2407. Aeroelastic Effects on the Weight of an Aircraft in the Pre-Design Phase

Paper

Abstract

In the pre-development phase of a new aircraft naturally the knowledge about the design is very limited. The inclusion of aeroelastic effects is therefore an ambitious task since specific data (e. g. stiffness or mass distributions) must be available. This paper describes the method and process for the calculation of aeroelastic effects on the weight of an aircraft. Here not only the primary influence on the structural weight is important. It has to be recognized also that aeroelastic effects on the aerodynamic efficiency influence the fuel consumption. This leads to a change of the maximum take off weight (MTOW) of the aircraft and has therefore a snowball effect on the structural weight since a change of the MTOW influences the dimensioning loads. A method appropriate for the inclusion of aeroelastic effects at the very beginning of a new aircraft project is presented. Even if only a simple three-sided view with a proper definition of the wing geometry is available first calculations can be performed. The software-tool FAME-W which is used in the future projects office at Daimler-Benz Aerospace AIRBUS in Hamburg is detailed with emphasis on the multidisciplinary character of the computational approach. The results show the effects of aeroelasticity particularly on the wing and tailplane weight. A procedure for the calculation of the stiffness and mass distribution is presented. Here the influence of geometric parameters like sweep angle or aspect ratio is identified. The effectiveness of a maneuver load control system including all relevant flexibility effects for a trimmed aircraft is shown. The redistribution of the lift and pitching moment and the effect on the lift to drag (L/D) ratio during a flight mission is pointed out. A precise calculation of the L/D ratio of a new aircraft is the basis for the assessment of its viability. Together with these results the paper demonstrates the strong influence of aeroelasticity in the pre-design phase beginning with minimum information and finishing with detailed knowledge about the new aircraft. The combination of classical weight estimation approaches with numerical aerodynamics and structural mechanics into one software-tool shows that weight engineering is more important than ever and still a challenging endeavor.