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1. AVIONICS

1.1 INTRODUCTION:

Avionics is a portmanteau word of "aviation electronics". It comprises

electronic systems for use on aircraft, artificial satellites and spacecraft, comprising

communications, navigation and guidance, display systems, flight management

systems, sensors and indicators, weather radars, electrical systems and various other

computers onboard modern aircraft and spacecraft. It also includes the hundreds of

systems that are fitted to aircraft to meet individual roles; these can be as simple as a

search light for a police helicopter or as complicated as the tactical system for an

airborne early warning platform.

1.2 HISTORY:

The term avionics was not in general use until the early 1970s. Up to this point

instruments, radios, radar, fuel systems, engine controls and radio navigation aids had

formed individual (and often mechanical) systems.

In the 1970s, avionics was born, driven by military need rather than civil

airliner development. Military aircraft had become flying sensor platforms, and

making large amounts of electronic equipment work together had become the new

challenge. Today, avionics as used in military aircraft almost always forms the biggest

part of any development budget. Aircraft like the F-15E and the now retired F-14

have roughly 80 percent of their budget spent on avionics. Most modern helicopters

now have budget splits of 60/40 in favour of avionics.

The civilian market has also seen a growth in cost of avionics. Flight control

systems (fly-by-wire) and new navigation needs brought on by tighter airspace, have

pushed up development costs. The major change has been the recent boom in

consumer flying. As more people begin to use planes as their primary method of

transportation, more elaborate methods of controlling aircraft safely in these high

restrictive airspace have been invented. With the continued refinement of precision

miniature aerospace bearings, guidance and navigation systems of aircraft become

more exact. Ring laser gyroscope, MEMS, fiber optic gyroscope, and other

developments have made for more and more complex and tightly integrated cockpit

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systems. Many of these advanced systems are known as a Flight management system

or FMS. These integrate the functions of communications radios, navigation radios,

GNSS sensors, distance measuring equipment (DME), transponder through a unified

user interface. The Garmin G1000 is an example of one such system in general use at

the present time (2009). Higher end, or commercial FMS units may rely on an Inertial

Measurement Unit or IMS to provide a self-contained navigational reference. Some of

these units use hemispheric resonating gyros or wine glass gyros (see vibrating

structure gyroscope) coupled with GNSS receivers to provide accurate navigation data

to flight crews and automated aircraft systems.

1.3 AIRCRAFT AVIONICS:

The cockpit of an aircraft is a major location for avionic equipment, including

control, monitoring, communication, navigation, weather, and anti-collision systems.

The majority of aircraft drive their avionics using 14 or 28 volt DC electrical systems;

However, large, more sophisticated aircraft (such as airliners or military combat

aircraft) have AC systems operating at 115V 400 Hz, rather than the more common

50 and 60 Hz of European and North American, respectively, home electrical

devices.[1]

There are several major vendors of flight avionics, including Honeywell

(which now owns Bendix/King, Baker Electronics, Allied Signal, etc..), Rockwell

Collins, Thales Group, Garmin, Narco, and Avidyne Corporation.

1.3.1 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 by 8.33 kHz.

Amplitude modulation (AM) is used. The conversation is performed by simplex

mode. Aircraft communication can also take place using HF (especially for trans-

oceanic flights) or satellite communication.

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1.3.2 NAVIGATION:

Main article: Radio 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), ground-based systems (such as VOR or LORAN), or any combination

thereof. 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, like the

Bendix/King KLN 90B, calculate the position automatically and display it to the

flight crew on moving map displays.

1.3.3 MONITORING:

Main article: Glass cockpit

Glass cockpits started to come into civilian use with the Gulf stream G-IV

private jet in 1985. However, these largely stemmed from the need of military pilots

to quickly deal with increasing amounts of flight data while concentrating on the task

(dogfight with enemy aircraft, detection of surface targets, etc.) Display systems

present sensor data that allows the aircraft to fly safely in a more flexible manner as

skipping unnecessary information was not possible with the earlier mechanical

(usually dial-type) instruments. ARINC 818, titled Avionics Digital Video Bus, is a

protocol used by many new glass cockpit displays in both commercial and military

aircraft.

1.3.4 AIRCRAFT FLIGHT CONTROL SYSTEM:

Airplanes and helicopters have means of automatically controlling flight. They

reduce pilot workload at important times (like during landing, or in hover), and they

make these actions safer by 'removing' pilot error. The first simple 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 old systems were electromechanical in nature until very recently.

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

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devices which were electro-mechanical had a finite life. With safety critical systems,

the software is very strictly tested.

1.3.5 COLLISION-AVOIDANCE SYSTEM:

To supplement air traffic control, most large transport aircraft and many

smaller ones use a TCAS (Traffic Alert and Collision Avoidance System), 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 collision with terrain, (CFIT) aircraft use systems such as

ground-proximity warning systems (GPWS), radar altimeter being the key element in

GPWS. A major weakness of (GPWS) is the lack of "look-ahead" information as it

only provides altitude above terrain "look-down". To overcome this weakness,

modern aircraft use the Terrain Awareness Warning System (TAWS).

