Clogging of nozzles by carbon deposits occurred in the 1950’s in military J57 engines, so the importance of oxidation stability has been recognized for decades. The ASTM Method D 3241 – Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels (JFTOT Procedures) – has proven over 35 years of testing that it can accurately determine the relative thermal oxidative stability of jet fuels. DVI's Aviation Fuels Experts works with labs that have this test equipment.
It is also very important that jet fuel be free from water contamination. During flight, the temperature of the fuel in the tanks decreases, due to the low temperatures in the upper atmosphere. This causes precipitation of the dissolved water from the fuel. The separated water then drops to the bottom of the tank, because it is denser than the fuel. From this time on, as the water is no longer in solution, it can freeze, blocking fuel inlet pipes. There are several methods for detecting water in jet fuel. A visual check may detect high concentrations of suspended water, as this will cause the fuel to become hazy in appearance. An industry standard chemical test for the detection of free water in jet fuel uses a water-sensitive filter pad that turns green if the fuel exceeds the specification limit of 30ppm (parts per million) free water.
