Research on loads applied on powered wheels and struts of civil aircraft at touchdown

Abstract

Pre-rotating aircraft wheels is a valid method to reduce the drag loads applied on such wheels by the ground at touchdown. The drag loads have the probability to cause landing strut binding, which has negative effects on the landing gear and requires further analysis. To analyse the probability of the binding of the landing struts, a novel friction triangle model of the landing strut is established in a two-dimensional configuration. This paper builds a 6-degree-of-freedom aircraft dynamic model, consisting of an aircraft fuselage, landing struts, nose and main wheels. On the basis of such model, a set of dynamic analysis is performed to output the forces applied on the landing struts and wheels during spin-up and spring back processes. The maximum values of such forces are studied considering different pre-rotation speeds of the wheels. Through the new models applied in this paper, three conclusions are obtained. The first is that the main landing struts have the highest probability of strut binding at the moment of the first touchdown. The second is that the wheel pre-rotation decreases the probability of landing strut binding when the aircraft initially touches the ground. The third is that the multi-body dynamic model considering the flexible deformation of landing struts outputs drag loads with more and higher-frequency vibrations than the rigid strut model.