Mercedes Mullins
The placement of fuel tanks in jet airplanes is a crucial aspect of aircraft design, and there are several reasons why they are commonly located in the wings rather than the fuselage. Firstly, wing fuel tanks improve the structural efficiency of the aircraft by counter-balancing the lift generated by the wings and the weight of the fuselage. This reduces the bending moment, allowing for a reduction in the size and weight of wing spars. Additionally, wing fuel tanks simplify the fuel supply system by minimizing complexity and enhancing passenger safety by isolating them from fire and fume hazards associated with jet fuel. Furthermore, the oscillations and vibrations of the wings during flight can cause fuel to slosh around, which is prevented by spars built between sections of the wing. These spars also enable fuel to pass through at a controlled rate. While most jet airplanes utilize wing fuel tanks, some aircraft, such as the Boeing 747, also have the option of installing additional fuel tanks in the fuselage or the aft cargo hold.
| Characteristics | Values |
|---|---|
| Location of fuel tanks in jet airplanes | The most common location for fuel tanks in jet airplanes is the wings. |
| In some cases, additional fuel storage may be installed in the aft cargo hold or the empange. | |
| Some older aircraft designs featured fuel tanks in the fuselage, typically between the engine firewall and cockpit. | |
| In modern multi-engine passenger or cargo aircraft, multiple fuel tanks may be located in both the wings and the fuselage. | |
| Fighter jets typically have inner tanks located close to the fuselage and outer tanks near the wingtips. | |
| Reasons for wing-based fuel tanks | Wing fuel tanks improve structural efficiency by counter-balancing the wing's lift and the fuselage's weight, reducing aircraft fuel system complexity, and improving passenger safety by isolating passengers from fire and fume hazards. |
| Wing tanks also reduce the size and weight of wing spars, minimize fuel supply system complexity, and help maintain the structural integrity of the wings. | |
| Types of fuel tanks | Internal tanks include integral tanks, rigid removable fuel tanks, and bladder tanks. External tanks include conformal fuel tanks and drop tanks. |
| Integral tanks are created from a structural perspective first and as a fuel tank second. The skin of the wing is connected to its internal structure, and the joints are sealed to prevent fuel leakage. | |
| Rigid removable fuel tanks are typically made of aluminum alloy or stainless steel and are held in place with quilted straps. | |
| Bladder tanks are similar to rigid tanks but do not require as large an opening in the aircraft skin. | |
| Drop tanks are auxiliary fuel tanks externally carried by airplanes, usually used first before shifting to internal tanks. |
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What You'll Learn
- Fuel tanks are commonly located in the wings, not the fuselage, for safety and
- Jet fuel tanks are often integral tanks, built into the aircraft's structure
- The most basic fuel system is a single, gravity-fed tank with a fuel line to the engine
- Multi-engine jets have multiple fuel tanks, often in the wings and fuselage
- Fuel tanks must be regularly inspected and maintained, with severe safety procedures to be followed
Fuel tanks are commonly located in the wings, not the fuselage, for safety and structural reasons
Fuel tanks are typically located in the wings of jet airplanes, rather than in the fuselage, for several safety and structural reasons.
Firstly, wing fuel tanks improve the structural efficiency of the aircraft by counterbalancing the wing's lift and the fuselage's weight. This reduces the size and weight of wing spars, which are structural components that provide support and stability to the wings. By placing the fuel tanks in the wings, the bending moment from lift is "cancelled out", reducing the overall structural load on the wings. This, in turn, helps to maintain the structural integrity of the aircraft, prolonging its lifespan.
Secondly, wing fuel tanks offer safety benefits by isolating passengers from fire and fume hazards associated with jet fuel. In the event of a fuel ignition, having the tanks in the wings reduces the risk of catastrophic damage to the fuselage and improves the chances of a successful emergency landing. Additionally, the oscillations and vibrations of the wings during flight can cause fuel to slosh around. Wing tanks have baffles, such as wing ribs, that help to prevent this and minimise the complexity of the fuel tank designs, pumps, and plumbing.
Furthermore, from a space-saving perspective, locating fuel tanks in the wings is more efficient. If fuel were stored exclusively in the fuselage, it would consume a significant amount of storage space, particularly in large commercial aircraft. By utilising the cavities within the wings, designers can save weight and optimise space utilisation.
While most jet airplanes have fuel tanks in their wings, it is worth noting that some aircraft, such as the Boeing 747, also have additional fuselage tanks located between the wings under the floor of the passenger cabin.
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Jet fuel tanks are often integral tanks, built into the aircraft's structure
Integral tanks are commonly located in the wings of the aircraft, rather than the main body or fuselage. This is due to several intentional structural and safety considerations. Firstly, locating the fuel tanks in the wings improves the overall structural efficiency of the aircraft by counter-balancing the wing's lift and the fuselage's weight. This reduces the size and weight of wing spars, as the fuel acts to "cancel" some of the bending moments from lift.
Wing fuel tanks also improve passenger safety by locating the fuel away from the passenger compartment. In addition, the use of wing tanks simplifies the aircraft's fuel supply system by minimising complexity in the tank design and the associated pumps and plumbing.
The design of integral tanks can vary depending on the wing design. For example, the Boeing 747 has both inner tanks, located close to the fuselage, and outer tanks, located near the wingtips. The inner tanks also serve as ballistic protection for the aircraft.
