Gyroscope

History:

HAL was established as Hindustan Aircraft in Bangalore in 1940 by Walchand Hirachand

to produce military aircraft for the Royal Indian Air Force. The initiative was actively

encouraged by the Kingdom of Mysore, especially by the Diwan, Sir Mirza Ismail. The

British Government bought a one-third stake in the company by April 1941 as it believed this

to be a strategic imperative. Later in April 1942, it bought out the stakes of Walchand

Hirachand himself and other promoters so that it can act freely. The decision by United

Kingdom was primarily motivated to boost British military hardware supplies in Asia to

counter the increasing threat posed by Imperial Japan during Second World War. However,

the Mysore Kingdom refused to sell its stake in the company but yielded the management

control over to the British Government. Thus, within 2 years of establishment, it was

nationalized.

In 1943 the Bangalore factory was handed over to the United States

Army Air Force but still using HAL management. The factory

expanded rapidly and became the centre for major overhaul and

repairs of American aircraft and was known as the 84th Air Depot.

The first aircraft to be overhauled was a PBY Catalina followed by

every type of aircraft operated in Indian and Burma. When returned to Indian control two-

years later the factory had become one of the largest overhaul and repair organizations in the

East.

After India gained independence in 1947, the management of the company was passed over

to the Government of India and was renamed as Hindustan Aeronautics Limited (HAL).

Though HAL was not used actively for developing newer models of fighter jets, the company

has played a crucial role in modernization of the Indian Air Force. In 1957 company started

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manufacturing Jet engines (Orpheus) under license from Rolls-Royce at new factory located

in Bangalore. During the 1980s, HAL's operations saw a rapid increase which resulted in the

development of new indigenous aircraft such as HAL Tejas and HAL Dhruv. HAL also

developed an advanced version of the MiG-21, known as MiG-21 Bison, which increased its

life-span by more than 20 years. HAL has also obtained several multi-million dollar contracts

from leading international aerospace firms such as Airbus, Boeing and Honeywell to

manufacture aircraft spare parts and engines.

Mission and Values :

Mission:

" To become a globally competitive aerospace industry while working as an 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:

CUSTOMER SATISFACTION

We are dedicated to building a relationship with our customers where we become

partners in fulfilling their mission. We strive to understand our customers ' needs and

to deliver products and services that fulfil and exceed

 all their requirements.

COMMITMENT TO TOTAL QUALITY

We are committed to continuous improvement of all our activities. We will supply

products and services that conform to highest standards of design, manufacture,

reliability, maintainability and fitness for use as desired by our customers. 

COST AND TIME CONSCIOUSNESS

We believe that our success depends on our ability to continually reduce the cost and

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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.  

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. 

TRUST AND TEAM SPIRIT

We believe in achieving harmony in work life through mutual trust, transparency, co-

operation, and a sense of belonging. We will strive for building empowered teams to

work towards achieving organisational goals. 

RESPECT FOR THE INDIVIDUAL

We value our people. We will treat each other with dignity and respect and strive for

individual growth and realisation of everyone's full potential. 

Evolution and Expansion:

Today, HAL has 19 Production Units and 9 Research and Design Centers in 7 locations in

India. The Company has an impressive product track record - 12 types of aircraft

manufactured with in-house R & D and 14 types produced under license. HAL has

manufactured over 3550 aircraft, 3600 engines and overhauled over 8150 aircraft and

27300 engines.

HAL has been successful in numerous R & D programs developed for both Defense and Civil

Aviation sectors. HAL has made substantial progress in its current projects:

Dhruv, which is Advanced Light Helicopter (ALH)

Tejas - Light Combat Aircraft (LCA)

Intermediate Jet Trainer (IJT)

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Various military and civil upgrades.

Dhruv was delivered to the Indian Army, Navy, Air Force and the Coast Guard in

March 2002; in the very first year of its production is a unique achievement.

HAL has played a significant role for India's space programs by participating in the

manufacture of structures for Satellite Launch Vehicles like

PSLV (Polar Satellite Launch Vehicle)

GSLV (Geo-synchronous Satellite Launch Vehicle)

IRS (Indian Remote Satellite)

INSAT (Indian National Satellite)

HAL has formed the following Joint Ventures (JVs) :

BAeHAL Software Limited

Indo-Russian Aviation Limited (IRAL)

Snecma HAL Aerospace Pvt Ltd

SAMTEL HAL Display System Limited

HALBIT Avionics Pvt Ltd

HAL-Edgewood Technologies Pvt Ltd

INFOTECH HAL Ltd

 Apart from these seven, 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 Defense Services, Coast Guards and Border

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Security Forces. 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.

 HAL was awarded the “INTERNATIONAL GOLD MEDAL AWARD” for

Corporate Achievement in Quality and Efficiency at the International Summit (Global

Rating Leaders 2003), London, UK by M/s Global Rating, UK in conjunction with the

International Information and Marketing Centre (IIMC).

HAL was presented the International - “ARCH OF EUROPE” Award in Gold

Category in recognition for its commitment to Quality, Leadership, Technology and

Innovation.

 At the National level, HAL won the "GOLD TROPHY" for excellence in Public

Sector Management, instituted by the Standing Conference of Public Enterprises

(SCOPE).

HAL is one of the largest aerospace companies in Asia with its annual turnover to be running

above US$2 billion. More than 40% of HAL's revenues come from international deals to

manufacture aircraft engines, spare parts, and other aircraft materials. The Company scaled

new heights in the financial year 2006-07 with a turnover of Rs.7,783.61 Crores.

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Organizational growth of HAL :-

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People :

Customers :

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List of the domestic customers and international customers as follows:

International Customers

Domestic Customers

Airbus Industrie, France

APPH Bolton, UK

BAE Systems, UK

Chelton, UK

Coast Guard, Mauritius

Corporate Air, Philippines

Cosmic Air, Nepal

Dassault Aviation, France

Dowty Aerospace Hydraulics, UK

EADS, France

ELTA, Israel

Gorkha Airlines, Nepal

Hampson, UK

Honeywell International, USA

Island Aviation Services, Maldives

Israel Aircraft Industries, Israel

Messier Dowty Ltd., UK

Mistubishi Heavy Industries, Japan

MOOG, USA

Namibian Air Force, Namibia

Peruvian Air Force , Peru

Rolls Royce Plc, UK

Royal Air Force, Oman

Royal Malaysian Air Force, Malaysia

Royal Nepal Army, Nepal

Royal Thai Air Force, Thailand

Smiths Industries, UK

Snecma, France

Strongfield Technologies, UK

The Boeing Aircraft Company, USA

Transworld Aviation, UAE

Vietnam Air Force, Vietnam

Air India

Air Sahara

Airports Authority of India

Bharat Electronics

Border Security Force

Coal India

Defence Research & Development

Organisation

Govt. of Andhra Pradesh

Govt. of Jammu & Kashmir

Govt. of Karnataka

Govt. of Maharashtra

Govt. of Rajasthan

Govt. of Uttar Pradesh

Govt. of West Bengal

Indian Airforce

Indian Airlines

Indian Army

Indian Coast Guard

Indian Navy

Indian Space Research Organisation

Jet Airways

Kudremukh Iron ore Company ltd.

