHz which is
modulated by a different for each marker. In addition the outer and middle marker modulation
frequencies are keyed for beacon identification purposes.
As an aircraft passes over each beacon, the information transmitted is received and
evaluated by marker receiver and the results are indicated to the pilot by different coloured lights
and different audio tones in the headset.
Outer marker: Blue color- located at a distance of 4.5 to 5.0 miles from touch down point. Its
modulating frequency is 400 cycles/sec.
Middle marker: Amber colour; located at a distance of 2.5 miles from touch down point. Its
Inner marker: White colour- located at a distance of 200-250ft. from touch down point. Its
Outer marker Middle marker Inner marker
Figure 3.11: Types of marker beacon
3.4.2. AUTOMATIC DIRECTION FINDER:
ADF works in frequency range of 190 to 1700 KHz in steps of 0.5 KHz. It consists of a
receiver and control unit. An interface unit is also required when two controllers are used with
one receiver. The purpose of the ADF is to point to a non-directional beacon and that is the only
purpose.
Figure 3.12: ADF operation and ADF instrument

Page | 33
ADF COMPONENTS
ADF Receiver: pilot can tune the station desired and to select the mode of operation. The
signal is received, amplified, and converted to audible voice or code transmission and powers the
bearing indicator.
Figure 3.13.: ADF Receiver and Bearing Indicator
Control Box (Digital Readout Type): Most modern aircraft has this type of control in the
cockpit. In this equipment the frequency tuned is displayed as digital readout. ADF automatically
determines bearing to selected station and it on the RM
Antenna: The aircraft consist of two antennas. The two antennas are called LOOP antenna and
SENSE antenna. The ADF receives signals on both loop and sense antennas. The loop
antenna in common use today is a small flat antenna without moving parts. Within the antenna
are several coils spaced at various angles. The loop antenna senses the direction of the station by
the strength of the signal on each coil but cannot determine whether the bearing is TO or FROM
the station. The sense antenna provides this latter information.
Bearing Indicator: displays the bearing to station relative to the nose of the aircraft.
Relative Bearing is the angle formed by the line drawn through the centre line of the aircraft and
a line drawn from the aircraft to the radio station.
Magnetic Bearing is the angle formed by a line drawn from aircraft to the radio station and a
line drawn from the aircraft to magnetic north (Bearing to station).
Magnetic Bearing = Magnetic Heading + Relative Bearing.
ADF COCKPIT OPERATION
Most ADF receivers have several modes that the pilot can select. If the "ANT" mode is
selected, the loop antenna is disabled and all receiving is done through the sense antenna. This
mode provides the clearest audio reception. The needle should park in the 90-degree position
when the receiver is in "ANT" mode; other brands may work differently.
In the "ADF" mode, the pointer is activated and the ADF tries to point to the station.
Some ADF systems have a "BFO" position. "BFO" stands for "beat frequency oscillator" and

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what it does is to generate an audio tone to identify beacons that identify themselves using
interrupted-carrier keying.
The ADF indicator consists of a needle and a compass card. The needle points to the
stations when the receiver is in "ADF" mode. The compass card may be fixed, manually
rotatable with a knob, or (in more expensive RMI systems) slaved automatically to the aircraft
heading. A slaved compass card is expensive, but sure makes it a lot easier to fly an ADF
approach.
ADF OPERATION
ADF operate in the low and medium frequency bands. By tuning to NDB station or
commercial AM radio stations. NDB frequency and identification information may be obtained
from aeronautical charts and Airport Facility Directory. The ADF has automatic direction
seeking qualities which result in the bearing indicator always pointing to the station to which it is
tuned.
The easiest and perhaps the most common method of using ADF is to “home “to the
station. Since the ADF pointer always points to the station, the pilot can simply head the airplane
so that the pointer is on the 0 (zero) degree or nose position when using a fixed card ADF. The
station will be directly ahead of the airplane.
Since there is almost always some wind at altitude and will be allowing for drift,
meaning that heading will be different from track. Off track, if the aircraft is left of track, the
head of the needle will point right of the nose. If the aircraft is right of track, the head of the
needle will point left of the nose.
FREQUENCY = 190-1750 KHz
ADF Time and Distance Checks
Good exercises to develop NDB awareness are the ADF Time and Distance Checks. Tune in
an NDB station; verify its Morse identifier, (Click the ID label in the centre of the radio face)
and then position the aircraft so that the needle points directly to the left or right, indicating
that the station is directly off the aircraft’s wing.
Note the bearing to the station and also the time, or set the timer. Then fly a constant heading
until the bearing changes 10°. Note the number of seconds it takes for the bearing to change
this 10°. Then simply divide that elapsed time by ten to determine the time to station in
minutes.
Time in seconds
Minutes to station =
(Degrees of bearing change)
You can then estimate the distance to the station:
TAS [kts] × Minutes flown
Nautical Miles to station =
(Degrees of bearing change)