1.3.6 WEATHER SYSTEM:

Main article: Weather radar

Main article: Lightning detector

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 Storm scope or Strike finder have become

inexpensive enough that they are practical for light aircraft. In addition to radar and

lightning detection, observations and extended radar pictures (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, traffic, etc. onto a

single screen, greatly simplifying navigation.

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1.3.7 AIRCRAFT MANAGEMENT SYSTEM:

There has been a progression towards centralized control of the multiple

complex systems fitted to aircraft, including engine monitoring and management.

Health and Usage Monitoring Systems (HUMS) are integrated with aircraft

management computers to allow maintainers early warnings of parts that will need

replacement.

The integrated modular avionics concept proposes an integrated architecture

with application software portable across an assembly of common hardware modules.

It has been used in Fourth generation jet fighters and the latest generation of airliners.

1.4 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) have

mission management computers. Police and EMS aircraft also carry sophisticated

tactical sensors.

1.4.1 MILITARY COMMUNICATIONS:

While aircraft communications provide the backbone for safe flight, the

tactical systems are designed to withstand the rigours of the battle field. UHF, VHF

Tactical (30-88 MHz) and SatCom systems combined with ECCM methods, and

cryptography secure the communications. Data links like Link 11, 16, 22 and

BOWMAN, JTRS and even TETRA provide the means of transmitting data (such as

images, targeting information etc.).

1.4.2 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.

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Besides its primary role as the main sensor for fighters, the military uses radar

in fast jets to help pilots fly at low levels. Earlier models were just separate devices

often mounted under the primary (e.g. air-to-air) unit and covered with the same

radome. Modern technologies allow the creation of multi-functional, weapon-

controlling radars that additionally perform such terrain-mapping. While the civil

market has had weather radar for a while, there are strict rules about using it to

navigate the aircraft.

1.4.3 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

(Sonobuoys) and these are also used to determine the location of hostile submarines.

1.4.4 ELECTRO -OPTICS:

Electro-optic systems include Forward Looking Infrared (FLIR), and Passive

Infrared Devices (PIDS). These are all used to provide imagery to crews. This

imagery is used for everything from Search and Rescue through to acquiring better

resolution on a target.

1.4.5 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.

1.5 AIRCRAFT NETWORK BUSES:

The avionics systems in military, commercial and advanced models of civilian

aircraft are interconnected using an avionics databus. Common avionics databus

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

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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

1.6 POLICE AND AMBULANCE:

Police and EMS aircraft (mostly helicopters) are now a significant market.

Military aircraft are often now built with the capability to support response to civil

disobedience. Police helicopters are almost always fitted with video/FLIR systems

allowing them to track suspects. They can also be equipped with searchlights and

loudspeakers.

EMS and police helicopters will be required to fly in unpleasant conditions

which may require more aircraft sensors, some of which were until recently

considered purely for military aircraft.

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2. ELECTRICAL

2.1 ELECTRICAL POWER GENERATION:

Two Integrated Drive Generators (IDG) normally supply the aircraft electrical

power in flight ; each engine drives one generator.

The APU drives a third, auxiliary, generator (APU GEN) which can replace

either main generator (GEN 1 or GEN 2).

The generators supply the distribution network with alternating current.

Two Transformer Rectifiers (TR) supply, in normal configuration, the

distribution network with direct current. In the event of major failure, a

constant-speed hydraulic motor drives an emergency generator (CSM/G) to

supply the systems required for aircraft control.

On the ground, an electrical Ground Power Unit (GPU) can supply the aircraft.

The APU GEN can also be an independant power source.

2.2 AC GENERATION:

The AC generation consists of:

Integrated Drive Generators (IDG)

A main generation corresponding to the two IDG channels and to the transfer

circuit

An auxiliary generation corresponding to the APU generator and its channel

An emergency generation corresponding to the constant speed

motor/generator, its associated GCU and its channel

The essential generation switching

The control circuits for galley and sheddable busbars supply

The monitoring and indicating circuits for the cockpit.

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2.2.1 INTEGRATED DRIVE GENERATOR:

The IDG converts variable speed shaft power directly into constant frequency

400 Hz AC electrical power.

This is accomplished by the Constant Speed Drive (CSD) which drives the AC

generator at constant speed.The AC generator produces thus constant frequency

power.

Each engine (HP rotor) drives its associated IDG through the accessory

gearbox. The drive speed varies according to the engine rating.The IDG provides a

115/200 VAC, 3-phase, 400 Hz AC supply at the Point of Regulation (POR).

The IDG has two parts: the Constant-Speed Drive (CSD) and the

generator.The hydromechanical Constant-Speed Drive drives the AC generator at

constant speed.