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The most basic fuel system is a single, gravity-fed tank with a fuel line to the engine
The most basic aircraft fuel system is a single, gravity-fed tank with a fuel line to the engine. This type of system is commonly found in high-wing aircraft, where the fuel tank is positioned above the engine. In this configuration, gravity is used to deliver the fuel to the engine, eliminating the need for pumps.
A gravity feed system is simple and reliable, with a basic shut-off valve mechanism. The tank is vented to maintain atmospheric pressure as the fuel level decreases, and multiple tanks can be vented to each other to ensure equal pressure when feeding the engine from both tanks. This type of system is often found in small, single-engine aircraft, where the simplicity and reliability of the gravity feed are advantageous.
The fuel tank in a gravity feed system is typically located in the wing, above the engine. This design improves the structural efficiency of the wing by counterbalancing the lift and weight of the aircraft. It also simplifies the fuel supply system and enhances passenger safety by locating the fuel away from the passenger compartment.
However, one downside of the gravity feed system is the challenge of refuelling due to the high tank placement. Additionally, this system is not suitable for low- and mid-wing aircraft where the fuel tank cannot be positioned above the engine. In such cases, a pump feed system is necessary to deliver the fuel to the engine.
Overall, the single, gravity-fed tank with a fuel line to the engine is a simple and effective solution for high-wing aircraft, offering advantages in terms of structural efficiency, fuel supply, and passenger safety.
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Multi-engine jets have multiple fuel tanks, often in the wings and fuselage
The wing structure is integral to the design of the fuel tanks, which are often called integral tanks. The skin of the wing is connected to its internal structure, and the joints are sealed to prevent fuel leaks. The wings are watertight and designed to hold aviation fuel, with spars built between sections to prevent the fuel from sloshing around. These spars have holes that allow fuel to pass through slowly.
The placement of fuel tanks in the wings has several benefits. Firstly, it improves the structural efficiency of the wings by counterbalancing the lift and the weight of the fuselage. This reduces the size and weight of wing spars and minimises the complexity of fuel tank designs. Additionally, it improves passenger safety by isolating them from fire and fume hazards associated with jet fuel.
The outer tanks, located near the wingtips, are typically filled first and emptied last to minimise the stresses at the wing root and counteract the load due to lift. The distribution of fuel among the tanks is automatically regulated by an onboard computer, and pilots can make manual adjustments if needed.
Overall, the design of fuel tanks in multi-engine jets, often incorporating both wing and fuselage tanks, is a well-thought-out combination of structural, safety, and operational considerations.
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Fuel tanks must be regularly inspected and maintained, with severe safety procedures to be followed
Fuel tanks in jet airplanes are commonly located in the wings instead of the main body or fuselage of the aircraft. This design improves the overall structural efficiency of the aircraft by counter-balancing the wing's lift and the fuselage's weight, reducing aircraft fuel system complexity, and improving passenger safety by locating fuel away from the passenger cabin.
Given the dangers of working in such confined spaces, fuel tanks must be regularly inspected and maintained, with severe safety procedures to be followed. Maintenance technicians face multiple hazards while performing aircraft fuel system inspections and repairs. Jet fuel and other chemicals used within the fuel tanks may contain toxins or irritants that can adversely affect the central nervous system. To protect technicians from these hazards, specialised training and procedures are implemented. Before entering a fuel tank, portable gas detectors are used to monitor oxygen and flammable vapour concentrations, with oxygen levels needing to be between 19.5 and 23.5 percent.
Technicians must be properly trained and maintain constant and accurate voice communication when inspecting fuel tanks. They must also continuously monitor the fuel tanks and their surroundings to prevent injury and costly damage to the aircraft. All aircraft service and maintenance procedures should include an emergency response plan.
A well-maintained aircraft fuel system ensures a clean fuel supply to the aircraft's engine and prevents contamination. If not properly maintained and inspected, the system can become a safety hazard. During an inspection, the fuel system is checked for potential design flaws and functional tests are performed to ensure everything is running smoothly. The entire system is inspected for potential wear and tear, and all units and parts are checked to ensure they are functional and attached properly. Valves and drain plugs are also inspected, and the filter and sump are checked for sediment, water, or dirt particles. If booster pumps are installed, the system is checked for leaks by operating the pumps to ensure they are functional.
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Frequently asked questions
The fuel tanks on jet airplanes are commonly located in the wings.
Locating the fuel tanks in the wings improves the overall structural efficiency by counter-balancing the wing’s lift and the fuselage’s weight, reduces aircraft fuel system complexity, and improves passenger safety by locating fuel away from the passenger cabin.
Integral tanks are created from a structural perspective first and as a fuel tank second. The skin of the wing is connected to the internal structure of the wing, and the joints are sealed to prevent fuel leaks. Integral tanks are commonly located in the wings or fuselage.
There are internal and external fuel tanks. Internal tanks include integral tanks, rigid removable fuel tanks, and bladder tanks. External tanks include conformal fuel tanks and drop tanks.
Jet airplanes get refueled before takeoff. During refueling, up to 800 kilograms of kerosene, or almost 1,000 liters, can flow into the tanks every minute. Commercial aircraft can hold several metric tons of fuel. The ideal distribution of fuel among the various tanks is automatically regulated by an onboard computer.