NALCO

Oil & Natural Gas Corporation Ltd.

Ordnance Factories

Reliance Industries

United Breweries

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Divisions :

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Accessories Division of HAL was established in 1970 with the primary objective of

manufacturing systems and accessories for various aircraft and engines and attains self

sufficiency in this area. Its facilities are spread over 94,000 sqm of built area set in sylvan

surroundings. At present it is turning out over 1100 different types of accessories. The

Division started with manufacturing various Systems and Accessories viz, Hydraulics,

Engine Fuel System, Air-conditioning and Pressurization, Gyro & Barometric Instruments,

Electrical System items, Undercarriages, Electronic items all under one roof to meet the

requirements of the aircraft, helicopters and engines being produced by HAL. This was

followed up with manufacturing the same range of accessories for MiG series of aircraft,

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International Jaguar and repair / overhaul of Mirage-2000 & Sea-Harrier accessories. In

addition the Division manufactures systems for Civil Aircraft i.e. Avro, Dornier and AN-32

& cheetah, chetak & Advanced Light Helicopters.

The Division diversified not only in other defense applications like tanks and armored

vehicles for Army, it look commercial applications of hydraulic items. Gyroscopic

Equipment, Special Purpose Test Equipment & Group Support Equipment and successfully

supplied in the market. The Division has been in the forefront of accessories development

and supply not only to Indian Force but to Army, Navy and various Defense Laboratories as

well as for Space applications.

The Division today has a prime name in the Aviation market and various international

companies are interested to join hands with it for future projects. The Division has also made

steady progress in the area of Export.

Products

Instruments, Sensors, Gyros

Flight instruments, Electrical Indicators, Fuel Gauging Probes, Gyros, Sensors and

Switches

Electrical power generation and control

AC/DC Generator, Control and Protection Units, Inverters, Transformer Rectifier

units ac dc, actuator.

Land navigation system

Microprocessor Controller

Undercarriage, Wheels and brakes

Hydraulics system and power control.

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Environmental control system

Pneumatics and Oxygen System, Cold Air Unit, Water Extractors, Valve - various

types

Ejection system

Ejection Seats, Release Units etc.

Engine fuel control system

Booster Pumps, Main and Reheat Fuel Systems, Nozzle Actuators

Ground support equipment and test rigs

Ground Power Unit, Hydraulic Trolley and  {Power Packs, Dedicated Test Rigs,

custom-built Fuel/Hydraulic Test Rig

 Export Products

Supply of Rotables and Spares of Jaguar International and Cheetah (Lama) / Chetak

(Alouette) Helicopters

Repair / Overhaul of aircraft accessories of MiG series Aircraft, Jaguar International Aircraft,

Cheetah (Lama) / Chetak (Alouette) Helicopters and Dornier Multi-role Aircraft

Supply of Ground Support Equipment for Aircraft such as MiG-23 / 27 / 29, Mirage-2000,

Jaguar, Light Combat Aircraft (LCA) Su-30 MKI, Sea Harrier, Dornier DO-228, Avro HS-

748 (Specific Version), Cheetah (Lama) / Chetak (Alouette lll), Ml - 17, Advanced Light

Helicopter (ALH).

Services

Repairs, Major servicing and supply of spares

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The Division carries out Repair and Overhaul of Accessories, with minimum turn-around-

time. Site Repair facilities are offered by the Division by deputing team of expert Engineers /

Technicians.Services provided for:

Military Aircraft

MiG Series

Jaguar

Mirage-2000

Sea – Harrier

AN-32

Kiran MK- I / MK- II

HPT - 32

SU-30 MKI

Civil Aircraft

Dornier-22B

AVRO HS-748

Helicopters

Chetak (Alouette)

Cheetah (Lama)14

ALH (IAF / NAVY / COAST GUARD  / C

Sub-contract Capabilities

The Division has comprehensive manufacturing capabilities for various Hi-tech

components, Equipment and Systems to customer's specifications and ensures high

quality, reliability and cost effectiveness.

The Division has over 25 years of experience in producing aeronautical accessories

making it an ideal partner for the International Aero Engineering Industry.

The Division also manufactures and supplies complete range of components of

Cheetah (Lama) & Chetak (Alouette) Helicopters, Jaguar and MiG series Aircraft to

Domestic and International Customers to support their fleet.

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SYSTEM AND EQUIPMENTS USED IN INSTRUMENT

FACTORY:

FLIGHT DATA RECORDER

A flight data recorder (FDR) (also ADR, for accident data recorder) is a kind of flight

recorder. It is a device used to record specific aircraft performance parameters. Another kind

of flight recorder is the cockpit voice recorder (CVR), which records conversation in the

cockpit, radio communications between the cockpit crew and others (including conversation

with air traffic control personnel), as well as ambient sounds. In some cases, both functions

have been combined into a single unit. The current applicable FAA TSO is C124b titled

Flight Data Recorder Systems.

Popularly referred to as a "black box", the data recorded by the FDR is used for accident

investigation, as well as for analyzing air safety issues, material degradation and engine

performance. Due to their importance in investigating accidents, these ICAO-regulated

devices are carefully engineered and stoutly constructed to withstand the force of a high

speed impact and the heat of an intense fire. Contrary to the "black box" reference, the

exterior of the FDR is coated with heat-resistant bright Red paint for high visibility in

wreckage, and the unit is usually mounted in the aircraft's empennage (tail section), where it 16

is more likely to survive a severe crash. Following an accident, recovery of the "black boxes"

is second in importance only to the rescue of survivors and recovery of human remains.

The flight data recorder is a repository of information about the operation of the aircraft.

Sensors positioned throughout the aircraft relay information about the plane for storage in the

data recorder.

