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Weather > Wx Hazards > Flashcards

Wx Hazards Flashcards

0
Q

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

A

Fair Wx cumulus clouds form at the top of up drafts

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1
Q

What are the 2 types of convective currents?

A

Up drafts

Down drafts

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2
Q

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

A

Buildings
Trees
Mountains

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3
Q

Definition of wind shear

A

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

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4
Q

What are the 5 possible causes of wind shear?

A 
Obstructions to wind flow
Surface friction
Frontal zones
Above stable layers and inversions 
Down drafts and microbursts
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5
Q

What is a microburst?

A

Precipitation induced down drafts

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6
Q

What are the hazards associated with a microburst?

A

Can cause tornado like damage

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7
Q

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

A

Apply takeoff power and climb at best climb speed

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8
Q

Where is clear air turbulence usually located?

A

At high altitudes near the tropopause

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9
Q

Describe light turbulence?

A

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

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10
Q

Describe moderate turbulence

A

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

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11
Q

Describe severe turbulence

A

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

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12
Q

Describe extreme turbulence

A

Aircraft tossed about, virtually impossible to control

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13
Q

What causes mountain wave turbulence?

A

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

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14
Q

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

A

Cap clouds
Rotor clouds
Lenticular clouds

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15
Q

Where is the turbulence in mountain wave turbulence?

A

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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16
Q

What are the 3 conditions necessary to form thunderstorms?

A

Sufficient moisture
Unstable air
Lifting mechanism

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17
Q

3 stages of a thunderstorm

A

Cumulus
Mature
Dissipating

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18
Q

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

A
  • 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
19
Q

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

A
  • 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
20
Q

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

A

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

21
Q

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

A

Not associated with any frontal Wx

Typically lasts up to an hour

22
Q

Where are embedded thunderstorms located?

A

Thunderstorms hidden in the clouds

23
Q

What are the 2 characteristics of a multicellular thunderstorm?

A

Long duration due to multiple cell formation

Gust front drives formation of new cells

24
Q

What are the 8 hazards of thunderstorms?

A 
Tornadoes 
Squall lines
Turbulence
Icing
Hail
Low ceilings
Low visibility
Lightning
25
Q

6 characteristics of a supercell thunderstorms

A

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

26
Q

3 characteristics that define a severe thunderstorm

A

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

27
Q

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

A

20 miles

28
Q

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

A

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

29
Q

What is structural icing?

A

Ice which forms on aircraft

30
Q

What temp range is conducive to clear ice formation?

A

0 to -5 degrees Celsius

31
Q

Where does clear ice come from

A

Drops from rain or cumulus cloud

32
Q

What does clear ice look like?

A

Solid clear appearance, child

33
Q

Where on an airfoil does clear ice strike

A

Past the leading edge!

Yarrrr

34
Q

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

A

Low pressure over airfoils may drop temperatures to freezing.

35
Q

List the eight adverse effects of structural icing?

A 
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.
36
Q

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

A

20-30 miles

37
Q

Do METAR reports include a descriptor for severe thunderstorms?

A

No.

38
Q

What temp range is conducive to rime ice formation?

A

-15 to -20

39
Q

Where does rime ice come from?

A

Drops from drizzle or stratus clouds

40
Q

What does rime ice look like?

A

White, brittle, rough, light

41
Q

Where on an airfoil does rime ice stick?

A

Leading edge

42
Q

What temp range is conducive to mixed ice formation?

A

-5 to -15 degrees Celsius

43
Q

What does mixed ice look like?

A

Very rough often growing out wards

Both clear and rime ice characteristics

44
Q

What 3 conditions must exist for structural icing to occur?

A

Visible moisture
Supercooled droplets
Freezing temps

45
Q

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

A

Water or supercooled droplets (the moisture)

46
Q

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

A

Turbulence and wind sheer under the storm could be disastrous.

Weather (6 decks)

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