The fuel nozzle is one of the most crucial parts of any aircraft fuel system. Regular inspection and maintenance of the fuel nozzle is an integral part of aircraft engine maintenance and overhaul, which should be performed only by trained, qualified individuals. Be sure to refer to the manufacturer’s maintenance manual to determine what type of inspection and maintenance is necessary for your aircraft.
Simplex vs. Duplex Nozzles
There are two types of fuel nozzles in the aircraft fuel system of PT6 engines. Simplex fuel nozzles have a primary and secondary nozzle with a single orifice. Duplex fuel nozzles have two passages and two concentric points in the tip that spray fuel. The difference between the two nozzles is that simplex nozzles are sometimes set as all primary or in a set ratio depending on the type of engine, while duplex nozzles are identical with the primary and secondary within each nozzle.
Removal of Fuel Nozzles
Follow the directions in the maintenance manual when removing the nozzles for inspection during aircraft fuel system maintenance. Experts recommend marking the position of each nozzle with the location in the engine to make troubleshooting easier. Use a permanent marker or place the nozzle in a small plastic bag and mark the location on the bag. In addition, only remove the fuel nozzles, not the igniters or glow plugs—otherwise the combustion chamber outer liner may go out of alignment. The nozzles should be sent to a qualified repair station for inspection as spray checking takes skill that many people do not have. Pack the nozzles to prevent shipping damage and be sure they are clean; residual fuel could cause problems during shipping.
After cleaning the nozzles, tests during aircraft fuel system maintenance program include a leak test and spray check. The leak check locates leaks between the nozzle tip and assembly and may also detect cracks in the weld of the nozzle. The spray check looks for several defects in the nozzle spray, including streakiness, spitting, drooling, and void, all of which can affect the performance of the aircraft fuel system. Once these tests have been performed, the nozzles are reinstalled and an additional leak check is performed.
Performing regular maintenance on your aircraft fuel system, including fuel nozzle maintenance, extends the life of your engine and allows for better performance. For more information about the fuel nozzle maintenance Covington Aircraft provides, give us a call at 918-756-8320. You can also follow us on LinkedIn and Twitter!