Sep 2012Lesson 4.8

Meteorology

Icing & Turbulence

Reference

From the Ground UpChapter 6.10 & 6.11:Icing & TurbulencePages 154 - 159

Introduction• Icing is the accumulation of ice on an

aircraft during flight or on the ground. Turbulence is the abrupt vertical movement of air.

• Icing and turbulence can create serious conditions for aircraft during flight.

Outline• Icing• Turbulence

Icing• Clear Ice

– Glass-like coating of ice– Formed by large supercooled water droplets that freeze slowly and

spread

Icing• Rime Ice

– Opaque, milky white ice– Formed by instant freezing of small supercooled water droplets

Icing• Frost

– White, feathery crystalline ice– Usually formed on the ground by sublimation on clear nights

Icing• Frozen Dew

– Clear, crystalline ice– Dew formed in the morning freezes

Icing Protection• Fluids

– Alcohol-based fluid released from leading edge of wings and propellers

– Makes it difficult for ice to form

Icing Protection• Rubber Boots

– Rubber membrane on leading edge that pulsates– Breaks off formed ice

Icing Protection• Heating Devices

– Heats ice-prone areas to melt or prevent ice

Turbulence

Turbulence Classes• Light

– Momentary, slight change in altitude and/or attitude– Occupants may feel slight strain against seat belts

• Moderate– Slightly more intense– Occupants feel strain on seatbelt– unsecured objects move around

• Severe– Large and abrupt changes in altitude, attitude and/or airspeed– Airplane may go out of control momentarily– Occupants forced violently against seatbelts

• Extreme– Airplane tossed around violently and impossible to control– Structural damage may occur

Turbulence Types• Mechanical Turbulence

– Friction between air and rough ground (hills, trees, buildings etc)

• Thermal Turbulence– Ground heating creates upward currents of warm air

• Frontal Turbulence– Warm air is forced over cold front, turbulence at boundary

• Wind Shear– Sudden change in wind speed or direction between layers of air– Usually associated with strong inversions or fast-moving cold fronts

• Clear Air Turbulence– Unexpected, violent turbulence at high altitudes in clear air

Next Lesson

4.9 – MeteorologyWeather Reports & Forecasts

From the Ground UpChapter 6.14.3 & 6.14.4:Aviation Weather Reports & ForecastsPages 163 - 172