DLS Regulatory Approach

EUROPEAN ORGANISATION FOR THE SAFETY OF AIR NAVIGATION

EUROCONTROL

SINGLE EUROPEAN SKY (SES) REGULATIONS

REGULATORY APPROACH

FOR

DATA LINK SERVICES

May 2006 Edition 1.1

REGULATORY APPROACH FOR DATA LINK SERVICES INTEROPERABILITY MANDATE

SES/IOP/DLS/REGAP/1.1

DOCUMENT CONTROL

DOCUMENT CHANGE RECORD The following table records the complete history of the successive editions of the present

document.

Edition Number Edition Date Reason for Change Pages

Affected

0.1 14-07-05 Creation All

0.2 22-07-05 Update after KOM discussions All

0.3 18-08-05 Initial merged draft chapters 2 & 3 All

0.4 30-09-05 Chapters 1 – 3 updated after internal review. Introduction of Chapter 4 material. All

0.5 21-10-05 Updated and restructured after internal review and further contributions. All

0.6 24-10-05 Updated and restructured after internal review and further contributions. All

0.7 28-11-05 Updated and restructured after internal review group meeting and further contributions. All

0.8 08-12-05 Interoperability Analysis review and merger with other parts of the Regulatory Approach. All

0.9 20-12-05 Update after internal review and read-through. All

0.10 19-01-06 Comments arising from Review Group meeting 11 Jan 06.

Most of main doc.+ Annexes D.4, E.7

1.0 24-01-06 Update of Executive Summary and Alternatives for Regulatory Approach. General review. All

1.1 25-05-06 Update to include comments received during formal consultation. All

Status: Released

Edition No: 1.1 Date: 25 May 2006 Document No: SES/IOP/DLS/REGAP/1.1

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TABLE OF CONTENTS

1. INTRODUCTION..........................................................................................................4 1.1 Data Link Services Mandate .....................................................................................4 1.2 Document Purpose and Scope .................................................................................4

1.2.1 Purpose .............................................................................................................4 1.2.2 Objective............................................................................................................4

1.3 Development of the Regulatory Approach ................................................................4 1.4 Consultation to Date .................................................................................................5

2. BACKGROUND ...........................................................................................................5 2.1 What is a Data Link Service?....................................................................................5

3. INTEROPERABILITY ANALYSIS ...............................................................................6 3.1 Introduction ...............................................................................................................6

3.1.1 Objective and Scope..........................................................................................6 3.1.2 Interoperability Analysis Process.......................................................................6 3.1.3 Functional Architecture ......................................................................................8

3.2 Assessment of Data Link Services .........................................................................10 3.2.1 Criteria for the Selection of Data Link Services ...............................................10 3.2.2 Results of Initial Assessment...........................................................................10 3.2.3 Statements of Issues .......................................................................................11 3.2.4 Contribution to Interoperability.........................................................................11 3.2.5 Impact on the Implementing Rule ....................................................................11

3.3 Assessment of Data Link Technology.....................................................................12 3.3.1 Air-Ground Data Link Technology ...................................................................12 3.3.2 Ground-Ground Data Link Technology............................................................15

3.4 Assessment of End-to-End Communication System ..............................................17 3.4.1 Criteria for the Selection of End to End Communication Systems...................17 3.4.2 Statement of Issues.........................................................................................17 3.4.3 Recommended Selection of End to End Communication System...................18 3.4.4 Contribution to Interoperability.........................................................................19 3.4.5 Impact on the Implementing Rule ....................................................................19

3.5 Assessment of Deployment Conditions in the EATMN...........................................20 3.5.1 Determination of Data Link Airspace ...............................................................20 3.5.2 Criteria for Mandatory Equipage of Aircraft and ATS Units .............................23 3.5.3 Airworthiness Certification and Operational Approval .....................................25 3.5.4 ATC Procedures for using Data Link Services ................................................27 3.5.5 Spectrum Planning ..........................................................................................29 3.5.6 Naming, Addressing and Registration Plan .....................................................31 3.5.7 Obligations of Stakeholders.............................................................................33

4. ALTERNATIVES FOR THE REGULATORY APPROACH .......................................35 4.1 Introduction .............................................................................................................35 4.2 Alternative 1 – Less Prescriptive.............................................................................36 4.3 Alternative 2 – ATN Prescription.............................................................................37 4.4 Alternative 3 – ATN with FANS Accommodation ....................................................38

5. CONFORMITY ASSESSMENT ANALYSIS ..............................................................39 5.1 Purpose...................................................................................................................39 5.2 Views of the Conformity Assessment Task Force ..................................................39 5.3 Recommendations for Conformity Assessment Requirements ..............................39

5.3.1 Verification Objectives .....................................................................................39 5.3.2 Verification Methods ........................................................................................40



5. CONFORMITY ASSESSMENT ANALYSIS ..............................................................39 5.1 Purpose...................................................................................................................39 5.2 Views of the Conformity Assessment Task Force ..................................................39 5.3 Recommendations for Conformity Assessment Requirements ..............................39

5.3.1 Verification Objectives .....................................................................................39 5.3.2 Verification Methods ........................................................................................40 5.3.3 Verification Evidence .......................................................................................40 5.3.4 Procedures for the Achievement of Conformity Assessment Activities ...........40

5.4 Impact on the Implementing Rule ...........................................................................40

6. ANALYSIS OF IMPLEMENTATION CONDITIONS ..................................................41 6.1 Purpose...................................................................................................................41 6.2 Factors Affecting Implementation Timescales ........................................................41

6.2.1 Notice to Aircraft Operators .............................................................................41 6.2.2 Equipment Availability......................................................................................41 6.2.3 Balancing Airborne and Ground Equipage ......................................................41 6.2.4 Business Case Issues .....................................................................................41 6.2.5 Transition Issues..............................................................................................42 6.2.6 Summary of the Implementation Timescale Options .......................................42 6.2.7 Impact on the Implementing Rule ....................................................................42

6.3 Airborne Exemption Policy Principles .....................................................................43 6.3.1 Applicability Criteria for Aircraft Equipage .......................................................43 6.3.2 Exemption Principles .......................................................................................43 6.3.3 State Aircraft ....................................................................................................43 6.3.4 Application of Exemptions ...............................................................................43 6.3.5 Impact on the Implementing Rule ....................................................................44

6.4 Minimum Equipment List (MEL) Policy Issues........................................................44 6.4.1 Data Link Equipment .......................................................................................44 6.4.2 Impact on the Implementing Rule ....................................................................44

7. IMPACT ASSESSMENT............................................................................................45 7.1 Stakeholders Affected.............................................................................................45 7.2 Economic and Efficiency Impact .............................................................................45 7.3 Safety Impact ..........................................................................................................46

7.3.1 Impact on the Implementing Rule ....................................................................47 7.4 Impact on Existing Rules and Standards ................................................................47 7.5 Recommendations ..................................................................................................48

8. OBJECTIVES AND SCOPE OF THE DRAFT IMPLEMENTING RULE....................49 8.1 Objective .................................................................................................................49 8.2 Scope......................................................................................................................49 8.3 Refinement of the Essential Requirements.............................................................49 8.4 Impact on the Implementing Rule ...........................................................................52

9. ARTICULATION OF THE DRAFT IMPLEMENTING RULE WITH EUROCONTROL SPECIFICATIONS.............................................................................................................53

10. OVERALL STRUCTURE OF THE DRAFT IMPLEMENTING RULE ........................55 10.1 Purpose...................................................................................................................55 10.2 Flexibility of the Implementing Rule ........................................................................55 10.3 Structure of the Implementing Rule ........................................................................56

11. CONCLUSIONS AND RECOMMENDATIONS..........................................................57 11.1 Regulatory Coverage ..............................................................................................57

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11.2 ECIP........................................................................................................................62

12. RESULTS OF THE FORMAL CONSULTATION.......................................................63 12.1 Formal consultation / workshop ..............................................................................63 12.2 Next Steps ..............................................................................................................65

13. REFERENCES...........................................................................................................66 13.1.1 Primary References influencing the Interoperability Analysis..........................66 13.1.2 Other Documents Referenced from the Text...................................................67 13.1.3 Other Background Documents ........................................................................68 13.1.4 Additional References for Data Link Recording...............................................71 13.1.5 Additional References for Airworthiness Certification and Operational Approval71

14. ABBREVIATIONS......................................................................................................72 14.1.1 General ............................................................................................................72 14.1.2 Data Link Services...........................................................................................74

ANNEXES Annex A Context and Relationships

Annex B Selection of Data Link Services

Annex C INTEROP and SPR Standards

Annex D Air-ground Communication Technology

Annex E Ground-ground Communication Technology

Annex F ATS Data Link Systems

Appendix 1: ATS Data Link Systems Description

Appendix 2: Data Link Applications

Appendix 3: System Profile Requirements

Annex G End-to-End Capacity, Performance and Security

Annex H Recording of Data Link Messages

Annex I Naming, Addressing and Registration Plan

Annex J Determination of Data Link Airspace

Annex K ATC Procedures for Using Data Link Services

Annex L Equipage, Certification and Approval

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EXECUTIVE SUMMARY In order to avoid fragmented deployment of air traffic services (ATS) supported by data link communications in the busy airspace of the European Air Traffic Management Network (EATMN), and to ensure interoperability of data link systems, constituents and procedures, the European Commission has issued a mandate for the development of an interoperability implementing rule on the provision and use of data link services, in the framework of the Single European Sky regulations. Without such an implementing rule, there is a risk that pilots and aircraft systems will not be able to gain access to seamless data link services, and stakeholder investment in the enabling data link technology may not produce the required ATM capacity and cost-effectiveness gains. The implementing rule is aimed at enabling the achievement of common performance levels, common data link services, standard operational concepts and contiguous coverage.

This regulatory approach document sets out proposals and supporting rationale for the regulatory coverage of the implementing rule, which have been formed from a detailed interoperability analysis and an analysis of safety aspects and implementation conditions. In particular, this document provides alternatives for how this regulatory coverage could be articulated in the implementing rule. A suggested outline structure, a recommended scope and associated objectives for the implementing rule are proposed for consideration.

The proposed regulatory coverage comprises the set of recommended subjects for prescription in the implementing rule, together with the nature of the prescriptions. The major recommendations for this regulatory coverage stem from the interoperability analysis, which started by conducting a ‘top down’ review of all potential data link services against a set of criteria based on operational requirements and safety and performance standards. From this process, an initial set of potentially suitable data link services was identified for further analysis. A ‘bottom up’ assessment of viable enabling technology with which to provide this set of services was then conducted, including air-ground and ground-ground technology, and end-to-end communication systems. From this pragmatic approach, the set of data link services was further refined and recommendations for a viable end-to-end communication system that could support the provision of these services were derived.

The resultant selection of data link services comprises the following Context Management and Controller Pilot Data Link Communications (CPDLC) point-to-point services:

• Data Link Initiation Capability (DLIC). • ATC Communication Management (ACM). • ATC Clearances (ACL). • ATC Microphone Check (AMC).

This is considered to be the initial set of mandatory data link services for the EATMN that could feasibly be covered by the implementing rule. The proposed implementing rule would not preclude the voluntary use of other data link services by stakeholders in local implementations, or expansion to prescribe other mandatory data link services in the future.

In terms of the regulatory coverage of the enabling technology needed to support these initial services, three possible alternatives for development of the implementing rule are identified. Under all three alternatives, the subjects for prescription would be the same but the extent and level to which the nature of the prescriptions is expressed in the implementing rule would differ. The proposed alternatives for consideration are:

Alternative 1: Development of an implementing rule that includes:

• Prescriptions for the interoperability and performance of data link applications, communications exchange mechanisms and air-ground communications link; these prescriptions are independent of any specific technology or standardised communication protocols.

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• Prescriptions identifying the means of compliance (MOC) with the above requirements.

Alternative 2: Development of an implementing rule that includes prescriptions of the interoperability and performance of data link applications, communications exchange mechanisms and air-ground communications link. These prescriptions are explicitly based on ICAO compliant Aeronautical Telecommunication Network (ATN) provisions using a VDL-2 air-ground subnetwork.

Alternative 3: As alternative 2, with, in addition, specific prescriptions will require that Air Navigation Service Providers (ANSPs) will support data link services with aircraft equipped with systems compliant with EUROCAE ED-100A (commonly known as Future Air Navigation Services (FANS) 1/A).

The first alternative for the regulatory approach is based on two complementary views:

• A view of the interoperability and performance of data link applications, communications exchange mechanisms and air-ground communications link independent from existing technical standards. This view favours the drafting of regulatory provisions with limited technical details.

• A view of the MOC for data link applications, communications exchange mechanisms and air-ground communications link. These MOC correspond to existing validated technology. The MOC are referred to and made mandatory by the implementing rule. The details are specified in a EUROCONTROL Specification, elaborated using the consultation mechanisms of the EUROCONTROL Regulatory and Advisory Framework (ERAF).

Alternative 1 could potentially open the door to two or more technical solutions, if alternative MOCs are identified in the future. Leaving airspace users the choice to implement one of these solutions will imply, in order to maintain interoperability, that ground systems have to implement all specified MOCs. The practical way to do it requires further investigation. More than one solution for communication exchange mechanisms and/or air-ground communication link could co-exist, each solution being compliant with the implementing rule requirements. However, the identification of MOCs within the implementing rule must allow for only a very limited number of MOCs, to avoid proliferation and fragmentation of air-ground communications solutions.

For the timeframe 2005 to 2015, the identified MOC are ATN CPDLC application (“Protected Mode” variant), ATN communication protocols and VDL-2 technology.

The second alternative for the regulatory approach is based on a single view of the interoperability and performance of data link applications, communications exchange mechanisms and air-ground communications link based on technical standards as validated by the EUROCONTROL-led LINK 2000+ Programme (Protected Mode CPDLC, ATN communication protocols, VDL-2). This approach leads to draft regulatory provisions including some level of technical detail. A EUROCONTROL Specification based on the LINK 2000+ specifications would be also necessary to support the implementing rule, ensuring end-to-end technical interoperability.

Cost-benefit analyses have indicated that either the first or the second alternative for the regulatory approach is expected to realise benefits of €1,714M for a cost of €191M.

The third alternative for the regulatory approach can be seen as an extension of the second one with prescriptions for the accommodation of ED-100A compliant aircraft. It would require ANSPs to make an additional investment at each air traffic control centre in order to implement the required communications ‘gateways’. Return for the extra investment should be assessed according to the geographical area concerned and should also consider the ultimate expansion of data link airspace retained by the implementing rule. There is ongoing

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work to assess the compliance of ED-100A with the relevant safety and performance requirements in continental airspace. The potential benefits of this alternative would include more rapid aircraft equipage rates and reduced controller training costs (through increased operational use leading to reduced refresher training needs).

Under each of the regulatory approach alternatives, exemptions for State aircraft are envisaged. However, as the number of flights made by State aircraft operating Instrument Flight Rules (IFR) as General Air Traffic (GAT) in the defined airspace is low compared to the total number of flights, these exemptions should not have an adverse impact on the realisation of the business case benefits of data link services for EATMN capacity and cost-effectiveness. It is also possible, in the first or second alternative, and subject to further investigation, that aircraft using ED-100A compliant services in oceanic/remote airspace regions may need to be exempted. Exempted aircraft would continue to be handled via voice communications. The exemption policy should be made consistent with that of the draft implementing rule on air-ground voice channel spacing.

Following stakeholders’ consultation, the Agency intends to proceed to the drafting of the implementing rule on data link services on the basis of the regulatory approach described in alternative 1, slightly amended on the basis of comments received. On the one hand, it clearly defines the level of requirements necessary for a safe and efficient implementation of data link services and it identifies the only technical means currently available for complying with the provisions of the rule. On the other hand, it leaves the door open for the development and possible recognition in the future of other MOCs.

The regulatory approach retained for the development of the draft implementing rule takes into account the results of the formal consultation conducted between 27 January and 27 March 2006, using the mechanisms of the EUROCONTROL Notice of Proposed Rule-Making (ENPRM) process.

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1. INTRODUCTION

1.1 Data Link Services Mandate Within the framework of the Single European Sky (SES) regulations, a mandate [6] has been issued to EUROCONTROL to assist the European Commission in the development of an interoperability implementing rule on Data Link Services.

The position of the Regulatory Approach with respect to the European Commission's mandate is examined in Annex A.

1.2 Document Purpose and Scope

1.2.1 Purpose The Regulatory Approach document is one of the deliverables required by the European Commission's mandate. It outlines the headlines of the regulatory provisions and identifies and analyses the subjects that shall be covered by the draft implementing rule in order to ensure the desired interoperability. It provides an outline of the draft implementing rule and key points of the impact and regulatory assessment. It also proposes several alternatives for the development of the implementing rule.

The document is now submitted for written consultation. Following the comments received from the stakeholders, one alternative or any suitable combination of them will be chosen as the basis for the development of the implementing rule.

1.2.2 Objective The objectives of the regulatory approach are:

• To clarify the objective and the scope of the implementing rule;

• To provide an interoperability analysis from the regulatory standpoint;

• To analyse different possible alternatives for the development of the draft implementing rule;

• To provide an analysis of the conformity assessment aspects;

• To propose an articulation between the implementing rule and its means of compliance;

• To define the overall structure of the draft implementing rule;

• To define an implementing rule which is extensible in allowing future evolution of enabling technologies whilst maintaining interoperability with systems compliant to earlier versions of the implementing rule.

• The implementing rule will also address relevant civil-military coordination aspects.

1.3 Development of the Regulatory Approach The regulatory approach document has been developed by the Implementing Rule Drafting Group set up by EUROCONTROL as described in the initial plan for the achievement of a draft implementing rule for interoperability concerning air-ground data link services.

Prior to submission to the European Commission, the regulatory approach will be the subject of a written consultation. On the basis of the regulatory approach retained, EUROCONTROL will develop the draft final report, which will include a first proposal for the draft implementing

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rule, the draft justification material and the draft identification of means of compliance. The draft implementing rule will be subjected to formal, widespread consultation. The outcome will be taken into account to amend the draft implementing rule before the Final Report is delivered to the European Commission.

A number of technical annexes provide more detailed information where deemed necessary to explain or substantiate the considerations in the body of the document.

1.4 Consultation to Date A preliminary questionnaire was distributed to focal points nominated by stakeholders during November 2005, the results of which were taken into account in the document submitted to formal consultation.

This formal consultation was conducted between 27 January and 27 March 2006, using the mechanisms of the EUROCONTROL Notice of Proposed Rule-Making (ENPRM) process.

2. BACKGROUND

Air-ground data link communication is increasingly being used for the efficient, accurate delivery of ATS to aircraft. Global interoperability of data link services is the ultimate goal, such that aircrew and aircraft systems will experience a seamless service not just within core Europe, but internationally. Hence the reliance upon global standards (ICAO Standards and Recommended Practices - SARPs, harmonised RTCA/EUROCAE specifications, etc.) is of prime importance.

2.1 What is a Data Link Service? A data link service can be defined (reference AGC-ORD-01 [10]) as:

"A set of related air traffic management transactions, both system supported and manual, which have a clearly defined operational goal and begin and end on an operational event."

The specification of data link services allows the ATM services provided via data link to be delimited, and facilitates the construction of safety assessments based on a well-defined and finite set of transactions. Each data link service has a specific purpose and performs its function according to a well-defined set of procedures using a specified set of air-ground data exchanges. Safety and performance requirements can then be derived for each individual data link service.

A brief description of each data link service under consideration is provided in Annex B. The list of data link services is consistent with public documents that have gained widespread industry acceptance, and with the data link services considered in the European Commission's roadmap study [20].

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3. INTEROPERABILITY ANALYSIS

3.1 Introduction

3.1.1 Objective and Scope The objective of this chapter is to record the results of the interoperability analysis part of the regulatory approach on data link services applicable to the continental EATMN airspace.

As noted in the ATM-CNS Interoperability Roadmap (AIR) report [21], section 3.3.1, the scope of interoperability in the context of the SES regulation is much wider than the narrow definition often employed in the information and communication technologies (ICT) sector, which is mainly concerned with the technical interworking of automated systems.

Interoperability in the EATMN includes the set of functional, technical and operational properties of the relevant systems and constituents, as well as operational procedures, in order to enable safe, seamless and efficient operation. Interoperability is achieved when systems and constituents comply with the Essential Requirements, refined as necessary by implementing rules.

The goal of the interoperability analysis is to identify and define the regulatory coverage of data link services suitable for the objective and the scope of the implementing rule. The regulatory coverage identifies all subjects for prescription, and the nature of the prescriptions.

The position of the interoperability analysis with respect to the Essential Requirements of the interoperability Regulation [5] is considered in section 8.3.

3.1.2 Interoperability Analysis Process The overall aim of the interoperability analysis is to:

• Identify a recommended regulatory coverage for a set of suitable data link services,

• Identify appropriate enabling data link technologies to support these services, and

• Assess the deployment of this enabling technology in the EATMN.

The analysis process employed is illustrated in Figure 1.

1. The initial step (shown at point ‘A1’ in Figure 1) employs a ‘top down’ approach to assess industry-recognised data link services against a set of criteria based primarily on operational requirements and safety and performance requirements (SPR) standards. This initial analysis is described in Annex B, which provides an overview of the principal data link services identified to date and assesses them from a high level operational perspective, including relationships to the air traffic management (ATM) operational process. The results of the analysis are summarised in section 3.2. From the analysis, an initial set of potentially suitable data link services is identified and carried forward to an assessment of associated and viable enabling technology.

2. A pragmatic ‘bottom up’ approach (shown at points ‘A2 and ‘A3’ in Figure 1) then assesses the suitability of candidate air-ground and ground-ground data link technology to support this initial selection of data link services in continental Europe at the present time. This analysis is described in Annexes D and E, which assess the properties of different link technologies, describe the selection criteria used and consider the necessity of some institutional principles for interconnection. The results of the analysis are summarised in section 3.3. From the analysis, recommendations for data link technology are identified and carried forward to the subsequent assessment of viable end-to-end communication systems.

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- A1 -Initial Selection of Data Link Services

- A4 -Assessment of end-to-endCommunication Systems

_________________________•ICAO ATN based system•FANS-1/A+ based system

- A3 -Assessment of Ground-Ground

Data Link Technology

- A2 -Assessment of Air-Ground

Data Link Technology

List of Data Link Services

Selected Data Link Services (Table B-11)

Subjects for prescription:

• Data Link Services

• Data Link Systems

Criteria DLS1…DLS3

Criteria AGL1…AGL7

Criteria GGL1…GGL3

Criteria SYS1…SYS11

•VDL-2•VDL-4•Military Data Link•…

VDL-2 Short term

Ground Network Organisational Principles

Figure 1. Interoperability Analysis Process

3. Based on the results of the above processes, a further step (shown at point A4 in Figure 1), is to assess alternatives for regulatory coverage of the viable end-to-end data link communication system to ensure interoperability between communications subsystems and supporting networks. This analysis is described in Annex F and its Appendices, where selection criteria applicable to actual systems (e.g. cost-benefit analyses, validated end-to-end performance) are employed. The results of the analysis are summarised in section 3.4. As a result of this analysis, a selection of viable data link services is made from the previous list of candidate services, and recommendations for the complete interoperable end-to-end communication system are obtained.

Data Link Services

Data Link Systems Subjects for Prescription[Deployment Conditions]

- A5 -Deployment in the EATMN

• Data Link Airspace

• Equipage of Aircraft and ATS Units

• Airworthiness and Operational Approval

• Data Link Recording

• ATC Procedures

• Spectrum Availability

• Naming, addressing and Registration

• Stakeholders’ responsibilities

Figure 2. Process for Analysis of Deployment Conditions

4. In parallel with the above process, a further step (shown as 'A5' in Figure 2) is to assess deployment conditions in the EATMN, to identify required subjects for prescription, together with the recommended nature of these prescriptions. This analysis is described in Annexes G – L and the results of the analysis are summarised in section 3.5. A list of conditions necessary for deployment of data link services within the EATMN is identified, including definition of the applicable airspace, criteria for prescribing minimum equipage of

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aircraft and ATS Units, certification / operational approval requirements, ATC procedures, spectrum planning, naming / addressing / registration and the obligations of stakeholders.

Step 1 is necessary but not sufficient to ensure the end-to-end interoperability of data link services. Steps 2 and 3 are necessary to ensure that interoperable technologies are selected for deployment. Note that no assumptions are made at this stage as to the level of detail of implementing rule prescriptions, or the articulation between implementing rule and supporting means of compliance.

3.1.3 Functional Architecture Figure 3 illustrates the assumed functional architecture for data link services.

The functional architecture represents the Interoperability Target. The diagram illustrates three system elements or "domains":

• The aircraft system element. Within this domain, the flight crew are responsible for applying defined data link communication procedures. They access the airborne communications end system by means of a human-machine interface (HMI) in the cockpit. In a more general scenario, automated systems in the aircraft could also interface to the communications end system. The communications end system then interfaces to one or more communication services.

• The ANSP system element. Within this domain, air traffic controllers are responsible for applying defined ATC procedures. They access the ground communications end system by means of a human-machine interface (HMI), typically integrated with the controller's work position. In a more general scenario, automated ATC systems could also interface to the communications end system. The communications end system then interfaces to one or more communication services.

• The Aeronautical Communications Service Provider (ACSP) element. The ACSP is responsible for conveying the data between the ANSP's ground system and the aircraft for which the ATS unit is responsible. The ACSP will typically have a network of radio transmitter/receiver sites controlled by an air-ground data link management function. The ACSP conveys data from the ANSP to the addressed aircraft ("uplinks") and conveys data from the aircraft to the appropriate ATS Unit ("downlinks"). The ACSP is a logical entity, whose functions may be performed by an ANSP or by one or more commercial organisations.

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Interfaceto commsservices

ANSP A-GData Link

Mgmt

“A”“B”

Aircraft System Element

Interface toCommunications

ServicesHMI

End System(Aircraft)

Flight Crew

ProceduresFlight Deck

HMI

End System(ATS Unit)

Controller

Procedures(ATS Unit)

End-to-endDialogue

“C”

ACSP Domain

G-GANSP

Interface

One or more interconnected ACSP networks

Figure 3. Data Link System Architecture

Three reference points are indicated in Figure 3:

• Reference point "A" is the ground interface between the ANSP system and the ACSP. This could for example be via the Pan-European Network Service (PENS) infrastructure discussed in section 3.3.2.

• Reference point "B" is the logical interface between the aircraft system and the ACSP

• Reference point "C" refers to the end-to-end interchange of data in a dialogue supporting the data link services.

These reference points are assumed throughout the interoperability analysis. The enabling technology for reference points "A" and "B" is assessed in section 3.3 below, while the data link services at reference point "C" are assessed in section 3.2 below. The necessary combination of elements to form a complete communications system with defined performance characteristics is considered in section 3.4, where candidate systems are assessed.

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3.2 Assessment of Data Link Services The purpose of the analysis in this section is to:

1. Propose a selection of data link services as candidates for regulatory coverage;

2. Provide recommendations about regulatory provisions addressing data link services.

Based on the ATM operational process defined in the Concept of Operations for 2011 [9], the analysis identifies which data link services are used in what types of airspace, and specifies criteria to ensure the interoperability of data link services within the EATMN.

3.2.1 Criteria for the Selection of Data Link Services To ensure end-to-end interoperability of data link services in the EATMN, it is necessary to achieve the implementation of a selection of validated, standardised data link services supported by a technology providing the required level of performance.

The initial step in the present analysis is to identify those data link services that have mature, validated operational requirements, and that have been analysed by a recognised organisation to determine their detailed SPR. The existence of a published SPR standard is a key prerequisite for the retention of a data link service as a candidate for prescription in the implementing rule.

The initial selection criteria are described in Annex B and may be summarised as shown in Table 1.

Table 1. Data Link Services Selection Criteria

Criterion Title

DLS1. Mature Operational Requirement

DLS2. Validated Operational Requirement

DLS3. SPR standard exists

3.2.2 Results of Initial Assessment The objectives of data link services selected for short-term implementation are threefold:

• To increase capacity and safety in en-route sectors with the automation of controller – pilot communications;

• To increase capacity and safety during ground movement of aircraft with the automation of controller – pilot communications;

• To increase capacity and safety with the automation of terminal information service.

Based on the analysis in Annex B, the data link services retained for further analysis are those whose operational safety and performance requirements are specified in EUROCAE standards ED-120 [4], ED-85A [33], ED-89A [34], and ED-106A [35].

However, operational data link services cannot be considered in isolation from the technology that supports their realisation. The selection of data link services for the regulatory coverage is therefore further refined in subsequent stages of this interoperability analysis.

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3.2.3 Statements of Issues At this stage of the analysis, the supporting communications mechanism (such as ATN and/or ACARS systems together with appropriate data link technology(ies)) has not been considered. The selected services could in principle be delivered over any medium that provides the appropriate safety and performance characteristics. The mapping to actual communication means is considered in chapter 3.4 below.

All of the candidate data link services identified in the European Commission roadmap for the implementation of data link services [20] and analysed in Annex B contribute to the improvement of the efficiency of ATS provision. The validation of these data link services requires coordination with many stakeholders with extensive trials, in pre-operational and operational conditions. Many of these data link services have not yet reached a sufficient level of maturity.

Implementation of the selected services requires changes to operating procedures and impacts the HMIs of aircraft systems and controller working positions.

3.2.4 Contribution to Interoperability To ensure seamless operation, a common set of data link services with internationally agreed operational requirements must be selected for implementation in the EATMN.

3.2.5 Impact on the Implementing Rule [IR-IAN-001] The selection of data link services should be a subject for prescription in the implementing rule.

The nature of prescription will be to specify an initial core set of services to ensure a basic level of interoperability, while not precluding the implementation of additional data link services by stakeholders, which may be the subject of later regulation.

It is foreseen that the nature of the prescriptions will be:

• The definition of data link services, based on recognised SPR standards for the airspace category in question (operating methods, safety requirements, performance requirements)

• The operational environment conditions for the provision and use of each of these services.

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3.3 Assessment of Data Link Technology This section aims to define the regulatory coverage relating to the enabling data link technology. The goal is to provide a rationale showing the appropriate technology choice for implementations in the timeframe 2005 - 2015.

In accordance with the European Commission’s mandate [6], the intention is to consider:

• Various technical alternatives with their strong and weak points particularly with respect to their capability to support current and foreseen ATM applications, including capacity of the link.

• Availability of spectrum (see section 3.5.5 - Spectrum Planning)

• Compatibility with existing civil air transport systems (e.g. non-interference with voice communications, SSR transponders, etc.)

• Compatibility with existing military data link systems.

3.3.1 Air-Ground Data Link Technology The purpose of the following analysis is to allow the choice of the air-ground data link technology to be justified:

• To propose an enabling technology for air-ground mobile data communications in the continental airspace.

• To provide recommendations about regulatory provisions addressing the air-ground data link technology supporting data link services.

The air-ground data link in this context means the Radio Frequency (RF) link between the aircraft and the ground station (at reference point "B" in Figure 3). This is one element of the end-to-end communications path, which is considered in section 3.4 below. At any given moment, a flight may be in contact (at the RF level) with zero, one or more ground stations, either directly or via communications satellite. A key function of the air-ground technology is to facilitate the transfer of the communication link as the flight moves between ground stations, such that a seamless data communication service is maintained, to the extent possible, given coverage constraints.

The features of various candidate air-ground data links are described in Annex D.

3.3.1.1 Criteria for Air-Ground Data Link Technology Selection To ensure interoperability between aircraft radio equipage and ground-based radio transmitter / receiver stations, possibly via an intermediate air/space link, it is necessary to achieve the implementation of a selection of validated communication standards supported by a technology providing the required level of performance.

The initial step in the present analysis is to recognise the significant results and consensus building achieved by the European Commission's data link roadmap study (2003) [20]. The findings of that study, together with recent updates, are summarised in Annex D.

The initial stage of "bottom up" selection merely identifies candidate data links with the potential to deliver data link services. The further step of selecting a technology with performance and deployment characteristics suitable for integration into the overall communication system is considered in section 3.4.

The initial selection criteria are described in Annex D and summarised in Table 2:

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Table 2. Air-Ground Data Link Technology Selection Criteria Criterion Title

AGL1. Existence of open, validated standards

AGL2 Retained by DL Roadmap Study

AGL3. Stakeholder support & deployment plans

AGL4. Spectrum planning & availability

AGL5. Geographical coverage

AGL6. Availability of certified products

AGL7. Actual performance & capacity

AGL8. Security Policy supported

3.3.1.2 Statement of Issues The European Commission roadmap study [20] concluded that there were two candidate paths for the data link roadmap up to 2020, the first based on VDL-2/Mode S/1090 Extended Squitter technologies and the alternative based on VDL-4.

For Step 1 of the ATM application roadmap (early air-ground ATM applications), it was concluded that the most appropriate data link technology for high and medium traffic density continental regions is VDL-2 and/or VDL-4, with the VDL-2 route being favoured by industry.

The roadmap report noted that the VDL-2 and VDL-4 scenarios were not necessarily mutually exclusive. For example, general aviation users might not be required to equip with VDL-2, assuming that only about 75% rate of equipage is required for applications in Step 1 of the roadmap to deliver significant benefits.

3.3.1.3 Results of Initial Assessment As it has been demonstrated to have the capability of meeting the performance and capacity requirements (see Annex D), and it satisfies the selection criteria identified above, VDL-2 is recommended as the preferred air-ground data link technology to support the selected data link services.

The baseline standard for VDL-2 is ARINC Specification 631 [62], which in turn references the ICAO VDL SARPs [60] and the ICAO Manual on VHF Digital Link Mode 2 (Doc. 9776) [61]. The profile requirements for the use of VDL-2 for current operational ATM systems in Europe are specified in [15]; note that these deviate slightly from the provisions of ARINC 631. This highlights the need for a baseline specification as part of the regulatory approach.

Existing military data links play a major role in conducting military operations; but they do not feature any specific ATM functions enabling civil-military interoperability. Identified options to foster interoperability have not been progressed. It could be envisaged that military aircraft, as well as other State aircraft, flying as IFR/GAT in airspace covered by the data link services implementing rule may be exempted from the requirements for data link communication capability. However, this is still a subject for discussion.

3.3.1.4 Contribution to Interoperability At least one air-ground data link technology must be prescribed, and any prescribed technology must be available in all airspace within the scope of the implementing rule. If this were not the case, it would be possible to equip an aircraft with an otherwise compliant air-ground data link technology but it would not be able to interoperate with the responsible ANSP.

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Avionics will not necessarily support all available air-ground data link technologies. Aircraft operators (AOs) will select the most cost-effective product that uses the desired ACSP air-ground communications service(s), and which is available for use and meets the interoperability requirements of the implementing rule.

An avionics system must, however, meet the interoperability requirements for the air-ground communications service(s) it supports.

For the interoperability of data link communications in the EATMN, a point-to-point air-ground mobile transmission data link must demonstrate the potential to:

• Meet the assumed performance requirements typical of ATS data link services;

• Meet the capacity requirements for the operation of all data link services in the data link airspace.

It must also comply with a standardised protocol for handling the mobility requirements and the transmission of data. This protocol must not hamper the airworthiness certification of communication equipment.

It should be noted that while the implementing rule must prescribe an air-ground data link technology to support the selected data link services, future regulations may additionally permit the use of alternative technologies that also meet the selection criteria.

3.3.1.5 Impact on the Implementing Rule [IR-IAN-002] The air-ground data link technology should be a subject for prescription in the implementing rule.

It is foreseen that the nature of prescriptions will be:

• The air-ground data link technology prescription should specify minimum performance and capacity requirements for a validated point-to-point data link conformant with current standards and interoperable with current products and services.

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3.3.2 Ground-Ground Data Link Technology

The purpose of the analysis is to identify an appropriate level of prescription for the ground communication mechanism. The features of various candidate ground-ground technologies are described in Annex E.

3.3.2.1 Criteria for Ground-Ground Data Link Technology Selection The initial selection criteria are described in Annex E, and are summarised in Table 3:

Table 3. Ground-Ground Data Link Selection Criteria

Criterion Title

GGL1. Existence of open, validated standards

GGL2. Consistent with DL Roadmap Study

GGL3. Stakeholder support and deployment plans

GGL4. Capacity planning & availability

GGL5. Geographical coverage

GGL6. Availability of approved products

GGL7. Actual Performance & capacity

GGL8. Security Policy supported

3.3.2.2 Statement of Issues The ground connection deployed to support air-ground communication is not necessarily the same as the ground-ground network that interconnects ANSPs for flight data exchange.

The approach adopted by European ANSPs will be to use IP-based networks for international ground-ground communication (EATM Communications Strategy [28]). However, a pan-European IP network is still in the early planning stages.

In the general case where a commercial ACSP provides the air-ground service (the ACSP domain in Figure 3), the ACSP will also operate an internal ground network both for the interconnection of radio transmitter sites and for interconnections with aircraft operators, ANSPs and other ACSPs. The internal technology and structure of the ACSP ground network is a matter internal to the ACSP. The actual capacity and performance will require careful monitoring to ensure that the allocated performance requirements are consistently met. The required capacity and performance should be specified in a service level agreement (SLA).

ACSPs providing air-ground data link services in the EATMN will be required to interconnect their data networks. This issue, and the related institutional principles, is discussed in detail in Annex E, and will be further investigated during the drafting of the implementing rule.

3.3.2.3 Results of Initial Assessment The preferred ground-ground technology is an IP-based network that is planned to evolve to become part of the emerging Pan-European Network Service (PENS). However, it is not proposed that this should be prescribed in the implementing rule. Rather, the technology employed for the ground segment of the end-to-end data link should be left as a local matter between ANSP and ACSP, provided that the allocated safety and performance requirements are demonstrably achieved, and an effective security policy is in place.

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3.3.2.4 Contribution to Interoperability The ground-ground data link is an essential infrastructure component of the overall communications system. It is fixed in nature (cf. the ICAO Annex 10 Aeronautical Fixed Service), in that the end points of the communication are relatively static. There are not considered to be any major issues that would impede seamless operation across the EATMN. It must demonstrably and continually satisfy performance requirements in terms of maximum latency, integrity, availability and continuity of function.

3.3.2.5 Impact on the Implementing Rule [IR-IAN-003] The actual technology employed by ANSPs and ACSPs to achieve ground-ground communication should not be a subject for prescription in the implementing rule.

Note: This is in contrast to the air-ground environment, where prescription is required in order to ensure that the data link technology employed in the aircraft is compatible with one or more ACSP systems throughout the region of applicability.

However, the ground-ground subnetwork will have to meet requirements for security and quality of service (e.g. availability, integrity, etc.) to qualify as a suitable communication means. The minimum performance and interconnection requirements should be addressed by the implementing rule.

The nature of prescriptions should therefore address the following items:

• Interoperability of interconnections (obligations for ACSPs and ANSPs to satisfy common institutional principles – see Annex E);

• Basic quality of service and performance (including SLA requirements);

• Requirements on application of appropriate security policy.

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3.4 Assessment of End-to-End Communication System The purpose of the analysis in this section is to justify the selection of elements that together form a viable data link communication system providing the selected data link services.

The goal is to provide a rationale showing that capacity and performance of the proposed system matches the needs of data link services (at reference point "C" in Figure 3) deployed and operated in a given airspace with a population of equipped aircraft.

The detailed analysis is described in Annex F.

3.4.1 Criteria for the Selection of End to End Communication Systems The general principle for selection of one or more end-to-end communication systems is “to provide maximum gain for minimum pain”. This is a pragmatic approach that recognises the difficulties of migrating ground ATM systems to support new concepts, and of retrofitting new avionics to existing aircraft.

The criteria summarised in Table 4 are used to select an appropriate package of data link services and supporting technology as subjects for the regulatory coverage. The criteria are explained and justified in Annex F.

Table 4. Communications System Selection Criteria

Criterion Title

SYS1. Based on open standards

SYS2. Complete profile specified

SYS3. Validation

SYS4. Stakeholder support

SYS5. Operational approval / experience

SYS6. Interoperability demonstrable

SYS7. Business Case

SYS8. Extensibility

SYS9. Concept of Operation

SYS10. SPR satisfied

SYS11. Impartiality

3.4.2 Statement of Issues ATN applications and protocols are specified by ICAO, and invoked by the Annex 10 SARPs [1]. However, industry has independently developed CNS/ATM functionality based on ACARS messaging (commonly called the FANS-1/A system), which is in widespread use in low-density airspace. While functionally similar, the two systems are not interoperable at the technical level.

Interoperability requirements for “ATN Baseline 1” are specified in the INTEROP specification ED-110A, and FANS-1/A interoperability requirements are specified in ED-100A. Safety and performance requirements (SPR) for ATS data link services in continental airspace are specified in the SPR standard ED-120.

The INTEROP specification ED-100 (Interoperability Requirements for ATS Applications using ARINC 622 Data Communications) has been revised as ED-100A, partly to address concerns regarding the possibility of expired clearances being executed. Systems

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implementing the original ED-100 requirements are not recommended for the regulatory coverage. However, some aircraft systems now comply with ED-100A (some new aircraft, and an optional retrofit) and could be considered within the scope of the coverage, provided that ED-120 [4] safety requirements are satisfied. This is a subject of ongoing study.

Meanwhile, military aircraft are equipped with tactical data link systems, which are not interoperable with civilian ATS data link systems. Some military aircraft are also equipped with ED-100 compliant data links. Taken together with the low proportion of military aircraft flying under civil control1, it is likely that military flights will be exempted from the provisions of the implementing rule.

Neither the ICAO ATN provisions nor the ACARS messaging system specifies data link services to the granularity believed necessary to achieve operational approval for the use of profile-changing messages in high-density continental airspace. This level of granularity is generally achieved in INTEROP and SPR specifications.

The EUROCONTROL LINK 2000+ Baseline 1 specification [15] is a complete “profile” for an ICAO-compliant continental data link system that satisfies ED-120 SPR. This specifies the relevant options, subsets and combinations of standards and imposes additional constraints shown to be necessary from operational experience.

The LINK 2000+ Baseline requires use of the "protected mode" of the ATN CPDLC application (“PM-CPDLC”), which was included in the ICAO ATN specifications to provide an appropriate level of mitigation for some of the hazards identified in ED-120 SPR. This includes an integrity check in every CPDLC message, providing additional protection against loss of data integrity and mis-delivery by the communication system. The support and use of "standard mode" CPDLC, which lacks the additional integrity check mechanism, is deprecated.

Some data link services (DCL and D-ATIS at several European airports, OCL for North Atlantic oceanic clearances) are already operational using ACARS as the communication exchange mechanism. This is dependent upon the aircraft operator equipping for ACARS and subscribing to a commercial provider of the ACARS service. Based on initial stakeholder feedback, and noting the emphasis in the initial implementing rule mandate on en-route controller-pilot communications in continental airspace, these services are not proposed for prescription in the current implementing rule. Data link services in lower airspace and terminal areas are based on different technical and operational requirements and operational concepts, compared to en route services. However, they may be the subject of a future implementing rule and meanwhile are not excluded by the current implementing rule.

3.4.3 Recommended Selection of End to End Communication System Based on the detailed analysis in Annex F, the following data link services are recommended for inclusion in the regulatory coverage, in compliance with EUROCAE documents ED-110A (modified for PM-CPDLC) and ED-120.

a) Data Link Initiation Capability (DLIC)

b) Data link services for ATC communications (without voice read back):

• ATC Communication Management (ACM)

• ATC Clearances (ACL)

• ATC Microphone Check (AMC)

1 Note that Article 1.2 of the Framework Regulation expressly provides that the SES Regulations and the implementing rules do not cover military operations and training. For military aircraft and other State aircraft, the regulatory approach considerations are only applicable to IFR/GAT flights.

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In order to ensure interoperability of critical ATS services in the core European area, these data link services should be based on the complete technical specification of a validated communications service, deployed over a validated complementary air-ground data link service. The specification should refer to the applicable set of established standards, including any additional constraints, subsets and divergences.

3.4.4 Contribution to Interoperability If an end-to-end communication system were not prescribed, there would be the potential for non-interoperable implementations (e.g. a mixture of different ATN profiles, or ATN and ED-100/ED-100A FANS-1/A, ACARS/AOA implementations).

The selection of common communication formats and protocols ensures seamless interoperability between elements of the end-to-end communications system.

From a harmonised, common baseline, it will be possible to build future end-to-end communication systems embodying the Essential Requirement of support for new concepts of operation.

3.4.5 Impact on the Implementing Rule The overall goal of convergence between ED-100A (FANS-1/A) compliant and ED-110A (ATN) systems should be encouraged. Meanwhile, the issues of coexistence of the two systems should be addressed. The resulting options for the regulatory coverage are considered in section 4 below.

[IR-IAN-004] The high level specification of a complete communication system should be the subject of prescription in the implementing rule.

The nature of prescriptions should address the following items:

a) Prescription of the data link services DLIC, ACL, ACM and AMC. (Not excluding the optional implementation of DCL, D-ATIS and OCL and other future data link services).

b) The definition of the selected end-to-end communication system:

• Basic functions offered to data link applications

• Basic functions to manage communications, send and receive data messages

• Basic quality of service and performance of communication exchange mechanisms

• Statements of security policy (appropriate for the communication exchange mechanisms).

c) Data link communications capacity and performance for a flight in en-route conditions. Capacity and performance indicators must be verifiable.

[MOC-IAN-001] A detailed and precise specification of an end-to-end communication systems profile is recommended for the achievement of technical interoperability. Such detailed specifications may be more appropriate as means of compliance rather than being embodied in the implementing rule.

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3.5 Assessment of Deployment Conditions in the EATMN This section aims at defining which subjects relating to the deployment conditions in the EATMN must be covered by the implementing rule. The assessment is broken-down into different items; the following subsections cover the regulatory approach and a summary of the issues for each item. Separate Annexes contain the detailed considerations.

3.5.1 Determination of Data Link Airspace The purpose of the analysis in this section is:

1. To investigate the area of application of the implementing rule in terms of airspace in which data link services are operated.

2. To provide recommendations about regulatory provisions addressing data link airspace2.

Further considerations relating to airspace in which data link services are operated are developed in Annex J.

3.5.1.1 Statement of Issues The deployment of data link services in the EATMN airspace faces the following issues:

• How to identify the EATMN airspace in which data link services are operated?

• How to mandate the area of application of data link services in terms of airspace in the implementing rule?

The traffic forecast for the period 2005-2011 indicates an average annual growth of at least 3.7% of IFR movements. ANSPs and airspace users must determine the appropriate operational and technical resources to support this growth forecast at an affordable cost for all stakeholders.

Data link services have been proven to enable increased capacity by decreasing the controller workload. The benefits of current data link services are most significant in airspace environments experiencing communications congestion between pilots and controllers. The level of traffic in terms of number of flights is not a significant indicator for the application of data link services.

A two-step approach is proposed:

Step 1: Identification of data link airspace. This will be conducted during the drafting of the implementing rule according to the following main lines:

• Application of communications status indicators, traffic metrics, airspace structure to the EATMN airspace leading to commentary on the opportunity to implement data link services in correlation with these indicators and metrics;

• Conduct an inquiry to get ANSPs' proposals on the data link airspace;

• Consolidation of results stemming from the application of communications indicators and traffic metrics, and ANSPs' proposals to form the data link airspace, avoiding discontinuity of data link service for flights once entered in the data link airspace, in order to maintain seamless operations.

For the long term, data link services should be deployed on a large-scale basis in the EATMN airspace. A phased approach of the deployment of data link services in the

2 Note that Community law (e.g. Regulations and related implementing rules) applies within the limits of the territorial applicability of the Treaty establishing the European Community.

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EATMN airspace is envisaged, ensuring seamless operations to flights at each phase of the deployment.

Step 2: Determine the appropriate level of prescription for the implementing rule. The following alternative approaches may be considered for these prescriptions:

Table 5. Possible approaches to airspace prescriptions

Case Implementing Rule EUROCONTROL Specification3

1 Geographic coverage is explicitly mandated in accordance with the result of the Step 1 airspace identification process. All airspace elements where data link services are operated are named (list of FIRs, UIRs, sectors, etc…).

Not required.

2 The geographic coverage is not explicitly specified. Instead, specific criteria are defined (based on upper/lower airspace, traffic load, traffic complexity, etc.). The application of these criteria to the overall EATMN airspace will determine the data link airspace. It should be in line with the result of the Step 1 identification process.

Defines the data link airspace, ensuring compliance with the requirements of the implementing rule.

3 No specific criteria are specified. The area of application makes direct reference to a EUROCONTROL Specification defining the data link airspace.

Geographic coverage is explicitly defined in accordance with the result of the Step 1 identification process. All airspace elements where data link services are operated are named (list of FIRs, UIRs, sectors, etc…) in a EUROCONTROL Specification.

Note 1: In cases 2 and 3, the geographic coverage of data link services can be updated by a new release of the EUROCONTROL Specification, without modifying the implementing rule.

Note 2: In case 1, there is the risk that any re-sectorisation or modification of FIRs would necessitate a modification to the implementing rule. Also, some FIRs do not align with continental airspace.

3.5.1.2 Contribution to interoperability To ensure the coordinated introduction of seamless data link services in the EATMN, the airspace for the provision and use of data link services must be addressed by the implementing rule.

3.5.1.3 Impact on the Implementing Rule [IR-IAN-005] The airspace in which data link services are operated should be a subject for prescription in the implementing rule.

3 EUROCONTROL Specification elaborated using the consultation mechanisms of the EUROCONTROL Regulatory and Advisory Framework (ERAF) http://www.eurocontrol.int/ru/public/standard_page/framework.html.

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The nature of prescription will be further investigated during the drafting of the implementing rule. The prescriptions specifying the area of application in the EATMN airspace could be specified as one or more of the three cases identified in Table 5:

These prescriptions may specify a progressive deployment of the selected data link services in the EATMN airspace, starting with a “core” area and expanding in defined stages.

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3.5.2 Criteria for Mandatory Equipage of Aircraft and ATS Units This section is concerned with the determination of criteria for mandatory equipage of aircraft and area control centres. The purpose of the analysis is:

1. To propose criteria applicable to aircraft and ATS Units for mandatory equipage with data link capability.

2. To provide recommendations about regulatory provisions addressing these criteria.

3.5.2.1 Statement of Issues In order to realise the capacity increase potential offered by data link services, it is essential that a large proportion of aircraft in the applicable airspace are equipped and make use of data link services.

The maximum benefits would be obtained if all aircraft in the designated airspace utilised data link services. However, it must be recognised that it is not practicable to require complete equipage from Day 1 of the regulation.

A large number of long range aircraft are already equipped for ED-100 (FANS-1/A) data link operations, and many have ED100A compliant systems to mitigate a hazard associated with message latency. It is not realistic to expect such aircraft to equip with an alternative data link package in the short term, but a longer term transition might be foreseen. FANS services are increasingly being offered in oceanic and low-density airspaces around the world, and long range aircraft operators operating in these regions will continue to demand equipage to use such services.

There are certain categories of aircraft for which data link equipage would be inappropriate or prohibitive, such as aircraft reaching the end of their life, aircraft very rarely in the affected airspace, etc.

In previous assessments undertaken by EUROCONTROL, it was recommended that the implementing rule should apply to operators of aircraft with a certificated maximum take-off mass (MTOM) between specified upper and lower limits4, and operating Instrument Flight Rules (IFR) flights as General Air Traffic (GAT) in the defined airspace.

It was further recommended that the implementing rule should not apply to

a) Aircraft using FANS-1/A (ED-100 or ED-100A) functionality where the operator intends to operate those aircraft in airspace controlled by ANSPs utilising FANS-1/A systems and capabilities, and provided that those ANSPs accept the use of that equipment by that aircraft operator. The derogation being reviewed periodically (e.g. annually).

b) State aircraft;

c) Aircraft that will cease operating within the defined airspace, or with an out of service date before a certain date, the date to be determined during detailed consultations.

The relevance of these criteria will be further reviewed during the drafting of the implementing rule. Exemption cases for aircraft must be clearly defined. Exemption policy principles are investigated in 6.3 below.

Conversely, in order to realise the capacity increase potential offered by data link services, it is essential that a large proportion of ATS Units are equipped and provide seamless data link services over a large contiguous airspace.

4 MTOM is one example of criteria that could be used when specifying the applicability. This point will be further investigated during the development of the implementing rule.

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The requirements for equipage of ATS Units depends upon the applicable airspace, considered in section 3.5.1 above. For ATS Units for which it is applicable, the equipage requirements will be to:

• Upgrade controller HMI/FDP systems to access data link services;

• Procure the ground communications end system (see Figure 3);

• Provide the interface to the selected ACSP.

3.5.2.2 Contribution to the Achievement of Interoperability The Essential Requirement to support new concepts of operation will not be realised until a significant proportion of aircraft and ATS Units are equipped with interoperable data link capability.

Note that carriage of VDL-2 radio equipment also enables "ACARS-over-AVLC" (AOA) for AOC communication and airport/TMA ATS applications.

3.5.2.3 Impact on the Implementing Rule

[IR-IAN-006] The definition of applicable aircraft categories and ATS Units should be a subject for prescription in the implementing rule.

The nature of prescription for aircraft will be concerned with the mandatory carriage of equipment meeting applicable interoperability and performance requirements to support the specified ATS data link services via specified communications exchange mechanism.

The nature of prescription will also be to specify the aircraft categories to which the provisions of the implementing rule will apply, together with relevant transition period(s).

The nature of prescription for ground systems will be concerned with the mandatory implementation at ATS Units of equipment and software supporting ATS data link services via a specified communications exchange mechanism. This will be linked to the specification of applicable airspace discussed in 3.5.1 above.

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3.5.3 Airworthiness Certification and Operational Approval The purpose of the analysis in this section is:

1. To review available materials relating to airworthiness certification and operational approval of data link systems.

2. To provide recommendations about potential impact on the implementing rule.

3.5.3.1 Statements of Issues

The selected data link services are supported by multi-segment data link systems including aircraft systems, ground systems and air-ground communication systems (see Figure 3). The specification of a comprehensive set of interoperability, safety and performance requirements (ED-110A [3] and ED 120 [4]) for CPDLC data link services has been driven in accordance with the ED-78A [11] method defined by RTCA/EUROCAE. The end-to-end interoperability and safety aspects have been duly taken on board during the requirements specification for data link systems.

These RTCA/EUROCAE standards need to be supplemented by specific materials to align with the concept of operations of data link services in each local operational environment.

In the case of the ACL service, for example, the EUROCAE documents specify a wide range of CPDLC message elements. Only a subset of these may be required in a given operational environment (e.g. LINK 2000+ Baseline 1 [15] specifies support of some message elements as mandatory and some as optional). If the operational concepts of different ANSPs require support of different subsets of optional elements, then the Essential Requirement of seamless operation may not be achieved, unless a common core of functions is supported.

The issue is to find out the right balance between the flexibility given to ANSPs operating in a particular operational context and the objective of global end-to-end interoperability.

Notice of Proposed Amendment (NPA) No 11/2005 includes AMC 20-11 "Acceptable means of compliance for the approval of use of initial services for air-ground data link in continental airspace." The closing date for comments was 16th January 2006. AMC 20-11 includes data link services DLIC, ACM, ACL, AMC, DCL, DSC and D-ATIS, compliant with EUROCAE ED-110A and ED-120. It will be reviewed when standards are frozen. An EASA Comment Review Document (CRD) has been created to support the review process,

EASA AMC-20 will define a means of compliance for aircraft type design approval and operational approval. The interoperability implementing rule will mandate the equipage of specific aircraft categories with data link capability. For those aircraft, airworthiness certification and operational approval can (should) be carried out by applying materials published in AMC-20. The AMC should address the same set of data link services as the implementing rule and make reference to the same technical standards. In due course, proper alignment should be ensured.

Mechanisms for the verification of compliance of ground systems are less well established. This point is addressed under Conformity Assessment Analysis in chapter 5 below.

3.5.3.2 Contribution to interoperability The advisory materials developed by the JAA CNS/ATM steering group will be used to define the appropriate means of compliance published in AMC-20.

These advisory materials make reference to relevant ICAO and EUROCAE technical standards reducing the risk of inconsistency between multiple sources of specifications. For the development of interoperability implementing rules addressing air-ground systems, it is

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deemed necessary to define a coordinated review process of materials to be included into an amended version of AMC-20 when the content of the implementing rule is clear.

Note that coordination mechanisms have been implemented between EUROCONTROL and JAA and EASA.

3.5.3.3 Impact on the implementing rule [IR-IAN-007] Airworthiness certification aspects are not subjects for prescription in the implementing rule.

Operational approval aspects for aircraft systems are not subjects for prescription in the implementing rule.

[JM-IAN-001] The justification material associated with the draft implementing rule should address the advisory materials used for certification airworthiness and operational approval:

• To verify the consistency between these advisory materials and the implementing rule

• To propose any required amendments of these advisory materials

• To propose a coordinated review process for the review of AMC material relating to data link.

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3.5.4 ATC Procedures for using Data Link Services The purpose of the analysis in this section is:

1. To review available materials relating to the ATC procedures applicable to ATS supported by the selected data link services.


The collection of ATC procedures extracted from ICAO documents and elsewhere is considered in Annex K of this document.

3.5.4.1 Statement of Issues ATC Procedures for the use of selected data link services (DLIC, ACL, ACM, AMC) are contained in the ICAO documents: Doc 4444 – PANS-ATM [23], and Annex 10 – Aeronautical Communications, Volume 2 – Communication Procedures, including those with PANS status [87]. These ICAO documents have a global applicability and each State is required to follow the ATC procedures in them. Any deviations from ICAO procedures will have to be published in the local AIP.

Following experience gained during the first steps of operations of CPDLC data link services, further refinements of ATC procedures have been drafted. These complementary materials are under scrutiny for potential integration into ICAO documents.

The enforcement of harmonised ATC procedures applicable to ATS supported by the selected data link services is necessary to ensure seamless operation and interoperability in the EATMN.

3.5.4.2 Contribution to Interoperability The Essential Requirement “seamless operation” is a network-wide requirement applicable to all ATM systems of the EATMN.