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3.5. RADAR SYSTEM
Radar is an object-detection system which uses radio waves to determine the range,
altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided
missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits
pulses of radio waves or microwaves which bounce off any object in their path. The object
returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same
site as the transmitter.
In aviation, aircraft are equipped with radar devices that warn of obstacles in or
approaching their path and give accurate altitude readings. The first commercial device fitted to
aircraft was a 1938 Bell Lab unit on some United Air Lines aircraft. They can land in fog at
airports equipped with radar-assisted ground-controlled approach systems, in which the plane's
flight is observed on radar screens while operators radio landing directions to the pilot.
Principle
A radar system has a transmitter that emits radio waves called radar signals in
predetermined directions. When these come into contact with an object they are
usually reflected or scattered in many directions. Radar signals are reflected especially well by
materials of considerable electrical conductivity— especially by most metals, by seawater, by
wet land, and by wetlands. Some of these make the use of radar altimeters possible.
The radar signals that are reflected back towards the transmitter are the desirable ones that make
radar work. If the object is moving either closer or farther away, there is a slight change in
the frequency of the radio waves, caused by the Doppler Effect.
Radar receivers are usually, but not always, in the same location as the transmitter.
Although the reflected radar signals captured by the receiving antenna are usually very weak,
these signals can be strengthened by electronic amplifiers. More sophisticated methods of signal
processing are also used in order to recover useful radar signals. Radar system can be further
classified into following:
Weather Radar, Radar Altimeter, D.M.E. System. And ELTA Radar
Weather Radar and Antenna
Fig 3.14: Display of WSR output and Weather Antenna

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3.5.1. WHEATHER SYSTEM
Weather systems such as weather radar and lightning detectors are important for aircraft
flying at night or in instrument meteorological conditions, where it is not possible for pilots to
see the weather ahead. Heavy precipitation (as sensed by radar) or severe turbulence (as sensed
by lightning activity) is both indications of strong convective activity and severe turbulence, and
weather systems allow pilots to deviate around these areas.
Lightning detectors like the Storm scope or Strike finder have become inexpensive
enough that they are practical for light aircraft. In addition to radar and lightning detection,
observations and extended radar pictures are now available through satellite data connections,
allowing pilots to see weather conditions far beyond the range of their own in-flight systems.
Modern displays allow weather information to be integrated with moving maps, terrain, traffic,
etc. onto a single screen, greatly simplifying navigation.
Modern weather systems also include wind shear and turbulence detection, terrain and traffic
warning systems. In-plane weather avionics are especially popular in Africa, India and other
countries where air-travel is a growing market, but ground support isn’t as well developed.
Clouds in space are electrically charged, more the charge more dangerous it is for the aircraft.
Clouds are categorized into following colours:
 Red colour (Heavy electrically Charged).
 Yellow Colour (Semi Electrically Charged).
 Green Colour (Indicates Safest Level)
3.5.2. RADIO ALTIMETER
RAM-700A/701A is a “C” band, FM/CW RADIO ALTIMETER capable of providing
accurate height of aircraft above the terrain over which it is flying. The equipment is
compact, light in weight and utilizes all solid-state circuitry. A new feature of the system is a
digital indicator. The output is available either as linear or linear –log or a combination of
both. The system is capable of selecting preset decision heights. A visual indication of the
ensuing danger of flying below the preset level is available on the indicator in the form of a
flickering LED lamp. An additional facility of audio warning to the pilot is also provided
whenever aircraft crosses the decision – preset level the main T/R unit is housed in 1/2ATR
short.
3.5.3. RADAR ALTIMETER
The altimeter shows the aircraft's altitude above sea-level by measuring the difference
between the pressure in a stack of aneroid capsules inside the altimeter and the atmospheric
pressure obtained through the static system. It is adjustable for local barometric pressure which
must be set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules
expand as the static pressure drops therefore causing the altimeter to indicate a higher altitude.
The opposite occurs when descending.

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3.6. SECURITY SYSTEM
System which is employed for emergency purposes, during war times or during calamities like
aircraft crash.
1. E.L.T.(Emergency Locator Transmitter)
2. C.V.R.(Cockpit Voice Recorder)
3. I.F.F.(Identification of Friend and Foe)
3.6.1. E.L.T.(Emergency Locator Transmitter)
ElT is security unit which in case of emergency transmits emergency signals through an omni
directional antenna to all nearby ground beacon when an aircraft crashes down his system
transmits emergency signals to all nearby ground beacons, and on receiving this emergency
signal rescue operations are initiated.
Function of ELT
This is a battery powered unit which automatically comes into operation when the force on
aircraft exceeds 5g force thereby activating the g switches, and thus the elt omni directional
antenna begins to radiate out emergency signals to the nearby ground beacons. This system can
also be used to send rescue signals manually during flight time emergency. This system
generally comes into operation when aircraft crashes down.
Technically Specification
 Operating Frequency : 121.5 MHZ +_ KHZ
I. 243.0MHZ+-12KHZ
II. 406.025MHZ+- 2KHZ
 ELT Battery Rating : 12 volts, 7.5 ampere hr
The installed continuous battery operating life the ELT transmitter is 24 hr at 121.5 MHZ, 243
MHZ and 406.025 MHZ and a minimum of a further 24 hr at 121.5 MHZ and 243MHZ with
Rectangular Wave.
 Modulation Depth 85 %
 Cycle Time : 2.3 Sec
 Sweep Range 1600 to 300 HZ
 Sweep Rate 2.8 Hz
 Modulation Frequency 406.025MHZ
3.6.2. IDENTIFICATION OF FRIENDS OR FOE
IFF stands for Identification of Friends or Foe. This system is used for identifying whether a
flying Aircraft is of friend or of enemy. This system is generally not used in civil aircraft that are

