Multi-Modal Morphing Wing Flaps for Next Generation Green Regional Aircraft: The CleanSky Challenge

Abstract

Regional aviation is an innovation driven sector of paramount importance for the European Union economy. Large resources and efforts are currently spent through the CleanSky program for the development of an efficient air transport system characterized by a lower environmental impact and unequalled capabilities of ensuring safe and seamless mobility while complying with very demanding technological requirements. The Green Regional Aircraft (GRA) panel, active from 2006, aims to mature, validate and demonstrate green aeronautical technologies best fitting the regional aircraft that will fly from 2020 onwards with reference to specific and challenging domains: from advanced low-weight and high performance structures up to all-electric systems and bleed-less engine architectures, from low noise/high efficiency aerodynamic up to environmentally optimized missions and trajectories management. The development of such technologies addresses two different aircraft concepts, identified by two seat classes, 90-pax with Turboprop (TP) engine and 130-pax, in combination with advanced propulsion solutions, namely, the Geared Turbofan (GTF), the Advanced Turbofan (ATF) and the Open Rotor (OR) configuration. Within the framework of the Clean Sky program, and along nearly 10 years of research, the design and technological demonstration of a novel wing flap architecture was addressed. Research activities aimed at demonstrating the industrial feasibility of a morphing architecture enabling flap camber variation in compliance with the demanding safety requirements applicable to the next generation GRA in both open rotor and turboprop configurations. The driving motivation was found in the opportunity to replace a conventional double slotted flap with a single slotted morphing flap assuring improved high lift performances — in terms of maximum attainable lift coefficient and stall angle — while lowering emitted noise, fuel-burnt and deployment system complexity. Additional functionalities for load control and alleviation were then considered and enabled by a smart architecture allowing for an independent shape-control of the flap tip region during cruise. The entire process moving from concept definition up to the experimental qualification of true scale prototypes, characterized by global and multi-zone differential morphing capabilities, is here described with specific emphasis on the adopted design philosophy and implemented technological solutions. Paths to improvements are finally outlined in perspective of a low-term item certification and series production.