Thunderstorms 19

CHAPTER 20
ICING
Not What You Want To See Out The Window

IT’S BAAADDD!
Icing is a cumulative hazard
1. Increases weight
2. Reduces lift – changes the shape of the airfoil
3. Decreases thrust – effects prop
4. Increases drag – sticks up into the wind

IT’S BAAADDD!
It can get on the antennas effecting nav/comm, gps and the transponder
It can set up a resonance causing a whistle or hum
It can get on the brakes, landing gear, induction system, pitot static system
In addition it can seriously impair engine performance
False indications on flight instruments
Foul flight controls

TO GET ICING
1. Must have visible water
2. Aircraft must be below freezing

SUPERCOOLED WATER
Water droplets existing at temps below freezing are said to be supercooled
At a temp of -10º C there is only 1 ice crystal for every 1 million liquid droplets
Water may exist in temps as low as – 40º F (C)
Only when the temp drops below -40º C will only ice crystals exist
A cloud droplet size of 25 microns freezes spontaneously at -36º C
The cloud droplet of a few microns will not freeze until -40º C
Why?

SUPERCOOLED WATER
For Homogeneous freezing or spontaneous freezing to occur without the benefit of a nucleus, an ice embryo needs to form.
Enough molecules must join together in a ridged pattern to form an ice crystal
It must grow to a critical size then other molecules will attach and the whole drop freezes
The chance of this happening in a small droplet decreases because of the size of the droplet

SUPERCOOLED WATER
Because of thermal agitation, the ice embryo is more likely to break apart in the smaller size droplet before other molecules can hook up with their homeys and freeze
But when they hit the wing they collect into bigger volumes and freeze instantaneously
This is referred to as Contact Freezing
Supercooled water is a big issue because ice can form rapidly from short exposure times

THREE TYPES OF ICING
1. Rime – stratiform
2. Clear – cumuliform clouds
3. Mixed – cumuliform or stratiform

RIME ICE
Small Cloud Droplets
Rime/Mixed most common
Usually confined to layer 3,000-4,000‟ thick
Max values occur in upper part of cloud
Large horizontal extent

RIME ICE
Stratiform clouds
Small droplets freezing before spreading out
Air gets trapped between the frozen drops
Very brittle easy to remove
Disrupts the airflow over the wings more than clear
Tends to build up more slowly than clear do to small droplet size

RIME ON A CONVAIR

RIME
http://www.cb7tuner.com/vbb/showthread.php?p=1917574

RIME
Boots were cycled just prior to landing
Boot deicing:

CLEAR ICE
Cumuliform clouds
Large water droplets hitting the surface and spreading out
Since the droplets spread a little then freeze there is little or no air trapped in the process
This forms a laminate of frozen water which is relatively strong
Very heavy and hard to remove
Generally short in duration but do to large droplet size builds very fast

CLEAR ICING

CLEAR

REPORTABLE ICING CATEGORIES
Memorize AIM Ch 7-1-20 Icing Intensities, Contractions and Airframe Ice Accumulation
1. Trace
Ice becomes perceptible. Rate of accumulation slightly greater than sublimation. Deicing/anti-icing equipment is not utilized unless encountered for an extended period of time (over 1 hour).
2. Light.
The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used.
3. Moderate
The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or flight diversion is necessary.
4. Severe
The rate of accumulation is such that ice protection systems fail to remove the accumulation of ice, or ice accumulates in locations not normally prone to icing, such as areas aft of protected surfaces and any other areas identified by the manufacturer. Immediate exit from the condition is necessary.

ICE FORMATION
Ice forms first on the shortest radius of curvature
Ice also forms about 3 times faster on the tail than wing

FORMATION
Clear vs Rime formation

WHERE IS THE ICE?
Ice is usually found within 5000 feet above the freezing level
Usually only about 2000 – 3000 feet thick between 0º C and – 20º C
More rain means more ice when below freezing
More than 50% of icing cases occur between -8 and -12°C
50% of all icing occurs between 5,000 and 13,000 feet

ICING AND CLOUD TYPES
Low and middle clouds is usually where the ice is located
Freezing rain is the most hazardous icing condition
High clouds have very little chance of icing since these clouds are composed of ice crystals

ICING AND CLOUD TYPE CUMULIFORM
Large Cloud Droplets
Icing found in “updraft” portion of cloud
Heavy rime most frequently in cloud tops
Clear icing most likely in building Cu
Rime often found in fully developed TS
Relatively small horizontal extent
BUT research has found…
–Mixed-phase clouds of all types may harbor sufficient amounts of Super-Cooled water.