Page | 38
used for passenger flights. However this system binds its importance during war time, thus all
the fighter planes are equipped with this system.
FUNCTION OF I.F.F.
Radar system of ground beacon sends an interrogating signal to the flying aircraft on
receiving interrogating signal IFF transponder fitted on to the aircraft send an automatic
coded reply signal to the ground beacon; which recognizes these codes and identifies the
plane as of friend or of enemy. It works on five modes;
 Mode 1: General Identify (3 usec)
 Mode 2: Personal Identify (5usec)
 Mode 3: Traffic Mode (8 usec)
 Mode 4: Altitude reporting (21 usec)
 Mode 5: secure Mode
Technical Specification
1. Operating Frequency: A.) Receiver 1030 MHZ
B.)Transmitter 1090 MHZ +- 3 MHZ
2. Operating Temperature: -40oC to +55o
C
3. Storage Temperature: -40oC to +80 o
C
4. Altitude: 17 Km
3.6.3. SOLID STATE COCKPIT VOICE RECORDER(SSCVR)
The ECIL Solid State Cockpit Voice recorder (SSCVR) is a four channel voice recorder
intended for installation in civil military (non-combat) aircraft/helicopter for the purpose of
automatically recording during flight the aural communication (conversation) within the aircraft
(among crew members) and outside the aircraft (by radio).
In the event of an accident/incident, the record of these aural communications give useful
information to the aircraft accident/ incident investigation personnel for analysing the reasons for
accident/incident, so that necessary precautions corrective actions could be taken to avoid
recurrence.
GENERAL DESCRIPTION
A cockpit voice recorder (CVR), often referred to as a "black box", is a flight recorder
used to record the audio environment in the flight deck of an aircraft for the purpose of
investigation of accidents and incidents. This is typically achieved by recording the signals of the
microphones and earphones of the pilot’s headsets and of an area microphone in the roof of the
cockpit. The ECIL SSCVR is designed to meet FAA (Federal Aviation Administrator, USA)
specification TSO-C84 and ARINC-557 and has been classified under environmental category as
En. Cat. FAA code: A AAAAX

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Figure 3.15: Cockpit Voice Recorder
Time recorded: 30 min continuous, 2 hours for solid state digital units
Number of channels: 4
Fire resistances: 1200 deg. C /30 min
Water pressure resistance: submerged 20,000 ft.
Underwater locator beacon: 37.5 KHz
Battery: 6yr shelf life
30 day operation
FUNCTIONAL DESCRIPTION OF SSCVR:
This system provides four separate channels of voice recording of either transmitted or
received signals that originate typically at
1. The pilot system.
2. The co-pilot station.
3. The passenger public address system or the third crew member station.
4. In the cockpit area.
The cockpit area microphone is strategically located to pick-up and record cockpit
voice signals while electronically suppressing engine or turbine noises. The MRU continuously
records all voice signals transmitted or received by aircraft crew members. During the received
process, the last 120 minutes of the recorded conversation only is retained and the previous
recording is automatically erased.
The voice stored in the memory is protected from damage against severe conditions like crash,
shocks, and fire and seawater hazards likely to be encountered in the event of serious aircraft
accident.
The MRU consists of an interface; control PCB, crash survivable solid state memory unit and
a power supply. The power supply consist s of two PCBs viz.
a) Power supply PS-1.
b) Power supply PS-2.
The PS-1 converts input of 115V AC, 400Hz to output of 28V dc and PS-2 converts the
28V dc to +5V dc @ 2A, +12V dc @ 333mA minimum and + 18V dc @ 200Ma

