Military jet fuel development has been somewhat dissimilar in Europe and America. The U.S. specification was most likely derived from the aviation gasoline specification, while the British specification reflected the properties of illuminating kerosene.
Because of differences in early development philoso- phies, a brief historical review is a valuable preamble to the discussion of the test requirements and their significance.
This review also reflects the chronological order of develop- ment, with the military demands preceding civil ones by more than two decades.
BRITISH MILITARY FUELS
The British jet fuel specification DERD 2482, issued shortly after World War II, was based on operating experience with illuminating kerosene. The first British jet engine fuel specifi- cation, RDE/F/KER (Provisional), was introduced by the end of World War II and covered what was virtually an illuminat- ing kerosene. It was rather restrictive on aromatics (12 % max.), sulfur content (0.1 % max.), and calorific value (18,500 BTU/lb min.) but contained no burning quality requirements.
Although further experience permitted relaxation of some early requirements, it became necessary to introduce new lim- itations and to amend some existing specification limits as new service problems were encountered. For example, the development of more powerful turbine-powered aircraft with greater range and higher altitude capability made the –40C freezing point inadequate during extensive cold soaking at altitude. After a few amendments, RDE/F/KER was super- seded in 1947 by D.Eng.RD. (DERD) 2482 and this was in turn reissued from time to time with increasingly stringent requirements. This specification became obsolete in 1965 when it was replaced by D.Eng.RD. 2494. DERD 2494, the replacement specification, issued in 1957, incorporated a freezing point of –50C (–58F). This fuel quality remained the optimum compromise between engine requirements, fuel cost, and strategic availability until recently. A minimum flash point of 38C (100F) was specified in both specifications, more for fiscal than technical reasons. One oil company intro- duced a –50C (–58F) freezing point kerosene in 1956 in anticipation of long-range, high-altitude operations. Some years later, this grade was covered by the British specification DERD 2494, which has evolved into the current Defence Standard 91-91 specification for Jet A-1.
It is interesting to note here that the British Ministry of Defence is responsible for the entire aviation specification system for both military and commercial fuels. In the United States, these requirements are handled by completely differ- ent entities, with the Department of Defense for military and ASTM International for civil or commercial fuels.
While DERD 2494 (now termed Def Stan 91-91) is the standard British civil jet fuel, a new DERD 2453 (now Def Stan 91-87) was issued in 1967 for military use, incorporat- ing fuel system icing inhibitor and corrosion inhibitor addi- tives in line with the latest military and NATO requirements.
During 1980, a freezing point relaxation to –47C was per- mitted in both specifications to increase availability.
High flash point kerosene was introduced as early as 1948 to reduce the fire risk aboard aircraft carriers. The first specification for this grade was RDE/F/KER 203 and called for a flash point similar to light diesel fuel. The 65C flash point was later amended to 60C in DERD 2488 because it was
too restrictive. Defence Standard 91-86 (DERD 2452) is the current British military specification for high flash kerosene.
In answer to a need for improved low-temperature perform- ance, a later specification, DERD 2498, dropped the maximum freezing point to –48C (–55F). In 1966, the freezing point was changed to –46C (–51F) max. Ultimately in 1976, DERD 2452 (now Def Stan 91-86) was issued to bring the British high flash naval fuel in line with U.S. military and NATO standards.
Because crude oils with high gasoline yields are not in abundant supply, wide boiling range jet fuel was never used in the United Kingdom to the extent it was in the U.S. military.
However, in the interests of commonality, DERD 2486 was issued to correspond to the U.S. Grade JP-4 (MIL-T-5624). Ulti- mately, this grade was brought completely in line with JP-4 with DERD 2454 (now Def Stan 91-88) by incorporating fuel system icing inhibitor and corrosion inhibitor. Table 5 lists current British and corresponding U.S. military specifications.
