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A novel morphing control surface design employing piezoelectric Macro Fiber Composite (MFC) actuators is compared to a servo-actuated system. The comprehensive comparison including aerodynamics, size, weight, power, bandwidth, and reliability has revealed several observations. The conformal morphing airfoil geometry increases the lift-to-drag ratio over a servo-actuated flapped airfoil design, showing benefits in aerodynamic efficiency. The embedded MFC actuators eliminate the servo actuator volume from vehicle packaging; however, the MFC drive electronics must be taken into consideration. While the weight of the current prototype morphing system exceeds that of a traditional servo and linkage implementation, the weight is comparable and may not be prohibitive for some applications. The comparable power requirement and superior bandwidth make the morphing actuation a feasible and attractive approach for certain air vehicle designs. An order of magnitude increase in bandwidth was observed using the morphing flight control actuation. Ongoing reliability testing of the morphing specimens has demonstrated that solid-state morphing actuation has not failed within 10 5 cycles. Flight tests are planned to fully prove the benefits of the morphing actuation over a servo-actuated design. NomenclatureA = Airfoil planform area, ft 2 C d = Drag coefficient (2D), D/(0.5!V 2 A) C l = Lift coefficient (2D), L/(0.5!V 2 A) D = Drag, lb L = Lift, lb ! = Angle of Attack, degrees "= Airfoil support angle, degrees # = Air density, slug/ft 3

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Multidisciplinary Design Optimization (MDO) has been used to investigate the use of a new concept for a transonic transport, the strut-braced wing. The incorporation of a strut into more traditional transonic transport concepts required the application of computational design techniques that had been developed at Virginia Tech over the previous decade. Formalized MDO methods were required to reveal the benefits of the tightly coupled interaction between the wing structural weight and the aerodynamic performance. To perform this study, a suite of approximate analysis tools was assembled into a complete, conceptual-level MDO code. A typical mission of the Boeing 777-200IGW was chosen as the design mission profile. Several single-strut configurations were optimized for minimum takeoff gross weight, with the best single-strut configuration showing a nearly20% reduction in takeoff gross weight, a 29% reduction in fuel weight, a 28% increase in the lift-to-drag ratio, and a 41% increase in seat-miles per gallon relative to a comparable cantilever configuration. The use of aeroelastic tailoring in the design illustrated ways to obtain further benefits. The paper synthesizes the results of the five-year effort, and concludes with a discussion of the effects various constraints have on the design, and lessons learned on computational design during the project.

A novel morphing control surface design employing piezoelectric Macro Fiber Composite (MFC) actuators is compared to a servo-actuated system. The comprehensive comparison including aerodynamics, size, weight, power, bandwidth, and reliability has been extended to include flight test comparisons. Flight agility and control response of the morphing-actuated and servo-actuated configurations were quantified through state measurement during identical automated maneuvers. The morphing actuation scheme demonstrated superior response times and a fully controllable vehicle, but was unable to match the magnitude of roll and pitch rates attained by the servo-actuated baseline aircraft. The servo-actuated aircraft exhibited velocity deficits during doublet maneuvers, while the morphing actuation negligibly decreased velocity, demonstrating lower drag and more efficient production of control forces and moments. Reliability cycle testing of an MFC bimorph achieved 1 million cycles without failure and minimal degradation in performance. Nomenclatureb = Wing span c = Wing chord C l = Roll moment coefficient D = Drag I xx = Roll moment of inertia L = Lift M x = Roll moment p = Roll rate S = Wing reference area V = Velocity ρ = Air density