2.2.2 MAIN GENERATION:

The two engine generators provide the AC main generation. The AC main

generation supplies the whole aircraft in normal flight configuration.

The generator is a three stage assembly which includes three machines

connected in cascade. The first machine (Pilot Exciter (PE)) is a twelve pole

Permanent Magnet Generator (PMG). Its rotor is constructed of small Rare Earth

Cobalt magnets. The output from the PE stator winding: has a generator excitation

function, provides power for other components of the electrical system which

comprises the generator (supply of the GCU, EGIU, and the external relays and

contactors). The generator is thus "self-flashing" and "self-sufficient".

The second machine (Main Exciter (ME)), 10 poles stator, receives its field

excitation from the pilot exciter via the voltage regulator in the GCU: this creates a

stationary field. Rotating diodes rectify the three phase output of the main exciter

rotor. This output feeds the main rotor winding. The DC output thus produced

supplies the rotating field system of the third machine.

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The third machine (main alternator) receives excitation for the rotating salient

four pole field from the rectified output of the main exciter.

The main alternator has a 3-phase star-connected stator-winding. The three

phases and neutral are taken to the generator output terminal block .The generator is

designed for use with an external voltage regulator forming part of the GCU.

Each main generator is driven by an engine HP compressor via an accessory

gearbox and an integrated hydromechanical speed regulator which transforms the

engine variable speed into constant speed for the generator. In the event of mechanical

failure, the IDG pushbutton switch protected by a guard and located on the ELEC

panel on the overhead panel, serves to disconnect the IDG (reset on ground only).

The AC auxiliary generation comes from the APU generator. This generator can:

In flight, replace either or both engine generator(s) in case of failure

On the ground, supply the aircraft electrical network when the

electrical ground power unit is not available.

The APU directly drives the APU GEN at constant speed. This maintains the

generator frequency constant.

General:

The operation principle is the same as that of the IDG generator

2.2.3 APU GENERATOR:

2.2.3 Auxiliary power unit

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The APU directly drives the APU generator at a nominal 24000 rpm

constant speed.

The APU gearbox supplies the oil for cooling and lubrication of the

generator. The cooling circuit is common to the APU and the

generator.

The APU supplies, scavenges, drains the oil.

The generator is a brushless oil-cooled generator with a nominal

115/200 volt, 90 KVA, 3 phase 400Hz output.

NOTE: The frequency range of the APU generator can be from 395Hz to 405Hz.

When the APU fuel-saving mode is used, the APU speed is reduced to 99%. In this

mode, the frequency of the APU generator decreases to 396Hz.

The generator includes three stages which are

The Pilot Exciter

The main exciter

The main alternator

A temperature bulb is included in the auxiliary generator. It senses the

generator-oil outlet temperature. This sensor is connected to the Electronic Control

Box (ECB) of the APU. Any high oil temperature causes the automatic shutdown of

the APU (by the ECB).This in turn causes the APU speed to decrease to zero.

2.2.4 GROUND AND AUXILIARY POWER UNIT (GAPCU):

The GAPCU controls the APU generator and the external Power channels. For

the APU generator channel control, the GAPCU has different functions:

Voltage regulation.

Control and protection of the network and the generator.

System test and self monitoring.

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2.2.5 AC EMERGENCY GENERATION

The AC emergency generation enables part of the distribution network to be

recovered in case of:

Loss of the two main generation sources

Unavailability of the auxiliary generation.

The emergency generation system is mainly composed of a Constant Speed

Motor/Generator (CSM/G) including a hydraulic motor and an AC generator, a

Generator Control Unit (GCU).

2.2.6 CONSTANT SPEED MOTOR/GENERATOR :

Hydraulic motor:

2.2.6 Ram Air Turbine

A hydraulic motor drives the emergency generator. A servo valve speed

regulator controls the speed: it transforms the oil flow of the Blue hydraulic system

into constant speed for the generator. When emergency conditions are met, this Blue

system is supplied by a Ram Air Turbine (RAT).

NOTE: The Blue hydraulic system is supplied by an electric pump in normal

configuration

AC Generator:

Three phase 115V/200V-400Hz with 12000rpm. It is oil cooled and gives

output power 5KVA continuously.

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2.2.7 GENERATOR CONTROL UNIT:

The main functions of the GCU are:

to regulate the generator voltage by the field current,

to protect the network and the generator by control of the associated GLC and

the generator field current,

to provide BITE information to the Ground Power Control Unit (GPCU),

to control the warnings associated with the corresponding channel.

2.2.8 ELECTRICAL GENERATION INTERFACE UNIT:

The main function of the EGIU is to process the parameters from the GCU and

associated generator. The EGIU then transmits the information to the cockpit

(ECAM) via the System Data Acquisition Concentrators (SDACs).

