= Perumal Shanthakumaran
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<Perumal Shanthakumaran> is an engineer whose documented work includes rotorcraft monitoring and <condition-based maintenance>. His2010 author biography identifies him as a technical fellow at Boeing Rotorcraft-Mesa, with training in aerospace engineering and mechanics/structures, and describes his leadership of helicopter condition-monitoring work at that time.<Gear Fault Detection Effectiveness as Applied to Tooth Surface Pitting Fatigue Damage by David G. Lewicki and others>[Gear Technology version, November/December2010, author biography, printed p.59]{ref}
Shanthakumaran coauthored the gear-pitting investigation with <David G. Lewicki>, <Paula J. Dempsey> and <Gregory F. Heath>. The work tested whether vibration and oil-debris indicators tracked observed <gear surface pitting>, rather than assuming that one indicator would work equally well for every damage pattern. The inspection history supplied a physical basis for judging detection performance.<Gear Fault Detection Effectiveness as Applied to Tooth Surface Pitting Fatigue Damage by David G. Lewicki and others>[NASA report, printed pp.1–5, apparatus, damage observations and indicator comparisons]{ref}
This is a practical problem in <condition-based maintenance>: a measured change must be related to component condition while accounting for changes in load, speed and the measurement path. For a simple linear measurement model, $X(\omega)=H(\omega)F(\omega)$, so a20% rise in vibration amplitude can result from a20% change in forcing at fixed <frequency response>, or from the response path changing at fixed forcing. It is not a unique measure of damage. Comparing a <gear vibration spectrum> with inspections and a different physical channel, such as metallic debris in the oil, makes the interpretation more testable. The coauthored study investigated those complementary channels in a controlled endurance-test dataset.
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