To ensure seamless operations of data link services, the implementing rule must mandate the applicable ATC procedures in terms of objectives, “WHAT HAS TO BE PERFORMED” by operational actors. The details of ATC procedures, how to achieve these objectives must be defined in a means of compliance.

3.5.4.3 Impact on the Implementing Rule [IR-IAN-008] ATC procedures applicable to the selected data link services are a subject for prescription in the implementing rule.

The nature of prescriptions should specify the basic principles for the use of the selected data link services supporting ATS:

• Co-existence of voice and data communications;

• Use in the context of non-time critical communications;

• Use at the discretion of the controller / pilot;

• Controlled flight under the control of only one ATC unit.

[MOC-IAN-002] The details of harmonised procedures for the following events should be defined and managed in an appropriate means of compliance:

• Construction of CPDLC messages,

• Responding to CPDLC messages,

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• Reverting from CPDLC to voice communications (including the ATC Phraseologies Related to the Use of CPDLC),

• Synchronisation of the CPDLC dialogue when reverting to voice communications,

• Use of CPDLC in the event of voice radio communication failure,

• Transfer of CPDLC,

• Intentional shutdown and testing of CPDLC,

• Failure of CPDLC equipment.

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3.5.5 Spectrum Planning This section is concerned with VHF spectrum planning issues arising from deployment of data link services in Europe. The purpose of the analysis is:

1. To analyse the requirements for VHF spectrum assignments to ensure global interoperability of airborne RF systems.

2. To identify relevant organisations and standards to ensure that the required VHF frequencies will be available for the foreseeable future.


The detailed results of the analysis are included in Annex D.

3.5.5.1 Statement of Issues VDL frequency channel assignments have to be coordinated between the various national bodies responsible for allocating access to the aeronautical radio spectrum, and have to fit within the aeronautical radio spectrum allocated by the ITU World Radiocommunication Conference (WRC-07 takes place 15 October - 9 November 2007).

ICAO Frequency Management Group (FMG) EUR is the ICAO regional planning subgroup managing allocations in the VHF aeronautical band in Europe. National bodies responsible for allocating access to the aeronautical radio spectrum should implement the progressive VDL sub-band deployment plan in each State (according to the recommendation of ICAO FMG EUR) in order to guarantee that VHF capacity will be available as required, in accordance with air traffic and data traffic growth projections.

Based on current plans and simulation results, a single VHF channel will be sufficient for VDL-2 operation until 2006-08. After that, provision will have to be made in air and ground radio systems for the seamless use of more than one VHF channel. According to current frequency assignment plans, 4 channels will be available for VDL-2 by 2010, so on current forecasts there should be adequate VDL-2 capacity to support currently defined data link services until well beyond 2014. Further studies are required to confirm that VDL-2 capacity will be sufficient to meet the requirements for 2020 and beyond.

RF equipment must be able to utilise the assigned frequencies effectively. For example, in the case of VDL-2, ACSPs and avionics manufacturers should implement the standardised auto-tune function which will soon be revisited in view of VDL-2 multi-channel deployment.

3.5.5.2 Contribution to the Achievement of Interoperability Deployment of VDL channels according to the ICAO FMG EUR sub-band plan ensures a common phased approach between ACSPs and avionics. Implementation of the frequency plan as specified guarantees interoperability at the RF level while ensuring that interference is limited to a tolerable level, and maintaining compatibility with regulations for 8.33 kHz voice channels.

Coordinated introduction of auto-tune functionality in air and ground radio systems will allow a seamless transition to multi-channel operation in the near future.

3.5.5.3 Impact on the Implementing Rule [IR-IAN-009] The VDL implementation requirements that will guarantee capacity and thus quality of data-link services should be a subject for prescription in the implementing rule.

The nature of the prescriptions will include:

• Obligations on National Bodies to implement the ICAO regional VDL sub-band deployment plan [67]

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• Obligations on RF equipment suppliers and users to utilise the assigned frequencies effectively.

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3.5.6 Naming, Addressing and Registration Plan The purpose of the analysis in this section is to analyse issues relating to the 24-bit aircraft address and addressing plan, to propose solutions to the issues, and to provide recommendations about potential impacts on the implementing rule.

Further discussion of naming, addressing and registration can be found in Annex I.

3.5.6.1 Statements of Issues ICAO Annex 10 (Volume III, Part 1, Chapter 9) requires that civil aircraft be assigned unique 24-bit aircraft addresses. These addresses are used for technical addressing in the ATN, as well as for various other purposes. However, there are known issues with the assignment and management of 24-bit aircraft address space. The issues, which are currently under investigation elsewhere, include not setting the correct digits in the transponder on delivery or after maintenance, and not re-assigning the address when an aircraft is re-registered with a different State.

From a civil-military interoperability viewpoint, the use of 24-bit addresses can cause problems if ground ATC systems need to know the 24-bit aircraft address in advance, rather than discovering it when the aircraft communicates. This is due to the dynamic nature of the use of addresses in military aircraft.

The LINK 2000+ Programme has identified the need for ANSPs to possess foreknowledge of the 24-bit aircraft address of a flight, to allow independent verification that the correct flight is in communication. This implies that aircraft operators must disseminate the 24-bit aircraft address via the flight planning process. ANSP systems must then correlate the downlinked aircraft address with the expected address. There is therefore an impact on ANSPs and aircraft operators, and interoperability will fail if the correct information is not available.

The communication initiator must be able to obtain the transport address of the recipient for communication to be possible. Aircraft systems need to be configured with the correct network addresses of the ANSP's ground systems with which they initiate communication. Ground facility address registration and publication is therefore required.

3.5.6.2 Contribution to Interoperability A consistent naming and addressing framework is a prerequisite for interoperability at the most basic technical level.

3.5.6.3 Impact on the Implementing Rule [IR-IAN-010] Naming, addressing and registration requirements should be a subject for prescription in the implementing rule:

The nature of prescription should address the following items:

• The need to assign a unique 24-bit aircraft address to every aircraft. (Note that this is a common requirement for many different ATS applications and may be appropriately a subject for a separate implementing rule).

• The need for the safety case for each system to consider the known issues associated with aircraft and flight identification.

• The need for ground facility address registration and publication.

[JM-IAN-002] The registration facility and obligations of different stakeholders with respect to assigning and managing elements of the global address space should be considered in the justification

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material associated to the implementing rule, as there is currently no identified need for mandatory prescriptions in this area.

The justification material should also consider procedures for an aircraft entering operation or restarting operations after a maintenance period to ensure that the aircraft identification is correctly entered or restored.

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3.5.7 Obligations of Stakeholders The purpose of the analysis is:

1. To outline obligations assumed by ANSPs, airspace users, air-ground communication providers for the implementation of data link services.


The goal is to identify obligations applicable to ANSPs, airspace users, and air-ground communication service providers to be turned into regulatory requirements for the implementing rule.

3.5.7.1 Statement of issues The deployment of data link services in the EATMN must be coordinated to achieve the expected operational benefits of data link services.

To ensure the coordinated deployment of data link services in the EATMN, the responsibility of each stakeholder must be outlined in the implementing rule. Stakeholders’ responsibilities must be properly balanced to avoid over-prescriptions for specific stakeholders.

ANSPs’ responsibilities should be outlined in the following areas:

• Deployment of data link systems in appropriate ATS Units

• Integration of data link systems with flight data processing systems and controller HMI

• Interconnection and service level agreements with one or more ACSP

• Training and qualification of controller and maintenance staff (with reference to ESARR 5 – ATM Services' Personnel [46])

• Management of airspace users’ documentation containing information on the provision and use of data link services

• Safety assessment

• Conformity assessment.

Aircraft Operator responsibility should be outlined in the following areas:

• Equipage of subject aircraft with data link capability

• Integration of data link systems with aircraft systems and cockpit HMI

• Training and qualification of aircrew staff

• Management of flight crew manual

• Conformity assessment of airborne constituents.

Responsibility of air-ground communication service providers should be outlined in the following areas:

• Provision of air-ground communication services compliant with required quality of service

• Operations of air-ground communication services compliant with agreed security policy

• Openness to implement interoperable solutions for users (AOs and ANSPs)

• Interconnections and service level agreements with ANSPs and other ACSPs.

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3.5.7.2 Contribution to Interoperability The deployment of new concepts supported by a new technology in the EATMN is an objective of the interoperability Regulation clearly stated in Article 1. The deployment of data link services in the EATMN must be properly addressed in the implementing rule with notably the responsibility of each stakeholder in terms of “WHAT HAS TO BE ENSURED”.

3.5.7.3 Impact on the implementing rule [IR-IAN-011] The obligations of stakeholders are a subject for prescription in the implementing rule.


• Responsibility of airspace users for the deployment of aircraft data link systems

• Responsibility of ANSPs for the deployment of ground data link systems

• Responsibility of air-ground communication service providers for the deployment of air-ground data communications supporting the selected data link services.

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4. ALTERNATIVES FOR THE REGULATORY APPROACH

4.1 Introduction The alternatives for the regulatory approach of the implementing rule stem from the foregoing interoperability analysis. Three heading lines provide the baseline of the regulatory approach:

a) The selected data link services.

In all of the considered alternatives, each data link service is prescribed in the implementing rule. The provisions relating to the definition of data link services are consistent with ED-120 SPR and are independent of the underlying technology.

b) The enabling technology supporting these selected data link services;

In all of the considered alternatives, the enabling technology is broken down into two parts:

i. Communication exchange mechanisms, ensuring data exchanges between airborne and ground end systems

ii. Air-ground communications link.

c) The deployment in the EATMN.

The following table outlines three candidate alternatives for the regulatory approach.

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Table 6. Possible Alternatives for Regulatory Approach Overview of prescriptions Regulatory

approach Alternative 1 Alternative 2 Alternative 3 (See Note 1)

Selected data link services

Prescriptions specifying the interoperability, safety and performance requirements of data link services (independent from technology aspects) i/ Prescriptions to ensure interoperability and performance of communication exchange mechanisms supporting data link services, specified in general terms. Prescriptions identifying the means of compliance by cross-referencing the EUROCONTROL Specification.

i/ Prescriptions to ensure interoperability and performance of communication services supporting data link services. These prescriptions are specified like high level requirements based on ATN communication protocols (upper and lower communication layers).

Enabling technology ii/ Prescriptions to ensure

interoperability and performance of the air-ground data communications link, specified in general terms. Prescriptions identifying the means of compliance by cross-referencing the EUROCONTROL Specification

ii/ Prescriptions of air-ground data communications link based on VDL-2.

Deployment in the EATMN

Prescriptions addressing: • Aircraft equipage • Data link airspace • ANSPs readiness • Aircraft operators readiness • ACSPs readiness • ATC procedures

As Alternative 1 and 2, plus: Prescription for the accommodation of ED-100A (FANS-1/A) compliant aircraft by ground systems during a transition period to be determined.

Note 1: As of today, the ability of ED-100A compliant systems to fully comply with Safety and Performance requirements for continental airspace is under investigation. Although some restrictions might apply to the accommodation of ED-100A compliant aircraft in the data link continental airspace, it is presented as a possible alternative for the regulatory approach.

4.2 Alternative 1 – Less Prescriptive In this alternative:

a) The selected data link services (ACM, ACL, AMC, DLIC) are specified in the implementing rule, consistent with their specification in the SPR standard ED-120 [4].

b) The communication exchange mechanisms are defined in the implementing rule. The provisions relating to the definition of communication exchange mechanisms specify:

• “WHAT HAS TO BE PERFORMED” interoperability and performance requirements in general terms.

• “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION” by identifying the means of compliance with a cross-reference to the relevant part of the

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EUROCONTROL Specification. These means of compliance ensure compliance with the WHAT-related requirements (above). The identification of MOCs within the implementing rule must allow for only a very limited number of MOCs, to avoid proliferation and fragmentation of air-ground communications solutions.

c) The air-ground communication link is defined in the implementing rule. The provisions relating to the air-ground communication link specify:

• “WHAT HAS TO BE PERFORMED” interoperability and performance requirements in general terms.

• “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION” by identifying the means of compliance with a cross-reference to the relevant part of the EUROCONTROL Specification. These means of compliance ensure compliance with the WHAT-related requirements (above).

d) The prescriptions relating to the deployment of data link services specify “WHAT HAS TO BE PERFORMED” to deploy and operate data link services in the EATMN.

Note: As of today, only ATN application and communication protocols have been validated as meeting the SPR of the selected data link services, and can be recognised as the unique means of compliance (MOC) with the provisions relating to communication exchange mechanisms. In the future, other MOCs might be envisaged depending on the evolution of the communication technology (e.g. ACARS protocols and/or TCP/IP with more advanced capability). In such cases, the impact on the implementing rule is limited to an update of the identified MOCs. For implementation aspects, it entails:

a. Aircraft5 data link systems must implement at least one of the recognised MOCs (applications, communication protocols and communication profiles) identified as a MOC in the implementing rule

b. Ground data link systems must implement all of the MOCs (applications, communication protocols and communication profiles) identified as a MOC in the implementing rule.

4.3 Alternative 2 – ATN Prescription In this alternative:

a) The selected data link services are specified as for Alternative 1.

b) The communication exchange mechanisms are prescribed in the implementing rule. The provisions relating to the definition of communication exchange mechanisms, based on ATN technical provisions, specify “WHAT HAS TO BE PERFORMED” and “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION”.

c) The provisions relating to the air-ground communication link, based on VDL-2 technology, specify “WHAT HAS TO BE PERFORMED” and “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION”.

d) The prescriptions relating to the deployment of data link services are the same as for Alternative 1.

Note: For implementation aspects, it entails:

a. Aircraft6 data link systems must implement applications and communication protocols compliant with ATN standards and standardised communication profiles

5 Aircraft that meet the conditions for mandatory equipage to support the selected data link services.

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b. Ground data link systems must implement applications and communication protocols compliant with ATN standards and standardised communication profiles.

c. ACSPs must provide a VDL-2 service and additionally support the ATN communication / routing protocols and communication profiles.

4.4 Alternative 3 – ATN with FANS Accommodation In this alternative:

a) The selected data link services are specified as for Alternative 1.

b) The communication exchange mechanisms are prescribed in the implementing rule. The provisions relating to the definition of communication exchange mechanisms, based on ATN technical provisions, specify “WHAT HAS TO BE PERFORMED” and “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION”.

c) The provisions relating to the air-ground communication link, based on VDL-2 technology, specify “WHAT HAS TO BE PERFORMED” and “HOW TO IMPLEMENT AN INTEROPERABLE SOLUTION”.

d) The prescriptions relating to the deployment of data link services specify “WHAT HAS TO BE PERFORMED” to deploy and operate data link services in the EATMN. Further, the accommodation of ED-100A compliant aircraft in some specific operational environment by ground systems is prescribed during a transition period (see Note 1 to Table 6 above). Criteria for determining an appropriate transition period would need to be elaborated.

Note: For implementation aspects, it entails:

a. Aircraft2 data link systems must implement applications and communication protocols compliant with ATN standards and standardised communication profiles

b. Ground data link systems must implement:

i. Applications and Communication protocols compliant with ATN standards and standardised communication profiles, and

ii. Applications and Communication protocols to support accommodation of ED-100A compliant systems.

c. ACSPs must provide a VDL-2 service and additionally support both the ATN and ACARS communication / routing protocols and communication profiles.

6 Aircraft that meet the conditions for mandatory equipage to support the selected data link services.

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5. CONFORMITY ASSESSMENT ANALYSIS

5.1 Purpose The purpose of this chapter is to determine the types of conformity assessment requirements for inclusion in the implementing rule.

5.2 Views of the Conformity Assessment Task Force The interoperability Regulation defines the conformity assessment regime applicable to EATMN constituents and systems. An implementing rule can describe the conformity assessment procedures to be used to assess either the conformity or the suitability for use of constituents as well as the verification of systems. These procedures can be based on modules defined in Decision 93/465/EEC.

From studies carried out with the Conformity Assessment Task Force (CATF), it appears that these generic modules, defined for industrial products, do not match the lifecycle of EATMN systems. The CATF members agreed:

• To define specific procedures with tasks allocated to ANSPs and Notified Bodies, whenever Notified Bodies are involved.

• To customize generic modules based on lessons learnt from the early application of the conformity assessment procedures to EATMN constituents and systems.

5.3 Recommendations for Conformity Assessment Requirements The conformity assessment requirements included in the implementing rule should address the following items:

• What are the verification objectives driving the verification activities?

• What are the verification methods applicable to EATMN constituents and systems implementing data link services?

• What is the verification evidence to be produced for the technical file supporting the EC declaration of verification of systems?

• What are the procedures for the achievement of conformity assessment activities?

The allocation of conformity assessment requirements to the air, air-ground and ground-ground segments of data link systems will be discussed with CATF members.

5.3.1 Verification Objectives Verification objectives aim to provide a clear baseline for the organisation of verifications of constituents and systems supporting data link services. These verification objectives are dependent on the layers of the regulatory coverage (see section 10). The level of detail of the verification objectives is dependent on the level of detail of regulatory provisions specified for each layer of the regulatory coverage. For example, if it is assumed that communication exchange mechanisms are covered by high-level interoperability and SPR requirements, it entails that the verification objectives relating to communication exchange mechanisms are also focused on the interoperability and SPR requirements.

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5.3.2 Verification Methods Verification methods are mandated to avoid divergent solutions for verification of compliance with regulatory provisions. Specific verification methods can be envisaged for each layer of the regulatory coverage.

5.3.3 Verification Evidence Verification evidence is mandated to avoid divergence on the contents of the technical file associated with the EC Declaration of verification of systems. Specific verification evidence can be envisaged for each layer of the regulatory coverage.

5.3.4 Procedures for the Achievement of Conformity Assessment Activities The procedures describe the organisational aspects of conformity assessment of EATMN constituents and systems. It is very likely that these procedures will be based on procedures as defined for the initial interoperability implementing rules on coordination and transfer, and flight message transfer protocol.

The development of conformity assessment requirements for the implementing rule on data link services will be coordinated with the CATF members during the drafting phase.

5.4 Impact on the Implementing Rule [IR-CA-001] The conformity assessment requirements of the implementing rule should address the following items:

• Verification objectives.

• Verification methods.

• Verification evidence.

• Applicable procedures.

The conformity assessment requirements of the implementing rule should be allocated to the different segments of data link systems (air, air-ground and ground-ground segments).

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6. ANALYSIS OF IMPLEMENTATION CONDITIONS

6.1 Purpose The purpose of this chapter is to:

• Determine the implementation timescales for ground and aircraft systems, including any transitional arrangements.

• Investigate the applicability of exemptions and alleviations policy for airborne data link equipment.

• Outline a recommended Minimum Equipment List (MEL) policy for airborne data link equipment.

6.2 Factors Affecting Implementation Timescales

6.2.1 Notice to Aircraft Operators In general, regulators should aim to give the aviation industry a 7-year notice period for new equipage requirements but this does not necessarily have to be from the publication date of a mandate. The mandatory equipage of aircraft with data link capability will apply only to aircraft fulfilling specific characteristics and operators must be informed throughout the development process of the implementing rule so that they may anticipate the required equipage in due time.

Retrofit equipage of “in service” aircraft with data link capability that can be completed during routine maintenance periods will significantly minimise the costs for operators. The period of time for retrofit equipage should be specified in the implementing rule.

New aircraft that are due for delivery before the equipage deadline specified in the implementing rule can normally be fitted with data link capability in a cost effective manner prior to delivery. A shorter notice period can also be given to operators for the equipage of new aircraft than that provided for retrofits. The period of time for this ‘forward fit’ equipage of new aircraft should be specified in the implementing rule.

6.2.2 Equipment Availability The implementing rule on data link services may result in a large demand for equipment within a relatively short time period. However, avionics and aircraft manufacturers, ACSPs and AOs have been involved in the development of the CPDLC services since the first trials in Europe and the USA. These stakeholders are also consulted throughout the development process of the implementing rule and can influence the implementation timescale to satisfy any foreseen constraint upon equipment availability. The risk of a significant unavailability of equipment is, therefore, considered to be unlikely.

6.2.3 Balancing Airborne and Ground Equipage The expected benefits of data link services will only be maximised if a contiguous coverage within the busy core EATMN airspace is implemented. Therefore, the implementing rule will mandate a deadline for the deployment of data link services by ANSPs in the EATMN. The required date could be linked to the earliest date for equipage of aircraft.

6.2.4 Business Case Issues The realisation of benefits and costs in the aviation industry is sensitive to implementation timescales in that the equipage dates are a major variable in a Cost Benefit Analysis (CBA).

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Return on investment takes longer to achieve for ANSPs than for AOs, the latter normally requiring a payback period of less than two years. Stakeholders will, therefore, need assurance that the mandate dates are achievable and will realise the earliest possible benefits and return on investment.

The CBA for LINK 2000+ assumed that ANSPs provide operational data link services from 2009 and all required retrofits are completed by 2012.

6.2.5 Transition Issues Informal consultation with focal points via a questionnaire contained specific questions on transitional issues. The responses highlighted a need only for transition aspects related to the equipage of aircraft to be considered in the implementing rule. Therefore, there is no foreseen transition period applicable to ANSPs in the implementing rule, but separate retrofit and forward fit timescales will be specified accordingly.

6.2.6 Summary of the Implementation Timescale Options Mindful of all the aforementioned issues, Figure 4 below summarises the most suitable timescale ranges within which the implementing rule could specify dates for ground and aircraft system equipage requirements.

LINK2000+ CBA Assumptions

ANSP Equipage Feasibility

• JURG Retrofit Support

• JURG Forward Fit Support Retrofit Equipage Feasibility

Forward Fit Equipage Feasibility

2008 2009 2010 2011 2012 2013 2014 2015 2016

Figure 4. Implementation Timescale Options

6.2.7 Impact on the Implementing Rule [IR-IC-001] Implementation timescales should be a subject for prescriptions in the implementing rule.


• Applicability criteria with which to define ‘in service’ aircraft requiring the retrofit of appropriate data link equipment.

• Applicability criteria with which to define ‘forward fit’ aircraft requiring equipage with appropriate data link equipment from the initial delivery by the manufacturer.

• Separate implementation dates should be prescribed for the retrofit of ‘in service’ aircraft and the ‘forward fit’ of new aircraft.

• Operators should be provided with a period of between 5 and 8 years notice in which to complete the retrofit of ‘in service’ aircraft with the appropriate data link equipment.

• Operators should be provided with a period of between 2 and 5 years notice in which to ensure that new aircraft are delivered with the appropriate data link equipment.

• Applicable dates for the ground equipage of ANSPs that provide ATS supported by data link communications, which are linked with the earliest mandate dates for

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airborne equipage. Noting the envisaged progressive geographical implementation (see 3.5.1.3), ANSPs in the geographic coverage defined for the initial phase must deploy data link services by the time that aircraft forward fit becomes mandatory.

[JM-IC-001] The justification material should comment on how the applicable dates for airborne and ground equipage ensure that the results of the CBA can be supported. It should include comments on, and take account of, the need for monitoring the successful equipage of aircraft and ANSPs prior to the applicable dates for mandatory equipage.

6.3 Airborne Exemption Policy Principles

6.3.1 Applicability Criteria for Aircraft Equipage The implementing rule should specify applicability criteria for airborne equipage as follows:

• The class of flight to which the rule will apply must be defined. For example, only those aircraft operating as GAT under instrument flight rules.

• The class of aircraft to which the rule will apply must be defined. For example, only those aircraft above a certain maximum take-off mass or a specified maximum approved passenger seating configuration.

• The airborne data link equipment must comply with the interoperability, safety and performance requirements of data link services that are specified in the implementing rule.

Exemption procedures can apply to those aircraft that fall within the applicability criteria but which have a genuine need to be temporarily or permanently exempted from compliance with the implementing rule.

6.3.2 Exemption Principles The scope and type of airborne exemption principles required to support the implementing rule on data link services could comprise some or all of the following aspects:

• ‘Case-by-case’ exemptions for particular aircraft or aircraft types, for particular flights, or for particular organisations. These must be initiated by the submission of specific applications by individual operators.

• ‘Blanket’ waivers for particular aircraft types, flights or organisations for which no individual applications are required.

• Permanent exemptions for which no specific expiry date applies.

The mechanism to support the administration and oversight of the exemption policy needs to be harmonised in the EATMN.

6.3.3 State Aircraft The number of IFR/GAT flights made by State aircraft in the applicable data link airspace will be a very low proportion of the overall number of flights. It is likely that the presence of non-compliant State aircraft will not unduly affect the realisation of the benefits of ATS supported by data link. It is expected that State aircraft will be exempted from mandatory data link equipage and will continue to be handled using voice communication facilities.

6.3.4 Application of Exemptions The exemption procedures can apply to:

• Aircraft requiring occasional or limited access to the data link airspace.

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• Aircraft transiting through the data link airspace to access maintenance or engineering facilities.

• Aircraft transiting through data link airspace and due to be taken out of service shortly after the mandatory dates for equipage.

• Aircraft transiting through the data link airspace where the operators are facing genuine equipage difficulties due to a shortage of equipment, additional delays in the delivery of equipment etc.

All exempted aircraft will make use of voice communications for ATS provision.

6.3.5 Impact on the Implementing Rule [IR-IC-002] Aircraft equipage is a subject for prescriptions in the implementing rule.

The nature of these prescriptions should address the following items:

• The class of flight to which the airborne data link systems equipage requirements will apply.

• The class of aircraft to which the airborne data link systems equipage requirements will apply.

• Exemptions for State aircraft from the mandatory data link equipage requirements.

• Exemptions for aircraft on maintenance and delivery flights from the mandatory data link equipage requirements.

[JM-IC-002] The justification material should clearly set out the scope and types of exemptions from the applicability criteria that will be granted and it should describe the exemption application process for operators in EC member states and for operators of non-EC member states. The exemption principles should be designed to minimise the need for case-by-case applications from individual aircraft operators.

6.4 Minimum Equipment List (MEL) Policy Issues

6.4.1 Data Link Equipment The requirements for data link systems fitted to aircraft have not yet been included in JAR-OPS Part 1. Consequently, there is no corresponding MEL policy for data link in JAR-MMEL/MEL. However, Section 5 of JAA TGL No 26 provides some additional recommended MEL policy guidance that might be used for data link systems.

6.4.2 Impact on the Implementing Rule [JM-IC-003] The justification material should include recommendations for a suitable MEL policy for data link equipment that is based on the JAA TGL 26 additional guidance.

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7. IMPACT ASSESSMENT

This preliminary impact assessment compares the three alternatives of the regulatory approach defined in section 4 in terms of impact on stakeholders, and makes recommendations for the drafting of the implementing rule.

7.1 Stakeholders Affected The implementing rule will affect the following stakeholders:

• ANSPs within EU Member States.

• Commercial aircraft operators.

• Private operators of executive jets.

• ACSPs.

• Military authorities and other State aircraft operators.

• National supervisory authorities.

• Aircraft and equipment manufacturers.

• Maintenance organisations.

7.2 Economic and Efficiency Impact CPDLC reduces the workload of the controller and thus produces higher capacity within the current sector structure. It represents a less expensive method of producing higher capacity than increasing sector numbers and, in the longer term, a solution to the problem of the limit to additional sectorisation. Studies and simulations by the EUROCONTROL LINK 2000+ Programme ([39], [40], [41]) have indicated that CPDLC could reduce the total workload of the tactical controller by about 29%, with 100% of flights equipped, and that this could lead to an increase of 14% in sector capacity. Assuming a maximum volume of flights by equipped aircraft of 75%, a capacity increase of 11% could be achieved and this would enable a reduction of about 8% in the number of sectors required by 2016 were CPDLC not to be introduced.

There are currently just over 11,000 aircraft operating regularly in the busy areas of western and central Europe where CPDLC is likely to be most beneficial. Of these, some 2,200 carry out more than half of the flights and could be retrofitted economically. Most of the remainder are either small or old aircraft, for which retrofit may not be economically viable, or are FANS-1/A (ED-100 or ED-100A compliant) aircraft. There are about 1,000 FANS-1/A equipped aircraft, which carry out about 5.6% of the flights.

The cost of airborne equipage can vary considerably, depending on the type and age of the aircraft but a typical cost would be of the order of €40,000. However, the costs of retrofitting some older types of aircraft may be considerably higher. The cost of ground equipage depends on the nature of the existing ground communications facilities and could vary between €5m and €15m per ATC centre.

An investment appraisal for the implementation of CPDLC services in Europe was prepared in 2000 and revised in early 2005. The results of the appraisal are exceptionally good and are summarised in Table 7.

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Table 7. Summary of CBA Results Net present value € 1523m

Benefit to cost ratio 9

Present value of benefits € 1714m

Present value of costs € 191m

Internal rate of return 123%

Break even year 2006 August

Payback period 2 years 8 months

When the cost benefit analysis was carried out, it was considered that the most likely method of implementation would be through the use of ATN over VDL Mode 2, with exemptions given to FANS-1/A (ED-100 or ED-100A compliant) aircraft, and these, therefore, were the assumptions built into the analysis. Thus the cost benefit analysis most closely reflects the consequences of regulatory approach alternative 2 (as described in section 4.3 above). Accommodation of FANS-1/A equipped aircraft will require the implementation of a communications gateway at each ATC centre, and the upgrade of ED-100 compliant aircraft systems to ED-100A level at a cost, as yet, unknown. For centres close to the western seaboard of Europe, receiving considerable volumes of trans-Atlantic traffic, Alternative 3 (see 4.4 above) is likely to represent a reasonable investment. However, for centres in central and Eastern Europe, this is unlikely to be the case.

7.3 Safety Impact In general, the use of data link communications is expected to increase the safety of air transport in the EATMN. Data link provides a supplemental communication means between controllers and pilots to facilitate redundancy for voice communications, and improves comprehension. Voice communications will also become less congested.

However, data link communication can also present specific safety risks if the hazards associated with the use of data link messages for separation of aircraft are not addressed. These issues have been overcome in Regulatory Approach alternatives 1 and 2 (see 4.2 and 4.3, respectively) for ATN based services, through the prescription of "Protected Mode" data link applications, but for alternative 3 (see 4.4) studies into the use of ED-100A compliant systems for profile-changing messages in busy continental airspace are still in progress.

The impact on safety of alternatives 1 and 2 would, in effect, be identical for ATN-based services, and has been thoroughly assessed as part of the EUROCONTROL LINK 2000+ programme activities. A pre-implementation safety case [16] has demonstrated that air-ground CPDLC applications over ATN, their generic implementation, and their environment context are, in principle, acceptably safe. However, to reduce the risk of messages being misdirected, the ICAO 24-bit aircraft address, the aircraft identification and the current controlling data authority are being included in all integrity checksum calculations. Also, in order to guarantee message integrity, PM-CPDLC should be prescribed, in which an application integrity check is added to all messages between the ground application and the aircraft application. Furthermore, the use of PM-CPDLC is considered essential to protect against message corruption and to ensure that messages are only processed by the intended recipient.

The reliance on ICAO 24-bit aircraft addresses does, however, need to be considered carefully in light of known problems with the integrity of the handling of the addresses and their correct input into aircraft systems. This may place additional obligations on aircraft

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operators to ensure that 24-bit aircraft addresses are correctly configured and communicated.

Depending upon the results of additional studies and safety work, ED-100A FANS-1/A may also in the future offer an acceptable means of compliance for the communications exchange mechanism under alternative 1. To prevent there being a risk to interoperability of systems from there being two potential technical solutions, ground systems will have to support all formally identified means of compliance, unless a common MOC is mandated for air and ground systems.

The ability to implement alternative 3 in compliance with identified safety requirements is currently under study. (Similar issues were analysed for ATN-based systems, and led to the development of an additional application message integrity check for CPDLC). Currently, it is considered that voice read-back of messages may be required, which may be operationally unacceptable, and the overall number of data link transactions with ED-100A compliant aircraft would have to be limited.

Overall, the safety requirements would be the same for all three regulatory approach alternatives, and an initial safety analysis has recommended that safety aspects be subject for prescription in the implementing rule. These safety requirements will not duplicate safety requirements specified in ED-120; they will re-assert the responsibility of ANSPs to develop a local safety argument and perform a local safety assessment in the framework of a pre-implementation safety case applicable to the selected data link services.

7.3.1 Impact on the Implementing Rule [IR-SAF-001] Safety should be a subject for prescription in the implementing rule.


• The obligations of stakeholders for the achievement of a local safety assessment when deploying data link services in their area of responsibility.

[MOC-SAF-001] ED-120 and the EUROCONTROL LINK 2000+ Pre-Implementation Safety Case [16] could be considered as a means of compliance with safety requirements.

7.4 Impact on Existing Rules and Standards ED-110A will be updated by EUROCAE to incorporate PM CPDLC. (Corresponding changes to ED-120 are mainly editorial, to reflect the existence of PM CPDLC). The implementing rule may need to include prescriptions under all three regulatory approach alternatives that differ from current versions of EUROCAE standards. The development of a EUROCONTROL Specification documenting the deviations from applicable standards and providing further detailed requirements considered as means of compliance with some regulatory provisions of the implementing rule is deemed necessary.

Alternatives 2 and 3 require specific ATN prescriptions in the implementing rule. However, linking the implementing rule so closely to current ATN technical provisions may cause traceability issues for existing implementations. In addition, future amendments to the ATN provisions may need to take account of the implementing rule and vice versa. This could provide an administrative burden or constraint. Other potential deviations from (or subsetting of) ICAO Doc 9705 in terms of security services, naming and addressing functions, Context Management functions, CPDLC message elements and extended transport checksum need to be considered.

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It is not envisaged that the implementing rule will prescribe requirements for the carriage of airborne data link recording equipment. Therefore, there would be no impact on ICAO Annex 6 SARPs under any the regulatory approach alternatives.

The impact upon existing materials for airworthiness certification and operational approval will be further investigated during the development of the draft implementing rule.

7.5 Recommendations Viability of Alternative 3 is subject to confirmation through on-going work that the accommodation of ED-100A compliant aircraft in continental airspace meets interoperability and performance requirements defined in the implementing rule. Return of investment has also to be considered. It should be assessed according to the geographical area concerned (e.g. accommodation of ED-100A compliant aircraft for ANSPs in central or Eastern Europe is unlikely to provide a reasonable return, with currently available information, for the investment that would be required to install suitable communications ‘gateways’ and should also consider the ultimate expansion of data link airspace retained by the rule.

The impact of Alternatives 1 and 2 in terms of economic, efficiency, civil-military organisation and safety aspects are likely to be broadly identical where ATN is implemented. However, under Alternative 1 interoperability of systems must be maintained (e.g. by “dual stack” and “gateway” techniques) if systems based on ED-100A can ever be offered as an acceptable means of compliance.

Under Alternative 2 there may be current and ongoing issues associated with the traceability and consistency between the prescriptions for ATN in the implementing rule and the ICAO ATN provisions. This could be particularly the case where the ATN provisions were amended or further developed in the future. Alternative 2 might also be less politically acceptable as the implementing rule would be much more prescriptive on stakeholders.

On balance Alternative 1 is recommended as the most suitable option. This is because it minimises the amount of detailed technical prescription in the implementing rule itself and enables accommodation of potential future alternative identified means of compliance.

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8. OBJECTIVES AND SCOPE OF THE DRAFT IMPLEMENTING RULE

8.1 Objective This chapter clarifies the objective and scope that will be reflected in Article 1 of the implementing rule.

The objective of the draft implementing rule is to ensure the coordinated and harmonised introduction of data link services in the EATMN, supported by interoperable data link systems using mobile air-ground data communications, as a means of improving the interoperability and efficiency of ATC communications between controllers and pilots.

8.2 Scope The scope of the draft implementing rule is the exchange of messages between controllers and pilots using data communications. In order to build up a well-balanced rule to meet the intended objective, the following subjects will be defined:

• The selected data link services for ATC communications;

• The application of data link services in the EATMN;

• The end-to-end communications supporting data exchanges between aircraft and ground data link systems;

• The air-ground, point-to-point data communications medium supporting the communication exchange mechanisms;

• The ATC procedures adapted for the selected data link services;

• The implementation conditions for data link services in the EATMN;

• The roles and responsibilities for ANSPs, ACSPs and aircraft operators to be ready for the use of ATS supported by data link communications by the required implementation timescales;

• The conformity assessment of EATMN constituents and systems implementing data link services.

8.3 Refinement of the Essential Requirements This section describes how the draft implementing rule on data link services is needed in order to complement and refine the relevant Essential Requirements, as follows:

For the purpose of the interoperability Regulation, the EATMN is subdivided into eight systems. The systems and procedures of greatest relevance to the implementing rule on data link services are identified in Annex I of the interoperability Regulation as:

• Communications systems and procedures for ground-to-ground, air-to-ground and air-to-air communications.

• Systems and procedures for ATS, in particular flight data processing systems, […] and human-machine interface systems.

Essential Requirements (ER) applicable to systems within the EATMN are categorised in Annex II of the interoperability Regulation under the following headings:

1. Seamless operation

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2. Support for new concepts of operation

3. Safety

4. Civil-military coordination

5. Environmental constraints

6. Principles governing the logical architecture of systems

7. Principles governing the construction of systems

ER1. Seamless Operation Seamless operation requirements specific to communications systems and procedures for ground-to-ground, air-to-ground and air-to-air communications are:

• Communication systems shall be designed, built, maintained and operated using the appropriate and validated procedures, in such a way as to achieve the required performances within a given volume of airspace or for a specific application, in particular in terms of communication processing time, integrity, availability and continuity of function.

• The communications network within the EATMN shall be such as to meet the requirements of quality of service, coverage and redundancy.

Data link services are enablers for ATS operational improvements. Data link services will provide significant operational benefits, improvement of ATS capacity, optimisation of radio frequency use, and decrease of controllers’ workload. The establishment of common interoperability and performance levels will contribute to the achievement of seamless operations.

The implementing rule contributes to ER1 by prescribing the implementation of

• The same data link services and operational concepts throughout the applicable airspace.

• The same communications system supporting a seamless relationship between airborne and ground based systems, so that a data link service is not disrupted by breaks in coverage or wide variations in quality of service.

ER2. Support for New Concepts of Operation Requirements specific to communications systems and procedures for ground-to-ground, air-to-ground and air-to-air communications are:

• Communication systems shall support the implementation of advanced, agreed and validated concepts of operation for all phases of flight.

Airborne and ground systems and their constituents supporting new, agreed and validated concepts of operation shall be designed, built, maintained and operated, using appropriate and validated procedures, in such as way as to be interoperable in terms of timely sharing of correct and consistent information and a common understanding of the current and predicted operational situation.

This implementing rule contributes to ER2 by prescribing the co-ordinated introduction of:

• New concept of operations based on validated air-ground data link communications;

• Validated technology(ies) supporting air-ground data link communications in the timeframe 2005 to 2015.

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ER3. Safety General requirements for safety, applicable to each of the identified EATMN systems, are as follows:

• Systems and operations of the EATMN shall achieve agreed high levels of safety. Agreed safety management and reporting methodologies shall be established to achieve this.

• In respect of appropriate ground-based systems, or parts thereof, these high levels of safety shall be enhanced by safety nets, which shall be subject to agreed common performance characteristics.

• A harmonised set of safety requirements for the design, implementation, maintenance and operation of systems and their constituents, both for normal and degraded modes of operation, shall be defined with a view to achieving the agreed safety levels, for all phases of flight and for the entire EATMN.

• Systems shall be designed, built, maintained and operated, using the appropriate and validated procedures, in such a way that the tasks assigned to the control staff are compatible with human capabilities, in both the normal and degraded modes of operation, and are consistent with required safety levels.

• Systems shall be designed, built, maintained and operated using the appropriate and validated procedures, in such a way as to be free from harmful interference in their normal operational environment.

This implementing rule contributes to ER3 by:

• Prescribing data link services based on air-ground data communications, providing a supplemental means of communication between controllers and pilots.

• Offering solutions to some of the problems of unintelligibility, mis-hearing, contention for access to the medium and lack of playback facilities commonly associated with voice communication.

ER4. Civil-Military Coordination At the present time, the concept of civil-military coordination based on data link services is not sufficiently mature. The implementing rule will not therefore contribute to refining ER4.

ER5. Environmental Constraints Indirectly, data link services enable concepts leading to reduced noise nuisance near airports, improved fuel efficiency and lower emissions. However, the implementing rule will not contribute directly to refining ER5.

ER6. Principles Governing the Logical Architecture of Systems Standardised data link services support a common view of the logical architecture, at least at the level of the communications subsystems and of the communicating application processes. However, the implementing rule will not prescribe any particular solution for the logical architecture of systems, and will not contribute directly to refining ER6.

ER7. Principles Governing the Construction of Systems This ER is mainly concerned with "plug-and-play" hardware modules. Standardised data link services are designed to be modular, and are decoupled from specific exchange mechanisms and communications subnetworks. However, the implementing rule will not prescribe the construction of systems in terms of modularity, high availability, redundancy and fault tolerance of critical constituents, and will not contribute directly to refining ER7.

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8.4 Impact on the Implementing Rule [IR-OSC-001] The regulatory provisions specifying the objective and scope of the implementing rule should be along the lines defined in sections 8.1 and 8.2 above.

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9. ARTICULATION OF THE DRAFT IMPLEMENTING RULE WITH EUROCONTROL SPECIFICATIONS

It is assumed that a EUROCONTROL Specification7, here designated "CPDLC Baseline 1," will be developed as a means of compliance with the implementing rule. The EUROCONTROL Specification must be based on international standards and specifications; it is not intended to be merely a regional standard. The CPDLC Baseline 1 sets up the relationship with ICAO and RTCA/EUROCAE standards and specifications, by refining and augmenting the requirements of these standards wherever appropriate.

The dependency between regulatory provisions and the EUROCONTROL Specifications is an issue for regulatory provisions addressing data link systems (see Chapter 10 for the overall structure of the implementing rule):

• Requirements for the definition of data link services

• Requirements applicable to data link applications

• Requirements for the end-to-end communication systems

• Requirements for the air-ground communication data link

• Requirements for ground-ground communications

• Requirements for the deployment in the EATMN.

For the other regulatory provisions relating to conformity assessment and implementation conditions, there are no specific Community or EUROCONTROL Specifications.

Three alternative formats are proposed to manage the dependency between regulatory provisions and the EUROCONTROL Specification:

Format 1 Regulatory provisions stem from the capture of the relevant properties and characteristics of validated operational and/or technical standards. These regulatory provisions are specified without any reference to external materials. There is no direct syntactic dependency between requirements in the implementing rule and the EUROCONTROL Specification.

Format 2 Regulatory provisions stem from the capture of the relevant properties and characteristics of validated operational and/or technical standards. Some of these provisions are specified with embedded cross-references to bounded sections of the EUROCONTROL Specification. The cross-referenced sections extend the regulatory provisions. Each cross-reference used in the implementing rule sets up a direct syntactic and semantic dependency between requirements in the implementing rule and the EUROCONTROL Specification. Cross-referenced sections of the EUROCONTROL Specification contain requirements detailing the interoperability and performance requirements of the implementing rule.

Format 3 Regulatory provisions point to relevant bounded sections of the EUROCONTROL Specification. This approach can apply when the pointed sections are self sufficient to ensure interoperability in the EATMN. There are no specific properties and characteristics captured by regulatory provisions. Each cross-reference used in the implementing rule sets up a direct 7 EUROCONTROL Specification elaborated using the consultation mechanisms of the EUROCONTROL Regulatory and Advisory Framework (ERAF) http://www.eurocontrol.int/ru/public/standard_page/framework.html.

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dependency between requirements in the implementing rule and the EUROCONTROL Specification.

The following table illustrates the application of these three formats to “requirements applicable to data link services” of the implementing rule.

Table 8. Possible Formats for Articulation

Format 1 Format 2 Format 3

Drafting of regulatory provisions

For each data link service, general requirements synthesising properties and characteristics of data link services defined in SPR of the CPDLC Baseline 1. These general requirements do not contain any cross-reference to external documents.

For each data link service, general requirements synthesising properties and characteristics of data link services defined in SPR of the CPDLC Baseline 1. These general requirements contain cross-references to bounded sections of the EUROCONTROL Specification.

For each data link service, a shortcut requirement pointing to the relevant sections defining SPR of the CPDLC Baseline 1. There is no synthesis or generalisation of properties and characteristics of data link services.

Dependency with EUROCONTROL Specification

No dependency The sections of the EUROCONTROL Specification referenced from regulatory provisions complement the extent of these regulatory provisions. These sections are considered as mandatory.

The sections of the EUROCONTROL Specification referenced from regulatory provisions complement the extent of these regulatory provisions. These sections are considered as mandatory.

To apply the appropriate format to regulatory provisions, it is deemed necessary to conduct the development of the EUROCONTROL Specification in parallel with the implementing rule.

Cross-references to EUROCONTROL Specification from regulatory provisions are used to limit the details of mandatory provisions of the implementing rule. The EUROCONTROL Specification contains the specifications of all of the means of compliance backing the implementing rule. These means of compliance are identified in the implementing rule.

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10. OVERALL STRUCTURE OF THE DRAFT IMPLEMENTING RULE

10.1 Purpose This chapter outlines the foreseen structure of the draft implementing rule that fits with the above analysis.

10.2 Flexibility of the Implementing Rule As indicated in the interoperability analysis, data link services and supporting technologies will evolve in the next decades. The data link services identified in the interoperability analysis focused on controller/pilot communications and can be seen as initial data link services. The implementing rule must be structured to accommodate further evolutions.

The foreseen structure of the implementing rule is based on the following principles:

• Identification of layers of the regulatory coverage with a core of regulatory provisions.

• Avoidance of undue dependency between regulatory provisions belonging to different layers.

The following table outlines the envisaged layers addressed within the implementing rule.

Table 9. Layers of Regulatory Coverage Regulatory coverage Layers of the regulatory

coverage Type of Provisions

Data link services 1.1 Data link services for controller/pilot communications

Provisions specifying the interoperability, safety and performance requirements of data link services (independent from underlying technology)

1.2 Future Data link services

Possible extensions with provisions relating to future data link services

Enabling technology 2.1 End to end communications

Prescriptions to ensure interoperability, safety and performances of communication services supporting data link services.

2.2 Mobile air-ground point to point data link communications

Prescriptions of air-ground data communications based on appropriate point-to-point mobile communication technology.

2.3 Future Mobile air-ground data link communications

Possible extensions with provisions relating to future data link communications.

Deployment in the EATMN

3.1 Deployment in the EATMN of data link services for controller/pilot communications

Prescriptions addressing: Aircraft equipage, Data link airspace, ANSPs readiness, Aircraft operators readiness, ACSPs readiness, ATC procedures

3.2 Deployment in the EATMN of future data link services

Possible extensions with provisions relating to the deployment of future data link services

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The number of layers is optimised to accommodate the whole range of regulatory prescriptions identified in the interoperability analysis. Provisions of each layer are almost independent from provisions of other layers.

Layers 1.2, 2.3 and 3.2 are not part of the initial implementing rule; they are given to illustrate possible extensions with limited impact on the other layers.

Due to technical progress, new air-ground data communications technology can emerge and the implementing rule could be revised accordingly.

In addition the implementation conditions are specified in a separate section of the implementing rule. The provisions dealing with implementation conditions can be updated independently from the provisions relating to the layers of the regulatory coverage.

10.3 Structure of the Implementing Rule The implementing rule should be structured along the following headlines:

1. Objective and scope of the implementing rule.

2. Definitions (required for the interpretation of regulatory provisions).

3. Field of application of the implementing rule.

4. Requirements for data link systems.

Requirements for the definition of data link services.

Requirements for the data link applications

Requirements for the end-to-end communication systems.

Requirements for the ground-ground communications.

Requirements for the air-ground communication data link.

Requirements for ATC procedures

5. Deployment of data link services.

Requirements for the area of application (aircraft mandatory equipage, airspace, etc.)

Requirements specifying the responsibility of aircraft operators.

Requirements specifying the responsibility of ANSPs.

Requirements specifying the responsibility of ACSPs.

6. Conformity assessment of data link constituents and systems.

Requirements for the conformity assessment of constituents and systems allocated to each segment.

7. Implementation conditions.

Requirements for transitional arrangements, if any.

Exemptions.

Requirements for implementation dates by AOs, ANSPs.

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11. CONCLUSIONS AND RECOMMENDATIONS

11.1 Regulatory Coverage The interoperability analysis in this document and its annexes has presented arguments for the selection of enabling technologies and deployment conditions to be included in the scope of the interoperability implementing rule for data link services.

The main recommendations are summarised in the following tables. The goal is to provide a consolidated view of the different aspects covered by the implementing rule. It will be used notably to get early feedback on the validity of the intended regulatory approach from all stakeholders.

The regulatory approach does not give the detailed specifications of regulatory requirements.

Table 10. Regulatory Coverage of the Enabling Technology

Subjects for prescriptions Nature of prescription

Selection of data link services [IR-IAN-001] (Page 11)

An initial core set of services will be specified to ensure a basic level of interoperability, while not precluding the implementation of additional data link services by stakeholders, which may be the subject of later regulation. • Definition of data link services for flights in continental en-

route airspace, based on recognised SPR standards for the airspace category in question (operating methods, performance requirements)

• The operational environment conditions for the provision and use of each of these services.

Air-Ground Data Link Technology [IR-IAN-002] (Page 14)

The air-ground communication technology prescription should specify minimum performance and capacity requirements for a validated point-to-point data link conformant with applicable standards.

Ground-Ground Data Link Technology [IR-IAN-003] (Page 16)

• Interoperability of interconnections (obligations for ACSPs and ANSPs to satisfy common institutional principles – see Annex E);

• Basic quality of service and performance (including SLA requirements);

• Requirements on application of appropriate security policy.

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Subjects for prescriptions Nature of prescription

High level specification of a complete communication system [IR-IAN-004] (Page 19)

a) Prescription of the data link services DLIC, ACL, ACM, AMC. b) Definition of the selected end-to-end data link communication system(s): • Basic functions offered to data link services • Basic functions to manage communications, send and receive

data messages • Basic quality of service and performance communication

requirements • Statements of security policy (appropriate for the data link

communication system).

c) Verifiable data link communications capacity and performance for a flight in en-route conditions.

[MOC-IAN-001] A detailed and precise specification of an end-to-end communication systems profile is recommended for the achievement of technical interoperability. The detailed specifications of this profile should be specified in a EUROCONTROL Specification associated with the implementing rule.

Table 11. Regulatory Coverage of Deployment Conditions

Subjects for prescription Nature of prescription

Applicable airspace categories and area(s) [IR-IAN-005] (Page 21)

To be further investigated during the drafting of the implementing rule. Prescriptions could be specified as: • A list of named airspace elements (FIRs, UIRs); and/or • Specifications of criteria based on indicators to delineate the

appropriate airspace portion; and/or • Direct reference to a EUROCONTROL Specification, to be

developed to define the data link airspace on a phased approach basis.

Aircraft equipage [IR-IAN-006] (Page 24)

The nature of prescription can be considered in two parts:

1. Mandatory carriage of radio equipment meeting applicable interoperability and performance requirements (cf. use for AOC and airport/TMA ATS applications based on AOA)

2. Mandatory carriage of equipment and software implementing specified ATS data link services via specified communications exchange mechanism. The nature of prescription will also be to specify the aircraft categories to which the provisions of the implementing rule will apply, together with relevant transition period(s). Due account should be taken of previous work to achieve consensus in this difficult area.

ANSP equipage Categories of ATS Unit (ACC, TWR, etc.) for which the specified data link functionality is required – No specific prescriptions: this is covered under airspace [IR-IAN-004].

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Airworthiness Certification and Operational Approval [IR-IAN-007] (Page 26)

Airworthiness certification aspects are not subjects for prescription in the implementing rule. Operational approval aspects for aircraft systems are not subjects for prescription in the implementing rule. [JM-IAN-001] The justification material associated with the draft implementing rule should address the advisory materials used for certification airworthiness and operational approval: • To verify the consistency between these advisory materials

and the implementing rule • To propose any required amendments of these advisory

materials • To propose a coordinated review process for the review of

AMC material relating to data link.

ATC Procedures for using Data Link Services [IR-IAN-008] (Page 27)

Specify the basic principles for the use of the selected data link services supporting ATS: • Co-existence of voice and data communications; • Use in the context of non-time critical communications; • Use at the discretion of the controller / pilot; • Controlled flight under the control of only one ATC unit. Mandate the application of harmonised procedures for the following events: • Construction of CPDLC messages, • Responding to CPDLC messages, • Reverting from CPDLC to voice communications (including

the ATC Phraseologies Related to the Use of CPDLC), • Synchronisation of the CPDLC dialogue when reverting to

voice communications, • Use of CPDLC in the event of voice radio communication

failure, • Transfer of CPDLC, • Intentional shutdown and testing of CPDLC, • Failure of CPDLC equipment [MOC-IAN-002] The details of procedures corresponding to these events should be defined and managed in an appropriate means of compliance.

Spectrum management [IR-IAN-009] (Page 29)

• Obligations on National Bodies to implement the ICAO regional VDL sub-band deployment plan [62]

• Obligations on RF equipment suppliers and users to utilise the assigned frequencies effectively.

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Naming, addressing and registration [IR-IAN-010] (Page 31)

• The need to assign a unique 24-bit address to every aircraft. (This is a common requirement for many different ATS applications and may be appropriately a subject for a separate implementing rule).

• The need for the safety case for each system to consider the known issues associated with aircraft and flight identification.

• The need for ground facility address registration and publication.

[JM-IAN-002] The registration facility and obligations of different stakeholders with respect to assigning and managing elements of the global address space should be considered in the justification material associated to the implementing rule.

Obligations of stakeholders [IR-IAN-011] (Page 34)

• Responsibility of airspace users for the deployment of aircraft data link systems

• Responsibility of ANSPs for the deployment of ground data link systems

• Responsibility of ACSPs for the deployment of air-ground data communications supporting the selected data link services.

Recording of data link messages [IR-IAN-012]

No prescription for the recording of data link messages by flight data recorders. See Annex H.

Specific requirements for the recording of data link messages by ground systems operated by ANSPs and ACSPs.

Table 12. Regulatory Coverage of Conformity Assessment

Subjects for prescription Nature of prescription Conformity assessment requirements [IR-CA-001] (Page 40)

Allocation to each segment of data link systems of requirements addressing: • Verification objectives. • Verification methods. • Verification evidence. • Applicable procedures.

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Table 13. Regulatory Coverage relating to Implementation Conditions

Subjects for prescription Nature of prescription Implementation timescales [IR-IC-001] (Page 42)

• Applicability criteria with which to define ‘in service’ aircraft requiring the retrofit of appropriate data link equipment.

• Applicability criteria with which to define ‘forward fit’ aircraft requiring equipage with appropriate data link equipment from the initial delivery by the manufacturer.

• Separate implementation dates should be prescribed for the retrofit of ‘in service’ aircraft and the ‘forward fit’ of new aircraft.

• Operators should be provided with a period of between 5 and 8 years notice in which to complete the retrofit of ‘in service’ aircraft with the appropriate data link equipment.

• Operators should be provided with a period of between 2 and 5 years notice in which to ensure that new aircraft are delivered with the appropriate data link equipment.

• Applicable dates for the ground equipage of ANSPs that provide ATS supported by data link services, which are linked with the earliest mandate dates for airborne equipage.

[JM-ICA-001] The justification material should comment on how the applicable dates for airborne and ground equipage ensure that the results of the CBA can be supported. It should include comments on, and take account of, the need for monitoring the successful equipage of aircraft and ANSPs prior to the applicable dates for mandatory equipage.

Aircraft equipage [IR-IC-002] (Page 44)

• The class of flight to which the airborne data link systems equipage requirements will apply.

• The class of aircraft to which the airborne data link systems equipage requirements will apply.

• Exemptions for State aircraft from the mandatory data link equipage requirements.

• Exemptions for aircraft on maintenance and delivery flights from the mandatory data link equipage requirements.

[JM-ICA-002] The justification material should clearly set out the scope and types of exemptions from the applicability criteria that will be granted and it should describe the exemption application process for operators in EC member states and for operators of non-EC member states. The exemption principles should be designed to minimise the need for case-by-case applications from individual aircraft operators.

Minimum Equipment List [JM-ICA-003] The justification material should include recommendations for a suitable MEL policy for data link equipment that is based on the JAA TGL 26 additional guidance.

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Table 14. Regulatory Coverage relating to Safety Impact

Subjects for prescription Nature of prescription Safety [IR-SAF-001] (Page 47)

Obligations of ANSPs to carry out a safety assessment before deploying data link services in their area of responsibility.

[MOC-SAF-001] ED-120 and the EUROCONTROL LINK 2000+ Pre-Implementation Safety Case [16] could be considered as a means of compliance with safety requirements.

Table 15. Regulatory Coverage relating to Objectives and Scope

Subjects for prescription Nature of prescription Objectives and Scope [IR-OSC-001] (Page 52)

The following subjects will be defined: • The selected data link services for ATC communications; • The application of data link services in the EATMN; • The end-to-end communications supporting data exchanges

between aircraft and ground data link systems; • The air-ground, point-to-point data communications medium

supporting the communication exchange mechanisms; • The ground-ground communications • The ATC procedures adapted for the selected data link

services; • The implementation conditions for data link services in the

EATMN; • The roles and responsibilities for ANSPs, ACSPs and AOs to

be ready for the use of ATS supported by data link communications by the required implementation timescales;

• The conformity assessment of EATMN constituents and systems implementing data link services.

11.2 ECIP A number of European Convergence and Implementation Plan (ECIP) objectives are currently related to data link services and appropriate coordination will have to be effected in order to ensure that related existing and future ECIP objectives are consistent with the implementing rule. The ECIP process can, notably, provide a means of monitoring the implementation of the implementing rule and this will be elaborated within the deliverable which describes EUROCONTROL’s actions to support stakeholder’s efforts to implement the implementing rule.

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12. RESULTS OF THE FORMAL CONSULTATION

12.1 Formal consultation / workshop As required by the European Commission’s Mandate, a written consultation was launched to collect the views and opinions of the stakeholders on the draft Regulatory Approach. The draft Regulatory Approach was submitted for formal consultation, using the mechanisms of the ENPRM process, from 27th January until 27th March 2006. The results of the consultation are described in the Summary of Responses (SOR) document published as a separate document, simultaneously to the Regulatory Approach. It shows notably that Alternative 1 was supported by 60 % of respondents.

