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EUROPEAN ORGANISATION FOR THE SAFETY OF AIR NAVIGATION

EUROCONTROL

EUROPEAN AIR TRAFFIC MANAGEMENT PROGRAMME

Aerospace Electronic Systems

VDL Mode 4 Airborne Architecture Study

(VM4AAS)

Deliverable D1:

Definitions, Assumptions and Baselines

Edition draft : VM4AAS-D1_V1.0 Edition Date : 20 October 2003 Status : Proposed Issue Intended for : EATMP Stakeholders

VDL Mode Airborne Architecture Study

Page ii Proposed Issue Edition Number: VM4AAS-D1_V1.0

DOCUMENT CHARACTERISTICS

TITLE

VM4AAS-D1: Definitions, Assumptions and Baselines

EATMP Infocentre Reference:

Document Identifier Edition Number: VM4AAS-D1_V1.0 Edition Date: 20 October 2003

Abstract This document is intended to promote the visibility of the assumptions and baselines that form the foundation of the VDL Mode 4 Architecture Study early in the study process. This document does not, in itself, contain any study conclusions. Stakeholder comments are welcome.

Keywords VDL Mode 4 Avionics Architecture

Contact Person(s) Tel Unit Nikos FISTAS + 32 2 7294777 DAS/CSM

STATUS, AUDIENCE AND ACCESSIBILITY Status Intended for Accessible via

Working Draft � General Public � Intranet � Draft � EATMP Stakeholders � Extranet � Proposed Issue � Restricted Audience � Internet (www.eurocontrol.int/vdl4) � Released Issue � Printed & electronic copies of the document can be obtained from

the EATMP Infocentre (see page iii)

ELECTRONIC SOURCE Path: http://www.eurocontrol.int/vdl4/library.html: VM4AAS Deliverable D1

Host System Software Size Windows_NT


Edition Number: VM4AAS-D1_V1.0 Proposed Issue Page iii

EATMP Infocentre EUROCONTROL Headquarters 96 Rue de la Fusée B-1130 BRUSSELS Tel: +32 (0)2 729 51 51 Fax: +32 (0)2 729 99 84 E-mail: [email protected] Open on 08:00 - 15:00 UTC from Monday to Thursday, incl.

© European Organisation for the Safety of Air Navigation (EUROCONTROL) 2003 This document is published by EUROCONTROL in the interests of exchange of information. It may be copied in whole or in part, providing that the copyright notice and disclaimer are included. The information contained in this document may not be modified without prior written permission from EUROCONTROL. EUROCONTROL makes no warranty, either implicit or express, for the information contained in this document, neither does it assume any legal liability or responsibility for the accuracy and completeness of this information.

DOCUMENT APPROVAL

The following table identifies all management authorities who have successively approved the present issue of this document.

AUTHORITY NAME AND SIGNATURE DATE

E. F. Charles Laberge

Honeywell

Christophe Hamel Honeywell

Nikos Fistas EUROCONTROL


Edition Number: VM4AAS-D1_V1.0 Proposed Issue Page iv

DOCUMENT CHANGE RECORD

The following table records the complete history of the successive editions of the present document.

EDITION NUMBER EDITION DATE INFOCENTRE REFERENCE REASON FOR CHANGE PAGES

AFFECTED

D1-3_V0.1 21 June 2002 Initial draft All

D1-3_V0.2 28 June 2002 Internal review All

D1-3_V0.3 11 July 2002 As modified during PM1, 11 July All

D1-3_V0.4 18 July 2002 With complete PM1 comments implemented All

D1-3_V0.5 8 August 2002 Final cleanup pending revisions necessary by WP3 (if any)

All

D1_V1.0 20 October 2003 Released version (editorial changes, renumbering and formatting)

All


Edition Number: VM4AAS-D1_V1.0 Proposed Issue Page 1

CONTENTS

DOCUMENT CHARACTERISTICS............................................................................ ii

DOCUMENT APPROVAL ......................................................................................... iii

DOCUMENT CHANGE RECORD ............................................................................. iv

EXECUTIVE SUMMARY ............................................................................................ 3

ACRONYMS............................................................................................................... 5

1. Introduction......................................................................................................... 7 1.1 Study Objectives....................................................................................................................... 7

1.2 Definition of Terms ................................................................................................................... 8

1.3 Assumptions, Baselines, and Classes ..................................................................................... 8

2. Reference documents ........................................................................................ 9

3. DEFINITION OF STUDY BASELINES................................................................. 9 3.1 Discussion of Assumptions .................................................................................................... 10

3.2 Underlying Assumptions for Operational Configurations ....................................................... 14

3.3 Definition of the Equipment Baselines ................................................................................... 14

3.3.1 Airframe Classes ............................................................................................................ 15

3.3.2 Definition of Surveillance Terms..................................................................................... 16

3.3.3 Equipment Baselines ...................................................................................................... 17

APPENDIX A: WORKING REFERENCE BIBLIOGRAPHY.................................... 21



(Intentionally left bank)



EXECUTIVE SUMMARY

As the VDL Mode 4 data link is expected to operate with other systems onboard an aircraft, it has to be shown that installation alongside these systems will not present any major problems. VDL4 is designed to support both communications data link (CDL) and surveillance data link (SDL) functions. The combination of these two functionalities may result in additional considerations.

EUROCONTROL commissioned the VDL Mode 4 Airborne Architecture Study to investigate feasible airborne architectures taking into account the constraints and identifying any potential issues. The purpose was not necessarily to identify the "optimum" airborne architecture for a specific implementation, as this is seen as a manufacturer's responsibility. The target implementation date for the architecture is the 2008 - 2015 timeframe.

