fileINTENT WP3 Implementation Roadmap, D3-1 Version: v04 Date: 22-03-2003 Classification: Public 3 ˘ ˇ ˆ Document title Implementation Roadmap, D3-1

EUROPEAN COMMUNITY

COMPETITIVE AND SUSTAINABLE

GROWTH PROGRAMME

Version: v04

Date: 22-05-2003

Classification: Public

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Project acronym: INTENT

Project full title: INTENT, “The Transition towards

Global Air and Ground Collaboration

In Traffic Separation Assurance”

Project number: GRD1-2000-25326

Contract number: G4RD-CT-2000-00394

Start date: 1 December 2000

Duration: 29 months

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Implementation Roadmap, D3-1

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Document title Implementation Roadmap, D3-1

Version V04

Date 22-05-2003

Classification Public

Workpackage WP3

Document identification INTENT_D3-1_v04_22-05-03_P.doc

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EUROCONTROL S. Ach [email protected]

A. Nuic [email protected]

C. Shaw [email protected]

ROCKWELL COLLINS O. Bleeker [email protected]

P. Serre [email protected]

E. Thomas [email protected]

SMITHS INDUSTRIES A. Starr [email protected]

I. Grace [email protected]

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National Aerospace Laboratory, NLR

Attn. Mr. R.C.J. Ruigrok

Anthony Fokkerweg 2

1059 CM Amsterdam

The Netherlands

Tel.: +31-20-5113595

Fax: +31-20-5113210

e-mail: [email protected]

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V01 16-04-2002 Eurocontrol First version of the document, all pages modified

V02 03-04-03 Eurocontrol Update

V03 14-04-03 Rockwell Update, airborne + roadmap included, all pages modified

V04 22-05-03 NLR Preparation for public delivery

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EC K. Liem, [email protected]

NLR R.C.J. Ruigrok, [email protected] , +31 20 511 3595

M.S.V. Valenti Clari, [email protected] , +31 20 5113012

L.J.J. de Nijs, [email protected] , +31 20 511 3737

ONERA J.L. Farges, [email protected]

N. Imbert, [email protected]

Eurocontrol E. Hoffman, [email protected]

A. Nuic, [email protected]

C. Shaw, [email protected]

DUT H.G. Visser, [email protected]

R. Wijnen, [email protected]

QinetiQ P. Platt, [email protected]

B. Booth, [email protected]

A. Magill, [email protected]

RC-F P. Serre, [email protected]

C. Alber, [email protected]

E. Corbi, [email protected]

E. Thomas [email protected]

O.F. Bleeker, [email protected]

SIA A. Starr, [email protected]

I. Grace, [email protected]

AIRBUS FRANCE D. Ferro, [email protected]

ECA / VNV R.C. Brons, [email protected]

R. Hoogeboom, [email protected]

AEA / BA

AEA / SAS

AEA / KLM

A. Fisher, [email protected]

A. Shand, [email protected]

A. Ellis, [email protected]

B. Nilsson, [email protected]

B. Berends, [email protected]

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�� 2.1.1 Voice communication ...................................................................................................................182.1.2 Data communication .....................................................................................................................18

�� 2.2.1 VOR (VHF Omni-directional Range) ...........................................................................................202.2.2 DME (Distance Measuring Equipment)........................................................................................202.2.3 VORTAC......................................................................................................................................212.2.4 NDB (Non Directional radio Beacon)...........................................................................................212.2.5 LORAN (Long Range Navigation) ...............................................................................................22

�� 2.3.1 Primary radar ................................................................................................................................242.3.2 Secondary radar ............................................................................................................................252.3.3 Surveillance Data Processing System ...........................................................................................27

�� !�� 2.4.1 Conflict detection..........................................................................................................................312.4.2 Conflict resolution ........................................................................................................................31

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�� 3.1.1 Voice evolution.............................................................................................................................333.1.2 Data evolution...............................................................................................................................33

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�� "3.3.1 Mode S Radar ...............................................................................................................................453.3.2 Surveillance Data Processing & Distribution System: ARTAS....................................................46

�� !�� #�� $�� %3.4.1 HIPS (Highly Interactive Problem Solver) ...................................................................................493.4.2 GEARS (Generic En route Algorithmic Resolution Service) .......................................................503.4.3 CORA (COnflict Resolution Assistance Tool) .............................................................................523.4.4 URET (User Requirements Evaluation Tool) ...............................................................................53

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3.4.5 PARR (Problem Analysis, Resolution and Ranking System) .......................................................543.4.6 ERATO (En-Route Air Traffic Organiser) ...................................................................................553.4.7 Arrival sequencing tools ...............................................................................................................56

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"�� &�� "�5.1.1 IRS ................................................................................................................................................585.1.2 DME .............................................................................................................................................595.1.3 GPS...............................................................................................................................................595.1.4 EGI................................................................................................................................................615.1.5 Altimeters......................................................................................................................................615.1.6 Other positioning systems.............................................................................................................62

"�� '��(� )�� * 5.2.1 Description....................................................................................................................................645.2.2 Working principle .........................................................................................................................645.2.3 RNAV ...........................................................................................................................................675.2.4 RNP...............................................................................................................................................685.2.5 BRNAV / PRNAV........................................................................................................................695.2.6 RNP RNAV ..................................................................................................................................70

"�� +�5.3.1 TCAS ............................................................................................................................................725.3.2 ADS ..............................................................................................................................................73

"� #�� , �� + 5.4.1 ACARS .........................................................................................................................................745.4.2 CPDLC..........................................................................................................................................765.4.3 Mode S..........................................................................................................................................775.4.4 Developmental Data Links............................................................................................................785.4.5 Summary.......................................................................................................................................80

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*�� &�� 6.1.1 GNSS-1.........................................................................................................................................826.1.2 EGNOS .........................................................................................................................................826.1.3 GNSS-2.........................................................................................................................................836.1.4 Galileo...........................................................................................................................................83

*�� '��(� )�� "6.2.1 ARINC-702A-1.............................................................................................................................856.2.2 RNP-1 RNAV ...............................................................................................................................86

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6.4.3 CDTI for CD&R ...........................................................................................................................906.4.4 Predictive ASAS ...........................................................................................................................91

*�" �� %�6.5.1 ADS-B ..........................................................................................................................................936.5.2 Hybrid Surveillance ......................................................................................................................946.5.3 Integrated Surveillance Systems ...................................................................................................946.5.4 Airborne Surveillance and Separation Assurance Processors .......................................................95

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�� /�0�� %+8.1.1 Overall system architecture...........................................................................................................978.1.2 Ground equipage...........................................................................................................................988.1.3 Airborne equipage.........................................................................................................................99

�� 0�� 8.2.1 Overall system architecture.........................................................................................................1028.2.2 Airborne equipage.......................................................................................................................1038.2.3 Ground equipage (optional) ........................................................................................................104

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%�� /�0�� "9.1.1 Ground equipage.........................................................................................................................1059.1.2 Airborne equipage.......................................................................................................................106

%�� 0�� +9.2.1 Airborne equipage.......................................................................................................................1079.2.2 Ground equipage (optional) ........................................................................................................107

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Figure 1: Primary Surveillance Radar................................................................................................... 25

Figure 2: Secondary Surveillance Radar .............................................................................................. 27

Figure 3 Aircraft Protected Zone........................................................................................................... 30

Figure 4: Planned Mode S Radar Coverage at 31st March 2005 ........................................................ 34

Figure 5: Enhanced Surveillance CAP Services in Operation by End 2007 ........................................ 35

Figure 6: Current ACARS versus Future ATN Configurations using VDL2.......................................... 38

Figure 7: TIS-B Schematics.................................................................................................................. 41

Figure 8: ARTAS Deployment Map ...................................................................................................... 48

Figure 9 HIPS Concept ......................................................................................................................... 50

Figure 10 GEARS Concept................................................................................................................... 51

Figure 11 GEARS Resolution ............................................................................................................... 52

Figure 12: Flight Management System Main Functions and Relationships ......................................... 65

Figure 13: Conventional and Area Navigation...................................................................................... 68

Figure 14: ICAO versus RTCA/EUROCAE Definition of RNP.............................................................. 69

Figure 15: Benefits of RNP and RNP RNAV on Route Width .............................................................. 71

Figure 16: Experimental CDTI Displays (NASA) .................................................................................. 88

Figure 17: CDTI for CD&R by NLR....................................................................................................... 91

Figure 18: Primary Flight Display with Predictive ASAS....................................................................... 92

Figure 19: ARINC 660 Surveillance Functions ..................................................................................... 95

Figure 20: Overall Hybrid System Architecture .................................................................................... 98

Figure 21: Overall Airborne System Architecture ............................................................................... 103

Figure 22: Ground Technology Roadmap .......................................................................................... 109

Figure 23: Airborne Technology Roadmap......................................................................................... 110

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1090ES 1090 MHz Mode S Extended Squitter

2D Two Dimension(al)

3D Three Dimension(al)

4D Four Dimension(al)

A/T Auto Throttle

ACARS Airborne Communications Addressing and Reporting System

ACAS Airborne Collision Avoidance System

ACC Area Control Centre

ACL ATC Clearance Information

ACM ATC Communication Management

ACMS Aircraft Condition Monitoring System

ADC Air Data Computer

ADI Attitude Director Indicator

ADS Automatic Dependent Surveillance

ADS-A Addressed ADS

ADS-B ADS-Broadcast

ADS-C ADS-Contract

ADF Automatic Direction Finder

ADLP Airborne Data Link Processor

AEEC Airlines Electronic Engineering Committee

AHRS Attitude and Heading Reference Systems

AM Amplitude Modulated

AOC Aeronautical Operational Control

APW Area Proximity Warning

ARINC Aeronautical Radio Inc.

ARTAS ATC Surveillance Tracker And Server

ARTCC Air Route Traffic Control Centre

ASAS Airborne Separation Assistance System

ASTERIX All-purpose Structured EUROCONTROL Radar Information Exchange

ASU ATM Surveillance Units

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ATC Air Traffic Control

ATCo Air Traffic Controller

ATCRBS Air Traffic Control Radar Beacon System

ATIS Aeronautical Traffic Information Service

ATM Air Traffic Management

ATN Aeronautical Telecommunications Network

ATS Air Traffic Service

BRNAV Basic Area Navigation

CD&R Conflict Detection and Resolution

CDTI Cockpit Display of Traffic Information

CDU Control and Display Unit

CENA Centre d’Etudes de la Navigation Aérienne

CMU Communications Management Unit

CNS Communication Navigation Surveillance

CORA Conflict Resolution Assistance

CPA Closest Point of Approach

CPDLC Controller Pilot Data Link Communication

CSMA Carrier Sense Multiple Access

CTAS Center/Terminal radar approach control Automation System

D-ATIS Data-link Airport Traffic Information Service

D8PSK Differential 8 Phase Keying

DAP Downlink Aircraft Parameter

DCL Departure Clearance

DFIS Digital Flight Information Service

DGPS Differential GPS

DME Distance Measuring Equipment

DME-P DME-Precision

DSP Data link Service Providers

EADI Electronic Attitude Director Indicator

EATMP European ATM Programme

ECAC European Civil Aviation Conference

EFIS Electronic Flight Instrument System

EGI Embedded GPS Inertial Reference System

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EGNOS European Geostationary Navigation Overlay System

EGPWS Enhanced Ground Proximity Warning System

EHSI Electronic Horizontal Situation Indicator

EICAS Engine Indication and Crew Alert System

ERATO En-Route Air Traffic Organiser

ETA Estimated Time of Arrival

ETD Estimated Time of Departure

ETE Estimated Time En-route

FAA Federal Aviation Administration

FAST Final Approach Spacing Tool

FCS Flight Control System

FDPS Flight Date Processing Systems

FIR Flight Information Region

FLIPCY Flight Plan Consistency

FLIR Front Looking Infra-Red

FLW Forward Looking Wind-shear Radar

FMC Flight Management Computer

FMS Flight Management System

FOM Figure of Merit

FPL Flight Plan

FRUIT False Replies Unsynchronised In Time

GDLP Ground Data Link Processor

GEARS Generic En route Algorithm Resolution Service

GLONASS Global Navigation Satellite System

GMSK Gaussian Minimum Shift Keying

GNSS Global Navigation Satellite System

GPS Global Positioning System

HDLC High Level Data Link Communication

HF High Frequency

HFDL High Frequency Data Link

HFDR HFDL Radio

HIPS Highly Interactive Problem Solver

HMI Human-Machine Interface

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HSI Horizontal Situation Indicator

IAS Indicated Air Speed

ICAO International Civil Aviation Organization

IFR Instrumental Flight Rule

ILS Instrument Landing System

INMARSAT International Maritime Satellite Organization

IRS Inertial Reference System

ISA International Standard Atmosphere

LAAS Local Area Augmentation System

LES Land Earth Station

LNAV Lateral Navigation

LORAN Long Range Navigation

LRU Line Replaceable Unit

MAICA Modelling and Analysis of the Impact of Changes in ATM

MASPS Minimum Aviation System Performance Standard

MCDU Multifunction Control and Display Unit

MEMS Micro Electro-Mechanical Sensor

METAR Meteorological Aviation routine Report

MIN Message Identification Number

MLS Microwave Landing System

MMR Multi Mode Receiver

Mode S Mode Selective

MOPS Minimum Operational Performance Specifications

MRN Message Reference Number

MSAW Minimum Safe Altitude Warning

MSK Minimum Shift Keying

MTBF Mean Time Between Failures

MTCA Medium Term Conflict Alert

MTCD Medium Term Conflict Detection

NAVAID Navigational Aid

NAVSTAR Navigation Satellite Timing and Ranging

ND Navigation Display

NDB Non Directional radio Beacon

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NOTAM Notice To Airmen

OLDI Online Data Interchange

OOOI Out-Off-On-In Reports

OPLINKP Operational Data Link Panel

pFAST passive FAST

PRNAV Precision Area Navigation

PARR Problem Analysis, Resolution and Ranking system

PDC Pre-Departure Clearance

PFD Primary Flight Display

PSK Phase Shift Keying

PSR Primary Surveillance Radar

RA Resolution Advisories

RAIM Receiver Autonomous Integrity Monitoring

RGS Remote Ground Station

RLG Ring Laser Gyro

RNAV Area Navigation

RNP Required Navigation Performance

R/T Radio Telecommunication

RTU Radio Tuning Unit

RVSM Reduced Vertical Separation Minimum

SA Selective Availability

SARPS Standards and Recommended Practices

SAT Static Air Temperature

SATCOM Satellite Communication System

SBAS Satellite Based Augmentation System

SDPD Surveillance Data Processing and Distribution

SDPS Surveillance Data Processing System

SIGMET Significant Meteorological Conditions

SITA Société Internationale de Télécommunications Aéronautiques

SSR Secondary Surveillance Radar

STCA Short Term Conflict Alert

STMA Self organising Time Division Multiplex Access

TA Traffic Advisories

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TACAN Tactical Air Navigation

TAS True Air Speed

TCAS Traffic Alert Collision Avoidance System

TDMA Time Division Multiplex Access

TIS-B Traffic Information Service-Broadcast

TWIP Terminal Weather Information for Pilots

UAT Universal Access Transceiver

UHF Ultra High Frequency

URET User Requirement Evaluation Tool

UTC Universal Time Coordinated

VDL VHF Data Link

VDL2, VDLM2 VDL Mode 2

VDLM3 VDL Mode 3

VDL4, VDLM4 VDL Mode 4

VDR VDL Radio

VERA Verification and Resolution Advice

VFR Visual Flight Rule

VHF Very High Frequency

VNAV Vertical Navigation

VOR VHF Omni directional Range

VORTAC VOR + TACAN

WAAS Wide Area Augmentation System

WXR Weather Radar

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%!&��'��The objective of this document is to assess the function allocation from the previous work package(WP 2) and to analyse technologies required for the implementation of these functions. It will producea technology roadmap for both ground based and airborne equipment: the TechnologyImplementation Plan.

This document is divided into three parts (1) ground based equipment, (2) airborne equipment and (3)the actual technology roadmap.

The objective of the first section is to assess and describe to what extent modifications or changeswould be needed to the ground [infrastructural] system to accommodate the new ATM system asdescribed at the end of WP 2.

The objective of the second section is to assess and describe to what extent modification or changeswould be needed to the airborne equipment to accommodate the new ATM system as described atthe end of WP 2.

These descriptions will be used as inputs to the technology roadmap and the conclusions andrecommendations.

Finally, the third section will establish the technology roadmap for both ground and airborneequipment needed to maximise capacity and applicable to highly congested airspace.

Some parts of the two first sections (ground and airborne systems) may seem redundant. Indeed,many communication and navigation systems rely on ground-based infrastructures and airborneequipment. An effort has been done to treat both sides with different stand points when possible.

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�� The objective of this task is to assess and describe to what extend modifications or changes would beneeded to the ground system to accommodate the new ATM system as described at the end of WP 2.

The first part will be to describe the ground system currently in use in air traffic control. In the secondpart, a brief presentation of the ground system under development is provided. The last task will be topresent the modification needed to accommodate the new ATM concept.

The existing, state-of-the-art and currently developed ground based equipment and processes will beinvestigated to identify the ability to generate and process the aircraft intent information as identifiedto be required in the new ATM system as described under WP 2.

The following ground based equipment will be addressed among other CNS systems:• Primary Radar,• Secondary Radar• ATC tools (CTAS, FAST, pFAST, STCA, HIPS, etc…)• Traffic Information Services – Broadcast (TIS-B)• Data link (air/ground)• Conflict Detection & Resolution (CD&R)

Potential modifications to the ground based equipment will also be described.

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�� 2.1.1.1 DescriptionThe current Air Traffic Control (ATC) system is based on voice communications between air trafficcontrollers and pilots to transmit control instructions and other information related to the flight. Thereis also communication between pilots in order to exchange information. These communications arerequired to support co-ordination of aircraft movement in all phases of flight and especially to ensureaircraft separation and to transmit advisories and clearances.

2.1.1.2 Working principleFlight information are transmitted and received using HF (high frequency), VHF (very high frequency)and UHF (ultra high frequency) voice radio. It is the main communication means between pilots andcontrollers. A 25 kHz channel wide in the frequency band of 118-136 MHz is currently used for VHF.

This mode of operation permits to have a permanent connection between controllers and pilots butseveral drawbacks can be noticed:

• Risk of misunderstanding between controllers and pilots,• Slow rate of information transfer, and• An increase of the crew and controllers workload.

As air travel continues to increase, controller-pilot communication has increased to the saturationpoint (one of the main problems is the congestion of the VHF frequencies) during peak traffic periodsat many locations.

�� Another means of communication, called data link, is based on the digitized data. This techniquepermits the exchange of data between air and ground systems and leads to a faster transfer ofinformation.

The network that is currently used is ACARS (Aircraft Communication and Reporting System). Thissystem is actually used only by airlines (the number of aircraft equipped is about 3500). The data aretransmitted using VHF frequency.

2.1.2.1 DescriptionThe Aircraft Communications Addressing and Reporting System (ACARS) is a communication data-link system which sends messages between an aircraft and the ground system including airline hostcomputers (for AOC messages), ATC host computers (for ATS messages), and other parties.

The ACARS ground system is made up of two parts:• The first part is the radio and message handling network, which is controlled by Aeronautical

Radio Incorporated (ARINC) in the United States, the Air Canada Network in Canada,AVICOM in Japan and the Société Internationale de Télécommunications Aéronautiques(SITA) in Europe and the other parts of the world.

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• The second part is composed of an airline’s operations or message centre. The network isconnected to the airline operations centre by a landline. At the airlines’ facilities, the messagehandling is performed by a computer system, which sends received messages to theappropriate department (operations, engineering, maintenance, customer services, andpayroll) for the appropriate action.

The ground network delivers the messages to the airline ground operations base or ATC facility.

2.1.2.2 Working principleThe ACARS system mainly uses analogue radios originally designed for ATS voice communicationsbased on Amplitude Modulation (AM). The ACARS modulation scheme is Amplitude Modulated -Minimum Shift Keying (AM-MSK) at a bit rate of 2.4 Kbps.

The channels in the VHF band are generally used for voice communications but with theimplementation of ACARS some channels in the AOC sub-band were reserved for ACARS use.

ACARS messages are transmitted on the following VHF frequencies (primary frequency):• 131.550 MHz: ARINC in the USA; SITA in Australia, Far East and Pacific.• 131.725 MHz: SITA in Europe, Middle East, Africa, South America (due to congestion a

secondary frequency is also used in Europe 131.525 MHz).• 131.475 MHz: Air Canada in Canada.

