In shortA radio mandatory zone (RMZ) is airspace of defined dimensions in which carrying and operating radio equipment is mandatory; a transponder mandatory zone (TMZ) is airspace of defined dimensions in which carrying and operating a pressure-altitude reporting transponder is mandatory.

Where RMZ and TMZ come from

Both zones are defined in the Standardised European Rules of the Air (SERA, Regulation (EU) No 923/2012), and their requirements are in SERA.6005. A competent authority designates them on top of the airspace class; they add equipment and communication rules but do not change the class.

They are used where the class alone would let aircraft fly unknown to air traffic services, typically an RMZ in class E, F or G, for example around an uncontrolled aerodrome with instrument approaches, and a TMZ where controllers and collision-avoidance systems need to see every aircraft. SERA requires both to be published in the AIP.

RMZ: what you must do

SERA.6005(a) applies to VFR flights in parts of class E, F or G airspace designated as an RMZ, and to IFR flights in parts of class F or G airspace designated as an RMZ:

  • Before entering, make an initial call on the appropriate frequency containing the station you are calling, your call sign, aircraft type, position, level, the intentions of the flight, and any other information the competent authority prescribes.
  • Inside, keep a continuous air-ground voice listening watch and establish two-way communication as necessary.
  • Without a working radio, you may enter only in compliance with the alternative provisions the air navigation service provider has prescribed for that RMZ.

An RMZ does not turn the airspace into controlled airspace. In a class E, F or G RMZ, a VFR flight still needs no clearance: the zone requires you to talk, not to be cleared.

TMZ: what you must do

SERA.6005(b) applies to all flights in airspace designated as a TMZ:

  • Carry and operate an SSR transponder capable of operating in Modes A and C, or in Mode S. A transponder without altitude reporting (Mode A only) does not meet the requirement.
  • Switch it on with altitude reporting before you enter, and set the code assigned by ATS or, if none is assigned, the code the AIP prescribes.
  • Without a suitable transponder, entry depends on the alternative provisions the air navigation service provider has prescribed for that TMZ.

A TMZ is not tied to a particular class, and it can be combined with an RMZ; the AIP and charts then show an RMZ/TMZ.

RMZ and TMZ side by side

The two zones compared:

Radio mandatory zone and transponder mandatory zone compared (SERA.6005)
RMZTMZ
RequirementCarry and operate radio; initial call before entry; continuous listening watchCarry and operate a Mode A and C or Mode S transponder
Applies toVFR in designated parts of class E, F or G; IFR in designated parts of class F or GAll flights in the designated airspace
ClearanceNot required by the RMZ itselfNot required by the TMZ itself
ExceptionsAlternative provisions prescribed by the air navigation service providerAlternative provisions prescribed by the air navigation service provider
SourceSERA.6005(a)SERA.6005(b)

Worked example: an illustrative RMZ transit

Illustrative scenario: a VFR pilot in a Cessna 172 plans to cross an RMZ in class G around an uncontrolled aerodrome with instrument approaches. The station, call sign and places below are invented.

EXAMPLEFIELD INFORMATION, D-EXYZ,
CESSNA 172, 5 NM NORTH OF EXAMPLEFIELD,
2500 FT QNH 1013,
VFR TO WESTTOWN, TRANSITING THE RMZ NORTH TO SOUTH
  • The call contains every element SERA.6005(a)(2) lists: the station called, call sign, aircraft type, position, level and intentions.
  • After the call, the pilot stays on the frequency until leaving the RMZ. There is no clearance to wait for, but instructions or traffic information may follow.
  • If the route also enters a TMZ, the transponder must already be operating with altitude reporting.

Before your next flight

Plan RMZs and TMZs like any other airspace boundary: