PURPOSE: To offset the torque generated by rotation of a rotor by arranging accessories such as a vertical tail wing and a power device asymmetrically with respect to the center line of an airframe on the plan view.

CONSTITUTION: A vertical tail wing 13 is installed asymmetrically with respect to the center line 24 of a helicopter l, and the front edge of the vertical tail wing 13 is inclined to the right as the vertical tail wing inclination 14. A rotor 2 is rotated counter-clockwise when viewed from above, and torque 11 is applied to the helicopter l. When the vertical tail wing inclination 14 is set, the air force is applied to it, and the yawing moment 15 by the vertical tail wing inclination 14 is applied around the center of gravity 9 to offset the torque 11. When the helicopter l is flying in a low-speed area, the yawing moment 15 by the vertical tail wing inclination 14 is insufficient, and a tail rotor 12 smaller than a conventional tail rotor 8 is fitted for supplement.