Key Issues

The comments received during the formal consultation raised several key issues that were addressed at the workshop. EUROCONTROL carefully noted the additional input from the audience and confirmed that it would consider these key issues with the utmost attention when developing the Data Link Services implementing rule and specification:

• Regulations & Specifications o EUROCONTROL and the European Commission clarified the different possible

relationships between implementing rules and their associated means of compliance:

An implementing rule can be complemented by a Community Specification (e.g. after the development of the implementing rule on COTR the European Commission mandated EUROCONTROL to develop a EUROCONTROL Specification, based on the OLDI standard, as a means of compliance (MOC) to the implementing rule on COTR), the application of which remains voluntary.

An implementing rule can address high-level requirements and make binding through reference a single external specification which addresses the detailed technical requirements (e.g. the implementing rule on FMTP makes the EUROCONTROL Specification on FMTP binding).

An implementing rule can address high-level requirements and can identify several alternative binding specifications (e.g. the implementing rule on DLS could in a first instance refer to the ATN/VDL-2 standard but in a later instance to other technical solutions as long as these would guarantee at least an equal level of performance and interoperability).

o It was underlined that EUROCONTROL Specifications will only be developed to complement and augment ICAO and EUROCAE/RTCA standards (i.e. to clarify the exact actions to be undertaken by stakeholders to ensure proper implementation of the implementing rule).

o EUROCONTROL provided first explanations on the processes which might be used for the introduction of new technologies into an implementing rule and the development of future means of compliance. Two steps could be identified. Drafting of specifications describing new MOCs would first be initiated when sufficient consensus exists amongst stakeholders. Development and approval of EUROCONTROL specifications would follow the process defined in the EUROCONTROL Regulatory and Advisory Framework (ERAF). In the context of



Alternative 1 such as described in the draft Regulatory Approach document, a second step would consist in proposing an amendment to the implementing rule, which would formally identify the new specification as another possible MOC. This would allow the rule to be open to innovative solutions, whilst avoiding the risk of proliferation and the associated impact on interoperability.

o It was clarified that the proposed implementing rule is not intended to limit implementation to those data link services identified in the Regulatory Approach but that at least these services shall be implemented. Additional data link services may become mandatory in the future.

o The meeting confirmed that proper alignment would be ensured between the implementing rule and EASA AMC-20 in order to avoid duplication of work for certification authorities. The implementing rule and the AMC will address the same set of data link services and make reference to the same technical standards.

• Data link services and air-ground communication technology o Data link services selected for the implementing rule are used for controller – pilot

communications as requested by the EC Mandate. The selection of data link services and the choice of technology underlying data link services stem from the selection process defined in chapter 3.1 of the Regulatory Approach document. Four CPDLC data link services are selected and for the short term, the only technology seen as compliant with the intended level of safety and performance requirements (such as described in ED 120) is ATN/VDL-2. The implementing rule must allow for future technology meeting the performance and interoperability requirements of selected data link services. Coexistence of different means of compliance to support data link services should be anticipated.

o The coexistence of different means of compliance to support data link services has significant impact on stakeholders. Two ideas were debated to allow for different means of compliance: use of a multi-mode communication equipment for aircraft and definition of a baseline means of compliance implemented by all ANSPs that might be progressively augmented by other means of compliance. EUROCONTROL explained that the implementing rule must not prescribe specific technical architecture of avionics equipment. The implementation of multi-mode communication equipment must be left to avionics manufacturer’s decision. On the ground side, it is acknowledged that ANSPs express some reluctance on the principle that they should implement several MOCs. The conditions to secure proper interoperability should however be kept in mind and explained the reasons why EUROCONTROL proposed Alternative 1.

o It was clarified that the implementing rule will refine some of the essential requirements in the interoperability Regulation and not necessarily all of them.

o The proposal of an RCP-based implementing rule independent from air – ground communication technology illustrated in slide 45 was debated. According to feedback from some participants, this approach should not be considered as a theoretical approach. The key issue is again how interoperability is ensured.

• Target aircraft population o It is well accepted that FANS-equipped aircraft must not be subject to mandatory

equipage with new data link equipment. The accommodation of FANS-equipped aircraft on a mandatory basis is generally not accepted by ANSPs. The accommodation of FANS-equipped aircraft should be left to ANSPs’ decision depending on the operational context.

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o The capability of FANS-equipped aircraft compliant with ED 100A performance requirements to comply with performance and interoperability requirements of the implementing rule should be considered.

o The mandatory equipage of aircraft having a Maximum Take-Off Mass (MOM) lying between a lower and an upper limit is not found satisfactory by many stakeholders. The definition of an upper MTOM value needs further justification.

o The synchronized deployment of data link services with the equipage of aircraft and ACCs is instrumental to reach the benefits expected from data link services.

12.2 Next Steps The participants’ contributions and requests for clarification were considered as very constructive and gave EUROCONTROL valuable feedback for the further development of the draft implementing rule.

It was agreed to undertake the parallel development of:

• An implementing rule containing high level mandatory requirements on data link services, (DLIC, ACM, ACL, AMC) enabling technology and deployment in the EATMN. This implementing rule would be open to new emerging technologies.

• A EUROCONTROL Specification containing the detailed technical requirements, to be made binding through reference in the implementing rule. Technical requirements would, in a first phase, describe an implementation based on CPDLC - ATN/VDL-2. The development of this specification should however not impede the development of other future Means of Compliance, as long as these would guarantee at least an equal level of performance and interoperability.

The dependency between the implementing rule and the EUROCONTROL specification needs further investigation.

On the basis of the Regulatory Approach, EUROCONTROL intends to develop, by February 2007, a draft Final Report which will include the draft implementing rule, the draft EUROCONTROL specification and the draft justification material. A formal consultation on the draft implementing rule and draft specification will be launched on basis of the draft final report, after this has been transmitted to the European Commission. It is anticipated that a further workshop, presenting the outcomes of the formal consultation, will be organised in the second quarter of 2007.

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13. REFERENCES

13.1.1 Primary References influencing the Interoperability Analysis [1] ICAO Annex 10 to the Convention on International Civil Aviation, Volume III,

– Communication Systems, Part I – Digital Data Communication Systems, First Edition – July 1995, Amendment 73 – Aeronautical Telecommunication Network (ATN)

[2] ICAO Doc. 9705-AN/956 – Manual of Technical Provisions for the Aeronautical Telecommunications Network; Edition 2, December 1999.8

[3] Interoperability Requirements Standard for ATN Baseline 1 (INTEROP ATN B1), Revision A, EUROCAE ED-110A / RTCA DO-280A (August 2004)9

[4] Safety and Performance Requirements Standard For Initial Air Traffic Data Link Services In Continental Airspace (SPR IC), RTCA DO-290 / EUROCAE ED-120 (May 2004)

[5] [Interoperability Regulation] Regulation (EC) No 552/2004 of the European Parliament and of the Council of 10 March 2004 on the interoperability of the European Air Traffic Management Network, OJ L 96, 31.3.2004, p. 26

[6] [DLS mandate] Mandate to EUROCONTROL to assist the European Commission in the development of an interoperability implementing rule on Data Link Services, letter TREN/F2/EMM/vh D(2005) 110532.

[7] EUROCONTROL Air Traffic Management (ATM) Strategy for the years 2000+ (ATM 2000+ Strategy), 2003 Edition, Volumes 1 and 2 http://www.eurocontrol.int/eatm/public/standard_page/library_strategic_doc.html#library_strates

[8] EUROCONTROL Operational Concept Document (OCD) – Volume 1 (The Vision), FCO.ET1.ST07.DEL01, Edition 2.1 (January 2004) http://www.eurocontrol.int/oca/gallery/content/public/docs/op_concept/OCD_2_1_Released.pdf

[9] [CONOPS] EUROCONTROL ATM Operational Concept – Volume 2 – Concept of Operations (Year 2011), Edition 1.0 (May 2005) http://www.eurocontrol.int/oca/public/standard_page/op_concept_conops.html

[10] Operational Requirements For Air-Ground Cooperative Air Traffic Services, AGC-ORD-01, Edition 1.0 (April 2001) http://www.eurocontrol.int/eatm/gallery/content/public/library/00cov_10.pdf

[11] Guidelines for Approval of the Provision and Use of Air Traffic Services Supported by Data Communications, EUROCAE ED-78A (RTCA DO-264) (December 2000)

[12] Interoperability Requirements for ATS Applications using ARINC 622 Data Communications, EUROCAE ED-100A (April 2005)

[13] Description of a first package of GS/AS applications CARE/ASAS/EUROCONTROL/02-040 - version 2.2

8 ICAO Doc 9705 is currently being updated to the Fourth Edition. 9 EUROCAE ED-110A is being revised to include inter alia the “protected mode” variant of CPDLC

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[14] ATC Data Link Manual for Link 2000+ Services, LINK2000+/OI//ATC DATA LINK MANUAL, version 3.0 (May 2005)

[15] LINK Baseline 1, LINK 2000+/PM/BASELINE/1, version 1.1 (April 2005)

[16] EUROCONTROL LINK2000+ Programme Pre-Implementation Safety Case, Edition 1.0 (June 2004)

[17] ICAO Annex 6 to the Convention on International Civil Aviation, Operation of Aircraft

[18] ICAO Annex 11 to the Convention on International Civil Aviation, Air Traffic Services

[19] EU Single European Sky website http://europa.eu.int/comm/transport/air/single_sky/index_en.htm

[20] Roadmap for the implementation of data link services in European Air Traffic Management (ATM), February 2003 www.europa.int/comm/transport/air/single_sky/index-en.htm

[21] AIR: ATM-CNS Interoperability Roadmap, Sofréavia-European Commission, 18/08/03

13.1.2 Other Documents Referenced from the Text [22] ICAO Doc. 9694-AN/955 - Manual of Air Traffic Services (ATS) Data Link

Applications, First Edition - 1999

[23] [PANS-ATM, formerly PANS-RAC] ICAO Doc. 4444-ATM/501 – Procedures for Air Navigation Services - Air Traffic Management, Fourteenth Edition — 2001

[24] ICAO Doc 9688-AN/952, Manual on Mode S Specific Services, Second Edition - 2004

[25] ICAO Doc. 9739 – Comprehensive Aeronautical Telecommunication Network (ATN) Manual, First Edition - 2000

[26] COOPATS CASE 3: Operational Concept for Cooperative Air Traffic Services for the years 2008 to 2011 Ed 1.1 July 2004, EUROCONTROL

[27] Concept of Operations for 2020 - EUROCONTROL

[28] EATMP Communications Strategy - Volume 1 - Management Overview, ECS_V1_E4.0, Edition 4.0 (August 2003) http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS_V1_E4.0.pdf

[29] EATMP Communications Strategy - Volume 2 - Technical Description, ECS_V2_E5.0, Edition 5.0 (August 2003) http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS-V2_E5.0.pdf

[30] EUROCONTROL Guidelines for Implementation Support (EGIS), Part 5 – Communication & Navigation Specifications, Chapter 7 – Service Level Agreement for Datalink Services (DCL, D-ATIS), ISS.1.ID-EGIS.COM.DL, Edition 2.0 (October 2002)

[31] Aeronautical Communications Technologies Simulator (ACTS) - Simulation Results for initial Link2000+ deployment (single VDL 2 channel), ACTS/Results/VDL2, Version 2.0 (October 2005)

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http://www.europa.int/comm/transport/air/single_sky/index-en.htm

http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS_V1_E4.0.pdf

http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS_V1_E4.0.pdf

http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS-V2_E5.0.pdf

http://www.eurocontrol.int/eatm/gallery/content/public/library/ECS-V2_E5.0.pdf



http://www.eurocontrol.int/vdl2/gallery/content/public/VDL2%20Capacity%20Simulations.zip

[32] ARINC Specification 623-3, Character-Oriented Air Traffic Service (ATS) Applications, AEEC (April 2005) http://www.arinc.com/aeec

[33] EUROCAE ED-85A DLASD for the "Departure Clearance" Data-Link Service (December 2003)

[34] EUROCAE ED-89A DLASD for the "ATIS" Data-Link Service (December 2003)

[35] EUROCAE ED-106A DLASD for "Oceanic Clearance" (OCL) Data Link Service (March 2004)

13.1.3 Other Background Documents [36] JAA - Notice of Proposed Amendment (NPA 20-11), June 2003

[37] EUROCONTROL Standard Document For On-Line Data Interchange (OLDI), Ed. 3, 31 Oct. 2003

[38] Flight Crew Data Link Guidance for Link 2000+ Services, Ed. 2.0, May 2005 (http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/FC_DL%20Guidance_v2.0.pdf)

[39] Controller Pilot Data Link supported by ATN in Europe: LINK2000+ Cost Benefit Analysis Review, Version 2.0, May 2004 (http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/LINK%202000+%20CBA_Review_2_0.pdf)

[40] European Data Link Focus Group – CNS/ATM Focused Team – European Data Link Investment Analysis – 22 August 2000 (http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/Euro_DL_Final.pdf)

[41] EUROCONTROL LINK2000+ Business Case Development Simulation – Final Report - February 2000 (http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/EECSimLINK2k.pdf)

[42] Assessment of VDL Mode-2 airborne co-site interference in Link 2000+ framework, Version 2.01, Oct 2004

[43] Link 2000+ ATN Naming and Addressing Plan, version 1.2, May 2004.

[44] EUROCONTROL Safety Regulatory Requirement (ESARR) 6 – Software in ATM Systems, Edition 1.0 (November 2003)

[45] EUROCONTROL Safety Regulatory Requirement (ESARR) 4 – Risk Assessment and Mitigation in ATM, Edition 1.0 (April 2001)

[46] EUROCONTROL Safety Regulatory Requirement (ESARR) 5 –ATM Services' Personnel, Edition 2.0 (April 2002)

[47] ARINC Characteristic 758-2, Communications Management Unit (CMU) Mark 2, AEEC (July 2005)

[48] European Strategy for the Initial Implementation of Mode S Enhanced Surveillance

[49] ARINC Specification 620-4, Data Link Ground System Standard and Interface Specification (DGSS/IS), AEEC (November 1999)

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http://www.eurocontrol.int/vdl2/gallery/content/public/VDL2 Capacity Simulations.zip

http://www.eurocontrol.int/vdl2/gallery/content/public/VDL2 Capacity Simulations.zip

http://www.arinc.com/aeec

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/FC_DL Guidance_v2.0.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/FC_DL Guidance_v2.0.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/LINK 2000+ CBA_Review_2_0.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/LINK 2000+ CBA_Review_2_0.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/Euro_DL_Final.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/Euro_DL_Final.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/EECSimLINK2k.pdf

http://www.eurocontrol.int/link2000/gallery/content/public/files/documents/EECSimLINK2k.pdf



[50] AOC Air-Ground Data and Message Exchange Formats, AEEC Project Paper 633, Draft 1

[51] Communications Operating Concept and Requirements for the Future Radio System (COCR), EUROCONTROL/FAA, Draft 0.9 (November 2005).

[52] ARINC Specification 622-3, ATS Data Link Applications over ACARS Air-Ground Network, AEEC (October 1998)

CASCADE

[53] CASCADE Programme – Overview AP/ACG/22/14 (ATM/CNS Consultancy Group 2.2.04)

[54] CASCADE Programme: http://www.eurocontrol.int/cascade, CASCADE Charter Document

[55] Cascade Package 1 OSED – RFG – July 2004

FANS-1/A

[56] Operational Issues FANS accommodation

[57] FANS 1/A+ a/c accommodation in ATN Baseline 1 ground systems – RTCA/EUROCAE draft PU40

VDL Mode 2

[58] EUROCONTROL VDL Mode 2 Implementation Project http://www.eurocontrol.int/VDL-2/public/subsite_homepage/homepage.html

[59] VDL Mode 2 Capacity Planning Issues http://www.eurocontrol.int/VDL-2/public/standard_page/Capacity.html

[60] VDL SARPs, ICAO Annex 10 - Aeronautical Telecommunications – Volume III, Part I (Digital Data Communication Systems) – Chapter 6 - VHF Air-Ground Digital Link (VDL), First Edition, July 1995 – amended by Amendment 76 (01/11/2001)

[61] ICAO Manual on VHF Digital Link (VDL) Mode 2, Doc 9776/AN970, First Edition - 2001

[62] ARINC Specification 631-4 VHF Digital Link (VDL) Mode 2 Implementation Provisions, AEEC (August 2005)

[63] ARINC Characteristic 750-4 VHF Data Radio, AEEC (August 2004)

[64] VDL 2 Frequency Planning Results, Version 2.2, B Desperier, P Delhaise (EUROCONTROL)

[65] Assessment of VDL Mode-2 Airborne Co-site Interference in Link2000+ Framework, Version 2.02, P Delhaise, B Desperier, M Esposito (EUROCONTROL) (November 2004)

[66] VDL Mode 2 Capacity Analysis Through Simulations – Analysis of Link2000+ initial deployment (single channel), EUROCONTROL DAS/CSM (August 2005)

[67] VDL Sub-band Deployment Plan, ICAO FMG EUR (September 2005)

VDL Mode 4

[68] Information paper about VDL 4 workprogram at EUROCONTROL – ICAO/ACP/WGW (Version 1.1c) – June 2005

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http://www.eurocontrol.int/vdl2/public/subsite_homepage/homepage.html

http://www.eurocontrol.int/vdl2/public/standard_page/Capacity.html



http://www.icao.int/anb/Panels/ACP/WG/W/WGW01/ACP-WGW01-IP06_EURO_VDL-4_IP_June05.pdf

[69] EUROCONTROL VDL Mode 4 website http://www.eurocontrol.int/VDL-4/public/subsite_homepage/homepage.html

[70] North European ADS-B Network (NEAN) Update Programme (NUP) http://www.nup.nu/

[71] EUROCAE ED-108 Interim MOPS for VDL Mode 4 Aircraft Transceiver for ADS-B (July 2001)

NETWORKING APPROACHES– ATN – IP

[72] ICAO ACP Use of TCP/IP – WP16 at http://www.icao.int/anb/Panels/ACP/WG/W/WGW01/wgw01.html

[73] EATM COM Team Extra Focus Group report: Towards a Management Structure for provision of a PEN (February 2005)

MILITARY

[74] Civil-Military CNS/ATM - Interoperability Roadmap 0.52 (May 2005)

[75] Determining Future Military Airspace Requirements In Europe - Final Version (April 2003)

STAKEHOLDER DOCUMENTS

[76] AATM IMPLEMENTATION ROADMAP - SHORT AND MEDIUM TERM – Deliverable from the Joint Industry Project to develop a Global ATM Transition Roadmap addressing - Conclusion 4 of the Meeting between the Air Navigation Commission and Industry held on the 18th and 19th of May 2004

[77] Final IATA/AEA JURG Position on the LINK2000+ Mandate - (IATA/AEA version 16 July 2004)

[78] IATA - ATM Implementation Roadmap – Short and Medium Term – Release Version 1.0 – 15th October 2004 http://www.iata.org/NR/ContentConnector/CS2000/Siteinterface/sites/whatwedo/file/One_Sky_Vol_2_Roadmap.pdf

PRU – PERFORMANCE

[79] EUROCONTROL PRU : Performance review report Year 2004 http://www.eurocontrol.int/prc/public/standard_page/doc_prr.html

[80] ICAO Global ATM Operational Concept, Eleventh Air Navigation Conference (November 2003)

[81] Surveillance Development Roadmap (Edition 1.1, 1st March 2002)

[82] ATC and Data Processing Strategy - Volume 1 - Objectives and Implementation Principles Version 1.4, May 1999 (http://www.eurocontrol.int/eatm/gallery/content/public/library/odpvolume1.pdf)

[83] ATC and Data Processing Strategy - Volume 2 - Concepts Elements, Version 0.5, Oct 1999 (http://www.eurocontrol.int/eatm/gallery/content/public/library/odpvolume2.pdf)

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http://www.icao.int/anb/Panels/ACP/WG/W/WGW01/ACP-WGW01-IP06_EURO_VDL4_IP_June05.pdf

http://www.icao.int/anb/Panels/ACP/WG/W/WGW01/ACP-WGW01-IP06_EURO_VDL4_IP_June05.pdf

http://www.eurocontrol.int/vdl4/public/subsite_homepage/homepage.html

http://www.nup.nu/



[84] Overall ATM/CNS Target Architecture (OATA) Project http://www.eurocontrol.int/eatmp/library/documents/oata/

[85] Study Report On Avionics Systems For The Time Frame 2007, 2011 and 2020

[86] JAA/EASA ACJ20x10 Advisory Material for the approval of use of initial services for air-ground data link in continental airspace (in the process of being revised), EASA

13.1.4 Additional References for Data Link Recording [87] ICAO Annex 10 to the Convention on International Civil Aviation, Volume II,

– Communication Procedures including those with PANS status, Sixth Edition – October 2001

[88] Minimum Operational Performance Specification for crash protected airborne recorder system, Part IV, EUROCAE ED-112.

[89] JAR-OPS 1.728 (in the process of being revised), JAA

13.1.5 Additional References for Airworthiness Certification and Operational Approval [90] Operational Scenarios - Controller Operational Concepts

[91] Regulation (EC) No 1702/2003 of 24 September 2003 laying down implementing rules for the airworthiness and environmental certification of aircraft and related products, parts and appliances, as well as for the certification of design and production organisations, OJ L 243/6, 27.9.2003, pp. 6 - 79

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14. ABBREVIATIONS

14.1.1 General ACARS Aircraft Communication Addressing and Reporting System ACAS Airborne Collision Avoidance System ACC Area Control Centre ACP ICAO Aeronautical Communications Panel ACSP Aeronautical Communications Service Provider ADS Automatic Dependent Surveillance ADS-C Automatic Dependent Surveillance - Contract AEA Association of European Airlines AEEC Airlines Electronic Engineering Committee AIP Aeronautical Information Publication AL Assurance Level AMAN Arrival Manager AM-DSB Amplitude Modulation – Double Sideband AMC Acceptable Means of Compliance AMSS Aeronautical Mobile Satellite Service ANSP Air Navigation Service Provider AO Aircraft Operator AOA ACARS over AVLC AOC Airline Operational Control ASOR Allocation of Safety Objectives and Requirements ATC Air Traffic Control ATIS Automatic Terminal Information Service ATM Air Traffic Management ATN Aeronautical Telecommunication Network ATS Air Traffic Services ATSC Air Traffic Services Communication AVLC Aviation VHF Link Control CAA Civil Aviation Authority CASCADE Cooperative ATS through Surveillance and Communication Applications

Deployed in ECAC (EUROCONTROL programme) CBA Cost Benefit Analysis CDM Collaborative Decision Making CLDS Connectionless Dialogue Service (of ATN) CLTP Connectionless Transport Protocol CM Context Management Application CMU Communications Management Unit CNS Communications, Navigation and Surveillance COCR Communications Operating Concept and Requirements COTS Commercial-off-the-Shelf CPDLC Controller Pilot Data Link Communication D-FIS Data Link Flight Information Service DLASD Data-Link Application System Document (EUROCAE) DLS Data Link Service EASA The European Aviation Safety Agency EATMN European Air Traffic Management Network EC European Community ECAC European Civil Aviation Conference

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ED EUROCAE Document EHS Enhanced Surveillance ELS Elementary Surveillance ER Essential Requirement (of the interoperability Regulation) ES Extended Squitter ESARR EUROCONTROL Safety Regulatory Requirement ETSI European Telecommunications Standards Institute EUR ICAO European Region EUROCAE The European Organization for Civil Aviation Equipment FANS Future Air Navigation System FDPS Flight Data Processing System FIR Flight Information Region FIS Flight Information Service FL Flight Level FMG ICAO EUR Frequency Management Group FMS Flight Management System FPL Flight Plan GA General Aviation GAT General Air Traffic HF High Frequency HFDL High Frequency Data Link HMI Human-Machine Interface IA Interoperability Assessment IATA International Air Transport Association ICAO International Civil Aviation Organisation ICS ATN Internet Communication Service IFALPA International Federation of Air Line Pilots' Associations IFATCA International Federation of Air Traffic Controllers' Associations IFPS CFMU Integrated Initial Flight Plan Processing System IFR Instrument Flight Rules ILS Instrument Landing System IOAPA International Council of Aircraft Owner and Pilot Associations IP Internet Protocol ISO International Organisation for Standardisation ITU-T International Telecommunication Union – Telecommunications Sector JAA Joint Aviation Authorities MEL Minimum Equipment List MTCD Medium Term Conflict Detection MTOM Maximum Take-Off Mass NATO North Atlantic Treaty Organisation NDB Non-directional Radiobeacon OHA Operational Hazard Assessment OPA Operational Performance Assessment OPC Operational Control ORCAM Originating Region (SSR) Code Assignment Method ORD Operational Requirements Document OSA Operational Safety Assessment OSED Operational Services and Environment Definition PDR Proposed Defect Report (on ICAO Doc 9705) PISC Pre-Implementation Safety Case PM-CPDLC Protected Mode Controller Pilot Data Link Communication PRC Performance Review Commission

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PRU Performance Review Unit RF Radio Frequency R/T Radiotelephony RNP Required Navigation Performance RTCA Radio Technical Commission for Aeronautics, Inc. RVSM Reduced Vertical Separation Minimum SARPs ICAO Standards and Recommended Practices SES Single European Sky SITA Société Internationale de Télécommunications Aéronautiques SLA Service Level Agreement SNDCF Subnetwork-dependent Convergence Function (of ATN) SPR Safety and Performance Requirements Specification SRC Safety Regulation Commission (EUROCONTROL) SSR Secondary Surveillance Radar SWIM System-wide Information Management TMA Terminal Management Area UAT Universal Access Transponder UHF Ultra High Frequency UIR Upper Airspace Information Region ULCS Upper Layer Communications Service (of ATN) VDL VHF Digital Link VFR Visual Flight Rules VHF Very High Frequency VOR VHF Omnidirectional Range X.25 ITU Standard for Packet-Switched Data Communication

14.1.2 Data Link Services ACL ATC Clearances and Information ACM ATC Communications Management ADS-B out Automatic Dependent Surveillance – Broadcast "out" ADS-B-ACC ATC Surveillance for en-route airspace ADS-B-ADD Aircraft derived data for ground tools ADS-B-APT Airport surface Surveillance for en-route airspace ADS-B-NRA ATC Surveillance in non-radar areas ADS-B-TMA ATC Surveillance in terminal areas AMC ATC Microphone Check AOC Airline Operational Control applications ARMAND Arrival Manager Information Delivery service AS Airborne Surveillance applications ASPA Airborne Spacing applications ASPA-C&P Airborne Spacing – Crossing and Passing ASPA-ITP Airborne Spacing – In-Trail Procedure ASPA-S&M Enhanced sequencing and merging operations ATSA Airborne Traffic Situational Awareness applications ATSA-AIRB Enhanced traffic situational awareness during flight operations ATSA-S&A Enhanced visual acquisition for see & avoid ATSA-SURF

Enhanced traffic situational awareness on the airport surface

ATSA-SVA Enhanced successive visual approaches

AUTO-CPDLC

Automatic Controller Pilot Data Link Communications

CAP Controller Access Parameters

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COTRAC Common Trajectory Coordination D-ALERT Data Link Alerting service DAP (Automated) Downlink of Airborne Parameters D-ATIS Data link Automatic Terminal Information Service DCL Departure Clearance D-FLUP Data Link Flight Update service DLIC Data Link Initiation Capability DLL Data Link Logon D-ORIS Data Link Operational “En-Route” Information Service D-OTIS Data Link Operational Terminal Information D-RVR Data Link Runway Visual Range DSC Downstream Clearance service D-SIG Data Link Surface Information and Guidance D-SIGMET Data Link Significant Meteorological Information D-TAXI Data Link Taxi support DYNAV Dynamic Route Availability FLIPCY Flight Plan Consistency FLIPINT Flight Path Intent GRECO Graphical (enabler for) Trajectory Co-ordination GS Ground Surveillance applications OCL Oceanic Clearance service PPD Pilot Preferences Downlink SAP System Access Parameters TIS-B Traffic Information Service – Broadcast URCO Urgent Contact service

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ANNEX A. CONTEXT AND RELATIONSHIPS

A.1 Relationship with EUROPEAN COMMISSION Mandate Requirements

EUROCONTROL is mandated to develop a draft interoperability implementing rule on the provision and use of data link services supported by air-ground communications. The implementing rule must also address civil-military coordination.

The implementing rule has to identify the minimum set of requirements to harmonise the provision and use of data link services.

A.1.1 General Issues The justification of the mandate [EUROPEAN COMMISSION mandate/3] specifically states:

"In order to improve the interoperability and efficiency of the controller-pilot communications there is a need to specify the regulatory provisions for Air Traffic Services that have to be supported by air-ground data link communications."

This emphasis on controller-pilot communications points to the need for a standardised point-to-point data communications capability. There is less emphasis on broadcast data link services, which typically depend upon automated systems on the ground or in aircraft to transmit and interpret messages, rather than a dialogue between aircrew and controller.

The interoperability of controller-pilot communications is improved by the use of standard message types encoded in a standard way for interchange between compatible systems. Thus many of the problems associated with voice communication (unintelligibility, garbling, mis-hearing) are obviated. Data link makes more efficient use of the available VHF bandwidth and enables an unambiguous display / record of the transmitted messages.

The efficiency of controller-pilot communications is improved by increased automation and less time spent sending routine messages by voice, and retransmission when a message is not received clearly (or at all) due to interference.

[European Commission mandate/5.1.1] Systems, constituents, and associated procedures of the EATMN shall comply with the relevant implementing rule (IR) throughout their lifecycle;

The implication is that the implementing rule must take due account of these lifecycles and must not impose any short-term requirements that are likely to be rapidly superseded by the development of new systems, constituents and procedures. Rather, the implementing rule should foresee future advances, such as increased automation of systems and expanded message sets and ensure to the extent possible that these will be accommodated without changes to the existing provisions. Future provisions should be able to build upon, rather than replace, the provisions in the initial data link services implementing rule.

[European Commission mandate/5.1.2] IR shall determine any specific requirement [sic] that complement or refine the essential requirements (ER), in particular in terms of safety, seamless operation and performance, and in accordance with the specific ER for a specific system of Annex II, Part B of the interoperability Regulation;

Annex A Context and Relationships 1.1.doc 24/05/2006 Page A-1



The relationships with the Essential Requirements of the interoperability Regulation are considered in the Regulatory Approach document, section 8.3. The specific requirements are developed throughout the interoperability analysis.

[European Commission mandate/5.1.3] IR concerning new, agreed and validated concepts of operation or technologies shall complement or refine the ER, in particular regarding their coordinated introduction;

The interoperability analysis aims to identify the appropriate validated technologies and concepts of operation to enable the coordinated introduction of data link services (sections 3.1 – 3.2 of the Regulatory Approach document). The required provisions to complement and refine the Essential Requirements of the interoperability Regulation are identified in this analysis.

[European Commission mandate/5.1.4] IR concerning a system shall determine the constituents;

The implementation of the draft implementing rule for data link services will concern several of the systems identified in Annex I of the interoperability Regulation, namely:

• Communications systems for ground-to-ground and air-to-ground communications,

• Systems for air traffic services, in particular flight data processing systems and human-machine interface systems.

Data link services typically involve a number of complementary constituents in several avionics and ground systems. However, the implementing rule itself will not prescribe any specific technical solutions in terms of EATMN constituents and systems.

[European Commission mandate/5.1.5] IR shall describe the specific conformity assessment procedures involving, where appropriate, notified bodies based in the modules defined in Decision 93/465/EEC1 to be used to assess either the conformity or suitability for use of constituents as well as the verification of systems;

[European Commission mandate/5.1.6] IR shall identify, where appropriate, the tasks pertaining to the assessment of conformity or suitability for use of constituents to be carried out by the notified body;

Conformity assessment is considered in the Regulatory Approach document, section 5.

[European Commission mandate/5.1.7] IR shall identify, where appropriate, the tasks pertaining to the verification of systems to be carried by the notified body;

System verification is not explicitly addressed by the draft interoperability implementing rule. Obligations of stakeholders (Regulatory Approach document, section 3.5.7) include tasks such as establishing and monitoring service level agreements (SLAs) and verifying that required communication performance is maintained.

1 Council Decision 93/465/EEC of 22 July 1993 concerning the modules for the various phases of the conformity assessment procedures and the rules for the affixing and use of the CE conformity marking, which are intended to be used in the technical harmonization directives. Official Journal L 220 , 30/08/1993 p. 0023 - 0039




[European Commission mandate/5.1.8] IR should rely on rules and standards developed by international organisations such as EUROCONTROL and ICAO;

The draft implementing rule is consistent with relevant ICAO SARPs and technical provisions, and relies upon relevant standards developed by international organisations, notably EUROCAE and AEEC. Use is made of EUROCONTROL procedures and specifications developed under the LINK 2000+ Programme. The interoperability analysis aims to provide:

• A rationale showing the dependency, if any, between regulatory provisions and relevant ICAO documents.

• A rationale on the validated data link services and the choice of the technology(ies) for the timeframe 2005..2015.

[European Commission mandate/5.1.9] IR shall specify the conditions of implementation including, where appropriate, the date by which all relevant stakeholders are required to comply with them;

Options and recommendations for the conditions of implementation, including the dates of implementation are considered in the Regulatory Approach document, section 6.

A.1.2 Specific Issues [European Commission mandate/5.2 para 1] EUROCONTROL is mandated to develop a draft implementing rule that identifies:

• The objective and scope with, in particular, aircraft categories (including State aircraft) with mandatory data link equipage, and airspace in which data link services can be used;

The assessment of deployment conditions in the main body of the Regulatory Approach document considers implementing rule options and requirements in these areas. Specifically, aircraft categories subject to mandatory data link equipage are addressed in section 3.5.2, and the airspace in which data link services can be used is considered in section 3.5.1.

• The communications infrastructure to be used;

The communications infrastructure is considered in dedicated chapters in the body of the interoperability analysis (sections 3.3 and 3.4).

• The data link services to be used;

Data link services are analysed in depth in the body and Annexes of the interoperability analysis (section 3.2 and 3.4 and related Annexes).

• The ATC procedures for the provision and use of data link services;

ATC procedures for the provision and use of data link services are specifically considered in the body and Annexes of the interoperability analysis (section 3.5.4).

• General requirements applicable to air navigation service providers, aircraft operators and air-ground data communication service providers;

Requirements applicable to the various types of stakeholder are considered in the body and Annexes of the interoperability analysis (section 3.5.7).

• Requirements defining the conditions and criteria of temporary exemptions applicable to aircraft;




Exemption criteria are considered as part of the analysis of implementation conditions (section 6 of the Regulatory Approach document).

• Implementation conditions in particular timescale for ground and aircraft implementation.

Implementation conditions and issues informing the decision on timescales for ground and aircraft implementation are considered throughout the interoperability analysis. The actual timescales are considered in the analysis of implementation conditions (section 6 of the Regulatory Approach document).

[European Commission mandate/5.2 para 2] During the preparatory work for the definition of the regulatory approach, EUROCONTROL shall consider the various technical alternatives with their strong and weak points particularly with respect their capability to support current and foreseen data link applications. The availability of spectrum and the compatibility with existing military systems shall also be considered.

The various technical alternatives, spectrum issues and issues of compatibility with existing military systems are considered in the body and Annexes of the interoperability analysis.

[European Commission mandate/5.2 para 3(a)] During the drafting of the implementing rule, EUROCONTROL shall consider carefully the areas of applicability, the extent of equipage, timescales, the phasing of implementation and appropriate operational concepts.

It is a goal of the Regulatory Approach to consider all of these items.

[European Commission mandate/5.2 para 3(b)] These provisions and timing shall be consistent with the draft implementing rule on Air/Ground Voice Channel Spacing.

This aspect is discussed in A.2 below.

[European Commission mandate/5.2 para 4] The necessary flexibility allowing the evolution of data link services and/or supporting technology shall also be considered.

This is recognised as an important topic. The initial implementing rule on data link services interoperability will prescribe a limited core set of data link services. The implementing rule will be structured in such a way that future evolutions of data link services and/or underlying technology might be accommodated in the implementing rule, while building upon the existing provisions. Issues of baseline maintenance (e.g. evolution of referenced standards and specifications) will also be addressed. The structure of the implementing rule will be thoroughly analysed during its development to avoid undue dependencies between different categories of regulatory provisions.

[European Commission mandate/5.2 para 5] The related community specifications will also be identified.

It is a goal of the interoperability analysis to identify relevant community specifications to support the implementing rule. The articulation of the draft implementing rule with community specifications is considered in the Regulatory Approach document, section 9.




[European Commission mandate/5.5] EUROCONTROL shall take into account and build further upon any relevant material available during the scheduled timetable (existing or under development), in particular:

• The European Commission’s study on ATM/CNS interoperability roadmap (September 2003) – see A.3 below.

• The European Commission’s study on the roadmap for the implementation of data link services in the European Air Traffic Management (ATM) (February 2003) – see A.4 below.

• The ICAO Chicago convention and its relevant Annexes and standards

• ESARRs

• EASA and JAA documents

• EUROCAE standards

• EUROCONTROL specifications

• ETSI standards.

Reference is made in the Regulatory Approach to all of these document types.

A.2 Relationship with Draft Implementing Rule on Air/Ground Voice Channel Spacing

The draft implementing rule on air-ground voice channel spacing will require equipage of certain classes of aircraft in defined airspace areas with radio equipment capable of 8.33 kHz channel spacing.

Similarly, the draft implementing rule on data link services will likely require equipage of certain classes of aircraft in defined airspace areas with radio equipment capable of supporting an appropriate mode of VHF Data Link (VDL).

For those airspace users who will need to upgrade their radio equipment for compliance with SES implementing rules, there should only need to be a single upgrade, to support both 8.33 kHz voice channel spacing and VDL. Further, the timescales, aircraft classes and airspace areas should be aligned to the greatest extent practicable.

It is possible that certain categories of aircraft may be exempted from 8.33 kHz requirements under certain circumstances (cf. current policy, which is under review, of exempting State aircraft provided they are UHF equipped and are infrequent users of the airspace). Similar considerations of retrofit feasibility and cost, would apply to equipage of these categories of aircraft with VDL radios.

Also relevant here for State aircraft is the situation where, if exempted from the data link services implementing rule, the State aircraft will be handled over voice. However, the voice channel might be 8.33 kHz, from which the State aircraft might also be exempted. There is the possibility of a ‘chain’ of exemptions occurring from these two implementing rules, so the provisions will need to be co-ordinated.

The introduction of VDL in the frequency band 136.600 to 137.000 MHz requires a number of pre-existing assignments, such as ACARS and OPC (Operational Control) frequency to be re-assigned. Transferring OPC assignments to an alternative OPC sub-band would require a number of OPC assignments to be converted to 8.33 kHz channels to accommodate the high demand for OPC frequencies. VDL thus has a dependency on 8.33 kHz implementation.




A.3 Relationship with European Commission Study on the Roadmap for the Implementation of Data Link Services in European ATM

The European Commission's roadmap [20] for the implementation of data link services in European ATM, published in February 2003, is based on an independent study and assessment of different candidate data link technologies with the aim of proposing the most suitable data link(s) in support of the European decision-making process.

The study established a list of ATM applications that would be particularly suited for enhancing safety and capacity, based on the definition of medium and long-term ATM objectives. The list of ATM applications was reviewed extensively by Stakeholders and agreement was reached as to the priority and timescales for each ATM application.

The roadmap also considers candidate data link technologies, taking account of factors such as the ability to meet the technical requirements of the ATM applications, technology maturity and cost.

The roadmap identifies 5 steps towards the delivery of needed capacity and safety benefits.

Table A-1. Steps in the European Commission Data Link Roadmap Step Scope Timescales

(“operational need”)

Stakeholder comments (“availability of technology and infrastructure”)

1 Early air/ground ATM applications

2006 (75% equipage)

2011/2012 (based on perception of market reaction assuming no incentive for early equipage.) (75% equipage)

2 ATM applications related to downlink of air derived data

2008 (75% equipage)

2006 (>75% of equipage)

3 Introduction of spacing 2010 (75% equipage)

Enhanced Visual Acquisition (EVA) only – 2007 Final approach spacing + EVA– 2008 Other spacing – 2012 (All dates – start of equipage)

4 Extension of air/ground ATM applications

2009/2010 (75% equipage)

2012 + (based on timescales for Step 1) (start of equipage)

5a Introduction of separation and self separation

2013+ (75% equipage)

Oceanic and remote –2012 Terminal and en-route – 2018 Sole means surveillance 2017 – 2019 (All dates – start of equipage)

5b Conflict free trajectory negotiation.

2013+ (75% equipage)

2011 (Start of equipage)

Step 1 was defined as "early air/ground ATM applications". At the time of the study, based on foreseen demand, widespread operational use of the Step 1 applications (75% equipage) was required by 2006 to avoid anticipated capacity shortfalls.

The study assessed candidate technologies in terms of performance, cost and maturity, and considered a number of implementation scenarios in which combinations of technologies were used to support the 5 steps in the ATM application roadmap.

It was concluded that the data link technologies necessary to deliver the ATM application roadmap up to and including step 4 are already available or close to being available and, assuming implementation constraints can be addressed, could be implemented in time to meet demand.




The study analysed a number of scenarios combining the data link technologies. All of the scenarios were shown to deliver benefits, provided that the identified issues are solved, but costs may vary from one scenario to the other.

Factors supporting the implementation of certain data link technologies included:

• The availability and capability of technologies.

• The availability of standards for airborne and ground equipment.

• Decisions and recommendations made by the community in support of the implementation of VHF Data Link Mode 2 (VDL-2) for airline operational communication (AOC) and a first set of ATM applications grouped under the name of LINK 2000+ and 1090 MHz Extended Squitter (1090 ES) for a first set of ADS-B applications.

• Consensus from at least France, the UK and Germany, their relevant ANSPs and some AOs towards implementation of Enhanced Surveillance based on Mode S (Mode S EHS) in core Europe, building on the current mandate for Mode S Elementary Surveillance.

• Investment by Aeronautical Communication Service providers in VDL-2 ground networks for AOC applications.

• Investment by Airbus in solutions to support a data link technology route based on VDL-2, Mode S EHS and 1090 ES.

• Emerging plans for a VHF digital link Mode 4 (VDL-4) AOC network.

• Investments made by EU and project partners in EU sponsored test and trials projects of VDL-4 for ADS-B ATM applications.

• Plans for implementation of VDL-4 based ATS networks in Sweden and Russia.

The barriers to reaching a decision on the implementation of data link technology included a number of technical issues with the proposed links raised by the study, which need to be resolved or alternative solutions must be pursued. The key issues were:

• Performance issues and spectrum consequences with each link, including uncertainty and lack of simulation data on the effective data rates of VDL modes 2, 3 and 4.

• Co-site issues including whether interference between one VDL radio and another VDL or current voice radios could be controlled or eliminated by technical means. A particular issue may arise when radios are transmitting repetitively.

• The need to understand how a transition to VDL-3 could be made.

• The need to derive frequency-planning criteria for VDL-3 and VDL-4 and to investigate frequency availability in Europe for Universal Access Transponder (UAT).

• Spectrum shortage in the VHF Communication band driven by the saturation of the spectrum by voice channels, exacerbated by an inefficient use of existing spectrum.

• Incomplete demonstration of data link technical and operational performance during all phases of flight.

• Incomplete assessments of integrity and availability requirements for ADS-B.

The roadmap study confirmed full consensus in the community that implementation of data link technology is essential to meet future needs and that it is urgent that the




community starts as soon as possible with implementation programmes. However, there was no consensus on how to move forward. No single solution appeared to be suitable for, or was supported by, all users. For the initial steps of the roadmap, the view of the community was split:

• ANSPs operating in core Europe, IATA, and Airbus saw a route starting from VDL-2, Mode S EHS and 1090 ES as the most pragmatic way forward with communications service providers supporting VDL-2 for AOC and ATM applications as described under the LINK 2000+ Programme.

• The General Aviation community, Swedish and Russian ANSPs, and a low cost carrier saw a solution based on VDL-4 as the cheapest way forward for a combined set of applications.

Options for Steps 1, 2 and 3 The deployment of VDL-2, Mode S EHS and 1090 ES to support the requirements of Steps 1, 2 and 3 in the ATM Application Roadmap is based on:

• The possibility to expeditiously deploy VDL-2, taking advantage of the maturity of the technology and of a business case starting with AOC services over VDL-2. Relevant factors include saturation of the ACARS system and the possibility to expand the utilisation of VDL-2 to non time-critical ATM applications as described in LINK 2000+ Programme documentation and in Step 1 of the European Commission roadmap's application assessment. There is consensus among some actors as to the implementation of such ATC services using ground infrastructure at the core-European area centres.

• Widespread equipage with Mode S EHS through a mandate in some core states and their current plans for establishment of a network of Mode S radar stations;

• The availability of 1090 ES "ADS-B out” resulting from equipage to support Mode S EHS, followed by a subsequent upgrade to support "ADS-B in”.

• It would result in a common decision with North America for 1090 ES as an interoperable link.

There was also some support for alternative solutions based on VDL-4. The driver for this scenario relies on:

• Exploiting the ability of VDL-4 to provide broadcast and point-to-point services as a “generic” enabler for all considered applications;

• Achieving a lower cost route for some operators and service providers;

• Progressing a system that might prove essential in roadmap Steps 4 and 5.

• Making more efficient use of available spectrum.

These scenarios are not mutually exclusive, e.g. general aviation may not need to be forced to equip with VDL-2 assuming only about 75% rate of equipage is required for step 1 applications.

The roadmap study showed that, in the absence of any remedial actions, the timescales based on industry implementation plans at the time of the study will probably not meet the increased traffic demand during the period 2003 - 2018.

It also noted there is no contingency to respond to an upturn in traffic demand. The study used EUROCONTROL STATFOR base case figures, which provide for a doubling of traffic levels by 2020. The IATA and Airbus expectation is that the increase in demand will be greater than this, amounting to three times the current levels in 2020.




The timescales for implementation of the ATM applications, agreed during stakeholder consultation, provided shorter timescales for ATM applications based on user needs for additional capacity.

The route based on VDL-2, Mode S EHS and 1090 ES is seen by some stakeholders as a pragmatic choice to deliver early benefits, although concerns with this route, raised during the public consultation process, need to be addressed by the community. In order to reduce the total costs it may require appropriate exemption policies exempting non frequent users of the core airspace whenever possible.

If both routes are supported it is important to determine under which conditions co-existence of data link technologies is possible and whether the disadvantages outweigh the advantages. The advantage is that, potentially, the requirements expressed by all airspace users including general aviation can be accommodated. The disadvantages include additional costs associated with supporting two routes and a requirement for additional VHF spectrum that might otherwise be reserved for just one link.

The roadmap study identified a number of actions to assess outstanding technical issues, which must be completed before a decision could be made. These urgent actions, which were agreed at a stakeholder workshop in February 2003, are summarised below.

Table A-2. Urgent Actions identified by the European Commission Roadmap Study Required Action (Feb 2003) Current Status (Oct 2005)

Large-scale simulations of VDL-2 performance to support determination of frequency requirements for VDL-2.

Simulations have been performed by EUROCONTROL (e.g. see reference [66])

Detailed analysis on the performance of 1090 ES in dense traffic/high interference environments, including the airport surface, and on the feasibility to certify it for ADS-B applications.

The following activities are performed by EUROCONTROL (CASCADE) - Analysis of 1090 data link capacity (results expected by Nov 2005) - Impact of TIS-B on 1090 data link capacity (results expected by early Spring 2006) - Certification roadmap for initial ADS-B applications (expected by Dec 2005)

Detailed studies to resolve the remaining technical issues surrounding VDL-3 and 4, including determination of performance, such as effective data rate and guard bands using high-fidelity large scale simulations to support the determination of frequency requirements, and work on onboard architectures.

There is an active EUROCONTROL project to fix spectrum requirements for VDL 4 per channel and the capacity available per channel, including airborne co-site effects. Results are due for end 2006. Spectrum investigation depends on production-radio availability. For VDL-3, there is some work but this action is "overtaken by events" as VDL-3 is not an option in Europe.

The specification of VHF DSB-AM communications radios should be re-visited to see if interference from voice and VDL can be reduced.

There has been no specific action. This point is believed to be obsolete, as a feasible frequency plan has been set up taking all interference between AM-DSB/ VDL-2 into account (including airborne co-site) and as this plan is currently being used for deployment across Europe.




Required Action (Feb 2003) Current Status (Oct 2005) Development of frequency planning criteria and assignments for VDL-3 and VDL-4.

There is an active EUROCONTROL project to fix spectrum requirements for VDL-4 per channel and the capacity available per channel, including airborne co-site effects. Results are due for end 2006. Spectrum investigation depends on production-radio availability. For VDL-3, there is some work but this action is "overtaken by events" as VDL-3 is not considered an option in Europe.

Investigation of the availability of a frequency for UAT.

The frequency 978 MHz has been identified as the UAT frequency. Work is ongoing (WRC2007) to introduce an appropriate footnote in the radio regulations providing the possibility to assign this frequency - where UAT will be operational. Therefore this "action" is completed.

Raising the need to consider technologies operating outside the VHF band at the World Radio Conference (WRC) in 2003 in order to begin any necessary processes to obtain spectrum allocation.

Action no longer applicable for WRC 2003. There is ongoing work for WRC 2007. There is no impact on the data link services implementing rule.

The results of this work could be used to determine which ATM applications could be delivered by the data link technologies as a function of traffic growth, equipage and spectrum availability.

Completion of the urgent actions will support the decision process for Steps 1, 2 and 3 of the roadmap. Thereafter, other actions must be carried out to support the early steps of the roadmap and to support decisions for later steps.

A.4 Relationship with European Commission ATM-CNS Interoperability Roadmap (AIR-2003)

The AIR-2003 roadmap [21] proposes the need for implementing rules in the Communications domain.

It analyses the OATA communications architecture and concludes that a more layered approach is needed. This is achieved by adopting the OSI reference model as applied to the ATN Technical Specifications.

It proposes that the need for interoperability regulatory documents to refine the Essential Requirements, i.e. to allow the communication system to achieve appropriate levels of performance, seems twofold:

• Intra-layer: within one layer of the hierarchy, performance has to be assessed; there are interoperability issues that need to be regulated and documented, e.g. the inter-network addressing plan;

• Inter-layer: at the interface between the different layers, defined notably by an exchange of information with given characteristics (of quality of service for example), regulation documents have to be defined to qualify these characteristics, e.g. concerning the communication data performance at the end-user level.

A.4.1 Need for Implementing Rules Thus, the study concludes, there seems to be a need for implementing rules, to clarify the performance requirements for every part of the communication model.




The classes of performance required by the Essential Requirements need to be qualified.

Implementing rules should not conflict with ICAO SARPs or question these documents due to their very nature of worldwide established standards; neither should they repeat ICAO rules or specifications. However, the specific European context generates the need to complement and/or refine the content of the ICAO documents through implementing rules.

The study concluded that implementing rules are necessary for the required performance specified in the specific Essential Requirements of the interoperability Regulation, for every layer of the communication model:

• Sub-networks: o Air-ground and ground-ground infrastructure performance o Data link layer performance o Network layer performance o Inter-network performance

• Operational level: o Data link performance o Voice performance (out of scope of the current European Commission

mandate).

Concerning the Essential Requirement requiring "support to new concepts of operation", a unique implementing rule dealing with air-air communication operations was proposed. However, this is considered out of scope of the current European Commission mandate.

A.4.2 Implementing Rules Roadmap From a consideration of the needs for implementing rules detailed above, a prioritisation derived from EUROCONTROL work (EATM Communications Strategy [28] in particular) and the estimated urgency of the issues, the following roadmap was drawn in AIR-2003:

The first package of regulatory material, i.e. of priority 1, details the interoperability Regulation "seamless operation" specific requirement for the air-to-ground sub-network layer of the model. The physical and data link layers performance need to be standardised, leading to two different proposed implementing rules and a prpopsed community specification. These are summarised in the left hand column of Table A-3. The right hand column of the table describes the proposed approach for the data link services implementing rule, derived from the present interoperability analysis.

Table A-3. AIR Roadmap High Priority Regulatory Material Roadmap First Package Proposed

Coverage Applicability to Data Link Services

Regulatory Approach

IR_COM_1.1: Concerning air-ground physical layer performance, particularly the frequency management and allocation, directly related to the Quality of Service available on the link considered.

VDL-2 to be prescribed.

Frequency management and allocation is out of scope – ICAO Frequency Management Group (FMG) responsibility.

Performance and capacity must match safety and performance requirements (SPR) allocation for communications.

IR_COM_1.2 concerning the data link layer characteristics, focusing on the data link layer channel sharing enabling required performance to be provided.

Not considered for the implementing rule.

EUROCONTROL VDL-2 frequency planning takes account of required ATS and AOC capacity.




Roadmap First Package Proposed Coverage

Applicability to Data Link Services Regulatory Approach

CS_COM_1.1 No need to regulate the functional specifications and performance of the ground-ground COM domain. Community specifications concerning ground-ground COM general architecture could promote a unified standard for a ground-to-ground communication network, e.g. based on EUROCONTROL current works (seamlessness).

Functional specifications are not a subject for prescription.

Performance and capacity must match SPR allocation for communications.

SLAs with aeronautical communications service providers (ACSPs) will be within the likely scope of the DLS implementing rule.

ACSPs will be required to interconnect.

ANSP ground network is out of scope. (There may be a future implementing rule covering the Pan-European Network Service)

The second package of regulatory material proposed in AIR-2003 is a set of rules concerning the "seamless operation" specific requirement that concerns all the layers of the COM model, from the sub-network to the operational level, through the inter-network layer. These are summarised in Table A-4, together with the proposed approach for the data link services implementing rule.

Table A-4. AIR-2003 Second Package Roadmap Second Package Proposed


Regulatory Approach

Implementing rule concerning the ground-ground physical layer functions and performance.

Performance and capacity must match SPR allocation for communications.

Details of ground-ground interconnections and interfaces are a local matter for ANSPs and ACSPs.

Generic implementing rule concerning air-ground sub-network connected service performance,

Industrial voluntary standards with details for each air-ground sub-network technology

The DLS implementing rule should prescribe ATN procedures and allocate performance requirements to the sub-network.

ATN/VDL-2 is the only proposed technology. A EUROCONTROL specification is envisaged to specify the Baseline requirements, with reference to EUROCAE and AEEC standards.

Voluntary community specification defining network architecture options and assessing the inter-network layer performance, e.g. standardising inter network addressing plan or sharing agreements among the different actors, so that seamless performance can be guarantied throughout the whole COM system.

The nature of prescriptions is described in Regulatory Approach Annex I.

End-to-end communications performance must match SPR allocations.

Implementing rule and voluntary community specification defining data link services operational characteristics and performance, based on current documentation but putting the emphasis on Quality of Service requirements for each data link service.

The DLS implementing rule will prescribe the data link services. Their operational characteristics are specified by reference to INTEROP and SPR standards (EUROCAE) via a new EUROCONTROL specification.




Roadmap Second Package Proposed Coverage

Applicability to Data Link Services Regulatory Approach

Implementing rule acting as a symmetric standard of the previous implementing rule, but in the framework of voice services performance. Adjacent community specifications concerning digital voice equipment could support the central implementing rule.

Voice services are considered out of scope of the current European Commission mandate on data link services.

A last package including a single implementing rule was proposed, to addresses the specific requirement, identified in the interoperability Regulation, "support to new concepts of operation". This is summarised in Table A-5, together with the proposed approach for the data link services implementing rule.

Table A-5. AIR-2003 Proposed Final Package Roadmap Final Package Proposed


Regulatory Approach

Long-term implementing rule dealing with airborne separation assurance system (ASAS) operations. The study noted that it seems necessary to complete the Essential Requirement on this subject, and to support the industrial standards in development. It would be completed by a voluntary community specification.

This topic, involving air-to-air communication, supporting broadcast data link services, is considered in Regulatory Approach Annex B.




ANNEX A. CONTEXT AND RELATIONSHIPS ......................................................... A-1 A.1 Relationship with EUROPEAN COMMISSION Mandate Requirements.............. A-1

A.1.1 General Issues ......................................................................................... A-1 A.1.2 Specific Issues ......................................................................................... A-3

A.2 Relationship with Draft Implementing Rule on Air/Ground Voice Channel Spacing.............................................................................................................. A-5

A.3 Relationship with European Commission Study on the Roadmap for the Implementation of Data Link Services in European ATM ..................... A-6

A.4 Relationship with European Commission ATM-CNS Interoperability Roadmap (AIR-2003) .......................................................................................... A-10

A.4.1 Need for Implementing Rules................................................................. A-10 A.4.2 Implementing Rules Roadmap............................................................... A-11




ANNEX B. SELECTION OF DATA LINK SERVICES

B.1 Introduction

The ICAO FANS concept recognises that significant benefits are expected to derive from the implementation of air traffic services (ATS) supported by data link communications. Compared to the existing ATC procedures using voice radiotelephony (R/T), the expected benefits include:

• Increased safety by reducing the potential for erroneous receipt of messages;

• Reduction of voice-channel congestion;

• Reduction of R/T workload for both the pilot and controller;

• Increased communication availability;

• Reduction of late transfer of communications;

• Reduction of re-transmissions caused by misunderstood communications;

• Increased flexibility in handling ATC communication tasks;

• More efficient use of airspace due to more time being allocated to providing a better service to user aircraft, rather than to routine communications tasks;

• Reduced controller stress/memory burden; and

• Reduced controller communication time.

B.1.1 Airspace Capacity Benefits Air-ground data link services are expected to decrease controller workload and increase the overall EATMN capacity.

B.1.2 Safety Benefits The availability of a data link communication channel in addition to the existing voice R/T communication will reduce communication errors, aircrew fatigue, controller fatigue and will thus contribute to higher safety levels. R/T communication has a number of drawbacks in today’s busy traffic environment:

• Pilots have to listen to each controller-initiated communication while approximately only one in twenty communications is addressed at the flight in question, contributing to aircrew fatigue. (However, loss of the "party line" effect can also be detrimental to the pilot's situational awareness).

