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The description, goals, and objectives of an improved global air navigation infrastructure emanate from the concept known as communications, navigation, and surveillance/air traffic management (CNS/ATM) systems. CNS/ATM was formally endorsed by the worldwide civil aviation community at the Tenth Air Navigation Conference in Montreal in 1991 (ICAO, 1991).
The primary goal of an integrated ATM system is to enable aircraft operators to meet planned times of departure and arrival and adhere to preferred flight profiles with minimum constraints and no compromise on safety. Therefore, although an integrated, global ATM system grew out of a need to meet growing demand, the ultimate effect will be enhanced operations and improved efficiency, primarily through less fuel burn for a given level of demand. ATM systems will therefore be developed and organized to overcome shortcomings discussed in this chapter and to accommodate future growth to offer the best possible service to all airspace users and to provide adequate economic benefits to the civil aviation community, with due regard for environmental concerns.
CNS/ATM has been defined as a system employing digital technologies, including satellite systems together with various levels of automation, applied in support of a seamless global air traffic management system. The main elements of CNS/ATM systems are described in detail in the ICAO Global Air Navigation Plan for CNS/ATM Systems (ICAO, 1998a). CNS/ATM systems will use very high frequency (VHF) and high frequency (HF) communication channels to transmit digital data between aircraft and between aircraft and ground stations. Satellite data and voice communications capable of global coverage are also being introduced. Improvements in navigation include progressive introduction of area navigation (RNAV) capabilities based on a global navigation satellite system (GNSS). Improvements in surveillance techniques will allow aircraft to automatically transmit their positions using data link technology.
It is generally agreed that these newer technologies will optimize the worldwide route structure. Planners will be less confined by the location of ground aids and more direct tracks will be used, allowing substantial savings in fuel. Ultimately, rigid route structures will be gradually eliminated or redesigned at a number of critical intersections. This flexibility has the potential to relieve congestion in very high density traffic areas.
In some regions, the increasing gap between traffic demand and capacity provided by the physical infrastructure at many key airports is a critical limiting factor. CNS/ATM systems can contribute to increasing capacity. Sophisticated automation and digital data links will help to make maximum use of available capacity and meet throughput requirements by improving the identification and predicted movement of aircraft and vehicles in the airport movement area. Additionally, increasing levels of collaboration and information-sharing between aircraft operators and ATM providers will create a more realistic picture of airport departure and arrival demand, allowing operators to make dynamic scheduling and flight planning decisions based on the ATM situation at any given time.
Enhanced instrument approach techniques will improve the flexibility of approach operations, thereby reducing noise and emissions levels. Parallel runways spaced as closely as 760 m or less are expected to routinely accommodate independent instrument flight rule (IFR) approaches based on high-data-rate secondary surveillance radars, data link technologies, improved cockpit and air traffic controller displays, and advanced automation. This technology will provide capacity increases in instrument meteorological conditions (IMC) at locations with such closely spaced runways. Also, automation tools will assist air traffic managers in establishing efficient flows of approaching aircraft for parallel and converging runway configurations.
The flow management process will monitor capacity resources and demand at airports and in terminal and en route airspace and will implement strategies, where required, to protect ATC from overloads and to provide an optimal flow of traffic by making best use of available airspace capacity. Clearances involving position and time, using an ATM data link interface with flight management computers, will be principal tools in assuring that ATM constraints are met with minimum deviation from user-preferred trajectories. The ability to predict optimum trajectory and monitor conformance of aircraft along these trajectories will allow the most efficient flight profiles and routes-resulting in an increase in overall efficiency, reductions in average fuel consumption per flight, and, consequently, reduced emissions levels for a given demand.
Future oceanic ATM operations will make extensive use of data link technologies, GNSS, HF and satellite-based digital communications, aviation weather system improvements, and collaborative decisionmaking techniques. Planned implementation of reduced longitudinal and lateral separation minima and reduced vertical separation (RVSM), along with more flexible handling of flights, is expected to lead to fuel savings. Implementation of RVSM above 8,850 m in the North Atlantic region has already resulted in increased capacity and reduced fuel consumption.
More timely weather information will be available as a result of two developments: Implementation of the final phase of the world area forecast system (WAFS), which uses direct satellite communications to deliver information to states, and increasing use of air-to-ground data link communications to uplink operational meteorological information. With these developments, the restrictions placed on the exchange of operational meteorological information are gradually being lifted.
With regard to the presentation of meteorological information, the increasing use of graphical information will be made possible by the introduction of air-to-ground data links.
With regard to the accuracy of meteorological information, introduction of the final phase of WAFS will increase the quality of meteorological information provided. However, future improvements in accuracy will depend significantly on the availability of frequent automatic dependent surveillance (ADS) reports, which include a meteorological information data block. Improved observing and forecasting techniques for volcanic ash and clear-air turbulence will eliminate overprediction of airspace affected by these phenomena, which can restrict the use of airspace. In the terminal area, integrated terminal weather systems will improve the accuracy of information provided regarding hazardous weather phenomena. Furthermore, real-time wind models run by ATC computers, based on ADS reports obtained during the climb-out phase, will be used to monitor the evolution of the wind field, which is required by ATC for sequencing of approaching aircraft.
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