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NIFE Academics > Weather 3: Weather Hazards > Flashcards

Weather 3: Weather Hazards Flashcards

1
Q

Turbulence

A

Any irregular or disturbed flow in the atmosphere producing gusts or eddies

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2
Q

What are the types of turbulence?

A
  1. Thermal
  2. Mechanical
  3. Frontal
  4. Large-scale wind shear

“WTF Man”

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3
Q

What are the PIREP intensity levels for turbulence?

A

Light
Moderate
Severe
Extreme

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4
Q

What is the PIREP turbulence reporting terms regarding time?

A
  • Occassional- less than 1/3 of the time
  • Intermittent- 1/3 to 2/3 of the time
  • Continuous- more than 2/3 of the time

OIC

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5
Q

What causes thermal turbulence?

A

It is caused by a rising vertical current of heated air from the surface (or when cold air moves over warmer ground which then pushes the air upwards)

Strength of turbulence depends on type of surface being heated and how heated the surface is which varies (dry, barren terrain tends to absorb more heat)

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6
Q

What causes mechanical turbulence?

A

It is caused by wind flowing over or around irregular terrain/obstacles and the normal wind flow turns into complicated eddies

Strength depends on:
1. Wind Speed (slower the wind = lighter the turbulence)
2. Terrain Roughness (the smaller/smoother the terrain, the lighter the turbulence)
3. Air stability

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7
Q

What causes frontal turbulence?

A

Caused by the lifting of warm air by a front leading to instability or by the abrupt wind shift between warm and cold air masses

Fast moving cold fronts typically have the worst of this turbulence

There is little to no lifting associated with warm fronts so there is no frontal turbulence associated with them

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8
Q

Wind shear

A

A suddent change in wind speed and/or direction over a short distance in the atmosphere

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9
Q

What causes high level wind shear turbulence?

A

The jet stream

The highest wind speed and turbulence is found about 5,000 ft. below tropical tropopause

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10
Q

What causes low level wind shear turbulence?

A

Temperature inversions

Occurs at the boundary between the inversion and stable atmosphere. The warmer air above the inversion is faster and can cause a sudden shift in wind speed and direction.

The most dangerous wind shear turbulence

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11
Q

What causes turbulence in thunderstorms?

A

The wind shear between the updrafts and down drafts near each other in the storm

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12
Q

What are the reccomended procedures for flying through turbulence?

A
  1. Establish/maintain thrust settings for turbulent air penetration airspeed and attitude (don’t chase airspeed)
  2. Trim for level flight at penetration airspeed
  3. Control pitch and bank using gyro indicators (use moderate control inputs to correct)
  4. Allow altitude to vary/sacrifice altitude for attitude (don’t chase the altimeter)
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13
Q

What are the types of icing?

A
  1. Structural icing
  2. Engine icing
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14
Q

What are the requirements for icing?

A
  1. Supercooled visible water droplets are present in the atmosphere
  2. The free air temperature and aircraft surface temperature are both below freezing
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15
Q

What are the types of structural icing?

A
  1. Clear ice
  2. Rime ice
  3. Mixed ice
  4. Frost
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16
Q

Describe clear ice.

A
  • Formed by the relatively slow freezing of large super-cooled water droplets
  • Glossy and clear/transulcent (difficult to break off)
  • Occurs between -10°C to 0°C
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17
Q

Describe rime ice.

A
  • Formed by the instantenous freezing of small super-cooled water dropletss
  • Rough and milky/opaque (brittle and easy to break off)
  • Occurs between -20°C to -10°C
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18
Q

Describe mixed ice.

A
  • A combination of clear and rime ice
  • Lumpy but also clear and dense
  • Most frequent kind of ice encountered
  • Occurs between -15°C to -8°C
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19
Q

Describe frost.

A

A thin layer of ice crystals that form on exposed surfaces due to deposition

20
Q

What are the effects of structural icing?

A

Most hazardous effect is the reduction in aerodynamic performance

  • Decrease in lift, thrust, and range
  • Increase in weight, drag, stall speed, and fuel consumption

Pitot tubes and static ports could also be blocked which can cause incorrect instrument readings

21
Q

What is induction icing? What are its hazards?

A

When icing forms on the air intake ducts

Can cause a FOD hazard if ice is ingest ahead of the compressor inlet

22
Q

What is compressor icing? What are its hazards?

A

Ice that forms on the compressor inlet screens and compress inlet guide vanes

Can restrict the flow of inlet air and cause an engine flameout

23
Q

How can pilots avoid structural icing inflight?

