Why are blade root and dovetail geometry critical in overhauls, and what inspection methods ensure compatibility?

• A. They are cosmetic features.
• B. They influence blade color.
• C. They affect boundary layer separation.
• D. They set retention, alignment, and load transfer; inspect root tangs and dovetails with visual, borescope, and dye penetrant or other NDT per OEM.

Answer: (D)

Blade root and dovetail geometry sets the retention, location, and load transfer between the blade and the disk. If this interface is out of tolerance or mismatched, the blade may not be securely held, can sit out of proper alignment, and the load path during rotation may be altered. That can lead to excessive vibration, fretting, and fatigue cracking, or even blade release under operating loads. Overhauls rely on replacing or reworking blades so their root and dovetail fit exactly with the disk geometry, ensuring correct retention, precise alignment, and proper load sharing.

To verify compatibility and detect damage, inspect the root tangs and dovetail features using approved methods: visual inspection for wear, chipping, cracks, or distortion; borescope inspection to view recessed areas and tangs; and dye penetrant or other OEM-specified nondestructive testing to reveal surface-breaking or near-surface cracks. Follow the OEM's guidance for any additional NDT like magnetic particle, eddy current, or ultrasonic testing as required.