This information received onboard the aircraft can be stored, deleted or printed by the crew. However,this system is constrained by the range of VHF: relays of broadcasting stations are needed, and timedelay has to be taken into account in the transmission of data.

Currently, only a few categories of information are exchanged between air and ground systems usingACARS system:

• Meteorological information• NOTAM (NOTice to AirMen): it is a notice containing essential information for flight operation

and not known sufficiently in advance to be disseminated (for example information theunavailability of a part of the airspace during a period of time).

• Information concerning aircraft maintenance

There are no systems that permit information exchange (especially concerning the flight progression)between air and ground for the en-route phase of flight. Only, a link is now used to transfer dataautomatically from one sector to another one when an aircraft passes through these two sectors. Thissystem, called Online Data Interchange (OLDI), is aimed at updating the flight plan and permitting anautomatic co-ordination between adjacent sectors.

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./.� ��'� �� 1 �� 2This is an important element of the ATC ground system because of its strong influence on the currentATM structure. The actual organisation of the airspace is based on structured airways, defined bynavigational aids located on the ground.

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2.2.1.1 DescriptionThe VOR is a ground based navigation aid that transmits a VHF navigational signal 360 degree inazimuth. It transmits to the aircraft an infinite number of navigation courses, which are selectable bythe pilot.

2.2.1.2 Working principleThis is the primary radio navigation aid that operates in the VHF band immediately below thefrequencies used for communications (from 108.10 MHz to 117.90 MHz).

The transmission is modulated by two signals:• Reference phase signal constant in all directions, and• Variable phase signal variable with azimuth.

The receiver onboard the aircraft measures the difference between the two signals to determine theazimuth angle of the aircraft with respect to the VOR ground transmitter.

2.2.1.3 PerformanceSome factors of inaccuracy exist and have to be taken into account:

• Inaccuracy of onboard equipment is about +/-3°.• Inaccuracy of the ground station is about +/- 2°.• The theoretical range of VOR depends on the VHF range and is computed using the

following formula: IW10 �� 23.1=

• Obstacles (mountains, building…) block VOR signal• Furthermore, the VOR cannot be used when the aircraft passes vertically to the station (within

an angle of θ = 45° also called cone-of-silence).

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2.2.2.1 DescriptionThe DME is a pulsed distance measuring equipment located on the ground. After determining inwhich radial the aircraft is located, the pilot uses DME to determine the aircraft’s distance from theground station. This system operates in the UHF frequency band.

2.2.2.2 Working principleThe DME consists of an interrogator (send pulse) located onboard the aircraft and a ground receiverwhich transmits back the signal at 63 MHz or lower.

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The interrogator transmits a coded pulse (the frequency is around 1000 MHz) and when the groundbased DME receives it, it replies using a different frequency. The DME equipment onboard computesthe elapsed time between the transmission of the signal and the reply. The distance from the DMEground station (named slant range) is then obtained by dividing this time by 12.361µs.

2.2.2.3 PerformanceAs for VOR ground station several drawbacks exist:

• Inaccuracy (about 0.2Nm) has to be taken into account.• Like VOR, the radio electric visibility depends on the altitude of the aircraft and is computed

using the following formula: IW10 �� 23.1=• Limited number of pulse pairs that lead to a maximum number of aircraft (i.e. less than 100).

DME ground station can be overloaded and in this case interrogations from new airbornetransponders are rejected.

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2.2.3.1 DescriptionThis system is a combination of two navigation aids, VOR and TACAN (tactical air navigation). Thelast one has been developed and used by military aircraft because of the inadequacy of VOR/DMEground station for specific military operation (VOR need an extended clear zone and DME groundstation can be saturated if too many aircraft are located in its vicinity). TACAN provides bearing anddistance information and its main advantage is that it is smaller and easier to handle compared to theVOR/DME station.

2.2.3.2 Working principle�%� see section 2.2.1

�� is an Ultra High Frequency electronic navigation aid, which provides an indication of bearingand distance to the selected TACAN station. The azimuth is measured, like VOR, as the phasedifference between a reference signal and an azimuth dependent signal.

The VORTAC system has the capacity to provide information about bearing and distance for bothmilitary and civilian aircraft. To use this equipment, the pilot has to select the appropriate VORfrequency and the DME interrogator can automatically contact TACAN UHF frequency so thatinformation regarding to distance and direction will be available.

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2.2.4.1 DescriptionThe non-directional radio beacon is a navigational aid instrument aimed to indicate to the pilot onlybearing information. This method of navigation is based on a ground station (called NDB) and areceiver located on the aircraft (called ADF).

1 The range time for a signal to travel 1NM and return is 12.36µs.

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2.2.4.2 Working principleThe NDB transmits a uniform signal omni-directionally (i.e. in all the direction) from the transmitter(located on the ground) using 190-540 kHz frequency band. The receiver located onboard the aircraft,called Automatic Direction Finder (ADF), automatically determines the bearing to the NDB anddisplays the information to the pilot.

Using ADF and the aircraft’s heading indicator, the pilot can easily determine the aircraft’s relativebearing from the station and then use this information to find the correct heading that would lead tothe beacon.

2.2.4.3 PerformanceAs for the others navigational aids, the range depend on the radio electrical visibility which

correspond IW10 �� 23.1=, where D is the distance (in nautical miles) and a represent the altitude

of the aircraft (in feet).

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2.2.5.1 DescriptionThe long-range navigation system differs from most aviation navigation systems in the sense that it isa hyperbolic navigation system instead of a rho-theta system like VOR/DME i.e. the pilot plots multiplehyperbolic lines of position to determine the aircraft’s position.

Different types of long-range Navigation system exist (LORAN A, LORAN B, LORAN C and LORAND) but the LORAN-C is the current civilian version and its functioning will be described in the followingparagraph.

2.2.5.2 Working principleThe system is based on the time displacement between signals from fixed shore based antennas.The operating principle is based on one master station (called station M) and two to five slave stations(called V, W, X, Y and Z) located hundreds of miles apart. Actually, seventeen LORAN C chains areused in operation.

At precise intervals, the master station transmits a coded pulse of 100 kHz with a unique time interval(called Group Repetition Interval, GRI, and each chain station has a proper and unique GRI). Theslave station receives this pulse (from its own master station), and in turn transmits a coded signal (onthe same frequency). The LORAN receiver (onboard the aircraft) receives these signals, identifieswhich chain is being received and computes the time difference between the master and each of theslave station transmissions.

These time differences are used by the computer located in the receiver onboard the aircraft, to plotmultiple lines of position. By repeating this procedure with a second pair of stations, a second line ofpositions can be drawn and the intersection between curves gives the exact position of the aircraft.

This system provides to the pilot information regarding ground speed, ground track, distance to theairport and Estimated Time of Arrival.

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2.2.5.3 Performance• Under certain atmospheric conditions, the aircraft can receive several distinct signals from

each master and slave.• The signal transmitted by the ground station can travel into space and reflect off the

ionosphere and return to the aircraft. This signal takes more time to reach the aircraft andlead to confuse the LORAN onboard the aircraft. Under this condition, the determination ofthe exact position becomes impossible and the receiver is designed to ignore this signal andto switch to another chain of stations.

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./�� +��'�� $��Within the surveillance system, the radar sensors are required to acquire information from aircraft(primary and secondary radar) and SDPS (Surveillance Data Processing System) to interpret thesurveillance information and to distribute it through a ground network to the users.

�� *�� +�� The basic concept of primary radar (radio detection and ranging) is quite simple: the radar operatesby radiating an electromagnetic energy and detecting the echo returned by the target. Frequenciesused are higher than 1000 MHz with short wave (less than 30cm long).

The echo signal provides information regarding the distance (called also range) between the targetand the antenna. The distance is computed from the time it takes for the radiated energy to reach thetarget and back. The maximum range of surface based radar is from 200Nm to 250Nm and this rangedepends on aircraft altitude.

2.3.1.1 DescriptionThe primary surveillance radar (PSR) used in ATC has a rotating (6 rotations/minute) and a highlydirectional antenna. This tool is used to locate and identify any aircraft (flying with VFR or IFR) in theairspace which is not equipped with a transponder (or when the transponder is not active).

This radar is mainly used by controllers in the neighbourhood of airports (especially during aircraftdepartures) to detect aircraft. Indeed, knowing that a runway is used only by one aircraft at a giventime, the controller can identify with certainty the aircraft just after take off.

2.3.1.2 Working principleFigure 1 depicts the principle of operation which consists on emitting electromagnetic energy. Timepulses are very short (around 1 µs) and regularly repeated (each 1 ms). A main lobe composes thediagram of radiation with a high gain in the axis (30dB). Between two pulses, the antenna works as areceiver.

If there is enough energy directed back (named backscattering) to the radar antenna, then the radarreceiver is able to detect a target. The detection is based on the reflected radar energy and does notdepend on the quantity of energy radiated by the target. This signal can be decomposed in threeelements: echo (energy reflected back by the target which is the most useful information), noise (thisperturbation has to be added because all physical measurement contains an error term) and clutter(the energy reflected back by a non relevant objects like ground, rain…).

The direction of the target is obtained from the position of the antenna, which corresponds to themaximum reception intensity. The distance is computed by measuring the time spend by the pulse to

travel from the antenna and back using the following formula: 2

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where C is the speed of lightand t is the time interval between the emission and the reception of one pulse.

The primary radar plot output provides the following information: range, azimuth and time stamp.

The main characteristics of a PSR are powerful transmitter, sensitive receiver, directive antenna and2D target positioning (range and azimuth). Its main advantage is that no co-operation is needed fromthe airborne component, i.e. the aircraft does not have to be equipped with a specific tool(transponder) onboard. Furthermore, this radar can be used to detect weather phenomenon.

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PSR has also several drawbacks such as a need for a very high-energy transmission. It does notpermit aircraft identification, it is sensitive for reflections and only provides an approximate height,which is not accurate enough to maintain minimum separation required (i.e. 1000ft).

Primary radar is in use in the ECAC area and many airports have their own PSR (departure andarrival). It constitutes the standard requirement for terminal areas.

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2.3.2.1 DescriptionTwo transmitting antennas compose the SSR (Secondary Surveillance Radar). The first one is adirectional antenna, which rotates at constant speed and is called main beam. The second one ismore or less omni-directional antenna aimed at producing the control pattern.

SSR is a method to identify aircraft and it is commonly in use today. The basic principle is similar tothe conventional primary radar, but in addition SSR is used to identify aircraft, which are equippedwith a transponder, and also provides information regarding the altitude of the aircraft.

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The dialogue between “conventional” secondary radar and “conventional” transponder uses twomodes called A and C.

When interrogated in mode A, the transponder replies by transmitting a code (allocated to the flight bythe ATC, and entered by the pilot into the transponder via the interface). When interrogated in modeC, the transponder replies by giving its altitude (digitised and entered into the transponderautomatically by means of a pressure altimeter plus an alti-encoder).

2.3.2.2 Working principleThe Secondary Surveillance Radar mode of operation is based on the same principle as PSR. Pulsesare sent out from the ground station (1030 MHz), the co-operative aircraft equipped with atransponder receives and replies (all transponders reply on 1090 MHz) by indicating identity andaltitude information (the standard delay time is 3µs).

Two interrogation pulses are sent out by the rotating antenna from the main beam (called P1 and P3)and in order to reduce the side lobes effect a third pulse is send out (called P2) from the controlpattern.

The lobe structure of the antenna radiation pattern outside the main beam (major lobe) regionconsists of a large number of small and minor lobes, usually called side lobes. These sides lobesconstitute one of the main problems of the radar system because in the transmit mode they radiate indirections other than the desired main beam direction and receive energy also from undesireddirection.

The interrogation starts with P1 pulse and is followed shortly (3µs) by a P2 pulse from the controlpattern. The first pulse (P1) is sent only to one direction and the second one (P3) is send to alldirections.

The transponder onboard the aircraft measures the signal strengths and responds if and only if the P1pulse is at least 9dB stronger than the P2 pulse.

Finally the third signal (P2) is send out by the main beam and the transponder measures thedifference (in time) between P1 and P3 signals:

• If P1 is followed 8µs later by P3 then the aircraft’s 4-digit identifier is given by the transponder(Mode A).

• If P1 is followed 21µs later by P3 then the aircraft’s altitude is given by the transponder (ModeC).

Figure 2 illustrates the SSR principles.

The working principle of the SSR is based on the calculation (in time and in noise) between threedifferent pulses. This system permits the deletion of the side lobe effect and only informationconcerning the aircraft in the antenna direction is provided.

The secondary radar plot output contains the following information: range, azimuth, mode A, mode C,code confidence and time stamp.

SSR can be used without PSR. In this case, the secondary radar is only used to detect and identifytargets (with altitude) that are equipped with SSR transponders but it cannot detect other non-equipped aircraft.

Some problems have to be pointed out:

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• One interrogation can lead to several replies (called garbling). This situation occurs whenaircraft are close to each other. The new Mode S radar solve this kind of problem because ofits capability to interrogate only one aircraft.

• False replies: if one station sends an interrogation and the reply is received by another one(called False Replies Unsynchronised In Time: FRUIT).

• The number of identification codes is quite limited (84 different codes).• There is an inaccuracy in the azimuth measurement due the main beam width (from 2.5° to

3°)

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As a conclusion, SSR offers more information compared to the PSR, but only for aircraft equippedwith a transponder.

�� ,��)�� *��,+��Radar data plays a critical role in the execution of the Air Traffic Control functions. In an environmentwhere surveillance information is derived from a number of sources it is necessary to have a function

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that will carry out some fusion of the surveillance information to produce a single unambiguous set ofaircraft tracks.

At the present time a multitude of different Radar/Surveillance Data Processing Systems (SDPS) existvarying from mono-radar, mosaic to real multi-radars.

After appropriate processing of the radar data, SDPS provide an up-to-date picture of the position andin certain cases also speed and other dynamic characteristics of all aircraft in the area of concern.They also provide the critical input for a number of functions making use of the radar derived aircraftdata. Such functions include Short Term Conflict Alert (STCA), MSAW (Minimum Safe AltitudeWarning), APW (Area Proximity Warning), Mode C vertical tracking, Flight Plan Correlation,Military/Civil Co-ordination, Flow Control etc.

Key functions of an SDPS are listed below:• Analogue to digital conversion and plot extraction• Data transmission• Plot filtering• Tracking (MONO or MULTI coverage)

2.3.3.1 TrackingThe tracking function associates radar plots belonging to the same aircraft and derives estimates ofthe aircraft’s current position, speed, heading and acceleration.

Two types of radar tracking exist:• A mono track/ local track (an aircraft trajectory calculated from plots received during several

rotations of one radar antenna)• A multi track / system track (an aircraft trajectory calculated from plots coming form several

radar sites or by combining several mono tracks)

Tracking is mandatory to:• Overcome misdetection of individual radar sensors• Reject false plots• Smooth the aircraft trajectory

A wide range of multi radar trackers exist in Europe and are in operational use today.

2.3.3.2 STCAShort Term Conflict Alert (STCA) aims at providing support to the ATCo by detecting potential futureloss of separation between aircraft. The objective is to maintain vertical and horizontal separation andto warn the controller such that there is enough time to take actions to avoid collision. Actually it isimplemented in the Aera Control Centre (ACC) or approach control centre computers, and most oftenon the radar data processing system computer. This system indicates, by an alarm visible on thecontroller radar screen, a predicted loss of separation. It is based on geometrical considerations(three dimensions) and distances between aircraft rather than the time to the closest point ofapproach (CPA) used for TCAS (traffic alert and collision avoidance system used onboard of aircraft).The inputs for the algorithms come from the radar data processing computer system. The positionsand velocity of aircraft are estimated (using linear prediction) through these inputs. Generally the firststep excludes all aircraft having sufficient horizontal or vertical separation from further considerations.A look-ahead time up to 2 minutes is generally used. This tool is used only if the aircraft is equippedwith a transponder having a Mode C capability.

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2.3.3.3 MSAWThe Minimum Safe Altitude Warning (MSAW) is aimed to detect aircraft that are approaching too lowan altitude so that they are in close proximity to the ground. In that case an alarm sound informs thecontroller that an aircraft is descending to a low altitude with an imminent danger of colliding with theground. The controller should give advice to the pilot in order to reach a safe altitude. This tool is notconsidered as a “control tool”, but it is seen as a “safety net”.

The operation of this equipment is based on the comparison between the altitude of an aircraft andthe ground (which is recorded in the terrain database).

The main idea is to divide the area, under radar approach surveillance, into small cells and assign avalue to each of these cells. The radar constantly compares the altitude (using Mode C informationprovided by the transponder onboard the aircraft) of the tracked aircraft to the database that containsterrain maximum altitude for each cell.

If an aircraft track is predicted to be close to the terrain then alarm sounds indicate to the controller adangerous situation. The controller indicates the situation to the pilot and gives him advice to returnthe aircraft to the proper flight path.

This tool is aimed to predict both an unreasonable low altitude and a too high descent rate that mightbe dangerous. During the final approach, all aircraft are monitored by the radar system and an alert issounded if an aircraft descends below 100 ft of the minimum altitude along this segment.

This system is based on the future position of the aircraft, and then the accuracy depends highly on:• Quality of the position, current speed and acceleration of the aircraft,• Look-ahead time used to predict the future position.

2.3.3.4 APWThe Area Proximity Warning (APW) is part of an overall concept called Safety Nets which can bedescribed as an ATC functionality intended to alert controllers of potentially hazardous situations in aneffective manner and with sufficient warning time for appropriate avoidance action to be taken by thepilot.

This tool is aimed to alert the controller in situations where an aircraft is, or is predicted to be, flying ina region of protected airspace. Protected airspace can be defined as an airspace which is prohibited,restricted or dangerous. The objective of this kind of tool is to warn the controller such that he/she hasenough time to take actions to avoid that an aircraft is penetrating a protected zone and to continuethe warning when the aircraft is inside the protected zone. The time horizon used for the prediction isabout two minutes.

The tool is based on data coming from the radar processor and the current aircraft position is used tocompute its future location with a 2 minutes look-ahead time.

If an aircraft is predicted to enter a protected zone, an alert window appears on the controller screen.The APW will be continuously displayed until the flight is outside or not predicted to penetrate theprotected airspace.

The APW will not be shown in the label, but only in the alert window. If the flight is involved in aMinimum Safe Altitude Warning (MSAW) or Short Term Conflict Alert (STCA), then these tools willhave higher priority than APW.

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./4� �� The standard minimum separation rule between aircraft is 5Nm to 10Nm horizontally (depending onthe distance between the aircraft and the radar antenna) and from 1000ft below FL290 to 2000ftabove FL290 vertically so that each aircraft is in a cylinder so called protected zone. Figure 3illustrates the aircraft protected zone.

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In January 2002, RVSM was introduced in Europe and new separation standard took place. This newstandard for minimum separation between aircraft is 1000ft vertically (above and below FL 290). Inthis mode of operation, aircraft should be equipped with an SSR transponder with altitude reportingsystem that can be connected to the altitude measurement system. There has been no changeregarding the horizontal separation.

One of the tasks of the ATCo is to maintain this minimum separation between the aircraft. A “conflict”is detected when an aircraft or several aircraft (this is called multi-conflict situation) enter or will enterthe protected zone of another aircraft. In this case the conflict has to be resolved by the controller whogives instructions to the pilot.

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The detection of conflict is based on the future position of the aircraft (with a certain look-ahead time)and is computed using the following principle:

• Knowing the actual position of an aircraft p0 = (latitude, longitude), the direction and thespeed vector (if no acceleration is assumed) then the future position of the aircraft for the nextx minutes can be computed (this principle is called extrapolation). However, with a look-aheadlarger than 5mn, the forecast position becomes quite inaccurate. This is due to technicalconstraints concerning ground equipment (the farther the aircraft is from the ground station,the more inaccurate becomes the radar position), but it can be caused by wind effect aswell...

��$�� #��-��Nowadays, there are no existing tools to help controllers to detect conflicts. The current mode ofoperation to avoid conflicts consists in using the position of the aircraft given by the radar, andestimating the future position of aircraft (with a given look-ahead time) based on flight plan information(like type of aircraft, speed, flight level, route…).

The tactical controller without any help detects conflicts by using a set of rules. Two majors groups ofrules exist:

• Look at all aircraft at the same FL/consider all the evolving aircraft.• Knowledge of typical conflict point and conflict area (waypoints, navigation aids points).

