De-Icing & Anti-icing Fluids - Holdover Times
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Transcript of De-Icing & Anti-icing Fluids - Holdover Times
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De-icing and Anti-icing fluids-
Holdover times
Operations Liaison Meeting
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2De-icing and Anti-icing fluids - Holdover times
Content
Clean aircraft concept De-icing / anti-icing fluids
Holdover times
Conclusion
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3De-icing and Anti-icing fluids - Holdover times
Clean aircraft concept
An aircraft ready for flight must not have ice,snow or frost adhering to its surfaces except as
authorized by the FCOM
A thin layer of hoarfrost is acceptable on theupper surface of the fuselage
A frost layer (due to cold fuel) not exceeding 3
mm is acceptable on the underside of the wing
as it will not penalize takeoff performance
Reminder
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4De-icing and Anti-icing fluids - Holdover times
Clean aircraft concept In winter conditions, de-icing and anti-icing
are the procedures used to prepare the aircraft
for takeoff in accordance with the clean aircraft
concept
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5De-icing and Anti-icing fluids - Holdover times
Clean aircraft concept
De-icing is a procedure by which frost, ice,slush or snow is removed from the aircraft in
order to provide clean surfaces
This may be done by
mechanical methods application of heated de-icing fluids
Anti-icing is a precautionary procedure, which
provides protection against the formation of
frost, ice and snow accumulation on treatedsurfaces of the aircraft for a limited period of
timecalled holdovertime.
This is done by application ofanti-icing fluids
Definitions
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6De-icing and Anti-icing fluids - Holdover times
Content Clean aircraft concept
De-icing / anti-icing fluids
Holdover times
Conclusion
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De-icing / anti-icing fluids
De-icing and anti-icing fluids are developed
and manufactured to industry standards
published by:
ISO (International Standard Organization)
SAE (Society of Automotive Engineers)
AEA (Association of European Airlines)
Fluids specification
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De-icing / anti-icing fluids
De-icing / anti-icing fluids must:
Remove / prevent precipitation accumulation
on aircraft surface up to takeoff start Flow off the aircraft surface during takeoff so
as not to degrade takeoff performance
Requirements
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De-icing / anti-icing fluids
The fluid which freezes at a very low temperature(e.g. -30C), is applied on a clean surface.
Process
It forms a protective layer.
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De-icing / anti-icing fluids This fluid layer absorbs the frozen precipitation.
It keeps the freezing temperature of the diluted fluidwell below OAT or aircraft skin temperature, thus
preventing frozen precipitation to accumulate
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De-icing / anti-icing fluids Then the layer becomes more and more diluted by the
melted precipitation; its freezing temperature increases When it reaches OAT or aircraft skin temperature, anti-
icing fluid fails and the frozen precipitation accumulates
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De-icing / anti-icing fluids
Exceeding the holdover time means that theanti-icing fluid has failed and lost its
effectiveness, i.e. frozen precipitation is no
longer absorbed by the diluted anti-icing fluid,
making the protection ineffective.
The precipitation accumulates
Clean aircraft concept not fulfilled
Danger !!!
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De-icing / anti-icing fluids
Type I fluids
Low viscosity
Viscosity reduces withtemperature
Limited holdover time
Blown off quickly Used mainly for de-icing
Type II, III, IV fluids
High viscosity (contain a
thickening agent)
Viscosity reduces with: shear force fluid concentration temperature
Longer holdover time
Blown off before rotation
Used for de-icing and anti-
icing
Different types of fluids
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De-icing / anti-icing fluidsViscosity of Type II/IV fluids is greater than
viscosity of Type I fluids:Type II/IV fluids stick more on the aircraft surface
than Type I
Type II/IV fluid layer is thicker than Type I fluid layer
A greater volume of Type II/IV remains on aircraftsurface and can absorb more water before freezing
point reaches OAT or skin temperature
Undiluted Type II/IV fluids give maximum holdover
times while water/fluid ratio has no practical effect
on holdover time for Type I fluids
Type II/IV fluids have longer holdover times than
Type I
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De-icing / anti-icing fluids As viscosity of Type II/IV fluids decreases with
increasing shear forces (increasing aircraft speed),they have been formulated to be blown off from
aircraft surface between 85 kt (Type II) and 100 to
110 kt (Type IV)
Both Type II and Type IV fluids are suitable for allAirbus aircraft which all have rotation speed above
110kt
Type IV fluids generally provide longer holdover
time than Type II Type I fluid are mainly used for de-icing
Note: Type III fluid are similar to Type II/IV fluids but are formulated to be
blown off during a low speed takeoff (used for turbo-propeller aircraft)
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Content Clean aircraft concept
De-icing / anti-icing fluids
Holdover times
Conclusion
