Effective Date: 22 June 98
Fuel Sample Analysis Propulsion performance testing will be conducted using Jet-A commercial specification aviation turbine fuel. Analysis of this fuel, from the performance standpoint, consists of determining the heating value, and the specific gravity- temperature relationship. During the engine performance phase of the testing, fuel samples will be taken and analyzed approximately every flight. The lower heating value (LHV) of the fuel sample will be determined using a Bomb Calorimeter using the 1969 ASTM Test Method D240-672. This analysis may be accomplished by an independent testing laboratory.
Fuel samples will be analyzed periodically to obtain statistical information on the specific gravity-temperature relationship, which is required to calculate fuel flow. The specific gravity- temperature relationship is determined by measuring the specific gravity of the fuel, using a Psycnometer, at various fuel temperatures. The results of each sample analysis are plotted as shown in Figure 1. This information can be converted to the change in density per change in temperature (dRho/dT) using the constants to convert specific gravity to density.
Prior to each performance test flight, the specific gravity and fuel temperature will be obtained from a fuel sample from the airplane. A hydrometer calibrated to 60 Deg F will be used, and the specific gravity reading will be corrected to 60 Deg F using the standard tables. This data point should fall on the specific gravity-temperature line generated from analysis of previous fuel samples. If this data point does not fall on the line (due to a new fuel batch, for example) or if there is more than one slope, the slope adjacent to the preflight sample will be used in computing fuel flow for that test.