Today's kerosene jet fuels have been developed from the illuminating kerosene used in the early gas turbine engines. These engines needed a fuel with good combustion characteristics and a high energy content. The kerosene type fuels used in civil aviation nowadays are mainly JET A-1 and Jet A. The latter has a higher freezing point (maximum minus 40 degrees C instead of maximum minus 47 degrees C) and is available only in North America.
JET FUEL GRADES
Jet A-1 is a kerosene grade of fuel suitable for most turbine engined aircraft. It has a flash point minimum of 38 degrees C (100°F) and a freeze point maximum of -47 degrees C. It is widely available outside the U.S.A. The main specifications for Jet A-1 grade (see below) are the UK specification DEF STAN 91-91 (Jet A-1) Nato code F-35, (formerly DERD 2494) and the ASTM specification D1655 (Jet A-1).
Jet A is a kerosene grade fuel, normally only available in the U.S.A. It has the same flash point as Jet A-1 but a higher freeze point maximum (-40°C). It is supplied against the ASTM D1655 (Jet A) specification.
Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to Jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. ASTM have a specification for Jet B but in Canada it is supplied against the Canadian Specification CAN/CGSB 3.23
TS-1 is the main jet fuel grade available in Russian and CIS states. It is a kerosene type fuel with slightly higher volatility (flash point is 28C minimum) and lower freeze point (<-50C) compared to Jet A-1.
AMERICAN CIVIL JET FUELS
The basic civil jet fuel specification used in the United States of America is ASTM Specification for Aviation Turbine Fuels D 1655, which defines the requirements for three grades of fuel:-
Jet A is used within the United States by domestic and international airlines.
Jet B is rarely available nowadays except in parts of northern Canada where its lower freeze point and higher volatility is an advantage for handling and cold starting.
UK JET FUELS
Although developed basically as a military jet fuel, D. Eng RD 2494, issued by the Ministry of Defence, was adopted as the standard UK civil jet fuel. It is now renamed as DEF STAN 91-91 and defines the requirements for a kerosine type fuel (Jet A-1 grade) having a maximum freeze point of -47 degrees C.
Jet A-1 according to the DEF STAN 91-91 specification is very similar to Jet A-1 defined by the ASTM D 1655 except for a small number of areas where DEF STAN 91-91 is more stringent.
FORMER SOVIET UNION AND EAST EUROPEAN JET FUELS
Soviet kerosene type jet fuels are covered by a wide range of specification grades reflecting different crude sources and processing treatments used. The grade designation is T-1 to T-8, TS-1 or RT. The grades are covered either by a State Standard (GOST) number, or a Technical Condition (TU) number. The limiting property values, detailed fuel composition and test methods differ quite considerably in some cases from the Western equivalents.
The principle grade available in Russia (and members of the CIS) is TS-1.
The main differences in characteristics are that Soviet fuels have a low freeze point (equivalent to about -57 degrees C by Western test methods) but also a low flash point (a minimum of 28 degrees C compared with 38 degrees C for Western fuel). RT fuel (written as PT in Russian script) is the superior grade (a hydrotreated product) but is not produced widely. TS-1 (regular grade) is considered to be on a par with Western Jet A-1 and is approved by most aircraft manufacturers.
Eastern European countries have their own national standards with their own nomenclature. Many are very similar to the Russian standards but others reflect the requirements of visiting international airlines and are similar to Western Jet A-1 in properties and test methods.
CHINESE JET FUELS
Five types of jet fuel are covered by current Chinese specifications. Previously, each grade was numbered with a prefix RP, they are now renamed No 1 Jet Fuel, No 2 Jet Fuel etc. RP-I and RP-2 are kerosines which are similar to Soviet TS-1. They both have low flash point (minimum 28 degrees C).
RP-1 freeze point is -60 degrees C and RP-2 is -50 degrees C. RP-3 is basically as Western Jet A-1, produced as an export grade. RP-4 is a wide-cut type fuel similar to Western Jet B and Soviet T-2. RP-5 is a high flash point kerosine similar to that used in the West by naval aircrafl operating on aircraft carriers. Virtually all jet fuel produced in China is now RP-3 (renamed No 3 Jet Fuel).
INTERNATIONAL SPECIFICATIONS - AFQRJOS checklist
As jet fuel supply arrangements have become more complex, involving co-mingling of product in joint storage facilities, a number of fuel suppliers developed a document which became known as the Aviation Fuel Quality Requirements for Jointly Operated Systems, or AFQRJOS, Check List. The Check List represents the most stringent requirements of the DEF STAN and ASTM specifications for JET A-1. By definition, any product meeting Check List requirements will also meet either DEF STAN or ASTM specifications.
