Statistical-discrete-gust method for predicting aircraft loads and dynamic response

The statistical-discrete-gust (SDG) method comprises a stochastic model for atmospheric turbulence and an associated technique for predicting the statistics of aircraft response. In the stochastic model, localized patterns of fluctuation are represented in terms of discrete ramp elements, and associated probability distributions are defined. With appropriate parameter settings, the model may be used to represent either continuous turbulence or relatively isolated gusts. The statistics of response, which may be linear or nonlinear, are derived by an application of the Laplace asymptotic approximation and are expressed in a form that shows the dominant influence of a particular tuned, or worst-case, gust pattern which is dependent on the aircraft dynamics. This paper reviews the basic concepts of the theory with particular reference to the incorporation of fractal representations of turbulence intermittency and to the problem of predicting the effects of nonlinear aircraft dynamics. The determination of numerical parameters from measured data is discussed, both for continuous turbulence and relatively isolated gusts.

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