Wx Hazards Flashcards by kristen stonecipher

Where is the stable air and the turbulence associated with fair Wx cumulus clouds?

Fair Wx cumulus clouds form at the top of up drafts

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What are the 2 types of convective currents?

Up drafts

Down drafts

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Name 3 obstructions to wind flow that can cause mechanical turbulence?

Buildings
Trees
Mountains

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Definition of wind shear

Change in direction and/or speed with altitude or horizontal distance

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What are the 5 possible causes of wind shear?

Obstructions to wind flow
Surface friction
Frontal zones
Above stable layers and inversions 
Down drafts and microbursts

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What is a microburst?

Precipitation induced down drafts

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What are the hazards associated with a microburst?

Can cause tornado like damage

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What are the 2 steps to take if a pilot encounters a microburst?

Apply takeoff power and climb at best climb speed

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Where is clear air turbulence usually located?

At high altitudes near the tropopause

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Describe light turbulence?

Momentary, slight, erratic changes in altitude and/or airspeed slight strains against the seatbelt

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Describe moderate turbulence

Change in attitude and/or altitude, able to maintain positive control definite strains against seat belts

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Describe severe turbulence

Large abrupt changes in attitude or altitude, momentary loss of control, forced violently against seat belts

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Describe extreme turbulence

Aircraft tossed about, virtually impossible to control

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What causes mountain wave turbulence?

Wind over mountainous areas causes wave like winds on the lee side

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What are the 3 types of clouds that may occur with mountain wave turbulence?

Cap clouds
Rotor clouds
Lenticular clouds

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Where is the turbulence in mountain wave turbulence?

Severe turbulence can be encountered on the leeward side

Turbulence can be encountered up to 3,000 ft above the mountain

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What are the 3 conditions necessary to form thunderstorms?

Sufficient moisture
Unstable air
Lifting mechanism

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3 stages of a thunderstorm

Cumulus
Mature
Dissipating

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What 3 things happen during the cumulus stage of a thunderstorm?

lifting can exceed 3,000 ft/min vertical development
small raindrops are lifted above the freezing level posing an icing hazard
raindrops grow in size and eventually begin to fall creating a downdraft

What 7 things happen during the mature stage of a thunderstorm?

precipitation begins to fall from the base
downdraft may exceed 2,500 ft/min
updrafts can exceed 6,000 ft/min
anvil forms when rising air reaches tropopause
gust front at surface
surface pressure rises and temp drops due to downdraft
thunderstorm reaches it’s greatest intensity

What 3 things happen during the dissipating stage of a thunderstorm?

Downdrafts greater than updrafts
Precipitation at the surface
Without updrafts providing moisture, thunderstorm begins to collapse

What are the 2 characteristics of an air mass or single cell thunderstorm?

Not associated with any frontal Wx

Typically lasts up to an hour

Where are embedded thunderstorms located?

Thunderstorms hidden in the clouds

What are the 2 characteristics of a multicellular thunderstorm?

Long duration due to multiple cell formation

Gust front drives formation of new cells

What are the 8 hazards of thunderstorms?

``` Tornadoes Squall lines Turbulence Icing Hail Low ceilings Low visibility Lightning ```

6 characteristics of a supercell thunderstorms

Can last over 2 hours May split Common in Midwest Tornadoes Has multiple cll structure but in different formation than multicell Rotational formation due to differing surface winds and

3 characteristics that define a severe thunderstorm

Wind gusts of 50 knots or more Hail 3/4 inch or larger in diameter Strong tornadoes

What is the minimum recommended distance to stay away from thunderstorms?

20 miles

What are 4 cloud types that could identify a severe thunderstorm?

Shelf or roll clouds Dark color clouds Mammatus clouds Towering cumulus clouds

What is structural icing?

Ice which forms on aircraft

What temp range is conducive to clear ice formation?

0 to -5 degrees Celsius

Where does clear ice come from

Drops from rain or cumulus cloud

What does clear ice look like?

Solid clear appearance, child

Where on an airfoil does clear ice strike

Past the leading edge! | Yarrrr

What can cause structural icing to occur in ambient temperatures that are slightly above freezing?

Low pressure over airfoils may drop temperatures to freezing.

List the eight adverse effects of structural icing?

``` reduced lift Decreased thrust Increased weight Increased drag Impairs engine performance False instrument indications Loss of radio communications Loss of operation of control surfaces, landing gear, hinges. ```

At what distance separating strong or very strong radar echoes can a flight path be considered free of severe turbulence?

20-30 miles

Do METAR reports include a descriptor for severe thunderstorms?

No.

What temp range is conducive to rime ice formation?

-15 to -20

Where does rime ice come from?

Drops from drizzle or stratus clouds

What does rime ice look like?

White, brittle, rough, light

Where on an airfoil does rime ice stick?

Leading edge

What temp range is conducive to mixed ice formation?

-5 to -15 degrees Celsius

What does mixed ice look like?

Very rough often growing out wards | Both clear and rime ice characteristics

What 3 conditions must exist for structural icing to occur?

Visible moisture Supercooled droplets Freezing temps

What is in the visible moisture that actually sticks to the structure of the helicopter?

Water or supercooled droplets (the moisture)

Why should a pilot not attempt to fly under a thunderstorm even if you can see through to the other side?

Turbulence and wind sheer under the storm could be disastrous.