In an attempt to increase the time between maintenance actions and to improve performance retention of turboprop engines installed in transport and maritime patrol aircraft, the Canadian Department of National Defence is evaluating an erosion and corrosion-resistant blade coating, for use on compressors. As coatings could appreciably alter engine performance by virtue of their application thickness and surface quality, the National Research Council of Canada was asked to quantify any performance changes that could occur. A project was initiated, utilizing a new Allison T56 turboprop engine, to assess not only the performance changes resulting from the coating, but also those from dismantling and reassembling the compressor, since the compressor must be completely disassembled to apply the coating. This paper describes the project objectives, the experimental installation, and the measured effects of the coating application on compressor performance. Performance variations due to compressor rebuilds on both engine and compressor characteristics are discussed. As the performance changes were small, a rigorous measurement uncertainty analysis is included. The coating application process and the affected overhaul procedures are examined. The results of the pre- and postcoating compressor testing are presented, with a discussion of the impact on engine performance.

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