• Blocking of voice frequencies by simultaneous transmissions and stuck microphone buttons are a common occurrence.

• A reduction of the pilot’s communication workload will allow greater time to concentrate on other tasks and thus contribute to higher safety levels.

• Mis-heard or misunderstood instructions occur more frequently as RF congestion increases, while controllers have less time to monitor operational responses as sector loads increase.

B.2 The ATM Operational Process

The goal of the ATM operational process is to meet the overall objective set out in the ATM Strategy for 2000+ [7]:

Annex B Selection of Data Link Services 1.1.doc Page B-1 24/05/2006



"A collaborative and co-ordinated layered planning framework for ATM operations in a gate-to-gate context based on the principles of Collaborative Decision Making and System Wide Information Management."

The Operational Concept Document (OCD) [8] divides ATM operations into a set of operational components, described as those invariant processes (or tasks) which necessarily have to occur for the ATM system to be able to function. They encompass such core ATM tasks as the management of airspace resources, the planning and management of flows of aircraft and of individual flights, the separation of aircraft from hazards, etc. Invariant processes provide a means to describe the basic building blocks, or “what”, of ATM, independent of the conceptually driven “who”, “how” and “where”.

This perspective of what ATM consists of has the advantage of breaking the concept down into understandable segments, independent of any pre-determined concept themes or organisations. By not being concerned with where things are done, who performs them, or how they are carried out, this approach helps to identify the main lines of action along which change has to be effected.

The ATM Components and their interactions are described in detail in the Concept of Operations (Year 2011) [9]. Each of these concept components fulfils one or more specific ATM purposes. Those concerned with Data Link Services comprise:

• Air Traffic Control (ATC), consisting of Traffic Synchronisation i.e. the management of the flow of traffic through merging (Sequencing, which includes smoothing and metering) and crossing points such as traffic around major airports or airways crossings; and Separation Assurance which is fundamental and relates to the application of separation between aircraft.

• Airport Operations concerns the traffic management and safety processes on or in the vicinity of airports. It includes the interaction with stand allocation, ground handling and other airport management functions. As an integral part of ATM, Airport Operations ensure the efficient use of capacity of the airside infrastructure.

B.2.1 Data Link Services in the ATM Process Model The position of data link services is analysed here with respect to the overall ATM process model drawn up in the Concept of Operations 2011 [9]. Data link services are enablers for ATS operational improvements. They can be used to support different parts of the ATM process model. Data link services designate a wide range of air-ground data exchanges. Each data link service must be associated to the relevant subset of the ATM process model.

The objective of the ATM process model itself is to provide a detailed description of how the Operational Concept (The Vision) stated in [8] is applied for the time frame 2011 and beyond (before 2020), taking into consideration the ATM 2000+ Strategy [7] roadmap (Volume 2, Chapter 5). In doing so it identifies through the planning phases the interactions between the ATM components, the information flows and the concerned actors.

Data link services belong primarily to the “ATC” ATM Component, which the ATM Process Model divides into its two principal functions: synchronisation and separation. During the tactical planning phase this division is not readily visible. On the day of operation, the planning processes display the division. The first process provides a synchronised traffic flow, which reduces the requirement for tactical intervention to ensure separation, and coincidentally increases capacity of the system. Two main processes are identified, involving ATC (AT) on the Day of Operations (DO):




• AT DO1: Traffic Synchronisation, Monitoring/Adjustment (Regional/Local);

• AT DO2: Planning, Co-ordinating, Monitoring, Reacting and Separation Assurance.

Each data link service supports the AT DO2 process identified in the EUROCONTROL concept of operations for 2011 [9]. The data link services are mainly significant for the following AT D02 sub-processes:

• Monitor separation between flights;

• Monitor and react to compliance monitoring tools;

• Issue clearances and instructions as appropriate;

• Provide advice and information as required by pilots;

• Coordinate decisions with adjacent sectors.

B.2.2 Data Link Service Categories There are two fundamental categories of data link services; those that rely on a point-to-point exchange of information between two identified partners, and those that rely on information being broadcast for receipt by any suitably equipped party. Similarly, ATM operational concepts tend to differentiate between point-to-point data link concepts and those that use the concepts of ADS-B/TIS-B (the latter are often considered to be surveillance rather than communications-oriented). This is illustrated in Figure B-1.

Point-to-Point(addressable)

Broadcast(ADS-B/TIS-B)

Functional architecture

(pt-to-pt)

Functional architecture

(b’cast)

Data link services

ATM Strategy 2000+

OCD CONOPS 2011

Strategy

Concept of Operation

Services

Architecture

Figure B-1. Point-to-point and Broadcast Services

All air-ground communications technologies are fundamentally broadcast in nature due to the nature of RF communication. Most can also be used in a point-to-point configuration, and whether an air-ground data link is used in a broadcast or point-to-point mode depends on the requirements of the data link service.

Note that there are examples where technologies normally used for point-to-point communication (e.g. VDL Mode 2) are used to broadcast information on dedicated frequencies for FIS. Similarly, there are cases where technologies normally used for broadcast communication (e.g. VDL Mode 4) are used in point-to-point mode.

Data link services may also be categorised according to the functions that they support in support of the CONOPS sub-processes. A broad categorisation would be along the lines of:




• ATC Clearances

• Surveillance

• Communication

• Information

Functional, Operational and Procedural, Human Factors, End-to-end certification, security, communications, recording, and legal requirements for the data link services may be found in the Operational Requirements Document (ORD) [10].

Different data link services are applicable to different phases of flight. This is illustrated in Figure B-2.

Flight Events

ATM Phase

Pro file

Units and Facilities Involved

Data link Serv ices

RequestStart-Up T ake-Off Cr uise Level

Param eterfromDestination

Landing

TacticalP lanning A irport D eparture E n-R oute/Oceanic/P olar A rriva l A irp ort

IFPSC FM UFM Ps

TW RAPPAC CIFPSFM Ps

APPAC C(s)IFPSFM Ps

AC C (s)IFPSFM Ps

AC C (s)APP

TW R

- A C M/D LL (incl A uto C PD LC)- A C L (Incl A uto C PD LC)- D C L- D SC- PPD- FLIPC Y- FLIPIN T- A MC - D-FIS (A TIS, OTIS , OR IS, SIGM ET , FLU P, R VR)

- D-TA XI- D-SIG- A D S-B - D-A LER T- SA P- A R MA N D- GR EC O- C OTR A C - U R C O- D YN A V

Data link Service Dom ain

Figure B-2. ATS data link services by flight phase

B.2.3 CPDLC Terminology One important category of point-to-point data link services makes use of direct, human, data communication between aircrew and air traffic controller.

However, the phrase "controller-pilot data link communications" or CPDLC can have different meanings depending upon the context and the level of discussion.

At the operational level, as considered in this Annex, "controller-pilot data link communications" can be used to refer to any data communication between pilot and controller, usually but not necessarily based on the ICAO Doc 4444 (PANS-ATM) message elements, and independent of any underlying technology.

At a more general level, the term is sometimes used as a synonym for any data link communication between aircraft and ground system.




The "CPDLC Programme" in the USA is another example of usage.

In FANS-1/A and equivalent products compliant with the interoperability requirements in EUROCAE ED-100 or ED-100A, "CPDLC" refers to a specific set of pre-defined messages, together with the interchange mechanism based on ACARS protocols, including conversions between bit-stream and character encodings. The message set is similar to, but not identical to, the PANS-ATM message set, as it pre-dates the current ICAO manual. Further, different operational implementations support different message subsets.

In the ATN world, CPDLC refers to "Application Type 02", and consists of the data link application formats and protocols defined in ICAO Doc 9705 Sub-Volume II, section 2.3. This supports the full set of message elements defined in the PANS-ATM, together with functions such as CPDLC-Start, CPDLC-message, CPDLC-end, DSC-Start, DSC-end, CPDLC-forward, CPDLC-user-abort and CPDLC-provider-abort. Different versions of the CPDLC protocol may support slightly different functionality (interface to security functions, additional message elements, etc.).

Protected Mode CPDLC (PM-CPDLC), or "Application Type 22", is essentially the same as ATN CPDLC with the addition of an application level integrity check sequence to every uplink and downlink message. PM-CPDLC is not interoperable with CPDLC at the message coding level.

Data link services such as ACL, ACM and AMC can be realised using selected elements of the CPDLC formats and protocols.

FANS-CPDLC and ATN CPDLC are not interoperable at the message coding level, even though both use the ASN.1 packed encoding rules to encode/decode the bit stream used for interchange.

In this document, the term "CPDLC" is used in the ATN data link application sense, unless otherwise stated. The term "FANS-CPDLC" is adopted to refer to FANS-1/A and equivalent products compliant with ED-100 or ED-100A.

B.3 Operational Requirements

The ICAO Manual of ATS Data Link Applications Doc. 9694 [22] defines an ATS operational requirement as:

"A statement of the operational attributes required of a system for the effective and/or efficient provision of air traffic services for users."

Operational requirements for data link services have been developed to varying levels of maturity and are available from a number of sources within EATM.

B.3.1 Air-Ground Cooperative ATS ATS operational requirements are specified and validated, both internationally within ICAO operational Panels and on a Regional basis. In ICAO, the Operational Data Link Panel (OPLINKP) (formerly known as Automatic Dependent Surveillance Panel - ADSP) develops operational requirements. In Europe, the former EUROCONTROL Air/Ground Cooperative ATS (AGC) programme was established to develop, validate and standardise gate-to-gate operational concepts, operational requirements and procedures for the provision of new forms of ATS.

The AGC programme produced the ORD (Operational Requirements for Air-Ground Cooperative Air Traffic Services AGC-ORD-01 [10]), whose purpose is to present a set of coordinated EATM air-ground data communications operational requirements in support of Cooperative ATS in the near term (2000-2015 time period).




The ORD contains Recommended Practices for ECAC Member states intending to provide ATM air-ground data communications services. It defines:

• The baseline operational requirements for future EATM technical work (e.g. development of the communications infrastructure);

• The consolidated EUROCONTROL Member States and aviation organisations operational requirements input to ICAO groups, in particular the Operational Data Link Panel (OPLINKP).

The current and transitional operational and functional environments for the services specified in the ORD are described in the ATM Strategy for the Years 2000+ [7] and the EATM OCD [8].

The ORD development also took into account, and provided input to, standardisation activities conducted within other groups such as the European Organisation for Civil Aviation Equipment (EUROCAE), the Airlines Electronic Engineering Committee (AEEC), ARINC, RTCA and relevant ICAO bodies. Significant parts of the ORD were used as input to the ICAO Manual of Air Traffic Services (ICAO Doc. 9694) in order to include consolidated European requirements in the global standards.

The ORD specifications [10] are not entirely compliant with the data link applications specified in the ICAO Manual of Air Traffic Services [22] and the ATN Technical Provisions [2]. The ORD proposes enhancements to the ICAO operational and technical material in order to best meet the European operational requirements, for example additional CPDLC message elements are proposed.

These enhancements may result in updated versions of the standards in the future, and may require software updates in airborne and ground end systems when additional data link services beyond the initial core set are deployed. Interoperability issues concerning message set conformance and data link application version numbers are considered further in Annex F.

In order to provide an operationally oriented description of the use of data communications for ATS, the definitions and treatment of the electronic messages that can be exchanged between aircraft/aircrew and ATS units/controllers are grouped into operational services. These services describe a set of actions and a set of data link messages which have a clearly defined operational goal and which begin and end on an operational event.

Interoperability requirements then need to be developed for each service to be implemented, as described in Annex C of the Regulatory Approach.

The data link services for which the ORD specifies stable operational requirements are listed in Table B-1.

Table B-1. ORD Data Link Services Data Link Service

Description

ACL ATC Clearances and Information

Specifies the dialogue procedures between aircraft and controlling ATS unit (C-ATSU) using air-ground data communications. Describes rules for combining voice and data link communications and abnormal mode requirements and procedures. Allows the request (aircrew) and delivery of (controller) en-route clearances such as level (including constraints based on time, position, vertical rate-of-change), heading, speed (IAS/Mach), direct route, and rate of climb/descent. The ACL service also enables SSR code change instructions and provides acknowledgements in both directions.




Data Link Service

Description

ACM ATC Communications Management

Provides automated assistance to the aircrew and controller for conducting the transfer of all ATC communications, both the voice channel and the data channel. The ACM service supports the transparent transfer of data communications, in synchronisation with the transfer of voice communications. It also retains the operational principle that there is only one controlling authority, and that the controlling authority is properly and unambiguously identified. (Current sector controller initiates this service to transfer ATC communications to next sector).

DSC Downstream Clearance

The DSC service enables flight crews to request and obtain clearances or information from downstream ATS Unit (i.e. ATS Unit which will assume the control of the flight in the future). Oceanic clearance delivery is one example – see OCL service in Table B-9.

The main objective is to provide flexibility to flight crews in the request and receipt of clearances and information, thus allowing them to optimise the workload in the cockpit and profile planning.

DCL Departure Clearance

Provides automated assistance for requesting and delivering departure information and clearance whilst an aircraft is at the airport.

CAP Controller Access Parameters

Makes specific flight information available to the controller by automatically extracting the relevant data from the airborne systems. The use of the CAP parameters by the controller should be considered as a means to provide enhancements to the existing ATC surveillance functions.

There is no change to flight crew procedures as the parameters are automatically down linked. Whilst the controller may use the parameters to assist in planning there is no obligation to do so.

The controller HMI should indicate aircraft about which valid CAP data is available. Since the provision of instantaneous indicated heading, air speed, vertical rate and wind vector through the CAP service does not have a radical impact on the controller working methods, the benefits introduced by the service are expected to be realised even with a small proportion of CAP equipped aircraft simultaneously in the same sector. As this proportion increases, the benefits will also increase. The CAP service is available in all phases of flight.

FLIPCY Flight Plan Consistency

Provides controllers and aircrew with automated support to confirm that flight plans in airborne and ground systems have consistent route information. The objective is to increase capacity by reducing controller workload per aircraft and by improving ATC planning tasks through confidence in flight plan information.

DYNAV Dynamic Route Availability

Automates route changes provision when an ATS Unit can offer alternative routings, even before the flight is under the control of that unit.




Data Link Service

Description

PPD Pilot Preferences Downlink

PPD automates the provision via data-link of selected flight crew preferences to controllers. The main objective is to allow flight crews, in all phases of flight, to provide the ATS Unit with updated information not available in the filed flight plan (e.g. maximum flight level, minimum speed, etc.).

DLL / DLIC Data Link Logon / Data Link Initiation Capability

Ensures all necessary technical and operational prerequisites are met for the exploitation of subsequently desired data link services. It is initiated by aircrew on first contact with an ATC Unit that supports data communications. It is a pre-requisite to the operational data-link services and supports flight plan/address association in the ATC system. The information provided to the ground system includes: airframe identification, aircraft identification, supported air-ground data-link services, departure airport, destination airport, and estimated off block time (EOBT), when available.

D-OTIS Data Link Operational Information Service

The D-OTIS service provides automated assistance to flight crews by delivering updated meteorological and operational flight information (based on METAR, ATIS, NOTAM/SNOWTAM and PIREPS) specifically relevant to the departure, approach and landing phases of flight. This is a generalisation of the D-ATIS service (see Table B-9).

The main objective is to provide pilots with easy access to the widest possible range of information to support the decision making process whilst reducing cockpit workload and enhancing safety.

D-RVR Data Link Runway Visual Range

Provides aircrew with automated assistance in requesting and delivering the Instantaneous RVR.

The ORD also outlines draft operational requirements for a number of less mature data link services, as listed in Table B-2.

Table B-2. ORD Draft Data Link Services Data Link Service

Description

SAP System Access Parameters

This data link service aims at constituting and keeping up-to-date a ground-based database of aircraft parameters to be used by several different ground functions. The service is foreseen to be primarily used in continental airspace, both in en-route and terminal areas.

(Draft service defined in ORD, not retained under this name in CASE 3)




Data Link Service

Description

D-SIGMET Data Link Significant Meteorological Information

The purpose of SIGMET information is to advise pilots of the occurrence or expected occurrence of en-route weather phenomena that may affect the safety of aircraft operations.

The preparation and issue of SIGMET reports is the prime responsibility of meteorological watch offices (MWO). The validity period of these reports is normally of 4 hours, 6 hours being the maximum, and they are written in abbreviated plain language, using approved ICAO abbreviations.

SIGMET information messages are distributed on ground initiative to aircraft in flight through associated ATS units

(Draft service defined in ORD, not retained under this name in CASE 3).

COTRAC Common Trajectory Coordination

The purpose of COTRAC is to establish and agree 4D-Trajectory contracts between flight crew and controllers using graphical interfaces, air and ground data communications and automation systems, by means of a structured negotiation method in order to significantly enhance ATM capacity and flexibility. To date only a 2D-COTRAC enabling the air-ground negotiation of 2D-Trajectory is evaluated, but the ultimate task remains the ability to negotiate 4D-trajectories. COTRAC can be air or ground initiated.

The data link services specified in the operational requirements for air-ground cooperative ATS are categorised in [10] into ATC services and data link flight information services (D-FIS), as illustrated in Figure B-3.




ATS

ATC FIS Alerting

receiveinformation

intent flightprogress

determinepositions

issueclearances

co-ordinatewith other units

ATS as defined inICAO Annex 11

Data LinkServices

FLIPCYAir and ground

flight planconformanceverification

DYNAVAutomatedproposal ofalternative

routes

CAPAutomatic

downlink ofparameters for

Controller accessSAP

Automaticdownlink of

parameters forsystem use

PPDAutomatic

downlink ofAircrew

preferences

ACLController/

Aircrewdialogues

ACM

DSC

Data andvoice

channelmanagement

DCLDepartureClearance

delivery

DownstreamController/

Aircrewdialogues

D-OTIS

D-RVR

D-SIGMET

compiledmeteo andoperationalinformation

delivery

InstantaneousRVR delivery

SIGMETdelivery

COTRACCommonTrajectory

Co-ordination

Other ATSSupport Functions

Surveillance OLDI/SYSCO

LEGEND

data link service defined in thisORD.

data link service underdevelopment.

function performed by the datalink service.

indicates relationship between anATC component and functions

describes the function of the datalink service.

other non data link functions

CPDLCServices

Figure B-3. Data link services in the ORD model

B.3.2 Ground Surveillance / Airborne Surveillance (GS/AS) Applications Another class of data link services supports Airborne Separation Assistance System (ASAS) and related applications.

Based on improvement steps defined in the EUROCONTROL ATM 2000+ Strategy [7], an ASAS activity was undertaken as one of the Co-operative Actions of Research and Development in EUROCONTROL (CARE) between September 1999 and December 2004 to establish a common view of such services, and to support their validation.

The 'Principles of Operation for the use of ASAS' (PO-ASAS) took into account conceptual, operational procedures, human factors, aircraft systems, enabling technologies, users' perspectives and implementation considerations and defined four definitive categories of ASAS application:

• Airborne Traffic Situational Awareness (ATSA) applications;

• Airborne Spacing applications (ASPA);

• Airborne Separation applications; and




• Airborne Self-separation applications.

The Joint Co-ordination Board (JCB), involving the European Commission and EUROCONTROL, was created in 2002 to co-ordinate research, development and validation work performed by the Commission's ADS-B related programmes and projects, and to expedite implementation.

CARE-ASAS, with the involvement of all stakeholders, developed the description of a first package of Ground Surveillance / Airborne Surveillance (GS/AS) applications to identify operational applications suitable for early (5-10 years) implementation in Europe. The so-called GS/AS "Package 1" is documented in 'Description of a first package of GS/AS applications' [13], which was endorsed at the third JCB meeting in September 2002 and at the Eleventh ICAO Air Navigation Conference in September 2003. The document is in line with the JURG ADS Fast Track Initiative (JAFTI).

Airborne surveillance (AS) applications supported as part of the "Package I" surveillance applications are classified into Airborne Spacing (ASPA) and Airborne Traffic Situational Awareness (ATSA) applications. Harmonised operational services and environment definition (OSED), safety and performance requirements (SPR) and INTEROP documents, as required by the ED-78A [11] guidelines for the approval of the provision and use of ATS supported by data communications (see Annex C), are in preparation by the ADS Programme Requirements Focus Group (RFG).

Ground surveillance (GS) services supported as part of the "Package I" surveillance applications are also referred to as "Automatic Dependent Surveillance – Broadcast out" or "ADS-B out" services, as they depend upon ground stations receiving and processing the information periodically broadcast by suitably equipped aircraft.

GS/AS applications also encompass operational applications often identified as TIS-B (Traffic Information Service – Broadcast) applications. TIS-B is a service to broadcast the air traffic situation obtained by ground systems (both radar and ADS derived tracks) for display in the cockpit.

GS/AS Package 1 includes the operational applications listed in Table B-3 and Table B-4, which have achieved very wide and strong European, US and international consensus.

Table B-3. Ground Surveillance (GS) applications Data Link Service

Description

ADS-B-RAD ATC Surveillance for radar areas (merger of ADS-B-ACC for en route and ADS-B-TMA for terminal areas)

The ADS B RAD application is designed to enhance ATC surveillance in en-route and terminal phases of flight.

The objectives are to improve safety and, on a longer term, to reduce surveillance infrastructure related costs replacing some of the SSR radar sensors with ADS B.

ADS-B-NRA ATC Surveillance in non-radar area.

The ADS B NRA application is designed to provide ATC surveillance in en-route and terminal phases of flight in airspaces where radar surveillance services currently do not exist.

The main objective is to enhance controller’s traffic situational awareness (by providing accurate traffic position) in a cost effective way, providing benefits in terms of capacity, efficiency and safety.




Data Link Service

Description

ADS-B-APT Airport surface surveillance

The ADS B APT application will provide ATC for ground movement control (for aircraft as well as for airport vehicles).

The main objective is to enhance safety and efficiency on the ground (stand alone or together with other surface surveillance means) in darkness and low visibility conditions.

ADS-B-ADD Aircraft derived data

The ADD application will automatically provide additional aircraft systems derived data to ground systems and controllers through the means of ADS B.

The objective is to enhance the performance of the ground applications (e.g. MTCD, AMAN, etc).

Table B-4. Airborne Surveillance (AS) applications

Data Link Service

Description

ATSA-SURF Enhanced traffic situational awareness on the airport surface.

This ATSA SURF application will enhance traffic situational awareness of flight crews providing information regarding the surrounding traffic during taxi and runway operations.

The objectives are to improve safety (e.g. at taxiways crossings, before entering an active runway, before take-off, etc) and to reduce taxi time in particular during low visibility conditions and by night.

ATSA-AIRB Enhanced traffic situational awareness during flight operations.

ATSA AIRB will enhance the traffic situational awareness of flight crews during flight operations by displaying surrounding traffic position in the cockpit.

The objectives are to improve traffic awareness and safety of flight in all airspace.

ATSA-S&A ATSA-S&A - Enhanced visual acquisition for see & avoid (No longer exists – part of ATSA-AIRB)

This application is an aid for flight crews to perform their collision avoidance task when separation service in not provided by ATC (e.g. IFR/VFR in class D and E airspace, class G airspace). The objective is safer flight operations. Surrounding traffic, which is within a visual range, will be displayed to the flight crews, including at least identification and position of the traffic. In addition, aircraft functions could include advisories when a traffic situation requiring the application of see & avoid rules is detected. This application is more dedicated to General Aviation or helicopter operations. For larger aircraft, the ATSA-AIRB will provide the same benefits.




Data Link Service

Description

ATSA-SVA ATSA-SVA - Enhanced successive visual approaches

Aids flight crews to perform successive visual approaches when they are responsible for maintaining visual separation from the aircraft they are following. The objectives are to perform successive visual approach procedures on a more regular basis to enhance the runway throughput, and to conduct safer operations especially in high-density areas. Surrounding traffic, which is within a visual range, will be displayed to the flight crew, including at least identification and position of the traffic. The aircraft to follow will be highlighted and specific parameters may be displayed for this aircraft (e.g. range and speed in a numerical format).

Contrary to most applications in the ATSA category, this application does not need all aircraft to be fitted with ADS-B equipment. This could be advantageous for an aircraft operator operating at a hub airport to equip its fleet.

(No longer exists – part of ATSA-VSA, described below)

ASPA-S&M Enhanced sequencing and merging

ASPA S&M will allow pilots to identify another aircraft and to maintain an instructed spacing with that flight.

The main objective is to assure more consistent aircraft spacing, potentially increasing capacity in en-route and TMA environments by transferring the spacing task from the ATS Unit to the cockpit.

ASPA-ITP Airborne Spacing – In-Trail Procedure

ITP in non-continental airspace is a procedure allowing in-trail airborne surveillance equipped aircraft to climb or descend through each other’s flight levels. The goal is to improve the utilisation of non-continental airspace by facilitating a higher rate of flight level changes than is currently provided, yielding better flight efficiency (e.g. fuel savings, avoiding turbulent flight levels).

ITP does not modify the core roles of flight crews and controllers. Under appropriate circumstances, the controller will clear the flight to climb or descend to a given flight level. In addition, during climb or descent, flight crews will be instructed to maintain a specified spacing value in distance or time from designated aircraft whose levels are going to be crossed vertically. Safety studies have to be performed to determine the spacing value (i.e. given time or distance) so that the risk of collision is maintained to at least the required target level of safety. In order to obtain maximum benefits from the use of ITP, provisions allowing the reduction of procedural separation minima between suitably equipped aircraft will have to be established.

The application is designed for non-continental airspace where aircraft are flying along predefined tracks. It may be possible to extend this application to non-radar airspace where aircraft are navigating on a fixed route network. For ATC and safety related purposes, the ITP application, as currently defined, requires aircraft to be suitably equipped to be able to broadcast and/or address position reports and to communicate via voice and CPDLC.




Data Link Service

Description

ASPA-C&P Airborne Spacing – Crossing and Passing

Provides controllers with new instructions to solve conflicts, e.g. directing flight crews to cross or pass a designated traffic while maintaining a given spacing value (greater than the separation minima for that airspace). The main goal is to enable the reorganisation and streamlining of tasks, allowing controllers to accept more aircraft in a given sector.

The core roles of controllers and flight crews remain unchanged. These new procedures will require specific aircraft functions for HMI (e.g. display of relevant traffic information, generation of advisories) and automation functions (e.g. new auto-pilot or FMS functions). Safety studies will be needed, to determine the spacing value (i.e. given time or distance) so that the risk of collision is maintained to at least the required target level of safety.

This application is designed for en-route airspace and TMA. All phases of flight are considered. To perform C&P only those aircraft involved in the procedure need to have equipment supporting airborne surveillance.

GS/AS Package 1 applications are intended to be taken as a whole in terms of standards and equipment. One objective was to facilitate the development of common standards between EUROCAE and RTCA for global interoperability. However, it is recognised that the GS/AS applications currently included in Package 1 may need to be reassessed during the next phases of development (i.e. harmonisation, validation, safety and costs), since:

• Some may be ready for earlier implementation than envisaged at present;

• Some may need to be made more specific to better match users’ needs;

• Some may be discarded because they do not have real customers; and

• Some may be postponed to future packages because they are not mature enough and they could delay the implementation of Package I.

ADS-B is recognised as a key enabler for GS/AS applications and GS/AS Package 1 is focused on the operational use of ADS-B data to improve the ATM system.

B.3.3 Mode-S Specific Services (MSS) The operational benefits to be gained from the employment of Mode S surveillance services apply to the ATC system, its controlling staff and to its users. Most of them are listed in the European Strategy for the Initial Implementation of Mode S Enhanced Surveillance [48] and have been confirmed by separate studies.

The main benefits expected from MSS are derived from the Downlink Aircraft Parameters (DAP) service, i.e. the availability of certain aircraft state vector information, leading to an improved air situation picture, thus enabling or improving:

• Enhanced controller awareness

• Trajectory prediction/monitoring (including consistency checks between ground and aircraft plan data)

• Tracking improvement (in particular in the terminal area and in turns)

• Consolidation of the safety nets Minimum Safe Altitude Warning (MSAW) and Short Term Conflict Alert (STCA) false alarms rate lowering




• Meteorological Nowcast

• ACAS resolution advisory (RA) information (downlinking of the alarm generated by the airborne ACAS system).

• Reduction in R/T occupancy (because the controller will not have to ask for airborne parameters obtained through Mode S).

• Reduction in controller workload.

Table B-5. Mode S Specific Services Data Link Service

Description

DAP (Automated) Downlink of Airborne Parameters

The objective of ADAP is to make specific flight information available to the controller by automatically extracting the relevant data from the airborne system. The parameters are automatically downlinked without controller or flight crew involvement.

Note: The CAP and SAP services, identified above, may also be implemented as Mode S services.

ICAO has developed a "Manual on Mode S Specific Services," (ICAO Document 9688-AN/952) [24].

Since 1994, the establishment of Enhanced Surveillance in Europe has been incorporated in the EATM "Initial Implementation of Mode S Enhanced Surveillance" (IIMSES) programme.

In the context of IIMSES, EUROCONTROL equipped several aircraft with MSS capabilities as part of the pre-operational validation of the enhanced surveillance capability of the Pre-Operational European Mode S (POEMS) radars. This installation enables the MSS enhanced surveillance capability; the POEMS ground stations may extract the DAP information.

B.3.4 Cooperative ATS Developments The ATM 2000+ Strategy [7] proposes an Overall Road Map of Change Through Time, in which operational enhancements are grouped into four steps. The Operational Concept for Cooperative ATS for 2008 - 2011 [26] summarises the potential contribution of data link services to the roadmap of change, as shown in Table B-6.

Table B-6. ATM 2000+ Roadmap Steps ATM 2000+

Step Contribution of data link

Step 1 (up to 2004)

Implementation of the delivery of DCL, D-ATIS and Oceanic Clearances (OCL) using the ACARS infrastructure. These data link services are already provided in several European States.

Step 2 (2005 to 2007)

Implementation of a basic set of down link of airborne parameters (i.e. the Controller Access Parameters (CAP) service) and a first set of CPDLC services (i.e. ACM, ACL and AMC). The requirements for this step have been produced and validated. Two EUROCONTROL implementation programmes (Mode S and Link 2000+) are coordinating their implementation.




ATM 2000+ Step Contribution of data link

Step 3 (2008 to 2011)

Enhancements to the CPDLC implemented in Step 2, additional DAPs and D-FIS, plus the introduction of the first procedures that allow the transfer of controller tasks to pilots (i.e. early airborne spacing applications). The implementation of these data link services will be co-ordinated by the CASCADE Programme (see B.4.2 below).

Step 4 (2012 to 2020)

Higher levels of transfer of tasks to pilots, including autonomous operations, and negotiation of full trajectories between aircraft and ATC using data link (i.e. COTRAC service).

The "CoopATS Concept" has been developed to present an operational vision for the implementation of data link for use in the provision of ATS in Step 3 of the ATM 2000+ Strategy (i.e. the years 2008 to 2011). This document builds on the EUROCONTROL OCD [8] and details how air-ground and air-air data communications contribute to the overall description of how the ATM system should develop within the target time frame.

The data link services included in ATM 2000+ Step 3 are often referred to as “Cooperative ATS Step 3" (CASE-3) services.

The CASE-3 document [26] includes the data link service descriptions listed in Table B-7.

Table B-7. "CASE-3" Data Link Services Data Link Service

Description

GRECO Graphical Trajectory Co-ordination

GRECO will allow establishing and re-planning trajectory contract based clearances between aircrew and controllers during flight through CPDLC and graphical interfaces, by means of a structured negotiation method.

The main objective will be to enhance ATM capacity and flexibility.

D-ALERT Data-link Alerting The D-ALERT service provides information concerning flight emergency and abnormal situations, supplemented with data from AOC and disseminated to ATC and appropriate Airport Authorities (e.g. fire and rescue, medical services, etc.)

The objective is to enable the transmission of more accurate, precise and complete data regarding the concerned aircraft, in a fast and reliable way, through data-link, to interested parties.




Data Link Service

Description

D-SIG Data Link Surface Information and Guidance

Provides automated assistance to flight crews by delivering operational graphical information, specifically compiled for the flight. The main goal is to improve safety and efficiency by presenting to the pilot an updated and integrated representation of all the airport elements necessary for his ground movements. Runway incursion prevention and ASMGCS in particular will also significantly benefit from this service.

Before start-up, airport maps, NOTAMs / SNOWTAMs, and airport PIREPS will be graphically integrated and sent as a map for display on a (specific) cockpit display of traffic information (CDTI). This display will also integrate the taxi instructions provided by the D-TAXI service. Upon arrival and in conjunction with the taxi instructions, the flight crew will receive a similar data compilation providing guidance from runway exit to stand. Such operational data may vary from simple airport mapping to the complete aircraft routing highlighting critical points, e.g. runway crossings, unavailable infrastructures, etc.

This service does not require a minimum number of aircraft equipped to provide benefits. Benefits are obtained from the first aircraft equipped.

D-ORIS Data Link Operational “En-Route” Information Service

Provides automated assistance to flight crews by delivering compiled meteorological and operational flight information, derived from “En-route” weather information, from NOTAMs and other sources, relevant to an area to be overflown or any area of interest. The goal is to provide pilots with data required to support decision making in the safe and optimised conduct of the flight.

Currently the flight profile is computed before departure, based on wind predictions available at the time. During flight, updated wind/temperature information will be uplinked upon pilot request allowing better computation of the remaining flight profile. The uplink of NOTAMS updates, Sigmets, and other information relevant to the airspace will significantly improve safety, especially when done automatically through “update contract” functionality. When enabled, graphical presentation of critical areas (like Clear Air Turbulence areas) on the cockpit display will allow aircrew to take appropriate decisions.

This service does not require a minimum number of aircraft equipped to provide benefits. Benefits are obtained from the first aircraft equipped.

FLIPINT Flight Path Intent

Provides ATS ground systems with the flight path intent, i.e. the expected future aircraft trajectory as computed by the avionics. The FDPS will validate the FMS trajectory before it is used by other functions and displayed to controllers. The FLIPINT service will be automatically initiated by the ATS Unit sending a FLIPINT contract request to the aircraft indicating the selected FLIPINT contract options. The aircraft automatically downlinks the part of the information activated in the aircraft FMS that corresponds to the FLIPINT request. The aircraft will downlink updates to the information already sent based on the contract options specified in the contract request.

The FLIPINT service will be transparent to both flight crew and controllers. When the ATS ground system detects an inconsistency between the future aircraft trajectory and the current cleared trajectory, the controller will be informed of the detected inconsistency.




Data Link Service

Description

URCO Urgent Contact service

URCO is a means of contacting an aircraft that is not responding. The goal is to provide assistance to controllers for establishing urgent contact (via voice or data link) with flight crews. In the operational context, two general cases of URCO utilisation are identified:

• Aircraft is not responding to ordinary data link or voice communications whilst under control of the current ATS Unit (e.g. communication failure).

• Controller has to urgently communicate with an aircraft not yet under control.

The provision of the URCO Service will be made possible through three main enablers: air-ground data link communications, a suitable human-machine interface and a set of operational procedures.

AUTO-CPDLC

AUTO CPDLC (Automatic CPDLC)

CPDLC is a means of communication between the controller and the flight crew using data link. The main objectives of Auto-CPDLC are to provide automation support to controllers for the preparation and sending of CPDLC messages and the transmission of the same messages to multiple aircraft (multicast).

Auto-CPDLC automates some FDPS functions, with little or no controller involvement. Auto-CPDLC functions may generate automated uplink messages, or may process downlinks (e.g. by gathering related information) to enhance the information displayed to the controller. Data link messages sent by Auto-CPDLC will always be ground initiated. Auto-CPDLC is required to be available in all phases of flight. Flight crew should have the ability to opt out of the receipt of multicast messages during critical flight phases (e.g. the arrival phase).

Auto-CPDLC does not change the basic CPDLC functionality or message structure, and has no impact on avionics or datalink infrastructure. Message elements already in the supported message set can be included with no impact on existing avionics or on the message handling part of the ground CPDLC implementation. The FDPS and controller HMI need to be modified to support these functions.

Maastricht UAC has already implemented the automatic uplink of SSR codes to aircraft well inside the airspace. This offers a great increase in efficiency in centres on an ORCAM Participating Area boundary, where many routine code updates are performed daily.

ARMAND Arrival Manager Information Delivery service

Automatically transmits relevant arrival manager (AMAN) information directly to flight crews, within the optimum horizon of the AMAN (that could be beyond the limits of the ATS Unit that contains the flight’s destination airport). The main goal is to convey the calculated sequence information which contains the assigned times and time corrections ('time to lose'/’time to gain’), beyond the ACC boundaries encompassing the destination airport (point of convergence).

The core roles of controllers and flight crews remain unchanged. The ground system (AMAN) generates the optimum arrival sequence and the ATS Unit automatically delivers the relevant information to the concerned traffic. The delivered information may consist of messages: “Target Approach Time”, “Expect Holding”, “Expected Approach Time” and “Revised EAT”. The message may also be transmitted to the current planning or executive controller. Interface with AMAN will be a pre-requisite.




The CASE-3 operational concept [26] also includes the following data link services described previously:

• Sequencing and Merging Application (S&M)

• In-trail climb/descent in non-continental airspace (ITP)

• Crossing and Passing Application (C&P)

• Dynamic Route Availability (DYNAV)

• Flight Plan Consistency Service (FLIPCY)

• Pilot Preferences Downlink (PPD)

• Controller Access Parameters (CAP)

• Data Link Operational Terminal Information Service (D-OTIS)

• Data Link Runway Visual Range (D-RVR)

• Downstream Clearance Service (DSC)

B.3.5 Other ATS Data Link Services Table B-8 provides a brief description of some of the data link services that are or have been under consideration, and are not covered in the above descriptions.

Table B-8. Miscellaneous Additional Data Link Services Data Link Service

Description

AMC ATC Microphone Check

Provides controllers with the capability to up-link an instruction for all aircraft to check that they are not inadvertently blocking a given voice channel.

ATSA-VSA Enhanced visual separation on approach

The ATSA VSA application will display the surrounding traffic position and speed in the cockpit.

The main objective is to facilitate successive approaches for aircraft cleared to maintain visual separation from another aircraft on the approach.




Data Link Service

Description

D-FLUP Data Link Flight Update service

Provides ATM-related operational data and information aiming at the optimisation of flight preparation, “in-flight” management, and airport efficiency. Examples of this data include information related to the departure sequence, to CDM to SLOT, as well as to airborne target approach times. Special operations such as de-icing will be included in this service. In addition, interactions between aircraft/ATC/AOC are considered in D-FLUP. The main goal is to achieve a reduction in the controller’s workload per aircraft and an increase of flight efficiency.

Pre-departure CFMU and other CDM elements will be available automatically to flight crews. These, together with multilateral communications, in particular with ATC & AOC, will allow the pilot a better management of the flight (e.g.: departure sequence information, de-icing notifications, holding/diversion decision). Optional “update contract” functionality will automatically provide the aircrew with the latest related information.

D-FLUP does not require a minimum number of aircraft equipped to provide benefits. Benefits are obtained from the first aircraft equipped. Ground system should be capable of maintaining an “up to date” and accurate database of the D-FLUP information.

D-TAXI Data-link taxi clearance delivery

The D-TAXI service provides data-link communications between aircraft and ATS Unit for all ground movements operations (e.g. push back, taxi clearances).

The objectives are to reduce delays and controller workload by the reduction of voice communications and enhance safety by avoiding misunderstandings.

B.3.6 Aeronautical Operational Control (AOC) Services Many aircraft operators use a variety of data link services between aircraft and operations centre. These range from basic "Out, Off, On, In (OOOI)" services to advanced loadsheet and weight/balance applications. Such applications are not in general standardised, though the outline message structures are specified in ARINC 620 [49].

The AOC data link services in use today are, therefore, not generally interoperable between different aircraft operators. Such services generally make use of ACARS communication between flight crew and aircraft operator, via a commercial aviation communications service provider.

There has been recent work in AEEC [50] to standardise a set of AOC applications. The initial task is to develop the format and content of the Weight and Balance message for use on the Airbus A380. Other new message definitions will be added as the need is identified. Messages exchanged with the Electronic Flight Bag (EFB) are candidates for future definition. Another potential message set consists of third party service provider (e.g., fuelling or de-icing) messages that bypass the airline host and need to be common among airlines. Refinements of existing message definitions will be made, in the form of new versions, in response to experience gained from operations and to complement the evolving use of the message(s) by airline users.

A list of AOC services can be found in the joint EUROCONTROL / FAA "Communications Operating Concept and Requirements (COCR) for the Future Radio System" [51].




However, AOC services are out of the scope of this analysis, which is concerned with ATS data link services.

B.3.7 FANS services Many aircraft have been equipped for data link for many years, using the ACARS system to transfer digital information over voice radio frequencies. Initially used for AOC communication, the potential of this system to provide ATS communications in line with the ICAO FANS concept was soon realised,

The first CPDLC message set was created in 1993 by RTCA Inc. (a non-profit industry body), and published in a manual designated DO-219. The intention was to capture the most common communications phraseologies used in the oceanic voice environment and to create a list of "pre-formatted" CPDLC text elements sorted into a number of categories. To cover unusual situations a free text capability was included to allow controllers and pilots to create their own specific messages.

In the 1990s an industry initiative resulted in data link functionality being available on long-haul aircraft. The ATS/ACARS communications system was called FANS-1 by Boeing and FANS-A by Airbus. These two systems are functionally equivalent and fully interoperable with ground systems designed to support the FANS-1/A capability.

Boeing added one extra downlink message element to the RTCA basic message set for the FANS-1 CPDLC package. The ICAO ADS Panel (ADSP) has since added many extra messages to the RTCA message set for use over the ATN. The FANS-1/A functionality is thus based on a subset of the ICAO PANS-ATM (Procedures for Air Navigation Services - Air Traffic Management) Doc 4444 [23].

These systems were developed before the practice of specifying air-ground communications as a number of discrete data link services became standard. FANS services therefore provide access to all ATS Application functions (e.g. all FANS-CPDLC message types).

Operational FANS services include:

• FANS-CPDLC, also known as Two-Way Data Link (TWDL)

• Automatic Dependent Surveillance Contract mode (ADS-C)

A third ATS application, known as ATS Facilities Notification (AFN), enables an ANSP system to become aware of an aircraft's data link capabilities, and provides an exchange of address information. This is equivalent to the DLIC service in Table B-1.

ANSPs provide ATS using FANS-1/A compatible ground systems, initially in the South Pacific and now in the majority of oceanic airspace areas and some remote continental areas, as well as the Maastricht UAC en-route airspace. International airlines operate the FANS-1/A services mainly on their long-range aircraft.

FANS-1/A and equivalent systems enable ATC communications and surveillance capabilities in Oceanic/Remote airspace to support the following main ATS operational objectives:

• Use of FANS-CPDLC as a primary means of communication in place of HF voice communication

• Use of ADS-C in place of voice position reporting

• Separation assurance at 30/30 NM (RNP4) lateral/longitudinal

• Route and flight level conformance monitoring

• Facilitation of in-flight rerouting and weather avoidance




• Tailored arrival procedures

Generally aircraft equipped with FANS-1/A (or equivalent) have access to the full AFN, FANS-CPDLC and ADS applications capabilities, though the specific capabilities of some installations differ.

The AFN application supports Logon and Contact services (supported by all FANS-1/A aircraft):

The FANS-CPDLC application provides data link communications between the controller and the pilot. It allows the exchange of messages that can be formed by the use of individual (or a combination of) elements chosen from a set of internationally agreed, preformatted, ATS message elements. Some of these elements are in agreement with the ICAO phraseology and some are not. They serve to exchange nominal clearances, acknowledgements, instructions, requests, reports, negotiations, emergency notifications and transfer of ATS facility or frequency.

Some aircraft implementations differ. Some have more messages that can be loaded to the FMS. Some may not support specific messages or specific (optional) data content in certain messages.

For the FANS-ADS application, ground systems generally establish ADS contracts automatically for routine flight handling. The ADS application uses the various systems aboard the aircraft to provide aircraft position, velocity, intent and meteorological data. These data can be transmitted to the ANSP system for estimating and predicting aircraft position, and for provision of route conformance and other navigational monitoring for a flight. The number of ADS connections may differ between implementations, and there are many additional potential differences, especially when it comes to how a route gets loaded into the FMS. There is no specific standard that states exactly how much optional functionality has to be implemented.

Recently, a modified version of the FANS-1/A product has become available for some aircraft types. The interoperability requirements are specified in EUROCAE ED-100A [12]. The main difference compared to the previous specification is the ability to handle ATC clearances that have exceeded a specified timeout period. Otherwise, the updated system is functionally similar to traditional ED-100 FANS-1/A. The potential impact on the regulatory coverage is considered in Annex F.

B.3.8 "ARINC 623" Services The data link services listed in Table B-9 were originally specified in ARINC 623 [32] and are now maintained as EUROCAE specifications ([33], [34], [35]). They are operational in several European States.

Table B-9. "ARINC 623" Data Link Services Data Link Service

Description

OCL Oceanic Clearance service

Used by flights that need to obtain an oceanic clearance before entering into oceanic airspace. This service can be included in the Downstream Clearance (DSC) service.

D-ATIS Data link Automatic Terminal Information Service

This service provides a digitised version of the ATIS information broadcast by voice. It includes departure and arrival ATIS messages.




Data Link Service

Description

DCL Departure Clearance

Provides automated assistance for requesting and delivering departure information and clearance at airports.

B.4 Validation of Operational Requirements

The service definitions in the ORD [10] express requirements for procedures, quality of service, performance, timers and information exchanges. From the list of candidate services, those which were mature and which promised the most benefits have been selected for validation by various projects and programmes.

The first stage of validation of a data link service is the peer review that takes place during the definition of operational requirements. Further validation steps may include any or all of the following:

• High level simulations and trials (independent of implementation means)

• Technical realisation (e.g. mapping to existing or new CPDLC messages)

• Cost-benefit analysis (usually as part of a "package" of related services)

• Pre-operational trials and real-time simulations.

The implementation feasibility of data link services has been demonstrated, through pre-operational trial projects such as

• Preliminary EUROCONTROL Trial of Air-Ground Data Link (PETAL II),

• ProATN

• European Pre-Operational Data Link Applications (EOLIA).

These and other programmes were supported by the European Commission's 4th Framework Programme for RTD&D 1994-1998.

The technical basis for the ATN point-to-point applications was developed by the EUROCONTROL ATN Project.

There have also been various programmes / projects to validate ASAS applications. These include the CoSpace and Mediterranean Free Flight (MFF) projects to determine the operational feasibility and potential benefits of the use of spacing instructions. A number of simulations have been carried out to define and validate operational procedures for Sequencing & Merging (S&M) applications.

Operational requirements have been developed to varying levels of maturity and are available from a number of sources within EATM.

Further validation has been achieved for selected services through a full end-to-end safety assessment, trials and actual operations.

B.4.1 LINK 2000+ Programme Building upon the experience gained following the initial validation projects, the EUROCONTROL LINK 2000+ Programme was created. The programme concentrates on implementation issues and reports directly to the EATM directors and the relevant EATM groups.

The LINK 2000+ services comprise a set of non-time critical services already extensively validated through PETAL II, various national trials and the EOLIA project.




The LINK 2000+ set of data link services for en-route CPDLC has as interoperability baseline document the EUROCAE ED-110A - "Interoperability Requirements Standard for ATN Baseline 1 (INTEROP ATN B1)" Red-lined Version.

The data link services included in the LINK 2000+ baseline are:

• Data Link Initiation Capability (DLIC)




Simulations by the LINK 2000+ programme have shown the following predicted increases in sector capacity:

3.4% for 25% data-link equipage;

8% for 50% data-link equipage;


B.4.2 CASCADE Programme The EUROCONTROL CASCADE (Co-operative ATS through Surveillance and Communication Applications Deployed in ECAC) programme is responsible for the validation and implementation of most of the "GS/AS Package I" applications in addition to other data link applications.

Initial CASCADE data link services will be in pre-implementation and operations validation trials in the period 2005-06, targeted for implementation from the early part of 2008-11 onwards. These are currently:

• ADS B NRA (ATC Surveillance in non-radar area)

• ADS B RAD (ATC Surveillance for radar areas)

• ADS B APT (Airport surface surveillance)

• ADS B ADD (Aircraft derived data)

• AUTO CPDLC (Automatic CPDLC)

• D-ALERT (Data-link Alerting)

• D-OTIS (Data-link operational information service)

• D-TAXI (Data-link taxi clearance delivery)

• PPD (Pilot preferences down-link)

CASCADE will also progress data link services that will be in pre-implementation and operations validation trials in the period 2006-08, targeted for implementation in the latter part of 2008-11. This also includes upgrades of the initial services:

• ATSA SURF (Enhanced traffic situational awareness on the airport surface)

• ATSA AIRB (Enhanced traffic situational awareness during flight operations)

• ATSA VSA (Enhanced visual separation on approach)

• ASPA S&M (Enhanced sequencing and merging)

• DSC (Down-stream clearance)

• FLIPCY (Flight plan consistency)




• GRECO (Graphical trajectory co-ordination)

The CASCADE programme will maximise the reuse of Mode S and LINK 2000+ Programme infrastructures. It will also consider technology to meet the longer-term requirements.

B.5 Selection of Data Link Services

B.5.1 Introduction The purpose of this section is to analyse each of the ATS data link services identified above, with the objective of determining which data link services may be suitable subjects for an initial implementing rule. This is not intended to be a roadmap for the development of data link services, but is based on an assessment of current status.

A useful comparison to consider is "Step 1" of the European Commission's data link roadmap of 2003 [20], which is summarised in Table B-10.

Table B-10. Data link roadmap Step 1: Early air-ground ATM applications

Airspace Region ATM Applications Data Link Services

Requirements Category

APP2b– Strategic controller/pilot messages

DLIC DCL ACL ACM

CPDLC-0

Surface operations

APP4a – Provision of terminal (automatic terminal information service, meteorological report) and runway information

D-ATIS METAR D-RVR

D-FIS-0

APP2b – Strategic controller/pilot messages

DLIC ACL ACM DCL DSC

CPDLC-0

Terminal operations

APP4a – Provision of terminal (automatic terminal information service, meteorological report) and runaway information

D-ATIS METAR D-RVR

D-FIS-0

En-route and transition applications

APP2b – Strategic controller/pilot messages DLIC ACL ACM DSC

CPDLC-0

Oceanic and remote operations

APP14b – ATS in oceanic and remote regions ADS-C ADS-C-1

Note: In Table B-10, the column "Requirements Category" is defined as follows: CPDLC-0: Data Link Application categories and associated ATM Applications requiring point-to-point (air-ground) communications - Strategic Data Link D-FIS-0: Data Link Application categories and associated ATM Applications requiring point-to-point (air-ground) communications - Uplink of Aeronautical Information ADS-C-1: Data Link Application categories and associated ATM Applications requiring point-to-point (air-ground) communications - Strategic ADS Service.

B.5.2 Selection Criteria The criteria used for the initial selection of data link services are explained below and summarised in Table B-11.




Table B-11. Data Link Services Selection Criteria

Criterion Title





It is a prerequisite that the data link service should have been identified in a suitable operational forum. The basic operational concept and data flows should have been documented and agreed, using a framework similar to the ORD [10].


The operational requirement should have been subject to validation exercises (e.g. real-time operational simulation) to ensure that it is realistic and effective, and has the potential to deliver operational benefits once implemented.


The key requirement for a data link service to be considered as a subject for the initial regulatory coverage is that safety and performance requirements pertaining to the data link service must have been documented by a recognised standards body.

Rationale: The development of SPR specifications is an essential step of the ED-78A methodology (see Annex C) for the approval of the provision and use of ATS supported by data communications.

B.5.3 Application of Criteria to Data Link Services The list of data link services tabulated in the preceding sections is consistent with public documents that have gained widespread industry acceptance, and with the data link services considered in the European Commission's roadmap study [20].

Broadcast services based on receiving and processing ADS-B messages on the ground and in the air may soon reach a sufficient level of maturity, but are not considered appropriate for the current data link services regulatory coverage. This is consistent with the European Commission roadmap, where "ADS-B out" services and additional point-to-point services are not introduced until Step 2.

Based on the above criteria, Table B-12 lists the data link services that are retained for further analysis.

There is good alignment between Table B-12 and Table B-10, such that an implementation of the selected candidate data link services would represent a significant step towards the achievement of European Commission Roadmap Step 1. The main differences are as follows:

• Table B-12 includes AMC, OCL and FLIPCY services, which were not explicitly identified for European Commission Roadmap Step 1.

• European Commission Roadmap Step 1 includes METAR, D-RVR and ADS-C position reporting services, which have not been retained as candidates for the initial regulatory coverage.




Table B-12. Candidate Data Link Services Data Link Service DLS1 DLS2 DLS3

Data Link Initiation Capability (DLIC)

ORD LINK 2000+ SPR is ED-120

ATC Communication Management (ACM)

ORD LINK 2000+ SPR is ED-120

ATC Clearance (ACL) ORD LINK 2000+ SPR is ED-120

ATC Microphone Check (AMC) ED-110A LINK 2000+ SPR is ED-120

Departure Clearance (DCL) ORD ED-85A

Operational experience

SPR is ED-120 and ED-85A

Downstream Clearance (DSC) ORD CASE-3 ED-120

EOLIA, PETAL SPR is ED-120

Oceanic clearances (OCL) ED-106A Operational experience

SPR is ED-106A

Data Link Automatic Terminal Information Service (D-ATIS)

ED-89A Operational experience

SPR is ED-89A

Flight Plan Consistency (FLIPCY)

ORD CASE-3

EOLIA, PETAL SPR is ED-120

B.6 Conclusions

This Annex has provided an overview of ATS data link services currently being developed. They are at various stages of definition, validation and standardisation. Future concepts such as system-wide information management (SWIM) may result in new classes of data link services, but these concepts are not sufficiently developed to consider for initial regulations. However, the need for a flexible, extendable communications infrastructure must be considered, to enable the seamless evolution of data link services.

Data link services other than those listed in Table B-12 are not considered further for the regulatory approach at this stage, as their SPR have not yet been fully evaluated using the methodology of EUROCAE ED-78A [11] (see Annex C). Other data link services may be subject to future regulation; their voluntary implementation will not be precluded by the data link services implementing rule, provided they satisfy suitably defined safety requirements, including non-interference with the prescribed services.

Note that the data link services in Table B-12 are only candidates for inclusion in the regulatory approach, selected on a largely theoretical basis. Further, practical, selection criteria are applied in Annex F.




ANNEX B. SELECTION OF DATA LINK SERVICES ............................................... B-1 B.1 Introduction .......................................................................................................... B-1

B.1.1 Airspace Capacity Benefits ...................................................................... B-1 B.1.2 Safety Benefits ......................................................................................... B-1

B.2 The ATM Operational Process............................................................................. B-1 B.2.1 Data Link Services in the ATM Process Model ........................................ B-2 B.2.2 Data Link Service Categories................................................................... B-3 B.2.3 CPDLC Terminology ................................................................................ B-4

B.3 Operational Requirements ................................................................................... B-5 B.3.1 Air-Ground Cooperative ATS ................................................................... B-5 B.3.2 Ground Surveillance / Airborne Surveillance (GS/AS) Applications....... B-10 B.3.3 Mode-S Specific Services (MSS) ........................................................... B-14 B.3.4 Cooperative ATS Developments............................................................ B-15 B.3.5 Other ATS Data Link Services ............................................................... B-19 B.3.6 Aeronautical Operational Control (AOC) Services ................................. B-20 B.3.7 FANS services ....................................................................................... B-21 B.3.8 "ARINC 623" Services............................................................................ B-22

B.4 Validation of Operational Requirements ............................................................ B-23 B.4.1 LINK 2000+ Programme ........................................................................ B-23 B.4.2 CASCADE Programme .......................................................................... B-24

B.5 Selection of Data Link Services ......................................................................... B-25 B.5.1 Introduction ............................................................................................ B-25 B.5.2 Selection Criteria.................................................................................... B-25 B.5.3 Application of Criteria to Data Link Services .......................................... B-26

B.6 Conclusions ....................................................................................................... B-27




ANNEX C. INTEROP AND SPR STANDARDS

C.1 Introduction

This Annex summarises the outcome of the considerable body of work in the aviation industry to derive a consistent set of guidelines enabling the specification of interoperability (INTEROP) requirements on the one hand, and operational, safety and performance requirements (SPR) on the other hand, for data link enabled air traffic services (ATS).

C.2 Approval Process

EUROCAE ED-78A (RTCA DO-264), “Guidelines for Approval of the Provision and Use of ATS Supported by Data Communications” [11], defines a process for gathering evidence to demonstrate to an approval authority that the minimum criteria for approving the provision and use of an ATS supported by data communications have been satisfied.

The ED-78A methodology, which is summarised in Figure C-1, describes a coordinated process of requirements determination, and how this leads to the Operational Services and Environment Definition (OSED), the SPR standard and the INTEROP standard. The SPR and INTEROP standards provide the basis for the development, qualification and entry into service of one or more constituents of the CNS/ATM system.

Evidence that the process objectives have been satisfied may take the form of standards such as the SPR and INTEROP standards.

ED-78A (DO-264) Methodology

Operational Services and Environment Definition

(OSED)

Operational Safety Assessment

(OSA)

Operational Performance Assessment

(OPA)

Interoperability Assessment

(IA)

Operational Hazard

Assessment(OHA)

Allocation of Safety Objectives &

Requirements(ASOR)

Safety and Performance Requirements Specification

(SPR)

Interoperability Requirements(INTEROP)

Figure C-1. ED-78A Process

Based on ED-78A guidelines, INTEROP and SPR standards provide recommendations intended for government organisations, conference of governments, or agencies having statutory jurisdiction over the use and provision of data link services. These recommendations are for use by such bodies to formulate official policy related to such matters for dissemination in aeronautical information publications (AIPs), notices to airmen (NOTAMs), aircraft flight manuals (AFMs), and operator specifications.

