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Typically, you can order these exchange kits in advance and then install them while you remove your current nozzles. Exchange kits keep downtime to a minimum.
If parts issues are found during the inspections, don’t ignore them. Replacement of the parts is easy, and the cost of ignoring them can be catastrophic. The maintenance manual describes burn-through on a vane ring, and that burnthrough can reject your set of compressor turbine blades. This past week, I became aware of 3 situations where the fuel nozzles are suspected of causing major damage to the engine.
The maintenance manual also instructs to perform a borescope inspection with each fuel nozzle maintenance event. Once the nozzles are returned to you, or you have your exchange set, you are ready to reinstall them. Use engine oil for the packings on your transfer tubes. DON’T use grease. If a product like DC-4 is used, there is potential that it can “clog” the transfer tube. Make sure to reference your maintenance manual for proper procedures and location of primary and secondary nozzles (as needed). The last step we take before starting the engine is to prime the fuel line to the fuel nozzles. Believe it or not, we have seen starting problems on a PT6 caused by air in the fuel line. We disconnect the fuel line to the #8 (bottom) nozzle and connect a hose. Then motor the engine with the fuel on until you get a solid stream. This also allows you to pull the fuel lever back to ensure it cuts off. Follow the guidance of the starter when doing the motoring runs, as you don’t want to overheat it. You are ready to get back to work when everything is back together and secured. Remember spending a little now can save a lot later.
Robert Craymer has worked on PT6A engine and PT6A powered aircraft for the past three decades, including the last 25+ years at Covington Aircraft. As a licensed A&P mechanic, Robert has held every job in an engine overhaul shop and been an instructor of PT6A Maintenance and Familiarization courses for pilots and mechanics. Robert can be reached at robertc@covingtonaircraft.com or 662-9109899. Visit us at covingtonaircraft.com.
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