A Study of the Aerodynamic Interactions of the Tail Rotor and Fin.

Abstract : The results of a wind tunnel investigation of the aerodynamic interaction of the tail rotor and fin are presented. Model loads data were measured for a 1/4.85 scale model of the YUH-61A. Tests were conducted deep in ground effect at wind speeds ranging from 0 to 45 knots; representative of Nap-of-the-Earth. Flow visualization studies provided additional insight into the flow mechanisms at work such as the ground vortex. Distributional flow characteristics, particularly the location and structure of the main rotor tip vortex, were measured by a hot film probe. A variable fin incidence mechanism was incorporated in the model to measure the integrated flow at the empennage. Adverse fin force and tail rotor power variations are measured as functions of airspeed, wind azimuth, tail rotor thrust and main rotor thrust. (Author)