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Specific circumstances which may require the application of greater radar separation than the minimum normally prescribed are outlined below :
a)-Aircraft relative positions and performance limitations. (...)
b)-Radar technical limitations (...)
c)-Radar coverage (...)
d)-Radar controller limitations
1)-Radar controller workload
The number of aircraft which can safely be provided with radar separation at the same time is limited and varies with individual controller proficiency. A radar controller should therefore take due account of the number of aircraft within his sector of responsibility for which he is providing radar control, his own limitations and the geographical extent of his area of responsibility (i.e. the possible requirement to provide radar separation between aircraft in two or more separate traffic complexes which are some distance apart).
2)-Communications congestion
Because the relative positions of aircraft may change rapidly, it is implicit in applying radar separation that a radar controller should be able to communicate promptly with any aircraft under his control. If the communications congestion is such that this cannot be assured, then the radar controller should apply greater radar separation, or, when this is not practicable, terminate radar control. in this respect it should be noted that of all factors affecting the safe application of radar separation, communications congestion is probably the most important and one on which the radar controller may have little influence. Congestion is also difficult to predict since, with rapidly changing traffic situations, the communications load can build up to saturation within minutes. (...)
(...) Regional air navigation agreements providing separation between aircraft with the use of SSR alone (...) should cover the following points :
(...)
f)-SSR accuracy in the affected airspace should be verifiable by means of appropriate monitoring equipment;
(...)
i)-control of all aircraft within the affected airspace should be exercised by a single ATC unit, unless adequate means of co-ordination exist between all ATC units concerned.
(...)
(...) Provided that the plot extractor can discriminate between separate aircraft targets, this system provides the controller with clearly distinguishable position symbols which do not overlap if they are 9.3 km (5 NM) apart in range or azimuth (whatever the beam width of the radar sensor or range of target from aerial head may be). a basic requirement in the use of radar separation is to ensure that aircraft in close proximity can continue to be resolved as separate targets. On raw video radar displays, this resolution is easily achieved by the controller himself by ensuring that displayed radar blips edges (particularly in azimuth) do not overlap. However, with digital displays the controller cannot see from his display when any two aircraft are getting too close to each other in azimuth to permit the plot extractor to continue to resolve the aircraft as individual plots. It is essential, therefore, to compensate for this deficiency of digital data display systems by increasing the azimuth separation minimum applied to cater for the azimuth resolution capability of the sensor used. In practical terms, this requirement is dependent primarily on the beam width of the sensor and the range of target from the aerial head. It means, in fact, that, for azimuth resolution purposes, for any radar sensor, the 9.3 km (5 NM) separation criterion applied between radar position symbols holds good only up to a calculable range from the radar head. thereafter, the minimum should steadily increase with range from the radar head. (...)
(...) Air traffic control systems need to keep pace with the continuing increase in air traffic which usually increases the controller’s workload disproportionately and causes the ATC system to approach the limits of its capabilities.
Reducing the size of the airspace assigned to individual controllers in order to alleviate this situation results in an increase in the number of control sectors. The net result is an addition to the number of controllers, and an increase in the required inter-sector co-ordination and transfers of control, workload and complexity in the ATC system. Further subdivision will not increase the system capacity significantly and often does not justify the increased cost. (...)
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GUIDELINES FOR THE APPLICATION OF THE ECAC RADAR SEPARATION(20)
