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RCMC™ Architecture

Current aircraft engine maintenance activities performed by the Air Force must account for both scheduled and unscheduled maintenance needs. These maintenance activities, whether scheduled or unscheduled, are characterized as following an on-condition maintenance (OCM) strategy: the maintenance work is performed to repair only what is broken or has already exceeded its time on wing (TOW) limits.

This OCM strategy, however, suffers from two shortcomings: the strategy does not opportunistically account for maintenance tasks that can be expected to occur before a defined TOW target and neither does it attempt to reduce the consequences of potential part failures as opposed to simply the number of failures. Equally important, OCM does not involve the advanced planning needed to optimize unit aircraft availability over time. This is in keeping with the goal of current engine maintenance approaches which is not to necessarily maximize overall unit aircraft availability, but instead to maximize earned labor hours against those available (measured as 'efficiency'). The assumption is that maximizing efficiency (i.e., utilization) will directly translate into increased aircraft availability. Instead, maximizing efficiency may (and often will) lead to sub-optimized availability and higher maintenance costs.

OCM also involves frequent inspections, part replacements, and rework in an attempt to maintain high standards of system reliability. Frequent maintenance requires that a large inventory of spare engines and engine components be maintained. However, how much of this cost is truly needed to ensure the same level of reliability and availability is not known.

The objective of the Reliability Centered Maintenance Costing (RCMC™) initiative is to provide the methods and tools needed to support the critical knowledge discovery, cost modeling, and maintenance cost projection needed by Reliability Centered Maintenance (RCM) decision makers. Unlike OCM, in which repairs or replacements are driven by policy (e.g., periodic maintenance schedules) and/or the failure to meet specified form, fit, or function specification limits, the RCMC™ methodology considers the effects of possible maintenance actions--including the risk of not performing those maintenance actions--on aggregate level metrics like engine availability, performance, and life cycle costs.

When determining how to cost different maintenance strategy options, decision makers must consider not only the costs that will be incurred today, but also the costs that will be incurred as a consequence of the actions under consideration. In other words, effectively weighing different maintenance strategy options requires both cost accounting and cost projection methods and tools. Cost accounting methods assist in appropriately allocating observed costs based on actual resource consumption. Methods like Activity Based Costing (ABC) provide a useful framework for this purpose. Cost projection involves determining that costs that will be observed and the timeframe in which they will be incurred.

In the first phase of the RCMC™ initiative, KBSI developed an advanced cost modeling toolkit specifically tailored for uncertainty-dominated RCM decision problems. The initiative also developed the methods needed to effectively apply the RCM technology in realistic settings.