Coaxial twin-rotor type helicopter

A coaxial twin-rotor type helicopter in which an upper rotor and a lower rotor disposed on the same axis are rotated in opposite directions, said helicopter comprising:

• an airframe, a vertical shaft that rotatably supports the rotors, and a control mechanism that, with respect to a gravitational force direction, can tilt the vertical shaft backward and forward and to either side to thereby tilt tips of blades of the rotors, and a drive transmission mechanism to rotate the twin rotors,
• said control mechanism comprising a first swing member that depends from a lower end portion of the vertical shaft so as to be freely swingable backward and forward or to either side about a swing center point on a center axis of the vertical shaft, a second swing member that depends from the first swing member so as to be freely swingable about the swing center point in a direction at right-angles to the swinging direction of the first swing member, and a control stick that can swing the vertical shaft backward and forward and to either side, and
• said drive transmission mechanism comprising first and second planet gear mechanisms, crown gears attached so that centers of rotation thereof are at right-angles with respect to internal gears of the first and second planet gear mechanisms, and a drive pinion in meshed engagement with both crown gears;
• wherein the first and second planet gear mechanisms are provided with a common carrier, a sun gear in the first planet gear mechanism is connected to rotate integrally with the upper rotor shaft, and a sun gear in the second planet gear mechanism is connected to rotate integrally with the lower rotor shaft.