However, if the controller has not seen future potential conflicts two tools are actually used and seenas a security system (safety net): STCA (Short-Term Conflict Alert) and the MTCA (Medium-TermConflict Alert). These two equipment are based on the Trajectory Predictor tool (TP), which predictsthe route of the aircraft and then determines, including uncertainty bounds and accuracy, conflictingaircraft and region. The main difference between them is that a different time horizon is used. STCAand MTCA are a part of the radar data processing system.

��$�� #��-��No tool is currently available to resolve conflicts. The controller gives instructions to the pilot tomaintain separation and to avoid collision (i.e. radar information is used to assist pilots by advisingthem about the relative position and altitude of any potentially conflicting traffic). This mode ofoperation is called traffic advisories.

In principle, controllers use the actual position of aircraft (given by radar) and estimate the futureposition of an aircraft with respect to fix points (generally, it corresponds to navigational aid or knownwaypoints).

Actually, four procedures are used to maintain separation and to avoid conflict:• �� : this is the easiest way to separate aircraft. It consists of imposing a

separation of at least 1000ft (2000ft above FL290 for non-RVSM region) between aircraft sothat the reserved airspace for each aircraft extends from 500ft above it to 500ft below. Thenormal procedure for the controller is to request that the pilot reports passing through orleaving off a particular altitude. When the pilot reports an altitude, the controller can giveanother altitude to another aircraft taking into account 1000ft separation. This rule isespecially applied for aircraft flying the same route or in the airport neighbourhood.

• #�� : it is applied for aircraft flying different routes. A distance of at least 8NMhas to be kept between aircraft. This distance corresponds in fact to the width of an airway.To maintain this spacing, the distance between aircraft and the navigation aid has to be taken

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into account otherwise a loss of separation may occur. Furthermore, if the aircraft is far fromthe navigation aid (VOR, DME), its positions may become quite inaccurate.

• #� �� : this technique is applied for aircraft flying on the same route. Ifaircraft are operating in the same direction then the controller has to maintain a distance of 5to 10 nautical miles depending on the difference of speed between both aircraft, and on thedistance between the radar station and the aircraft.

• �� : this is the most flexible method (generally applied by terminal controllers)but it requires that pilots can see other aircraft which does not occur very often in en-routecontrol or in low visibility conditions.

As for conflict detection, there are basic rules that ATCo has to respect for de-conflicting:• Not to create other conflicts when a conflict resolution is implemented: avoid domino effect

(when a new conflict is created due to the resolution of a previous one).• Try to find a solution as close as possible to the initial flight plan.• Be careful not to lose control of the situation (by an increase of the workload for example).

However, a tool, VERA (VErification and Resolution Advice), is used in Maastricht (upper airspace) tohelp controllers (planner/tactical) in resolving conflicts. It consists in the graphical presentation ofvarious information concerning the aircraft in conflict, as well as possible solutions.

First, the conflict has to be detected by the controller (it can be the planner or the tactical) and he/shehas to select on the screen the two conflicting aircraft. After this selection, VERA presents graphicallyand alphanumerically some information on the controller screen. This tool is especially efficient todetect where the conflict will occur, to determine the position of the two aircraft at the closest point ofapproach and also to indicate the severity of the conflict (distance between the two at the closestpoint of approach). The different information are presented in the following form on the radar screen:

Aircraft A Aircraft B Time to CPA: x minL L Min separationR R

The two left columns present alternative left or right turns (in degree) for the two aircraft A and B.information regarding the time and minimum separation are provided in the last column.

VERA resolution is based on a separation of 8NM between aircraft.

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�� )��Voice communications between pilots and controllers are central to the ATS strategy for the short andmedium term. In the longer term, increasing use of data link could mean a reduction of voice traffic forroutine ATC communications. However, voice will remain the primary mechanism for emergency andcritical safety related exchanges.

The key element is for controllers and pilots to have immediate access to radio channels whenneeded for the communication of safety messages between them.

Today, communication is made primarily by VHF radio between controllers and pilots by use ofroutine predetermined channels, which are continually monitored in the air, and by ground stations.There are, however, problems of congestion and the availability of channels in the VHF band. Withtraffic growth, there will be a need to move to a more effective use of existing communication media,and possible use of other communication channels such as satellite.

3.1.1.1 DescriptionThe current voice communication system becomes more and more congested and a new system hasto be developed. This constitutes one of the major problems of the ATM system.

The 8.33 kHz European transition program is aimed at providing more frequencies for air/groundcommunication.

3.1.1.2 Working principleThe idea is quite simple and consists of sharing the current channel spacing (25 kHz) in three so thatspacing between frequencies will be 8.33 kHz. This system will permit to have more channelsavailable for the communication.

�� )��Air/ground data communications provide information exchange between aircraft and ground facilities.

This information will address ATC Clearances, Trajectory Negotiation, Downlink of AircraftParameters and Flight Plan Consistency Verification.

Many projects are under study concerning the exchange of data between air/ground systems. TIS-B,considered as a transition program before ADS-B, Controller-Pilot Data Link Communications(CPDLC) and Flight Information Services (FIS), along with Mode S and other data link technologies.

3.1.2.1 Mode S sub networkMode S is an evolution of the traditional Secondary Surveillance Radar. A Mode S radar is able toperform surveillance (i.e. to output the aircraft position, in addition to the standard SSR modes (Mode3/A, Mode C)) and also has data-link capabilities, i.e. the ability to send or extract frames containingbinary data.

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The Mode S programme is being implemented in two stages:• Stage 1 - Elementary Surveillance• Stage 2 - Enhanced Surveillance which will entail the use of eight Downlink Aircraft

Parameters (DAP) for initial implementation and these are:• Magnetic Heading• Air Speed• Selected Altitude• Vertical Rate• Track Angle Rate• Roll Angle• Ground Speed• True Track Angle

The following map illustrates the planned Mode S Radar coverage at 31st March 2005.

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The map below illustrates the geographical area composed of ATC centres, where EnhancedSurveillance CAP Service is planned to be in operation by end of 2007. The darker shade of blueindicates implemented areas.

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Programme milestones are:• Mode S ground station development: 1997-2002• Pre-Operational Mode S evaluation: 2000-2002• Start of deployment of Operational Mode S sensors in the ECAC High Traffic Density Area:

2002• Start of operational ATM deployment of Mode S Elementary Surveillance: March 2003• Mode S Enhanced Surveillance operational deployment from 2005 onwards

Common designs within the Mode S Programme include:• Pre-Operational European Mode S (POEMS) stations, validated against procurement

specifications and specific test and evaluation tools (POEMS Test Environment – PTE)• Upgraded ATC suRveillance Tracker And Server equipment (ARTAS). Two versions are

foreseen; the first one to handle Elementary Surveillance, the second one EnhancedSurveillance

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• Upgraded RADar NETwork (RADNET) to transmit new categories of ASTERIX Mode S data• Surveillance Analysis Support System (SASS) which will enable both the Agency and Air

Navigation Service Providers (ANSP) to validate the performance of the Mode S system

./0/1/0/0� 2�+��!��!��The Mode S sub-network consists of two systems located one on the ground (composed by the ModeS interrogator and the Mode S Ground Data-Link Processor (GDLP)) and the other on the airborneside (Mode S transponder and Mode S Airborne Data-Link Processor (ADLP)). In this section only theelements related to the ground part will be presented and described.

The Mode S interrogator is responsible for the Mode S RF (Radio Frequency) protocol and iscomposed of four entities:

• An antenna system• A power transmitter• A receiver and a reply processor• A processor dedicated to particular tasks

The Mode S Ground Data-Link Processor (GDLP): provides the entry point to the Mode S sub-network on the ground, as does the ADLP onboard. A GDLP could be connected to severalinterrogators, but a given interrogator may be connected to only one GDLP.

The following functions are provided:• SVC (switched virtual circuit)• SSE (service specific entity)• Sub-network management entity (SNME)• Frame processing

3.1.2.2 VDL (VHF Data Link)In the VHF system, two systems can be identified. The fist one is the ACARS, currently used anddescribed § 2.1.2, and the second one, still under development, is the VHF Data Link.

This later system, defined by ICAO, supports bit-oriented air/ground data transfer and is intended toallow VHF air/ground access in the frame of the ATN architecture.

./0/1/1/0� $��!��VDL (VHF Digital Link) defines the protocols needed to exchange bit-oriented data across anair/ground VHF data link in an ATN environment. This environment may consist of an accumulation ofdata processing networks, either public or private, which can be accessed by any user connected toATN and employing a compatible application process. All networks and intermediate nodes in theenvironment must be compatible with the OSI environment.

Accommodation of the VDL protocol by the ground network will permit bit-oriented data transferbetween the aircraft and the customer host via the service provider's ground network. In order to useVDL protocol, an aircraft must be equipped with a VHF Data Radio (VDR) transceiver, antenna and aCommunications Management Unit (CMU).

Equipment is necessary on the ground side and known as a Remote Ground Station (RGS). Itconsists of a microcomputer connected to a VHF transceiver or VDR and an antenna. These RGSmust be installed in all locations where data link communications are required.

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./0/1/1/1� 2�+��!��!��The VDL protocol stack is composed of:

• Physical layer using 25 KHz channel spacing with:• AM-MSK modulation (compatible with present ACARS equipment) providing a channel bit

rate of 2.4 Kbps• D8PSK modulation (available only with future VDR equipment) providing a channel bit

rate of 31.5 Kbps• Link layer which is connection oriented (similar to HDLC) using:

• CSMA or TDMA Medium Access Control algorithm• Data Link Service• Link Management Entity (LME)

• Sub-network layer connection oriented based on ISO 8208 packet layer protocol

Four frequencies are already foreseen for VDL/CSMA in the band 136.900 - 136.975 MHz.

Several VDL modes are being defined based on different Medium Access Control (MAC) techniques:• CSMA p-persistent with AM-MSK (VDL mode 1): it is an intermediate step from ACARS to

VDL Mode 2.• CSMA p-persistent with D8PSK (VDL mode 2)• TDMA integrating digital voice and data, with D8PSK (VDL mode 3): this system proposes an

integrated voice and data TDMA scheme.• Self-organising TDMA for data only, with GMSK (9.6 Kbps) or D8PSK (VDL Mode 4): It is

optimised for broadcast of short messages (typically for surveillance and navigationinformation).

��#�-��., which stands for "VHF Digital Mode 2", is an air/ground link using 25 kHz channels,specified by ICAO AMCP since 1997. VDL Mode 2, or rather ‘AOA’, its minimal version requested forsupporting AOC, is today on the market. VDL2-AOA deployments are undertaken by the majorACARS service providers both across Europe and in United States.

Link2000+ Programme that co-ordinates ATS data link implementation in the EUROCONTROLEATMP framework has recognised VDL2 as the first requested sub-network for the same reasons ofavailability, commonality with the AOC communications needs and suitability for supporting ATN andICAO CNS/ATM concept.

Figure 6 depicts current ACARS terminals in airlines premises, ACARS network and ACARSimplementation onboard (aircraft at bottom of picture), as well as data link implemented on ATN/VDL2 (aircraft and network on top of picture).

With the initial VDL2/AOA, the VDL2 air/ground transmission (new radio onboard and on ground)replaces the ACARS transmissions, while other ACARS elements remain unchanged.

��#�-��4, which stands for "VHF Digital Mode 4”, is a digital data link designed to operate in theVHF frequency band using one or more standard 25 kHz VHF communication channels. It is capableof providing digital communications and surveillance services between a combination of mobilestations (aircraft or ground vehicles), as well as between mobiles and ground stations. It ischaracterised by its ability to exchange short repetitive messages with the exchange managed by anumber of protocols.

VDL4 employs a time division multiple access (TDMA) scheme. Such a scheme divides thecommunication channel into 'time-slots' (13.33 milliseconds/19,200 bps), each of which may be used

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by a radio unit for transmission of data, whether mounted on aircraft, ground vehicles or at fixedground stations.

VDL4 is distinct from other TDMA systems in that it is based on the self-organising TDMA concept(known as STDMA). In STDMA, access to the slots is organised so that each station is responsible forprior selection and reservation of the slots it wishes to use. In VDL4, the time-slots are allsynchronised to UTC time, normally provided by a GNSS receiver, in order to provide global co-ordination between all participating stations. Each of the time slots is available to any station fortransmitting or receiving. A position report typically occupies one time-slot while other transmissions,such as ground station transmissions, may occupy more.

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VDL4 supports two different types of communication services:• VDL4 Specific Services which include broadcast and point-to-point (addressed)

communications for exchange of time-critical data.• VDL4 ATN Data Link Services as VDL4 constitutes an ATN sub-network and thus provides

fully ATN-compliant communications services.

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Together these services provide broadcast and end-to-end communication functions that in turnsupport a range of air-ground and air-air ATM applications as illustrated hereafter.

3.1.2.3 HF Data Link

./0/1/./0� $��!��The HF data link is a complete packet data communications system which uses High Frequency (3-30MHz) bands of the radio spectrum assigned for aeronautical applications. It currently supports aircraftequipped for ACARS data communications, and is intended and designed to function as a sub-network ATN in the future. This system on the aircraft automatically searches for a suitable (or thebest available) frequency from all HF Data link frequency assignments. Having established aconnection, the aircraft may proceed to send data on slots assigned to downlinks and to receive dataon slots reserved for uplinks by the ground station.

./0/1/./1� 2�+��!��!��The HF Data Link system on the aircraft automatically searches for a suitable (or even the bestavailable) frequency from all HF Data link frequency assignments. To assist with the search, each HFData Link ground station broadcasts system management uplink packets (this is called ’squitters’)every 32 seconds on 3 or more active (monitored) frequencies. The squitters on each of thefrequencies are staggered by roughly 5 seconds and synchronised to Universal Time (UTC) to allow aquick search through the frequencies. In order to speed up the search process, an aircraft may limitthe search to all active frequencies assigned to all ground stations within 5000 to 6000 km of thecurrent aircraft position.

When a suitable frequency is found, the aircraft establishes a connection by sending a log-onmessage to the ground station and waiting for a log-on configuration uplink before continuing. Havingestablished a connection, the aircraft may proceed to send data on slots assigned to downlinks and toreceive data on slots reserved for uplinks by the ground station. In order to facilitate the frequencyand slot management process, slots are grouped into 32 seconds frames of 13 slots. The slotassignments for each of the 13 slots in a 32 seconds frame are broadcast by the ground station in thesquitters that use the first slot in the frame. An aircraft logged on a particular frequency will continue touse that frequency until it fails to detect the squitters broadcast every 32 seconds or when the groundstation fails to acknowledge three consecutive downlinks sent by the aircraft. At that point the aircraft

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will initiate a search for a new frequency and log-on the new frequency. The hand-off of theconnection from one frequency to another and from one ground station to another is totallytransparent to the user if successful.

The major benefit by using this technology is that the crew does not have to assume responsibility forfinding and tuning to a good frequency and an HF ground controller trying to reach a specific aircraftdoes not have to hope that the aircraft is monitoring the appropriate frequencies.

3.1.2.4 ApplicationsSeveral applications can be used through one of these networks to exchange information between airand ground systems. These applications could contain information such as exact aircraft position andinformation concerning the intended flight plan (Intent information) with a given time horizon.

./0/1/3/0� ��-�(��-��)This system will permit to send information concerning the traffic to the aircraft, which are ADS-Bequipped, so that these aircraft will have the same information as the controller. It is considered as atransition program before the complete implementation of ADS-B because there is no necessity tohave all aircraft equipped with ADS-B.

In the following, ADS-B is not presented because it is related to the airborne system. Indeed, aircraftcompute their own position (using onboard equipment like inertial navigation system or GNSS) andsend it to the ground component. The traffic situation is then build using these data and radarinformation and presented to the controller.

./0/1/3/0/0� $��!��Traffic Information Service-Broadcast (TIS-B) provides the pilot with situational awareness anddecision support tools based on the same surveillance data used by the controller. This approachwould provide data usable for Cockpit Display of Traffic Information (CDTI) and Conflict Detection andResolution in partial ADS-B equipage environment.

./0/1/3/0/1� 2�+��!��!��Traffic Information Services-Broadcast (TIS-B) consists in broadcasting the radar information, thuscompleting the traffic situation picture, to aircraft using ADS-B data-link (aircraft should be ADS-Bequipped to receive this kind of information).

This system permits pilots have knowledge of the surrounding situation of the traffic load in the entireairspace and also to have the same kind of information as the ATCo. TIS-B permits aircraft that arenot equipped with ADS-B to be seen by the others without adding any further equipment onboard.This is considered as an intermediate solution before ADS-B will equip all aircraft.

Two modes for TIS-B can be considered:• “full picture” mode by broadcasting a real picture of the airspace situation,• “gap filling” mode by broadcasting information only to the other ADS-B equipped aircraft in the

following cases: position provided by ADS-B seems to be wrong or inaccurate, the entireairspace is not covered by ADS-B.

One of the major problems of this kind of system is the correlation between the different informationcoming from different sources; so a standardisation is needed between the different equipment.

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"� ��83��+�*�+��

./0/1/3/1� ��4��$��+�� (�4$��)The main idea of this system is to replace (or at least reduce) the current voice communicationbetween controllers and pilots by data link messages.

Controllers could be equipped with a tool that enables instructions (clearances) to be given, to requestgeneral information and to inform the pilot.

Pilots could be provided with a tool that permits them to request general information, to requestclearances and to inform the controller.

./0/1/3/1/0� $��!��The CPDLC technology is a data-link between the ground component (controller) and the aircraft(pilot). The pilot and the controller will be equipped with a tool that permits exchange of informationbetween them. The messages exchanged will be in text format. The main objective is the reduction ofVHF frequency congestion.

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./0/1/3/1/1� 2�+��!��!��These data consist of a group of messages that should be transmitted using data-link. Thesemessages should respect several rules defined in the OPLINKP (operational data link panel). Ingeneral, all messages that are exchanged today via radio VHF are defined in the future CPDLC.

CPDLC are organised in three different services:• �� (DCL): provide information to the pilot before leaving the parking.• �� (ACL): controller can send (using data link) clearances to an

aircraft regarding flight level, speed, trajectory and to receive pilot responses (acceptance ornot). The pilot can also send to the controller, who is in charge of his aircraft, a request. Thissystem also allows sending information messages.

• �� (ACM): permits co-ordination between sectors. When anaircraft is leaving a sector, the controller sends to the pilot the frequency of the next sector.

./0/1/3/.� $��"��($"��)

./0/1/3/./0� $��!��This application will be used to exchange information between the ground and the aircraft. Theinformation will be related to the airspace situation, ATIS (Aeronautical Traffic Information Service) orMETAR (METeorological Aviation routine Report).

./0/1/3/./1� 2�+��!��!��The telecommunication network used for this application is ACARS, which is a ground/aircommunication network (mainly based on VHF transmission). The information will be broadcast ondata link with voice synchronisation.

./0/1/3/3� "��!��#�("��4�5)In the current mode of operation, the controller does not have the time to ask the pilot to give him his2D profile in order to check it with the ground flight plan. Furthermore, the controller has theknowledge of the aircraft route which is limited to his area of responsibility.

./0/1/3/3/0� $��!��The objective of FLIPCY is to automatically detect inconsistencies between the ATC used flight planand the one activated in the aircraft Flight Management System (FMS). This service description isinitially restricted to the check of the 2D route information before the aircraft enters a new ASU.

./0/1/3/3/1� 2�+��!��!��The FLIPCY mode of operation is based on four steps:

1. The ground system sends a message called an ‘ADS Demand Contract’ requesting theextended projected profile. The number of waypoints covered by the contract is defined by aspecified time interval.

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2. In response, the aircraft automatically downlinks the ADS report containing the basic ADSinformation and the extended projected profile information (next waypoint, estimated altitudeat next waypoint, estimated time at next waypoint…). When an activated route is not availablein the FMS, the aircraft shall downlink the notification of the unavailability of route data.

3. The ground system receives, stores, and compares FDPS/airborne flight plans.

4. The Controller shall be informed of the inconsistency at the moment that it is detected if hehas already received Flight Plan data for the flight. Otherwise, the Controller shall be informedof the inconsistency at the moment that he receives the Flight Plan data. Consistent meansthe same number of waypoints and they are identical, or less waypoints but identical as well.

Several advantages can be pointed out in terms of:• Safety improvement: conflict detection by anticipation.• Reduction in voice communication for the pilot and decongestion of voice channel.• Potential for increased capacity by reducing controller workload (by obviating the need for

route checking upon first contact).

However, the implementation of such a technology will lead to some constraints:• Adoption of a standard to describe the flight plan routes• Definition of the portion of route that will be checked (this definition will take into account a

number of waypoints and/or flight duration.

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�/.� ��'� �� The current mode of operation is quite rigid and based only on navigation aids located on the groundand different RNAV applications have been identified regarding the area navigation mode ofoperation.

