1.1.  With the global evolution of Automatic Dependant Surveillance-Broadcast (ADS-B) statements such as:

“air traffic controllers this week began separating aircraft for the first time using the next generation of tracking technology and one of the most innovative surveillance advancements since radar”

will become standard press release(s). Air Navigation Service Providers (ANSPs) are competing for the title of ‘The most advanced Air Traffic management system (ATM)’. With this explosion comes the daunting task of regulating the environment. ICAO has seen the ground that has been covered in the United States, Europe and Australia and the various simulated and live trials conducted around the world and is responding carefully. ICAO is aware of the difficult task of regulating all of the technical details/designs but needs to develop performance requirements for the use of these technologies.

1.2.  Within this wave of development and implementation comes the role of IFATCA. What is becoming of all this technology? Can the civil aviation regulator(s) protect the controllers that need to train on and work these new systems? This paper is to provide an update on what is developing globally and to follow on from Working Paper (WP) 85 Buenos Aires. The future is here and we need direction and policy.

1.3.  This paper needs to be read in conjunction with WP85 from Buenos Aires (As found in the ‘Professional and Technical Manual of IFATCA’) a lot of the detail discussed here is assumed knowledge.

2.1. General – Motivation for Implementation (Overview of the FAA ADS-B Link decision)

2.1.1. Increased Safety

• Improved visual acquisition (supplemented by Traffic Information Service-Broadcast (TIS-B));
• Reduced Runway incursions on the airport surface through improved aircraft situational awareness;
• Enhancements to Short Term Conflict Alert (STCA).

2.1.2.  Increased capacity and efficiency

• Enhanced visual approaches (air to air);
• Closely spaced parallel approaches (air to air and air to ground);
• Reduced spacing on final;
• Reduced aircraft separations;
• Enhanced operations for incremental evolution of the “Free Flight” concept (air to air and air to ground);
• Surface operations in lower visibility conditions;
• Near Visual Meteorological Condition (VMC) capacities at airports in most/all weather conditions;
• Support for improved ATC services in non-radar airspace.

2.1.3.  With the detailed list above it is easy to see why the ATM world is excited about the possibilities of ADS-B technology. Increasing capacity in Instrument Meteorological Conditions (IMC) was once considered impossible but with the potential of an Airborne Separation Assistance System (ASAS) unforeseen delays may be a thing of the past. Being able to space aircraft closer on parallel approaches, assigning responsibility to the pilot to monitor spacing and the possibility of free flight with self separation is the future of ATM. Financial investment in this development has been easily motivated by the potential of the technology once it is developed. Applications have been tested and guidance and direction is required to manage the change.

2.2. World Applications

2.2.1.  To begin to summarise in any form the explosion of ADS-B on a global level will not do the work justice. The amount of research, development and implementation from many of the world’s leading ANSPs would take a massive amount of study and preparation to deliver in an information paper of this kind. The following is a brief outline of what is happening (as of late 2005) with some of the development (some of this information may well be incomplete or outdated due to the rapid evolution of this technology).

2.2.6.4. The two sub sets (Eurocontrol CASCADE CHARTER Edition 1.0) of applications which will be addressed by CASCADE are:

“Stream 1”, containing a set of applications that will be in Pre-implementation and Operations Validation trials in the period 2005-2006 and for which operational use is foreseen in 2008. The main objective of this first phase is to “make the first benefits happen”, build experience, achieve consensus and develop the basis for the subsequent implementation steps. The following applications will be in Stream 1 (ADS-B):

• ATC surveillance for en-route airspace (ADS-B-ACC)
• ATC Surveillance in terminal areas (ADS-B-TMA)
• ATC Surveillance in non-radar areas (ADS-B-NRA)
• Airport surface surveillance (ADS-B-APT)
• Aircraft derived data for ground tools (ADS-B-ADD)

“Stream 2” contains the set of applications for which operational use is expected to begin in 2010.. The “Stream 2” includes the following applications:

• Enhanced traffic situational awareness on the airport surface (ATSA-SURF)
• Enhanced traffic situational awareness during flight operations (ATSA-AIRB)
• Enhanced visual acquisition for see & avoid (ATSA-S&A)
• Enhanced successive visual approaches (ATSA-SVA)
• Enhanced sequencing and merging operations (ASPA-S&M)

2.2.7.  Australia

2.2.7.1.  The ADS-B trial (ADS-B SITF/4 Australia’s ADS-B Program – Greg Dunstone) at Bundaberg comprises a single duplicated ADS-B ground station that receives ADS-B transmissions from aircraft in which ADS-B avionics have been installed. The system presents ADS-B data on Australian ATC displays and following regulator approval, 5 NM ATC separation services were introduced earlier in 2005, with full operational use.

