Analysis of Flight Test Results of the Optical Ice Detector 2015-01-2106
Cloud phase discrimination, coupled with measurements of liquid water content (LWC) and ice water content (IWC) as well as the detection and discrimination of supercooled large droplets (SLD), are of primary importance in aviation safety due to several high-profile incidents over the past two decades. The UTC Aerospace Systems Optical Ice Detector (OID) is a prototype laser sensor intended to discriminate cloud phase, to quantify LWC and IWC, and to detect SLD and differentiate SLD conditions from those of Appendix C. Phase discrimination is achieved through depolarization scattering measurements of a circularly polarized laser beam transmitted into the cloud. Optical extinction measurements indicate the liquid and ice water contents, while the differential backscatter from two distinct probe laser wavelengths implies an effective droplet size.
The OID is designed to be flush-mounted with the aircraft skin and to sample the air stream beyond the boundary layer of the aircraft. The volume of the sampled airstream is several orders of magnitude greater than that of traditional airborne cloud probes, such as the Forward Scattering Spectrometer Probe (FSSP). The OID has flown on the University of North Dakota (UND) Cessna Citation-II research aircraft in a wide variety of atmospheric conditions, which cloud probes on the aircraft have verified to corroborate the OID data. In this paper, we compare UND cloud probe measurements with those from the UTC Aerospace Systems OID to demonstrate the possibility of using the OID to meet the need for measurements of various icing parameters.