Abstract: A dual lobe, split ring, variable displacement roller vane pump is provided for supplying an aircraft engine varying amount of fuel. In a preferred application, the pump is used with a gas turbine engine. The pump includes a housing having an inlet and an outlet, a rotor rotatably mounted within the housing and having a plurality of slots, and a plurality of roller vanes operatively mounted within the slots. The pump further includes a pair of port plates mounted on either side of the rotor and two cam segments received around the rotor. The cam segments each have a curvilinear surface for cooperating with the rotor, the port plates, and the roller vanes to define a plurality of pumping chambers. The cam segments are independently movable to create varying volumetric pumping chambers along the curvilinear surface of the cam segments.