| Summary: | 博士 === 國立成功大學 === 航空太空工程學系碩博士班 === 92 === The effects of windshear on airplane flight safety during take off and landing are examined. The main focus is to study the aerodynamic characteristics based on flight data from Flight Data Recorders (FDR) to provide an insight in the clues that cause accidents or incidents. A fuzzy logic modeling (FLM) algorithm is adopted to establish the nonlinear dynamic aerodynamic models for a jet transport in a flight accident. Modeling is applied to a set of flight parameters from the compatibility analysis of FDR data through an Extended Kalman Filter (EKF) algorithm. The fuzzy-logic model provides a numerical aerodynamic database from which the aerodynamic coefficients under oscillatory conditions can be extracted to demonstrate the hysteresis effects. It is also used to provide data for the static and dynamic ground effects analyses, which are particularly difficult to perform when the aircraft is near the ground in the presence of varying crosswind.
In this study, a Boeing 737-800 landing under strong wind and heavy rain conditions is investigated. A fuzzy logic modeling technique is applied to model the nonlinearities associated with wind-affected aerodynamics. The results indicate that the fuzzy-logic modeling is capable of handling many motion variables at the same time in the nonlinear manner and providing reasonable unsteady aerodynamics. Unsteady and nonlinear aerodynamic phenomena are observed from the analysis of stiffness, damping, and control effectiveness derivatives. The hysteresis effects are demonstrated by the harmonic oscillation response loops to show the unsteady effects that appear in both longitudinal and lateral-directional motions. The results of ground effect analysis show that ground effect appears to be significant as the sink rate increases, and the crosswind tends to induce adverse dynamic ground effect (i.e. lift reduction) when the aircraft flaring to touch-down. The sideslip, as produced by crosswind, will make the pitching moment more negative. It also reduces the control effectiveness. The adopted approach not only has the potential to help understand the flying characteristics but also is more effective than the current windshear identification method in identifying the degree of windshear hazards and improving the flight simulator’s aerodynamic database for pilot’s trainings.
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