Wind and air turbulence are factors that tend to dissipate the energy in aircraft wake vortices, or to displace them from the track of a following aircraft, says the Eurocontrol Experimental Centre (EEC). Improved knowledge of wake vortex behaviour and better technology for observing wake patterns under different meterorological conditions look likely to let air traffic controllers space aircraft more closely on approach and departure. For example, says EEC senior operational adviser Jean-Pierre Nicolaon, a strong headwind means approaching aircraft, separated by a prescribed distance under today’s rules, have a greater time separation because of their reduced groundspeed than they would have in still air. Wake vortex energy dissipates with time, not distance, and its attenuation is accelerated by the turbulence wind creates near the ground. Under these conditions aircraft spacing by time could safely reduce distance separation. Under certain crosswind conditions, the wake of the leading aircraft could be displaced sideways, taking it clear of the following aircraft.
Source: Flight International
