A simulation analysis of the vari-metric repairable inventory optimization procedure for the U.S. Coast Guard

This paper documents a simulation study undertaken to gain insights into the vari-metric multi-echelon repairable inventory optimization method. The method was analyzed in the context of the Coast Guard´s fleet of fixed and rotary wing aircraft, for which operational availability is the key performance metric. Failure rates of parts in this system exhibit variance-to-mean ratios higher than one, and we outline a procedure for generating a failure arrival process described by a negative binomial distribution. Previous studies of the vari-metric model examined a single repairable part; in this study we analyzed a system comprised of three repairable parts. This allowed us to gain insights into how the vari-metric procedure selects part stock levels to attain a desired level of system availability. Further analysis of the simulation model allowed us to examine the efficient frontier for this multi-criteria problem (maximizing spare part availability rates while minimizing the cost of part inventories)