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The National Research Council Altitude Icing Wind Tunnel liquid water content calibrations have historically relied on a 2.4 mm diameter rotating cylinder for drop sizes up to 50 μm and a 6.2 mm diameter rotating cylinder for drop sizes from 50 μm to 200 μm. This study compares the facility calibration, derived from rotating cylinder measurements, to water content measurements from the Science Engineering Associates Multi-Element Probe and the National Research Council Compact Iso-Kinetic Probe over a range of airspeeds and drop sizes. The data show where the rotating cylinder measurements may start to underestimate the liquid water content (LWC), possibly due to splashing at higher airspeeds and drop sizes. The data also show that the LWC read by the Multi-Element Probe is higher than that provided by the rotating cylinders, and the Compact Iso-Kinetic Probe (CIKP) reads higher than both other methods.

As a result of new regulations pertaining to the airworthiness of aircraft exposed to in-flight icing conditions where maximum water drop size is greater than 100 microns (referred to as Supercooled Large Droplet (SLD) conditions), updates are required to the test facilities and simulations that will enable manufactures to certify their products under these new rules. While a number of facilities report achieving some of the conditions specified in the new regulations, questions remain as to the suitability of the instrumentation used to measure the Liquid Water Content (LWC) and drop size distributions of the SLD icing cloud. This study aims to provide baseline LWC data through ice accretion measurement techniques on a NACA 0012 airfoil and rotating cylinders of varying diameters.