Main Report

PREFACE

The report on the following pages is the outcome of six weeks training at the

industry.

The report is the outcome of the practical knowledge that we acquire during our

training. This report presents the brief summary of our industrial training.

I had the privilege of receiving such training at HINDUSTAN

AERONAUTICS LIMITED ,LUCKNOW.

There could not be a better place to learn…

ACKNOWLEDGEMENT

I would like to express my sincere gratitude to the management of

HINDUSTAN AERONAUTICS LIMETED for having given this opportunity

to carry out my training.

I am grateful to my esteemed guide Mr.Dy. General manger of instrument

department for his whole hearted cooperation and support.

I also acknowledge my gratefulness to Mr. Nirmaljeet Singh, training and

placement officer, H.E.C. Jagadhri, for giving me the opportunity to undergo

this training

And last but not the least, I would like pay my sincere gratitude to all the

employees of the HAL , LUCKNOW, for there valuable help and technical

support at various times.

COMPNY PROFILE

HINDUSTAN AERONAUTICS LIMITED

LUCKNOW

The history of the Indian Aircraft Industry can be traced to the founding of Hindustan Aircraft Limited at Bangalore in December 1940 in association with the erstwhile princely State of Mysore and late Shri Seth Walchand Hirachand, an Industrialist of extra -ordinary vision. Govt. of India became one of its shareholders in March 1941 and took over the management in 1942. Hindustan Aircraft Limited was merged with Aeronautics India Limited and Aircraft Manufacturing Depot, Kanpur to form Hindustan Aeronautics Limited (HAL) on 01st October 1964.

Today HAL has got 16 production units and 9 research and design centers spread out in seven different locations in India. Its product track record consists of 12 types of aircraft from in house R &D and 13 types by license production. HAL has so far produced over 3300 aircraft, 3400 Aeroengines and overhauled over 7700 aircraft and 26000 engines.

HAL has engaged & succeeded in number of R & D programs for both the military and civil aviation sectors. Substantial progress has been made in the current projects like Dhruv -Advanced Light Helicopter (ALH), Tejas-Light Combat Aircraft (LCA), Intermediate Jet Trainer (IJT) and various military and civil upgrades. The deliveries of Dhruv were effected to Indian Army, Navy, Air Force and Coast Guard in March 2002, in its first year of production which is a unique achievement.

HAL has played a significant role for India's space programs in the manufacturing of satellite launch vehicles like PSLV (Polar Satellite Launch Vehicle), GSLV (Geo Stationary Launch Vehicle), IRS (Indian Remote Satellite) & INSAT (Indian National Satellite).

HAL has also two joint venture companies, BAeHAL Software Limited and Indo- Russian Aviation Limited (IRAL). Apart from the two, other major diversification projects are Industrial Marine Gas turbine and Airport Services. Several co-production and joint Ventures with international participation are under consideration.

HAL's supplies / services are mainly to Indian Defence Services, Coast Guard and Border Security Force. Transport aircraft and Helicopters have also been supplied to Airlines as well as State Governments of India. The Company has also achieved a foothold in export in more than 30 countries, having demonstrated its quality and price competitiveness.

HAL, has won several International & National Awards for achievements in R&D, Technology, managerial performance, exports, energy conservation,

quality and fulfillment of social responsibilities. M/S Global Rating, United Kingdom in conjunction with The International Information and Marketing Center (IIMC) has awarded the “INTERNATIONAL GOLD MEDAL AWARD” AT THE INTERNATIONAL SUMMIT (GLOBAL RATING LEADERS 2003) LONDON, UK to M/s. Hindustan Aeronautics Limited for Corporate Achievement in Quality and Efficiency. HAL was also presented the INTERNATIONAL “ ARCH OF EUROPE” AWARD IN GOLD CATEGORY in recognition for its commitment to Quality, Leadership, technology & Innovation. At National level, HAL won the top award instituted- by SCOPE (Standing Conference of Public Enterprises) -The "GOLD TROPHY" for excellence in Public Sector Management.

The Company scaled new heights in the financial year 2002-2003 with a turn over of Rs. 3120 Crores and export of Rs. 103.89 Crores.

“To become a globally competitive aerospace industry while working as aninstrument for achieving self reliance in design, manufacture and maintenance ofAerospace equipment, civil transport aircraft, helicopter and missiles and diversifying to related areas, managing the business on commercial lines in aclimate of growing professional competence.”

In the six decades, HAL has spread its wing to cover various activities in the areas of Design, Development, Manufacture and Maintenance. Today HAL has 16 production divisions spread over at Bangalore, Nasik, Koraput, Kanpur, Lucknow, Korwa, Hyderabad and Barrackpore. These divisions are fully backed by nine Design Centres, which are co-located with the production divisions. These centres are engaged in the Design and Development of combat aircraft, helicopter, Aeroengine, Engine Test Beds, Aircraft communication and Navigation systems and Accessories of mechanical and fuel systems and instruments. Its product track record consists of 12 types of aircraft from in house R &D and 13 types by license production. HAL has so far produced over 3300 aircraft, 3400 Aeroengines and overhauled over 7700 aircraft and 26000 engines.

The current programme are series production of ALH and delivery to our defence and civil customers, production of Jaguar, the deep penetration strike aircraft, Dornier Do-228, Multi Mission Aircraft and LANCER the Light Attack Helicopter and upgrades of MiG-21 BiS, MiG-27 M and Jaguar. With the signing of Inter Governmental Agreement and General Contract the license manufacture of SU MkI has been launched.

HAL is the major design partner for aircraft and system / equipment as well as for system integration of Light Combat Aircraft (LCA) which

successfully completed the first block of flights.The new initiative in R & D will include an Intermediate Jet Trainer ( IJT ), a trainer for the 21st century, Light Observation Helicopter, replacement for Cheetah and Chetak Helicopter and a Light Attack Helicopter, a follow- on project for ALH.Partnership for co-production of ATR-42, an invitation from Airbus to participate in A-380 project, and the new project to design and develop a Multirole Transport Aircraft (100 seater) are signs of growth for the largely military aircraft manufacturing company in the commercially competitive aerospace industry.Design capabilities, modern facilities and skills combined with competitive pricing and prompt deliveries, make HAL a valuable partner for challenging programmes in Aerospace and related fields.

MAJOR PRODUCTS OF THE H.A.L. DIVISION

The major products of the Division are:

Undercarriage systems

Wheels and Brake systems

Hydraulic Systems

Aircraft and Engine Fuel Systems

Panel Instruments (Barometric and gyroscopic)

Electric Power Generation and Control systems

Environmental control systems.

Flight Control Actuators

Ground Support Equipment and test Rigs.

Main Customers

i) Indian Air Force, Army, Navy, Coast Guard, BSF

ii) Defence R&D Laboratories and Deptt of Space;

iii) Civil Aviation, State Govt., Ordnance Factories, Corporate Sectors;

iv) Flying Academies & Educational Institutions;

v) Airlines, Air Taxi, Air Cargo;

vi) Overseas customers for civil and military applications.

vii) Collaborators and Licensors.

ORGANISATIONALGROWTH OF HAL

Expansion of Nasik Division as Aircraft Manufacturing &

Overhaul Division

Establishment of SUKHOI ENGINE DIVISION at Koraput200

2

Establishment of Airport Service Center for coordinating the operation of HAL airport -Bangalore 2000

Establishment of Industrial &marine Gas Turbine Division for aero derivative gas turbines/industrial engines1998

Establishment of AEROSPACE DIVISION for structure of Aerospace Launch Vehicles1988

Establishment of KORWA DIVISION for Advanced Avionics1982

Establishment of FOUNDARY & FORGE DIVISION at Bangalore197

4

Establishment of HELICOPTER DIVISION at Bangalore197

0

Establishment of LUCKHNOW DIVISION for Accessories &

instruments

Establishment of HINDUSTAN AERONAUTIC LIMITED by merging of 3 companies196

4

Establishment of Aeronautics India LTD. At Nasik, Koraput & Hyderabad for MiG Airframe, Engines & Avionics196

2

Establishment of aircraft Manufacture DEPOT at

Kanpur for HS-7481960

Establishment of Engine Division at Bangalore1956

Hindustan Aircraft Limited at Bangalore1940

HAL ACCESSORIES DIVISION - LUCKNOW

The Division was established in 1970 with the primary objective of manufacturing systems and accessories for various aircraft, helicopters and engines with a view to attain self-sufficiency in this field in the country. The Division started with the manufacture of hydro-mechanical accessories and instruments under license for Marut and Kiran aircraft. This was followed by license manufacture of accessories for MiG-21 aircraft, Cheetah/Chetak helicopters, Dornier and other defense applications. Additionally repair and overhaul of Lucknow manufactured accessories as well as those fitted on directly purchased aircraft, such as Mirage and Sea Harrier was undertaken. At present, it is manufacturing, repairing and overhauling more than 800 different types of systems and accessories under license. The range of items cover units for hydraulics, engine fuel system, environment control system, pressurization system, gyroscopic instruments, barometric instruments, electrical system items, undercarriages, and electronic items. The number of licensors exceeds twenty.

