Ground Icing Operations - Deice And Anti-Ice Fluids

GROUND ICING CONDITIONS

"No pilot may take offin an aircraft that has frost, ice or snow adhering to any rotor blade, propeller, windshield, wing or stabilizing or control surface, to a power-plant installation, or to an airspeed, altimeter, rate-of-climb or flight-attitude instrument system," according to the FAA basis for the “clean-aircraft concept.”

- Richie Lengel

RELEVANT DISCUSSION: FAR 91.527, 91.1101, 121.629, 125.221, 135.227, 135.345, AIM 7-5-14, OPSPEC A023, AC 20-73, AC 20-117, AC 120-58, AC 120-60, AC 135-17, NASA

There are four standard aircraft deicing and anti-icing fluid types: Type I, II, III and IV.

Type I fluids (red-orange in color) are the thinnest of the fluids. They are essentially deicing fluids but can also be used for anti-icing. Because they’re not thickened, they will shear or blow off the airplane at relatively low airspeeds (around 60 knots). However, their low viscosity results in the shortest set of holdover times (HOT). Type I is always applied heated and diluted; it flows off easily, and can fail suddenly. Type I is available throughout the world.

Type II fluids (clear or straw color) add thickening agents to increase viscosity and provide better protection against refreezing than Type I fluids, but require a minimum 100-knot rotation speed. The thickeners allow fluid to remain on the aircraft longer to absorb and melt the frost or freezing precipitation. They’re applied when a long elapse time is anticipated between deicing and takeoff. Type II is common throughout Europe, but has limited availability in North America.