Central-positioned pitch control device for a coaxial helicopter

A central-positioned pitch control device used in a coaxial helicopter, comprising:

• an upper propeller hub;
• a lower propeller hub;
• a first blade mounted on the outside of the upper propeller hub;
• a second blade mounted on the outside of the lower propeller hub;
• and
• a central-positioned pitch control device placed between the upper propeller hub and the lower propeller hub,
• wherein the central-positioned pitch control device used in the coaxial helicopter is placed in a middle part of a center shaft between the upper propeller hub and the lower propeller hub,
• wherein the middle part of the center shaft has a stepped cross arm uplifting along the circumference, and on an upper end of the cross arm outside the center shaft, an upper outer shaft is installed, and on a lower end of the cross arm outside the center shaft, a lower outer shaft is installed, and
• wherein on an upper end of the lower outer shaft, a first conical gear is installed, followed downward by a lower variable pitch ring and a lower swashplate, and the first conical gear is meshed with a lower part of a fan-shaped reversing gear.