The Measurement of Water Film Thickness on Airfoils in Heavy Rain Conditions Using Conductance Sensors

Calibration results of liquid film thickness using electric conductance sensors are presented. Two sensor types are analyzed. First, a double electrode sensor whose calibrations compensate liquid conductivity and secondly, a triple electrode sensor that, when properly calibrated, also compensates capacitive effects. For this second type, the electrolytic effects can also be corrected without excessive errors. Tests conducted on a large-scale airfoil under simulated heavy rain conditions, at NASA Langley Research Center are described, and the film thickness that develop, measured.