These new concepts, BRNAV, PRNAV, RNP RNAV, 4D RNAV, impact more the airborne capabilitiesand will be described in the next sections.

The principal future navigation system will rely on satellite-based system such as GPS (GlobalPositioning System) which is proposed as the future standard for en route and approach navigation.

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�/�� +��'�� $��

� �� ,�� 3.3.1.1 DescriptionMode S (selective) is a new type of secondary surveillance radar, which is based (like conventionalSSR) on the use of a transponder (called Mode S transponder) onboard the aircraft. Thesetransponders respond to ground interrogations and also permit to reply on classical Mode A and C.

Mode S improves conventional secondary radar and it operates at the same frequencies (1030/1090MHz). Once the radar has managed to acquire the aircraft, the "selectivity" is based on unambiguousidentification of the aircraft by its 24-bit address.

3.3.1.2 Working principleAs for conventional SSR, a pulse is sent out and is received by a transponder onboard the aircraft.This Mode S transponder has a unique identifier code (24-bit address that leads to a total 224 differentcodes) which permits the ground station to send an interrogation to only one precise aircraft. Thissystem permits to unambiguously identify an aircraft and eliminate the problem of false replies. Thismode of interrogation is called “selective”.

Three different types of pulses are sent by the ground station:• ��call (only sent to classical transponders): No reply from Mode S transponder.• �� 1�� -�� +� �� 2: it works as conventional SSR

interrogation. All aircraft reply and those equipped with Mode S reply by indicating theirunique identification code.

• +��'�� 1�� -�� +� �:�� 2: this message is only for aircraftequipped with Mode S transponder and may contain several pieces of information. Thetransponder replies with a message containing the required information using the uniqueaircraft code identification.

According to the Mode S functional capabilities level, the "Mode S" radar station can also carry outtwo other types of surveillance:

• The first is enhanced surveillance (transmission to the ground of certain flight data: heading,speed, etc.).

• The second is data transmission (air-ground or ground-air transmission of control messages,meteorological information, airport information, etc.).

The implementations of Mode S will lead to the following benefits for the surveillance system:• Improving correlation between radar and flight plan data by the use of aircraft identity.• Elimination of garbling and a reduction of FRUIT.• Reduction of controller/aircrew workload.• Radar data are more accurate and more useful for STCA, MSAW.

Mode S radar systems will progressively replace the mono-pulse radar systems, with priority given tothe high-density traffic areas.

The operational ATM deployment of Mode S elementary surveillance is planned for 2003 and theoperational implementation of Mode S enhanced surveillance will take place in 2005.

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� �� ,��)�� *��.��/��,+��0�"�!",

3.3.2.1 DescriptionToday, most air traffic control units still use dedicated radar sensors which provide surveillance datadirectly to the unit. Although radar data is frequently shared - for example, one radar may supplysurveillance data to more than one unit - the principle is still the same and each ATC unit processesthe data individually. The present situation in Europe involves approximately thirty different types ofradar data processing systems implemented in more than fifty ATC centres. Almost all ATC units havedifferent systems, using different hardware and software with different levels of performance andsystem enhancement capability. The current systems have been developed in isolation and nosystem makes optimum use of all available radar coverage.

In contrast, ARTAS is designed as a distributed system consisting of an assembly of identical co-operating ATM Surveillance Units (ASU). The various radar are connected in a regional radar WideArea Network and the Units are also connected to this network. Each Unit processes all thesurveillance data received on the network and acts as a server providing continuous processedaircraft track data to the air traffic control units and other user systems (e.g. military Air Defencesystems, flow management units) which are connected to the network. An ATM Surveillance Unit will,for ease of maintenance and support, normally be located in an Area Control Centre (ACC) and willbe connected to the ACC Local Area Network (LAN).

The initial version of ARTAS uses data from current conventional primary and secondary radar. Inaddition to conventional sensor data, future versions of the system will be able to work with aircraftsurveillance data from Mode-S, Automatic Dependent Surveillance (ADS) and ADS-Broadcast (ADS-B).

This approach, applicable world wide, makes the ARTAS system one of the greatest advances inATM surveillance since the introduction of radar itself.

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The new system, ARTAS, is currently under extended trial at a number of Pilot Sites and is usedoperationally in the Netherlands since Spring 98. It will not only improve the efficiency and reliability ofATM surveillance systems across Europe, but will also provide a means for States participating in theEuropean ATM Programme (EATMP) to readily exploit new surveillance technology, such as Mode-Sradar and Automatic Dependent Surveillance (ADS), as they become available.

3.3.2.2 Functional ArchitectureEach ARTAS ASU has three main sub-systems:

• The ��;�� is the heart of the system. It processes the radar input data and maintains theTrack Database. The Tracker can process multiple radar surveillance data from up to thirtysurveillance sensors to form a best estimate of the current air traffic situation, which ismaintained in the Track Database (up to 2,000 tracks simultaneously). It makes use of themost up-to-date tracking techniques and takes advantage of dynamically assessed radarcoverage and performance characteristics. The Tracker has proven ability to resolve allknown problems of trackers currently in use. Full advantage of aircraft-derived data will betaken in future versions of the Tracker, with the use of Mode-S radar and AutomaticDependent Surveillance data.

• The +��'�� provides the tracking and service continuity functions and manages the provisionof the Track Information Service. In the latter function, the Server distributes sub-sets of thetrack data-base information to the users. A wide range of selection criteria will permit eachuser to specify exactly the Track Information Service he requires. Flight Plan information will

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be associated with the tracks in the Track Data Base, making it possible to serve "labelled"tracks containing supplementary flight plan data.

• The +$�� -� � �� incorporates all the functions necessary for the technical andoperational management of the Unit, and the recording and related data analysis facilities. Itcarries out the supervision, recording and data analysis.

3.3.2.3 ARTAS Project statusThe short term evolutions, referred to as ARTAS 1, concern system upgrades based on requirementsfrom Administrations using or planning to use operationally the system. The requirements arecollected and discussed in the context of the AUG/CCB (ARTAS Users Group/ Configuration ControlBoard),

The medium term evolutions, referred to as ARTAS 2, are driven by requirements stemming from theEATMP Programmes, i.e. at this moment the Mode S Surveillance and ADS Programmes. The so-called ARTAS 2 Feasibility Study executed in 98/99 resulted in the delivery of documentation andprototypes demonstrating the feasibility and the benefits of an SDPD system working in a mixedsurveillance environment. Depending on decisions that will be taken within the Mode S and ADSProgrammes and by the SAC (Surveillance Architecture Cell), 2 main evolutions of the ARTASsystem are foreseen to be developed :

• One version for processing static enhanced surveillance.

• One version for processing dynamic enhanced surveillance.

3.3.2.4 ARTAS deployment map

"� ��<3��+��$� ��-�

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�/4� �� Many studies and projects address this scope and are aimed to define new concepts and proceduresin order to assist controllers in detecting and resolving conflicts.

Here, some algorithms and projects dealing with conflict detection and resolution will be presented. Itis not a complete list but it is just aimed to present the main algorithms and concepts that are used inalmost all of the projects.

�$�� 1*,��2�+�1�� )�*��/��,��)��

3.4.1.1 DescriptionThe Highly Interactive Problem Solver (HIPS) is a graphical planning tool, developed by Eurocontrolfor en-route applications. It was developed within the Programme for Harmonised ATC Research inEurocontrol (PHARE). A prototype of this tool has been developed in order to assess its applicabilityfor oceanic control.

HIPS uses a system of geometrical projections and transformations of trajectories in 4D to showaircraft-free manoeuvrable space. This tool is aimed to help the controller (by giving three differentgraphical views: horizontal, vertical and speed time dimension) where the solutions have to be foundbefore trying a new proposal.

3.4.1.2 Working principleThis technique is based on “no-go zones”. The tool provides the ATCo with a presentation of a“forbidden zone”, i.e. the new trajectory implemented to solve conflict should not cross this area.

This method can be applied in multi-conflict cases but to make the scheme simple let’s consider aconflict between two aircraft denoted A and B, where only aircraft A is allowed to manoeuvre asillustrated Figure 9.

The aircraft A trajectory is predicted to cross the aircraft B path, so that a solution should beimplemented assuming a certain start of turn point (denoted by x). Instead of deriving several possibleconflicts solutions (graph 1) which lead to a set of trials plan (for each solution, a check has to beperformed to verify if this solution found is conflict free), the solution is presented in the form of a “no-go zone” (graph 2). The advantage of this method is to provide a visual representation to thecontroller in order to display what kind of deviation has to be done to resolve conflict.

However, some problems have to be pointed out:• Controller has to choose the start-of turn-point.• The previous example is quite unrealistic. The aircraft trajectory is, in most cases, not linear

i.e. aircraft can change speed, heading and altitude at the same time.• The “no-go zone” is computed assuming a single trajectory segment, which is quite restrictive.• Aircraft should be equipped with a 4D trajectory FMS (altitude, latitude, longitude and time).

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"� ��=�>��+��

HIPS is likely to be implemented in the near future in Prestwick (Scotland, UK), a part of UK controlledairspace.

�$�� 3�"�,��3��"��2��,�)��3.4.2.1 DescriptionGEARS is an algorithm developed by Eurocontrol in order to assist controllers in detecting andresolving conflict. This algorithm is based on “no go zones” called forbidden area (the same idea asHIPS) and takes into account the aircraft type, i.e. the new trajectory computed must be flyable by theaircraft. In this algorithm, two aircraft are considered: the first one is the “obstacle aircraft” (doesn’thave to execute any manoeuvres) and the second one is the “manoeuvred aircraft” (has to implementmanoeuvres to resolve conflict). The derived solution takes into account the following elements:aircraft dynamics (the solution should be compatible with aircraft dynamic capability), wind anduncertainty in the future aircraft position. The resolution proposed is a set of possible trajectories andthe more efficient one has to be implemented.

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3.4.2.2 Working principleIn order to explain this concept more easily, let’s consider the following example with two aircraftnamed manoeuvred and obstacle aircraft as illustrated Figure 10.

A and B represent the two aircraft trajectories and if no action is implemented, these aircraft will be inconflict. The area represented by an ellipse is called a “forbidden area”, i.e. the solution of the conflictshall propose a trajectory that is outside this area.

The size of this area depends on the separation that is imposed between aircraft, the nature of themanoeuvre that will be implemented and on the trajectory of the obstacle aircraft.

"� ��6�(��+��

This algorithm uses the following step:

1. �� '��: it is the preferred trajectory for the manoeuvredaircraft. A conflict check has to be performed in order to be sure that no conflict will occur. Ifthere is no conflict then the preferred trajectory is a solution. If one or several conflicts aredetected then a manoeuvre has to be executed.

2. +�� '��: the aim of this second step is to find a tangentpoint to the forbidden area, i.e. a trajectory which is conflict free with a given obstacle aircraft

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but not with another obstacle aircraft. A possible solution to search and find a candidatemanoeuvre is to take successive steps in heading (for each one a conflict check has to beperformed) to one side of the initial manoeuvre. This process is repeated until a conflict freetrajectory is found.

3. �� : this is defined by the candidate manoeuvre and the turning time.

4. �'�� '��: this is a candidate manoeuvre which is conflict free between thestarting point and the turning point i.e. there is no other conflict before reaching the nextturning point. The candidate manoeuvre and the turning point define an avoiding manoeuvre.

"� ��(��+��

This algorithm can be applied also in a multi-conflict situation, i.e. the manoeuvred aircraft has toavoid more than one forbidden area.

�$� � #��"��#��-��"�� !��

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3.4.3.1 DescriptionCOnflict Resolution Assistant (CORA) is part of an operational concept developed byEUROCONTROL under a program entitled Automated Support to ATM (ASA). This project is aimed toassist en route controllers (principally the planner) to resolve conflicts.

CORA provides automated support to the controller for solving detected conflicts. It will be consideredcomplementary to MTCD capability and will assist controllers in resolving conflicts with optimalresolution manoeuvres.

The approach taken is more human oriented.

3.4.3.2 Working principleCORA is a controller-oriented tool, aimed to help and not to replace the controller for de-conflicting soa good understanding of how the controller resolves conflict is necessary.

The solution that will be proposed by CORA should be compatible with a controller’s resolution and itis also necessary to take into account the different techniques used by controllers for conflictresolution.

This tool could offer the controller a set of ranked solutions for the detected conflicts. The task of theplanner will be to select and to implement the more appropriate one. It is also possible for thecontroller to ignore the different solutions that are proposed and to choose another one.

CORA will provide the following capability:• Conflict free resolution advisories through a set of pre-defined rules applicable to the detected

conflict.• A means by which a controller selected conflict resolution can be simply input as a system

update.

�$�$� 4��!��4��) �� !��The URET tool was developed by the FAA to assist the controllers in free flight operation and isaimed at supporting the sector team planning function.

3.4.4.1 DescriptionURET is only a conflict detection tool dealing with aircraft to aircraft and aircraft to airspace conflicts.Conflicts are detected up to 20 minutes ahead. This tool will be initially used and tested by the plannercontroller in the US.

3.4.4.2 Working principleThe tool uses flight plans (available on paper strips), aircraft performance characteristics, wind andtemperature data in order to build four-dimensional flight profiles or trajectories for all flights.

These calculated trajectories define:• The horizontal route,• The altitude profile,• The airspeeds,• Ground speeds being flown,• The times that the aircraft will reach various points along the route.

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Each incoming track report is compared to the predicted trajectory position of the aircraft at the time ofthe report. If the track report differs from the trajectory position by more than a given distance in thelateral, longitudinal, or vertical direction, a new trajectory is built starting at that track report. Themodelled speed, climb rate, or descent rate may be adjusted at this time based on the aircraftobserved track history.

URET uses the trajectories of all aircraft to check for conflicts. A “potential” conflict is declared whenthe trajectories of two aircraft indicate that the horizontal and vertical separations will both decreasebelow corresponding thresholds.

URET evaluates the time before conflict, as well as the conflict configuration, to estimate theprobability that the current situation will actually develop into a close approach. Empirical statistics areused for this evaluation. If the estimated probability is low enough, and there is adequate time beforethe conflict, URET will defer notification to a future time. Otherwise, URET will notify one and only onesector immediately. URET will notify no earlier than 20 minutes, and will defer to no later than 10minutes, before the start of conflict.

The earlier 10-20 minute notification from URET will add a considerable margin of safety to thesystem (today ATCo receives warning three minutes before conflict).

In order to determine which sector is to be notified URET takes into account which sectors currentlycontrol each of the aircraft in a conflict, and where the actual conflict is predicted to occur. In general,it will notify the sector where the conflict will occur.

The sector team (tactical and planner) should be aware that if its sector is notified of a conflict, noother sector will be notified of the same conflict.

This tool is actually under study in Indianapolis and Memphis ARTCC on a daily basis. It was plannedto develop this experiment in five additional sites by the end of 2002.

�$�'� *"��*��/��"� �+��5�� 6��,+��PARR is envisioned as an improvement of the URET tool capability and is developed as a series ofincremental enhancements to URET. The first step will be to provide an additional tool to the plannerATCo to resolve aircraft to aircraft and aircraft to airspace problems. The second step is dedicated tostudy the capability to avoid severe whether area.

3.4.5.1 DescriptionPARR is a conflict resolution tool aimed at searching for conflict free trajectories. One of theobjectives in developing this tool is the reduction of the controller workload.

The initial PARR capability is to give a set of candidate solutions to the controller in the form of URETtrials plans.

3.4.5.2 Working principleThe PARR algorithm has the following functionality:

• Each resolution manoeuvres only one aircraft.• If a specific aircraft is selected, the tool computes resolution manoeuvre only for the aircraft

selected.

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• If no aircraft is selected, the tool generates a ranked set of resolution for each aircraft: 2lateral (left turn or right), 2 altitude (up and down) and one speed change (decrease orincrease).

The system computes conflict free trajectories and can deliver the following type of resolutionmanoeuvre:

• Vertical: changing flight level• Lateral: heading instruction• Longitudinal: decrease or increase speed.

�$�7� ��"!��"��!� --�� ERATO is a tool developed by the French centre of the studies of air navigation (CENA) in order tohelp the controller, mainly by organising and presenting the different information that is available(aircraft potentially in conflict, deleting non-relevant information, sorting the tasks that have to beperformed…).

3.4.6.1 DescriptionThe main difference of this project compared to all the other developed tools is that its concept isbased on a controller cognitive model (i.e. this model integrates all mechanisms and tasks that acontroller uses to control traffic) and not based on an automation of the controller tasks.

The purpose of ERATO is not to perform the ATCo tasks automatically but only to present and sortthe information in order to be easier for the controller to use it (for example by filtering and deleting allthe non-relevant information on the screen).

The expected benefit of such a tool is to reduce the controller workload and so to increase theairspace capacity.

3.4.6.2 Working PrincipleTwo major tools have be identified and used in ERATO:

• Filtering techniques: it consists on deleting all non-relevant information to the controller; theaim is not to overload ATCo by presenting large quantity of information.

• Function to manage the controller workload, called “agenda”: it has been identified that thecontroller workload is one of the major limitations of the actual system. This function is in facta window where each potential problem (aircraft that will be in conflict for example) isrepresented by a label (the different labels are sorted according to the severity of theproblem). The display of these labels will permit to the controller to organise his/her work sothat his/her attention is not focused on minor tasks. It permits also to not forget any potentialproblem and works as a reminder.

This project is still under development and this function is planned to be integrated in the new ODS(Operational Display System) which is the new controller working position in France.

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�$�8� "��) ��3.4.7.1 GeneralArrival sequencing tools are used for helping air traffic controllers build and maintain sequences ofaircraft in zones of convergence like the TMA of an airport. After several decades of research anddevelopment there are a few examples of operational systems in TMAs on both sides of the Atlantic.

3.4.7.2 EuropeCOMPAS (Computer Oriented Metering Planning and Advisory System): is operational in Frankfurtsince 1989.

MAESTRO (Means to Aid Expedition and sequencing of Traffic with Research of Optimisation): isoperational at Paris (Orly since 1989) and Copenhagen.

CALM (Computer-assisted Approach and Landing System): is operational at Zurich airport since2001.

3.4.7.3 USACTAS (Center/Terminal radar approach control Automation System): is partially operational withDescent Advisor tool at specific TMAs. Its implementation is slower than expected for FAST (FinalApproach Spacing Tool) and pFAST (passive FAST).

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��*%��,)��-��

4� � �� The objective of this section is to assess and describe to what extend modifications or changes wouldbe needed to the airborne system to accommodate the new ATM concept as described at the end ofWP2.

From the functional allocation, the functions allocated to the aircraft are isolated and identified. Thesefunctions are assessed in terms of their specific performance requirements, so that the conversion totechnology can be performed. The existing, state-of-the-art and currently developed airborneequipment will be investigated to identify the possibilities to provide and receive the required aircraftintent information as identified at the end of WP2. The following airborne equipment will beaddressed:

• Position determination systems (IRS, DME, GPS)• Flight Management System (FMS)• Data link (air/ground, air/air)• Automatic Dependent Surveillance• Conflict Detection & Resolution (CD&R)• Cockpit Display of Traffic Information (CDTI)• Controller Pilot Data Link Communication (CPDLC)• Traffic alert and Collision Avoidance System (TCAS)

This description is used as input for the technology roadmap and the conclusions andrecommendations.

Potential modifications to the airborne equipment will be described in the deliverable of this task.

The first part of this section will describe the airborne systems currently in use for air traffic control,whereas airborne systems under development are described in the second part.

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7� �� !�� $��This section presents and describes airborne equipment currently in use regarding to positiondetermination, flight management, surveillance and data link systems.

7/�� $��

'�� 1�,The inertial reference system (IRS) provides aircraft position, attitude and speed in response tosignals resulting from inertial effects on system components.

The IRS is a totally self-contained system (independent of ground based navigation aids), and doesnot require information from external references. After being supplied with initial position information,it is capable of updating accurately position, attitude, and heading.

5.1.1.1 DescriptionThe IRS senses angular rates and linear accelerations about the aircraft’s pitch, roll and yaw axes.The sensed data is resolved to local vertical coordinates and used to compute:

• Position (latitude, longitude, altitude),• Attitude (pitch, roll, yaw),• Velocity,• Accelerations,• Angular rate data, and• True heading and magnetic heading when combined with a worldwide magnetic variation

database,• Wind speed and direction when combined with air data inputs.

5.1.1.2 Working principleDifferent technologies are used to build IRS, but the principle remains the same; sense the movementof the aircraft, and integrate accelerations over time to update the position based on an initial positionprovided before the flight (alignment).

