Evaluating Physical Size
Figure 2-31.—Power turbine shroud wear.
You determine physical size in several ways. By
using dimensional data in the manufacturer’s technical
manual, you can estimate size by making a comparison
to a known dimension in the field of view. Another way
you can evaluate size, particularly in regard to cracks, is
to use a lockwire of a known diameter. The lockwire is
inserted into the field of view and placed next to the
crack for size comparison. When using this method, you
should be sure that the lockwire cannot fall inside the
engine. Using an absolute reference for size, such as the
lockwire or a known dimension, is more reliable than
estimating the size through a borescope.
Color Evaluations
During inspections, you can observe deposits or
various forms of deterioration. Table 2-3 is an engine
color chart that lists the color of common deposits and
Table 2-3.—Engine Condition Color Chart
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