The common nomenclature for the FDR, the "black box," is actually a misnomer, since the

unit is typically bright red or orange to facilitate visual location after a crash. The FDR is

encased in heavy steel and surrounded by multiple layers of insulation to provide protection

against a crash, fire, and extreme climatic conditions.

The device records actual flight conditions, including altitude, airspeed, heading, vertical

acceleration, and aircraft pitch. A second device, the cockpit voice recorder (CVR), keeps

tabs on cockpit conversations and engine noise. Both are installed in the rear of the aircraft.

In the 1970s, FDR technology was combined with a flight-data acquisition unit (FDAU),

located at the front of the aircraft. The unit acts as the relay for the entire data-recording

process. Sensors run from various areas on the plane to the FDAU, which in turn sends the

information to the FDR.

Solid-state recorders track a much greater number of parameters; 700 are tracked compared

to the magnetic tape parameter recording potential of 100. Faster data flow allows the solid-

state devices to record up to 25 hours of flight data. In 1997, the United States Federal

Aviation Administration (FAA) issued a requirement that all aircraft manufactured after

August 19, 2002, record at least 88 parameters. The action came in the wake of two B-737

airplane crashes in which insufficient data was available to determine the cause of the

accidents.

Modern day devices also track time, control-column position, rudder-pedal position, control-

wheel position, horizontal stabilizer, and fuel flow.

Since its inception, the FDR has played a vital role in establishing the probable cause of a

crash or other unusual occurrences and has allowed safety regulators to implement corrective

actions. The value of flight data recorders was clearly evident in the investigation of the

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ATR-72 accident in Roselawn, Indiana, in October 1994. The FDR captured information on

115 parameters. Analysis of the data revealed a telltale, rapid wing movement that prompted

the National Transportation and Safety Board to immediately issue urgent safety

recommendations to improve flying in icy conditions.

Design of FDR

The design of today's FDR is governed by the internationally recognized standards and

recommended practices relating to flight recorders which are contained in ICAO Annex 6

which makes reference to industry crashworthiness and fire protection specifications such as

those to be found in the European Organization for Civil Aviation Equipment documents

EUROCAE ED55, ED56 fiken A and ED112 (Minimum Operational Performance

Specification for Crash Protected Airborne Recorder Systems). In the United States, the

Federal Aviation Administration (FAA) regulates all aspects of U.S. aviation, and cites

design requirements in their Technical Standard Order, based on the EUROCAE documents

(as do the aviation authorities of many other countries).

Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of

3400 g (33 km/s²) for 6.5 milliseconds. This is roughly equivalent to an impact velocity of

270 knots (310 mph) and a deceleration or crushing distance of 450 cm. Additionally, there

are requirements for penetration resistance, static crush, high and low temperature fires, deep

sea pressure, sea water immersion, and fluid immersion.

Modern day FDRs receive inputs via specific data frames from the FDAU units. They record

significant flight parameters, including the control and actuator positions, engine information

and time of day. There are 88 parameters required as a minimum under current U.S. federal

regulations (only 29 were required until 2002), but some systems monitor many more

variables. Generally each parameter is recorded a few times per second, though some units

store "bursts" of data at a much higher frequency if the data begins to change quickly. Most

FDRs record approximately 17–25 hours’ worth of data in a continuous loop. It is required by

regulations, that an FDR verification check (readout) is performed annually, in order to verify

that all mandatory parameters are recorded.

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This has also given rise to flight data monitoring programs, whereby flights are analyzed for

optimum fuel consumption and dangerous flight crew habits. The data from the FDR is

transferred, in situ, to a solid state recording device and then periodically analyzed with some

of the same technology used for accident investigations.

GYROSCOPE

A gyroscope is a device for measuring or maintaining orientation, based on the principles of

conservation of angular momentum.

Any heavy rotating mass can be called gyro.

BASIC PROPERTIES OF GYROSCOPES

Gyroscopes have two basic properties: rigidity and precession. Those properties are defined

as follows:

1. RIGIDITY — The axis of rotation (spin axis) of the gyro wheel tends to remain in a fixed

direction in space if no force is applied to it. 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 19

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).

Universally Mounted Gyroscope

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 — The axis of rotation has a tendency to turn at a right angle to the

direction of an applied force. The idea of maintaining a fixed direction in space is simple to

illustrate. When any object is spinning rapidly, it tends to keep its axis pointed always in the

same direction. A toy top is a good example. As long as the top is spinning fast, it stays

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balanced on its point. Because of this gyro action, the spinning top resists the tendency of

gravity to change the direction of its axis.

In helicopters, gyros are typically used to dampen the tail movements or in the case of the

heading hold gyro, to keep the tail in a constant position.

However, the modern RC helicopter gyro isn’t really a gyroscope at all – it’s an

accelerometer. Accelerometers produce a signal as they’re rotated about an axis just like a

traditional gyro and the more it accelerates, the stronger the signal is.

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, above). This turning

movement, or precession, places the rotor in a new plane of rotation, parallel to the applied

for 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 process. 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

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erected have caging devices to hold the gimbals in place. Even 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 a simple pictorial representation of gyroscope

Fig.a

Itead 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.

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Fig .b

Fig.c

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 a. 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 travelling in the upward direction when it is at

the 90 degrees position in Fig b, and point C will be travelling in the downward direction.

The combined motion of A and C cause the axis to rotate in the "precession plane" to the

right Fig.b This is called precession. A gyro's axis will move at a right angle to a rotating 23

motion. In this case to the right. If the gyro were rotating counter clockwise, 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.c, 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 gimbals. Gyroscopes, when

gimballed, only resist a tilting change in their axis. The axis does move a certain amount

with a given force.

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Fig.d gyro in a plane perpendicular to tilting force

Figure d shows a simplified gyro that is gimballed in a plane perpendicular to the tilting

force. As the rim rotates through the gimballed 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 gimballed gyro functions

Here it is explained that how much the axis will rotate around a gimballed axis. That

is to say, how fast it rotates in the direction of a tilting force.

In figure d, the precession plane in the gimballed example functions differently than

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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.e-average mass and distance from axis in the tilting plane

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 e 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

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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 a. 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.

Types of Gyro

There are three main types of gyros:

1. Mechanical rate gyro: The first is the mechanical rate gyro uses an electric motor to

spin a small disc or flywheel that can pivot on one axis and has springs to return it to center.

When the gyro was moved about the axis that it’s sensitive to, the spinning disc tilts and this

tilt is picked up electronically by a potentiometer.