It is a key criterion in the regulatory approach that the ED-78A process (or equivalent level of analysis) has been demonstrably followed. This is necessary in order to ensure that the

Annex C Interop and SPR standards 1.1.doc 24/05/2006 Page C-1



selected data link services satisfy the minimum criteria for their operational approval for deployment in Europe.

In order for a data link service to be considered for prescription in the regulatory coverage, INTEROP and SPR standards (or equivalent) must exist, and validation activities must have been performed to ensure that, with appropriate deployment conditions, the operational, safety and performance requirements can be met.

C.3 Safety and Performance (SPR) Standard for Continental Airspace

EUROCAE ED-120 (RTCA DO-290) [4] specifies the SPR for the implementation of data link services that support ATS in continental airspace.

ED-120 is the reference standard for data link services independent of the underlying technology (e.g. it is equally applicable to the ATN-based CPDLC services in ED-110A and to services based on the FANS-1/A CPDLC application in ED-100A).

ED-120 complies with the criteria for SPR standards specified in the ED-78A guidelines, and is intended for use with interoperability requirements (INTEROP) standards. It provides the minimum operational, safety, and performance requirements and allocations based on the results of a coordinated requirements determination process, which includes an operational services and environment information capture, operational safety assessment (OSA), and an operational performance assessment (OPA). As part of the coordinated requirements determination process, these requirements were validated based on operational experience, simulations and analyses.

These requirements are necessary to provide adequate assurance that the elements of the CNS/ATM system, when operating together, will perform their intended function in an acceptably safe manner.

ED-78A is recognised as a partial Means of Compliance for ESARR 4 "Risk Assessment and Mitigation in Air Traffic Management" [45]. The LINK 2000+ Pre-Implementation Safety Case [16] provides a discussion of how ED-78A was used to perform the Operational Safety Assessment in ED-120 in compliance with ESARR 4.

The SPR standard allocates requirements to the necessary elements of the CNS/ATM system.

ED-120 includes the definition of data link services, the environmental conditions relevant to their implementation in continental airspace, and the operational, safety, and performance requirements for using them. The following data link services are covered:

a) Data Link Initiation Capability (DLIC)

b) Data link services for ATC communications:


• ATC Clearance (ACL)


• Departure Clearance (DCL)

• Downstream Clearance (DSC)

c) Flight Information Service (FIS):

• Data Link Automatic Terminal Information Service (D-ATIS)

d) Data link services for surveillance

• Flight Plan Consistency (FLIPCY)




The scope is limited to the requirements for operational data link services and related ATS functions when operations, safety, and performance are relevant to the ATS. Assumptions for the environment and other ATS functions may be stated when necessary to establish the operational, safety and performance requirements for the above data link services.

This SPR standard is intended to provide the basis for demonstrating that an implemented system, considering its inherent design and technologies, can meet the relevant operational, safety, and performance requirements for the data link services described. It is not intended to limit the use of an implementation only to the data link services and operational context defined. However, in cases where it is intended to support additional or define new data link services, the operational, safety and performance requirements for such operational contexts and/or new data link services will need to be established as a basis for approval qualification of the implemented systems.

ED-120 provides a hazard analysis and identifies the hazards applicable to systems implementing the ATC Services listed above. It then derives the safety objectives for such systems and the safety requirements with which they must comply.

The safety requirements apply to all systems; each system must either comply with each safety requirement, or it must be demonstrated that they cannot impact the corresponding safety objective.

The situation is different with performance requirements, which need to be analysed and allocated to different parts of the system.

Beyond the scope of ED-120 are:

• Interoperability requirements, which are covered in associated INTEROP standards, such as ED-110A;

• Requirements related to securing data link services that would provide for protection against malicious or intentional behaviour causing harm. The impact of this on the regulatory approach is considered in Annex G.

• Requirements related to the recording of data communications for accident/incident investigation purposes. The impact of this on the regulatory approach is considered in Annex H.

C.4 Other Safety and Performance (SPR) Standards

The SPR standard for data link services in Oceanic and Remote airspace areas is still under development in RTCA/EUROCAE at the time of writing.

The following ATS data link services are defined in ARINC 623 [32] and are now specified in EUROCAE “Data Link Application System Document” (DLASD) specifications, which include safety and performance requirements.

ED-85A - DLASD for the "Departure Clearance" Data-Link Service [33]

This document is intended to capture minimum interoperability, performance and safety requirements for a service based on data-link communications used for Departure Clearance. It allocates these requirements to the airborne, communication and ATS domains and describes acceptable means of demonstrating compliance. It clarifies the previous version ED-85 particularly the field of message processing.

ED-89A - DLASD for the "ATIS" Data-Link Service [34]

This document provides minimum interoperability, performance and safety requirements for the ATIS service based on data communications. The ATIS service is a tower control service, a direct communication from ATC to aircrew of takeoff information (runway




condition, weather, ceiling, etc.). It clarifies the previous version ED-89 particularly the field of message processing.

ED-106A - DLASD for "Oceanic Clearance" (OCL) Data Link Service [35]

This document is intended to capture minimum interoperability, performance and safety requirements for a service based on data-link communications used for Oceanic Clearance. It allocates these requirements to the airborne, communication and ATS domains and describes acceptable means of demonstrating compliance. It clarifies the previous version ED-106 particularly the field of message processing.

C.5 Interoperability Standard for ATN Baseline 1

In compliance with the ED-78A guidelines, EUROCAE ED-110A (RTCA DO-280A) [3] specifies the interoperability requirements (INTEROP) standard for the initial implementation of the Aeronautical Telecommunication Network (ATN), referred to as "ATN Baseline 1". The interoperability requirements are based on a subset of the ICAO Manual of Technical Provisions for the ATN [2].

ED-110A specifies the minimum set of interoperability requirements and allocations necessary to provide adequate assurance that the elements of the CNS/ATM system are compatible with each other, and when operating together will perform their intended function. These elements comprise the aircraft system, the ANSP system, and the operator’s provisions to use the ATS. The ANSP system and the operator’s provisions may include third party or contracted communication services.

ATN Baseline 1, as defined in ED-110A, comprises the data link services listed in C.3 above, whose operational safety and performance requirements are covered in ED-120. (Note that DCL, DSC and D-ATIS services were added in ED-110 Revision A (2004)).

These services are described in ED-110A to the extent necessary to establish the INTEROP for the ATN Baseline 1 functions needed to support them.

The communication services assumed in ATN Baseline 1 are the ATN upper layer communications service (ULCS) and internet communications service (ICS) necessary to use any ATN mobile subnetwork as defined in ICAO Annex 10. A more detailed description of these communication services can be found in ICAO Doc 9739, the Comprehensive ATN Manual (CAMAL) [25].

The ED-110A interoperability requirements are independent of any particular air-ground or ground-ground communications technology (e.g. VHF data link for air-ground, X.25 or IP for ground-ground). It does not consider the functional or interoperability aspects of the subnetworks or switching between multiple mobile subnetworks.

It is not intended to restrict the use of ATN applications for ATS, or to restrict communication services from operating over subnetworks other than those ATN mobile subnetworks defined in ICAO Annex 10. However, the interoperability requirements for such expanded implementations are outside the scope of ATN Baseline 1. Some parts of the ICAO ATN provisions are identified as “out of scope” in ED-110A; their interoperability requirements would need to be evaluated if they needed to be included in any regulatory provisions.

Based on ED-120 safety requirements, it was concluded that the standard ATN CPDLC specification, referred to in ED-110A, does not provide sufficient protection against possible mis-delivery of messages to the wrong flight to allow operation without voice read-back of profile-changing clearances. Consequently, "Protected Mode CPDLC (PM-CPDLC)" was developed. It is likely that ED-110A will be updated to refer to PM-CPDLC.




C.6 Interoperability Standard for ACARS ATS Applications

In compliance with the ED-78A [11] guidelines, EUROCAE ED-100A (RTCA DO-258A) [12] specifies the INTEROP standard for the implementation of the ATS applications using data communication as defined in ARINC Specification 622 ("ATS Data Link Applications over ACARS Air-Ground Network") [52], referred to as "FANS-1/A (Version 1) systems".

In the FANS-1/A implementation of CPDLC, the binary coded messages are converted into character codes for exchange by ACARS, using ARINC 622 procedures.

The scope of ED-100A covers:

• The ATS Facilities Notification (AFN) application;

• The Automatic Dependent Surveillance (ADS) application;

• The FANS-CPDLC application;

• The ARINC 622 data communication.

Based on a safety analysis pre-dating ED-120, it was concluded that a "latency timer" to detect expired messages would need to be added to existing implementations in order to allow the use of the ACL service without voice read-back. This was one of the updates introduced in ED-100A. The ability of ED-100A compliant systems to fully satisfy ED-120 SPR for continental airspace is the subject of ongoing study.

C.7 Interoperability Standard for FANS-1/A-ATN

RTCA SC-189/EUROCAE WG-53 has a work programme that includes the development of a FANS-1/A-ATN interoperability standard specifying the use of ED-100A services in the ATN environment (draft document PU 40 [57]):

• For using a mixture of data link technologies in the provision and use of ATS data link services

• To support the goal of converging oceanic and continental data link applications.

Once the standard is finalised, it should be possible to demonstrate how ED-100A compliant systems are capable of satisfying the SPR specified in ED-120.

The INTEROP standard for the implementation of ATN Baseline 1 services in the ED-100A environment is still under development in RTCA/EUROCAE at the time of writing.

C.8 Conclusions

It is a fundamental requirement in selecting data link services for prescription that the SPR of each service should have been evaluated and agreed, and documented in a recognised standard.

ED-120 is the appropriate SPR standard for data link services in en route continental airspace. ED-110A is the INTEROP standard for ATN Baseline 1. Both of these documents need to be updated to refer to "Protected Mode" CPDLC, which was developed in order to satisfy ED-120 requirements.

Standards work is in progress to demonstrate how ED-100A FANS-1/A technology is capable of satisfying the SPR specified in ED-120. This may lead to the possibility of an alternative means of compliance to the implementing rule for data link services interoperability. (This topic is developed further in Annex F).




ANNEX C. INTEROP AND SPR STANDARDS ........................................................ C-1 C.1 Introduction .......................................................................................................... C-1 C.2 Approval Process................................................................................................. C-1 C.3 Safety and Performance (SPR) Standard for Continental Airspace .................... C-2 C.4 Other Safety and Performance (SPR) Standards ................................................ C-3 C.5 Interoperability Standard for ATN Baseline 1....................................................... C-4 C.6 Interoperability Standard for ACARS ATS Applications....................................... C-5 C.7 Interoperability Standard for FANS-1/A-ATN ....................................................... C-5 C.8 Conclusions ......................................................................................................... C-5




ANNEX D. AIR-GROUND COMMUNICATION TECHNOLOGY

D.1 Introduction This Annex considers candidate air-ground communication technologies for mobile data communications in continental airspace in support of the data link services identified in Annex B.

Candidate technologies in the timeframe to 2015 were extensively analysed in the European Commission's 2003 data link roadmap study [20]. The technologies analysed in that study are summarised in the following table.

Table D-1. Communication Technologies in European Commission Roadmap

Point-to-point technologies Broadcast technologies Aviation Packet Radio (AVPAC) – used for "Plain Old ACARS" (POA)

1090 MHz Extended Squitter (1090 ES)

High Frequency Data Link (HFDL) Mode S Enhanced Surveillance (EHS)

Aeronautical Mobile Satellite Service (AMSS)

Universal Access Transponder (UAT)

Very High Frequency Data Link (VDL):

• Mode 2 (VDL-2)

• Mode 3 (VDL-3)

• Mode 4 (VDL-4)

Very High Frequency Data Link (VDL):

• Mode 4 (VDL-4)

Gatelink

Next Generation Satellite Service (NGSS)

Satellite Data Link Service (SDLS) Boeing Connexion

Third Generation / Universal Mobile Telecommunications System (3G/UMTS)

3G/UMTS

Detailed descriptions of the candidate technologies can be found in Annexes of the document: "Roadmap for the implementation of data link services in European Air Traffic Management (ATM): Technology Assessment", v4.0 (February 2003) [20].

All of the technologies in the left-hand column of Table D-1 are technically capable, at least in principle, of supporting the point-to-point data link services identified in Annex B.

In addition, this Annex also reviews ACARS over VDL-2 (known as AOA), and Military data links.

D.2 European Commission Data Link Roadmap Conclusions Candidate data link technologies were assessed in the European Commission's 2003 data link roadmap study [20]. The technologies were analysed against a number of criteria, under the general heading of technology assessment.

A number of scenarios were then defined, where each scenario specified one or more data link technologies considered feasible for each step of the ATM application roadmap.

Annex D A-G Comms Technology 1.1.doc 24/05/2006 Page D-1



The method for technology assessment included:

• Technical assessment - consideration of the general characteristics and services supported by the media, including:

o Capability assessment - detailed description of the technical strengths and weaknesses of the media.

o Maturity assessment - consideration of when the media could be deployed, by analysis of simulations and trials activities, standards maturity, equipment development and system deployment.

o Complexity assessment - assessment of airborne and ground architectures including complexity of proposed solutions.

• Cost assessment: Assessment of relative cost of each technology.

• Industrial assessment: Assessment of stakeholder, avionics manufacturer and aircraft manufacturer support for the technologies.

A number of weighted criteria were used to select the most appropriate scenario for inclusion in the European Commission roadmap. The criteria used were, in order of weighting (most significant first):

• Ability to deliver the ATM application roadmap;

• Overall cost;

• Frequency (spectrum) availability;

• Global interoperability;

• Support for voice communications;

• Support for non-ATC communications.

The study concluded that there were two candidate paths for the data link roadmap up to 2020, the first based on VDL-2/Mode S/1090 ES technologies and the alternative based on VDL-4.

For Step 1 of the ATM application roadmap (early air-ground ATM applications, summarised in Annex B, section B.5.3 of the Regulatory Approach), it was concluded that the most appropriate data link technology for high and medium traffic density continental regions is VDL-2 and/or VDL-4, with the VDL-2 route being favoured by industry.

The roadmap report [20] noted that the VDL-2 and VDL-4 scenarios were not necessarily mutually exclusive. For example, general aviation might not be required to equip with VDL-2, assuming that only about 75% rate of aircraft equipage is required for Step 1 applications to deliver significant benefits.

D.2.1 VDL-2/Mode S/1090 ES path – Step 1 In this scenario, the data link technology support for high-and-medium-traffic-density continental regions in Step 1 would be based on VDL-2.

For remote/oceanic regions, the equipage would be based on AMSS using FANS-1/A (or equivalent) systems. Subject to safety studies, FANS-1/A aircraft would be accommodated when departing/arriving in VDL-2 airspace, or would be updated to VDL-2/AOA.

Rationale:

• VDL-2 was found to be (in 2003) the most mature of the proposed technologies with the potential to be operational by 2004.




• The study found strong support in Europe to use VDL-2 as the prime enabler for ATN compliant data link, due to the airline operational control (AOC) usage of VDL-2 making the investment more productive.

• VDL-2 can meet the early requirements of ATM applications in Step 1 of the roadmap.

The study identified the following issues for VDL-2:

• The proposed EUROCONTROL frequency plan for the EUR region allows for four VDL-2 channels including AOC. It was uncertain how many channels would be required to provide an adequate level of performance as traffic grows and new ATM applications are added. This issue will become particularly important when an extension of air-ground services is provided in Step 4 of the ATM application roadmap (extension of air-ground ATM applications, e.g. to include FLIPCY, DYNAV, PPD services).

• VDL-2 simulations, and simulations with point-to-point applications would be needed to confirm the real ability of the media to support simultaneous point-to-point communications by the forecast population of aircraft and to provide information to support frequency planning for VDL-2.

Since the completion of the Roadmap study, EUROCONTROL’s Aeronautical Communications Technologies Simulator (ACTS) has been used to model the use of VDL-2 for both AOC and ATS applications. The simulation results [31] found that:

“Within the busiest air traffic hour, a total of 1220 flights operating AOC data exchange plus 730 flights operating Link 2000+ applications can be connected through a single VDL-2 channel.

"The on-time roundtrip transmission reaches 95% for uplink application messages and 97% for downlink messages.

"The average uplink transmission delay is 1.4 sec, significantly higher than the downlink at 0.23 sec.”

The report of the simulation work [31] also concluded:

“Depending on the actual AOC migration from ACARS to VDL-2, the Link 2000+ deployment progress and the air traffic increase in coming years, the first VDL-2 channel could be expected to come to saturation within the 2007-2010 time-frame.

"The final Link 2000+ deployment targets to equip 75% of the flights in upper airspace, around 2014. Assuming again a full AOC migration to VDL-2 at that stage, 2 or 3 VDL-2 channels would be required.”

Operational use of VDL-2 has grown rapidly. In May 2005, ARINC reported that over 700 aircraft worldwide are now VDL-2 equipped and regularly use its 200+ ground stations. Approximately 1.6M messages were exchanged with VDL-2 during that month.

D.2.2 Alternative path based on VDL-4 – Step 1 The European Commission roadmap study [20] found support by some stakeholders for alternative solutions in Steps 1, 2 and 3 based primarily on VDL-4 technology, in particular for regional air traffic operations, general aviation and military users.

The data link technology support for European Commission roadmap Step 1 for some operators would be based on VDL-4. The required airborne equipment would be a VDL-4 aircraft/ground point-to point-package (though the later cost analysis assumed that a full package, including broadcast functions would be implemented at this step).




Rationale:

• The driver for this scenario relies on providing lower cost avionics;

• Plans had been announced for an AOC network based on VDL-4, which would provide additional non-ATS benefits;

• ATS requirements can be met via use of this network;

• VDL-4 has potential to meet early requirements, subject to confirmation through simulations and trials;

• VDL-4 is able to provide services such as ATN communications and air-air point-to-point communications (it is the only link with an air-air data link, though this needs to be demonstrated);

• VDL-4 was expected to provide a more efficient use of the VHF spectrum and higher data rates than VDL-2, though detailed simulations are required to demonstrate this.

The study identified the following issues for VDL-4:

• Further work was required to demonstrate that low cost solutions could be provided;

• Simulations are required, to establish the number of VHF channels required to provide performance;

• Resolution of issues concerning VDL integration within airframe;

• Deployment of VDL-4 will require a concerted effort to free sufficient bandwidth in the congested VHF bands;

• Work on a channel management plan, including identification of the number of VHF channels required, is critical and urgently required. It was noted that there were no activities to provide a channel for VDL-4 point-to-point;

• Subject to cost-effectiveness, frequency availability and channel management plan (which are serious constraints) VDL-4 could be in widespread use by 2006. This represented a delay in the benefits obtained from Step 1 for operators choosing this path relative to the VDL-2 path;

• VDL-4 point-to-point simulation results were needed to confirm the VDL-4 ability to support ATM applications that are most capacity demanding.

• This route for equipage was strongly opposed by a large part of the European aviation community for reasons that included:

o Requiring additional VHF spectrum that should be reserved for VDL-2;

o Delaying the start of the roadmap;

o Not compatible with current plans for large air transport aircraft equipage in the next 10 years.

These issues are still outstanding, and a VDL-4 service provider has yet to be established. There is ongoing work in EUROCONTROL to validate VDL-4 data link, including the development of frequency separation criteria, airborne co-site interference tests and performance and capacity simulations.




D.2.3 Conclusion on VDL Technology The European Commission Roadmap study concluded that VDL-2 and/or VDL-4 were the only viable alternatives to support initial data link services in busy continental European airspace.

It identified a number of issues inhibiting the use of these technologies. Given that the issues applicable to VDL-2 have all now been resolved, while many of those associated with VDL-4 are outstanding, and given the weight of stakeholder support in favour of its deployment, VDL-2 is recommended as the only air-ground communications technology to be considered for the initial regulatory coverage.

This does not exclude other technologies, which may be subject to regional deployment, but VDL-2 is proposed as the common technology to ensure seamless operations across Europe and other continental regions.

D.3 Alternative Data Link Technologies

D.3.1 Aircraft Communication Addressing and Reporting System (ACARS)

D.3.1.1 ACARS Background The Aircraft Communications Addressing and Reporting System (ACARS) is a data link system capable of exchanging messages between an aircraft and ground system, including airline host computers (for AOC), ATC host computers (for ATS messages), and other parties. ACARS is available as an option on most commercial aircraft currently in production or as a retrofit.

Messages to be downlinked from the aircraft can be typed manually by the flight crew using a control unit keyboard or may be generated automatically by the ACARS or one of its interfacing aircraft systems.

Current ATS use of ACARS includes Pre-departure Clearances (PDC), Oceanic Clearances (OCL) and the services supported by the FANS-1/A package.

There are many AOC applications currently using ACARS, some of which are listed in the FAA/EUROCONTROL Communications Operating Concept and Requirements for the Future Radio System (COCR) [51].

The ACARS communications service is provided by aeronautical communications service provider (ACSP) organisations rather than ATC authorities. SITA and ARINC are the two largest such organisations, with ARINC initiating the ACARS service in 1976. Most ACARS use is via a shared VHF channel. However, ACARS is also available via satellite services (Inmarsat Data-2) and HF Data link. VHF ACARS provides a relatively low capacity data link (channel data rate = 2.4 kbps) in a standard 25 kHz channel assignment.

ACARS is specified in AEEC Specifications, and uses a protocol based on the upper-case alphanumeric character set for the exchange of text messages. Binary exchanges are enabled by conversion of the interchanged data into character format according to the provisions of AEEC Specification 622 [52].

D.3.1.2 ACARS over VDL-2 The original VHF ACARS service is now known as “Plain Old ACARS” (POA). However this service suffers from frequency congestion and poor performance. ACARS services are now also available over VDL-2; the technique used is known as "ACARS over Aviation VHF Link Control (AVLC)" (AOA). Airlines are now upgrading their systems to take advantage of the increased performance offered by VDL-2.




For aircraft operators, the transition from POA to AOA consists only of replacing the air-to-ground VHF path by a new physical and link layer defined by ICAO [56], supporting the AEEC 618 ACARS layer.

For AOC applications, this makes sense as it minimises the differences between the existing aircraft using POA and new or upgraded aircraft using AOA. However, the new ATS services are not constrained by this (legacy) issue.

The implication is that there would be little value in considering POA for the prescription of data link services, as the obsolete POA is in the process of being replaced by VDL-2. ACARS-based ATS services can be supported over AOA in airspace where there is a VDL-2 service.

ATN-based data link services use the ATN communications service, which can also use VDL-2. Therefore, ATN-based data link services can co-exist with AOC services and ACARS based services such as DCL and D-ATIS, all using the same VDL-2 technology.

D.3.1.3 Future Directions Although the performance of AOA is much better than POA, it is still recognised as only an interim step for data link services. This is because the ACARS service is based on transmission of characters of text rather than binary data. With AOA, the character mode protocol is “tunnelled” over a binary data path, which is an inherently inefficient approach. In FANS-1/A and equivalent systems, the application data (e.g. FANS-CPDLC messages) is binary coded for interchange between systems. This binary data has to be expanded into a stream of characters (using AEEC 622 techniques) for ACARS communication, and then sent over a binary data path when AOA is used. Clearly, it would be much more efficient to send the encoded application data directly over the binary data path without the intermediate character conversion process.

By contrast, ATN/CPDLC services make full use of the binary data transport mechanism, and are efficient users of VDL-2 bandwidth.

The preferred and efficient use of VDL-2 is to transport binary formatted data rather than the text-oriented AOA, and that is what the ATS data link services have been developed to do. At some point, pressure on bandwidth availability is expected to lead to AOC application upgrade to a full binary capability.

However, provided safety assessment outcomes are favourable, existing ACARS based ATS applications could potentially continue to be used (for a transitional period) over VDL-2, alongside ATN/VDL-2 applications, despite their inefficient bandwidth usage.

D.3.2 The Aeronautical Mobile Satellite Service (AMSS) A range of voice and data services is available via the Inmarsat Data-3 service, otherwise known as AMSS. Data services are available as both circuit-switched and packet-switched data services. However, the full capability of a system depends on both the avionics equipment and the satellite in use.

Inmarsat services for aircraft are supported by four systems:

Aero-L offers low-speed (600 bits/sec) real-time data communications, mainly for airline operational and administrative purposes. It uses a low gain antenna (0 dB) and does not support circuit-mode operation.

Aero-I uses an intermediate-gain terminal (6 dB) exploiting the power of the Inmarsat-3 satellites. It takes advantage of both the spot beam capability of the new Inmarsat-3 satellites and the adoption of the latest voice codec technology, which allow aircraft flying within spot-beam coverage to receive multi-channel voice, fax and data services through systems that are smaller, lighter and cheaper (less bandwidth required) than previous




aeronautical satellite communications systems. Packet-mode (up to 4.8 kbit/s) and distress voice are provided using global beam. Aero-I complies with the proposed revisions to the AMSS SARPs, currently in ICAO Annex 10 Volume III, Part I, Chapter 4.

Aero-H is a high-speed (up to 10.5 kbit/ sec) service supporting multi-channel voice, fax and data communications for passengers and airline operational and administrative applications. It uses a high gain antenna (12 dB) that is either mechanically or electronically steerable. Aero-H+ is an evolution of the Aero-H service that uses the higher power of the Inmarsat-3 satellites when operating within the spot-beam coverage area. When operating outside these areas, the terminal operates as a standard Aero-H system. Aero-H+ supports the same services as Aero-H.

Aero-C is a low-rate data system that allows store-and-forward text or data messages (up to 32 kByte in length) to be sent and received by aircraft operating anywhere in the world. It is based on the Inmarsat-C mobile earth station, used in the maritime/ land environment and uses a small omnidirectional antenna. The main electronics unit is compact, weighing only 3-4 kg. Briefcase terminals are also available. The performance characteristics make this option unsuitable for flight safety communications.

One of the major advantages of the geostationary Earth orbit (GEO) satellite system is that it is already operational and it offers a very wide geographic coverage. It is the only alternative to HF communications in oceanic regions and offers a solution in remote continental areas since there is no requirement to invest in a ground communication infrastructure.

The disadvantages are chiefly associated with cost. The altitude of the geostationary orbits pushes up the cost of terminals, and the ongoing costs of satellite services are relatively high.

The perception of high cost has limited stakeholder interest in AMSS and restricted its use to wide-bodied inter-continental flights and where installation is justified by revenue from voice calls.

The lack of stakeholder interest and product availability for short-haul aircraft rules out AMSS for the continental airspaces that are the subject of the interoperability analysis.

D.3.3 HF Data Link The high frequency (HF) radio spectrum medium has been used since the early aviation days for air-ground communications. Before the introduction of satellite communications, HF was the only long-range medium for communications and was used by military and civil aviation. Although it was not highly reliable, HF was the only available mode of communications over oceanic regions.

Several efforts have been made since the early 1980s to use HF commercially for data communications. Most of these efforts failed, as it was not cost effective to develop a frequency agile transmitter/receiver that had sufficient power to transfer data reliably. With the advancement of digital signal processing technology, HF data link (HFDL) became practical.

A commercial HFDL service is offered by at least one ACSP, and ICAO has developed HFDL SARPs for inclusion in Annex 10, and an HFDL technical manual.

HFDL is perceived as lower cost than AMSS and can operate in polar regions where geostationary satellite coverage is limited. However, there are performance issues due to the medium used and, like AMSS, stakeholder interest is limited to wide-bodied inter-continental flights.




As with AMSS, the lack of stakeholder interest and product availability for short-haul aircraft, as well as performance issues, rule out HFDL for the continental airspace that are the subject of the draft implementing rule on data link services.

D.3.4 Military Data Links

D.3.4.1 Link 11 Link 11 (also referred to as Tactical Digital Information Link A (TADIL-A) in the United States) is a digital communications system, utilising standard military UHF or HF communications systems for the exchange of tactical information between the Tactical Data Systems of different military units (platforms).

Link 11 was designed and implemented originally as a maritime data link, and as such is fitted very widely to surface combatant units of many navies. Later, to enable co-operation, particularly with air forces, Link 11 was fitted to air defence ground environment sites as an auxiliary link. Thus, whilst remaining a mainly maritime link, Link 11 fulfils other requirements.

D.3.4.2 Link 16 Link 16 (also referred to as Tactical Digital Information Link J (TADIL-J), in the United States) is a NATO term for a message standard that features anti-jam, secure data and voice, with standard waveforms and messages used for exchanging tactical information between different military platforms. Link 16 provides a common communications network to a large community of airborne, surface and even subsurface or space elements.

Since 1994, Link 16 has been the tactical data link of choice for the US Department of Defense (DoD) and is widely used in most NATO platforms. Link 16 does not significantly change the basic concepts of tactical data link information exchange, but it provides technical and operational improvements and increased capability to existing tactical data link features. Link 16 is supported by Joint Tactical Information Distribution System (JTIDS) and Multifunctional Information Distribution System (MIDS) hardware terminals.

Link 16 Frequencies Link 16 transmissions are pseudo-randomly hopped among 51 frequencies, which are spaced at 3 MHz intervals in the band ranging from 969 to 1206 MHz. Within this band are two Identification Friend or Foe (IFF) frequencies at 1030 and 1090 MHz; Link 16 does not use the bands within ± 20 MHz of these IFF frequencies. Due to the spread of the power across a wide band to protect the signal from interference and detection, the operational bandwidth for each MIDS channel is 6 MHz.

Link 16 Nets LINK 16 uses a Time Division Multiple Access (TDMA) Architecture with a Time Slot duration of 7.8 ms. This, combined with the use of frequency hopping, provides the capacity to operate simultaneously in up to 127 nets in the same network. A terminal can operate (transmit or receive) in only one net in any one time slot but can operate in any net in any time slot as determined by the time slot assignment.

The Link 16 multiple nets concept comes from the idea of grouping participant units into functional groups or Network Participation Groups (NPGs). Units only participate in the NPGs used for functions that they perform. The same set of timeslots may be used for more than one net simply by assigning a different frequency-hopping pattern to each.

An NPG is defined by its function and by the type of messages that will be transmitted. There are 31 standard internationally agreed NPGs, including:

● Initial Entry




● Network Management

● Precise Participant Location and Identification (PPLI) and Status

● Surveillance

● Air Control

Link 16 features the possibility of defining new NPGs according to future needs, up to a maximum growth capacity of 511 NPGs.

Link 16 Operation Modes LINK 16 can operate in four different communication modes:

● Mode 1: Uses encryption and frequency hopping.

● Mode 2: Uses encryption and a single frequency (969 MHz).

● Mode 3: Only used for compatibility with Class 1 (old) terminals.

● Mode 4: No encryption, single frequency (969 MHz).

JTIDS Joint Tactical Information Distribution System (JTIDS) is the terminal hardware that supports the Link 16 message standard. As Link 16 is operational on multi-environment platforms (ships, aircraft, ground facilities, submarines) the technical requirements for the different platforms may differ (size, power, etc.), although they have to be completely interoperable.

The family of terminals that supports Link 16 interoperability between units is the JTIDS Class II terminal family, which supports different hardware configurations based on the needs of the different platforms.

MIDS Multifunctional Information Distribution System (MIDS) is the next generation of terminals, fully compatible and interoperable with JTIDS Class II terminals. These terminals represent a technology insertion program to reduce the size and weight of the components while maintaining JTIDS functionality.

D.3.4.3 Suitability for ATS Use Existing military data links play a major role in conducting military operations; they cover a broad range of services mainly oriented to command and control activities and do not feature any specific ATM functions enabling civil/military interoperability.

In 2003, EUROCONTROL commissioned a short feasibility study to look at the broad possibilities that might exist in adapting or developing the military MIDS/Link 16 technology for civil aviation. The study reached the overall conclusion that such a system might be feasible from technical, economic and planning viewpoints but there were significant institutional issues that would have to be solved before such a system could be used as a data link to support ADS-B for civil aviation.

Options to foster interoperability were discussed in an open forum in 20041; however they were not received with the necessary support for further investigations.

There are no suitable products available for civilian aircraft. There have been no known flight tests or other validation activities.

1 Study on "Civil Aviation Data Link for ADS-B based on MIDS / Link 16", Open Discussion Forum, 10th March 2004, Summary Report, R Darby EUROCONTROL DAS/CSM.




For the medium term, ground coordination must be considered as the only option for civil/military interoperability. Transmission of ATM messages from/to military aircraft could be envisaged using data messages between civil and military ATC centres, with a voice link between the military ATC centre and military aircraft.

D.3.5 Mode-S Data Link Secondary surveillance radar (SSR) Mode S (select) is a development of conventional SSR. Its "selectivity" is based on unambiguous identification of an aircraft by a 24-bit aircraft address, which acts as its technical telecommunications address.

There are two types of Mode S data link:

• The "interoperable" Mode S data link was designed to allow air-ground exchanges using Mode S as a packet switching data transmission network (e.g. as an ATN subnetwork). The message segments to be transmitted are sent in the Mode S data frames, which are exchanged between ground station and the selected transponder, where the data fields are extracted and reconstituted for routing to the addressee. This is not now expected to be widely deployed.

• The "specific" Mode S data link is more closely linked to the Mode S system itself. In particular, there is a highly optimised "aircraft data collection" protocol using the COMM-B frames. In the transponder, there is a series of 256 buffers of 56 bits each, in which information concerning the flight and aircraft status are stored and continually refreshed. Each buffer, identified by an order number, contains data of a precise nature formatted according to a predetermined code.

The principle is that the aircraft system continuously writes flight data to the transponder buffers without knowing whether or not the buffers will be selected for transmission to the ground. The ground station reads the data asynchronously. This process is thus optimised as it avoids having to initiate a communication connection with the aircraft system possessing this information.

The use of airborne data via this specific protocol is referred to as "Mode S Enhanced Surveillance (EHS)".

The operational benefits to be gained from the employment of Mode S surveillance services apply to the ATC system, its controlling staff and to its users. Most of them are listed in the European Strategy for the Initial Implementation of Mode S Enhanced Surveillance [48] and have been confirmed by separate studies.

The implementation of Mode S enables the following benefits and improvements:

• Improved and unambiguous correlation between radar and flight plan data through the use of aircraft identity.

• Elimination of synchronous garbling and a reduction in SSR "fruit" leading to improved discrimination of aircraft whose radar tracks are in close proximity.

• Reduction in the use of the finite pool of Mode 3/A SSR codes, with fewer code changes and hence reduction in controller and pilot workload.

The take-up of the "interoperable" Mode S data link, which would enable general support of ATS data link applications, has not received wide support from stakeholders. There are known performance issues when used in this mode.

The lack of stakeholder interest and product availability rules out Mode S as a general-purpose data link technology to support the data link services that are the subject of the interoperability analysis. Work is continuing to validate and deploy Mode S specific services, but this is out of the scope of the current regulatory approach, since such




services are aimed at surveillance applications rather than point-to-point data link communication between pilots and controllers.

D.3.6 3G/UMTS There has been some experimental work in EUROCONTROL to assess the use of Third Generation / Universal Mobile Telecommunications System (3G/UMTS) – Code Division Multiple Access (CDMA) Wideband as an aeronautical data link technology.

While initial experiments were encouraging, there remain many issues to be solved, including allocation of RF spectrum, and lack of an aeronautical communications service provider.

This technology is not considered sufficiently mature for inclusion in the current implementing rule for data link services.

D.3.7 FAA/EUROCONTROL Future Communications Study EUROCONTROL and the United States FAA have initiated a joint Future Communications Study (FCS) to identify potential communications technologies to meet future safety and regularity of flight communications requirements, i.e. those supporting ATS and AOC.

The FCS addresses the need for globally harmonised planning of future aviation communications taking into account the needs of civil aviation and State aircraft operating as General Air Traffic (GAT). A key output of the FCS will be the recommendation of the most appropriate technologies to meet the communication requirements to support future ATM concepts.

The first step was to review the expected operational concepts in the period in which a future communication system will be used, i.e. starting in 2020 with a lifetime of at least 15 years. The starting date of 2020 was chosen as the date at which a new communication system was required to start operation to complement the existing communication system in the high density areas of the world where deficiency in communication capability will be a major limitation to airspace capacity.

As an aid to comprehension of the operational concepts, example scenarios in 2020 and 2035 illustrate how communication is being used for ATS and AOC applications. For each time frame, a set of generic operational services was identified, many of which could be supported by voice or data link, while some can only be supported by data link.

Civil-military interoperability is being addressed through co-ordination with military representatives (e.g. the EUROCONTROL Military Business Unit). This helps refine requirements in the area of integrity, reliability, human-machine interface (HMI) and security. Certification aspects for both civil and military ATM systems will be carefully considered and spectrum issues covered.

New technologies may be required to support different types of voice and data communications including air-ground and air-air using broadcast/multicast and addressable modes. The FCS work plan identifies communications operating concepts and requirements as prerequisite, critical path elements in the process of making such a recommendation. An important element is the requirements on the communications that take place through the aircraft and ground radios, collectively referred to as the Future Radio System (FRS). The primary drivers for the FRS are the need for increased capacity, and the need for a consistent global solution to support the goal of a seamless ATM system.

A goal is that any new system must be capable of supporting not only current, but also emerging operational concepts. The new system must be capable of supporting new and better ways of working that generate higher levels of efficiency, safety, and economy.




The Communications Operating Concepts and Requirements (COCR) document [51] identifies concepts and trends supporting the selection of the FRS. The need to co-ordinate and develop consensus on the essential themes in the work plan will require dissemination and co-ordination of this document among the wider civil aviation and industry communities.

The FRS operational requirements have been derived from a range of documents including the ICAO Global ATM Operating Concept [80] and the IATA ATM Roadmap [78] supplemented by information in regional implementation documents such as those from the FAA and EUROCONTROL concept and strategy documents. The operational requirements are drawn from the ATM and AOC operating concepts that are expected to be implemented in the highest density airspace regions of the world, to achieve the capacity and safety requirements. Lower density regions of the world are also considered, but the communication requirements for those regions may be less demanding. Therefore these regions can continue to utilise current technology for a longer period of time. However, these areas would benefit from use of the new communication technology that will result from global carriage of the equipment by airspace users from other regions.

The scope of the COCR is limited to analysing trends and operational concepts as part of the FRS needs, and by the fact that both government and industry are in the formative stages of determining many of the underlying future concepts.

The concepts and underlying service requirements are used to estimate the amount of communication traffic generated in representative operational volumes. As part of this process, volumes of airspace were defined in which the services are required. Airspace types used are: airport, TMA, en route (continental), oceanic, and remote. A representative traffic model is derived to estimate the size of a communication system to support the traffic load in each airspace volume. Also, the peak communication requirements have been identified to determine the peak capability needed.

Throughout the period covered in the COCR, voice communication was considered to be available at all times. It was assumed that the voice performance of the FRS should be the same as that of the existing analogue technology and that the amount of traffic would vary depending on the airspace and timeframe.

Clearly, the FCS work is ongoing, but it is expected to help define the communications technology that will be available to support data link services in the 2020 – 2035 time frame.

D.4 Criteria for Selection of Air-Ground Communications Technology The criteria used in selecting suitable air-ground communications technologies for the regulatory coverage may be summarised as follows. An air-ground technology specified in the implementing rule must have been analysed in terms of the following aspects:

• AGL1. Open, validated standards must exist.

• AGL2. Retained by DL Roadmap Study

The European Commission’s Roadmap study [20] concluded that VDL-2 and/or VDL-4 are the only viable alternatives to support initial data link services in busy continental European airspace.

• AGL3. Stakeholder support and deployment plans.

Independently of the other criteria, stakeholders may make technology choices for internal reasons. It is important that the selected technology enjoys widespread support and features in stakeholder plans; otherwise any attempt to impose regulations would be resisted by stakeholder groups.




• AGL4. Spectrum planning & availability

RF spectrum requirements must be assessed and spectrum availability identified.

For the air-ground subnetwork, the total bandwidth (number of RF channels) required to support the data link services throughout their operational life must have been evaluated. If the proposed technology is proposed for several applications (not only ATS data-link), the total capacity requirements must be assessed.

The total spectrum requirements in the aeronautical band of the proposed technology must be known, taking into account the required separation channels for maintaining the data link free of interference with any of the other services operated in the same frequency band. This needs also to take into account the airborne co-site risks of interference translated into possible additional spectrum requirements.

A deployment plan for the required channels must have been prepared and the conditions for this deployment must be known and realised.

• AGL5. Geographical coverage

One or more operators must provide complete service coverage for the airspace covered by the implementing rule.

• AGL6. Certified products available

Avionics products supporting the subnetwork must exist and be certified.

• AGL7. Actual performance

The subnetwork must meet the performance requirements analysed in Annex G. The capacity required by the data link applications must have been translated into terms appropriate for the proposed ground-ground and air-ground subnetworks.

• AGL8. Security Policy supported

The selected technolog(ies) must be able to support the security provisions specified in the applicable security policy.

D.4.1 Comparison of Technologies AMSS and HFDL services are both available in the continental airspace to be covered by the draft implementing rule on data link services. However, for cost/performance reasons, the aeronautical industry has not invested in the development of avionics support for these technologies in short haul aircraft. The limited availability of commercially available products for AMSS and, additionally, performance concerns with HFDL, are the reasons why these technologies are not recommended to support the selected data link services.

The VHF ACARS service is also available in the airspace covered by the implementing rule. However, "Plain Old ACARS" offers an unacceptably poor performance for ATS applications, its allocated RF bands are becoming saturated and this service is being replaced by VDL-2. It is thus not recommended.

VDL-4 has also been proposed for the support of air-ground ATS applications. However, neither product nor infrastructure is available for VDL-4 and hence it cannot be recommended at present.

Existing military data links play a major role in conducting military operations; they cover a broad range of services mainly oriented to command and control activities, and do not feature any specific ATM functions enabling civil/military interoperability. Studies have




shown some options to foster interoperability; however, they were not received with the necessary support for further investigations.

Various stakeholders, including aircraft operators, ACSPs and avionics vendors, have invested in developing a set of products and infrastructure designed to deliver a VDL-2 based communications service in both the European Region and globally. VDL-2 has been developed in support of AOC and as an ACARS replacement. However, it is also suitable for ATS applications; both AOC and ATS applications share the same hardware and infrastructure.

D.4.2 Capacity and Performance Requirements For the proposed technology (or several technologies at some future time) to deliver the required quality of service, the following conditions must be met:

• A detailed and validated study of each proposed sub-network must exist that analyses its performance and capacity. It must be detailed enough for operators and implementing States to be able to apply the conclusions and hence guarantee the quality-of-service.

• The exact radio spectrum requirements must be identified for each sub-network channel, and the total number of channels required for the intended data-link services must be accurately assessed.

The spectrum requirement per channel must cover worst-case operational interference scenarios including the airborne co-site interference risks.

The total requirement for the number of channels must take into account the data link traffic, its growth and the growth of air traffic, but also the communications traffic volume of other applications that would make use of the same data-link channels (like AOC in the case of ACARS and VDL-2).

• An adequate number of frequency channels must be licensed and made available at any time for the quality of service to be maintained in all phases of the deployment. The service providers must deploy the adequate infrastructure on time for all channels in the whole implementation area.

D.4.3 VDL-2 Validation Results For VDL-2, the sub-network assessed as the only current viable means of compliance for the implementing rule, the following validation activities have been performed:

• Exact spectrum requirements have been established per VDL-2 channel and in total for Europe. This is defined and granted at ICAO Aeronautical Communications Panel (ACP) level and at the ICAO European Frequency Management Group (FMG) level, respectively.

VDL-2 frequency separation criteria have been developed in the relevant ICAO working group. Reference [64] describes the method applied for interference testing, together with an overview of the laboratory tests and the results (separation criteria).

Those separation criteria guarantee that interference possibly encountered in worst case operational conditions remain tolerable. The criteria cover aircraft in flight close to each other, aircraft on the ground close to each other, aircraft and ground-station close to each other, and include any combination of one or several VHF voice signals and/or VDL-2 signals.

A further analysis [65] assessed the potential impact of airborne co-site interference involving VHF voice AM-DSB and VDL-2 communications on safety




and on data-link performance and quality of service. It confirmed that VDL-2 frequency separation criteria developed in 2001 are not impacted by airborne co-site interference.

• Detailed simulations have been performed to assess the VDL-2 capacity and the total number of channels required [66].

Since 2002, EUROCONTROL has co-ordinated capacity analysis for single and multi-channel VDL-2 deployment. A very detailed modular simulator has been developed that uses air traffic records in high-density airspace, and analysis of the impact on VDL-2 channels of different aircraft equipage rates. It covers AOC traffic (legacy ACARS traffic) and CPDLC traffic, as required for data link implementation.

A principal aspect of this work is the very detailed and documented validation work that has been achieved for each module of the simulator. A cross-check has been run with a totally independent simulator, to consolidate the simulator results.

The results of the simulation are expressed in terms of a maximum number of flights equipped per hour in a certain air volume (about 1220 flights running AOC traffic with 730 of them running CPDLC, per hour in a 600 NM–radius air volume), and a total number of channels required for a full AOC traffic migration from ACARS to VDL-2 in addition to the final CPDLC data-link deployment level. The conclusion was that 2 - 3 channels would be required in the 2006-08 time frame.

Based on those separation criteria, and the total channel requirements developed, ICAO FMG EUR developed a gradual deployment plan [67] for a VDL sub-band at the top of the VHF aeronautical band.

That sub-band provision consists of a minimum of 4 VDL-2 channels planned for deployment from 2000 to 2008 onwards. This is compatible with the total requirements established by the detailed capacity study. The sub-band is extendable in future for at least a few more VDL channels, in addition to ACARS channels that will be replaced by VDL-2 progressively.

Data link operators and national frequency managers meeting at ICAO FMG EUR also have the task to monitor the VDL-2 total traffic evolution and plan capacity. Service providers who are requesting access to VDL-2 channels in application of the VDL sub-band deployment plan will regularly (annually at least) be requested by ICAO FMG to report on their traffic statistics and future traffic predictions.

Initial operational deployment of VDL-2 in Europe uses a single VHF channel. In the near future (from 2008 on), VDL-2 avionics will be equipped with the VDL-2 "auto-tune" function, allowing the radio to respond flexibly to the traffic level according to local conditions, and to switch to a different channel when required. The auto-tune function is defined by AEEC VDL-2 standards and by the ICAO VDL-2 SARPs.

Reciprocally, all ACSPs must implement the VDL-2 auto-tune function according to the standards and equip all covered areas with sufficient channels as required by the peak traffic figures.

D.4.4 Spectrum Planning Status Since 1999, ICAO FMG EUR (the ICAO regional planning subgroup that takes care of the allocations in the VHF aeronautical band) has envisaged the progressive provision of several channels for deployment of data link in Europe. In 2002, based on the available separation criteria for VDL-2, an initial deployment plan was developed. The plan has been progressively refined, most recently at the FMG/9 meeting (September 2005).

The plan presents a progressive deployment, starting from the 2002 situation. The current agreed target deployment for around 2008-2010 contains:




• Four VDL-2 channels, and

• A provision for two VDL-4 channels

In the case of VDL-4, this allocation is based on the assumption that the separation criteria are equivalent to those determined for VDL-2; and that a decision for implementation needs to be confirmed latest in 2008-2010.

The ACARS channels that were present at the top of the aeronautical band in 2002 were too close to VDL-2 channels needing protection, and have been re-allocated. They will be maintained for an interim phase allowing stepwise migration from ACARS to VDL-2.

As part of the initial step, originally foreseen for September 2004, almost all ADS-B / VDL-4 pre-operational services have been migrated from 136.950 MHz to 136.925 MHz, and all other services on that frequency have been cleared.

In the next step, targeted for 2006:

• A second channel for VDL-2 needs to become protected.

• A VDL-4 channel is further temporarily maintained for pre-operational trials and validation, but confirmation for VDL-4 separation criteria and confirmation by EANPG of operational needs on VDL-4 need to be obtained before 2008 as a prerequisite for further VDL-4 channel allocation.

• A temporary additional ACARS channel is deployed on 136.725 MHz for addressing ACARS saturation at some major airports, but this channel is designated for migration to VDL-2 from 2008.

D.5 Conclusions The European Commission Roadmap study [20] found VDL-2 to be the most mature of the reviewed data links. Since then, VDL-2 deployment has grown rapidly and the issues identified in the roadmap report have been resolved.

VDL-2 technology is capable of supporting all of the ATS and AOC point-to-point data link services identified in Annex B.

In particular, EUROCONTROL simulation work has also shown that VDL-2 is capable of meeting the forecast demand, at least up to 2014, within current and planned frequency allocations.

Meanwhile, the expected VDL-4 service provider has failed to materialise and there is no significant use of VDL-4 for data link services.

AMSS and HF Data Link have a role to play in Oceanic data link but do not have stakeholder support for continental use.

There is no obvious alternative to VDL-2 being the only and unique air-ground communication technology to support the selected data link services. However, this should not prevent other data links being advanced as alternative means in the longer term, provided they meet the minimum requirements for air-ground communications in support of the implementing rule.

The LINK 2000+ programme aims to equip 75% of flights in designated upper airspace areas by 2014. Assuming a full AOC migration to VDL-2 at that stage, 2 or 3 VDL-2 channels would be required. Further detailed studies will confirm whether 2 channels can cover the 2014 requirements for AOC and ATS data link, and confirm their optimal deployment parameters.

According to current frequency assignment plans, 4 channels will be available for VDL-2 by 2010, so on current forecasts there should be adequate VDL-2 capacity to support




currently defined data link services until well beyond 2014. Further studies are required to confirm that VDL-2 capacity will be sufficient to meet the requirements for 2020 and beyond.

Appropriate regulatory provision must be made to prescribe the implementation of VDL-2 air-ground communication technology to support the selected data link services.




ANNEX D. AIR-GROUND COMMUNICATION TECHNOLOGY ............................... D-1 D.1 Introduction ........................................................................................................ D-1 D.2 European Commission Data Link Roadmap Conclusions ................................. D-1

D.2.1 VDL-2/Mode S/1090 ES path – Step 1 .................................................... D-2 D.2.2 Alternative path based on VDL-4 – Step 1............................................... D-3 D.2.3 Conclusion on VDL Technology............................................................... D-5

D.3 Alternative Data Link Technologies ................................................................... D-5 D.3.1 Aircraft Communication Addressing and Reporting System (ACARS)..... D-5

D.3.1.1 ACARS Background..................................................................... D-5 D.3.1.2 ACARS over VDL-2...................................................................... D-5 D.3.1.3 Future Directions .......................................................................... D-6

D.3.2 The Aeronautical Mobile Satellite Service (AMSS) .................................. D-6 D.3.3 HF Data Link ............................................................................................ D-7 D.3.4 Military Data Links.................................................................................... D-8

D.3.4.1 Link 11.......................................................................................... D-8 D.3.4.2 Link 16.......................................................................................... D-8 D.3.4.3 Suitability for ATS Use.................................................................. D-9

D.3.5 Mode-S Data Link .................................................................................. D-10 D.3.6 3G/UMTS ............................................................................................... D-11 D.3.7 FAA/EUROCONTROL Future Communications Study.......................... D-11

D.4 Criteria for Selection of Air-Ground Communications Technology .................. D-12 D.4.1 Comparison of Technologies ................................................................. D-13 D.4.2 Capacity and Performance Requirements ............................................. D-14 D.4.3 VDL-2 Validation Results ....................................................................... D-14 D.4.4 Spectrum Planning Status...................................................................... D-15

D.5 Conclusions ..................................................................................................... D-16




ANNEX E. GROUND-GROUND COMMUNICATION TECHNOLOGY

E.1 Introduction This Annex considers candidate ground-ground communication technologies and procedures required to support the data link services for continental airspace, which were identified in Annex B.

The generic data link system architecture described in section 3.1.3 of the Regulatory Approach includes not only air and ground end systems and an air-ground data link, but also a ground infrastructure, providing connectivity between ANSPs and the air-ground data link system. The aim of this Annex is to determine the impact, if any, on the implementing rule for data link services, of the requirements and options for the ground data communications between an ANSP's data link processing system and the ground station of an air-ground data link.

In general, there are a number of distinct elements to this ground-ground communication:

a) The internal network of the Aeronautical Communications Service Provider (ACSP)

b) The connection(s) between the ANSP's internal network and the ACSP(s)

c) Interconnections between ANSPs, for ground coordination between ATS Units in support of air-ground data link services

d) Interconnections between the different ACSPs providing data link services

e) Interconnections between civil and military ATS Units.

Collectively, these elements must inter-operate to ensure that the safety, performance and security requirements of the supported data link services are satisfied, in order to deliver a seamless communications service to ANSP and aircraft systems.

Safety and performance requirements (SPR) standards, such as ED-120 [4], tend to allocate requirements to "the operator's provisions to use the data link services." The ANSP and the ACSP may include third party or contracted communication services, but ED-120 does not provide any individual requirements for them; requirements may be derived from ANSP requirements.

E.2 Ground Communications Supporting Data Link Services The ground data communication necessary to support air-ground data link services consists of:

a) Ground coordination between ATS Units

b) The ground segment of the end-to-end air-ground communication path.

E.2.1 Ground Coordination Between ATS Units Ground coordination is used in support of data link services to exchange flight information between ATS Units that have, or are expected to have, responsibility for the control of the flight. This can help to ensure a seamless service as the aircraft passes between ATS Units, and can optimise the use of scarce air-ground communications bandwidth by ensuring that an aircraft only has to convey static information (e.g. data link capability and equipage, departure and destination airports) to the first ATS Unit that it communicates with.

Within Europe, the messages specified in the EUROCONTROL Standard Document for On-Line Data Interchange (OLDI) [37] are widely used for co-ordination and transfer

Annex E Ground-ground comms 1.1.doc 24/05/2006 Page E-1



between ATC Centres. The set of OLDI messages and procedures to be used are typically agreed between neighbouring States via Letters of Agreement (LoA). This will be regulated by the interoperability implementing rule on co-ordination and transfer (COTR).

To support the air-ground data link services, the LINK 2000+ Baseline 1 [15] requires that participating ANSPs shall interconnect their national and regional networks and that OLDI is implemented, supporting the exchange of the "Logon Forward Message" (LOF) and the "Next Authority Notified" (NAN) message.

The OLDI standard specifies quality of service requirements. The actual performance achieved will need to be analysed to ensure that the quality of service matches the performance requirements allocated to this component of ground-ground communications.

E.2.2 Ground Segment of End-to-End Air-Ground Communication The end-to-end communication path between aircraft and ATS Units includes a ground element as well as the air-ground element.

To support the point-to-point data link services identified in Annex B, the ACSP is contracted by the ANSP to provide an air-ground data link service by deploying a suitable network of ground transmitter / receiver sites. These are interconnected by the ACSP's internal ground data network, which in turn interconnects with other ACSPs and with the ANSP.

ED-120 [4] allocates performance requirements to the communication system as a whole. These requirements must be apportioned between the various sub-links. This process is elaborated in Annex G. In summary, any point-to-point data link service can be supported over the ground-ground communications network provided that:

a) Suitable interconnectivity exists between the ACSP and ATS Units supporting the data link service

b) The performance requirements of the data link service are known, and are apportioned between air-ground and ground-ground system elements

c) The achieved communications performance of the ground-ground networks and interconnections over which the data link service information flows continually matches at least the minimum performance requirements.

The ground elements must satisfy the SPR allocated to them, as well as providing an adequate level of security. These aspects might require prescription in the implementing rule.

E.3 Use of ACSP Network ACSPs provide air-ground data link services. They take responsibility for accepting uplink messages from aircraft operators or ANSPs and delivering them to the intended aircraft, and accepting downlink messages from aircraft and delivering them to the intended destination. The role of ACSP can be taken by a commercial organisation, by an ANSP, or any other suitably qualified organisation.

ANSPs already have to maintain a number of network connections and subscriptions, and will tend to minimise the number of ACSPs they need to connect to.

The data link used to interconnect the ANSP and ACSP domains is a matter for local agreement, and may be any suitable network that is compatible with the safety and performance requirements allocated to each domain.




E.3.1 Service Level Agreements In general, the structure and technology of the internal data network of an ACSP is the responsibility solely of that ACSP, and would not be visible to users of the ACSP services. As it is essential that SPR for ATS services are complied with, there will normally be a contractually binding service level agreement (SLA) between the ACSP and ANSP to guarantee the required availability, performance, etc.

EUROCONTROL guidelines for implementation support (EGIS) include a model SLA related to the provision of ACARS-based ATS data link services (DCL, D-ATIS) [30]. This could in principle be extended to include requirements for the provision of any specified ATS data link services.

The SLA specifies the requirements for the interface between the ATS domain - under the responsibility of the ANSP, and the communication domain - under the responsibility of the ACSP.

This generic model aims at being used for the drafting of the SLA that could be part of the final contract between the ACSP and the ANSP or/and a safety case dealing with aeronautical mobile data link services.

The data link communications services are under the sole responsibility of the ACSP, and the users of these services are, in the context of the SLA, the ANSP.

The SLA could then be considered as the technical part of the contract made between the ACSP and the ANSP, which includes clear specification of the data link communications services in terms of services definition, requirements for interoperability, performance and safety, and monitoring and reporting.

E.4 ANSP Networks

E.4.1 Existing AFTN/CIDIN Provision Many States have their own internal data networks, and it is likely that these existing networks will also be used for data link services communications, both with ACSPs and with adjacent ANSPs.

Most if not all European ANSPs are today connected to the international AFTN/CIDIN network. This is used inter alia for the exchange of flight plan and airspace management information. Thus, ANSPs already have the capability to communicate with ACSPs, using AFTN addresses and message formats.

However, these existing connections tend to be non-deterministic in performance terms, and it is not clear that they will be able to meet the SPR allocated to ground systems supporting data link services.

Currently, network interconnections are being established and managed by States on a bilateral basis. The procurement of compatible multiplexers is coordinated between States. Some States have a trilateral management arrangement for transit traffic over bilateral connections.

E.4.2 ANSP Interconnectivity The EUROCONTROL OLDI Standard [37] specifies requirements for availability, reliability, data security and data integrity. Within the specified performance requirements, the data communications medium is required to provide a rapid and reliable application-to-application data exchange by assuring the integrity of OLDI message transmission and monitoring either point-to-point connections or the status of the communications network, as applicable.