2.2.7.2.  The ADS-B Upper Airspace Project (UAP) will install 28 duplicated ADS-B ground stations across the continent. The ground stations have been purchased and delivered. Installation is to occur progressively during the next 12 months.

2.2.7.3.  ATC procedure development and training has commenced for this project. It is envisaged that the Bundaberg UAP ground station will be commissioned first as a one-for-one replacement of the existing commissioned system. Then as other sites come on line, and as ATC training is completed, the new sites will provide a situational awareness service. When ground station installation is complete and, following CASA (Civil Aviation Safety Authority) approval, Airservices Australia anticipate authorisation to use a 5NM separation standard across the complete continent.

2.2.7.4.  The Australian aviation community is currently considering a project called ATLAS (Australian Transition to Satellite Technology) which envisages the fitment of ADS-B out avionics and Global Navigation Satellite System (GNSS) receivers to a large number of aircraft. The project is exploring the replacement of enroute radars with ADS-B ground stations which may also allow the removal of a large number of NDBs and VORs. A cross industry funding package and a fitment mandate are also being considered to expedite transition to the new technologies. An industry commitment to ATLAS is expected in the first quarter 2006.

2.2.7.5.  Airservices Australia has begun testing two cockpit display systems that are suitable for low cost installation in General Aviation (GA) and micro-light aircraft. These systems use GPS and extended squitter ADS-B technology to provide pilots with navigation, terrain and traffic information on a moving map display. The information can be shown on a CDTI 2000 multifunction display or, as a lower cost alternative, on a pocket PC.

2.2.8.  World Summary

2.2.8.1.  A brief look at the world stage is overwhelming as to the magnitude of development and change in the world of ADS-B. Australia and the U.S. have begun using ADS-B with local regulator approved standards and there are many simulations and live trials being completed elsewhere. Whether the development will slow to allow for international regulators to catch up and provide directives only time will tell.

2.2.8.2.  Differences will exist in the implementation of ADS-B. An example of this is hardware choice for FIS-B/TIS-B. Where the U.S. has chosen UAT, certain states in Europe have recommended VDL mode 4.

2.2.8.3.  ICAO has placed emphasis on this interoperability with recommendation 7/1 from Eleventh Air Navigation Conference (AN-Conf/11):

Nevertheless some differences in technology and procedures will be evident across the states.

2.3.  International Civil Aviation Organisation (ICAO)

2.3.1.  Much of the research been carried out by ICAO in the last few years can be seen through the work of the various panels. The following is a brief summary of the progress as reported at ADS-B SITF/4 (Study and Implementation Task Force, 4th Meeting) in October 2005 and from SCRSP (Surveillance and Conflict Resolution Systems Panel) meeting in Paris 2005.

2.3.2.5.  The reports generated will now be considered by the ANC. Consultation with States is planned for 2006 with the likely effective date for changes being November 2007.

2.3.3.  Separation and Airspace Safety Panel (SASP)

2.3.3.1.  As mentioned above SASP has been working closely with OPLINKP on the chapter 8 amendments for PANS ATM Doc 4444. In particular, it has been noted that in the November 2004 (6th Meeting) of SASP, the project team had assessed on the basis of the technical comparison that a 5NM standard minimum could be used in conjunction with ADS-B.

2.3.3.2.  At the seventh meeting (IP/16-ADS-B SITF/4 ICAO APAC) in May 2005, a SASP Working Group was informed that the Secretariat had raised a number of issues related to the proposed amendment to Chapter 8 of PANS ATM Doc 4444, specifically in relation to issues raised by OPLINKP. This involved the proposed inclusion in PANS ATM Doc 4444 Chapter 8 of values for some of the technical requirements for ADS-B relative to the use of a 5 NM separation minima.

2.3.3.3.  Following a review of the issue, the project team strongly advised that it did not agree with providing minimum values for performance criteria to be included in PANS ATM Doc 4444 and that this had been the team’s position following similar discussions at its November 2004 meeting. The Working Group supported the project team view that technical requirements should only be identified in the same document as all the other requirements in the comparative assessment. As such, it was agreed that placing only technical requirements in the PANS ATM Doc 4444 could be misleading. The main driver for this position was to ensure States took account of the total requirements and their interrelationship and did not see any specific values in a single document such as PANS ATM Doc 4444 as being all that was required for implementation.

