Gust and Maneuver Load Alleviation in Conceptual Overall Aircraft Design

Abstract

Aerodynamic load alleviation is a promising technology to increase aircraft efficiency and to reduce fuel burn within aircraft design. To fully benefit from the potential, this technology should be considered already during the early design stage when the shape of the wing can still be changed to a larger extent. A multidisciplinary simulation approach, incorporating the disciplines aerodynamics, structures, and flight dynamics is required. This paper presents an aircraft design framework, including coupled and physics-based models for these three disciplines. The software ASWING is integrated into the framework and provides an unsteady lifting-line solver coupled with nonlinear Euler beam theory. Within a nine-dimensional design space of wing parameters, optimizations are performed using a surrogate model approach based on the DLR Smarty Toolbox. The target parameter for these optimizations is a combined multi-point mission block fuel related to the transport work. The results demonstrate that, in the absence of active load alleviation, the optimized wing structures tend to have a higher deformation under maneuver load conditions. The potential of active load alleviation is dependent on the aspect ratio of the wing and therefore also the span. For geometrically constrained optima with and without load alleviation, a 1.6 % reduction in combined block fuel is shown. The optimization with gust and maneuver load alleviation, when compared to a baseline, yields an 11.6 % reduction in combined block fuel. The main part of this reduction can be attributed to snowball effects. Both, the aerodynamic and structual improvements reduce the maximum takeoff mass and, consequently, lead to a reduced total drag, smaller engines and lower fuel mass.