Estimation of uncertain unscheduled activities in aircraft maintenance using ER Rule

Uncertainty is inherent in almost any project and complex system, and aircraft maintenance is not an exception. During its execution, unexpected damage, failures and discrepancies may be found, which must be corrected by programming unscheduled tasks. However, due to the stochastic nature of these unforeseen events, it is difficult to plan unscheduled activities and then to estimate the resources required to accomplish them. On the other hand, managing these additional maintenance tasks is critical, as they might affect aircraft´s return time, costs and even the quality of the maintenance service. The aim of this paper is to propose a novel approach to estimate the non-routine rate by using the evidential reasoning rule to analyse historical data of different operational variables related to the usage and maintenance of an airplane. The proposed approach allows estimating more precisely the non-routine rate. The contribution of this work lies mainly in the combination of different types of evidence, to analyse the uncertainty that can create delays and disruption in complex projects.