Optimised energy absorber elements for helicopter seats

Within the EU funded project ‘HeliSafe TA’ (2004 – 2007), DLR carried out different parametric studies in order to optimise the properties of the energy absorbers used in helicopter cockpit seats and to propose a concept which leads to the lowest possible injury rates for occupants of different weights and sizes in a crash landing. 15 different injury criteria are considered in the IRSIX calculation which is used in ‘HeliSafe TA’ to judge the injury risk of helicopter occupants. Out of these criteria, the lumbar spine load criterion is the most important one in mainly vertical load cases. MADYMO models were developed to simulate the seat, the dummy and the cockpit environment. The report describes the results of a parametric study in which 3 different energy absorber groups (with ‘increasing force’, ‘constant force’ or ‘decreasing force’ characteristics) were investigated for two different occupant dummy sizes: 50%-ile and 95%-ile dummy. For each dummy size an optimised absorber characteristic could clearly be identified. It was shown that a non-adaptive attenuator system can only be optimised for a specific dummy weight and size. An adaptive attenuator system was proposed in which absorbers are supplied being optimised for a 50%-ile dummy. For heavier occupants, additional absorbers which act in parallel could then be activated