In-Cloud Icing and Large-Drop Experiment (ICICLE). Part I: Overview

The Federal Aviation Administration recently sponsored a flight program, the In-Cloud ICing and Large-drop Experiment (ICICLE). The ICICLE program was conducted in support of two FAA aircraft icing research projects: the Terminal Area Icing Weather Information for NextGen (TAIWIN) project and the In-Flight Icing (IFI) project. TAIWIN is focused on terminal area icing, working to develop a diagnosis and forecast capability that will provide discrimination of icing conditions at high spatial and temporal resolution within the terminal area. IFI is focused on en-route icing, working to improve operational national-scale icing products, such as the Current Icing Product (CIP) and Forecast Icing Product (FIP). A specific challenge for the TAIWIN and IFI projects is obtaining a high-quality validation dataset that distinguishes between icing environments critical to aircraft operations, both at the surface and aloft. This includes discriminating between small-drop icing, large-drop icing and its subsets (freezing drizzle vs freezing rain), and other icing and non-icing environments. As a result, a need for a robust dataset to support the evaluation and development of icing weather tools was identified by both projects.

To address this need, the FAA planned the ICICLE program with other key participants, including the National Research Council of Canada (NRC), the Environment and Climate Change Canada (ECCC), and the National Center for Atmospheric Research (NCAR). Objectives were developed and a wide variety of environments targeted. The NRC Convair-580 was deployed to Rockford, Illinois for approximately 6 weeks, from January through March, 2019. The aircraft was heavily instrumented with microphysical probes, remote sensing instruments, ice detectors, and state and aircraft parameter sensors. To complement the airborne measurements, surface-based instruments were also deployed at five locations across the domain. An overview of the flight program mission and a summary of the 26 ICICLE research flights will be presented. This presentation will be supplemented by two other presentations, one relating to the ICICLE Airborne Measurements and another to the ICICLE Supplemental Datasets.

This research is in response to requirements and funding by the FAA. The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA.