Cold Weather Operations

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Cold Weather Operations
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REFERENCES
FM 1-202, Environmental Flight, February 1983 FM
1-301, Aeromedical Training for Flight Personnel,
May 1987 TC 1-218, Aircrew Training Manual
Utility Aircraft, March 1993 Aircraft Operators
Manual AR 95-1, Flight Regulations, Sept.
1997 Meteorology Education and Training Website
(http//meted.ucar.edu/icing)
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OUTLINE

• Cold Injury Factors
• Types of Cold Injuries
• Cold Injury Prevention
• Flight Operations and Weather
• Flight Techniques

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Cold Injury Factors

• Defensive Position - Static
• Age lt17 or gt40
• Prior cold injury
• Fatigue level
• Training and experience
• Nutrition, activity, drugs and medication,
  especially alcohol.

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Injuries

• Dehydration
• Trenchfoot
• Frostbite
• Hypothermia

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Dehydration

• Loss of water or the elements of water.
• As prevalent in cold regions as it is in hot, dry
  areas.
• More difficult in realizing the amount of water
  loss due to cold and amount of absorbing clothes
  worn in cold weather.

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Trenchfoot

• Tissue injury sustained as a result of prolonged
  exposure to cold temperatures (usually greater
  than 48 hours) in a damp or wet environment.
• Occurs between 32 and 50 degrees F.
• Because early stages are not painful, individual
  must be alert and use preventative measures.
• Treatment - Dry and Warm the injury

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Frostbite

• Freezing of a body part by exposures to
  temperatures below freezing.
• Strong, sustained winds substantially increase
  the probability of injury.
• Classification Superficial or Deep.
• Treatment and management are based solely upon
  the classification.
• Treatment - Gradually warm area to body temp

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Hypothermia

• Gradual or rapid cooling of the body core
  temperature.
• Begins to cause damage at 96o F.
• Individual may not be aware of the impending
  danger because of a feeling of well being.

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Cold Injury Prevention

• Keep the body dry.
• Limit exposure to the cold.
• Avoid wearing wet clothing.
• Keep activity below perspiration level.
• Avoid direct contact of bare skin and cold metal.
• Avoid alcohol intake.
• Monitor the Wind Chill Factor

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WIND CHILL CHART FOR FAHRENHEIT
TEMPERATURES (0 F)
ACTUAL THERMOMETER READING (0 F)
ESTIMATED WIND SPEED (IN MPH)
50 40 30 20
10 0 -10 -20
-30 -40 -50 -60

EQUIVALENT TEMPERATURE (0 F)
CALM
40
50
30
20
10
0
-10
-20
-30
-40
-50
-60
5
27
16
6
-5
-15
-26
-36
-47
-57
-60
37
48
10
40
28
16
4
-9
-21
-33
-46
-58
-70
-83
-95
15
36
22
9
-5
-18
-32
-45
-58
-72
-85
-99
-112
20
32
18
4
-10
-25
-39
-53
-67
-82
-96
-110
-124
25
30
16
0
-15
-29
-44
-59
-74
-88
-104
-118
-133
30
28
13
-2
-18
-33
-48
-63
-79
-94
-109
-125
-140
35
27
11
-4
-20
-35
-51
-67
-82
-98
-113
-129
-145
40
26
10
-6
-22
-37
-53
-69
-85
-100
-116
-132
-148
GREAT DANGER
INCREASING DANGER
LITTLE DANGER
WINDS GREATER THAN 40 MPH HAVE LITTLE
ADDITIONAL EFFECT
lt5 hrs with dry skin Greatest hazard
from false security
Exposed flesh may freeze within 1 minute
Exposed flesh may freeze within 30 sec.
GREATEST HAZARD FROM FALSE SECURITY
Trenchfoot and Immersion foot may occur at any
point on this chart.
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COLD INJURY PREVENTION

• Keep clothing clean
• Avoid overheating
• Wear clothes loose and in layers
• Keep clothing dry

• C -
• O -
• L -
• D -

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Flight Operations
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Winter Weather

• Temperature / Dew Point Watch out for Fog
• Ice fog -25 F and colder
• Icing conditions
• Warm front over a cold air mass or land form
• Mountainous uplift
• 04 C to -20 C
• Flying or driving into visible moisture surface
  icing

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Icing
Aircraft Icing is the most hazardous condition
associated with the cold

• Conditions for Icing
• Temperatures between 32oF(0oC) and -4oF (-20oC)
• Visible Moisture (Clouds, Drizzle, Rain, Wet
  Snow)
• Rarely found at temps below -4oF (-20oC)

• AR 95-1
• Aircraft will not be flown into known or
  forecast severe icing
• If flight is to be made into known moderate
  icing, aircraft must be equipped with adequate
  operational deicing or anti-icing equipment.

