2005 Canadian Aeronautics and Space Institute Annual General Meeting Aircraft Design & Development Symposium Optimization of a Business Jet M. Abdo * , P. Piperni † , A.T. Isikveren ‡ and F. Kafyeke § Bombardier Aerospace, Montreal, Quebec, H4S 1Y9 * Engineering Specialist and Flutter & MDO Team Integrator, NCAP Technical & Aerodynamics, AIAA Member, mohammed.abdo@aero.bombardier.com † Group Leader, Advanced Aerodynamics, CASI Associate Fellow ‡ Senior Technical Focal, Conceptual Design & Benchmarking, Advanced Design Department, Bombardier Aerospace Post-Doctoral Researcher, Royal Institute of Technology (KTH), Stockholm, Sweden § Manager, Advanced Aerodynamics, AIAA Associate Fellow ABSTRACT This paper discusses the structural design methodology embedded in a Multidisciplinary Design Optimization (MDO) of a complete aerodynamic representation of a business jet, including winglets, rear-mounted engines, and a T-tail configuration. Particular emphasis is placed on the development of the quasi-analytical structural design methodology, including the layout of the ribs, the design of the spar webs, spar-caps and the skin-stringer panels, and the computation of the wing structural properties and weight. The statement of the MDO problem is reviewed and the MDO methodology is applied to the optimization of an aircraft for a fixed range mission assuming a constant Maximum Take-Off Weight. INTRODUCTION One of the essential components of an MDO methodology for aircraft design is a tool to automatically define and lay out a conceptual wing structure. In order to efficiently integrate this capability within an automated MDO process, it must be able to design a representative wing structure given only the external lines of the wing, and compute the flexural properties of the wing as well as its weight. This capability must be accurate enough to properly capture not only the overall wing weight and deformation but also the correct sensitivities to both the small and large changes that occur during the optimization process. This paper presents in detail the conceptual wing-box structural design and analysis methods that are used in the optimization including the spar-cap and the skin-stringer sizing schemes. It also describes the semi-empirical wing weight prediction method that is based on the General Aviation Synthesis Program, GASP. 22 A review of the CFD method integrated into the MDO process is also provided, as well as a description of the en route performance analysis that is utilized to formulate an objective function that represents the aircraft’s COC by correlating structural weight changes to mission fuel weight. An application to the design of a complete business jet configuration is included to illustrate the overall capability. AIRCRAFT AERODYNAMICS IN THE TRANSONIC REGIME The CFD code that is currently used to compute the aerodynamic characteristics of the aircraft is a fast turn-around code developed at Bombardier called KTRAN. 23-27 KTRAN solves a modified transonic small disturbance equation using Cartesian grid embedding techniques. This program has traditionally been used to perform preliminary wing design ahead of higher-order CFD codes. However, despite its low order formulation, at design (aircraft typical cruise) conditions, KTRAN provides reliable predictions of wing pressure distributions and aerodynamic loads. This program can be used to model full aircraft configurations that include fuselage-mounted or wing-mounted nacelles, wing-tip winglets and horizontal tail components. KTRAN includes a mixture of semi-empirical and CFD-based routines to compute the aircraft total drag (trimmed) to within engineering accuracy. In Figure 1, the drag prediction capability of the code is illustrated on the well-known DLR-F6 wing-body-engine configuration.