Calculation method of fuel temperature conforming to requirements of airworthiness certification

Based on the requirements of airworthiness certification，the measured fuel temperature change curve of the central wing fuel tank compartment of a certain aircraft under specified working conditions was taken as the input，and the high-order functional expression of the fuel temperature change rule in each stage was obtained by means of MATLAB polynomial piecewise fitting function.The exponential attenuation equation stipulated in the Monte Carlo evaluation model was used to characterize the change law of fuel temperature.The total ambient temperature （TAT） was obtained by the method specified in the evaluation model，and the equilibrium temperature difference and time constant were obtained by the improved genetic algorithm.The equilibrium temperature difference and time constant obtained by the inversion were then input into Monte Carlo evaluation model for calculation，the calculated temperature data and the measured polynomial data were compared.The results showed that both trends were exactly the same，the temperature difference between each moment did not exceed 1.67 K，the mean difference between the calculated value and the measured value of fuel temperature during the entire flight segment was about 0.050 1 K; in the stage with large error value，the value calculated by program was higher than the value measured by flight，which met the relevant requirements of airworthiness standards.The inversion method of time constant and equilibrium temperature difference is scientific and reliable，which can solve the bottleneck problem in airworthiness certification process and can effectively support the smooth development of airworthiness certification of large aircraft.