ICING AND CLOUD TYPE STRATIFORM
Probability is high for rime ice in these clouds
Small droplet size
Expect to encounter ice for longer periods of time
Builds slowly but steadily

ICE STRATEGY
Change altitude immediately upon first encounter
Use your lapse rate to compute what the temp will be at a higher altitude
Remember your looking for temps below -15 C
Realize that climbing at a lower airspeed will change your angle of attack
This will cause the ice to build on a different part of the airfoil
During your briefing make sure you know where the above freezing air is located

ICE STRATEGY
Get a complete 3D picture of the air aloft
Complex weather systems like the Frontal Wave, Warm front overrunning a cold airmass, the Occluded front
Ice pellets indicate freezing rain above your altitude
Wet snow indicates freezing temps above your altitude
Freezing rain indicates warmer temps above your altitude

Ice Strategy

TERRAIN
Mountain areas are good place to find ice
Up currents lift water droplets above the freezing level
Your usually flying higher to avoid the terrain and Presto ice

ICE STRATEGY
The Cascade Ice Machine
The Concord was brought to MWH for icing certification
Orographic lifting provides the worst icing on the windward side and at the crest
Can reach up 5,000 feet above the crest
High MEAs can effect your escape plan
It is illegal to fly if an AIRMET for icing exists unless your aircraft is certified for “known ice”

“COLD SOAKED”
Cold Soaked Aircraft can be a cause
– Sustained flight in below freezing air
– Descends to warm air, but…

LIKELIHOOD OF TYPE

WATER DROPLET SIZE

Icing patterns change with droplet size. But…
In relation to icing hazards, type and severity in order of importance are
LWC (liquid water content)
Temperature (altitude)
Droplet size
Aircraft type and design
Aircraft speed
Cessna Caravan has been referred to as an ice magnet
The book refers to SLWC but remember the temperature of the airplane matters also

LIKELIHOOD OF GETTING ICE
Amount of available water
Varies from cloud to cloud
Varies within same cloud

OCCURRENCE OF ICING
Aircraft type and speed affect icing occurrence
Just keep your speed above 575kts and your good

INDUCTION SYSTEM ICING
Induction areas have small radius edges allowing ice to build up more rapidly
Jet engine nacelles have heat
Reciprocating engines have alternate air doors and carb heat

CARBURETOR ICE
Adiabatic expansion in the venturi lowers air temp
32º F to 80º F or 0º C to 20º C and high humidity
Moisture freezes restricting air flow
Usually accumulates in curves or where there are obstructions in the flow

GROUND ICING
Taxiing through puddles when temp is at or below 32
Accumulate water and or mud
Problem for retracts
Warm hanger is the only remedy
Deicing the wing may be accomplished with a 50/50 mix of isopropyl alcohol and water
Watch out for aircraft washers in winter

REMOVAL OF ICE OR FROST
No hangar available? No problem.
There are several hangar-in-a can “solutions” available:
Glycol is the most expensive and generally only available at select FBOs.
Polypropylene antifreeze is pink in color, not harmful if swallowed, and is available at RV, automotive or marine stores and is used for winterizing portable water systems.
Placed in a small garden sprayer it works quite well, especially if heated to room temperature.
Automotive windshield de-icer in a spray can is inexpensive and can be purchased at gas stations and department stores.
Do not use it on aircraft windshields or windows.
It’s the easiest to carry and unless the airframe is
heavily iced, will yield several applications.
Rubbing alcohol, sold in relatively small quantities in drugstores and supermarkets, can work in a pinch using a spray bottle with a hand pump.
With the exception of Glycol, these products are inexpensive to purchase and should be used liberally.

Cessna 402
I happened to get some good pics of what ice does to a 402 last week, and thought I would share them with you guys (good for your students on what to expect when they get out of the sheltered world of bbcc). This was in what Boise approach was calling “light mixed icing,” i was in this for about 20 minutes when I was getting vectored for the ILS into Boise. I did the approach at 135kts and kept that speed to the flare where the trusty 402 stopped flying at 120kts. Quite a surprise considering VS1 is around 73kts. Anyway that was my adventure for the week, more too come….bet you wish you were out here too! Talk to ya later
AIR INTAKE
SPINNER
FUEL TANK VENT
TAIL

MIKE’S ICE
Key Lime Air
Piper Navajo
Flight from Centennial to Grand Junction
Clear Ice 1/30/2014

ROUTE OF FLIGHT
Centennial airport KAPA to Grand Junction KGJT

WX AT THE TIME
KAPA 301653Z 06003KT 10SM FEW025 SCT070 BKN120 OVC150 04/M04 A2969 RMK AO2 SLP042 SHSN OMTNS DSNT W-NW T00441039

KAPA 301553Z 06003KT 10SM FEW030 OVC070 03/M04 A2968 RMK AO2 SLP041 SHSN OMTNS DSNT W-NW T00331044KAPA 301453Z 00000KT 10SM FEW035 OVC085 02/M02 A2967 RMK AO2 SLP049 SHSN OMTNS DSNT W-NW T00171022 51016

