What is the purpose of a fuel vent in modern aircraft?

• A. Equalize pressure from the outside.
• B. Regulate fuel temperature
• C. Supply extra fuel during high power
• D. Remove water condensate

Answer: (A)

Fuel tanks need to stay at the same pressure as the surrounding air as fuel is used and as the aircraft climbs or descends. A vent lets air and any fuel vapor escape to the atmosphere so the tank doesn’t become over-pressurized when fuel expands with heat or altitude, and it also lets air enter as fuel is drawn off to prevent a vacuum that could negate fuel flow or dent the tank.

So the vent’s job is to equalize pressure between the tank and the outside world, not to regulate temperature, supply extra fuel, or remove water condensate.