The PGA is a pressure compensated, hydraulic governor that uses an air signal to establish the engine speed setting of the governor.
An internal oil pump, relief-valve, and accumulator system controls governor operating pressure. A self-contained sump stores oil and reduces the possibility of contamination from outside sources.
Oil flow to and from the governor power cylinder assembly is controlled by a centrifugal flyweight and pilot-valve assembly. The power cylinder (servomotor) positions the fuel racks, fuel valve or steam valve of the engine or turbine.
A pneumatic signal operates a bellows (direct or reverse) to change the engine speed setting of the governor. Manual speed adjustment may be made with a knob on the governor. An adjustable compensation system provides stability.