From inception, the Division has laid emphasis on developing indigenous capability through design and development of various systems and accessories. This capability has culminated in indigenous design and development of a variety of systems and accessories for the Light Combat Aircraft (LCA), Advanced Light Helicopter (all versions i.e. Army, Airforce, Navy & Civil) and Intermediate Jet Trainer (IJT-36). The Division has also developed and has made successful strides into the area of Microprocessor based control systems. Design and Development capabilities include Environmental Control Systems & Pneumatics, Fuel Management, Engine Fuel Control & aircraft fuel systems, Microprocessor based Controllers, Hydraulic System & Power Controls, Wheels and Brakes, Cockpit instruments and sensors, Gyroscopes, Electrical Power Control Protection, Navigation and Display, Land Navigation, Ground support equipment, Dedicated Test rigs, and Computerised test equipment. The Division has diversified in other defence applications like tanks and armoured vehicles for Army, and took commercial applications of Hydraulic items, Gyroscopic Equipment, Special Purpose Test Equipment & Ground Support Equipment.

The Division has also made steady progress in the area of Exports. The range of products and services available for exports include:

1. Rotables and spares of Jaguar International and Cheetah (Lama), Chetak (Alouette) Helicopters;

2. Ground Support Equipment for MiG 23, 27, 29 Mirage-2000, Jaguar, LCA, Su-30, Sea-Harrier, Dornier DO-228, Avro HS-748, Cheetah, Chetak, MI-17, and

ALH.3. Repair and Overhaul of aircraft accessories of MiG series, Jaguar International,

Cheetah (Lama), Chetak (Alouette) and Dornier. The Division today has a prime name in the aviation world and a number of international companies are interested to join hands with it for future projects.

H.A.L. accessory division , Luknow is divided into three main factories namely1. Mechanical Factory2. Instrument Factory3. Fuel Factory

INSTRUMENT FACTROY

This factory deals with the testing and assembly of electronics instruments used in aircraft e.g. Altimeter,RMI, Gyro-magnetics compass , black box etc.

This INSTRUMENT FACTORY is further divided into four units which are as follows:

CLEAN ROOMS ASSEMBLY AND TEST SHOP 2 & 3 ELECTRO ROTATING MACHINES GROUND LAND NAVIGATION SYSTEM SHOP (G.L.N.S Shop)

» Clean room In Clean room those subunits are assembled and tested that are sensitive to dust, temperature and humidity. All these parameters are kept under control because these can have adverse effect on their functional efficiency. The required specification for the instruments assembled and tested are different .so Clean room is further subdivided into three units. The following chart is given for the classification of clean room.

STANDARD CLEAN ROOM CONDITIONS:

ROOM ITEM Temp Limits

°C

Humidity R/H %

Dust CountParticle size

0.5 /ft3

AIRCRAFT

ROOM 1

ROOM 2

ROOM 3

Gyroscopic Instruments of Russian Origin

Barometric Instruments, Accelerometers, RPM Indicator of Western Origin

Gyroscopic Instruments of Western Origin

15 to 25 ° C

15 to 25 ° C

15 to 25 ° C

45 -55

45 -55

45 -55

<100,000CLASS C – UNMONITORED

<100,000CLASS B

<10,000CLASS A - MONITORED

MIG 21, 27, AN – 32

Kiran MK-I&II, HPT-32, Jaguar, AN-32, Mirage, Dornier, Avro Aircraft, Cheetah, Chetak, ALH Helicopters

Kiran MK-I&II, HPT-32, Jaguar, AN-32, Mirage, Dornier, Avro Aircraft,Lakshya, Cheetah, Chetak Helicopters

» Assembly and test shop 2 & 3

The major products of H.A.L. are fighter aircrafts. An aircraft comprises of many small units or accessories, which play significant role in their successful flight . any fault, may lead to an catastrophic end. Here comes the role of assembly and test unit .it forms an integral part of any manufacturing unit. The main instrument were KCN-2 compass system, flight data recorder, gyro magnetic compass, fuel gauging system, radio magnetic indicator, millivolt meter temperature indicator.

» Electromagnetic rotating shop (E.R.M) In the E.R.M department of the instrument factory the assembly and testing of the dc Starter Generators, AC Generator system, Constant speed alternator, Regulators, Inverter, of the Russian and French origin. These products are basically those products which takes the principle of the electro magnetic rotating which can be elaborated as follows i.e., electrical energy is converted into mechanical energy or vice versa. These products are of mig-21 & mig-27 aircrafts which is of Russian origin and jaguar aircraft is of France origin.

» Ground land navigation system shop (G.L.N.S)

Ground land navigation system shop is one of the most different & unique shop. As in this shop it manufacture the only ground land navigation system in world. As due the different applicability of the gyros therefore these gyros have been placed in the road transportation system which is used in ground e.g. trucks, cars. The instrument which uses the property of any type of gyro and is installed in road transportation system is known as ground land navigation system. The Gyro land navigation system is an electronic navigation device used for guiding any army vehicle to its destination point. The principle objective of system is not only to ease the in more precise and quicker manner whether in plains, hills or sand dunes, where there are no special remarks. In the G.L.N.S shop it assembles and test the ground land navigation system of Vijayanta tank

INSTRUMENT SYSTEMS OF AN AIRCRAFT

Instrument Systems

Just as in a car, there are instruments that monitor the engine, and instruments that monitor the "flight" or drive. So in aircraft the same way we can separate the gizmos, dials and whirligigs into two groups by function in any aircraft. So these two group are as fowllows:

1. Engine Instruments2. Flight Instruments

» Engine Instruments

Every car has an indicator to let you know when you need petrol. A red light comes on if oil pressure drops, or oil temperature is increasing. There is a gauge to tell you if the battery is charging. The general condition of the running motor is available to the driver at all times. The same is true in an airplane. Airplanes have added redundancy increasing the options if one system fails, since you cannot pull over and call road-side service. Engine instruments in the simple single-engine airplanes are:

Fuel gauges Oil pressure Oil temperature Cylinder Head temperature Exhaust gas temperature Nainfold temperature RPM Altimetere/genrator

For multi-engine airplanes, there is a complete set of these instruments for each engine. That's why some cockpits look so confusing. These instruments alert the pilot to engine operation and condition as the flight progresses.

The more complex the aircraft systems, the more instruments needed to monitor the health of those systems. Aircraft with hydraulic systems have to allow for redundancy and often have dual hydraulics with mechanical back up capabilities all as individual indicators.

» Flight Instruments

As pilot flew there aircraft with only "needle, ball and airspeed". This is refered to the compass, a level, and a speedometer or airspeed indicator. Now these are still in use, but added with a few things to keep up with technological advances and flight research. What does a pilot want to know? Airspeed, altitude, heading, rate of turn, feet per minute in climb or descent, and the attitude of the airplane as compared to the horizon.

These are the basic six instruments. Here's a review of the Basic Six instruments found in the cockpit of any plane. Their position varies, but these six are always there

Fig.1. The Basic Six Instrument inside any cockpit

Fig.2.The basic six

Airspeed Indicator

Altimeter

Vertical SpeedIndicator

Attitude Indicator

Directional Gyro

Turn Indicator

The flight instruments give the pilot feedback on the three axes and his own skill and coordination. Instructors like to cover them up, just to see how well a pilot can fly by the seat of his or her pants or strictly by "feel". The instructors also like to place a "view limiting device" on the pilot to ensure that the pilot is relying on the instruments alone and not using outside visual references. Pilots must trust the instruments since the human body often gives false sensations. That is why there are redundant instrument systems. As these flight instruments were basically based on the principle of GYRO. So also sometimes these are called GYROSCOPIC INSTRUMENTS.

Gyroscopic Systems and Instruments

» GENERAL

The gyro instruments include the heading indicator, attitude indicator and turn coordinator (or turn-and-slip indicator). Each contains a gyro rotor driven by air or electricity and each makes use of the gyroscopic principles to display the attitude of the aircraft. It is important that instrument pilots understand the gyro instruments and the principles governing their operation.