The faster the gyro is rotated, the greater the deflection is and based on the deflection, the

corrective signal can be fed into a servo.

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2. Piezoelectric gyro: The second type of gyro is the piezoelectric gyro which uses a

quickly vibrating crystal. As the crystal vibrates, an applied rotational force will cause

disturbances in it’s wobble which create a small, but measurable electric current proportional

to the rate at which the gyro is rotated.

The piezo element is similar to that used in a gas lighter system like those found on a

barbeque.

Piezo electric gyros are much more sensitive than a mechanical gyro and because there are no

moving parts, they are a lot smaller.

(Piezoelectric gyro)

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A disadvantage of piezoelectric gyros systems is that they’re very temperature sensitive and

going from hot to cold or vice versa will casue them to act erradictly. Most have built in

temperature protection circuits, but they’re not perfect, so if you’re going to take a gyro from

warm your car and fly in cold weather, give it 10 or 15 minutes to adjust before flying.

3. Micro Electric-Mechanical System gyro: MEMS are molecule sized machines that

are fabricated on top of a piece of silicon, along with the electronics to interface to them.

They vibrate at a high rate just like the piezoelectric gyro and the As the gyro rotates, so does

the displacement of the mass and the signal generated by the gyro.

(MEMS gyro)

Besides the different makups and types of gyros, there are two primary ways that gryo’s

operate, rate and heading hold mode.

Rate Mode Vs. Heading Hold Gyros

There are two types of gyro functions, rate mode and heading hold.

Rate Gyros

Rate gyro’s are often used in scale RC helicopters because they lend themselves to a more

realistic flying experience, while heading hold gyros are used by almost eveyone else because

they make flying easier.

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Rate gyros only sense the turn rate or angular acceleration of your helicopter, not the absolute

orientation of the helicopter and do not provide a heading hold capability. For example, once

the helicopter has been turned, it cannot return the helicopter to the original orientation, nor

keep the helicopter facing a constant direction.

Rate gyros will simply control your RC heliecopter’s tail servo so as to resist rotation in the

direction they measure. In other words, it “dampens” the tail movement.

Because a rate gyro “slips” when trying to counteract the main rotor’s thrust, it can’t

effectively counteract the main rotor’s thrust on it’s own.

The amount of thrsust provided by the tail is set by the revo mixing function on your radio

transmitter.

Revo mixing allows you to set the tail rotor thrust to match the throttle curve so that it exactly

counters the main rotor’s thrust. There’s no formula for setting the values – they must be set

by experience and trial and error.

Heading Hold Gyros

Heading hold or heading lock gyros are a conceptually simple extension of rate gyros.

In a heading hold gyro, a built microprocessor that keeps track of and remembers how far the

helicopter has turned from its set position. Based on the deflection from the set position, the

gyro will control the rudder servo such that the gyro returns the helicopter to the set position.

Therefore, as you increate the throttle or head speed of your heli, the holding hold gyro will

counter the main rotors thrust automatically keeping your heli’s tail in its original position.

Heading hold gyros are very popular and pretty much standard among RC helicopter pilots

for that very reason - they’ll hold your tail in a constant position no matter what you’re doing

as long as you don’t input a rudder command, even if you’re doing 3D aerobatics or flying in

a strong wind.

With a heading hold gyro, the rudder signal from your transmitter no longer directly controls

the tail – it simply tells the gyro how many degrees to turn per second. It will also reset the

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gyros stored position to the new position you move your heli to. Revo mixing on your radio

must be disabled when using heading hold gyros.

In conclusion, unless you’re going scale, and are looking for the more real characteristics

often associated with scale RC helicopter flight, you’ll want to purchase a heading hold gyro,

preferably of the piezoelectric or MEMS .

FUEL CONTENT GAUGE

A fuel gauge (or gas gauge) is an instrument used to indicate the level of fuel contained in a

tank. Commonly used in cars, these may also be used for any tank including underground

storage tanks.

As used in cars, the gauge consists of two parts:

The sensing unit

The indicator

The sensing unit usually uses a float connected to a potentiometer. As the tank empties, the

float drops and slides a moving contact along the resistor, increasing its resistance. In

addition, when the resistance is at a certain point, it will also turn on a "low fuel" light on

some vehicles.

Meanwhile, the indicator unit (usually mounted on the dashboard) is measuring and

displaying the amount of electrical current flowing through the sending unit. When the tank

level is high and maximum current is flowing, the needle points to "F" indicating a full tank.

When the tank is empty and the least current is flowing, the needle points to "E" indicating an

empty tank.

The system is fail-safe; a fault that opens the electrical circuit causes the indicator to show the

tank as being empty (which will provoke the driver to refill the tank(in theory)) rather than

full (which would allow the driver to run out of fuel with no prior notification). However this

system has a potential risk associated with it. An electric current is sent through the variable

resistor to which a float is connected, so that the value of resistance depends on the fuel level.

In most of automotive fuel gauges such resistors are on the inward side of gauge i.e inside

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fuel tank. Sending current through such a resistor has fire hazard (and a explosion risk)

associated with it. Therefore there is demand for another safer (and cheaper) method to be

invented.

Systems that measure large fuel tanks (including underground storage tanks) may use the

same electro-mechanical principle or may make use of a pressure sensor, sometimes

connected to a mercury manometer.

TEMPERATURE SENSOR

PIN 1722.00.000

Function:

Temperature sensor used in helicopter to sense the temperature of the medium in

which sensitive ports (bulb) of the unit is immersed and sent out signal to a temperature

indicator

Principle of operation:

Increase in resistance of metal with increase in temperature.

Construction:

Consists of mixed resistance temperature detector, wound on an insulated former,

these are mounted in a tabular body closed at one end.

This end of element is soldered to two pins of electrical connector receptor assembly

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Working:

Due to change in temperature resistance of temperature detector changes and

appropriate signal is sent to temperature detector

Specification:

1. Insulation resistance > 20m ohm

2. length = 82.5-83.5mm

3. Weight = 25gms max.

Ground Power Protection Unit

It monitors the output parameters of ground power contactor, protects aircraft utilization

equipment from unhealthy ground power by fault signalling processing and tripping the

ground contactor.