KAPA 301353Z 00000KT 10SM BKN085 BKN110 02/M02 A2967 RMK AO2 SLP046 T00171022KAPA 301253Z 34013G20KT 10SM SCT070 OVC100 04/M04 A2963 RMK AO2 SLP029 T00441039KAPA 301153Z 32006KT 10SM SCT050 BKN095 OVC110 04/M01 A2961 RMK AO2 SLP019 60001 70001 T00441011 10100 20044 51024

KAPA 301550Z 3016/3112 03007KT P6SM FEW040 SCT060 BKN080
FM301800 08007KT P6SM SCT040 BKN070 FM302200 12011KT P6SM VCSH SCT035 OVC060 TEMPO 3022/3101 3SM -RASN BKN015 OVC030
FM310100 09011KT 2SM -SN SCT008 OVC015 TEMPO 3101/3103 1/2SM SN FZFG VV008
FM310300 06014KT 1SM -SN SCT005 OVC008 TEMPO 3103/3107 1/4SM SN FZFG VV004
FM310700 03010KT 3SM -SN SCT008 OVC012 TEMPO 3107/3110 1SM -SN OVC008 KGJT 301653Z 00000KT 10SM SCT050 OVC065 01/M04 A2978 RMK AO2 SLP095 T00061044

KGJT 301553Z 00000KT 10SM OVC060 00/M06 A2977 RMK AO2 UPE11 SLP090 P0000 T00001056KGJT 301453Z 00000KT 10SM UP OVC060 00/M04 A2976 RMK AO2 UPB48 SLP088 P0000 60000 T00001044 50003KGJT 301353Z 08005KT 10SM OVC065 00/M06 A2976 RMK AO2 UPB1256E19SNE1256 SLP087 P0000 T00001056KGJT 301253Z 00000KT 10SM -SN OVC060 M01/M04 A2976 RMK AO2 UPB50E52SNB52 SLP087 P0000 T10061044KGJT 301153Z AUTO 11004KT 10SM OVC060 M01/M06 A2975 RMK AO2 SLP079 T10061061 11006 21017 55005

KGJT 301140Z 3012/3112 10004KT P6SM VCSH OVC070 FM301500 15006KT P6SM VCSH SCT050 OVC070
FM301800 26008KT 6SM -RA BR SCT020 OVC030
FM310100 27003KT 5SM -SN BR OVC030
FM310700 31009KT 3SM -SN BR BKN015

Layers of ice
Failure to Remove
Spinner Ice
“Luke I am your Father”

DEICING AND ANTIICING

Approach with Ice
Stall speed will increase with ice accumulation
If you have ice make your approach faster than normal
Consider not using flaps on approach
Uncontrolled pitch and roll may result from the unexpected stall
The penalty is a longer landing roll out on a possibly slick runway

FLYING IN ICE

Alcohol Deicing System

FROST
Collects when the surface and the Dew point are below freezing and the temp cools to the dew point
Little crystals form fingers that interrupt the boundary layer
Remove all frost before takeoff
Polish the frost smooth (old school method)

NEW INFO
In recent publications, the FAA has recommended that all the frost be removed prior to flight, especially on laminar flow wings.
According to wind tunnel data, a wing upper surface roughness caused by particles of only 1-2 mm [millimeter] diameter [the size of a grain of table salt], at a density of about one particle per square centimeter, can cause lift losses of about 22 and 33 percent, in ground effect and free air, respectively.
Research has shown that almost imperceptible amounts of ice on an airplane’s wing upper surface during takeoff can result in significant performance degradation. Therefore, the Safety Board has urged pilots to conduct visual and tactile inspections of airplane wing upper surfaces in past safety recommendations (including Safety Recommendation A-04-66, which was issued to the FAA on December 15, 2004).

FREEZING FROST CRYSTALS

Chapter 21
Arctic Weather

NORTH TO ALASKA
North of the arctic circle 66.5º
Suns rays strike at shallow angles in both summer and winter
North pole has 6 months of sun and 6 months of darkness

SKY COVER
Less clouds in winter because its dryer
The permanent ice pack grows reducing the chance for evaporation
Cloudiest in summer more moisture
Thunderstorms generally move from northeast to southwest because of the polar easterlies
Great source region because of the uniform properties
Mostly Occluded fronts

ARCTIC WEATHER
Polar lows are small but mighty
They form over the ocean and produce severe weather, winds and precip
Winds are typically light except along the coast
Great source region for airmasses
Temperature inversions are common over land

VISUAL ILLUSIONS
Temp inversion Looming illusion, object appears to be above the horizon
Northern lights – like a neon sign, particles illuminate rarified gases along the magnetic lines of flux
Light – reflection into areas that usually have shadows
night time lighting from moon and stars more intense in arctic

HAZARDS
Fog most prevalent wx problem for pilots
Ice fog steam fog advection fog, blowing snow, icing, frost, white out conditions
White out cloud layer of uniform thickness breaks up and diffuses sunlight.
Parallel rays then reflect back and forth several times eliminating all contrast and shadows.
Blowing and drifting snow