Weather Theory

Cloud Types (Cirroform and cumuliform)

Cirriform - Thin wispy clouds of ice crystals. No sig weather comes from this type of cloud

Cumuliform - Puffy fair weather type clouds. Indicates unstable air and can develop into towering cumulus

Cloud Types (Nimbus clouds and lenticular)

Nimbus - Shallow and broad (nimbostratus) or tall/powerful (cumulionimbus)

Lenticular - Lens shape and indicates severe turb, common in mountainous areas

What are the characteritics of stratiform and cumuliform clouds?

Stratus clouds - Low liquid water content, climb or descent to exit the clouds as they are horizontally developed

Cumuliform - High liquid water content, laterally deviate around these clouds as they are vertically developed

How does cloud formation occur?

Air is forced aloft and it cools to its saturation point. Water vapor condenses or sublimates creating clouds

How does fog form

Temperature reaches the dewpoint (radiation fog, advection fog, upslope fog)

Addition of moisture to the air elevating its dewpoint (precipitation induced fog or steam fog)

What is important to remember about the temps that ice can form at?

Aerodynamic cooling can cause ice to form even if the temperature is above cooling

What are some obstructions to visibility caused by clouds?

Rain
Sleet
Snow
Hail
Freezing Rain

Smoke

Caused by the suspension of combustible particles

Creates the illusion of being at greater distance than actual from runway resulting in lower approach

Haze

Caused by fine dry particles from fire

Creates the illusion of being at greater distance than actual from runway resulting in lower approach

What is needed for clouds and fog to form

Condensation nuclei

Dewpoint

Moisture

Radiation fog

Forms over land on calm clear cool humid (small temp/dewpoint spread) nights

Occurs at night or daybreak

Produced by condensation of water vapor due to condensation cooling. Dissipates in the morning quickly unless cloud layers form above

Advection fog

Forms when a layer of warm moist air moves over a colder surface

Intensified by winds up to 15knots anything greater will dissipate it or lift it to stratus

Common along coastlines and can occur day or night, regardless of clouds or wind

Upslope fog

Moist stable air is forced up a slope

Similar to advection fog

Once the upslope wind ceases the fog dissipates

Common in mountain ranges

Precipitation induced fog

Formed when warm rain/drizzle falls through a layer of cooler air near surface and if cold air below is near its dewpoint the evaporation of the precipitation may form fog

Associated with warm fronts but can occur with slow moving cold/stationary

Ice fog

Formed in cold WX when temp is much below freezing

Caused by sublimation of water vapor directly into ice

Steam fog

Caused by very cold air moving over warmer water

Enough water evaporates from the water to elevate the dewpoint and cause fog to form

Common over lakes and streams in fall and in the winter when a cold air mass from land moves over the warmer ocean

How can you detect fog occuring?

Temps and dewpoints - Review weather reports for current temps and dewpoints

Sun - Consider how the sun will change the temp

Rate of change of temps and dewpoints - If in a decreasing trend or they are getting closer together expect fog

Airport location - If near oceans or up a mountain expect fog. To counter these find an airport further inland or at a lower elevation

What is needed for the formation of a thunderstorm?

Unstable air

High moisture content of the air

Lifting action

Cumulus stage of TS

Lifting action indicating the vertical movement of air

Water vapor condenses as it rises releasing energy for further vertical growth

Mostly strong updrafts result no precip

Towering cumulus clouds form rapidly and reach mature stage in about 15minutes

Mature stage of TS

Starts when precip begins to fall at the surface

Precip becomes too heavy to support triggering downdrafts

Updrafts will still dominate in this stage

Lightning occurs here

Dissipating stage of TS

Downdrafts begin to disspiate the updrafts

Entire storm weakends

Storm is considered dead when rain is no longer produced

What are some of the hazards of TS?

Severe turb/wind shear - microbursts, downdrafts exceed 6000fpm lasts for 15min
Icing - Severe or greater
Hail - occurs in mature dissipating stage
Low visibility - Caused by hail and precip

What are squall line TS?

