Unsteady Aerodynamic Experiments And Characteristics For The Aircraft Oscillation In Large Amplitude

A dynamic test equipment of two freedom was used to measure unsteady aerodynamic characteristics of Su-27 aircraft model in NH-2 low-speed wind tunnel at Nanjing University of Aeronautics & Astronautics. The dynamic test equipment not only can be used to simulate the pitching, rolling and yawing motion of the model around its body axes,but also can be used to simulate the pitching-rolling and yawing-rolling couple motion. It was introduced in this thesis that the means of test in wind tunnel about the motion of model oscillating in large amplitude, and the attitude angle be translated into the angle of attack and sideslip.The unsteady aerodynamic characteristics of the model was measured as oscillation in pitching, rolling, yawing or yawing-rolling. Dealing with the data of experiment with the method of least aquares fit and FFT wave filtering. The result indicates that it is better by least aquares fit method in low frequency ,but in high frequency ,the better results based on the method of least aquares fit and FFT wave filtering.Finally,the data of the test in wind tunnel was adopted. The rolling moment character and yawing moment character of the model is analyzed in different motion. The dynamic derivative is negative or positive connect with the direction of the unsteady moment character is analyzed. Results show that the dynamic stability was affected by the angle of support.