Don't exactly know if this is the right word to use but when making flying things i like to use a cog to spin the propeller blades and so far its worked fairly good besides the fact that you can't switch the direction of the propeller blades but i see that's already been mentioned quite a bit. The other thing that would make it perfect is if we could set it so the speed of a cog goes up or down in intervals to so it doesn't jerk the helicopter around when i want to land or take off.