Aerodynamic Modeling and Flight Simulator Evaluation of Aircraft's Response to Varying Crosswind

摘要

Varying crosswind is the crosswind with varying magnitude and/or direction as that being encountered by an aircraft. It includes horizontal gust wind and horizontal wind shear. As a result of this encounter, the aircraft may develop roll oscillation with large amplitude to affect flight safety. The main purpose of this paper is to show that this phenomenon can be reproduced in an existing flight simulator with high fidelity for pilot training based on unsteady aerodynamic models developed in a tabulated form. Five sets of flight data involving various varying crosswind in landing are available and are combined for developing into one set of unsteady aerodynamic models for six aerodynamic coefficients at low Mach numbers. A least-square-error method is used to smooth any discrepancy among these five sets of flight variables which are in the form of dynamic similitude. The tabulation is arranged only in the subspace of angles of attack because of low Mach numbers. It has been demonstrated that the same set of aerodynamic models in tabulated form is applicable to all five flights with good prediction accuracy. In this paper, the prediction accuracy will be demonstrated only for one flight. One unique feature of the aerodynamic models is that the models can predict the main reasons for flights becoming uncontrollable in a motion with large amplitudes and highly coupled longitudinal and lateral-directional modes. Another feature is that in addition to predicting accurate response for display in a simulator, it can predict the unsteady aerodynamic loads as well. These aerodynamic models, when implemented in a flight simulator, are shown to produce realistic response to varying crosswind. Fidelity of the simulation has been verified by pilots.