What is a borescope inspection of an APU and when is it performed?

What is a borescope inspection of an APU and when is it performed?

• A. A surface external inspection using a borescope
• B. A visual internal inspection of turbine/compressor passages via a borescope; performed during major overhauls or when internal damage/deposits are suspected
• C. A diagnostic test of electrical systems in the cockpit
• D. A routine leak check of fuel lines

Answer: (B)

An internal visual check of the APU using a borescope examines the inside of the turbine and compressor passages through a small access port. The goal is to look for wear, cracks, fouling, corrosion, or foreign deposits that you can’t see from the outside. This inspection is typically done during major overhauls when the unit is opened up, or whenever there are symptoms or evidence suggesting internal damage or deposit buildup. It’s not for external surfaces, not for electrical cockpit diagnostics, and not a routine fuel-line leak check.

An internal visual check of the APU using a borescope examines the inside of the turbine and compressor passages through a small access port. The goal is to look for wear, cracks, fouling, corrosion, or foreign deposits that you can’t see from the outside. This inspection is typically done during major overhauls when the unit is opened up, or whenever there are symptoms or evidence suggesting internal damage or deposit buildup. It’s not for external surfaces, not for electrical cockpit diagnostics, and not a routine fuel-line leak check.