Governors for Hydraulic Constant Speed Propellers

The P-8( )-( ) hydraulic propeller governors are regular single acting, base mounted centrifugal governors, suitable for any hydraulic variable pitch propeller with or without feathering capability, installed on single or twin engine aircrafts. They are smaller in size and lighter in weight when compared with other designs on the market.

The governor regulates aircraft engine speed (RPM) by continuously varying the pitch of the propeller to match propeller torque (and hence, engine load) to engine developed torque whenever changes in the flight condition occur.
These governors are single acting using oil pressure either to increase or decrease (counterweighted propellers) pitch. Pitch change in the opposite direction is accomplished by the force of the propeller blade twisting moment and hub internal spring, or by the propeller counterweights, if installed.
The pilot valve plunger is balanced with the flyweights in order to eliminate axial movement of the plunger due to engine vibration parallel to the axis of the plunge. This feature increases the propeller governing stability on engines with lateral vibration characteristics.

The principal parts of each governor are a geartype oil pump with pressure relief valve, flyweights pivoted on a rotating flyweight head, a spring loaded pilot valve positioned by the flyweights and an external control lever that varies the spring load on the pilot valve.
The body, cover and base are made of aluminum. The body contains the necessary ducts for channelling the oil to the propeller pitch changing mechanism and the base is designed to fit a standard AND20010 engine pad.

The sensing element of the governor is a set of pivoted flyweights mounted on a rotating flyweight head and linked mechanically to the engine gears through a hollow drive gear shaft.
The flyweights, actuated by the centrifugal force that is developed by the speed of rotation, position a pilot valve so as to cover or uncover ports in the drive gear shaft and regulate the flow of oil to and from the pitch changing mechanism of the propeller. The centrifugal force generated by the flyweights is opposed by the force of an adjustable speeder spring. The preload generated by the speeder spring determines the engine RPM required to develop sufficient centrifugal force of the flyweights for centering the pilot valve. The necessary oil for operating the propeller's pitch changing mechanism is supplied by a gear type oil pump, pressure limited by a relief valve.

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