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CHAPTER 4
Instrument Shop
4.1. AUTO PILOT INTRODUCTION -
In long flights, to relieve pilot from physical and mental fatigue, so that he can devote his
attention to management and direction of flight. Auto Pilot provides accurate control over
long range periods which invaluable in air and helps to maintain schedule more readily.
Smith’s S.E.P.2 is the name of the automatic pilot employed in Do-228. It controls the flight
providing stability in three axes of Pitch, Roll and Yaw. It uses the rate/rate principle, ratio of
the rate at which controlled is being applied to the ratio at which disturbance is introduced.
Autopilot can be used to maintain a steady climb to operation altitude or to maintain orbit
around airfield while waiting to land. It can also maintain constant altitude.
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle
without assistance from a human being. An autopilot can refer specifically to aircraft, self-
steering gear for boats, or auto guidance of space craft and missiles. The autopilot of an aircraft
is sometimes referred to as "George", after one of the key contributors to its development.
The six dimensions are usually roll, pitch, yaw, altitude, latitude, and longitude. Aircraft
may fly routes that have a required performance factor; therefore the amount of error or actual
performance factor must be monitored in order to fly those particular routes. The longer the
flight, the more error accumulates within the system. Radio aids such as DME, DME updates,
and GPS may be used to correct the aircraft position.
It’s a composite of some instruments like:
Flight panel, Engage, & Trim Indicator, Heading Selector, Gyro unit, Amplifier, Coupling Unit,
Safety Switching, and Roll error cut out, Heading Control Unit, V.O.R Filter, Rudder
servomotor, Aileron servomotor, Elevator servomotor, Auto trims Relay Unit.
The approach to an airfield equipped with Instrument Landing System (I.L.S.) can be made
automatically by coupling the aircraft’s I.L.S. radio receiver. On arrival at the break off
height, the aircraft is correctly positioned for landing and pilot takes over to perform the
landing manoeuvre.
Principle of operation –
Autopilot consists of disturbance detection system (which measures rate of disturbance)
connected to a disturbance corrector. Disturbance detecting devices in S.E.P.2 are Rate
Gyroscopes. One gyroscope can detect disturbance in only one direction so 3 gyroscopes are
mounted mutually at right angles for 3 axes.
4.2. AUTOMATIC FLIGHT CONTROL SYSTEM Automatic flight control system is a
device that automatically steers aircraft. The device controls aircraft using information
provided by sensors along with a detailed set of computerized instructions.

Page | 41
An AFCS reduces the amount of work a pilot must do, makes navigation easier and
improves economy and flight safety. In addition, an aircraft can take over control of particularly
difficult flight operation from a pilot.
It can thus aid a pilot faced with such situations as landing in poor visibility or flying low to
avoid the RADAR detection.
Feedback control system in AFCS obtain the aircraft state e.g. altitude, altitude rates, air
speed, altitude acceleration, etc. from sensors. It uses this information and based on predefined
process, converts them into inputs to actuators.
Audio Flight Control System consists of the following units:
a) Sensors
b) Computer(s)
c) Actuators-parallel and series
d) Annunciator panels
e) Switches on pilot grip and other cockpit location.
The sensor package provides the data need for implementation of all the desired functions,
including acceleration, body rate, air data, velocity data, altitude, altitude heading, etc. to the
flight control computer. The AFCS functions and modes like damping, augmentation, control
and guidance commands are generated in the flight control computer’s system software using
control laws. The control laws define logic, gain & interfaces between the pilot controls, sensors,
feedbacks and actuators. The output electrical signal is provided to the actuator EHSV (Electro
Hydraulic Servo Valves)/ ESV (Electro Servo Valves).
4.3. Gyroscopic Instruments:
A gyroscope is a device for measuring or maintaining orientation, based on the principles of
conservation of angular momentum. In essence, a mechanical gyroscope is a spinning wheel
or disk whose axle is free to take any orientation. This orientation changes much less in
response to a given external torque than it would without the large angular momentum
associated with the gyroscope's high rate of spin. Since external torque is minimized by
mounting the device in gimbals, its orientation remains nearly fixed, regardless of any motion
of the platform on which it is mounted.
Fig 4.2: Gyroscope

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4.3.1. Gyroscopic Principles: principle of gyroscope is based on two properties that are
Rigidity and Precession
 Rigidity in Space: A wheel with a heavily weighted rim spun rapidly tends to
remain fixed in the plane in which it is spinning. It is mounted on a set of gimbals for
free rotation of Gyro in any plane. As the gimbals’ base tilts and twists, the gyro
remains spinning in its original plane. Allows a gyroscope to measure changes in the
attitude or direction of an airplane
 Precession: When an outside force tries to tilt a spinning gyro, the gyro responds as if
the force had been applied at a point 90 degrees in the direction of rotation.
4.3.2. Amplification of gyro signal –
Magnetic Amplifiers are used to provide the necessary amplification with negative feedback
system. The negative feedback signal the S.E.P.2 servo control amplifiers is obtained from a
tacho generator mounted in the servo motors itself so that the feedback signal is directly
proportional to the speed at which servo motor runs. Heading of a modern high speed aircraft
is controlled more readily by ailerons than by rudder.
4.4. FLIGHT ATTITUDE DIRECTION INDICATOR
An attitude indicator (AI), also known as gyro horizon or artificial horizon or Attitude
Director Indicator (ADI, when part of an Electronic flight instrument system), is an
instrument used in an aircraft to inform the pilot of the orientation of the aircraft relative to
Earth's horizon. It indicates pitch (fore and aft tilt) and bank (side to side tilt) and is a primary
instrument for flight in instrument meteorological conditions. Attitude indicators are also
used on manned spacecraft, where they indicate the craft's yaw angle (nose left or right) as
well as pitch and Roll, relative to a fixed-space inertial reference frame.
The essential components of the Indicator are "Miniature airplane", horizontal lines with a
dot between them representing the actual wings and nose of the aircraft. The centre horizon
bar separating the two halves of the display, with the top half usually blue in colour to
represent sky and the bottom half usually dark to represents earth. Degree indices marking
the bank angle. They run along the edge of the dial. On a typical indicator, there is a zero
angle of bank index; there may be 10 and 20 degree indices, with additional indices at30, 60
and 90 degrees. If the symbolic aircraft dot is above the horizon line (blue background) the
aircraft is nose up. If the symbolic aircraft dot is below the horizon line (brown background)
the aircraft is nose down. The fact that the horizon moves up and down and turns, while the
symbolic aircraft is fixed relative to the rest of the instrument panel, tends to induce
confusion in trainees learning to use the instrument; standard mental corrective provided by
flight instructors is "Fly the little airplane, not the horizon."A 45 degree bank turn is made by
placing the indicator equidistant between the 30 and 60 degree marks. A 45 degree bank turn
is usually referred to as a steep turn .The pitch angle is relative to the horizon. During
instrument flight, the pilot must infer the total performance by using other instruments such
as the airspeed indicator, altimeter, vertical speed indicator, directional gyro, turn rate
indicator, and power instruments, e.g. an engine tacho meter.

