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Figure 2-10.—Zero indexing the compressor rotor. | Up
Gas Turbine Systems Supervisor - Supervisor manual for Gas Turbine Engines | Next
Figure 2-13.—Compressor rotor blade tip clang damage. |
side of the dovetail and is leaning in the forward
direction (fig. 2-12). If a leaner is detected, it must be
verified and the engine should be removed from service.
Airfoil and Tip Tears.—The most critical area of a
torn blade is the area around the end of the tear and its
location on the airfoil. You should inspect this area for
cracks that lead from the tear and are susceptible to
propagation. This condition could lead to the loss of the
airfoil section that would create downstream impact
damage.
You should record all information such as
stage, blade locations, area of the blade in which the
defect was found, and the condition of the rest of the
airfoil and adjacent airfoils. Section A of figure 2-11
shows the nomenclature of a blade.
Leading and Trailing Edge Damage.— Random
impact damage can be caused throughout the
compressor rotor stages by FOD and DOD. The leading
and trailing edge of an airfoil is the area of the
compressor blade extending from the edge into the
airfoil. You must assess both sides or faces of the airfoil
when determining the extent of a given defect. If you
observe a defect, estimate the percentage of damaged
chord length. Observe the defect and the condition of
the airfoil area around the defect. If the observed
damage is assessed to be “object damage,” the most
difficult determination is the differentiation between
cracks, scratches, and marks made by the passing
objects. Cracks are usually tight in the airfoils, but the
apex of the damage usually allows viewing into the
airfoil thickness. This provides a direct inspection of
the area around the crack You may have to use all the
probes at varying light levels to determine the extent of
the damage.
Tip Curl.— Compressor rotor blade tip curl is a
random and infrequent observation. tip curl is usually
the result of blade rub on the compressor case. Tip curl
also can be the result of objects being thrown to the outer
circumferential area of the flow path and then being
impacted by the rotating blade tip (either leading or
Figure 2-12.—Compressor blade leaners.
2-11
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