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Private & Commercial Pilot (DA 40NG) > PPL Oral - Weather Theory > Flashcards

PPL Oral - Weather Theory Flashcards

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Charter Pilot (Part 135) - Oral flashcards
1
Q

What is the main driving force behind all weather on earth?

A

Uneven heating of the earths surface by the sun.

*Transfers of heat

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2
Q

In what part of the atmosphere does most of the weather occur?

A

Troposphere
- Which is the first and lowest layer
- Goes as high as 48,000ft

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3
Q

What is the atmosphere made of?

A
  • Mostly
    NITROGEN (78%)
  • and a little
    OXYGEN (21%)
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4
Q

In what part of the atmosphere does most of the weather occur?

A

Troposphere
- Which is the first and lowest layer
- Goes as high as 48,000ft

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5
Q

What can you say in regards to how heat effects Land vs Water?

A

-Land heats up AND cools down FAST

-Water heats up AND cools down SLOW

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6
Q

How does air flow around H & L pressure systems?

A

L = Counter-Clockwise (left) and UPWARDS (unstable)

H = Clockwise (right) and INWARDS (more stable)

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7
Q

What kind of weather would you associate with a L pressure system?

A

Bad weather

  • Rising air creates a lifting force leading to, precipitation, visible moisture.
  • Air flows towards (winds) L pressure systems
  1. Low pressure systems contain warm air that wants to rise because it is less DENSE than cool air.
  2. As the air rises it cools to its dew point. Creating visible moisture. Especially when agitated by frontal activity.
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8
Q

What kind of weather would you associate with a H pressure system?

A

Generally good weather

  • Descending air, dissipating clouds
  • air flows away (wind) from H pressure areas
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9
Q

What is a Cold Front?

A

When a FAST Moving, COLD, DENSE and unstable air advances and replaces warmer air.

C\W

Why does this happen?
- Because winds may push Cold air into warm air, and warm air is Less Dense and will rise above the cold air.

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10
Q

What is a Warm Front?

A

When a SLOW Moving Warm mass of air overtakes a cold mass of air.

W/C

Why does this happen?
- Winds may push the warm air into the cold air
- Because Warm air is LESS Dense than Cool air, the warm air begins to rise above the cold air.
- As it it rises the Warm Air will begin to cool to its dewpoint and if humidity is high, visible moisture will occur

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11
Q

What can hold more Water Vapor, warm or cold air?

A

Warm air

Why?
- Because warm air is Less Dense and has more room to fit particles of water

  • Warm moist air will rise more quickly because water vapor is lighter than air.
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12
Q

Why does the air spin around L and H pressure systems?

A

Because of the Coriolis effect (rotation of the earth).

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13
Q

How does air Travel in respect to H and L pressure systems?

A

Air travels from H TO L pressure systems.

Why?
- Because H pressure air is More DENSE than L pressure air.
-The H pressure air moves in to replace the rising L pressure air.

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14
Q

Why does the air spin around L and H pressure systems?

A

Because of the Coriolis effect (rotation of the earth).

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15
Q

Why does the air spin around L and H pressure systems?

A

Because of the Coriolis effect (rotation of the earth).

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16
Q

How does air Travel in respect to H and L pressure systems?

A

Air travels from H TO L pressure systems.

Why?
- Because H pressure air is More DENSE than L pressure air.
-The H pressure air moves in to replace the rising L pressure air.

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17
Q

Why does the air spin around L and H pressure systems?

A

Because of the Coriolis effect (rotation of the earth).

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18
Q

How does air Travel in respect to H and L pressure systems?

A

Air travels from H TO L pressure systems.

Why?
- Because H pressure air is More DENSE than L pressure air.
-The H pressure air moves in to replace the rising L pressure air.

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19
Q

Why does the air spin around L and H pressure systems?

A

Because of the Coriolis effect (rotation of the earth).

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20
Q

What direction does air travel in respect to H and L pressure systems?

A

Air travels from H TO L pressure systems.

Why?
- Because H pressure air is More DENSE than L pressure air.
-The H pressure air moves in to replace the rising L pressure air.

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21
Q

What happens when a Warm, Moist air mass reaches its Dewpoint?

A

Visible moisture will occur

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22
Q

What is Dewpoint?

