螺旋桨调速器是通过螺旋桨轮毂上的螺距改变机构，通过增加或减少螺旋桨的螺距来调节发动机或螺旋桨转速的装置。

APropeller governor is a device that adjusts the speed of the engine or propeller by increasing or decreasing the clearance of the propeller through the clearance changing mechanism on the propeller hub.

BPropeller governor is the device that regulates the rpm of the engine or propeller by increasing or decreasing the propeller pitch, through a pitch change mechanism in the propeller hub.

CPropeller governor is through the propeller hub of the propeller pitch changing machine, adjusts the speed of the propeller or engine by increasing or decreasing the propeller gap.