Structural Analysis of a Rotorcraft Fuselage in a Multidisciplinary Environment

Abstract

The helicopter constitutes a very important branch of the aeronautical industry despite being expensive, tricky to operate and requiring a high maintenance effort. Its ability to hover and operate under low airspeed, combined with the ability to land in almost every spot makes helicopters superior to fixed wing aircraft in certain missions. Moreover, helicopters also compete with earth bound vehicles when it comes to operations in sparsely populated areas or when the infrastructure impedes the use of automobiles. Therefore, the field of application for helicopters is wide ranging from aerial observation over general transport of passengers and cargo up to medical transport of severely injured patients. Recently, interest has grown to improve typical limitations of rotorcraft, such as to reduce noise and to extend the flight envelope by increasing cruise velocity. Novel and more effective helicopter designs might work in a wider operating range and/or could transport more payload in terms of mass and volume, for instance enhanced medical equipment allowing a better and faster treatment of the patient. These objectives lead to unconventional design concepts, e.g. compound helicopters that feature additional lifting surfaces and propellers. To date the statistical knowledge of such configurations that could be beneficial during early design phases is limited. However, the rotorcraft design process is very challenging since it is mainly driven by the desired functionality. Accordingly, helicopter fuselages often feature cut-outs that influence the load path and hence the structure and mass. In turn, a sufficiently precise estimation of the helicopter total mass is required for a feasible performance analysis, thus calling for an iterative design process. With the aim to create and evaluate traditional but also new unconventional rotorcraft concepts, an integrated, automated multidisciplinary process chain covering the conceptual and preliminary design stages has been established within the German Aerospace Center (DLR). It allows the design of virtual rotorcraft configurations starting from scratch, based on few minimum input parameters, e.g. mission range, cruise velocity, payload, blade number and rotor configuration. This process chain features a modular approach to allow for high flexibility concerning the redefinition of certain parameters that become available during the design process. The presented paper describes the process chain and the common data format used to combine the different tools. Particular attention is turned on the analysis of the fuselage structure. Exemplary, the generation of a generic rotorcraft is shown gradually from the very beginning by evaluating the required input parameters up to the structural analysis of the fuselage.