Ecology fuel return systems

A shut-off valve comprising:

• a tank having an inlet and an outlet, and a flow path in a positive G direction defined between the tank inlet and the tank outlet;
• a float configured to occlude the tank outlet at a first fluid level and 1 G and unocclude the tank outlet at a second fluid level and 1 G;
• and
• a negative G control component operatively connected to the float to limit fluid communication between the tank outlet and an ejector pump during negative G events, wherein the negative G control component is a check valve in fluid communication with the float, wherein the check valve is configured to block fluid flow from the tank outlet to an ejector pump during negative G events, wherein the check valve includes a valve inlet and a poppet configured to translate between a first position and a second position along a valve axis, wherein the poppet is free of any biasing members between the valve inlet and the ejector pump wherein in the first position at 1 G or greater the poppet is in an unoccluded position, and wherein in the second position a mass force of the poppet is less than a pre-determined negative G event force such that the poppet is in an occluded position to block fluid flow to the ejector pump while under the pre-determined negative G event force.