Abstract: The approximate dominant pole values of the linearized aerodynamic system(such as a wing with airflow can be obtained only with the concept of "equivalent system" and an indicial function f (t) of . general unsteady " aerodynamic obtained by numerical method, if flight Mach number (subsonic and supersonic speed) and the parameters of the wing are given. According to the principle of the indicial function, it can be considered that there are two dominant poles for the linearized aerodynamic system. So that the rest of indicial functions of the wing ftek ( t ) (k=j) are able to be obtained by its corresponding value at t =0, t = ts. This simplifies the calculation of the unsteady aerodynamic coefficient of the wing and reduces the order of the eigenfunctiou of the dynamic system

Key words: unsteady flow, wings, aerodynamic coefficients