Before the first engine start, a procedure must be followed which purges air bubbles from nooks and crannies, and most notably the valve lifters, throughout the engine. This is accomplished by removing the spark plugs to allow easy engine rotation, removing the oil return line at the oil tank and providing a clean container to collect any oil which makes it that far, and turning the prop vigorously until a 40 psi reading shows on the pressure readout in the cockpit. This causes the oil pump to move oil from the tank throughout the engine and back to the now-disconnected tank return line (maybe). The instructions say that this may take 40 - 60 revolutions of the prop. As with all things these days, many Ewe-Tube (they're a bunch of sheep, but that's another story) videos exist showing this process. The best I found is here.
This process can be sped up by capping the oil tank overflow line and pressurizing the oil tank to 10 psi with an air source before turning the prop. It is claimed that this step is optional and simply speeds things up. My friend and ace Light Sport mechanic Bill Snodgrass had done this procedure before and had fabricated a rig to facilitate this. We first tried it without the air pressure and couldn't produce any reading on the oil pressure gage by turning the prop. With the air pressure, however, we quickly saw an oil pressure of 55 psi and declared it done. No oil made it to the catch container but Bill said this is normal in his experience.
After the purge, I did a normal "burp" of the system, which is done before every engine start with a Rotax. This being a dry sump oiling system, oil which leaves the crank shaft, rods and rockers and accumulates in the crank case must be returned to the oil tank. This is done in a novel way: rather than using a pump the way race cars do, blow-by from the piston rings pressurizes the oil, forcing it back to the oil tank. After the engine is run and shut down, oil is left in the crank case, making it impossible to check the oil level in the oil tank. With the engine off and the cap off the oil tank, the prop is rotated in the normal direction until the distinct sound of a flushing toilet is heard, indicating that the oil is now back in the tank and ready to be checked.
Now it's show time. With my ex-fireman friend Chad Rennicke, complete with fireman's hat, manning the fire extinguisher, I inclined my head a few degrees and said a silent prayer that I had hooked everything up right -- all the wiring, gas line fittings, oil line fittings -- then turned the ignition key for the first time. It cranked immediately, oil pressure came up, gages looked good, relief flooded over me, then it quit! Instantly I knew I had forgotten to turn the fuel valve on. This done, it fired back up and ran great. No fire, no smoke, no funny sounds.
Incredibly, after working on this airplane since 2011, I feel for the first time that I'm within sight of the end of the build. I'm ready to fly.
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