Couldn't resist having a go at this one. Most model aircraft engines are designated 2 cycle. Briefly, (2) cycle signifys that the fuel/air mixture is ignited EVERYTIME the piston comes to the top of the cylinder. However, what ignites the fuel/air mixture when the piston gets to the top of the cylinder is the, "glow plug". A conventional 2 cycle engine would use a, "spark plug". The glo plug retains enough heat from the previous ignition to ignite the fresh fuel/air (cylinder) charge when the piston comes to the top of the cylinder; the properties of compression make the fuel/air mixture much more volatile (explosive). The fuel/ air is ignited and the, "glow plug", retains enough heat to, do-it-again, the next time the piston comes to the top of the cylinder. The, glo-starter that is employed is just a battery connected across the cold glo-plug. Once ignition takes place the glo-starter can be removed and the ignition cycle repeats as described above, eh?