Damage Repairable by Insertion. Any damage that can be repaired by
cutting away the damaged part, replacing it with a like portion, and
securing the replacement with splices at each end is damage
repairable by insertion.
Damage Requiring Replacement.
Generally, damage that cannot be
repaired or is so severe that the time needed to repair it is not
warranted is classified as damage requiring replacement.
Examples
are--
A complicated part which is extensively damaged.
The surrounding structural
members
or
inaccessibility
makes
repair impractical.
The damaged part is relatively easy to replace.
Forged or cast fittings are damaged beyond negligible limits.
CORROSION CONTROL
The act or process of dissolving or wearing metal away by a chemical
action is corrosion. It can also be defined as the deterioration of
a metal by reaction to its environment.
Most metals are subject to
such deterioration; however, the reaction can be minimized by using
corrosion-resistant metals and finishes within the aircraft's design
limits. In airframe structures this is done by using aluminum alloy
sheets coated on both sides with pure aluminum (alclad).
Internal
structures are generally painted with an organic finish (carbon
base).
Cadmium or zinc plating, conversion coating, paint, or all
three are used to protect steel (except most stainless steel),
bronze, and brass.
The paragraphs that follow discuss briefly the need for corrosion
control and the kinds of corrosion. For more detail, see TM
1-1500-344-23.
Need for Corrosion Control. Without protection from corrosion, an
aircraft's capability and operational integrity are endangered. As a
result, tactical and combat service support missions cannot be flown.
Economy is another reason for corrosion control because in severe
cases corrosion can weaken primary structures sufficiently to require
their reinforcement or replacement. Either repair can be costly and
time-consuming. Moreover, aircraft effectiveness is lost.
Common Types of Corrosion.
Many ways have been used for
classifying corrosion.
For simplicity, corrosion is discussed here
under the titles most generally used.
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