AMERICAN MILITARY JET FUELS
In the United States, jet fuel progress followed a different pat- tern. In 1944, the United States published specification AN-F- 32 (which later changed to MIL-T-5616) for JP-1, a –60C (–76F) freezing point paraffinic kerosene. This very restric- tive requirement drastically limited fuel availability, and the grade soon became obsolete (although the term JP-1 is still used incorrectly to describe any kerosene-type jet fuel). The MIL-T-5616 was superseded by various wide-cut fuels: JP-2 (1945), JP-3 (1947), and JP-4 (1951, AVTAG [Aviation Turbine Fuel Wide Cut], NATO F-40). These wide-cut fuels are mix- tures of naphtha and kerosene that greatly increase availabil- ity because of the gasoline component in the product.
The first wide-cut grade (JP-2) had a vapor pressure of 14 kPa (2.0 psi) max., obtained by the addition of heavy gas- oline fractions to kerosene. Experience soon indicated that an increase in vapor pressure would facilitate low tempera- ture starting. The resulting fuel (JP-3) had a vapor pressure range of 35–49 kPa (5–7 psi), similar to aviation gasoline.
However, excessive venting losses occurred in the high- powered F-100 fighter and other Century fighters, due to fuel boiling during rapid climb. Reducing the vapor pres- sures to 14–21 kPa (2.0–3.0 psi) corrected this problem. With slight modifications and the inclusion of certain additives, this fuel called JP-4 (MIL-PRF-5624) was the mainstay of the U.S. Air Force and of the air forces of many countries until it was replaced by JP-8 (MIL-DTL-83133).
The first U.S. Navy aircraft used aviation gasoline, but the lead in the fuel attacked the hot section components in the engine. One proposed approach was to blend aviation gasoline with kerosene to form Jet Mix, a product similar to JP-4. JP-5 (AVCAT, NATO F-44), a high flash point kerosene developed by the Navy for use in Jet Mix, that was first cov- ered by the specification MIL-F-7914 in 1952. Subsequently, JP-5 was included in MIL-F-5624B in 1953. Although consid- erable work was done on Jet Mix, this product was never used operationally and JP-5 remains the primary jet fuel for most navies around the world. Grade JP-5, a low-volatility fuel in carrier use by naval aircraft with its high minimum flash point of 60C (140F) is dictated by shipboard combat conditions, while its low freezing point of –46C (–51F) is based on aircraft demands. There are several other special military grades of aviation kerosene that exist today or have been made redundant for specific reasons. JP-6 was a kero- sene fuel developed in 1956 for the supersonic bomber XB- 70 aircraft. JP-6 was similar to JP-5 but with a lower freezing point and improved thermal oxidative stability. The cancella- tion of the XB-70 program resulted in the cancellation of the JP-6 specification, MIL-J-25656 in 1956. JPTS is a special pur- pose jet fuel developed in 1956 to power the high-flying U-2 reconnaissance aircraft. JPTS is an extremely thermally sta- ble jet fuel with a low freezing point to support this type of mission. JPTS, produced to specification MIL-DTL-25524, is still used today in the U-2 and the newer TR-1 aircraft flown by the National Aeronautics and Space Administration (NASA). The development of the SR-71 Blackbird in the late 1960s required a new fuel having low vapor pressure and excellent thermal oxidative stability to meet the require- ments of high altitude and Mach 3þ cruising. JP-7 is not a distillate fuel like most other jet fuels but is composed of special blending stocks to produce a very clean hydrocarbon mixture low in aromatics (typically<3 %) and nearly void of the sulfur, nitrogen, and oxygen impurities found in other fuels. The combustion characteristics are also tightly speci- fied to ensure adequate combustor life, initially specified in terms of luminometer number, but later changed to hydro- gen content. A high net heat of combustion was also speci- fied. The JP-7 specification, MIL-DTL-38219, was first published in 1970. The SR-71 was retired twice and is not in the U.S. Air Force (USAF) inventory.
