What is Control Line?
Control Line or C/L is a method of flying a powered model airplane where the plane is connected to the flyer (pilot) by some sort of line or lines. The lines, along with the control system in the airplane itself, and the handle the flyer is holding, gives the flyer the ability to make the plane climb (gain altitude) or dive (lose altitude). The plane flies in a circle, around the flyer (who stands in the center of the circle), and the plane orbits around the flyer until the engine either runs out of fuel, in the case of a plane with an internal combustion engine, or a timer shuts off the electric power, in the case of a plane with an electric motor.



Diagram image credit: Academy of Model Aeronautics