Aeroelastic Design of the oLAF Reference Aircraft Configuration

Abstract

One of the main aims of the EU Flightpath 2050 is to significantly reducet he fuel consumption of upcoming designs for transport aircraft. To achieve this challenging goal, new technologies have to be investigated. In this context, the development of the 'optimally load adaptive aircraft' (oLAF) for a conventional design is one of the main goals of the DLR project oLAF. Since the lift-to-drag ration, the structural mass and the thrust specific fuel consumption are the main drivers of the aircraft's fuel consumption, an improvement in all three topics seems to be a promising approach to fulfill the intended aims of the European Union. That's why the design of the new oLAF configuration is equipped with a next generation three shaft geared turbofan engine with an ultra-high bypass-ration and an optimized aerodynamic performance combined with aggressive loadalleviation (LA) techniques to lighten the load-carrying structure of the aircraft significantly compared to a conventional state-of-the-art aircraft. Multiple design cycles with different degree of fidelity and LA approaches are planned to be performed within oLAF. At the current state of the project, three different designs are available. On the one hand, there is the more basic configuration of the overall aircraft design (OAD) further called 'oLAF_SLv1'. On the other hand, there are configurations with more mature aerodynamic characteristics further called the oLAF_ASv0 configuration as start design for a multidisciplinary-design-optimization (MDO) process and the 'oLAF_ASv1' as the optimized result of the MDO. All configurations have been analyzed and evaluated using the aeroelastic structural design tool cpacs-MONA. The optimized 'oLAF_ASv1' configuration has furthermore been checked on aeroelastic stability. Conclusively, the stiffness of the structural pylon model has been adapted to shift a hump-mode of the new generation engine to higher airspeeds, so that the instability occurs outside of the flight envelope.