JP-8 (AVTUR, NATO F-34), a kerosene fuel very similar to commercial Jet A-1, was developed by the USAF to reduce
TABLE 5—U.S. and British Military Fuel and Related Specifications
British
Designation U.S. Specification NATO No. Designation
DefStan
Specification Description
JP4 MIL-PRF-5624 F-40 AVTAG/FSII 91/88 Wide-cut fuel
JP5 MIL-PRF-5624 F-44 AVCAT/FSII 91/86 High flash kerosene
JP8 MIL-PRF-83133 F-34 AVTUR/FSII 91/87 Standard military kerosene
. . . . . . F-35 AVTUR 91/91 Standard civil kerosene
FSII MIL-DTL-27686 F-1745 FSII 68/252 DiEGME
Corr./lubricity improver MIL-PRF-25017 S-1747 . . . 68/251 Corrosion inhibitor/lubricity improver
the fire hazards associated with wide-cut fuels, which became apparent during the Southeast Asian conflict. JP-8 replaced JP-4 as the primary military jet fuel for USAF operations in Great Britain in 1979 and is currently the primary jet fuel for NATO. The USAF completed its conversion to JP-8 in 1995. JP-8 is covered by the specification MIL-DTL-83133 and British Defence Standard 91-87. Although JP-8 has replaced JP-4 in most every case, the potential need for JP-4 under emergency situations necessitates maintaining this grade in specifications MIL-DTL-5624 and Defence Standard 91-88.
After extensive service trials, the USAF started a change- over to JP-8 MIL-DTL-83133 and British Defence Standard 91-87, a kerosene type product, beginning in the late 1970s.
The changeover to JP-8 from JP-4 was essentially completed by 1995 (UK in 1979, NATO in 1988, Pacific and Continental U.S. in 1995). JP-8 (AVTUR, NATO F-34), a kerosene fuel very similar to commercial Jet A-1, was developed by the USAF to reduce the fire hazards associated with wide-cut fuels. Small arms fire accounted for 63 % of USAF aircraft losses while the U.S. Navy under similar flight conditions did not experi- ence similar losses. The USAF issued a Required Operational Capability in 1967 for all USAF aircraft to have the capabil- ity to fly on JP-8. JP-8’s primary difference with JP-4 is its decreased volatility and considerably higher freezing point.
The volatility change improved ground-handling and combat safety, but significant changes were needed to obtain adequate low temperature starting with the lower-volatility, higher-viscosity fuel in some older aircraft. The adoption of JP-8 in aircraft became an important logistic improvement, because it allowed JP-8 to become the single battlefield fuel in the air and on the ground where diesels and gas turbines took the place of gasoline-powered vehicles. Having the same base fuel as commercial airlines has allowed the mili- tary to use the commercial fuel transportation system by
incorporating the military additives at the point of entry into the military system. As mentioned, Table 5 lists U.S. military specifications for jet fuels and some related products.
AMERICAN CIVIL JET FUELS
In the United States, ASTM created the first commercial jet fuel specification drawing on both the British Ministry of Defence and USAF specifications for experience in relating fuel properties to performance. The effect of kinetic heating due to increases in aircraft speed reduced the need for a –50C (–58F) freezing point and allowed this parameter to be relaxed slightly to relieve problems with availability. The current ASTM D1655 specification covers two commercial fuel grades: Jet A and Jet A-1. Jet A and Jet A-1 are kerosene fuels that are essentially identical except for their freezing points; Jet A has a maximum freezing point of –40C, whereas Jet A-1’s freezing point is –47C (–53F). Jet A is used almost exclusively by commercial airlines operating within the conti- nental United States, while Jet A-1 is used in most other coun- tries. Jet B is a wide-cut distillate fuel that is the commercial equivalent of JP-4 but without the mandatory additives. Jet B is not widely used as its volatility makes it less safe than Jet A or Jet A-1 and certain aircraft engines are not certified to operate with this fuel. Prior to 2000, Jet B was included in D1655 but since then was transferred to a separate specifica- tion (ASTM D6615, Specification for Jet B Wide-Cut Aviation Turbine Fuel). Details of the two kerosene grades in D1655, as well as the characteristics of Jet B in D6615, are contained in Table 6. Jet A with its –40C freezing point is the general domestic jet fuel in the United States and accounts for about half the civil jet fuel used throughout the world. It satisfies the requirements of both domestic flights and most of the international flights originating in the United States. The Jet A-1 freezing point of –50C was originally intended to satisfy the unusual demands of long-range, high-altitude flights, but
TABLE 6—Detailed Requirements of Aviation Turbine FuelsA
Property Jet A or Jet A-1 D1655 Jet B D6615
COMPOSITION
Acidity, total mg KOH/g max 0.10 . . .
