25 also reduced influence that the flight airspeed poses between the rotor sets 20 to reduce the airspeed between and noise of the rotor sets 20 more importantly the windshields 25 further lower risks of stalling of the rotor sets resulted by downwind when the helicopter is in a high speed flight as shown in fig6 in the present invention a parachute 70 may be further installed to an upper part of the front region 11 when power loss occurs in the rotor sets a pilot may activate the parachute 70 and utilize the parachute 70 to achieve an effect of a slow landing thereby safely landing both the passenger and the helicopter since the distance between the pair of front rotor sets 30 is greater than that between the pair of rear rotor sets 40 instead of being influenced by the pair of front rotor sets 30 to undesirably affect operations of the parachute 70 the parachute 70 is ensured to open up reliably referring to fig7 and 8 in the present invention a weight proportion of each propeller 24 in the rotor sets 20 may be independently adjusted in the embodiment each propeller 24 includes a body 241 an adjustment screw 242 a weight block 243 an elastic element 244 and a cladding layer 245 the adjustment screw 242 is disposed at an interior of the body.