trailing edge). These curled tips are usually smooth in
the bend area of the airfoil distortion. However, you
should inspect the area at the change in normal airfoil
for tears or cracks. When you report tip curl, estimate
the percent of the chord length, the number of blades
with curl, and the condition of the adjacent airfoil area.
Record any evidence of impact and inspect for the origin
of the impact. Always look at the adjacent blades for
evidence of tip clang.
Missing Metal.— Missing metal from compressor
rotor blade airfoils is a result of the progression of
cracked or tom airfoils that release part of the airfoil into
the flow path. Crack propagation in the root fillet area
can result in the separation of the entire blade. Severe
FOD or DOD may result in several random rotor and
stator airfoils with missing metal. The inspection report
should include the stage, the number of blades with
missing metal, the amount, and the location on the
airfoil. Estimate the percent of chord, the span of the
airfoil that is missing metal, and the condition of the
remaining airfoil.
Airfoil Surface Defects.— Surface defects are the
result of object damage or adjacent blade interference
(tip clang). Impacts in the center section of the airfoil
are not common. Tip clang damage is the result of a
blade leading edge tip contacting the adjacent blade tip
at approximately one-third of the chord length forward
of the trailing edge on the low-pressure (convex) side of
the blade (fig. 2-13). This is the result of compressor
stall and is observed in stages 3 through 6. You should
report any observed defect on the airfoil surfaces in the
inspection record.
Your report should contain
Figure 2-13.—Compressor rotor blade tip clang damage.
2-12
