avionics unit 1 notes

UNIT-I
INTRODUCTION TO AVIONICS
NEED FOR AVIONICS IN CIVIL AND MILITARY AIRCRAFT AND SPACE
SYSTEMS:
‘Avionics’ is a word derived from the combination of aviation and electronics.
The term ‘avionic system’ or ‘avionic sub-system’ is used in the aircraft which is
dependent on electronics for its operation, although the system may contain electromechanical
elements.
For example, a Flyby-Wire (FBW) flight control system depends on electronic digital
computers for its effective operation, but there are also other equally essential elements
in the system.
These include solid state rate gyroscopes and accelerometers to measure the angular and
linear motion of the aircraft and air data sensors to measure the height, airspeed and
incidence.
The avionics industry is a major multi-billion dollar industry world-wide and the
avionics equipment on a modern military or civil aircraft can account for around 30% of
the total cost of the aircraft.
Modern general aviation aircraft also have significant avionics content. For example,
colour head down displays, GPS satellite navigation systems, radio communications
equipment. Avionics can account for 10% of their total cost.
Other very important drivers for avionic systems are increased safety, air traffic control
requirements, all weather operation, reduction in fuel consumption, improved aircraft
performance and control and handling and reduction in maintenance costs.
In civil airlines
The avionic systems are essential to enable the flight crew to carry out the aircraft
mission safely and efficiently, whether the mission is carrying passengers to their
destination in the case of a civil airliner.
In the case of a modern civil airliner, this means a crew of two only, namely the First
Pilot (or Captain) and the Second Pilot. This is only made possible by reducing the crew
workload by automating the tasks which used to be carried out by the Navigator and
Flight Engineer.
The reduction in weight is also significant and can be translated into more passengers or
longer range on less fuel.
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In Military
In the military case, intercepting a hostile aircraft, attacking a ground target,
reconnaissance or maritime patrol.
A major driver in the development and introduction of avionic systems has been the
need to meet the mission requirements with the minimum flight crew.
In the military case, a single seat fighter or strike (attack) aircraft is lighter and costs
less than an equivalent two seat version.
The elimination of the second crew member (Navigator/Observer/Radar Operator) has
also significant economic benefits in terms of reduction in training costs. (The cost of
training and selection of aircrew for fast jet operation is very high.
Military avionic systems are also being driven by a continuing increase in the threats
posed by the defensive and offensive capabilities of potential aggressors.
CORE ARCHITECTURE COMMON FOR BOTH CIVIL AND MILITARY
AIRCRAFT:
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Display systems:
It consisting of 3 types of displays
i. Head up displays (HUDs),
ii. Helmet mounted displays(HMDs)
iii. Head Down displays (HDDs).
Head up displays (HUDs):
Most combat aircraft are now equipped with a HUD. A small but growing number of
civil aircraft have HUDs installed.
The HUD now provides the primary display for presenting the essential flight
information to the pilot and in military aircraft has transformed weapon aiming
accuracy.
The HUD can also display a forward looking infrared (FLIR) video picture one to one
with the outside world from a fixed FLIR imaging sensor installed in the aircraft. The
infrared picture merges naturally with the visual scene enabling operations to be carried
out at night or in conditions of poor visibility due to haze or clouds.
Helmet mounted displays(HMDs)
The HMD is also an essential system in modern combat aircraft and helicopters.
The HMD enables the pilot to be presented with information while looking in any
direction, as opposed to the limited forward field of view of the HUD.
An essential element in the overall HMD system is the Helmet Tracker system to
derive the direction of the pilot’s sight line relative to the aircraft axes.
The HMD can also form part of an indirect viewing system by driving a gimballed
infrared imaging sensor to follow the pilot’s line of sight.
Communications Systems:
The Communications Systems play a vital role; the need for reliable two way
communication between the ground bases and the aircraft or between aircraft is self
evident and is essential for air traffic control.
A radio transmitter and receiver equipment was in fact the first avionic system to be
installed in an aircraft.

The communications radio suite on modern aircraft is a very comprehensive one and
covers several operating frequency bands.
Long range communication is provided by high frequency (HF) radios operating in the
band 2–30 MHz.
Near to medium range communication is provided in civil aircraft by very high
frequency (VHF) radios operating in the band 30–100 MHz, and in military aircraft by
ultra high frequency (UHF) radio operating in the band 250–400 MHz. (VHF and UHF
are line of sight propagation systems).
Satellite communications (SATCOM) systems are also installed in many modern
aircraft and these are able to provide very reliable world wide communication.
Data entry and control systems:
The Data Entry and Control Systems are essential for the crew to interact with the
avionic systems.
Such systems range from keyboards and touch panels to the use of direct voice input
(DVI) control, exploiting speech recognition technology, and voice warning systems
exploiting speech synthesisers.
Flight control systems:
The Flight Control Systems exploit electronic system technology in two areas,
namely
1) Auto-Stabilisation (or stability augmentation) systems and
2) FBW flight control systems.
Auto-Stabilisation :
Most swept wing jet aircraft exhibit a lightly damped short period oscillatory motion
about the yaw and roll axes at certain height and speed conditions, known as ‘Dutch
roll’, and require at least a yaw auto-stabiliser system to damp and suppress this
motion; a roll auto-stabiliser system may also be required.
Most combat aircraft and many civil aircraft in fact require three axis auto-stabilisation
systems to achieve acceptable control and handling characteristics across the flight
envelope.
