Why are borescope inspections used in APU maintenance?

• A. To inspect internal components for wear or damage without disassembly.
• B. To measure oil depth.
• C. To check external paint.
• D. To calibrate sensors.

Answer: (A)

Borescope inspections provide a visual look inside the APU to check internal components for wear, damage, or abnormalities without disassembling the unit. In an APU, parts like bearings, gears, turbine blades, and cooling or oil passages sit in confined spaces behind housings, so they aren’t visible from the outside. A borescope—a slim probe with a camera and light at the tip—can be inserted through service ports to inspect surfaces for scoring, cracks, corrosion, fouling, or foreign-object damage, and to verify lubrication routes and clearances. This approach lets technicians detect issues early, plan the appropriate maintenance, and reduce downtime because a full teardown isn’t always needed. Other tasks such as measuring oil depth, checking external paint, or calibrating sensors use different tools and procedures, not a borescope.