To ensure safe air traffic, DFS operates numerous technical air navigation service facilities. Exposed locations, such as hilltops or mounds as well as open spaces, offer ideal conditions for these facilities. This is because interference-free transmission is essential to ensure that our air traffic controllers have access to reliable radar information and that pilots can adhere to the specified flight path.
However, the expansion of wind energy in Germany means that DFS facilities are increasingly facing competition. This is because wind turbines benefit from the same geographic conditions that are optimal for air navigation facilities. The problem with this is that wind turbines can interfere with these facilities. This applies in particular to radar installations and ground-based navigation facilities, so-called omnidirectional radio beacons.
Transmitting and receiving stations for the radio communication service ensure communication between pilots and air traffic controllers.
Radar facilities ensure that air traffic controllers always know the exact position of aircraft.
Navigation facilities help pilots determine their position.
Protection zones around omni-
directional radio beacons
VORs (very high frequency omnidirectional radio range) and DVORs (Doppler very high frequency omnidirectional radio range) are the lighthouses of the skies. These facilities continuously broadcast a rotating radio signal – hence the term omnidirectional – as well as a reference signal for the magnetic north pole. These signals are received and processed by aircraft and are used by pilots as an orientation aid.
If wind turbines or other structures stand too close to such beacons, they can interfere with the signal of the navigation facility by reflecting it. This reflection reaches the receiver on the aircraft in addition to the original signal and leads to bearing errors, i.e. distorted directional information.
To avoid such interference, the International Civil Aviation Organisation (ICAO) provides for the establishment of protected areas around these facilities. There is no blanket ban on building in such areas. However, these areas are relevant in any process for issuing building permits. In these areas, each construction project must be assessed separately to determine whether the construction could interfere with air navigation facilities.
With regard to the size of these protected areas, DFS is guided by new scientific findings that we developed together with the National Metrology Institute of Germany (PTB) as part of a research project funded by the German Federal Ministry for Economic Affairs and Climate Protection. A reassessment is now being made on this basis. Until the end of 2022, we are looking at reducing the protected areas of Doppler VHF omnidirectional radio beacons to a seven-kilometre radius. In this way, we are improving the compatibility of air traffic control and wind energy.
The assessment process
DFS, as the operator of the air navigation facilities, plays an important role in the approval of construction projects within protection zones. At the request of the German Federal Supervisory Authority for Air Navigation Services (BAF), DFS examines whether the planned structure may interfere with the signals of air navigation facilities. This process is stipulated in the German Aviation Act (LuftVG).
If the structure in question is a wind turbine, DFS has been using a new, modified assessment method since mid-2020. It is based on the latest scientific findings of the National Metrology Institute of Germany (PTB) in Braunschweig, Germany. With their help, we can estimate the specific interference caused by wind turbines better than before.
We use ICAO standards and recommended practices when assessing these results. Subsequently, DFS draws up an expert opinion. On this basis, the Federal Supervisory Authority for Air Navigation Services (BAF) decides whether the construction project applied for may interfere with air navigation facilities. The decision of the BAF is binding for the competent permit-granting authority.
www.baf.bund.de (German only)
DFS facilitates the expansion of wind energy
By 2030, we will have converted the approach and departure procedures at all designated international airports in Germany to predominately satellite-based navigation procedures as part of a European programme. This creates space for the decommissioning of omnidirectional radio beacons, and thus for new wind turbines.
However, we cannot completely do without ground-based navigation facilities. In Germany, there is currently no obligation to use satellite navigation and equip aircraft with satellite receivers. In addition, the ground-based facilities serve as a backup in case the satellite signals should ever be unavailable or disrupted.
Therefore, we must continue to maintain our ground-based navigation facilities but on much smaller scale. Our existing facilities are continuously being renewed in the process. We are replacing conventional omnidirectional radio beacons with the more technically sophisticated Doppler VHF omnidirectional radio range (DVOR), which are less susceptible to interference.
DFS also checks whether a planned structure may pose an obstacle to the aircraft themselves in addition to the requirements for the protection of facilities. This assessment is carried out on behalf of the aeronautical authorities of the federal states (Landesluftfahrtbehörde), without the involvement of the German Federal Supervisory Authority for Air Navigation Services (BAF). Here, DFS may recommend certain constraints, for example, height restrictions, day and night markings for better visibility or publication, for example in the Aeronautical Information Publication (AIP). If imposing constraints is not sufficient to ensure safety, DFS may recommend to the competent aeronautical authority that the construction project be rejected.
In Germany, all structures that reach a certain height or that are located near airports are monitored all over the country. The basis for this is the German Aviation Act Air (LuftVG). The act obliges construction projects to be submitted to the competent aeronautical authority. Due to their height and scale, wind turbines are also subject to this obligation.
Obstacle protection also applies to cross-country flights because pilots need to know where tall obstacles are to be expected on the flight path. For low-flying aircraft, such as rescue helicopters, all structures above a height of 100 metres above ground are therefore published on aeronautical charts. At night, obstacles must have sufficient lighting to be visible to pilots.
Navigation aids of DFS
DFS is continuously modernising its navigation infrastructure. VHF omnidirectional radio beacons (VOR) make up one part of this infrastructure. These are of particular importance for the further expansion of wind energy as wind turbines can interfere with the operation of these facilities. Since 2002, we have decommissioned 17 VORs, and another 20 or so will follow by 2032, as part of the switch to satellite navigation. In addition, conventional VORs (CVOR), which are more susceptible to interference, are being replaced with more robust Doppler VORs (DVOR). This creates even more space for wind turbines and thus supports the energy transition Germany is striving for.
The following facilities are planned to be decommissioned in the next few years:
- Luburg VORDME (2023)
- Fürstenwalde VORDME (2025)
- Roding (2022)
- Gedern (2023)
- Cola (2024)
The following facilities are planned to be converted from CVOR to DVOR in the next few years:
- Cologne Bonn (2022)
- Düsseldorf (2023)
- Frankfurt, Charlie (2023)
- Nienburg (2023)
- Frankfurt, Metro (2024)
- Rügen, Trent (2024)
- Magdeburg (2025)
- This list reflects the current planning as at June 2022. Changes may be made at any time for operational or technical reasons. This applies both to the installations scheduled for decommissioning and to the time of decommissioning.
- The list is therefore not binding and not suitable as a basis for planning building projects.
- Technical decommissioning does not include the actual dismantling of the antenna system. Initially, the system will only be switched off and the protection zone revoked.
- After the VORs have been decommissioned, distance measuring equipment (DME) will continue to be operated at most of the sites. With a radius of three kilometres, their protection zone is significantly smaller.