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u7 Flashcards

1
Q

what are mountain waves

A

oscillations on the leeward side of a mountain caused by disturbances in horizontal airflow from the mountains in the way

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2
Q

where is mountain waves most severe

A

downdrafts is most severe near the top of the mountain (5000 FPM)

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3
Q

can pilots always see mountain waves

A

when air is moist = clouds form = visual indicator that mountain waves are here

air is dry = no clouds = can’t see visual indicator

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4
Q

conditions to form a mountain wave: wind direction, speed, stable/unstable airmass aloft

A
  • direction: must be 30º perpendicular to the mountains
  • speed: at least 25KT perpendicular to mountain
  • wind aloft must increase with height
  • need stable airmass aloft
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5
Q

what is stable air mass over the mountains needed for mountain waves

A

it encourages oscillations
- wind tries to rise, stable air mass says no and pushes air down, repeat

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6
Q

average total distance from mountain to end of mountain waves

A

150 NM

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7
Q

an unstable atmosphere will result in a ____ mountain wave length

A

longer

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8
Q

the faster the wind, the _____ the wave length

A

longer

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9
Q

mountain waves near the surface have ______ amplitudes because of _____

A

small
friction

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10
Q

unstable atmosphere results in a mountain wave with _____ amplitude

A

small

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11
Q

a large mountain will generate mountain waves that have _____ amplitudes

A

large

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12
Q

can you fly over a lenticular cloud?

A

no because wind from the mountain wave extends to the tropopause so you can’t fly over because hella turbulence at top of lenticular

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13
Q

if you must pass through an area with roll clouds, where do you fly

A

over or around, but never beneath

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14
Q

what does a cap cloud indicate

A

strong downdraft

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15
Q

can mountain waves tell us the intensity of the turbulence

A

no just tell us position of wave crests and rotors, but nothing about how strong the waves are. just assume its always strong turbulence

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16
Q

flying towards mountain, your ground speed ______, experiencing mountain waves for ____ time, feel ____ bumpy turbulence

A

decreases
longer
less

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17
Q

flying away from mountain, your ground speed ______, experiencing mountain waves for ____ time, feel ____ bumpy turbulence

A

increases
shorter
more

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18
Q

GFA will indicate mountain wave activity when turbulence is ____ (level)

A

moderate or severe

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19
Q

when flying into a mountain wave, the altimeter will read ______

A

higher than you actually are becase wind speed increases = drop in pressure = alt thinks ur higher

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20
Q

anabatic wind vs katabatic wind

A

anabatic wind: sunny side of mountain heats up so updrafts

katabatic wind: shady side of maountain cools down so downdrafts

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21
Q

what is galcier wind

A

extreme katabatic wind from cooling

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22
Q

what are funnel winds

A

wind through valley: small zone = drop in pressure = increase wind speed

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23
Q

it’s recommended to fly _____ ft or ___% higher than mountain range at a ___º angle

A

3000 ft
50%
45º

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24
Q

what is convective/thermal turbulence

A

hot pockets of air rise (updraft), expand, cool, form clouds and cool air falls from the side of the cloud downwards (downdrafts)

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25
Q

how to avoid convective/thermal turbulence.

A

fly over the clouds

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26
Q

what is mechanical turbulence

A

smooth air strikes ground objects (home, terrain) = friction = turbulence

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27
Q

what is frontal turbulence

A

turbulence caused by friction between two fronts or when one front is moving really fast

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28
Q

what is orographic turbulence

A

turbulence from air currents along mountains (leeward side has strong downward currents)

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29
Q

T/F: mountain waves are stationary

A

true

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30
Q

what speed should be my limit when flying through MWT

A

Va

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31
Q

what is increased vs decreased-performance wind shear

A

increased-performance = headwind increases = more lift

decreased-performance = tail wind increases = less lift

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32
Q

when do you report low level wind shear within 1500 AGL

A

when pilot reports a loss or gain of IAS of 20 KT or more

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33
Q

causes of low-level wind shear

A

low level jet
nocturnal inversion
microbursts
virga
funnel cloud

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34
Q

what is virga

A

rain that falls brings cold air with it
rain falls into dry air below
rain evaporates into dry air
cold air still descends downwards = strong downdraft

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35
Q

what is clear air turbulence

A

high level turbulence from jet stream aloft

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36
Q

light, moderate, severe vs extreme turbulence

A

light - slight changes in altitude, less than 15 KT airspeed flux

moderate - stronger bumps but plane still in control

severe - large changes, momentarily out of control, over 25 KT airspeed flux

extreme - can’t control plane its getting tosses around, maybe even structural damage

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37
Q

explain the Coriolis force in terms of air circulation

A
  • air doesn’t fly straight north/south from high to low pressure because earth rotates
  • in northern hemisphere , air flow is deflected right due to earth rotation
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38
Q

how the coriolis effect affects wind flow ALOFT

A

causes resultant wind to flow parallel to isobars

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39
Q

what is the buys ballot law

A

if you stand with your back to the wind in the northern hemisphere, the low pressure is always on the left and the high pressure on the right

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40
Q

why is arazona always hot desert?

