What is a key reason for venting all aircraft fuel tanks?

Venting all aircraft fuel tanks is crucial primarily to limit the pressure differential between the tank and the atmosphere. As fuel is consumed during flight, the volume of liquid fuel decreases, which can create a vacuum or negative pressure inside the tank. Without proper venting, this could lead to structural damage or fuel flow issues due to the inability of fuel to refill from the tank’s surroundings.

Furthermore, positive pressure can also build up within the tank due to temperature increases or a change in altitude. If not managed, this pressure could force fuel out of the tank and potentially lead to leaks or failure of the tank. By maintaining a balanced pressure relative to the atmosphere through venting, the fuel system ensures safe and efficient operation of the aircraft.

While reducing weight, monitoring fuel levels, and preventing evaporation are all important considerations in aircraft operations, they do not address the critical aspect of pressure management that proper venting accomplishes.