With the advent of U.S. military aviation changing from the fixed-cycle inspection concept to the On-Condition Maintenance (OCM) concept, it has become readily apparent to the aircraft maintenance people that their existing inspection methods and diagnostic tools are not adequate to keep pace with the new concept. Some of those components which required removal and disassembly to facilitate inspection should now be inspected on-the-wing to maintain the inspection flow time. Some means of gaining visual access to those components is required. A method has been developed to inspect the gas path of a turbine engine with sufficient accuracy to provide the user with the decisive information on whether to continue the engine in service or remove it for repair. The genesis of using controlled light and vision for engine internal inspection is presented and progress from the early days on the flightline to the future is discussed.

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