Aromatics, volume percent D1319 max 25 25
D6379 max 26.5 26.5
Sulfur, mercaptan,cmass percent max 0.003 0.003
Sulfur, total mass percent max 0.30 0.30
VOLATILITY
Distillation temperature,C: D86 D2887 D86
10 % recovered, temperature max 205 185 . . .
20 % recovered, temperature min . . . . . . 90
max . . . . . . 145
50 % recovered, temperature report report
min . . . . . . 110
max . . . . . . 190
(Continued)
in 1980 the freezing point was raised to –47C to respond to availability concern and to take advantage of better defini- tions of long-range flight requirements. For international and domestic flights outside the United States, Jet A-1 is the stand- ard fuel. Although Jet A would meet many local requirements,
the design of most airport fuel systems limits them to a single grade. To differentiate commercial from military grades (which often contain additives not found in civil fuel), the terms “Jet A-1” and “Jet B” are used worldwide to describe civil fuels, although Jet B usage is extremely limited.
TABLE 6—Detailed Requirements of Aviation Turbine FuelsA(Continued)
Property Jet A or Jet A-1 D1655 Jet B D6615
90 % recovered, temperature report report
max . . . . . . 245
Final boiling point, temperature max 300 340 1.5
Distillation residue, vol percent max 1.5 . . . 1.5
Distillation loss, vol percent max 1.5 . . . 1.5
Flash point,C min 38 . . .
Density at 15C, kg/m3 775 to 840 751 to 802
Vapor pressure, 38C, kPa . . . 14 to 21
FLUIDITY
Freezing point,C max 40 Jet A 50
max 47 Jet A-1
Viscosity—20C, mm2/s max 8.0 . . .
COMBUSTION
Net heat of combustion, MJ/kg min 42.8 42.8
One of the following requirements shall be met:
(1) Smoke point, mm, or min 25 25
(2) Smoke point, mm, and min 18 18
Naphthalenes, vol percent max 3.0 3.0
CORROSION
Copper strip, 2 h at 100C max No. 1 No. 1
THERMAL STABILITY
D3241 (2.5 h at control temperature of 260C min)
Filter pressure drop, mm Hg max 25 25
Tube deposits less than 3 3
NoPeacockorAbnormalColor Deposits CONTAMINANTS
Existent gum, mg/100 mL max 7 7
Microseparaometer, rating
Without electrical conductivity min 85 85
With electrical conductivity min 70 70
ADDITIVES See specification See specification
Electrical conductivity, pS/m
if used max 600 450
if specified at point of delivery 50 to 600 50 to 450
AFor additional requirements contained in specification footnotes, refer to Table 1 in ASTM D1655 or Table 1 in ASTM D6615.
Major U.S. aircraft engine manufacturers and certain airlines also issue jet fuel specifications. These are either sim- ilar to the ASTM specification or possibly less restrictive than one or more of the ASTM grades. Should a manufacturer’s specification be more restrictive than ASTM, it would create major problems because the manufacturer’s specification is normally used for certification and would, therefore, have to be followed by the users. In turn, the ASTM specification would become an unused piece of paper in such cases.
