M D O APPLICATION FOR ACTIVE FLEXIBLE AIRCRAFT DESIGN

Due to the increasing performance requirements for fighter aircraft during the past decades, aeroelastic effects have become more and more important for their designs. In order to meet these requirements, a considerable amount of structural weight has to be spent to fight negative aeroelastic effects on aircraft performance and stability. In the future these effects will also become more important for ultra high capacity transport aircraft as well as for unmanned air vehicles, operating under extreme conditions. In recent years several theoretical and experimental studies have demonstrated how aeroelastic effects can be used in a beneficial way to improve aircraft performance and reduce the weight. These concepts can be realized in different ways. In a more conventional approach, multiple control surfaces are used to deform the main structure in order to create higher control forces or adjust the aerodynamic pressure distribution for minimum drag or reduced loads. New concepts are now possible by means of active materials or active structures which are used to deform the main surface internally to initiate aeroelastic deformations. Both concepts allow optimum modulation of the steady or unsteady aerodynamic pressure distributions throughout the entire flight envelope and for all fuel and payload conditions. To apply this technology efficiently, multidisciplinary analysis and optimization tools are mandatory. In an ongoing study, several concepts are investigated to improve the roll performance of a low aspect ratio wing. In addition to the description of the features of the used program, the needs for simulation and optimization of active structures are discussed and possible approaches are shown. First results are presented for the multiple control surface concept which indicate a great potential for future designs. The feasibility and potential of active material applications is briefly addressed.