Flying with Ice
--Avoid abrupt and steep maneuvers while carrying ice.
--Reduce the angle of attack in climbs to get out of icing.
--Do not use flaps and add speed on approach.
--Visible moisture
--Aircraft external surface temperature at or below freezing
--Ambient air temperature a degree or two above freezing
--These textbook requirements do not ALWAYS apply.
--Light aircraft should not fly in clouds and freezing temperatures.
--Plan a no-flap landing any time you have icing.
--Be aware that aircraft handling will be degraded by:
...........Loss of stability
............Reduced or loss of control
.............Possible tail stall

Rising air causes water vapor to rise and condense into water droplets. Some of these droplets may form ice crystals but others remain liquid. As cloud droplets cool to freezing and below they may fail to become ice crystals. Clouds from 0 to -10 Celsius are likely to be only super cooled droplets. The droplets do not have the required nuclei to trigger the creation of ice. Below -20 Celsius only ice crystals will exist. If these droplets become too large to be lifted they will fall as freezing rain or drizzle. A wing meeting this super cooled water will make ice on a wing surface. Icing is more likely in a cloud when the sky is clear overhead. This is because any falling ice crystals form at the expense of water droplets. The biggest cloud drops are confined to small areas or shear zones. Turbulence is a characteristic of a shear zone.

Major effects of structural icing on the aircraft itself consist of airfoil changes, weight, blocking of air intakes, loss of visibility, radio, interference, and corruption of static instrument readings.

When moisture and sub-freezing temperature are combined you have the basic ingredients for icing. The major effect of ice on an airplane is that it disrupts the smooth flow of air, increases drag and thereby the stall speed. Weight is not as critical as is the effects on airflow. For ice to accumulate the temperature has to be below freezing and the moisture visible. Icing decreases speed, lift, range, climb performance, service ceiling, visibility, radio reception, thrust, engine cooling and combustion. Icing increase gross weight, stall speed, fuel consumption, flight time and heart rate. Icing at high altitudes is not as usual as at low altitudes and when occurring is rime ice. Accumulation rate will be less.

About Ice
--Have an ice escape plan.
--Preflight pitot heat.
--Know icing characteristics of flight path.
--Know where the warm air is.
--Cloud tops (ice) rises toward the low pressure center.
--Cycle boots to assure operation.
--Use shallow climb in icing conditions.
--Give PIREPs on 122.0
--Land without flaps.
--There is still a lot we do not know about aircraft icing.

Icing Checklist
1. Make a 180° turn.
2. Climb if your performance allows.
3. Use carburetor heat or alternate air.
4. Apply pitot heat
5. Defrost the windows in preference to cabin heat.
6. Apply partial flaps in the descent but not in the approach.

What's New
Metal-coated electro-thermal system imbedded in paint are in the offing. Electric eddy currents and magnetic repulsion can move ice and cause it to be shed from lifting surfaces. Another system pumps anti-freeze through small holes in the wing surfaces to prevent the formation of ice.

Icing Accidents
For the formation of ice it is required that you be in freezing temperature and visible moisture. A parked aircraft can get ice at less than freezing temperature. The worst ice occurs in freezing rain below clouds. Such icing will be quite rapid in build up. Icing disrupts lift, jams controls, chokes engines, disrupt radios, and clog inlets. It is not a safe assumption that you can tell the existence of icing conditions by visual means. The FAA finds any flight into forecast ice as 'careless operation' under FAR 91.13. FAA weather forecasts are consistently conservative because there has been no appreciable improvement in forecasting capability.

Icing as a cause of accidents seldom remains as evidence. Unless the pilot has revealed the existence of ice the investigators can only make presumptions from assumed flight conditions. About 45 General Aviation accidents due to airframe ice happen every year. PA-28s and C-182s, perhaps because of presumed performance capability, are worst offenders. In flight icing accumulation usually results in approach or touchdown accidents. Structural icing accidents are most apt to result in fatalities. While only one in six aircraft accidents result in fatalities, 56% of icing accidents result in fatalities. Almost 50% of the structural icing accidents/fatalities occurred during takeoff. A millimeter of ice on a wing will reduce lift 25%. What does this say about preflight? I once found ice on one wing and not on the other of a PA-32 during a preflight. The ice was detectable only by feel.