FBW flight control systems:
FBW flight control enables a lighter, higher performance aircraft to be produced
compared with an equivalent conventional design by allowing the aircraft to be
designed with a reduced or even negative natural aerodynamic stability.
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It does this by providing continuous automatic stabilisation of the aircraft by computer
control of the control surfaces from appropriate motion sensors.
A very high integrity, failure survival system is of course essential for FBW flight
control
Aircraft state sensor systems:
These comprise the
i Air data systems and
ii.The Inertial sensor systems.
Air data systems:
The Air Data Systems provide accurate information on the air data quantities, that is the
altitude, calibrated airspeed, vertical speed, true airspeed, Mach number and airstream
incidence angle. This information is essential for the control and navigation of the
aircraft.
The air data computing system computes these quantities from the outputs of very
accurate sensors which measure the static pressure, total pressure and the outside air
temperature. The air-stream incidence angle is derived from air-stream incidence
sensors.
Inertial Sensor Systems:
The Inertial Sensor Systems provide the information on aircraft attitude and the
direction in which it is heading which essential information for the pilotfor is flying in
conditions of poor visibility, flying in clouds or at night.
Accurate attitude and heading information are also required by a number of avionic subsystems
which are essential for the aircraft’s mission – for example, the autopilot and
the navigation system and weapon aiming in the case of a military aircraft.
Navigation systems:
Accurate navigation information, that is the aircraft’s position, ground speed and track
angle (direction of motion of the aircraft relative to true North) is clearly essential for
the aircraft’s mission, whether civil or military.
i. Dead reckoning (DR) systems and
ii. Position fixing systems
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Dead Reckoning Navigation:
The Dead Reckoning Navigation Systems derive the vehicle’s present position by
estimating the distance travelled from a known position from a knowledge of the speed
and direction of motion of the vehicle.
They have the major advantages of being completely self contained and independent of
external systems.
The main types of DR navigation systems used in aircraft are:
(a) Inertial navigation systems. The most accurate and widely used systems.
(b) Doppler/heading reference systems. These are widely used in helicopters.
(c) Air data/heading reference systems These systems are mainly used as a reversionary
navigation system being of lower accuracy than (a) or (b).
The Position Fixing Systems:
The Position Fixing Systems used are nowmainly radio navigation systems based on
satellite or ground based transmitters.
A suitable receiver in the aircraft with a supporting computer is then used to derive the
aircraft’s position from the signals received from the transmitters.
Outside World Sensor Systems
i. Radar and
ii. Infrared sensor
Radar Systems:
The Radar Systems installed in civil airliners and many general aviation aircraft aircraft
provide weather warning. The radar looks ahead of the aircraft and is optimized to
detect water droplets and provide warning of storms, cloud turbulence and severe
precipitation so that the aircraft can alter course and avoid such conditions, if possible.
These radars can also generally operate in ground mapping and terrain avoidance
modes.
The Infrared Sensor Systems:
Infrared Sensor Systems have the major advantage of being entirely passive systems.
Infrared (IR) sensor systems can be used to provide a video picture of the thermal image
scene of the outside world either using a fixed FLIR sensor, or alternatively, a
gimballed IR imaging sensor. The thermal image picture at night looks very like the
visual picture in daytime, but highlights heat sources, such as vehicle engines,
Task automation systems:
i.Navigation Management
ii.Autopilots and FlightManagement Systems
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iii.The Engine Control and Management Systems
iv.House Keeping Management
Navigation Management:
Navigation Management comprises the operation of all the radio navigation aid systems
and the combination of the data from all the navigation sources, such as GPS and the
INS systems, to provide the best possible estimate of the aircraft position, ground speed
and rack
Autopilots and FlightManagement Systems:
The Autopilots and FlightManagement Systems have been grouped together. Because
of the very close degree of integration between these systems on modern civil aircraft. It
should be noted, however, that the Autopilot is a ‘stand alone’ system and not all
aircraft are equipped with an FMS.
The tasks carried out by the FMS include:
Flight planning.
• Navigation management.
• Engine control to maintain the planned speed or Mach number.
• Control of the aircraft flight path to follow the optimised planned route.
• Control of the vertical flight profile.
• Ensuring the aircraft is at the planned 3D position at the planned time slot; often
referred to as 4D navigation. This is very important for air traffic control Flight envelope
monitoring.
• Minimising fuel consumption
The Engine Control and Management Systems:
The Engine Control and Management Systems carry out the task of control and the
efficient management and monitoring of the engines.
The electronic equipment involved in a modern jet engine is very considerable: it forms
an integral part of the engine and is essential for its operation. In many cases some of
the engine control electronics is physically mounted on the engine.
Many modern jet engines have a full authority digital engine control system (FADEC).
Other very important engine avionic systems include engine health monitoring systems
which measure, process and record a very wide range of parameters associated with the
performance and health of the engines. These give early warning of engine performance
deterioration, excessive wear, fatigue damage, high vibration levels, excessive
temperature levels, etc.
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House keeping management:
House Keeping Management is the term used to cover the automation of the
background tasks which are essential for the aircraft’s safe and efficient operation.
Such tasks include:
• Fuel management. This embraces fuel flow and fuel quantity measurement and
control of fuel transfer from the appropriate fuel tanks to minimise changes in
the aircraft trim.
• Electrical power supply system management.
• Hydraulic power supply system management.
• Cabin/cockpit pressurisation systems.
• Environmental control system.
