Drag Identification and Reduction Technology (DIRECT) for Commercial Aircraft

The variable camber continuous trailing edge flap (VCCTEF) concept offers potential improvements in the aerodynamic efficiency of aircraft through real time wing shaping. NASA and Boeing have been studying the suitability of this concept to address the drag reduction problem in aircraft with reduced-stiffness wings. However, reduced stiffness may lead to wing flutter. In addition, displacements of VCCTEF control surfaces are limited and subject to highly nonlinear and time-varying constraints. Hence control design needs to solve a constrained multiobjective optimization problem. To address these challenges, under a recent SBIR project SSCI carried out initial development and testing of the Drag Identification and Reduction Technology (DIRECT). The DIRECT estimates aeroservoelastic states on-line and uses that information in a robust predictive controller to suppress flutter. DIRECT also estimates wind disturbances and selects optimal controller parameters form a table lookup to achieve on-line drag minimization. In the paper we describe our initial development of the DIRECT technology along with plans for wind tunnel testing under the current Phase II SBIR project.