The rounded leading edge is one of the last places to accumulate ice although it is where pilots look first. The sharper the surface the more likely it is to get ice. This is one of the reasons tail surfaces are first to accumulate ice. The divided airflow around lifting surfaces carries most of the water droplets to freeze on the surfaces. A trace of ice on the wing implies a lot on the horizontal tail. Under-wing icing is most likely to occur during climb. The suggestion that you attempt to climb out of icing conditions may not be applicable to GA aircraft. The mention of possible icing along your flight-planned route in an Area Forecast (FA) is sufficient to make the trip 'flight into known icing'. A confirmation of ice means, 'known' icing conditions'.

Roll upset is an aerodynamic stall caused by self-deflection of ailerons that occurs in aircraft with un-powered ailerons and pneumatic deicing. Freezing super-cooled drizzle drops (SCDD) does this. The upset is triggered by some change in configuration.

Icing creates unique airfoil shapes with unique lift, drag, critical angles of attack and pitching characteristics. Once ice accumulates you become a test pilot. In icing conditions any vibration, buffet or change in handling serves as a warning that you are in serious trouble. The problem may be irreversible. It is not a good practice to fly in ice with flaps and gear extended. The accumulation of weight and drag will adversely affect performance.

Icing is not always forecast accurately since it is based on relative humidity and temperature. Anytime the OAT is at +5 C consider icing as possible. This is especially true if you are descending out of even colder air and the cold aircraft surfaces may provide a welcome home for icing. A standard lapse rate loses 2°C or 4°F for every thousand-foot increase in altitude. Knowing this basic and the airport altitude you can surmise the freezing level by subtracting 32° from the surface temperature given AWOS or ATIS, divide this difference by 4 and multiply the dividend by a thousand. This must be added to the surface altitude to find the flight altitude of freezing level.

Birth of a Thunderstorm
The warm earth begins to release heat into cooler moist air. Puffs of cumulus begin to form and rise. Two or three of the puffs merge, are warmed more and rise faster while gathering in the warm moist air from nearby. The tops of the cloud have reached colder regions of surrounding air that condenses and forms slush balls of graupel. These balls begin to fall through the cloud. The rising air from below raises the graupel hundreds of feet where it falls. This is repeated over and over as the puffy cumulus has darkened and become a cumulonimbus. The positive and negative electrical charges within the cloud have begun to separate top and bottom. The big show is yet to come.

Only 1000 of the 10,000 major thunderstorms develop tornadoes. China has a many storms but only 10 tornadoes. This is because of differences in geography and the presence or non-presence of water.

Any thunderstorm is capable of destroying an airplane. Some just do it quicker. The higher the top the greater the violence by 16,000' will be enough to do you in. The south side is worse than the north side if you for destructive violence and tornadoes.

Thunderstorm Features
A thundercloud can weigh 100,000 tons. (This does not include air pressure). The energy in an average thunderstorm is that of ten atomic bombs. (400 kilotons) Thunderstorms often go above cruising levels of commercial aircraft. The downburst of descending air underneath a thunderstorm have proven to be extremely dangerous to low-flying aircraft. Thunderstorm can breed tornadoes with wind speeds up to 285 mph. The vortex of a tornado may extend from the ground well into the cloud. Any flight into a thunderstorm could encounter a tornado. Never fly in the vicinity of cumulonimbus mammatus clouds. Hazardous turbulence is present in all thunderstorms. Maneuvering greatly increases the stress (G-forces) on an aircraft and should be avoided in any turbulence.

For a thunderstorm to exist you must have water vapor in huge amounts which means a very high humidity, an unstable lapse rate of over 3.5/2 degrees Fahrenheit/Celsius, and a lifting action cause by terrain or heating. When temperature increases or decreases by a 20-degree increment the relative humidity reciprocates (the opposite way) by halving or doubling. Ex: 60-degree temperatures with relative humidity of 25%. Temperature rise of 20-degrees to 80 will cause relative humidity to drop to 12 and 1/2%. Temperature drop of 20-degrees to 40 will cause relative humidity to rise to 50%.

The more lightning the more severe the storm. Thunderstorms have rounded bases with severe up and down drafts best not fought but ridden to avoid over stressing aircraft. Once caught do not turn since this also increases stress on the aircraft. Don't knowingly fly under a thunderstorm since turbulence is a given feature and is usually accompanied by a downburst or microburst of wind and water capable of increasing the aircraft gross weight beyond its climb capability.

Basic requirements are:
1. Unstable air---
2. Initial updraft---latent heat released by condensation will increase buoyancy of rising air column and create a 'burner chamber'
3. Air with high moisture content

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