A comparison of Continuous Turbulence and Statistical Discrete Gust for the development of aircraft design loads

Atmospheric turbulence can cause internal forces that design large portions of aircraft structure. The current gust loads criterion, Continuous Turbulence, is applied to the structure as velocity Power Spectral Density (PSD). Gust velocity is represented as stationary, random, and Gaussian. Structural response is obtained through probabilistic frequency domain analysis. Statistical Discrete Gust (SDG) is a deterministic time domain analysis providing tuned gust histories representative of large gusts that design primary structure. SDG assumes gust velocity has a stretched exponential distribution, which is more representative of observed data. This paper presents a method of deriving load cases using the gust profiles of SDG scaled to meet the continuous turbulence envelope. Statistical assumptions of the current criterion and SDG are presented. The implication to developed design loads is discussed. A structural response simulation is used to illustrate the design loads development and their statistically appropriate nature compared to the continuous turbulence criterion.