Background: Why TMZ is being further expanded
Transponder Mandatory Zones are airspaces in which aircraft are obliged to operate an activated transponder with automatic altitude transmission and to transmit an assigned or published code without being requested to do so, even during VFR flights. The aim of this measure is to make uncontrolled visual air traffic more visible to air traffic control and thus improve the separation between IFR and VFR traffic and traffic information as a whole.
The increasing traffic at and around larger commercial airports, but also the rising density of VFR flights in lower airspace, have led to the increased use of TMZs as a comparatively low-threshold safety measure in recent years. Unlike controlled airspaces, they do not require clearance, but do require minimum technical standards.
Basic requirements in a TMZ
For flights under visual flight rules within a TMZ, it is mandatory to be equipped with a functioning secondary radar responder including Mode C or Mode S. The transponder code published or assigned by air traffic control must be active. The transponder code published or assigned by air traffic control must be activated; in addition, the pilot must be ready to listen on the corresponding frequency.
The obligation applies regardless of whether radio contact is actually established. Military aircraft and flights on behalf of the Federal Ministry of Defence are exempt from this regulation if they are carried out as part of radar-based military procedures.
Exceptions may be authorised in justified cases. These are only granted after consultation with the responsible radar control centre and only if the safety of air traffic is not impaired.
New and expanded TMZ at a glance
With the current announcement, several TMZs will be newly established or their structure adjusted. The Bremen, Dortmund, Dresden, Egelsbach and Erfurt regions are particularly relevant.
In the Bremen area, a large TMZ will be established between flight level 65 and flight level 100. It lies above the classic VFR altitude band, but applies in particular to higher performance aircraft and cruising flights in the upper visual flight range. Exceptions can be coordinated via Bremen Radar.
In the Dortmund area, there is a complex structured TMZ with several differently staggered lower limits between 3500 and 4500 feet above sea level. The TMZ is active around the clock and extends up to flight level 65. Due to the staggered lower limits, careful altitude planning is required, especially for crossings in close proximity.
The regulation is particularly extensive in the Dresden area. Here, a large-scale TMZ with an upper limit up to flight level 100 is set up, which consists of several sub-areas. Parts of this TMZ are defined as HX airspace and are flexibly activated or deactivated depending on the operating direction of the runways. In addition, certain areas are permanently activated during the winter months between November and March. This significantly increases the complexity for VFR pilots, as not only the geometry but also the activation status must be taken into account.
At Egelsbach aerodrome, a TMZ is set up from the ground to 1500 feet above sea level. Transponder codes are assigned flexibly by the aerodrome information service. For approaching aircraft, this means that an active radio link is required before or at the latest when entering the close-in area. Aircraft that are already travelling with a plausible individual code will retain this code. Historic aircraft or aircraft that are not transponder-capable due to their design are expressly excluded.
A TMZ is set up in the Erfurt area, which is activated depending on the IFR traffic at the airport. The lower limits are staggered between 2500 and 3500 feet above sea level, the upper limit at flight level 65. This TMZ is not permanently active, but requires increased attention during flight preparation, as it is activated dynamically.
Effects on flight preparation
With the expansion of TMZs, the importance of a thorough airspace analysis continues to increase. In addition to classic airspaces, pilots will in future have to increasingly check whether their planned route leads through a TMZ, which lower and upper limits apply and whether there are any time or operational dependencies.
Airspaces with HX status or variable activation are particularly challenging. Here, a glance at the ICAO chart alone is no longer sufficient. NOTAMs, up-to-date information from air traffic control and, if necessary, enquiries with FIS or radar centres become an integral part of flight preparation.
Technical and operational consequences
For general aviation, the further expansion of the TMZ effectively means an increasing transponder obligation. Aircraft without a functioning transponder can only use certain regions with explicit special authorisation or not at all. This applies in particular to vintage aircraft, gliders with auxiliary engines or special models.
At the same time, the importance of correct transponder operation is increasing. Incorrectly set codes, missing altitude transmission or switched-off devices can not only be relevant to safety in TMZ, but can also lead to reportable incidents.
Classification and outlook
The establishment of additional transponder mandatory zones follows a clear trend: more traffic safety through better electronic visibility without formally controlling the airspace. For many pilots, this means additional requirements and more complexity, especially in busy airspace.
In the long term, it is becoming apparent that the electronic recognisability of aircraft will become the standard. The current TMZ regulations should therefore be seen less as an exception and more as an intermediate step on the way to an increasingly transparent lower airspace. Those who familiarise themselves with the new structures at an early stage and adapt their flight preparations accordingly will be able to continue to fly safely and in compliance with the rules in German airspace in the future.
Source references:
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