Separation at the edge of CAS
At a GA safety evening, I asked the question below, but didn't get a clear answer. Can anybody comment:
In VMC or IMC I can legally fly very close to the edge of CAS, say the Luton or Stansted class D CTA. Controllers provide standard separation to IFR traffic within the CTA. How close to the edge of the CTA will they vector their traffic? If they are applying 3 m separation, does this mean they must keep their traffic at least 3m from the CTA boundary, to allow for possible invisible traffic at unknown altitude just outside CAS?
Does it make any difference if a) the controller has me on radar, ie an unidentified target b) if I am working the controller outside CAS with a squawk and verified mode C?
Is the lowest level you would descend your traffic 500' above the base of CAS? If so, this might only be 600' above me. This is then less than standard separation, isn't it?
This is not just a theoretical question as I often route along the NE boundary of the Stansted CTA in order to avoid the two gliding sites in the vicinity by flying through the small gap betweem them.