Proportional force modification of passive spool for control of secondary nozzle circuits

A system comprising:

• an injector including a scheduling valve assembly and a nozzle in fluid communication with the valve assembly, wherein the scheduling valve assembly is configured for regulation of flow from an inlet of the injector to the nozzle, wherein the injector includes two fluid circuits between the inlet of the injector and two respective outlets of the nozzle for staged flow output from the nozzle, wherein a first one of the two fluid circuits is a primary circuit, and wherein a second one of the two fluid circuits is a secondary circuit;
• and a separate valve connected in fluid communication with the scheduling valve assembly, wherein the separate valve is configured to adjust position of a hydromechanical valve spool of the valve assembly, wherein the valve spool includes a scheduling surface configured to vary flow area through the secondary circuit based on position of the valve spool within the scheduling valve assembly;
• wherein the valve spool is biased to a closed position by one or more biasing members of the scheduling valve assembly, wherein the valve spool is configured to regulate flow from the inlet of the injector to each of the primary and secondary circuits;
• wherein the separate valve is a three-way valve including:
• a first port in fluid communication with the secondary circuit;
• a second port in fluid communication with the inlet of the injector;
• and a third port in fluid communication with the valve spool for selectively adjusting position of the valve spool in the valve assembly based on pressure from the inlet of the injector or pressure from the secondary circuit;
• wherein the first port of the separate valve is connected in fluid communication with a portion of the secondary circuit downstream of the valve spool.