To solve a problem wherein a collision accident against the ground takes place when a helicopter makes a forced landing due to autorotation in an engine trouble of an airframe, etc. while the helicopter is on the fly, or the military helicopter in a battlefield is targeted by an antiaircraft machine gun, a missile, etc. due to development of military weapons.

This sweepback wing shape half hollow main rotor blade rotary wing of the helicopter has a shape extensively curved over the whole width of the rotary wing as that of a supersonic jet airplane. The sweepback wing shape half hollow main rotor rotary wing is reduced in weight, the inside of the rotary wing is structured and formed half hollow and it has air intakes (ventilating holes) on a front edge part and an upper surface part or a lower surface part of a main rotor blade, high speed rotating air quantity passes the inside of the rotary wing, and a multiple lift is provided together with an air foil (profile).