Within the CEC Joule program, a joint investigation project was started up concerning dynamic inflow effects. These effects describe the wake induced unsteadiness of the flow in the rotorplane. Aim of the project is the definition and implementation of engineering models within the current state-of-the-art computer codes for dynamic load calculations. These models are to be qualified by means of comparison with both existing sophisticated models (dynamic vortex wake calculations) and with experiments to be carried out on the Danish Tjaereborg 2 MW turbine. The first results of the project are discussed. Proposed engineering models are presented. Comparisons between results of the proposed models and the free vortex wake model of the University of the Bundeswehr, Muenchen are shown, for simplified cases, viz.: a step on the wind speed and simple pitching transients. Finally, some first measurements for a pitching transient are shown and compared with calculations for some of the models. Both measurements and calculations show important effects of dynamic inflow, resulting in large overshoots of loads compared to stationary values. The agreement between measurements and calculations is very encouraging. 12 figs., 2 tabs., 6 refs.