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Today, wake turbulence related aircraft separations are a limiting factor for the capacity of airports worldwide. Detailed knowledge about the severity of potential wake encounters is necessary for a safe revision of the current ICAO separation requirements. Vortex encounter simulation is an important part in building an understanding how the encountering aircraft is adversely affected by the vortex-induced disturbances. Whereas most research has focused on aircraft encounters with a pair of straight vortices, this paper describes the simulation of encounters with perturbed vortices as they are observed under various atmospheric conditions. A method to account for unsteady aerodynamic effects during computation of vortex-induced forces and moments is presented. These effects are becoming especially important for vortex-induced disturbances of higher frequency as they appear during encounters with perturbed vortices. In combination with existing models for vortex deformation due to long-wave Crow instability, the realism of encounter simulations is increased. The simulation models are suitable for real-time and fast-time applications such as piloted simulator experiments and fast-time Monte Carlo simulations. First results of a simulator study with airline pilots are discussed. Nomenclature c = chord length a 1 …c 2 = vortex ring shape parameters A V = deformation amplitude for wavy vortices b = generator aircraft wing span b V = span of straight vortex pair C L = lift curve slope dv = induced velocity due to an infinitesimal straight vortex segment k = reduced frequency m = generator aircraft weight n = vortex ring counter N* = nondimensional Brunt-Väisälä frequency r = distance to vortex center r C = vortex core radius r V = position vector from origin of vortex coordinate system to point on vortex axis s = local variable for vortex rings t 0 = time of incremental gust step change T V = deformation parameter for vortex rings V = airspeed V t = tangential vortex velocity v V , w V = vortex-induced velocities w g = gust downwash  V ,  V = lateral end vertical encounter angles  = local vortex-induced angle of attack  = vortex circulation  = wavy vortex wave number * = nondimensional deformation growth rate * = nondimensional eddy dissipation rate  V = spatial phase shift of vortex deformation  1 ,  2 = lag states of unsteady downwash  V = wavelength of Crow instability  V = inclination angle of wavy vortex deformation t* = nondimensional times  = frequency of disturbance Subscripts g = gust i = strip number qs = quasi-steady step = step change us = unsteady V = vortex

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