TM 1-1500-20423-3
Table 2-3. Visual Contaminant Characteristics
Type contaminants
Appearance
Characteristics
Water
Dissolved water
Not visible.
Fresh water only. Appears as
cloud when fuel is cooled.
Free water
Light cloud; heavy cloud;
Free water may be saline water
droplets adhering to sides
or fresh water.
Cloud usually in-
of bottle or gross amounts
dicates water-in-fuel emulsion.
settled in bottom.
Particulate Matter
Rust
Red or black powder; rouge,
Red rust - non-magnetic
or grains.
May appear as Black rust - magnetic
dye-like material in fuel.
Most particulate matter is
generally rust.
Grit, sand, or rust
Crystalline, granular or
Usually present in main fuel
glass-like.
filter or fuel inlet strainer
and servo supply filter.
Occasionally constitutes major
constituent.
Aluminum or magnesium
White or gray powder or
Sometimes very sticky or gela-
compounds
paste.
tinous when wet with water.
Usually present and occasionally
represents major constituent.
Microbiological
Growth
Red-brown, gray, or black.
Usually found with other
Stringy or fibrous.
contaminants in the fuel. Very
light weight; floats or swims in
fuel longer than water droplets
or solid particles. Develops
only when free water is present.
Emulsions
Water-in-fuel emulsions
Light cloud; heavy cloud.
Finely divided drops of water in
fuel. Same as free water cloud.
Will settle to bottom in minutes,
hours, or weeks depending
upon nature of emulsion.
2-4