Two EGIUs are installed on the aircraft.One EGIU is associated with the

GCU1 and the GPCU.Each channel sends its own parameters to SDAC1 and SDAC2

through two isolated ARINC 429 data links.The second EGIU is connected in the

same manner to generator 2 and to the APU generator.

2.2.9 EXTERNAL POWER - DESCRIPTION AND OPERATION:

General:

The aircraft network can be supplied by a ground power unit. For this, an

external power receptacle is provided forward of the nose landing gear well. This

receptacle enables to supply the whole network via the transfer circuit or only part of

it, the ground service network which comprises:

the AC ground service bus control

the DC ground service bus control

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2.2.10 STATIC INVERTER:

2.2.10 Static Inverter

The static inverter, with a 1000 VA nominal power, transforms the direct

current from the battery 1 into a single phase, 115 V 400 Hz, alternating current. The

static inverter is automatically activated if AC BUS 1 and AC BUS 2 are lost and the

CSM/G is unavailable.

For maintenance purposes, the static inverter delivers FAULT indication to the

Centralized Fault Display System (CFDS) through the two Battery Charge Limiters

(BCL).The static inverter defect is sent to the battery charge limiter 1 which stores it

in a memory as a class I failure.When the network is supplied, STATIC INV FAULT

message appears on the upper ECAM display unit.

The fault indication will be available during BCL BITE reading from the

Centralized Fault Display System (CFDS).

2.3 DC GENERATION

The power sources of direct current are three identical transformer rectifiers

and two batteries. In normal configuration, the two normal TRs (TR 1 and TR 2) and

possibly the batteries supply direct current. In the event of loss of one or both TR, part

of the DC network is transferred to the ESS TR.

They are supplied with three phases 115 VAC/400 Hz voltage from the normal

Alternating Current (AC) distribution network.

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2.3.1 TRANSFORMER RECTIFIER:

2.3.1 Transformer Rectifier

The TR unit converts aircraft primary AC power to 28 VDC power from a 3-

phase, 115 VAC, 400 Hz generator. This light weight 40 Amp TR Unit has been

developed for commercial airborne applications. Its proven reliability recorded and

confirmed by several airlines exceeds a MTBF of 100,000 hours. Its efficiency is >

86%.

Each TR control its via an internal TR logic. This logic, which is intended to

protect the Direct Current(DC) network and the TR, controls contractor opening in

case of no current flow to the DC BUS (minimum current detection),

To ensure these protections, each TR sends a fault signal to the Centralized

Fault Display System (CFDS) for maintenance purpose. Main TR’s are ventilated by

air extracted from the aircraft ventilation network.

2.3.2 BATTERIES:

General:

The Alkaline battery has 20 semi open nickel-cadmium VHP 23KA-3 cells with

welded .polyamide cases It used to start the APU (Auxiliary power unit). On the

ground, before electrical ground power is supplied to the aircraft system. In flight, if a

malfunction or a failure occurs in the power supply system.

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2.3.2 Battery

Specifications:

Nominal voltage: 24 v.

Rated capacity: 23Ah at rate of 1hr.

Consumable volume of electrolyte: 60cm³ per cell.

Max. dimension of the battery base: L=254mm.

W=248mm.

H=215mm.

Max. weight: 25.5kg.

Electrolyte: sol.KOH s.g.1.24

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3. RADIO

3.1 INTRODUCTION:

Transmission of signals by modulation of electromagnetic waves with

frequencies below visible light (400THz).

Electromagnetic waves longer than (lower frequency) microwaves (300MHz)

are called Radio waves. Mostly, Radio is used for Communication and Navigation

purposes.

3.2 COMMUNICATIONS:

The communication system is used for speech communications and optionally

for data communications.

Communication is done between the crew members and ground personnel.

Also, to communicate with the passengers, other aircraft and the ground stations

(speech and data).

3.2.1 SPEECH COMMUNICATON:

3.2.1 Speech Communication

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3.2.1.1 HIGH FREQUENCY (HF) SYSTEM:

The High Frequency (HF) system is used for all long-distance voice and data

communications between:

a) Different aircraft (in flight or on the ground)

b) The aircraft and one or several ground stations.

The HF system operates within the frequency range defined by ARINC 719

(i.e. 2.8 to 23.999 MHz, with 1 KHz spacing between channels). This system has two

HF transceivers, two couplers, a HF antenna.

Each HF system has an interface with the following systems and components:

Radio Management Panels (RMP)

Audio Management Unit (AMU)

Centralized Fault Display Interface Unit (CFDIU)

Landing Gear Control Interface Unit (LGCIU)

System Data Acquisition Concentrator (SDAC)

Air Data/Inertial Reference Units (ADIRU)

Air Traffic Service Unit (ATSU)

Ground HF DATA LINK (GND HF DATA LINK)

International Civil Aircraft Organization (ICAO) address

Multipurpose Disk Drive Unit (MDDU) or Portable Data Loader

(PDL)

3.2.1.2 VERY HIGH FREQUENCY SYSTEM:

The Very High-Frequency (VHF) system is used for all short-range voice

communications between:

Different aircraft in flight

Aircraft (in flight or on the ground) and ground stations.

