TMZ (transponder mandatory zone)

Airspace & rules

A TMZ is airspace in which aircraft must carry and operate a pressure-altitude-reporting transponder. It makes VFR traffic visible to ATC and collision-avoidance systems.

German term: Transponder Mandatory Zone (TMZ)
Abbr.: TMZ

TMZs are often established near busy airports in class E or G airspace. Some states publish a listening squawk combination for a TMZ: you squawk the code and monitor the frequency.

In practice

Check the AIP or VFR chart for the published squawk and frequency of each TMZ on your route.

Related in Altimate Pilot

Moving map & airspace

Related terms

Transponder (Mode S)
Squawk (transponder code)
RMZ

Official sources

EASA Easy Access Rules – SERA (Reg. (EU) 923/2012)
DFS – AIP Germany (VFR)

Content reviewed: 2026-11

For general information only. Always use official sources, your aircraft's flight manual and current national rules for flight decisions.