Legislative Council Panel on Economic Services

Satellite-based Communications, Navigation, Surveillance/
Air Traffic Management (CNS/ATM) Systems


In the briefing on the policy objectives of the Economic Services Bureau on 13 October 1998, we informed Members of the plan of the Civil Aviation Department (CAD) regarding the study, trial and implementation of satellite-based CNS/ATM systems for air traffic control (ATC) operation. This project will enable us to modernise our ATC facilities and comply with the Global Implementation Plan of the International Civil Aviation Organisation (ICAO), and is important for the enhancement of flight safety and efficiency as well as the maintenance of Hong Kong's status as a centre of international and regional aviation.

2. Subject to approval of necessary funds by the Finance Committee of the Legislative Council, the project would be implemented in phases between 1999 and 2016.

Background of CNS/ATM Systems

3. The existing ATC systems rely mainly on ground-based radar and communications equipment which face a number of limitations including limited range of coverage, susceptibility to impact of adverse weather and lack of capability for digital data transfer (which is much more efficient than voice communications) between aircraft and ground control stations.

4. In the early 1980's, it became evident to ICAO that the present ground-based ATC systems would not be adequate to meet the needs of the 21st century. In consequence, a Special Committee on Future Air Navigation Systems (FANS) was established in 1983 to study, identify and assess new technologies as well as to make recommendations for the future development of navigation systems for civil aviation.

5. The systems developed by the FANS Committee are known as the satellite-based CNS/ATM systems and include the following major elements -

  1. Communications

    This mainly involves the introduction of satellite data and voice communications capable of global coverage. The regular use of data communications, as opposed to voice communications under existing systems, will offer new opportunities for improvements in air traffic management, particularly real-time sharing of aeronautical information among ATC centres of different aeronautical authorities, aircraft in flight and airlines operation centres.

  2. Navigation

    This involves the use of another set of satellite signals (for example, the Global Navigation Satellite System (GNSS)) for navigation, as opposed to ground based beacons and navigational aids under existing systems. The new systems will provide a high-integrity, high-accuracy and all-weather world-wide navigation services.

  3. Surveillance

    This involves multiple efforts to improve surveillance of aircraft. Mode S radar (which provides the capability for individual addressing and thereby facilitates aircraft identification) will be gradually introduced to supplement traditional Secondary Surveillance Radar in high-density traffic airspace. Automatic Dependent Surveillance (ADS) will be employed to automatically and continuously transmit the aircraft's position and other data such as heading and speed via satellite or other communication links, to an ATC unit. The real time information will permit the ATC unit to control air traffic more effectively, particularly in areas where it would not be cost effective to provide radar coverage. Furthermore, Enhanced Ground Movement Control System (EGMCS) will be provided to allow more effective surveillance of moving targets such as aircraft, vehicles and ships on or adjacent to the airfield including the taxiway, apron, runway and adjacent sea area.

  4. Air Traffic Management (ATM)

    It involves air traffic services, air traffic flow management, airspace management and the ATM-related aspects of flight operations. An integrated global ATM system would exploit the potential of new technologies through international harmonisation of standards and procedures. Ultimately, this will enable the aircraft operators to dynamically adjust the preferred trajectories in the optimum and most cost-efficient manner and conduct their flights accordingly.

The CNS/ATM systems comprise a large number of components each providing certain functionality. A table setting out the more important components of the CNS/ATM systems is at the Annex.

Benefits of CNS/ATM Systems

6. The CNS/ATM systems will tremendously improve the handling and transfer of updated information on weather, status of aircraft and ATC facilities between an aircraft and the ATC centre. They will also extend surveillance coverage and improve navigational accuracy. This will reduce the required distance of separation between aircraft and allow for greater airspace capacity. The advanced ATC automation system will exchange data directly with aircraft through data link and help improve conflict detection and resolution. It will also offer the means to adapt quickly to the changing traffic environment for preferred flight profile.

7. In brief, the direct and indirect benefits of the CNS/ATM systems include enhancement of flight safety, increase in airspace capacity, savings in flight time and fuel, as well as reduction in disruption to air services arising from adverse weather.

Implementation of CNS/ATM Systems

8. The first Global Implementation Plan for the satellite-based CNS/ATM systems was worked out by ICAO in 1993 and has subsequently been updated. All Contracting States, including China, are required to comply with the Plan. At the same time, the Asia Pacific Economic Co-operation (APEC) has also established a Satellite Navigation & Communications (SN&C) Systems Advisory Committee to monitor and co-ordinate, in conjunction with the ICAO Regional Office and various APEC Economies, the implementation of such systems within APEC.

9. Many countries have commenced the study, operational trial and evaluation of the CNS/ATM elements with a view to complying with the Global Implementation Plan and launching the services of the new CNS/ATM systems for use by airlines at an early date. In this regard, USA, Japan, Singapore and the Mainland have started the design and trial of at least five key elements of the CNS/ATM systems.

10. CAD commenced preliminary planning and investigation on the satellite-based CNS/ATM systems for Hong Kong in 1992. Initial trial on two elements of the systems, i.e. ADS and the Controller-Pilot Data Link Communication (CPDLC), has started since June 1994. The results have been satisfactory.

11. To maintain the competitive edge of Hong Kong in the civil aviation field, CAD has worked out a 3-phase CNS/ATM Implementation Plan as follows -

  1. Phase 1 - System Study & Analysis Phase (1999-2004)

    To carry out a full CNS/ATM systems study and analysis of various CNS/ATM elements so as to define a master plan for Hong Kong on the evolution of and transition to the new satellite-based systems, including the formulation of time schedule for the trials and implementation of CNS/ATM elements for Hong Kong.

