Application of XTRAN3S and CAP-TSD to fighter aircraft

Abstract

Two unsteady transonic small-disturbance (TSD) codes, XTRAN3S and CAP-TSD, were used to perform aeroelastic analyses of four fighter aircraft configurations. The XTRAN3S code was used for a wing-alone analysis of the F-15 and F/A-18 aircraft, whereas the CAP-TSD code, with its more flexible geometric modeling capability, was used to analyze a canard, wing, and tail arrangement of the F-15 S/MTD and a wing, launcher, and tip missile arrangement of the F/A-18. Static and dynamic aeroelastic calculations were performed using both the linear and nonlinear forms of the small-disturbance equation. Comparisons are made between the F-15 and F/A-18 wing-alone flutter results and those from a linear flutter analysis computed using doublet lattice aerodynamics. These comparisons show good agreement for the linear aerodynamic TSD solutions but significant changes in the flutter speed for the nonlinear aerodynamic TSD solutions. Comparisons were also made for the canard/wing/tail and the wing/launcher/tip missile configurations with the corresponding wing-alone configurations to assess the effects of multiple lifting surfaces and tip stores on flutter.