Issue II 02.07.2009 Rev. 0
FLUID CHARACTERISTICS
22.1 De-icing/anti-icing fluids - characteristics
22.1.1 Although numerous fluids are offered by several manufacturers worldwide, fluids can be principally divided into two classes, Type I and Type II/IV fluids.
22.2 Type I fluid characteristics
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No thickener system
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Minimum 80% glycol content
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Newtonian fluid: Viscosity depends on temperature
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Relatively short holdover time
22.2.1 Depending on the respective specification, these contain at least 80 percent per volume of monoethylene, diethylene or monopropyleneglycol or a mixture of these glycols. The rest comprises water, inhibitors and wetting agents. The inhibitors act to restrict corrosion, to increase the flash point or to comply with other requirements regarding materials’ compatibility and handling. The wetting agents allow the fluid to form a uniform film over the aircraft’s surfaces.
22.2.2 Type I fluids show a relatively low viscosity which changes as a function of temperature. Glycols can be well-diluted with water. Concentrated Type I fluids must be diluted with water to achieve a freezing point that is in accordance with the appropriate application procedure. This is achieved with a mixture of approximately 60% glycol and 40% water (freezing point below -50°C). The freezing point of the concentrated monoethylene, diethylene or propyleneglycol is in the range of - 10°C. Therefore Type I fluids are normally diluted with water of the same volume. This 50/50 mixture has a lower freezing point than the concentrated fluid and, due to the lower viscosity, it flows off the wing much better.
22.3 Type II/IV fluid characteristics
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With thickener system
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Minimum 50 percent glycol
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Pseudo-plastic or non Newtonian fluid: Viscosity depends on temperature and shear forces to which the fluid is exposed
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Relatively long holdover time
22.3.1 Type II/IV fluids contain at least 50% per volume monoethylene-, diethylene-or Propyleneglycol, different inhibitors, wetting agents and a thickener system giving the fluid a high viscosity.
Issue II 02.07.2009 Rev. 0
22.3.2 Although the thickener content is less than 1%, it gives the fluid particular properties. The viscosity of the fluid and the wetting agents causes the fluid to disperse onto the sprayed aircraft surface, and acts like a protective cover.
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