GROUND SERVICING
AIRPLANE
OPERATIONS
MANUAL
1-12-20
Page
2
Code
01
REVISION 37
AOM-145/1114
APPLICATION OF DEICING AND ANTI-ICING FLUIDS
ANTI-ICING AND DEICING FLUIDS
When airplane surfaces are contaminated by frozen precipitation or
frost before departure, they must be deiced. When the risk of freezing
precipitation exists at dispatch or freezing precipitation is actually
taking place, the airplane must be anti-iced. While deicing removes
ice, anti-icing protects against additional icing for a certain period of
time, called hold-over time. A combination of both anti-icing and
deicing may be performed based on the judgment of the flight crew
and procedures developed by the operator.
Deicing and anti-icing fluids lower the freezing point of frozen
precipitation thus delaying the accumulation of contamination on the
airplane. When applied to a clean surface, the fluid forms a thin layer
that has a lower freezing point in precipitation. The fluid is highly
soluble in water, thus the precipitation or ice melts on contact with
fluid. These fluids also delay the onset of frost on airplane surfaces. As
the ice melts, the fluid dilutes with the water, thereby causing the
mixture to become less effective or to run off. Ice can begin to form
again after enough dilution has occurred and freezing point begins to
rise.
Deicing/anti-icing fluids are not intended to provide icing protection
during flight. The fluid must flow-off the surface during takeoff, or they
may cause undesirable performance effects. EMBRAER performed
flight tests to investigate the effects of approved fluids on performance
and handling characteristics. These tests demonstrated these fluids
did not have a measurable effect on takeoff and climb performance.
Fluids are generally mixtures of glycol, water, inhibitors, thickening
agents and wetting agents. Glycol lowers the freezing point and
prevents the formation of ice contamination at temperatures below
freezing. The wetting agent allows the fluid to conform to the airplane
surfaces. The inhibitors prevent corrosion and increase the flash point.
The thickening agent, normally propylene glycol with polymers,
enables the coating of fluid to remain on airplane surfaces for longer
periods.
Type I Fluid is unthickened, while fluids from Type II to IV are
thickened.
Type I Fluid characteristically forms a thin wetting film which provides
relatively limited holdover time, and provides protection against
refreezing when no precipitation is present.
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