Abstract: The present invention relates to a lightweight helicopter with features of coaxial, contra-rotating rotors and weight shift control. It has a rotary wing unit attached to a tricycle assembly through a hang bolt. The rotary wing unit has an engine mounted below a keel post, which drives a pair of contra-rotating coaxial rotors through a primary gearbox and a secondary gear box. The keel post is attached to a triangular control frame, the base of which forms the control bar. The keel post also supports a fuel tank connected to the engine and a tail plane having one or more articulated vertical flaps actuated by cables. The secondary gearbox is provided with a free-wheeling clutch, a pinion gear and bevel gears for transmitting the rotary movement of the engine to the counter rotating coaxial vertical shafts each carrying two rotor blades of airfoil cross section fixed by pitch bearing on teetering plates and teetering hinges to form horizontal rotors.