Research On Aero-engine Maintenance Decision And Overhaul Cost Estimation

The engine maintenance strategies have great influence not only on on-wing performance and reliability,but also on operating costs of airlines,and the engine shop visit cost estimation is an important tool to evaluate workscope.Accounting for varying environmental and engine operating conditions,the discrete event simulation was used to set up the engine maintenance decision model and shop visit cost estimation model.Firstly,based on the engine's EGTM data and engine removal data,which was driven by hardware damage,the stochastic Wiener process,Weibull distribution,and exponential distribution are used to represent engine performance degradation,hardware damage,and accidental damage respectively,and the severity factor was used to modified the distributions,and based on the competitive failure criteria the engine removal predictive model is established to predict the engine removal time and the drivers.Based on the engine removal model,and the queuing rule of first-in-first-out was adopted to establish the spare engine simulation model.With a 3-year planning period,a spare engine plan for the life cycle of 15 years was developed for the fleet and the maintenance capability MRO's was evaluated as well.The results show that the maximum spare engine rate is 8% in the life cycle of 15 years,and 10 slots can meet the maintenance requirements of the fleet for the MRO.Compared with the current spare engine rate of airlines,it is within a reasonable range.Finally,based on the workscope planning guide of engine V2500 and CFM56,the logical process for determination of module repair levels was created.Taking engine V2500 as an example,an estimation model of engine life cycle overhaul cost was established.The simulation results show that the numbers of times of engine removals were 4 in the life cycle of 15 years with the severity factor of 1.2696,and the hourly maintenance cost is 291.1$/FH.Varying the severity factor,the relationship between severity factor and hourly maintenance cost was generated.Taking 4 times of engine removals as an example,the maintenance cost per flight hour for the first engine removal and mature engine removal were calculated.In the case of severity factor of 1,maintenance costs per flight hour for the first engine removal and mature engine removal are $221.56 and $320.48 respectively.Comparing with the respective reference values,the errors are 3.7% and 7.9% respectively.