OLDI performance is "real time" and the quality of service requirements are well understood. Message delivery is assured by explicit acknowledgement from the receiving application. The reliability of every OLDI link is required to be at least 99.86% (equivalent to a down-time of not more than 12 hours per year based on 24-hour availability). A reliability of 99.99% (down-time of not more than 52 minutes per year) is recommended where operationally justified. The failure rate at application level is required to be less than 0.05% (one transmission error per 2000 messages).

The Flight Data Exchange Interface Control Document (FDE-ICD) is the EUROCONTROL standard that specifies the "traditional" interface used to exchange OLDI messages between ATC Centres in Europe. It is based on X.25 interfaces for either point-to-point or networked connections. It provides X.25 communication services to OLDI and the civil/military co-ordination of flight data. OLDI communications via X.25 are mature and operational.

As the FDPS at many ATC Centres have existing OLDI interfaces, there should be minimal impact in requiring the support of additional messages in support of data link services.

The Flight Message Transfer Protocol (FMTP) is an evolution of the FDE-ICD protocols. It replaces the X.25 interface with a TCP/IP network service. FMTP does not make any assumptions about the existence of a network infrastructure, and the IP communication could take place over dedicated links. FMTP implementation is subject to an implementing rule under the interoperability Regulation of the EU Single European Sky (SES) regulations.

It seems likely that the combination of SES regulation and X.25 obsolescence will force ATC Centres to migrate to the IP-based FMTP, unless they have alternative bi-lateral arrangements.

In Europe, the international distribution of surveillance data (radar tracks) between neighbouring States is fairly common and has been regionally standardised. This data distribution is currently accomplished via the interconnected national X.25 WANs and there is a planned migration to IP-based services toward the end of this decade. Although bilateral data communication arrangements would be suitable, it is intended that this service would make use of the pan-European IP Wide Area Network (WAN), when it comes into existence.

E.4.3 Pan-European Network Service It is a strategic goal within the EATM framework to establish a pan-European Network Service (PENS) to serve the future communication needs of ANSPs. This is reflected in the EATM Communications (COM) Strategy [28].

The EATM Communications Team identified the applicability of the Internet Protocol (IP) suite for existing and planned ATS and CNS applications, especially in the light of diminishing industry support for the X.25 protocol, which today is the basis for extensive ATM/CNS application data exchanges.

States in the core area of Europe already have an extensively meshed high capacity wide area network (WAN). AFTN/CIDIN runs over these WAN interconnects, as do other data flows such as OLDI, some Radar data exchange, etc. Connections to ATS Units have a variety of performance characteristics in terms of line speeds (hence maximum data throughput) and reliability.

It would be relatively straightforward to implement TCP/IP over the existing X.25 network infrastructure as a migration step. However, this infrastructure is reaching the end of its lifetime, and will no longer be supported by manufacturers by the end of the decade.




In the 2005-09 timeframe, the PENS concept is to upgrade all bilateral international connections. Existing data services (OLDI, CIDIN, etc) will then be migrated to these connections. Data services will be migrated from X.25 to IP and voice services will also be migrated.

From 2009 onwards, a European-wide IPv6 based backbone will be required to further reduce the cost of the international infrastructure and to meet the capacity demands of more demanding services.

Once a suitably dimensioned Pan-European Aeronautical IP service is established, it could provide all the ground-ground connectivity needed. The PENS is being designed from the outset to handle all existing and planned message flows. The PENS service would offer more predictable and responsive performance than X.25 based services, and would not suffer from sporadic delays due to the build-up of packet queues.

IP networking is well understood by the technical community and support to deal with problems, performance issues, etc. should be widely available.

However, the timescale for PENS is not firmly established and the institutional issues regarding network management have yet to be resolved.

Current FDPS do not in general have suitable interfaces to IP-based networks. The impact of modifying the FDPS would, therefore, need to be taken into account.

Another potential problem is that the use of IP would open up possible security threats. There are well-publicised attacks on IP-based networks. Standard countermeasures exist, but the cost of procuring, operating and managing these would need to be evaluated following a full risk analysis.

Meanwhile, ANSPs and ACSPs will be required to establish and maintain a robust and auditable security policy.

E.5 Use of Public Internet If IP technology is used for ground-ground communication, it is possible that one or more communication links could be routed via the public Internet. It has been demonstrated that, given appropriate security measures, such access is feasible.

Traditionally, the civil aviation community has insisted on having its own dedicated communication systems on grounds of reliability, integrity, security and their impact on aviation safety. This has caused a degree of reluctance by many aviation personnel to the formalisation of the use of the Internet, which is not under control of any aviation entity. Nevertheless, due to widespread availability, accessibility (especially by the public), affordability, speed and ease of use, some States have started using the Internet for certain applications (e.g. meteorology and aeronautical information services). Also, in some parts of the world, where dedicated aeronautical communication systems are inadequate or cannot be economically justified due to very low traffic levels, the Internet is being used as a means of ground-ground communications.

E.5.1 ICAO Guidelines The ICAO view of the use of the Internet is summarised in the following statement from the ICAO EUR/NAT Office in co-ordination with the ICAO HQ Montreal in June 2002:

"Internet is not a communication means recognized by ICAO for operational purposes due to the uncontrolled nature. AFS and ATN are the only recognized ICAO communication systems for this purpose."

More recently, ICAO has circulated draft "Guidelines for the Use of the Public Internet for Aeronautical Applications" [72]. The intention of the document is to assist Contracting




States in dealing with the increasing use of the Internet for certain operational aeronautical purposes. The document contains guidelines on the use of the public Internet as a means of communication for non-time critical aeronautical ground-ground applications. The term "non-time critical" implies that the information being transferred over the Internet has no immediate effect on an active flight.

The ICAO guidelines are intended to minimise the possibility of non-compatible / diverging procedures being adopted by those States and international organisations that choose to use the Internet for certain operational applications.

The guidelines are intended to indicate high-level best practice rather than detailed technical specifications, and are based upon proven operational procedures and Commercial Off The Shelf (COTS) products. It is recommended that the most appropriate solution be deployed at the time of any implementation. Moreover, the guidelines do not cover those services that are normally provided via dedicated communications infrastructure, such as leased lines or intranets that may use Internet-based technologies.

The document does not contain any statement of ICAO position as to where and when the Internet should or should not be used for aeronautical applications. ICAO may develop such position at a later stage if deemed necessary.

In general, the use of the Internet, as a means of communication for provision or exchange of operational information, does not relieve States from their obligations and responsibilities for the implementation of aeronautical fixed service (AFS) and other facilities/services that have been established by regional agreement and are documented in the ICAO regional air navigation plan publications.

Furthermore, like any other facility or service, any use of the Internet for inter-State data/message exchange should be subject to bilateral, multilateral or regional agreements and be properly reflected in the regional air navigation plan publications.

States that permit use of the Internet should:

• Accredit the Internet Aviation Service Providers (IASPs) that propose to provide Internet-based provision/exchange of information; and

• Ensure that they have adequate information technology and information security expertise for overseeing the accreditation process.

In any implementation of Internet-based AFTN-type communications, procedures contained in ICAO Annex 10 - Aeronautical Telecommunications, Volume II - Communication Procedures including those with PANS status [87] relating to format, processing and retention of messages should be adhered to. Based on the message categories and their priority indicators (for transmission over the AFTN), the draft ICAO guidelines conclude that the following message categories should be considered non-time critical, hence suitable for transmission over the Internet:

• Certain MET messages;

• Flight regularity messages;

• Certain AIS messages;

• Flight plans and related messages;

• Administrative messages; and

• Service messages.

Certain message types considered time critical for aircraft in flight could be regarded as non-time critical when used in a pre-flight context.




E.5.2 Security Requirements The Internet protocol suite ensures the integrity of the transmitted messages in normal circumstances. However, being a public medium, the Internet is susceptible to certain security attacks (e.g. denial of service or infecting servers/users with computer viruses) that may seriously slow down or even temporarily stop its useful operation.

Information security schemes can be employed to ensure the authenticity, integrity or confidentiality of messages. Those measures, however, cannot counter network congestion (due to randomly high traffic or intentional malicious jamming). As such, the use of the Internet for aeronautical operational purposes should be limited to exchange of non-time critical messages, information or data.

Due regard should be given to risk assessment and management processes.

E.6 Ground-Ground Communications Systems Interconnection

E.6.1 Issues The interconnection of ANSPs and ACSPs is described as “Interface A” in the generic data link functional architecture (see Annex F). This is a ground-ground interface where an ANSP's communications system is interconnected with an ACSP using a suitable ground-ground network.

ACSP interface to ANSP

ANSP ‘A’

Airline Host System

ACSP ‘X’ Network ACSP ‘Y’ Network

Interconnection Agreement

VDL service

AOC Communication

ATS Communication

Figure E-1. ACSP Interconnection

The generic functional architecture described in Annex F is actually an over-simplification as far as the ground domain is concerned. In practice, there can be multiple ACSPs providing data link services for AOC and ATS. This is illustrated in Figure E-1, which shows an aircraft using the VDL service of ACSP "Y". In this example, the airline has a contract with ACSP "Y" to convey AOC messages via the ACARS system between aircraft and airline computer systems. The ACARS service is provided over the VDL connection using AOA. The same VDL connection is used for ATS data traffic. However, ANSP "A" has contracted with ACSP "X" to provide an air-ground communications service in support of ATS data link services. In order for the aircraft to access the ATS data link services, there must be an interconnection between the ACSPs "X" and "Y".

If a single ACSP provides all air-ground communications, then for interconnection to take place, it is simply a matter of selecting an appropriate ground-ground network. However:




• The ACSP role may be performed by an ANSP or by a separate commercial operator.

• In any one area, there may be more than one ACSP.

• ACSPs provide AOC facilities to airlines on a commercial basis; the airline chooses the ACSP and negotiates the best price.

• With current avionics it is not technically feasible to use different ACSPs for AOC and ATS communications, when using VDL-2 and multiple communication frequencies.

• For ATS communications, the ANSP is responsible for ensuring that an appropriate air-ground communications service is available in the operational area and that it is available for all aircraft that need to use it.

• The ANSP either operates the service itself or selects a commercial operator to provide the service.

• The ANSP recovers the costs of providing the ATS service by a suitable mechanism (e.g. from en-route charges).

The basic problem is that the AOC communications service provider is selected by the airline, while the ATS communications service provider is selected by the ANSP, and it is not technically possible to use different providers simultaneously for ATS and AOC purposes. More advanced avionics may solve this problem, but this is not a realistic option in the near term.


AN SP

“A”

Flight Crew

Proc eduresFlight D eck

ACSP Network

ACS P

G-GANSP

Interface

A-GD ata L ink

Mgmt

“B”


Interface toC om munications

ServicesHMI

End S ystem(A ircraft)

HMI

End S ystem(ATS Unit)

C ontroller


End-to-endDialogue

“C”

ACSP Network

ACS P

G-GACS P

Interface

A-GD ata L ink

Mgmt

“B”


Interface toC om municat ions

ServicesHMI

End S ystem(A ircraft)

G -GACS P

Interface

“D”

Figure E-2. Data Link System Architecture - Two ACSPs

Figure E-2 illustrates the case where different aircraft operators contract with two different ACSPs. Four reference points are indicated:

• Reference point "A" is the ground interface between the ANSP system and the ACSP

• Reference point "B" is the logical interface between the aircraft system and the ACSP

• Reference point "C" refers to the end-to-end interchange of data in a dialogue supporting the data link services.

• Reference point “D” refers to the ground interface between two ACSPs.

These reference points are assumed throughout the interoperability analysis. The enabling technology for reference points "A", "B" and “D” is assessed in section 3.3 of the




Regulatory Approach document, while the data link services at reference point "C" are assessed in section 3.2. The necessary combination of elements to form a complete communications system with defined performance characteristics is considered in section 3.4 of the Regulatory Approach, where candidate systems are assessed.

It should be noted that an ANSP must connect either directly or indirectly to all ACSPs offering an air-ground data link communication service covering its airspace, and which is permitted to offer ATS services.

E.6.2 Institutional Principles In order to resolve these issues, EUROCONTROL has developed a number of institutional principles that together describe the framework necessary for interoperability. Although developed for the LINK 2000+ Programme, the principles are generally applicable. The principles are as follows:

Principle 1 – ATC data link services must be available to all airspace users, whether or not they use AOC services. Compliance with this basic principle is essential to avoid forcing aircraft operators to contract with an ACSP for AOC services in order to comply with the implementing rule. Many aircraft operators do have contracts for AOC messaging, but those that do not have such contracts should not be obliged to.

In practice, this means that there must be an ACSP operating in each part of the airspace that will support ATS communication with any aircraft that requires it. It is considered to be the ANSP’s responsibility to ensure that such an ACSP is available.

For example, at Maastricht UAC (MUAC), a commercial ACSP has been contracted to provide a VDL-2 service throughout the MUAC airspace, to be available to any airline that wishes to use it.

Principle 2 – Aircraft need to connect to only one ACSP for ATC and AOC purposes at the same time. This principle reflects the current state of VDL-2 avionics, which can only operate on a single frequency at any one time.

Simulation studies have shown that at least two VHF channels will be required to ensure that sufficient VDL-2 capacity is available in Europe when VDL-2 is used for both AOC and ATS communications. In turn, when multiple ACSPs operate in the same area, it is not possible to guarantee that they will all use the same VHF frequency. Therefore, there must be no requirement for aircraft to use different ACSPs for ATS and AOC purposes.

However, it should be noted that avionics vendors have stated an interest in developing products that can operate concurrently on multiple frequencies.

Principle 3 – Qualified ACSPs1 shall be permitted to provide data link services in support of ATS in the applicable area. A qualified ACSP providing AOC services to airlines must also have the opportunity to provide ATS communications. If this principle were not enforced, there would be an effective restraint on trade. If an AOC provider were not free to provide ATS communications services, the AOC business would be lost for those aircraft required to use ATS data link services.

1 A "qualified" ACSP is here defined as one that demonstrably satisfies the established minimum ATC data link performance requirements, at regional and national level.




Principle 4 – Airlines shall have the freedom to select any ACSP for data link services in an applicable area. Some airlines already contract for AOC services, and will continue to do so. If an airline were forced to use a particular ACSP in order to use ATS data link services, this commercial freedom would be lost. An alternative would be to make AOC service provision a regulated service, but there seems to be no justification for this.

Principle 5 – An ANSP shall connect directly or indirectly with all qualified ACSPs in its airspace. This is a necessary requirement for the ACSP to be able to offer an ATS service.

The data link functional architecture does not require direct connection between an ANSP and every ACSP. Instead, it is possible for an ANSP to interconnect with a single ACSP and for that ACSP to interconnect with other ACSPs and to route traffic between them and the ANSP. This is illustrated in Figure E-1 and elaborated in Figure E-2.

For example, the ACSP contracted by MUAC to provide the VDL-2 service also provides interconnection services with other ACSPs as part of the contracted service. The MUAC ATM system thus only has to concern itself with a single interconnection.

There are charging model implications from this principle that are in the process of being established.

The expectation is that as more European ANSPs offer ATS data link services, they will contract with one of the available ACSPs and a rough balance will result, in terms of the contracts awarded to each ACSP. The volumes of ATS traffic are much smaller than AOC traffic volumes, so the costs are comparatively small.

This is an area that may require monitoring in the future in order to ensure a fair price for the service and a fair return for the operators. In the short term, the charging arrangements are not seen as a subject for the regulatory coverage.

Principle 6 – Aircraft must be able to send data link messages to all adjacent ANSPs. This is a technical requirement necessary for interoperability. Overlapping VDL-2 coverage is required for the seamless transfer of communications as an aircraft moves from one ANSP to another. An aircraft must be able to communicate with the next ANSP on its route prior to entering that ANSP’s airspace. Transfer of communications occurs in a “make before break” fashion with an aircraft establishing communication with the next ANSP before relinquishing the communication link with the current ANSP.

Therefore ANSPs must be interconnected not just with the ACSPs providing coverage of their airspace, but also with ACSPs covering adjacent airspaces.

This would not be a problem for an ACSP with a wide coverage of European airspace. However, if an ANSP provides air-ground communications in its region of responsibility, then this becomes an important principle necessary for interoperability.

E.6.3 Regulatory Coverage Considerations A number of issues resulting from the above principles may affect the regulatory coverage in terms of stakeholder obligations:

1. ANSPs are required to ensure that suitable ATS air-ground communications are available throughout their airspace, for all airspace users (irrespective of whether or not they also use an AOC service provider).

2. The minimum performance requirements for the provision of air-ground ATS communications within the airspace covered by the implementing rule must be clearly




stated and compliance with the requirements must be readily verifiable. (Any lack of clarity could be perceived as a restraint on trade by an ACSP other than that contracted by the ANSP responsible for a given airspace).

3. The performance requirements must include the area of applicability, i.e. the airspace controlled by and adjacent to a given ANSP, where aircraft need to establish communication with the ANSP.

4. When an ACSP offers an ATS communication service, that service must support communication with both the ANSP responsible for the airspace and those responsible for adjacent airspaces, if they also provide data link services.

5. ANSPs should have a “right of interconnection” to an ACSP that provides coverage in the area of applicability, which demonstrably meets the minimum performance requirements for the provision of air-ground ATS communications. This interconnection may be either direct or via a designated intermediary.

6. The SLA performance requirements for ACSP to ANSP interconnection should be standardised and fully specified. Otherwise, an interconnection profile that is obscure, unpublished or difficult to implement could be perceived as a restraint on trade by an ACSP other than that contracted by the ANSP.

7. Where a “designated intermediary” is used to provide interconnection between the ACSP and an ANSP, this intermediary and the network used for interconnection must also meet clearly defined minimum performance requirements. Otherwise, there is the risk that this intermediary or the network used for interconnection may be a “weak link” in the system leading to a possible degradation of service.

There is a particular problem of cumulative risk. For example, a ground-ground interconnection between two ACSPs may be carrying ATS traffic on a European-wide basis. Loss or interruption of the interconnection could lead to service disruption across the whole region.

The minimum performance requirements for interconnection via a “designated intermediary” must take into account that a loss of service may affect multiple airspaces, and be specified accordingly.

E.7 Criteria for Selection of Ground-Ground Communications Technology The criteria used in selecting suitable ground-ground communications technologies for the regulatory coverage may be summarised as follows. A ground-ground technology specified in the implementing rule must have been analysed in terms of the following aspects:

• GGL1. Existence of open, validated standards

The ground-ground data communication technology should be based on stable standards rather than proprietary solutions.

• GGL2. Consistent with DL Roadmap Study

The European Commission’s Roadmap study [20] does not analyse the ground-ground data communications requirements in depth. The selected communications technologies must have the ability to support the retained air-ground data link technologies in terms of performance and interconnectivity.

• GGL3. Stakeholder support and deployment plans.

Independently of the other criteria, stakeholders may make technology choices for internal reasons. It is important that the selected technology enjoys widespread




support and is included in stakeholder plans; otherwise any attempt to impose regulations would be rejected by stakeholder groups.

• GGL4. Capacity planning & availability

For the ground-ground segment, the total bandwidth required to support the data link services throughout their operational life must have been evaluated. If the proposed technology is proposed for several applications (not only ATS data-link), the total capacity requirements must be assessed. The ground-ground data communication technology must be capable of satisfying the present and future capacity requirements.

A deployment plan for the required capacity must have been prepared and the conditions for this deployment must be known and realised.

• GGL5. Geographical coverage

One or more operators must provide complete service coverage for the area covered by the implementing rule.

• GGL6. Availability of approved products

Products supporting the subnetwork must exist and be approved to the required performance level.

• GGL7. Actual Performance & capacity

The subnetwork(s) collectively must meet the apportioned performance requirements analysed in Annex G. The capacity required by the data link applications must have been translated into terms appropriate for the proposed ground-ground and air-ground subnetworks.

• GGL8. Security Policy supported.

The selected technolog(ies) must be able to support the security provisions specified in the applicable security policy.

E.8 Conclusions Due to the nature of ACSP service provision, and existing interconnections between ANSPs, it is not considered that the technology used (e.g. choice of X.25 or Asynchronous Transfer Mode) in ground-ground data communications provision should be a subject for prescription in the data link services interoperability implementing rule.

However, the SPR allocation to the ground-ground communications segment of data link services requires that suitable provisions be put in place to ensure that the requirements are continually met.

Further, due regard should be given to the assessment and management of risk when specifying the ground-ground communications paths. ANSPs and ACSPs should have in place a suitable security policy and mechanisms to protect against unlawful interference with the ground networks.

Ground-ground interconnection has a number of important issues associated with it that also affect the air-ground environment. As a result the two environments cannot be considered to be entirely separate.

EUROCONTROL has, with the agreement of stakeholders participating in the LINK 2000+ Programme, defined a number of institutional principles from which the potential regulatory issues can be determined, as described above.

The support of certain OLDI message types may be a subject for prescription in the data link services implementing rule.




Requirements for a SLA should be analysed for possible applicability to the regulatory coverage, as they are essential to the seamless operation of the data link communications system.




ANNEX E. GROUND-GROUND COMMUNICATION TECHNOLOGY.................. E-1 E.1 Introduction ........................................................................................................ E-1 E.2 Ground Communications Supporting Data Link Services.................................. E-1

E.2.1 Ground Coordination Between ATS Units................................................ E-1 E.2.2 Ground Segment of End-to-End Air-Ground Communication .................. E-2

E.3 Use of ACSP Network ....................................................................................... E-2 E.3.1 Service Level Agreements ....................................................................... E-3

E.4 ANSP Networks ................................................................................................. E-3 E.4.1 Existing AFTN/CIDIN Provision................................................................ E-3 E.4.2 ANSP Interconnectivity ............................................................................ E-3 E.4.3 Pan-European Network Service............................................................... E-4

E.5 Use of Public Internet......................................................................................... E-5 E.5.1 ICAO Guidelines ...................................................................................... E-5 E.5.2 Security Requirements............................................................................. E-7

E.6 Ground-Ground Communications Systems Interconnection.............................. E-7 E.6.1 Issues....................................................................................................... E-7 E.6.2 Institutional Principles .............................................................................. E-9 E.6.3 Regulatory Coverage Considerations .................................................... E-10

E.7 Criteria for Selection of Ground-Ground Communications Technology........... E-11 E.8 Conclusions ..................................................................................................... E-12




ANNEX F. ATS DATA LINK COMMUNICATION SYSTEM

F.1 Introduction In establishing the regulatory coverage, it is not sufficient to consider individual data link services or communications technologies in isolation. The business and safety cases for deploying data link services depend on analysis of a complete data link communication system.

This Annex considers options for the selection of elements that together form a viable end-to-end data link communication system providing the selected data link services. The Annex has three appendices providing more detailed explanation where considered necessary:

Appendix 1 describes a generic functional architecture for data link systems and uses this to consider aspects of real-world data link systems.

Appendix 2 introduces the standardised CNS/ATM data link applications, describes how are used in the implementation of data link services and considers Protected Mode variants.

Appendix 3 considers the need for an ATS data link system baseline, or "profile" specification.

F.2 System Requirements The communication system must provide harmonised, interoperable communication services in the EATMN to the end systems (in ANSP and aircraft systems), which are responsible for delivering the operational data link services.

In the end-to-end communication system, interoperability must be separately demonstrated for each data link service between each avionics system and each ground ATS Unit, and for each transaction and message exchanged end to end.

ANSPs' data link systems need to:

• Get access to air-ground communications services in accordance with a harmonised, interoperable procedure;

• Have the capability to manage communication context with remote aircraft data link systems using harmonised and interoperable procedures;

• Have the capability to send and receive data to and from aircraft data link systems in accordance with a harmonised, interoperable procedure.

Aircraft data link systems need to:

• Get access to air-ground communications services in accordance with a harmonised, interoperable procedure;

• Have the capability to manage communication context with remote ATS Units' data link systems using harmonised and interoperable procedures;

• Have the capability to send and receive data to and from ATS Unit data link systems in accordance with a harmonised, interoperable procedure.

The rationale for this is that aircraft operators must be able to procure avionics that satisfy the requirements of the implementing rule and are interoperable with ground systems.

Appendix 1 to this Annex considers the available data link communication systems. The candidate systems in existence today that may be considered capable of providing point-to-point communication services in support of the identified data link services are:

Annex F ATS Data Link Systems 1.1.doc 24/05/2006 Page F-1



a) ICAO ATN based systems

b) ACARS based systems:

a. ED-100A FANS-1/A and equivalent systems

b. The Character Oriented ATS Applications based on ARINC Specification 623 [32].

Interoperability demands that one or all of these systems are recognised as appropriate means of compliance with the implementing rule for data link services.

F.3 Global Interoperability

F.3.1 FANS-1/A ATS Data Link Services in Continental Airspace There has been continued interest in the possibility of using the FANS-1/A system in continental airspace, and in 2002 an “Industry Rapid Reaction Force” (IRRF) prepared a report on this subject for the EUROCONTROL LINK 2000+ Programme.

The IRRF identified 17 issues needing resolution. Of these, only one issue had to be resolved before FANS-1/A could be used for flight profile changing messages (i.e. support of the ACL Service). This relates to the identification of out-of-date messages and required an upgrade to the product before it could be used for such services.

This upgrade is documented in the FANS 1/A INTEROP standard ED-100A [12], and compliant avionics implementations are becoming available.

A new RTCA/EUROCAE standard is being developed to specify how data link services such as DLIC, ACL, ACM and AMC can be provided using FANS-1/A. The standard is currently at draft status, identified in draft form as PUB-40 [57].

The other IRRF issues relate to subjects such as “missing message elements” in the FANS-1/A specification, that mean that some clearances cannot be processed, and are of a generally lesser significance.

Since the IRRF report, the continental SPR standard EUROCAE ED-120 [4] has been published. This is significant because the IRRF was not able to assess FANS-1/A against a formal set of safety and performance requirements.

In particular, the requirements identified in ED-120 led to the development of the “protected mode” variant of CPDLC and its standardisation by ICAO. This was in consequence of the need for stronger provisions to detect potential delivery of ATC clearance messages to unintended recipients using the ATN communication service.

Similar issues may apply to ED-100A FANS-1/A, and review of this issue is being undertaken.

The importance of this issue depends on the number of aircraft in operation, and becomes significant as the number increases.

F.3.2 Convergence of Data Link Systems ATM services based on FANS-1/A and equivalent implementations are available in many oceanic and low-density continental airspace regions worldwide, using satellite based ACARS services for data transport. In the South Pacific region, such services are now effectively replacing HF voice radio as the primary means of communication, providing a more efficient and performant communications capability. HF voice is still available as a backup communications path but is no longer the preferred medium of communications.

Aircraft operators with flights in these regions have become accustomed to using data link services, both FANS-CPDLC and ADS-C, in many cases with close integration into the




aircraft FMS, and real operational benefits are being experienced today. Asia/Pacific aircraft operators that operate in Europe will be reluctant to implement ATN Data Link Services until most of the capabilities that they experience with FANS-1/A (and equivalent) systems are provided.

The issue is one of international harmonisation and seamless operation between regions.

High-density continental airspace regions do not in general suffer the voice communication issues experienced in oceanic and low-density continental airspace regions. VHF voice communications in such regions provide a much more efficient and capable service than HF voice. Data link services, although superior to voice communication in many ways (e.g. more efficient spectrum usage, greater integrity, better integration with automation) are also slower, or less immediate, than voice communications. There is hence no desire to completely replace voice-based ATC with data link based ATC in such airspaces. Data link based ATC is therefore seen here as supplementary to voice communications, with services being deployed only where there is a clear operational or safety benefit.

Today, FANS/ACARS and ATN/VDL-2 are not compatible. ICAO in the context of the joint EUR/NAT Data Link Steering Group (DLSG) has endorsed an action aiming at ensuring convergence between FANS/ACARS and ATN/VDL-2 technologies. Such convergence is not expected in the short term, however.

F.4 Data Link Services Regulatory Coverage Currently, the end-to-end data link system that has been most thoroughly analysed and validated against the operational, safety and performance standards is that specified for operational use by the EUROCONTROL LINK 2000+ Programme.

The LINK 2000+ baseline specification [15] appears to be the only complete data link system specification that addresses all of the known issues.

The air-ground communications technology adopted by LINK 2000+ is VDL-2, which is being deployed worldwide to support AOC as well as ATS communications. LINK 2000+ is based on the ICAO ATN communication services (ICS and ULCS) and the CM and PM-CPDLC data link applications, all specified in ICAO Doc 9705 [2], plus specified defect resolutions.

The set of data link services in the LINK 2000+ baseline for en-route CPDLC implementations has, as the interoperability baseline document, the EUROCAE ED-110A - "Interoperability Requirements Standard for ATN Baseline 1 (INTEROP ATN B1)" Red-lined Version.

The data link services included in the LINK 2000+ baseline are:

• Data Link Initiation Capability (DLIC)




The data link services included in the LINK 2000+ baseline are a subset of the services documented in ED-110A and ED-120. The reasons for not adopting the full ATN Baseline 1 set of data link services are as follows.

• DLIC, ACM, AMC, DSC, D-ATIS and DCL services can be handled entirely by aircrew using local input and output devices without the added complexity of a link to the aircraft Flight Management System (FMS).




• The ACL service includes some clearance types involving detailed route information. For these, a link to the FMS is desirable but not essential. When route clearances are received by the avionics, then it is essential that auto-load into the FMS is provided.

• The FLIPCY service in ED-110A/ED-120 is intended to operate without aircrew intervention, and therefore requires interoperability with FMS systems in order to extract route information. This degree of interaction with automated systems involves an additional level of complexity compared with CPDLC-based services and requires additional standardisation and implementation activities.

Further, FLIPCY is the only ED-110A/ED-120 data link service that is based on the ADS-C application (the other data link services in ATN Baseline 1 are based on CPDLC, CM or D-FIS). Including FLIPCY in the LINK 2000+ baseline would, therefore, considerably increase the complexity and expense of the air and ground end systems.

On the other hand, FANS-1/A users are accustomed to using ADS-C, for its position reporting services in remote airspace. Providing an ATN implementation of ADS-C may be an important step in establishing global convergence of data link systems. However, it is beyond the scope of the current programme.

For initial ATN data link operations, therefore, the FLIPCY service is not selected. It is currently allocated to stream 2 of the CASCADE programme with planned operational deployment from 2010.

• Of the other ED-110A/ED-120 data link services, Departure Clearance (DCL) and Data Link Automatic Terminal Information Service (D-ATIS) are mainly applicable at airports, rather than the en-route airspace, which is the focus of LINK 2000+. These two services are becoming widely deployed at European airports using ACARS, and this will continue to be the case as ACARS service provision transitions to VDL-2, which is compatible with LINK 2000+ communications.

• Downstream Clearance (DSC) and Oceanic clearances (OCL) are not within the current scope of LINK 2000+ on grounds of additional complexity, lack of downstream data link equipped centres in the short term, and applicable airspace.

The LINK 2000+ programme recognises the feasibility of accommodation of ED-100A FANS-1/A equipped aircraft in ATN airspace, subject to operational and safety acceptability.

The LINK 2000+ data link services are currently in operational use at Maastricht Upper Area Control Centre. (However, the initial avionics implementations are not developed according to the required software assurance level, so voice read-back procedures are employed).

F.5 Selection of Data Link Systems

F.5.1 Introduction The purpose of this section is to analyse each of the ATS data link systems identified above against the selection criteria defined below.

F.5.2 Selection Criteria The criteria used for the selection of an end-to-end data link communication system are summarised in Table F-1 and explained in more detail below.




Table F-1. Selection Criteria for Data Link Communications Systems

Criterion Title

SYS1. Based on open standards

SYS2. Complete profile specified

SYS3. Validation

SYS4. Stakeholder support.

SYS5. Operational approval / experience

SYS6. Interoperability must be demonstrable.

SYS7. Business case.

SYS8. Extensibility

SYS9. Concept of operation.

SYS10. SPR satisfied.

SYS11. Impartiality

SYS1. Based on Open Standards

The selected data link services must be fully defined, both technically and operationally, through openly available standards, with no constraints on their use and free of patent restrictions. The standards must be published and maintained by a recognised standards body such as ICAO or EUROCAE, and must be priced fairly, commensurate with their size and production medium.

Rationale: There must be clearly defined standards if the implementing rule is to be useful. That the standards are open is important when making regulations. Any degree of proprietary control over the standards, or patents relating to their implementation, would be unacceptable, for competition reasons.

SYS2. Complete Profile Specified

Interoperability must be possible without any requirement for additional profiling, selection of options or additional specification.

To ensure technical interoperability of data link services, it is necessary, but not sufficient, to refer to a list of ICAO and EUROCAE documents. As discussed in Appendix 3 to this Annex, a detailed specification is required, refining the combination of standards, their relevant subsets and options, and any necessary divergences, together with version and amendment numbers.

Rationale: The standards must be complete, with no gaps or open issues, as any lack of completeness will tend to lead to a lack of interoperability between otherwise compliant products.

SYS3. Validation

Validation may be defined as confirmation, through the provision of objective evidence, that the requirements for a specific intended use or application have been fulfilled (ISO 9000:2000). ICAO has defined the meaning of validation in the context of data link applications and, for this purpose, validation includes the development of two or more implementations from the selected standards for which interoperability has been demonstrated in operational use.




Rationale: Validation of the selected set of standards is important for interoperability. Without validation, there is a risk that the standards have “open issues” associated with them and hence a risk of lack of interoperability.

SYS4. Stakeholder Support.

Systems and supporting services must be available from more than one vendor. Implementation plans must exist for ANSPs, airspace users and air-ground communication service providers.

Rationale: Stakeholder support is a prerequisite in order to ensure that suitable products are available for use and hence deployment is feasible and the cost of deployment is well known. Any conflict with existing stakeholder systems and constituents must be understood and planned for.

SYS5. Operational Approval / Experience

Avionics must be certified and ground systems must be commissioned for operational use. The certification of airworthiness and operational approval must be supported by appropriate documents. Avionics must be certified as required by the safety requirements.

Ground systems must be approved on the basis of an implementation safety case and demonstration of interoperability.

Rationale: As safety requirements are known to apply to some aspects of the data link systems, implementations must satisfy appropriate certification or approval regimes.

SYS6. Interoperability Must be Demonstrable.

One or more test and validation facilities must exist for proving interoperability between new data link systems and constituents and existing installed systems, both ground based and airborne. The reference systems used for interoperability testing must comply with the relevant standards recognised as means of compliance with the implementing rule. An example is the LINK 2000+ test facility at the EUROCONTROL Experimental Centre.

Rationale: The interoperability of each constituent must be demonstrable if interoperability is to be ensured. That is, facilities need to be available to test interoperability of implementations prior to operational use. Otherwise, there is a risk that a newly introduced constituent may compromise an existing operational service.

SYS7. Business Case.

A business case must exist and demonstrate a cost/performance benefit justifying the introduction of the data link service. However, it should be noted that very few of the individual data link services will be able to stand alone when it comes to creating a business case for it. In real-world terms, the benefits are only considered for groups, or packages, of services. The main cost of data link implementation on the aircraft is the additional hardware plus software that creates the basis for using any service. Adding individual services in an incremental manner is not necessarily a major cost.

Rationale: In order to justify its selection, there must be a clear business case for each data link service, providing a cost/performance justification for its introduction. Comparative analysis of the business cases for different data link services may be used to justify the introduction of one data link service earlier than another. The time to realise the projected benefits must be commensurate with stakeholder planning cycles.




SYS8. Extensibility

The set of data link services specified by the implementing rule must be extensible. The selection of a given data link service or supporting infrastructure must not preclude the development of other services or infrastructure, which might offer additional advantages. Each selected data link service must remain useful throughout its projected lifetime, and not be rendered obsolete by foreseen new services.

Rationale: Regulations for selected data link services should not be based on purely short-term considerations. Introduction of a given data link service should not unnecessarily preclude the introduction of other data link services unless there is a very clear justification for this.


The selection of data link services must be backed up by the concept of operations adopted for the foreseen lifetime of the implementing rule.

Rationale: Data link services must not be considered in isolation, but as part of an integrated concept within the context of an overall strategy to realise the benefits.

SYS10. SPR Satisfied.

Validated safety and performance requirements (SPR) must have been enumerated as part of an approved safety case.

Rationale: The development of safety and performance requirements is an essential step of the ED-78A [11] methodology (see Annex C) for the approval of the provision and use of ATS supported by data communications.

SYS11. Impartiality

The selection of a data link service and supporting technology must be impartial and not offer long-term commercial advantages to any single supplier to the disadvantage of other suppliers.

Rationale: The interoperability regulation should be fair and impartial. The data link services and supporting technology subject to the implementing rule should be selected according to justified and accepted criteria.

For comparison, the European Commission's 2003 data link roadmap study [20] performed a similar assessment of ATM applications based on slightly different criteria, namely: capacity, safety, flight efficiency, cost effectiveness, environmental impact and "enabler and other benefits". This high-level assessment was then mapped to the required data link services.




F.5.3 Application of Criteria to Data Link Systems

ED-110A ATN based system ED-100A FANS-1/A system

ARINC 623 applications

SYS1. Based on Open Standards

The data link services retained for implementation in the LINK 2000+ programme (ACM, ACL, AMC and DLIC) are all specified in the ATN Baseline 1 INTEROP standard ED-110A [3], and have operational safety and performance requirements allocated in the SPR standard for continental airspace ED-120 [4]. They are subsets of the PM-CPDLC and CM CNS/ATM applications, specified in the ICAO technical provisions for the ATN [2]. The VDL 2 data link is fully specified in ICAO and AEEC documents.

FANS-1/A applications are specified in the INTEROP standard ED-100A. A new RTCA/EUROCAE standard is being developed to specify how data link services such as DLIC, ACL, ACM and AMC can be provided using FANS-1/A. The standard is currently at draft status, identified in draft form as PUB-40 [57].

DCL, D-ATIS and OCL operating over ACARS are specified in EUROCAE data link application specification documents (DLASDs).

SYS2. Complete Profile Specified

The LINK 2000+ baseline specification [15] appears to be the only complete data link system specification that addresses all of the known issues. It defines the CPDLC messages to be used (though some remain as "optional" for individual deployments), as well as the relevant subsets and combinations of standards.

FANS-1/A operating procedures are being harmonised of around the globe. The FANS Operations Manual (FOM), covers FANS operations in the North Pacific, Central Pacific, South Pacific, Indian Ocean, Bay of Bengal, and South Atlantic Regions.

SYS3. Validation

ACM, ACL, AMC and DLIC have been the subject of pre-operational trials and simulations (e.g. PETAL-II and EOLIA projects). A fast time simulation using the CAPAN computer model was conducted in support of a Cost Benefit Analysis for the LINK 2000+ Programme, with as a main objective an assessment of the benefits in terms of EATMN capacity increase, which could be expected with the introduction of data link services in Europe. The LINK 2000+ data link services are currently in operational use at Maastricht UAC.

FANS-1/A applications are in operational use in oceanic and remote airspace areas around the world.

DCL and D-ATIS are in operational use at several major European airports. Oceanic clearances via data link are used operationally for North Atlantic air traffic.






SYS4. Stakeholder Support

The VDL 2 network is being rolled out by ACSPs and ANSPs, and is supported by aircraft operators for AOC use (ACARS over AVLC). Avionics vendors and ATM system suppliers are implementing products that conform to the LINK 2000+ baseline. Stakeholders supporting the LINK 2000+ programme include ANSPs, aircraft operators and ACSPs.

The FANS-1/A system enjoys wide stakeholder support globally, though not in high-density continental airspace. The ACARS system has very wide support by ACSPs and airlines.

The applications are supported at several airports and oceanic centres. The ACARS system has very wide support by ACSPs and airlines.

SYS5. Operational Approval / Experience

The LINK 2000+ programme is working with approval authorities to ensure that the data link systems achieve appropriate levels of approval and certification (see Annex L).

SYS6. Interoperability Must be Demonstrable

The LINK 2000+ test facility at the EUROCONTROL Experimental Centre provides a platform for testing interoperability of implementations prior to operational use.

SYS7. Business Case

A number of business case analyses have been carried out on the package of data link services in the LINK 2000+ baseline. A thorough economic analysis, conducted by the CNS/ATM Focused Team (C/AFT) demonstrated the costs and benefits of equipping with VDL-2 for AOC and ATC operations in European airspace. Details can be found on the programme website1

SYS8. Extensibility

The set of data link services specified by the LINK 2000+ programme includes a minimum core set of CPDLC messages, which must be fully implemented, and a wider range of messages that must be correctly handled by a receiving system, but need not be operationally supported.

FANS-CPDLC already includes support for all message elements, and a level of integration with other airborne systems.

1 http://www.eurocontrol.int/link2000/public/standard_page/specific_docs.html







The LINK 2000+ data link services are part of the "CASE-3" concept of operations [26] and are consistent with the EUROCONTROL Concept of Operations (Year 2011) [9], as described in Annex B.

Consistent with the ICAO FANS concept.

SYS10. SPR Satisfied

The ED-120 SPR for the data link services retained by LINK 2000+ have been analysed, and a Pre-Implementation Safety Case [16] has been produced. Individual deployments will have to produce their own safety cases; this has been achieved for Maastricht UAC.

SYS11. Impartiality

The VDL-2 technology adopted by LINK 2000+ is supported by multiple ACSPs and equipment manufacturers. ATN routers and avionics are available from different vendors. All suitably equipped aircraft will be provided with the option of data link service.

ACARS services POA and AOA) are available from more than one ACSP.

ACARS services POA and AOA) are available from more than one ACSP.

F.6 Conclusions For the busy en-route continental airspace under consideration, only the data link services implemented over ATN and VDL-2 as profiled by the LINK 2000+ baseline specification [15] appear to have reached a suitable degree of maturity for inclusion in the scope of the regulatory provisions.

The data link services selected for initial regulatory coverage are therefore:

• Service based on Context Management (CM) application:

o Data Link Initiation Capability (DLIC)

• Services based on protected mode controller-pilot data link communication (PM-CPDLC):

o ATC Communication Management (ACM)

o ATC Clearances (ACL)

o ATC Microphone Check (AMC)

Based on stakeholder feedback from an initial questionnaire, other communications systems in use at European airports (DCL and D-ATIS provided over ACARS) should continue to be supported, but are not proposed as subjects for prescription.

The services provided by ACSPs (based on VDL-2) in the data link airspace and the services provided by ground-ground communication service providers should be a subject for prescription in the implementing rule.




The nature of prescriptions should address the applicable following items:

• Geographic coverage consistent with the data link airspace

• Basic functions of the communication protocols

• Basic Quality of Service and performance of the communication medium

• Interoperability with communication exchange mechanisms used by data link applications

• Statements of security policy.

To ensure technical interoperability, a detailed profile specification is necessary. Such a document could be specified as a means of compliance with the regulatory provisions.

Many aircraft are equipped for data link operations over oceanic / remote airspace using FANS-1/A (or equivalent) systems. Extensive use is made of these services in the Pacific region, for example. The impact of these aircraft in the continental data link airspace must be considered.




ANNEX F. ATS DATA LINK COMMUNICATION SYSTEM .................................. F-1 F.1 Introduction ........................................................................................................ F-1 F.2 System Requirements........................................................................................ F-1 F.3 Global Interoperability ........................................................................................ F-2

F.3.1 FANS-1/A ATS Data Link Services in Continental Airspace .................... F-2 F.3.2 Convergence of Data Link Systems......................................................... F-2

F.4 Data Link Services Regulatory Coverage.......................................................... F-3 F.5 Selection of Data Link Systems ......................................................................... F-4

F.5.1 Introduction .............................................................................................. F-4 F.5.2 Selection Criteria...................................................................................... F-4 F.5.3 Application of Criteria to Data Link Systems ............................................ F-8

F.6 Conclusions ..................................................................................................... F-10




APPENDIX 1 TO ANNEX F. ATS DATA LINK SYSTEMS DESCRIPTION

F1.1 Introduction This Appendix provides an overview of candidate end-to-end communication systems that may be considered capable of providing point-to-point communication services in support of the identified data link services. It analyses the candidate systems in terms of their functional architecture, and identifies the issues that may arise if the systems were included in the regulatory coverage of the data link services implementing rule.

F1.2 Functional Architecture of DL Systems

F1.2.1 Overview A generic functional architecture of an end-to-end communications system supporting ATS data link services is presented. This allows the candidate systems to be compared systematically.


ANSP A-GData Link

Mgmt

“A”“B”


Interface toCommunications

ServicesHMI


Flight Crew


HMI

End System(ATS Unit)

Controller


End-to-endDialogue

“C”

ACSP Domain

G-GANSP

Interface

One or more interconnected ACSP networks

Figure F1-1. Data Link System Architecture

Figure F1-1 illustrates the overall system architecture assumed for the provision of point-to-point data link services. This organises the system into three principal domains: the ANSP domain, the Aeronautical Communications Service Provider (ACSP) domain and the Aircraft domain.

The functional architecture must be designed to encapsulate all the communications system elements that ensure end-to-end interoperability. To ensure this, interoperability principles must separately apply to each of the following elements:

• The air-ground communications service

• Communication between ATS Units and the ACSP.

• Avionics

• ATS Unit systems (e.g. the Flight Data Processor).

Ann F App 1 Comm Systems Descriptions 1.1.doc 24/05/2006 Page F1-1



• End-to-end transactions and message exchanges in support of each selected data link service.

In this functional model, the ANSP domain comprises:

• The ground ATS data link service user, typically part of the Flight Data Processing System (FDPS).

• A communications end system, which could be part of the FDPS or an auxiliary front-end processor.

• An interface to the ACSP. This component is responsible for managing the ground-ground communications; it could include security mechanisms (such as a firewall), designed to protect the ANSP from external data communication threats.

The air traffic controller accesses the ground user component via a suitable HMI, according to the procedures specified for the ATS Unit.

The ACSP domain comprises:

• The ground system supporting the air-ground communications network,

• An interface to each supported ANSP

• Systems that manage the air-ground communications service.

The aircraft domain comprises:

• The airborne ATS data link service user,

• A communications end system,

• An interface to the air-ground communications network.

The aircraft data link functions could be combined in a single physical system or distributed over several physical systems as a result of greater integration with the Flight Management System and the aircrew interface. The aircrew access the air user component via a suitable HMI, according to the procedures specified by the aircraft operator.

F1.2.2 Interfaces There are two exposed interfaces in the system architecture, shown as reference points ‘A’ and ‘B’ in Figure F1-1:

• ANSP to ACSP Interface The interface at reference point ‘A’ is between the ANSP and the ACSP. It uses a suitable ground-ground data link, as discussed in Annex E.

• Avionics to ACSP Interface The interface at reference point ‘B’ is between the avionics and the ACSP.

In principle, any air-ground data link that is compatible with the safety and performance requirements allocated to the avionics and ACSP could be used for air-ground communications, as discussed in Annex D. In order to ensure interoperability, the choice for avionics must be constrained to those data links available in the airspace(s) where access to ATS data link services is required.

The actual interoperability requirements for these interfaces depend on the data link system chosen.

For the interoperability of supporting communication systems in the EATMN, the following conditions must be satisfied:




• The airborne data link applications must access communication services based on interoperable communication mechanisms handling message exchanges with ground systems based on validated international standards.

• The ground data link applications must access communication services based on interoperable communication mechanisms handling message exchanges with airborne systems based on validated international standards.

• Indicators of the quality of service of communication services must be made available to pilots and controllers.

F1.2.3 End to End Communications The end-to-end exchange of information between the aircraft end system and the ATS Unit end system is indicated as reference point 'C' in Figure F1-1, and is independent of the interfaces described above.

The actual interoperability requirements for this interface depend on the data link system chosen.

F1.2.4 Human Interfaces The pilot interface to the data link system must be efficient and easy to operate. Pilot-controller messages require a rapid entry mechanism, which is easy to operate in the in-flight cockpit environment (i.e. taking account of noise and vibration and other ergonomic issues). Procedures and systems are designed to minimise system input and reading errors.

The controller interface contains the required tools for the composition and display of air-ground data link messages. ANSPs are responsible for defining and developing specific controller interfaces tailored to their particular needs. The controller interface should be efficient, easy to operate and provide a rapid message input mechanism (e.g. pull-down menu accessed from the flight label on the main traffic display).

Following the ORD [10], the HMI should be tailored to each individual data link service supported, rather than be a general interface to the underlying ATS Application. Specific requirements/guidelines for HMI design may be found in the ORD, sections 3.3.1, 3.3.2 and 3.3.3.

F1.2.5 End Systems The function of the ground and airborne end systems is to host the ATS Application and provide it with access to end-to-end communications. The ATS Application implementation must be compliant with the applicable standards if end-to-end interoperability is to be maintained. However, the means of access to end-to-end communications is a local issue, as this only covers the interface to the system responsible for managing the interface to the communications services.

F1.2.6 ACSP The ACSP is the operator of the air-ground communications service used to support ATS data link communications between aircraft and ANSPs. It operates its own ground-ground communications infrastructure and one or more air-ground data links. It also operates systems to interface with each ANSP and to manage use of air-ground data links.

F1.2.7 Air-Ground Data Link Management The role of this component is to manage the use of the air-ground data link in support of ATS communications. It also provides a gateway between the local communications infrastructure of the ACSP and the air-ground data link, and has an important security role




acting as a firewall between the ACSP’s communications infrastructure and the air-ground data link.

This component’s functions depend on the local communications infrastructure, the air-ground data link used, and the end-to-end data link system the ACSP supports. Only those aspects of the component’s functions that relate to the end-to-end data link system and the air-ground data link will have interoperability requirements associated with them that are within the scope of the implementing rule.

To ensure the interoperability of communication exchange mechanisms between data link applications, the following conditions must be satisfied:

• The air-ground mobile subnetwork must be interconnected and interoperable with ground – ground subnetworks used by ground systems hosting data link applications and ATM applications.

• The technology of the ground – ground subnetworks must not impose specific technical constraints upon the air-ground mobile subnetwork and vice versa.

• The management of communications between users of the air-ground mobile subnetwork and ground – ground subnetwork must be fair, transparent in compliance with the agreed service level agreement.

F1.3 Aeronautical Telecommunication Network (ATN)

F1.3.1 ATN Background The rationale for the Aeronautical Telecommunication Network (ATN) came originally from the ICAO FANS Committee, which foresaw a global network that would integrate various communications media, including the Aeronautical Mobile Satellite Service (AMSS), VHF data link (VDL), Secondary Surveillance Radar (SSR) Mode S data link, HF data link (HFDL) and private/public ground-ground networks. Based on the International Organisation for Standardisation (ISO) open systems interconnection (OSI) reference model, the ATN would span organisational and international boundaries resulting in a common aeronautical data transfer service.

The ATN was designed as an internet, or a "network of networks" and was developed to enable performance targets developed by the ICAO ADS Panel (which evolved into the OPLINK Panel) to be satisfied, provided that a suitable infrastructure was implemented. The high availability, reliability and continuity of service targets are achieved partly through network design, enabled by the internetwork approach.

The "ATS Class" of an application specifies transit delay requirements. The transit delay and latency requirements place demands on air-ground communications technology and ultimately determine the suitability of a given class of data link for a particular ATS Application.

The ATN internet communications service (ICS) is able to select between alternative air-ground networks using the ATSC Class requirement given by the application. This way it is possible to have multiple air-ground networks in use, with different Quality of Service characteristics, and to select the most appropriate of the available networks for the data communications of each application.

The need for open industry standard communications was a key feature of the original intent behind the ICAO ATN. Earlier developments such as the AFTN, CIDIN and ACARS were specific to the aeronautical community and, as a result, expensive to develop and maintain. By using international standards, the intent was to avoid that problem.

The FANS Committee did not specifically require that the ATN should be based on an internet approach. The emphasis was more on the use of open standards. The internet




approach was a technical choice that resulted from an initial consideration of the requirements placed on the ATN.

F1.3.2 ATN Objectives ICAO has specified SARPs in Annex 10 [1] for air-ground data communications. The air-ground applications CPDLC, CM, ADS and FIS are specified to operate over the ATN communications service.

When the ATN internet was first specified, the requirements for ATS Applications such as CPDLC had yet to be formulated. Instead, the ATN was developed to meet a set of objectives, independent of any specific application requirements. These objectives may be summarised as:

• Use of Existing Infrastructure The ATN was to be an internetwork built using existing networks through the use of routers as gateways between those networks. In this way, investment in existing LANs, leased lines, CIDIN and X.25 networks is preserved. The ATN would also enable full use of emerging network technologies such as Frame Relay and Asynchronous Transfer Mode (ATM).

• High Availability The ATN was designed to provide a high availability network by ensuring that there is no single point of failure, and by permitting the availability of multiple alternative routes to the same destination with dynamic switching between alternatives. The same techniques would apply to both fixed and mobile communications giving mobile communications an availability level that would have been unrealistic for older technologies based on directory lookups (e.g. ACARS).

• Mobile Communications The ATN was designed to fully support mobile communications over a wide variety of mobile communications networks including AMSS, VDL and SSR Mode S. With the ATN, it would be possible for a ground system to communicate with airborne avionics in any part of the world.

• Prioritised End-to-End Resource Management All ATN user data would be given a relative priority on the network in order to ensure that low priority data does not impede the flow of high priority data. Advanced congestion management techniques would ensure that high priority data always gets a low transit delay.

• Scaleability The ATN was designed to provide both a large address space and an approach to routing that would ensure the scaleability of the network well beyond currently foreseen requirements.

• Policy Based Routing The ATN’s routing procedures were designed to support a wide range of Organisational and National policies, including the enforcing of restrictions on what types of traffic can pass over both ground and air-ground data links, and control over which air-ground data link types are used by which applications. Administrations and Organisations that interconnect the networks would be free to enforce routing policies that control which types of data are exchanged and whose data is routed through their networks, and whose data is not.




• Future Proofing The ATN was designed to use networking technologies in a way that could be readily extended to include new ground and air-ground data links technologies, with local rather than global impact resulting from the use of new networking technologies.

F1.3.3 ATN Standards The ATN is based on the ISO/IEC 8473 Connectionless Network Protocol (CLNP) for packet forwarding, and ISO/IEC 10747 Inter-Domain Routing Protocol (IDRP) for dynamic exchange of routing information, including mobility support, i.e. aircraft addressing. The ISO/IEC 8073 Class 4 Connection Oriented Transport Protocol (TP4) provides robust end-to-end communication.

Based on the operational requirements in PANS-ATM (ICAO Doc 4444) [23], ICAO technical Panels (ATNP, then ACP) developed the technical requirements necessary for interoperability between air and ground systems operating over the ATN Internet Communications Service (ICS). These technical provisions were published as the Manual of Technical Provisions for the Aeronautical Telecommunications Network, ICAO Doc 9705, Edition 1 (1998). ICAO Doc 9705, Edition 2 was issued in 1999, ICAO Doc 9705, Edition 3 was issued in 2002.

The set of air-ground data link applications currently specified in ICAO Doc 9705 [2], Sub-Volume II, sometimes called "CNS/ATM-1 Package" comprises:

• Context Management (CM)

• Controller-Pilot Data Link Communication (CPDLC and PM-CPDLC)

• Automatic Dependent Surveillance (Contract) (ADS-C)

• Flight Information Services (FIS), including ATIS and METAR.

The detailed technical interoperability requirements in ICAO Doc 9705 are invoked by the high level ATN SARPs in ICAO Annex 10 [1].

EUROCAE ED-110A [3] specifies a set of data link services based on the ICAO ATS applications.

F1.3.4 System Architecture Figure F1-2 illustrates the overall system architecture as applied to the provision of data link services using the ICAO ATN. The differences compared with the generic architecture in F1.2 above are described below.




ATN G/G

Router

ACSP Network

ANSP

ACSP

ATN G/G

Router

ATN A/G

Router

AB


Airborne RouterHMI


Flight Crew


HMI

End System(ATSU)

Controller

Procedures(ATSU)

End-to-endDialog

Figure F1-2. ATN Data Link System Architecture

The ANSP domain comprises the ground ATS data link service user, an ATN end system and an ATN ground-ground router. The ground ATS data link service user is typically part of the FDPS, while the ATN end system is either part of the FDPS or an auxiliary front-end processor.

The ACSP domain comprises the ground system supporting the air-ground communications network, and air-ground and ground-ground ATN routers operated by the ACSP.

The aircraft domain comprises the airborne ATS data link service user and ATN end system, an ATN airborne router (as required by the ATN SARPs) and the airborne components of the air-ground communications network.

F1.3.5 ATN Interfaces

F1.3.5.1 Reference Point ‘B’ Interface The ATN reference point ‘B’ interface is between an ATN airborne router and an ATN air-ground router. These take on the roles of the airborne “interface to communications services” and “air-ground data link management” functions identified in the generic functional architecture for data link systems in F1.2 above.

In principle, any air-ground data link that is compatible with the safety and performance requirements allocated to the avionics and ACSP could be used for air-ground communications between the two routers. However, in order to ensure interoperability, the choice for avionics must be constrained to those data links available in the airspace(s) where access to ATS data link services is required. Likewise, to ensure wide area interoperability for aircraft, and without aircraft having to support many different data links, the choice for ACSPs is similarly constrained.

In order to ensure interoperability, the ATN internet protocol (CLNP) and the routing protocol (IDRP) exchanged over this interface must comply with ICAO technical provisions. In practice, additional profile requirements must also be specified (e.g. the LINK 2000+ baseline).




F1.3.5.2 Reference Point ‘A’ Interface The ATN reference point ‘A’ interface is between two ATN ground-ground routers operated by the ANSP and ACSP (or an ANSP in the ACSP role), respectively.

The ground-ground data link used to interconnect the two domains is a matter for local agreement and may be any suitable network that is compatible with the safety and performance requirements allocated to each domain.

In order to ensure interoperability, the ATN protocols (CLNP and IDRP) exchanged over this interface must comply with ICAO technical provisions. In practice, additional profile requirements must also be specified (e.g. the LINK 2000+ baseline).

F1.3.5.3 End-to-End There is an end-to-end exchange of information between the aircraft end system and the end system in the ATS Unit, which is independent of each of the above interfaces. This exchange encompasses the ATN transport protocol and dialogue service, and the data link application protocols (CM, CPDLC, etc).

