A study of lift characteristics of an upper surface blown jetwing with a rectangular nozzle

A study was conducted to determine the lift characteristics of an upper surface blown (USB) jet-flapped aircraft with rectangular nozzle. An empirical criterion was used to replace the jet sheet leaving the trailing edge with an equivalent mechanical flap extension. Lifting line analysis was used to obtain the spanwise load and induced angle of attack distribution. Additional supercirculation, because of the presence of a high energy jet on the wing upper surface, was obtained from momentum considerations. The predicted values of lift and pitching moment coefficient (C_L and C_M) were compared with full scale wind tunnel and flight test data on the Ball-Bartoe JETWING USB aircraft and show good agreement in C_L. However, theoretical C_M values did not compare favorably with wind tunnel data though the slope (dC_L/dC_M) agreed fairly well. The semi-empirical model developed here, can handle a part span flap with variable jet momentum distribution and chordwise location of the nozzle. This simple method is considered to be a valuable tool for the preliminary design of an USB aircraft with a rectangular nozzle.