Aviation Hazard Awareness Training Aviation Hazard Awareness Training

Jody James, Senior ForecasterJody James, Senior Forecaster

IcingIcing

Aircraft IcingAircraft Icing…not often encountered……not often encountered…

Dangerous for all AviationDangerous for all Aviation

The Worst Conditions for IcingFrom USA Today Website

We Will Cover:We Will Cover:

Types of IcingTypes of Icing

Where is Ice Encountered?Where is Ice Encountered?

De-Icing EquipmentDe-Icing Equipment

What to Do If Ice Is Encountered?What to Do If Ice Is Encountered?

Icing ForecastsIcing Forecasts

Types of Icing

• Clear - A glossy, clear or translucent ice formed by the relatively slow freezing of large supercooled water droplets.

• Rime - Rough, milky, opaque ice formed by instantaneous freezing of small supercooled water droplets.

• Mixed - Mixture of rime and clear ice.

What Temperature Ranges…for

0 to –20 degrees 0 to –20 degrees CelsiusCelsius

WarmerWarmer – No Ice– No Ice

ColderColder – water droplets – water droplets convert to ice crystalsconvert to ice crystals

What Temperature Ranges…for

Can…However get Can…However get Ice in Temperatures Ice in Temperatures

–25 or colder–25 or colder

Especially in T-stms…Especially in T-stms…

Big Droplets and Big Droplets and Strong Lifting…Strong Lifting…

Where are Icing Conditions Usually Worse??

• Near the tops of Clouds…larger drops – still very small, on the order of 10 to 50 microns. (A human hair is around 100 microns.)

• Freezing Precipitation - The worst icing occurs when aircraft encounter supercooled liquid water in the drizzle drop size (30-300 microns diameter).

The ATR crash was in freezing drizzle – not well understood.

Thunderstorm – Severe IcingThunderstorm – Severe Icing

20 miles!!

ATR Icing Accident

A twin turbo-prop ATR-72 nose-dived into a soybean field near Roselawn, Indiana, on Oct. 31, 1994, killing everyone on board: four crewmembers and 64 passengers.

The NTSB attributed the aircraft's loss of control to a sudden and unexpected movement of an aileron -- a flight control on the wing -- that occurred after a ridge of ice formed behind the plane's deice boots -- mechanisms that shed in-flight ice buildup from the wings.

This occurred behind the ice boots and resulted in aileron reversal.

On October 31, 1994, an ATR-72 commuter aircraft crashed near Roselawn, Indiana, killing 64 passengers and 4 crew members. Aircraft icing was the cause.

Safety Rules in Ice

• Hand Fly the Aircraft to Check Aerodynamics

• In GA Aircraft – Use De-ice equipment to flee from the ice, not fly in the ice… Read POH

•Most Ice Accidents occur not in the ice, but during landing after acquiring ice. Stall Speed will increase….be careful with slow and low maneuvering.

• Keep Speed Up on Approach if heavily iced!!

Safety Rules in Ice

Treat Ice Like Smoke in the Cockpit, –

Do something about it!

Options:

• Climb – May be warmer temperatures above

• Descend – to warmer temperatures, watch out for MSA/terrain.

• Divert – alternate airport

• Return – 180 course reversal…this may be best option.

Aircraft De-Icing and Anti-icing

Pitot Icing - Responsible for a lot of accidents. Airspeed indicator will act like altimeter

Partial Protection – prop de-ice, windscreen de-ice – use when in clouds below 0 degrees C.

Ice Boots – some equipment not approved for flight in icing.

Has Aircraft been tested in ice – ex. Homebuilts. Wanna be a test pilot??

OF INTEREST>>>

The weight of 1 inch of ice is usually negligible…50 to 100 lbs…most of the loss of efficiency is due to the disfiguring of the airfoil. Ice on propeller also small effect compared to airframe ice.

Other Icing Information can be obtained from Aviation Weather Center Page at:

www.aviationweather.gov

Official Icing Forecasts are obtained from AIRMETS - ZULU

DFWZ WA 121445 AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL 122100 . NO SGFNT ICE EXPCD OUTSIDE OF CNVTV ACT. . FRZLVL...060-080 N OF INK-SAT-MLU-MSL-HMV LN RSG TO 120-140 OVR LWR RIO GRANDE VLY OF S TX . ....