A

The temperature at which a mass of air needs to be cooled to reach 100% Relative Humidity
- At this point Water Condensation will occur
and droplets will form

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23
Q

What is Relative Humidity?

A

The existing moisture in a mass of air compared to how much moisture it could hold.

  • 100% Relative Humidity means that the air is completely saturated and any additional moisture will result in VISIBLE MOISTURE
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24
Q

Which air mass will Cool Down more slowly.

Warm Moist air
OR
Cold Dry Air?

A

Warm Moist air will cool down at the slowest rate

Why?
- Because water resists changes in temperature.
- So Moist air will cool more slowly than Dry air

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25
Q

How can you calculate the height of clouds in AGL?

A

Take the difference between Temp and Dewpoint and divide it by the dew point/temp convergence rate of 2.5, then multiply it by 1,000.

EXAMPLE:
Temp: 22c
Dewp: 18c

4/2.5 = 1.6

Cloud Base = 1,600ft AGL

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26
Q

What is Atmospheric Stability?

A

The ability of an air mass to Resist Vertical Motion

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27
Q

What are the signs of a Front Passing through?

A
  • A rapid change in WIND Direction
  • A rapid change in PRESSURE
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28
Q

What are the characteristics of an Unstable Air Mass

A

CONS
- Cumulus clouds
- Vertical development
- Heavy rain
- Turbulent

PROS
- Good Visibility

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29
Q

What are the characteristics of a Stable Air Mass?

A

CONS
- Steady Precip
- Low Stratiform Clouds OR fog
- Low visibility
- Temperature Inversions

PROS
- Smooth air

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30
Q

What are the 3 ingredients that form a TS?

A
  • Lifting Force
  • Moisture (High Relative Humidity)
  • Atmospheric Instability
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31
Q

Describe the different types of Lifting Forces that can form a TS?

A
  1. Fronts
    • Especially Cold fronts because they
      produce the most Lifting Force
  2. A Dry Line
  3. Orographic lifting (terrain)
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32
Q

What is a Dry Line?

A

When a WARM, DRY air mass is pushed under a WARM MOIST air mass.
- When this occurs the Moist air is lighter due to water vapor and rises above the warm air, the rising will cause it to cool and reach its dewpoint, resulting in visible moisture

-Typically results in an INTENSE line TS in the great plains. (Squall line)

*usually happens when warm dry air from the western deserts meets the warm moist air from the gulf coast
*looks like an orange warm front on prog charts

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33
Q

What does a Dry Line Look like on a Prognostics Chart?

A

Like a an Orange Warm Front

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34
Q

What are the 3 Stages of a TS and describe their characteristics.

A
  1. Developing (Cumulus) stage
    • Updrafts
    • Vertical Cumulus clouds
  2. Mature Stage
    • Heavy Rain
    • Heavy updrafts/downdrafts
    • Microbursts
  3. Dissipating Stage
    • Downdrafts
    • Light rain
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35
Q

What are the 2 ways that Water Vapor may be Added to the atmosphere?

A

Evaporation and Sublimation (rare)

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36
Q

What is Evaporation?

A

The Sun HEATS up Water causing it to turn into VAPOR and be Added to the atmosphere

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37
Q

What are the 3 Categories of Clouds?

A

Low (up to 6,500ft)
- Stratus
- Stratocumulus
- NimboStratus
- Cumulus
- CumuloNimbus

Middle (up to 20,000ft)
- AltoStratus
- AltoCumulus
- NimboStratus
- CumuloNimbus

High (above 20,000ft)
- Cirrus
- CirroStratus
- CirroCumulus

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38
Q

Name all the Low Clouds

A

Low Clouds (up to 6,500ft)
- Stratocumulus
- Stratus
- Cumulus
- NimboStratus
- Cumulonimbus/Towering
Cumulonimbus

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39
Q

Name all the Middle Clouds

A

Middle Clouds (up to 20,000ft)
- AltoCumulus
- AltoStratus
- CumuloNimbus

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40
Q

Name all the High Clouds

A

High Clouds (above 20,000ft)
- Cirrus
- CirroStratus
- CirroCumulus
- CumuloNimbus/Towering CumuloNimbus

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41
Q

What is the most Hazardous type of storm to aircraft?

A

A Squall Line

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42
Q

What is a Squall Line?

