Underwing Fueling
Underwing fueling, also known as single-point fueling or pressure fueling, is a method where fuel is pumped into the aircraft's fuel tanks through a valve located under the wing. This system is prevalent in larger aircraft and allows for rapid refueling under pressure.
Here's a more detailed look at its history and evolution:
Early Experiments and Development
1920s: Some of the earliest aerial refueling experiments involved two slow-flying aircraft flying in formation, with one aircraft providing fuel to the other via a hose.
1923: The first mid-air refueling occurred between two DH-4B biplanes of the U.S. Army Air Service, demonstrating the potential of this method.
1930s: As jet engines were introduced, the need for specialized fuel arose, and the first true jet fuel, Jet A, was developed.
1950s: The development of pressure fueling systems for larger aircraft like the de Havilland Comet and Sud Aviation Caravelle marked a significant step forward.
Modern Application and Refinements
Single-Point Fueling: Underwing fueling is typically referred to as single-point fueling because only one attachment point (or sometimes multiple points, with any point capable of fueling all tanks) is used to refuel the entire aircraft.
High Pressure: Fuel is pumped in at high pressure (typically 40–60 psi for commercial and military aircraft) to speed up the fueling process.
Automated Systems: Automated systems and control panels allow for precise fuel level management and prevent overfilling.
Ventilation: Air displaced in the tanks during refueling is usually vented overboard through a single vent on the aircraft.
Benefits of Underwing Fueling
Rapid Turnaround: The high-pressure system and automated processes allow for quick refueling, minimizing ground time.
Safety: Underwing fueling minimizes the risk of fuel spills and ensures accurate fuel delivery.
Efficiency: The streamlined process and ability to refuel multiple tanks simultaneously make it an efficient method for large aircraft.
