Describe how compressor and turbine blade height (airfoil) inspection is performed and common defects found.

• A. Check only blade weight.
• B. Compare blade color to standard.
• C. Visual and borescope for cracks; NDT as needed; inspect for erosion, cracking, coating loss, and tip rub damage; verify with OEM tolerances.
• D. Measure only blade tip thickness.

Answer: (C)

Compressor and turbine blade height inspection relies on a combination of surface checks and nondestructive evaluation to confirm the airfoil remains within geometry and free of damaging flaws. Start with a visual check of the airfoil for obvious wear, then use a borescope to view along the blade path for cracks, corrosion, or other anomalies not visible on the exterior. If concerns arise, apply nondestructive testing as needed (such as dye penetrant or eddy current) to detect subsurface flaws. Look for erosion on the leading edges and other surfaces, cracking in the airfoil or at the root, coating loss that reduces protection, and any tip rub damage from contact with adjacent components. Finally, verify blade height and other critical dimensions against OEM tolerances to decide if the blade is acceptable, repairable, or must be rejected.