• Warning systems, Maintenance and monitoring systems.
INTEGRATED AVIONICS SYSTEM:
Major avionic systems generally comprise a number of smaller sub-systems which are
combined to form an overall system. The combination, interconnection and control of
the individual sub-systems so that the overall system can carry out its tasks effectively
is referred to as ‘systems integration’.
Aircraft/Spacecraft Design often involves integrating parts, large and small, made by
other vendors, into an airframe or space frame (also called “the bus.”)
Parts include engines, landing gear, shock absorbers, wheels, brakes, tires, avionics
(radios, antennae, flight control computers)cockpit instruments, actuators that move
control surfaces, retract landing gears, etc...
The number of sub-systems which need to be integrated to form a major system can be
appreciated from the previous chapter on flight management systems.
• Radar – target acquisition in all weather conditions.
• Doppler – accurate ((4 knots) velocity sensor for DR navigation. (Note: IN
systems capable of accurate initial alignment at sea on a moving carrier were still under
development in the early 1960s.) The Doppler radar velocity sensor system is ussed to
measure the aircraft’s ground speed and drift angle. The aircraft heading is provided by the
AHRS.
• Attitude heading reference system (or master reference gyro system – UK
terminology) attitude and heading information for pilot’s displays, navigation computer,
weapon aiming computer, autopilot.

• Air data computer – height, calibrated airspeed, true airspeed, Mach number
information for pilot’s displays, weapon aiming, reversionary DR navigation, autopilot.
• Radio altimeter – very low level flight profile during attack phase and all
weather operation.
• Navigation computer – essential for mission.
• Autopilot – essential for reduction of pilot work load.
• Weapon aiming computer – essential for mission.
• HUD – all the advantages of the HUD plus weapon aiming for low level
attack;
for example, ‘toss’ bombing.
• Stores management system – control and release of the weapons.
• Electronic warfare (EW) systems – radar warning receivers, radar jamming
equipment. Essential for survivability in hostile environment.
• Identification system (identification friend or foe – ‘IFF’) – essential to avoid
attack by friendly forces.
• Radio navigation aids – location of parent ship on return from mission.
• Communications radio suite – essential for communicating to parent ship,
cooperating aircraft, etc.
A significant degree of integration was required between the avionic sub-systems.
For example, the weapon aiming system required the integration of the HUD, weapon aiming
computer, AHRS, air data computer and the radar system.
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Interconnections of avionic sub-systems by multiplexed data bus.

Civil integratedmodular avionic systems:
As in military systems, the use of new hardware, software and communication
technologies has enabled the design of new system architectures based on resource
sharing between different systems.
Current microprocessors are able to provide computing capabilities that exceed the
needs of single avionics functions. Specific hardware resources, coupledwith the use of
operating Systems with a standardised Application Programming Interface provide the
means to host independent applications on the same computing resource in a
segregated environment.
The AFDX Communication Network provides high data throughput coupled with low
latencies to multiple end users across the bus network..
The basic Line Replaceable Unit, LRU, becomes an avionics application which is
hosted on one, or more, Integrated Avionic Modules (IAMs), providing shared
computing resources (processing and memory and I/O).
External components like displays, sensors, actuators and effectors can be connected to
standard or specific interfaces in the module or to Remote Data Concentrators (RDCs),
normally located close to the sensors and actuators. The RDCs are connected to the
IMA modules through data buses ARINC 429.
DESIGN APPROACHES:
Design constraints:
i. Purpose
ii. Aircraft regulations
iii. Financial factors and market
iv. Environmental factors
v. Safety
Purpose:
The design process starts with the aircraft's intended purpose. Commercial airliners are
designed for carrying a passenger or cargo payload, long range and greater fuel
efficiency whereas fighter jets are designed to perform high speed maneuvers and
provide close support to ground troops.
Some aircraft have specific missions, for instance, amphibious airplanes have a unique
design that allows them to operate from both land and water, some fighters, like the
Harrier Jump Jet, have VTOL (Vertical Take-off and Landing) ability, helicopters have
the ability to hover over an area for a period of time.
The purpose may be to fit a specific requirement, e.g. as in the historical case of a
British Air Ministry specification, or fill a perceived "gap in the market.
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Aircraft regulations:
Another important factor that influences the design of the aircraft are the regulations put
forth by national aviation airworthiness authorities.
Airports may also impose limits on aircraft, for instance, the maximum wingspan
allowed for a conventional aircraft is 80 m to prevent collisions between aircraft while
taxiing.
Financial factors and market:
Budget limitations, market requirements and competition set constraints on the design
process and comprise the non-technical influences on aircraft design along with
environmental factors. Competition leads to companies striving for better efficiency in
the design without compromising performance and incorporating new techniques and
technology.
Environmental factors:
An increase in the number of aircraft also means greater carbon emissions.
Environmental scientists have voiced concern over the main kinds of pollution
associated with aircraft, mainly noise and emissions.
Aircraft engines have been historically notorious for creating noise pollution and the
expansion of airways over already congested and polluted cities have drawn heavy
criticism, making it necessary to have environmental policies for aircraft noise.
Noise also arises from the airframe, where the airflow directions are changed. [8]
Improved noise regulations have forced designers to create quieter engines and
airframes. Emissions from aircraft include particulates, carbon dioxide (CO 2 ), Sulfur
dioxide(SO 2 ), Carbon monoxide (CO), various oxides of nitrates.