The study examines feasible airborne architectures for each of three implementation options: 1) VDL Mode 4 for both communications and surveillance applications; 2) VDL Mode 4 for surveillance applications only; and, 3) VDL Mode 4 for communications applications only.

In addition, the study examines the constraints of, and the impact on different types of aircraft. One of the major aspects of the feasibility of the architecture is the investigation about potential interference between VDL Mode 4 and other systems onboard the aircraft and in particular, with other systems operating in the VHF band.

The work of the study is organized in four major work packages. Work Package 1 lays the groundwork for the study in the form of establishing a reference list and a series of baseline equipment configurations against which installation of VDL Mode 4 capability can be evaluated. Work Package 2 identifies the requirements of the applications intended to be used with VDL Mode 4 and the requirements of the architecture which will support these applications. Work Package 3 uses the requirements identified in Work Package 2 to define one airborne architecture for each of the implementation options. Finally, Work Package 4 describes how the possible architecture definitions could be implemented.

This document is intended as the interim report on Work Package 1, tasks WP1.2 (Reference List) and WP1.3 (Baseline Configurations). The report on task WP1.1 (Program Management Plan) is contained in a separate document. This document is "interim" in nature not due to lack of effort or incompleteness in its preparation, but due to the realisation that certain assumptions may prove unworkable and certain reference information may need updating in the course of the study.

This report provides a reference list of documents relative to various aspects of the VDL Mode 4 Architecture study. These documents are grouped by their applicability to the study. This report provides 16 core assumptions on which the study can build. These assumptions are explicitly listed so that they can obtain the visibility and review by various stakeholders necessary for a complete and accurate study. Finally, this report provides detailed tables defining the equipment for four classes of aircraft under the different communications and surveillance baselines, This document is intended to promote the visibility of the assumptions and baselines early in the



study process. This document does not, in itself, contain any study conclusions.

The VDL Mode 4 Airborne Architecture Study is being performed for EUROCONTROL by technical experts at multiple business units of Honeywell International.

The draft deliverables of this study have been circulated within an extensive review group of interested parties. The released versions of the deliverables have considered the comments received during the review process. EUROCONTROL acknowledges the input received by the organizations that participated in the review process. Participation in the review process does not necessarily mean approval of the study conclusions as the final responsibility of the study conclusions remains with Honeywell and EUROCONTROL. For this deliverable (D1), comments were received from BA, BOEING, CNS Systems, LFV and Rockwell-Collins. EUROCONTROL acknowledges and thanks the individuals and the organizations for their input.

The EUROCONTROL VDL Mode 4 web page, which may be found at:

http://www.eurocontrol.int/vdl4/architecture.html,

provides information on the study. The VM4AAS deliverables (D1, D2, D3.1, D3.2, D4 and D5), as well as the comments received and their resolution, can be found through links at this site.

IMPORTANT NOTE

This deliverable should be read in connection with Deliverable D5 of the final released version of the overall VM4AAS deliverables. Deliverable D5 summarises the outcome of the VM4AAS study. Therefore, this deliverable is Attachment 1 of Deliverable D5. Any changes (other than editorial and formatting) in this deliverable, following the first release (version 0.5, August 2002) are reflected in the main body of Deliverable D5.



ACRONYMS

ACARS Aircraft Communication And Reporting System ACAS Airborne Collision Avoidance System ADAP Automated Downlink of Airborne Parameters ADS Automatic Dependent Surveillance ADS-B ADS Broadcast ADS-C ADS Contract AIRSAW Airborne Situation(al) Awareness AOA ACARS over AVLC ASAS Airborne Separation Assurance System AT Air Transport class of aircraft ATM Air Traffic Management ATN Aeronautical Telecommunications Network ATS Air Traffic Services ATSAW Air Traffic Situation(al) Awareness AVLC Aviation Link Control (protocol) CDTI Cockpit Display of Traffic Information CNS/ ATM Communications, Navigation, Surveillance/ Air Traffic

Management COOPATS Co-operative ATS (Concept) CPDLC Controller/ Pilot Data Link Communications (Services) DSB-AM Double Sideband Amplitude Modulation FAA Federal Aviation Administration (United States) GBAS Ground Based Augmentation System (augmentation of GNSS) GNSS Global Navigation Satellite System ICAO International Civil Aviation Organisation ILS Instrument Landing System NASA National Aeronautics and Space Administration (United States) ORD Operational Requirements Document POA "Plain Old ACARS" PSR Primary Surveillance Radar QoS Quality of Service R/T Radio Telephony SARPs (ICAO) Standards and Recommended Practices SSR Secondary Surveillance Radar VDL VHF Digital Link VOR VHF Omni-Range



1. INTRODUCTION

VDL Mode 4 has been designed to support a number of diverse applications. The SARPS for VDL Mode 4 were initially accepted by AMCP/7 for surveillance applications. Extension of SARPs applicability to support point-to-point communication applications has been recommended by AMCP/8, and an ICAO State Letter to this effect has been issued. VDL Mode 4 is considered in EUROCONTROL as a candidate surveillance data link (SDL) for automatic dependent surveillance (ADS-B) and as a candidate communications data link (CDL) to support air traffic control (ATC) related communications applications requiring a stringent Quality of Service. One of the important elements for a decision to implement VDL Mode 4 is the feasibility of integrating this technology onboard the aircraft. This study will provide input to such a decision.

As the VDL Mode 4 data link is expected to operate with other systems onboard an aircraft, it has to be shown that installation alongside these systems will not present any major problems. VDL4 is designed to support both communications data link (CDL) and surveillance data link (SDL) functions. The combination of these two functionalities may result in additional considerations.

