In 2005, the German Aerospace Center (DLR) started an internal project, called TIVA, with the main goal to strengthen the multidisciplinary collaboration in the field of conceptual aircraft design. This approach was intended not only to couple disciplinary analysis tools from different institutes, but also to establish a process which keeps the disciplinary experts in the loop as well. Linking the tools and corresponding experts, this process should finally enable each discipline to study the consequences of their new concepts and technologies on overall aircraft level. One major component of this process is a new data exchange file format called CPACS, which serves as central interface and common language between the disciplinary analysis tools. The second key component is the integration framework, which allows the user to couple the single tools to multidisciplinary process chains for analysis and optimization tasks. Since the end of the TIVA project in 2009, the system is continuously being enhanced and extended in TIVA's successor-project VAMP, as well as in several other research projects which are based on this technology. For the near future, it is further planned to open the system with its major components to external partners and to use it for common projects with Industry and Universities.

Applying DLR's conceptual aircraft design system to military flying wing configurations, the design of a generic UCAV configuration is presented. For its outer shape, the SACCON geometry specified by NATO STO/AVT-161 Task Group was taken. For mission analysis and structural sizing, aerodynamic data from fast and robust conceptual design methods (i.e. potential flow theory) were used. In order to assess the validity of these simple methods for such configurations, a comparison with results from RANS aerodynamics and wind tunnel measurements was performed. The results of this design task were included into the stability and control investigations performed within the AVT-201 task group. Nomenclature C A Axial force coefficient [−] C D Drag force coefficient [−] C L Lift force coefficient [−] C N Normal force coefficient [−] C S Body-fixed side force coefficient [−] C Y Side force coefficient [−] C l Rolling moment coefficient [−] C m Pitching moment coefficient [−] C mx Body-fixed X-moment coefficient [−] C my Body-fixed Y-moment coefficient [−] C mz Body-fixed Z-moment coefficient [−] C n Yawing moment coefficient [−] I xx Mass moment of inertia (X-axis) [−] I yy Mass moment of inertia (Y-axis) [−] I zz Mass moment of inertia (Z-axis) [−] V Freestream velocity [ m s ] p, q, r Rotation rates (X, Y , Z-axis) [ • s ] Conventions X, Y, Z Coordinate system Symbols α Angle of attack [ • ] β Angle of yaw [ • ]

The characteristics of highly swept aircraft configurations have been studied in a series of consecutive research projects in DLR for more than 15 years. Currently, the investigations focus on the generic SACCON UCAV configuration, which was specified in a common effort together with the NATO STO/AVT-161 task group. This paper is the first one in a series of articles presenting the SACCON-related research work within DLR. First, the article describes the conceptual design studies being performed for this aircraft configuration. At this point the question is raised, whether the simple aerodynamic methods used within conceptual design can be applied to such type of aircraft configurations with sufficient accuracy. Thus, the second part of this article provides a comparison of the aerodynamic characteristics of the SACCON configuration predicted by low-and high-fidelity aerodynamic methods, as well as some results from wind tunnel experiments. Keywords Conceptual aircraft design Á Multi-fidelity Á Highly swept aircraft configurations Á SACCON Á UCAV aerodynamics Abbreviations C A Axial force coefficient [-] C D Drag force coefficient [-] C L Lift force coefficient [-] C N Normal force coefficient [-] C S Body-fixed side force coefficient [-] C Y Side force coefficient [-] C l Rolling moment coefficient [-] C m Pitching moment coefficient [-] C mx Body-fixed X-moment coefficient [-] C my Body-fixed Y-moment coefficient [-] C mz Body-fixed Z-moment coefficient [-] C n Yawing moment coefficient [-] I xx Mass moment of inertia (X-axis) [kg m 2 ] I yy Mass moment of inertia (Y-axis) [kg m 2 ] I zz Mass moment of inertia (Z-axis) [kg m 2 ] V

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