NASA tests new probes for supercooled droplet icing

NASA is testing new probes in its Icing Research Tunnel at the Glenn Research Center in Cleveland to help aviation engineers deal with a rare but real hazard: supercooled large droplet icing.

The problem happens when an aircraft flies through a cloud that contains unusually large, very cold water drops that are still liquid. Normal aircraft ice-protection systems are designed for droplets 2 to 100 microns wide — roughly the thickness of a human hair (about 70 microns). But supercooled large drops can be up to 2,000 microns across, big enough that you may have encountered them on the ground as freezing rain.

These oversized droplets can strike areas behind the protected surfaces, freezing where standard equipment doesn't reach.

Current engineering tools model typical icing well, but NASA says engineers have questions about how well those tools handle the physics of these larger drops. So NASA is upgrading the equipment that generates and measures experimental clouds in the tunnel.

New probes can detect drops larger than 45 microns in real time and analyze their sizes. NASA will combine those results with data from a different probe that measures droplets smaller than 45 microns, giving a complete picture of the droplet size spectrum.

The work is part of NASA's Subsonic Flight Demonstrator project under the agency's Research and Technology Mission Directorate. Once the analysis is complete, NASA plans to share the results with the broader aerospace community.

• aviation safety
• Glenn Research Center
• icing
• Icing Research Tunnel
• NASA
• supercooled droplets