getting to grips with COLD WEATHER OPERATIONS 寒冷天气运行(45)

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B3.6.4 Takeoff
Recommendations provided in the aircraft-specific FCOM, regarding performance corrections or procedures applied when operating in icing conditions should be considered.

B3.6.5 General remarks

In special situations, flight crews must be encouraged not to allow operational or
commercial pressures to influence decisions. The minimum requirements have been
presented here, as well as the various precautions.

If there is any doubt as to whether the aircraft is contaminated - do NOT takeoff.

As in any other business, the key factors to ensuring efficient and safe procedures are:
Awareness, understanding and communication.
If there is any doubt or question at all, ground and flight crews must communicate with
each other.

B4 FLUID CHARACTERISTICS AND HANDLING
B4.1 De-icing/anti-icing fluids - characteristics
Although numerous fluids are offered by several manufacturers worldwide, fluids can be principally divided into two classes, Type I and Type II/IV fluids.
B4.1.1 Type I fluid characteristics
.
No thickener system

.
Minimum 80% glycol content

.
Newtonian fluid: Viscosity depends on temperature

.
Relatively short holdover time

Depending on the respective specification, they contain at least 80 percent per volume of either 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.
Type I fluids show a relatively low viscosity which only changes depending on temperature. Glycols can be well-diluted with water. The freezing point of a water/glycol mixture varies with the content of water, whereas the concentrated glycol does not show the lowest freezing point: 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.
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B4.1 - Type II/IV fluid characteristics
.
With thickener system

.
 Minimum 50 percent glycol-

.
Pseudo-plastic or non Newtonian fluid: Viscosity depends on temperature and shear forces to which the fluid is exposed

.
 Relatively long holdover time

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. The rest is water.
　
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