A

permanent high pressure zone - no clouds, always direct sun

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41
Q

climbing to high altitudes, winds ____ and ______

descending to surface, winds ____ and _____

A

veer and increase
back and decrease

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42
Q

why is wind parallel to isobars at high altitudes

A

because no friction

43
Q

how much do wind tend to back and decrease in speed when flowing over ocean, small grass terrain, city rough terrain

A

ocean = back 10º and slows slightly
grass hill = back 20º and slows more
city = back 40º and slows most

44
Q

i’m flying low from a city to the ocean. how will the winds change?

A

LESS friction
- winds veer 30º to an angle close to the isobars
- winds speed up

45
Q

i’m flying low from ocean to flat land. what happens to the winds

A

MORE friction
- winds back 10º further from isobars
- winds slow down

46
Q

at night, surface winds tend to ____ and _____

A

back and decrease

47
Q

which direction does the wind flow at night on the coast?

A

land to sea

48
Q

which way does the wind flow during the day on the coast?

A

from sea to land

49
Q

what are rossby waves

A

as the jet stream flows from west to east, it can develop (rossby) waves which can result in small low/high pressure systems detaching from jet stream and moving around globe

50
Q

the polar jet stream moves ____ during winter and ____ during summer

A

south (becomes stronger)

north (weaker)

51
Q

why does the sub-tropical jet stream (STJS) move less than the polar front jet stream (PFJS)

A

smaller temperature difference between ferrell and hadley cell than ferrell and polar cells

52
Q

the source region of an airmass always an area of ____ pressure

A

high

53
Q

which air masses are most common in canada (from north to south) and what seasons do they form in?

A

cA - winter
mA - summer and winter
mP - summer and winter
mT - summer

54
Q

why don’t we see cP and cT air masses in canada

A

cP made in canada and moves downwards to USA
cT only made in few locations like arazona and even if it tries to move upwards towards canada its blocked by rockey mountains

55
Q

mA location in winter vs summer

A

winter - mA along coast
summer - mA in central canada because starts as cA but passes over lakes before hitting central canada so it turns into mA

56
Q

what does it mean for a weather chart to have an airmass labeled as cAk

A

cA = continental arctic
cAk = moves to new region that’s warmer on the surface so the bottom of this airmass is colder than the surface below

57
Q

at the tropopause, the temperature of warmer air masses (mT and mP) will be colder than the cold airmasses (cA and mA). why

A

because warm air masses reaches higher into troposphere so more adiabatic cooling

58
Q

the weather that happens at a front is determined by:
___ and ____ of the warm air mass
____ of the cold air mass

A

stability and moisture

speed

59
Q

cold front moves ____ so the bad weather lasts for a ___ period of time

A

fast
short

60
Q

cold front causes the wind to _____

A

veer

61
Q

bad weather _____ the cold front

A

behind

62
Q

does a warm front or cold front have worse weather typically

A

cold front

because has a much steeper slope for air to rise = faster rise = more clouds/precipitaiton

63
Q

cold front causes the wind to _____

A

veer

64
Q

what is an occluded front / trowal?

A

a cold front catches up to a warm front , overtaking it and undercutting the warm front from behind. this forces the warm air to be pushed above the joined cold air mass

65
Q

the clouds ahead of the trowal is similar to a ____ front, and the clouds behind the trowal is similar to a ____ front

A

warm
cold

66
Q

what is the weather like at a stationary front

A

neither airmass is moving so there’s clouds and prolonged precipitation

67
Q

frontogenesis vs frontolysis

A

genesis = form a front
lyrics = front dissipating because weakened

68
Q

what is frontal fog

A

a warm front produces rain, it falls into cold air below. the cold air becomes saturated and results in fog

69
Q

why can thunderstorms be formed during a fast moving cold front?

