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Metering Tools: Several types of metering tools are already in use in Europe’s major Terminal Airspaces and these tend to facilitate pre-sequencing into the Terminal Airspace to avoid a ‘traffic bunching’ in an airspace which is naturally constrained in size. Although these metering tools can be tailored to meet the needs of individual airspaces, 4D traffic managers are being developed to improve the sequencing assistance within Terminal Airspace.

Figure 7- 3: Flattened lower limit of Terminal Airspace ‘system’ (Example)
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Whilst many large Terminal Airspaces co-exist in ECAC, it is seldom that the design and planning of these large Terminal Airspaces are treated as a seamless Terminal Airspace system. This is undoubtedly because the switch from Stage 4 to Stage 5 is not as natural a step as those which evolve from Stages 1-4. Though the operational requirements may signal the need to develop a Terminal Airspace system, these requirements need to be supported by high-level policy decisions given the implications of creating such a system. Examples of such implications may include human resource management, considerable investment in new ATC system architecture, increased requirements for environmental mitigation as public awareness grows of the level of traffic density and complexity.
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7.4.1 OPERATIONAL DRIVERS1
Given Europe’s geography, it is not surprising to find a significant number of large airports and their associated Terminal Airspace in close proximity. But geography in itself is not enough to trigger the need for the development of a Terminal Airspace system. The factors are usually cumulative – the compounding of factors and the accommodation of modern-day realities. These (European) factors include: -
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Co-ordination difficulties between sectors/centres;

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Requirement to mitigate environmental impact;

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Capacity shortfalls;

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Safety ‘alert’ e.g. frequent airspace violations; aircraft unable to comply with climb profile published in SID;

7.4.2 CORE AREA
Considering the operational drivers above, it is unsurprising that the next ‘upward’ step in the complexity ladder – beyond the Terminal Airspace System – is that of a cluster of Terminal Airspace systems and /or other high- or medium Terminal Airspaces. This configuration already exists in Europe in what is generally described as the ‘Core Area’. Covering the general area of south-east England, the northern half of France, the south-western part of Germany, Switzerland, the Netherlands and Belgium, this Core Area is often colloquially described as a huge Terminal area below (approximately FL285). In the future, it is not impossible to imagine the development of a Core Area System, along the lines of a Terminal Airspace system.

Figure 7- 4: Terminal Airspace ‘system’ and ‘Core’ Area
7.4.3 OPERATIONAL REQUIREMENTS
In order to keep ahead of the evolution of a Terminal Airspace to a Terminal Airspace system (or beyond), designers should periodically assess their operational requirements and work on their realisation. Given the dependence on aircraft equipage as regards some of these requirements, it may be necessary to define these requirements some 10 to 15 years in advance of the anticipate implementation time-frame. (Readers are referred to Part B, Planning, concerning the discussion on Requirements/Objectives in C.
　
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本文鏈接地址：EUROCONTROL MANUAL FOR AIRSPACE PLANNING 2(72)