Comparison of Variance-to-Mean Ratio Methods for Reparables Inventory Management

In an effort to improve aircraft availability, this research compared the efficiency of ten methods of determining variance-to-mean ratios VTMRs, VMRs, VMs for repairable, spare aircraft parts known as reparables. These methods are base pipeline quantity, Hill-Stevens 220 LRUs, a variation of Hill-Stevens 10 1s, Hill-Stevens 230 LRUs, the Sherbrooke, a variation of Sherbrooke 10 1s, historical data, a new regression function, variance-to-mean ratio equals 1.00 or variance-to-mean ratio equals 1.01. Using VTMRs derived from quarterly organizational intermediate maintenance OIM demands for line-replaceable units LRUs from the D200A Secondary Item Requirement System SIRS databases in aircraft sustainability model scenarios and Excel spreadsheet simulation, this research concluded the VTMRs have an impact on aircraft availability and the cost of inventory.