The German Aerospace Center is currently developing a new design environment for rotorcraft, which combines sizing, simulation and evaluation tasks into one toolbox. The complete environment applies distributed computation on the servers of the various institutes involved. A uniform data model with a collaboration and interface software, developed by DLR and open source, are used for exchange and networking. The tools used apply blade element methods in connection with full six degrees of freedom trim, panel methods for aerodynamic loads, different empirical models for sizing, engine properties and component mass estimation and finite element methods for structural design. A special feature is the integration of a higher fidelity overall simulation tool directly into the sizing loop. The paper describes the use of the several tools for the phases of conceptual and preliminary design. A design study is presented demonstrating the sensitivity of the process for a variation of the input parameters exhibiting a broad range for trade-off studies. The possibility to continue for analyzing and sizing of the structural properties is also demonstrated by applying a finite element approach for specific load cases. These features highlight the core of the new design environment and enable the development of goal-oriented design processes for research especially of new and unconventional rotorcraft configurations. The work presented in this paper was conducted throughout the DLR internal project, namely the Technologies for Rotorcraft in Integrated and Advanced Design (TRIAD). TRIAD is a joint project of the institutes of Flight Systems, the institute of Aerodynamics and Flow Technology, the institute of Structures and Design, the System Architectures in Aeronautics and Institute of Aerospace Medicine and receives basic founding.

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Like the design of fixed-wing aircraft the design of rotorcraft is generally divided into the three consecutive phases of conceptual, preliminary and detailed design. During each phase the acquired results in turn serve as input for new calculations, thus increasing the detail level and information about the new concept, while uncertainties about the new design are reduced. An important aspect of the overall design process is the mass estimation in early design stages. The weight of the rotorcraft drives the design of many important components, such as the rotor(s), the propulsion system and, therefore, the required fuel. The fuselage is considered as the central structural part, since it connects all other components to each other and serves as protection of the occupants but in the past it often turned out to also be the heaviest part of all rotorcraft components. This paper shows an approach to estimate rotorcraft component masses using statistical methods based on existing rotorcraft but also an approach to use finite element methods that determine the structural airframe mass based on mission profiles, respectively, bearable load cases.

For many years, the primary design objective of new helicopters was the design of the main rotor(s). Within the last couple of years, this approach has changed into an assessment of all helicopter components as an overall system, thus turning rotorcraft design into a highly interdisciplinary process. For instance, aerodynamics, flight mechanics, and the structural evaluation strongly affect each other, and these mutual influences are taken into account from the early phase of the conceptual design. Weight prediction in early design stages represents an essential part of the design process as it determines the basic properties of the rotorcraft. Owing to its function to carry crew and payload but also to serve as the central mounting for all components, the fuselage represents a major part of the rotorcraft. Therefore, the structural design of the fuselage airframe constitutes a significant factor of the rotorcraft design at the preliminary level.In this paper, an approach to include a higher fidelity method using finite elements for the structural analysis of rotorcraft fuselages within an integrated design environment is presented. Model generation and static analysis are conducted automatically. The helicopter is described using a common parametric data model during the complete design process, therefore providing a fast analysis of model changes. The generic finite element model presented in this paper was generated and structurally sized in about 2.5 min using a standard office computer, thus offering the integration of higher fidelity methods into early design sizing loops.