The study examines feasible airborne architectures for each of three implementation options: 1) VDL Mode 4 for both CDL and SDL applications; 2) VDL Mode 4 for SDL applications only; and, 3) VDL Mode 4 for CDL applications only. In addition, the study examines the constraints of, and the impact on different types of aircraft. One of the major aspects of the feasibility of the architecture is the investigation about potential interference between VDL Mode 4 and other systems onboard the aircraft and in particular, with other systems operating in the VHF band.

The target time span for the study is for aircraft in regular service during any part of the period 2008-2015.

1.1 Study Objectives

The objective of this study is to analyse the feasibility of the airborne architecture for VDL Mode 4, taking into account the existing constraints and identifying any important issues. The purpose of the requested analysis is not necessarily to identify the “optimum” airborne architecture for a specific VDL Mode 4 implementation, as this is seen as a manufacturer's responsibility. The intention is to identify an architecture which satisfies the requirements and which shows that a VDL Mode 4 airborne architecture could be implemented.

The constraints on the installation and integration of VDL Mode 4 functionality are such that different answers might apply depending on whether the architecture is required for retrofit into the existing fleet, which will be assumed to have certain baseline equipment, or into the new fleet as part of buyer- or seller-furnished equipment. Therefore, this study will consider both approaches.



1.2 Definition of Terms

This study considers a number of combinations of aircraft equipage and operational usage of VDL Mode 4. To establish a consistent means of describing the various options, this study defines the following terms.

Aircraft Class – a set of aircraft satisfying a specific set of physical and, possibly, equipment criteria. This study will define four aircraft classes based on takeoff weight and on-board equipment.

Communications Data link – a data link that is primarily or exclusively used to transfer information for the purpose of exchanging information related to the operation of the aircraft, but not related to its current position. Examples of communications data link information include various requests for clearances (air-to-ground) and clearance approvals (ground-to-air). Communications data link does not include information derived from the current position or intended future position of the aircraft, except in the "clearance/approval" sense.

Data link – a means of wireless communications by which packets of digital data are exchanged between a source and an destination.

Equipment Baseline – for the purpose of this study, a specific list of avionics supporting communication, navigation, and surveillance functions that is installed in an aircraft of a particular class prior to the installation of VDL Mode 4 capability.

High end aircraft – aircraft implementing significantly more than the minimum required equipment. In general terms, all Large and most Small aircraft, as defined in Section 3.3.1 are considered high end.

Navigation Data link – a data link that is primarily or exclusively used to transfer information for the purpose of improving the estimate of the current aircraft position and velocity. Examples include the various data links associated with augmentation of GNSS position information, including the FAA's Wide Area Augmentation Service and Local Area Augmentation System. Navigation data link does not include information about the either current or intended future position of the aircraft or clearance/approval for specific operations.

Surveillance Data link – a data link that is primarily or exclusively used to for the purpose of providing information about the current and, possibly, intended future position of the aircraft. Surveillance data link does not include either information necessary to improve the estimate of the aircraft position or clearance/approval for specific operations.

VDL Mode 4 Operational Configuration – for the purpose of this study, a specific configuration of VDL Mode 4 onboard an aircraft so as to provide either communications data link service or surveillance data link service, or both.

1.3 Assumptions, Baselines, and Classes

To assist in organizing the other Work Packages in the study, this document provides, definitions of terms, references, definitions of aircraft classes and equipment baselines, and a list of high-level assumptions. Each of these items is subject to further review and modification as the study progresses. Items where further review and modification may be necessary will be specifically identified.



2. REFERENCE DOCUMENTS

A detailed bibliography of the reference documents used in this study is provided in Appendix A. The documents are roughly grouped according to their applicability to the study, as shown in Table 1. The list of the referenced documents will be updated as the study progresses.

Table 1: Document Categories and Reference Designations

DOCUMENT CATEGORY REFERENCES

Documents related to VDL Mode 4 operation and background that are directly applicable to this study

[1-5]

Documents related to ADS-B Operation and Background that are specifically applicable to this study

[6-12]

Documents providing background on functions and content for data link operations

[13-18] [20]

Documents providing background on functions, content, and applications for ADS-B.

[18]

Documents providing general background on development, installation, and operation of avionics

[21, 22]

Technical papers addressing topics closely related to this study.

[23-26]

Documents providing minimum equipage requirements for aircraft in various airspace

[27-29]

3. DEFINITION OF STUDY BASELINES

Any study is based on a set of agreed-upon assumptions. The key assumptions for this architecture study are shown in Table 2, and discussed in the following sub-paragraphs. In the following section, these assumptions are used to develop the baselines for the study.

Table 2 Assumptions for the VDL Mode 4 Airborne Architecture Study Assumption 1: ADS-B is an accepted means of surveillance. Assumption 2: SSR continues to be a required means of surveillance. Assumption 3: SSR transponder functionality is required on all aircraft, with the

capability of the transponder varying with the aircraft category. Assumption 4: ACAS will continue as the primary anti-collision technology. Assumption 5: Communications data link is used for ATS/ATM Assumption 6: Dual voice capability is required, but redundant elements may be

shared with an element of the communications data link. In the event of a failure, voice capability has priority access to transceiver resources.

Assumption 7: Initially, for the first set of data link communication applications, redundant communications data link capability is not required, as voice is assumed to be fall back for data link.

Assumption 8: When other data link communication applications will be required in the future, redundancy of airborne elements of the communications data link may be required to support time- and safety-critical applications.



Assumption 9: In the time-frame of this study, high end aircraft must allow simultaneous operation of communications data link, surveillance data link, and two voice communications channels

Assumption 10: The GBAS uplink is a navigation data link function, and not a communications data link function to be supported by VDL Mode 4.

