A system for detecting defects in a combustion duct of a combustion system of a combustion turbine engine while the combustion turbine engine operates, wherein the combustion duct comprises a hot side, which is exposed to combustion gases and, opposing the hot side, a cold side. The heel rest including a mounting base adapted to connect to the exhaust pipe and a heel pad coupled to the mounting base. The logic unit performs logic operations on the output of the column counter, the row counter, and the codeword selector to generate the 2D spreading code of desired order designated by the codeword selector. The inner carriage can be formed in varying shapes such as a sphere, hemisphere, semicircle, tube or a circle.