» PRINCIPLES

1. RIGIDITY IN SPACE:

The primary trait of a rotating gyro rotor is rigidity in space, or gyroscopic inertia. Newton's First Law states in part: "A body in motion tends to move in a constant speed and direction unless disturbed by some external force". The spinning rotor inside a gyro instrument maintains a constant attitude in space as long as no outside forces change its motion. This stability increases if the rotor has great mass and speed. Thus, the gyros in aircraft instruments are constructed of heavy materials and designed to spin rapidly (approximately 15,000 rpm for the attitude indicator and 10,000 rpm for the heading indicator).

Fig.3. Universally Mounted Gyro

The heading indicator and attitude indicator use gyros as an unchanging reference in space. Once the gyros are spinning, they stay in constant positions with respect to the horizon or direction. The aircraft heading and attitude can then be compared to these stable references. For example, the rotor of the universally mounted gyro (See Universally Mounted Gyro figure, on the right) remains in the same position even if the surrounding gimbals, or circular frames, are moved. If the rotor axis represents the natural horizon or a direction such as magnetic north, it provides a stable reference for instrument flying.

2. PRECESSION :

Another characteristic of gyros is precession, which is the tilting or turning of the gyro axis as a result of applied forces. When a deflective force is applied to the rim of a stationary gyro rotor, the rotor moves in the direction of the force. When the rotor is spinning, however, the same forces causes the rotor to move in a different direction, as though the force had been applied to a point 90° around the rim in the direction of rotation (See the Precession Force figure, below right). This turning movement, or precession, places the rotor in a new plane of rotation, parallel to the applied force.

Fig.4. Precession Force

Unavoidable precession is caused by aircraft maneuvering and by the internal friction of attitude and directional gyros. This causes slow "drifting" and thus erroneous readings. When deflective forces are too strong or are applied very rapidly, most older gyro rotors topple over, rather than merely precess. This is called "tumbling" or "spilling" the gyro and should be avoided because it damages bearings and renders the instrument useless until the gyro is erected again. Some of the older gyros have caging devices to hold the gimbals in place. Even though caging causes greater than normal wear, older gyros should be caged during aerobatic maneuvers to avoid damage to the instrument. The gyro may be erected or reset by a caging knob. Many gyro instruments manufactured today have higher attitude limitations than the older types. These instruments do not "tumble" when the gyro limits are exceeded, but, however, do not reflect pitch attitude beyond 85 degrees nose up or nose down from level flight. Beyond these limits the newer gyros give incorrect readings. These gyros have a self-erecting mechanism that eliminates the need for caging.

» How a gyroscope works

Here is a pictorial of a simplified version of a gyro.

Fig.5.

Instead of a complete rim, four point masses, A, B, C, D, represent the areas of the rim that are most important in visualizing how a gyro works. The bottom axis is held stationary but can pivot in all directions.

Fig.6. Fig.7. When a tilting force is applied to the top axis, point A is sent in an upward direction and C goes in a downward direction. Fig 5. Since this gyro is rotating in a clockwise direction, point A will be where point B was when the gyro has rotated 90 degrees. The same goes for point C and D. Point A is still

traveling in the upward direction when it is at the 90 degrees position in Fig 6, and point C will be traveling in the downward direction. The combined motion of A and C cause the axis to rotate in the "precession plane" to the right Fig.6 This is called precession. A gyro's axis will move at a right angle to a rotating motion. In this case to the right. If the gyro were rotating counterclockwise, the axis would move in the precession plane to the left. If in the clockwise example the tilting force was a pull instead of a push, the precession would be to the left. When the gyro has rotated another 90 degrees Fig. 7, point C is where point A was when the tilting force was first applied. The downward motion of point C is now countered by the tilting force and the axis does not rotate in the "tilting force" plane. The more the tilting force pushes the axis, the more the rim on the other side pushes the axis back when the rim revolves around 180 degrees. Actually, the axis will rotate in the tilting force plane in this example. The axis will rotate because some of the energy in the upward and downward motion of A and C is used up in causing the the axis to rotate in the precession plane. Then when points A and C finally make it around to the opposite sides, the tilting force ( being constant) is more than the upward and downward counter acting forces. The property of precession of a gyroscope is used to keep monorail trains straight up and down as it turns corners. A hydraulic cylinder pushes or pulls, as needed, on one axis of a heavy gyro. Sometimes precession is unwanted so two counter rotating gyros on the same axis are used. Also a gimbal can be used.

» THE GIMBALED GYROSCOPE

The property of Precession represents a natural movement for rotating bodies, where the rotating body doesn’t have a confined axis in any plane. A more interesting example of gyroscopic effect is when the axis is confined in one plane by a gimbal. Gyroscopes, when gimbaled, only resist a tilting change in their axis. The axis does move a certain amount with a given force.

Fig.8

A quick explanation of how a gimbaled gyro functions

Figure 8 shows a simplified gyro that is gimbaled in a plane perpendicular to the tilting force. As the rim rotates through the gimbaled plane all the energy transferred to the rim by the tilting force is mechanically stopped. The rim then rotates back into the tilting force plane where it will be accelerated once more. Each time the rim is accelerated the axis moves in an arc in the tilting force plane. There is no change in the RPM of the rim around the axis. The gyro is a device that causes a smooth transition of momentum from one plane to another plane, where the two planes intersect along the axis.

A more detailed explanation of how a gimbaled gyro functions

Here it is explained that how much the axis will rotate around a gimbaled axis. That is to say, how fast it rotates in the direction of a tilting force. In figure 8, the precession plane in the gimbaled example functions differently than in the above example of figures 1-3, and I have renamed it "stop the tilting force plane". The point masses at the rim are the only mass of the gyro system that is considered. The mass and gyroscope effect of the axis is

ignored. At first consider only ½ of the rim, the left half. The point masses inside the "stop the tilting force plane" share half their mass on either side of the plane, and add their combined, 1/4kg, mass to point mass A of 1/2kg. So then the total mass on the left side is ½ the total mass of all 4 point masses, or 1kg. The tilting force will change the position of point mass B and D very little and change the position of point mass A the most. So we must use the average distance from the axis of all the mass on the left-hand side.

Fig.9.

The mass on the left side is 1kg. The average distance the mass is from the "stop the tilting force" plane is 1/2 meter. Figure 9 shows a profile of the average mass in the tilting plane and the average distance from the axis that the mass is situated. We are concerned at how far the mass at the average distance will rotate within the tilting plane when a given force is applied to the axis in the direction indicated. Point mass A is rotating at 5 revolutions per second. This means that it is exposed to the tilting force for only .1 seconds. The tilting force of 1 newton, if applied for .1 second, will cause the mass at the average distance to move .005 meter in an arc, in the tilting force plane. Since the length of the axis is twice as long as the average distance of the rim’s mass, the axis will move .01 meter in an arc. At the end of .1 second the point mass will be in the "stop the tilting force plane" and all the energy transferred to point mass A is lost in the physical restraint of the gimbal bearings.

The same thing happens when point mass A is on the right side of figure 4. Only now, the tilting force will move point mass A down, and the axis will advance another .01meter. .01 meter every .1 second is not the whole story because the mass on the right side of the gyro hasn’t been considered. The right side has the same mass as the left and has the same effect on the axis as the left side does. So the axis will advance half as much, half of .01 meter,

or .005meters. Both halves of the rim mass will pass through the stop the tilting force plane 10 times in one second. Each time a half of the rim passes though the "stop the tilting force plane", it losses all its momentum that was added by the tilting force. The mass has to undergo acceleration again so we continually calculate the effect that 1 newton has for .1 second on the rim mass at the average distance, 10 times a second. So then; at the point that the 1 newton force is applied, the axis will move 5cm per second along an arc. The gyro will rotate at .48 RPM within the tilting force plane.

What considerations does the rim speed have on the distance that the axis will rotate along an arc in the tilting force plane? The gyro will rotate in the tilting force plane, half as fast if the rim speed is doubled.