Assumption 11: VDL Mode 4 is used as a communications data link. Assumption 12: VDL Mode 4 is used as a surveillance data link. Assumption 13: Radios built to an ARINC 750-X Characteristic will be available and

will provide Mode 2 Data via ATN and/or ACARS and Mode 3 Digital Voice, Mode 3 Digital Data and 25 kHz DSB-AM Voice and 8.33 kHz DSB-AM voice.

Assumption 14: Integration and display of surveillance information is performed at the output of the surveillance process, regardless of surveillance source.

Assumption 15: High-end aircraft are equipped with a Flight Management System (FMS), basic Area Navigation (BRNAV), or equivalent capability.

3.1 Discussion of Assumptions

Assumption 1: ADS-B is an accepted means of surveillance. Reference [6] states: "The ADS Programme aims at the initial

implementation of ADS system in the ECAC area in 2007,as foreseen by the Surveillance Strategy." Assumption 2: SSR continues to be a required means of surveillance.

Reference [6] states:

"The potential role of ADS overlaps with ...other surveillance systems which could be available in the airspace, i.e.:

Classical radars (PSR/SSR)...will remain available at least for the foreseeable future.

SSR Mode S Elementary Surveillance in TMAs and En-Route, which in the future can evolve to Mode S Enhanced Surveillance..."

This assumption is a necessary condition for the continued use of the current Airborne Collision Avoidance System (ACAS), which relies on Mode S transponder capability to obtain alerts of traffic.

Assumption 3: SSR transponder functionality is required on all aircraft, with the capability of the transponder varying with the aircraft category.

This assumption is necessary to fulfill the requirements of [29], and to assure the continued use of ACAS, as required by Assumption 4. High end business and air-transport class aircraft will have ACAS interrogator capability, as required by , while smaller aircraft will have transponder capability only. Current FAA and JAA standards require only a single transponder. AT aircraft typically carry dual transponders for the purpose of allowing dispatch in the event of a failure. Virtually all air transport aircraft carry dual SSR transponders to permit dispatch even in the event of a single transponder failure.

In the time-frame associated with this study, ADS is not expected to replace SSR as a primary means of surveillance.



Assumption 4: ACAS will continue as the primary anti-collision technology.

The use of ADS-B will not replace ACAS for tactical warning and threat resolution in the term of this study, or in the foreseeable future beyond that term. This assumption does not preclude enhancement of the ACAS function by use of ADS-B or other surveillance-derived information. Such strategies are not yet widely accepted.

Assumption 5: Communications data link is used for ATS/ATM Reference [9] states that the capabilities of Level One Co-operative Air

Traffic Service (COOPATS) will be available and fully integrated in the 2008/2010 time frame. In the COOPATS assumptions, services supported by communications data link capability in this time frame will be based on current ICAO Rules of the Air and Air Traffic Services. Implicit in this assumption are the COOPATS Level One operational improvements, including Controller/Pilot communications, provision of more information from the aircraft, ATM automation, and Air Traffic Situational Awareness (ATSAW) within the aircraft. Availability of ATSAW implies that either TIS-B or ADS-B, or both, are provided.

Assumption 6: Dual voice capability is required, but redundant elements may be shared with an element of the communications data link. In the event of a failure, voice capability has priority access to transceiver resources.

In today's ATC system, which is predominately dependent on voice with relatively low data rate utilization, a requirement for dual and independent communications means a requirement for dual VHF voice radios. In Europe, this is a requirement of the JAR/OPS document, dated 1 April 1995 [27]. In some cases, one of these radios is used for an implementation of communications data link services by means of "plain old ACARS" as well, with the provision that the data traffic is interrupted if the second voice channel is necessary. This assumption is based on that of current usage. Redundant voice communications capability may also be used for company communications while simultaneously serving as the backup for ATC voice communications. A white paper to the Data Link Users Forum [28] suggests potential allocations for modern current installation containing three radios as shown Table 3.

Table 3 Current Typical VHF Radio Utilization [28] Right VHF Radio Center VHF Radio Left VHF Radio

ATC Voice ACARS data Voice Backup

Company Voice ATC Voice backup

Assumption 7: Initially, for the first set of data link communication applications, redundant communications data link capability is not required, as voice is assumed to be fall back for data link.

In today's ATC system, redundant voice is required so that communication with the ATC system is not lost in the event of a radio failure. As a result of Assumption 6, voice will always be available for tactical and emergency situations. Therefore, at least one voice-capable radio will provide a fall back capability. A fall back to voice operations in a data link-enabled



ATM environment will necessitate some reduction in operational capabilities. While it is acknowledged that the advanced ATM procedures envisioned by the COOPATS concept [9] will require communications and surveillance data links, and that such procedures will almost certainly not be supported by voice operations, retention of voice capability as a risk mitigation measure will continue to be mandated for the foreseeable future.

Assumption 8: When other data link communication applications will be required in the future, redundancy of airborne elements of the communications data link may be required to support time- and safety-critical applications.

This assumption of voice as a fall back for communications data link (Assumption 7) is acceptable for basic Link 2000+ applications expected to be operational in the 2008 timeframe. Data link applications beyond this time-frame, however, may require redundancy to support time-critical and safety-critical for surveillance and communications. Provision for redundant data link operations should be considered in the current study. Assumption 9: In the time-frame of this study, high end aircraft must

allow simultaneous operation of communications data link, surveillance data link, and two voice communications channels

The 2008-2010 time-frame of this study covers a period of transition from the current voice-intensive environment to the data-intensive environment envisioned by COOPATS [9]. During this transition, voice will be retained for tactical and emergency communications, while data applications such as CPDLC will become increasingly important. Use of ADS-B as an enabler of advanced surveillance functionality will increase throughout the period [6]. Therefore, the interference analysis assumes that two DSB-AM voice channels (ATC and company) and a communications data link channel and a surveillance data link channel are active simultaneously.