Safety:
The high speeds, fuel tanks, atmospheric conditions at cruise altitudes, natural hazards
(thunderstorms, hail and bird strikes) and human error are some of the many hazards
that pose a threat to air travel.
Airworthiness is the standard by which aircraft are determined fit to fly. The
responsibility for airworthiness lies with national aviation regulatory bodies,
manufacturers, as well as owners and operators.
The International Civil Aviation Organization sets international standards and
recommended practices for national authorities to base their regulations. The national
regulatory authorities set standards for airworthiness, issue certificates to manufacturers
and operators and the standards of personnel training Every country has its own
regulatory body such as the Federal Aviation Authority in USA, DGCA (Directorate
General of Civil Aviation) in India, etc.
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The aircraft manufacturer makes sure that the aircraft meets existing design standards,
defines the operating limitations and maintenance schedules and provides support and
maintenance throughout the operational life of the aircraft. The aviation operators
include the passenger and cargo airliners, air forces and owners of private aircraft. They
agree to comply with the regulations set by the regulatory bodies, understand the
limitations of the aircraft as specified by the manufacturer, report defects and assist the
manufacturers in keeping up the airworthiness standards.
Design Optimization:
Aircraft designers normally rough-out the initial design with consideration of all the
constraints on their design. Historically design teams used to be small, usually headed
by a Chief Designer who knows all the design requirements and objectives and
coordinated the team accordingly.
As time progressed, the complexity of military and airline aircraft also grew. Modern
military and airline design projects are of such a large scale that, every design aspect is
tackled by different teams and then brought together. In general aviation a large number
of light aircraft are designed and built by amateur hobbyists and enthusiasts. [26]
Computer-aided design of aircraft[edit]
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The external surfaces of an aircraft modelled in MATLAB
In the early years of aircraft design, designers generally used analytical theory to do the
various engineering calculations that go into the design process along with a lot of
experimentation. These calculations were labour-intensive and time consuming.
. With the rise of programming languages, engineers could now write programs that
were tailored to design an aircraft. Originally this was done with mainframe computers
and used high level programming languages that required the user to be fluent in the
language and know the architecture of the computer. With the introduction of personal
computers, design programs began employing a more user-friendly approach

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DESIGN ASPECTS:
The main aspects of aircraft design are:
1. Aerodynamics
2. Propulsion
3. Controls
4. Mass
5. Structure
All aircraft designs involve compromises of these factors to achieve the design mission.
Aerodynamics (Wing design):
The wings of a fixed wing aircraft provide the necessary lift for take-off and cruise
flight. Wing geometry affects every aspect of an aircraft’s flight.
The wing area will usually be dictated by aircraft performance requirements (e.g. field
length) but the shape of the planform and other geometry may be influenced by wing
layout factors. The wing can be mounted to the fuselage in high, low and middle
positions.
The wing design depends on many parameters such as selection of aspect ratio, taper
ratio, sweepback angle, thickness ratio, section profile, washout and dihedral. The
cross-sectional shape of the wing is its airfoil. The construction of the wing starts with
the rib which defines the airfoil shape. Ribs can be made of wood, metal, plastic or even
composites.
Aerodynamics (Fuselage):
The fuselage is the part of the aircraft that contains the cockpit, passenger cabin or
cargo hold.
Propulsion:
Aircraft propulsion may be achieved by specially designed aircraft engines, adapted
auto, motorcycle or snowmobile engines, electric engines or even human muscle power.
The main parameters of engine design are:
Maximum engine thrust available
Fuel consumption
Engine mass
Engine geometry
The thrust provided by the engine must balance the drag at cruise speed and be greater
than the drag to allow acceleration. The engine requirement varies with the type of
aircraft. For instance, commercial airliners spend more time in cruise speed and need

more engine efficiency. High-performance fighter jets need very high acceleration and
therefore have very high thrust requirements.
Weight:
The weight of the aircraft is the common factor that links all aspects of aircraft design
such as aerodynamics, structure, propulsion together. An aircraft's weight is derived
from various factors such as empty weight, payload, useful load, etc.
The various weights are used to then calculate the center of mass of the entire aircraft.
The center of mass must fit within the established limits set by the manufacturer.
Structure:
The aircraft structure focuses not only on strength, stiffness, durability (fatigue),
fracture toughness, stability, but also on fail-safety, corrosion resistance, maintainability
and ease of manufacturing. The structure must be able to withstand the stresses caused
by cabin pressurization, if fitted, turbulence and engine or rotor vibrations.
DESIGN PHASES:
i. Conceptual Design
ii. Preliminary design phase
iii. Detail design phase
Conceptual Design:
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The first design step, involves sketching a variety of possible aircraft configurations that
meet the required design specifications. By drawing a set of configurations, designers
seek to reach the design configuration that satisfactorily meets all requirements as well
as go hand in hand with factors such as aerodynamics, propulsion, flight performance,
structural and control systems. This is called design optimization.
Fundamental aspects such as fuselage shape, wing configuration and location, engine
size and type are all determined at this stage.
Constraints to design like those mentioned above are all taken into account at this stage
as well. The final product is a conceptual layout of the aircraft configuration on paper or
computer screen, to be reviewed by engineers and other designers.

Preliminary design phase:
The design configuration arrived at in the conceptual design phase is then tweaked and
remodeled to fit into the design parameters. In this phase, wind tunnel testing and
computational fluid dynamic calculations of the flow field around the aircraft are done.