What happens when the mass of the rim is doubled? The gyro will rotate in the tilting force plane, half as fast if the rim mass is doubled

How does the rim diameter effect rotation in the tilting force plane? The gyro will rotate in the tilting force plane, half as fast if the rim diameter is doubled   If left undisturbed, a gyro on the surface of the Earth would turn 360 degrees once every 24 hours. The top of the gyro would normally go westward. But if the top axis were held so that it could not rotate from east to west, due to precession, the gyro will rotate in the north and south direction depending on the direction the rim is rotating. The gyro would turn due to precession until it reaches 90 degrees with it's axis pointing north and south. Then it would be in the same plane as the rotation of the Earth and gyroscopic precession would stop. To get the gyro out of the Earth's rotational plain a small force could be applied to the gyro axis and precession would put the axis back in the original position. The 90 degree precession rotation would be much faster than the once per 24 hours opposing forces rotation, but some gearing would probably still be needed to run a generator. The generator would be mechanically linked to the precession back and forth motion in one direction only so it will turn the same direction all the time. The amount of energy needed to keep the gyro's rim spinning and the energy needed to turn the gimbals back 90 degrees would determine the overall efficiency. This is NOT a free energy thing. The energy comes from the rotation of the Earth and therefore the Earth rotational speed is slowed as energy is tapped from a gyro-generator type machine. If this method of generating energy is used to a great extent, days and nights would become longer. If this should happen.

let me be the first credited to use the term "rotation pollution" or "motion pollution".

» GYRO POWER SOURCES.

Air or electricity supply the power to operate gyro instruments in light aircraft. If the directional indicator and attitude indicator are air-driven (as they generally are), the turn-and-slip indicator is electrically powered. The advantage of this arrangement is that if the vacuum system (which supplies air) fails, the instrument pilot still has the compass and the turn indicator for attitude and direction reference, in addition to the pitot-static instruments.

1. VACUUM POWER SYSTEM: Air-driven gyros normally are powered by a vacuum pump attached to and driven by the engine. Suction lines connect the pump to the instruments, drawing cabin air through the filtered openings in the instrument case. As the air enters the case, it is accelerated and directed against small "buckets" cast into the gyro wheel. A regulator is attached between the pump and the gyro instrument case to control suction pressure. There is normally a vacuum gauge, suction gauge (See the Typical Suction Gauge figure, below) or warning light. Because a constant gyro speed is essential for reliable instrument readings, the correct suction pressure is maintained with a vacuum pressure regulator.

Fig.10. Typical Suction GauGe

The air is drawn through a filter, to the instruments and then to the pump where it is vented to atmosphere. The pilot should consult the aircraft operating manual for specific information with regard to vacuum system normal operating values. Low gyro rotation speeds cause slow instrument response or lagging indications, while fast gyro speeds cause the instruments to overreact in addition to wearing the gyro bearings faster and decreasing gyro life.

2. ELECTRICAL POWER SYSTEM:

An electric gyro, normally used to drive the turn coordinator or turn-and-slip indicator, operates like a small electric motor with the spinning gyro acting as the motor armature. Gyro speed in these instruments is approximately 8,000 rpm. Aircraft that normally operate at high altitudes do not use a vacuum system to power flight instruments because pump efficiency is limited in the thin, cold air. Instead, alternating current (a.c.) drives the gyros in the heading and attitude indicators. The a.c. power is provided by inverters that convert direct current to alternating current. In some cases, the a.c. power is supplied directly from the engine-driven alternator or generator.

» GYROSCOPIC INSTRUMENTS

1. ATTITUDE INDICATOR

BASIC COMPONENTS AND OPERATION The purpose of the attitude indicator is to present the pilot with a continuous picture of the aircraft's attitude in relation to the surface of the earth. The figure (below) shows the face of a typical attitude indicator. It should be noted that other attitude indicators differ in details of presentation.

Fig.11.Attitude Indicator

Pitch attitudes are depicted by the miniature aircraft's relative movement up or down in relation to the horizon bat, also called the gyro or attitude horizon. Usually at least four pitch reference lines arc incorporated into the instrument. Two are below the artificial horizon bar and two are above.

The bank indicator, normally located at the top of the instrument, shows the degree of bank during turns through the use of index marks. These are spaced at 10° intervals through 30°, with larger marks; placed at 30°, 60° and 90° bank positions. The nose of the aircraft is depicted by a small white dot located between the fixed set of wings or by the point of the triangle as in the figure (See the bottom centre of the Attitude Indicator figure, above right). The sky is represented by a light blue and the earth is shown by black or brown shading. Converging lines give the instrument a three-dimensional effect.

The small knob near the bottom of the instrument is used for vertical adjustment of the miniature aircraft. During straight-and-level flight the miniature aircraft should be adjusted so that it is superimposed on the horizon bat.

Once the artificial horizon line is aligned with the natural horizon of the earth during initial erection, the artificial horizon is kept horizontal by the gyro on which it is mounted. An erection mechanism automatically rights the gyro when precession occurs clue to manoeuvres or friction. When the older-type gyro tumbles as a result of extreme attitude changes, the rotor normally precesses slowly back to the horizontal plane.

Even an attitude indicator in perfect condition can give slight erroneous readings. Small errors due to acceleration and deceleration are not significant because the erection device corrects them promptly; nonetheless, the pilot should be aware of them (refer to the paragraphs below). Large errors may be caused by wear, dirty gimbal rings, or out-of-balance parts. Warning flags (see Attitude Indicator figure, above right) may mean either that the instrument is not receiving adequate electrical power or that there is a problem with the gyro.

Principal Attitude Indicator Errors

TURN ERROR

During a normal coordinated turn, centrifugal force causes the gyro to precess toward the inside of the turn. This precession increases as the bank steepens; therefore, it is greatest during the actual turn. The error disappears as the aircraft rolls out at the end of a 180 degrees turn at a normal rollout rate.

Therefore, when performing a steep turn, the pilot may use the attitude indicator for rolling in and out of the turn, but should use other instruments (VSI and altimeter) during the turn for specific pitch information.

ACCELERATION ERROR

As the aircraft accelerates (e.g., during takeoff), there is another type of gyro precession which causes the horizon bar to move down, indicating a slight pitch up attitude. Therefore, takeoffs in low visibility require the use of other instruments such as the altimeter to confirm that a positive rate of climb is established immediately after takeoff.

DECELERATION ERROR

Deceleration causes the horizon bar to move up, indicating a false pitch down attitude.

2. HEADING INDICATOR

The heading indicator, shown in the figure below , formerly called the directional gyro, uses the principle of gyroscopic rigidity to provide a stable heading reference. The pilot should remember that real precession, caused by maneuvers and internal instrument errors, as well as apparent precession caused by aircraft movement and earth rotation, may cause the heading indicator to "drift".

In newer heading indicators, the vertical card or dial on the instrument face appears to revolve as the aircraft turns. The heading is displayed at the top of the dial by the nose of the miniature aircraft (see the figure to the right). Another type of direction indicator shows the heading on a ring similar to the card. in a magnetic compass.

Fig.12.Heading indicator

Because the heading indicator has no direction-seeking qualities of its own, it must be set to agree with the magnetic compass. This should be done only on the ground or in straight-and-level, unaccelerated flight when magnetic compass indications are steady and reliable.

The pilot should set the heading indicator by turning the heading indicator reset knob at the bottom of the instrument to set the compass card to the correct magnetic heading. On large aircraft, this function is done using a compass controller (See the Compass Controller figure, below).

Fig.13.compass System

The pilot of a light aircraft should check the heading indicator against the magnetic compass at least every 15 minutes to assure accuracy. Because the magnetic compass is subject to certain errors , the pilot should ensure that these errors are not transferred to the heading indicator.

3. RATE AND QUALITY OF TURN INDICATORS

There are two types of rate and quality of turn indicators

1. The Turn Coordinator and

2. The Turn-and-Slip Indicator .

Both of these gyroscopic instruments indicate the rate at which the aircraft is turning. The turn co-ordinator contains a miniature schematic aircraft to shown when the actual aircraft is turning. The turn-and-slip indicator, on the other band, has a vertical needle which deflects in the direction the aircraft is turning.

› TURN-AND-SLIP INDICATOR

The turn-and-slip indicator provides the only information of either wing's level or bank attitude if the other gyroscopic instruments should fail. This indicator is sometimes called the "needle and ball". This instrument, along with the airspeed indicator, magnetic compass and altimeter, can assist the pilot

in flying through instrument weather conditions, even when it is the only gyro instrument operating.

The turn needle of the turn-and-bank indicator gives an indirect indication of the bank attitude of the aircraft. When the turn needle is exactly centred, the aircraft is in straight flight. When the needle is displaced from centre, the aircraft is turning in the direction of the displacement. Thus, if the ball is centred, a left displacement of the turn needle means the left wing is low and the aircraft is in a left turn. Return to straight flight is accomplished by coordinating aileron and rudder pressures.

The ball of the turn-and-bank indicator is actually a separate instrument, conveniently located under the turn needle so the two instruments can be used together. This instrument is best used as an indication of attitude. When the ball is centred within its glass tube the manoeuvre is being executed in a coordinated manner. However, if the ball is out of its centre location, the aircraft is either slipping or skidding . The side to which the ball has rolled indicates the direction of the slip or skid.

