icing. categories of icing structural icing –forms on the surface of the airframe induction icing...
TRANSCRIPT
ICINGICING
Categories of IcingCategories of Icing
• Structural Icing– Forms on the surface of the airframe
• Induction Icing– Forms in air intakes of engines
• Instrument Icing– Forms on pitot tube and other exterior
instruments
Necessary ConditionsNecessary Conditions
• Temperature of 0 Celsius or colder
• Supercooled liquid droplets– Liquid cloud or precipitation droplets at below
freezing temperatures
• Wet snowflakes– Snowflakes at temperatures near 0C– Mixture of ice particles and supercooled water
droplets
Supercooled Droplets – Why do Supercooled Droplets – Why do they exist?they exist?
• Ice Condensation Nuclei typically do not exist at temperatures warmer than -10C
• Ice Condensation Nuclei levels are present at 50% between -10C and -14C
• Ice Condensation Nuclei are present nearly to 100% by -20C
• Several types of clay particles are common ice nuclei, silver iodide is another.
ICING INTENSITIES
TRACE - PERCEPTIBLE, NO SIGNIFICANTACCUMULATION
LIGHT - SIGNIFICANT ACCUMULATION FOR A PROLONGED FLIGHT (OVER 1 HOUR)
MODERATE - SIGNIFICANT ACCUMULATION FOR SHORTER PERIODS OF FLIGHT
SEVERE - RAPID, DANGEROUS ACCUMULATIONS
CLEAR ICING
FAVORABLE CONDITIONS
LARGE DROPLETS IN CUMULIFORM CLOUDS OR FREEZING RAIN
TEMPERATURES 0°C TO -20°C
Clear IcingClear Icing• Clear appearance (glaze)• Associated with strong upward motion• Favorable conditions
– Large droplets• Cumuliform clouds• Freezing rain
– Temperatures 0 to -10 C (sometimes down to -20 C)
• Formation Process– Supercooled droplets impact, flow, conform,
and then freeze on the aircraft surface.
Clear Icing - CharacteristicsClear Icing - Characteristics
• Rapid accumulation– Droplets are large– Droplets are highly concentrated
• Smooth surface
• Hard
• Difficult to remove
FAVORABLE CONDITIONS
SMALL SUPERCOOLED DROPLETS IN STRATIFORM CLOUDS
TEMPERATURES 0°C TO -20°C
RIME ICING
Rime IcingRime Icing
• White, frosty appearance
• Favorable conditions– Small water droplets– Stratiform clouds– Temperatures 0 to -20 C
• Formation Process– Droplets freeze on impact– Air is trapped between frozen particles
Rime Icing - CharacteristicsRime Icing - Characteristics
• Accumulates more slowly than clear icing– Droplets are smaller– Droplets are less concentrated
• Irregular, pebble-like surface
• Structurally weaker than clear icing– Effect of trapped air
FAVORABLE CONDITIONS
LARGE AND SMALL DROPLETS COEXIST
LIQUID AND FROZEN PARTICLES COEXIST
WET SNOW
MIXED ICING
FREEZING TEMPERATURES
Mixed IcingMixed Icing• Glossy white appearance• Associated with strong upward motion• Favorable conditions
– Large and small droplets coexist– Liquid and frozen particles coexist– Wet snow– Freezing temperatures (Often much colder
than -10C)
• Formation Process– Combines clear and rime icing processes
and/or wet snowflakes
Mixed Icing - CharacteristicsMixed Icing - Characteristics
• Rapid accumulation– Particles are large– Particles are highly concentrated
• Rough surface– Creates turbulent flow over wing– Most effective in reducing aerodynamic
efficiency (turbulent flow over wing reduces lift)
– Difficult to remove
RESPONSE ITEM
WHAT INTENSITY OF ICING IDENTIFIES
SIGNIFICANT ACCUMULATIONS AFTER
RELATIVELY SHORT PERIODS OF FLIGHT?
A. LIGHT
B. MODERATE
C. SEVERE
A. LIGHT
B. MODERATE
C. SEVERE
RESPONSE ITEM
SOLID, SMOOTH ICE FORMED EITHER FROM
SUPERCOOLED WATER DROPS OR FROM
FREEZING RAIN IS CALLED ________ ICE.
