Visual Contaminant Characteristics -cont

TM 1-1500-204-23-3 Table 2-3. Visual Contaminant Characteristics - CONT Type contaminants Appearance Characteristics Emulsions - continued Fuel and water or Reddish, brownish, grayish, Finely divided drops of fuel in stabilized or blackish. Sticky material water. Contains rust or micro- emulsions variously described as biological growth which stab- gelatinous, gummy. lizes or firms-up the emulsion. Will adhere to many materials normally in contact with fuels. Usually present as globules or stringy, fibrous-like material in clear or cloudy fuel. Will stand from days to months without separating. This material con- tains half to three-fourths water, a small amount of fine rust or microbiological growth and is one third to one half fuel. Miscellaneous Interface material Lacy bubbles or scum at Extremely complicated chemi- interface between fuel and cally. Occurs only when emul- water. Sometimes resembles sion and free water is present. jellyfish. Air bubbles Cloud in fuel. Disperses upward within a few seconds. Insects Specks in fuel. Float on top, within fuel, or settles to bottom. Figure 2-2. Micron Particle Size c. Microbiological Growths. Microbiological growth is growth of living organisms (protozoa, fungi, or bacteria) at the interface between fuel and water wherever there are pockets of water in fuel tanks. If there is no water in the fuel, microbes cannot grow. The growth is brown, black, or gray and looks stringy or fibrous. Microbiological growth contaminates fuel and causes problems because the organisms hold rust and water suspended in the fuel and act as stabilizing agents for fuel/water emulsions. These suspensions cling to glass and metal and can cause false, fuel-quantity readings. They also make fuel controls operate sluggishly and make fuel flow-dividers stick. Microbiological growth in aircraft fuel is a reliable indication that the fuel filters have failed, that the water has not been properly stripped from the fuel, or that the fuel storage tanks need to be cleaned more frequently. 2-5