Active Control for Elastic Wing Structure Dynamic Modes

Boeing and NASA are conducting a joint study program to design a wing flap system that will provide mission-adaptive lift and drag performance for future transport aircraft having light-weight, flexible wings. This Variable Camber Continuous Trailing Edge Flap (VCCTEF) system offers a lighter-weight lift control system having two performance objectives: (1) an efficient high lift capability for take-off and landing, and (2) reduction in cruise drag through control of the twist shape and camber of the flexible wing. This control system during cruise will command varying flap settings along the span of the wing in order to establish an optimum wing twist for the current gross weight and cruise flight condition, and continue to change the wing twist as the aircraft changes gross weight and cruise conditions for each mission segment. The more flexible lightweight wing also has the property of decreasing wing structure mode stability and consequent flutter margins, with possible unstable wing modes at lower altitude and higher speed conditions. This paper addresses modeling and control stabilization using the VCCTEF high speed camber sections that will provide control of these flexible wing properties at all flight conditions.