Two methods for determining the aerodynamic stability derivatives of an airplane in wind tunnels are investigated. The principles of measurement are as follows : (1) Determining the stability derivatives from the frequency response characteristics of a second order dynamic system with application of a forced oscillation of constant amplitude ; (2) Determining the stability derivatives from the transient response data of the model to a step control deflection input. The former is suitable for low speed wind tunnel tests, and the latter is mainly for high speed wind tunnel tests. In this paper the theoretical calculation and the preliminary experimental results are reported