Input

• Voltage range: 3 x 400 V ±15%

• Frequency: 50/60 Hz ±5%

• Rectification: 6 pulse

• Line current: 28 A

• Power factor: >0.9

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Output

• Current: 600 A continuously

(can be limited to 300 A upon request

• Voltage: 28 VDC (or as adjusted)

• Output voltage: 19-33 V

• Voltage compensation: 0-3 V

Protection

• Protection class: IP55

• Over/under voltage at in/output

• Phase sequence at input

• Over temperature

• Internal voltage error

• Short circuit at output

• Over and under voltage at output

• Trip in case that:

U<20 VDC for more than 4 seconds

U>32 VDC for more than 4 seconds

U<40 VDC for more than 1 second

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Weight

• Fixed unit approx. 200 kg

• Mobile unit approx. 275 kg

Environmental

• Operating temperature:

-40°C to +52°C (125°F)

• Relative humidity 10-95%

• Noise level <65 dB(A)at1m -

Typically 60 dB(A)

Overload ratings - 600 A

• 1200 A for 30 seconds

• 1800 A for 10 seconds

INVERTER:-

The output of the inverter (for CHETAK), gives the supply of single phase 115 Vrms

sinusoidal AC at 400Hz, while energized from the aircraft DC bar of 28V. The inverter can

handle a maximum of continuous load of instruments or equipments.

The inverter basically converts the DC source to AC.

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The inverter can be divided into the following:-

Main power circuit

Control unit

Protection circuit

The main power circuit consists of an power amplifier.

The control circuit consists of the power supply controller, oscillator, regulator and a buffer

amplifier.

Protection circuit performs the function of protecting the inverter from

Output over voltage

Output over current

Output under voltage

Input reverse polarity

input under voltage

Ratings for the inverter used in JAGUAR:

Maximum input current: 16 amp dc

Input voltage: 24V to 29V dc

Output Voltage:115 +/- 4 Vrms AC

Output Frequency:400Hz +/- 10Hz

Maximum Power: 250 VA

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Efficiency: 51% at 24 to 29 V dc

The 28 V DC flows into the unit through a relay to the single phase push pull power amplifier

consisting of power transistors and the primary winding of the output transformer. The

secondary of the output transformer is made available as the inverter output giving the supply

of 115 Vrms, 400Hz.

Uses: It is used in CHETAK helicopters

FUEL INJECTION SYSTEM

Fuel injection is a system for mixing fuel with air in an internal combustion engine. It has

become the primary fuel delivery system used in automotive petrol engines, having almost

completely replaced carburetors in the late 1980s.

A fuel injection system is designed and calibrated specifically for the type(s) of fuel it will

handle. Most fuel injection systems are for gasoline or diesel applications. With the advent of

electronic fuel injection (EFI), the diesel and gasoline hardware has become similar. EFI's

programmable firmware has permitted common hardware to be used with different fuels.

Carburetors were the predominant method used to meter fuel on gasoline engines before the

widespread use of fuel injection. A variety of injection systems have existed since the earliest

usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection atomizes

the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor

relies on low pressure created by intake air rushing through it to add the fuel to the airstream.

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The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from a pump

or a pressure container farther back in the fuel supply.

AVIATION FUEL

Aviation fuel is a specialized type of petroleum-based fuel used to power aircraft. It is

generally of a higher quality than fuels used in less critical applications such

as heating or road transport, and often contains additives to reduce the risk of icing or

explosion due to high temperatures, amongst other properties.

Most aviation fuels available for aircraft are kinds of petroleum spirit used in engines with

spark plugs i.e. piston engines and Wankel rotaries or fuel for jet turbine engines which is

also used in diesel aircraft engines. Alcohol, alcohol mixtures and other alternative fuels may

be used experimentally but are not generally available.

Avgas is sold in much lower volumes, but to many more individual aircraft, whereas Jet

fuel is sold in high volumes to large aircraft operated typically by airlines, military and large

corporate aircraft.

The Convention on International Civil Aviation, which came into effect in 1947, exempted

air fuels from tax. Australia and the USA oppose a worldwide levy on aviation fuel, but a

number of other countries have expressed interest.

FLIGHT CONTROL SURFACES

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Aircraft flight control surfaces allow a pilot to adjust and control the aircraft's flight attitude.

Development of an effective set of flight controls was a critical advance in the development

of aircraft. Early efforts at fixed-wing aircraft design succeeded in generating sufficient lift to

get the aircraft off the ground, but once aloft, the aircraft proved uncontrollable, often with

disastrous results. The development of effective flight controls is what allowed stable flight.

This article describes controls used on a fixed wing aircraft of conventional design. Other

fixed wing aircraft configurations may use different control surfaces but the basic principles

remain. The controls (stick and rudder) for rotary wing aircraft (helicopter or autogyro)

accomplish the same motions about the 3 axes of rotation, but manipulate the rotating flight

controls (main rotor disk and tail rotor disk) in a completely different manner.

Axes of motion

(Rotation along three axis)

An aircraft is free to rotate around three axes which are perpendicular to each other and

intersect at the plane's center of gravity (CG). To control position and direction a pilot must

be able to control rotation about each of them.

Vertical axis

The vertical axis passes through the plane from top to bottom. Rotation about this axis

is called yaw. Yaw changes the direction the aircraft's nose is pointing, left or right.

The primary control of yaw is with the rudder. Ailerons also have a secondary effect

on yaw.

Longitudinal axis

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The longitudinal axis passes through the plane from nose to tail. Rotation about this

axis is called bank or roll. Bank changes the orientation of the aircraft's wings with

respect to the downward force of gravity. The pilot changes bank angle by increasing

the lift on one wing and decreasing it on the other. This differential lift causes bank

rotation around the longitudinal axis. The ailerons are the primary control of bank.

The rudder also has a secondary effect on bank.

Lateral axis

The lateral axis passes through the plane from wingtip to wingtip. Rotation about this

axis is called pitch. Pitch changes the vertical direction the aircraft's nose is pointing.

The elevators are the primary control of pitch.

It is important to note that these axes move with the aircraft, and change relative to

the earth as the aircraft moves. For example, for an aircraft whose left wing is

pointing straight down, its "vertical" axis is parallel with the ground, while its

"lateral" axis is perpendicular to the ground.

Main control surfaces

The main control surfaces of a fixed-wing aircraft are attached to the airframe on

hinges or tracks so they may move and thus deflect the air stream passing over them. This

redirection of the air stream generates an unbalanced force to rotate the plane about the

associated axis.

