Flight Test Design and Nonlinear Model Identification for Landing Gear Aerodynamics

In this study, a nonlinear aerodynamic modeling method for landing gear extension and retraction process based on the least square method is proposed and corresponding flight tests are designed performed with a simulator. Firstly, the least square method is used to determine the baseline aerodynamic model from simulated flight test data. Then landing gear extension and retraction maneuver are conducted on the same simulator under quasi-steady conditions to acquire the increment of aerodynamic coefficients caused by the change of landing gear position. Thus, the nonlinear aerodynamic model considering the effect of landing gear can be obtained. Based on the above method, flight tests using a simulated Boeing 737-800 model is carried out, and nonlinear landing gear aerodynamic characteristics of the 737-800 model is acquired. Compared with the linear interpolation model, the fidelity of the nonlinear landing gear aerodynamic model proposed in this work is obviously improved.