This test method is intended for use as a guide in cases in which an experimental determination of hydrogen content is not available. Table 1 shows a summary for the range of each variable used in developing the correlation. The mean value and its distribution about the mean, namely the standard deviation, is shown. This indicates, for example, that the mean density for all fuels used in developing the correlation was 783.5 kg/m³ and that two thirds of the samples had a density between 733.2 and 841.3 kg/m³, that is, plus and minus one standard deviation. The correlation is most accurate when the values of the variables to be used in the equation are within one standard deviation of the mean, but is useful up to two standard deviations of the mean. The use of this correlation may be applicable to other hydrocarbon distillates similar to aviation fuels, but only limited data on nonaviation fuels were included in the correlation.

Hydrogen content is required to correct gross heat of combustion to net heat of combustion. Net heat is used in aircraft calculation because all combustion products are in the gaseous state, but experimental methods measure gross heat.

1.1 This test method covers the estimation of the hydrogen content (mass percent) of aviation gasolines and aircraft turbine and jet engine fuels.

1.2 This test method is empirical and is applicable to liquid hydrocarbon fuels that conform to the requirements of specifications for aviation gasolines or aircraft turbine and jet engine fuels of types Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7, and JP-8.

Note 1—The procedure for the experimental determination of hydrogen in petroleum fractions is described in Test Methods D1018 and D3701.

Note 2—The estimation of the hydrogen content of a hydrocarbon fuel is justifiable only when the fuel belongs to a well-defined class for which a relationship among the hydrogen content and the distillation range, density, and aromatic content has been derived from accurate experimental measurements on representative samples of that class. Even in this case, the possibility that the estimates may be in error by large amounts for individual fuels should be recognized. The fuels used to establish the correlation presented in this test method are defined by the following specifications: