Active Aeroelastic Aircraft Structures (3AS)
The structure of an aircraft is not completely rigid; it changes its shape in flight. The net weight of the structure, the fuel stored in the wings and aerodynamic forces all cause deformations. But even the smallest deformations can dramatically affect the aerodynamic qualities, and have hitherto been regarded as a disadvantage. This, in turn, may reduce the effectiveness of control surfaces or tail units. At high speeds, furthermore, the structure is endangered by so-called flutter instability. In extreme cases the strong forces that emerge in fractions of a second are capable of destroying the structure. EADS Military Air Systems is investigating innovative design concepts in which the interaction between external aerodynamic forces and the elastic behaviour of the structure is to be exploited in order to ensure optimum efficiency for different flight conditions and loads. The aim is to increase the performance and investment value of an aircraft. In the meantime, a European research consortium is addressing the topic of Active Aeroelastic Aircraft Structures (3AS). In the research project, which is being coordinated by EADS Military Air Systems, three groups of design concepts are being examined: firstly, active elastic deformation of the structure using new types of control surface that generate the desired aerodynamic characteristics; secondly, elements of variable stiffness in which aerodynamic surfaces, for example tail units, are installed; and thirdly, structurally integrated elements of variable stiffness.