2.3.4.  Surveillance and Conflict Resolution Systems Panel (SCRSP)

2.3.4.1.  ASAS (SCRSP Working Group Meetings Paris, October 3-14, 2005 Report from Christoph Gilgen)

Many concerns and issues have been reported to SCRSP Working Ground A (WG A). For instance there is concern that the ground ATC unit could use SSR Mode A and C only, but the cockpit would use Mode S and ADS-B flight ID features as call sign designation on the CDTI. This would mean different sources of information would be used, and the risk of wrong correlation would be real. It’s true that the ASAS-procedures are only in early development, but problems are clearly seen and they will need clear and unambiguous solutions.

2.3.6. ICAO Conclusion

• ICAO Assembly (ICAO Journal Volume 59, October 04) moves from technical Standards and Recommended Practices (SARPs) to performance-based SARPs, including acknowledgement of industry work on standards.
• The requirement to ensure system interoperability will also fall to industry, leaving ICAO to concentrate on functionality.
• The change results in a three-level hierarchy of requirements and specifications for complex aeronautical systems.
  • At the first or “core” level, the ICAO standards and recommended practices consist of broad, high-level requirements contained in annexes to the Chicago Convention.
  • These SARPs are augmented by technical specifications which are published in appendices to the annexes.
  • Lastly, the related detailed technical specifications will appear in separate documents published by ICAO or other organizations.
• The challenge for ICAO is to ensure global interoperability of complex systems such as ASAS without dictating detailed or specific solutions to industry.
• For ASAS applications, will Required Surveillance Performance (RSP) etc be sufficient to derive architectural solutions?
• Work progress in ICAO panels is heavily dependent on State’ expertise, contributions and resources

2.4. International Air Transport Association (IATA)

2.4.1.  IATA (IATA Technical Operations Policy Manual Part B Resolutions ‘Implementation of ADS-B’) recognises ADS-B as a prime enabler of ATM, bringing substantial safety and capacity benefits. It also supports the cost effective early implementation of ADS-B. ADS-B in this context means receive as well as broadcast capability.

2.4.2.  IATA’s position is that ADS-B shall be interoperable worldwide, including operational procedures, supporting data link and the ATM applications.

2.4.3.  IATA supports 1090 Extended Squitter (1090 ES) as the single, interoperable link for the foreseeable future.

2.4.4.  Different link(s) may be deployed and used on a voluntary basis or based on regional agreement between the airspace users and the Air Navigation Service Providers concerned. IATA maintains that this shall under no circumstances penalise aircraft equipped only with 1090 ES.

2.4.5.  IATA is aware of the limitations in the current ATM environment reaching their limits by 2008-2010. New technology is required to meet the forth coming demand. Many areas of the world have inadequate surveillance systems and the implementation of ADS-B in conjunction with new ATM operating concepts, can provide cost effective solutions.

2.4.6.  IATA’s member airlines have expressed their desire to see ADS-B implemented at the earliest possible time.

2.5. Requirements Focus Group (RFG)

2.5.1.  The RFG (FAA RFG Overview https://adsb.tc.faa.gov/RFG.htm) is an international group consisting of members from the FAA, RTCA, Eurocontrol, EUROCAE, and other interested parties. The RFG is operating as a joint RTCA/EUROCAE activity. The primary object of the RFG is to internationally harmonize operational concepts and minimum safety and performance requirements for ground surveillance (GS) and aircraft surveillance (AS) applications. To accomplish these objectives, the RFG will produce three (3) documents for each application. This document suite will consist of an Operational Services and Environment Description (OSED), a Safety and Performance Requirements (SPR) specification, and an Interoperability specification. The OSEDs will be developed by the Application Description (AD) subgroup, while the SPRs are developed by the SPR subgroup. (Both subgroups will contribute to the Interoperability specification.)

2.5.2.  The RFG activities are directly related to SC-186 (Special committee for ADS-B, involving definitions and regulatory challenges) and its work. Much of the work done on the applications specified in the Aircraft Surveillance Applications (ASA), Minimum Aviation System Performance Specifications (MASPS) will be used as a starting point for the OSEDs and SPRs developed by the RFG. Further, it is anticipated that the documents delivered by the RFG will be published by RTCA/EUROCAE and be the basis for a joint revision of the ASA MASPS.

