NASA Upgrades Cleveland Icing Tunnel to Measure Supercooled Droplet Hazards

NASA researchers at the Glenn Research Center in Cleveland are conducting a series of tests in the facility's Icing Research Tunnel to evaluate supercooled large droplet icing, a rare atmospheric condition that can deposit ice beyond standard airframe protection zones, as reported by TechXplore (https://techxplore.com/news/2026-10-tunnel-track-large-supercooled-droplets.html).

Supercooled water forms when cloud droplets cool below 32 degrees Fahrenheit (0 degrees Celsius) without freezing, solidifying only upon encountering dust particles or physical structures. Standard aircraft systems are built to handle typical cloud droplets ranging from 2 to 100 microns in diameter—a human hair averages roughly 70 microns. However, certain conditions produce supercooled large droplets measuring up to 2,000 microns across, similar to freezing rain at ground level. Due to their mass, these larger drops can splash farther aft onto airframe surfaces situated behind conventional ice protection hardware.

Aviation design tools model conventional cloud physics well, but engineers lack complete empirical data on the behavior of supercooled large drops. To improve these design models, NASA updated its experimental cloud generation and measurement hardware in the Cleveland tunnel.

The research team deployed new probes capable of detecting droplets larger than 45 microns and calculating their dimensions in real time. NASA is comparing these automated readings against a more time-intensive process that relies on post-processing image data captured inside the tunnel. When combined with data from a separate probe that measures droplets under 45 microns, the combined setup captures the full droplet size spectrum.

The test campaign marks a milestone for the Subsonic Flight Demonstrator project within NASA's Research and Technology Mission Directorate. Detailed data analysis remains underway, and the project team plans to release its findings to the broader aerospace industry once the evaluation concludes.