Engine Component Retirement-for-Cause: A Nondestructive Evaluation (NDE) and Fracture Mechanics-based Maintenance Concept

Historically, cyclic life limited gas turbine engine components have been retired when they reached an analytically determined life where the first fatigue crack per 1,000 parts could be expected. By definition, 99.9% of these components are being retired prematurely as they have considerable useful life remaining. Retirement-for-cause is a procedure which would allow safe use of the full life capacity of each component. Since gas turbine engine rotor components are prime candidates and are among the most costly engine components, adopting an RFC maintenance philosophy could result in substantial engine systems life cycle cost savings. Two major technical disciplines must be developed and integrated to realize such cost savings: fracture mechanics and nondestructive evaluation. This paper discusses the methodology and development activity required to integrate these disciplines to provide a viable RFC system for use on military gas turbine engines, and illustrates potential benefits of its application.