Aircraft Fuel Tank Flammability Exposure Evaluation Research

Aircraft fuel tank explosion is a serious threat to aviation safety. Since 1959, the world has a total of 18 tank explosion accidents, occurred an average of every three years, and caused a total of 542 people were killed and major economic losses.In order to prevent fuel tank explosions, ensure the fuel tank safety of transport category airplanes, aircraft fuel tank system safety evaluation must be conducted to determine if the aircraft type design and change meet the requirements of FAR / CCAR 25.901 and 25.981(a) and(d). To avoid aircraft fuel tank system ignition source, maintenance and inspection procedures must be developed for aircraft fuel tank system design features that may result in an ignition source. Aircraft fuel tank flammability exposure must be limited to a safe level. FAR / CCAR 25.981(b) provides that: no fuel tank Fleet Average Flammability Exposure on an airplane may exceed three percent of the Flammability Exposure Evaluation Time, or that of a fuel tank within the wing of the airplane model being evaluated, whichever is greater.In this paper,first expiain the evolution history of FAR/CCAR25.981 and its inherent requirements; Research the aircraft fuel tank ignition sources and flammability reduction compliance methods, including the failure modes of the fuel tank system, qualitative and quantitative evaluation of ignition source. Research fuel tank inerting system, and developed a mathematical model for fuel tank ullage space;Based on the fuel tank flammability evaluation model, conducted a detailed analysis and further study on the aircraft fuel tank flammability exposure evaluation method and its application; Research the principles, processes and procedures of fuel tank flammability exposure evaluation method. Deduced the relationship between fuel tank thermal data(Equilibrium DeltaTemp and Exponential Time Constants), and the calculation method using time constants to obtain fuel temerature. Finally, calculation and verification of the fuel tank flammability exposure with an example.