Traditionally, Initial Provisioning (IP) has been carried out using a Poisson-based approach where inventory quantities are calculated separately for each part based on a Protection Level target, taking into account Fleet Size, Flight Hours (per aircraft), Mean Time Between Unscheduled Removals (MTBUR), Repair Turnaround Time and Quantity per Aircraft.
The D-SIMSPAIR IP function allows to carry out Initial Provisioning calculations based on Protection Level targets individually for each part number (e.g. 98% Protection Level for each ESS1 P/N) or Service Level targets individually for each part number (e.g. 90% Service Level for each ESS3 P/N).
Alternatively, a more sophisticated optimisation-based method based on an aggregate Service Level target (e.g. 95% SL for a group of [for example all ESS1] part numbers) to exploit cost arbitrage opportunities can also be applied. This also takes into account that – despite a target service level to be met, no matter how high or low it is – eventually 100% of demands for spare parts need to be fulfilled. A cost optimisation that would push all the demands fulfilled in time to cheaper and the no-fill instances to expensive part numbers would not be cost-optimal because the cost of making expensive part numbers available from 3rd parties quickly upon a no-fill instance could be overproportionally high. This is achieved through attributing some late cost to each no-fill instance and minimising the aggregate of inventory and late cost.