Design of a morphing test-article for large-scale, high-speed wind tunnel tests of an adaptive wing flap

Large efforts are currently being spent in Europe for the maturation of innovative technologies enabling the application of morphing systems on next-generation civil transport aircraft. Running along with the CleanSky2 platform, the AirGreen2 project aims to evolve the proofs of concept addressed during the CleanSky program into true-scale demonstrators for a more comprehensive validation of morphing architectures both on the ground and in flight. In this challenging framework, research activities have been carried out to design a novel multi-modal camber morphing flap for the enhancement of the aerodynamic performances of a new-generation regional aircraft. Referring to CFD analyses, very relevant benefits in terms of CLmax increase and stall angle delay were proved to be achievable by properly morphing the camber of the flap; the extra-lift produced by flap cambering resulted more than adequate to allow for takeoff and landing at a single flap deployment angle, in turn much lower than those required by a standard flap in both settings. As a side positive effect, a dramatic simplification of the flap deployment system was shown to be practicable, together with the adoption of fairing-less (no-drag) solutions with flap tracks fully embedded into the wing. In addition, wing aerodynamic efficiency in cruise was demonstrated to be enhanced by locally morphing the tip of the flap still exposed to the aerodynamic flow in flap-retracted configuration. The design and validation of the smart architecture enabling the different morphing modes required for low speed (take-off / landing) and high speed (cruise) conditions, consisted of a complex process involving both wind tunnel and ground tests. To increase the relevance of the wind tunnel test campaign, a large scale-factor (1:3) was selected for the test-article, in combination with the realization of the very same Mach numbers expected in flight. Standing the un-scalability of the flap architecture conceived for ground tests and flight operations, a very challenging design was faced for the test article, in order to define a totally new morphable system (Fig.1), assuring the same functionalities of the true-scale device. The path followed to accomplish this task has been outlined in this work, with emphasis on adopted design philosophy, implemented methodologies, and technological solutions.