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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.