Assessment of dynamic response to store ejection solution methods

The paper presents a study of the various modeling and computational elements that control, or affect, the dynamic response of a complex aircraft system to store ejection. Section loads due to store-ejection via pyrotechnic force are computed for two store configurations of the F-16 fighter: a heavy-weight, single-carriage store case, and a light-weight, multiple-carriage case. The dynamic response is computed in the timeand frequency domains, and section loads are computed for several sections and compared with those from flight tests. The study examines the relative roles of the inertial, aerodynamic, ejection, and store gravitational forces on the section loads. The Fictitious Mass method is applied in order to supplement the modal-based dynamic response analysis with modes that contain local deformations at the span sections where loads are computed, in an attempt to improve the loads prediction as compared with flight test data. Special emphasis is given to damping modeling and its effect on loads. Simulations are performed with proportional modal damping of various damping ratios, where an optimization process is used for damping values calibration. Several forms of nonlinear damping models are suggested, and optimized for minimization of the discrepancies between the computed and flight test sectional loads.