IDAC were provided with an assembly model of the seat geometry from Martin-Baker's Unigraphics system. The individual parts in the assembly were then imported into the ANSYS program via the ANSYS Connection for Unigraphics product. Due to the size of the FE model, the substructuring method was employed to solve the problem. Subtructuring is a procedure, which condenses a group of finite elements into one element represented as a matrix. This single matrix is called a superelement. Each component making up the seat frame was modeled as a superelement, with the armoured bucket and connecting pins being modeled with shell and line elements respectively. The graphic to the left shows a plot of all the superelements. It was found that by employing superelements in the analysis the solution was carried out more efficiently, drastically reducing the total number of degrees of freedom.
The graphic to the right illustrates the finite element model used in the analyses. Seven loadcases were run in total, each loadcase comprising inertial loads and occupant loads. The occupant loads were applied directly as forces on the shell model for the crew seat armoured bucket. Two of the seven loadcases simulated dynamic loading. The dynamic loading was achieved by applying an equivalent quasi-static loading plus an imposed racking load. The racking load involved one of the seat legs being lifted by 10 degrees, this amount of lift represents the distortion of the aircraft floor in a crash situation. The seat was restrained at the helicopter mounting points, which allowed for the calculation of the helicopter floor loads.