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Flight Insight/Checkride Prep > WX Therory PHAK > Flashcards

WX Therory PHAK Flashcards

1
Q

What percentage of the atmosphere is nitrogen?

A

78%

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2
Q

What percentage of the atmosphere is oxygen?

A

21%

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3
Q

What are the main layers of the Earth’s atmosphere based on thermal characteristics?

A

Troposphere, Stratosphere, Mesosphere, Thermosphere

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4
Q

In which atmospheric layer do most weather phenomena occur?

A

Troposphere

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5
Q

How does temperature change with altitude in the troposphere?

A

Decreases by about 2°C per 1,000 feet

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6
Q

What happens to air pressure as altitude increases in the troposphere?

A

Decreases by about 1 inch per 1,000 feet

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7
Q

What is the name of the boundary between the troposphere and stratosphere?

A

Tropopause

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8
Q

Which atmospheric layer extends from the tropopause to about 160,000 feet?

A

Stratosphere

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9
Q

Why does warm air rise in the atmosphere?

A

Warm air is less dense than cooler air

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10
Q

What causes the Coriolis force?

A

The rotation of the Earth

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11
Q

How does the Coriolis force affect air movement in the Northern Hemisphere?

A

Deflects air to the right

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12
Q

What is the standard atmospheric pressure at sea level?

A

29.92 inches of mercury (Hg) or 1013.2 millibars (mb)

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13
Q

How does air pressure change with altitude?

A

Decreases by 1 inch of mercury for every 1,000 feet

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14
Q

What happens to atmospheric pressure when altitude increases?

A

Atmospheric pressure decreases

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15
Q

What instrument is used to measure atmospheric pressure in most aircraft?

A

Aneroid barometer

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16
Q

How does altitude affect takeoff and landing distances?

A

Higher altitudes increase takeoff and landing distances.

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17
Q

Why do aircraft engines and propellers become less efficient at higher altitudes?

A

Air density decreases at higher altitudes, reducing engine and propeller efficiency.

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18
Q

What is the effect of altitude on climb rates in aircraft?

A

Climb rates decrease at higher altitudes due to reduced air density.

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19
Q

At what altitude does oxygen deprivation (hypoxia) start to affect human performance?

A

Around 10,000 feet, though some may experience effects as low as 5,000 feet.

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20
Q

How does wind flow around high-pressure systems in the Northern Hemisphere?

A

Clockwise (anticyclonic) circulation.

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21
Q

How does wind flow around low-pressure systems in the Northern Hemisphere?

A

Counterclockwise (cyclonic) circulation.

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22
Q

What type of weather is typically associated with high-pressure systems?

A

Good weather, due to descending dry air.

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23
Q

What type of weather is typically associated with low-pressure systems?

A

Cloudy, bad weather with precipitation, due to rising air.

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24
Q

What are convective currents and how do they form?

A

Small, localized circulations caused by uneven heating of the Earth’s surface.

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25
Q

What is a sea breeze and when does it occur?

A

An onshore wind that occurs during the day when land heats faster than water.

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26
Q

What is a land breeze and when does it occur?

A

An offshore wind that occurs at night when land cools faster than water.

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27
Q

How do convective currents affect an aircraft during final approach?

A

Rising air from warm terrain can cause overshooting, while sinking air over water or vegetation can cause undershooting.

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28
Q

How can ground obstructions like buildings or mountains affect wind?

A

They can create gusts and turbulence that change wind direction and speed rapidly.

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29
Q

What is low-level wind shear and why is it hazardous to aircraft?

A

A sudden change in wind speed and/or direction close to the ground, potentially causing violent turbulence.

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30
Q

What atmospheric conditions are commonly associated with low-level wind shear?

A

Passing frontal systems, thunderstorms, temperature inversions, and strong upper-level winds.

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31
Q

What is a microburst and how does it affect aircraft?

A

A sudden, intense downdraft that can produce severe turbulence and wind direction changes, dangerous during takeoff or landing.

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32
Q

How do isobars on a weather map help pilots understand wind conditions?

A

Closely spaced isobars indicate strong winds, while widely spaced isobars indicate light winds.

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33
Q

How does wind at 2,000 feet above ground level compare to surface winds?

A

It is faster and blows 20-40° to the right of surface winds.

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34
Q

What determines the stability of the atmosphere?

A

Its ability to resist vertical motion.

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35
Q

What happens in an unstable atmosphere?

A

Small vertical movements become larger, leading to turbulence and convective activity.

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36
Q

How does rising air cool in the atmosphere?

A

By expansion due to decreasing air pressure with altitude.

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37
Q

What is the dry adiabatic lapse rate for unsaturated air?

A

3°C (5.4°F) per 1,000 feet.

38
Q

How does moisture affect air density and stability?

A

Moist air is less dense and rises, making it generally less stable than dry air.

39
Q

What is a temperature inversion?

A

A situation where air temperature increases with altitude, trapping weather and pollutants below.

40
Q

How do surface-based temperature inversions typically form?

A

On clear, cool nights when the ground cools the air near the surface.

41
Q

How does humidity affect the air’s moisture-holding capacity?

A

Every 20°F increase in temperature doubles the air’s moisture-holding capacity.

42
Q

What is relative humidity?

A

The actual amount of moisture in the air compared to the maximum it can hold at that temperature.

43
Q

What is the dew point?

A

The temperature at which air becomes fully saturated and can hold no more moisture.

44
Q

What happens when air temperature and dew point converge?

A

Clouds often form as air reaches saturation.

45
Q

How do you estimate cloud base altitude using temperature and dew point?

A

Subtract dew point from temperature, divide by 4.4°F, then multiply by 1,000 feet.

46
Q

What are the four methods by which air reaches the saturation point?

