u14 Flashcards
can you fly over mountain waves
no they extend to tropopause so you’ll feel turbulence no matter what
conditions for mountain waves to occur:
- wind direction to mountain
- wind speed to mountain
- aloft winds
- type of airmass aloft
wind must be within 30º perpendicular to mountain
wind speed perpendicular to mountain must be at least 25 KT
wind aloft must increase with height
stable airmass aloft (inversion)
why does a stable airmass encourage mountain waves oscillations
air rises over mountain, inversion says no and pushes airmass down. it tries to rise again but gets pushed down…
how does stability, wind speed and ridge spacing affect the wavelength of mountain waves
stable atmosphere = short wave length
greater wind speed = long wave length
multiple ridges spaced at least 5 NM apart = more build up = longer wave length
the amplitude of mountain waves is _____ at the surface compared to above the mountain top due to ______
smaller amplitude at surface because of surface friction
aloft waves don’t have any friction so they can get large amplitude
how does stability of atmosphere, mountain height, multiple rides and a sharp downward leeward slope affect amplitude of mountain wave
stable atmosphere = large amplitude
tall mountain = large amplitude
multiple ridges = more build up = large amplitude
sharp leeward slope = large amplitude
you’re flying towards a mountain and don’t see any rotor or lenticular clouds ahead. does this mean there’s no mountain waves?
NO
cloud presence ≠ mountain waves
clouds are only there because airmass is moist
a strong wind will still flow past the moutanin and form mountain waves
lenticular clouds:
- location
- what does a torn lenticular indicate
top of wave crests
torn lenticular = turbulence
due to high wind shear (speed shear) between crest layers which causes turbulence
if you must pass through a mountainous area but see rotor clouds in the distance, where should you fly to avoid the worst turbulence
fly over rotor clouds (but still expect turbulence)
fly around
never fly beneath
cap clouds indicate
a strong downdraft
what are banner clouds
air rises over side of mountain, forms cloud, but as it reaches the top, there’s a strong wind that pushes the cloud backwards so it can’t move on other side of mountain
mountain clouds can tell us _________ of wave crests and rotors but no the ________ of turbulence
location
intensity
your altimeter can over-read by 3000 ft when you’re in a mountain wave! why
greater wind speed = drop in pressure = alt thinks you’re higher than you area
what is funnel wind and how does it affect your altimeter
funnel wind = wind flows through constricted area so increases speed = drop pressure = alt over reads
are large eddies more or less turbulent to fly through at slow speeds
less turbulent when slow since you can ride it out
t/f: heavy plane with high wing loadings can withstand turbulence better
true
convective turbulence
- how does it form
- worse in morning or afternoon?
- avoid how
uneven heating of surface = pockets of hot air rise faster than other sections = sporadic updrafts. also under clouds you have rising and sinking air which makes convective turbulence worse
afternoon
fly over clouds
what is mechanical turbulence and what conditions make it bad
friction between air and ground/terrain
unstable air + rough = terrain = worsens mechanical turbulence
what is frontal turbulence
what 3 waves can it be formed
caused by friction / wind shear between two air masses
big wind difference between fronts
big temperature difference between fronts
when front is moving very fast
what is orographic turbulence
where are the up and down drafts
caused by friction in air currents around a mountain
updraft on windward side
downdraft on leeward side
what is mountain wave turbulence
what are the 3 mountain wave conditions
do you feel MWT worse flying upwind or downwind
after passing over mountain, series of strong up/down drafts aloft
stable atmosphere, wind speed perpendicular to mountain is 25 KT, wind speed aloft increases with height
downwind: plane has faster ground speed so hit bumps faster
t/f: wind shear doesn’t always cause turbulence
true
how does a nocturnal inversion cause low level wind shear
winds aloft uncouple to surface winds at night + higher wind speed aloft = change in wind speed/direction during to and landing
how does a frontal system cause low level wind shear
front can cause a low level jet = wind shear between two
how does a microburst cause low level wind shear
thunderstorms have strong downdraft that creates violent gusts (microbursts) and wind shear
how does virga cause low level wind shear
rain falls into a dry layer of air below and evaporates but the strong downdraft is still there and continues towards the ground
clear air turbulence usually occurs with a jet stream at high levels. where is the turbulence greatest when facing downstream?
CAT worse on left side of jet core (on the side of the jet stream that faces the COLD airmass because larger wind speed difference)
what is light turbulence
slight erratic change in attitude/altitude (less than 15KT airspeed change)
what is moderate turbulence
bumpy but plane remains in control at all times
what is severe turbulence
large changes in altitude/attitude, airspeed flux 25KT, plane momentarily out of control
what is extreme turbulence
plane violently tossed, control is impossible, structural damage
what is light chop turbulence
slight bump but no change in altitude or attitude
what are the 3 key ingredients for thunderstorms to form
high moisture
steep lapse rate
lifting agent
explain the cumulus developing stage of a thunderstorm
- how does it keep growing
- is there precipitation
warm, moist unstable air rises -> cools and precipitates into cumulus clouds
as water vapour condenses into liquid (cloud) , latent heat is released = warms the surrounding air = that pocket of warm air rises and condenses into more cumulus cloud (feeds itself)
updrafts hold the small water molecules so no precipitation yet
explain the mature stage of thunderstorm development
- what happens when it reaches the statosphere
- precipitation?
