Demonstration of A Reliability Centered Maintenance (RCM) Tool to Extend Engine's Time-On-Wing (TOW)

Time-on-wing (TOW) is a measure of the operational reliability of an engine (or aircraft system). The operational reliability falls short of the design reliability due to various constraints imposed on the modules of an engine. This shortcoming is even greater for military engines, because they are subject to more demanding performance and operability cycles. TOW is inversely proportional to operational availability and spare part inventory, hence there is a strong motivation to increase or restore the operational reliability. The two most common causes for the low Time-On-Wing of military engines are Foreign Object Damage (FOD) and module replacement due to life limits. While there is little we can do about FOD, we can reduce the module replacement frequency by applying reliability centered maintenance (RCM) concepts; specifically, the concept of module matching (or module alignment) to extend TOW and reduce the engine rejection (or removal) rate. Module matching is an optimization technique that matches the remaining life of engine modules whenever an engine is in the shop to be built up. A module matching tool has been developed and tested on a fleet of active fighter engines of the Royal Air Force (RAF) of United Kingdom. The results of this field test are presented in this paper. The results also show that the TOW extension and its benefit are significant even in a period as short as 12 months. By doubling (or tripling) the TOW, the RAF can realize a significant cost benefit and increase engine/aircraft availability.