Significant improvements in propulsion system hardware reliability, life, and safety, with associated reductions in life cycle cost and maintenance turnaround time can be realized by implementing Advanced Condition Monitoring (ACM) methods and technologies. The strategy of ACM systems is to use novel technologies to continuously monitor critical system components during operation to provide in situ, noncontacting measurements of component degradation. When used in conjunction with dedicated electronics and knowledge-based systems, diagnosis of component failure modes and prognosis of remaining useful life can be automatically provided without time-consuming disassembly and manual inspection. Such a system can keep users informed of upcoming maintenance requirements and system availability. The need for scheduled maintenance of monitored components is eliminated while component maintenance, provided well in advance of problems affecting safety or performance, is ensured. Previous papers have provided overviews of ACM systems for turbomachinery and for specific ACM technologies. This paper provides an overview of two advanced optical ACM technologies developed for in situ and between-flight propulsion system monitoring applications.
