This International Standard describes a procedure for the estimation of the net specific energy of aviation turbine fuels using hydrogen content data. It is not applicable to pure hydrocarbons. The method is purely empirical and is applicable only to liquid hydrocarbon fuels derived by normal refining processes from conventional crude oil which conform to the requirements of specifications for aircraft turbine and jet engine fuels of limited boiling ranges and compositions. NOTE 1 The method is intended for use as a guide in cases where an experimental determination of net specific energy is not available and cannot be made conveniently, and where an estimate is considered satisfactory for specifications and similar purposes. It is not intended that estimated values of the net specific energy be used in place of experimentally determined values. NOTE 2 The estimation of the net specific energy of hydrocarbon fuel from its sulfur content, hydrogen content and density is justifiable only when the fuel belongs to a well-defined class for which a relationship between net specific energy and sulfur content, hydrogen content and density has been derived from accurate experimental measurements on representative samples of this class. Even in this class, the possibility that the estimates can be in error by large amounts for individual fuels must be recognized. NOTE 3 The fuels used to establish the correlation presented in this International Standard are defined in annex A.