Major structural and control analysis is also carried out in this phase.
Aerodynamic flaws and structural instabilities if any are corrected and the final design
is drawn and finalized. Then after the finalization of the design lies the key decision
with the manufacturer or individual designing it whether to actually go ahead with the
production of the aircraft.
At this point several designs, though perfectly capable of flight and performance, might
have been opted out of production due to their being economically nonviable.
Detail design phase:
This phase simply deals with the fabrication aspect of the aircraft to be manufactured. It
determines the number, design and location of ribs, spars, sections and other structural
elements.
All aerodynamic, structural, propulsion, control and performance aspects have already
been covered in the preliminary design phase and only the manufacturing remains.
Flight simulators for aircraft are also developed at this stage.
“ILITIES” OF AVIONICS SYSTEM:
Major Ilities of Avionics System
• Capability
• Reliability
• Maintainability
• Certificability
• Survivability(military)
• Availability
• Susceptibility
• vulnerability
• Life cycle cost(military) or cost of ownership(civil)
• Technical risk
• Weight & power
Capability:
• How capable is avionics system?
• can they do the job and even more?
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• Designer to maximize the capability of the system within the constraints that are
imposed.
Reliability:
• Designer strives to make systems as reliable as possible.
• High reliability less maintenance costs.
• If less reliable customer will not buy it and in terms of civil airlines the
certificating agencies will not certify it.
Maintainability:
• Closely related to reliability
• System must need preventive or corrective maintenance.
• System can be maintained through built in testing, automated troubleshooting and
easy access to hardware.
Availability:
• Combination of reliability and maintainability
• Trade of between reliability and maintainability to optimize availability.
• Availability translates into sorties for military aircraft and into revenue flights for
civil aircrafts.
Certificability:
• Major area of concern for avionics in civil airlines.
• Certification conducted by the regulatory agencies based on detailed, expert
examination of all facets of aircraft design and operation.
• The avionics architecture should be straight forward and easily understandable.
• There should be no sneak circuits and no noobvious modes of operation.
Avionics certification focus on three analyses: preliminary hazard, fault tree, and
FMEA
Survivability:
It is a function of susceptibility and vulnerability.
Susceptibility: measure of probability that an aircraft will be hit by a given threat.
Vulnerability: measure of the probability that damage will occur if there is a hit
by the threat
Life cycle cost(LCC)or Cost of ownership:
It deals with economic measures need for evaluating avionics architecture.
It includes costs of varied items as spares acquisition, transportation, storage and
training (crew and Maintenance personnel's), hardware development and test,
depreciation and interest.
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Risk:
Amount of failures and drawbacks in the design and implementation.
Overcome by using the latest technology and fail proof technique to overcome
both developmental and long term technological risks.
Weight and power:
Minimize the weight and power requirements are two fundamental concepts of
avionics design.
So the design must be light weight and power consuming which is possible
through the data bus and latest advancement of electronics devices.
TYPICAL AVIONICS SUBSYSTEMS:
The cockpit of an aircraft is a typical location for avionic equipment, including control,
monitoring, communication, navigation, weather, and anti-collision systems. The
majority of aircraft power their avionics using 14- or 28-volt DC electrical systems;
however, larger, more sophisticated aircraft (such as airliners or military combat
aircraft) have AC systems operating at 400 Hz, 115 volts AC.
There are several major vendors of flight avionics, including Panasonic Avionics
Corporation, Honeywell (which now owns Bendix/King), Rockwell Collins,.
One source of international standards for avionics equipment are prepared by the
Airlines Electronic Engineering Committee (AEEC) and published by ARINC.
Communications:
Communications connect the flight deck to the ground and the flight deck to the
passengers. On-board communications are provided by public-address systems and
aircraft intercoms.
The VHF aviation communication system works on the airband of 118.000 MHz to
136.975 MHz. Each channel is spaced from the adjacent ones by 8.33 kHz in Europe,
25 kHz elsewhere.
VHF is also used for line of sight communication such as aircraft-to-aircraft and
aircraft-to-ATC. Amplitude modulation (AM) is used, and the conversation is
performed in simplex mode. Aircraft communication can also take place using HF
(especially for trans-oceanic flights) or satellite communication.
Navigation:
Navigation is the determination of position and direction on or above the surface of the
Earth. Avionics can use satellite-based systems (such as GPS and WAAS), groundbased
systems (such as VOR or LORAN), or any combination thereof.
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Navigation systems calculate the position automatically and display it to the flight crew
on moving map displays. Older avionics required a pilot or navigator to plot the
intersection of signals on a paper map to determine an aircraft's location; modern
systems calculate the position automatically and display it to the flight crew on moving
map displays.
Monitoring:
The Airbus A380 glass cockpit featuring pull-out keyboards and two wide computer
screens on the sides for pilots.
A "glass" cockpit refers to the use of computer monitors instead of gauges and other
analog displays. Aircraft were getting progressively more displays, dials and
information dashboards that eventually competed for space and pilot attention.
Glass cockpits started to come into being with the Gulfstream G-IV private jet in 1985.
One of the key challenges in glass cockpits is to balance how much control is automated
and how much the pilot should do manually. Generally they try to automate flight
operations while keeping the pilot constantly informed.
Aircraft flight-control systems:
Aircraft have means of automatically controlling flight. Today automated flight control
is common to reduce pilot error and workload at key times like landing or takeoff.
