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A preliminary design technique for the prediction of aerodynamic loads acting on external stores has been established through an empirical correlation of wind tunnel results obtained on a scale model of the F-111. Approximately 30,000 engineering data points were surveyed for various combinations of external stores. These data, originally stored on magnetic tape, were transferred to CDC 6600 disk packs. This was done to reduce the amount of computer run time required to collect the desired samples of data. For this study, correlations were performed of each aerodynamic component of load or moment acting on a particular store grouping as a function of various geometry parameters. The work was accomplished primarily through the utilization of numerical programs in which, through a series of trial and error calculations, an equation composed of various key geometry parameters was generated. The equations obtained for the numerical programs predict normal force, side force, pitching moment, yawing moment, and rolling moment for various external store arrangements.
In a series of wind tunnel tests, measurements were made of the aerodynamic loads acting on eight different store configurations mounted in the external captive position on a one-twentieth-scale model of the F-4C aircraft. Store models included blunt and contoured afterbody shapes, stable and unstable designs, and large (one per pylon) and small (rack-mounted) configurations. The tests were conducted in an effort to evaluate sting effects on captive store loads. Sting effects were considered to consist of two contributions: the effect of altering the afterbody of a store to allow insertion of a sting, and the effect of the presence of the sting. Altering the afterbody of an unstable store influenced captive loads less than altering a stable configuration. It was also determined that the presence of a sting affected most the pitching and yawing moments.