TechAlert —: (Research Reports)

Turbomachinery blade clearance and time of arrival sensors based on the Vatell eddy current principle, and suitable for operation at temperatures up to 200 degrees C, were designed, built and tested on the first fan stage of a JT15‐D. The sensors produced robust, low noise signals whose general shape is virtually independent of speed, and those amplitudes are related to speed and clearance. The signals of individual blades were readily resolved and identified.