CODE Supply from FCU Oil to reduction gearbox Propeller servo oil Py To sump Counterweights Speeder spring cup Reset lever Py bleed to atmosphere Air bleed orifice Py seal Pivot Figure 7-53.  Nf overspeed governor.  the piston opposite this high-pressure oil returns to the intake  side of the governor pump and is used over again. Engine oil  at engine supply pressure does not enter the propeller directly  but is supplied only to the governor. During constant-speed  operations, the double-acting governor mechanism sends oil  to one side or the other of the piston as needed to keep the  speed at a specified setting. the propeller governor oil line to auxiliary oil. The oil flows  through the engine transfer rings, through the propeller shaft  governor oil passage, through the distributor valve port,  between lands, and finally to the inboard piston end by way  of the valve inboard outlet. The distributor valve does not shift during the feathering  operation. It merely provides an oil passageway to the inboard  piston end for auxiliary oil and the outboard piston end for  engine oil. The same conditions described for underspeed  operation exist in the distributor valve, except that oil at  auxiliary pressure replaces drain oil at the inboard end of  the land and between lands. The distributor-valve spring is  backed up by engine oil pressure, which means that at all  times the pressure differential required to move the piston is  identical with that applied to the distributor valve. The propeller piston moves outboard under the auxiliary oil  pressure at a speed proportional to the rate the oil is supplied.  This piston motion is transmitted through the piston rollers  operating in the oppositely inclined cam tracks of the fixed  cam and the rotating cam and is converted by the bevel gears  into the blade-twisting moment. Only during feathering or  unfeathering is the low mechanical advantage portion of the  A typical hydromatic propeller feathering installation is  shown in  Figure 7-57 . When the feathering push-button  switch is depressed, the low current circuit is established  from the battery through the push-button holding coil and  from the battery through the solenoid relay. As long as the  circuit remains closed, the holding coil keeps the push button  in the depressed position. Closing the solenoid establishes  the high current circuit from the battery to the feathering  motor pump unit. The feathering pump picks up engine oil  from the oil supply tank, boosts its pressure, if necessary,  to the relief valve setting of the pump, and supplies it to the  governor high-pressure transfer valve connection. Auxiliary  oil entering the high-pressure transfer valve connection shifts  the governor transfer valve, which hydraulically disconnects  the governor from the propeller and at the same time opens  Feathering Operation 7-38