Safe Limits for Wake Vortex Penetration

Abstract

The strength of the vortices increases with the weight of the vortex generating aircraft. Therefore, weight dependent separation distances have been established to avoid dangerous wake vortex encounters. To solve the future capacity problems at airports these proven separation distances have to be investigated carefully with the aim to discover possible margins. This demand forms the need for more flexible separation procedures taking into account the actual weather situation and the parameters of the individual aircraft pairing. In any case the separation distance of approaching aircraft has to be determined in such a way that the approach corridor is free of hazardous vortex flows for the trailing aircraft. The question to be answered is what is the meaning of “hazard free”, respectively how close is an aircraft allowed to approach a vortex without adversely affecting undisturbed flight operation? The determination of a reliable threshold is only possible with pilot-in-the-loop investigations. This paper presents the results of flight simulator studies and in-flight simulations using real flight test aircraft. Based on the required normalized roll con¬trol power tolerable and safe situations can be distinguished from unacceptable encounters and a threshold value can be established. The tolerable threshold value can be increased if the pilots control task is supported by an automatic controller.