The VHF system operates within the frequency range defined by ARINC 716

(i.e. 118 to 136.975 MHz, with 25KHz spacing between channels). The VHF3 system

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(if installed) is also used to transmit data (Aircraft Communication Addressing and

Reporting System (ACARS) or Air Traffic Service Unit (ATSU).

Each VHF system is composed of:

A transceiver

An antenna

Each VHF system has an interface with the following systems and components:

Radio Management Panels (RMP)

Audio Management Unit (AMU)

Centralized Fault Display Interface Unit (CFDIU)

Landing Gear Control and Interface Unit (LGCIU)

System Data Acquisition Concentrators (SDAC)

Air Traffic Service Unit (ATSU).

3.2.1.3 RADIO MANAGEMENT SYSTEM:

3.2.1.3Radio Management System

The RMPs enable a centralized frequency control of the VHF and HF radio

communication equipment.The RMPs also enable the frequency control of the radio

navigation equipment (VHF Omni directional Range (VOR), Distance Measuring

Equipment (DME), Instrument Landing System (ILS), Automatic Direction Finder

(ADF)) in case of failure of the Flight Management and Guidance System (FMGC).

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The radio management system is connected to:

The VHF radio-communication equipment

The VOR, DME, ADF (if installed) and ILS radio-navigation

equipment

The Flight Management and Guidance Computers (FMGC)

The Centralized Fault-Display Interface-Unit (CFDIU)

The Landing Gear Control and Interface Unit (LGCIU).

MMR radio-navigation equipment

3.2.2 DATA TRANSMISSION:

3.2.2.1 ACARS:

The ACARS management unit allows the management of the data entered by

the crews and transmitted to the ground (SDAC, AIDS, CFDS, FMGEC). It also

allows the reception, printing and display of ground messages on the Multipurpose

Control and Display Unit (MCDU).

These data are transmitted through the VHF3 system (or through the Satellite

Communication (SATCOM) system if installed.

3.2.2.2 SATCOM:

3.2.2.1 Satcom

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The function of the SATCOM system is the reception and processing of

signals via satellites providing aeronautical services in the L-Band (1525-1660.5

MHz).

The Aero-I SATCOM system (conformed to ARINC 761) uses an

intermediate gain terminal, exploiting the higher power of the Inmarsat 3 satellite.

Aero-I allows the aircraft flying within spot beam coverage to transmit and receive

multichannel voice, fax and circuit mode data services. Packet mode data services and

emergency calls are available world-wide in the global beam.This system is used for

all aeronautical satellite communications (cockpit voice, passenger telephone and data

services) with the ground.

3.2.3 PASSANGER ADDRESS AND ENTERTAINMENT:

This system comprises:

Prerecorded Announcements and Music (PRAM) system

Passenger Entertainment System (Music)/Passenger Services System

(PES (Music)/PSS)

Passenger Visual Information System (PVIS)

Passenger Air-to-ground Telephone System (PATS)

Passenger Entertainment System (Video) (PES (Video))

Passenger facility (AM/FM radio)

The Passenger Address System is part of the Cabin Intercommunication Data

System (CIDS)

3.2.4 INTERPHONE:

The Interphone system comprises:

3.2.4.1 Cockpit-to-ground crew call system

The cockpit-to-ground crew call system is used to:

Call a ground mechanic from the cockpit

Call a crew member from the ground.

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It has also an aural warning function when the aircraft is powered by batteries

for the systems given below:

APU fire

ADIRS powered by batteries

Equipment ventilation faulty.

3.2.4.2 Flight crew interphone

The flight crew interphone system is part of the CIDS.

3.2.4.3 Cabin and service interphone

The cabin and service interphone system is used for the telephone

communications on the ground between the flight crew and the ground service

personnel.

3.2.5 AUDIO INTEGRATING:

The audio management system provides the means for using:

a. All the radio communication and radio navigation facilities installed on the aircraft:

In transmission mode: it collects the microphone inputs of the various

crew stations and directs them to the communication systems.

In reception mode : it collects the audio outputs of the communication

systems and the navigation receivers and directs them to the various

crew stations.

b. The flight interphone system:

Telephone links between the various crew stations in the cockpit.

Telephone links between the cockpit and the ground crew from the

external power receptacle

c. The SELCAL (Selective Calling) system:

Visual and aural indication of calls from ground stations equipped with a

coding device used by the aircraft installation.

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3.2.6 STATIC DISCHARGING:

During flight, the aircraft becomes charged with static electricity. If the

discharge of the static electricity is not controlled, it causes interference in the

communications and navigation systems. To decrease the effect of this interference,

static dischargers are installed.