A

Manuever the plane to temperatures outside of the icing band (-20°C - 0°C)

Climb to temperatures colder than -20°C or descend to temperatures warmer than 0°C

24
Q

How can pilots prevent icing?

A

Be utilizing de-icing and anti-icing equipment

Avoid flying in clouds with temperatures from -20°C to 0°C

25
Q

Obscruing Phenomena

A

Any collection of particles that reduce horizontal visibility to less than seven miles (can be surface based or aloft)

Fog, haze, smoke, volcanic ash, snow, blowing spray

26
Q

Fog

A

A visible aggregate of water droplets that meets the following conditions:

  • Cloud base is within 50ft. of the ground
  • Greater than 20ft. in depth/thickness
  • Reduces visibility to less than 5/8 mile
27
Q

What are the requirements for fog to form?

A
  1. Condensation nuclei must be in the air
  2. The air must have a high water content (be close to saturation = 2°C or less dew point spread)
  3. Light surface winds are present
28
Q

What are the types of fog?

A
  1. Radiation fog
  2. Advection fog
29
Q

Radiation fog

A

Fog that is due to nocturnal cooling (radiation is released at night and the surface air is cooled. If the air reaches close to saturation, then fog will develop)

Can be dissipated by solar heating

30
Q

Advection fog

A

Fog the forms when a warm, moist air mass moves over a cold surface and is cooled to the dew point

Only a wind shift can dissipate this fog (fog is too dense/thick for solar heating)

31
Q

What is the thunderstorm lifecylce?

A
  1. Developing stage
  2. Mature stage
  3. Dissapating stage
32
Q

Describe the developing stage of the thunderstorm cycle.

A
  • Has updrafts
  • No preciptiation

Most cumulus clouds do not become thunderstorms but all thunderstorms start with a cumulus cloud

33
Q

Describe the mature stage of the thunderstorm cycle.

A
  • Has updrafts and downdrafts
  • Has hazards/precipitation (hail, rain, lightning, strong winds)
34
Q

Describe the dissipating stage of the thunderstorm cycle.

A
  • Has downdrafts
  • Has hazards (lighter rain and severe weather can still be present)
35
Q

What are the hazards posed by a thunderstorm?

A
  • Hail
  • Icing
  • Microbursts
  • Extreme turbulence
  • Lightning
  • Tornadoes

“HIMELT”

36
Q

Describe hail as a thunderstorm hazard.

A

Large hailstones (larger than 1/2-3/4 inch) can cause significant damage to the aircraft in seconds

Can be found 10-20 miles away from the storm

Typically the larger the storm, the more likely it will produce hail

37
Q

Describe extreme turbulence as a thunderstorm hazard.

A

Can cause significant damage to the airframe and serious injuries to crew/passengers

Caused by the vertical wind shear of the updrafts and downdrafts

38
Q

Desribe lightning as a thunderstorm hazard.

A

Can cause catestrophic fuel ignition or temporary flash blindness for crew

39
Q

Describe tornadoes as a thunderstorm hazard.

A

A violent, highly localized column of air that descends in a funnel/tube like shape.

Winds over 300mph and movement speed of 30-40kts can pose a threat to aircraft in the air

40
Q

Describe microbursts as a thunderstorm hazard.

A
  • An intense, highly localized downward atmospheric flow with veloticities of 2000-6000+ feet per minute
  • Has a vortex ring of wind from 20-200 kts
  • Short life span of 5-10mins

Poses a major hazard during take-off and landing

41
Q

What is the best course of action when dealing with microbursts?

A

Avoidance

42
Q

What are the signs that may indicate a microburst?

A
  1. Doppler radar can help detect low-level wind shear, gusty winds, heavy rain
  2. Visual cues like localized blowing dust, roll clouds, virga
43
Q

Describe icing as a thunderstorm hazard.

A

Can accumulate on airfoils (wings) and aircraft surfaces

Very common when air temperature is at/below freezing

44
Q

What are the reccomended procedures for thunderstorm avoidance?

A
  1. Fly around the storm/circumnavigate
  2. Fly over the top of the storm (1000ft for ever 10kts of wind speed)
  3. Fly below the storm (be care to avoid terrain…use 1/3 height rule)
  4. Fly through the storm (penetrate the lower 1/3 of the storm since the upper 2/3s is where hail/icing is likely to occur)
45
Q

If avoidance is not possible, how should a pilot penerate a thunderstorm?

A
  • Remain in the lower 1/3 of the storm
  • Establish penetrate airspeed and attitude
  • Focus on maintaining attitude while in storm
46
Q

Gust Front

A

Dangerous gusty winds that occur 5-20 miles in front of an approaching thunderstorm

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