GM1 SERA.6005 Requirements for communications and SSR transponder
CAA ORS9 Decision No.10
OBJECTIVE OF RADIO AND TRANSPONDER MANDATORY ZONES
(a) The objective of a radio mandatory zone (RMZ) and a transponder mandatory zone (TMZ) is to enhance the conspicuity of aircraft operating within, or in the vicinity of, complex, or otherwise busy airspace when the establishment of a more restrictive classification of airspace is not warranted, in order to maintain a balance between safe, efficient operations and fair, equitable access for all airspace users. Enhanced conspicuity can enable, as appropriate:
(1) airborne collision warning and/or avoidance systems;
(2) a ‘known’ or ‘recognised’ air traffic environment which, in turn, permits ATS to provide more specific traffic information on collision hazards; and,
(3) ground-based safety nets such as short-term conflict alert (STCA) and minimum safe altitude warning (MSAW)
(b) In addition, a RMZ may also be notified to facilitate:
(1) the provision of flight information, alerting and search and rescue services; or,
(2) coordination with appropriate military units or with ATS units in adjacent States in order to avoid the possible need for interception for the purpose of identification.