a dual function rapid shutdown and ecology system for fuel delivery systems for engines , specially aircraft gas turbine engines , is disclosed . the dual function is accomplished in a single module operated by a single electro - magnetic solenoid valve commanded by the engine electronic control unit . upon actuation of the solenoid valve , a large spring loaded piston strokes to the extreme of its travel creating a cavity having a volume sufficient to accommodate all fuel leftover in the fuel manifold and distribution system at shutdown , thus preventing atmospheric pollution or engine damage upon subsequent operation . simultaneous with actuation of the solenoid valve , fuel pressure differentials cause a small piston to stroke to the extreme of its travel opening fuel passageways and causing all the fuel being delivered to the engine combustion chamber to be bypassed back to pump inlet , thus effectively accomplishing the rapid shutdown function . an alternate embodiment allows for use of the dual function system on engines employing low pressure differentials along the various stages of the fuel control system manifold or where the ecology function is not required .