Research On Replacement Policy Of Civil Aircraft Structure In Uncertain Environment

Civil aircraft may result in some spare parts failed as it working in a special environment with high altitude,temperature,pressure,and high-speed.In the references of classical replacement policy,the life of spare part was usually assumed as random variable.While in the field of civil aviation maintenance,we can only gain the belief degree of life for the spare part by means of experts.However,the probability theory may not explain the subjective uncertainty of experts,which makes a difference between the research and the actual situation,and then cause unreliable conclusions.The uncertain theory as an effective tool in dealing with the subjective belief provides us an important method to solve this kind of problems.This paper is to research the maintain and replacement problems with new spare parts based on the uncertainty theory:1.Consider the periodic（N,T）preventive maintenance block replacement policy for aircraft under corrosion conditions.Taking the corrosion tolerance of the structural as a constraint condition,and then build an objective function with minimum cost.Finding the optimal number of preventive maintenance N*,cycles T*,and the sensitivity analysis of the parameters by assuming the life of structural obey the uncertainty distribution.2.Block replacement policy with failed aircraft structural replaced in stages.Assuming that the life of the structural is an uncertain variable,and building（T₀,T）block replacement model where the failure is replaced before T₀,and then replacement until T.Finally,the condition for satisfying the optimal replacement time is given.The sensitivity analysis of the model parameters shows that the optimal replacement period is shortened with the increasing of the downtime cost,while is prolonged with the increasing of the replacement cost,and the distribution parameter of the life affects the change of the optimal solution significantly.