Generic Global Aerodynamic Model for Aircraft

Abstract

Multivariate-orthogonal-function modeling was applied to wind-tunnel databases for eight different aircraft to identify a generic global aerodynamic model structure that could be used for any of the aircraft. For each aircraft database and each nondimensional aerodynamic coefficient, global models were identified from multivariate polynomials in the nondimensional states and controls, using an orthogonalization procedure. A predicted-square-error criterion was used to automatically select the model terms. Modeling terms selected in at least half of the analyses, which totaled 45 terms, were retained to form the generic global aerodynamic model structure. Least squares was used to estimate the model parameters and associated uncertainty that best fit the generic global aerodynamic model structure to each database. The result was a single generic aerodynamic model structure that could be used to accurately characterize the global aerodynamics for any of the eight aircraft, simply by changing the values of the model parameters. Nonlinear flight simulations were used to demonstrate that the generic global aerodynamic model accurately reproduces trim solutions, local dynamic behavior, and global dynamic behavior under large-amplitude excitation. This compact global aerodynamic model can decrease flight-computer memory requirements for implementing onboard fault detection or flight control systems, enable quick changes for conceptual aircraft models, and provide smooth analytical functional representations of the global aerodynamics for control and optimization applications. All information required to construct global aerodynamic models for nonlinear simulations of the eight aircraft is provided in this paper.