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WP 2: Structural models and load cases definition

The scope of Workpackage 2 is to prepare the ground for the theoretical and experimental research activity to be performed in WP3 and WP4. The targets of WP2 are:

  • Critically review and understand the definition of sizing loads for a civil aircraft
    fuselage
  • Define the analysis models to be adopted for the different stages of analysis
  • Identify numerically/experimentally the typical time history loads related to landing, manoeuvres and turbulence (gust loads).

WP leader: Giuliano Cattaneo, Alenia Aermacchi SpA

WP 2 Results

In Task 2.1 (Current Design Process Review), a specific aircraft structural configuration is defined (Figs. 1 and 2), and the procedures currently used in structural design are reviewed (Fig. 3). Practices used in the current design process are tightly related to the requirements of the regulations. The selection of the certification bases (airworthiness regulations) has a great impact on the subsequent work in Task 2.2 (Structural Analysis Using Current Design Process). The Airworthiness Category for the specific airplane described here is FAR/CS 25 (Large Airplane). Structural elements suitable for demonstrating new approaches are also defined. The review has some focus on dynamic load cases (Figs. 4 and 5) and an upgraded approach is proposed for subsequent use within the project.

In Task 2.2 structural and aerodynamic models to be used for dynamic load analysis are described. In particular DAEDALOS requires the development of a wide set of models:

  • Coarse model of aircraft. This model is the basis for the development of any other structural model. It represents, by means of a fine mesh, every part of aircraft. Mass, inertial and stiffness properties are associated at finite elements and simulate the actual physical
    properties of the airframe.
  • Condensed model. This is a model with few degrees of freedom. This model is the baseline for assessing the dynamic behaviour. It represents the structure of the aircraft but properties as mass, inertia and stiffness are associated to beam element properly tuned to match full model dynamic response. Condensed model or stick model is used to perform dynamic analyses because less complex than detailed model.
  • Hybrid models. Since the detailed models may take very long time to calculate dynamically, in order to shorten calculation times it is possible to combine detailed models at some critical areas with the simple models at uncritical areas.

In Task 2.3 of WP2, the following topics have been addressed:

  • Review of the general aircraft definition, including design weights and design airspeeds
  • Discussion the types of dynamic loading conditions selected for the DAEDALOS project
  • Explanation of each type of dynamic load condition selected, analysis method and samples of results
Figure 1: Reference FEM Coarse Model - isometric view.
Figure 2: Reference FEM Coarse Model - three plane view.
Figure 3: Overview of Design Process: "Design Wheel"
Figure 4: Dynamic Landing Analysis - Step 1
Figure 5: Dynamic Landing Analysis - Step 2