Ailerons

Ailerons  are mounted on the trailing edge of each wing near the wingtips, and move

in opposite directions. When the pilot moves the stick left, or turns the wheel counter-

clockwise, the left aileron goes up and the right aileron goes down. A raised aileron

reduces lift on that wing and a lowered one increases lift, so moving the stick left

causes the left wing to drop and the right wing to rise. This causes the plane

to bank left and begin to turn to the left. Centering the stick returns the ailerons to

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neutral maintaining the bank angle. The plane will continue to turn until opposite

aileron motion returns the bank angle to zero to fly straight.

Fig. Position of Ailerons

Elevator

An elevator is mounted on the back edge of the horizontal stabilizer on each side of

the fin in the tail. They move up and down together. When the pilot pulls the stick

backward, the elevators go up. Pushing the stick forward causes the elevators to go

down. Raised elevators push down on the tail and cause the nose to pitch up. This

makes the wings fly at a higher angle of attack which generates more lift and

more drag. Centering the stick returns the elevators to neutral and stops the change of

pitch. Many aircraft use a stabilator— a moveable horizontal stabilizer — in place of

an elevator. Some aircraft, such as an MD-80, use a control tab within the elevator

surface to aerodynamically backdrive the main surface into position. The direction of

travel of the control tab will thus be in a direction opposite to the main control

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surface. It is for this reason that an MD-80 tail looks like it has a 'split' elevator

system.

Rudder

The rudder is typically mounted on the back edge of the fin in the empennage. When

the pilot pushes the left pedal, the rudder deflects left. Pushing the right pedal causes

the rudder to deflect right. Deflecting the rudder right pushes the tail left and causes

the nose to yaw right. Centering the rudder pedals returns the rudder to neutral and

stops the yaw.

Turning the aircraft

Unlike a boat, turning an aircraft is not normally carried out with the rudder. With aircraft,

the turn is caused by the horizontal component of lift. The lifting force, perpendicular to the

wings of the aircraft, is tilted in the direction of the intended turn by rolling the aircraft into

the turn. As the bank angle is increased the lifting force, which was previously acting only in

the vertical, is split into two components: One acting vertically and one acting horizontally.

If the total lift is kept constant, the vertical component of lift will decrease. As the weight of

the aircraft is unchanged, this would result in the aircraft descending if not countered. To

maintain level flight requires increased positive (up) elevator to increase the angle of attack,

increase the total lift generated and keep the vertical component of lift equal with the weight

of the aircraft. This cannot continue indefinitely. The wings can only generate a finite amount

of lift at a given air speed. As the load factor (commonly called G loading) is increased an

accelerated aerodynamic stall will occur, even though the airplane is above its 1G stall speed.

Secondary control surfaces

Trim

Trimming controls allow a pilot to balance the lift and drag being produced by the

wings and control surfaces over a wide range of load and airspeed. This reduces the

effort required to adjust or maintain a desired flight attitude.

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Elevator trim

Elevator trim balances the control force necessary to maintain the aerodynamic down

force on the tail. Whilst carrying out certain flight exercises, a lot of trim could be

required to maintain the desired angle of attack. This mainly applies to slow flight,

where maintaining a nose-up attitude requires a lot of trim. Elevator trim is correlated

with the speed of the airflow over the tail, thus airspeed changes to the aircraft require

re-trimming. An important design parameter for aircraft is the stability of the aircraft

when trimmed for level flight. Any disturbances such as gusts or turbulence will be

damped over a short period of time and the aircraft will return to its level flight

trimmed airspeed.

Trimming tail plane

Except for very light aircraft, trim tabs on elevators are unable to provide the force

and range of motion desired. To provide the appropriate trim force the entire

horizontal tail plane is made adjustable in pitch. This allows the pilot to select exactly

the right amount of positive or negative lift from the tail plane while reducing drag

from the elevators.

Control horn

A control horn is a section of control surface which projects ahead of the pivot point.

It generates a force which tends to increase the surface's deflection thus reducing the

control pressure experienced by the pilot. Control horns may also incorporate

a counterweight which helps to balance the control and prevent it from "fluttering" in

the airstream. Some designs feature separate anti-flutter weights.

Spring trim

In the simplest cases trimming is done by a mechanical spring (or bungee) which adds

appropriate force to augment the pilot's control input. The spring is usually connected

to an elevator trim lever to allow the pilot to set the spring force applied.

Rudder and aileron trim

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Trim doesn't only apply to the elevator, as there is also trim for the rudder and

ailerons. The use of this is to counter the effects of slip stream, or to counter the

effects of the centre of gravity being to one side. This can be caused by a larger

weight on one side of the aircraft compared to the other, such as when one fuel tank

has a lot more fuel in it than the other, or when there are heavier people on one side of

the aircraft than the other.

EJECTION SEAT

In aircraft, an ejection seat is a system designed to rescue the pilot or other crew of an aircraft

(usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by

an explosive charge or rocket motor, carrying the pilot with it. The concept of an eject-

able escape capsule has also been tried. Once clear of the aircraft, the ejection seat deploys

a parachute. Ejection seats are common on certain types of military aircraft.

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History

United States Air Force F-15 Eagle ejection seat test using a mannequin

A bungee-assisted escape from an aircraft took place in 1910. In 1916 Everard Calthrop, an

early inventor of parachutes, patented an ejector seat using compressed air.

45

The modern layout for an ejection seat was first proposed by Romanian inventor Anastase

Dragomir in the late 1920s. The design, featuring a parachuted cell (a dischargeable chair

from an aircraft or other vehicle), was successfully tested on August 25, 1929 at the Paris-

Orly Airport near Paris and in October 1929 at Băneasa, near Bucharest. Dragomir patented

his "catapult-able cockpit" at the French Patent Office (patent no. 678566, of April 2,

1930, Nouveau système de montage des parachutes dans les appareils de locomotion

aérienne).

The design was perfected during World War II. Prior to this, the only means of escape from

an incapacitated aircraft was to jump clear ("bail-out"), and in many cases this was difficult

due to injury, the difficulty of egress from a confined space, g   forces , the airflow past the

aircraft, and other factors.