In order to ensure interoperability, the ATN transport protocol and dialogue service, and the data link application must be compliant with ICAO technical provisions, specifically the protocols supporting the ATN Upper Layer Communications Service (ULCS) and the ATN Internet Communications Service (ICS) as standardised in ICAO Doc 9705 [2] Sub-Volume IV and Sub-Volume V, respectively.

Note: The ATN communication service offers both connectionless and connection-oriented modes; the ATN data link applications are designed to use only the ATN connection mode transport service.

The ATN applications assume that the probability of transport connection loss is low (i.e. that the ATN communication service provides both high availability and reliability) and hence do not consider specific recovery actions in the event of connection failure.

For ADS-C and D-FIS this is not a serious issue. Automated recovery from connection loss could be achieved by re-establishing the communications path and the contracts.

For CPDLC, the assumption has been that voice communications will still be available and loss of the data link service will be handled procedurally by a return to voice only communications.

The communication path between the air-ground ATN router and an ANSP's ground ATN router can be left as a local matter between the ANSP and the chosen ACSP.

F1.3.6 ATN Ground-Ground Networks The ATN Technical Provisions (ICAO Doc 9705) specify two ground-ground applications; the ATS Message Handling Service and the ATS Interfacility Data Communications (AIDC) application. Neither of these are intended or suited for the ground part of the end-to-end air-ground data link.

Instead, the ATN Technical Provisions assume that the air-ground router will convey data packets to the ANSP's ground end system via any number of ground routers (intermediate systems) using appropriate subnetworks.

Using the ATN as the communications mechanism ensures that any local communications / network provision can be incorporated as an ATN subnetwork, provided:

a) It meets the required quality of service

b) A suitable Subnetwork Dependent Convergence Function (SNDCF) is implemented.




The ATN internetwork can be built up using existing networks through the use of routers as gateways between those networks. Investment in existing LANs, leased lines, CIDIN and X.25 networks is preserved. Furthermore, the ATN could also make full use of emerging network technologies such as Frame Relay and Asynchronous Transfer Mode (ATM).

The use of alternative subnetworks is accommodated by means of an ATN SNDCF. For example, the Internet Protocol (IP) SNDCF allows ATN data packets to be carried over an IP-based network.

F1.3.7 Implementation in Europe The ATN technical provisions In ICAO Doc 9705 [2] include CM and CPDLC functions for the ground forwarding of downlinked information between ATS Units. In the LINK 2000+ implementation, these functions are not used. Instead, OLDI [37] messages are used for inter-centre coordination.

The LINK 2000+ programme requires that ACSPs providing ATN/VDL-2 communications services to compliant aircraft shall own and operate at least one ATN air-ground router1. It further requires that ACSPs and ANSPs shall own and operate ground-ground ATN routers, in order to support interoperations with each other. This is potentially an area for regulatory coverage.

Alternatively, an ACSP may offer ATN ground end system provision. Communication between this end system and the ANSP system may then be by bilateral proprietary means. This could obviate the need for ANSPs to invest in specialised ATN Routers, but would have consequences for the end-to-end quality of service. The implementing rule should not preclude such an arrangement.

ATN air-ground and ground-ground routers have local interfaces to ground networks, such as X.25 and Ethernet. These interfaces are outside the scope of the LINK 2000+ Baseline.

One of the ground-ground interconnectivity principles established by LINK 2000+ is that aircraft must be able to send data link messages to all adjacent ANSPs. This is a technical requirement necessary for interoperability. Overlapping VDL-2 coverage is required for the seamless transfer of communications as an aircraft moves from one ANSP to another. An aircraft must be able to communicate with the next ANSP on its route prior to entering that ANSP’s airspace. Transfer of communications occurs in a “make before break” fashion with an aircraft establishing communication with the next ANSP before relinquishing the communication link with the current ANSP.

Therefore ANSPs must be interconnected not just with the ACSPs providing coverage of their airspace, but also with ACSPs covering adjacent airspaces. The airborne ATN router must be informed of the data path to ground ATN routers corresponding to adjacent ANSPs. In technical terms, communication routes advertised to airborne ATN routers (using IDRP) shall include routes to all adjacent ANSPs. This is a configuration requirement for ACSP routers.

This would not be a problem for an ACSP with a wide coverage of European airspace. However, if an ANSP provides air-ground communications in its region of responsibility, then this becomes an important principle necessary for interoperability.

1 ATN air-ground and ground routers, or Intermediate Systems (IS), are specified in ICAO Doc 9705 [2], Sub-Volume V.




F1.4 ARINC 623 ATS Applications

F1.4.1 Background In practice today, most air-ground data communication is achieved using the commercially provided Aircraft Communication Addressing and Reporting System (ACARS). ACARS is a character-based protocol, using the upper-case alphanumeric character set. Binary exchanges are enabled by conversion of the interchanged data into character format according to the provisions of AEEC Specification 619.

Although ACARS was designed to support Aeronautical Operational Communications (AOC), aircraft operators (primarily but not exclusively airlines) have worked with ANSPs to expand the ACARS message set to include a number of ATS data link services:

• Departure clearance (DCL),

• Digital ATIS (D-ATIS), and

• Oceanic clearances (OCL).

These messages are defined in a combination of AEEC and EUROCAE documents.

No special support is required on board an aircraft except for ACARS itself, although the ACARS management unit support functions may be sold as a separate package.

Apart from the fact that the messages are exchanged with an ATC Centre rather than an airline, there is little to distinguish ARINC 623 applications from any other use of ACARS.

F1.4.2 Standards ACARS is specified in a number of AEEC Specifications in the ARINC 600 series.

ARINC 623 defines a set of messages that are exchanged using ACARS for ATS purposes.

DCL, D-ATIS, and OCL services are specified in EUROCAE Data Link Application System Documents (DLASD) ED-85A, ED-89A and ED-106A, respectively.

F1.4.3 System Architecture The architecture for the implementation of the ARINC 623 based data link services is illustrated in Figure F1-3. The differences compared with the generic architecture in Figure F1-1 are described below.




ACARSInterface

ACSP Network

ANSP

ACSP

ANSPInterface

ACARSDSP

AB


ACARS MUMCDU

Flight Crew


HMI

End System(ATSU)

Controller

Procedures(ATSU)

End-to-endDialog

Figure F1-3 ARINC 623 ATS Applications Architecture

The avionics configuration requires an ACARS Management Unit (MU) and a Multi-function Control and Display Unit (MCDU). This is the same hardware as required for AIS ACARS use. The only enhancement usually required is software support for the additional messages.

The ACARS air-ground communications service as used for AIS Applications is also used for these applications. It is usually provided by a commercial service provider, such as ARINC or SITA.

An ACARS data link service provider (DSP) must be operated by each ACARS ACSP. This fulfils the role of the “air-ground data link management” functions identified in the generic functional architecture for data link systems.

ANSP End Systems may be at an ATC Centre or an Airport. The latter is more usual for Pre-departure Clearances.

F1.4.4 Interfaces

F1.4.4.1 Reference Point ‘A’ Interface The Reference Point ‘A’ Interface is bilaterally agreed between the ANSP and the ACSP. Message exchange using an X.25 data link is still common. However, an IP based interface, defined in RFC 2351 “Mapping of Airline Reservation, Ticketing, and Messaging Traffic over IP” is also being used.

The messages passed over this interface must be compliant with ARINC 620 and ARINC 623, and the EUROCAE Documents referenced above.

ACARS services are traditionally provided on a contract basis between individual aircraft operators and commercial communication service provider (CSP) organisations.

EUROCONTROL guidelines for implementation support (EGIS) include a model Service Level Agreement (SLA) related to the provision of ACARS-based ATS data link services (DCL, D-ATIS) [30].




All the requirements contained in the EUROCAE DLASDs and addressing the communication domain are reproduced in the model SLA with some clarifications and slight rewording in order to make the requirement suitable for both DCL and ATIS.

F1.4.4.2 Reference Point ‘B’ Interface The air-ground interface must be compliant with the requirements specified by ARINC 618 and the ACSP, and is subject to their approval. There are four different data links in use for ACARS message exchange:

a) “Plain Old ACARS” (POA)

POA uses the same VHF channel structure and frequencies as used for analogue ATC voice communications. Typically, each service provider uses a single shared frequency over a wide geographical area with a data rate of 2.4 kbit/s. Occasionally, multiple frequencies are available to an ACARS ACSP. POA is slow and inefficient and is being replaced by:

b) ACARS over AVLC (AOA)

AOA is a procedure for the implementation of ACARS using the VDL-2 air-ground data link. VDL-2 is similar to POA in that it uses the same VHF channels and frequencies but has a much higher data rate (32 kbit/s) and offers much improved uplink transfer times. AOA is also compatible with simultaneous of VDL-2 by the ATN applications.

c) Satellite Based ACARS

In oceanic and some low-density airspace, the Inmarsat Data-2 service is used to support ACARS communications. Satellite based ACARS is seen as an expensive solution by airlines and is only used where VHF solutions are not available.

d) HF Data Link

In oceanic and some low-density airspace, the ARINC HFDL link service is also used to support ACARS communications. HFDL is slower than satellite based ACARS but is cheaper and gives better coverage of polar regions.

F1.4.4.3 End-to-End There is an end-to-end exchange of information between the aircraft end system and the end system in the ATS Unit, which is independent of each of the above interfaces. This exchange encompasses the exchange of messages specified in ARINC 623 and the EUROCAE standards referenced above.

In order to ensure interoperability, both End Systems must be compliant with these provisions.




F1.5 FANS-1/A

F1.5.1 Background Based on the ICAO Future Air Navigation System (FANS) concept, a group of ANSPs, airlines, airframe manufacturers, and avionics vendors defined a set of functionality called FANS-1/A. This specification set defines the carriage of CPDLC and ADS messages over the ACARS network.

Today, ATS data link communication in airspace over most of the oceanic and remote parts of the earth is provided using FANS-1/A and equivalent implementations, and more than 1,000 aircraft use the service.

FANS-1 is a Boeing-developed package with ADS and CPDLC communications via Satcom. The certification for the Boeing 747 and 777 was completed in 1995. It is now in widespread use in Boeing wide-bodied airliners, such as the 747-400 and 777.

FANS-A is the Airbus package providing ADS and CPDLC via Satcom or VHF. Certification was completed in 1997. It is in use on the A-340 and A-350 and will be standard equipment on the A-380.

The two products are collectively known as FANS-1/A.

FANS-1/A is an implementation of early draft ATN CPDLC and ADS-C functionality being developed in ICAO operational panels. Consequently, CPDLC and ADS message sets and functions of the FANS-1/A package are not identical to their ATN equivalents.

F1.5.2 ATS Data Link Services in FANS-1/A The specification of FANS-1/A does not include the concept of data link services. For example, instead of being divided into subsets to support data link services such as ACL or ACM, the full set of CPDLC messages is available for use by the controller and pilot systems.

This means that users of FANS-1/A and equivalent systems in applicable airspaces are accustomed to a wide range of functionality that is not always present in the tightly specified data link services.

The Boeing FANS-1 and Airbus FANS-A packages (FANS-1/A) are products that are early implementations of the ICAO ADS-C and CPDLC ATS Applications. These products provide access to all ATS application functions (e.g. all CPDLC message types).

The stringent operational safety and performance requirements applicable to high-density airspace areas will generally require the development of an approved safety case for each use of data link based ATC.

The FANS-1/A method of operations can be included in this model by defining data link services that make all of a given ATS application's functions available to the user. However, in high-density airspace, the safety case for such a data link service becomes very complex due to the large number of possible combinations of air-ground exchanges.

The data link service approach also fits within the ATM process model much better than direct use of the CNS/ATM applications, since each data link service can be positioned as supporting all or part of a given ATM Component.

F1.5.3 Standards FANS-1/A is specified by two related standards:

• ARINC 622 [52] specifies how bit-oriented FANS applications can operate over the character-oriented ACARS service.




• EUROCAE ED-100A, which specifies INTEROP requirements for ADS and CPDLC for FANS-1/A, replacing the earlier RTCA documents.

ED-100A includes enhancements related to message latency. Compliant implementations are becoming available, but retrofit is optional.

A further RTCA/EUROCAE standard (identified in draft form as PUB-40 [57]) will specify how data link services such as DLIC, ACL, ACM and AMC can be provided using FANS-1/A and equivalent systems.

F1.5.4 System Architecture The System Architecture for the ED-100A FANS-1/A System is shown in Figure F1-4. The airborne component illustrates the Boeing 747-400 implementation. Different approaches are used for the B-777 and Airbus implementations, with a different functional distribution.

ACARSInterface

ACSP Network

ANSP

ACSP

ANSPInterface

ACARSDSP

AB


ACARS MUMCDU

Flight Crew


HMI

End System(ATSU)

Controller

Procedures(ATSU)

End-to-endDialog

FMS

Figure F1-4 FANS-1 System Architecture (Boeing)

FANS-1 messages are identified in the ACARS air-ground protocol by means of specific "message labels." In the B747-400 implementation, such messages are passed to the Flight Management System (FMS). These messages are processed according to ARINC 622, which may mean decoding from text to binary format. They are then identified and processed as either ADS or CPDLC messages according to ED-100A.

CPDLC messages will normally be displayed to the pilot via the MCDU. Pilot responses are also processed via the MCDU and FMS.

FANS-1/A messages are transferred to and from the ANSP is the same way that ARINC 623 ATS messages are transferred, using one of the ACARS service providers.

When received by the ANSP, a FANS-1/A message is recognised as such by its message label, processed according to ARINC 622 and then processed as an ADS or CPDLC message.




F1.5.5 Interfaces

F1.5.5.1 Reference Point ‘A’ Interface Same as for ARINC 623 ATS Applications (see F1.4.4.1 above).

F1.5.5.2 Reference Point ‘B’ Interface Same as for ARINC 623 ATS Applications (see F1.4.4.2 above).

F1.5.5.3 End to end End-to-end FANS-1/A communications must be compliant with ARINC 622 and ED-100A.

F1.5.6 Assessment of FANS-1/A When considering the FANS-1/A system (and equivalent implementations) as a potential means of delivering data link services in continental European airspace, two questions arise:

1. Can FANS-1/A be considered as a means of delivering data link services in the European airspace that is the subject of the interoperability implementing rule?

2. If not, then can FANS-1/A equipped aircraft be accommodated within the scope of the implementing rule? That is, while not strictly compliant with the rule, can ED-100A FANS-1/A aircraft access and make use of data link services.

Similar questions to these were considered in 2002 by an Industry Rapid Reaction Force (IRRF). The IRRF report2 resulted in updated versions of the FANS-1 and FANS-A packages, which were included in EUROCAE ED-100A.

The findings of the IRRF report have been put into practice as part of the FANS-1/A accommodation strategy at the EUROCONTROL Maastricht UAC, which has implemented an ATN-based operational data link service.

However, the work of the IRRF pre-dated the publication of the EUROCAE ED-120 safety and performance requirements standard [4], and therefore does not fully take into account these SPR requirements.

F1.5.6.1 The IRRF Report The purpose of this report was threefold:

1. To provide a list of the issues which could prevent accommodation of FANS-1/A aircraft in initial ATN continental airspace, and a set of potential resolutions to those issues for formal validation by LINK 2000+ safety and operational groups.

2. To provide an indication of the percentage of aircraft movements that represent, or could represent, FANS-1/A aircraft within various European ATS facilities. This indication was intended to provide additional and earlier investment incentives for candidate LINK 2000+ ATS facilities considering data link services implementation.

3. To provide an initial examination of the potential ways to converge the divergent oceanic and congested continental data link systems, procedures, and operations.

The report assumed the implementation of a conceptual “communications gateway” that would permit FANS-1/A compatible aircraft to communicate with an ATN compliant ATC Centre. With this assumption:

2 IRRF Report to LINK 2000+, Version 8 (May 2002)




• None of the 17 issues retained prevented use of FANS-1/A for CPDLC services that would not affect the aircraft flight profile (e.g. transfer of communications and squawk instructions).

• One of the 17 issues retained was identified as preventing the safe use of FANS-1/A for CPDLC services that could affect the aircraft flight profile.

F1.5.6.2 Use of FANS-1/A for Profile Changing CPDLC Services This issue identified by the IRRF was concerned with the “un-notified delivery of out-of-date messages”. When a clearance is released by a controller, the clearance is given a timestamp accurate to within 1 second. A response to the clearance must be received within a specified period (currently 120 seconds) otherwise the clearance ceases to be valid and must not be executed. This is an unambiguous safety requirement and failure to meet this requirement could result in loss of aircraft separation.

However, the FANS-1/A package did not display the release time of the clearance or give any other indication to the pilot when a clearance had expired. This issue rendered the FANS-1/A package unsuitable for use in continental airspace, without some means of mitigating this problem.

In order to overcome the problem, the IRRF proposed:

a) A short-term mitigation strategy based on pilot voice read-back to the controller of a data link clearance before it could be executed.

b) A longer-term solution, consisting of an updated avionics package to include resolution of this issue. ED-100A compliant systems include provisions to resolve this issue without resorting to voice read-back.

F1.5.6.3 Other IRRF Issues The issues identified by the IRRF varied in importance. They are listed in Table F1-1. The relevant subset of these issues may need to be addressed in the implementing rule, if ED-100A FANS-1/A is to be considered as a means of delivering data link services in the European airspace. In that case, the conceptual “communications gateway” assumed in the IRRF report for ATN-FANS-1/A interworking may require further specification.

Table F1-1. FANS-1/A Accommodation Issues (IRRF)

IRRF No.

Name Description

1 No Message Order Assurance

This is no longer seen as an issue. In both FANS-1/A and ATN/CPDLC, the means to ensure that dependent clearances are executed in the order intended by a controller, are procedural, and do not depend upon features of the communications service.

The relevant procedures may be a subject for prescription in the implementing rule.

4 No end-end delivery assurance (uplink CPDLC only)

FANS-1/A does include the logical acknowledgement (LACK) message used to provide an end-to-end technical acknowledgement. This is of limited value operationally but is very useful for monitoring performance of the system and giving forward information on future failures or capacity problems.




IRRF No.

Name Description

5 Message Delivery Times (performance)

This issue is primarily due to the use of POA as the data transport mechanism. It is avoided by the use of AOA by FANS-1/A equipped aircraft that are upgraded to use VDL-2.

6 Routing (delivery to the correct aircraft)

When the report was prepared, the IRRF concentrated on the gateway functions needed to ensure correct routing to FANS-1/A equipped aircraft. However, ED-120 [4] associates a “Hazard Class 3” with undetected mis-delivery of a clearance to the wrong aircraft. The safety requirement is that the probability of this happening is "Remote". There is on-going analysis by industry of whether ED-100A FANS-1/A meets the ED-120 requirements in this area.

7 No notification of CPDLC “enabled” status (dm99)

Downlink message dm99 is not part of the FANS-1/A CPDLC message set. It is used by the ACM service for an aircraft to notify an ATS Unit when it is now the Current Data Authority. This is an important event as, prior to the completion of the transfer and hence the ATS Unit becoming the Current Data Authority, any message received from the ATS Unit will be rejected as an error. The IRRF recommended that this message be generated in a communications gateway on behalf of the aircraft as soon as a CPDLC connection is established with the aircraft. This can result in confusion should a message be uplinked too early. However, this is unlikely as long as a CPDLC connection is not attempted until after voice contact has been made.

8 Duplicate fixname / navaid identification in aircraft

Some airborne systems treat non-directional beacons (NDB) as fixnames, while ground systems treat them as navaids. When there is an NDB that has the same ident as navaid, this issue can lead to a position being loaded into the FMC that is not the intended position.

9 FLIPCY waypoints ADS-C issue: out of scope for this analysis.

10 ATN <> FANS-1/A transfers

There is a lack of agreed standards for transfers between FANS-1/A and ATN ground systems. However, this is not seen as a technical issue, rather it is an issue where work needs to be done to ensure common procedures.

11 Message differences (ATN Messages not in FANS-1/A and FANS-1/A Messages not in ATN Baseline 1)

FANS-1/A defines a smaller message set than that defined for ICAO CPDLC. On the other hand, not all ICAO CPDLC messages are required for compliance to ED-110A. In the current context, this issue is concerned with CPDLC message elements that are used for ED-110A services but which are not part of the FANS-1/A message set. The IRRF report recommends that either such message elements are not used, or gateways translate them into free text messages.

12 Un-notified delivery of "old" messages

Serious issue resolved in ED-100A. See section F1.5.6.2 above.

16 ADS demand connection termination delayed for 16 minutes

ADS-C issue: out of scope for this analysis.




IRRF No.

Name Description

21 No rearming of ADS event contracts


22 Provision of only Mach in FANS-1/A ADS


30 No error + free text capability in FANS-1/A

Unlike ATN/CPDLC, it is not possible with FANS-1/A to include a free text explanation with an Error message. The IRRF report recommends that a communications gateway removes any such free text from Error messages when such messages pass from the ATN Domain to the FANS-1/A Domain. In practice, this only affects uplinks. The consequence is that if errors occur, pilots may lack explanation and hence may need to use voice communications in order to overcome the problem.

33 Cannot use facility designator and facility name in uplinks (e.g. transfer of comm)

This is a minor incompatibility resolved by a gateway removing the facility designator from an uplink.

35 Duplicate messages (downlink direction)

The use of ACARS results in the probability that messages may be duplicated by the communication system, and that both ground and air users must be able to detect and ignore duplicates. However, the ICAO ATN uses a connection mode transport service that avoids the risk of duplicates being received and hence ATN users do not necessarily make such a check. The IRRF report recommends that a communications gateway detects and discards downlink duplicate messages.

38 Lack of full timestamp in ADS (need date & hhmm)


F1.5.6.4 The Voice Read-back Issue The IRRF report recommended the use of voice read-back of clearances by a pilot to a controller, as a means of mitigating the hazard associated with out-of-date messages. (Maastricht UAC currently uses this strategy). It is also used for LINK 2000+ Pioneer aircraft that do not yet implement Protected Mode CPDLC (PM-CPDLC) and are only certified to DO-178B Level D).

Within the LINK 2000+ Programme, it is planned that ATN/CPDLC aircraft will be upgraded to use PM-CPDLC certified to DO-178B Level C. The requirement for voice read-back will then no longer apply to these aircraft.

However, it is highly undesirable that controllers should be required to perform voice read-back with some aircraft and not others. It is, therefore, possible that data link service in the continental LINK 2000+ area may be withdrawn from FANS-1/A equipped aircraft at this point.

Voice read-back is used with ED-100 FANS-1/A aircraft in order to mitigate two hazards: one concerned with out-of-date clearances, and the other concerned with the potential mis-delivery of messages by the communications system.

For ED-100A FANS-1/A equipped aircraft, the first of these hazards is removed, but the latter still remains to be analysed in detail. While this remains the case, the only justification for not requiring the voice read-back mitigation strategy for FANS aircraft is




statistical. If there is only a “small” number of FANS-1/A aircraft in the airspace, the probability of the hazard occurring would be correspondingly small. Such a justification is airspace and ATS Unit specific.

Such a decision is further complicated since it is not possible for a ground system to determine dynamically whether a given aircraft is ED-100 or ED-100A compliant, and hence which hazards apply.

In practice, the continued provision of data link service to FANS equipped aircraft will have to be considered on a case-by-case basis for each ATS Unit and each airline. The need to consider each airline separately is due to the expected need to know whether or not their avionics systems comply with ED-100A FANS-1/A.

F1.6 IP Communications The EATM Communications Strategy [28] observes that:

“The evolution of new technology and the use of Commercial Off-the Shelf (COTS) technical solutions may bring opportunities to reduce costs, or increase performance and reliability, or both. Alignment with industry development trends and adoption of commercially successful products and standards will reduce development costs.”

This emphasises the importance of choosing a communications system that has wide stakeholder support and which is already deployed.

F1.6.1 IP for Mobile Air-Ground Communication The use of the Internet Protocol Suite (IPS) is now all-pervasive in the communications and networking world. It might, therefore, be foreseen that the relevant IP based protocols will eventually replace the equivalent ATN and ACARS protocols used for data packet forwarding and mobility support.

The Airlines Electronics Engineering Committee (AEEC) has developed a discussion document on the use of the IPS for air and ground data communications. The information is documented in ARINC Specification 664, Part 8. The air-ground material has not been operationally validated, and there are known to be some technical issues in providing an IP-based air-ground communications service.

Several broadband companies have launched broadband aeronautical Internet connection service that uses the IPS. These services allow aircraft passengers to access the Internet, corporate intranet, or email services. None of them have targeted ATS service provision due the higher safety and security requirements of this small market.

The use of IP over air-ground subnetworks is currently under investigation in ICAO. A number of issues remain to be solved (e.g. adequate mobility support and security) before SARPs or guidance material are produced. The air-ground use of IP is therefore not applicable within the timescale of the implementing rule, but could be considered as part of a future protocol specification.

F1.6.2 IP for Fixed Ground-Ground Communication Meanwhile, ATN implementations can make use of an IP ground network, by means of the IP SNDCF, which is standardised in ICAO Doc 9705.

The air-ground CNS/ATM applications specified in ICAO Annex 10 and Doc 9705 (CPDLC, CM, ADS-C, FIS) are specified to operate over the ATN TP4 transport layer. The communications path has a ground-ground component in support of air-ground data link applications. Some applications also have a ground-ground forwarding component.




For these data link applications, the ATN Internet Communication Service (ICS) can be used, as specified in Doc 9705, using the IP SNDCF to operate over an IP ground subnetwork as specified in the standard. This is illustrated in Figure F1-5.

CPDLC

ATN Router

ATN A/G Router

VDL-2

IP SNDCF

ATN Router

IP SNDCF

CPDLC FDPS

IP GroundNetwork

Front-end Processor

ATN end-to-end

Figure F1-5. Use of IP SNDCF with Ground IP Network

The preferred ground-ground technology is an IP-based network that is planned to evolve to become part of the emerging Pan-European Network Service (PENS), using the IP SNDCF standardised in ICAO Doc 9705 (added by PDR M5020001 to Editions 2 and 3).

F1.7 Civil-Military Interoperability Military data links are currently non-interoperable with ATN and ACARS technology.

It could be envisaged that State aircraft flying as IFR/GAT in airspace covered by the data link services implementing rule would be required to carry the same ATN/VDL-2 communication capability as civil aircraft. However, this is still a subject for discussion.

For the medium term, ground coordination must be considered as the only option for civil/military interoperability.

For the longer term, a global data link approach incorporating civil and military requirements and supported by common technology should be envisaged and encouraged.

Note that in the voice environment, State aircraft are commonly equipped with UHF radios. When operating in 8.33 kHz voice channel spacing airspace, such aircraft may have to be accommodated using UHF radio.

F1.8 Conclusions The only candidate systems in existence that may be considered capable of providing point-to-point communication services in support of the selected data link services in the short term are identified as:

a) ICAO ATN based systems

b) ACARS based systems:

i. ED-100A compliant implementations




ii. The Character Oriented ATS Applications based on ARINC Specification 623 [32].

Interoperability demands that one or all of these systems are recognised as appropriate means of compliance with the implementing rule for data link services.

The relevant issues identified by the industry rapid reaction force in 2002 may need to be addressed in the implementing rule, if ED-100A FANS-1/A is to be considered as a means of delivering data link services in the European airspace. In that case, the conceptual “communications gateway” assumed in the IRRF report for ATN-FANS-1/A interworking may require further specification.

Where an IP ground infrastructure is deployed, use of the IP SNDCF for ATN over the ground portion of the air-ground data link should be specified.




APPENDIX 1 TO ANNEX F. ATS DATA LINK SYSTEMS DESCRIPTION .................1-1 F1.1 Introduction .........................................................................................................1-1 F1.2 Functional Architecture of DL Systems...............................................................1-1

F1.2.1 Overview ...................................................................................................1-1 F1.2.2 Interfaces ..................................................................................................1-2 F1.2.3 End to End Communications.....................................................................1-3 F1.2.4 Human Interfaces......................................................................................1-3 F1.2.5 End Systems .............................................................................................1-3 F1.2.6 ACSP ........................................................................................................1-3 F1.2.7 Air-Ground Data Link Management ..........................................................1-3

F1.3 Aeronautical Telecommunication Network (ATN) ...............................................1-4 F1.3.1 ATN Background.......................................................................................1-4 F1.3.2 ATN Objectives .........................................................................................1-5 F1.3.3 ATN Standards..........................................................................................1-6 F1.3.4 System Architecture ..................................................................................1-6 F1.3.5 ATN Interfaces ..........................................................................................1-7

F1.3.5.1 Reference Point ‘B’ Interface.........................................................1-7 F1.3.5.2 Reference Point ‘A’ Interface.........................................................1-8 F1.3.5.3 End-to-End ....................................................................................1-8

F1.3.6 ATN Ground-Ground Networks.................................................................1-8 F1.3.7 Implementation in Europe .........................................................................1-9

F1.4 ARINC 623 ATS Applications ...........................................................................1-10 F1.4.1 Background .............................................................................................1-10 F1.4.2 Standards................................................................................................1-10 F1.4.3 System Architecture ................................................................................1-10 F1.4.4 Interfaces ................................................................................................1-11

F1.4.4.1 Reference Point ‘A’ Interface.......................................................1-11 F1.4.4.2 Reference Point ‘B’ Interface.......................................................1-12 F1.4.4.3 End-to-End ..................................................................................1-12

F1.5 FANS-1/A..........................................................................................................1-13 F1.5.1 Background .............................................................................................1-13 F1.5.2 ATS Data Link Services in FANS-1/A .....................................................1-13 F1.5.3 Standards................................................................................................1-13 F1.5.4 System Architecture ................................................................................1-14 F1.5.5 Interfaces ................................................................................................1-15

F1.5.5.1 Reference Point ‘A’ Interface.......................................................1-15 F1.5.5.2 Reference Point ‘B’ Interface.......................................................1-15 F1.5.5.3 End to end ...................................................................................1-15

F1.5.6 Assessment of FANS-1/A .......................................................................1-15 F1.5.6.1 The IRRF Report .........................................................................1-15 F1.5.6.2 Use of FANS-1/A for Profile Changing CPDLC Services ............1-16 F1.5.6.3 Other IRRF Issues.......................................................................1-16 F1.5.6.4 The Voice Read-back Issue ........................................................1-18

F1.6 IP Communications...........................................................................................1-19 F1.6.1 IP for Mobile Air-Ground Communication ...............................................1-19 F1.6.2 IP for Fixed Ground-Ground Communication..........................................1-19

F1.7 Civil-Military Interoperability ..............................................................................1-20 F1.8 Conclusions ......................................................................................................1-20




APPENDIX 2 TO ANNEX F. DATA LINK APPLICATIONS

F2.1 Introduction This Appendix describes the data link applications that are specified to support the realisation of data link services. This includes the development of "Protected Mode" variants.

F2.2 Data Link Applications As a result of the work of the ICAO FANS committee, a number of standard CNS/ATM Applications have been specified in ICAO documents. These are communications applications that support one or more ATM functions. The development of the requirements for the CNS/ATM applications has both top-down and bottom-up aspects. The top-down requirements came from ICAO Operational Panels (ADSP and subsequently OPLINKP). The bottom-up requirements came from the communications service offered by the ATN.

Specifically, the data link applications applicable to air-ground services are:

• Automatic Dependent Surveillance (ADS): A surveillance technique in which aircraft automatically provide, via a data link, data derived from on-board navigation and position-fixing systems, including aircraft identification, four-dimensional position, and additional data as appropriate. There are two distinct types of ADS implementation:

o Contract Mode (ADS-C), in which an ATS Unit uses a point-to-point data link to establish a "contract" with an aircraft, and then receives the requested ADS reports over the established connection.

o Broadcast Mode (ADS-B), which is a surveillance application in which selected aircraft information, such as position, track and ground speed, is transmitted via a broadcast mode data link, at specified intervals, for utilisation by any air and/or ground users requiring it.

• Controller Pilot Data Link Communications (CPDLC), providing a means of communication between controller and pilot, using data link for ATC communications. CPDLC provides a communications capability similar in scope to air-ground ATC voice communications using message oriented data communications instead of voice, but retaining ICAO phraseology and message semantics.

Downstream Clearance (DSC) is a service within the CPDLC application. Unless specifically indicated, DSC uses all generic CPDLC functionality, including message handling as well as operational and performance requirements as described in the ACL service. The CPDLC SARPs specify specific DSC services – DSC-Start and DSC-end – for controlling dialogues with downstream ATS Units. They have the same parameters as their CPDLC equivalents.

• Context Management (CM): providing the ability to exchange capability information, including addresses, names and version numbers necessary to initiate data link applications.

• Data Link Flight Information Services (D-FIS), providing flight information to aircraft via data link.

These data link applications were seen as sufficient to support the initial set of point-to-point data link enabled services discussed in Annex B.

Ann F App 2 Data Link Applications 1.1.doc 24/05/2006 Page F2-1



Formally, a data link service makes use of the services offered by a given ATS application and there can be many different data link services using the same ATS application. Figure F2-1 illustrates the relationship between data link services such as ACL, ACM, FLIPCY and ADS Position Reporting and the ICAO ATS Applications.

CPDLC ADS

ACL ACM FLIPCY PositionReporting

Air-GroundCommunications

Service

Figure F2-1 Data Link Services and ATS Applications

Figure F2-2 illustrates this concept in greater detail, showing the possible mapping of data link services specified for the LINK 2000+ and CASCADE programmes to appropriate data link applications, and hence to specific air-ground communication services.

1090 ES VDL/2 ACARS

GS AS

ADS-B-ACCADS-B-TMAADS-B-NRAADS-B-APTADS-B-ADD

ATSA-SURFATSA-AIRBATSA-S&AATSA-SVAASPA-S&M

DLA?PM-CPDLCCM

DLIC

ACMDSC(OCM)

D-ATIS

FIS

D-OTIS

GRECO D-ALERTD-TAXI

ACL

AMC

DCLDSC

Auto CPDLC

PPDFLIPCY

Included in LINK 2000+

CASCADE Stream 1

CASCADE Stream 2

Figure F2-2. Example of Data Link Services Mapping

For example, the standard CPDLC message set and communications protocol is capable of supporting many different services based on communication between controller and aircrew. In an operational environment, the distinction between, say, ACM and ACL services would not be visible to the users of the services. They would only be aware of the capabilities offered by the particular implementation of CPDLC, which would support only a subset of the possible CPDLC message elements.

The selection of validated data link application standards ensures technical interoperability between air and ground end systems. That is, one end system will be able to format a specified message as a bit stream and another end system will be able to interpret the received bit stream unambiguously and process the message content accordingly.




F2.3 "Protected Mode" Applications The CNS/ATM data link applications were designed assuming that they would be implemented over a reliable communications medium, such as a connection oriented transport service. CPDLC uses the transport connection to maintain the relationship between data authority and pilot. For example, the connection between a current data authority (CDA) and a pilot represents the control relationship.

EUROCAE ED-120 [4] identifies the hazards applicable to systems implementing the "ATN Baseline 1" data link services described in EUROCAE ED-110A [3]. It derives safety objectives for such systems, and the safety requirements with which they must comply. The safety requirements applicable to the communications service concern integrity and prevention of mis-delivery.

In the context of the LINK 2000+ Programme, EUROCONTROL conducted a system-wide analysis of the mis-delivery hazard and identified potential shortcomings in the then existing CPDLC system design.

As a result, a modified version of CPDLC, known as Protected Mode CPDLC (PM-CPDLC), was developed. PM-CPDLC incorporates an integrity check field in every message exchanged between air and ground end systems. This provides a strong check on both message integrity and detection of mis-delivery. In addition to hazards that result from mis-operation of the communications services, it also reduces the dependency on the maintenance and timely ground distribution of CM related information. PM-CPDLC is intended to be the basis of all future CPDLC deployments.

Similar considerations are leading to the specification of Protected Mode variants of ADS-C and D-FIS applications within ICAO working groups.

The PM-CPDLC standard has been incorporated into the ICAO Technical Provisions for ATN by means of the defect resolution procedure. It will be published in the fourth edition of the ATN Technical Provisions, ICAO Doc 9705.

These developments are not yet reflected in the INTEROP standard for ATN Baseline 1, ED-110A [3].

F2.4 Conclusions For the interoperability of data link applications in the EATMN, the following conditions must be satisfied:

• A common set of data link applications must be selected for implementation in the EATMN

• These data link applications must ensure global interoperability by complying with validated international standards.

• These data link applications must be properly integrated with pilots and controllers HMIs.

• The scenario to operate data link applications in the EATMN must be specified.


• The definition of data link applications in terms of supported data link services;

• The scenario to activate and establish communications between data link applications;

• The scenario to maintain communications between data link applications;

• The scenario to close and deactivate communications between data link applications;




• Statements of security policy (appropriate for data link applications).

"Protected Mode" data link applications should be specified, in order to mitigate the identified mis-delivery hazard.




APPENDIX 2 TO ANNEX F. DATA LINK APPLICATIONS..........................................2-1 F2.1 Introduction .........................................................................................................2-1 F2.2 Data Link Applications ........................................................................................2-1 F2.3 "Protected Mode" Applications............................................................................2-3 F2.4 Conclusions ........................................................................................................2-3




APPENDIX 3 TO ANNEX F. SYSTEM PROFILE REQUIREMENTS

F3.1 Introduction This Appendix describes the need for an ATS data link system baseline, or "profile" specification.

To ensure technical interoperability of data link services, it is not sufficient to refer to a list of ICAO and EUROCAE documents. A detailed specification is required, refining the combination of standards, their relevant subsets and options, and any necessary divergences, together with version and amendment numbers.

This concept of "functional standards" or "standardised profiles" was first recognised by ISO, and resulted in the publication of International Standardised Profiles for many communication functions.

The LINK 2000+ baseline specification [15] appears to be the only complete data link system specification that addresses all of the known issues.

F3.2 Message Subsets The ICAO Technical Provisions for CPDLC (and PM-CPDLC) were derived from the operational messaging requirements established in Doc 4444 (PANS-ATM). The CPDLC technical provisions, therefore, include support for all 237 uplink message elements and all 114 downlink message elements in the PANS-ATM.

This compares with the ED-100A FANS-1/A CPDLC application, which has 183 uplink message elements and 81 distinct downlink message elements

In practice, the data link services defined and validated to date do not make use of all of the available message elements. ED-110A specifies which message elements are required for each operational service, together with constraints on how the message elements may be combined and used. ED-110A specifies the use of 96 uplink message elements and 38 downlink message elements. The document also specifies 3 operational subsets, of which the LINK 2000+ CPDLC baseline corresponds most closely to "subset 0."

No of CPDLC message elements

0

50

100

150

200

250

FANS ICAO ED110 LINK LINK (M)

umdm

Figure F3-1. Subsets of CPDLC Message Elements

Ann F App 3 Profile Requirements 1.1.doc 24/05/2006 Page F3-1



The histogram in Figure F3-1 illustrates this subsetting process for uplink (um) and downlink (dm) message sets. The columns "LINK (M)" indicate the small number of message elements whose support is mandatory in the LINK 2000+ baseline.

The LINK 2000+ baseline includes 62 uplink and 26 downlink CPDLC message elements, some of which are optional to implement. An aircraft system is required to be able to receive all uplink message elements specified in Doc 9705, and a ground system is required to be able to receive all specified downlink message elements. If a message element is received that is not supported, an appropriate error response is returned to the sender.

F3.3 Standards Versions The ATN is the communication exchange mechanism required by ICAO SARPs in Annex 10, Volume III, Chapter 3 [1]. The ATN SARPs specify high-level requirements and invoke the technical provisions of ICAO Doc 9705 [2], and the ATN guidance material in ICAO Doc 9739 [25], by reference. The technical provisions for end-to-end interoperability at the communication exchange level are specified in Sub-Volumes IV (Upper Layer Communications Service - ULCS) and V (ATN Internet Communications Service - ICS) of ICAO Doc 9705 [2].

ICAO Doc 9705 is currently at Edition 3 and will soon be updated to Edition 4. Edition 3 is the only edition currently available from the ICAO catalogue of publications. However, current operational ATN implementations in Europe conform to Edition 2 of the ICAO Technical Provisions (plus selected defect resolutions), as specified for the LINK 2000+ baseline [15].

Of relevance to the selection of communication mechanisms, Edition 3 adds security services for IDRP and Upper Layers and naming/addressing extensions, as well as incorporating the IP Subnetwork Dependent Convergence Function (IP SNDCF).

The profile adopted for ULCS and ICS components of current operational ATN implementations in Europe diverges from the profile specified in Doc 9705 Edition 2 (plus selected defect resolutions) in one respect, as follows:

Support of the extended transport checksum is mandatory for compliance with the ICAO technical provisions but is optional in the LINK 2000+ profile. It is possible that an ICAO-compliant implementation expecting to use the extended checksum would be forced to negotiate down to using the ISO-standard checksum when communicating with an implementation conforming to the LINK 2000+ profile and not supporting the extended transport checksum.

Note. With the introduction of a 32-bit integrity check at application level (PM-CPDLC, with PM-ADS and PM-FIS to follow), the ATN-specific extended transport checksum functionality is considered superfluous. The ATN transport service provides a robust end-to-end communication channel over multiple (air-ground and ground-ground) sub networks, using the ISO standard Class 4 transport protocol (TP4), which provides error detection and recovery mechanisms. However, the LINK 2000+ pre-implementation safety case identified that the transport protocol alone is not sufficient to mitigate a potential mis-delivery hazard, therefore Protected Mode applications are specified.

F3.4 The Need for Profiling In order to ensure interoperability of data link services using ATN communication services, the ATN transport protocol and dialogue service, and the data link application must be compliant with ICAO technical provisions, specifically the protocols supporting the ATN ULCS and ICS.




Note: The ATN communication service offers both connectionless and connection-oriented modes; the ATN data link applications are designed to use only the ATN connection mode transport service.

In practice, additional profile requirements must also be specified to ensure interoperability, such as:

• Support for the extended transport checksum, although mandated in the ICAO technical provisions, should be made optional.

• Support for the Secure Dialogue Service in the ATN ULCS should be excluded, as many of the technical complexities of a Europe-wide security solution remain to be investigated.

• Implementation of the ATN connectionless dialogue service (CLDS) and connectionless transport protocol (CLTP) is not required.

• The ULCS and ICS profile is as specified for LINK 2000+ Baseline 1 (section 4.2 and 4.3 of reference [15]).

F3.5 Selected Data Link Applications For the interoperability of data link services in the EATMN, the following conditions must be satisfied:

• To ensure seamless operation, a common set of data link services must be selected for initial implementation in the EATMN (based on the list established in Annex B)

• These selected data link services must be implemented by applying validated international standards to ensure global interoperability.

• The selected data link services must be consistent with the Concept of Operations [27]

• The coordinated introduction of these selected data link services in the EATMN must be enforced by implementation dates and transitional arrangements, if needed.

The data link services recommended for regulation in the short term are realised over a suitable communications medium by means of a subset of the ICAO-specified CNS/ATM applications.

The ATS data link services can be implemented using data link applications CM (for the DLIC service), CPDLC (for ACM, AMC, ACL, DSC) and D-FIS (for D-ATIS).

Of the other ED-110A [3] "Baseline 1" ATS data link services, FLIPCY can be implemented using the ADS-C data link application. Since FLIPCY is not selected for initial deployment, implementation of ADS-C is also not required for initial ATN data link operations.

The data link applications required to support the selected data link services therefore consist only of CM and PM-CPDLC.

The relevant applications are the following, operating over the ATN communication service:




Table F3-1. Data Link Application Functional Subsets

CNS/ATM application Relevant functional subset

Context Management (CM)

Logon and Contact services only, no support for the "maintain dialogue" option.

Protected Mode Controller-Pilot Data Link Communication (PM-CPDLC)

Excluding Downstream Clearance (DSC) and Ground Forwarding services. Only the subset of message elements in the LINK 2000+ Baseline 1 specification [15] is selected.

It is recommended that the regulatory coverage should include PM-CPDLC, while standard mode CPDLC should not be retained for inclusion in the implementing rule. (It may, however, be required for interoperability with initial pioneer LINK 2000+ implementers).

The use of PM-CPDLC ensures the required level of protection against message content or address corruption within the communication system, and ensures that messages are processed only by the intended recipient.

The regulatory coverage applies to only a subset of the available PM-CPDLC message elements.

It should be noted that there are no specific provisions for data link security mechanisms in the proposed regulatory coverage to protect against deliberate interception and manipulation of the exchanged messages, or masquerade of the message originator.

A detailed threat analysis would need to be performed before contemplating use of the ATN cryptographic security provisions.

F3.6 Extensibility Considerations One potential issue that may inhibit the future extensibility of any CPDLC deployment is that there is no standardised way for an implementation to indicate dynamically to a communicating peer which message elements are supported and which are not. EUROCAE ED-110A [3], section 3.1.3.2.1.2.8, specifies a limited approach using the application version number to indicate message set support. However, this is not widely supported. The LINK 2000+ Baseline [15] explicitly excludes this version number mechanism, and is non-compliant with ED-110A in this respect.

The issue of how to communicate CPDLC message set capabilities between aircraft and ground systems remains to be resolved in the aeronautical standards community.

The introduction of new CPDLC-based services such as Auto-CPDLC may introduce some new message elements not supported in the current baseline. These could be:

• Message elements that are currently defined in ICAO Doc 9705 [2] but not in the baseline message set.

• Message elements that are not in the ICAO Doc 9705 CPDLC specification.

Thus, to implement a new data link service, even one whose operational requirements are stable, might require changes to ICAO specifications. This would bring attendant CPDLC Version issues, and would require modifications to the message handling parts of air and ground CPDLC implementations. There have been proposals that new data link services could be realised using a new, transaction-based class of applications. However, given the tight coupling of many data link services with the existing CPDLC service, there would be little short-term benefit in migrating to an alternative approach.




F3.7 Conclusions The ED-110A [3] requirement to use Application Process Version Numbers 110 or 210 in the CM Logon process (ED-110A section 3.1.2.1.2.10) to distinguish different message subsets should be excluded from the regulatory provisions.

Note: LINK 2000+ compliant implementations are required to use only version number 1 as specified by ICAO Doc 9705. The LINK 2000+ baseline deviates from ED-110A in this respect.

The extension of CPDLC services in the future will not be a straightforward issue. A policy for managing such extensions needs to be defined. This is an important issue because many stakeholders will perceive the first set of core data link services to be rather limited. The road to expansion of services should therefore be clear from the outset.

The regulatory coverage should address the need for a clear evolution strategy for future extensions of the CPDLC message set.

Current operational ATN data link applications in Europe are based on the LINK 2000+ baseline. This in turn references Edition 2 of the ICAO ATN Technical Provisions (plus selected defect resolutions). However, Edition 2 is no longer included in the ICAO publications catalogue; the current edition published by ICAO is Edition 3, with Edition 4 well advanced. Updating to the current ATN Technical Provisions would cause traceability / compliance issues (but not interoperability issues) for existing certified implementations.

The regulatory coverage should address the issue that the current version of the ICAO Technical Provisions for ATN differs from the version referenced by existing air and ground implementations. More generally, procedures to handle the evolution of based standards and reference document over the lifetime of the data link systems need to be specified.

Considering that implementation of the implementing rule is likely to be in the 2010 – 2015 timescale, a strategy for the evolution of the technical baseline must be defined.




APPENDIX 3 TO ANNEX F. SYSTEM PROFILE REQUIREMENTS ...........................3-1 F3.1 Introduction .........................................................................................................3-1 F3.2 Message Subsets ...............................................................................................3-1 F3.3 Standards Versions ............................................................................................3-2 F3.4 The Need for Profiling.........................................................................................3-2 F3.5 Selected Data Link Applications .........................................................................3-3 F3.6 Extensibility Considerations................................................................................3-4 F3.7 Conclusions ........................................................................................................3-5




ANNEX G. END TO END CAPACITY, PERFORMANCE AND SECURITY

G.1 Introduction This Annex considers the end-to-end capacity and performance requirements for the deployment of the selected data link services. It also considers the end-to-end security of the data link.

G.2 ED-120 Performance Requirements

G.2.1 Overview EUROCAE ED-120 [4] specifies the operational, safety and performance requirements (SPR) for selected data link services in continental airspace. The safety requirements apply to all systems; each system must either comply with each safety requirement, or it must be demonstrated that they cannot impact the corresponding safety objective. This is a subject for the safety analysis of each system as part of the operational approval process prior to deployment in the EATMN, and is not considered further in this Annex.

The situation is different with performance requirements, which need to be analysed and allocated to different parts of the system.

The DLIC, ACM, ACL and AMC Services defined by the ATN Baseline 1 INTEROP standard ED-110A [3] all operate according to a transaction oriented request / response model. AMC is the trivial case consisting of a request only (no response). The performance requirements all relate to this transaction model, illustrated in Figure G-1.

‘ ’‘ttr’ or ‘ETresp

=100 s (ED110A+ED120)

T_dwn(response)

ATCO / ground system

Flight Crew

voiceintervention

ATCO notified

‘ ’ClearanceExpiry Timer

voiceintervention

OptionalT_dwn

(ERROR)

T_dwn(LACK)

T_upl(clearance)

‘tts’ or ‘Ettrn’

Figure G-1. CPDLC Transaction Model

The first performance requirement is the required probability that the system is available when the transaction initiator (pilot or controller) needs to start a transaction.

The second performance requirement is the required probability that the system continues to be available for the duration of the transaction.

For this second requirement to be meaningful there has to be an upper bound on the length of time a transaction has to complete (Elapsed Time (ET) in ED-120, or tts in ED-110A). ED-120 also provides a target time (TT(95)) for 95% of transactions to complete.

Annex G Capacity Performance Security 1.1.doc 24/05/2006 Page G-1



The continuity requirement is therefore expressed as the probability that the transaction will complete in ET seconds.

There is also a data integrity requirement expressed as an undetected message error rate.

G.2.2 Requirements Allocation ED-120 [4] provides an initial allocation of the performance requirements to different parts of the system. Figure G-2 illustrates the model used in ED-120 for requirements allocation.

The allocation starts with the overall required communications performance (RCP), which is the performance requirement for the transaction from initiation to completion. The RCP is divided into components for initiation and termination processing, and the transaction (TRN) itself. The transaction starts when the request message is issued and completes when the response message is received.

The TRN budget is then divided between the responder and the required communications technical performance (RCTP). The RCTP is the allocation of the requirement to the end-to-end communications service.

ED-120 does not further subdivide the RCTP allocations.

Figure G-2. ED-120 Transaction Model (Aircraft initiated Transactions)

G.2.3 RCTP Requirements Allocation ED-120 [4] allocates the RCTP requirements to the aircraft and the ground system.

In order to reflect the fact that the ANSP’s systems are separate from the ACSP’s systems, it is also necessary to quantify the ACSP performance requirements separately from the ANSP performance requirements.




For example, the LINK 2000+ Programme has developed a different, though compatible, allocation strategy to that presented in ED-120. This uses the system model presented in Figure G-3.

The principal differences between this model and the ED-120 system model are:

a) The division of the ED-120 air traffic service provider (ATSP) into separate ACSP and ATS Unit components, and

b) The explicit distinction between the end-to-end requirements and internet requirements.

ATN G/G

Router

ACSP Network

ATS Unit

ACSP

ATN G/G

Router

ATN A/G

Router


Airborne RouterHMI


Flight Crew


HMI

End System(ATSU)

Controller

Procedures(ATSU)

End-to-endDialogue

Figure G-3. LINK 2000+ Data Link System Architecture

The ATS Unit domain comprises the data link service ground user, an ATN end system and an ATN ground-ground router. The controller accesses the data link service ground user component via a suitable HMI, according to the procedures specified for the ATS Unit.

The ACSP domain comprises the ground system supporting the air-ground communications network, and air-ground and ground-ground ATN routers operated by the ACSP. (As noted in Annex E, there could be more than one interconnected ACSP in a real system).

The aircraft domain comprises the data link service air user and ATN end system, an ATN airborne router and the airborne components of the air-ground communications network. The pilot accesses the data link service air user component via a suitable HMI, according to the procedures specified by the airline.

Applying this system model, the allocation of ED-120 performance requirements assumed for the LINK 2000+ programme is as described in Table G-1.




Table G-1. Allocation of Performance Requirements (LINK 2000+)

Parameter Avionics ACSP ATS Unit

ET 99.83% of incoming and outgoing messages shall be transferred in better than 2 seconds

99.83% of messages shall be transferred without error in better than 8.5 seconds

99.83% of incoming and outgoing messages shall be transferred in better than 5 seconds

TT(95) 95% of incoming and outgoing messages shall be transferred in better than 1.5 seconds

95% of messages shall be transferred in better than 7 seconds

95% of incoming and outgoing messages shall be transferred in better than 4 seconds

Availability The system shall be available for use 99.39% of the time during which the aircraft is powered up.

The communications service shall be available for use 99.91% of the scheduled hours during which

a) Data link service is available, and

b) Over the entire area in which service is provided, and

c) Available at the minimum power levels required for normal operations.

The system shall be available for use 99.99% of the scheduled hours during which data link service is available.

Integrity The undetected bit error rate of messages presented to the pilot shall be better than 1.67 X 10-7, where a message is assumed to be no longer than 300 bits.

No Requirement The undetected bit error rate of messages presented to the controller shall be better than 1.67 X 10-7

G.3 Security Requirements To date, there are no formalised end-to-end security requirements for data link services.

An early study by EUROCONTROL suggested that the main security requirements for ATS data link services would be:

• Data Integrity – Assurance that data has not been interfered with in transit

• Authentication – Assurance that the communicating partners are who they claim to be.

Confidentiality was not thought to be a requirement, since there are benefits of "open line" communication for situational awareness, and current ATC voice procedures are in any case not confidential.

Information security measures will become increasingly important as use is made of IP-based ground networks, as there is a worldwide community of would-be hackers with expertise in compromising such networks.

It is, therefore, important that ANSPs and ACSPs should have a well-defined information security policy in place, including procedures for maximising data link security (such as




access control including physical security and HMI logon procedures), and for handling suspected security breaches.

The ATN Technical Provisions in ICAO Doc 9705 [2] include optional end-to-end security procedures based on strong cryptographic mechanisms. To date, these have not been validated in an operational scenario. Some of the issues to be resolved include how an ATS Unit should handle an aircraft if authentication fails – it might be better to provide limited data link service rather than force a reversion to voice procedures.

The LINK 2000+ programme has issued a security statement in which no specific technical security mechanisms are proposed. Security measures will be limited to aspects such as physical protection, access control (password protection) etc. The justification for this is based on a high level consideration of the system vulnerabilities.

Work is in progress in AEEC and RTCA/EUROCAE committees to develop information security requirements for future aeronautical systems, but this work is not yet mature.

G.4 Conclusions The allocation of performance objectives to domains in the SPR standard is not sufficient to separate the responsibilities of systems and subsystems in the real end-to-end communication system. The regulatory coverage should take account of the performance requirements for different stakeholder types (ATS Unit, ACSP and avionics), based on the LINK 2000+ system model.

Security mechanisms will not be a subject for prescription in the implementing rule. Rather, stakeholders will be obliged to demonstrate that an appropriate information security policy is defined and implemented.




ANNEX G. END TO END CAPACITY, PERFORMANCE AND SECURITY ..........G-1 G.1 Introduction ........................................................................................................G-1 G.2 ED-120 Performance Requirements..................................................................G-1

G.2.1 Overview ..................................................................................................G-1 G.2.2 Requirements Allocation ..........................................................................G-2 G.2.3 RCTP Requirements Allocation ...............................................................G-2

G.3 Security Requirements ......................................................................................G-4 G.4 Conclusions .......................................................................................................G-5




ANNEX H. DATA LINK RECORDING REQUIREMENTS

H.1 Introduction The purpose of the analysis in this Annex is to review materials (regulations, technical standards) relating to the recording of data link messages applicable to the aircraft and ground side, and to provide recommendations about potential impact on the implementing rule.

The primary purpose of recording aeronautical communications is to aid investigators in establishing the facts surrounding incidents and accidents. As such, the recording requirements have an important indirect contribution to safety.

From the perspective of recording communications, ICAO Annex 11 [18] is applicable to units providing an ATS of any kind, ICAO Annex 10 [87] covers the communications service and procedure aspects while ICAO Annex 6 [17] contains the provisions applicable to aircraft.

The overall requirement for recording communications specified by ICAO relate to any communication between ATS Units and between ATS Units and aircraft, whether by voice, digital link or any other means.

The practical implementation of the overall ICAO requirements has led to air-ground data link communications being recorded at three distinct points along the communications chain:

• At the ATS Unit generating or receiving the message (based on ICAO Annex 11),

• At the communications service provider having transmitted the message (based on ICAO Annex 10) and

• On board the aircraft having initiated or received the message (based on Annex 6).

The costs and other complexities involved in recording air-ground data link messages are very different when viewed from an ANSP perspective and an airline perspective.

Some of the most important issues are considered in the following discussion.

H.2 Statements of Issues

H.2.1 General The overall requirements to record communications conducted between ATS Units and other ATS Units, and between ATS Units and aircraft, are set out in ICAO Annex 6, Annex 11 and Annex 10. The overall ICAO requirements are reflected in a series of consequential regulatory and guidance provisions, published as stand-alone documents or parts of other documents from EUROCAE, JAA and EASA.

H.2.2 Issues Related to Cost

Recording on the ground

Air Navigation Service Providers and Communications Service Providers have long been under an obligation to record air-ground and ground-ground ATS communications (not to mention the recording of surveillance and other data) and are generally well equipped to start recording air-ground data link messages when these are introduced. In most cases, no new equipment and/or even upgrading of existing equipment is needed and hence the costs on the ground are low.

Annex H Data Link Recording Requirements 1.1.doc Page H-1 24/05/2006



Airborne recording

Modern aircraft carry flight recorders (this generic term covering the Flight Data Recorder-FDR and the Cockpit Voice Recorder-CVR), which are required to record a wide range of parameters related to the aircraft systems and operation. In most cases, the flight recorder was not designed to record air-ground data link messages and pilot actions associated with such messages (e.g. calling up a message from the queue). The newest generation of flight recorders do have this capability and when fitted in new 'digital' aircraft, their price is absorbed in the price of the aircraft and hence meeting the air-ground data link recording requirement does not constitute a cost issue.