Autopilot was first invented by Lawrence Sperry during World War II to fly bomber
planes steady enough to hit precision targets from 25,000 feet.
. Nowadays most commercial planes are equipped with aircraft flight control systems in
order to reduce pilot error and workload at landing or takeoff.
The first simple commercial auto-pilots were used to control heading and altitude and
had limited authority on things like thrust and flight control surfaces.
In helicopters, auto-stabilization was used in a similar way. The first systems were
electromechanical. The advent of fly by wire and electro-actuated flight surfaces (rather
than the traditional hydraulic) has increased safety. As with displays and instruments,
critical devices that were electro-mechanical had a finite life. With safety critical
systems, the software is very strictly tested.
Collision-avoidance systems:
To supplement air traffic control, most large transport aircraft and many smaller ones
use a traffic alert and collision avoidance system (TCAS), which can detect the location
of nearby aircraft, and provide instructions for avoiding a midair collision.
Smaller aircraft may use simpler traffic alerting systems such as TPAS, which are
passive (they do not actively interrogate the transponders of other aircraft) and do not
provide advisories for conflict resolution.
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To help avoid controlled flight into terrain (CFIT), aircraft use systems such as groundproximity
warning systems (GPWS), which use radar altimeters as a key element.
One of the major weaknesses of GPWS is the lack of "look-ahead" information,
because it only provides altitude above terrain "look-down". In order to overcome this
weakness, modern aircraft use a terrain awareness warning system (TAWS).
Black Boxes:( Flight recorder):
Commercial aircraft cockpit data recorders, commonly known as a "black box", store
flight information and audio from the cockpit. They are often recovered from a plane
after a crash to determine control settings and other parameters during the incident.
Weather systems:
Weather systems such as weather radar (typically Arinc 708 on commercial aircraft)
and lightning detectors are important for aircraft flying at night or in instrument
meteorological conditions, where it is not possible for pilots to see the weather ahead.
Heavy precipitation (as sensed by radar) or severe turbulence (as sensed by lightning
activity) are both indications of strong convective activity and severe turbulence, and
weather systems allow pilots to deviate around these areas.
Lightning detectors like the Stormscope or Strikefinder have become inexpensive
enough that they are practical for light aircraft. In addition to radar and lightning
detection, observations and extended radar pictures (such as NEXRAD) are now
available through satellite data connections, allowing pilots to see weather conditions
far beyond the range of their own in-flight systems.
Modern displays allow weather information to be integrated with moving maps, terrain,
and traffic onto a single screen, greatly simplifying navigation.
Modern weather systems also include wind shear and turbulence detection and terrain
and traffic warning systems. In-plane weather avionics are especially popular in Africa,
India, and other countries where air-travel is a growing market, but ground support is
not as well developed
Aircraft management systems:
There has been a progression towards centralized control of the multiple complex
systems fitted to aircraft, including engine monitoring and management.
It has been used in fourth generation jet fighters and the latest generation of airliners.
Mission or tactical avionics:
Military aircraft have been designed either to deliver a weapon or to be the eyes and
ears of other weapon systems. The vast array of sensors available to the military is used
for whatever tactical means required.
19

As with aircraft management, the bigger sensor platforms (like the E-3D, JSTARS,
ASTOR, Nimrod MRA4, Merlin HM Mk 1) have mission-management computers.
Police and EMS aircraft also carry sophisticated tactical sensors.
Military communications:
While aircraft communications provide the backbone for safe flight, the tactical systems
are designed to withstand the rigors of the battle field. UHF, VHF Tactical (30–
88 MHz) and SatCom systems combined with ECCM methods, and cryptography
secure the communications.
Data links such as Link 11, 16, 22 and BOWMAN, JTRS and even TETRA provide the
means of transmitting data (such as images, targeting information etc.).
Radar:
Airborne radar was one of the first tactical sensors. The benefit of altitude providing
range has meant a significant focus on airborne radar technologies. Radars include
airborne early warning (AEW), anti-submarine warfare (ASW), and even weather radar
(Arinc 708) and ground tracking/proximity radar.
The military uses radar in fast jets to help pilots fly at low levels. While the civil market
has had weather radar for a while, there are strict rules about using it to navigate the
aircraft.
Sonar:
Dipping sonar fitted to a range of military helicopters allows the helicopter to protect
shipping assets from submarines or surface threats.
Maritime support aircraft can drop active and passive sonar devices and these are also
used to determine the location of hostile submarines.
Electro-Optics:
Electro-optic systems include devices such as the head-up display (HUD), forward
looking infrared (FLIR), and passive infrared devices (Passive infrared sensor).
These are all used to provide imagery and information to the flight crew. This imagery
is used for everything from search and rescue to navigational aids and target
acquisition.
ESM/DAS:
Electronic support measures and defensive aids are used extensively to gather
information about threats or possible threats. They can be used to launch devices (in
some cases automatically) to counter direct threats against the aircraft. They are also
used to determine the state of a threat and identify it.
