Borescope inspection in gas turbine maintenance is primarily used to:

• A. It is used to measure turbine rotor speed.
• B. It is a visual inspection using a flexible borescope to evaluate internal components (compressor, combustor, turbine) for damage, wear, or deposits.
• C. It calibrates fuel control systems.
• D. It tests lubrication oil viscosity.

Answer: (B)

Borescope inspection is a visual inspection of the engine’s interior using a long, slender optical probe. Its main purpose is to examine internal components—the compressor, combustor, and turbine—for damage, wear, or deposits without fully disassembling the machine. This allows technicians to spot issues such as blade damage, cracks, fouling, foreign object damage, and hot spots, guiding maintenance decisions like cleaning, repairs, or more extensive disassembly if needed. It isn’t used to measure rotor speed, calibrate fuel control systems, or test lubrication oil viscosity, which rely on other specialized tools and procedures.