Hazards due to helicopter wakes

The local velocities induced in the wake of a helicopter can be a serious hazard to light aircraft operating nearby. A theoretical model is developed which makes it possible to estimate the rolling moment induced on a light aircraft entering the wake of a helicopter. The model shows good agreement with the limited amount of flight test data available. An annotated bibliography of the literature available on helicopter wakes is presented in order to identify specific areas in which further research is required.