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Figure 7- 1: Sample Evolution of Terminal Airspace system
 
Edition: 2.0 Released Issue Page  C-7-3 Amendment 1 – 17/01/05
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7.2.1 EVOLUTION OF THE APPROACH CONTROL FUNCTION
The evolution of the Terminal Airspace through various stages the vertical dimension also tends to follow a pattern when a Terminal Airspace system is created. This is illustrated in the next diagram which has used Terminal Airspace X (above) as an example for Stages 1-4.
Extended-APP function Ref. Figure 7-1 (above): Evolution of Terminal Airspaces in the vertical dimension and associated sample ATC functions X 1 2/3 4 XX X  Extended-APP function APP Control Function Terminal Airspace System -Sectorisation & ATC function 5 
Terminal Airspace Approach Control Area Control  Hybrid ACC-APP Control 

Figure 7- 2: Evolution Terminal Airspace dimensions and ATC ‘functions’
Comments on Figure 7-2:
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ATC Sectorisation is frequently the first ‘solution’ when traffic levels increase significantly in a Terminal Airspace X; this is shown at Stage 2.

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In turn, Stage 3 does not reveal a change in dimensions but as shown in Figure 7-1, the holding system has been increased;

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At Stage 4, the Terminal Airspace has grown in size – both vertically and laterally to accommodate the increased traffic and traffic complexity.

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Significantly, from Stages 1 – 4, the Approach Control function is likely to be carried out by the ATC Unit responsible for X but this is not the case in Stage 5. In this stage, the importance of the Terminal Airspace structure is superseded by the emphasis on ATC sectorisation across the Terminal Airspace system (See Note 2). Here the extended approach function is raised and spread through the greater part of the Terminal Airspace system between an extensive network of sectors and the ‘pure’ Approach function ‘limited’ to a small Final Approach Director sector.

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In Stage 5, extended-approach functions in a Terminal Airspace system typically involve a hybrid of (Lower) Area Control and (Extended) Approach Function. These can be executed by controllers specially trained for these (hybrid) tasks or ACC or Approach Controllers.

Note 1: In context, ‘extended approach function’ refers to pre-sequencing, or first phase sequencing prior to sequencing for Final Approach.
Note 2: Whilst ICAO’s division of airspace system makes no provision for a change in emphasis from airspace structure to ATC Sectorisation, Terminal Airspace systems in ECAC appear to share this characteristic.
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本文鏈接地址：EUROCONTROL MANUAL FOR AIRSPACE PLANNING 2(69)