This paper provides, for the first time, a physical explanation of the dynamic fluid–structure stability response of an unconventional aircraft configuration called PrandtlPlane, which has been recently acknowledged as a possible candidate to foster the ambition of a greener aviation. As observed in previous literature efforts on this configuration, flutter onset is significantly different when considering the aircraft being free in the air or fixed in space. Thanks to the formulation adopted in this effort, it is shown how the aerodynamic coupling of elastic and rigid modes has a beneficial effect on dynamic aeroelastic instability (flutter) onset. However, the different modal properties, consequence of the diverse boundary conditions, when switching from fixed-in-space to free-flying aircraft, also play a relevant role in determining the flutter occurrence. Whereas for the longitudinal case both effects are synergistic, contributing to increase flutter speed, for the lateral-directional case the variation in modal properties has a detrimental and dominating effect, leading to a flutter speed well within the flight envelope. Not only effects of rigid and elastic modes interaction have been addressed with respect to the aeroelastic side but the consequent effect on the flexible flight dynamics in terms of deterioration of the flying qualities has been quantified. Within the adopted formulation, unsteady aerodynamic forces are modeled by means of an enhanced Doublet Lattice Method able to take into account terms typically neglected by classic formulations. The work also discusses the relevance of such extra contributions to the dynamic response of the aircraft.

本文首次对一种名为 PrandtlPlane 的非常规飞机配置的动态流固耦合稳定性响应进行了物理解释，该配置最近被认为是促进绿色航空雄心的可能候选者。正如在之前关于这种配置的文献中所观察到的那样，考虑到飞机在空中自由或固定在空间中时，颤振的发生是显着不同的。由于在这项工作中采用的公式，显示了弹性和刚性模式的空气动力学耦合如何对动态气动弹性不稳定性（颤振）开始产生有益影响。然而，当从固定空间切换到自由飞行的飞机时，不同的模态特性，不同边界条件的结果，在确定颤振发生方面也起着相关作用。而在纵向情况下，两种效应是协同的，有助于增加颤振速度，而对于横向情况，模态特性的变化具有不利和主导作用，导致颤振速度完全在飞行包线内。不仅在气动弹性方面解决了刚性和弹性模式相互作用的影响，而且在飞行质量劣化方面对柔性飞行动力学的后续影响也已量化。在采用的公式中，非定常空气动力通过增强型双线格方法进行建模，该方法能够考虑经典公式通常忽略的项。