Propeller and Governor Operation
This animation shows the operation of the flyweights, pilot valve, lift rod, and piston inside the propeller hub. The cockpit control will put the flyweights into an underspeed or overspeed condition, moving the pilot valve and either returning oil from the propeller or sending pressure oil to it.

Because of the change in propeller pitch, engine speed will then change, returning the flyweights to their onspeed position. The flyweights and governor oil pump are geared to the engine and are spinning during operation, a movement left out of the animation for clarity.