This paper deals with the numerical simulation of unsteady aerodynamics effects in horizontal-axis wind turbines. In particular, an unsteady three-dimensional potential method is presented whose aim is to predict time-dependent forces and moments on wind turbines operating in a field environment. The algorithm structure is such that the wake is not prescribed; instead, its shape and motion are obtained self-consistently from the solution of the problem. Flow separation effects are not considered. Once the mathematical formulation is discussed, the results of the solver validation campaign, including a parametric sensitivity study of the solutions, are presented. Then, the solver is applied to a practical case involving a wind turbine specifically constructed to collect unsteady aerodynamics data. It is found that the comparison between experimental data and computed results shows a good agreement. Finally, conclusions are drawn.