A Reduced-Order Model for LCO Dependence on Mach Number in F16 Flight Tests

A normal form for the LCO bifurcation as deduced from F16 ∞ight test data is developed. The data analysis makes use of wavelets to yield variations in LCO amplitude over difierent ∞ight regimes. Variations in the nonlinear parameter of the normal form are associated with difierent types of nonlinearities afiecting the LCO response in these regimes. The results show a signiflcant drop in the value of the nonlinear coe‐cient of the normal form over the Mach number range between 0.85 and 0.9. This large drop indicates that the aerodynamic nonlinearity is unfavorable in this regime. This stands in contrast to a favorable aerodynamic nonlinearity that has been determined in the transonic regime over the Mach number range between 0.92 and 0.94.