Multidisciplinary optimization of load adaptive wings for highly efficient long-haul airliners

Abstract

As part of the DLR project oLAF (optimal load-adaptive aircraft), a long-haul airliner with maneuver load alleviation limited to aileron deflections and the use of a geared turbofan engine is being designed and optimized. Adaptive wing technologies based on trailing edge control surface deflections to reduce drag at cruise and for optimal load reduction are introduced and supplemented by other structural technologies with increased strain allowable to reduce wing mass. In this work the results of the aero-structural wing optimizations of the aircraft with advanced structural wing technologies and the aircraft with a load adaptive wing will be presented. High-fidelity simulation methods are used in the optimization process to determine the flight performance in the transonic cruise flight, the loads of the wing in maneuver flight and the mass of the wing box made of fiber composite materials. Static aeroelastic effects are considered in all flight conditions. The minimization of the fuel consumption for three typical flight missions represents the objective function. The geometric integration of the control surfaces and aircraft trimming are considered. The selected design parameters describe the twist distribution and the control surface deflections. The consideration of structural technologies with increased strain allowable and local buckling after limit load result in a 2.9% reduction of fuel consumption after aero-structural optimization of the twist distribution. With the introduction of adaptive wing technologies based on trailing edge control surface deflections a further fuel burn reduction between 0.8% and 1.9% depending on the flight mission is predicted.