Tests of a 45 Degree Sweptback-wing Model in the Langley Gust Tunnel

Abstract : A series of tests of a 45 deg sweptback-wing model with and without fuselage and of an equivalent straight-wing model were conducted in the Langley gust tunnel to provide information on some of the problems encountered in the prediction of gust loads for airplanes incorporating swept wings. A comparison of test results with calculated results indicated that the maximum acceleration increment resulting from the penetration of a gust by a sweptback-wing airplane may be assumed to be dependent on the slope of the lift curve of the equivalent straight wing multiplied by the cosine of the angle of sweep, rather than on the steady flow slope of the lift curve. In addition, it appeared that the maximum acceleration increment also depends on the effect on the unsteady-lift function of the gradual penetration of the sweptback wing into the gust. A comparison of the maximum acceleration increments obtained for the swept-wing model with those obtained for the straight-wing model indicated that, although the airplane with a swept wing would show positive pitching motion, it would undergo a much lower acceleration increment than the same airplane with the equivalent straight wing.