- weather phenomena
- how long does it last
warmed air continues to rise until it reaches stratosphere = expand into anvil shape
ice crystals and water droplets hit each other and grow until they’re too heavy for updrafts to keep them afloat = fall as precipitation + strong downdrafts
rain, turbulence, lightning, thunder
15 mins to 1h (until it chokes itself off)
explain the dissipating stage of thunderstorm development
heavy rain falls through cloud = cloud cools (loses energy)
heavy rain brings strong downdrafts that cut off the updrafts = storm disappears
would a low or high dew point permit a larger (more vertical depth) CB cloud?
high dew point = lower cloud base = more room for CB to grow vertically
a squall line is found where
ahead of a fast moving cold front
how does lightning occur
when the electric difference between the ground and cloud is large enough to overcome the electrical resistance in the air, the electrons flow from the negative ground to positive cloud = lightning
or cloud to cloud
lightning occurs between what temperature
-5 to +5ºC
how does hail form
strong updraft pushes the water droplets above the freezing level = freeze into hail
as hail falls it collects water
another updraft pushes the droplets up
water freezes onto outside of hail stone
cycle repeats until hail is heavy enough for gravity to pull it down
severe turbulence can occur ______ NM from a thunderstorm
20 NM
explain radar attenuation with thunderstorms
radar only picks up front section of thunderstorm and might not show more powerful section behind it due to attenuation
what happens if a bunch of rain gets in your turbine engine
flameout
if flying over a thunderstorm, clear the thunderstorm by 1000 ft per ____ KT of wind speed at the top of the storm
10KT
why can’t you fly under a thunderstorm
the downdrafts are so strong they can exceed your climb capacity
hurricane vs tornado
- how are they formed
- wind speed
- area of destruction
hurricane = extremely low pressure system in the tropics that’s just an organized collection of thunderstorms. slow wind but large area of destruction
tornado = rotating funnel cloud that links the ground to one large thunderstorm. extreme winds and small area of destruction
what ingredients form fog
high moisture / relative humidity
condensation nuclei (dust,smoke,salt)
light surface winds (for mixing because if no wind, then just dew forms)
cooling process or something adds moisture for condensation
what is radiation cooling
- what ingredients do you need for it to occur
- how does the cloudiness of the sky affect radiation fog from forming
- where does the strongest radiation fog form - does it form due to a cooling process or adding water to saturate dry air?
radiation cooling occurs at night when the surface cools past dew point and fog forms
- clear night, high humidity and light winds
- cloudy night = heat trapped. but when the sky is clear, heat can escape and ground can cool enough for fog to form
- thick radiation fog form in valleys and low areas first because cold air sinks into them (from katabatic cooling at night)
- cooling process
what is advection fog
- what season does it occur
- lasts until _______ increases. explain
- does it form due to a cooling process or adding water to saturate dry air?
warm, moist air moves horizontally over a colder surface (ocean to land). warm air is cooled from below = fog forms
end of winter/early spring
lasts until wind speed increases above 15 KT because more mixing and lifts the fog to become a low stratus cloud instead
cooling process
what is upslope fog
- does it occur on both sides of the mountain?
- does it form due to a cooling process or adding water to saturate dry air?
light upslope winds cause moist air to rise = cool = condense into cloud on the side of the mountain
* but since the cloud is touching the ground = “fog”
occurs on windward side only
on leeward side, cold air sinks and warms up (subsidence)
cooling process
what is frontal fog
- does it form due to a cooling process or adding water to saturate dry air?
- occurs at a ______ front or _____
aka precipitation fog
precipitation ahead of a warm front falls into cold, dry air below. as the rain evaporates into the cold air, the cold air reaches saturation = condenses into stratus clouds and fog
adding water to saturate dry air
warm front or trowal
what is steam fog
- does it form due to a cooling process or adding water to saturate dry air?
cold, dry air blows over a warm body of water. as warm air from the lake rises, it mixes with the cold air = saturates the cool air and condenses as fog
adding water to saturate air
what is ice fog
- ingredients
- how long does it last
- does it form due to a cooling process or adding water to saturate dry air?
cold air (-30) + engine exhaust with water vapour = saturates the cold air = condense into fog
lasts for a long time
adding water to saturate cold air
what is industrial fog
- ingredients
- does light wind make industrial fog thinner or thicker
- does it form due to a cooling process or adding water to saturate dry air?
