Wind Tunnel Measurement of Pitch-Damping Derivative Using Forced Oscillation Technique

The main task of dynamic experiments in wind tunnels is to obtain model-scale stability information of an aircraft at realistic Reynolds and Mach numbers. The forced oscillation technique is the most widely used wind tunnel technique for stability derivatives measurements. The oscillatory motion is induced to a model in one (the primary) degree of freedom. The aerodynamic reaction measured in the primary degree of freedom determines direct damping derivatives. Stability derivatives are obtained from in-phase and out-of-phase components of the measured aerodynamic reactions. This paper describes the determination of the pitch-damping derivative in the T-38 wind tunnel. The T-38 pitch/yaw apparatus is a full-model forced oscillation apparatus with primary angular oscillation around the wind tunnel model transversal axis. The model is forced to oscillate at constant amplitude. Test results obtained in the T-38 wind tunnel are compared with published experimental data of one of the world’s leading wind tunnels: Arnold Engineering Development Center-von Karman (AEDC, USA).