The fir tree section of a turbine blade is associated with which feature?

• A. Root
• B. Fir tree section
• C. Shank
• D. Platform

Answer: (B)

The main idea here is how a turbine blade is attached to the rotor using a fir-tree geometry. The fir-tree section is the root portion of the blade that engages with the slots in the turbine disk. This dovetail-like shape provides a secure, precisely located joint that transfers the centrifugal loads from the blade into the disk while accommodating thermal growth. It distributes stresses smoothly along the root and prevents sharp corners that could concentrate stress. So the fir-tree section is essentially the root interface—the part that mates with the rotor slots to hold the blade in place. The shank and platform are other blade regions, but they are not the primary features defined by the fir-tree geometry.