Former IRS used mechanical spinning gyroscopes, present IRS use ring laser gyros (RLG)technology based on interferometry, and future IRS will probably be solid-state (inertial sensors insilicon using Micro Electro-Mechanical Sensor (MEMS) technology).

5.1.1.3 PerformanceThe accuracy of the IRS is dependent on the accuracy of the initial position information programmedinto the system. Therefore, system alignment before flight is very important. Accuracy is very highinitially following alignment, and decays with time at the rate of about 1-2 NM per hour (best IRSprovide 0.3 to 0.7 NM drift). Position updates can be accomplished in flight using ground basedreferences with manual input or by automatic update using multiple DME or VOR inputs, or usingGPS inputs.

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'�� Distance measuring equipment (DME) provides distance information relative to a ground facility (slantdistance). Some systems also provide ground speed.

DME information can also be received from a TACAN station. As opposed to DME, TACAN systemsprovide azimuth and distance information from a fixed ground station. This is equivalent to a co-located VOR/DME ground station.

5.1.2.1 DescriptionThis position determination system consists of an airborne transceiver transmitting to and receivingpaired pulses from the ground station.

These reply pulses are sensed by timing circuits in the aircraft’s receiver that measure the elapsedtime between transmission and reception. Electronic circuits within the radio convert thismeasurement to distance and ground speed information.

5.1.2.2 Working principlePosition is determined relatively to one or more ground stations.

VOR/DME, or VORTAC, systems providing distance and bearing are known as rho-theta systems,whereas DME/DME systems are known as rho-rho systems. These later use triangulation algorithmsto determine the aircraft’s position based on the actual position of at least two DME ground stations,and measured distance from these stations.

5.1.2.3 PerformanceThe DME operates in the ultra-high frequency (UHF) band and therefore is restricted to line-of-sighttransmission.

With adequate altitude, the pilot can receive en route DME signals at distances over 200 nauticalmiles (NM), with an error of ±0.25 (NM) or 1.25% of the distance, whichever is greater.

'�� 3*,The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of24 satellites placed into orbit by the U.S. Department of Defence (US DoD). Navigation SatelliteTiming and Ranging (NAVSTAR) is the official US DoD name for GPS.

GPS was originally intended for military applications, but in the 1980s, the government made thesystem available for civilian use. GPS works in any weather conditions, anywhere in the world, 24hours a day. There are no subscription fees or setup charges to use GPS.

GPS is a component of the ICAO designated Global Navigation Satellite System (GNSS), along withthe European INMARSAT and the Russian GLONASS systems.

5.1.3.1 DescriptionThe 24 satellites that make up the GPS space segment are orbiting the Earth about 19,000 km aboveus, making two complete orbits in less than 24 hours.

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Unlike ground based navigation systems, GPS provides global coverage with virtually no signalinaccuracies associated with propagation in the Earth’s atmosphere. Signal masking can occur withmountainous terrain, man-made structures and with poor antenna location on the aircraft.

GPS receivers take the information satellites transmit to earth and use triangulation to calculate theuser’s exact location. Automatically selecting the signals from four or more satellites, receiverscalculate a three-dimensional position, velocity and time.

Stations located around the world monitor the performance of the satellites, and a master controlstation in Colorado Springs has the capability to send up corrections if errors are detected.

5.1.3.2 Working principleEach satellite continuously transmits its identification (pseudorandom code), ephemeris and status,and almanac data on two low power radio frequencies, designated L1 (1575.42 MHz) and L2 (1227.6MHz). The signals travel by line of sight, meaning they will pass through clouds, glass and plastic butwill not go through most solid objects such as buildings and mountains.

Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time itwas received. The time difference tells the GPS receiver how far away the satellite is. Now, withdistance measurements from a few more satellites, the receiver can determine the user’s position.

A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position(latitude and longitude) and track movement. With four or more satellites in view, the receiver candetermine the user’s 3D position (latitude, longitude and altitude). Once the user’s position has beendetermined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance,distance to destination, sunrise and sunset time and more...

5.1.3.3 PerformanceIt is significant that GPS accuracy is better than anything ever installed before for en route and non-precision approach guidance.

System accuracy is at least 100 meters horizontally and 140 metres vertically, 95% of the time[GPS_FAA]. Since Selective Availability (SA) has been turned off by US government (02-May-2000),the system accuracy is close to 15 meters horizontally and vertically.

5.1.3.4 DGPSUsers can also get better accuracy with Differential GPS (DGPS), which corrects GPS signals towithin an average of three to five meters. This is achieved by locating a receiver on the ground at aprecisely-surveyed position. This receiver is also able to calculate the errors in the satellite signals.These errors can be data linked to aircraft in the form of corrections which can be applied by theaircraft receiver to reduce position error. This is local DGPS (20 mile range) or Local AreaAugmentation System (LAAS).

Wide area DGPS or Wide Area Augmentation System (WAAS) uses ground stations spacedhundreds of miles apart feeding a master control station which sends correction data up togeostationary satellites. This correction accounts for GPS satellite orbit and clock drift plus signaldelays caused by the atmosphere and ionosphere. The geostationary satellites broadcast thecorrection signals. GPS receivers with WAAS capability improve accuracy to less than three meterson average.

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5.1.3.5 RAIMReceiver Autonomous Integrity Monitoring (RAIM) is one way to achieve integrity2 through receiverdesign (TSO-C129). RAIM works by comparing position solutions using different combinations of atleast 6 satellites. Comparing these solutions can lead to the conclusion that a satellite is broadcastingincorrect data, and the receiver can then ignore that satellite.

5.1.3.6 Accuracy (summary)The following table summarizes GPS accuracy depending on system configuration.

100 meters Accuracy of the original GPS system, which was subject to accuracydegradation under the government-imposed Selective Availability (SA)program

15 meters Typical GPS position accuracy without SA

3-5 meters Typical differential GPS (DGPS) position accuracy

< 3 meters Typical WAAS position accuracy

'��$� �31The EGI (Embedded GPS Inertial Reference System) is a combined GPS/IRS system which takesbenefit of GPS and IRS qualities to reduce position noise by combining IRS and GPS solutions:

• The GPS part is a position sensor that starts with relatively large position noise whichdecrease with time,

• The IRS part is an acceleration sensor that starts with zero position noise which grows withtime. Error in the first minute of free inertial is typically less than 5 inches.

Advantages: Service continuity, accuracy (0.04 to 0.15 NM).

Drawbacks: IRS/GPS tight coupling is hard to implement, IRS/GPS approval by FAA is on-going.

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5.1.5.1 Barometric AltimeterThe barometric altimeter is one instrument that almost all aircraft use to measure altitude. This simpledevice contains a sealed bellows that expands or contracts as the aircraft climbs or descends and issubject to the change in air pressure that comes with a change in altitude. This altitude, uncorrectedaltitude, needs to be compensated for local pressure variations. The corrected barometric altitudemay nevertheless be in error when compared to the true altitude, especially under extremetemperatures or non-standard atmospheric conditions such as inversion layers or strong pressuregradients. Corrected Altitude is also prone to errors induced by altimeter miss-sets (local pressurecorrection as entered by the flight crew).

2 Integrity is the ability of the system to warn a user when there is something wrong with the system.

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5.1.5.2 Air Data ComputerThe Air Data Computer (ADC) digitizes pneumatic inputs from the pitot/static system using solid-statepiezo-resistive pressure transducers, and also combines electrical signals from the aircraft outsidetemperature probe to compute altitude, airspeed, Mach and temperature parameters. In turn thisinformation provides outputs for the flight control system, navigation system, aircraft control systemand ATC transponder as well as for the primary air data instruments.

Current ADC can provide Pressure Altitude and Corrected Barometric Altitude from -2,000 to +60,000ft with a resolution of +/-2 ft.

5.1.5.3 Radio AltimeterThe radio altimeter bounces a radio signal off the ground and measures the return time to calculatethe aircraft altitude relatively to the ground. Radio altimeters were developed to ascertain the aircraftheight above terrain for low altitude phases of flight (take-off and landing) regardless of atmosphericconditions.

The radio altimeter measures radar height above terrain up to 2,500 ft nominally and are accurate towithin two feet at the critical low altitudes (0 to 500 ft) and within +/- 2% above.

5.1.5.4 GPSAn alternate source of altitude information is GPS, which provides a Geometric Altitude and is notsignificantly affected by atmospheric conditions. Geometric Altitude can be used in combination withother signals to provide a reliable estimate of its real time accuracy, which then can be used forreasonableness checking of other altitude sources.

'��7� ��2��+��This section describes other positioning systems that are used in en-route flight phase.

Positioning systems used for approach and landing (DME-P, MLS, ILS and other MMR) are notconsidered.

5.1.6.1 ADFThe Automatic Direction Finder (ADF) system receives transmissions from a selected ground station,indicates relative bearing to that station, and provides audio for determining station identification andlistening to voice announcements.

Radio beacons are subject to disturbances that may result in erroneous bearing information. Suchdisturbances result from such factors as lightning, precipitation, static, etc. At night, radio beacons arevulnerable to interference from distant stations.

Accuracy: ±3°.

Positioning mode: Theta-theta, at least two beacons required.

5.1.6.2 VORThe VHF Omni-directional Range (VOR) system receives transmissions from a selected groundstation and provides relative bearing to that station.

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The receiver on board of the aircraft measures the difference between two signals (a reference phasesignal constant in all directions, and a variable phase signal that varies with azimuth) to determine theazimuth angle of the aircraft with respect to the VOR ground transmitter:

VOR system inaccuracies are mainly attributable to receiver geometry relative to ground transmitterbaselines, and propagation anomalies associated with the earth’s surface.

Accuracy: ±3°.

Positioning mode: Theta-theta, at least two beacons required.

5.1.6.3 LORANLong Range Navigation (LORAN) is a pulsed hyperbolic system operating in the 90 to 110 kilohertz(kHz) frequency band which is used for marine and air navigation where signal coverage is available.The system is based upon the measurement of the time difference in the arrival of signal pulses froma group or chain of stations. A chain consists of a master station linked to a maximum of foursecondary stations with all of the signals synchronized with the master.

The LORAN receiver measures the time difference between the master and at least two of thesecondary stations with a precision of about 0.1 microseconds3 to provide a position fix.

LORAN system inaccuracies are mainly attributable to distance from the ground station, receivergeometry relative to ground transmitter baselines, and propagation anomalies associated with theearth's surface.

Accuracy: 0.25 nautical miles.

Positioning mode: Position and more provided automatically by the receiver.

5.1.6.4 Doppler radarDoppler radar is a semiautomatic self-contained dead reckoning navigation system (radar sensor pluscomputer) which is not continuously dependent on information derived from ground based or externalaids [FAA_AIM].

The system employs radar signals to detect and measure ground speed and drift angle, using theaircraft compass system as its directional reference.

Doppler is less accurate than IRS however, and the use of an external reference is required forperiodic updates if acceptable position accuracy is to be achieved on long range flights.

As a positioning system, Doppler radar is nowadays mainly used by military aircrafts, helicopters forhovering (null ground speed).

It is more likely used for wind shear detection when operated at different frequencies.

3 As a rule of thumb, 0.1 microseconds is equal to about 100 feet.

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7/.� "�� -� � �� +$��Flight Management System (FMS) is an integrated system that uses navigation, atmospheric and fuelflow data from several sensors and provides a centralized control system for flight planning, and flightand fuel management.

The main peripheral systems the FMS is connected to are (basically):• Navigation sensors (GPS, VOR, DME, IRS or AHRS, …)• Air Data Computer (ADC) and radio altimeter,• Engine Indication and Crew Alert System (EICAS),• Flight Control System (FCS) and Auto Throttle (A/T),• Multifunction Control and Display Unit (MCDU),• Electronic Flight Instrument System (EFIS) with Primary Flight Display (PFD4) and Navigation

Display (ND5),• Communication means through Communications Management Unit (CMU) and even Airborne

Communications Addressing and Reporting System (ACARS),• Database loader.

Stand-alone FMS integrate the Flight Management Computer (FMC), the CDU and often a GPSreceiver into a single unit (LRU).

FMS can consist of single, dual or triple FMC/CDU configurations, depending on availabilityrequirements of the function for the aircraft.

'�� The FMS basically provides the functions of flight planning, navigation, lateral and vertical guidance,and aircraft performance optimisation to assist the pilot with the flight management and control of theaircraft. These functions provide the capability of automated flight control.

The FMS contains computation resources, input and output processing resources, and access to anavigation database and, for more sophisticated ones, access to the aircraft performance database.

A typical navigation database6 contains a regional or worldwide library of ground-based NAVAID ('s),waypoints, airports and runways, and en-route airways as well as company routes.

The performance database is generated using the aircraft’s performance and flight manuals. Itprovides data for time and fuel consumption computations based on weight, altitude and speed, aswell as data for take-off and landing speeds computations based on weight, runway length andaltitude, flaps and slats position, and obstacle height and distance.

'�� 9��6��Figure 12 depicts the main functions of the FMS and their relationships [MFEARY].

4 PFD is an EFIS presentation substituting for the Attitude Director Indicator (ADI).5 ND is an EFIS presentation substituting for the Horizontal Situation Indicator (HSI)6 The navigation data is valid for a specified period of time (Jeppesen issues new data every 28 days). At the end of the timeperiod a new navigation data base must be loaded into the FMC.

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"� ��.3�"�� -� � �� +$��-�� "� ��

5.2.2.1 Flight planningThe flight planning function computes route segments for a given flight to define a trajectory (usuallyfrom the origin airport to the destination).

The flight plan can be manually input, data loaded from a floppy disk or from an onboard file server, ordata linked from an airport structure (gate link) or from a service provider structure appointed by theairline.

The route is defined by both:• A lateral flight plan that is described as a series of waypoints linked together by lateral legs,

and,• A vertical flight plan that specifies altitude, speed and time constraints, flight path angles,

glide-slopes, and earth-referenced approach paths.

The FMS also calculates predicted cost profiles (time and fuel) for climb, cruise and descent, basedupon the defined route and aircraft performances. All computed values are displayed to aid the pilot inselecting and flying the optimum profile.

The generation of an appropriate flight plan in both a vertical and lateral sense requires knowledge of:

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• Airspace regulations,• Airline policies,• Aircraft performance limits,• Passenger-comfort considerations,• Weather conditions,• Airline cost index, and• Required time of flight.

Weather data such ISA deviation, wind direction and speed at a specified altitude also add constraintson each leg (leg data). These have an effect on both flight and steering performances. As for the flightplan input, leg data can be manually entered or data linked from a service provider as an update ofthe flight plan (route).

5.2.2.2 NavigationThe navigation function determines the position of the aircraft at a given point along the flight path byintegrating information from air-data sensors, inertial sensors, and radio data. The FMS processessensed data to calculate and update a best computed position based on the known system accuracyand reliability of the positioning sensors7 (described in §5.1 ).

The Lateral Navigation (LNAV) ensures that the estimated aircraft’s position conforms to the plannedlateral flight path. Deviations, cross-track errors, are continuously monitored and are inputs to theguidance function.

The Vertical Navigation (VNAV) ensures that altitude and speed constraints are observed, and thepilot specified vertical profile is followed along any phase of the flight.

Much of the navigation performance comes from the ability for the system to fly the planned lateralflight plan, as well as the vertical flight plan, accurately with sufficient integrity. This is the basis of theRequired Navigation Performance (RNP) concept that will be discussed later.

5.2.2.3 Guidance and steeringThe guidance function performed by the FMS compares the actual position of the aircraft to thecurrent leg of the lateral and vertical flight plan to generate a set of targets (e.g. heading, altitude,speed, flight-path angle, vertical speed, and thrust) and control-modes (e.g. lateral axis control-modes, such as heading, and vertical axis control-modes defining the position of the elevators andthrottles to control the altitude of the aircraft).

5.2.2.4 Control and Stability AugmentationThe Flight Control System (FCS) is then in charge of:

• The control function that adjusts the pitch, roll, yaw, and thrust of the aircraft to maintainguidance targets. This function includes standard automation equipment, such as autothrottles and autopilot.

• The stability function converts control commands into specific elevator, rudder, trim, andengine settings.

7 Using a Kalman filter, the computation makes optimal use of the available sensor input [ROCKWELL]; usually weightingGPS to the highest possible degree, to continuously determine accurate airplane position and velocity.

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Both functions perform aircraft control by using feedback from the aircraft and knowledge of vehicledynamics.

5.2.2.5 Flight managementThe flight management function monitors and logs the flight parameters and compares predictedversus measured performance.

This function computes and stores data that can be presented to the pilot on different pages on aMulti-Function Display (MFD) or even on the Control and Display Unit (CDU), but also can be down-linked to the ground. These data (among others) concern navigation sensors status, aircraft positionsummary, navigation status, and flight log.

5.2.2.6 Radio tuningThe radio tuning function mainly selects the best NAVAID in the area and automatically tunes thenavigation receivers (basically VOR and DME) to them. This function also allows for frequency andmode selection for radio communication transceivers (VHF, HF and UHF for military applications), andaids the pilots in frequency selection otherwise performed manually through specific radio controlheads or centralized radio tuning units (RTU). It requires an up to date database (usually thenavigation database).

'�� %"�Area Navigation (RNAV) was developed to provide more lateral freedom and thus more complete useof available airspace. This method of navigation does not require a track directly to or from anyspecific radio navigation aid, and has three principal applications:

1. A route structure can be organized between any given departure and arrival point to reduceflight distance and traffic separation,

2. Aircraft can be flown into terminal areas on varied pre-programmed arrival and departurepaths to expedite traffic flow, and

3. Instrument approaches can be developed and certified at certain airports, without localinstrument landing aids at that airport.

Unlike conventional radio navigation that sequentially linked radio navigation fixes (NAVAID), RNAVpositions "virtual fixes" along the route and flies a more or less straight line from departure todestination. Figure 13 illustrates the conventional navigation and area navigation differences.

RNAV systems are recognized for their horizontal 2D capability to utilize one or more navigationsensor source to determine the aircraft position, compute flight paths referenced to navigation aids orpoints defined by latitude and longitude, and provide guidance cues or tracking of the flight path. Inaddition to this capability, many RNAV systems include a 3D capability to define vertical path profilesbased upon altimetry and a built-in model of the aircraft and engine performance, and provideguidance cues or tracking of this vertical path. A more recent capability added to RNAV systems hasbeen 4D, in the form of determining and managing time of arrival to a specific point along the flightprofile. [BOEING_RNX]

One way to establish RNAV flight paths is the use of an on-board navigation database, where pre-stored information and data such as for airports, navigation aids, departure/arrival procedures,routes/airways, altitudes, speed, frequencies, elevation, distance, and magnetic variation is located.

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These databases can contain virtually all available aeronautical information that is published. TheRNAV system uses this information to facilitate flight crew definition of the flight path for the operation.It is also common for the flight crew to alter the flight path through manual entry of fixes, and reportingpoints, as well as responding to ATC.

"� ��3�� '� �� '� ��

'��$� �%*RNP is defined by ICAO as a "statement of the navigation performance accuracy necessary foroperation within a defined airspace."

ICAO Manual on RNP defines RNP as a 95% containment value and its relationship to navigationperformance accuracy, but does not cover other aspects such as integrity and availability as RTCASpecial Committee 181 and EUROCAE Working Group 13, Standards of Navigation Performance will(DO-236 & ED-75 respectively).

Figure 14 illustrates both definitions of RNP.

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'��'� &�%"��:�*�%"�*�� (BRNAV) means that a precision of RNP-5 must be maintained (track-keeping accuracyof ±5NM for at least 95% of flight time both laterally and along-track).

BRNAV as currently defined can be achieved by any single FMS system that is certified to AC90-45A,TSO C115A or AC20-130. The navigation accuracy (accuracy 95%) typically demonstrated are ±3.8NM and ±2.8 NM for oceanic en-route and domestic en-route respectively, using inputs fromVOR/DME, DME/DME, GPS or IRS (less than 2 hours after the last update).

The following table provides lateral navigation performance typically demonstrated by differentposition determination systems:

�� $�� $

IRS/VOR/DME 0.50 - 1.65 NM

IRS/DME/DME 0.2 - 0.48 NM

IRS/GPS 0.04 - 0.15 NM

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The vertical navigation performance typically demonstrated for systems (accuracy 99.7%) is ±50 ftindependently of flown flight level. VNAV performance is compatible with the recent and broadeningapplication of1000 ft vertical separation minima for FL290 and above.

�� (PRNAV) requires RNP-1.

