Civil Jet Fuel
Grades and specifications.
Today's kerosine jet fuels have been developed from the illuminating kerosine used in the early gas turbine engines. These engines needed a fuel with good combustion characteristics and a high energy content. The kerosine 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.
Summary of Jet Fuel Grades
Jet A-1 is a kerosine 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).
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Jet A is a kerosine 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 kerosine 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 kerosine 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, a kerosine type fuel having a maximum freeze point of -40 degrees C.
- Jet A-1, a kerosine type fuel, identical with Jet A but with a maximum freeze point of -47 degrees C.
- Jet B, a wide-cut type 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 kerosine 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.