Fuel delivered to the Check List embodies the most stringent requirements of the following specifications: -
(a) DEF STAN 91-91
(b) ASTM D1655 Kerosine Type Jet A-1,
The Check List is recognised by eight of the major aviation fuel suppliers - Agip, BP, ChevronTexaco, ExxonMobil, Kuwait Petroleum, Shell, Statoil and Total - as the basis of their international supply of virtually all civil aviation fuels outside North America and former Soviet Union.
OTHER NATIONAL CIVIL JET FUEL SPECIFICATIONS
There are many individual national specifications. Typcially, these are based on the US, UK or former Soviet specifications with minor differences. There are increasing moves to harmonise the small differences between the ASTM and DEF STAN specifications. This process of harmonisation is also in progress with many national specifications.
CIVILIAN JET FUELS
Jet A-1 is a kerosene grade of fuel suitable for most turbine engine aircraft. It is produced to a stringent internationally agreed standard, has a flash point above 38°C (100°F) and a freeze point maximum of -47°C. It is widely available outside the U.S.A. Jet A-1 meets the requirements of British specification DEF STAN 91-91 (Jet A-1), (formerly DERD 2494 (AVTUR)), ASTM specification D1655 (Jet A-1) and IATA Guidance Material (Kerosine Type), NATO Code F-35.
Jet A is a similar kerosene type of fuel, produced to an ASTM specification and normally only available in the U.S.A. It has the same flash point as Jet A-1 but a higher freeze point maximum (-40°C). It is supplied against the ASTM D1655 (Jet A) specification.
Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to Jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. In Canada it is supplied against the Canadian Specification CAN/CGSB 3.23
The DEF STAN 91-91 (UK) and ASTM D1655 (international) specifications allow for certain additives to be added to jet fuel, including:
As the aviation industry’s jet kerosene demands have increased to more than 5% of all refined products derived from crude, it has been necessary for the refiner to optimize the yield of jet kerosene, a high value product, by varying process techniques. New processes have allowed flexibility in the choice of crudes, the use of coal tar sands as a source of molecules and the manufacture of synthetic blend stocks. Due to the number and severity of the processes used, it is often necessary and sometimes mandatory to use additives. These additives may, for example, prevent the formation of harmful chemical species or improve a property of a fuel to prevent further engine wear.
WATER IN JET FUEL
It is very important that jet fuel be free from water contamination. During flight, the temperature of the fuel in the tanks decreases, due to the low temperatures in the upper atmosphere. This causes precipitation of the dissolved water from the fuel. The separated water then drops to the bottom of the tank, because it is denser than the fuel. Since the water is no longer in solution, it can form droplets which can supercool to below 0 °C. If these supercooled droplets collide with a surface they can freeze and may result in blocked fuel inlet pipes. This was the cause of the British Airways Flight 38 accident. Removing all water from fuel is impractical; therefore, fuel heaters are usually used on commercial aircraft to prevent water in fuel from freezing.
There are several methods for detecting water in jet fuel. A visual check may detect high concentrations of suspended water, as this will cause the fuel to become hazy in appearance. An industry standard chemical test for the detection of free water in jet fuel uses a water-sensitive filter pad that turns green if the fuel exceeds the specification limit of 30 ppm (parts per million) free water. A critical test to rate the ability of jet fuel to release emulsified water when passed through coalescing filters is ASTM standard D3948 Standard Test Method for Determining Water Separation Characteristics of Aviation Turbine Fuels by Portable Separometer.
MILITARY JET FUELS
Military organizations around the world use a different classification system of JP (for "Jet Propellant") numbers. Some are almost identical to their civilian counterparts and differ only by the amounts of a few additives; Jet A-1 is similar to JP-8, Jet B is similar to JP-4. Other military fuels are highly specialized products and are developed for very specific applications.
Jet fuels are sometimes classified as kerosene or naphtha-type. Kerosene-type fuels include Jet A, Jet A-1, JP-5 and JP-8. Naphtha-type jet fuels, sometimes referred to as "wide-cut" jet fuel, include Jet B and JP-4.
JP-1 was an early jet fuel specified in 1944 by the United States government (AN-F-32). It was a pure kerosene fuel with high flash point (relative to aviation gasoline) and a freezing point of −60 °C (−76 °F). The low freezing point requirement limited availability of the fuel and it was soon superseded by other "wide cut" jet fuels which were kerosene-naphtha or kerosene-gasoline blends. It was also known as avtur.
