AIRPLANE
OPERATIONS
MANUAL
GROUND SERVICING
REVISION 37
1-12-20
Page
5
Code
01
AOM-145/1114
DEICING AND ANTI-ICING PROCEDURES
Application of deicing and anti-icing fluid must be done by trained and
qualified personnel. It is the pilot’s responsibility to decide whether or
not to accept the airplane for flight. Therefore, it is essential that pilots
understand not only how the fluid works and how it is applied, but also
the flight crew must be able to determine if the airplane is safe for flight
following treatment.
Deicing is required to clean airplane surfaces contaminated by ice,
snow, frost or slush. Anti-icing is required to prevent ice accumulation.
If both anti-icing and deicing are required, the procedure may be
performed in either one or two-step process depending on weather
conditions, available equipment, available fluids and the holdover time.
However, the frequent use of thickened de/anti-icing fluids in one-step
process can result in the accumulation of fluid residues in
aerodynamically quiet areas. These residues may re-hydrate when
exposed to moisture (e.g., rain or humidity) and subsequently freeze at
low temperatures, possibly restricting the movement of the airplane’s
control surfaces.
Thus, a two-step deicing/anti-icing fluid application is recommended to
be performed so that the residues accumulation in the critical areas is
minimized. The use of hot water or heated mix of type I fluid/water for
the first step of a two step deicing/anti-icing process may also help to
clean away residues of thickened fluids from previous applications.
In two separate steps, the airplane is first deiced using heated water
only, or a heated mixture of deicing fluid and water. After completion of
the deicing operation, anti-icing is performed with diluted or undiluted
anti-icing fluid. The second step must be applied before residual
liquids from the first deicing step freezes, typically within three
minutes. This is especially important where only heated water is used
to deicing. Mixing fluids in a two-step procedure may only be
performed if approved by the fluid manufacturer.
It is important to keep in mind that in case of a one-step deicing/anti-
icing procedure, holdover time starts to run from the beginning of the
procedure. With a two-step procedure, the holdover time starts to run
at the beginning of the second step.
Under no circumstances should an airplane that has been previously
anti-iced receive a further spray of anti-icing fluid directly on top of the
anti-icing contaminated film. If an additional protection is necessary
before flight, a complete deicing/anti-icing procedure must be
performed. Residues from previous treatment must be flushed off first.
All fluids must be used in accordance with the manufacturers’
recommendations.
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