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stuart
Mar 23, 2023
In Hirth Engine Maintenance
NOTE: I submitted this report to Fusioncopter Poland. This is a Hirth manufacturing defect, NOT FC's fault. If you notice weeping of burnt oil at the exhaust port, best to check and if necessary weld around the joint on the outside. Aircraft: Fusioncopter JK-2 Nano Serial no: FCG014 Engine: Hirth F23 Serial no:MO-01000570 TIS: 15 hours History: At about 5 hours TIS some exhaust weeping was noted around the LH exhaust port. It was assumed to be leaking at the flange gasket, so the exhaust flange was retorqued. The weeping continued, but as it was slight I continued operation intending to replace the gasket at next major service. During the last flight I noticed a change in engine sound with a slight reduction in rpm. On landing the engine sound immediately changed to unmuffled. On inspection the LH exhaust pipe had disconnected at the exhaust port flange. Analysis: The exhaust spigot had pulled out of the flange. The flange/spigot is assembled with the spigot inserted full depth in the flange, swaged(?) and welded around the spigot end. On close examination it appears only 1/3 to 1/2 of the weld fused with the spigot end. The muffler security was inspected prior to every flight with no evidence of excessive movement wrt the engine. The conclusion is the problem was due to inadequate welding spigot to flange. Corrective action: The flange and spigot were cleaned and dressed and assembled with the spigot reinserted full depth. The spigot was welded to the flange on the outside around the circumference. Not as tidy as the internal weld, but more substantial. Ground run- no leaks. Good to go!
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stuart
Dec 12, 2022
In Hirth F23 Engine
I have noticed with my Nano that the motor tends to '4 stroke' at intermediate power settings, indicating the mixture is too rich. I was tending to avoid those settings on descent/landing just in case... The plugs looked fine, but the exhaust was throwing a bit of black stuff onto the rudder. I decided to have a look at the carb settings. The jet needle was set at the 3rd slot down, whereas the Hirth manual specifies first clip position. That made sense- I suspect the Fusioncopter guys had purposely set the mixture on the rich side while the motor was bedding in. I reset to the first (top) slot, did a ground run then a longer flight to check operation, temps and fuel burn. The motor runs sweet across the throttle range- EGTs and CHTs well within the green, plugs light tan. Fuel burn over a 1 hour cruise at 5000rpm 75km/hr was 15 litres. I'm happy with that.
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stuart
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