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Continental cylinders
I know this is supposed to be about 337s, but 206s have big Continentals in them, and I fly them Part 135 occasionally. We were having lots of problems with cracked cylinders in those IO520s, and our inhouse genius, turned hero, suggested that a hot start with boost pump was pouring cold liquid on a hot head and starting the cylinder cracks that plagued us continually.
We implemented a hot start procedure that reduced our cylinder cracking problem by 2/3. When we know that we will be making a quick turn, we shut the engine off with the ignition switch while advancing the throttle to full forward, then retarding the mixture to cutoff, finishing the procedure just as the prop stops turning. This locks a fuel charge in the combustion chamber, and if a restart is attempted within a few minutes, hitting the starter and letting the engine catch and immediately returning the throttle to idle usually will do the trick. If not, go ahead and boost, but it usually will work.
We replace about 1/3 of the cylinders that we used to with this procedure.
Does this apply to 337s? If you are cracking cylinders, then maybe.
Another fellow applied the same logic to full rich mixture as part of the landing procedure. Same principle - introducing cold fuel to a hot surface starts a small crack around the exhaust valve and leads to eventual cylinder failure. So the suggested procedure is to leave the mixture lean on approach for smooth engine performance, and then on go around, if necessary, reach over and push ALL levers forward simultaneously to accomplish full power. A little different than we learned to fly, and certainly hazardous if it not practiced and well understood, but theoretically a cylinder saver.
Ken
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