Hot spots seen on borescope inspection indicate malfunctions in which component group?

• A. Combustion chamber lining
• B. Turbine blades
• C. Air intake filter
• D. Fuel nozzles or other fuel system malfunctions

Answer: (D)

Hot spots seen on a borescope indicate abnormal high-temperature regions in the combustion zone, which almost always point to problems with fuel delivery and combustion rather than the structure being heated. When fuel is not delivered correctly—such as a damaged or clogged fuel nozzle, improper spray pattern, or fuel-control issue—the fuel-air mixture becomes uneven. This can cause localized combustion extremes where certain areas burn hotter, showing up as hot streaks on the inspection. That’s why the fuel nozzles and other fuel system components are the most likely source of the hot spots.

Issues with the combustion chamber lining would show heat damage or wear patterns, but they don’t typically create the hot spots observed unless the combustion itself is already abnormal. An air intake filter primarily affects airflow and overall performance, not the localized hot spots caused by fuel distribution. Downstream turbine blade problems would manifest differently and are not the typical cause of hot spots in the combustion zone.