condensation nuclei, humid, small temp-dew spread, cooling
thicker
cooling
what is the visibility considered to be mist vs fog in terms of visibility
visibility is equal or better than 5/8 SM = mist
visibility is worse than 5/8 SM = fog
when does haze form and what does the sky look like
hot day with lots of dust/smoke/salt
milky sky
rime ice
- ________ freezing of _____ supercooled water droplets
- appearance
- type of cloud
- strength / how easy is it to remove
instantaneous freezing of small supercooled water droplets
rough, milky, opaque
stratus clouds
brittle. = easy removal
clear ice
- ______ supercooled water droplets _______ freeze onto plane
- appearance
- what cloud / conditions does it form in
- easy/hard to remove
large supercooled water droplets slowly freeze onto plane
smooth and transparent
CU, lenticular, freezing rain
hard to remove
how does the airfoil shape affect rate of ice accumulation (thick vs thin)
thin airfoil = collect more ice
how does the plane speed affect rate of ice accumulation
fast plane = hit more water = collect more ice
how does water droplet size affect rate of ice accumulation
large droplet = collect more ice
large droplets when big cloud with vertical currents (CB) + high moisture airmass (warm)
worst plane icing between _________ ºC. why?
0 to -10ºC
mostly supercooled water droplets at this altitude = plane icing
at higher altitude (colder temp), those water droplets would have already frozen to ice crystals so that won’t cause plane icing
unless vertical currents sent supercooled water droplets up higher
trace icing
- rate of accumulation / is it hazardous
- do we need de/anti-icing
not hazardous (don’t need de/anti icing) unless you’re in it more than an hour
light icing
- rate of accumulation
- is it hazardous
- do we need de/anti-icing
rate of accumulation will be a problem if the flight is longer than an hour
moderate icing
- rate of accumulation
- is it hazardous
- do we need de/anti-icing
rate of accumulation is quick enough to be hazardous in a short period of time so we need de/anti icing
severe icing
- rate of accumulation
- is it hazardous
- do we need de/anti-icing
too much accumulation that de/anti icing is useless
what do you do if you encounter icing?
why don’t you climb
descend/ turn around and pitot heat ON
to climb we need excess thrust but with ice our thrust decreases and also we don’t know how high the clouds are
how does icing affect stall speed / critical AoA / bank
does this affect horizontal stabilizer
what about propeller thrust
radio reception
icing = changes wing shape = increases stall speed (lower AoA)
high stall speed = can’t bank more than 5º or yhou might stall
thin horizontal stabilizer collects ice faster than wing so it can stall faster than wing
propeller icing = asymmetric thrust
antenna is so thin it accumulates ice quickly so bad receipton
how do you modify your approach when your plane has icing
more power and extra airspeed
because your plane has higher stall speed
flapless
clear ice forms in _______ clouds -> worst at ___________ºC
clear ice = CU clouds = 0 to -10ºC
rime ice forms in _______ clouds -> worst at ___________ºC
rime ice = stratus = -10 to -20ºC
what are examples of anti-icing processes on big boy jets
for propeller, leading edge of wing, and wing/tail surface
electric heating on propellers and windshields
bleed air from engine sent to leading edge
TKS fluid pumped through mesh screens on wing and tail
frost decreases lift by ______ and increases drag by _____
lift 30%
drag 40%
explain the cold soaked fuel process
can you takeoff with cold soaked fuel frost on wing
cold plane descends into warm, moist air. the moisture touches the cold wing = instantly freezes
can takeoff with frost on underside of wing due to cold soaked fuel and if you’re following manufacturer instructions
uh oh, impact icing is blocking your regular intake air. what will happen if you do nothing?
what can you do to prevent it
engine failure
carb heat to bypass air filter + lean mixture
or alternate air intake on a fuel injected plane
why should you fly through a front directly head on, instead of at an angle in the winter time?
so you limit your time spent in clouds/icing conditions
why should you always avoid a winter warm front
freezing rain
you encounter icing and start to turn around to get out of the bad conditions. what bank angle should you use?
under 5º because since you have ice you have a higher stall speed so can’t afford to lose vertical lift
why are tail stalls common when you quickly encounter icing
how can you recognize a tail stall is approaching
what does a tail stall feel like
how do you modify your approach if you suspect icing on HS
HS thinner airfoil = accumulates ice quicker
abnormal pitch forces when you put flaps down
violent nose down (because tails job is to keep nose up)
flapless landing, small bank angles and pitch changes
how does hoar frost form in flight
cold plane descends into warm and moist airmass in clear air (like cold soaking) and will instantaneously turn to frost on plane. lasts until the plane itself warms to the new temperature
what is aerodynamic heating?
can it melt ice?
extra fast plane wont collect ice due to the heat produced by skin friction as it quickly moves through air
if ice is already on the plane, aerodynamic heating wont remove it
