Dominik Schwinn

Integration of Crashworthiness Aspects into Preliminary Aircraft Design

Crashworthiness proof is a certification requirement by aviation authorities for new aircraft types. The objective of static design is a sufficiently stiff and strong structure to carry bending and torsion during flight and ground maneuvers. High stiffness, however, is critical for good crashworthiness behavior. Therefore, crashworthiness investigations should be included at early design stages of the overall aircraft design process. This paper introduces the crash analysis tool AC-CRASH and shows an approach of integrating it into the preliminary design phase.

Parametrised fuselage modelling to evaluate aircraft crash behaviour in early design stages

Trade studies during the preliminary design phase play an important role in the design process of a new aircraft. However, the generation and adaption of appropriate finite element (FE) models still takes a lot of time which in turn may prevent comprehensive trade studies and, therefore, lead to time- and cost-intensive redesign during the detailed design phase. Based on a standardised aircraft description, a fuselage modelling tool was developed to automatically generate global FE models for preliminary sizing purposes using beam elements for the fuselage stiffening structure. To be also used in crash simulations these models can be extended in a way that certain regions – where high plastic deformations or failure is expected – may be modelled much finer by the use of extruded profiles and shell elements. Nevertheless, this fine representation is still based on the same standardised aircraft description. In this paper the crash analysis tool AC-CRASH is presented introducing various modelling options and applications. They range from standard section drops with a pure vertical velocity up to full fuselage models under realistic crash and ditching conditions. As an exemplary application of AC-CRASH a vertical drop of a generic fuselage rear section is evaluated in detail.

Coupling of static and dynamic fuselage design

Purpose – The purpose of this paper is to present a methodology for the evaluation of transport aircraft fuselages constructed in a semi-monocoque design. Design/methodology/approach – A fuselage barrel was computed statically and dynamically using finite element methods. Static analysis was conducted using a global/local approach in which the section loads of the global model were used as load introduction in the local model. Subsequently, a crash analysis was performed, and the results from both disciplines were evaluated by either an optimization or parameter variation algorithm. Findings – The presented process chain has been developed for use in preliminary design stages to assess aircraft configurations with regard to statics and dynamics. Parameter variation and optimization were conducted, proving functionality of the methodology. Research limitations/implications – In this early stage of methodology development only one exemplary static load case is considered and the fuselage design is limited t...

Applied parametrized and automated airframe modeling methods in the preliminary design phase

The design process of new air- and rotorcraft is commonly separated into three different consecutive phases. In the conceptual design phase, the viability of different designs is investigated with respect to customer requirements and/or the market situation. It usually ends with the identification of a basic aircraft lay-out. In the subsequent preliminary design stage the various disciplines are introduced, thus redefining the design process as a multidisciplinary optimization (MDO) task. The objective of this design stage is to enhance the initial aircraft configuration by establishing an advanced design comprising a loft provided with primary structure. This updated aircraft configuration represents a global optimum solution for the specified requirements which will then be optimized on a local level in the concluding detailed design phase with particular regard to manufacturing aspects. The investigations in the preliminary design phase comprise the generation of numerous similar but still different analytical and finite element (FE) models. Even though computational power is constantly increasing the model generation process is still a time-consuming task. Moreover, it is also a potential source of errors which — in the worst case — may lead to time- and cost-intensive redesign activities during the detailed design. As the preliminary design stage, therefore, is of particular importance during the overall design process the model generation process benefits from parametric models and automated process chains. The presented paper overviews the tools used for the automated generation of FE models developed and used at the Institute of Structures and Design (BT) of the German Aerospace Center (DLR) for the subsequent use in numerical simulations. Furthermore, basic requirements for the effective use of parametrization and automation like a common data format and infrastructure will be introduced. Exemplary models and applications will be presented to illustrate the positive impact on efficiency in aircraft design. Concluding, future development steps and possible applications will be discussed.

Advances in Numerical Ditching Simulation of Flexible Aircraft Models

Abstract This paper deals with explicit numerical simulation of fixed-wing aircraft ditching using a coupled approach of Smoothed Particle Hydrodynamics and Finite Elements. Particular focus is put on recent advances toward simulation of flexible full aircraft models, which comprises significant challenges with respect to the numerical efficiency as well as the model complexity. First, the pursued numerical approach is briefly presented. In order to deal with aforementioned challenges, an automated modular tool, which generates numerical models and launches ditching simulations, is presented. The paper provides a brief explanation of state-of-the-art aircraft as well as fluid modelling techniques used and furthermore presents an integrated model that computes aerodynamic loads during the simulation. The developed tool is used to conduct various numerical studies. First, the improved efficiency of such simulations over the state of the art is shown. Next, results of parameter studies are presented, demonstrating the effects of impact conditions on the aircraft motion. Finally, the structural deformation experienced during ditching of a detailed finite element aircraft model is analysed and its effects on the aircraft motion are discussed.