3.2.7 AUDIO-VIDEO MONITORING

This system comprises:

a. Cockpit Voice Recorder (CVR):

The Solid State Cockpit Voice Recorder (SSCVR) is designed to record crew

conversations and communications into memory block unit in flight and on ground,

when at least one engine is running or up to five minutes after the last engine is shut

down irrespective of which engine is shut down first. The system can also operate in

manual mode on the ground. The recorder is a four-track system and all tracks are

recorded simultaneously.

The SSCVR provides storage for 2 hours of consecutive recording for each of

the four audio input channels.

When the memory block unit is fully recorded, the system progressively erases

recordings made in the previous 2 hours and simultaneously records new information;

thus only information recorded in the last 2 hours of operation is retained. The

recorded information can be intentionally erased when the aircraft is on the ground

with the parking brake on, locked and electrically powered. Bulk erasure is also

possible during manual operation of the system.

b. Cabin Intercommunication Data System (CIDS)

The Cabin Intercommunications Data System (CIDS) is a microprocessor-

based system used to operate, control, monitor and test various cabin functions. The

functions are managed by CIDS dependent on the configuration of the aircraft and the

CIDS software.

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3.3 NAVIGATION:

The aircraft navigation systems provide the crew with the data required for

flight within the most appropriate safety requirements.

These data can be divided into four groups:

Air Data/Inertial Reference System (ADIRS)

Landing and taxing aids

Independent position determining

Dependent position determining.

3.3.1 AIR DATA/INERTIAL REFERENCE SYSTEM (ADIRS):

The main air data and heading/attitude data are provided by a three-channel

Air Data Inertial Reference System (ADIRS).

This configuration provides for triple redundant information for all inertial and

air data functions.

Each channel is isolated from the others and provides independent information

as defined by ARINC Characteristic 738.

The ADIRS comprises:

Three Air Data/Inertial Reference Units (ADIRU)

A control and Display Unit (CDU)

Three pitot probes

Six static probes

Eight Air Data Modules (ADM) Linked to the pitot and static probes

Two Total Air Temperature (TAT) sensors

Three Angle of Attack (AOA) sensors

Each of the ADIRUs contains two portions:

The Air Data Reference (ADR) portion which supplies air data

parameters.

The Inertial Reference (IR) portion which supplies attitude and

navigation parameters.

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The parameters are transmitted to the user systems on ARINC 429 buses.

The Built-In Test Equipment (BITE) is included in the ADIRUs and the

ADMs. It detects and identifies a failure related to the ADIRS and reports it to the

Centralized Fault Display System (CFDS)

3.3.2 INTEGRATED STANDBY INSTRUMENT SYSTEM (ISIS)

The standby heading is given by a magnetic compass, which is an independent

instrument. The Integrated Standby Instrument System (ISIS) indicator replaces the

three conventional standby instruments i.e.:

the standby altimeter (and standby altimeter in meters -optional-)

the standby airspeed indicator

the standby horizon indicator.

The ISIS indicator, provides the following standby data on a Liquid Crystal

Display (LCD) installed in place of the standby horizon:

Attitude

Standard or baro-corrected altitude and related barometric pressure

Indicated airspeed and Mach number

Lateral acceleration and the following optional parameters:

ILS deviation

V-bar aircraft symbol

Barometric pressure in hPa or in hPa and in.Hg

Altitude in meters.

3.3.3 LANDING AND TAXING AIDS:

This part of the navigation system comprises:

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3.3.3 Landing and Taxing Aids

3.3.3.1 Para visual Indicator (PVI)

The aircraft is equipped with one PVI installed on the glare shield panel

131VU, Captain's side. This system provides the Captain with an image which serves

as a piloting aid for take-off and landing in reduced visibility conditions.

The system receives parameters from the DMC1 which can be switched to the

DMC3, and generates the image.

3.3.3.2 Head Up Display (HUD)

The aircraft is equipped with:

HUDC (Head Up Display Computer)

OHU (Optical Head Unit).

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This system provides the Captain with an image superimposed on the outside

world in his field of view. This image gives the guidance information in take-off,

landing or approach configurations. The HUDC processes the input parameters

received from the Display Management Computer 1 (DMC1), which can be switched

to the DMC3, and sends them to the OHU after transformation.

3.3.3.3 Instrument Landing System (ILS)

Either ILS or MMR receivers are controlled from FMGCs and Radio

Management Panels (RMPs) featuring two output channels, one command output and

one dialog output. All data are shown on the EFIS displays.

a. The ILS system enables to know the aircraft position during the landing phase with

respect to a predetermined descent path.

This system is composed of:

Two ILS receivers

Localizer antenna

Glide slope antenna.

b. The MMR system is a navigation system with two internal receivers, the

Instrument Landing System (ILS) and the Global Positioning System (GPS).

1. The ILS function is to provide the crew and the airborne system users with lateral

(LOC) and vertical (Glide/Slope) deviations signals, with respect to the approach ILS

radio beam transmitted by a ground station.

