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Self-sealing fuel tank

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Self-sealing fuel tank ofMe 262

Aself-sealing fuel tank(SSFT) is a type of fuel tank, typically used inaircraft fuel tanksorfuel bladders,that prevents them from leakingfueland igniting after being damaged.

Typical self-sealing tanks have layers ofrubberand reinforcing fabric, one ofvulcanizedrubber and one of untreated natural rubber, which can absorb fuel when it comes into contact with it. When a fuel tank is punctured the fuel seeps into these layers, causing the untreated layer to swell, closing and thus sealing the puncture. A similar concept is also employed for making self-sealingrun-flat tires.

History

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World War I

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George J. Murdock applied for the patent "War Aeroplane Fuel Tanks" on February 7, 1917 but was temporarily blocked by an order of theFederal Trade Commission,on February 6, 1918, to keep any discussion or publication of the invention secret. The order was rescinded by theUnited States Patent Officeon September 26, 1918 and Murdock was eventually grantedU.S. patent 1,386,791"Self-Puncture Sealing Covering for Fuel-Containers" on August 9, 1921. Military aircraft built by theGlenn L. Martin Companyused this self-sealing fuel tank.

Howard Hughesused neoprene to self-seal his fuel tanks on his1938 around the world flight.[1]

World War II

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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 range but was also a significant fire hazard. Damaged fuel tanks could also rupture, destroying theairframeor critically affectingflight 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 theexitof the projectile, rather than the entry, was the greater problem, as it often tumbled, thus creating a larger exit hole. Among the earliest versions of these types of tanks were those manufactured in the UK atPortsmouth AirportbyFireproof Tanks Ltd(formed in 1939). These tanks were first installed in theFairey Battlelight bomber with other versions installed inSupermarine SpitfireandHawker Hurricanefighters and larger aircraft such as theAvro Lancasterheavy bomber. The Henderson Safety Tank Company provided crash-proof self-sealing fuel and oil tanks which were fitted "as standard" to theMiles Mastertrainer.[2]

German aircraft designers used layers of rubber laid over leather hide with a treated fiber inner surface for the self-sealing tanks on theJunkers Ju 88early in the war.[3]

Manufacture of self-sealing gas tanks at Goodyear, 1941

In the United States, Ernst Eger ofUnited States Rubber Company(laterUniroyal) patented[4]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 forFirestone Tire and Rubber Companyfiled a patent for self sealing tanks on January 21, 1941,U.S. patent 2,404,766.Goodyearchemist 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.[5]In 1942, he received aWar Production Boardcitation and the Goodyear tanks were subsequently placed in service in Goodyear-producedVought F4U Corsairfighters, as well as other aircraft. By 1942 Fireproof Tanks had developed the first flexible fuel bladders as range extender tanks for theSpitfire Mk IX.These tanks were flexible containers, made of a laminated self-sealing material likevulcanized rubberand with as few seams as possible to minimize leak paths.

As early tests showed that impact could over-pressurize a fuel tank, the self-sealing fuel cell is suspended, allowing it to absorb shocks without rupture.U.S. Navyfuel tanks during the war were able to withstand.50 in (12.7 mm) bullets and, on occasion,20 mm (0.79 in)autocannon shells.

Not all fighters were fitted with the relatively new invention. Self-sealing tanks tended to have lower capacity than non-sealed tanks.[6]Nonetheless, aircraft that were fitted with self-sealing tanks managed to withstand much more damage than those with conventional fuel tanks. Combat experience in thePacific Warshowed 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 theMitsubishi A6M Zero.The same principles were applied to give self-sealing fuel lines in aircraft (MIL-PRF-7061C).

Modern use

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Mostjet fightersand allU.S. military rotary wing aircraftuse some type of self-sealing tanks. Military rotary wing fuel tanks have the additional feature of beingcrashworthy.[7]High altitudes require the tanks to be pressurized, making self-sealing difficult. Newer technologies have brought advances like inertfoam-filledtanks 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 fuelslosh.Major manufacturers of this technology include Hutchinson, Amfuel (ex.Zodiac) (formerlyFirestone),Meggitt(formerlyGoodyear), Robertson Fuel Systems,GKNUSA,FPT Industries,andSafranAerosystems.[8]FPT is now part of GKN.[9]For military use, tanks are qualified to MIL-DTL-27422 (includescrashworthinessrequirements) 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.[10]

In addition to military aircraft, some military vehicles feature self-sealing fuel tanks, such as theUnited States Marine Corps'LAV-ATarmored vehicles.[11]A notable example of a non-military vehicle that uses self-sealing fuel tanks is theU.S. presidential state car,having used them sinceJohn F. Kennedy'sSS-100-X.[12][13]

Self-sealing fuel tanks using military technology are also required in somemotorsportcategories.[citation needed]

See also

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References

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Notes

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  1. ^Dietrich, Noah; Thomas, Bob (1972).Howard, The Amazing Mr. Hughes.Greenwich: Fawcett Publications, Inc. p. 136.
  2. ^"Henderson (advertisement)".Flight.25 July 1940. p. 2. Archived fromthe originalon 25 October 2012 – via flightglobal.
  3. ^"the Ingenious Ju-88",Flight:f, 1940, archived fromthe originalon 5 March 2016
  4. ^Puncture Sealing Gas Tank
  5. ^US patent 2424701,Merrill, "Fuel tank casing", issued 1947-07-29USPTO text and images
  6. ^Panko, Ray (29 November 2017)."The Problem with Self-Sealing Fuel Tanks: Capacity, not Weight".Pearl Harbor Aviation Museum.Retrieved29 December2022.
  7. ^A Study of Helicopter Crash-Resistant Fuel Systems
  8. ^"About Safran Aerosystems".
  9. ^"About GKN (Company History - Portsmouth)".RetrievedDecember 5,2011.
  10. ^"UH-60A Student Handbook"(PDF).United States Army Warfighting Center. 2008. pp. D-3. Archived fromthe original(PDF)on January 5, 2012.RetrievedDecember 5,2011.
  11. ^Jones, Colton."U.S. Marine Corps' Light Armored Vehicles to receive new self-sealing fuel tanks".Defence Blog.Retrieved12 September2022.
  12. ^Magazines, Hearst (January 1993).Popular Mechanics.Hearst Magazines.
  13. ^Greenberg, Peter (2013-10-17)."Inside the President's armored limo".Autoweek.Retrieved2021-01-12.

Sources

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  • Dunn, Richard L. (2011). Exploding Fuel Tanks - Saga of technology that changed the course of the Pacific air war.ISBN978-1-4507-7305-8
  • Gustin, Emmanuel (1999).Fighter Armour.Retrieved Aug. 4, 2005.
  • "The Story of the Self-Sealing Tank". (Feb. 1946).US Naval Institute Proceedings,pp. 205.
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