Approach for Ensuring Fuel Tank Crashworthiness Using LS-Dyna Simulation

Helicopters are widely used in military and civil fields owing to its unique vertical take-off and landing, excellent hover performance and low speed characteristics. During the operative life of helicopter, it is possible that it could incur into emergency landing or crashes could generate serious injuries and even death of occupants may be due to fuel tank failures. Hence, the crashworthiness is crucial concern for the design of the helicopter fuel tank and to improve the survivability of helicopter with its surrounding structures under crash situations. FAR 29.952 provides the certification regulations to ensure safe and crashworthy fuel system. The drop test involves 50 ft drop of fuel tank with its surrounding fuselage structure filled with 80% water inside the fuel tank. The acceptance criteria are to ensure that there is no leakage of fuel from the fuel tank after ground impact. In case of leakage of fuel, redesigning and repetition of drop test will incur high cost and time delay for certification of fuel tank. In this paper, a simulation model using LS-DYNA has been developed and validated through drop test and describes the detailed FE idealization and contact definition to accurately predict drop test simulation. The smooth particle hydrodynamics (SPH) technique has been used to model fluid structure interaction (FSI) coupling. It is observed that good correlation between simulation and drop test results. Further, the validated FE model is utilized for design modifications without repeating experimental tests to achieve airworthiness certification.