HIWC 2022

Since the 1990's, a significant number of engine power loss/damage events (>174) and air data probe anomalies occurred on transport airplanes while flying in or near deep convective clouds where high concentrations of ice crystals may have been encountered. To address the aviation hazard, international teams from industry, regulators, and science agencies set out to characterize the environment through a series of flight campaigns with instrumented research aircraft to develop and assess new atmospheric ice crystal icing envelope conditions for engine and air data probe certification. Prior to 2018, three flight campaigns were conducted.  Two High Altitude Ice Crystal-High Ice Water Content (HAIC-HIWC) flight campaigns (Darwin, Australia, January – March 2014 and Cayenne, French Guiana, May – June 2015) using the French SAFIRE Falcon 20, and a NASA/FAA High Ice Water Content (HIWC) RADAR I (Ft Lauderdale, FL, August 2015) using the NASA DC-8. Data from these three flight campaigns were analyzed and reported in the FAA technical report TC-18/1. In August 2018, NASA and the FAA conducted the HIWC RADAR II flight campaign with a primary objective to verify a newly developed radar processing method for identifying regions of high ice water content to enable avoidance.

Later In 2018, an Aviation Rulemaking Advisory Committee (ARAC) Ice Crystal Icing Working Group (ICIWG) was convened to assess the ice crystal icing atmospheric envelopes that were defined in the 14 CFR, part 33, Appendix D and the European CS-25, Appendix P. The assessment relied on the data reported within FAA TC-18/1 report, which identified specific gaps in the global representativeness of the data. One gap was the dataset was primarily collected in regions of low aerosol.  A 1st order hypothesis indicated that deep convection in regions of high anthropogenic aerosols may have higher ice water content than in regions of low aerosols by reducing or cutting off warm rain below the freezing level. To determine the effects of aerosol on the IWC 99th percentile values, the ICIWG recommended that NASA and the FAA conduct another HIWC flight campaign in regions of high anthropogenic aerosols.

The FAA, NASA and Nagoya University conducted the HIWC-2022 flight campaign in July 2022 using the NASA DC-8 to collect in-situ HIWC and aerosol measurements in environments expected to have high aerosols off the east and southern coasts of the United States. The campaign also included flights in varying development stages of towering cumulus (TCu) environments. Ten research flights were completed. Post flight assessment indicated that 8 flights were in low aerosol; 1 flight was in high aerosol and 1 flight was dedicated to collecting aerosol effects on TCu.