What precaution must be observed if a gravity feed fuel system is permitted to supply fuel to an engine from more than one tank at a time?

When a gravity feed fuel system is supplying fuel from more than one tank simultaneously, it is essential that the tank airspaces be interconnected. This precaution ensures that any changes in atmospheric pressure or fuel level in one tank can equalize with the other tanks, preventing the occurrence of a vacuum or pressure buildup. Without interconnection, one tank could inadvertently siphon fuel from another, leading to inconsistencies in fuel availability and potentially resulting in an engine performance issue.

Interconnecting the airspaces helps promote stable fuel flow and allows for the equal distribution of pressure, which is crucial when drawing fuel from multiple tanks. Proper tank management in a gravity feed system enhances safety and operational efficiency by reducing the risk of fuel starvation or imbalances during engine operation.