Flight Testing and Response Characteristics of a Variable Gull-Wing Morphing Aircraft Mujahid Abdulrahim * and Rick Lind † University of Florida Contemporary morphing designs are focused towards enabling a vehicle to transition from one distinct flight regime to another. Such a change often requires highly complex morphing that is designed to address both aerodynamic performance and handling criteria. The University of Florida has developed a morphing demonstrator to investigate the effect of a biologically-inspired gull-wing morphing on the flight characteristics of a small aircraft. The vehicle, equipped with sensors and data logging devices, is flight tested using a variety of maneuvers and techniques. The flight data from several morphing conditions is analyzed to determine the extent of the change in the dynamic properties. Modeling of the lateral-directional dynamics indicates that gull-wing morphing has a considerable effect on the handling qualities and stability. I. Introduction Morphing aircraft design continues to evolve as new technologies in actuators and flexible structures become available. New ideas in morphing encompass more than the simple span extension or wing twisting initially envisioned. Instead, these new designs allow vehicles to undergo a much more complex shape change than can easily be described by one or two parameters. This form of morphing is in-line with the original need for the technology, which is to change the vehicle shape dramatically to address two or more sets of conflicting requirements. As envisioned morphing designs become increasingly complex, the need for accurate flight dynamic analysis be- come even more important. 15 The complex shapes achievable by the new generation of actuators and structures can create difficulties in representing the vehicle using existing methods. For instance, an aircraft that morphs asymmet- rically can undergo aerodynamic and inertial changes that cannot be described by the commonly used equations of motion. Thus, in order to properly model a morphing aircraft with many degrees of freedom, the complete nonlinear coupled equations must be used. Such a requirement eliminates many or all of the simplifications that are necessary for the equations to be practical. The modeling predicament underscores one of the current realities of morphing research; the majority of morphing is being conducted in optimal aerodynamic shapes and static aeroelastic effects. The field of morphing vehicle flight dynamics is still highly underdeveloped. Part of this void is understandable, since few, if any, morphing aircraft exist today to perform flight test experiments. However, the lack of work also points to potential future problems in morphing research. Flight dynamics work must be developed in parallel to other morphing efforts in order to be able to assess and control prototype vehicles. The work presented here represents an initial foray into such an effort. The focus is the changing flight dynamics of a simple morphing vehicle (Figure 1). Vehicle design and morphing actuators are considered only enough to develop a testbed for flight dynamics experiments. No claim is made as to the optimality of the vehicle shape or morphing method. However, it is sufficient to consider that the morphing used causes a change in the flight performance, which is then the basis for studying any accompanying change in stability and control characteristics. In addition to the variable gull-wing morphing, the vehicle is equipped with articulating wingtip mechanism at that morphs the outboard section of the wing in twist. This form of morphing has been implemented on several vehicles at the University of Florida and is similar to the roll control used on the NASA AAW F-18. 10 It is used here to preserve the flexibility of the structure while retaining effective roll control. * Graduate Student, mujahid@ufl.edu † Assistant Professor, ricklind@ufl.edu Department of Mechanical and Aerospace Engineering 231 MAE-A Bldg PO 116250 Gainesville, FL 32611 1 of 16 American Institute of Aeronautics and Astronautics AIAA Guidance, Navigation, and Control Conference and Exhibit 16 - 19 August 2004, Providence, Rhode Island AIAA 2004-5113 Copyright © 2004 by Mujahid Abdulrahim. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.