The first ejection seats were developed independently during World War

II by Heinkel and SAAB. Early models were powered by compressed air and the first aircraft

to be fitted with such a system was the Heinkel He 280 prototype jet fighter in 1940. One of

the He 280 test pilots, Helmut Schenk, became the first person to escape from a stricken

aircraft with an ejection seat on 13 January 1942 after his control surfaces iced up and

became inoperable. The fighter, being used in tests of the Argus As 014 impulse jets

for Fieseler Fi 103 missile development, had its regular HeS 8A turbojets removed, and was

towed aloft from Rechlin, Germany by a pair of Bf 110C tugs in a heavy snow-shower. At

7,875 feet (2,400 m), Schenk found he had no control, jettisoned his towline, and ejected. The

He 280, however, never reached production status. Thus, the first operational type to provide

ejection seats for the crew was the Heinkel He 219   Uhu  night fighter in 1942.

In Sweden a version using compressed air was tested in 1941. A gunpowder ejection seat was

developed by Bofors and tested in 1943 for theSaab 21. The first test in the air was on a Saab

17 on 27 February 1944, and the first real use occurred by Lt. Bengt Johansson (who later

changes it to Järkenstedt) on 29 July 1946 after a mid-air collision between a J 21 and a J 22.

46

In late 1944, the Heinkel He 162 featured a new type of ejection seat, this time fired by an

explosive cartridge. In this system the seat rode on wheels set between two pipes running up

the back of the cockpit. When lowered into position, caps at the top of the seat fitted over the

pipes to close them. Cartridges, basically identical to shotgun shells, were placed in the

bottom of the pipes, facing upward. When fired, the gases would fill the pipes, "popping" the

caps off the end, and thereby forcing the seat to ride up the pipes on its wheels and out of the

aircraft. By the end of the war, the Do-335   Pfeil  and a few prototype aircraft were also fitted

with ejection seats.

After World War II, the need for such systems became pressing, as aircraft speeds were

getting ever higher, and it was not long before thesound barrier was broken. Manual escape at

such speeds would be impossible. The United States Army Air Forces experimented with

downward-ejecting systems operated by a spring, but it was the work of Sir James Martin and

the British company Martin-Baker that was to prove crucial.

The first live flight test of the Martin-Baker system took place on 24 July 1946, when

Bernard Lynch ejected from a Gloster Meteor Mk III. Shortly afterward, on 17 August 1946,

1st Sgt. Larry Lambert was the first live U.S. ejectee. Martin-Baker ejector seats were fitted

to prototype and production aircraft from the late 1940s, and the first emergency use of such a

seat occurred in 1949 during testing of theArmstrong-Whitworth AW.52 Flying Wing.

Early seats used a solid propellant charge to eject the pilot and seat by igniting the charge

inside a telescoping tube attached to the seat. As aircraft speeds increased still further, this

method proved inadequate to get the pilot sufficiently clear of the airframe. Increasing the

amount of propellant risked damaging the occupant's spine, so experiments with rocket

propulsion began. In 1958 the F-102 Delta Dagger was the first aircraft to be fitted with a

rocket-propelled seat. Martin-Baker developed a similar design, using multiple rocket units

feeding a single nozzle. The greater thrust from this configuration had the advantage of being

able to eject the pilot to a safe height even if the aircraft was on or very near the ground.

47

In the early 1960s, deployment of rocket-powered ejection seats designed for use at

supersonic speeds began in such planes as the F-106 Delta Dart. Six pilots have ejected at

speeds exceeding 700 knots (1,300 km/h; 810 mph). The highest altitude at which a Martin-

Baker seat was deployed was 57,000 ft (from a Canberra bomber in 1958). Following an

accident on 30 July 1966 in the attempted launch of a D-21 drone, two Lockheed M-21 crew

members ejected at Mach 3.25 at an altitude of 80,000 ft (24,000 m) The pilot was recovered

successfully, however the observer drowned after a water landing. Despite these records,

most ejections occur at fairly low speeds and altitudes, when the pilot can see that there is no

hope of regaining aircraft control before impact with the ground.

Pilot safety

The purpose of an ejection seat is pilot survival. The pilot typically experiences an

acceleration of about 12–14 g (117–137 m/s²). Western seats usually impose lighter loads on

the pilots; 1960s-70s era Soviet technology often goes up to 20–22 g (with SM-1 and KM-1

gunbarrel-type ejection seats). Compression fractures of vertebrae were (and are) a recurrent

side effect of ejection, and are often a career-ending (if not fatal) injury for pilots and

aviators.

The U.S. government selected the Martin-Baker seat for the U.S.A.'s new Joint Strike

Fighter. The F-22 Raptor uses a variant of the ACES II ejection seat. The capabilities of the

Zvezda K-36 were unintentionally demonstrated at the Fairford Air Show on 24 July 1993

when the pilots of two MiG-29 fighters successfully ejected after a mid-air collision.

48

The minimal ejection altitude for ACES II seat in inverted flight is about 140 feet (43 m)

above ground level at 150 KIAS. While the Russian counterpart - K-36DM has the minimal

ejection altitude from inverted flight of 660 feet (200 m) AGL. When an aircraft is equipped

with the Zvezda K-36DM ejection seat and the pilot is wearing the КО-15 protective gear, he

is able to eject at airspeeds from 0 to 1,400 kilometres per hour (870 mph) and altitudes of 0

to 25 kilometres (16 mi). The K-36DM ejection seat features drag chutes and a small shield

that rises between the pilots legs to deflect air around the pilot.

As of July 2010, Martin-Baker ejection seats had saved 7325 lives. They give survivors

a unique tie and lapel pin. The total figure for all types of ejector seats is unknown, but might

be considerably higher.

Egress systems

49

A warning applied on the cockpit side of all aircraft using an ejection seat system.

Intended especially for the maintenance and emergency crews.

The "standard" ejection system operates in two stages. First, the entire canopy or hatch above

the aviator is opened or jettisoned, and the seat and occupant are launched through the

opening. In most earlier aircraft this required two separate actions by the aviator, while later

egress system designs, such as the Advanced Concept Ejection Seat model 2 (ACES II),

perform both functions as a single action.

50

The ACES II ejection seat is used in most American-built fighters. The A-10 uses connected

firing handles that activate both the canopy jettison systems, followed by the seat ejection.

The F-15 has the same connected system as the A-10 seat. Both handles accomplish the same

task, so pulling either one suffices. The F-16 has only one handle located between the pilot's

knees, since the cockpit is too narrow for side-mounted handles.

Non-standard egress systems include Downward Track (used for some crew positions in

bomber aircraft, including the B-52 Stratofortress), Canopy Destruct (CD) and Through-

Canopy Penetration (TCP), Drag Extraction, Encapsulated Seat, and even Crew Capsule.

