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A self-sealing fuel tank is a type of fuel tank, typically used in
aircraft fuel tanks Aircraft fuel tanks are a major component of aircraft fuel systems. They can be classified into internal or external fuel tanks and can be further classified by method of construction or intended use. Safety aspects of aircraft fuel tanks were exa ...
or
fuel bladder Fuel bladders, fuel storage bladders are a type of Flexi-bag used as a fuel container. They are collapsible, flexible storage bladders (also known as tanks) that provide transport and storage (temporary or long term) for bulk industrial liquids ...
s, that prevents them from leaking
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
and igniting after being damaged. Typical self-sealing tanks have multiple layers of
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
and reinforcing fabric, one of
vulcanized Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to inclu ...
rubber, and one of untreated natural rubber, which can absorb fuel, swell, and expand when it comes into contact with the fuel. When a fuel tank is punctured, the fuel seeps into the layers, causing the untreated layer to swell and thus seal the puncture. A similar concept is also employed for making self-sealing run-flat tires.


History


World War I

George J. Murdock applied for the patent "War Aeroplane Fuel Tanks" on February 7, 1917 but was temporarily blocked by an order of the
Federal Trade Commission The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) antitrust law and the promotion of consumer protection. The FTC shares jurisdiction ov ...
, on February 6, 1918, to keep any discussion or publication of the invention secret. The order was rescinded by the
United States Patent Office The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that serves as the national patent office and trademark registration authority for the United States. The USPTO's headquarters are in Alex ...
on September 26, 1918 and Murdock was eventually granted United States Patent 1,386,791 "Self-Puncture Sealing Covering for Fuel-Containers" on August 9, 1921. Military aircraft built by the Glenn L. Martin Company used this self-sealing fuel tank.
Howard Hughes Howard Robard Hughes Jr. (December 24, 1905 – April 5, 1976) was an American business magnate, record-setting pilot, engineer, film producer, and philanthropist, known during his lifetime as one of the most influential and richest people in th ...
used neoprene to self-seal his fuel tanks on his 1938 around the world flight.


World War II

In the newer generations of pre-war and early-war aircraft, self-sealing tanks were tanks used to minimize the damage from leaking or burning fuel. A conventional fuel tank, when hit by gunfire, could leak fuel rapidly. This would not only reduce the aircraft's effective range, but was also a significant fire hazard. Damaged fuel tanks could also rupture, destroying the airframe or critically affecting flight characteristics. It was realized that, because of weight limitations, it was not practical to simply add armor plate to aircraft fuel tanks; a method of stopping fuel leaking from damaged tanks was necessary. Early attempts at protecting fuel tanks consisted of using metal tanks, covered inside or outside by a material that expanded after being pierced. Research revealed that the ''exit'' of the projectile, rather than the entry, was the greater problem, as it often tumbled, thus creating a large exit hole. Among the earliest versions of these types of tanks were those manufactured in the UK at Portsmouth Airport by Fireproof Tanks Ltd (formed in 1939). These tanks were first installed in the
Fairey Battle The Fairey Battle is a British single-engine light bomber that was designed and manufactured by the Fairey Aviation Company. It was developed during the mid-1930s for the Royal Air Force (RAF) as a monoplane successor to the Hawker Hart and Hi ...
light bomber with other versions installed in
Supermarine Spitfire The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and other Allied countries before, during, and after World War II. Many variants of the Spitfire were built, from the Mk 1 to the Rolls-Royce Grif ...
and
Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness by ...
fighters and larger aircraft such as the
Avro Lancaster The Avro Lancaster is a British Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to the same specification, as well as the Short Stirlin ...
heavy bomber. The Henderson Safety Tank Company provided crash-proof self-sealing fuel and oil tanks which were fitted "as standard" to the
Miles Master The Miles M.9 Master was a British two-seat monoplane advanced trainer designed and built by aviation company Miles Aircraft Ltd. It was inducted in large numbers into both the Royal Air Force (RAF) and Fleet Air Arm (FAA) during the Second Wor ...
trainer. German aircraft designers used layers of rubber laid over leather hide with a treated fiber inner surface for the self-sealing tanks on the
Junkers Ju 88 The Junkers Ju 88 is a German World War II ''Luftwaffe'' twin-engined multirole combat aircraft. Junkers Aircraft and Motor Works (JFM) designed the plane in the mid-1930s as a so-called ''Schnellbomber'' ("fast bomber") that would be too fast ...
early in the war. In the United States, Ernst Eger of
United States Rubber Company The company formerly known as the United States Rubber Company, now Uniroyal, is an American manufacturer of tires and other synthetic rubber-related products, as well as variety of items for military use, such as ammunition, explosives, chemical ...
(later
Uniroyal The company formerly known as the United States Rubber Company, now Uniroyal, is an American manufacturer of tires and other synthetic rubber-related products, as well as variety of items for military use, such as ammunition, explosives, chemical ...
) patented a self-sealing fuel tank design in 1941, one of many companies involved in developing this technology during the war. Elmo E. Hanson, lead chemist for
Firestone Tire and Rubber Company Firestone Tire and Rubber Company is a tire company founded by Harvey Firestone (1868–1938) in 1900 initially to supply solid rubber side-wire tires for fire apparatus, and later, pneumatic tires for wagons, buggies, and other forms of wheeled ...
filed a patent for self sealing tanks on January 21, 1941, Patent 2,404,766. Goodyear chemist James Merrill filed a patent in 1941 (published in 1947) for refining and successfully testing his method for manufacturing self-sealing tanks using a two-layer system of rubber compounds encased in a metal outer shell or the wing lining of the aircraft. In 1942, he received a
War Production Board The War Production Board (WPB) was an agency of the United States government that supervised war production during World War II. President Franklin D. Roosevelt established it in January 1942, with Executive Order 9024. The WPB replaced the Sup ...
citation and the Goodyear tanks were subsequently placed in service in Goodyear-produced
Vought F4U Corsair The Vought F4U Corsair is an American fighter aircraft which saw service primarily in World War II and the Korean War. Designed and initially manufactured by Chance Vought, the Corsair was soon in great demand; additional production contracts ...
fighters, as well as other aircraft. By 1942 Fireproof Tanks had developed the first flexible fuel bladders as range extender tanks for the Mk IX Spitfire. These tanks were flexible containers, made of a laminated self-sealing material like
vulcanized rubber Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to includ ...
and with as few seams as possible to minimize leak paths. As early tests showed that impact could overpressurize a fuel tank, the self-sealing fuel cell is suspended, allowing it to absorb shocks without rupture.
U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage o ...
fuel tanks during the war were able to withstand bullets and, on occasion, autocannon shells. Not all fighters were fitted with the relatively new invention. Self-sealing tanks tended to be heavier with lower capacity than non-sealed tanks. Nonetheless, aircraft that were fitted with self-sealing tanks managed to withstand much more damage than those with conventional fuel tanks. Combat experience in the
Pacific War The Pacific War, sometimes called the Asia–Pacific War, was the theater of World War II that was fought in Asia, the Pacific Ocean, the Indian Ocean, and Oceania. It was geographically the largest theater of the war, including the vast ...
showed that the self-sealing fuel tank-equipped American aircraft could sustain far more damage than the lightly armored Japanese designs without self-sealing fuel tanks, such as the
Mitsubishi A6M Zero The Mitsubishi A6M "Zero" is a long-range carrier-based fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and was operated by the Imperial Japanese Navy from 1940 to 1945. The A6M w ...
. The same principles were applied to give self-sealing fuel lines in aircraft (MIL-PRF-7061C).