Assumption 10: The GBAS uplink is a navigation data link function, and not a communications data link function to be supported by VDL Mode 4.

The Ground Based Augmentation System (GBAS) is a means of providing locally derived corrections to GNSS signals for the purpose of enabling extremely precise and very high integrity GNSS-based operations, such as precision approach and landing. At the current time, the standard uplink for the GBAS corrections is by means of the VHF Data Broadcast (VDB). At the physical layer, VDB is similar to VDL Mode 2 and VDL Mode 3, but it is not interoperable with either. Although it is likely that GBAS will be operational at a limited number of sites by 2008, this study does not assume that GBAS data link will become part of a mandatory equipment list in that time frame. Because of its very close coupling to precision guidance applications, the GBAS data uplink application may be considered to be a navigation data link function and not a communication data link function. Therefore, this study will assume that GBAS installation on any aircraft is a matter of owner/operator preference and not a requirement for operation in terminal and landing airspace. GBAS will be included in the interference consideration, however. In accordance with current ICAO standards, GBAS is not supported by VDL Mode 4.



Assumption 11: VDL Mode 4 is used as a communications data link. This assumption forms the basis for of the Operational Configurations

1 and 2 discussed in the next section. Under this assumption, VDL Mode 4 will be used as an ATN subnetwork to implement communication data link capabilities. The use of VDL Mode 4 for AOC communications will be discussed, but is not the primary focus of this study. Depending on the operational configuration, use of VDL Mode 4 as an ATN subnetwork may be combined with use of VDL Mode 4 as a surveillance data link (Assumption 12). VDL Mode 4 operation will be as described in [1-4], with additional details drawn from [5] as necessary.

There is, within the aeronautical communication community, an on-going debate about the use of Internet Protocol (IP) as an alternative for ATN at various stages of the end-to-end communication process, including the air-to-ground subnetwork. At the time of this study, there are no standards or draft standards regarding the IP for air-to-ground radio communications that can be used as a basis for study conclusions. ATN, on the other hand, is well and thoroughly defined by ICAO. Therefore, this study will use ATN as the baseline for all air-to-ground digital communications.

Assumption 12: VDL Mode 4 is used as a surveillance data link. This assumption forms the basis for Operational Configurations 1 and

3 discussed in the next section. Under this assumption, VDL Mode 4 will be used to implement surveillance data link capabilities, principally to communicate ADS-B and TIS-B data. Depending on the operational configuration, use of VDL Mode 4 as a surveillance data link may be combined with use of VLD Mode 4 as an ATN subnetwork (Assumption 11). VDL Mode 4 operation will be as described in [1-4], with additional details drawn from [5] as necessary.

Assumption 13: Radios built to an ARINC 750-X Characteristic will be available and will provide Mode 2 Data via ATN and/or ACARS and Mode 3 Digital Voice, Mode 3 Digital Data and 25 kHz DSB-AM Voice and 8.33 kHz DSB-AM voice.

This assumption is based on the activities of the AEEC 750-X Working Group charged with developing the ARINC 750-X characteristic. The intent of this assumption is to establish the expected functional capability of ARINC 750 radios in the 2008-2010 time frame. It is important to note that VDL Mode 3 is mentioned only the context of inclusion in the basic ARINC 750-X characteristic. This study does not specifically consider VDL Mode 3 as an alternative for either voice or communications data link functionality. The study methodology could be extended in a straightforward manner to assess VDL Mode 3/VDL Mode 4 integration issues, but these issues are beyond the current scope of effort.

Assumption 14: Integration and display of surveillance information is performed at the output of the surveillance process, regardless of surveillance source.

Although surveillance information received via ADS or TIS-B over the Mode 4 link may be new to each aircraft, this study assumes that integration of such information for Air Traffic Situational Awareness (ATSAW) or Airborne Separation Assurance (ASAS) is not part of the VDL Mode 4 upgrade.



Assumption 15: High-end aircraft are equipped with a Flight Management System (FMS), basic Area Navigation (BRNAV), or equivalent capability.

Full implementation of ADS-B, which is expected beyond the 2010 time frame, will require that participating aircraft provide intent information as well as position and velocity information. It is unreasonable to assume that this information will be continually input by the flight crew, therefore it must be automatically obtained from some flight management entity. It is also unreasonable to assume that FMS capability will be available on a large portion of Light or Small aircraft within the timeframe of the study. Many of the functions can be provided by basic RNAV capability, which apply to most aircraft above the Light class. Therefore, this assumption applies only to "high end", i.e., the Large and Small classes. This is not to say that no Light aircraft will have this capability, but is only for the purpose of establishing a working assumption for this study.

Upgrades of both FMS and RNAV capability may be required to support ADS-B operations is attributable to the ADS application, not to VDL Mode 4 in particular. That is, any ADS implementation (1090ES or UAT included) would require such modifications.

RNAV is envisioned as lesser capability than FMS, and so is identified separately. Assumptions relating to FMS and/or RNAV capability and the modifications (if any) to that capability will be refined as the study continues.

3.2 Underlying Assumptions for Operational Configurations

This study investigates the use of VDL Mode 4 under three operational configurations conditions:

Operational Configuration 1: VDL Mode 4 for surveillance and data link communications (Assumption 11 and Assumption 12);

Operational Configuration 2: VDL Mode 4 for data link communications only (Assumption 11), and;

Operational Configuration 3: VDL Mode 4 for surveillance only (Assumption 12).