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"Performance = Attitude + Power".
Figure 4.3: Attitude Director Indicator
4.5. PRESSURIZATION SYSTEM AND PRESSURE GAUGE
A system which ensures the comfort and safety of crew and passengers by controlling the
cabin pressure and the exchange of air from the inside of the aircraft to the outside. Aircraft
engines become more efficient with increase in altitude, burning less fuel for a given
airspeed. In addition, by flying above weather and associated turbulence, the flights smoother
and the aircraft less fatigued. Crews will therefore normally fly as close to the aircraft’s
Cruise Ceiling as they can depending on flight rules and any other constraints such as the
aircraft oxygen system. In order to be able to fly at high attitudes, the aircraft needs to be
pressurized so that the crew and passengers can breathe without the need for supplemental
oxygen. The cabin and cargo holds (or baggage compartments) on most Aircraft are
contained within a sealed unit which is capable of containing air under pressure higher than
the Ambient Pressure outside of the aircraft. Bleed Air from the turbine engines is used to
pressurize the cabin and air is released from the cabin by an Outflow Valve. By using cabin
pressure regulator, to manage the flow of air through the outflow valve, the pressure within
the aircraft can be increased or decreased as required, either to maintain a set Differential
Pressure or a set Cabin Altitude.
FIGURE 4.4: PRESSURE GAUGE & PRESSURIZATION SYSTEM

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4.6. HYDRAULIC SYSTEM
The hydraulic system is powered by two engine-driven pumps, one on each engine, and
operates the following services: landing gear retraction and lowering; nose-wheel steering; and
wheel brakes.
4.7. FUEL SYSTEM
The fuel capacity of the aircraft is approximately 12,240 pounds. The fuel is carried in
two integral wing tanks each with a usable fuel capacity of 720 Imperial gallons. There are two
electrically operated boost pumps in each tank that feed fuel to the engine driven pumps. During
all phases of flight, all boost pumps are normally selected ON. With no boost pumps operating,
the engines will continue to operate; however, there is a risk of cavitations of the engine driven
fuel pumps when operating with the boost pumps off, and this risk increases with an increase in
altitude and/or engine power. The four boost pumps were found to be operable.
Figure 4.5: Fuel flow indicator
4.8. FLIGHT INSTRUMENTS
These are those instruments which are used in the Aircraft cockpit
FIG 4.6: Cockpit Instruments and Indicating Devices
In the cockpit of an aircraft there are various instruments that provide the pilot with
information about the flight situation of that aircraft, such as height, speed and altitude. These
flight instruments are of particular use in conditions of poor visibility, such as in clouds,
when such information is not available from visual reference outside the aircraft. The
following are the basic instruments that can be found in the cockpit of the aircraft:

Page | 45
Altimeter
The altimeter shows the aircraft's altitude above sea-level by measuring the difference between
the pressure in a stack of aneroid capsules inside the altimeter and the atmospheric pressure
obtained through the static system. It is adjustable for local barometric pressure which must be
set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules expand and
the static pressure drops, causing the altimeter to indicate a higher altitude. The opposite effect
occurs when descending. With the advancement in aviation and increased altitude ceiling the
altimeter dial had to be altered for use both at higher and lower altitudes. Hence when the
needles were indicating lower altitudes i.e. the first 360 degree operation of the pointers was
delineated by the appearance of a small window with oblique lines warning the pilot that he is
nearer to the ground. This modification was introduced in the early sixties after the recurrence of
air accidents caused by the confusion in the pilot's mind. At higher altitudes the window will
disappear.
Principle and Working:
Altimeter works on the principal of pressure difference at the sea level and the height at
which aircraft is flying. Pressure measurement can be done by either mechanical or electrical
means.
Different types of altimeter:
 Radar altimeter
 Digital altimeter
 Digital encoding altimeter
Radar altimeter:
It measures altitude directly using the time taken for a radio signal to reflect from the surface
back to the aircraft and used to measure height above ground level during landing in
commercial and military aircraft. It generally forms a component of terrain avoidance
warning systems hence warn the pilot if the aircraft is flying too low, or if there is rising
terrain ahead.
Air Speed Indicator (ASI):
The airspeed indicator shows the aircraft's speed (usually in knots ) relative to the
surrounding air. It works by measuring the ram-air pressure in the aircraft's piton tube. The
indicated airspeed must be corrected for air density (which varies with altitude, temperature
and humidity) in order to obtain the true airspeed, and for wind conditions in order to obtain
the speed over the ground. Digital airspeed indicator indicates airspeed on a display having
high contrast LCD in digital format and by a stepper motor driven pointer. This type of air
speed indicator has continuous Built-In-Test.
Principle: The ASI is a sensitive, differential pressure gauge which measures and promptly
indicates the difference between pitot (impact/dynamic pressure) and static pressure.

