Research for Reliability

This study reviews three problem areas of aircraft engine maintenance in the Navy: the setting of maximum operating times, the performance of overhauls for cause instead of repairs, and the site of engine repair. All of the problem areas affect in some way the number of engine overhauls performed annually. The study assesses the effectiveness of engine overhaul from a safety and reliability standpoint by analyzing Navy data on engine-related aircraft mishaps and engine removals. The analysis revealed that within the current range of operations engines wear in but under current policies of continued repair/replacement and relatively short times between overhauls, engines as a system do not wear out. Consequently, policies which would decrease the number of overhauls performed annually and increase the time between overhauls appear to be reasonable from a reliability and safety standpoint. Using a model of the engine repair and overhaul pipeline, the study finds that three new policies, two of which would increase the time between overhauls, result in lower annual maintenance costs and improved spare engine availability.