Abstract: To study t he g lobal effects of unsteady aerodynamics on aircraft motio n, topological structur e diag ramsw ere computed, w hich were based on the 6??deg ree??of??freedom model o f motion and an unsteady aerody namic modelof the deriv ative t ype, and include information of equilibria, periodic or bits, turn points, static bifur cations andHopf bifurcations. The mechanism of effects was further abstr acted by evaluation of the loci of t he Jacobian matrixeig envalues and by time??dependence simulations. As the results show, unsteady aerodynamics has gr eat effects onoscillatory unst able motion and can delay the unstable tr end and Hopf bifurcations. How ever, unsteady aerodynamicshas little effect on monotonously unstable motio ns. Stable periodic motions such as wing??ro ck and oscillatory spintend to be suppressed or the amplitudes be lessened due to the rotational damping of the unsteady aer odynamic delay.

Key words: unsteady aerodynamics, topological structure diagram, Hopf bifurcation, rotational damping