Aeroservoelastic Gust Response Analysis for the Design of Transport Aircrafts

Abstract

Frequency-domain and time-domain approaches to the calculation of dynamic loads due to response of aeroservoelastic systems to atmospheric gust excitations are presented. The discrete and continuous gust inputs are defined in either time-domain or stochastic terms. The various options are formulated in a way that accommodates linear control systems of the most general form. The frequency-domain approach is based on the interpolation of generalized aerodynamic force coefficient matrices and the application of Fourier transforms for timedomain solutions. The time-domain approach uses state-space formulation that requires the frequency-dependent aerodynamic coefficients to be approximated by rational functions of the Laplace variable. Specific difficulties associated with the spiral nature in the complex plane of the gust-related aerodynamic terms is discussed and resolved. The two approaches are adapted for efficient application in realistic design environment with numerous combinations of flight conditions and weight configurations. An actual process of calculating gust-response design loads for the A400M transport aircraft is demonstrated, showing significant controlsystem effects.