RUSSIAN JET FUELS
Several jet fuels covered by various GOST specifications are manufactured for both civil and military use. The main grades are also covered by specifications issued by a number of east European countries, although a number of these countries are changing to Western specifications as they pur- chase and operate Western aircraft. While Russian fuel char- acteristics in some cases differ considerably from those of fuels made elsewhere, the main properties are controlled by test methods similar to their ASTM/IP equivalents. A few additional test methods, such as iodine number (related to olefin content), hydrogen sulfide content, ash content, and naphthenic soaps, are sometimes included. Thermal stability is usually specified but by completely different test proce- dures. However, a recent research program sponsored by the International Air Transport Association (IATA) is intended to
establish the relationship between Russian and Western test methods.
Brief details are given in Table 7. TS-1 and sometimes RT are the only grades normally offered to international airlines at civil airports. Both the RT grade and the more common TS-1 Premium normally satisfy current Jet A-1 spec- ification requirements, with the exception of a flash point minimum of 28C (82F). However, Western engine manu- facturers are also concerned about the thermal stability of Russian jet fuels because of basic differences in test meth- ods. Efforts are currently under way to reconcile specifica- tion limits set by ASTM D3241, the thermal oxidation stability test method procedure, and GOST 11802-88, the Russian test method.
Other National Specification
Several other counties also issue jet fuel specifications, and the most important are listed in Table 8. In most cases, these specifications are identical with their U.S. or British counter- parts, particularly for countries committed to multinational military standardization agreements, such as NATO. In many of these countries, little or no use is made of the national specification, and most fuels are manufactured as Jet A-l to the commercially accepted Joint Check List (see later). How- ever, a few countries, including Brazil, Canada, France, and Sweden, make considerable use of their national standards.
TABLE 7—Russian Jet Fuel Specifications
Specification Grade Type Use
GOST 10227 TS-1 (premium) Kerosene (SR)A Most common civil GOST 10227 TS-1 (regular) Kerosene (SR)A Most common civil
GOST 10227 T-1 (regular) Kerosene Common civil
GOST 10227 T-1S (special) Kerosene Special application
GOST 10227 T-2 Wide cut Standby (reserve) fuel
GOST 10227 RT Kerosene (HT)B Military/occasionally
civil
GOST R 52050-2006 Jet A-1 Kerosene Commercial
ASR = straight-run.
BHT = hydrotreated.
TABLE 8—Other National Aviation Fuel Specifications
Country/Issuing Agency Kerosene Wide-Cut High-Flash Kero
Australia/A. Dept. Defence DEF (AUST) 5240 QAV-1 DEF (AUST) 5280 QAV-4. . . DEF (AUST) 5207
Canada/CAN/CGSB 3.23 3.22 3.24
Peoples Republic of China GB 1778 (No. 2 Jet Fuel) SH 0348 (No. 4 Jet Fuel) GBJ 560A (No. 5 Jet Fuel) GB 6537 (No. 3 Jet Fuel) GJB 2376 (No. 4 Jet Fuel)
France/Service des Essences des Armees DCSEA 134 Jet A-1 AIR 3407 AIR 3404
Germany Joint Check List Jet A-1 DefStan 91/88 . . .
Japan/Japan Defense Agency JIS K 2209 Jet A-1 DSP K 2206 (JP-4) DSP K 2206 (JP-5)
Sweden/SDMA FSD8607 FSD8608 . . .
