What is the reason for venting all aircraft fuel tanks?

Venting all aircraft fuel tanks is primarily necessary to limit the pressure differential between the tank and the atmosphere. Fuel tanks are subject to changes in temperature and altitude, which can cause the fuel inside to expand or contract. Without proper venting, the resulting pressure differences could lead to several issues, including structural damage to the tank or difficulty in drawing fuel into the engine.

When fuel expands due to temperature increases, it creates pressure within the tank. Venting allows this pressure to equalize with the atmospheric pressure, preventing the tank from becoming over-pressurized. Conversely, when the aircraft ascends, the air pressure surrounding the tank decreases, and without proper venting, a vacuum could form inside the tank. This vacuum might complicate the flow of fuel, leading to potential fuel starvation or engine performance issues during flight.

The other options, while they touch on important aspects of fuel management and system design, do not directly address the primary purpose of venting in relation to pressure differentials.