Apparatus for measurement of pitch and yaw damping derivatives in high Reynolds number blowdown wind tunnel

The pitch/yaw apparatus designed for the measurement of the moment derivative due to an aircraft or missile model angular oscillatory motion in a wind tunnel test section is presented. A model is forced to oscillate with the primary angular oscillation around its transversal axis (pitch or yaw). Damping derivatives are obtained as a difference between total damping measured in the presence of aerodynamic load and mechanical damping measured in the absence of aerodynamic load. The main requirements for a new apparatus were: high load capacity, high structural rigidity, high range of the experimental frequencies and high sensors sensitivity. The choice of the hydraulic drive is made considering these requirements. Amplitude of the excitation moment is measured either by internal wind tunnel balance or by a specially designed excitation moment sensor. The T-38 wind tunnel data for the Modified Basic Finner Model and Basic Finner Model obtained using the pitch/yaw apparatus are shown.