Cold Weather Operations

1. Cold Weather Operations

2. 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 Operator’s Manual AR 95-1, Flight Regulations, Sept. 1997 Meteorology Education and Training Website (http://meted.ucar.edu/icing)

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

4. Cold Injury Factors • Defensive Position - Static • Age <17 or >40 • Prior cold injury • Fatigue level • Training and experience • Nutrition, activity, drugs and medication, especially alcohol.

5. Injuries • Dehydration • Trenchfoot • Frostbite • Hypothermia

6. 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.

7. 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

8. 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

9. 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.

10. 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

11. 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 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -36 -57 5 48 37 27 16 6 -5 -15 -26 -47 -60 40 10 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 11 35 27 -4 -20 -35 -51 -67 -82 -98 -113 -129 -145 40 26 10 -6 -22 -37 -53 -69 -85 -100 -116 -132 -148 INCREASING DANGER GREAT DANGER LITTLE DANGER WINDS GREATER THAN 40 MPH HAVE LITTLE ADDITIONAL EFFECT <5 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.

12. COLD INJURY PREVENTION • Keep clothing clean • Avoid overheating • Wear clothes loose and in layers • Keep clothing dry • C - • O - • L - • D -

13. Flight Operations

14. 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

15. 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.

16. Icing Intensities • Trace • Light • Moderate • Severe

17. 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.

18. 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.

19. 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.

20. 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

21. Icing Types • Rime Icing • Clear Icing • Mixed Icing

22. 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.

23. 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.

24. 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

25. 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.

26. 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

27. 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.

28. 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.

29. 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 operator’s 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 operator’s 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.

30. Summary • Cold Injury Factors • Cold Injury Prevention “COLD” • Icing Conditions • Flight Techniques

31. QUESTIONS?