Towards Flying Qualities Constraints in the Multidisciplinary Design Optimization of a Supersonic Tailless Aircraft Craig C. Morris, * Cornel Sultan, † Darcy L. Allison, ‡ Joseph A. Schetz, § and Rakesh K. Kapania ¶ Virginia Tech, Blacksburg, VA, 24061, USA The increased complexity of next generation aircraft and the resulting highly-coupled interactions between aircraft systems has popularized Multidisciplinary Design Optimiza- tion (MDO) as an aircraft design tool. However, MDO efforts routinely neglect aircraft stability and control analyses beyond simple static assessments. Not only does this limit the potential of the MDO to identify an optimal design, but it also fails to assess the MILSPEC or FAR flying qualities requirements the aircraft must achieve. In an effort to bring flying qualities and dynamic performance into the MDO of a tailless Efficient Supersonic Air Vehicle, an H∞ control methodology combined with pole placement constraints is adopted to automate the feedback control system design and assess the aircraft’s performance. As a preliminary investigation, and to assist in software development, the longitudinal dy- namics of a relaxed static stability transport aircraft are studied, and the path forward to implementation on a supersonic tailless aircraft is outlined. I. Introduction S ince before the Wright Flyer left the ground, aircraft designers have struggled with the necessary and challenging task of maintaining stability and control of the vehicle. In 1809, George Cayley became the first to recognize the force balance needed for flight in the first part of his three-part treatise on aerodynamics entitled, ”On Aerial Navigation.” 1 Through observations of nature and his experiments with gliders, Cayley soon after discovered the need for wing dihedral and center of gravity positioning as crucial elements for stability in aircraft design. 2, 3 Even in the 21 st century, stability and control continues to pose a challenge to aircraft designers. The traditional design process all too often delays thorough study of aircraft stability and control until after the conceptual design process. 4 While control integration efforts have been made on specific configurations (so-called control-configured aircraft), 5, 6 there are many examples of modern aircraft which suffer from control design limitations that went unnoticed until late in the design process. This strategy of aircraft design is not only costly, as late redesigns are expensive, but also performance limiting. The B2 Stealth Bomber, for example, underwent an aft planform redesign after the conceptual design stage due to unpredicted aeroservoelastic phenomena between the outboard elevon and the first wing bending mode. 7 At the conceptual design level, aircraft stability and control design consists of little more than volume coefficients and static analyses. 4, 8 This approach has proven successful in the design of the conventional tube- and-wing transport aircraft with reasonably stiff structures and lightly coupled wing/tail/body aerodynamics. It isn’t until the preliminary design stage is reached that performance analyses involving particular effectors and their sizes is accomplished, and even then aircraft dynamics are still often ignored in favor of simpler static analyses. While static analyses are necessary to properly characterize the behavior of an aircraft, they are far from sufficient. In the case of a tailless supersonic aircraft, where the aerodynamic influence of effectors is significant about all three axes, the dynamics cannot be ignored. * Graduate Research Assistant, Department of Aerospace & Ocean Engineering. Student Member AIAA. † Assistant Professor, Department of Aerospace & Ocean Engineering. Senior Member AIAA. ‡ Graduate Research Assistant, Department of Aerospace & Ocean Engineering. Senior Member AIAA. § Frederick D. Durham Chair, Department of Aerospace & Ocean Engineering. Life Fellow AIAA. ¶ Mitchell Professor, Department of Aerospace & Ocean Engineering. Life Associate Fellow AIAA. 1 of 16 American Institute of Aeronautics and Astronautics 12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSM 17 - 19 September 2012, Indianapolis, Indiana AIAA 2012-5517 Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Go Downloaded by Massachusetts Institute of Technology (MIT) Cambridge on May 8, 2013 | http://arc.aiaa.org | DOI: 10.2514/6.2012-5517