2.6. Human Factors

2.6.1.  Air traffic management is advancing so rapidly that managing change at the controller’s workstation has never been more important than now. Over the last decade we have seen vast electronic improvements in the systems that drive ATS.. Information (both new data and updated) has to be inputted into these system(s) to update the electronic strip displays, electronic sequencing and system coordination functions. With the adoption of conflict tools, route and level adherence alarms and electronic flow control (just to name a few) more and more sophistication is distracting us from the core business of separation.

2.6.2.  When we begin to discuss track symbols on an Air Situation Display (ASD), we think about the work that has been done by panels such as OPLINK and the distinguishable differences between ADS-C aircraft and non ADS-C aircraft. How do we then safely implement another track symbol to indicate ADS-B? Will the controller(s) always notice the difference and apply the required separation minima? Answers to these questions (and many more) may lie in the guidance and support from IFATCA.

2.7. Considerations for use of ADS-B (ICAO ADS-B Implementation and Operations Guidance Document Edition 1.0 August 2005)

Use of ADS-B level Integrity
Accuracy of pressure altitude derived level information is the same as with SSR and subject to the same operational procedures. Where the ATM system uses metric level display, the data should not be used until verified by comparison to pilot reported metric level.

Position reporting Performance
ADS-B reports include categorization of accuracy and integrity of the horizontal position data. If the data is less than prescribed minima, it may be presented on the ASD, provided the controller is alerted, as it has implications for the provision of separation.

GNSS Integrity Prediction
Alarms need to be incorporated to indicate when GNSS degradation is likely to occur. Controllers need to be alerted to areas where unreliable GNSS reports might exist. With degraded GNSS operations ADS-B separation should not be applied by ATC

Sharing of ADS-B Data
Agreements in sharing of surveillance data across states should be considered. Service benefits and improved safety could be expected. Any agreement should be incorporated in Letters of Agreement.

Reporting rates
Equivalency to radar, ADS-B reporting rates should maintain current operational integrity. Aircraft reports may be 0.5 sec, ASD update should not be less than the prescribed radar minimum.

Separation
In a mixed surveillance environment, consideration must be given to establishing individualised separation. Processed alarms such as Short Term Conflict Alert (STCA)/Medium Term Conflict Alert (MTCA) should work in environments displaying this concurrent data. Vertical tolerance for ADS-B should be consistence with Mode C level information.

Identification methods
Methods approved by ICAO for establishing identification with radar, may be used:

• Direct recognition of the aircraft identification in an ADS-B label
• Transmit of ADS-B ident

Use of Flight ID may be required to verify correct correlation.

Clearance Monitoring
ADS-B track data can be used to monitor flight path conformance with air traffic control clearances. ATC requirements to monitor ADS-B traffic on the ASD should be similar to PANS ATM Doc 4444 chapter 8.

Phraseology
States should note the requirement for standard ADS-B specific phraseology, equivalent to standard radar phraseology and generic surveillance phraseology.

This is in no way an exhaustive list, but an indication of some of the considerations necessary to introduce ADS-B. ICAO and RFG through their many panels are producing MASPS and SARPs related to what and how ADS-B is to be introduced.

3.1.  It is predicted that ADS-B is going to be a saviour for future capacity problems. Where capacity was limited by controller workload and environmental conditions these new applications will result in further increases in terminal capacity (with minimal spacing, assigning ‘following style’ commands to pilots) and in non-radar areas (with the introduction of low cost surveillance options to apply radar-like separation and the possibility of dedicated free flight). All these options will change how we currently operate ATC.

3.2.  Regardless of future plans, the initial start lies in the simple introduction of ADS-B, including selecting the right equipment; making sure it complies with the regulators specifications; integrating it into our local ATM plan; and structuring our implementation with consideration to all the necessary requirements.

3.3.  Human Factor issues must be considered and addressed. A simple task of pilot monitored separation presents an enormous challenge to cultural perceptions. The integration of mixed surveillance environments with different separation standards required will have to be thoroughly assessed (safety management) and adequately trained for.

3.4.  Interoperability is a principal concern; ICAO and IATA have stated that limitations shouldn’t be expected for aircraft installing/having only 1090 ES. The challenge is to make sure that technology such as TIS-B and FIS-B is compatible with all aircraft operating in the intended airspace or full capacity using these technologies won’t be realised.