A

A Long, Narrow Band of TS that often forms in front of a Cold Front.
- Single most dangerous weather hazard to aircraft
- Depicted on Prog Charts by Red Lines
with Red Dots

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43
Q

What is a good rule of thumb for how far to stay clear of a Thunderstorm or Extreme Radar Echo?

A

Stay 20 NM clear of the storm

Why?
- Because HAIL and gusts can exist for
miles around the TS

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44
Q

What is an Occluded Front?

A

When a COLD Front catches up to a Warm Front.
C W/Cool

  • They are purple on Prog Charts
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45
Q

Explain how an Occluded Front works

A

Cold Air mass catches up to a Warm air mass that is already overtaking a COOL air mass.

  • The Cold Front rapidly accelerates the rate of WX formation already happening on the Warm Front
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46
Q

What can be said about Warm Fronts vs Cold Fronts in respect to their speed?

A

Cold Fronts move faster than Warm Fronts
- Cold Front = More wind

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47
Q

What could be expected if you flew through the Middle Cloud known as Alto Stratus?

A

Moderate Turbulence and Moderate Icing

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48
Q

What could be expected if you flew through the Middle Cloud known as AltoCumulus?

A

Light Turbulence and Light Icing

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49
Q

What is Convection?

A

The tendency for Warmer, Lighter air to Rise.

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50
Q

Between a Warm Front and a Cold Front, which one would create worse weather?

A

A Cold Front

Why?
- Because Cold Fronts move fast and
can send the Warmer air Rising at a
rapid rate

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51
Q

What is a Stationary Front?

A

When Warm and Cold Fronts of equal strength meet.
- They look like a mixture between cold
and warm fronts on Prog Charts
- Stable air
- Bad weather for days

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52
Q

What are the 2 types of Occluded Fronts

A

Cold Front Occlusion
Warm Front Occlusion

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53
Q

Which type of Occluded Front is worse?

A

Warm Front Occlusion

Why?
- Because the Colder air under the Warm Front resists movement from the advancing Cold Front because the advancing Cold Front is not quite as cold as the Cold air that was already there (under the warm front).

  • Advancing cold front = cold
  • Already existing cold air = even COLDER
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54
Q

What is a Warm Front Occlusion?

A

Cold Front overtakes a Warm front that is overtaking even COLDER air
- Creates even worse weather than a standard Cold Front

  • Advancing cold front = cold
  • Already existing cold air = even COLDER
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55
Q

What is a Cold Front Occlusion

A

When a Cold Front overtakes a Warm Front and pushes both air masses forwards.

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56
Q

What is a Trough?

A

An elongated area of L pressure
- An area of rising air
- Expect bad weather

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57
Q

What kind of weather can be associated with a Cold Front?

A

Bad storms
- Towering Cumulus/CumuloNimbus
- Heavy rain
- TS
- Wind shear
- Drop in Temps

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58
Q

What kind of weather can be associated with a Warm Front?

A

Bad weather (but not as bad as a cold
front)
- Stratiform clouds
- Low clouds
- Rise in temps

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59
Q

What is a Ridge?

A

An elongated area of H Pressure
- Good weather due to downdrafts dissipating clouds

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60
Q

What is ISA?

A

International Standard Atmosphere

Temps - 15c (59f)
Pressure - 29.92 Hg
Altitude - Sea Level

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61
Q

What are Isobars?

A

Lines of equal pressure on weather charts

62
Q

What does it mean if the Isobars are close together?

A

That means there is a STEEP pressure gradient (pressure changes quickly)
- It will be windy in these areas

63
Q

Why do SURFACE winds flow ACROSS the Isobars instead of WITH the bars?

A

Because of Ground Friction
(Surface Friction)

64
Q

At what is the standard lapse rate for Pressure as Altitude increases?

A

-1 inch Hg per 1,000ft of altitude gain

65
Q

What is the standard Lapse Rate for Temperature as Altitude increases?

A

-2c per 1,000ft of altitude gain

66
Q

What factor will primarily determine the type and extent of cloud development?

A

Atmospheric Stability

67
Q

What can be said about the thickness of clouds during heavy rain?

A

They are at least 4,000ft thiccc

68
Q

During preflight planning, what can you do to be sure you avoid icing?

