How many ports are used during gravity refueling?

During gravity refueling, typically three ports are utilized. These ports are designed to facilitate the process of transferring fuel from a storage tank into the aircraft's fuel system without the need for pumps. The arrangement generally includes one or more ports for fuel intake, which allows the fuel to flow into the aircraft, as well as an additional vent port. The vent is crucial because it prevents pressure buildup within the fuel tanks during the refueling process, ensuring safe operation and efficient fuel movement.

The necessity of using multiple ports, specifically three, stems from the need to manage fuel flow effectively and to maintain safety. The design allows for optimal refueling rates and helps to minimize the risk of spillage or over-pressurization. This coordinated use of ports is integral to gravity refueling systems, which rely purely on the force of gravity to move the fuel without any mechanical assistance.