Dynamic characteristics of wingtip-jointed composite aircraft

The aerodynamic coupling effect of the composite flight of aircraft via wingtip-jointed structure determines the dynamic characteristics different from those of its independent flight, where safety risks might exist. In order to investigate the dynamic characteristics of the wingtip-jointed composite aircraft, the Newton-Euler method and Robberson-Wittenburg method are used to derive the 7-degree-of-freedom nonlinear dynamics and kinematics equations of the multi-body system of the wingtip-jointed composite aircraft composed of two aircraft. Under the aerodynamic quasi-steady assumption, uncoupling aerodynamic force formula for two-aircraft composite system is established, and the composite aircraft system's three-dimensional modeling and unstructured meshing are further carried out based on the CFD method to obtain the aerodynamic data. The dynamic simulation platform is built, and the dynamic simulations under the quasi-trimming strategy and the full-trimming strategy are carried out on the dynamic simulation platform. The result proves that the aircraft cannot continue to fly stably under the quasi-trimming strategy, while the motion parameters of the composite system under the full-trimming strategy always tend to be stable. Under the full-trimming strategy, the decoupling linearization method using small disturbance hypothesis is used to rearrange the terms of the 7-degree-of-freedom dynamic equations, and study the two new divergent eigenvectors in the eigenvalues of the composite system motion modes, which shows that the two divergent modes are dominated by the relative roll angle and angular velocity. Meanwhile, the characteristics of other modes compared with the single-plane flight are summarized and analyzed.