Over a much longer period, research in the area of wake vortices has been stimulated by the European Commission by co-financing many European research programs. The interest in wake vortices stems from the fact that airport capacity is becoming increasingly a bottle neck for the air transportation system. Also the introduction of the A380 has stimulated research as the adequacy of separation standards for new and larger aircraft has to be demonstrated.

Wake vortex research is presently at interesting cross-roads. EUROCONTROL is of the opinion that we are at the transition phase to introduce changes to the present system within the next 5 years, e.g. by introducing time based arrivals and weather based departures. This is partly based on (high level) studies that indicate substantial capacity benefits for e.g. time based separations. Similar cost / benefit studies in the US also show large benefits. Yet at Frankfurt Airport the original expectations that the proposed procedural changes with a weather dependent Wake Vortex Advisory System (WSWS) will increase capacity while still maintaining safety, have not been realised so far in spite of a considerable effort. It might be the right time to step back a bit to see if knowledge is sufficient to implement real changes.

Wake turbulence separations, which are in many cases in excess of the radar separation, are a major factor limiting the capacity at many European airports. Several additional movements per hour and per airport seem possible, if the behaviour of the trailing vortices could be predicted accurately enough. Separation distances and flight paths tailored according to the ambient meteorological conditions can be employed to safely avoid potential wake encounters and therefore maintaining the current level of operational safety of the air transport system.

The expected capacity benefits seem achievable at comparably low cost; however no-one so far has succeeded to develop, implement and operate such a system or procedure on a routine basis. Several concepts of operation, CONOPS, are currently investigated. Some successful attempts corroborate the overall feasibility of novel wake turbulence avoidance procedures, but they also reveal that there are still remaining issues that need to be solved prior to a much broader and more frequent application.

Among other aspects, the successful proof that the safety requirements can be met constitutes a major chal