Early models of the F-104 Starfighter were equipped with a Downward Track ejection seat

due to the hazard of the T-tail. In order to make this work, the pilot was equipped with

"spurs" which were attached to cables that would pull the legs inward so the pilot could be

ejected. Following this development, a number of other egress systems began using leg

retractors as a way to prevent injuries to flailing legs, and to provide a more stable centre of

gravity. Some models of the F-104 were equipped with upward-ejecting seats.

Similarly, two of the six ejection seats on the B-52 Stratofortress fire downward, through

hatch openings on the bottom of the aircraft; the downward hatches are released from the

aircraft by a thruster that unlocks the hatch, while gravity and wind remove the hatch and arm

the seat. The four seats on the forward upper deck (two of them, EWO and Gunner, facing the

rear of the airplane) fire upwards as usual. Any such downward-firing system is of no use on

or near the ground unless the aircraft is upside-down at the time of the ejection.

Aircraft designed for low-level use sometimes have ejection seats which fire through the

canopy, as waiting for the canopy to be ejected is too slow. Many aircraft types (e.g., the BAe

Hawk and the Harrier line of aircraft) use Canopy Destruct systems, which have an explosive

cord (MDC - Miniature Detonation Cord or FLSC - Flexible Linear Shaped Charge)

embedded within the acrylic plastic of the canopy. The MDC is initiated when the eject

handle is pulled, and shatters the canopy over the seat a few milliseconds before the seat is

launched. This system was developed for the Hawker Siddeley Harrier family

of VTOL aircraft as ejection may be necessary while the aircraft was in the hover, and

jettisoning the canopy might result in the pilot and seat striking it.

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Through-Canopy Penetration is similar to Canopy Destruct, but a sharp spike on the top of

the seat, known as the "shell tooth," strikes the underside of the canopy and shatters it. The A-

10 Thunderbolt II is equipped with canopy breakers on either side of its headrest in the event

that the canopy fails to jettison. In ground emergencies, a ground crewman or pilot can use a

breaker knife attached to the inside of the canopy to shatter the transparency. The A-6

Intruder and EA-6 Prowler seats are capable of ejecting through the canopy, with canopy

jettison a separate option if there is enough time.

CD and TCP systems cannot be used with canopies made of flexible materials, such as

the Lexan polycarbonate canopy used on the F-16.

Soviet Yakovlev Yak-38 VTOL naval fighter planes were equipped with automatically

activated ejection seats, mandated by the notorious unreliability of their vertical lifting

powerplants.

Drag Extraction is the lightest and simplest egress system available, and has been used on

many experimental aircraft. Halfway between simply "bailing out" and using explosive-eject

systems, Drag Extraction uses the airflow past the aircraft (or spacecraft) to move the aviator

out of the cockpit and away from the stricken craft on a guide rail. Some operate like a

standard ejector seat, by jettisoning the canopy, then deploying a drag chute into the airflow.

That chute pulls the occupant out of the aircraft, either with the seat or following release of

the seat straps, who then rides off the end of a rail extending far enough out to help clear the

structure. In the case of the Space Shuttle, the astronauts ride a long, curved rail, blown by

the wind against their bodies, then deploy their chutes after free-falling to a safe altitude.

Encapsulated Seat egress systems were developed for use in the B-58 Hustler and B-70

Valkyrie supersonic bombers. These seats were enclosed in an air-operated clamshell, which

permitted the aircrew to escape at airspeeds high enough to cause bodily harm. These seats

were designed to allow the pilot to control the plane even with the clamshell closed, and the

capsule would float in case of water landings.

52

Some aircraft designs, such as the General Dynamics F-111, do not have individual ejection

seats, but instead, the entire section of the airframe containing the crew can be ejected as a

single capsule. In this system, very powerful rockets are used, and multiple large parachutes

are used to bring the capsule down, in a manner very similar to the Launch Escape System of

the Apollo spacecraft. On landing, an airbagsystem is used to cushion the landing, and this

also acts as a flotation device if the Crew Capsule lands in water.

Zero-zero ejection seat

A zero-zero ejection seat is designed to safely extract upward and land its occupant from a

grounded stationary position (i.e., zero altitude and zero airspeed), specifically from aircraft

cockpits. The zero-zero capability was developed to help aircrews escape upward from

unrecoverable emergencies during low-altitude and/or low-speed flight, as well as ground

mishaps. Before this capability, ejections could only be performed above minimum altitudes

and airspeeds.

Zero-zero technology uses small rockets to propel the seat upward to an adequate altitude and

a small explosive charge to open the parachute canopy quickly for a successful parachute

descent, so that reliance on airspeed and altitude is no longer required for proper deployment

of the parachute.

Other aircraft

The Kamov Ka-50, which entered service with Russian forces in 1995, was the first

production helicopter to be fitted with an ejection seat. The system is very similar to that of a

conventional fixed-wing aircraft; the main rotors are equipped with explosive bolts and are

designed to disintegrate moments before the seat rocket is fired. Prototype #9 (s/n 66-8834)

of the AH-56 Cheyenne was fitted with downward firing ejection seats in 1970 after a fatal

testing accident the previous year.

The Lunar Lander Research Vehicle (LLRV)/Training Vehicle (LLTV) used ejection

seats; Neil Armstrong ejected on 6 May 1968; Joe Algranti & Stuart M. Present, later.

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Early flights of the NASA's Space Shuttle were with a crew of two, both provided with

ejector seats, (STS-1 to STS-4), but the seats were disabled and then removed as the crew

size was increased.

The Soviet shuttle "Buran" was planned to be fitted with K-36RB (K-36M-11F35) seats, but

it was unmanned on its single flight; the seats were never installed.

The only spacecraft ever flown with installed ejection seats are the Space Shuttle, the

Soviet Vostok and American Gemini series. During the Vostok program, all the returning

cosmonauts would eject as their capsule descended under parachutes at about 7,000 m

(23,000 ft). This fact was kept secret for many years as the FAI rules at the time required that

a pilot must land with the spacecraft for the purposes of FAI record books.

The Sukhoi Su-31M is a single-engine aerobatic aircraft factory-equipped with a Zvezda

SKS-94 ejection seat.

Some ultra light, single-engine and glider general aviation aircraft such as the Cirrus SR-

22 or Schempp-Hirth Discus 2c have been fitted with ballistically deployed

parachutes recently. However, these systems cannot be considered "ejection" systems because

the entire aircraft with occupants is suspended by the chute.

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Bibliography

www. hal -india.com

www.wikipedia.org

www.google.com

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