W. Unkelbach, P.J. González, B. Herlambang, M. Ritter, F.J. Silvestre

Increasing efficiency in fuel consumption and reducing the environmental impact of aviation can be achieved by load alleviation methods which allow lighter wing structures. This paper presents the implementation and numerical validation of a flight dynamics model for a high aspect ratio aircraft configuration, along with the development of three static load alleviation strategies aimed at reducing the wing root bending moment (RBM) while considering the resulting drag increase. The aerodynamic model was generated using the vortex lattice method via Athena-Vortex-Lattice (AVL) adjusted by computational fluid dynamics (CFD) simulations. Utilizing aerodynamic, geometric, mass and performance data, the flight dynamics simulation was implemented within the modular flight simulation environment of the Department of Flight Mechanics, Flight Control and Aeroelasticity (FMRA). An optimization process with three different optimization targets was implemented and will be described in the paper. The first Pre-Setting (PS) achieves maximum load alleviation. PS 2 penalizes drag increase and performs weighted load alleviation. PS 3 uses only 5 instead of 8 control surfaces. These load alleviation PS, along with the clean configuration, were input into the flight simulation tool and subjected to discrete (1-cos)-shaped gusts with various gradients and amplitudes, as described in the certification specifications CS-25. The configurations were also tested under stochastically distributed turbulence using the von Kármán model of the Matlab/Simulink Aerospace Toolbox. The results were analysed to evaluate the reduction in RBM and the increase in drag. To evaluate the RBM, a routine between the simulation output and AVL was established. The flight dynamics model was further numerically verified through typical characteristic time domain responses of commercial aircraft. Using the evaluation routine, the RBM was calculated through AVL. The analysis focuses on the reduction of RBM and load peaks following different gust encounters. Results indicate that PS 1 offers the maximum load alleviation with all control surfaces, providing the most significant load peak and cycle alleviation but also resulting in a substantial drag increase. The weighted PS 2, designed as a compromise between drag and RBM reduction, shows less reduction than PS 1, but cuts the drag increase significantly, thereby enhancing overall performance. PS 3, which employs fewer control surfaces, proves impractical due to its lower RBM reduction and higher drag increase compared to PS 2, demonstrating the ineffectiveness of using fewer control surfaces.

Deutscher Luft- und Raumfahrtkongress 2025, Augsburg

Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2025

Conference Paper

englisch

21,0 x 29,7 cm, 8 Seiten

urn:nbn:de:101:1-2512221105448.253340465428

10.25967/650052

Aircraft Performance, Landing, Approach, Cruise, Flap Deflection, Flight Mechanical Model, Load Alleviation, Transport Aircraft, High-Lift System

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Unkelbach, W.; González, P.J.; et al. (2025): Numerical Analysis of Static Load Alleviation for Transport Aircraft. Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V.. (Text). https://doi.org/10.25967/650052. urn:nbn:de:101:1-2512221105448.253340465428.

22.12.2025