$15 is only about twice the cost of an OS 'F' plug or the YS equivalent. How long do they last (# of flights on average) in a DZ? It seems a sparkplug would last a lot longer than a glowplug which has a pretty fragile element that has to 'glo' continuously for the duration of the run time where the spark plug is only 'firing' once every other revolution. Very interesting engineering effort on the part of YS. I wish I could buy an engine ignition device for my car that would double the mileage!!!
-Will