Abstract
Four forward swept wing and three aft swept wing generic four post STOVL (Short Take-Off and Vertical Landing) aircraft configurations were tested to determine variation in suckdown caused by wing sweep direction at various model heights above the ground. Comparison was made with theoretical predictions for each configuration. Flow visualization was conducted to help understand the basic nature of the flow. It was found that first order theoretical predictions failed to accurately predict suckdown for the configurations tested. Also, fountain effect played a much greater role in the results than indicated by the theoretical predictions. At heights greater than three equivalent nozzle diameters above the ground neither aft nor forward swept wings proved favorable. At heights less than three nozzle diameters the forward swept wing configurations suffered less suckdown than their aft swept counterparts. NOMENCLATURE Ah Wing height above nozzle exit. AL Lift loss. Aj Total nozzle exit area. B Fuselage alone (subscript). c Local chord. 0 Planform effective diameter. d Nozzle diameter. de Diameter of equivalent single jet of area Aj. E Ratio between largest and smallest distances between adjacent nozzles. ea« Average of half the distances between adjacent nozzles.
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