It is outside the scope of this study to assess the relative merits of VDL Mode 4 versus other technologies for these Operational Configurations: this task has been performed in other forums for example in [19] and in [20]. The VDL Mode 4 Airborne Architecture study will, however, identify any significant advantages or shortcomings that may arise as a result of our consideration of VDL Mode 4 with respect to the assumed applications.

The following sub-paragraphs discuss assumptions appropriate to three configurations. As noted earlier, the underlying assumptions vary with the configuration, and some of the assumptions are mutually exclusive.

3.3 Definition of the Equipment Baselines

For the purpose of this study, an equipment baseline is a specific list of avionics supporting communication, navigation, and surveillance functions that is installed in an aircraft of a particular class prior to the installation of VDL Mode 4 capability. The focus of the study is the integration of VDL Mode 4 capabilities with the existing equipment and the effects of VDL Mode 4



operation in the various Operational Configurations on the baseline equipment.

There are a large number of variables involved in any baseline. This study seeks to confine the permutations to a manageable few that are representative of broad classes of user aircraft. Section 3.3.1 limits the number of aircraft classes under consideration to three, based on an earlier, more detailed classification given in [10]. Section 3.3.2 provides specific definitions of surveillance terms used to further specify the equipment baseline. Section 3.3.3 establishes the three equipment baselines that will be used throughout the study.

3.3.1 Airframe Classes

To retain some consistency with previous work, we will adopt the underlying aircraft classification used in [10], and then group the classes appropriately for the purposes of this study. Reference [10] identifies seven classes of aircraft based on weight/propulsion, as follows:

• Class A: piston aircraft with a maximum take-off mass below 5,700kg

• Class B: turboprop aircraft with a maximum take-off mass below 5,700kg

• Class C: turboprop aircraft with a maximum take-off mass between 5,700kg and 15,000kg (class subject to ACAS Phase 2)

• Class D: jet aircraft with a maximum take-off mass between 5700kg and 15,000kg (class subject to ACAS Phase 2)

• Class E: turboprop with a maximum take-off mass in excess of 15,000kg (class subject to ACAS Phase 1)

• Class F: jet aircraft with a maximum take-off mass in excess of 15,000kg (class subject to ACAS Phase 1)

• Class G: high-performance (tactical military) jets.

We will further group these classes as follows:

• Light: Class A and Class B, e.g., Cessna 172, King Air C90B, or CJ1/2

• Small: Class C and Class D, e.g., King Air 350, Learjet 4 and 5, most Citation aircraft

• Large: Class E and Class F, e.g., Citation X, FalconJets (F-50, F-2000, F900), Gulfstreams (G-IV, G-V), Bombardier CRJ, Embraer ERJ, all Airbus and Boeing aircraft

• Tactical: Class G

Tactical aircraft are outside the scope of this study, and will not be considered further. Strategic and cargo military aircraft are included in the Large class.

Based on this classification, this study will consider the integration of the VDL Mode 4 into three aircraft classes: Light, Small, and Large. The primary focus of this study is the Large (air transport and large business jet)



class. Other classes, with slightly difference basic equipment lists, will be considered after the AT class has been thoroughly evaluated and discussed.

The definition of aircraft classes will be reviewed as the study progresses. Minor adjustments may be made to the class definitions should they be warranted by the efforts of WP 2 and WP 3.

3.3.2 Definition of Surveillance Terms

The advent of ADS-B as a new approach to surveillance has created the opportunity for some confusion about various surveillance capabilities. This confusion arises by the use of various terms in multiple contexts Table 4 specifically defines these terms as used in this study. Definitions are referenced to Mode S or ADS, as appropriate. To avoid confusion, acronyms will not be used for these terms.

Table 4 Definition of Surveillance Terms Term Context Definition Reference ADS Airborne Basic Surveillance

ADS The “Airborne ADS Basic Surveillance Level” is expected to support “Air Traffic Situational Awareness” (ATSAW) related applications as defined in [9]. For the provision of the “Airborne ADS Basic Surveillance Level” the data content is Time, Identification, Three-dimensional Position, Position Uncertainty, Status, Ground Vector Information (optional), Velocity Uncertainty (Optional depending on provision of Ground Vector Information)

[7]

Airborne ADS Enhanced Surveillance

ADS The notion of "Airborne ADS Enhanced Surveillance" is expected to support future Co-operative Separation Assurance applications. The data content includes all ADS Airborne Basic Surveillance data items, including all optional data items, as well as Ground Vector Information, Track Angle Rate,Selected Altitude. Meteorological data including Wind Speed, Wind Direction, Temperature, and Turbulence may also be provided.

[7]

Ground ADS Basic Surveillance

ADS The notion of an “Ground ADS Basic Surveillance Level” corresponds with the Eurocontrol surveillance standard for classical surveillance. Ground Basic Surveillance includes the following information, Time , Identification, Three-dimensional Position, Position Uncertainty, and Status.

[7]

Ground ADS Enhanced Surveillance

ADS The notion of an “Ground ADS Enhanced Surveillance Level” corresponds with the provision of “Downlinking of Aircraft Parameters” (DAP), comprising both “Controller Access Parameters” (CAP) and “System Access Parameters” (SAP), including the following data elements: Ground Vector, Air Vector, Velocity Uncertainty, Selected Altitude, Roll Angle. Enhanced Surveillance may also include meteorological information, including Wind Speed, Wind Direction, Temperature, Turbulence.