Most sevever form of thunderstorm

Long line of TS that forms ahead of a cold front but can also form anywhere with unstable air

Due to length and height you can’t really pass them (best option is to land and let it go over)

By how many miles should you avoid a TS?

20 miles including the anvil of the TS

Keep in mind that FIS-B onboard datalink weather is not real time and can be delayed by 15min

How should you deal with turbulence

Reference AOPA TS guide it should be like a quiz sorta thing also we need to talk about not extending flaps

Tighten seatbelts and secure all loose objects

At or below Va and AP off

Eyes on instrument panel with max brightness to avoid temporary blindness

Maintain constant attitude and ride the waves

Course through the storm don’t turn back it increases stresses on aircraft

Ice avoidance

• Enter above freezing level

• Use carb heat and pitot heat

Formation of hail

Hail is formed by precipitation carried above and below the freezing layer by up and down drafts
Water than refreezes as the droplet is carried above the freezing level
Hail occurs in mature/disspiating stage

What is the danger of ice pellets hitting the aircraft?

Indicates that freezing rain or SLD aloft that would be hazardous if encountered

What are the types of aircraft icing

Structual icing - Ice that forms on aircraft surface and components

Induction icing - Ice that forms on engines induction system

In what WX conditions would you find certain types of icing?

Rime - Warn front, stratiform clouds, occurs when going through a cloud

Clear - Cold front, cumuliform clouds (size of cumulus cloud determines intensity (rime at higher levels) precipitation, supercooled water droplets

Mixed - Stratiform and cumuliform clouds

What are the types of icing

Clear
Mixed
Rime

Clear Ice

Formed by large water droplets that freeze slowly after striking the airframe forming a blanket (supercooled droplets)

Avoid cumulus clouds, freezing rain, especially if below temp.

Warmer than -10*C

Rime Ice

Formed by small water droplets that freeze quickly to an aircraft

Milky, rough appearance

Avoid stratiform clouds

Colder than -15*C

Mixed Ice

Possess negative quality of rime and clear

Combination of liquid water, snow and ice results in mixed ice

Ice particles become imbedded in what wouldve become clear ice that results in a rough accumulation of ice

What conditions are needed to cause icing

Contact surface temp below freezing
Visible moisture (clouds or rain)

Will snow cause icing?

Snow will not cause icing because its not liquid it has to be liquid and not already frozen

What informatoin should you be aware of with respect to icing?

Location of fronts - Speed, type, size, direction

Cloud layers - Bottom and tops to climb out of ice

Freezing levels -

Air temps or pressures - Ice found in low pressures and temps at or around freezing

Precipitatoin - Know the location and type

What is freezing level

Lowest altitude where the temp is 0*C

Multiple possible in temp inversion

To determine location use PIREPs, AIR/SIGMET, Winds aloft, Low level sig weather charts

Freezing rain is found in

Temperature inversions when we have warmer temps aloft and colder temps below

Highest icing accumulation rate

How should you escape freezing rain

Immeadietly make a 180 back to conditions that didn’t have freezing rain

Change altitudes by climbing to warmer air

Icing reports

Report icing to ATC with the following levels of intensity

Trace - Not a whole lot of ice (<1/4in)

Light - Could create a problem for you if it accumulated for more than 1 hour

Moderate - Short encounters could create a problem in just a little bit of time (boot usage, immediate diversion)

Severe - Anti ice or de-ice cannot keep up with the rate of accumulation and you need to take immediate action.

