AIRCRAFT STRUCTURAL CONFIGURATION

Aircraft structural configuration

Aircraft structural configuration

Introduction

Current trends in aircraft development indicate that requirements linked to environment friendliness, such as emissions and noise limits, are strongly gaining importance. Only by considering these requirements will it be possible to handle the expected growth in worldwide air traffic. One of the goals is to enable unrestricted night-time traffic at airports in order to elevate their capacity. To achieve this and other goals, it is expected that environmental requirements may become driving parameters for a given aircraft design. This means, among other things, that unconventional aircraft configurations will have to be considered in order to fulfil all requirements. Once environmental requirements become driving parameters, it is necessary to consider them within the preliminary design phase of aircraft development. (Austin, 2008)

Aircraft structural configuration

The design process has to be adapted. If unconventional configurations are necessary to comply with all requirements, the methods used in the design process have to be able to properly consider the special features of these configurations. Statistical approaches and semi-empirical methods, on which preliminary design processes usually rely, are not likely to produce useful results, and should be replaced by methods that provide higher fidelity. At the Institute of Aircraft Design and Lightweight Structures (IFL), the Preliminary Aircraft Design and Optimization (PrADO) tool has been under development for over 20 years, as an automated multidisciplinary integrated preliminary design process. Currently, PrADO is able to use higher fidelity methods for key tasks such as structural sizing. The Structural Sizing Module (SSM) combines an aerodynamic panel method with finite element (FE) based Fully-Stressed-Design . (Austin, 2008)

As part of a joint research project, a Low Noise Aircraft (LNA) design with an unconventional configuration has been developed at the Institute of Aerodynamics and Flow Technology (AS) of the German Aerospace Center (DLR). At IFL, this LNA design is subjected to preliminary design using PrADO. Special emphasis in the analysis is placed on topics pertaining to structural sizing. A conventional reference aircraft designed for the same transport mission is subjected to the same design process in order to provide a basis for comparison. (Austin, 2008)

The Preliminary Design Process

The Preliminary Aircraft Design and Optimization tool is a modular system of computer programs. Input from the user is required in the form of an ASCII data file, which includes a basic parametric description of the configuration layout, the transport mission and data on applicable design targets and relevant constraints. From this input file, the database files are constructed. They form a set of ASCII files which contain all information relevant to the current design problem in a thematically sorted manner. The design process itself consists of a set of basically independent programs, the design modules. Each module is responsible for a certain task (e.g. wing geometry conversion, calculation of the longitudinal control and stability margins, etc.). (Austin, 2008)

These modules interact with the database files through a common library, the Data Management System (DMS). Through the DMS, the design modules are able to read input data and write their ...