What is crossfeed in the fuel system, and when is crossfeed permitted?

• A. Crossfeed transfers fuel between wing tanks; it is used to balance CG or supply an engine if a pump fails, within prescribed limits.
• B. Crossfeed transfers fuel from the center tank to the wings automatically.
• C. Crossfeed is only used when the aircraft is in parking.
• D. Crossfeed is used exclusively for fuel cooling.

Answer: (B)

Crossfeed is a controlled mechanism that lets fuel be moved between tanks to keep an engine fed and to balance the aircraft’s fuel distribution. In many airplanes, this includes the ability to draw from the center tank and feed the wing tanks, and it can be automatic under the aircraft’s fuel-management system. This automatic center-tank-to-wing transfer helps ensure continuous engine supply if a pump or feed line is inoperative, and it is allowed only within prescribed limits and during the appropriate phases of flight. The other descriptions describe transfers that are incomplete (wing-to-wing only), or situational (only on the ground), or unrelated (cooling), and thus don’t capture how crossfeed is typically used.