'��7� �%*��%"�An RNAV system developed for RNP operations provides reliable, repeatable and predictableperformance through specific RNP RNAV capabilities and features, one of which is defined as RNPRNAV containment.

RTCA and EUROCAE, in developing a Minimum Aviation System Performance Standard (MASPS)for RNP RNAV, established:

• Requirements for:o Positioning accuracy of 95% at RNP,o Integrity of the positioning accuracy of 99.999% at 2 x RNP,o Continuity of the required positioning accuracy,o Availability of a navigation capability,o Integrity against misleading navigation information,

• Standards for:o Navigation database processes (DO-200A)

• Navigation data (DO-201A)

Figure 14 illustrates RTCA & EUROCAE definition of RNP RNAV containment.

Figure 15 illustrates the benefits of RNP and RNP RNAV on the route widths.

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"� ��73�*� ��

The performance of the navigation depends highly on RNAV application (i.e. the functionality of thenavigation computer onboard the aircraft) and also on the sensor of the navigation aid used todetermine the aircraft position.

The current mode of operation in Europe uses BRNAV which meets a track keeping accuracy equalto or better than 5 NM for 95% of the flight time (defined as RNP 5). This requirement includesNAVAID inaccuracy.

RNAV has for main consequence the increase of the airspace capacity by:• Reduction of the lateral separation between aircraft (according to the navigation performance

requirement for the RNAV route).• Implementation of routes without the need to follow routes delimited by radio navigation aids.• Possibility to create more direct routes to increase the airspace capacity.

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'� �� !#",Traffic Alert and Collision Avoidance Systems (TCAS) detects and displays nearby traffic and, whennecessary, computes appropriate avoidance manoeuvres.

5.3.1.1 DescriptionThe TCAS system is also called “active system” as it uses interrogation replies from other aircrafttransponders to compute range, bearing, relative altitude and closure rate, as a difference to “passivesystems” which are only triggered by the Air Traffic Control (ATC) Radar surveillance.

The system typically consists of a TCAS Receiver/Transmitter (R/T) computer, a single (or dual ifrequested) directional TCAS antenna, a single (or dual if requested) Mode S transponder tocommunicate aircraft to aircraft and a variety of controls and displays. The display can either bestandalone or completely integrated into the EFIS.

5.3.1.2 Working principleTCAS is a relatively simple system. Basically, the system identifies the location and tracks theprogress of aircraft equipped with beacon transponders (namely the transponder of the Air TrafficControl Radar Beacon System (ATCRBS)).TCAS can detect and track as many as 35 to 40 intruderssimultaneously within an approximate 40 nautical mile range. Each of these intruders is filed andprioritized by level of threat and displayed on the traffic display for pilot and co-pilot viewing.

Currently, there are three versions of the TCAS system in use or in some stage of development:• TCAS I that interrogate Mode-C transponders to indicate approximate bearing and relative

altitude of all aircraft within the selected range and indicate which aircraft in the area pose apotential threat (Traffic Advisory (TA)).

• TCAS II that is capable of interrogating Mode-C and Mode-S transponder offering the samebenefits as TCAS I but will also advise the pilot to execute a vertical evasive manoeuvre thatwill de-conflict the aircraft from the intruder (Resolution Advisory (RA)), and

• TCAS III that will be virtually the same as TCAS II but will allow pilots who receive RA toexecute lateral deviations to evade intruders. The system will also be capable of transmittingthe aircraft’s position and velocity vector to other TCAS-equipped aircraft thus providing muchmore accurate information (ADS-B/1090MHz Extended Squitter).

5.3.1.3 PerformanceCurrently the TCAS II must meet the Minimum Operational Performance Specifications (MOPS)software version 6.04A and such requirements are explained and contained in an RTCA documentDO-185. This (MOPS) 6.04A software has also been revised and upgraded to the newest (MOPS) 7.0documented in DO-185A, recently approved by the FAA and the ICAO implementing improvements inthe performance of the collision systems, avoiding the nuisance traffic alerts when flying in the newReduced Vertical Separations Minimums (RVSM), and meeting the new requirements for futureoperations in the very crowded European airspace and in the rest of the world.

Tracking capability: 30 to 100 targets

Surveillance range: 14 NMI min. 30-40 NMI Typical

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Bearing accuracy: < 5° RMS

Closing Rate: 600 to 1200 knots

'� �� "�,Automatic Dependent Surveillance (ADS) is a method of surveillance that relies on (is dependent on)downlink reports from an aircraft's avionics that occur automatically whenever specific events occur,or specific time intervals are reached.

ADS does not require an independent surveillance source, such as a radar antenna, to operate. Dueto this capability, ADS can provide accurate surveillance reports in remote and oceanic areas that, fora variety of reasons, will never be inside radar coverage. The ADS reports are converted by data linkequipped ground stations into an ADS track and presented on the controller's air situation display toprovide enhanced situational awareness and the potential for reduced separation standards.

5.3.2.1 DescriptionThere are currently two prominent implementations of ADS that are inherently different:

• ADS-Contract (ADS-C): This type is controlled by contracts established by the ground station.This system goes by the generic name of ADS (and is also known as Addressed ADS (ADS-A)). ADS reporting is controlled by the ground station in all situations other than emergencycontracts. Only the flight crew can declare and cancel ADS emergency reporting. Althoughthe crew can initiate the emergency reporting mode, the aircraft cannot initiate a contract.

• ADS-Broadcast (ADS-B): This type operates in a broadcast mode where the aircraftbroadcasts positional information on a regular basis. Any appropriately equipped station,including other aircraft, can intercept ADS-B reports from one aircraft. The reporting rate forADS-B is significantly higher than ADS, which makes ADS-B a good candidate as a pseudoradar replacement system in high-density traffic situations.

This section discusses ADS-Contract only. ADS-B is discussed in section §��?�� /.

5.3.2.2 Working principleICAO defines ADS-C (or ADS-A) as a surveillance application in which an aircraft automaticallytransmits data derived from on-board systems, via a data link (e.g. satellite or VHF) [EC_ADS].

The transmission of ADS data will be based on a contract between a ground system and an aircraft.Various contracts are foreseen including demand, periodic and event driven.

Surveillance data which can be provided using ADS-C include the basic ADS message (e.g. aircraftposition, time, figure-of-merit and aircraft identification) and optional ADS information (e.g. groundvector, air vector, projected profile, meteorological information, short term intent and extendedprojected profile).

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'�$�� "#"�,The Aircraft Communications Addressing and Reporting System (ACARS) is a digital link betweenaircraft and ground stations and vice-versa.

Data Link Service Providers (DSP) such as ARINC, SITA and AVICOM use a variety of different air-to-ground data links (VHF, HF and satellite) as well as an operation centre and terrestrial data linknetwork (ground-to-ground) to provide a high reliability, availability and integrity message service thatensures the end-to-end delivery of the information being transferred between end systems.

5.4.1.1 DescriptionACARS is a communication method that fits many modern short and long haul commercial, militaryand business aircraft, and is also being retrofitted to older aircraft.

ACARS messages are transmitted to and from aircraft before, during and after flights.

Downlink messages from the aircraft does not simply comprise of text messages telling the airline atwhat time it closed its doors, pushed back, took off and landed (OOOI), and crew messagesidentifying passenger needs ahead of arrival. The aircraft also sends in flight reports on position,altitude, speed, outside temperature, wind, fuel, engine performance etc… These data areautomatically collected from the management unit and control units onboard the aircraft and istransmitted by ACARS.

Uplink messages from ground stations include, among others, clearances, route reports from otheraircraft and weather conditions.

A typical list is provided here under (Table 1).

5.4.1.2 Working principleSimply stated, the subscriber connects to the ACARS system and through the system's data-linkcapability has direct communications to and from their aircraft. Communications can be originatedfrom either source (aircraft or ground) automatically or manually.

With a direct connection to the host company's computer system, the aircrew has direct and real-timeaccess to an abundance of information available through a computer terminal, and which will makethe flight safer, more labour efficient, and allow greater flexibility than ever available in the past.

Communication means used by ACARS include VHF, HF and SATCOM. The system automaticallyselects the communication means based on airline’s policies (cost, performance, availability) andtunes frequencies depending on the actual position of the aircraft and provider coverage maps.

5.4.1.3 PerformanceDSP provide a variety of air-to-ground data links operating in different frequency bands to ensurecontinuous coverage in a cost-effective manner on a global basis.

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Flightphase

ACARS Message To / From

A/C

Comments

Initialization data To Flight number, date, origin airport, destinationairport, ETD

Crew list and passenger list To

Flight Plan To

SIGMET To

Take-Off Data Calculations (TODC) To

D-ATIS To Origin airport information

Departure delay From

Departure clearance To

Out report From Clear of the gate and ready to taxi

Take-off delay From

On

grou

nd

Off report and ETA From Lifted off the runway

Climb ACMS report From

Oceanic clearance To

Free text From

Weather report To/From

SIGMET To

Flight plan updates To

En-route delay From

ETA update From

Technical malfunction reports From

Cru

ise

D-ATIS To Destination airport information

ETA update From

Descent Transfer information To Connecting flight information, terminal, gate,ETD, carrousel

On report From Landed

Gate delay From

On

grou

nd

In report From Arrived at gate

��!��3��+�-�� "��

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6/3/0/./0� 78"�$��+VHF data links are the most commonly used civil aviation data links today. VHF data links areeconomical to implement and provide excellent operational performance (fast response times (2 to 8seconds)), but are limited to line of sight coverage.

Low-speed VHF, character oriented data link provides a data rate of up to 2.4 kbps. Low-speed VHFis the basic VHF data link for ACARS used on a global basis to transmit approximately 35 million VHFmessages per month to about 10,000 data link equipped aircraft. Unfortunately the low-speedcharacteristic of the data link requires a number of frequencies to fully service all users. As examples,ARINC uses 10 VHF frequencies in the United States to provide reliable service and SITA uses 3frequencies in Europe

High-speed VHF will gradually replace low-speed VHF over the next few years. VDL Mode 2 (VDLM2)is a high-speed VHF data link that transmits at 31.5 kbps. The higher data rate of VDLM2 will allow areduction (8 to 1) in the number of VHF frequencies used.

6/3/0/./1� ��$��+Satellite data links can provide global coverage but the current implementation provides no coveragein the Polar Regions north or south of about 80 Degrees of latitude. Satellite data links are moreexpensive per message transmitted and also slower than VHF in response time (12 to 25 seconds).Satellite data link is based on IMARSAT service offerings that are resold as ARINC and SITA data linkservices. AERO L at 600 bps, AERO I at up to 4.8 kbps and AERO H at 9.6 kbps are all certified forair traffic management services. Service at 64 kbps is now available but not yet certified for ATC.

6/3/0/./.� 8"�$��+HF data link, as implemented, provides near global coverage including over the northern PolarRegions. HF is an economic alternative to satellite data link for wide area coverage, but its messagetransit time (80 seconds) is slower than satellite. HF data link transmits at 300, 600, 1200 and 1800bps.

'�$�� #*�(#The Controller Pilot Data Link Communication (CPDLC) system reduces the number of voicemessages exchanged between pilots and aircraft traffic controllers by using a special link for routinemessages. These messages are digitally displayed on a computer screen in the cockpit. Shiftingroutine transmissions from voice to data link communications frees up voice frequencies and reducesdelays [FAA_CPDLC].

5.4.2.1 DescriptionCPDLC is a data link application that allows for the direct exchange of text-based messages betweena controller and a pilot.

CPDLC should greatly improve communication capabilities in oceanic areas, especially in situationswhere controllers and pilots have to rely on a Third Party HF communications relay.

Apart from the direct link, CPDLC adds a number of other benefits to the ATS system[BOEING_ATC], such as:

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• Allowing the flight crew to print messages,• Allowing the upload of the Flight Management System (FMS), thus reducing crew-input

errors,• Allowing the crew to downlink a complex route clearance request, which the controller can re-

send when approved,• Allowing automatic report down-linking on an event such as crossing a waypoint. The FMS is

previously armed by a specific uplink message. This automation assists with workloadmanagement for the flight crew and the controller.

5.4.2.2 Working principleCPDLC provides the capability to exchange messages between air traffic controllers and flight crewsutilizing the ARINC VDLM2 as the air/ground sub-network.

The messages are defined in the International Civil Aviation Authority’s AeronauticalTelecommunications Network (ATN) Standards and Recommended Practices (SARPS). The intentionwas to capture the most common communications phraseologies used in the oceanic voiceenvironment and to create a list of "pre-formatted" CPDLC text elements sorted into a number ofcategories. To cover unusual situations a free text capability was added to allow controllers and pilotsto create their own specific messages. Nevertheless, current applications (still in an experimentalphase) only use a subset of these messages.

5.4.2.3 PerformanceCPDLC is being deployed in phases called Builds for FAA/Miami Trials [FAA_CPDLC].

CPDLC Build 1 will reach initial daily use at Miami Center on October 7, 2002 and CPDLC Build 1A isscheduled for December 2005. American Airlines is the CPDLC Build 1 launch airline with 16 aircraftbeing readied for operations in the Miami Center area in the fall of 2002. During 2003, Miami Centerwill be controlling CPDLC equipped aircraft from American Airlines, Delta Air Lines, ContinentalAirlines, FedEx, and the U.S. Air Force.

Build 1A increases the message capability and functions of Build 1. When fully implemented, CPDLCwill provide a global, seamless, secure, and error-free communications application for air-ground-based systems.

'�$� � ��,Mode S data link was developed to be used with Mode S Mono-pulse Secondary Surveillance Radar.The only operational use of Mode S data link at this time is in the Mode S Transponder air-to-air modefor coordinating Airborne Collision Avoidance System (ACAS) manoeuvres that has been operationalsince 1991 (ref. §5.3.1).

The 1090 MHz Mode S Extended Squitter (1090ES) proposed for ADS-B has been developed as anextension of Mode S technology. These squitters are “extended” in the sense that prior Mode Ssquitters contained 56-bit messages. Each extended squitter message consists of 112 bits, 24 bits ofwhich are used for parity. The data rate used for downlink is 1 Mbps, within a message, whereas the1030 MHz uplink transmits at 4.0 Mbps. Access to the 1090 MHz channel is randomized, and thechannel is shared with current Air Traffic Control Remote Beacon System (ATCRBS) and Mode Sresponses to interrogations from ground-based radars and TCAS.

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Mode S transponders will not only transmit the 24 bit fixed identifier address (call sign). 1090ES willprovide Mode S transponders with additional Downlink Aircraft Parameter (DAP) for:

• Elementary Functionality:o Automatic reporting of Flight ID,o Transponder Capability Report,o Altitude reporting (in 25ft intervals if available on the aircraft),o Flight Status (airborne /on the ground),

• Enhanced Functionality (Elementary Functionality plus)o Magnetic Heading,o Speed (IAS/TAS/Mach),o Roll Angle,o Track Angle Rate,o Vertical Rate (barometric rate or, preferably, baro-inertial),o True Track Angle,o Ground Speed,

• Extended Functionality (Enhanced Functionality plus)o Selected Flight Level / Altitude,o Selected Magnetic Heading,o Selected Track (Previously Selected Course),o Selected Indicated Air Speed / Mach.

1090ES message formats for ADS-B and transmission rates have been defined in detail by the ICAOSecondary Surveillance Radar Improvement and Collision Avoidance System Panel (SICASP), inconjunction with RTCA Special Committee 186 and EUROCAE Working Group 51.

Mode S transponders are currently part of normal aircraft equipage and modern Mode S transpondersare being updated for 1090ES ADS-B with a minimal wiring change for delivery 1st quarter 2003.Currently a small number of aircraft have implemented Mode S 1090ES capable of ADS-Broadcast.

The United States Federal Aviation Administration (US FAA) announced in July 2002 that Mode S1090ES had been selected as the ADS-B link for air transport and other high performance categoriesof aircraft. The Enhanced Mode S surveillance services being planned for implementation in Europewill use the addressed Mode S data link for the readout of various onboard data items.

'�$�$� �)�� (��6�Other data links that have been demonstrated include VDL Mode 3 (VDLM3), VDL Mode 4 (VDLM4),Universal Access Transceiver (UAT) and Broadband.

5.4.4.1 VDLM3VDL Mode 3 (VDLM3) is intended to allow the transmission of voice and data over the same linkoperating at 31.5 kbps. As a voice and data combination, VDLM3 should provide substantialimprovement in frequency utilization.

VDLM3 is an ATN-compliant digital technology with ICAO SARPS proposed as a means of spectrumconservation. It is under development; limited testing has been done, but actual technologydemonstrations are expected in 2003/2004.

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5.4.4.2 VDLM4VDL Mode 4 (VDLM4) technology has evolved from a VHF link that was first tested in 1988 as abroadcast link, initially in Sweden but more recently in a number of States.

Based on the Self-organising Time Division Multiple Access (STDMA) technology, VDLM4 wasdeveloped to meet the requirements for a high capacity data link supporting demanding CNS/ATMapplications including broadcast applications (e.g. ADS-B) and point-to-point communications (e.g.ADS-C). The capabilities of VDLM4 aim to meet the following requirements:

• To operate from gate-to-gate, on the ground and in all types of airspace, with globalimplementation.

• To operate without the need for complex ground infrastructure, although additional benefitsmay be gained if this is available.

• To offer a solution for all user groups with appropriate cost-effectiveness and performance fordifferent user requirements.

• To support a range of ATM applications across all CNS domains.

The most prominent properties of VDLM4 are its efficient exchange of short repetitive messages andits ability to support time-critical applications.

VDLM4 transmits digital data in standard 25 kHz VHF communication channels and employs Self-organising Time Division Multiple Access (STDMA). With this ‘self-organising’ protocol, VDLM4 doesnot require any ground infrastructure to operate and can therefore support air-air as well as ground-aircommunications and applications. Access to the VDLM4 medium, within a channel, provides a datarate of 19.2 kbps within a message.

MOPS for VDLM4 aircraft transceiver for ADS-B, ED-108, was published by EUROCAE July 2001.

The current ATN-compliant VDLM4 data link has ICAO SARPS for surveillance applications only. Theextension of VDLM4 ICAO SARPS as an addressable data link is being examined.

Eurocontrol initiated 1-year VDLM4 airborne architecture study in June 2002.

5.4.4.3 UATThe Universal Access Transceiver (UAT) is a “clean sheet” design optimized toward the support ofbroadcast applications, both air- and ground-based, to support surveillance and situationalawareness. UAT was developed under an Independent Research and Development (IR&D) project atthe Mitre Corporation.

The UAT is a wideband, broadcast type data link operating around 975 MHz outside the crowdedVHF band. Initial UAT operations have been conducted using the experimental frequency of 966MHz. Operational demonstrations in Alaska (CAPSTONE demonstrations) are using 981 MHz as theUAT frequency.

The UAT data rate is approximately 1 Mbps within a message. Access to the UAT medium is time-multiplexed within a 1 second frame between ground-based broadcast services (the first 188milliseconds of the frame) and an ADS-B segment. While the design presumes time synchronizationbetween ground-based broadcasts to reduce/eliminate message overlap, medium access within theADS-B segment is randomized.

UAT was selected by the US FAA in July 2002 as the U.S. ADS-B link for use on the majority ofgeneral aviation aircraft. Nevertheless, UAT is still a developmental system operating in a low-density

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traffic environment, and that offers a surveillance only capability. A separate data link would berequired for other applications such as CPDLC.

5.4.4.4 BroadbandBroadband, defined as a carrying capacity greater than 200 kbps, is a developing technology thatoffers high data rates for a variety of applications on an aircraft. Broadband is currently in limitedoperational use providing high data rate communications to aircraft passengers for internet, email,television and other business/entertainment applications.

Connexion by Boeing should shortly use satellite transponders aboard the Loral Skynet Telstar-6offering services with a potential download (satellite-to-aircraft) capability of 20 Mbps and a 1 Mbpstransmission (return link) from the aircraft to the satellite.

The Airshow™ system, which is also based on Code Division Multiple Access (CDMA) technology,should allow connection speeds that can be expected around 130 kbps due to limitations within theGlobalStar network.

ARINC is announcing successful tests of SkyLink services, claiming the system has the potential toreceive data at 8 to 10 Mbps.

Broadband solutions have concentrated on passenger applications more so than ATC applications.The solutions it is based upon are too infantile to start assessing its use for ATS service, whenconsidered in the context of certification for the safety and regularity of flight.

'�$�'� ,� �+The following table summarizes data link applications and usable data link systems.