A. CLEAR
B. RIME
C. MIXED
A. CLEAR
B. RIME
C. MIXED
RESPONSE ITEM
THE TYPE OF ICING USUALLY
ASSOCIATED WITH STRATIFORM CLOUDS
IS
A. CLEAR.
B. RIME.
C. MIXED.
A. CLEAR.
B. RIME.
C. MIXED.
Icing LocationsIcing Locations
• Icing locations are layer and positions in the atmosphere with icing potential
• Determined by temperatures, generally in the range of 0 to -20C– Temperatures statistically most favorable for
supercooled droplets
GROUND LEVEL
SEA LEVEL
1000
2000
3000
4000
5000
6000
7000
8000
9000
-20°C 0°C
MOST PROBABLE ICING LAYER
ICING LAYER
SINGLE FREEZING LEVEL
0°C
STRATUS CLOUDS
ICING ZONE
0°C 0°C
FAST ACCUMULATION
CUMULUS CLOUDS
OR LESS
OR LESS
TEMP 0°C OR LOWER
RAIN, DRIZZLE, OR WET SNOW
PRECIPITATION
WARM FRONTWARM AIR
MOIST AND STABLEABOVE FREEZING TEMPERATURES
STRATIFIED CLOUDS
FRONTS
COLD AIR
0°C
BELOW FREEZING TEMPERATURES
SUPERCOOLED RAIN FREEZES ON IMPACT
(FREEZING RAIN) {
WARM RAIN
RESPONSE ITEM
A PILOT FLYING AT 4,000 FEET REPORTS ICING CONDITIONS.BASED ON THE SOUNDING, TO AVOID THE ICING YOU WOULDADVISE THE PILOT TO
A. CLIMB TO 5,000 FEET. B. DESCEND TO 3,000 FEET. C. CLIMB ABOVE 8,000 FEET.
A PILOT FLYING AT 4,000 FEET REPORTS ICING CONDITIONS.BASED ON THE SOUNDING, TO AVOID THE ICING YOU WOULDADVISE THE PILOT TO
A. CLIMB TO 5,000 FEET. B. DESCEND TO 3,000 FEET. C. CLIMB ABOVE 8,000 FEET.
RESPONSE ITEM
DURING CLIMBOUT INTO THE CUMULIFORM CLOUD, ATWHAT ALTITUDE WOULD YOU EXPECT INITIAL ICING?
A. 3,000 FEET B. 5,000 FEET C. 7,000 FEET
DURING CLIMBOUT INTO THE CUMULIFORM CLOUD, ATWHAT ALTITUDE WOULD YOU EXPECT INITIAL ICING?
A. 3,000 FEET B. 5,000 FEET C. 7,000 FEET
7,000 FT
5,000 FT
3,000 FT
0oC
DefinitionsDefinitions
• Frost – Deposition of ice crystals from water vapor– Must have temperatures at or below freezing
with a high relative humidity
• Cold Soak – Occurs when an aircraft flies from a region of very cold temperatures to a region of warmer temperatures with high humidity, causing atmospheric moisture to deposit into ice crystals onto the aircraft.
DefinitionsDefinitions
• Fog – Condensation of water vapor into cloud droplets near the ground (cloud on the ground)– BR (3/4SM or Greater)– FG (1/2SM or Lower)– Light winds, clear skies and high low level humidity
• Freezing Fog (FZBR or FZFG) – The development of fog at temperatures below freezing– Causes deposition of ice onto exposed surfaces
DefinitionsDefinitions• Sleet (PL) – Snow that partially melts in the
atmosphere then refreezes into a small ice pellet by the time it reaches the ground.
• Hail (GR) – Ice particles that get suspended in a thunderstorm and fall to the ground once the thunderstorm updraft can no longer sustain its weight.
• Freezing Rain (FZRA) – Rain that falls into a shallow layer of subfreezing air near the ground and freezes on contact with surfaces on or near the ground.
DECREASESLIFTINCREASES
DRAG
DECREASESTHRUST
INCREASESWEIGHT
HAZARDOUS EFFECTS TO FLIGHTHAZARDOUS EFFECTS TO FLIGHT
ICING INTENSITY EFFECTS(WITHOUT DEICERS/WITH DEICERS)
TRACE - NO HAZARDS/ NO DEICERS REQUIRED
LIGHT - HAZARDOUS IF CONTINUED/ OCCASIONAL USE OF DEICERS REQUIRED
MODERATE - HAZARDOUS, REQUIRES DIVERSION/CONTINUOUS USE OF DEICERS REQUIRED
SEVERE -IMMEDIATE HAZARD/ UNCONTROLLED BY DEICERS
RESPONSE ITEM
THE ICING INTENSITY THAT REQUIRES CONTINUOUS USE OF DEICERS IS
A. LIGHT.
B. MODERATE.
C. SEVERE.
THE ICING INTENSITY THAT REQUIRES CONTINUOUS USE OF DEICERS IS
A. LIGHT.
B. MODERATE.
C. SEVERE.
OBSERVED REPORTS OF ICING CONDITIONS
METAR KORD 152355Z 12010KT 5SM PL BR OVC008 M11/M13 A3045 RMK SLP315
METAR KOMA 092355Z 09015KT 7SM FZRA OVC010 M07/M09 A3040 RMK SLP300
UA/OV KTUL225050/TM 2335/FL080/TP PA28/ SK OVC025-TOP060/TA M06/IC LGT RIME 045-060/RM FRZLVL 045 DURC
Icing Forecasts Available from Icing Forecasts Available from NWSNWS
Airmets
Sigmets
http://adds.aviationweather.gov/icing/
Other Aviation Weather ResourcesOther Aviation Weather Resources• National Weather Service
– www.nws.noaa.gov or www.weather.gov
• National Weather Service Detroit/Pontiac– www.crh.noaa.gov/dtx or www.weather.gov/detroit
• NWS Detroit/Pontiac Area Forecast Discussions– www.crh.noaa.gov/dtx/wxnow/sfd_index.php
• Aviation Weather Center– http://aviationweather.gov
• The Front Publication– Http://aviationweather.gov/general/pubs/front
The EndThe End