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. The tricycle
assembly has a
pilot seat and
landing gear as well as controls for operation of the engine, rotors,
tail plane and
landing gear. The directional control of the helicopter is achieved through the
weight shift principle by manipulating the control bar, thereby causing a tilt of the contra-rotating rotors, which cause a corresponding tilt in the aerodynamic thrust of the rotors, propelling the helicopter in the required direction.