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Fig. 4.7: Air Speed indicator and Digital Airspeed Indicator
Vertical speed indicator
The VSI (also sometimes called a barometer, or rate of climb indicator) senses changing air
pressure, and displays that information to the pilot as a rate of climb or descent in feet per
minute, meters per second or knots.
Magnetic compass
The compass shows the aircraft's heading relative to magnetic north. While reliable in steady
level flight it can give confusing indications when turning, climbing, descending, or accelerating
due to the inclination of the Earth's magnetic field. For this reason, the heading indicator is also
used for aircraft operation. For purposes of navigation it may be necessary to correct the
direction indicated (which points to a magnetic pole) in order to obtain direction of true north or
south (which points to the Earth's axis of rotation).
Attitude indicator
The attitude indicator (also known as an artificial horizon) shows the aircraft's relation to the
horizon. From this the pilot can tell whether the wings are level and if the aircraft nose is
pointing above or below the horizon. This is a primary instrument for instrument flight and is
also useful in conditions of poor visibility. Pilots are trained to use other instruments in
combination should this instrument or its power fail.
Heading indicator
The heading indicator (also known as the directional gyro, or DG; sometimes also called the
gyrocompass, though usually not in aviation applications) displays the aircraft's heading with
respect to magnetic north. Principle of operation is a spinning gyroscope, and is therefore subject
to drift errors (called precession) which must be periodically corrected by calibrating the
instrument to the magnetic compass. In many advanced aircraft (including almost all jet aircraft),
the heading indicator is replaced by a horizontal situation indicator (HSI) which provides the
same heading information, but also assists with navigation.
Additional panel instruments that may not be found in smaller aircraft:
Course deviation indicator
The CDI is an avionics instrument used in aircraft navigation to determine an aircraft's lateral
position in relation to a track, which can be provided by a VOR or an instrument landing system

Page | 47
(ILS).This instrument can also be integrated with the heading indicator in a horizontal situation
indicator.
Radio magnetic indicator
An RMI is generally coupled to an automatic direction finder (ADF), which provides bearing
force.
The following basic instruments used in aircrafts are mentioned below:
TACHO METER
It Measures the speed of the engines in order to measure the accurate house power due to its
rotations.
PRESSUMARISATION SYSTEM
It used to test the pressure controller, discharge valve and mass flow controller in order to
overcome the difference of pressures at the mean sea level and at the particular height at
which the aircraft is flying. The pressurization of aircraft cabin is carried out with the help of
this system.
STALL TRANSDUCER
The purpose of this transducer is to indicate the stalling conditions of aircraft. i.e. to know the
conditions of failure occurring in the aircraft.
AUTO PILOT SYSTEM
Its main purpose is to relieve the human pilot from stresses and strains during long flights and
engage the flight of aircraft automatically.
FUEL QUANTITY INDICATOR
It is used to know the quantity of fuel required or left during flight.
DESIGYN SYSTEM
It is used to check the spill valve indicator, fuel datum indicator, flap position indicator, water
methanol indicator and torque pressure indicator.
WARNING CAUTION PANEL
To provide Audio & Visual indications to pilot in case of faults.
NAVIGATION CONTROL PANEL
It is used to select the designed VOR frequency.
TURBINE GAS TEMPERETURE INDICATOR (T.G.T.) & TURBINE
TEMPERETURE INDICATOR (I.T.T.)
It Works on the see-back effect is used to know the exact temperature required for the proper
working of the engine during flight in order to avoid accident and it is installed in jet pipes.