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Holdover times Guidelines for application and for holdover times
achieved by various fluid mixtures are issued andpublished by various organizations (ISO, SAE or
AEA) and in the Aircraft Maintenance Manual
Holdover time begins at the start of the anti-icing
operation
Published holdover time charts are for
information only as protection period is affected
by multiple factors such as high wind velocity,aircraft skin temperature, jet blast, solar radiation
The indicated times should only be used
in conjunction with a pre-takeoff check
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18De-icing and Anti-icing fluids - Holdover times
Holdover timesExample of Type I fluid holdover times chart
(*)
(**) Use Light Freezing rain holdover times if positive identification of Freezing Drizzle is not possible
During conditions that apply to aircraft protection for ACTIVE FROST
ISO Type I fluid / water mixture is selected so that freezing point of the mixture is at least 10C below actual OAT
- Short Holdover
times
- Not affected by
fluid
concentration
Estimated time of protection during
heavy-light precipitation
OAT
(C)
Approximate holdover time anticipated under various weatherconditions (hours:minutes)
Frost
(*)
Freezingfog
Snow FreezingDrizzle
(**)
LightFreezing
rain
Rain oncold
soakedwings
Above 0 0:45 0:12-0:030 0:06-0:15 0:05-0:08 0:02-0:05 0:02-0:05
0 to -10 0:45 0:06-0:15 0:06-0:15 0:05-0:08 0:02-0:05
Below -10 0:30 0:06-0:15 0:06-0:15
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19De-icing and Anti-icing fluids - Holdover times
Holdover times
(*) During conditions that apply to aircraft protection for ACTIVE FROST
(**) The lowest authorized temperature is limited to -10C
(***) Use Light Freezing rain holdover times if positive identification of Freezing Drizzle is not possible
OAT
(C)
Type II fluidmixture
concentrationundiluted
Fluid / water
(%Vol / %Vol)
Approximate holdover time anticipated under various weather
conditions (hours:minutes)
Frost
(*)
Freezingfog
Snow FreezingDrizzle
(***)
LightFreezing
rain
Rain oncold
soakedwings
above
0
100/075/25
50/50
12:006:00
4:00
1:15-3:000:50-2:00
0:20-0:45
0:20-1:000:15-0:40
0:05-0:15
0:30-1:000:20-0:45
0:10-0:20
0:15-0:300:10-0:25
0:05-0:10
0:10-0:400:05-0:25
0 to -3100/075/2550/50
8:005:003:00
0:35-1:300:25-1:000:15-0:45
0:20-0:450:15-0:300:05-0:15
0:30-1:000:20-0:450:10-0:20
0:15-0:300:10-0:250:05-0:10
below
-3 to
-14
100/0
75/25
8:00
5:00
0:35-1:30
0:25-1:00
0:15-0:40
0:15-0:25
0:25-1:00
0:20-0:45
(**)
0:10-0:30
0:10-0:25
(**)
below
-14 to
-25
100/0 8:00 0:20-1:30 0:15-0:30
below
- 25
100/0 ISO Type II fluids may be used below -25C provided that the freezing pointof the fluid is at least 7C below OAT and that aerodynamic acceptance criteriaare met. Consider the use of Type I fluid when Type II fluid cannot be used
Example of Type II fluid holdover times chart
- Longer
holdover times
which increasewith fluid
concentration
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20De-icing and Anti-icing fluids - Holdover times
Holdover times
(*) During conditions that apply to aircraft protection for ACTIVE FROST
(**) The lowest authorized temperature is limited to -10C
(***) Use Light Freezing rain holdover times if positive identification of Freezing Drizzle is not possible
OAT
(C)
Type II fluidmixture
concentrationundiluted
Fluid / water
(%Vol / %Vol)
Approximate holdover time anticipated under various weather
conditions (hours:minutes)
Frost
(*)
Freezingfog
Snow FreezingDrizzle
(***)
LightFreezing
rain
Rain oncold
soakedwings
above
0
100/075/25
50/50
18:006:00
4:00
2:00-3:001:05-2:00
0:20-0:45
0:45-1:250:25-0:40
0:05-0:20
0:40-1:000:30-1:00
0:10-0:20
0:35-0:550:15-0:30
0:05-0:10
0:10-0:500:05-0:35
0 to -3100/075/2550/50
12:005:003:00
2:00-3:001:05-2:000:20-0:45
0:35-1:000:20-0:350:05-0:15
0:40-1:000:30-1:000:10-0:20
0:35-0:550:15-0:300:05-0:10
below
-3 to
-14
100/0
75/25
12:00
5:00
0:40-3:00
0:30-2:00
0:20-0:40
0:15-0:25
0:25-1:00
0:25-1:00
(**)
0:20-0:40
0:15-0:30
(**)
below
-14 to
-25
100/0 12:00 0:20-2:00 0:15-0:30
below
- 25
100/0 ISO Type IV fluids may be used below -25C provided that the freezing pointof the fluid is at least 7C below OAT and that aerodynamic acceptance criteriaare met. Consider the use of Type I fluid when Type II fluid cannot be used
Example of Type IV fluid holdover times chart
- Longer
holdover times
specially athigh fluid
concentration
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21De-icing and Anti-icing fluids - Holdover times
Holdover times Before departure under icing conditions or after a
de-icing / anti-icing operation, the aircraft mustreceive a final check by a responsible authorized
person
The flight crew must be notified the type of de-
icing / anti-icing operation performed including theanti-icing code to assess holdover time:
Type of
fluid used75% fluid /
25% waterLocal time at start
of last application
Ex: ISO Type II / 75 / 16.43 local PEK / 17 Nov 99
Date
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22De-icing and Anti-icing fluids - Holdover times
Content Clean aircraft concept
De-icing / anti-icing fluids
Holdover times
Conclusion
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23D i i d A ti i i fl id H ld ti
Conclusion Never underestimate the hazards of ice, snow or frost
Respect holdover times keeping in mind thatpublished data are affected by many factors
A check just prior to takeoff that the aircraft surfaces
are not contaminated is always necessary
Flight crew must be encouraged not to allowoperational or commercial pressure to influence
their decision
If there is any doubt as to whether the
aircraft is contaminated, do not go on