  2. Phase 2 - CNS/ATM Trial & Evaluation Phase (2000-2007)

    To conduct extensive and/or full scale trials and evaluations of various CNS/ATM elements to assess and establish the operational and engineering requirements, system configuration and the suitable implementation option.

  3. Phase 3 - CNS/ATM Implementation & Transition Phase(2003-2016)

    To procure operational CNS/ATM systems including equipment tendering/selection, testing and commissioning and parallel operations of both the existing ground-based and the future satellite-based systems, as well as the final overall system integration for CNS/ATM operations.

Financial Implications

12. The total non-recurrent cost for the study, trial and implementation of the CNS/ATM systems is estimated to be $1.04 billion at 1998-99 prices, to be expended between 1999-00 and 2016-17. Since the project would take 18 years to complete, the Administration intend to seek funds from the Finance Committee in stages. Detailed breakdown is being worked out.

13. The recurrent cost for the study, trial and implementation of the CNS/ATM systems is estimated to be about $6 million in 1999-2000. We will assess the recurrent cost in future years as the project proceeds.

Implications for fees/charges

14. The amortised project cost of the CNS/ATM systems will be recovered via the Air Traffic Control and En-route Navigation Services Charges.

15. The CNS/ATM project would not result in any increase in these charges in the coming six to seven years. For a few years after 2006-07, it is expected that there would be a modest increase in the costs of Air Traffic Control Services to be recovered from the Airport Authority (AA) as a result of the introduction of the CNS/ATM systems. The increase is estimated to be less than 2% of the total operating costs of AA based on its present cost structure. The increase in the costs for En-route Navigation Services provided to aircraft overflying Hong Kong's air space is expected to be around 10%. The above increases would be more or less offset when the amortised project cost for the existing ground-based ATC systems has been fully recovered and taken out from the above costs. It should also be noted that even if there is no need for introduction of the CNS/ATM systems in compliance with the Global Implementation Plan, CAD would have to gradually upgrade or replace the existing ground-based systems to keep up with advancement in technology and growth in demand for ATC services. The proposal therefore should have no significant impact on these costs in the long run.


16. The implementation of the CNS/ATM systems is supported by the Aviation Advisory Board, the International Air Transport Association (IATA) and the airlines.

Way forward

17. Subject to any views Members may have, CAD will proceed to seek approval from the Finance Committee for the funding of the CNS/ATM project in stages.

Economic Services Bureau / Civil Aviation Department
February 1999


Major Components of the CNS/ATM Systems

Major ElementsMain Functions
1 Communications
1.1 Satellite Voice
  • To replace the noisy High Frequency (HF) communications currently used for long range applications.
1.2 Controller-Pilot Data Link Communication (CPDLC)
  • To make use of the uplink and downlink of satellite data for exchange ATC instructions and pilot-controller communications, which is much more efficient than voice communications.
1.3 High Frequency/Very High Frequency (HF/VHF) Data Link
  • To exchange ATC data between pilots and controllers to supplement and in the long term to replace voice communication.

    Applications include pre-departure clearance delivery, ATIS (Automatic Terminal Information System)/Volmet (Meteorological) Data Broadcast etc.
1.4 Aeronautical Telecommunication Network (ATN)
  • To cover the inter-networking infrastructure for the global aviation telecommunications network.

  • To allow data communications services for different user groups and will eventually operate globally encompassing all aeronautical data communication service users associated with the international aviation environment.
1.5 Air Traffic Services (ATS) Interfacility Data Communication (AIDC)
  • To exchange ATC information related to flight notification, flight coordination, transfer of control, surveillance data etc. between two ATS units.

    Applications include exchange of information such as notification of flights approaching a Flight Information Region (FIR) boundary, coordination of boundary conditions and transfer of control or communication etc.
2 Navigation
2.1 Global Navigation Satellite System (GNSS)
  • To eventually replace long range ground-based navigational aids for enroute and terminal navigation.
2.2 Wide Area Augmentation System (WAAS)
  • To broadcast the correction signals for aircraft to process the 'erroneous' GNSS satellite data to define its accurate position in air. The system can be upgraded to provide Category I precision landing function and thereby replace Category I Instrument Landing System.
2.3 Local Area Augmentation System (LAAS)
  • Functions similar to those of WAAS except that it would provide even more accurate correction data to provide up to Category III precision landing function and replace Category II/III Instrument Landing Systems.
3 Surveillance
3.1 Automatic Dependent Surveillance (ADS)
  • To provide aircraft position in space through satellite and VHF data links, for air traffic controllers for closer monitoring and/or control of aircraft movements, particularly in areas outside radar coverage.
3.2 Mode 'S' Secondary Surveillance Radar (SSR)
  • To enable individual addressing to each aircraft with uniquely allocated identification code.

  • To provide the capability of transmitting digital data between air and ground on air temperature, wind speed, wind direction, airport and runway serviceability status, etc.
3.3 Enhanced Ground Movement Control System (EGMCS)
  • To provide more positive and accurate surveillance of moving targets on or adjacent to the airfield, e.g. taxiway, apron, runway, sea area for aircraft, vehicles and ships.

  • To provide runway intrusion alert.
4 Air Traffic Management (ATM)
4.1 An Integrated Global ATM System
  • To merge and provide various ATM functions like:

      • ADS Data Processing;

      • Conflict Alert;

      • Minimum Safe Altitude Warning;

      • Flow Control Management;
      • Conflict Prediction;
      • Arrival Metering, Sequencing and Spacing;
      • Trajectory Conformance Monitoring etc.

  • To enable aircraft operators to conduct their flights in accordance with their preferred trajectories, dynamically adjusted, in the most optimum and cost-efficient manner.