This information report provides a review of liquid drop and ice crystal particle sizing instruments used for facility based icing research and in-flight testing commonly used for aircraft certification icing envelopes. This report will provide an overview of the theory of operation of these instruments and practical considerations when using them for cloud characterization. Methods in use for data reduction (including combining output from multiple probes) as well as potential error sources are provided for information. Measurement methods from prior revisions of this AIR that are no longer commonly used (e.g. oil slides and rotating cylinders) will be retained for reference. This document does not include other icing cloud measurements such as liquid or total water contents, or measurement of other types of phenomena such as snow, sleet or hail.
The prior version of AIR4906 contains a review of icing instruments used in research facilities as available circa 1995. This revision will contain technology updates and expands the scope to include new environments driven by new regulatory requirements as well as expanded requirements for testing in facilities and in-flight.