Radio Mandatory Zones (RMZ)

Radio Mandatory Zones (RMZ) are designated volumes of airspace, often found around airports, which require aircraft to be appropriately equipped. They can be established with or without accompanying controlled airspace. RMZs are utilised to enhance the ‘visibility’ or conspicuity of aircraft operating within or in the vicinity of complex or busy airspace for the safety of all airspace operators. The airspace is established under SERA.6005* and is implemented to enhance the safe operation of flights into and out of an airport or area by providing as much information as possible to ATC without the need for excessive controlled airspace. Exceptionally, non-equipped aircraft may be permitted to enter the zones subject to compliance with pre-agreed specific criteria or Letters of Agreement.

An RMZ is annotated on a chart with a border of blue semicircles. Details of the zones can be found in the UK AIP both in the AIP General Section and, in the case of the Hawarden and Land’s End RMZ, the Aerodrome Section. In some cases, RMZs are temporary and established to address a short-term requirement such as radar maintenance which would otherwise have to be addressed by a Restricted Areas (Temporary) or TMZ. Before entering an RMZ, pilots are to make an initial call containing:

  1. the designation of the station being called;
  2. callsign;
  3. type of aircraft;
  4. position;
  5. level;
  6. the intentions of the flight; and
  7. other information as prescribed by the competent authority shall be made by pilots on the appropriate communication channel.

Once this information has been passed to and acknowledged by ATC, a pilot may enter the RMZ. However, if a pilot is requested to ‘stand by’ before the required information is passed, they must remain outside of the RMZ. RMZ Controlling Authorities are required to resume communications with pilots as soon as possible after having instructed them to ‘stand by’.

* From 1 January 2021 the UK law that applies to such aviation rights and obligations are the retained EU Regulations, as amended by various UK Statutory Instruments (made under the European Union (Withdrawal) Act 2018)