Fig.14.Turn and Slip Indicator

In a slip, the rate of turn is too slow for the angle of bank, and the lack of centrifugal force causes the ball to be displaced to the inside of the turn. (To correct, decrease the angle of bank, or use rudder to increase the rate of turn, or both). In a skid the rate of turn is too fast for the angle of bank, and excessive centrifugal force causes the ball to be displaced to the outside of the turn. (To correct, increase the bank angle, or use rudder to decrease the rate of turn, or both).

In coordinated flight, the needle may be used to measure the rate of turn; in a "standard rate turn", the needle is aligned with the left or right marker (dog-house) and the aircraft will turn at the rate of 3° per second or 180° in one minute. Hence, in these conditions, the needle indicates both direction and rate of turn.

The answer to controlling and trimming an aircraft in straight and level flight by means of the turn-and-bank indicator requires a return to basic control principles - i.e., control yaw with the rudder and keep the wings level with aileron. Therefore, when flying straight and level through the use of the turn-and-bank indicator, prevent yawing with appropriate rudder pressure, and keep the wings level with appropriate aileron pressure. The needle will not deflect while heading is constantly maintained, since no turn exists.

In other words, control the ball with rudder since the ball moves parallel to a plane passing through the rudder pedals, and control the needle with aileron since the ailerons affect bank angle, a primary requirement for a normal turn.

It is important that both the needle and ball are used together. The problem associated with using these instruments separately is that although the ball will positively indicate that the aircraft is slipping or skidding, just which one of these the aircraft is doing can only be determined by reference to the needle. Furthermore, the needle will not positively indicate a bank attitude. An aircraft could be in a bank attitude and yet the needle could remain centred or indicate a turn in the opposite direction, if controls are not coordinated.

› TURN CO-ORDINATOR

Most current aircraft have a turn coordinator that replaces the older turn-and-slip instrument. A small aircraft silhouette rotates to show how the aircraft is turning (see the figure below). When the aircraft turns left or right, the aircraft silhouette banks in the direction of the turn. When the wing of the aircraft silhouette is aligned with one of the lower index marks, the aircraft is in a standard-rate turn 30°/sec.).

Fig.15. Turn Co-ordinator

This instrument also senses the roll rate because the gyro is tilted on its fore and aft axis. The electric gyro is canted approximately 35°; therefore, the miniature aircraft banks whenever the actual aircraft rotates about either the yaw or roll axis. This freedom of movement enables the gyro to indicate

immediately when the aircraft is turning. After the bank angle for a turn is established and the roll rate is zero, the aircraft symbol indicates only the rate of turn.

The miniature aircraft moves independently of the ball or inclinometer. The position of the ball indicates the quality of the turn. When the miniature aircraft depicts a turn and the ball is not centred, it shows that the turn is not coordinated (see black ball in figure on the right).

If the miniature aircraft is level and the ball is displaced to either side (see ball in above figure on the right), the aircraft is flying straight but with one wing low.

The pilot should understand the relationship of true airspeed and angle of bank as it affects the rate and radius of turn.  The Aircraft at Same Bank Angle But Different Speeds figure (right) shows three aircraft flying with the same angle of bank but at different airspeeds. The aircraft with the greatest rate of turn is aircraft A. If two aircraft arc turning at the same angle of bank, the slower aircraft has the shorter turning radius and also a greater rate of turn.

Fig.16. Aircraft at the same bank angle but different speeds

A common misconception is that faster aircraft will complete a 360° turn in the least time. For example, a jet in a 20° bank flying at a true airspeed of 350 kts requires approximately 5.3 minutes to complete a 360° turn. Aircraft A, with also a 20° bank but a true airspeed of 130 knots (kts), requires just two minutes to complete a 360° turn.

The radius of turn also increases with an increase in airspeed, varying with the square of the true airspeed. Therefore, because the speed of aircraft C is about three times that of aircraft A, the turning radius of aircraft C is approximately nine times that of aircraft A.

4. THE GYROSYN COMPASS SYSTEM

A gyrosyn compass system has a remotely located unit for sensing the earth's magnetic field. It incorporates a gyroscope to provide stability. Electrical power is required for its operation.

A variety of cockpit indicators may be driven by a gyrosyn compass system, including fixed-card instruments, or moving-card indicators such as a radiomagnetic indicator (RMI) or a horizontal situation indicator (HSI).

All gyrosyn compass systems have a set of basic components whose operation is similar, regardless of the aircraft type:

a) REMOTE COMPASS TRANSMITTER

The remote compass transmitter senses the earth's magnetic field. It is usually remotely located to reduce aircraft magnetic disturbances. The sensing element is pendulously suspended within a sealed bowl (fluid-filled to prevent excessive swinging) and maintains a horizontal plane within a pitch attitude of +30 degrees. During large changes in heading, airspeed or pitch the sensing clement is displaced from the horizontal plan and produces erroneous signals. These generally have little effect because of the stability provided by the gyro, and a return to straight-and-level, unaccelerated flight again provides correct orientation signals;

b) GYROSCOPE

The gyroscope principle of rigidity in space is applied to retain a fixed position during any aircraft turns. Turning motion of the aircraft about the gyro is then electrically relayed to the heading indicator;

c) ERECTION MECHANISM

An erection torque motor is used to keep the gyro spin axis in a horizontal plane;

d) AMPLIFIER

The amplifier is the coordination and distribution center for all system electrical signals. Remote compass transmitter signals arc phase detected to resolve for the 180-degree ambiguity and arc sent to the slaving torque motor to keep the gyro spins axis aligned with magnetic north-south. The amplifier also provides high voltage to the slaving torque motor for any periods of fast slaving; and

e) HEADING INDICATOR UNIT

NOTE:  Some gyrosyn compass systems are capable of non-slaved operation in extreme northern or southern latitudes where the earth’s magnetic field is distorted or weak. In this situation:

a. The remote compass transmitter does not-function;

b. The gyro must be oriented manually for heading and then serves as the only directional reference;

c. Aircraft turning motion about the gyro is still relayed electrically to the heading indicator; and

d. Some form of latitude correction is necessary to overcome the effects of apparent precession.

INSTRUMENTS ASSEMBLED IN THE INSTRUMENT FACTROY OF THE H.A.L.

1. INSTRUMENTS OF CLEAN ROOM 1

A.) KC -2 COMPASS SYSTEM

PURPOSE: The KC -2 compass system designed for installations in a fighter aircraft, is employed for determining and indicating the aircraft heading, landing course and radio station bearings as well as for feeding heading signals to the consumers.

PRINCIPLE OF OPERATION OF COMPASS SYSTEM: The KC -2 compass system is a directional gyro operating without gimbals errors with remote transmission of aircraft, headings to indicators and consumers. Heading signals fed by the directional gyro are initially slaved with the magnetic heading by means of the magnetic corrector. The compass system makes it possible to determine the aircraft heading, relative and true bearings of the radio station and to feed heading signals to consumers for solving piloting, navigation, firing, bombing, etc. tasks. Like most of the modern reading compasses, the compass system employs the principle of combined operation of directional gyro and a heading selector (corrector). This principle consists in the following: the used heading selector (corrector) determines the aircraft heading relative to magnetic meridian and presents the result for correcting heading signal picked up from the gyro.

B.) REMOTE CONTROLLED GYRO HORIZON

PURPOSE: The main purpose of remote controlled gyro horizon A D-1 is to ensure the pilot of highly perceptible broad scale indication of position of aircraft in wide range of angles of bank and pitch during retaining correct readings after any evolution.

Visual indicator of gyro horizon A D-1 is the following system, reproducing angles of bank and pitch in accordance with electrical signals fed by distant located gyro horizon (gyro – pick – up). Use of remote transmission of output signals permits to set some visual indicators from gyro pick-up in action. Gyro pickup may feed electrical signals proportional to angles of rolling and pitch not only on visual indicator of A D-1 but also on others available instruments of these signals (altitude control, avigraph system, radar and so on) on aircraft.

C.) VERTICAL GYRO 458 M

PURPOSE: Modified vertical gyro 458 M develops electrical signals proportional to the aircraft roll and pitch angles within 360° in all modes of operation and maneuvers of the aircraft.