By reg you must exit severe icing the rest you can stay in

Why should you click off the autopilot in icing conditions

You will be unable to feel the loss of effectivness of flight controls and percieve the loss of lift

How should you fly in icing conditions differently

Declare emergency, advise you would like to stay above cloud as long as possible and request descent at pilot discretion

Apply carb heat during icing conditions, window heat, pitot heat before icing conditions

Propeller to max RPM

180* Turn around to conditions where you didnt have ice

• Get PIREPs from ATC and determine where conditions are

Climb above/below clouds

• Rapidly to limit build up of ice

• Use 2* per 1000ft to find the altitude above freezing and request a descent to the MVA

• Based on cloud type (stratiform or cumulus) laterally or vertically deviate

• Find temps above freezing or below -10C because at these temps air can’t hold liquid water

• Find areas free of visible moisture

• If descending know temps and terrain, if climbing pay attention to climb performance which could have you stuck if too slow

Fly faster (5-10kts on appch)

• Longer runway likely needed

Don’t change configuration (flaps or gear) until neccecary

• Flaps - Deploy in stages and note deficiency in performance, if neccecary retract to last stage

• Brakes - limit use of brakes due to LOC from ice build up

What are the different kinds of deicing system

Anti icing - Prevents ice accumulation (pitot heat, hot props, and wings that “weep” anti ice fluid TKS. Essentially there is a reservoir of glycol and microdrilled holes in the wing that allow it to weep)

Deicing  - Removes accumulated ice by inflating rubber boots that have tubes in them (pneumatic boots)

When should deicing systems be used?

At first indication of icing, but check with manufacter too

Keep in mind that the wing may not be clean after one cycle and there will likely be some residual icing

Residual ice increases

As tempertaure or airspeed decreases

What are the icing regulations

FIKI regulation
FIKI is restricted by this regulation and by POH/limitatoins
IFR cant fly into known or forecast - light or moderate icing conditions
VFR cant fly into known - light or moderate icing conditions

By regulation no person may takeoff in an aircraft when frost, ice or snow adheres to the wing, control surfaces, propellers, engine inlets or other critical surfaces of an aircraft

ICTS

Tailplane will collect ice the fastest due to its thin size relative to the wing

Ice contaminated tailplane stalls occur when a tailplane accumulated with ice is put at a significant negative AOA that causes it to stall

To recover

• Recover in the reverse that you would of a normal stall meaning pull back which increases the camber of the wing

• Retract flaps to previous setting

• Nose up elevator trim

• Make nose down changes slowly

• No autopilot

What are some considerations for icing conditions?

Climb performance - If you hit ice climb performance will drop which causes a problem in terrain or for SID/STAR

Weight to load the aircraft - Consider taking less fuel if you may be in icing conditions to mitigate their affect

Know your exit plan - Altitudes and places to fly to avoid it but consider terrain, airspace, DPs

Fuel consumption - Ice will cause you to fly faster meaning you will burn more fuel also this means you need a longer runway to land on so consider it with alternates

What are the types of icing

Structual - Ice on the exterior of the aircraft

• Rime, mixed, clear

Induction - Ice that limits air avlaible for combustion

Insturment - Ice that forms over instruments and sensors

What is a sign you are getting induction icing (carb ice)

Induction icing is loss of air available for the engine

Loss of RPMs in fixed pitch

Loss of manifold pressure in constant speed prop

What is roll upset?

Uncommanded and uncontrollable roll of the aircraft

Could be due to airflow separation or the aileron being deflected in a certain manner

How do you recover from roll upset?

Level the nose and wings

Set power and monitor ASI/AOA

If flaps extended do not retract as this will raise the AOA unless that you can determine there is no ice on the upper wing

What are the different flight categories

LIFR - <500, <1SM
IFR - 500-1000, 1-3SM
MVFR - 1000-3000 - 3-5SM
VFR - >3000 - >5SM

Why should you be alert for turbulence?

Turbulence can lead to spatial disorientation in IMC if it is light or moderate

What is the defintion of the term “ceiling”

Height above the Earth’s surface of the lowest layer of broken clouds

What is the windward and leeward side?

Leeward side - Weather is coming from this side

Windward side - Weather is going to this side

Review precipitation static in systems under “Grounds”

Review precipitation static in systems under “Grounds”