What is the primary purpose of venting fuel tanks in aircraft?

The primary purpose of venting fuel tanks in aircraft is to equalize pressure. Aircraft fuel tanks must maintain an appropriate pressure level to ensure safe and efficient operation. As fuel is consumed, the volume of the liquid decreases, creating a vacuum or reduced pressure in the tank. Venting allows outside air to enter the tank, which equalizes the pressure and prevents the development of a vacuum that can lead to issues such as fuel starvation or structural damage to the tank.

Proper venting also helps accommodate changes in fuel volume due to temperature fluctuations, as the expansion and contraction of fuel can create pressure variations. Although preventing overfilling, allowing for static discharge, and managing temperature are important considerations in aviation fuel management, they are secondary to the critical role that pressure equalization plays in the safe operation of fuel systems.