Vortex Drag Reduction by Diffusing Vanes: Design for the “Thrush” Agricultural Aircraft

The use of low aspect ratio, often untapered wings on agricultural aircraft leads to strong tip vortices, high induced drag and disruption of spray patterns. Wing tip devices which modify the trailing vortex offer performance and flow improvements.

A systematic experimental program has lead to a patented vortex diffuser device for drag reduction which comprises a winglet-like vane mounted from a boom which trails a wing tip.

Flight test experiments on an RCRV model indicate slight degradation of lateral stability with such vortex diffusers fitted but substantial degradation for winglets. Analysis indicates this is due to increases in C_ℓβ with the tip devices present.

The design of Vortex Diffuser Vanes for the “Thrush” agricultural aircraft is described. Instrumented flight tests are scheduled for Spring, 1981.