C. Other environmental factors are readily controllable by the operator, such
as the salt-laden atmosphere in marine locations or the airborne pollutants
of industrial areas. In these circumstances, inspection and corrosion pre-vention frequencies become a variable.
2. Environment
A. Actual assessments of environmental conditions have to be made Locally by
the operator. The environment is a combination of many factors and some of
those which should be considered are as follows:
(1)Marine atmosphere -Areas adjacent to salt water normally result in an
atmosphere containing salt particles or salt saturated moisture. The
degree of salinity of the body of water, temperature and the direction
of the prevailing winds create wide variations in the corrosive proper-ties of the atmosphere in coastal regions. It must be remembered that
salt water is an excellent medium for the promotion of electrolytic cor-rosion.
(2)Contaminated atmosphere -In industrial areas the atmosphere usually
contains pollutants. There pollutants combine with water to form highly
corrosive liquids, for example, sulphur compounds are frequently found,
which form sulphur based acids. This can be an even greater hazard when
the prevailing winds carry pollutants from a nearby industrial plant to
the airplane parking area.
(3)Rainfall -Moderate rainfall in temperate or cold climates does not con-stitute an environmental problem. Heavy rainfall or hail can result in
damage to the finish which will help to initiate corrosion. Tropical
rains result in a hot, humid atmosphere which promotes corrosion. Refer
to the subparagraphs on relative humidity and heat.
(4)Relative humidity -High relative humidity coupled with high temperature
results in a water-saturated atmosphere in the airplane while on the
ground. After takeoff, condensation occurs providing the medium for the
onset of corrosion. High humidity at lower temperatures is less of a
problem, while ideal conditions are those with a Low relative humidity.
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20-30-00
Page 1 OCT 01/01
(5)Temperature -High temperature and low humidity are the best conditions
because any moisture in the airplane is dried out. Similarly, an
extremely cold atmosphere is also usually dry. However, combinations of
high temperature and high humidity provide the least desirable environ-ment from the corrosion standpoint.
(6)Runway conditions -Airplanes operating from gravel, dirt or grass run-ways or from runways treated with sodium chloride for ice removal are
exposed to adverse conditions due to deterioration of the finish and the
deposit of corrosive materials.
(7)Operating altitude -Airplanes operating at relatively low altitudes are
obviously exposed to a greater extent to airborne pollutants and a
marine atmosphere than airplanes operating at higher levels.
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