Aircraft networks:
20

The avionics systems in military, commercial and advanced models of civilian aircraft
are interconnected using an avionics data bus. Common avionics data bus protocols,
with their primary application, include:
Aircraft Data Network (ADN): Ethernet derivative for Commercial Aircraft
Avionics Full-Duplex Switched Ethernet (AFDX): Specific implementation of ARINC
664 (ADN) for Commercial Aircraft
ARINC 429: Generic Medium-Speed Data Sharing for Private and Commercial Aircraft
ARINC 664: See ADN above
ARINC 629: Commercial Aircraft (Boeing 777)
ARINC 708: Weather Radar for Commercial Aircraft
ARINC 717: Flight Data Recorder for Commercial Aircraft
IEEE 1394b: Military Aircraft
MIL-STD-1553: Military Aircraft
MIL-STD-1760: Military Aircraft
TTP – Time-Triggered Protocol: Boeing 787 Dreamliner, Airbus A380, Fly-By-Wire
Actuation Platforms from Parker Aerospace
TTEthernet – Time-Triggered Ethernet: NASA Orion Spacecraft
Disaster relief and air ambulance:
Disaster relief and EMS aircraft (mostly helicopters) are now a significant market.
Military aircraft are often now built with a role available to assist in civil obedience.
Disaster relief helicopters are almost always fitted with video/FLIR systems to allow
them to monitor and coordinate real-time relief efforts. They can also be fitted with
searchlights and loudspeakers.
EMS and disaster relief helicopters will be required to fly in unpleasant conditions, this
may require more aircraft sensors, some of which were until recently considered purely
for military aircraft.
RECENT ADVANCES -
Advances in fusing EFVS with SVS:
Development of operational credits for enhanced flight vision systems (EFVS) by FAA
and certification agencies in other countries is expanding the operational utility of the
technology for both bizav and airline operations.
EFVS technology allows a pilot to see using a weather-penetrating real-time imaging
sensor when the human eye cannot due to low visibility.
Bombardier's launch of the Global Vision flight deck with Rockwell Collins Pro Line
Fusion is aimed at integrating EFVS and SVS on the HUD. In an industry first,
21

Transport Canada and FAA recently approved the display of SVS on HUDs by
Bombardier.
The tests are also evaluating the integration of EFVS and SVS as an additional means to
support the head-down to eyes-out transition during the visual segment of landing.
FAA has also moved recently to increase the use of HUD and auto land for lower than
standard minimums at selected Cat I runways, with a new 150 ft DH in visibility as low
as 1400 ft RVR.
FAA Order 8400.13D is based on the agency's recognition that new technology in the
aircraft may be compensating for a lack of ground infrastructure.
In addition, FAA has commissioned RTCA Special Committee 213 with developing a
path for future system standards and system safety criteria in parallel with industry.
This group has provided FAA with minimum system performance standards for
displays, EFVS sensors and SVS for current instrument operations, which have been
incorporated within the new AC 20-167 for EVS.
Potential uses of EFVS for trajectory based operations, first proposed by Gulfstream,
could save tremendous amounts of fuel (read money), but will require a new mindset by
air traffic control to clear an operator at the top of descent 200 miles away at 50,000 ft
for an approach in 1000-ft RVR fog.
SVS on the Bombardier Global Vision flight deck for the HUD and PFD. Bombardier,
in collaboration with Rockwell Collins, is now moving to the next phase of fusing the 2
images—SVS and EFVS IR sensor—to provide continuous vision to the pilot in all
phases of flight.
For NextGen implementation, FAA is sponsoring NASA in advanced testing of EFVS
and SVS technology in low visibility to explore the potential for additional operational
credit.
Testing includes having sample pilots from industry, the military and FAA conduct
landings in low visibility to validate potential new operations.
Current flight testing requires sample pilots to fly and evaluate EFVS's ability to
provide the required visibility at standard minimums, and then continue to land in
visibilities as low as 1000 ft RVR solely on enhanced vision. FAA's end goal is
expanded EFVS operational rules.
APPLICATION TECHNOLOGIES:
Communications:
Communications connect the flight deck to the ground and the flight deck to the
passengers. On-board communications are provided by public-address systems and
aircraft intercoms.
22

The VHF aviation communication system works on the airband of 118.000 MHz to
136.975 MHz. Each channel is spaced from the adjacent ones by 8.33 kHz in Europe,
25 kHz elsewhere.
VHF is also used for line of sight communication such as aircraft-to-aircraft and
aircraft-to-ATC. Amplitude modulation (AM) is used, and the conversation is
performed in simplex mode. Aircraft communication can also take place using HF
(especially for trans-oceanic flights) or satellite communication.
Navigation:
Navigation is the determination of position and direction on or above the surface of the
Earth. Avionics can use satellite-based systems (such as GPS and WAAS), groundbased
systems (such as VOR or LORAN), or any combination thereof.
Navigation systems calculate the position automatically and display it to the flight crew
on moving map displays. Older avionics required a pilot or navigator to plot the
intersection of signals on a paper map to determine an aircraft's location; modern
systems calculate the position automatically and display it to the flight crew on moving
map displays.
Monitoring:
The Airbus A380 glass cockpit featuring pull-out keyboards and two wide computer
screens on the sides for pilots.
A "glass" cockpit refers to the use of computer monitors instead of gauges and other
analog displays. Aircraft were getting progressively more displays, dials and
information dashboards that eventually competed for space and pilot attention.
Glass cockpits started to come into being with the Gulfstream G-IV private jet in 1985.
One of the key challenges in glass cockpits is to balance how much control is automated
and how much the pilot should do manually. Generally they try to automate flight
operations while keeping the pilot constantly informed.
Aircraft flight-control systems:
Aircraft have means of automatically controlling flight. Today automated flight control
is common to reduce pilot error and workload at key times like landing or takeoff.
