Refresher: Sicht- und Instrumentenflüge in der TMZ Nordostschweiz

The Transponder Mandatory Zone North-East (TMZ NE) has been in existence since 2022 and is located in the area of instrument approaches to St. Gallen-Altenrhein and Friedrichshafen airports. It enables Skyguide air traffic control to make all aircraft visible on radar and to communicate with them by radio. However, this solution alone does not replace the situational awareness of pilots. This means that all pilots must actively monitor the airspace and operate according to the “see and avoid” principle – which prompts IFR pilots in particular, but also VFR pilots, to sharpen their situational awareness and, if necessary, change their flight pattern. In order to reduce the number of aircraft approaches in the TMZ NE in the future, we would like to once again focus our attention on visual and instrument flight procedures.

TMZ North-East: A brief overview

The TMZ NE was established to reduce the risk of dangerous approaches (AIRPROX). It is an area with VFR and IFR traffic in Echo airspace. The most important information at a glance:

• Minimum requirements: Mode S transponder of at least Level 2 with SI code and elementary surveillance functionality with code 7000. Hang gliders, parachutes, and model aircraft (excluding drones) are generally exempt from the requirement to carry and operate a transponder.
• Voluntary standby: Before entering the TMZ NE, select the Alps Radar frequency 119.925 MHz and set the transponder code to 2677 (no initial call required by pilots!). This signals your standby status and allows air traffic control to reach you quickly, for example, for traffic information on IFR traffic. Please note: In the neighboring TMZ EDNY, standby listening on the Alps radar frequency is mandatory.

The dimensions and procedures of TMZ North-East are described in detail and published in the VFR Manual (RAC) and AIP (ENR 2.2).

Situational awareness in visual flight (VFR)

As a VFR pilot, it is not intuitive to know which routes IFR traffic is taking. Where are the IFR flights?

Satellite-based approaches are common today. In such procedures, the T-configuration according to ICAO is common: In Friedrichshafen, this “T” is very clearly visible (marked in yellow). The blue triangle shows the VFR reporting point Victor from St. Gallen-Altenrhein.

IFR aircraft are often guided to the final approach segment with vectors via the approach path illustrated above in the T configuration. Important: The alignment with the final approach takes place in Echo airspace, outside the TMA and CTR.

In addition to vectors to final, there are also standardized approach routes (STAR) and departure routes (SID). Below FL100, these routes are also mostly located in Echo airspace. One example is the STAR to the ILS in St. Gallen-Altenrhein, where airspace Echo begins shortly after the Zurich East VOR (ZUE), below 6,500 ft MSL. The diagram above shows the CTR/TMA of St. Gallen-Altenrhein in blue dotted lines.

Useful tips for flights in TMZ NE:

Tip 1: Be reachable. VFR and IFR flights are often not on the same frequency. However, air traffic controllers (ATCO) and flight information service officers (FISO) are well connected with each other. It is therefore worth maintaining listening watch at all times. Thanks to the Mode S transponder, the ATCO can see the identification directly and can issue a traffic advisory in good time if necessary.

Tip 2: As a VFR pilot, it is worth taking a look at the lateral and vertical approach paths of IFR traffic. This promotes situational awareness. However, it should be noted that there are often deviations from the published IFR routes and flight altitudes (direct-to, vectoring, etc.).

Tip 3: If your flight path crosses the extended centerline of a runway (EDNY and/or LSZR) or the immediate vicinity of an airport with instrument approaches, then see-and-avoid, transponders, radio standby, or contact with the Flight Information Center are particularly important.

Tip 4: When cruising, always follow the semicircle rule to ensure a vertical separation of 500 feet between VFR and IFR traffic.

Tip 5: Cloud distances are important. IFR crews are required to use see-and-avoid outside of clouds, but a visual scan of the airspace takes 10 to 20 seconds. At the speed of a typical IFR general aviation aircraft, the cloud separation distance of 1,500 meters is flown through in this time. The vertical cloud separation of 1,000 feet allows for traffic scanning after an aircraft descends or ascends from a cloud. The cloud separation on the part of VFR traffic thus significantly improves the probability of success of see-and-avoid.

Situational awareness in instrument flight (IFR)

It is important for IFR pilots to be aware that they are sharing the airspace with many other aircraft, especially those operating under visual flight rules. The VFR ICAO chart quickly shows that VFR motorized aircraft, gliders, hang gliders, and parachute drop aircraft are to be expected in the TMZ North-East area.

Tip 1: Warnings about unknown VFR traffic on IFR charts should be taken seriously. A glance at the VFR ICAO chart helps to assess airspace usage in the approach and departure area.

Tip 2: Air traffic control does not separate VFR and IFR traffic in Golf, Echo, or Delta airspace. Any traffic information provided by air traffic services (ATCO and/or FISO) is only intended to assist in the application of see-and-avoid.

Tip 3: The avoidance rules according to SERA, the Standardized European Rules of the Air, apply regardless of the type of flight. There is no right of way according to instrument flight rules.

Tip 4: If a conflict is imminent, safety comes first. According to SERA Section 3, the PIC is obliged to perform evasive maneuvers to avoid dangerous approaches. This applies regardless of the type of flight in relation to VFR or IFR. Outside of clouds, you have to anticipate such situations and react flexibly.

Conclusion

Both visual flight and instrument flight traffic must perform very important tasks to ensure that the see-and-avoid principle works effectively. Situational awareness is hard work and requires knowledge of the activities in the shared airspace. Every aid is an additional safety net, be it a transponder, contact with the Flight Information Center, listening watch, or collision warning systems.

Documents

VFR ICAO chart for download

Safety first, every flight, every time.