Maximum lift of upper surface blowing STOL aircraft with swept wings

In a recent large scale wind tunnel investigation of a 4 engine upper surface blowing configuration in the Ames 40- by 80-Foot Wind Tunnel, the large nacelles extending well above the wing upper surface had a sizable adverse effect on maximum lift. The presence of the nacelles produced high upwash angles between the nacelles and near the fuselage. The severity and alleviation of this problem is discussed with the use of calculated spanwise loadings. The combined effects of wing leading edge stall control, wing sweep, and nacelle cross section modification were considered in maximum lift improvement. Experimental results of these effects are presented.