.
shorter updating period;

.
higher resolution display, providing position prediction and deviation alert.

6.3 OPERATIONAL assessment
6.3.1 Reduction of horizontal separation
As stated in the introduction, the appropriate ATS authority is authorised to reduce the radar separation minima. Once that the radar separation minima are established, it is incumbent on ATC to ensure that these minima are not compromised. A reduction of the horizontal separation minima to values such as 3 NM and 2.5 NM, should be carefully evaluated and due notice taken of following factors :
a) Navigation accuracy based upon airborne and ground components;
b) The time interval between position information; c) Rapid and reliable air-ground communication;
In TMAS, by consistently applying radar separation minima, especially to incoming aircraft on the approach track, controllers can optimise throughput. This sometimes leads to a reduction of the length of time for which peak traffic loading is experienced. In comparison , and sometimes paradoxically, in busy periods in the en-route environment, the controller often tends to increase the radar separation to avoid an unacceptable high workload for the given circumstances
6.3.2 ECAC common radar separation
There is an objective to implement common radar separation minima in the ECAC States as follows :
a) High complexity TMAs : 3 NM when radar capabilities at a given location permit; and
b) Category 1 airport : 2.5 NM between succeeding aircraft which are established on the same final approach track within 10NM of the landing threshold (Cf. Examples in Annex 3, Attachments B, C and D for Germany/Frankfurt, UK/Heathrow and Austria/Vienna).
Note : Category I airport as used in EATCHIP terminology
This minimum can be applied provided that:
1) the average runway occupancy time of landing aircraft is proven, by means such as data collection and statistical analysis and methods based on a theoretical model, not to exceed 50 seconds ( an example of Runway Occupancy Time calculations at Frankfurt Main is set out in Annex 3, Attachment E);
2) braking action is reported as good and runway occupancy times are not adversely affected by runway contaminants such as slush, snow or ice;
3) a radar system with appropriate azimuth and range resolution and an update rate of 5 seconds or less is used in combination with suitable radar displays; and
4) the aerodrome controller is able to observe, visually or by means of surface movement radar (SMR) or a surface movement guidance and control system (SMGCS), the runway-in-use and associated exit and entry taxiways;
5) wake turbulence radar separation minima as per ICAO Doc 4444,
7.4.4 or as may be prescribed by the appropriate ATS authority
(e.g. for specific aircraft types), do not apply;
6) aircraft approach speeds are closely monitored by the controller and when necessary adjusted so as to ensure that separation is not reduced below the minimum;
7) aircraft operators and pilots have been made fully aware of the need to exit the runway in an expeditious manner whenever the reduced separation minimum on final approach is applied; and
8) procedures concerning the application of the reduced minimum are published in Aeronautical Information Publication.
7. COMMUNICATION FACILITY PROPERTIES
7.1 General
Although in previous chapters both the operational and technical aspects related to radar separation minima have been discussed, it is felt appropriate to dedicate a separate paragraph to the two-way controller/controller communication properties.
Material related to this issue has been taken from the following documents :
-ICAO documents :
.
Doc 4444/PANS-RAC;

.
Annex 10 - Aeronautical communication, Volume II; and

.
Annex 11 - ATS requirements for Communication;
　
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