A
  1. Check frontal activity
    • Ice is especially easy to form in H
      pressure systems
  2. Check cloud base and tops (PIREPs)
    • Can you climb or descend to avoid
      visible moisture?
  3. Check Freezing levels - Avoid
  4. Winds/Temps Aloft
  5. Check Airmet Z
69
Q

What is a Temperature Inversion

A

When the air at altitude is warmer than the air underneath it.
- Temperature has Increased at altitude
instead of decreasing

70
Q

What are the 2 main types of Temperature Inversions?

A
  1. Ground base TI
  2. Frontal TI
71
Q

What is a Ground Based Temperature Inversion?

A

This happens when the ground is cold and cools the air near it to a lower temperature than the air above it.
- The air above the cold layer near the
surface is now warmer and we have a
TI

72
Q

When might you expect a Ground Based Temperature Inversion?

A
  • Calm, COOL, stable Nights OR Mornings
    with little wind
  • When you can see a low layer of fog
73
Q

Why do low layers of fog appear near Ground Based Temperature Inversions?

A
  1. When the air that is cooled by the ground has MOISTURE in it, it may cool enough for it to reach its dewpoint and form visible moisture in the form of fog.
  2. At this point, since the air has water vapor in it, it will try to rise. But it cant rise above the slightly warmer layer that is above it.
  3. Now you have a low layer of fog

**Essentially durring radiation fog

74
Q

Explain what is happening during a Frontal Temperature Inversion.

A
  • Usually happens happens with slow
    moving Warm Fronts
  • The Warm air moves over and rises
    above the Cold air
  • TI will be closer to the ground nearest
    to the Warm Front boundary
75
Q

What dangerous hazard may be encountered near a Ground Based Temperature Inversion?

A

LLWS!

76
Q

What is WindShear?

A

A rapid change in wind speed or direction at different altitudes

77
Q

What is so dangerous about WindShear?

A

Because it can cause..
1. Rapid decrease or increase in
Airspeed low to the ground rather
unexpectedly
2. Can significantly blow us off course or
cause unexpected cross winds when
landing

78
Q

When are the 3 most likely times you can expect LLWS?

A
  1. Near Frontal activity
    • Especially with steep pressure
      gradients
    • Especially when the temp difference
      on either side of the front is > 5c
  2. Near Thunderstorms
    • Microbursts
    • Can be expected as far out as 20nm
      from the storm
  3. When a Temperature Inversion is
    present
79
Q

What are the 2 types of WindShear in relation to aircraft performance?

A
  1. Performance Decreasing Windshear
    • Happens when High winds rapidly
      DECREASE.
    • Carry extra airspeed with you on
      final if WS is expected
  2. Performance Increasing Windshear
    • Happens when the winds rapidly
      INCREASE
    • Watch your airspeed, make sure you
      don’t exceed Vno
80
Q

How can you tell if WindShear is present near a Ground Based Temperature Inversion?

A

If the winds aloft above the inversion are greater than 25 Kts.

81
Q

WindShear Scenario:

METAR:
Winds at surface = 10kts
*WS010/18040

What’s going on here?

A

WS010/18040 = Windshear at 1,000ft AGL, 180 at 40kts

Here’s what is going on
- Winds at 1,000ft are 40kts. Check surface winds to see difference between surface and 1000ft.
- This is Performance DECREASING
Windshear

What should you do?

  • Carry an extra 30kts with you until about 500ft AGL
82
Q

What is an Embeded Thunderstorm?

A

A TS hidden within other clouds

83
Q

How can you make sure your landings are smooth even in Gusty conditions?

A

Add a Gust factor to your landing speed
- Take half of the difference between
the winds and the gusts and add it to
your airspeed on final

Winds 10kts
Gusts 20kts
- Add 5kts to your approach speed
(82kts with flaps T/O)

84
Q

If there was a thunderstorm near your arrival airport, what would you do?

A

**DIVERT

BUT, if you HAD to land
- Pick the RWY farthest away from the
storm.

Why?
- Because winds flow out of storms and you want to land with a Headwind
- Especially if it begins to gust

85
Q

What is a hazard you need to be aware of when flying near Mountains?

A

Mountain Wave Turbulence

86
Q

What is Mountain Wave Turbulence?

