Browse Publications Technical Papers 2019-01-1934

SLD and Ice Crystal Discrimination with the Optical Ice Detector 2019-01-1934

Recent years have seen increased awareness within the aerospace community of icing hazards posed by conditions beyond those described by 14 CFR Part 25, Appendix C. Engine and airframe manufacturers are now required to certify their products for operation in the presence of supercooled large droplets (SLD) and high ice water content (HIWC) conditions, or alternatively, to implement a detect-and-exit strategy. The latter option implies a need for the capability of detecting Appendix C, SLD, and HIWC conditions, and to discriminate between them. The Optical Ice Detector (OID) technology under development at Collins Aerospace provides the ability to detect and differentiate Appendix C, Appendix O, and Appendix D conditions with a compact cloud lidar system. The OID’s ability to determine bulk cloud phase and water content has been previously demonstrated. Recent development efforts have focused on expanding the OID’s capabilities to also enable differentiation between small droplet clouds and bimodal clouds such as those described by Appendix O. This is enabled through statistical analysis of ensembles of individual lidar cloud reflection signals. Combined with the large sampling volume inherent to the OID’s optical design, the new method enables rapid differentiation of Appendix O clouds from the more benign Appendix C conditions. OID prototype hardware was recently installed aboard the NASA DC-8 Airborne Science Laboratory as part of the HIWC RADAR-II flight campaign. A comparison of OID measurements to those acquired by research probes has further confirmed the OID’s ability to alert crew to the presence of hazardous HIWC conditions.


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