Chapter 3 - Deicing/Anti-icing Fluids

SAE Type II Fluids (Clear or Pale Straw)

26.  SAE Type II fluids were introduced in North America in 1985 with widespread use, which began in 1990. Similar fluids, but with slight differences in characteristics, have been developed, introduced, and used in Canada.

27.  Fluids such as those identified as SAE Type II will last longer in conditions of precipitation and afford greater margins of safety if they are used in accordance with aircraft manufactures' recommendations.

28.  Flight tests performed by manufacturers of transport category aircraft have shown that SAE Type II fluids flow off lifting surfaces by rotation speed (Vr), although some large aircraft do experience performance degradation and may require weight or other take-off compensation. Therefore, SAE Type II fluids should be used on aircraft with rotation speeds (Vr) above 100 knots. Degradation could be significant on aeroplanes with rotation speeds below this figure.

29.  As with any deicing or anti-icing fluid, SAE Type II fluids should not be applied unless the aircraft manufacturer has approved their use, regardless of rotation speed. Aircraft manufacturers' manual may give further guidance on the acceptability SAE Type II fluids for specific aircraft.

30.  SAE Type II fluids are considered "thickened" because of added thickening agents that enable the fluid to be deposited in a thicker film and to remain on the aircraft surfaces until the time of take-off. These fluids are used for deicing when heated, and anti-icing. Type II fluids provide greater protection (holdover time) than do Type I fluids against frost, ice or snow formation in conditions conducive to aircraft icing on the ground.

31.  These fluids are effective anti-icers because of their high viscosity and pseudo-plastic behavior. They are designed to remain on the wings of an aircraft during ground operations, thereby providing anti-icing protection. However, when these fluids are subjected to shear stress, such as that experienced during a take-off run, their viscosity decreases drastically, allowing the fluids to flow off the wings and causing little adverse effect on the aircraft's aerodynamic performance.

32.  The pseudo-plastic behavior of SAE Type II fluids can be altered by improper deicing/anti-icing equipment or handling. Therefore, some North American airlines have updated deicing and anti-icing equipment, fluid storage facilities, deicing and anti-icing procedures, quality control procedures, and training programs to accommodate these distinct characteristics. Testing indicates that SAE Type II fluids, if applied with improper equipment, may lose 20 to 60% of their anti-icing performance.

33.  All Type II fluids are not necessarily compatible with all Type I fluids. Therefore, refer to the fluid manufacturer or supplier for compatibility information. As well, the use of Type II fluid over badly contaminated Type I fluid will reduce the effectiveness of Type II fluid.