A

Winds in excess of 25kts flowing over (perpendicular) a mountain ridge

Windward Side -> A -> Leeward Side

Turbulence can be expected on the Leeward side

87
Q

What are some signs that Mountain Wave Turbulence is present?

A
  • Winds in excess of 25kts flowing over (perpendicular) a mountain ridge
  • Standing Lenticular Clouds over the top
    of a mountain
  • Lines of Rotor clouds on the Leeward
    Side
88
Q

What are the different types of fog?

A
  1. Ground/Radiation Fog
  2. Upslope Fog
  3. Advection Fog
  4. Steam Fog
89
Q

Explain Ground/Radiation Fog

A

The cold ground Cools the moist/humid air above it to its dewpoint, causing fog to form. (provided there is high moisture and low winds)

90
Q

Explain Upslope Fog

A

A light wind pushes Moist air up a slope until it cools to its dewpoint and condenses into fog.

91
Q

Explain Advection Fog

A

Occurs when Warm Moist air flows over a cold surface and is cooled to its dewpoint

92
Q

Explain Steam Fog

A

Occurs when evaporation from a warmer body of water lifts moisture into colder air, allowing it to reach its dewpoint and fog forms.

93
Q

What is necessary for Structural Icing to occur?

A
  • Visible moisture
  • Freezing temperatures on the COLLECTING SURFACE
94
Q

What are the 2 main categories of Aircraft Icing?

A
  1. Structural
  2. Induction (air intake, carb ice)
95
Q

What are the 3 types of Structural Icing?

A
  1. Clear Ice
  2. Rime Ice
  3. Mixed Ice
96
Q

What is Clear Structural Icing?

A

Clear ice that slowly freezes as it moves across the surface of the wing
- Formed by large water droplets

97
Q

What is Rime Structural Icing?

A

A milky, opaque, rough looking ice that form in bulk on the leading edge
- formed by smaller water droplets

98
Q

What is Mixed Structural Icing

A

A mix between Rime (worst aerodynamics) and Clear (heaviest)

99
Q

Why is ice on our aircraft a bad thing?

A
  1. Changes the shape of the wing (less
    lift)
  2. Creates more Drag
  3. Adds weight
  4. It will increase your stall speed!
  5. Can clog sensors like our Pitot or
    Static ports
100
Q

Under what conditions can you expect Carburetor Icing?

A

When..
1. Relative Humidity is high
2. Temps between -7c - 21c

*BUT it CAN occur in higher temps than these!

101
Q

What are some indications of Carburetor Icing?

A
  1. Engine running rough
  2. Loss of RPM (fixed pitch) OR Manifold
    Pressure (constant speed prop)
102
Q

If you suspect Carburetor Icing how can you check to be sure?

A
  1. Turn on carb heat (RPM and Man Pressure
    will drop further)
  2. Wait a bit and IF RPM/Man Pressure
    increases, (ice melting) you have carb icing!
103
Q

If you suspect induction icing in the DA 40 what should you do?

A
  1. Open alternate air
  2. Pitot heat on
  3. Increase power to prevent ice build up on
    prop
  4. Descend, and or turn around for warmer
    air
104
Q

What would be an indication for Induction Icing in the DA 40?

A

Loss of power

105
Q

Is frost dangerous to aircraft?

A

Yes.

Why?

  1. Its enough to disrupt smooth airflow over the wing resulting in a LOSS of LIFT
  2. It can increase your stall speed

FAR 91.527 prohibits T/O with frost, ice, or snow on the aircraft

106
Q

What is needed for fog to form?

A
  • Low temp/dewpoint spread
  • High relative humidity (moisture)
  • Stable air
  • Calm winds (calm, not necessarily zero winds)
107
Q

What are some conditions that contribute to High Density Altitude?

A
  • High elevations
  • Higher than standard temperature
  • Lower than Standard atmospheric pressure
  • High humidity (moist air. Decreases air density)
    ..Or a combination of these factors
108
Q

What are some conditions that contribute to Low Density Altitude?

A
  • Low elevation
  • Lower than standard temp
  • Higher than standard pressure
  • Low humidity (dry air. Increases density)
    ..Or a combination of these
109
Q

What are the weather minimums to obtain a special VFR clearance?

A

FAR 91.157

  1. 1 SM vis
  2. Clear of Clouds
110
Q

Why is Low-Level Wind Sheer often associated with the passage of Fronts?

A

Due to the relatively rapid change in wind direction near Fronts

111
Q

Where would WindShear be expected along a passing Warm Front?

A
  • AHEAD of the Warm Front
  • Within 6hrs of its passing
  • Below 5,000ft
112
Q

How long does a Microburst typically last?

A

Up to 15 mins

113
Q

What are all the conditions that are conducive to Low Level Wind Shear?

A
  • Passing fronts
  • Thunderstorms
  • Temperature Inversions with strong upper level winds in excess of 25kts
114
Q

When is an aircraft most likely to be struck by lightening?

A

When the OAT is between -5c and +5c

115
Q

Under what conditions should you be very wary of icing?

A
  • Temps from -20c to +5c
  • Flying in visible moisture
116
Q

What determines the stability of an atmosphere?

A

The Adiabatic Lapse rate (temperature lapse rate)

Rapid cooling as altitude increases will result in an unstable atmosphere, while normal to slow cooling will result in a stable atmosphere.

*average temperature lapse rate is -2c per 1,000ft altitude gain

117
Q

In regards to icing, what meteorological information should pilots be aware of?

A

AC-91-74

  1. Frontal locations
  2. Cloud layers
  3. Freezing level
  4. Temperature and Pressure (low pressure is conducive to icing)
  5. Precipitation
118
Q

Is icing more likely to form near areas of Low or High Pressure?

A

AC-91-74

Low pressure

119
Q

What are the reporting categories for aircraft icing?

A

AIM 7-1-19

  1. Trace
  2. Light
  3. Moderate
  4. Severe
120
Q

What effect does aircraft icing have on performance? ( 5 things, get them all right)

A

AIM 7-1-19

  1. Thrust is reduced
  2. Drag Increases
  3. Lift decreases
  4. Weight increases
  5. Result: Stall speed increases

*these effects are cumulative

121
Q

Where can icing be expected?

A

AIM 7-1-19

Anywhere visible moisture or precipitation is present and the OTA is +2c to -10c

but can occur at +5c to -20c

122
Q

What should you do if you encounter aircraft icing?

A

AIM 7-1-19

  1. Leave the area of visible moisture by turning around
  2. Leave the area of near freezing temps by descending OR climbing (temp inversion)
123
Q

What should you do after you have successfully left an area where icing conditions have been encountered? (2 things)

A

AIM 7-1-19

  1. Let ATC know the type and severity of icing encountered
  2. Obtain an amended clearance with a new route away from the icing, or DIVERT if needed.
124
Q

What is Trace icing, what is its rate of accumulation, and what action should be taken?

A

AIM 7-1-19

  1. Trace icing is when icing first becomes noticeable
  2. 1/4 inch per hour on outer wing
  3. Consider exiting icing conditions before they worsen
125
Q

What is Light icing, at what rate does it accumulate, and what action should be taken?

A

AIM 7-1-19

  1. Light icing requires the occasional cycling of deicing systems
  2. 1/4 to 1 inch accumulation per hour
  3. Exit icing conditions
126
Q

What is Moderate icing, at what rate does it accumulate, and what action should be taken?

A
  1. Moderate icing requires the FREQUENT cycling of deicing systems
  2. 1-3 inches per hour
  3. Exit icing conditions ASAP
127
Q

What is Severe Icing, at what rate does it accumulate, and what action should be taken?

A

AIM 7-1-19

  1. Severe icing is occurring when ice protection systems fail to remove the ice and ice accumulates in areas normally not prone to icing
  2. More than 3 inches per hour
  3. Exit IMMEDIATELY, by regulation
128
Q

What is Clear Ice?

A

1 . Glossy, translucent ice formed by the relatively slow freezing of large droplets.

  1. Clear ice forms as the droplets slowly freeze as they roll backwards on the surface of the aircraft
  2. Can forms horns that disrupt airflow

** MOST DANGEROUS **
*Usually form in warmer temps than Rime ice

128
Q

What is Rime Ice?

A

Rough, milky, ice formed by the rapid freezing of supercooled droplets upon impact.

**Most common type.
**Rime ice gets its milky appearance from air bubbles trapped in-between the ice as it rapidly freezes

128
Q

When are you most likely to encounter Rime Ice?

