Ice Protection System Guards Against Super-Cooled Water Droplets

Pilots operating aircraft into known icing conditions must always guard against an encounter with super-cooled large water droplets (SLD), blotches of water that exist in a liquid state until they strike something solid, such as an airframe, and turn to ice. SLDs were virtually unknown until they were blamed for the 1994 crash of an ATR72 southeast of Chicago. Pilots today consider SLDs to be the worst creators of airframe icing.

CAV Ice Protection recently announced SLD Guard, an anti-ice system designed to meet new FAA aircraft SLD certification regulations that took effect a year ago. The SLD Guard system is designed to allow aircraft that encounter severe freezing rain and freezing drizzle to safely exit these icing conditions.

SLD Guard uses thin titanium strips less than an inch wide installed in the upper wing surfaces ahead of ailerons, as well as upper and lower surfaces on the horizontal stabilizer, preserving natural laminar flow. The strips perform as both a de-ice and anti-ice system by dispensing an ethylene glycol-based fluid, with a freezing point below minus 70 degrees F, from thousands of .0025-inch laser-drilled holes in each strip. Natural airflow over the wings disperses the fluid.

SLD Guard can be retrofitted into any existing ice protection system including pneumatic boots, thermal, expulsive and freezing point depressants. It can also be incorporated into new aircraft designs regardless of the primary ice protection system technology selected by the manufacturer, the company says.