Boroscope. Bore + Scope. A long skinny gadget with a lens that can be directed through small holes to visually inspect the internals of a machine, or similar. Particularly useful for inspecting rotor and stator vanes in gas turbine engines, to see what failed.
http://www.boroscope.com/
Vibration. Unless perfectly formed and perfectly in balance, spinning masses, such as gas turbine engine components, vibrate. If a gas turbine engine rotor is unbalanced, it will vibrate. Usually expressed as inches/sec. Therefore 2.8 inches/sec.
Want to know more... not a bad explanation from
http://www.patentstorm.us/patents/59...scription.html
The modern jet engine includes several concentrically mounted shafts, each rotating at a slightly different frequency. Each of the rotating shafts or spools can include a compressor-turbine assembly which in turn includes fan and turbine blades. In the intake stages the blades are used to compress incoming air, and in the output stages the blades drive the compressor.
Machinery having massive rotating components, such as jet aircraft engines, may experience shaft bearings or shaft housing failures. In addition, these rotating components may become unbalanced and impose loads upon the bearings and housing well beyond acceptable specifications. These problems may be a result of any variety of causes which include, manufacturing defects, design defects, wear, misuse, accidental damages and the like. In the case of an aircraft while in operation, failure of these engine components can lead to, not only engine loss, but catastrophic loss of aircraft.
Vibration amplitudes and patterns, induced by the rotation of jet engine sub-components, are indicative of sub-component degradation and decreased reliability. SNIP....
Thus, vibration detection is not only an invaluable safety tool used to monitor engines while in operation, but has been incorporated into scheduled engine maintenance procedures.