At the beginning of April, the German air navigation service provider, DFS Deutsche Flugsicherung, started operation of its Precision Approach Monitor (PAM) for approach control at Frankfurt Airport. For this purpose, DFS integrated a Wide Area Multilateration (WAM) system from the firm Thales into its air navigation services environment. This is the first operational WAM system in Germany and was specially developed for use in congested airspace. It is one of a kind worldwide with respect to its size and performance capabilities.
With the PAM, the display of aircraft on the radar screen is updated every second instead of every five seconds as had been the case until now. The technology provides air traffic controllers with an improved and more exact display of aircraft arriving at or departing from Frankfurt Airport. This will improve the already high standard of safety. Much less time will be needed, for example, to identify and correct deviations from assigned routings.
A total of 34 sensors,evenly distributed in the area around the airport up to a distance of about 120 kilometres (exactly 128 x 80 NM) provide the data needed for the display at the control centre in Langen, south of Frankfurt. Conventional radar systems use the two-way propagation delay of electromagnetic signals emitted from transmitters to determine the position of aircraft. In the PAM system by contrast, the aircraft themselves send the signals and their position is calculated and displayed within one second. Within the approach control area, the lower limit for the system is about 150 metres (500 feet) and the upper limit is about 300 metres (1000 feet) above ground level. The remaining area is covered from approximately 900 metres (3000 feet) above ground level. In addition, the system provides information about aircraft all the way down to ground level both at Frankfurt Airport as well as Frankfurt-Hahn Airport.