What is blade root dovetail retention and why is it critical?

• A. It seals the blade root to prevent leakage of cooling air.
• B. It provides the blade tip with a curved shape for aerodynamics.
• C. It securely locks the blade to the disk; proper fit prevents blade release under high loads and temperatures.
• D. It sets the blade crack propagation direction for maintenance.

Answer: (C)

Blade root dovetail retention is the mechanism that keeps the turbine blade securely attached to the disk. The dovetail geometry provides a positive lock and a clear load path so that the blade can carry centrifugal and thermal loads into the disk without moving or pulling out, even under high rotational speeds, temperature, and vibration. Proper fit ensures correct alignment and transfer of forces between blade and disk, preventing blade release and reducing the risk of blade-out failures. This retention also helps maintain the required clearance and prevents rubs at the root under thermal growth differences.

Sealing cooling air, shaping the blade tip for aerodynamics, or directing crack propagation for maintenance are not what this feature governs.