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Icing Intensities

• Trace
• Light
• Moderate
• Severe

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Trace Icing
The trace category is used when the rate of ice
accumulation is just slightly greater than the
rate of loss due to sublimation. This category of
icing is not hazardous. De-icing, anti-icing
equipment, or an altitude change are not
necessary unless this category is encountered for
one hour or more.
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Light Icing
The light icing category means that the rate of
ice accumulation may create a problem if the
aircraft remains in this environment for one hour
or more. Occasional use of de-icing or anti-icing
equipment is necessary to remove or prevent
accumulation. When prolonged flight in this
environment is likely, a heading or altitude
change becomes necessary.
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Moderate Icing
When the rate of ice accumulation is so great
that even a short encounter can become hazardous.
The use of de-icing or anti-icing equipment is
necessary. Often a heading or altitude change is
also required especially if the aircraft remains
in the moderate icing environment for more than a
very short period. This photo represents a
moderate icing condition.
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Severe Icing
Icing is severe whenever the rate of ice
accumulation is such that de-icing or anti-icing
equipment cannot control or reduce the hazard.
Typically an immediate heading and/or altitude
change is necessary
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Icing Types

• Rime Icing
• Clear Icing
• Mixed Icing

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Rime Icing
Rime ice grows when droplets rapidly freeze upon
striking an aircraft. The rapid freezing traps
air and forms a brittle, opaque, and
milky-colored ice. Rime ice grows into the air
stream from the forward edges of wings and other
exposed parts of the airframe.
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Clear Icing
In clear ice formation, only a small portion of
the drop freezes immediately while the remaining
unfrozen portion flows or smears over the
aircraft surface gradually freezing. Since few
air bubbles are trapped during this gradual
process, the end result is ice less opaque and
denser than rime ice that can appear either as a
thin smooth surface or as rivulets, streaks, or
bumps of clear ice.
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Mixed Icing
Due to variations in Liquid Water Content,
temperature, and droplet sizes, an airplane can
encounter both rime and clear icing along its
flight path. Known as mixed icing,
this can appear as layers of relatively
clear and opaque ice when examined from the
side.
Mixed ice is similar to clear ice in that it can
spread over more of the airframe's surface and is
more difficult to remove than rime ice
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Frequency and Occurrence
Rime icing is the most frequently reported
icing. The type of icing is dependent on the
temperature, liquid water content, and other
aircraft-dependent variables.
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Frequency and Occurrence
Temperature can be a good indicator for
diagnosing the type of icing expected. The
relationship between temperature and icing type
that is typically used is outlined in the
following table Clear 0 C to -10
C Mixed -10 C to -15 C Rime -15 C to - 40
C These relationships are meant to be used
as general guidance
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Flight Techniques

• Before starting engine(s). Check all controls for
  full travel and freedom of movement.
• Starting engine(s). If applicable, start engines
  with the propellers feathered to prevent the
  tires from sliding.
• Warm-up and ground operation. If so equipped, use
  the brake de-ice, as required, to thaw frozen
  brakes. Allow adequate warm-up time for gyro
  instruments.
• Taxiing. Use an outside observer, if available,
  to confirm that the wheels are turning and not
  sliding.
• When possible, avoid taxiing through snow and
  slush.
• Do not set the parking brake when the aircraft
  is stopped.
• Use chocks or sandbags and the brake de-ice, if
  installed.

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Flight Techniques

• Before takeoff.
• Activate anti-icing systems, allowing sufficient
  time for the equipment to become effective.
• If the possibility of ice accumulation on flying
  surfaces exists, do not attempt to take off.
• Accumulations of slush/snow on the runway
  greatly increase the takeoff distance and should
  be taken into consideration during planning.
• Takeoff.
• Procedures are the same as for a normal takeoff,
  except for a possible decrease in aircraft
  performance caused by the use of the
  anti-icing/de-icing equipment.
• Before starting takeoff roll, check all controls
  for full travel and freedom of movement.
• Smoothly apply power to avoid asymmetrical
  thrust conditions.

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Flight Techniques

• During flight. Refer to the aircraft operator's
  manual for after-takeoff procedures.
• Climb at a higher-than-normal airspeed to
  prevent ice accumulation on unprotected surfaces.
• Allow ice to accumulate according to the
  aircraft operators manual before activating the
  surface deicing equipment.
• Higher-than-normal stall speeds should be
  expected and,
• As ice accumulates the stall warning system may
  become unreliable.
• Landing. Landings on icy runways should be made
  only when necessary.
• (Refer to the aircraft operators manual for any
  limitations and special procedures.)
• To avoid impairing visibility, reverse power
  should be used with caution when landing on a
  runway covered with snow or standing water.
• Before leaving the aircraft. Refer to the
  aircraft operator's manual for procedures.

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Summary

• Cold Injury Factors
• Cold Injury Prevention COLD
• Icing Conditions
• Flight Techniques

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QUESTIONS?