During manual rotation of the PT rotor some scraping noises have been observed and MFS has been requested to investigate the matter. In order to determine the root cause of the scraping sounds, it was decided to remove the LPT top case in order to perform a detailed inspection.
Once the top case was removed the top case was visually inspected, and the lower half was inspected by borescope. No abnormalities or irregularities have been found. As the interstage seals and turbine casing is designed with honeycomb shrouds, the seal cutter teeth will carve into the honeycombs and create the desired sealing. What has happened is that during transport, or storage, the blades and nozzles have moved very slightly and therefore the cutter teeth are now touching the honeycombs. The sounds observed are perfectly normal, and can be expected on an engine which has been removed from the enclosure and been on transport. Ones the engine is re-installed and started, the parts will all set to their downstream position and the sounds will be gone.
