What is an RMZ
RMZ stands for Radio Mandatory Zone. It's an airspace area, usually in class G (uncontrolled), in which VFR pilots are required to tune to the local ATS frequency and maintain active listening, even though no clearance is required.
RMZs exist to:
- Improve traffic awareness in zones with high VFR traffic density
- Allow FIS or non-active towers to know who's flying in the area
- Guarantee a contact point in case of emergency
Typical RMZ characteristics:
- Located around an uncontrolled aerodrome or below/near an inactive CTR
- Published in the AIP with precise horizontal and vertical limits
- Inside, VFRs must announce on entry and provide position reports
What is a TMZ
TMZ stands for Transponder Mandatory Zone. In a TMZ, every aircraft must have operating transponder set to Mode C/S (with altitude encoding).
TMZs protect areas where:
- IFR traffic in arrival/departure descends below the TMA
- Military airspace borders civilian airspace
- VFR concentration creates collision risk invisible to radar
In a TMZ the pilot sets the transponder to a specific code (usually 7000 — generic VFR code — or a code assigned by ATC if in radio contact).
RMZ + TMZ together
Often the same area is both RMZ and TMZ at once — meaning radio AND transponder are required. It's one of the most common situations in Switzerland.
INFOHB-PMR, Lugano Information.
HB-PMRHB-PMR, Cessna 172, position 3 NM south of Bironico, altitude 3500 feet, VFR Locarno to Lugano, entering RMZ.
INFOHB-PMR, Lugano Information, roger, QNH 1018, no significant traffic in your area.
HB-PMRQNH 1018, copied, HB-PMR.
What to do before entering RMZ
Three steps:
- Tune to competent ATS frequency (usually FIS or TWR of main field).
- Announce entry with the standard formula: callsign + aircraft type + position + altitude + intentions + "entering RMZ".
- Maintain listening throughout transit. Report significant changes (altitude, route) and exit.
You don't need to wait for "clearance": as soon as you announce, you're authorized. But contact must be maintained.
Entering an RMZ without announcing yourself and without active listening. It's a violation of air rules (SERA). Not as serious as violating a CTR, but still a reportable infraction, and — more importantly — it makes you invisible to the system in case of emergency.
What to do before entering TMZ
Just one thing: operating transponder on Mode C/S, code 7000 (or assigned code if in radio contact).
If your transponder is broken or off, you can't enter a TMZ. You must deviate to avoid it, or (if necessary) request special authorization from APPROACH/FIS.
Typical RMZ and TMZ in Switzerland
Swiss RMZs/TMZs are numerous. The most relevant for Ticinese and general Swiss VFR:
- RMZ Lugano (around the field, class G)
- RMZ Locarno (around the field)
- RMZ Sion (Valais)
- TMZ in various corridors below Zurich and Geneva TMAs
- TMZ Bern (under the CTR during extended hours)
Precise limits change periodically. Always check AIP/VFR Manual and NOTAMs before flight.
Below the large Zurich and Geneva TMAs there are often LSAS — Low-Level Airspace Structures — that combine RMZ + TMZ. VFR flying below must have operating radio + transponder and announce entry.
Swiss specifics
Switzerland is one of European countries with the highest density of RMZ/TMZ relative to total airspace. This is because:
- Space is tight (mountains, multiple borders) - VFR traffic is very intense (tourism, flight schools) - Skyguide manages both civilian and military traffic
For the VFR pilot this means: carefully prepare your route consulting AIP, VFR Manual, NOTAMs. Skyguide has published a free manual with all routes, RMZs, and TMZs. Load it on tablet/EFB and keep it open.
Summary — to remember
- RMZ = Radio Mandatory Zone, listening and announcement mandatory (no clearance).
- TMZ = Transponder Mandatory Zone, Mode C/S transponder mandatory.
- They can coexist (RMZ + TMZ together).
- In Switzerland they're frequent, especially below TMAs.
- Announce on entry + maintain listening + report exit.
- Without transponder, no TMZ — you must deviate.
Sources
- ICAO Annex 11 — Air Traffic Services
- EU SERA Part 4 — Standardised European Rules of the Air
- AIP Switzerland — ENR 2.2 (Other Regulated Airspace)
- VFR Manual Switzerland — Skyguide
The wiki gives you the parts. The course teaches you to assemble them.
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