JP-2 an obsolete type developed during World War II. JP-2 was intended to be easier to produce than JP-1 since it had a higher freezing point, but was never widely used.
JP-3 was an attempt to improve availability of the fuel compared to JP-1 by widening the cut and loosening tolerances on impurities to ensure ready supply. In his book Ignition! An Informal History of Liquid Rocket Propellants, John D. Clark described the specification as, "remarkably liberal, with a wide cut (range of distillation temperatures) and with such permissive limits on olefins and aromatics that any refinery above the level of Kentucky moonshiner's pot still could convert at least half of any crude to jet fuel". It was even more volatile than JP-2 and had high evaporation loss in service.
JP-4 was a 50-50 kerosene-gasoline blend. It had lower flash point than JP-1, but was preferred because of its greater availability. It was the primary United States Air Force jet fuel between 1951 and 1995. Its NATO code is F-40. It is also known as avtag.
JP-5 is a yellow kerosene-based jet fuel developed in 1952 for use in aircraft stationed aboard aircraft carriers, where the risk from fire is particularly great. JP-5 is a complex mixture of hydrocarbons, containing alkanes, naphthenes, and aromatic hydrocarbons that weighs 6.8 pounds per U.S. gallon (0.81 kg/l) and has a high flash point (min. 60 °C or 140 °F). Because some US naval air stations, Marine Corps air stations and Coast Guard air stations host both sea-based and shore-based (e.g., "land based") naval aircraft, these installations will also typically fuel their shore-based aircraft with JP-5, thus precluding the need to maintain separate fuel facilities for JP-5 and non-JP-5 fuel. In addition, JP-5 may well have been used by other countries for their military aircraft. Its freezing point is −46 °C (−51 °F). It does not contain antistatic agents. JP-5 is also known as NCI-C54784. JP-5's NATO code is F-44. It is also called AVCAT fuel for Aviation Carrier Turbine fuel.
The JP-4 and JP-5 fuels, covered by the MIL-DTL-5624 and meeting the British Specification DEF STAN 91-86 AVCAT/FSII (formerly DERD 2452), are intended for use in aircraft turbine engines. These fuels require military-unique additives that are necessary in military weapon systems, engines, and missions.
JP-6 This is a type of jet fuel developed for the General Electric YJ93 jet engine of the XB-70 Valkyrie supersonic aircraft. JP-6 was ideal for the high altitude bomber, being similar to JP-5 but with a lower freezing point and improved thermal oxidative stability. When the XB-70 program was cancelled, the JP-6 specification, MIL-J-25656, was also cancelled.
JP-7 was developed for the twin Pratt & Whitney J58 turbojet/ramjet engines of the SR-71 Blackbird and has a high flash point to better cope with the heat and stresses of high speed supersonic flight.
JP-8 a jet fuel, specified and used widely by the U.S. military. It is specified by MIL-DTL-83133 and British Defence Standard 91-87. JP-8 is a kerosene-based fuel, projected to remain in use at least until 2025. It was first introduced at NATO bases in 1978. Its NATO code is F-34.
JP-10 is a gas turbine fuel for missiles, specifically the ALCM. It contains a mixture of (in decreasing order) endo-tetrahydrodicyclopentadiene, exo-tetrahydrodicyclopentadiene, and adamantane. It is produced by catalytic hydrogenation of dicyclopentadiene. It superseded JP-9 fuel, achieving a lower low-temperature service limit of −65 °F (−54 °C).
Zip fuel designates a series of experimental boron-containing "high energy fuels" intended for long range aircraft. The toxicity and undesirable residues of the fuel made it difficult to use. The development of the ballistic missile removed the principal application of zip fuel.
Syntroleum has been working with the USAF to develop a synthetic jet fuel blend that will help them reduce their dependence on imported petroleum. The USAF, which is the United States military's largest user of fuel, began exploring alternative fuel sources in 1999. On December 15, 2006, a B-52 took off from Edwards Air Force Base for the first time powered solely by a 50-50 blend of JP-8 and Syntroleum's FT fuel. The seven-hour flight test was considered a success. The goal of the flight test program was to qualify the fuel blend for fleet use on the service's B-52s, and then flight test and qualification on other aircraft.
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This video explains the differences in the flammability characteristics of various fuels and removes the myths.
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