Can anyone explain to me why an aeroplane at 3,499' is not a problem to the radar cover but 3,501' would be? i.e. why a cut off at 3,500'
Because NATS wants to have radar cover extending to 2000ft below the base of controlled airspace, to be able to detect potential vertical infringers and/or provide traffic info for anyone descending out of CAS. Base of CAS here is 5500ft.
NS