Research On Fuel Tank Flammability Assessment Method Based On Monte Carlo Simulation For Civil Aircraft

Fuel tank ignition will seriously affect the safety of civil aircraft, and cause catastrophic accidents involving wreckages of aircraft and casualties of occupant. Therefore, it's necessary to carry out an assessment on the aircraft fuel tank flammability in aircraft development and certification phases. An assessment method of fuel tank flammability is studied to show compliance with requirements of Section 25.981 "Fuel tank explosion prevention".The criterions of flammability limits and oxygen concentration limits for fuel tank flammability assessment is presented for aircraft fuel tanks with or without Flammability Reduced Method(FRM), and the principle of the flammability assessment method is proposed based on Monte Carlo simulation.To fuel tanks without FRM, the fuel tank flammability assessment procedure based on Monte Carlo simulation is presented by using the criterion of flammability limits. The program simulates specific conditions of the aircraft to get fuel tank temperature changes in each flight. Each flight is divided into a number of time units, and the fuel temperature of each time unit is compared with the upper and lower flammability limits to determine whether the fuel tank is flammable in this time unit. Finally, the flammability of fuel tanks without FRM can be obtained by several simulations.To fuel tanks with FRM, the fuel tank flammability assessment procedure based on numerical simulation is presented by using both criterions of flammability limits and oxygen concentration limits. The procedure gets the oxygen concentration in each time unit, compares it with the oxygen concentration limits, and determines the flammability of the fuel tank in the time unit. Finally, the flammability of fuel tanks without FRM can be obtained with consideration of the results determined by the criterion of flammability limits.