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Optimizing Calculation of Maintenance Revision Times in Maintenance Repair Organizations

Maintenance planning and calculation of maintenance turnaround time require consideration of many influences. This leads to the calculated turnaround time usually not being precise. This paper deals with the time estimation of unscheduled works which may occur during maintenance of an aircraft and which can lead to financial losses or reduced usability of the aircraft for flying missions due to extended stay in a hangar bay. The main assumption is that there exists dependence between unscheduled works and predictors known prior to the maintenance. Two methods were considered to estimate the turnaround time, namely maximum likelihood estimation and Bayesian regression. The study was done in cooperation with Czech Airlines Technics company which provided necessary data from aircraft maintenance. The results indicate that, given the data normally available, only the model based on maximum likelihood estimation managed to reproduce reality when proposed for each aircraft type individually. The model was validated in the Czech Airlines Technics company and implemented into software environment.