but I have knowledge of several instances recently where collisions appear to have been narrowly avoided. Circumstances varied but some were saved by TCAS, some by timely radio calls coincidentally and some by radar.
But - how do you know these 'instances' would have resulted in collisions or merely the aircraft being a bit too 'adjacent' than the occupants would have liked. You only know aircraft were in danger of colliding by either a) it actually happening or b) accurate simulation / modelling after the event. As such you can't really make the statement above - it just isn't true.
I thought RIS or RAS was available.....where is the official definition of 'Limited radar'?!!
MATS Pt1, Section 1, Chapter 5
1.6 Limiting a Service
1.6.1 Outside controlled airspace in circumstances where controllers cannot continue to provide the following primary requirements:
a) traffic information and traffic avoidance in respect of all conflicting unknown aircraft for a radar advisory service; and
b) traffic information in respect of all conflicting unknown aircraft for a radar information service, controllers may elect to continue to give the service by limiting the extent to which it is provided.
1.6.2 Controllers must inform pilots when they limit the service and ensure that pilots are made fully aware of the implications of any limitation.
1.6.3 In particular the service should be limited when:
a) the aircraft is operating within 10 miles* of:
i) the edge of the radar display;
ii) weather clutter; or
iii) permanent echoes.
b) the aircraft is operating in an area of high traffic density;
c) the aircraft is operating near to the limits of solid radar cover; or
d) The service is being provided using secondary radar only.
* Except where the range selected (e.g. 3, 10, 15 miles) will not enable these criteria to be met during an approach to an aerodrome.