Modernisation of classic radio navigation
DFS Deutsche Flugsicherung GmbH has completed a multi-year modernisation programme together with the Federal Ministry for Economic Affairs and Energy. In the period from mid-2021 to the end of 2025, older conventional VOR systems (CVOR) were replaced by modern Doppler VOR systems (DVOR) at four locations.
The locations affected are Nuremberg, Cologne/Bonn, Düsseldorf and Nienburg. Following technical and operational approval, the new systems are now fully operational. The conversion was implemented as planned and financed from federal funds.
However, no DVOR conversion was necessary for the Frankfurt am Main, Rügen and Magdeburg sites. The classic VOR components were decommissioned there; instead, navigation is now primarily based on DME systems (Distance Measuring Equipment), which are less susceptible to external influences.
Why DVOR is less susceptible to interference
Rotating beacons (VOR - VHF Omnidirectional Range) have been part of the basic equipment of conventional aeronautical navigation for decades. They transmit a reference and a varying signal, the phase shift of which is used to determine the direction of bearing to the station in the on-board receiver.
With the classic CVOR, the varying signal is simulated mechanically or electronically, which makes the system more sensitive to reflections and signal distortions. Wind turbines can cause electromagnetic interference due to their rotating rotor blades and large metal structures, which can lead to directional inaccuracies.
DVOR technology, on the other hand, utilises the Doppler principle. Several antennas arranged in a ring generate a virtual rotating signal. This method is significantly more robust against multipath propagation and reflections. Interference from nearby wind turbines therefore has a much smaller impact on accuracy.
Conflict between wind energy and air traffic control
Exposed locations such as hilltops, hills or open spaces offer ideal conditions for both radio navigation systems and wind turbines. Good visibility, low shadowing and stable wind conditions are ideal for both infrastructures.
However, the politically desired expansion of wind energy has repeatedly led to conflicts of interest between air traffic control and energy projects in the past. In certain constellations, wind turbines had to be relocated, reduced in height or cancelled altogether in order to protect the integrity of the navigation facilities.
Converting to DVOR significantly reduces this conflict. The modernised systems tolerate greater interference, resulting in greater planning security for energy projects. The project therefore also makes an indirect contribution to the energy transition.
Significance for general aviation
VOR and DME systems continue to play an important role in general aviation despite the increasing use of GNSS navigation. Although modern cockpits are increasingly using satellite-based procedures such as RNAV and RNP, ground-based radio navigation remains essential:
- as a backup in the event of GNSS interference
- for classic IFR procedures
- for training purposes
- as part of the European minimum network
As part of the PBN (Performance Based Navigation) strategy, Europe is pursuing the goal of reducing the number of conventional navigation systems, but not completely abandoning them. A so-called VOR minimum network is intended to guarantee basic navigation even if satellite systems fail.
In this context, the modernisation of existing systems is a strategic step. Instead of operating outdated systems that are highly susceptible to faults, robust systems are being installed that can remain part of this security network in the long term.
DME is gaining in importance
At some locations - including Frankfurt am Main, Rügen and Magdeburg - no DVOR conversion was carried out. DME systems play a central role there.
DME systems provide distance information between aircraft and ground station. In combination with GNSS or several DME stations, precise positioning can be determined. Modern concepts such as DME/DME positioning are considered a robust alternative in the event of GNSS failures.
For pilots, this means no immediate change in cockpit operations, but a long-term shift in the structure of the navigation infrastructure.
Investing in resilience
The modernisation underlines a strategic trend: air traffic control systems are not only designed for efficiency, but increasingly for resilience. Cyber risks, GNSS jamming, interference and infrastructural dependencies require robust backup structures.
With the successful upgrade of the four sites in Nuremberg, Cologne/Bonn, Düsseldorf and Nienburg, DFS is sustainably strengthening the stability of the German navigation network.
Conclusion
The planned replacement of CVOR systems with DVOR systems marks an important step in the further development of the German air traffic control infrastructure. The measure increases the technical robustness of navigation, minimises conflicts with the expansion of wind energy and at the same time ensures the functionality of ground-based backup systems.
For general aviation, this means more planning security and a stable basis for navigation - even in an increasingly satellite-based aviation world.
Source references:
Flieger.News
