Aeroelastic stability analysis of a large civil aircraft equipped with morphing winglets and adaptive flap tabs

The in-flight control of the wing shape is widely considered as one of the most promising solutions to enhance the aerodynamic efficiency of the aircraft thus minimizing the fuel burnt per mission ([1]-[26]). In force of the fallout that the implementation of such a technology might have on the greening of the next generation air transport, ever increasing efforts are spent worldwide to investigate on robust solutions actually compliant with industrial standards and applicable airworthiness requirements. In the framework of the CleanSky2, a research program in aeronautics among the largest ever founded by the European Union, the authors focused on the design and validation of two devices enabling the camber-morphing of winglets and flaps specifically tailored for EASA CS-25 category aircraft ([29]). The shape transition was obtained through smart architectures based on segmented (finger-like) ribs with embedded electromechanical actuators. The combined actions of the two smart systems was conceived to modulate the load distribution along the wing while keeping it optimal at all flight conditions with unequalled benefits in terms of lift-over-drag ratio increase and root bending moment alleviation. Although characterized by a quasi-static actuation, and not used as primary control surfaces, the devices were deeply analysed with reference to their impact on aircraft aeroelastic stability. Rational approaches were adopted to duly capture their dynamics through a relevant number of elastic modes; aeroelastic coupling mechanisms were identified in nominal operative conditions as well as in case of systems’ malfunctioning or failure. Trade off flutter and divergence analyses were finally carried out to assess the robustness of the adopted solutions in terms of movable parts layout, massbalancing and actuators damping