OPERATING PRINCIPLE: Operation of the 458M vertical gyro is based on the feature of a free gyro to retain the direction of the rotor axis unchanged in space and the feature of a pendulum to align itself with the true geographical vertical of the earth. In flight, the present position of the true vertical is fixed by a liquid level pendulum type switch employing the 11XM-9M elements. If the spin axis of the gyroscope departures from the true vertical, the torque motors (torquers) of the pendulum erection system develop torques on the axles of the outer gimbals due to electrical signals proportional to the departure angles. The torques cause the gyroscope spin axis to process toward the true vertical. During aircraft maneuvering the axis of the gyroscope rotor retains its vertical position and the housing of the vertical gyro, rigidly connected to the aircraft structure, turns with respect to the rotor axis through angles equal to the aircraft turn angles in roll and pitch. These angles converted into electrical signals are transmitted through the synchro system either to a miniature aircraft or to the card of the artificial horizon. The roll and pitch angles are taken off the artificial horizon scales. Due to the Earth rotation, friction of the axle of the outer gimbal, unbalancing and other factors, the spin axis of the gyroscope departures from its vertical. The errors caused by the above factors are eliminated by means of the pendulum erection system. Besides, the vertical gyro is equipped with a special follow up system which protects the gyroscope from tumbling at any maneuvers of the aircraft. To increase the accuracy of the roll and pitch during the aircraft maneuvers, acceleration and decelerations; and to prevent action of the noon gravitational forces tending to align the pendulum and the gyroscope spin axis

connected with it through the erection system with so called apparent vertical, provision is made to cut out the gyroscope during turns by means of the bar type erection switch connected in series with the contacts of erection cutout switch as well as to cutout pitch erection system by means of the liquid switch when longitudinal acceleration are imparted.

2. INSTRUMENTS OF CLEAN ROOM 2

A.) ASI (SENSITIVE AIRSPEED INDICATORS)

PURPOSE & OPERATING PRINCIPLE:It is designed to provide continuous indication of the airspeed of aircraft. The instrument is basically a differential air pressure gauge consisting of a twin capsule assembly connected, via suitable linkage and gearing to pointers which move over a circular dial calibrated in knots. 1 knot = 1.85 km/hourWhen installed, the interior of the capsule is connected by a capillary tube to the aircraft’s pitot pressure line while the exterior of the capsule is open to static pressure via the aircraft static system. One side of capsule is secured to the instrument frame, but the other side is free to move in response to pressure differences and it is this movement which is transmitted to the pointers. The instrument has two concentric pointer consisting of a fast and a slow hand. The fast hand indicates on an outer scale which is calibrated 0 – 100 knots. The slow hand moves over a inner or subsidiary scale and indicates hundreds of knots.

B.) VERTICAL SPEED INDICATORS:

PURPOSE: The Vertical Speed Indicators are sensitive to the rate of change of pressure in the aircraft static air system and indicate by means of a pointer moving over an integrally lit dial, the vertical component of aircraft speed. The scale, for both climb and descent is linear over its first part and logarithmic over the remainder and is calibrated in ft/min for group A indicators and m/s for group B indicators. The other main difference between the indicators is in the type of electrical connector fitted.

OPERATING PRINCIPLE:

The purpose in an aircraft static system is proportional to the height of the aircraft; therefore the rate of change of static pressure is proportional to he vertical component of aircraft speed. The static system is connected directly to the inside of the capsule, and via a calibrated is zero, but when the static pressure changes the pressure difference cited is proportional to the rate at which the static pressure changes. A pressure differential across the capsule causes the capsule to expand or contract. Movement of the capsule is transmitted via the rocking shaft assembly, sector gear and pinion to drive the indicator pointer. Thus the position of the pointer represents the rate of change of static pressure and the vertical component of aircraft speed.The ranging spring block increasingly restricts the movement of the capsule as the pressure differential across the capsule increases, to provide a non – linear response. The response is chosen to retain readability at low rates of climb and descent.

C.) INDICATING ACCELEROMETERS

PURPOSE: Indicating accelerometers provide a visual indication of the acceleration experienced in the vertical axis of an aircraft. The scale is calibrated in unit of ‘g’ the unit of normal gravitational acceleration. The accelerometers are housed in a 2 ½ inch diameter case with detachable bezel. On KAE-0504/3, one corner of the bezel is removed. The presentation comprises three concentric pointers moving over a linearly divided scale. The front pointer registers the instantaneous acceleration, and the middle and rear pointers register the maximum positive (upward) and negative (downward) acceleration respectively.

OPERATING PRINCIPLE: An acceleration force acting upon a weight tends to cause the shafts to rotate against the control spring. Symmetrical duplication of the shaft and weights, ensure that rotation of the shafts is due to the vertical component of acceleration only. When the unit is stationary in its normal operating position, the front point indicates the force due to the gravity as + 1 ‘g’ and the middle and rear pointer indicates the maximum positive and negative acceleration experienced since the reset button was last depressed. The eddy currents drag – cup provides damping to ensure that higher frequency acceleration, due to vibration , are not included.

D.) MACHMETER

GENRAL:It indicates Mach number within the range of 0.4 to 0.85 Mach, at altitudes between zero and +50,000 feet. The instrument mechanism is contained within a square section metal case which is sealed at the front end by a flange and glass assembly. At the rear the case is sealed by a gasket sandwiched between a clamping plate and the rear cover. The rear cover carrier a 3 pin electrical receptacle together with the pitot and static pressure inlet. The instrument is fitted with a rotating lubber mark which can be adjusted by a setting screw located in the case back plate. Four internal lamps with red filters, situated behind the top corners of the flange provide illumination at the dial, lubber mark and pointer. Each lamp is energized by a low voltage ac or dc supply connected through the 3 pin receptacle at the rear of the instrument.

3. INSTRUMENTS OF CLEAN ROOM 3

A.) GYRO MAGNETIC COMPASS (TYPE 512-3)

PURPOSE: The gyro magnetic is a part of heading system. It is a bay mounted equipment item which, in normal operation, provides gyro magnetic heading from magnetic heading information supplied another unit in the system. It can also, should the latter become defective, supply a directional heading. If the gyro is defective it retransmits in the emergency mode the magnetic heading it receives from the system.

DESCRIPTION : The gyro magnetic compass is in the form of a combined cylindrical and rectangular case. This case is attached to the aircraft at 3 points by shock mounts. Two of these are secured to the lugs screwed to the bosses on the upper half of the cylindrical section. The third is secured to the boss under the rectangular section of the case. A bonding strip is installed between a securing lug and a boss of the case provides electrical connection between the case ground and the aircraft structure on which it is mounted. The cylindrical section forms a sealed compartment filled with a mixture of helium – nitrogen gas and in which the directional gyro is installed. Its lower surface is closed bya cover secured by 4 screws including two lead sealed screws. The latter ensure that the gyro compartment will not be opened by unauthorized personnel.

This compartment is filled with helium through a plug. The rectangular section contains the electronic unit which groups all the electronic circuits of the equipment. This unit is integral with the cover which is secured to the case by six screws. To remove the electronic unit from its housing, it is recommended to screw the special tool into 2 holes, tapped in the cover. On the cover are the following components:

A timer counter totalizing the gyro magnetic compass energization timer. The overhaul record plate giving the index of the modifications applied to the

unit and the date of the latest overhaul.

OPERTING PRINCIPLE:It uses a conventional directional gyro. The synchronous rotor motor is of the hystersis type. Its speed is 24,000 rpm. The rotor is mounted in an elevation gimbal slaved in such a way that it remains in the horizontal plane.

The heading information is delivered by the stator of two synchro Transmitters whose rotors are connected in rotation with the azimuth gimbal of the gyro.

The operating mode of the gyro magnetic compass can be selected externally so as to give the following heading information:

Gyro magnetic Directional Magnetic

B.) ARTIFICIAL HORIZON (AIR DRIVEN) TYPES 950,955

PURPOSE: The Horizon is a gyroscopic flight instrument which provides a permanent visual indication of the aircraft attitude, in the roll and pitch planes, with regard to the local vertical. It thus makes up for the absence of fixed references external to the aircraft.OPERATING PRINCIPLE: The horizon is composed of a gyroscope the axis of rotation of which is slaved to a position close to the local vertical, by means of a pneumatic system with pendulum type erecting devices. This system is used to compensate the apparent precession of the gyroscope, due to the rotation of the Earth, as well as the spurious precessions caused by the various friction loads on the suspension axis. The instrument case, secured to the airframe, moves with regard to the gyroscopic system which indicates the vertical. The aircraft attitude is indicated

to the pilot, by the relative position of the pointer linked to the gyroscope, and of the model secured to the case. When the aircraft dives the pointer indicates a displacement of the horizon in the upward direction and inversely. Similarly when the aircraft banks to the right, the horizon line rotates to the left, and inversely. The amount of banking is indicated on the roll dial, by the roll index.

