Wake Vortex Encounter Assessment

From wake vortex velocity distribution models the velocity field induced by vortices can be quantified. The effect on a following aircraft that flies into this field ('encounters the wake vortex') can then be derived from flight mechanical calculations in an offline simulation or from flight simulator studies with a pilot-in-the-loop. Extensive studies have been made in the European S-Wake program and during the development of the VESA program of Airbus. The wake vortex velocity field models and the aerodynamic interaction models (AIM) used in these studies have been validated against wind tunnel and flight tests. Even with the present separation rules, wake vortex encounters may occur during normal operation and pose a potential hazard. For a quantitative risk assessment it is essential to have severity criteria that relate objective aircraft parameters to the subjective pilot's assessment of a wake vortex encounter (based on extensive pilot-in-the-loop wake vortex encounter severity investigations). Although relevant parameters have been proposed (e.g. a maximum roll angle or sink rate) a set of agreed criteria has not been established yet. Also, automatic detection of wake encounters will be very valuable to assess the present situation and to validate the severity criteria for weak encounters