Parametric nonlinear flutter analysis of the semi-aeroelastic hinges during manoeuvres and gust encounters

A recent consideration in aircraft design is the use of semi-aeroelastic hinges, with the aim of enabling higher aspect ratio wings with less induced drag but also meeting airport gate limitations. Of particular interest is the concept of using in-flight free-floating wingtips in order to reduce aircraft gust and manoeuvre loads. On a previous work, a multibody formulation was introduced to account for finite rotations of rigid folding wingtips attached through flared hinges on a flexible airframe structure including aerodynamic follower forces for the folding wingtip components. This study uses the same formulation to investigate the effect of geometric nonlinearities on the aircraft aeroelastic stability. A time marching flutter analysis is used to depict how the stability of the aircraft varies during static and dynamic conditions like manoeuvres and gusts. It is shown that the aeroelastic stability of the aicraft is strongly influenced by the aicraft deformed shape leading to a reduction of stability the higher the tips coasting angles. Preliminary results show the emergence of unstable flutter mechanisms which have the tendency to become more and more unstable the higher the wing deformation and wingtip coasting angle. The aim of the paper is to show in which scenarios, such a degradation might be critical.