Autopilot was first invented by Lawrence Sperry during World War II to fly bomber
planes steady enough to hit precision targets from 25,000 feet.
. Nowadays most commercial planes are equipped with aircraft flight control systems in
order to reduce pilot error and workload at landing or takeoff.
The first simple commercial auto-pilots were used to control heading and altitude and
had limited authority on things like thrust and flight control surfaces.
23

In helicopters, auto-stabilization was used in a similar way. The first systems were
electromechanical. The advent of fly by wire and electro-actuated flight surfaces (rather
than the traditional hydraulic) has increased safety. As with displays and instruments,
critical devices that were electro-mechanical had a finite life. With safety critical
systems, the software is very strictly tested.
Collision-avoidance systems:
To supplement air traffic control, most large transport aircraft and many smaller ones
use a traffic alert and collision avoidance system (TCAS), which can detect the location
of nearby aircraft, and provide instructions for avoiding a midair collision.
Smaller aircraft may use simpler traffic alerting systems such as TPAS, which are
passive (they do not actively interrogate the transponders of other aircraft) and do not
provide advisories for conflict resolution.
To help avoid controlled flight into terrain (CFIT), aircraft use systems such as groundproximity
warning systems (GPWS), which use radar altimeters as a key element.
One of the major weaknesses of GPWS is the lack of "look-ahead" information,
because it only provides altitude above terrain "look-down". In order to overcome this
weakness, modern aircraft use a terrain awareness warning system (TAWS).
Black Boxes:( Flight recorder):
Commercial aircraft cockpit data recorders, commonly known as a "black box", store
flight information and audio from the cockpit. They are often recovered from a plane
after a crash to determine control settings and other parameters during the incident.
24
Weather systems:
Weather systems such as weather radar (typically Arinc 708 on commercial aircraft)
and lightning detectors are important for aircraft flying at night or in instrument
meteorological conditions, where it is not possible for pilots to see the weather ahead.
Heavy precipitation (as sensed by radar) or severe turbulence (as sensed by lightning
activity) are both indications of strong convective activity and severe turbulence, and
weather systems allow pilots to deviate around these areas.
Lightning detectors like the Stormscope or Strikefinder have become inexpensive
enough that they are practical for light aircraft. In addition to radar and lightning
detection, observations and extended radar pictures (such as NEXRAD) are now
available through satellite data connections, allowing pilots to see weather conditions
far beyond the range of their own in-flight systems.

Modern displays allow weather information to be integrated with moving maps, terrain,
and traffic onto a single screen, greatly simplifying navigation.
Modern weather systems also include wind shear and turbulence detection and terrain
and traffic warning systems. In-plane weather avionics are especially popular in Africa,
India, and other countries where air-travel is a growing market, but ground support is
not as well developed
Aircraft management systems:
There has been a progression towards centralized control of the multiple complex
systems fitted to aircraft, including engine monitoring and management.
It has been used in fourth generation jet fighters and the latest generation of airliners.
Mission or tactical avionics:
Military aircraft have been designed either to deliver a weapon or to be the eyes and
ears of other weapon systems. The vast array of sensors available to the military is used
for whatever tactical means required.
As with aircraft management, the bigger sensor platforms (like the E-3D, JSTARS,
ASTOR, Nimrod MRA4, Merlin HM Mk 1) have mission-management computers.
Police and EMS aircraft also carry sophisticated tactical sensors.
Military communications:
While aircraft communications provide the backbone for safe flight, the tactical systems
are designed to withstand the rigors of the battle field. UHF, VHF Tactical (30–
88 MHz) and SatCom systems combined with ECCM methods, and cryptography
secure the communications.
Data links such as Link 11, 16, 22 and BOWMAN, JTRS and even TETRA provide the
means of transmitting data (such as images, targeting information etc.).
Radar:
Airborne radar was one of the first tactical sensors. The benefit of altitude providing
range has meant a significant focus on airborne radar technologies. Radars include
airborne early warning (AEW), anti-submarine warfare (ASW), and even weather radar
(Arinc 708) and ground tracking/proximity radar.
The military uses radar in fast jets to help pilots fly at low levels. While the civil market
has had weather radar for a while, there are strict rules about using it to navigate the
aircraft.
Sonar:
Dipping sonar fitted to a range of military helicopters allows the helicopter to protect
shipping assets from submarines or surface threats.
25

26
Maritime support aircraft can drop active and passive sonar devices and these are also
used to determine the location of hostile submarines.
Electro-Optics:
Electro-optic systems include devices such as the head-up display (HUD), forward
looking infrared (FLIR), and passive infrared devices (Passive infrared sensor).
These are all used to provide imagery and information to the flight crew. This imagery
is used for everything from search and rescue to navigational aids and target
acquisition.
ESM/DAS:
Electronic support measures and defensive aids are used extensively to gather
information about threats or possible threats. They can be used to launch devices (in
some cases automatically) to counter direct threats against the aircraft. They are also
used to determine the state of a threat and identify it.
Disaster relief and air ambulance:
Disaster relief and EMS aircraft (mostly helicopters) are now a significant market.
Military aircraft are often now built with a role available to assist in civil obedience.
Disaster relief helicopters are almost always fitted with video/FLIR systems to allow
them to monitor and coordinate real-time relief efforts. They can also be fitted with
searchlights and loudspeakers.
EMS and disaster relief helicopters will be required to fly in unpleasant conditions, this
may require more aircraft sensors, some of which were until recently considered purely
for military aircraft.