Validation of Numerical Models of a Rotorcraft Crashworthy Seat and Subfloor

Abstract

The present work explores some critical aspects of the numerical modeling of a rotorcraft seat and subfloor equipped with energy-absorbing stages, which are paramount in crash landing conditions. To limit the vast complexity of the problem, a purely vertical impact is considered as a reference scenario for an assembly made of a crashworthy helicopter seat and a subfloor section, including an anthropomorphic dummy. A preliminary lumped mass model is used to drive the design of the experimental drop test. Some additional static and dynamic tests are carried out at the coupon and sub-component levels to characterize the seat cushion, the seat pan and the honeycomb elements that were introduced in the structure as energy absorbers. The subfloor section is designed and manufactured with a simplified technique, yet representative of this structural component. Eventually, a finite element model representing the full drop test was created and, together with the original lumped mass model, finally validated against the experimental test, outlining the advantage of using both the numerical techniques for design assistance.

Diseño de estructuras tipo panal de abeja basadas en el caparazón de armadillo para un helicóptero ligero

“…Sus principales ventajas son bajo costo, geometrías simples y efectividad para absorber energía. En este sentido diversas investigaciones numéricas [4], [5], computacionales [6], [7], [8] y teóricas [9], [10] se han desarrollado para optimizar estructuras tipo celular. Yan et al [11] diseñaron componentes a resistencia al impacto de un avión ultraligero considerando una estructura de absorción de energía.…”

Numerical investigation on energy absorption characteristics of impact-resistant lightweight structure of bio-mimetic micro aerial vehicle

“…In addition, the seat system has also received more study. 11,12 Lamanna et al 13 developed a finite-element program to simulate the collision caused by the passenger dummy when the plane falls, in order to make reasonable suggestions for cabin design to avoid human head injury. Russo et al 14 compared four kinds of foam materials for the seat cushions, simulating the mechanical properties of different materials to ensure that the cushions in the cabin were comfortable and safe.…”

On the Crashworthiness Behaviour of Innovative Sandwich Shock Absorbers

“…The development of concepts aimed to improve the passive safety of transport vehicles is one of the most popular challenges in contemporary engineering. Among the proposed solutions, a significant contribution to this issue was reached by introducing shock absorbers in strategic structure locations [ 5 , 6 , 7 , 8 , 9 ]. In particular, shock absorbers have been found to be a good alternative to the high-pressure chamber landing system usually installed on helicopters, showing appreciable energy absorbing capabilities during crash events [ 5 ].…”

“…In [ 7 ], crushable hybrid energy absorbers have been incorporated as vertical struts in a fuselage structure to improve the crashworthiness of aircrafts. In [ 8 ], the employment of energy absorbing devices incorporated in the seats and subfloor section of a helicopter has been investigated as an effective way to reduce the impact loads transferred to passengers. Furthermore, the increase in the shock absorber’s energy damping capability, resulting from the structural combination of ductile and composite materials, is demonstrated in [ 9 ], where a hybrid metal/composite shock absorber system was placed in the bottom of an ejection seat, absorbing more than 50% of the resulting energy.…”