What is the most frequent defect found in the combustion section of a turbine engine?

• A. Cracking
• B. Erosion
• C. Coking
• D. Corrosion

Answer: (A)

Extreme heat and rapid temperature changes in the combustion chamber drive thermal fatigue cracking. The combustor area is exposed to very high gas temperatures and experiences sharp thermal gradients during starts, shutdowns, and varying power settings. This causes parts like liners, transition ducts, and burner hardware to expand and contract repeatedly. Those cycles create stresses that concentrate at welds, cooling holes, joints, and other geometric discontinuities, allowing microcracks to form and then propagate over time. That repeated cycle is what makes cracking the most common defect in this section.

Erosion, while present, is more tied to particle impact and flow direction on surfaces that are exposed to particulates and high-velocity gas streams; it’s not as universally dominant as thermal-fatigue cracking in the combustion region. Corrosion requires specific aggressive environments that aren’t as consistently present across all combustor areas, and coking depends on fuel composition and local rich zones, which can be sporadic. The pervasive, cycle-driven stress fatigue explains why cracking tops the list of frequent defects here.