Modern use

Most
jet fighter Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
s and all U.S. military rotary wing aircraft utilize some type of self-sealing tanks. Military rotary wing fuel tanks have the additional feature of being
crashworthy Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different crit ...
. High altitudes require the tanks to be pressurized, making self-sealing difficult. Newer technologies have brought advances like inert foam-filled tanks to prevent detonation. This foam is an open cell foam that effectively divides the gas space above the remaining fuel into thousands of small spaces, none of which contain sufficient vapour to support combustion. This foam also serves to reduce fuel
slosh In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion). Strictly speaking, the liquid must have a free surface to constitute a slosh dynamics problem, where the dynamics of t ...
. Major manufacturers of this technology include Hutchinson, Amfuel (ex.
Zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the Sun path, apparent path of the Sun across the celestial sphere over the course of the year. ...
) (formerly Firestone),
Meggitt Parker Meggitt (formerly Meggitt plc) is a British international company specialising in components and sub-systems for the aerospace, defence and selected energy markets. It was listed on the London Stock Exchange and was a constituent of the ...
(formerly Goodyear), Robertson Fuel Systems,
GKN GKN Ltd is a British multinational automotive and aerospace components business headquartered in Redditch, England. It is a long-running business known for many decades as Guest, Keen and Nettlefolds. It can trace its origins back to 1759 an ...
USA,
FPT Industries FPT Industries was formed in July 1939 as Fireproof Tanks Ltd (commonly known as FPT) as a subsidiary of Airspeed Ltd at Portsmouth Airport in response to an Air Ministry requirement for the development and manufacture of self-sealing fuel tanks f ...
, and Safran Aerosystems. FPT is now part of GKN. For military use, tanks are qualified to MIL-DTL-27422 (includes
crashworthiness Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different crit ...
requirements) or MIL-DTL-5578 (non-crashworthy). An aircraft fuel tank sometimes consists of several interconnected fuel cells. The interconnecting hoses are typically also self-sealing. In addition to military aircraft, some military vehicles feature self-sealing fuel tanks, such as the United States Marine Corps' LAV-AT armored vehicles. A notable example of a non-military vehicle that uses self-sealing fuel tanks is the U.S. presidential state car, having used them since
John F. Kennedy John Fitzgerald Kennedy (May 29, 1917 – November 22, 1963), often referred to by his initials JFK and the nickname Jack, was an American politician who served as the 35th president of the United States from 1961 until his assassination ...
's
SS-100-X The United States presidential state car (nicknamed "the Beast", "Cadillac One", "First Car"; code named "Stagecoach") is the official state car of the president of the United States. United States presidents embraced automotive technology in ...
. Self-sealing fuel tanks using military technology are also required in some
motorsport Motorsport, motorsports or motor sport is a global term used to encompass the group of competitive sporting events which primarily involve the use of motorized vehicles. The terminology can also be used to describe forms of competition of two ...
categories.


References


Notes


Sources

*Dunn, Richard L. (2011). Exploding Fuel Tanks - Saga of technology that changed the course of the Pacific air war. *Gustin, Emmanuel (1999)
Fighter Armour
Retrieved Aug. 4, 2005. *"The Story of the Self-Sealing Tank". (Feb. 1946). ''US Naval Institute Proceedings'', pp. 205.


External links


James A Merrill receiving citation from President Roosevelt (1942)Installation of a Self-Sealing Materials Systems in a C-130 Integral Fuel Tank Wing
- DTIC
''Popular Science'', November 1941 ''Lining Will Seal Bullet Holes In Bombers Fuel System''
see bottom half of page
Gunfire Qualification Test of Self-Sealing Fuel CellsSelf-sealing Fuel Tank Demonstration
{{DEFAULTSORT:Self-Sealing Fuel Tank Aircraft fuel system components Fuel containers Military aviation