A rare but persistent aviation hazard — icing from supercooled large droplets — has prompted NASA to expand its testing capabilities at the Glenn Research Center in Cleveland. The phenomenon occurs when aircraft pass through clouds containing unusually large water droplets that remain liquid below freezing temperatures until striking an aircraft surface, where they rapidly freeze and accumulate ice. These droplets, exceeding 2,000 microns in diameter, can bypass standard ice protection systems, particularly on aft-facing components.

Current industry engineering tools, designed for typical cloud conditions with droplets between 2 and 100 microns, lack validation for interactions with these oversized droplets. To address this gap, NASA researchers have upgraded the Icing Research Tunnel with advanced measurement probes capable of detecting droplets larger than 45 microns and analyzing their size distribution in real time. Data from these instruments will be combined with measurements from complementary sensors to create a complete spectrum of droplet sizes present during tests.

The initiative supports the Subsonic Flight Demonstrator project under NASA’s Research and Technology Mission Directorate. Engineers emphasize that while supercooled water is common in clouds, the specific behavior of large droplets during flight requires targeted study to improve predictive models. Results from the ongoing test campaign will be shared with the aerospace industry upon completion, aiming to refine design standards for aircraft operating in cold-cloud environments.