Summary

There have been at least 200 engine icing events involving transport aircraft in HIWC (High Ice Water Content) ice crystal environments over the last several years, and these events continue to occur at the rate of as many as 10 per year. These events include power-loss events and/or damage events, where a power-loss event is a surge, stall, rollback, or flameout of one or more engines. There is a current lack of knowledge on the ice crystal properties and the atmospheric processes of ice crystal formation and extinction. Flight research has been conducted to evaluate HIWC ice crystal engineering standards to develop simulation methods for ground testing and computational modeling and to develop ice crystal weather forecast and diagnostic products that can mitigate the operational threat. A major goal of the flight research is to identify the atmospheric characteristics of HIWC ice crystal convective weather environments and to use this information to develop weather tools and simulation methods that provide safer operations. The FAA has joined with partners in the U.S., Canada, and Australia in forming the High Ice Water Content (HIWC) ice crystal project to address these needs, among others. HIWC collaborated with the European High Altitude Ice Crystal (HAIC) project, and successfully completed two campaigns, Darwin January – March 2014 and Cayenne May – June 2015. A third campaign, RADAR I, was led by NASA in August 2015 in Florida that focused on the collection of data to (1) investigate the suitability of current on-board weather radar for detection and avoidance of potentially hazardous high ice water content ice crystal conditions; and (2) add to data collected from other sources for research purposes. A fourth campaign, RADAR II, led by NASA but heavily supported by the FAA, occurred in August 2018 in Florida, California, and Hawaii. This field campaign extended upon the 2015 Florida campaign, evaluating the ability of a modified airborne weather radar to detect and identify HIWC conditions. Particle Size Distribution (PSD) data collected was processed by NCAR and used in analyses and subsequent comparisons to previously collected HIWC PSD data. The FAA and NASA, along with the University of Nagoya, are planning another flight campaign for July 2022 to collect in-situ HIWC and aerosol measurements in an environment that is expected to have high aerosols off the east and southern coasts of the United States. PSD data will again be collected and need processing.