Well first of all, CAP493 is MATS - manual of air traffic services - and doesn't form any part of pilot training syllabus nor air law nor licensing exams. It's a document written by the ATC club for the ATC club to use. In the same way, I wouldn't expect Controller training to take in aircraft Flight Manuals nor Operations Manuals (even generic ones, such as JAR-OPS 3).
Secondly, although you could argue that the terms is defined in MATS, its a definition not a description, and a rather convoluted one at that. I could read the definition and still not really understand the implications. For something so often used, I continue to maintain that its very badly described even in MATS and not at all in any material considered relevant to a pilot.
It would be so easy if it were described in the AIP, or if UK used the same terminology as the rest of the world. I have never heard the term in France, Italy, Netherlands nor Malta (recent trips) and having flown a helicopter from UK to Borneo and back can't recall hearing it then either (although it was some time ago). ATSOCAS is similarly non-standard and causes a hoot in the channel area when listening to UK pilots asking French ATC for one of the services, or French pilots being told by London what service they are getting, to a blank and confused response.
I suppose I sound as though I have a bit of a downer on ATC and its true, I do. But not on the individuals, most of whom are great, but on the system. My feeling is that since privatisation of ATC, priority 1 is to not be liable / get sued, with flight safety coming in a distant second.
Last edited by HeliComparator; 14th Jun 2013 at 14:00.