Effective Measurement of Reliability of Repairable USAF Systems
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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The USAF generally does not know the reliability of its fielded repairable systems. The reported metric, Mean Time Between Failure MTBF, is too lagging to be actionable in the best case, and is not representative of actual system reliability in the worst case. This thesis investigates the statistical techniques for measurement and analysis of the reliability of fielded repairable systems, which are very different than nonrepairables. To frame the investigation, a comparison is made between the generally accepted definitions and metrics and those used across the US Air Force USAF. Reliability can be analyzed in four context areas reliability prediction of nonrepairable and repairable items and reliability measurement of nonrepairable and repairable items. This research is focused on the latter. An algorithmic process for effective measurement of reliability of fielded repairable USAF systems, based on recurrent event analysis, is proposed and demonstrated using a non-parametric approach on USAF maintenance data. The approach provides a new capability that can identify even short term changes in system Rate of Occurrence of Failure ROCOF, which can identify daily or hourly trends across the fleet subsystems. This new approach is compared to USAF calculations of MTBF over the same period.