Research On Economic Evaluation Of Aircraft Modification Based On Bayesian Theory

With the expansion of the fleet size of airlines,kinds of aircraft modification activities received annually as well as their cost rise up year by year,more than 60%of which are derived from the service announcements released by aircraft and parts manufacturers,meanwhile whose cost will be over hundreds of million.As a result,the economy evaluation of the aircraft modification activities has become increasingly concerned about by airlines.Aiming at the economic evaluation in the environment of lacking data,the paper put forward the methods of test modification in small scales,made full use of prior information,such as service bulletin and expert experience,and converted the parameter estimation problem of modified parts into the parameter estimation problem of life distribution of modified parts.Weibull distribution and exponential distribution of the life of modified parts were taken as the study objects,MCMC Bayesian estimation method and maximum likelihood estimation method were used respectively to construct the model of reliability index estimation,the MATLAB simulation was used to analyze the relationship between the reliability sample size in modification test and the curves of different life distributions in different estimation methods were compared in pairs,and the regularity of the effect between the amount of modified parts and the error of parameter estimation in small-scale test was obtained.Through comparison,it was found that when the life of parts obeyed Weibull distribution and exponential distribution,the estimated value obtained by Bayesian estimation was more accurate,when the sample size of the refit test was small,the exponential life distribution could obtain better estimation value and became more economical.Finally,combining with the theory of engineering economy,the models of the net present value,dynamic payback period and internal yield rate in economical evaluation indexes were established,and the effect on economic evaluation index of the change of different cost parameters in different modification schemes was analyzed through the case calculation.The estimated error analysis of modified parameter of MTBUR provides a newway of thinking of keeping the balance of the lack and economy of modified information for airlines in modified decision,which is of significance in practical engineering and can provide the amount of economic modification samples for small-scale tests of modification activities,so as to achieve quantitative assessment of the aircraft modification.