Demand for air travel is growing rapidly. Shortfalls in capacity and other constraints on the efficiency of airport and aircraft operations have negative effects on airline costs, passenger convenience, and the environment. Making efficient use of finite airspace and airport resources while ensuring high levels of safety is the primary mission of ATM which involves considerable coordination of planning and operations among regulators, service providers, and users at the global, regional, and national levels.
This section discusses the conventional ATM system in the context of operational phases of flight, highlighting constraints and limitations and the negative effects they have on airport and aircraft operations-including unnecessary fuel burn and, consequently, excessive emissions. The section then describes changes anticipated for the future based on new technologies and improved procedures that are expected to lead to the creation of a more efficient and integrated global ATM system.
Improved ATM as envisaged will encompass traditional elements of air traffic services (ATS)-air traffic control (ATC), air traffic flow management (ATFM), and airspace management (ASM)-but will also functionally integrate these elements with ATM-related aspects of flight operations into a total system. Today, ATC accounts for the greatest percentage of ATS on a global basis; ATC serves primarily to prevent collisions between aircraft and between aircraft and obstructions in the airport maneuvering area and to expedite and maintain an orderly flow of air traffic. For current (i.e., 1998-99), worldwide aircraft fleet operations, improvements to the ATM system alone could reduce fuel burn per trip by 6-12% (EUROCONTROL, 1997b; FAA, 1998a; ICAO, 1998b).
Improving ATM requires that advanced technological and management systems and procedures be adopted more rapidly and on a broader scale than is presently the case. Specific improvements related to ATM and the operation of aircraft that could reduce fuel burn are covered in this chapter; institutional, regulatory, and economic policy measures that could also have an important influence on future traffic growth and associated fuel burn are covered in Chapter 10.
In 1983, the ICAO Council established a committee to identify and assess new technologies and make recommendations for the future development of air navigation. After close analysis, the special committee on the future air navigation system (FANS) recognized that the existing air navigation system and its subsystems suffered from technical, operational, procedural, economic, and implementation shortcomings. In addition to infrastructure constraints, conventional airspace organization of flight information regions and their supporting infrastructure of routes and ground-based facilities and services are based largely on national rather than international requirements. For these reasons, aircraft must plan their flights along strictly defined routes and be channelled, to a certain degree, so that air traffic controllers can keep aircraft safely separated from each other.
In some regions, limited airport capacity is one of the main constraints on continued growth in air transport; this limited capacity results in congestion and delays. There is also a lack of adequate awareness and shared decisionmaking among ATC, ramp, and taxi areas. In low-visibility conditions, movements are severely restricted, and there is increased risk of runway incursion. Insufficiently developed taxiways and aprons also limit runway and airport capacity. Operational limitations for noise control may also have a negative effect on access to and from key airports. Automated ground-based systems to manage departures and arrivals efficiently are not available in most cases, and onboard automation is therefore underutilized. Published arrival and departure procedures-created to ease controller workload and ensure separation between departures and arrivals-are often inflexible, indirect, and less than optimum.
The existing worldwide route structure often imposes mileage penalties compared to the most economic routes (generally great-circle routes); it also takes into account wind, temperature, and other factors such as aircraft weight, charges, and safety. Use of a fixed-route network often results in concentration of traffic flows at major intersections, which can lead to a reduction in the number of routes and flight levels that are available. Studies on penalties to air traffic associated with the European ATS Route Network alone suggest that ATM-related problems add an average of about 9-10% to the flight track distance of all European flights en route and in terminal maneuvering areas (TMA) (EUROCONTROL, 1992). Lack of international coordination in the development of ground ATC systems exacerbates these problems. Examples include inconsistent separation standards in radar and non-radar airspace and operation at less than optimum flight levels in oceanic airspace as a result of communication deficiencies.
Currently, three main areas can be distinguished in which improvements need to be made in the way meteorological information is provided to international civil aviation: Timeliness, presentation, and accuracy.
Timeliness problems are largely related to the inability of telecommunications channels in some regions to cope with increasing message traffic. As a result, tight restrictions have been established concerning the exchange of operational meteorological information, which now does not fully meet flight planning requirements for increasingly long-range aircraft operations. The presentation of meteorological information has also been largely dictated by the telecommunications channels used, which have imposed a predominance of alphanumeric messages over graphical information, especially in the cockpit.
Finally, the accuracy of meteorological information needs improvement. For the en route phase of flight, the information provided is not always based on output from the most advanced numerical weather prediction models. In the terminal area, up-to-date and accurate meteorological information may not be available to the pilot because of congestion of voice channels and/or lack of modern observing systems.
The fundamental premise that every state has complete and exclusive sovereignty over the airspace above its territory can be traced to the Convention on International Civil Aviation (ICAO, 1997). States implement restrictions on the use of airspace for a variety of reasons, including technological limitations, political considerations, security, and environmental concerns. However, by far the most important reason for restricted airspace is to accommodate the needs of states' military forces. Restricted airspace does not allow aircraft to minimize their emissions by direct routing between two points. Significant regions of airspace are permanently reserved or restricted, thereby forcing civil air transport to circumnavigate these areas.
The extent of the problem varies by region. In the European region, for example, 24 states are applying the flexible use of airspace (FUA) concept (EUROCONTROL, 1998a). The basis for FUA is that airspace should no longer be considered as either military or civil airspace but should be considered as a continuum, shared in accordance with user needs and used flexibly on a day-to-day basis. Although national security requirements must be key factors in revising a nation's restricted airspace allocation, problems related to restricted and military airspace could partly be solved by modernization of the ATM system. Negotiation of overflying rights to shorten routes would also contribute to solving the problems.
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