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WATER METHENOL TRANSMITTERN & INDICATOR
Water methanol transmitter& indicator display the level liquid in aircraft water and oil tanks.
FUEL FLOWINDICATOR
Fuel quantity indicator gives an indication of the rate of consumption of fuel.
RPM INDICATOR
The RPM indicator provides the speed of the engine in RPM. It is essential during take-off
and landing, testing, idle running etc. of engine and further to as certain economic operation
of engine at cruising speed.
ENGINE SPEED GENERATOR
The electrical Engine speed Generator is used on aircraft engines, and may be operated in
conjunction with a Techometer indicator to obtain a remote indicator of engine speed. The
generator is fitted with two permanent magnet rotor and provides an AC Voltage which
varies in frequency proportional to engine speed.
SYNCHROSCOPE
The Synchroscope are used in four engine and two engine aircraft to indicate the degree of
synchronism existing between one engines, designed “master” and the remaining engine or
engines.
OIL PRESSURE AND TEMPERATURE INDICATORS
The Oil Pressure and Temperature indicators are used with an indicator Pressure transmitter
and a resistance thermometer bulb to provide remote information of the pressure and
temperature at a point in engine or an aircraft system.
QNH
It is one of the many Q codes. It is defined as, "barometric pressure adjusted to sea level." It is a
pressure setting used by pilots, air traffic control (ATC), and low frequency weather beacons to
refer to the barometric setting which, when set on an aircraft's altimeter, will cause the altimeter
to read altitude above mean sea level within a certain defined
SERVOMOTOR SYSTEM IN THE AIRCRAFT:
Three types of servomotor are used in the aircraft
 rudder servomotor:
 elevator servomotor:
 aileron servomotor:
Basically servomotor is used to rapidly sudden change in angular position in the wing
Pressure controller type: -- in overhaul process it is a mass flow controller; the controller is
designed so that the rate of cabin altitude and the actual altitude at which the cap in pressure
is to be maintained are controlled by aircraft;
 Isobaric control:
 Rate of change:

Page | 49
CHAPTER 5
RESULTS, DISCUSSION AND CONCLUSION
5.1 RESULTS
5.1.1 AVRO aircraft HS-748
5.1.1.1 INTRODUCTION
The Hawker Siddeley HS 748 is a medium-sized turboprop airliner originally designed by
the British firm Avro in the late 1950s as a replacement for the now-aged DC-3s then in
widespread service as feeder liners. Avro concentrated on performance, notably
for STOL operations, and found a dedicated market. 380 aircraft were built by Hawker Siddeley.
Figure 5.1: AVRO aircraft, Hawker Siddeley HS 748
5.1.1.2. DEVELOPMENT
The original 748 design started in 1958 after the infamous Duncan Sandy’s 1957 Defence
White Paper ended most military manned aircraft development in the UK, and Avro decided to
re-enter the civilian market.
The first Avro 748 flew from the company's Woodford, Cheshire plant on 24 June 1960,
and the two prototypes quickly proved the type's short field performance. 18 Avro 748 Series
1aircraft were produced, the first for Skyways Coach-Air being delivered in April 1962.
However, the majority of the series 1 were delivered to Airlines Argentina’s. By this point,
Avro's individual identity within the Hawker Siddeley Group had ended and the design became
known as the HS 748.
The 748 Series 1 and Series 2 were license-produced in India by Hindustan
Aeronautics as the HAL-748. HAL built 89 aircraft in India, 72 for the Indian Air Force and 17
for the Indian Airlines Corporation.
The ICAO designator as used in flight plans is A748.

Page | 50
Table 5.1 VHF CHANNEL FREQUENCY IN HS-748 (MHz)
CH. NO FREQUENCY CH. NO FREQUENCY
1) 122.35 2) 123.75
3) 119.8 4) 119.6
5) 122.7 6) 123.5
7) 122.3 8) 118.3
9) 124.85 10) 127.9
11) 118.1 12) 121.9
13) 132.7 14) 119.7
15) 118.6 16) 120.9
17) 126.4 18) 126.8
19) 129.2 M:- MANUAL FOR SELECTING FREQUENCY
5.1.1.3. SPECIFICATION OF AVRO
Power plant Performance capacity
Engine dry weight = 1583 lbs. Maximum take-off wt. =43,500 lbs.
Propeller diameter = 12FT Loading wt. = 41,500 lbs.
Wings Max. Zero fuel wt. = 36, 300 lbs.
Span = 98FT 6 INCH Max. Passenger= 40
Incidence angle = 3 DEGREE
5.1.2. DORNIER 228
5.1.2.1. INTRODUCTION
The Dornier 228 is a twin-turboprop STOL utility aircraft, manufactured by Dornier
GmbH (later DASA Dornier, Fairchild-Dornier) from 1981 until 1998. In 1983, Hindustan
Aeronautics (HAL) bought a production license and manufactures the 228 for the Asian market
sphere. Approximately 270 Do228 were built at Germany and Kanpur, India. In August 2006,
127 Dornier Do 228 aircraft (all variants) remain in airline service.
Figure 5.6: DORNIER 228 aircraft

Page | 51
It is basically the same aircraft with improved technologies and performances, such as a
new five blade propeller, glass cockpit and longer range. The first delivery was in September
2010.
5.1.2.2. DORNIER 228 SPECIFICATIONS
GENERAL CHARACTERISTICS
Crew: 2 Pilots
Capacity: 19 Passengers
Length: 16.56 M (54 Ft 4 In)
Wingspan: 16.97 M (55 Ft 8 In)
Height: 4.86 M (15 Ft 11 In)
Wing Area: 32.0 M² (344 Sq. Ft)
Empty Weight: 3,739 Kg (8,243 Lb.)
Max. Take-off Weight: 6,600 Kg (14,550 Lb.)
5.1.2.3. ROLES
Maritime Surveillance
Pollution Prevention
Troop Transport
Aerial Survey
Search and Rescue
Commuter Transport
Calibration of airport NAV-COM Aids
Remote Sensing Applications
Causality Evacuation
Executive Transport
Cargo & Logistics Support
5.1.3. IJT
Figure5.7: IJT

