Crash simulations of aircraft fuselage section in water impact and comparison with solid surface impact

Abstract

Aircraft water landing emergency provisions 14 CFR 25.801 demand requirement of ditching provision if requested in certification. This requires evaluation of the dynamic behaviour and response of aircraft in water impact to analyse the immediate injury to occupants. A correlated finite element model of a narrow-body Boeing-737 fuselage section and smoothed-particle hydrodynamics model of a body of water are coupled and utilised to investigate the structural response of the aircraft fuselage section when subjected to vertical drop test. The vertical drop of the fuselage section onto a body of water is simulated at an impact speed of 9.14 m/s, and also at higher impact speeds of 10.67 and 12.19 m/s. The vertical drop simulations are modelled using the non-linear explicit code, LS-DYNA, to predict the deformation of the fuselage section and acceleration pulses of the cabin floor, as well as the energy absorbed by the fuselage structure. The acceleration pulses from the cabin floor are then utilised as input for the occupant simulation performed using the mathematical code, MADYMO 7.5. The occupant model consists of a MADYMO FAA Hybrid-III 50th percentile dummy, a 2-point lap belt and a rigid seat. The lumbar loads experienced by the occupants in relation to both types of impacts are also presented. The dynamic simulation results from this study suggest that the fuselage section in water impact may be less severe than solid surface impact.