What criteria are applied in the determination of "relevant" traffic.
What is "relevant"?
The CAAP for CA/GRS defines relevant traffic as;
"Aircraft that the CA/GRO knows to be operating within the MBZ and that may constitute a hazard to a broadcasting aircraft."
This has obviously has not been updated since the demise of MBZs, and probably should read "within the vicinity of a CTAF(R) aerodrome".
We use experienced people, and could train others if we were allowed to, who can make these determinations. To achive this we start off with a basic criteria of any aircraft with 10nm and 1000ft. However, if a light twin is departing to the east and a slower aircraft is arriving from the west and would get within 5nm of each other we would not pass it as the slow one is not going to catch up with the quicker one. Conversly, if a C172 departed AYE for AS and was 15nm distant when a faster aircraft departed on the same track and altitude, that traffic would be passed as they will meet and pass before arriving as AS. The key word is "flexibility".
It is just common sense really. We disregard any traffic that is clearly not going to conflict just as the pilot would. We do however keep a continual eye on the situation as it is always changing and we update as required.
The current Unicom rules will not allow this. On first contact at a Unicom aerodrome, taxiing or inbound, the Unicom operator must pass everything they have and let the pilot sort it out. CA/GRS sorts it out for the pilots.
Cheers,
John.