A
  1. Usually forms in colder temps
  2. In stable conditions like Stratus clouds
129
Q

What is Mixed Icing?

A
  1. A mix of Clear and Rime ice that forms when flying through varying conditions of cold, and moisture.
  2. Can form horns
130
Q

What is the most dangerous type of icing to encounter and why?

A

Clear Ice
- Heavy, adds weight
- Ice can accumulate behind where the de-icing equipment is installed
- Hard to see
- Forms horns that further disrupt the airflow

131
Q

What are Super Cooled Water Droplets?

A
  1. Pure water that does not freeze until -20c, due to surface tension
  2. They will freeze instantly if sufficiently disturbed (like by an aircraft flying into them)
132
Q

What are the two main categories of Aircraft Icing?

A
  1. Induction icing (engine)
  2. Airframe icing
133
Q

At what temperatures will it be too cold for icing to occur and why?

A
  1. Usually less than -20c
  2. Because most water content is already frozen as ice crystals
134
Q

At what temperatures are you mostly likely to encounter Rime, Clear, and Mixed icing respectively?

A

Rime = Temps less than -15c

Clear = 0c to -10c

Mixed = -10c to -15c

135
Q

In Stratiform type clouds, what type of icing can you expect, and at what intensity, and what can be said about the thickness of the icing layer?

A
  1. Rime and Mixed
  2. Trace and light
  3. Generally, the icing layer in a Stratiform cloud is about 3,000-4,000ft thick, so climbing above it is an option.
136
Q

In Cumuliform type clouds, what type of icing can you expect, and at what intensity, and where will the worst icing be?

A
  1. All types of icing
  2. All intensities
  3. Worst icing will occur near the top of the Cumuliform formation
137
Q

What is the worst weather phenomenon to encounter in regards to aircraft icing?

A

Freezing rain

138
Q

In what scenario would it be possible to achieve multiple freezing levels over one area?

A

AC-91-74

A temperature inversion

139
Q

What are some good preflight planning things to consider when the possibility of encountering icing is present?

A

AC-91-74

  1. Pre-determine exit strategies, will a climb or descent, or turn-around be most appropriate given the conditions?

2.Extra fuel may be needed due to the drag that icing may cause or due to drag from de-icing systems

  1. When choosing alternate airports, remember that icing will require a higher approach speed and therefore, a longer RWY!
140
Q

How can you visually identify the Jet Stream (and possible Clear Air Turbulence)?

A

Long streaks of Cirrus clouds

Shephard Air: Commercial question

141
Q

Why would you expect lower aircraft performance when Relative Humidity is high?

A

Because water vapor is LESS DENSE than air, and since there is a lot of water in the air durring High Relative Humidity conditions, the air also becomes LESS DENSE due to the excess moisture.

142
Q

When are convective currents most active?

A

Warm Summer afternoons when winds are Light

Aviation Weather Handbook

143
Q

What two conditions would cause an air mass to become unstable?

A

High Temps & High Humidity

144
Q

You approach a mountanous area at 10,000ft from the East with winds 50kts from the West, you also see flat, lense shaped clouds ahead. What is this an indication of?

A

Very strong Mountain Wave Turbulence.
Avoid

145
Q

Your weather investigating has revealed that there is High Humidity, Higher than average Lapse Rate, & Turbulent conditions.

What do these signs point to?

A

The possibility for..
* 1. Thunderstorm activity
* 2. Unstable air

146
Q

When are you most likely to encounter Clear Air Turbulence (CAT)?

A

Between 20,000 and 50,000ft, in a cloud-free area

Aviation Weather Handbook

147
Q

What weather conditions indicate the passage of a cold front?

A

High Dew Point
Falling pressure

PHAK 12-20

148
Q

What should you do if you encounter moderate or severe turbulence?

A

Slow to Manuevering Speed (Va) and maintain wings level

You should accept altitude and speed deviations

149
Q

What are two clues that Windshear associated with frontal activity may be present?

A
  1. The temp difference at the surface on either side of the front is greater than 10c
  2. The front is moving at a speed of 30kts or more

Source: Boldmethod

https://www.boldmethod.com/blog/lists/2023/09/four-most-common-sources-of-wind-shear-at-low-altitude/

Private & Commercial Pilot (DA 40NG) (28 decks)

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