Borescope, boroscope or endoscope: the right word and the right tool

The words

• Borescope: an optical instrument for looking inside a machine through a small opening — a bore. Rigid or flexible. This is the term in the AMM, and "BSI" means borescope inspection.
• Boroscope: the same word, spelled by ear. Common enough that we use it once on every page so people find us; it does not appear in any manual.
• Endoscope: the medical cousin. Industrial endoscopes exist, but a hospital endoscope is not built for a hot gas path and has no measurement.
• Fiberscope: a flexible borescope that carries the image through a fibre-optic bundle. Older technology; the image is a honeycomb of fibres.
• Videoscope (video borescope): a flexible borescope with a camera chip in the tip and a screen at the other end. This is what engine inspections use today.

What an engine inspection needs

A flexible videoscope with an articulating tip, a diameter that fits the engine's ports (commonly 4 mm or 6 mm), enough length to reach the stages, a light source that copes with dark turbine hardware, and recording of stills and video. The feature that separates a maintenance tool from a camera on a stick is measurement: stereo or phase-shift tips that size a crack, a dent or a missing corner in millimetres, because the AMM limit is a number and the inspector has to compare against it.

Rigid or flexible

Rigid borescopes give the sharpest image in a straight line and are used where access is direct. Engine gas paths twist around blades and vanes, so almost all engine work is done with a flexible, articulating videoscope, sometimes with a guide tube to steer the tip through the port.

Why the tool shows up in the report

A good report names the instrument, the tip and the measurement method, because a finding sized with a measurement tip carries more weight than one estimated by eye. InspectView records the equipment with the inspection so the report is complete without retyping.