C.) TURN AND SLIP INDICATORS:

GENERAL: The turn and slip indicators provide indication of the rate at which an aircraft is turning about its normal axis, and an indication of slip arising from an incorrectly banked turn. Rate of turn indicator is given by a pointer, actuated by an electrically driven rate gyroscope, reading against a scale calibrated to indicate three rates of turn (1, 2 and 3), in each direction.

OPERATION:

a.) Turn Indicator

The turn indicator depends for its operation on a property of a rotating gyroscope which may be stated as follows: if the spin axis of a rotating gyroscope is itself rotated about a second axis (axis of turn) at right angles to the spin axis, the gyroscope will exert a torque so as to cause rotation of precession about a third axis at right angles to the other two. In straight flight, the rotor’s axis tends to be held horizontal by the force exerted by the rate spring and the pointer remains at zero. During a turn, the rotor precesses and the gimbal rotates to a point at which the torque balanced by an equal and opposite torque exerted by the rate spring, the displacement being related to the torque and therefore to the aircraft’s rate of turn. The response rate of the instrument is accelerated by the fact that he direction of precession is opposite to the direction of turn; the rotation of the gimbal is transmitted to the pointer through the gears which reverse the direction so that the rate of turn is indicated on the appropriate side of the scale.

b.) Slip Indicator

Slip occurs when an aircraft’s vertical axis deviates from the direction of gravity in straight flight, or apparent gravity, i.e. the resultant of actual gravity and centrifugal force, during a turn. The aircraft’s longitudinal altitude here is disregarded.

The ball in the slip indicator constantly gravitates to the ‘lowest’ point of the curved tube so that the direction of gravity, actual or apparent, is indicated by a line passing through the centre of radius of the tube and the centre of the ball. The vertical axis of the aircraft is parallel to a line drawn through the centre of radius and a centre datum on the dial.

During straight flight in the normal lateral attitude, or during a correctly banked turn, the aircraft’s vertical axis is parallel with the direction of real or apparent gravity (the aircraft’s angle of attack being disregarded) and the ball remains at the central datum. When slip or skid occurs, the direction of gravity deviates from the vertical axis and the ball is displaced from the central datum in the direction of slip or skid by a related amount. Transient movement is damped by the fluid in the tube.

4. INSTRUMENTS OF THE ASSEMBLY & TEST SHOP – 2

A.) F.C.G (FUEL CONTENT GAUGING SYSTEM)

PURPOSE: It indicates the volume of fuel whatever available in the fuel tank of helicopter and also alerts the pilot by giving him a visual warning, when the fuel level falls below a certain limit. This system is designed by HAL, Lucknow division and has been under production 1978.

OPERATING PRINCIP[LE: The function of F.C.G is based upon the principle that the capacitance of two concentric tubes (cylindrical in shape) is different when there is air in between and when there i.e. aviation fuel, acting as dielectric in between the gap. The capacitance increase or decrease as the level of fuel changes in the gap. This change in capacitance is measured by meter.

B.) TRANSFORMER RECTIFIER UNIT

Operation

(i) The unit consists essentially of a 3-phase step down transformer (T1) and a rectifier circuit which produces a nominal 28 V dc output from a 200 V, 400 Hz 3-phase ac input.

(ii)The transformer has two 3-phase secondary windings one in delta connected and other star connected to produce a 6-phase output. Each secondary output

is full-wave rectified by a 3-phase silicon diode rectifier bridge. The interphase reactor (T2) balances the bridge rectifier outputs.

(iii)The 3-phase motor driven fan unit draws cooling air through the fin unit and case. The contacts of the thermostats situated on the upper fin are open under normal operating temperatures but should the fan unit fail, the contacts close when a fin temperature of approximately 200.C is reached thus providing an output signal on fan unit failure.

(iv) Radio interference suppression is provided by capacitors ( C1 to C11) which are connected from each input, output and transformer secondary terminal to chassis.

C.) Regulator

PURPOSE: The regulator <12310-31> controls the energizing current of alternator exciter, eddy current brake and of clutch in a way to obtain a 3-phase voltage 115/200 V + 2% and a frequency of 400 Hz + 1% of output alternator whatever may be the delivered current by alternator.

OPERATING PRINCIPLE: The magnetic power supplies (through thyristors) the brake inductors and alternator exciter; and its supplies are controlled by voltage regulation circuit and frequency regulation circuit respectively. Voltage detection is carried out at terminal stud network, while the frequency is detected on magnetic power. The detected data (proportional to voltage or frequency) is compared to a reference and the error signal thus obtained is amplified, in order to act on the circuits controlling the inductor power supplies.The magnetic tachometer furnishes a signal proportional to the drivng speed of vario-alternator, and this signal acts:- In the one part, a clutch circuit that controls the power supply of wound clutch, On the other hand, “accelerator frequency limiting” circuit that has the

purpose to discharge (if necessary) the alternator on frequency limiting resistors.

At last, the stabilized power supply is provided by magnetic power.

D.) RADIO MAGNETIC INDICATOR

GENRAL: Radio magnetic indicator is a panel mounted air borne instrument that provides the pilot with the following information:

A) Heading of the aircraft.B) Relative bearing of a Radio station, andC) Deviation from asset course

The heading operation is servo controlled, receiving signal either from gyro magnetic, magnetic or directional heading mode from a gyrocompass as desired by the pilot. A knob is provided to set the course, which is to be followed. Bearing of the radio transmitting station is obtained by a signal from the receiver unit of Automatic Direction Finder (A.D.F). The aircraft heading indication is read on a circular dial against a fixed lubber mark on the unit.

E.) INDICATED AIR SPEED SWITCH (I.A.S S/W)

PURPOSE: This switching unit contains a pressure sensitive mechanism, an optical sensing unit and an electronic unit. It operates integral relays at four pre – determined indicated air speeds to provide an external information at each of these airspeeds. The interior of the case is connected to static pressure whilst the airspeed capsule of the mechanism is connected to pitot pressure.

Cyclic ratio of a pulse = On time/On time + Off time

OPERATING PRINCIPLE:(a) Air Speed Mechanism:

The air speed capsule is directly connected to pitot (P) pressure and is surrounded externally with static pressure. It will expand in response to an increased differential and contract in response to a reduced differential, thus creating a linear movement of the free side of the capsule.

(b)Sensing Unit: The PCBs of the sensing unit constitute four optical detectors which are identical in operation. In the absence of an obstacle, the photo transistor intercepts the infra – red radiation from the emitting diode, the relay contained within the corresponding module of the electronic unit is then energized normally.

Each of the four identical channels composed by the electronic and sensing units can be functionally divided into four elements:- an oscillator, an optical detector, an amplifier and a relay control circuit.

The oscillator and its matching mechanism network provides a pulsating current for the diode.

Optical Detector: When the diode is fed by the oscillator, it emits an infrared radiation which is intercepted by the phototransistor. The diaphragm mounted on top of the phototransistor controls the width of the beam intercepted by the photo transistor. This arrangement provides accurately determined triggering speeds.

The amplifier amplifies the obtained potential difference. The capacitor and resistance network is used to provide good noise elimination and isolate the amplifier from any D.C. voltage liable to occur, should the photo transistor intercept undesired light.

The relay is controlled by means of another transistor.

F.) GENERATOR CONTROL AND PROTECTION UNIT (G.C.P.U)

PURPOSE: The G.C.P.U is a solid state device which can be directly fitted across the dc generators, to give a regulated/stabilized dc output for all loading and speed conditions. This unit also has facilities to indicate to the pilot over current and under voltage conditions. The unit automatically disconnects the generator from the aircraft dc bus bar and itself in case of over voltage. This unit replaces, the existing carbon pile regulator and the over voltage protection unit. G.C.P.U

OPEREATING PRINCIPLE: GCPU is fully solid state unit having 2 circuits one for regulation and the other for protection. Even though these are encased in one box, their functions are independent. DC generator positive and negative voltages are supplied through the connector to the radio interference suppression filters, which suppress the radio frequency noise. These filter out the noise developed during ON & OFF of the transistor switching. Output from filter goes through the over voltage protection relay to the power transistor, the regulation and protection PCB’s and to the starting relay. Starting relay is connected across the field and +G terminal. The

relay is operated by a transistorized circuit such that the relay contacts are normally closed until the generator voltage builds up to a predetermined voltage of 18 ± 1 volts. Above this voltage the circuit energizes the relay which opens the circuit and the transistorized regulator takes over to control the generator. The main power transistor is connected across +G of the generator and the field. Forced commutation techniques is adopted so that transistor switches ON & OFF, alternately at a fixed frequency of 500 ± 100 Hz which is totally independent of individual generator characteristics. Since the field circuit is highly inductive in nature a re-circulating power rectifier is connected parallel to the field (between the field and – G terminal). This is done in such a way that when the power transistor is ON and pumping current from the field, the re-circulating diode (rectifier) remains off, and when the transistor switches off, the diode takes over the slowly decaying field current due to the back e.m.f. of the highly inductive field. The average of the transistor ON time over each switching cycle determines the field current (Higher the ON time, higher is the field current). A sensing circuit senses generator voltage and accordingly controls the power transistor in such a way that if the generator voltage falls below a preset voltage (nominally 28 V) the ON time increases. This in turn increases the field current to increases the generator voltage and vice versa until a balance state is achieved due to negative feedback.Protection circuit senses generator voltage which if exceeds limit will disconnect the regulator from the generator and also de – energize differential contactor which will immediately disconnect the generator from the bus bar.

