FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesEasy
A mechanic removes a compressor rotor blade from its disc slot and notices the blade root is machined into a wedge-shaped, serrated profile that matches a corresponding slot in the disc rim. What type of blade attachment is this?
- AShrouded tip attachment
- BWelded root attachment
- CBolted flange attachment
- DFir-tree or dovetail attachment
Show answer & explanationAnswer & explanation
Correct answer: D. Fir-tree or dovetail attachment
Compressor and turbine blades are commonly retained by fir-tree or dovetail root designs that slide into matching disc slots, allowing individual blade replacement while securely transferring centrifugal loads to the disc.
Why the other options are wrong
- A. Shrouded tips are at the blade tip, not the root attachment.
- B. Welding would prevent individual blade removal, unlike this design.
- C. Blades are not bolted; this describes a different type of joint.
Fir-Tree/Dovetail Blade Root
A serrated, wedge-shaped blade root that slides into a matching disc slot, securing the blade against centrifugal loads while allowing removal for maintenance.
- Used on compressor and turbine blades
- Transfers centrifugal load to disc
- Allows individual blade replacement
- Common shapes: fir-tree, dovetail
Memory trick: Fir-tree root = a pine tree locked into the disc