[7]

Ground ADS Enhanced Surveillance with intent

ADS For the provision of the “Ground ADS Intent Surveillance Level”, the set of data includes TCP-n or TCP-∆t, Latitude, Longitude, Altitude, Time to go, Point type, Turn direction, Turn radius

[7]

Mode S Elementary Surveillance

Mode S The minimum capability of Level II transponders, Mode S Elementary Surveillance includes the digital transmission of Aircraft ID, transponder capability, altitude, flight status (air/ground), and the capability for transmitting S/I code

[18]

Mode S Enhanced Surveillance

Mode S Mode S Enhanced Surveillance capability includes Elementary Surveillance plus the transmission of Magnetic Heading, Speed (IAS/TAS/Mach No), Roll Angle, Track Angle Rate (if this is unavailable then True Airspeed, TAS, can be an alternative), Vertical Rate (barometric rate or, preferably baro-inertial), True Track Angle, Ground Speed, Selected Flight Level / Altitude.

[18]



3.3.3 Equipment Baselines

Based on the assumptions given above and the airframe classes just defined, the baseline equipment assumed for the cases to be investigated are shown in Table 5, Table 6, and Table 7. These tables are intended to represent the baseline equipment installed on the aircraft at the time the decision is made to equip with VDL Mode 4. The tables are divided into retrofit and forward fit cases. The term "retrofit" refers to aircraft that are already in operation with a given equipment list to which VDL Mode 4 capability is to be added. The term "forward fit" refers to new aircraft that are produced with the established capability plus VDL Mode 4 at the time of delivery. The following baseline cases have been defined.

Equipment Baseline 1R In Equipment Baseline 1R, integration of VDL Mode 4 is considered as a retrofit 1 (thus the "R" prefix) to an existing aircraft with a standard equipment list shown in Table 5. All aircraft classes are assumed to have GNSS, ILS, and VOR as navigation systems. Large, Small, and Light aircraft are assumed to have ILS Category III, Category II, and Category I performance, respectively. Surveillance is provided by dual Mode S transponders for the Large classes, a Mode S transponder and a Mode C transponder for Small and only Mode C transponders for Light class. All small and large aircraft are assumed to comply with the European mandate for Elementary Mode S surveillance by 2005. We assume that this compliance is by means of a transponder that complies with ARINC 718A. In accordance with Assumption 14, both a CDTI and a surveillance processor are assumed to be appropriately integrated on small and large aircraft at the time of VDL Mode 4 installation. This integration is not part of the VDL Mode 4 upgrade. All aircraft are assumed to have a digital avionics suite, that is, all of the communications, navigation, and surveillance functions use digital data interfaces, e.g., ARINC-429, for local input and output.

The defining feature of Class 1R aircraft is the inclusion of ACARS capability by means of a DSB-AM analog voice radio in the baseline. This service is the "Plain Old ACARS" service mentioned in relevant literature.

Equipment Baseline 2R Equipment Baseline 2R also considers integration of VDL Mode 4 as a retrofit activity. The basic equipment list is the same as in Equipment Baseline 1R, except that that VDL Mode 2 capability replaces Plain Old ACARS in the installed equipment list. The VDL Mode 2 capability is used in the broadest possible sense, and is intended to include both ACARS over AVLC (AOA) and ATN-compliant services. Either or both may be installed on the aircraft at the time of VDL Mode 4 installation. VDL Mode 4 integration issues are assumed to be the same regardless of the subnetwork (AOA or ATN).

Equipment Baseline F This composite case corresponds to forward fit2, i.e., new aircraft construction, with integrated VDL Mode 4. In this case, the equipment configurations shown in Table 7 correspond to the functionality exclusive of VDL Mode 4. Table 7 differs from Table 5 and Table 6 in that several of the cells are marked by "C". The "C" indicates that the actual configuration of this function is determined by which of the specific VDL Mode

1 The term "retrofit" means that the VDL Mode 4 capability is added to an equipment baseline that already exists in an aircraft in regular service. That is, VDL Mode 4 is added after initial certification of the aircraft and not as part of the originally installed equipment. 2 The term "forward fit" means that VDL Mode 4 capability is installed as part of the initial equipment list at the time of aircraft construction. That is, VDL Mode 4 is part of the original equipment list.



4 operational configuration (communication data link + surveillance data link, communication data link only, surveillance data link only) is being investigated. All aircraft classes are assumed to have GNSS, ILS, and VOR as navigation systems. Large, Small, and Light aircraft are assumed to have ILS Category III, Category II, and Category I performance, respectively.

Case F has been combined from the forward fit cases corresponding to the retrofit cases 1R and 2R. The cases were combined under the assumption that Plain Old ACARS (DSB-AM data) is not a realistic option for new aircraft. With the widespread use of VDL Mode 4 (a basic assumption of the study) and VDL Mode 2 data capability, the probability that the old-fashioned Plain Old ACARS would be installed as new equipment is very small. Therefore, only a single Case F is needed.

For a Large aircraft, then, the baseline equipment includes dual voice, dual SSR surveillance, and a communications data link capability, all of which must operate simultaneously (Assumption 9). This communications equippage is sufficient to support a variety of flight crew configurations. No other assumptions are made about the actual configurations of the flight crew which may be used by the airline or aircraft operator.



