Evaluating Physical SizeFigure 2-31.—Power turbine shroud wear.You determine physical size in several ways. Byusing dimensional data in the manufacturer’s technicalmanual, you can estimate size by making a comparisonto a known dimension in the field of view. Another wayyou can evaluate size, particularly in regard to cracks, isto use a lockwire of a known diameter. The lockwire isinserted into the field of view and placed next to thecrack for size comparison. When using this method, youshould be sure that the lockwire cannot fall inside theengine. Using an absolute reference for size, such as thelockwire or a known dimension, is more reliable thanestimating the size through a borescope.Color EvaluationsDuring inspections, you can observe deposits orvarious forms of deterioration. Table 2-3 is an enginecolor chart that lists the color of common deposits andTable 2-3.—Engine Condition Color Chart2-25
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