Modern aircraft store fuel primarily in their wings, a design choice driven by performance and safety considerations.
The Primary Location for Aircraft Fuel
Most commercial and many private aircraft primarily store fuel within their wings. This design applies to large airliners like the Boeing 737 and Airbus A320. Jet fuel, a type of aviation turbine fuel, is typically used. While wings are the predominant storage area, some long-range aircraft may use additional tanks in the fuselage or tail for extended flights.
Why Aircraft Fuel is Stored in Wings
Storing fuel in the wings offers engineering and aerodynamic advantages. The fuel’s weight helps manage the aircraft’s balance, keeping the center of gravity stable during flight. This distribution reduces stress on the fuselage and contributes to a more balanced aircraft.
Fuel in the wings also enhances structural efficiency, known as “wing-bending relief.” As wings generate lift, they experience upward bending forces. The fuel’s downward weight counteracts these forces, reducing the bending moment and allowing for a lighter wing design. Wings provide significant internal volume for efficient fuel storage. Locating fuel in the wings also places it further from the passenger cabin, separating flammable material from occupants.
How Wings Serve as Integrated Fuel Tanks
Modern large aircraft employ a “wet wing” design, where the wing’s internal structure forms the fuel tank itself. This means there are no separate bladders or containers; instead, wing spars and ribs define sealed compartments to hold fuel. Specialized sealants are applied to every rivet, bolt, and joint within these compartments to prevent leaks, requiring careful attention during manufacturing and maintenance.
To manage fuel movement during flight maneuvers, the wing tanks incorporate baffles. These are typically ribs with cutouts that allow fuel to flow through but at a controlled rate, preventing excessive sloshing. Dampening fuel sloshing is important for maintaining the aircraft’s center of gravity and overall flight stability. Access panels are built into the wing design, allowing maintenance personnel to inspect and service the fuel compartments.
Managing Fuel and Ensuring Safety
Aircraft fuel systems are complex, designed for precise management and high safety standards. Fuel is delivered from the wing tanks to the engines by a series of pumps and fuel lines. These systems include selector valves, allowing pilots to manage fuel flow from different tanks, and shut-off valves for emergency situations like engine fires. Filters are also integrated into the system to ensure the fuel reaching the engines is clean and free of contaminants.
Sophisticated sensors and gauges continuously monitor fuel levels, temperature, and pressure within the tanks, providing critical information to the flight crew. Fuel tanks are also equipped with venting systems to prevent pressure imbalances; these vents allow air to enter as fuel is consumed and to equalize pressure changes due to altitude or temperature.
For enhanced safety, many modern aircraft incorporate inerting systems. These systems, often called Onboard Inert Gas Generation Systems (OBIGGS), inject nitrogen-enriched air into the empty space above the fuel (the ullage) to reduce oxygen concentration and minimize the risk of a fuel vapor ignition. During refueling, strict protocols are followed, including the use of bonding cables to prevent static electricity and the presence of fire safety equipment.