Table 5 Study Case 1R Equipment List Prior to Installation of VDL Mode 4 Capability Airframe Class

ILS VOR Mode S Tpdr #1

Mode S Tpdr #2

Mode S Int

(ACAS)

Mode C

DSB AM Voice 1

DSB AM Voice 2

DSB AM Data

VDL M2 Data

GNSS CTDI

Large X X X X X X X X X X Small X X X X X X X X X X Light X X X X X "X" = installed on aircraft prior to retrofit with VDL Mode 4

Table 6 Study Case 2R Equipment List Prior to Installation of VDL Mode 4 Capability Airframe Class


Mode S Tpdr #2

Mode S Int

(ACAS)

Mode C

DSB AM Voice 1

DSB AM Voice 2

DSB AM Data

VDL M2 Data

GNSS CTDI

Large X X X X X X X X X X Small X X X X X X X X X X Light X X X X X "X"=installed on aircraft prior to retrofit with VDL Mode 4

Table 7 Study Case 1F/2F Functionality Exclusive of VDL Mode 4 Capability Airframe Class


Mode S Tpdr #2

Mode S Int

(ACAS)

Mode C

DSB AM Voice 1

DSB AM Voice 2

DSB AM Data

VDL M2 Data

GNSS CTDI

Large X X X X X X C C X X Small X X X X X X C C X X Light X X X X C C "C" = configuration determined by VDL Mode 4 operational configuration



APPENDIX A: WORKING REFERENCE BIBLIOGRAPHY

This annex contains an integrated reference bibliography. The reference numbers are keyed to Table 1.

[1] _______, Standards and Recommended Practices for VDL Mode 4, III, Part I, Chapter Annex 10, Montreal: ICAO, 2001.

[2] _______, (Draft) Manual on Detailed Technical Specificatiaons for the VDL Mode 4 Digital Link, Montreal: ICAO AMCP WGM-2, 2002.

[3] "Manual on the Implementation of VDL Mode 4," 8 May 2002.

[4] _______, Interim MOPS for VDL Mode 4 Aircraft Transceiver for ADS-B, ED-108, Paris: Eurocae, 2001.

[5] L. Johnsson, "VDL Mode 4 in CNS/ATM Master Document v2.0," LFV, Malmo-Sturup, Sweden, 19 Sept. 2001.

[6] "Automatic Dependent Surveillance Concept," EUROCONTROL, Brussels, ADS/SPE/CR/D1-06 v. 1.7, 28 Sept. 2001.

[7] "Automatic Dependent Surveillance Requirements," EUROCONTROL, Brussels, ADS/SPE/CR-TF-REQ/D1-08, 28 Sept. 2001.

[8] "Traffic Information Broadcast Service Requirements," EUROCONTROL, Brussels, ADS/URD/TISB/0001, 5 Dec. 2001.

[9] "Toward Cooperative ATS: the COOPATS Concept," EUROCONTROL, Brussels, DIS/ATD/AGC/MOD/DEL 01, 18 June 2001.

[10] "1090 MHz Extended Squitter Assessment Report," FAA/Eurocontrol Experimental Centre, Washington, D.C., June 2002.

[11] "Principles of Operation for the Use of Airborne Separation Assurance Systems," EUROCONTROL, Brussels, PO-ASAS-V7.1, 19 June 2001.

[12] "CARE/ASAS Activity 5 Proposal for a first package of GS/AS applications (DRAFT)," Eurocontrol, Brussels, Belgium, CARE/ASAS/EUROCONTROL/02-040 (Version 1.2), May 14 2002.

[13] _______, Guidelines for Approval of the Provision and Use of Air Traffic Services Supported by Data

Communications, DO-264, Washington, D.C.: RTCA, Inc., 2000.

[14] _______, Signal-in-Space Minimum Aviation System Performance Standards (MASPS) for Advanced VHF

Digital Data Communications Including Compatibility with Digital Voice Techniques, DO-224A including change 1, Washington, D.C.: RTCA, Inc., 2001.

[15] _______, Minimum Operational Performance Standards for Aircraft VDL mode 3 Transceiver Operating in the Frequency Range 117.975-137.000 MHz, DO-271, Washington, D.C.: RTCA, Inc., 2001.

[16] _______, Minimum Operational Performance Standards for Airborne Radio Communications Equipment Operating within the Radio Frequency Range 117.975-137.000 MHz, DO-186A including Change 1 and Change 2, Washington, D.C.: RTCA, Inc., 2002.



[17] _______, Minimum Operational Performance Standards for Aircraft VDL Mode 2 Physical, Link and Network Layers, DO-281, Washington, D.C.: RTCA, Inc., 2002.

[18] _______, ICAO Manual on Mode S Specific Services, Document 9688, First Edition, Montreal, Canada: ICAO, 2000.

[19] "Technical Link Assessment Report," FAA/EUROCONTROL, Washington, D.C., March 2001.

[20] "Future VHF Systems - Architecture Implementation Study," Eurocontrol, Brussels, COM.ET2.ST12, 2 Nov 2000.

[21] _______, Software Considerations in Airborne Systems and Equipment Certification, DO-178B, Washington, D.C.: RTCA, Inc., 1992.

[22] _______, Environmental Conditions and Test Procedures for Airborne Equipment, DO-160D, Washington, D.C.: RTCA, Inc, 1997.

[23] N. Fistas, "VHF Datalinks for point to point Communications," AMCP/WGM3, Tianjin, China, 10-18 Dec. 2001 2001.

[24] S. Heppe and S. Friedman, "An Integrated Airborne Architecture for Voice and Data Link CNS Systems." 2nd Integrated CNS Technologies Conference and Workshop NASA Glenn Research Center, 2002.

[25] A. Malaga, "White Paper Discussing Practical Considerations for the Installation of VHF Data-Link Mode 4 on Commercial Air Transport Aircraft," Honeywell, 2001.

[26] M. Balin, D. Wing, M. Hughes, and S. Conway, "Airborne Separation Assurance and Traffic Management: Research of Concepts and Tehcnology," NASA Langley Research Center/AIAA, Langley, VA, AIAA-99-3989, 1999.

[27] "JAR/OPS," 1 April 1995.

[28] B. Tremain, "ATN Transition Issues," Data Link Users Forum, Brussels, Belgium, Feb. 4-5 2002.

[29] _______, [ACAS TGL-8], ACAS TGL-8, Brussels, Belgium: Eurocontrol, 2000.