Experimental study of tail rotor-fin interference ratio in hover

Abstract

The paper presents an experimental study of tail rotor and fin interference in hover and in the absence of a main rotor. A high and a ventral/dorsal low tail design are investigated on a model rotor. For the high tail conception in tractor configuration previous observations are substantiated. By contrast, in pusher configuration, besides early-identified factors the direction of rotation and tail rotor longitudinal position appear to control the interference. Accordingly a widened parametric model is proposed. The connected power increment, observed to scale with the thrust interference ratio, completes the description. For the low tail conception, on the one hand, low values of the fin/rotor separation distance are seen to handicap adequate thrust interference ratios as compared to the high tail constellation. On the other hand, with growing tail rotor/fin spacing, a substantial gain shows up. Finally, the ventral/dorsal arrangement is seen to benefit from a slightly improved power required.