�� ;��$� �� ;��$��

CPDLC Addressable VDL, SATCOM, HF

VDLM2 >9'/0��9'/0�@

Low density traffic areas

High density traffic areas

ADS-C Addressable VDL, SATCOM, HF

VDLM2

Low density traffic areas

High density traffic areas

PDC Addressable VDL, VDLM2

D-ATIS Addressable VDL, VDLM2

Non

tim

e cr

itica

lap

plic

atio

ns

TWIP Addressable VDL, VDLM2

ADS-B Broadcast 1090ES, VDLM4, UAT

TIS-B Broadcast 1090ES, VDLM4, UAT

Tim

ecr

itica

lap

plic

atio

ns FIS-B Broadcast 1090ES, VDLM4, UAT

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,�� ,��1::�� .::�� /��<�� +��(�� !!��)� ,�� = �� 8"� ��+/

1/� %��+�� 0:;:��&� 7$�93� �� %�� ,�� = �� ,� �� ,� �� !��/

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9� ��!�� $�� $This section presents and describes airborne equipment under study or being developed regarding toposition determination, flight management, surveillance and data link systems.

9/�� $��

7�� 3%,,��GNSS-1 is the first generation of Global Navigation Satellite Systems (GNSS), in which GPS andGLONASS remain the core of a global positioning system, with space and ground basedaugmentations providing enhanced services on a regional or local basis.

GNSS-1 improves the accuracy, integrity and availability of the basic GPS (and GLONASS) signals,and can be used as a primary means of navigation for en-route operations and non-precisionapproaches, as well as Category 1 approaches to airports throughout the coverage areas.

However, GNSS-1 can not be considered a totally satisfactory solution by many (especially inEurope), because if it solves a number of technical weaknesses, it does not address the institutionalquestions (liability, control by one country’s military authorities etc).

GNSS-1 includes three regional augmentation systems, globally known as Satellite BasedAugmentation System (SBAS) that are fully compatible with each other in order to provide a seamlessglobal improved service. SBAS employs a ranging function to generate GPS-like signals and enableusers to use the concerned geostationary satellite as a 25th GPS satellite. Information on the real-time condition of the GPS constellation is transmitted to each user via the integrity function of SBAS,while the differential correction function provides ranging error data to each user.

7�� 3%�,The European Geostationary Navigation Overlay System (EGNOS) is Europe’s contribution to GNSS-1. Unlike WAAS (ref. §5.1.3.4) or the Japanese MTSAT Satellite-Based Augmentation System(MSAS), it includes the Russian GLONASS system. EGNOS will provide ranging, integrity and widearea differential functions relying on the availability of the geostationary satellites equipped withnavigation payloads to broadcast a GPS look-alike signal.

Its main components are:• 3 geostationary satellites: Inmarsat III Atlantic Ocean Region-East (AOR-E), Inmarsat III

Indian Ocean Region (IOR), plus ESA ARTEMIS-1,• 4 Master Control Centres (MCC) monitoring and controlling the geostationary satellites and

also providing EGNOS wide area differential corrections,• 34 Ranging and Integrity Monitoring Stations (RIMS) performing pseudo-range code/phase

measurements towards the GPS and GLONASS satellites, and supporting the detection ofanomalies in signals from space,

• Navigation Land Earth Stations (NLES) generating the GPS-like signal and transmitting italong with the correction and wide area differential messages to the geostationary satellites,

• The EGNOS Wide Area Network (EWAN) linking all the EGOS components together.

EGOS is expected to be fully operational in 2004. In the meantime, a test signal is broadcast by twoInmarsat satellites allowing potential users to acquaint themselves with the facility and test itsusefulness [ESA_EGNOS].

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The table here after lists indicative performance levels expected with EGOS [DSPN_SBAS]

Accuracy Availability(navigation)

Time to alarm Availability(integrity)

GPS Alone 100 m (95 %) 95.9 % 2 to 6 hours Not Applicable

Ranging with onboardaugmentation toprovide integrity

100 m (95 %) 99.9 % Depends on on-board system

99.4 %

Ranging andIntegrity

100 m (95 %) 99.9 % 10 s 99.9 %

Ranging, Integrityand Wide AreaDifferential

10 m (95 %)

(5 m GPS +GLONASS)

99.9 % 10 s 99.9 %

7�� 3%,,��GNSS-2 is the second generation of Global Navigation Satellite System, independent of (butinteroperable with) GPS (or GLONASS), with a civilian and international status. Being designedalmost 30 years after GPS or GLONASS, GNSS-2 will benefit from all the experience gathered withthese systems and from all the progress achieved during the intervening years. It will therefore bebasically compliant with the requirements of the civil aviation community, and its international civilstatus will greatly ease the institutional questions.

GNSS-2 will provide a global infrastructure of positioning and timing using second generation satelliteconstellation(s), under international civilian control.

Although it is too early to know precisely what GNSS-2 will look like, it will most likely be based on theEuropean-led Galileo, complemented or not by other space components. The modernised GPSconstellation, as good and helpful as it can be, lacks the essential quality of being under civiliancontrol. Consequently, the most likely hypothesis today is that there will be two full-blownconstellations, Galileo and GPS, in the future.

7��$� 3 ��Galileo is a European led project designed to be an autonomous navigation system, able to provide aguaranteed level of performance to users independently of external systems such as GPS.

Galileo is based on a constellation of 30 satellites and ground stations that will complement GPS andGLONASS. Galileo and GPS will be interoperable which will improve the performance of satellitenavigation in general, in a transparent manner for the user. In addition, Galileo will cover GPSshortfalls, namely [EU_GALILEO]:

• Service guarantees for certain types of civil users in terms of accuracy, availability, continuityand integrity of the signal,

• Integrity monitoring increasing the overall safety, in particular in aviation, because the TimeTo Alarm is less than 10 seconds,

• Improved service performance and signal which is of paramount importance for safety relatedapplications,

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• Search and rescue by improving time-to-detection and accuracy of location of distressbeacons by extending the current COSPAR-SARSAT mission, also providing anacknowledgment to the user that the distress message has been received.

Galileo Advanced Operational Capability should be reached in 2008.

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9/.� "�� -� � �� +$��

7�� "�1%#�8;�"��ARINC Characteristic 702A-1 “Advanced Flight Management Computer System”, published 31January 2000, provides recommendations to support the anticipated requirements for operations inthe future CNS/ATM environment of flight management computers, in terms of:

• Navigation,• Flight Planning,• Lateral and Vertical Guidance,• Trajectory Predictions,• Performance Calculations,• Air-Ground Data Link,• Pilot Interface via the MCDU, and• Electronic Flight Instrument System Display.

ARINC-702A-1 (Attachment 2 to 7) also defines interfaces between the FMC and other airbornesystems as well as data link uplink and down link messages and syntax rules.

ARINC-702A-1 (Attachment 8) defines the Trajectory Intent Data Files output on the Trajectory Bus.

6.2.1.1 Accuracy and PerformanceAccuracy requirements for both lateral and vertical navigation rely on RTCA/DO-236, MASPS RNP forRNAV.

Response time standards recommend that full flight plan predictions (including vertical data) beperformed in less than 15 seconds, though performance depends on factor such as flight plan lengthand number of waypoints).

6.2.1.2 Trajectory PredictionsAll aircraft trajectories (active, modified, alternate…) should account for the aircraft performance,selected speed schedule and speed transitions, altimeter baro-setting, aircraft flap configurationchanges, environmental conditions, intended control mode and other crew entered vertical flightplanning selections (e.g. thrust operation).

Altitude, speed, estimated time of arrival (ETA), fuel on board should be computed for each waypointin the flight plan, including the various vertical trajectory points like speed change points, Top of Climb(TOC), step climb, Top of Descent (TOD)…

Accuracy for the RTA capability should be ±30 seconds en-route and ±5 seconds in terminal area.

6.2.1.3 Performance CalculationsPerformance calculations should be based on lateral and vertical flight plan elements, winds andtemperatures, aircraft lift and drag models, engine thrust and fuel flow characteristics, aircraft speedand altitude limitations, aircraft weight and centre of gravity…

6.2.1.4 Data Link InterfacesThe system should provide data link interfaces with:

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• Airline Operations Communication (AOC) to allow for uplink and crew controlled insertion ofparameters such as:

o User preferred flight plan defined by the airline dispatch office,o Wind profiles at multiple altitudes,o Waypoints where automatic position reports are required,o Performance initialization data,o Navigation database amendments,o NOTAM,o …

• CNS/ATM functions using:o ACARS (ARINC-623) for Pre-Departure Clearance (PDC), Oceanic Clearance,

Automatic Terminal Information Service (ATIS) and future Terminal WeatherInformation for Pilots (TWIP)…

o ATS over ACARS (ARINC-622) supporting ATS Facilities Notifications (AFN),Automatic Dependent Surveillance (RTCA/DO-212, ARINC-745) and CPDLC(RTCA/DO-219)…

o Aeronautical Telecommunications Network (ATN) for ATN, ADS, CPDLC, FlightInformation Service (FIS)…

o Broadcast data link for applications such as Surveillance by ADS-B, air-to-air conflictresolution, ground-to-air traffic information, hazardous weather alerts andatmospheric data… considering 1090ES and VDLM4.

6.2.1.5 Standard InterfacesARINC 702A-1 lists:

• Digital data input ports connected to:o Navigation sensors (VOR, DME, ILS/MMR, ADC, IRS/AHRS, GNSS),o Flight systems (FCS, propulsion, MCDU and EFIS),o Data loader and Data link,o ��+�� +$��…

• Digital data output ports for:o General data,o EFIS and MCDU,o Data loader and Data link,o �� …

7�� %*��%"�Conflict Detection algorithms rely on the definition of protected zones surrounding each aircraft. Thisassumes that the actual aircraft positions remain within these protected zones with a certain degree ofconfidence.

A 5 NM radius protected zone requires system performances defined by RNP-1 RNAV (or better).

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9/�� A Cockpit Display of Traffic Information (CDTI) refers to a generic avionics device in an aircraft cockpitthat is capable of displaying position information for nearby aircraft. Based on conventional NavigationDisplays, it may also include display of ground reference points and navigation information to increasea pilot’s situation awareness and improve the safety and efficiency of flight operations.

CDTI should only be considered as an airborne display feature offered to traffic related applicationssuch as ACAS, ASAS, CD&R and others. Though often associated to ADS-B, CDTI could use datastreams from many different surveillance sources such as TCAS, TIS-B, WXR, etc…

While general guidance concerning the format, content and control of the information to be presentedon cockpit displays is given by RTCA SC-186 through DO-243, specific requirements concerningplacement, presentation and integration of CDTI data on multifunction displays are not addressed.[RTCA_DO243]

It is recommended that a CDTI consists of:• Minimum display features and target information including target aircraft location relative to

own aircraft• Application dependent display features and target information8 including call sign, closure

rate, ground speed, vertical rate, ground track indication, alerts, intentions …

Figure 16 illustrates experimental CDTI displays.

CDTI should also aid in target selection for applications such as Conflict Resolution, and providerange selection, application type and data selection as well as de-cluttering capabilities.

CDTI for Conflict Detection and Resolution (CD&R) proposed by NLR is described in §6.4.3.

8 Depending on a particular application’s needs, optional target information and capabilities may be provided.

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"� ��93��@�� $��1��+�2

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9/4� �� More than 20 recent studies propose Conflict Detection and Resolution (CD&R) methods.

Some are based on probabilistic or on force field models, others rely on geometrical (4D)computations or on flight rules-based approaches. Some are extensions of TCAS.

7�$�� #��-��The Conflict Detection function performs predictions of intrusions of the protected zones surroundingown and nearby aircraft. These protected zones will be chosen to reflect Reduced Vertical SeparationMinimum (RVSM), i.e. 5 nautical mile radius and a height of ±1000 feet today.

A conflict is defined as an intrusion of the protected zone that takes place in the near future (a look-ahead time that should be set at 5 to 20 minutes depending on method and use of intent informationor not). The predicted minimum distance with other traffic is calculated, based on current 3-dimensional position and the velocity vector to predict future aircraft positions and intent informationwhen available. Should the Closest Point of Approach (CPA) be less than the required separation andthe time of intrusion is within the look-ahead time, the conflict data is stored in a conflict database,together with predicted positions of both own and other aircraft as well as time of intrusion. Thisinformation will be presented to the crew (CDTI), and will also be passed on as input to the resolutionmodule.

�� = ��#��#��!��#�>��?�@&�� <�� /

%��&�,��#�� &�� !��/�2�� !��/

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7�$�� #��-��The Conflict Resolution function computes possible resolution manoeuvres to be implemented by theown aircraft resulting in a flyable and conflict free trajectory changes with other aircraft within the look-ahead time.

Manoeuvres will consist of minor heading, altitude or speed changes, or more sophisticated flight pathmodifications.

The Conflict Resolution function will base its computations on (not limited to):• State vectors and intent information gathered from own and conflicting aircraft,• State vector and intent information gathered from surrounding aircraft,• Airspace description including restricted areas,• Own aircraft performance,• Cost index, and airline policies.

9 Only few studies make use of intent data for CD&R. INTENT experiments indicate that its use reduces workload andoptimizes solutions. Basically, pilots seem favourable to its use with a look-ahead time set at 12-15 minutes.

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Possible manoeuvres, once sorted, will be presented to the crew (CDTI/FMS-EFIS) for acceptanceand implementation.

Proposed Conflict Resolution algorithms sometime assume some form of cooperation betweenaircraft is anticipated for resolution. Some models will assume sequential handling of multiple conflicts(pair wise model), while others will assess the entire traffic situation in order to find a solution (globalmodel).

�� = ��#��#��!��#>��?�@&��(�= �!�� )��!��(��<��)/��&�� (��!��&��!��&��!��!��)/

7�$� � #�!1�-��#�.�NLR proposed CDTI symbology and features for several experiments related to Airborne SeparationAssistance Systems (ASAS) and the Free Flight concept. [NLR_FREE]

Because of the expected importance of vertical manoeuvres, the CDTI also integrates VerticalNavigation display below a Navigation Display as depicted Figure 17.

The information consists of:• Vertical and horizontal track of own aircraft,• Traffic information including:

o Call sign,o Direction,o Altitude,o Ground speed, ando Vertical speed (climbing or descending arrow),

• Conflict information including:o Protected zone around predicted position of intruder at minimum distance,o Predicted track-line of the intruder, which connects the traffic symbol with the conflict

symbol indicating the predicted position of the intruder,o Time to intrusion,

• Resolution information to prevent intrusion by means of:o Graphical coplanar avoidance (vector on NAV Display),o Steering bugs on NAV Display (heading change) and PFD (altitude and/or speed

change)

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7�$�$� *��)�",",The goal of using intent is to avoid sudden manoeuvres which would trigger short term conflicts. If thecrew/aircraft knows what manoeuvre would trigger a short term conflict, they could avoid suchconflicts by not initiating any such manoeuvres. Adding a "rule of the road" stating that no suchmanoeuvres are allowed would theoretically eliminate the problem of short term conflicts. At NLR aso-called "Predictive ASAS" has been developed which shows the crew on the PFD and theNavigation display which manoeuvre (if any) will trigger a conflict within 5 minutes. The figure belowshows the PFD with "Predictive ASAS"

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As long as the aircraft is flying in a straight line (and other aircraft obey the above mentioned rule) noconflict will be triggered at less than 5 minutes (the look-ahead time used by the NLR). If a manoeuvreis called for (e.g., at the top of descent), the crew is expected to avoid manoeuvres which wouldtrigger a conflict at short notice. This is achieved by selecting parameters which are outside the amberand/or red regions on the heading, speed and vertical speed scale of the PFD. Initial pilot-in-the-looptesting demonstrated very positive results for inclusion of "predictive ASAS". Short term conflicts areavoided completely and even conflicts at 5 minutes are seldom encountered, because the system canbe used to anticipate and avoid conflicts. On one occasion, a crew during training was set in anenvironment in which 110 aircraft were flying in their direct vicinity (120 nmi range +/- 10000ft). Thecrew was capable of avoiding all conflicts. Also, at some time during the training they were observedto deviate from their path, because they simulated on their own accord an additional thunderstorm inthat region.

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7�'�� "�,�&Automatic Dependent Surveillance-Broadcast (ADS-B) is a system (currently under definition) thattransmits information about an aircraft’s state and intent at a predefined interval for use by bothground-based air traffic control and other aircraft. The uses for this data are situational awarenessand conflict resolution.

6.5.1.1 DescriptionADS-B is a new technology that should:

• Allow pilots in the cockpit and air traffic controllers on the ground to "see" aircraft traffic withmuch more precision than has been possible ever before,

• Provide the same real-time information to pilots in aircraft cockpits and to ground controllers,so that for the first time, they can all "see" the same data.

Unlike conventional radar that works by bouncing radio waves off of airborne targets and then"interpreting" the reflected signal, ADS-B:

• Doesn’t need to interrogate targets to have them displayed,• Is intended to work at low altitudes and on the ground, so that it can be also used to monitor

traffic on the taxiways and runways of an airport,• Should be effective in remote areas or in mountainous terrain where there is no radar

coverage, or where radar coverage is limited.

Indeed, each ADS-B equipped aircraft10 broadcasts its precise position in space (as determined bythe avionics on board) via data link along with other data.

6.5.1.2 Working PrinciplesAircraft (or other vehicles or obstacles) will broadcast a message on a regular basis, which includestheir position (latitude, longitude and altitude), velocity, and other information such as the type ofaircraft, identification, heading, airspeed, altitude and possibly short or long term intent information.

All the information to be transmitted by ADS-B resides in the FMS function.

Other aircraft and ground stations within about 200 miles receive this information for use in a widevariety of applications such as display on a Cockpit Display of Traffic Information (CDTI), or oncontrollers’ regular traffic display screens along with other radar targets.

RTCA Special Committee 186 is currently defining the ADS-B message set and associatedoperational usage. [RTCA_DO242A]

The work of the common FAA/Eurocontrol Technical Link Assessment Team(TLAT) [TLAT_ADSB]clearly demonstrated that, considering the present status of the candidate link technologies foreseenfor ADS-B (i.e. 1090ES, VDLM4 and UAT), none of the 3 links can meet the long-term (2015+)requirements for ADS-B. There should be no problems for any of the links to meet local short timerequirements. For the longer term solutions have to be elaborated based on improvements of thepresent links or use of combinations of links (multi-link) [EATMP_FAQ].

10 ADS-B is not only intended for aircraft. Any ground vehicle and even obstacle can be equipped with an ADS-Btransceiver.

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6.5.1.3 PerformanceAn ADS-B based system listens for position reports broadcast by the aircraft. These position reportsare based on accurate navigation systems, such as satellite navigation systems (e.g. GPS). Theaccuracy of the system is now determined by the accuracy of the navigation system, notmeasurement errors (assuming data is received in a timely manner).

With the radar, detecting aircraft velocity changes requires tracking the received data. Changes canonly be detected over a period of several position updates. With ADS-B, velocity changes arebroadcast almost instantaneously as part of the state vector report.

Moreover, accuracy is unaffected by the range to the aircraft. These improvements in surveillanceaccuracy can be used to support a wide variety of applications and increase airport and airspacecapacity while also improving safety.

7�'�� +/��,��)�� Hybrid surveillance is defined by ICAO as the process of using active surveillance (namely Mode S) tovalidate and monitor other aircraft being tracked principally using passive surveillance (namely ADS-B) in order to preserve ACAS independence.

This technique requires refining algorithms to allow use of ADS-B data by ACAS. Currently ACASdepends solely on active surveillance for intruder detection and tracking, and advisory generation.Hybrid surveillance would allow distant targets to be tracked and displayed based on the passiveADS-B messages and require active surveillance (and the accompanying advisory generation) onlyfor the small number of intruders that pose a near-term threat. In this way, TCAS-based hybridsurveillance reduces the active interrogation rate, thereby lessening the spectrum impact, while at thesame time providing increased target display range. (TESIS)

7�'� � 1�� ,��)�� ,+��The AEEC Systems Architecture and Interfaces (SAI) Subcommittee expressed the desire for aconfigurable Integrated Surveillance System (ISS) standard. This would include traffic, terrain, andweather surveillance capability. The goal is prepare a common standard for Airbus and Boeingairplanes. [AEEC 03-011/SAI-823, January 31, 2003]

In light of formal proposals from Airbus and Boeing, the SAI Subcommittee recommended theformation of an Integrated Surveillance System (ISS) working group to prepare the standard.

ARINC-660 CNS/ATM Avionics, Functional Allocation and Recommended Architectures provide thefollowing schematic for possible surveillance system architecture.

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7�'�$� "��/��,��)�� ,� � ��"�� *��Airborne Surveillance and Separation Assurance Processors (ASSAP) capable of receivingsurveillance input from more than one source (e.g. ADS-B, TIS-B, ACAS) are currently under study.

