Active aeroelastic wing concepts, sometimes also called active flexible wing concepts, have been investigated for several years to improve aircraft performance and stability. Two aspects are addressed in these studies: static aeroelastic effects like control surface effectiveness and the redistribution of aerodynamic forces for load reduction or drag minimisation, and dynamic aspects like enhancement of flutter stability or reduction of aerodynamically induced vibrations of the structure. Static aeroelastic applications can be realised in two ways. In a more conventional approach, control surfaces are used to deform the main structure, thus creating the desired aerodynamic pressure distribution by the aeroelastic deformation. The developments of active materials and active structure concepts are now offering new approaches. Here the direct, active deformation of the main structure by means of internally generated strains can generate the resulting, passive aeroelastic deformations. Therefore control surfaces can be reduced in their size, their strength and stiffness capacity, and the required actuation power, or they may in some cases not be required at all. For the design and analysis of these concepts, new methods are required to simulate and optimize the deformation behaviour of the passive and active structure simultaneously. New approaches are also required for the aeroelastic analysis of active structures. For designs with conventional control surfaces, their deflections can be specified in advance in the aerodynamic model. The aeroelastic analysis will then deliver deformations and the resulting aerodynamic pressure distribution at the specified Eight conditions. For active structures however, the achievable initial deformations from the activation of active elements in the aerodynamic system must first be determined. The paper will describe a possible approach for this task. It will be described, how the behaviour of active elements within a passive structure can be simulated and how their placement can be optimized. Examples for possible aeroelastic applications are presented for the wing and vertical tail of a typical fighter aircraft. For the wing, different approaches are discussed, how the desired aircraft roll performance can be achieved most efficiently. For the vertical tail, a conventional design approach for sufficient lateral stability is compared with two other concepts to reduce the tail's size and weight. These first results indicate that active aeroelastic aircraft concepts can improve aircraft performance and efficiency. The amount of the achievable gains largely depends on how these concepts can by analysed and optimized in an integrated design process for all involved components and aeronautical disciplines. For further improvements and more accurate prediction methods, it is required to modify existing analysis and optimization tools and incorporate the description of the physical characteristic of active structural components into them.