A

cold dense air moves fast = warm air ahead of it is forced to rise violently
if the warm air is moist and unstable, a squall line of thunderstorm can develop along here

70
Q

stable vs unstable frontal waves

A

stable = there’s a wave but it doesn’t develop further

unstable = deepening waves causes the cold front to catch up to the warm front and forms a trowel

71
Q

two conditions for icing to occur

A

visible moisture (clouds/rain)
OAT below 0ºC

72
Q

three types of airframe icing

A
  1. rime ice = instantaneous freezing of small super cooled water droplets
  2. clear ice = large supercooled drops slowly freeze and wrap around the wing
  3. mixed ice = rime + clear
73
Q

ice forms the most when water drops are ____, airfoil shape is ____ and plane speed is _____

A

large
thin
fast

74
Q

differences between ice intensity: trace, light, moderate, severe

A

trace = can see but not hazard (unless encountered for +1h)

light = might be a hazard if encountered for over 1h

moderate = accumulates quick enough to be a hazard so must use de or anti-icing. may need to divert.

severe = too much that de or anti-icing is useless. will need to divert

75
Q

how does ice make worse aerodynamics

A
  • less lift and thrust because of turbulence and separated flow
  • more drag = need more power to sustain flight
  • propellers are thin so accumulates ice easy = less power
76
Q

some effects of plane icing

A
  • increase stall speed
  • trim less effective because thinner than regular wing so collects more ice
  • asymmetric vibration of prop
  • damaged flaps
  • fuel vents blocked
  • pitot blocked
  • worse radio reception
77
Q

what temperatures does clear ice vs rime ice form

A

clear = 0-10ºC
rime = -10 to -20ºC

78
Q

why does cold soaked fuel occur

A

wing itself is super cold because of the cold fuel
when plane descends into warm climate with lots of moisture, when the moisture touches the cold wing, frost forms

79
Q

i have impact icing over my air filter outside so i turn on carb heat to bypass this. how must i change my mixture setting?

A

carb heat= hot air = less dense = mixture becomes rich with less dense air
so must lean mixture

80
Q

why should i definitely avoid flying in a winter warm front?

A

because freezing rain can happen

81
Q

what is aerodynamic heating

A

increasing temperature of planes skin from the compression and friction as the plane moves through air

82
Q

is aerodynamic heating enough to de-ice a plane?

A

no, if the ice is already on the plane, aerodynamic heat cannot remove it

but if there’s no ice on plane and once you’re going really fast, you won’t form any

83
Q

3 ingredients to form a thunderstorm

A
  1. high moisture and high dew point
  2. steep lapse rate
  3. lifting agent
84
Q

3 stages of thunderstorm

A
  1. cumulus/developing stage
  2. mature stage
  3. dissipating stage
85
Q

the ____ the lapse rate, the quicker the vertical development of thunderstorms. why?

A

steeper

parcel of air rises faster when steep ELR because greater temperature difference

86
Q

the _____ the troposphere, the more room for vertical development of storm

A

higher

87
Q

the ____ the dew point, the more vertical depth of clouds formation. why?

A

higher

lower cloud base = quicker releases of latent heat = that parcel of air warms up a bit more = can continue to rise further = larger thickness of cloud

88
Q

a squall line is ___ of a fast moving cold front

A

ahead

89
Q

for lightning to form, there must be an ________ between two objects.

the electrons flow to the ___ charge to form lightning

A

electrical potential difference

positive

90
Q

the highest probability of lightning to hit a plane at an altitude where the temperatures are between ____ to ____ ºC

A

-5 to 5ºC

91
Q

a supercell thunderstorm results in the downdraft _____ of the updraft

A

ahead of

92
Q

avoid flight near thunderstorms within ___ NM

A

20 NM

93
Q

T/F: you can tell how severe a thunderstorm is by looking at it

A

FALSE

94
Q

what is radar attenuation for thunderstorms

A

sometimes radar only picks up one side of rain showers, and doesn’t catch the other side of the storm (even if it’s heavier)

95
Q

what is virgo

A

rain that evaporates before reaching ground but the downdrafts still continue to reach ground

96
Q

key ingredients for fog

A

high moisture/relative humidity
condensation nuclei
light surface winds
cooling process

97
Q

if the temp-dew point spread is ______ and _______ = anticipate FOG

A

3º or less and dropping

98
Q

what is radiation fog

A

at night, land cools -> close to dew point -> radiation fog

especially in valley, it’ll collect a pool of cold air

99
Q

what is advection fog

A

horizontal movement of warm, moist air over cold land = cooled from below = fog

100
Q

what is upslope fog

A

moist air moves up rising terrain = expands and cools = condense into fog (because it’s still resting on the ground)

101
Q

what is frontal fog

A

precipitation from warm front falls into colder air below = rain evaporates into cold air as stratus clouds (above ground) or fog (on ground)

102
Q

what is steam fog

A

cold dry air flows over a body of water = cold air moves with the warm moist air over water = moist air cools until the excess water vapour condenses and fog forms

103
Q

what is ice fog

A

when temperature less than -30ºC and exhaust from jet engines when doing run up on ground

104
Q

when is it considered mist vs fog

A

mist (BR) if visibility greater or equal to 5/8 SM
fog (FG) if visibility less than 5/8 SM

PPL (14 decks)

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