The invention provides a coaxial helicopter and a flexible variable-
pitch rotor
system. The coaxial helicopter comprises a helicopter body, an upper rotor
assembly and a lower rotor
assembly; the overall shape of the helicopter body is drop-shaped, and the outer contour of any cross section of the helicopter body is one of a circle, a long circle or an oval; a first blade of the upper rotor
assembly is tilted upwards and connected with a first blade clamp assembly, the first blade clamp assembly is rotatably installed at one end of a first variable-
pitch journal, and the first variable-
pitch journal is fixed to a first blade hub; and a second blade of the lower rotor assembly tilts downwards and is connected with a second blade clamp assembly, the second blade clamp assembly is rotatably installed at one end of a second variable-pitch journal, and the second variable-pitch journal is fixed to a second blade hub. According to the coaxial helicopter, through the design that the helicopter body is in a water
drop shape, the structure is simple and compact, the first blade deviates upwards, the second blade deviates downwards, the phenomenon that the first blade and the second blade are subjected to a
paddle beating accident when the helicopter flies in a high-speed maneuvering mode is avoided, and the operation stability and safety are high.