Usually a 3 channel means an extra channel for throttle control ,therefore ,there is a carb on the engine that has to be controlled
through the 3 rd channel!
2 channel planes are usually fixed rev engines with out a carb much like a Cox engine that is revved up by a needle leaning
the fuel flow!
3 channel you want full throttle for ground run & climb out ,after you get the plane up an in level flight ,you dont need too much
throttle ,it can also need more throttle depending on what the plane needs if it is losing altitude ,then you may need to apply
more throttle ,or even if you want to fly faster you would apply more throttle!...