2. The GPS function is a radio aid to worldwide navigation which provides:

the crew with a readout of accurate navigation information, e.g.

position, track and speed.

the Flight Management and Guidance Computer (FMGC) with position

information, for accurate position fixing.

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The MMR system is composed of:

two MMR receivers

a Localizer antenna

a Glide/Slope antenna

two GPS ACTIVE antennas.

3.3.4 INDEPENDENT POSITION DETERMINING:

This part of the navigation system, which is basically independent of ground

installations, provides data on the position of the aircraft. It comprises :

3.3.4.1 WEATHER RADAR SYSTEM:

3.3.4.1 Weather Radar System

The weather radar system is a X-band system which can be capable of the

Predictive Windshear function. This system enables:

detection and localization of the atmospheric disturbances in the area

defined by the antenna scanning with visual display of their intensity

presentation of terrain mapping information by the combination of the

orientation of the radar beam and of the receiver gain

detection and presentation of windshear events in the area defined by

the antenna scanning (if the Predictive Windshear function is

operative).

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Note: The Electronic Flight Instrumental System (EFIS) controls the operation

and superimposes the weather picture on the Navigation Display.

This system is made up of the following components :

one or two transceivers (transceiver 2 is optional)

a control unit

a flat plate antenna and its drive unit.

3.3.4.2 RADIO ALTIMETER:

The function of the radio altimeter is to determine precisely and continuously,

the height of the aircraft from 0 to 2500 ft above the terrain independently of the

atmospheric pressure.The Height and Decision Height data are displayed on the PFD.

The selection and reading of Decision Height are performed on the Multipurpose

Control and Display unit (MCDU).

The radio altimeter system is composed of:

two transceivers

four identical antennas, one for transmission and one for reception for

each transceiver.

3.3.4.3 TRAFFIC COLLISION AVOIDANCE SYSTEM (TCAS):

The TCAS is designed to protect a volume of airspace around the TCAS

equipped aircraft. The function of the TCAS II is to determine the range, altitude and

bearing of other aircraft equipped with ATC transponders. The system monitors the

trajectory of the other aircraft for the purpose of determining if any of them constitute

a potential collision hazard. If a potential conflict exists, the system provides the

pilots with aural and visual advisories which indicate the vertical avoidance

maneuvers.

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3.3.4.3 Traffic Collision Avoidance System (TCAS)

The aircraft is equipped with:

a TCAS computer unit

two TCAS antennas.

The system exchanges data with the Air Traffic Control (ATC) System.

Traffic advisories are shown on the EFIS displays.

3.3.4.4 GROUND PROXIMITY WARNING SYSTEM (GPWS):

This system is used to inform the crew if the aircraft is in a dangerous

configuration when approaching the ground in a non-predetermined manner.

The GPWS generates aural and visual warnings if the aircraft adopts a

potentially hazardous condition with respect to:

Mode 1 – Excessive rate of descent

Mode 2 – Excessive closure rate with terrain

Mode 3 – Descent after takeoff and minimum terrain clearance

Mode 4 – Unsafe terrain clearance

Mode 5 – Descent below glide slope.

The system is operative between 30ft and 2450ft radio altitude.

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3.3.4.5 ENHANCED GROUND PROXIMITY WARNING SYSTEM

(EGPWS):

3.3.4.5 Enhanced Ground Proximity Warning System (EGPWS)

The purpose of the Enhanced Ground Proximity Warning System (Enhanced

GPWS) is to alert the flight crew of potentially hazardous conditions with respect to

the terrain.

The system achieves this objective by accepting a variety of aircraft

parameters as inputs, applying alerting algorithms, and providing the flight crew with

aural alert messages and visual annunciations and displays in the event that the

boundaries of any alerting envelope are exceeded.

The following Enhanced features has been added to existing basic Ground

Proximity Warning Modes 1 to 5 which are the backbone of the system:

Terrain Clearance Floor (TCF) function. It creates an increasing terrain

clearance envelope around the intended airport runway directly related

to the distance from the runway. The TCF function generates aural and

visual alerts.

Terrain Awareness alerting and Display (TAD) function. This function

uses aircraft geographic position, aircraft altitude and a terrain data

base to predict potential conflicts between the aircraft flight path and

the terrain, and to provide graphic displays of the conflicting terrain on

the NDs.

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The terrain awareness alerting algorithms continuously compute terrain

clearance envelopes ahead of the aircraft.

3.3.5 DEPENDENT POSITION DETERMINING:

This part of the navigation system comprises:

3.3.5.1 DISTANCE MEASURING EQUIPMENT:

The principle of the DME navigation is based on the measurement of the

transmission time. Paired interrogation pulses go from an onboard interrogator to a

selected ground station. After 50 microseconds, the station transmits the reply pulses

to the aircraft.

The Distance Measuring Equipment (DME) is a radio aid to medium range

navigation which provides the crew with :

A digital readout of the slant range distance of the aircraft from a

selected ground station

Audio signals which identify the selected ground station.

