Ditching Simulation of Generic Transport Aircraft: Implementation of a Mass Distribution Model (Masterarbeit)

Abstract

In the framework of an aircraft certification for overwater operations, manufacturers must investigate ditching capabilities to show conformity with airworthiness regulations. By using computational methods and especially numerical methods, the prediction of the structural response of the airframe to hydrodynamic loading is possible. Aimed by the implementation of ditching analysis in early aircraft design phases, the German Aerospace Center (DLR) is been developing a tool for the complete pre‐processing of ditching simulations, called AC-Ditch. Since 2017, with an increase in the computation performance, ditching simulations using flexible aircraft models became feasible. However, contrary to rigid aircraft models with predefined global mass properties, more detailed models integrate total mass, inertias, and the coordinate of the center of gravity from the physical properties of the elements of the model, evidencing the necessity of the creation of a mass distribution model. The present thesis contributes to enhance ditching simulations of generic transport aircraft with the development of a mass distribution model, with its implementation into AC‐Ditch, and with investigations of flexible aircraft models in terms of numerical studies. To accomplish these objectives, the mass data was generated using an aircraft predesign workflow, which was then filtered according to existing masses in the FE model. The remaining masses were attached to the aircraft structure as lumped masses. The model of the mass attachment was verified employing a minimal FE model. In addition, the mass model was validated using the flexible aircraft model in free flight conditions. Therewith, the accuracy of the mass properties, the stability of the mass attachment, and the computational effort were investigated in a set of numerical studies. Finally, major findings were considered for the simulation of the Hudson River accident, in which significant structural deformation due to hydrodynamic loading was observed.