The effects of a wind turbine wake on General Aviation and the behaviour of helicopters in the tip vortex of large fixed-wing aircraft has been topic of research in the past years, but less is known about the interactions of helicopters operating in a wind turbine wake. A dedicated GARTEUR Action Group, HC-AG23, consisting of European universities and research institutes was formed to investigate helicopter behaviour in a wind turbine wake and to study the consequences for helicopter handling and safety of flight. The activities are structured in work packages addressing wind turbine wake identification, wake experiments and computations, offline and piloted simulations and management and dissemination activities. This paper presents an over-view of the partners’ activities and provides a short overview of the results that have been achieved in the past three years.