The DME uses the frequency band from 962 MHz to 1213 MHz for reception

and transmission.

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3.3.5.1 Distance Measuring Equipment

3.3.5.2 AIR TRAFFIC CONTROL:

The ATC allows an operator of the corresponding equipment on the ground to

locate and identify the aircraft in flight without having to communicate with the crew.

The system is made up of the following components:

two ATC transponders

a ATC/TCAS control unit

four ATC antennas: two bottom antennas and two top antennas

3.3.5.2 Air Traffic Control

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3.3.5.3 AUTOMATIC DIRECTION FINDER:

3.3.5.3 Automatic Direction Finder

The ADF enables the bearings of one or two ADF ground transmitter stations

to be permanently indicated with respect to the aircraft heading.

The system is made up of the following components:

one or two transceivers (transceiver 2 is optional)

two ADF loop and sense antennas.

The system receives frequency information from FMGCs or RMPs. The ADF

bearings are displayed on:

two EFIS Navigation Displays (in Rose mode).

a Radio Magnetic Indicator (RMI)

3.3.5.4 VHF OMNI RANGE (VOR):

The VOR firstly enables the bearings of one or two VOR ground transmitter

stations to be permanently indicated with respect to the aircraft heading, and secondly

it indicates the aircraft course deviation with respect to a preselected course.The

system is made up of the following components:

two VOR/MKR receivers

a VOR antenna to supply the two VOR/MKR receivers

a MARKER antenna to supply the VOR/MKR receiver 1 which is the

only one to ensure the MARKER function.

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3.3.5.4.a VOR Radial 3.3.5.4.b VOR

The system receives frequency information from FMGCs or RMPs.VOR data

are displayed on:

two EFIS PFDs

two EFIS NDs

a VOR/DME Radio magnetic Indicator (RMI) or a VOR/ADF/DME

RMI

Marker data are displayed on CAPT and F/O PFDs and NDs.

3.3.5.5 GLOBAL POSITIONING SYSTEM (GPS):

3.3.5.5 Global Positioning System (GPS)

The GPS system is a radio aid to worldwide navigation which provides:

the crew with a readout of accurate navigation information, e.g.

position, track and speed.

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the Flight Management and Guidance Computer (FMGC) with position

information for accurate position fixing.

The GPS system uses signals broadcast by a constellation of 24 satellites at a

frequency of 1575.42 MHz.

The GPS system is composed of:

two GPS Sensor Units (GPSSUs)

two GPS antennas.

3.3.5.6 Primary Flight Display (PFD):

3.3.5.6 Primary Flight Display

Primary flight display is a modern aircraft instrument dedicated to flight

information. They are built around an LCD or CRT display device.While, the PFD

does not directly use the Pitot static instruments to physically display flight data, it

still uses the system to make altitude, airspeed, vertical speed and other measurements

precisely using air pressure and barometric readings. An air data computer analyzes

the information and displays it to the pilot in a readable format.

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3.3.5.7 NAVIGATION DISPLAY (ND):

3.3.5.7 Navigation Display

The Flight management system sends the flight plan for display on navigation display.

3.3.5.8 ECAM DISPLAY:

3.3.5.8 ECAM Display

Electronic Centralized Aircraft Monitor (ECAM) is a system that monitors

aircraft functions and relays them to the pilots. It also produces messages detailing

failures and in certain cases, lists procedures to undertake to correct the problem.

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CONCLUSION

This article offers a comprehensive view of Technology and Elements of

system in Avionics. It will not make one an expert in avionics but will provide the

knowledge to approach the Technological developments.

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FIGURE CHART

2.2.3 Auxiliary Power Unit 10

2.2.6 Ram Air Turbine 12

2.2.10 Static Inverter 14

2.3.1 Transformer Rectifier 15

2.3.2 Battery 16

3.2.1 Speech Communication 17

3.2.1.3 Radio Management System 19

3.2.2.2 Satcom 20

3.3.3 Landing and Taxing Aids 25-26

3.3.4.3 Traffic Collision Avoidance System 30

3.3.4.5 EGPWS 31

3.3.5.1 Distance Measuring Equipment 32-33

3.3.5.2 Air Traffic Control 33

3.3.5.3 Automatic Direction Finder 34

3.3.5.4 VOR 35

3.3.5.5 Global Positioning System 35

3.3.5.6 Primary Flight Display 36

3.3.5.7 Navigation Display 37

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BIBLIOGRAPHY

References of this article are taken from:

1. E.H.J.PALLETT, Aircraft Instruments and Integrated Systems, Longman Scientific &

Technical, England, UK, 1992.

2. J.POWELL, Aircraft Radio Systems, Pitman, UK, 1981.

3. A320 Aircraft Maintenance Manual “AIR INDIA”, AIRBUS INDUSTRIE, France,

1988.