Ft. Worth AIRMET ZuluIcing and Freezing Levels

Official Icing Forecasts are obtained from AIRMETS - ZULU

MIAZ WA 121445 AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL 122100 . AIRMET ICE...NC SC GA FL AND CSTL WTRS FROM 170E ORF TO 140SSE ILM TO CRG TO 50SW ABY TO GQO TO HMV TO 170E ORF OCNL MOD RIME/MXD ICGICIP BTN 140 AND FL270. CONDS CONTG BYD 21Z THRU 03Z. . FRZLVL...100-120 NW OF MGM-ORF LN SLPG TO 140-160 S OF 180SSW CEW-140SSE ILM LN.

Miami AIRMET ZuluIcing and Freezing Levels

Other Forecasts Useful When Icing is a Concern

TAF

TAF KLBB 121130Z 061212 36014GKT 3SM –FZDZ BR OVC020

Winds and Temps Aloft

3000 6000 9000 12000 18000……

39000 LBB 3409+03 3410-03 3314-10 3475-12 3387-24

Other Forecasts Useful When Icing is a Concern

PIREP

JFK UA /OV JFK180005/TM 1649/FL250/TP LR25/IC MOD RIME=

Be careful using PIREPS…

1. Not all ice is reported…

2. Ice Can Develop or Dissappear Quickly

3. What Type of Aircraft Reported the Ice?

A Jet at 250 knots may report no ice…while in a Cessna 172…you report a light frost…WHY???Several degrees warming of skin temp due to friction!

Other Forecasts Useful When Icing is a Concern

Icing Airmets and Sigmets

Aviation Weather Center - aviationweather.noaa.gov

Icing Forecasts

Icing Potential Forecasts

CIP and FIP

Aviation Weather Center - aviationweather.noaa.gov

Icing Forecasts

Freezing Level Graphics

Aviation Weather Center - aviationweather.noaa.gov

Icing Forecasts

Pilot Reports

Aviation Weather Center - aviationweather.noaa.gov

Aviation Hazard Awareness Training – Aviation Hazard Awareness Training – Thunderstorms Thunderstorms

Jody James, Senior ForecasterJody James, Senior Forecaster

Aircraft icing is one of the major aviation hazards for which forecasters must advise pilots. Significant icing is very dangerous because accumulation of ice affects aircraft performance. In just a matter of minutes, an aircraft can ice up to a point where maintaining control becomes very difficult. The worst icing occurs when aircraft encounter supercooled liquid water in the drizzle drop size (30-300 microns diameter). Obvious weather conditions are temperatures below zero degrees Celsius and environments with high relative humidity. However, in order for these drizzle drops to form, the atmosphere must be undergoing upward vertical motion at slightly faster speeds than the large-scale lifting that forms large cloud masses (about 1 cm/sec). Too much upward vertical motion and water drops larger than drizzle-size quickly develop. The optimum vertical motion is on the order of 10 cm/sec. One likely cause of vertical motion of this magnitude is the slowing down of convective bubbles as they encounter decelerating forces. This condition occurs frequently at cloud tops, and is a good explanation of why significant icing is often observed there.

The patterns of the conditions for significant icing (temperature, relative humidity, and slight convective potential) are numerous and quite complex. They do not lend themselves to typical input/output prediction schemes. An artificial intelligence tool that does very well at pattern recognition is a neural network. A neural network is a simple version of a mammalian brain. A neural network is "taught" to recognize input data patterns and to identify with what conditions these input patterns are associated. A neural network is pure rote learning, like a gradeschooler learning multiplication tables. Neural networks work well in complex pattern recognition because they are very non-linear. That means that they can handle situations which cannot be expressed in a straight-forward logical thought-stream.

The maps of icing intensity are composites of the output of two neural networks taught to predict icing intensity from input data of temperature, relative humidity, and convective potential from the Rapid Update Cycle model. Actual output to the Aviation Weather Center forecasters is in layers approximately 1000 ft thick. The output values range from zero to six with zero representing no icing and six severe icing. A two is light icing and a four is moderate icing. The contours begin at the two level. While fours are very common, a five (moderate to severe icing) is rare. Because of the contouring routine, you will never see a six.

This is experimental output. The Experimental Forecast Facility at the Aviation Weather Center is evaluating the output to see if there are any flaws. Anyone using this product as a flight-briefing aid should always consult the latest Aviation Weather Center icing advisories.

Donald W. McCann AWC Research Meteorologist