(8)Stage length -Frequent cycling of the airplane, especially in hot,
humid zones, will create a greater moisture buildup than can be expected
on airplanes used on long stage lengths. This is due to the airplane
being exposed to a fresh supply of water-saturated air at every landing,
which will condense out in the subsequent flight.
(9)Volcanic gases -Corrosive gases from volcanos are carried in the atmo-sphere in some regions. There is also a "fallout" zone downwind of
active volcanos which could be an undesirable element in some areas.
(10)Airborneabrasives -Blowing sand or coral dust has an erosive effect on
the finish and may find its way into the interfacing surfaces of moving
parts or into bearings. This abrasion not only creates a wear problem,
it exposes unprotected metal to corrosion. The abrasive material itself
may also be corrosive, as would be the case with sand from salt water
beaches.
B. To establish a corrosion prevention program to meet the operator's individ-ual requirement, it must first be ascertained how severe the operating envi-ronment is geographically, and then establish frequencies of inspection and
prevention procedures to suit the route structure. Three categories of oper-ating environment have been established as follows:
(1)Severe -Areas in which there is a marine atmosphere or industrial atmo-sphere containing contaminants. Hot, humid tropical areas also come
within the severe category.
(2)Moderate -Temperate regions with other than marine or industrially pol-luted atmospheres.
(3)Mild -Warm arid zones or areas subject to extremely Low temperatures.
However, the use of chemicals on runways and taxiways to prevent ice
formation may transfer cold zones to the severe category.
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C. Frequencies of inspection or corrosion prevention action throughout this
manual will be given for these three categories where the operating environ-ment is a contributing factor. The operating environment is defined as being
equivalent to the worst area of operation on the route structure on which
the airplane is being used. Thus, an airplane starting in a mild location
but flying to a severe area would be considered as operating in a severe
environment.
NOTE: Some operators chose to assign only part of their fleet to routes in
severe zones to reduce the maintenance cost on the remainder of the
fleet.
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1. General
A. When you remove corrosion, complete removal is most important. If all of the
corrosion is not removed, the corrosion will continue. For example, if you
find corrosion around fastener locations, you must remove the fastener and
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