FAA Powerplant Written Practice Test

Where do stress rupture cracks on turbine engine blades typically appear?

1. At the blade root

2. Along the leading edge or trailing edge

3. On the flat surfaces of the blades

4. At the tip of the blade

The correct answer is: Along the leading edge or trailing edge

Stress rupture cracks on turbine engine blades typically appear along the leading edge or trailing edge due to the high-temperature and high-stress conditions these areas experience during operation. The leading and trailing edges of turbine blades are subjected to significant aerodynamic forces and thermal stresses, making them more susceptible to fatigue and eventual cracking. These blades operate under extreme conditions, and the materials used are often pushed to their limits. As a result, cracks can initiate in these regions, where the concentration of stress is higher. This is critical to understand, as identifying the location of potential stress rupture cracks enables maintenance personnel to conduct more effective inspections and ensure the integrity of the turbine blades. Understanding the mechanics at play, including the effects of thermal cycles and material properties at elevated temperatures, further clarifies why these specific areas are prone to stress rupture cracking.