Page | 52
5.1.3.1. DESCRIPTION
The Intermediate Jet Trainer (IJT) christened as HJT-36 is indigenously designed and
developed by HAL to replace ageing fleet of KIRAN Jet Trainer aircraft in service with
Indian Air Force for Stage II training of its pilots. IJT will be fitted with AL-55i Jet engines
produced in house at Engine Division Koraput. IJT incorporates the simplicity necessary for
ease of conversion from Basic Piston Trainer and the sophistication required for quick
conversion to the complexities of an Advanced Jet Trainer.
 MAIN DIMENSIONS
Span - 10.00 m
Length - 11.00 m
Height - 4.40m
 WEIGHTS
Clean aircraft weight - 4250 kg
Max. all up weight - 5400 kg
Max. usable fuel (without drop tank) - 900 kg
Max. usable fuel (with drop tank) - 1370 kg
 FUSE LAGE
Fuselage Length - 11.00 m
Maximum Width (without intakes) - 1.00 m
Maximum height - 1.82 m
 PERFORMANCE
Max Speed / Mach No. - 750 Km/h / 0.75
Max permitted load factors - +7.0/ -2.5 g
Max. rate of climb - > 1500 m/ min
Stall speed (clean Configuration) - < 185 km/h
Take off run - < 500 m
Landing Roll - < 500 m
5.1.3.2. ROLES
Pilot Training
General flying
Navigation formation flying
Instrument & cloud flying
Basic air to ground & air to air weapon aiming
Tactical flying
Night flying

Page | 53
5.2. DISCUSSION
In HAL TAD there is a Dornier final assembly section which is generally divided in some
sections which are as follows:
FUSELAGE
It’s has also a 3 sections they are classified as:
- FCS (Fuselage Centre Section)
- FRS (Fuselage Rear Section)
- FFS (Fuselage Front Section)
In all of three sections several things are made are as follows:
Seat rail, NLG, Lower Shell, Panels & Frames, FCS real Coupling, FFS-Nose, FRS-Upper, FRS-
Lower, FRS Coupling, FFS Assembly.
CONTROL SECTION
In this section several things are made are as follows:
RH wing, Centre Wing, Aileron, Elevator, Rudder, Fin (Vertical Stabilizer), Tail plane
(Horizontal Stabilizer).
Some points about Dornier
 it has high wings
 for preventing leakage in wings we used “thikol”
AVIONICS SECTION
In this several systems are used like NAVIGATION, COMMUNICATION, and BLACK
BOX etc.
ELECTRICAL SECTION
In this several systems are used like Alternators, Generators, Invertors, Motor &
Regulators, Control & Potential units, Booster pump, and Voltage regulators.
MECHANICAL SECTION
In this several systems are used like Landing gear, Actuator & Their Accessories,
Hydraulic System, and Wheel& Brake Assembly.
PROPELLER & ENGINE SECTION
In this several systems are used like Propeller, Gear Box, Propeller Control Unit, Fuel
System Valve, and De-icing System.

Page | 54
5.3. CONCLUSION
HINDUSTAN AERONAUTICS LIMITED is a leading aerospace company of India engaged
in design, manufacture & overhaul of a variety of aviation products from basic air trainer
Aircraft to highly sophisticated fighters, bombers, helicopters, transport A/C, power plant.
Being a student of B.Tech from University Institute of Engineering & Technology, C.S.J.M.
University KANPUR, I have completed my six weeks training at Hindustan Aeronautics
Limited - Transport Aircraft Division, Kanpur after 6th semester of my B.Tech. During six
weeks summer training, I have concluded that really this organization has been playing a
crucial role in strengthening defence forces of country.
In the periods of six weeks I deeply studied & analyzed all the considerable facts
regarding HAL, TAD Kanpur. I concentrated my attention towards working of
instrumentation and Avionics shops of Rotables Overhaul department of TAD, Kanpur.
It is difficult to elaborate all the things which I learned during the summer training project. I
have accumulated the desired information through personal observation, study of documents
& discussion. In these six weeks of summer training I came to know how theoretical
knowledge can be applied in practical and learned a lot of other engineering concepts.
.
Shikha Prajapati
B.Tech 6th
Semester (E.C.E.)
Vocational Trainee
(HAL-TAD Kanpur)

Page | 55
Reference
1. www.wikipaedia.org
2. www.aerospaceweb.org
3. www.hal-india.com
4. en.wikipedia.org/wiki/Flight instruments
5. www.aviastar.org/theory/basics_of_flight/index.html
6. aerospace.honeywell.com
7. Becker Avionics (AS-3100 Reference Manual)
8. Avionics International Incorporation (Static Inverter Reference Manual)
9. Collins Ltd. (Navigation Systems Reference Manual)
10. Honeywell (GPS – KLN 900 Reference Manual)
11. Google Image Results – for various images used in Report
12. Warren F. Phillips, Professor Mechanical and Aerospace Engineering Utah State
University “Mechanics of Flight” Published by John Wiley and Sons, Inc.
13. Max F. Henderson “Aircraft Instruments and Avionics”

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