Efficient High Resolution Modeling of Fighter Aircraft with Stores for Stability and Control Clearance

Abstract

This paper documents recent advances towards an efficient computational method for accurately determining the static and dynamic stability and control (SC. In contrast to the “brute force” approach to filling an entire S&C database for an aircraft, the present approach is to reduce the number of simulations required to generate a complete aerodynamic model of a particular configuration at selected flight conditions by using one or a few complex dynamic motions and nonlinear system identification (SID) techniques. The approach is demonstrated by gathering high-fidelity computational fluid dynamics (CFD) data for a rigid F-16 in prescribed motion that approximates dynamic wind-tunnel testing techniques and SID input signals. The motions are optimized to minimize the computational expense and to take full advantage of the tighter control of the CFD environment. They are specified interactively using a newly developed, GUI-based maneuver file generation tool. Global nonlinear parameter modeling and other SID techniques are then used to identify parametric models from the computed aerodynamic force and moment data. These compact models are used to predict the aerodynamic response to maneuvers that were computed for validation purposes and that were not used to derive the models. Partial derivatives of the analytical models can be used to determine the corresponding static and dynamic stability derivatives. The models can also be used to perform real time 6-DOF/aeroelastic simulations of the vehicle in conditions susceptible to spin, tumble, and lateral/longitudinal instabilities. The main benefits of this effort are: 1) early discovery of complex aerodynamic phenomena that are typically only present in dynamic flight maneuvers and therefore not discovered until flight test, and 2) rapid generation of an accurate aerodynamic model to support aircraft and weapon certification by reducing required flight test hours and complementing current stability and control testing.