However, the cost penalty for aircraft with older types of flight recorders (which need replacement with newer models and possibly also wiring changes) is substantial. The price of a new flight recorder may increase the cost of implementing air-ground data link on such an aircraft by as much as 50 %. This has a serious negative impact on the otherwise favourable business case.

H.2.3 Issues Related to Recording Content

Recording on the ground

Due to the characteristics and capacity of recording equipment on the ground, recording the full content of data link messages (including all reference data as well as content) is generally not a problem. For the same reason, the range of messages (e.g. ATS, other) to be recorded is also not an issue as such.

AOC is already recorded today by the ACSP as well as the airlines themselves. Passenger communications is not within the scope of the current discussion, so issues of confidentiality and data protection, not to mention the sheer volume of data due to passenger web browsing etc. are not considered. They may in fact flow via completely different channels physically or logically or both and completely different rules may apply to them (as is the case today for satellite and terrestrial airborne telephone services).

Airborne recording

The volume and type of data exchanged between aircraft and the ground has steadily increased in recent years and will increase further in the future.

This exchange of data represents various categories of communications not all of which is relevant to ATM.

At first sight, it might seem appropriate to require that all digital data traffic be recorded on board the aircraft, on the claim that this is the only way to reliably establish what contribution, or lack of it, digital communications may have had in an incident or accident. However, this is not a practicable approach, and the requirements of incident investigators can be satisfied by limiting the recording scope to:

a) Data link communications related to ATS to and from the aeroplane.

b) All messages whereby the flight path of the aircraft is authorised, directed or controlled, and which are relayed over a digital data-link rather than by voice communication.

It is possible that, at some time in the future, non-ATS requirements (e.g. security) may focus on the need to record data link messages not covered by the above categories. However, such additional needs will have to be addressed and met using the facilities and characteristics of digital systems that obviate the need for on-board recording/storage, eliminating the additional costs to the airlines. For this purpose, ground systems that store messages sent to the aircraft, together with an acknowledgement of receipt from the




aircraft, have been proposed. The impact on the available communications bandwidth and the cost issues will need to be further explored should the need for recording a broader scope of data become inevitable at some time in the future. From an ATS perspective, this is not an issue at this time.

H.3 Applicable Technical Documents and Standards The details of the applicable ICAO provisions are as follows:

• Recording of air traffic control service communications: ICAO Annex 11 [18], Chapter 6, para. 6.1.1.2

• Recording by aeronautical communications stations (covers also communications service providers): ICAO Annex 10, Volume II [87], para. 3.5

• On-board recording: ICAO Annex 6 [17], Part I, Chapter 6.

Note: The relevant provisions in ICAO Annex 6 have been the subject of considerable debate within the aviation industry and a consensus has been reached whereby ICAO will be requested to review the provisions currently applicable. In the meantime, in Europe the JAA will publish requirements for aircraft operators that have revised dates and which do not require retrofit. The recording scope will also be limited to ATS communications. The JAA material is expected to be published before the end of 2005.

Other applicable documents are:

• EUROCAE ED-112 “Minimum Operational Performance Specification for crash protected airborne recorder system” Part IV [88]

• JAA JAR-OPS 1.728 (in the process of being revised) [89]

• EASA ACJ 20x10 (in the process of being revised) [86]

H.4 Proposed European Requirements Appropriate text, reflecting the proposed European requirements for recording of air-ground data link messages, has been developed by EUROCONTROL and approved by the Operations Committee of the Association of European Airlines. It is being considered by the JAA for adoption. The text is as follows:

Note: The following provisions are not applicable to Mode S communications, which is already being recorded as primary data on the Flight Data Recorder.

a) An operator shall not operate any aeroplane with a maximum certificated take-off mass over 5700 kg which has the capability to use one or more types of data link communications applications, unless it is equipped with a flight recorder which shall record:

1) For aircraft first type certificated on or after 1 January 2008 those data link communications applications listed in [Table H-1] that are capable of being used.

2) From 1 January 2010, for aeroplanes first type certificated before 1 January 2008 and first issued with an individual certificate of airworthiness on or after 1 January 2010 those data link communications applications listed in [Table H-1] that are capable of being used.

b) Aircraft that do not fall under (a), (1) or (2) are exempted from the requirement to record data link communications.

Note: The worldwide provisions concerning the recording of data link communications are contained in ICAO Annex 6. ICAO has been requested to review the existing provisions




with a view to bringing them more in line with the industry’s safety requirements and realistic technical capabilities.

c) The flight recorder shall use a digital method of recording and storing data. A method of readily retrieving that data from the storage medium shall be available.

d) The flight recorder shall be capable of retaining the data recorded during at least the last two hours of operations.

e) The flight recorder must start automatically to record prior to the aeroplane moving under its own power and continue to record until the termination of the flight when the aeroplane is no longer capable of moving under its own power. In addition, depending on the availability of electrical power, the flight recorder must start to record as early as possible during the cockpit checks prior to engine start at the beginning of the flight until the cockpit checks immediately following engine shutdown at the end of the flight.

f) The flight recorder must have a device to assist in locating that recorder in water.

Recording scope

1. The expression “as far as is practicable” means that the recording of the specified information may be omitted if the existing source systems involved would require a major upgrade.

In determining whether the modification constitutes a “major upgrade”, account shall be taken of the following:

a) The extent of the modification required;

b) The down-time involved;

c) Equipment software development

2. The flight recorder shall record the messages, with the detail specified, as contained in Table H-1.

3. The following timing information associated with the data link communication application messages shall be capable of being determined from the airborne based recording, as far as is practicable given the architecture of the system:

a) The time each message was generated

b) The time each message was available to be displayed by the crew

c) The time a given message was actually displayed and/or printed.

4. The flight recorder shall record the message priority when defined by the protocol of the digital communication application being recorded, as far as practicable given the architecture of the system.

5. Where parametric data is reported within a message, it shall be recorded unless data from the same source is recorded on the FDR.

6. If acceptable to the Authority, graphics applications may be considered as AOC messages when they are part of a digital communication application service run on an individual basis by the operator itself in the framework of the Air Operational Control approved under JAR-OPS 1.195.




Table H-1. Recording Details for Data Link Services

Item Nr

Application Type Services/Messages Recording

Detail Comments

1 CM DLIC C CM is an ATN term 2 AFN DLIC C AFN is an ED-100A FANS-1/A term.

Similar to CM ACL C All implemented up and downlink

messages recorded ACM C All implemented up and downlink

messages recorded AMC C All implemented up and downlink

messages recorded DCL C All implemented up and downlink

messages recorded

3 CPDLC

DSC

C All implemented up and downlink messages recorded

FLIPCY C All contract requests and reports recorded

4 ADS-C

Position reports C* Only used within FANS-1/A.

5 ADS-B Surveillance data M* 6 D-FIS D-ATIS

D-OTIS C All implemented up and downlink

messages recorded 7 TWIP messages M 8 AOC Not yet defined M* AOC as defined by ICAO

9 Graphics Weather Maps and other

graphics M

10 Surveillance CAP, SAP C* Symbols used in Table H-1:

C = Complete contents recorded M = Minimum contents recorded. Sufficient content shall be recorded to enable the correlation with the full content recorded on the ground. * = Indicates that recording shall be done only as far as is practicable given the architecture of the system.

H.5 Conclusions Meeting the on-board recording requirements, based on a recording scope limited to ATS communications, is not expected to be a problem for new aircraft, but can be extremely costly for aircraft that need to be retrofitted with appropriate recorders.

The recording of air-ground data link messages should be limited to non-retrofit cases and the scope of messages should be limited to those of ATM concern.

The requirement to record air-ground data link messages is imposed by the ICAO provisions specifying the recording of aeronautical communications. These provisions are of worldwide applicability.

The provisions currently in ICAO Annex 6 have been opposed by the industry from the outset, the most important reasons being too wide a scope and unacceptably high costs in the case of retrofit. The European regulatory bodies (JAA, EASA) have recognised the industry’s concerns and a European rule different from the present ICAO Annex 6 provisions will be published in the near future

Data recording requirements for airborne systems should be left to EASA/JAA.

The recording of air-ground data link messages does not in itself constitute an issue of interoperability for data link service provision. There are secondary interoperability




concerns, e.g. that a consistent set of data is recorded, in a standardised format, so that incident investigations are not hindered.

H.5.1 Impact on the Implementing Rule The implementing rule should be consistent with the position that will be agreed by the industry in the near future. It is proposed to present the position agreed in Europe and propose a deviation to ICAO material in the justification material associated with the draft implementing rule.

Requirements for ground systems data recording could be a subject for prescription in the interoperability implementing rule. In particular, the division of responsibility between ACSP and ANSP systems should be addressed.




ANNEX H. DATA LINK RECORDING REQUIREMENTS ..................................... H-1 H.1 Introduction ........................................................................................................ H-1 H.2 Statements of Issues ......................................................................................... H-1

H.2.1 General .................................................................................................... H-1 H.2.2 Issues Related to Cost ............................................................................. H-1 H.2.3 Issues Related to Recording Content ...................................................... H-2

H.3 Applicable Technical Documents and Standards .............................................. H-3 H.4 Proposed European Requirements.................................................................... H-3 H.5 Conclusions ....................................................................................................... H-5

H.5.1 Impact on the Implementing Rule ............................................................ H-6




ANNEX I. NAMING, ADDRESSING AND REGISTRATION PLAN

I.1 Introduction The aim of this Annex is to describe the different addressing schemes based on ATN, FANS, ACARS, etc. and to identify any related issues and requirements.

In particular, provisions for the assignment and management of unique addresses for air and ground systems should be examined.

I.2 ICAO Provisions

I.2.1 Aircraft Address ICAO Annex 10 (Volume III, Part 1, Chapter 9) specifies that an aircraft address shall be one of the (16,777,214) 24-bit aircraft addresses allocated by ICAO to the State of registry or common mark registering authority and assigned as prescribed by ICAO.

The assignment of ICAO 24-bit addresses to aircraft is managed in two steps.

1. ICAO Annex 10 allocates 24-bit aircraft address value segments to States. Each segment is under the control of the national CAA and does not intersect with other segments administered by different CAAs.

2. ICAO delegates value assignments within each segment to the CAAs.

I.2.2 Ground System Identification ICAO ground facility designators are 4-letter codes used to identify aerodromes and aeronautical facilities around the world. The first letter of the code identifies a region. Most regions contain several countries, while some regions are considered large enough to have a letter allocated to a single country. The second letter then indicates the country within the region, and the third and fourth letters identify the particular facility within the country.

Four characters may be added to the indicator to determine the destination agency at the location.

Facility designators for ATC ground facilities are identified and assigned in ICAO Doc 7910 for the first 4 letters and ICAO Doc 8585 for the remaining letters.

I.3 Mandating 24-bit Aircraft Address in the FPL

I.3.1 ICAO and LINK 2000+ Requirements The 24-bit aircraft address provides a way to identify a single airframe uniquely worldwide. The ICAO flight plan (FPL) format (Doc 4444 [23]) allows the 24-bit aircraft address of the aircraft to be used for the flight to be specified in Field 18/CODE.

The LINK 2000+ pre-implementation safety case [16] identified the need for an independent identifier to add mitigation means to ensure that clearance mis-direction probability is reduced to an acceptable level. The independence may be achieved by requiring the aircraft address to be included in the FPL sent to the ATS Unit. This is then verified against the aircraft address used in data link communication.

This gives rise to several issues:

• There are numerous occurrences (Mode S experience) of aircraft systems having incorrect values for the 24-bit aircraft address.

Annex I Naming Addressing Registration 1.1.doc 24/05/2006 Page I-1



• Aircraft address is currently not routinely included in the filed FPL. Aircraft operators may not know in advance which aircraft will be used for a flight (e.g. if using repetitive flight plans (RPL), or in the event of a last-minute aircraft change for operational / technical reasons).

ICAO Requirement The ATN Technical Provisions (ICAO Doc 9705 [2]) require the use of the 24-bit aircraft address in the CM-logon request for the airborne user (as part of the DLIC data link service). The 24-bit aircraft address is a mandatory ICAO requirement for establishing connections for the applications under ATN.

LINK 2000+ Requirement The LINK 2000+ Programme requires that it shall be possible for the ACCs committed to LINK 2000+ to use the 24-bit aircraft address in the FPL, to enable FPL data stored by an ACC to be associated with the flight data from the ATN equipped aircraft obtained during logon.

Note: The FPL association is based on airport departure, airport of destination, aircraft flight identification, and 24-bit aircraft address.

The safety case executed at Maastricht UAC (MUAC) has shown that unambiguous identification for the provision of ATN based data link operations can only be guaranteed if the FPL includes a unique identifier of the airframe (which must at least map to the 24-bit aircraft address). Unambiguous identification becomes critical when the rate of aircraft data link equipage increases, together with the use of profile-changing data link messages without voice read back.

The ATC Data Link Manual for LINK 2000+ Services [14] specifies the following new procedure (additional to ICAO procedures):

"Operators of CPDLC equipped aircraft shall insert in Item 18 of the ICAO flight plan form the aircraft address (expressed in the form of an alphanumerical code of six hexadecimal characters) preceded by CODE/. "Example: CODE/ F00001 "While the provisions for insertion of the aircraft address already exist in Doc 4444, this paragraph mandates the insertion of the aircraft address for all the flights that intend to use CPDLC."

I.3.2 Impact on Civil Aircraft Operators Currently AOs do not normally include the CODE indicator in their FPL filings. The impact is:

• All AOs wishing to use data link services have to make changes to insert the CODE indicator in the FPL.

• AOs using RPLs would have to file CHG containing the CODE, or abandon the RPL procedure (either way a big impact).

I.3.3 Impact on Military Aircraft Operators There is apparently a security issue for military aircraft to downlink their 24-bit aircraft address. Additionally, military AOs have the right to modify the 24-bit aircraft address at any time when they are not airborne.

It seems unclear how military aircraft operating IFR GAT could comply with LINK 2000+ requirements.




I.3.4 Impact on Civil and Military ANSPs and Airport Operators Some existing ANSP and airport systems do not recognize the CODE item in FPL field 18, and will forward messages containing this item for manual correction. This may cause some extra load on their manual positions if the CODE item is mandated before the systems can be upgraded to accept it.

ANSP systems would have to be upgraded not only to recognize the CODE indicator in the FPL, but also to use it in the data link logon process.

I.4 ATN Addressing

I.4.1 General Principles The ATN Technical Provisions (ICAO Doc 9705 [2] Sub-Volumes IV, V and IX) specify naming and addressing rules for the ATN internet layers, upper layers and applications. These rules are common to any ATN-compliant network.

The ATN naming and addressing scheme is based on the OSI Reference Model (ISO 7498-3) which supports the principles of unique and unambiguous identification of information objects and global address standardisation, which are essential features for an international, mixed-user communications system such as the ATN.

Unambiguous ATN names and ATN addresses are achieved through the use of naming / addressing domains with firmly allocated naming / addressing authorities.

The overall authority for the ATN naming / addressing domains is ICAO, which controls and manages these domains through the ATN provisions. Besides partitioning the ATN naming / addressing domains into appropriate sub-domains and specifying the syntax, semantics and encoding for these sub-domains, the ATN provisions also directly allocate and register names / addresses within these sub-domains, where appropriate or required.

Furthermore, the ATN provisions delegate full or partial responsibility for certain sub-domains (i.e. certain address fields) to organisations other than ICAO, such as IATA, regional ATS organisations and national civil aviation authorities.

I.4.2 ATN Network Addresses An ATN network service access point (NSAP) address is a 20-octet string used to uniquely identify and locate a given NSAP (i.e. a network service user) within the context of the ATN. The ATN NSAP address format (illustrated in Figure I-1) starts with the Initial Domain Part (IDP), which comprises the Authority Format Identifier (AFI) and Initial Domain Identifier (IDI) fields, and is followed by the Domain Specific Part (DSP).




ATN NSAPAddress Format

AddressAdministrationAnd Assignmentby:

IDIAFI

AFI IDI DSP

Area Address System ID SEL

SYS SELVER ADM RDF ARS LOC

ISO 8348 NSAP Address Format

ISO/IEC 10589 NSAPAddress Interpretation

IDP

Domain Address (11 bytes)

Area Address (13 bytes)

ISO ICAO ICAOIATA

ICAOICAO Region Authorities

State AuthoritiesAeronautical Industry Authorities

Figure I-1. ATN NSAP Address Format

The (decimal) IDP value 470027 forms the common, initial part of all ATN NSAP addresses and network entity titles (NETs). This address prefix defines the ATN Network Addressing Domain as a sub-domain of the Global OSI Network Addressing Domain, under addressing authority of ICAO and using a binary format for the DSP.

The DSP of the ATN NSAP address format is structured into seven individual address fields, which allows a hierarchical approach to co-ordination of the allocation of ATN addresses.

The Table below summarises the rules for the allocation of values to the different NSAP fields, depending on the ICAO subordinate addressing domain to which the addressed element belongs.




Table I-1. Allocation of Values to NSAP Fields

Domain Field

ATSC-fixed ATSC-mobile AINSC-fixed AINSC-mobile

AFI 47 47 47 47 IDI 0027 0027 0027 0027

VER 81 C1 01 41 ADM The first octet

must be set to an ICAO Region identifier and the remainder is assigned by the region

The first octet must be set to an ICAO Region identifier and the remainder is assigned by the region

Registered with IATA by the identified organisation Should be derived from the IATA airline or aeronautical stakeholder designator

Registered with IATA by the identified organisation Should be derived from the IATA airline or aeronautical stakeholder designator

RDF 00 00 00 00 ARS Assigned by the

state/organisation identified by the ADM field

24-bit aircraft address

Assigned by the organisation identified by the ADM field

24-bit aircraft address

LOC Assigned by the addressing authority of the Routing Domain identified by the ARS field

SYS Assigned by the addressing authority of the Routing Area identified by the LOC field

SEL 00 for the NET of intermediate systems (IS) of Class 1,2,3,4,5 and 6 Hex FE for the NET of Class 7 IS Hex FF is reserved Any other value may be assigned to NSAPs

I.4.3 Transport Selector The ATN transport service access point (TSAP) Selector element (TSEL) locates the Transport service user within the ATN system. In ATN, session and presentation address selectors are not used, and the TSEL directly locates the ATN application within the ATN system.

The ATN TSEL is a one- or two-octet hexadecimal string. TSEL values have only a local scope and do not need global registration.

I.4.4 Application Types Application type values are assigned to ATN applications in document ICAO Doc 9705 [2] Sub-Volume IV (Editions 1 and 2).

The application type component of the ATN application entity title gives the nature of the application. Textual and numeric values are standardised by ICAO. Those relevant to the selected data link services are listed in Table I-2.




Table I-2. Assigned Application Type and Values

ATN ASE type ATN app-type name and numeric value

Context Management application CMA (1) Protected Mode CPDLC PMCPC (22)

I.5 ACARS / FANS-1/A Addressing Several addressing elements are required for ACARS message exchange. Over air-ground data links, ACARS messages contain some or all of the following addressing and message routing information:

• Aircraft Address (Aircraft Registration Number or Flight ID)

• ACARS Label and optional sub-label

• Flight Number

• Supplementary Address(es), including optional Message Function Identifier (MFI).

Over the ground-ground networks between ACSP and ANSP or Aircraft Operator, ACARS messages are addressed using 7-character IATA "Type B" addressee designators, according to the provisions of ARINC Specification 620 [49].

Each ANSP is connected to only one ACSP's ground network [ED-100A]. The 7-character address assignment of each ANSP is unique and must be configured in the networks of all ACSPs.

I.5.1 ARINC 618 Aircraft Addressing Messages are transferred over the air-ground data link in message blocks formatted according to the provisions of ARINC Specification 618. Each message block has a 14–octet heading field and a 4-octet suffix, including a 16-bit Block Check Sequence (BCS). Each octet in the message block, apart from the BCS, consists of a 7-bit IA5 character plus a parity bit. The fixed format of the heading field includes a 7-character Address field.

In downlink (air-to-ground) messages, the information in the Address field identifies the aircraft with which the ACSP's ground processor is communicating. The Address field contains the aircraft registration mark (Tail Number) only, as derived from the aircraft. The aircraft registration mark may be provided by physical wiring or supplied by an external avionics subsystem or entered by the aircrew, and is encoded using upper-case alphanumeric characters plus dash and dot characters. If the registration mark occupies less than 7 characters, it is right justified and filled with leading dot characters.

In uplink messages, ARINC 618 requires the avionics to compare the address of each incoming uplink block with the addresses of the aircraft to screen out messages destined for other aircraft. The avionics should be capable of recognising both the Aircraft Registration Mark and the Flight Identifier as valid addresses for the aircraft. The avionics should also accept squitter messages as having a valid address. Only if a valid address is recognised in an uplink message is the message block accepted for processing. The Aircraft Registration is the preferred address scheme, and must be used for all ATS messages.

I.5.2 ARINC 622 Supplementary Address ACARS downlink messages include a message sequence number (MSN) and Flight Identifier as the first two fields of the ARINC 618 Text field. For AOC messages, the 2-character Airline Identifier in the Flight Identifier is sufficient to identify the destination to




which the ACSP should route the message content (after converting it to ARINC 620 ground-ground format). For ATS messages, additional addressing is needed.

[ARINC 622] ATS messages consist of two main elements: the Supplementary Address field and the Application text field. Together, these form the "ACARS free text" field in the ARINC 618 message format.

For ATS messages, the Supplementary Address field contains the address of the ANSP system. It begins with a slash character and ends with a dot character (e.g. "/ABCD.").

For ATS downlink messages, the Supplementary Address field contains the ANSP address to which the ACSP should deliver the message. For some ATS applications, this may be entered by the pilot.

A Supplementary Address may be 4 or 7 characters in length. In the case of the 7-character format, the address information is copied by the ACSP, without any translation, from the ACARS downlink block to the address line of the ACARS ground-ground message. In the case of 3 or 4 character formats, a conversion table maintained by the ACSP is used to derive the associated 7-character address to be entered in the Destination Address of the ground-ground message.

[ED-100A] When a downlink message is received at the ACSP, it is routed to the unique address of the ANSP. The ACSP is required to use both of the following mechanisms to provide this routing:

• Mapping of the 4 character Supplementary Address to the corresponding 7-character IATA Type B address, and

• Use of the actual 7-character Supplementary Address in the downlink message.

Some uplink messages also permit the inclusion of a Supplementary Address field. If present in an uplink message, this field will contain the address of the source ground end-system to which the downlink response should be routed. For ATS messages, this will typically be that of the ATC facility that is responsible for the airspace in which the aircraft is located, or into which the aircraft is expected to travel.

I.5.3 Message Function Identifier [ARINC 620] A second addressing mechanism is defined in order to augment the routing of ATS messages originating from ACARS peripherals (e.g. FMS). The optional 2-character Message Function Identifier (MFI) field is used for this purpose. By including the MFI as the first element of the Supplementary Address field, it is possible for the ACSP to route messages from ATS applications in an ACARS peripheral to peer applications on the ground. The ACSP uses the MFI as an additional index into its lookup table in order to determine the ground address(es) of the ATS message.

For example, the Supplementary Address field in an air-ground downlink message originating from an avionics subsystem might appear as "/B1 LAX05xx."

I.6 Link 2000+ Naming and Addressing Plan The Naming and Addressing Plan (NAP) adopted by the Link 2000+ Programme was elaborated with the following assumptions:

• The NAP is strictly compliant with the ATN Technical Provisions (Doc 9705) [2], and augments the addressing rules by defining the naming and addressing elements more specific to the LINK 2000+ communications infrastructure.

• The proposed addressing scheme is derived from the ATN Compliant Communications European Strategy Study (ACCESS) and from lessons learnt




from PETAL II operations, and is an enlargement of the best practices used in the context of the PETAL II programme;

• The proposed naming and addressing scheme applies to the ATS communications fixed and mobile domains;

• The detailed network design and in particular, the routing topology is to be further defined;

• The names and addresses are hierarchically defined down to the point where information from the detailed network design is available;

The NAP is organised with two main parts; the naming and addressing plan of the ATN internet, and the naming and addressing plan of ATN upper layers and applications.

I.6.1 LINK 2000+ Naming and Addressing Requirements Airlines and ANSPs participating in LINK 2000+ are required to assign ATN application entity titles (AETs) and ATN addresses in accordance with the data link services they decide to support.

Table I-3 summarises for each data link service which AETs and addresses have to be defined.

Table I-3. LINK 2000+ ATN AE Titles and Addresses

Service Required AE title Required ATN address Remark

DLIC Air and ground CM AET Air and ground CM ATN address

CM link air initiated for logon and ground initiated for contact

ACM Air and ground PM CPDLC AET

Air PM CPDLC ATN address CPDLC link always ground-initiated

ACL Air and ground PM CPDLC AET

The CPDLC link is assumed to be already established

AMC Air and ground PM CPDLC AET

The CPDLC link is assumed to be already established

All air entities participating in LINK 2000+ shall be identified by a 24-bit aircraft address

All ground entities participating in LINK 2000+ shall be identified by an ICAO Facility Designator.

States participating in LINK 2000+ shall define the organisation of their ground space in terms of application addressing areas, or CM contexts. A "CM context" is the basic naming and addressing reporting unit to the aircraft: it identifies which ATN applications are available on the ground and the application protocol version operated. It may contain in addition the ATN application address, when used by the peer to establish a dialogue with this application. There should be a single CM application per CM context, responsible to send to peer systems the context through the CM-logon and CM-update data exchanges.

Although several CM contexts may in theory be supported in the aircraft, it is assumed that aircraft in LINK 2000+ will represent a single CM context.

Any aircraft entering the LINK 2000+ area or departing from an airport of the LINK 2000+ area will establish communication with the appropriate CM addressing server to initiate the data link capability with the ground.

ED-110A [3] requires ANSPs to publish rules applicable in their airspace to associate a CM address with an ATS ground facility for each provided application (e.g. in AIPs).

Aircraft operators should ensure that the addresses of the initial CM servers available in this area are previously loaded in the avionics system.




An ANSP can operate more than one CM server in its data link area. Each ANSP providing data link services via ATN must register at least one ATN address corresponding to a CM application operated in its data link domain. Each ANSP must clearly specify the procedure by which an aircraft identifies the appropriate CM server when entering the area of the ANSP.

These addresses could be published in ICAO Doc 9705 [2] Edition 3 - Sub-Volume IX: "ATN Identifier Registration" in section 9.3.1 "State Addresses". Because the ICAO publication process is long and not flexible, a European registration authority may be established to maintain this CM Address database and interface with ICAO when required.

The ANSP is responsible for providing the aircraft with the addressing information required to initiate the data link capability with the next ANSP along the flight path.

I.7 Conclusions To ensure global interoperability and seamless operation of the data link system, an overall name and address allocation plan is needed, together with mechanisms for disseminating this information.

For data link services using ATN, the naming and addressing plan adopted by the LINK 2000+ programme could be used as a model.

The nature of prescription will be to specify the obligations of different stakeholders with respect to assigning and managing elements of the global address space.

The regulatory coverage could specify the establishment and operation of a registration authority to maintain a register of European ANSP addresses. The nature of prescription would include a description of the way addresses would be allocated (similar to the intended approach for Mode S interrogator codes).

It is necessary to identify a clear way forward for 24-bit aircraft address handling. This should be consistent with related work being undertaken by EUROCONTROL. Possible outcomes could include actions towards ICAO to amend e.g. Doc 7030, which might be referred to in the implementing rule.




ANNEX I. NAMING, ADDRESSING AND REGISTRATION PLAN .......................I-1 I.1 Introduction ..........................................................................................................I-1 I.2 ICAO Provisions...................................................................................................I-1

I.2.1 Aircraft Address..........................................................................................I-1 I.2.2 Ground System Identification .....................................................................I-1

I.3 Mandating 24-bit Aircraft Address in the FPL ......................................................I-1 I.3.1 ICAO and LINK 2000+ Requirements ........................................................I-1 I.3.2 Impact on Civil Aircraft Operators ..............................................................I-2 I.3.3 Impact on Military Aircraft Operators..........................................................I-2 I.3.4 Impact on Civil and Military ANSPs and Airport Operators ........................I-3

I.4 ATN Addressing...................................................................................................I-3 I.4.1 General Principles......................................................................................I-3 I.4.2 ATN Network Addresses............................................................................I-3 I.4.3 Transport Selector......................................................................................I-5 I.4.4 Application Types.......................................................................................I-5

I.5 ACARS / FANS-1/A Addressing ..........................................................................I-6 I.5.1 ARINC 618 Aircraft Addressing..................................................................I-6 I.5.2 ARINC 622 Supplementary Address..........................................................I-6 I.5.3 Message Function Identifier .......................................................................I-7

I.6 Link 2000+ Naming and Addressing Plan............................................................I-7 I.6.1 LINK 2000+ Naming and Addressing Requirements .................................I-8

I.7 Conclusions .........................................................................................................I-9




ANNEX J. DETERMINATION OF DATA LINK AIRSPACE

J.1 Introduction

To ensure the coordinated introduction of seamless data link services in the EATMN, the airspace for the provision and use of data link services must be addressed by the implementing rule.

The objective of this Annex is to analyse the factors relevant to the determination of the applicable airspace for the data link services.

The European airspace where ATS is provided is typically designated by the following terms:

a) Flight Information Regions (FIRs) - airspace of defined dimensions within which a Flight Information Centre provides flight information service and alerting service.

b) Control Areas (CTA) established so that they cover that airspace which will encompass the flight paths of those instrument flight rules (IFR) flights within an FIR to which it is believed necessary to provide ATC. CTAs are formed by:

• Terminal management areas (TMAs) - control areas normally established at the confluence of ATS routes in the vicinity of one or more major aerodromes, within which approach control service is provided by an approach control unit (APP).

• Area-type control areas where specific ATS routes have been defined for the purpose of flight planning and which provide for the organisation of an orderly traffic flow; In these areas, area control service is provided by area control centres (ACC).

c) Control Zone; a controlled airspace extending upwards from the surface of the earth to a specified upper limit, within which aerodrome control service is provided by aerodrome control tower (TWR).

FIRs normally encompass the entire airspace over the territory of a State. Adjacent FIRs should be contiguous and, if possible, be delineated so that operational considerations regarding the route structure encompassed by them take precedence over their alignment along national borders

In certain areas, FIRs and CTAs are divided so that an upper and a lower airspace are provided. When this is done, an FIR and/or CTA in the upper airspace may laterally encompass the areas of more than one lower FIR or CTA.

Control zones are normally kept as small as possible, consistent with the need to accommodate the flight paths of controlled IFR flights between the lower limits of a CTA and the aerodrome for which the control zone is established.

J.2 Communication

Communications are a vital part of the provision of ATS and their timely and dependable availability have a most significant bearing on the quality of the service provided by ATS.

The primary means of air-ground communication used by controllers for providing ATS in European airspace today is voice communication (R/T) by VHF radio. Voice communication is particularly suited where a rapid-exchange, short-transaction communication style is required.

Annex J Determination of Data Link Airspace 1.1.doc 24/05/2006 Page J-1



Voice communication has become the limit to attached sector capacity in many European ACC sectors today. This is one of the key motivating drivers for the introduction of ATS supported by data link communications (data link).

Voice and data link will co-exist as a means of ATS communication. Implementation of CPDLC in European continental airspace is intended as a supplementary means of communication to the use of voice communication.

CPDLC will only be used in the context of non-time-critical communications. Time-criticality is determined by the following factors: ATC traffic situation, end-to-end performance (systems and flight crew/controller response time) and recovery time.

It is generally accepted that the approach control service requires more rapid exchanges between controllers and pilots, compared with area and aerodrome service, thus would make CPDLC less used in these areas/phase of flight.

For the purpose of this analysis, it is assumed that the overall beneficial and cost-efficient nature of data link as a capacity enabler has been amply demonstrated and the task is only to provide criteria for selecting the airspace where these benefits and cost efficiencies can in fact be substantiated.

The data link services in LINK 2000+ provide their benefits via a controller workload reduction mechanism.

• A substantial part of the workload associated with routine communications is eliminated, freeing up the controller for other tasks.

• Another benefit mechanism enables the sector suite team to organise their work more efficiently, whereby not only the radar controller may communicate with the aircraft.

Both of the above benefit mechanisms result in a reduction in communication workload. This is a very important consideration, since it highlights the fact that the benefits of data link usage are dependant primarily on the communications workload and not the absolute number of aircraft handled by a sector.

ATC sectors handling a lot of air traffic in vertical evolution, or being relevant to each other in other ways, will tend to have the highest loading on the voice channel. In many cases, the constraints posed by the sequential nature of traditional VHF voice communications will become the major capacity issue. Very often, this constraint will act much sooner than other capacity constraints that the sector may have. Introducing the alternative communications afforded by data link, the constraint related to communications can be eliminated, i.e. the full benefits of data link can be realised.

J.3 Traffic Load and Capacity Requirements

The PRC PRR8 report [79] indicates that significant air traffic growth is forecast in the medium term, with an average annual growth in IFR movements for the period 2005-2011 of 3.7% (en-route traffic). The same report also clearly states that in parts of the European core area the sector throughput is already high and, more important, that the sectors are getting close to the smallest efficient size. This means that in such areas the traditional techniques of increasing capacity, e.g. splitting sectors, no longer provide the same efficiency as they used to. The report calls for resolute action so that effective capacity continues to meet rapidly growing demand in a cost-effective way.

Air-ground data link will reduce the controller’s and the pilot’s workload through a decrease in R/T workload. Simulations by LINK 2000+ have shown the following predicted increases in sector capacity, as a function of aircraft equipage:

3.4% for 25% data-link equipage;






As data link services are expected to decrease controller workload and increase the overall ATM capacity, ATM delays and thus operating flight costs would be reduced significantly.

J.4 Business Case

As air-ground data link implementation requires investments in both ground and airborne systems, implementation of such functionality will need to be supported by a robust business case.

From the perspective of the LINK 2000+ Programme, all cost/benefit analyses carried out to date show a compelling case, for both ANSPs and airlines, to implement CPDLC data link services as a very cost effective capacity enabler. Taking into account the fact the analyses have all been based on very conservative assumptions and included increasingly refined and accurate input data, the results can lead to only one recommendation, namely to continue and if possible, to accelerate the implementation of CPDLC, as this will increase the overall benefit.

J.5 LINK 2000+ Airspace

The airspace covered by ANSPs participating in the EUROCONTROL LINK 2000+ Programme serves as an example of what can be achieved on a voluntary basis by ANSPs, via an ongoing pioneer and incentives programme.

Extensive consultations and coordination with EUROCONTROL stakeholders has resulted in the definition of the airspace where the initial implementation of data link services in the scope of the LINK 2000+ Programme will take place. This airspace is defined as being the airspace above Flight Level (FL) 285 in the following Flight Information Regions (FIR) and Upper Flight Information Regions (UIR): - Wien FIR - Brussels UIR - France UIR - Hannover UIR - Rhein UIR - Roma UIR - Milano UIR - Lisboa UIR - Barcelona UIR - Madrid UIR - Amsterdam FIR - Swiss UIR.

The geographical scope considered for the LINK 2000+ cost/benefit analyses (mentioned above) coincides with the airspace defined above, plus the UK and Canarias FIRs. This airspace is called for simplicity "LINK Airspace".

The States/ANSPs providing ATS service in the LINK Airspace have also indicated their plans for implementation of the ECIP ATC06 Objective – "Implement ATC Air-Ground Data Link Services – implement the first set of non-time critical ATS air-ground data link services."




J.6 Stepped / Incremental Implementation

The LINK Airspace as defined above is in line with the ATM Strategy 2000+ [7] Uniformity Objective – “To ensure that ATM operations are compliant with ICAO CNS/ATM plans and global interoperability requirements, provide a seamless service to the user at all times throughout Europe.”

It is unrealistic to believe that all the ANSPs will be ready in the same time, e.g. a “big-bang” scenario when data link communications are started simultaneously, therefore a stepped/incremental deployment should be considered.

Maastricht UAC is the only centre that presently has in operational use the selected data link services. An incremental deployment could foresee a first phase catering for an increased continuous area of data link services, and a second phase when the remaining centres complete deployment.

J.7 Conclusions

To ensure the coordinated introduction of seamless data link services in the EATMN, the airspace for the provision and use of data link services must be addressed by the implementing rule.

The applicable airspace must be contiguous, to ensure seamless operations.

Existing ATM systems throughout Europe are at different uncoordinated stages in their operational and investment lifecycles. Therefore the impact of introducing data link services will vary widely between European ANSPs. This will reflect in the degree of willingness of different ANSPs to deploy data link services in their areas of responsibility.

The regulatory provisions should build upon the considerable achievements of the EUROCONTROL LINK 2000+ Programme in establishing with ANSPs a target area of contiguous data link airspace in core Europe.

It may be possible to define criteria for selecting a particular airspace area in terms of traffic density/complexity or ATC communications loading, for example. This could be used to determine the optimal area of coverage.

The data link equipage requirements will apply to all of the EATMN FIRs and UIRs. There will be a coordinated transition to this end-state by a phased expansion of contiguous airspace areas (refer to section 6.2 of the Regulatory Approach).




ANNEX J. DETERMINATION OF DATA LINK AIRSPACE...................................J-1 J.1 Introduction .........................................................................................................J-1 J.2 Communication...................................................................................................J-1 J.3 Traffic Load and Capacity Requirements............................................................J-2 J.4 Business Case....................................................................................................J-3 J.5 LINK 2000+ Airspace..........................................................................................J-3 J.6 Stepped / Incremental Implementation ...............................................................J-4 J.7 Conclusions ........................................................................................................J-4




ANNEX K. ATC PROCEDURES FOR USING DATA LINK SERVICES

K.1 Introduction The purpose of the analysis in this Annex is to highlight the supporting guidance material that exists for the implementation of harmonised ATC procedures based on the data link services selected for the implementing rule.

K.2 ATC Procedures for CPDLC Procedures for Air Navigation Services (PANS) defined in ICAO Doc 4444 (PANS-ATM) [23] are approved by the ICAO Council and recommended to contracting States for worldwide implementation. They are supplemented when necessary by regional procedures defined in the Regional Supplementary Procedures. The implementation of procedures is the responsibility of contracting States. They are applied in actual operations after States have enforced them.

The definition of a common set of ATC procedures for the use of CPDLC in the EUR Region is instrumental to ensure the interoperability of ATS supported by data link communications. The use of ATC procedures defined in ICAO Doc 4444 [23], complemented by specific provisions defined in the ATC Data Link Manual (ICAO Doc 9694) [22] will be required. The complementary part will be included in the EUR Supplementary Procedures Doc 7030.

The implementation of harmonised ATC procedures for CPDLC in the EUR region can be obtained by enforcing:

• The basic principles of operations for the use of CPDLC.

• The application of ATC procedures for CPDLC defined in ICAO documents Doc 4444 and Doc 7030.

K.3 LINK 2000+ Procedures The EUROCONTROL LINK 2000+ Programme has produced an ATC manual [14] for the supported CM and CPDLC data link services (ACM, ACL, AMC and DLIC), which collects all the procedures that can be found in ICAO Doc. 4444 [23] and ICAO Annex 10 – Aeronautical Communications, Volume 2 – Communication Procedures, including those with PANS status [87]. It provides traceability to the source of each of the procedures identified.

In some cases, the necessary procedures have not yet been formalised internationally. These are indicated in the LINK 2000+ ATC manual as

• "NEW" for those procedures developed specifically for LINK 2000+ implementation in Maastricht UAC

• "OPLINK Proposal" for those procedures proposed within the ICAO operational data link panel

• "Proposal contemplated by OPLINK" for possible procedures to be progressed by the ICAO OPLINK Panel working groups.

Note that some of the procedures are already implemented through the EUROCAE ED-110A Interoperability standard [3] (e.g. ‘When CPDLC is transferred, the transfer of voice communications and CPDLC shall commence concurrently’).

ICAO procedures are globally applicable; their implementation ensures a harmonised and seamless service as aircraft move from one ATS Unit to another.

Annex K ATC procedures for using DLS 1.1.doc 24/05/2006 Page K-1



K.4 Conclusions ATC procedures are a subject for prescription in the implementing rule.

To determine the nature of prescriptions:

1. An analysis should be undertaken to identify those procedures that must be made mandatory for the purpose of interoperability, and those that can be left voluntary.

2. A practical approach for prescription of mandatory elements should be defined. Several options are possible in principle:

a) Inclusion of the full text in the implementing rule,

b) Reference to existing recognised documents (e.g. ICAO PANS-ATM or Doc 7030)

c) Reference to a EUROCONTROL Specification, which would be developed for that purpose, and which would be made mandatory through the implementing rule.

3. Voluntary elements could be addressed e.g. by development of a Community specification by EUROCONTROL.

Additional ATC procedures found necessary in deploying the LINK 2000+ services may in any case be subjects for the regulatory coverage.

ANSPs implementing data link services should provide evidence of implementation of respective ATC procedures covering as a minimum:

• Construction of CPDLC messages,

• Responding to CPDLC messages,

• Reverting from CPDLC to Voice communications (including the ATC Phraseologies Related to the Use of CPDLC),

• Synchronisation of the CPDLC dialogue when reverting to voice communications,

• Use of CPDLC in the event of Voice Radio Communication Failure,

• Transfer of CPDLC,

• Intentional Shutdown and Testing of CPDLC,

• Failure of CPDLC Equipment




ANNEX K. ATC PROCEDURES FOR USING DATA LINK SERVICES ............... K-1 K.1 Introduction ........................................................................................................ K-1 K.2 ATC Procedures for CPDLC.............................................................................. K-1 K.3 LINK 2000+ Procedures .................................................................................... K-1 K.4 Conclusions ....................................................................................................... K-2




ANNEX L. EQUIPAGE, CERTIFICATION AND APPROVAL

L.1 Introduction

The purpose of this Annex is to analyse the interoperability issues arising from the equipage, certification and approval of aircraft and ground systems, and to determine the consequences for the regulatory coverage.

One key objective of the implementing rule should be to encourage FANS/ATN convergence.

In the past the worldwide interoperability of aircraft communications, navigation and surveillance (CNS) systems was relatively easy to ensure. Both the ground and airborne elements of NDB, VOR and ILS, for example, were standardised (with notable differences in respect of ILS in the Soviet Union) and once 25 kHz VHF channel spacing spread worldwide, standard VHF communications was also assured where needed. Primary radar had never posed a compatibility issue and even initial SSR was sufficiently standardised not to create any problem anywhere in the world.

The situation was different, however, when Europe opted to implement an 8.33 kHz VHF voice channel spacing, and SSR Mode S was developed. Aircraft flying in or into Europe had to be fitted with 8.33 kHz capable radios and some of the communications procedures had to be amended. Due to some initial uncertainties around the Mode S standards, not all Mode S transponders met the requirements. With the introduction of RVSM in Europe, the original basic worldwide compatibility of the average aircraft had to be re-evaluated even more fundamentally. RNP also has a similar effect.

What is common in the above changes in required capability is that they did not directly impact the work of the controllers and pilots. Maintaining a cleared level is the same task irrespective of the vertical distance between the Flight Levels. Tuning a radio with 8.33 kHz capability does need some knowledge of the peculiarities of the channel spacing system, but otherwise is no different from what a pilot does in a 25 kHz environment. The need to indicate the respective capabilities in the flight plan was not anything radically new either.

The above changes did require that the aircraft flying into Europe, for instance, meet specific requirements that were different from those imposed upon an aircraft that would never leave Africa. But for the pilots and air traffic controllers the changes, after the introductory period, were all but invisible.

The airborne and ground systems communicate in both directions and the systems must be fully compatible on all levels (hardware, applications, procedures). It is not acceptable operationally to force pilots to follow different procedures and communicate differently depending on the country or region they happen to be flying in.

Historically, the idea of reducing communications congestion and the resulting limits on capacity arose at about the same time in the United States and Europe. However, the European continental trials program proceeded substantially faster and Europe has maintained its edge in VDL-2/ATN based air-ground data link development and implementation. In spite of the different pace of development, the US and European programmes have always been closely aligned to ensure that no divergence or incompatible developments take place.

This does not mean that the use of air-ground data link applications is identical in Europe and the US. Some messages are used only in Europe, for instance. But the content of the messages used and the associated procedures are aligned and coordinated so that the few differences do not constitute an operational issue of any kind.

Annex L Equipage Certification Approval 1.1.doc 24/05/2006 Page L-1



These developments in the US and Europe have resulted in the corresponding standards and procedures becoming the worldwide standard, to be used without changes in other regions where ATN based air-ground data link services are introduced.

L.2 Criteria for Mandatory Equipage of Aircraft and ACCs

L.2.1 Criteria for Aircraft The goal is to provide criteria to select aircraft categories to be equipped with data link capability. Possible criteria include:

• All IFR/GAT flights in the defined airspace,

• Number of seats / cargo capacity,

• Take-off mass

• Aircraft type

• Engine class (e.g. jet, turboprop, etc).

Other criteria applicable to individual aircraft might be considered such as flight-hours spent by an aircraft in the data link airspace during the last x months.

The goal is to provide a rationale addressing permanent exemptions (e.g. State aircraft, old aircraft, etc.), and temporary exemptions granted on the basis of case-by-case requests. These exemptions should be consistent with the minimum equipment list (MEL) policy applicable to data link equipment.

The data link subsystems subject to mandatory equipage will include:

• Digital radio(s) with approved antenna(e)

• Communications Management Unit (CMU – ARINC 758-2) or equivalent

• Communications software (ATN airborne router)

• Data link applications software

• Aircrew HMI (display, alerting device, input device, hardcopy, etc.).

Certain critical software elements will have to be developed to specified assurance levels, in compliance with ESARR 6 [44] requirements, and certified by the relevant airworthiness authority.

The implementing rule can be considered in 2 parts:

• Mandatory carriage of VDL-2 radio equipment

• Mandatory carriage of specified data link applications.

It is likely that many aircraft operators will be equipping with VDL-2 anyway for their AOC/ACARS over AVLC (AOA) communications.

The impact of equipping with VDL radios will be comparable to the impact of equipping with new radios for 8.33 kHz voice channel spacing. It is therefore likely that many State aircraft will be unable to equip.

The introduction of air-ground data link services is taking place at a time when aircraft operators are cost conscious as perhaps never before, and investments are limited to systems with potential for positive returns. Air-ground data link is seen as such a system. However while it is cost-efficient, it is not necessarily cheap to start with. The industry will not accept any additional cost that may result from diverging and/or incompatible systems developed on a regional basis.




L.2.2 Comparison with Other Areas of Mandatory Equipage The following table lists some other programmes that have had to consider criteria for mandatory equipage. The objective is to profit from the lessons learnt and to work towards a harmonised approach, in an attempt to minimise the number of equipage permutations in the various applicable airspace areas.

Table L-1. Comparison with Other Areas Involving Equipage Requirements

Programme Nature of Requirement LINK 2000+ preliminary draft rule

Operators of aircraft with a certificated maximum take-off mass (MTOM) in excess of 19,800 kg and less than 180,000 kg, and operating Instrumental Flight Rules (IFR) flights as General Air Traffic (GAT) in the defined airspace. Excluding: a) Aircraft using FANS 1/A functionality where the operator intends to operate those aircraft in airspace controlled by ANSPs utilising FANS 1/A systems and capabilities, and provided that those ANSPs accept the use of that equipment by that aircraft operator (to be reviewed annually); b) State aircraft; c) Aircraft that will cease operating within the defined airspace before [Date] or with an out of service date before [Date].

8.33 kHz VHF channel spacing

Mandatory carriage of 8.33 kHz equipment came into effect above FL 245 for the whole of the ICAO EUR Region on 07/10/99. State aircraft not equipped with an 8.33 kHz capable radio may operate in the designated airspace provided that they are UHF equipped and they are infrequent users (not exceeding 30 hours flying time as GAT per airframe per annum) of that airspace. (This policy is currently under review) Some aircraft types have ceiling levels that are at or around FL 250. Some aircraft operators elect to fly below FL 245 to avoid the need for 8.33 kHz retrofit. These aircraft operators may find that additional fuel costs and a lack of operational flexibility (e.g. avoiding weather problems) mean that it is not attractive to fly below FL 195 after 8.33 kHz vertical expansion. However, some may be forced to consider this possibility due to the costs of retrofitting and shortage of flight deck panel space for installation of equipment.




Programme Nature of Requirement Mode S elementary surveillance (ELS)

For aircraft flying IFR/GAT, latest dates for the carriage and operation of Mode S elementary surveillance airborne equipment in designated airspaces are: - New production aircraft to be compliant by 31/03/04 - Completion of aircraft retrofits by 31/03/05 (partial alleviation if EHS equipment being fitted) For aircraft flying VFR, latest dates for the carriage and operation of Mode S elementary surveillance airborne equipment in designated airspaces are: - New production aircraft to be compliant by 31/03/05 - Completion of aircraft retrofits by 31/03/08 (subject to individual State agreements) Exemptions apply for: - Aircraft with an out of service date before 31/12/07 - Aircraft conducting flights, under existing rules, for the purpose of flight testing, delivery and for transit into and out of maintenance bases - Aircraft that intend to conduct only occasional IFR/GAT flights (under 30 hours per annum)

Mode S enhanced surveillance (EHS)

Some States mandate the carriage and operations of Mode S EHS airborne equipment. Applicable to all aircraft flying in designated airspace as IFR/GAT with a maximum take-off mass exceeding 5,700 kg or a maximum cruising true airspeed in excess of 250 knots, with effect from 31/03/05. A transition period applies until 30/03/07, during which a coordinated exemption policy applies through the EUROCONTROL Mode S exemption coordination cell.

Reduced Vertical Separation Minima (RVSM)

RVSM applies in the volume of airspace between FL 290 and FL 410 inclusive in the designated flight information regions/upper flight information regions (FIRs/UIRs). State aircraft have an exemption to the RVSM compliance rule. Such aircraft may use RVSM airspace. To accommodate them, air traffic controllers provide these aircraft with 2000 ft vertical separation from other RVSM approved flights instead of the normal 1000 ft separation between RVSM approved flights.

ACAS II Phase 2 mandate in Europe

1 January 2005: all civil fixed-wing turbine aircraft having a maximum take-off mass exceeding 5,700 kg, or a maximum approved passenger seating configuration of more than 19 seats must be equipped with ACAS II.

The LINK 2000+ preliminary draft rule referred to in Table L-1 also proposed a policy of exemptions to the application of the implementing rule on the basis of the following criteria:

a) To aircraft operators for aircraft operating under existing rules for flights conducted for the purpose of flight testing, delivery and for transit into and out of maintenance bases;

b) To aircraft operators that have undertaken in a timely manner the required steps to meet the requirements of the implementing rule but experience technical issues or supply problems beyond their control. Aircraft operators would be required to substantiate any request for exemption.

Operators of aircraft equipped with data link systems that become unserviceable may be granted a temporary exemption for a specific aircraft for a period of up to x days from the




date of commencement of the unserviceability. This will probably be covered by the MEL rules / requirements rather than the exemption arrangements.

L.2.3 Impact of FANS-1/A Equipage As noted for the LINK 2000+ Programme in Table L-1, there was originally a proposal to exclude aircraft using FANS-1/A equivalent functionality from the scope of the regulatory coverage, provided the operator intends to operate those aircraft in airspace controlled by ANSPs utilising FANS-1/A systems and capabilities, and provided that those ANSPs accept the use of that equipment by that aircraft operator.

A large number of (mainly long haul) aircraft are already equipped for FANS-1 (Boeing) or FANS-A (Airbus) operation using ACARS over VHF and satellite networks. ATM services using these and equivalent systems are increasingly being offered in certain regions worldwide.

EUROCAE ED-100A [12] specifies interoperability requirements for ATS applications that use ARINC 622 data communications, including FANS-CPDLC. Based on ED-120 [4] safety requirements, it was concluded that a "latency timer" to detect expired messages would need to be added to existing implementations in order to allow the use of the ACL service without voice read-back. This is included in ED-100A and is becoming implemented in aircraft systems, though is not a mandatory retrofit.

RTCA SC-189/EUROCAE WG-53 has a work programme that includes the development of a FANS-1/A-ATN interoperability standard:

• For using a mixture of data link technologies in the provision and use of ATS data link services

• To support the goal of converging oceanic and continental data link applications.

In general, FANS-1/A equipment was not originally designed to the same assurance levels now required for data link equipment (see L.3.3 below), so there may be safety case issues. The provisions of ESARR 6 "Software in ATM Systems" [44] are relevant here.

L.2.4 Criteria for ACCs All Area Control Centres with responsibilities for the identified airspace will be required to equip with data link ground end system functionality. This includes:

• Data link end system, with identified ground data link applications

• Data link capable controller working positions (CWPs)

• Communication interface to ground data link infrastructure (e.g. connection to ATN ground router, with logical connectivity to ATN air-ground router and VHF subnetwork)

Ground system software should be developed to appropriate assurance levels, and the system approved by an appropriate authority.

Operational procedures and controller training programmes will need to be established. ESARR 5 [46] regarding controller training is applicable.

For ATC centres that will accommodate ED-100A FANS-1/A aircraft, "dual stack" implementation and operation will be necessary. The technical differences between the data link services deployed over ATN and the FANS-CPDLC application should be hidden as far as possible from the controllers, to avoid the need for different operational procedures depending upon aircraft equipage.




L.3 Airworthiness Certification and Operational Approval

L.3.1 General The certification and operational approval process and conditions have been developed to ensure the continued total interoperability already achieved. This is one of the most significant achievements of the air-ground data link development in recent years and is one of the key contributions to keeping the corresponding business case solid and attractive to aircraft operators.

The Regulation (EC) 1702/2003 [91] lays down implementing rules for the airworthiness and environmental certification of aircraft and related products, parts and appliances, as well as for the certification of design and production organisations.

EASA certification specifications include airworthiness codes (technical interpretation of the airworthiness essential requirements) and acceptable means of compliance (AMC). Compliance with a published AMC (AMC-20, Acceptable means of compliance for airworthiness products, parts and appliances) will give presumption of compliance with the related specification. A drafting group has been tasked with the definition of the acceptable means of compliance for aircraft type design approval and operational approval for the use of air traffic services supported by data communications in accordance with the terms of reference, TOR: AMC-20/007. This means of compliance should be based on the advisory materials drafted by the CNS/ATM steering group.

AMC-20 will not mandate the equipage of aircraft with data link capability. AMC-20 defines a means of compliance for aircraft type design approval and operational approval. The interoperability implementing rule will mandate the equipage of specific aircraft categories with data link capability. For those aircraft, airworthiness certification and operational approval can (should) be carried out by applying materials published in AMC-20. The AMC should address the same set of data link services as the implementing rule and make reference to the same technical standards. In due course, proper alignment should be ensured.

Notice of Proposed Amendment (NPA) No 11/2005 includes AMC 20-11 "Acceptable means of compliance for the approval of use of initial services for air-ground data link in continental airspace," with a closing date for comments of 16th January 2006. AMC 20-11 includes data link services DLIC, ACM, ACL, AMC, DCL, DSC and D-ATIS, compliant with EUROCAE ED-110A and ED-120.

L.3.2 Issues Related to Authority At the time of writing, an issue exists concerning the scope of the authority vested in JAA and EASA, regarding the approval for use of air-ground data link services in continental airspace. Definition of respective responsibilities is still in a transition period. For the initial phase of the EUROCONTROL LINK 2000+ programme, this problem of authority is being managed by close coordination between JAA, EASA and EUROCONTROL. This close coordination will be maintained throughout the development of the draft implementing rule.

A prerequisite for CAA operational approval is that NPA 20-11 [36] is adopted as a rule by EASA.

L.3.3 Software Assurance Requirements In order to mitigate some of the hazards identified in the SPR standards, it is necessary to identify the appropriate level of software design and implementation assurance allocated to the various elements of the end-to-end data link system.




The assurance levels now required for data link equipment are typically assessed according to DO-178B/ED-12B for avionics and ED-109/DO-2781 for ground systems. The provisions of ESARR 6 "Software in ATM Systems" are relevant here.

The software assurance level to which a given system must be built depends on the airspace in which it will be used and the SPR. For example, in the European airspace covered by LINK 2000+, the safety authority has ruled that in order to exchange profile-changing CPDLC messages, ground systems on which a safety requirement has been placed must be compliant with ED-109 AL4, while avionics must be compliant with DO-178B Level C (ED-109 AL3).

L.4 Conclusions

The definition of applicable aircraft categories for mandatory equipage to support the identified data link services should be a subject for the regulatory coverage.

The nature of prescription will be to specify the aircraft categories and ground ATM systems to which the provisions of the implementing rule will apply, together with relevant transition period(s).

Due account should be taken of previous work to achieve consensus in this difficult area.

Airworthiness certification and operational approval aspects are covered by existing regulations and procedures and are not subjects for prescription in the implementing rule.

The justification material associated with the draft implementing rule should address the advisory materials used for certification of airworthiness and operational approval:

• To verify the consistency between these advisory materials and the implementing rule

• To propose any required amendments to these advisory materials

• To propose a coordinated review process for the review of acceptable means of compliance (AMC) material relating to data link.

1 “Guidelines for Communication, Navigation, Surveillance, and Air Traffic Management (CNS/ATM) Systems Software Integrity Assurance”




ANNEX L. EQUIPAGE, CERTIFICATION AND APPROVAL ............................... L-1 L.1 Introduction .........................................................................................................L-1 L.2 Criteria for Mandatory Equipage of Aircraft and ACCs .......................................L-2

L.2.1 Criteria for Aircraft .....................................................................................L-2 L.2.2 Comparison with Other Areas of Mandatory Equipage.............................L-3 L.2.3 Impact of FANS-1/A Equipage ..................................................................L-5 L.2.4 Criteria for ACCs .......................................................................................L-5

L.3 Airworthiness Certification and Operational Approval.........................................L-6 L.3.1 General .....................................................................................................L-6 L.3.2 Issues Related to Authority .......................................................................L-6 L.3.3 Software Assurance Requirements...........................................................L-6

L.4 Conclusions ........................................................................................................L-7
