An analytical investigation has been made to determine the effect of frequency-dependent stability derivatives on the lateral stability of a delta-wing airplane for a flight condition where test results had shown large variations of the stability derivatives with frequency over a range of frequencies. Time histories of rolling velocity and angle of sideslip are obtained by using the Fourier transform to solve the lateral equations of motion. In order to illustrate the frequency effects of the stability derivatives, time histories calculated by using constant values for these derivatives are presented for comparison.nThe results of the investigation show that the frequency effects of the stability derivatives can cause considerable changes in predicted airplane motions. Moreover, the results indicate that amplitude effects of these derivatives can also be important in calculating airplane responses.
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