Definition
A valve in a multi-tank fuel system that allows fuel from a tank on one side of the aircraft to be routed to an engine on the opposite side. When opened, it connects the left and right fuel supply lines so either engine can draw from either tank, helping balance fuel load between wings or feed a working engine after a pump or tank failure on its own side.
Plain English
A valve that lets fuel from one wing's tank flow across to feed an engine on the other wing.
Context Anchor
Seen in aircraft fuel system diagrams, cockpit fuel controls, and checklist procedures for fuel balancing or abnormal fuel-system operation.
Derivation
Cross-feed' literally means 'feed across.' The name describes exactly what the valve does — it lets fuel cross from one side of the aircraft to feed the other side.
Why Pilots Care
Enables fuel balancing between tanks and provides a backup supply route if one tank or fuel pump fails.
Intuition Check
Do not assume a cross-feed valve pumps fuel from one tank into another. Its main job is to open or close a path so fuel can be supplied across the aircraft fuel system, as that aircraft is designed.
Example Sentence 1
After the right engine lost its fuel pump, the pilot opened the cross-feed valve so the left tank could supply the left engine while the right tank fed across to keep options open.
Example Sentence 2
During an engine-driven fuel pump failure, the cross-feed valve allowed the remaining engine to draw fuel from both tanks.