Crash tests and simulation analysis for civil aircraft equipped with an auxiliary fuel tank

A study was conducted to investigate the crash impact response of the lower fuselage structure of a typical civil aircraft with an auxiliary fuel tank installed. The results of vertical crash tests conducted at impact velocities of 1.53, 2.78 and 5.96 m/s were obtained. These results include the influence of installing auxiliary fuel tanks on the impact response and the structural deformation and damage of the lower fuselage structure. The validity of the corresponding finite element model was verified through a correlation analysis between the simulation and test results. The impact energy absorption form during the vertical crash process was analyzed through simulation results. The results show that the structure mainly deforms elastically with only slight plastic deformation under the impact condition of 1.53 m/s. Under the impact condition of 2.78 m/s, the fuselage frames, skin, and T-shaped support components of the cargo floor are mainly deformed by bending, and the total structures were slightly compressed. The T-shaped support components connected to the left cargo floor slide rails extended upward and did not touch the fuel tank. Under the impact condition of 5.96 m/s, the lower fuselage structures were seriously compressed and the left diagonal brace was fractured under pressure. The auxiliary fuel tank sank to the cargo floor. The simulation analysis can effectively model the deformation and damage of the structure during the vertical crash process at different impact velocities. The impact force on the ground and the trend of acceleration at typical locations obtained by analysis are in good agreement with the test results. The analysis results show that the fuselage frame is the main deformation and energy absorption component in the crash of the lower fuselage structure equipped with auxiliary fuel tanks. The skin and auxiliary fuel tank are the secondary structures that participate in deformation and energy absorption. As the auxiliary fuel tank is filled with more fuel, the simulation results show that the energy absorption capacity of the auxiliary fuel tank and the lower fuselage structure components increases, i.e., the degree of damage becomes more serious. The research results can provide support for the anti-crash design, analysis, and verification of the fuselage structure of civil aircraft with auxiliary fuel tanks installed.