Jet fuel is a specific type of kerosene fuel for aircraft with gas-turbine engines. There are different grades of fuel; Jet A and Jet A-1 are the most popular. Jet fuel is a mix of many different hydrocarbons in varying proportions. It is also designed with a low flash point (110 degrees in military jets) to improve ignition.
The first jet engines were used in World War II by the Germans. Hans von Ohain built a jet engine that flew a plane on Aug. 27, 1939. The engine was powered by gasoline. Englishman Frank Whittle developed his own jet engine, but it wasn't used to fly a plane until May 14, 1941. Because of a gasoline shortage caused by the war, Whittle's engine used kerosene, which remains the base of modern jet fuels.
Though the earliest jet engines could use most types of fuel, as the engines improved so did their need for quality fuel. More efficient engines required fuels that could provide the power the engines needed. Two of the basic improvements were higher flash points (temperature at which the fuel ignites) and lower freeze points. Higher flash points reduced the risk of fire. As jets began to climb to higher altitudes, the outside temperature of the plane dropped so lower freeze points minimized the risk of the fuel freezing.
The first jet fuel was developed at the end of World War II. The specifications were published in 1944 and it was called JP-1 or Jet Propellant 1. While the fuel worked, the military began looking for ways to improve it and thereby, improve the performance of its jets. Other variations included JP-2 (it proved too flammable) and JP-3, which had vapor lock and fuel-loss problems.
JP-4 or Jet Propellant 4 was a kerosene-gasoline mixture that worked well and was used by the U.S. Air Force from 1951 until the mid-1990s. It was similar to the Jet B fuel used by privately owned planes.
JP-5 came about in 1952. It had a higher flash point, which made a good fuel for use aboard aircraft carriers where fires were always a danger. It continues to be used by most navies today. This fuel is also called F-44 or avcat.
The Air Force switched from JP-4 to J-8 in the 1990s, though it was developed in 1978. It has a higher flashpoint than JP-4 and is less carcinogenic. Its formulation is similar to Jet A-1 fuel, which is used by commercial aircraft.