A

Cooling by surface contact, mixing of warm and cold air, cooling at night, and lifting in the atmosphere.

47
Q

How does frost affect aircraft performance?

A

Frost disrupts airflow over wings, reducing lift and increasing drag.

48
Q

How does radiation fog form?

A

On clear nights, when the ground cools rapidly and the air near the surface reaches its dew point.

49
Q

How does advection fog form?

A

When warm, moist air moves over a cooler surface, typically requiring light winds.

50
Q

What is steam fog?

A

Fog that forms when cold air moves over warm water, resembling smoke.

51
Q

What are the main types of clouds based on height?

A

Low, middle, high, and clouds with vertical development.

52
Q

What type of clouds typically pose a significant hazard to flight due to turbulence?

A

Cumulonimbus clouds.

53
Q

What cloud type is associated with thunderstorms?

A

Cumulonimbus clouds.

54
Q

What is virga?

A

Rain that evaporates before reaching the ground.

55
Q

What is an air mass?

A

A large body of air with uniform temperature and moisture characteristics.

56
Q

What type of air mass brings cool, dry air from polar regions?

A

Continental polar air mass.

57
Q

What type of air mass brings warm, moist air from tropical waters?

A

Maritime tropical air mass.

58
Q

What is the boundary between two different air masses called?

A

A front.

59
Q

What are the four main types of fronts?

A

Warm, cold, stationary, and occluded.

60
Q

What type of air mass replaces colder air in a warm front?

A

A warm air mass.

61
Q

What types of clouds are typically seen before a warm front passes?

A

Cirriform or stratiform clouds, sometimes cumulonimbus in summer.

62
Q

What happens to visibility after a warm front passes?

A

Visibility improves, but hazy conditions may persist for a short period.

63
Q

What weather is associated with the passage of a warm front?

A

Light to moderate precipitation, fog, poor visibility, and stratiform clouds.

64
Q

What type of air mass replaces warmer air in a cold front?

A

A cold, dense air mass.

65
Q

What clouds are commonly associated with a passing cold front?

A

Towering cumulus or cumulonimbus clouds.

66
Q

What type of severe weather can be produced by strong cold fronts?

A

Thunderstorms, lightning, hail, and possibly tornadoes.

67
Q

What happens to temperature and dew point during a cold front passage?

A

Both drop rapidly.

68
Q

How does the weather change after a cold front passes?

A

Skies clear, visibility improves, and temperatures remain cooler.

69
Q

What is a squall line, and why is it hazardous to pilots?

A

A continuous line of thunderstorms that forms ahead of a cold front, causing intense, fast-moving storms.

70
Q

How do cold fronts differ from warm fronts in terms of speed and weather?

A

Cold fronts move faster (20-35 mph) and bring sudden storms, while warm fronts move slower (10-25 mph) with steady precipitation.

71
Q

What is a stationary front?

A

A boundary between two air masses that are relatively equal, causing weather to linger for days.

72
Q

What is an occluded front?

A

A front formed when a fast-moving cold front overtakes a slow-moving warm front.

73
Q

What weather is typical before the passage of an occluded front?

A

Cirriform and stratiform clouds with light to heavy precipitation.

74
Q

How does a cold front occlusion differ from a warm front occlusion?

A

In a cold front occlusion, the cold air behind the cold front is colder than the air ahead of the warm front; in a warm front occlusion, the cold air ahead of the warm front is colder.

75
Q

What types of clouds and weather can occur during the passage of an occluded front?

A

Nimbostratus, cumulonimbus, and towering cumulus clouds with light to heavy precipitation and poor visibility.

76
Q

How do winds change with the passage of a front?

A

Winds shift direction, especially with cold fronts.

77
Q

What are the three stages of a thunderstorm’s life cycle?

A

Cumulus, mature, and dissipating stages.

78
Q

What characterizes the mature stage of a thunderstorm?

A

Strong updrafts and downdrafts, rain or hail, and violent turbulence.

79
Q

What happens during the dissipating stage of a thunderstorm?

A

Downdrafts replace updrafts, and the storm loses its energy.

80
Q

How high can severe thunderstorms reach in altitude?

A

50,000 to 60,000 feet, depending on latitude.

81
Q

What are the three main conditions needed for a thunderstorm to form?

A

Sufficient water vapor, unstable lapse rate, and an initial lifting action.

82
Q

What is an air mass thunderstorm?

A

A thunderstorm caused by surface heating, usually lasting an hour or two.

83
Q

What is a squall line, and why is it dangerous?

A

A narrow band of intense thunderstorms, often associated with cold fronts, presenting significant hazards to aircraft.

84
Q

What is a tornado, and how does it form in a thunderstorm?

A

A concentrated vortex of rapidly rotating air extending from the cloud base, formed when strong updrafts create intense rotation.

85
Q

What type of turbulence is most dangerous in thunderstorms?

A

Shear turbulence between updrafts and downdrafts, both inside and outside the storm.

86
Q

Why is hail dangerous to aircraft in thunderstorms?

A

Hailstones can grow large and damage aircraft, even several miles from the storm.

87
Q

How can thunderstorms affect altimeters?

A

Rapid pressure changes can lead to altimeter errors of more than 100 feet.

88
Q

How can lightning affect an aircraft?

A

It can puncture the skin, damage electronics, and cause temporary blindness.

89
Q

What can happen to turbine engines in thunderstorms with high water concentration?

A

Engine flameout or structural failure due to excessive water ingestion.

90
Q

How far should you circumnavigate a thunderstorm to avoid hail and turbulence?

A

At least 20 nautical miles.

91
Q

What type of icing occurs in thunderstorms, and where is it most hazardous?

A

Clear icing from supercooled water droplets, especially between 0°C and -15°C.

Flight Insight/Checkride Prep (25 decks)

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