INTERNATIONAL STANDARD SPECIFICATIONS
Modern civil aviation recognizes few frontiers, and a need, therefore, exists to have aviation fuels of similar characteris- tics available in all parts of the world. This is especially important for jet fuels used by the international airlines. An early attempt to simplify the specification picture was the establishment of a checklist to be used by eleven major fuel suppliers where more than two suppliers furnished fuel to commingled terminals or airports. This checklist is formally termed “The Aviation Fuel Quality Requirements for Jointly Operated Systems (AFQRJS)” and applies outside the United States. This checklist included the most severe requirements of ASTM Jet A-1, Def Stan 91-91, and the IATA guidance material for Jet A-1 grade. A major shortcoming of this approach has been that over time more and more suppliers, such as govern- ment-owned oil companies, manufactured jet fuel but were not part of the group issuing the checklist. IATA has, therefore, issued “guidance material for aviation fuel” in the form of four specifications. Included are the domestic U.S. fuel (Grade Jet A) based on ASTM D1655, the internationally supplied Jet A-1 grade meeting Def Stan 91-91 and ASTM Jet A-1, and the Rus- sian specification TS-1. Although the first three are all kerosene- type fuels, which are basically similar, the differences between specifications are sufficient to prevent combining them into a single grade. Thus, Jet A differs from the others in having a higher freezing point, while the Russian fuel has both a lower flash and freezing point. An international airline is, therefore, likely to obtain Jet A in the United States, TS-1 in Russia and some other Eastern countries, and Jet A-l in the rest of the world. Jet B is included because of its use in a few northern locations where an airline might have to take the fuel on an emergency basis. Table 9 summarizes some of the significant differences between the various major specifications. Over the
past few years, a great deal of effort has gone into harmonizing the worlds jet fuel specifications to reduce the confusion caused by having different limits for the same quality parameters. This effort is particularly important today as air travel is on the rise and the barriers that prevented global travel have all but disap- peared. The International Air Transport Association (IATA) Guidance Material for Aviation Turbine Fuels Specifications (Edition 6)has been substantially revised to include the require- ments for Jet A, Jet A-1, and the Russian civil fuel TS-1. With this change, the guidance material now includes all grades of jet fuel used for civil aviation. Although every effort was made to har- monize the kerosene grades, differences still exist, which will most likely remain for the near future.
Illuminating kerosene was the first true aviation turbine fuel developed more 50 years ago. Today, after all the amaz- ing technological advances, the fuels used by the world’s jet aircraft are still kerosene based, whether they are Jet A in the United States, TS-1 in Russia, or Jet A-1 elsewhere in the world. Minor changes to specification properties will result over time as dictated by new equipment requirements and environmental pressures to reduce aircraft emissions. Due in part to the long service life of aircraft and the lack of commercially viable alternatives, jet fuel, much as we know it today, will remain the principal aviation fuel well into the 21st century.
Composition and Manufacture
Aviation turbine fuels are manufactured predominantly from straight-run (noncracked) kerosene obtained by the atmo- spheric distillation of crude oil. Straight-run kerosene from some sweet crudes meet all specification requirements with- out further processing, but for the majority of crudes certain trace constituents have to be removed before the product
TABLE 9—Comparison of Critical Properties Among Major Specifications
ASTMD1655 DefStan 91-91 GOST 10227 ASTM D6615 MIL-PRF-5624
Property Jet A Jet A-l TS-1 Jet B JP-5
Prem. Reg.
Flash point,C, min 38 38.0 28 <18 60
Vapor pressure, kPA @38C Approx. 0.28–0.62 Approx. 0.28–0.62 Approx. 0.48–1.38 14–21 <1
Freeze point,C, max –40 –47 –60 –50 –46
Density @ 15C, kg/m3 775–840 775.0–840.0 780 min 775 min
751–802 788–845
Smoke point, mm 25 min or 25.0 min or 25 min 25 min or 19.0 min
Or smoke point, min þ naphthalenes, vol %
18 19.0 18
3.0 max 3.00 max 3.0 max 13.4A
Aromatics, vol percent, max D6379 max
25.0 or 26.5
25.0 or 26.5
22 m % 25.0 or
26.5
25.0
Distillation,C 10 % recov.,
max flash boiling point max 205 300
205 300.0
165 250B
90 minC 145 maxC 245D
206 300
APercent hydrogen.
B98%recovered.
C20 % recovered.
D90 % recovered.