Health monitoring and prognostics of blades and disks with blade tip sensors

Blade tip sensors embedded in the engine case have been used for decades to measure blade tip clearance and blade vibration. Many sensing technologies have been used: capacitive, inductive, optical, microwave, infrared, eddy-current, pressure and acoustic. This paper outlines the technology of blade and disk health monitoring with such sensors. The basic measurement techniques are reviewed, along with damage signatures which might be recognized with such sensors. The compromise between system complexity (in terms of sensor count) and data quality is discussed