Parametric studies of the influence of the degree of fuselage ovality on compliance with the requirements of structural impact resistance under dynamic loading in the event of an emergency landing

Аuthors

Balunov K. A.^*, Zaytsev A. M.^**, Kudrayshov M. A.

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), Zhukovsky, Moscow region, Russia

*e-mail: kirill.balunov@tsagi.ru
**e-mail: artem.zaytsev@tsagi.ru

Abstract

The development of civil transport aviation highly depends on increasing air flight capacity, which requires incorporating new and effective design solutions into aircraft engineering practice. As such, research focused on finding these layout solutions is becoming more relevant because the shape of the fuselage cross-section is crucial for maximizing internal space for payload placement. Important aspect of designing passenger aircraft is to provide the occupant’s safety during emergency landing. The fuselage structure plays a vital role in ensuring safety for passengers and crew in the event of a crash-landing event, since due to deformation, crumpling and failure of structural elements under the passenger floor a safe space maintains inside the passenger cabin, and the impact forces transmitted to passengers are reduced to a level of injury acceptable to human. The conditions of an emergency landing are reproduced by vertical drop tests of full-scale fuselage sections on a rigid base. These tests provide the necessary data to evaluate the crashworthiness criteria of aircraft structure: maintenance of a survivable volume, maintenance of occupant emergency egress paths, maintenance of acceptable acceleration and loads experienced by the occupants, as well as maintaining the integrity of seat fastenings, equipment, cargo, and any other masses upon impact. The paper presents a comparative analysis of how the ovality of the fuselage and the stiffness of the cargo floor elements affect compliance with crashworthiness criteria during emergency landing. The emergency landing conditions are reproduced by numerical simulation of the fuselage section drop test onto a rigid base with the impact vertical velocity of 9.14 m/s, which corresponds to a fuselage section drop from a height of 4.27 meters. Simulation is performed using the explicit nonlinear dynamic finite element LS-DYNA code, recording kinetic and internal energies during the process, as well as accelerations at typical points of the fuselage structure. Based on the analysis of the structural deformation and the efficiency of kinetic energy absorption by the structure together with the acceleration values observed during the deformation process at typical points of the structure, it is concluded that, from the point of meeting the crashworthiness criteria, the fuselage failure mode with the gradual flattening of the lower fuselage section relative to the impact surface is better. The results show that rational selection of the sub-cargo crossbeams stiffness allows to meet compliance with the crashworthiness requirements for all considered fuselage ovality variants. Nevertheless, layouts with large and small degrees of fuselage ovality are shown to be preferable compared to a fuselage with a circular cross-section shape in terms of absorbing kinetic energy by the structure.

Keywords:

aircraft fuselage, oval fuselage cross-section, parametric studies, numerical modeling, dynamic analysis, emergency landing, crashworthiness

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