A new simplified transition model for wind turbine blades is described along with the implementation in the EllipSys3D code. The method is based on a sectional treatment of the turbine blade under the assumption of chordwise flow, and lookup tables oftransition point location computed by external 2D programs. The coupling of the 2D transition point location and the 3D sectional flow is performed through the stagnation point location. The method is applied to a single rotor case, the NORDTANK 500/41rotor with LM19.1 blades. The transitional computations show improved agreement with measurements for wind speeds between 11 and 15 m/s. For higher wind speeds, the validity of the transition location computed by the 2D XFOIL code is questionable, and theresults cannot be trusted. Analysis of the results comparing fully turbulent and transitional spanwise distributions of tangential forces, reveal that the decrease in power production when applying the transition model is mainly a consequence of thedecrease in driving force on the inboard part of the blade between 5 and 12 meter radius. The results are very encouraging, and further studies of other rotors are needed for further validation.