These processors would support correlation and tracking functions as well as processing algorithmsfor specific ASAS applications such as traffic situation awareness, spacing and airborne conflictmanagement.

These processors would be interfaced with Surveillance systems (e.g. ADS-B transceivers, TCAS),Display systems (displays and pilot input devices) and other Aircraft systems (flight control, flightmanagement and navigation data) [RTCA_ASA].

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8� � �� This section establishes the implementation roadmap for systems aiming to increase the air trafficcapacity based on the use of intent information broadcast by equipped aircraft.

This section will first present the end-to-end system architecture as allocated by WP-2.

Then it will assess the existing and under development products described in the two previoussections and that could fit the allocated function.

Finally, required changes if any will be listed and the implementation roadmap will be established.

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<� � �� $�� This chapter summarizes two of the interesting architectures defined in previous work package WP2“Functional Allocation” [D2-4], i.e. the hybrid system and the airborne system, and lists potentialcandidate solutions based on products described in previous sections of this document.

It shall be noted that this description, and later the roadmaps, are provided for information only.

The decision of which end-to-end system is to be deployed can not be based on these sections, butshall result from the recommendations and resolutions of issues listed in [D2-4].

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<�� )� ��+�� 2��As described in [D2-4], roles between the aircraft and the ground are distributed as follows.

1. All aircraft:a) Fly accurately their own planned 4-dimensional (4D) trajectory,b) Broadcast their 4D trajectory.

2. The Ground:a) Receives all 4D trajectories,b) Performs Conflict Detection and Resolution,c) Transmits constraints for conflicting trajectories to assigned aircraft.

3. The assigned aircraft:a) Receives the constraint,b) Iterates a modified 4D trajectory that takes the constraint into account (de-conflicting the

situation), as well as performance data, cost index, flyable airspace description…c) Transmits this modified 4D trajectory.

4. The Ground:a) Receives all 4D trajectories,b) Performs Conflict Detection and Resolution,c) Transmits a clearance for the de-conflicting trajectory to assigned aircraft.

5. The assigned aircraft implements the modified trajectory now to be flown.

This brief sequenced description presumes the use of the following products.

1. On the airborne side:a) An RNP-1 RNAV Flight Management System (FMS) with associated navigation sensors

capable of distributing both active and modified 4D trajectories,b) An ADS-B transmitter capable of broadcasting such trajectories,c) An addressed ground-to-air data link receiver capable of up-linking both the constraints

and the clearances, and that can be linked to the FMS depending on the considered levelof automation,

d) A potential addressed air-to-ground transmitter capable of down-linking the modified 4Dtrajectory, though it would be recommended to down-link both active and modifiedtrajectories through the same link.

2. On the ground side:a) An ADS-B receiver capable of receiving all broadcast 4D trajectories,b) A Surveillance Data Processing and Distribution (SDPD) system capable of tracking all

4D trajectories,

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c) A Conflict Detection and Resolution (CD&R) system capable of detecting conflicts and ofissuing constraints to be used for resolution as well as clearances for received de-conflicting trajectories,

d) An addressed ground-to-air transmitter capable of up-linking both constraints andclearances,

e) A potential addressed air-to-ground receiver capable of down-linking the modified 4Dtrajectory, though it would be recommended to down-link both active and modifiedtrajectories through the same link.

Figure 20 depicts this architecture (“Towards global air and ground collaboration in traffic separationassurance”).

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8.1.2.1 ADS-B receiverThe ground-based ADS-B receiver is the counter-part of the airborne ADS-B transmitter(s). Theremight indeed be different technologies in use depending on airborne equipage.

Same features and limitations listed in §8.1.3.3 apply.

8.1.2.2 Surveillance data processing and distribution systemThe ground-based surveillance data processing and distribution (SDPD) system should provide theADS-B data tracking capability used to collect all broadcast data down-linked by each aircraft.

ARTAS-2 is being designed to do so.

8.1.2.3 Conflict detection and resolution systemThe ground-based conflict detection and resolution (CD&R) system should provide the followingcapabilities:

• Detect short, medium and long term conflicts using the received trajectories (both active andmodified),

• Issue a constraint to be applied to de-conflict trajectories by assigned aircraft, or• Issue a clearance to inform the assigned aircraft that its modified trajectory is indeed conflict

free.

HIPS, GEAR, CORA, or URET are being designed11 to assist controllers in the conflict detection andresolution tasks. The more automation is performed, the lower the workload, the greater the trafficincrease.

8.1.2.4 Addressed ground-to-air data link transmitterThe ground-based addressed ground-to-air data link transmitter is the counter-part of the airborneaddressed ground-to-air data link receiver used to up-link constraints and clearances.


8.1.2.5 Addressed air-to-ground data link receiverThe ground-based addressed air-to-ground data link receiver is the counter-part of the airborneaddressed air-to-ground data link transmitter used as an alternate solution to down-link the modifiedtrajectories.


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11 STCA is implemented in several centres in Europe. MTCA is still in research and development evaluation inthe field. HIPS was planned for operational use in the UK but has been delayed. GEARS and CORA are still inresearch and development.

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8.1.3.1 Navigation sensorsTo achieve the required navigation accuracy with “good” quality factors (integrity, availability…),recommended sensors would be:

• DME,• IRS, and• GNSS.

8.1.3.2 Flight management systemThe FMS should provide (among others) the following functions as defined by ARINC Characteristic702A-1:

• Multi-sensor and RNP-based (in accordance with RTCA/DO-236A) navigation,• Flight planning using an ARINC 424 navigation database containing description of Flight

Information Region (FIR) boundaries and Special Used Areas (SUA),• Performance optimized guidance along 4D paths,• Performance calculations based on Cost Index,• Support to navigation data display with an Electronic Flight Instrument System (EFIS), and• Data link functions supporting Airline Operations Communication (AOC) and CNS/ATM which

includes Controller/Pilot Data Link Communication (CPDLC) and Automatic DependentSurveillance-Broadcast (ADS-B).

The FMS should also provide (among others) the following interfaces as defined by ARINCCharacteristic 702A-1:

• Navigation sensors input ports,• Data link input and output ports,• Primary display output ports, and• Aircraft state and intent path output port (trajectory bus).

8.1.3.3 ADS-B transmitterThe ADS-B transmitter should be capable of transmitting “huge” trajectory files formatted with severaltens of Trajectory Change Points (TCP). Current definition of the ADS-B frame does not allow forbroadcasting more than 2 TCP, neither does it allow to broadcast modified intent data.

Moreover, among the candidate technology, (i.e. 1090 MHz Extended Squitters (1090ES), VHF DataLink Mode 4 (VDLM4) and Universal Access Transceiver (UAT)), it is unlike that 1090ES technologybe capable of broadcasting these trajectory files in high traffic density airspace. The emerging UATtechnology is not considered yet in Europe though it could be ready and available well before VDLM4.

8.1.3.4 Addressed ground-to-air data link receiverThe addressed ground-to-air data link receiver should be capable of up-linking short data files forconstraints and clearances coming from the ground and designated to the specific receiver. CPDLCon VHF Data Link Mode 2 (VDLM2) was designed for this type of pre-formatted exchanges betweenthe ground and an aircraft.

8.1.3.5 Addressed air-to-ground data link transmitterThe addressed air-to-ground data link transmitter, an alternate solution used to transmit the modifiedtrajectory to the ground for conflict free verification, should be capable of down-linking “huge”

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trajectory data files. ACARS and ATN data link technologies (e.g. VDLM2) are already meant to doso.

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<�� )� ��+�� 2��As described in [D2-4], roles of the aircraft are distributed as follows.

1. All aircraft:a) Fly accurately their own planned 4-dimensional (4D) trajectory,b) Broadcast their 4D trajectory.

2. All aircraft:a) Receives all 4D trajectories,b) Performs Conflict Detection and assess trajectories to be modified,c) Broadcast their conflict assessment.

3. All aircraft:a) Receive all conflict assessments,b) Assess the received conflict assessment with own conflict assessment.

4. The aircraft required to modify its own trajectory:a) Resolves the conflict(s) it is part of,b) Iterates a modified 4D trajectory:

• Conflict free,• Flyable, and• Flight efficient.

5. Optionally, the ground:a) Receives all 4D trajectories,b) Performs Conflict Detection as a monitoring system,c) Warns aircraft of their conflicting situation.

This brief sequenced description presumes the use of the following products.

1. On the airborne side:a) An RNP-1 RNAV Flight Management System (FMS) with associated navigation sensors

capable of distributing both active and modified 4D trajectories,b) An ADS-B transmitter capable of broadcasting such trajectories,c) An ADS-B receiver capable of receiving all broadcast 4D trajectories,d) An airborne surveillance data processing system (traffic computer),e) A conflict detection system (airborne separation processor / traffic computer, plus CDTI),f) A broadcast data link, or an air-to-air addressed data link, capable of transmitting and

receiving conflict assessments,g) A conflict resolution system that can be linked to the FMS.

2. Optionally, on the ground side:a) An ADS-B receiver capable of receiving all broadcast 4D trajectories,b) A Surveillance Data Processing and Distribution (SDPD) system capable of tracking all

4D trajectories,c) A Conflict Detection monitoring system,f) An addressed ground-to-air transmitter capable of up-linking warnings to conflicting

aircraft.

Figure 21 depicts this architecture.

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8.2.2.1 Navigation sensorsSame as 8.1.3.1

8.2.2.2 Flight management systemSame as 8.1.3.2

8.2.2.3 ADS-B transmitterSame as 8.1.3.3

8.2.2.4 ADS-B receiverSame as 8.1.2.1

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8.2.2.5 Traffic computerThe traffic computer should be capable of tracking all ADS-B targets, broadcasting or not intent data,within the look-ahead horizon.

8.2.2.6 Conflict detection systemThe airborne conflict detection system should:

• Detect short, medium and long term conflicts using the received trajectories,

• Display the associated data on the CDTI.

8.2.2.7 Addressed air-to-air data linkThe addressed air-to-air data link transmitter may be an alternate solution used to exchange theconflict assessment between aircraft in order to co-ordinate airborne elaborated traffic situations.

8.2.2.8 Conflict resolution systemThe airborne conflict resolution system should:

• Provide assistance to the FMS in computing conflict free, flyable and efficient trajectories,

• Display the associated data on the CDTI.

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8.2.3.1 ADS-B receiverSame as 8.1.2.1

8.2.3.2 Surveillance data processing and distribution systemSame as 8.1.2.2

8.2.3.3 Conflict detection systemThe ground-based conflict detection system should detect short, medium and long term conflictsusing the received trajectories. STCA and MTCA are developed and currently under evaluation.

8.2.3.4 Addressed ground-to-air data link transmitterThe ground-based addressed ground-to-air data link transmitter is the counter-part of the airborneaddressed ground-to-air data link receiver used to up-link conflict warnings.

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Before any intent-based system (e.g. hybrid or airborne) and associated equipment can be deployed,corresponding airspace and operational procedures must be designed and agreed at ICAO andEuropean airspace user level. Package 1 of European airborne surveillance and ground surveillanceapplications is planned for implementation between 2007 and 2012.

Free Routes are still under evaluation in projects like Mediterranean Free Flight.

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9.1.1.1 ADS-B receiverThere is still much to do with the definition of the ADS-B frames that could lead to an upgrade ofRTCA/DO-242A, as well as with the definition of operational requirements for the candidatetechnologies (especially VDLM4 and UAT).

According to Eurocontrol ADS Master Plan, ADS-B Package 1 applications are due for ECAC wideimplementation between 2007 and 2012. These include ATC surveillance for en-route airspace.

9.1.1.2 Surveillance data processing and distribution systemARTAS-2 is presently being developed.

Consortium led by Thales ATM. Contract started in 1993. First ARTAS was operational LVNL 1998. 3sites among the 21 that will support the 39 units are now in operation. Average forecast is +8/year.

9.1.1.3 Conflict detection and resolution systemThe tool should be automated to issue constraints and clearances automatically and ready to betransmitted.

Moreover, the horizon (look-ahead) should be as long as possible or scalable. Indeed, re-routingefficiency is obtained for with long look-ahead (5 to 90 min, strategic planning) rather than short look-ahead (< 5 min, tactical planning). [FAA_INTENT]

;/0/0/./0� ��Eurocontrol is currently evaluating a medium term conflict detection tool (MTCD) in the field based onradar data and flight plans. Initial MTCD trials were held in Malmo, Sweden in 2002. Trials arecontinuing in 2003 at the Rome ACC in Ciampino looking at medium density traffic behaviour and ifsuccessful Maastricht high density in autumn 2003.

URET is gradually being introduced in to selected operational centres in the US.

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CORA, URET implementation has only recently started in selected centres in US and there are noimplementation plans so far in Europe.

The constraint identification and negotiation process was addressed in the PHARE (Program forHarmonisation of ATM in Eurocontrol) during the 1990s but the research was not continued. Majorissues identified were:

• Complexity of negotiation process and definition of constraints,• Availability of ground based high fidelity trajectory predictor, i.e. aircraft model data difficult to

obtain due to commercial in confidence and maintaining coverage for all aircraft types.

;/0/0/./.� ��,��9��= ��Although the INTENT hybrid system is targeted at en-route airspace it will have to interface with someexisting and future TMA systems such as arrival sequencing tools and ASAS sequencing andmerging systems which tend to have horizons in the extended-TMA. Integration of an arrivalsequencing tool with en-route tools still at R&D stage in Europe.

9.1.1.4 Addressed ground-to-air data link transmitterCPDLC based on VDLM2 has been successfully implemented around some trial sites (USA, SouthPacific…).

9.1.1.5 Addressed air-to-ground data link receiverACARS, ADS-C, VDLM2 and ATN data links are available or under development already.

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9.1.2.1 Navigation sensorsGNSS based on GPS augmentation through EGNOS will be available shortly.

The Galileo solution is expected to be operational by 2008.

9.1.2.2 Flight management systemStandards such as ARINC 702A-1 and RTCA/DO-236A already defining what is required for theIntent-based system, design, development and certification of compliant FMS should be a matter oftime, and follow airlines and/or airframers interest in the upgrade.

Many FMS will have to be modified to reach this standard. These changes might not consist in“simply” loading new software. Indeed, new interfaces thus hardware might be required to cope withthe new definition input and outputs listed §6.2.1.5 (especially for the new trajectory bus transmittingthe intent information). Moreover, implementation of all FMS functions might require greaterprocessing power, thus new processor boards might need to be designed to handle the navigation,performance calculations, data link and other features as well as all interfaces and protocols. This willhave a significant impact on cost that retrofitted aircraft will not afford.

9.1.2.3 ADS-B transmitterRefer to §9.1.1.1.

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9.1.2.4 Addressed ground-to-air data link receiverRefer to 9.1.1.4.

9.1.2.5 Addressed air-to-ground data link transmitterRefer to §9.1.1.5.

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9.2.1.1 Navigation sensorsSame as §9.1.2.1

9.2.1.2 Flight management systemSame as §9.1.2.2

9.2.1.3 ADS-B transmitter and receiverSame as §9.1.2.3 and §9.1.1.1

9.2.1.4 Traffic computerSpecification and design activities for the airborne surveillance data processing system, or trafficcomputer, have started recently with projects such as TESIS (FAA), ASFA (Eurocontrol), NUP-II andothers.

ASA MAPS for defining ASAS applications and ASSAP have started to be drafted.

Refer to §6.5.3 and 6.5.4

9.2.1.5 Conflict detection and conflict resolution systemsAirborne conflict detection and conflict resolution algorithms (and associated displays on CDTI) havebeen designed for many ASAS projects such as INTENT.

These algorithms and displays will need further evaluation (performance) and specification (reliability)in order to be implemented in certified airborne platforms.

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9.2.2.1 ADS-B receiverSame as §9.1.1.1

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9.2.2.2 Surveillance data processing and distribution systemSame as §9.1.1.2

9.2.2.3 Conflict detection systemSame as §9.1.1.3.1

9.2.2.4 Addressed ground-to-air data linkSame as §9.1.1.4

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[D2-4] INTENT: D2-4 “Report on the function analysis and allocation in the system”

ARINC 702A-1 Advanced Flight Management Computer System

ARINC Characteristic 702A-1, 31-Jan-2000

[RTCA_DO212] Minimum Operational Performance Standards for Airborne Automatic DependantSurveillance (ADS) Equipment

RTCA DO-212, Oct. 26, 1992

RTCA/DO-242A MASPS: Automatic Dependent Surveillance Broadcast (ADS-B)

RTCA DO-242A, 25-Jun-2002

[RTCA_DO243] Guidance for Initial Implementation of Cockpit Display of Traffic Information

RTCA DO-243, Feb. 19, 1998

RTCA/DO-326A MASPS: Required Navigation Performance for Area Navigation

RTCA DO236A, 13-Sep-2000

[ALLSTAR] Aeronautics Learning Laboratory for Science, Technology, and Research

http://www.allstar.fiu.edu/

[BOEING_ATC] Boeing, ATC Data Link News

http://www.boeing.com/commercial/caft/reference/links.htm

[BOEING_RNX] General Information on the Functional and Technical Aspects of RequiredNavigation Performance (RNP) Area Navigation (RNAV) And Applications

BOEING, Dave Nakamura, Feb. 9, 2000

[CROSSBOW] Crossbow Solid-State Inertial Systems and the Solid-State-Gyro.

http://www.xbow.com/html/gyros/gyro_ov.htm

[EATMP_FAQ] European Air Traffic Management Programme (EATMP) Frequently AskedQuestions, ADS-B

[EC_ADS] Eurocontrol, EATMP, ADS

http://www.eurocontrol.int/ads/

[FAA_ADSB] GOMEX and ADS-B, FAA What is ADS-B

http://gomwg.faa.gov/ads-b.htm

ADS-B Sub Frames

http://adsb.tc.faa.gov/ADS-B/186-subf.htm

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[FAA_AIM] Aeronautical Information Manual, August 10, 2000. Chapter 1. Navigation Aids

http://www.faa.gov/AIM/Chap1/aim0101.html

[FAA_CPDLC] FAA: Free Flight Tools, CPDLC

http://ffp1.faa.gov/tools/tools_cpdlc.asp

CAASD MITRE, CPDLC

http://www.caasd.org/proj/cpdlc/index.html

[GARMIN] Garmin: About GPS / What is GPS?

http://www.garmin.com/aboutGPS/

[GPS_FAA] Satellite Navigation / SATNAV / Basics

http://gps.faa.gov/gpsbasics/index.htm

[HW_ADSB] Honeywell CNS/ATM Documentation

Business & Commuter Aviation Systems, An overview of CNS/ATM

[MFEARY] Michael Feary, Aiding Vertical Guidance Understanding, NASA Ames

[NLR_FREE] NLR, Free Flight with Airborne Separation Assurance

http://www.nlr.nl/public/hosted-sites/freeflight/main.htm

[ROCKWELL] Rockwell Collins, Flight Management Systems

http://www.rockwellcollins.com/ecat/

[SAS_ACARS] SAS Scandinavian Flight Operations, Introduction to data link

http://www.sasflightops.com/dlk/datalink.htm

[SITA_AC] SITA-Solutions / Aircraft Communications

http://www.sita.com

[TLAT_ADSB] ADS-B Technical Link Assessment Team Report, March 2001

Web sites:

http://www.stna.dgac.fr

http://www.cena.dgac.fr

http://www.eurocontrol.int/vdlmode2/overview/need.html

http://www.eurocontrol.int/vdl4/system_description.html

http://www.eurocontrol.int/mode_s/

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�.�*�!�� $(1) M.S Nolan, “fundamentals of air traffic control”.

(2) V. David Hopkins, “Human factor in air traffic control”.

(3) JM. Lescure, “Navigation Aerienne”, Ecole Nationale de l’Aviation Civile Tome1&Tome2.

(4) M.Skolnik “Radar handbook” second edition.

(5) M.Combes “Avionique de la navigation aerienne”

(6) B. Kirwan, ”Towards a cognitive tool for conflict resolution assistance: a literature Review”.

(7) Eurocontrol experimental centre “The GEARS conflict resolution algorithm”

(8) Pice, C.Meckiff “HIPS and its application to oceanic control”

(9) NLR, “Overview of NLR free flight project 1997-1999”

(10) INTENT, deliverable document 1-1.May 2001.

(11) MAICA, “Possible changes in the future ATM system”

Documents

fileINTENT WP3 Implementation Roadmap, D3-1 Version: v04 Date: 22-03-2003 Classification: Public 3 ˘ ˇ ˆ Document title Implementation Roadmap, D3-1