This paper presents the Multidisciplinary Integrated Conceptual Aircraft Design and Optimization (MICADO) environment that has been developed during the last years at the Institute of Aeronautics and Astronautics (ILR) of RWTH Aachen University. The MICADO environment allows for automated aircraft design and assessment with a minimum of user input, i.e. a set of top-level requirements and specifications. The homogeneous software environment allows for fast parameter studies and optimizations in a wide parameter space and with low computational effort. Due to the integrated design and assessment approach, variations of top-level requirements, local parameter changes as well as integration of new technologies or systems are captured into overall aircraft evaluation parameters such as block fuel or costs. The MICADO software architecture in terms of control and data flow, program structure and parameterization principles is presented. Further, the aircraft design and assessment methodology including the underlying models are discussed, as well as applications of MICADO for aircraft design studies and operational studies. Finally, functionalities and strengths of the proposed methodology are demonstrated by a case study, in which MICADO is used for the design and optimization of a conventional short-range aircraft. For the designed aircraft, variations of initial sizing parameters as well of Mach number and wing sweep angle are performed and overall aircraft design results are discussed.

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This paper presents an economic assessment of aircraft design studies with natural flow technology (NLF). Focus is put on off-design considerations, e.g. destabilization of laminar flow due to external influences, which are incorporated into the overall aircraft design synthesis. These off-design considerations directly impact the aircraft design as well as mission characteristics. Thus, they also influence direct operating costs (DOC). For estimating DOC in preliminary aircraft design, a DOC model is presented that is fully integrated into the ILR preliminary aircraft design synthesis. The required sensitivities towards aircraft, mission, scenario, and operating company related parameters are shown. Application of the proposed DOC model allows for economic assessment already in preliminary design stage. In the presented case study, NLF aircraft are designed and assessed for different off-design considerations and compared to a conventional single-aisle aircraft with conventional technology. Differences in direct operating costs are discussed. Furthermore, impact of different fuel price scenarios is analyzed. NomenclatureDOC Direct operating costs ETOPS Extended-range twin-engine operational standards LAOPS Laminar aircraft operational standards MICADO Multidisciplinary Integrated Conceptual Aircraft Design and Optimization NLF Natural laminar flow RPK Revenue passenger kilometer AF inhouse In-house airframe maintenance ratio, -AH f a Annual work hours per flight attendant, h/yr AP P Aircraft purchase price, 2010-USD AS f a Annual salary per flight attendant, 2010-USD/yr BH Block hours, h C delay Unit delay rate, 2010-USD/min C noise Unit noise rate, 2010-USD C N OX Emission-related unit rate, USD-2010 Engine dry mass, kg m blockf uel Block fuel, kg M LRC Long-range cruise Mach number M T OW Maximum take-off weight, kg N E Number of engines, -N f a,f light Number of flight attendants required per

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