An over current annunciating circuit is provided to energize a doll’s eye. When the generator load current exceeds its preset value for more than 3 ± 1 seconds, over current annunciating circuit senses the over current and de – energizes the doll’s eye.An under voltage annunciating circuit is provided which senses the generator voltage. It energizes an externally fitted magnetic doll’s eye at normal conditions and de – energizes it when generator voltage is below 23.2 ± .8 V and also remains in this condition for more tan 3 ± 1 seconds.

USE: The unit not only regulates (control) a D.C. generator voltage, but also protects the generator and the electrical system from any damage due to fault in a circuitry totally isolated from regulator circuitry.The G.C.P.U. is designed for fitment in any altitude and in any position with any type of highly maneuverable military aircraft. It is not designed to be fitted on the aircraft engine. Combined temperature, humidity and pressure tests, tropical test, resistance to fungus growth test, radio interference, magnetic interference tests constant and crash acceleration tests.It also provides protection of itself as well as utilization equipment.G.C.P.U. is basically not

designed for the starting mode function of the Starter – Generator and is recommended for functional use only during generation mode.

5. INSTRUMENTS OF THE ASSEMBLY & TEST SHOP – 3

A.) Totalizing Fuel Flow Meter Type PTC1-1 (RTS)

PURPOSE: It is designed for remote measuring the fuel contents in the fuel tanks of one engine of the airplane in volume units by means of measuring the fuel returning from the pipeline behind the PTCT50 transmitter into the service tank (when the fuel pipelines and the tanks are in good order) and for transmitting those information data into the K3A system.

OPERATING PRINCIPLE: The operating principle of the flow meter are based on the conversion, realized by transmitter, of the fuel volumetric flow rate, Q, into a pulse voltage, V1 which is in proportion to flow rate Q on the conversion and the power amplification of the transmitter signal in the Amplifier (V2=KV1) and on the indication of the fuel contents available in the plane tanks with the aid of the indicator.

Transmitter Amplifier Indicator

Fig.17. Block diagram of Fule Flow Indicator

OPERATION:

The operating principles of the flow meter are based on the fact that the fuel flowing helical impeller whose rotation speed is in proportion to the speed of the flow and, hence, to the amount of fuel that flows through the fuel flow transmitter. The impeller drives, through the reduction gear, the core of the pulse – induction gear. The impeller of the main flow rate type PTCT50 transmitter is calculated in such a manner that a single pulse could correspond to every 2.51 of the fuel that has passed through the transmitter. The transmitter

signal is fed to the input circuit of amplifier Y -4 located in the Y 2-1 amplifier; then this signal gets converted into rectangular pulses, power amplified and supplied to the winding of motor P of the indicator.

The indicator P operates and turns, by one tooth, the ratchet – wheel which is coupled to the pointer through the differential gear and the reduction gear.

Since the number of revolutions of the pulse – induction gear core is in proportion to the number of revolutions of the impeller, the number of operations of motor P will be also in proportion to the number of revolutions of the impeller, and hence to the amount of the fuel that has passed through the transmitter.

B.) Flight Data Recorder

Purpose and working:

System records automatically 6 continuously changing parameters which are:

Altitude Engine speed Aircraft speed Vertical acceleration Horizontal acceleration Turn Angle of stabilizer

Five single command signal,Eight single command signals superimposed on Three continuously variable parameters, and timer line to indicate the time on black and white aero photo film and preserves it in normal and crash conditions for study and analysis of flight conditions.

WORKING: In this, mechanical motion is converted into electrical signals and then it is converted in to optical signals,. There is a fixed mirror in the vibrator which moves accordingly to the moving light beam. The light beam is moved under the effect of a permanent magnetic field and flux and shifts the light beam accordingly. Now the mirror will move and thus light will move and thus further the photographic film is printed.

5. INSTRUMENTS OF G.L.N.S SHOP

G.L.N.S (GROUND LAND NAVIGATION SYSTEM)

OVERVIEW: The Gyro land navigation system is an electronic navigation device used for guiding any army vehicle to its destination point. The principle objective of system is not only to ease the in more precise and more quicker manner whether in plains, hills or sand dunes, where there are no special remarks.

Besides instantaneous display of present vehicle position in terms of Eastings and Northings coordinate to facilitate quicker movement, the following indications are additionally provided.

“Approach Blip” indication, when the vehicle reaches within 1.2 km of the destination point.

“Bearing Rotation” indication, when the vehicle reaches within 200 m (visible range) of destination point.

Description:The Ground Land Navigation System comprises four units together with one Static Inverter as an A.C. supply source, two auxillary units and four optional associated items.

Basic Units Major Function

1. Directional Gyro To supply vehicle Heading Signal2. Land Navigation Computer To compute and display present vehicle

position c coordinates and indicate vehicle’s Heading and

Bearing angle

3. Junction Box (a) To interconnect all units (b) To control the Gyro (c) To cater slope correction

4. Speed Pickup Unit To generate vehicles speed signal

Supply Unit:

1. Static Pickup Unit Type To supply A.C. power 115 V, 400 Hz, single – phase, 110 VA

Auxillary Unit:

1. Commander’s Control Unit To control the system remotely 2. Driver’s Repeater Unit Type To indicate vehicle’s ‘Heading’ to RMI-3

Optional (Associated Items)

1. Interconnection Harness Set To interconnect all the units within the Vijayanta tank

2. Variable Position Cradle To protect computer from vibration

3. Compass Kit To read externally vehicle heading during day as well as night

Detailed Description of Important Instrument

Directional Gyroscope: This unit supplies vehicles heading signal. The gyro rotor is spherical in shape and supported in the inner gimbal ring, which fitted with osing the Gyro motor. Gyro motor is three – phase induction motor driven at 24000 rpm.

Static Inverter: It converts 28 V DC in to 115 V A.C., 400 Hz, single – phase output, 28 V D.C. input coming from JBV is to feed through the RI filter to the control card via one pole of the protective relay. Control card generates the oscillation with frequency of 400 Hz. This signal is preamplified at a frequency of 400 Hz. This signal is preamplified in Base drive card. The output of the power transistor fixed on the chassis for power amplification. This gives 115 single – phase A.C. output. Signal proportional to the output is fed to the protection card. The protection card senses under voltage (D.C.), over voltage (A.C.) and overload. If any of the above parameters goes beyond the specified limit it de-energizes the protective relay cutting off supply to the base drive.

Land Navigation Computer:

It consists of eight subassemblies. 115 V A.C. is stepped down in transformer base plate assembly and is fed to power supply card. Tuned A.C. supply is given to base unit to generate A.C. signal for providing slow signal to gyro through ven to generate resolved in sin /cos output signals. 28 V D.C. supply is given to power supply card to generate various D.C. supplies required for PCB’s given from CCU and processed with feedback from the Tacho – generator of the Heading Indicator. The resultant servo signal is fed to the Heading indicator, which indicates the vehicle – heading angle. Vehicle speed input signal is processed in the analog card with resolved Sin Cos and RK signal to give incremental Easting and Northings distance pulses CPE and CPN. These signals are divided by 10 in Digital card and sent to heading indicator to have a selected clock pulse, which is again fed to Digital card. Analog card generates the direction signals S/N and W/E, which are fed to Digital card. Depending upon the thumbwheel switch set (destination) position and the displayed (present), the digital cards give the signals proportional to the difference (H-P) E and (H-P) N. These signals proportional to the difference (H-P) E and (H-P) N. These signals are sent to bearing card to generate E, N output signals for bearing synchro to indicate bearing angle in the heading indicator. To give approach indication the difference signals are processed and output controls display blipping and bearing pointer notation for 1.2 km and 200 m range respectively.