Effects of Weather on UAS Flashcards
What should an airman be able to demonstrate knowledge of?
Weather effects on sUAS performance
What is the minimum visibility for flying?
At a minimum sUAS pilots must have 3 SM of visibility 500 feet below the clouds
Define Density Altitude
the density of the air given as a height above MSL
and is an interpretation of how an aircraft will feel, performance-wise,
at a certain altitude
Define Indicated altitude
Altitude: the height displayed on your altimeter
Define Pressure Altitude
Pressure Altitude: the altitude indicated with the barometric pressure
is set to 29.92 inches of mercury (inHg)
What happens with high density altitude
There is thinner air and a reduced aircraft performance
____ occurs at lower elevations, higher atmospheric presure and lower temperature and/or lower humidity
Low density altitude
Does low density altitude have thin or thick air?
Thicker air
What is the aircraft performance in low density altitude
Better aircraft performance
What do tree do to the air?
Trees and water can cause cooling and sinking air
What type of air do crop land bare earth and paved surfaces have?
Crop land, bare earth and paved surfaces can cause warm rising air
What are the winds like on east side of cascades?
More violent, have katabatic winds, turbulent
What is the wind like in Urban areas?
Effects similar to katabatic winds. Rotating wind, spinning on the corners of buildings.
How is GPS in urban area
HORRIBLE!
Cool, dry air is _____ and leads to what time of weather?
Cool, dry air is very stable and leads to good,
clear weather
What type of air is generally Unstable?
Warm moist air is generally unstable, the more
so, the greater the instability
What type of clouds produce thunderstorms?
Cumulonimbus clouds produce thunderstorms when sufficient water vapor,
unstable lapse rate and updrafts of warm air are present that prevent moisture
from falling until the top of the cloud formation is high enough in the atmosphere
that it can no longer hold moisture
What is wind shear?
Wind shear refers to a change in wind speed or direction with height in
the atmosphere
Wind shear can also refer to a rapid change in winds over a short horizontal
distance experienced by aircraft, conditions that can cause a rapid change in
lift, and thus the altitude, of the aircraft
Microburst defined?
A microburst is a localized column of sinking air (downdraft) within a
thunderstorm and is usually less than or equal to 2.5 miles in diameter
What can microburst produce?
Can produce severe downdrafts that can exceed 80 MPH
Can produce hazardous wind change direction in a matter of seconds
Effects are not limited purely to the localized column and can extend outward many
miles
Temperature Inversions
Warm air comes on top of cool air and cool air is trapped.
Pollution is trapped in cold air
Inversion do what to VLOS
make it harder to see, reduce VLOS
The amount of moisture present in atmosphere is dependent on?
The air temperture
Ever 20 degrees F increase in temperature does what to air moisture?
Doubles the moisture the air can hold
What are two ways to add water vapor to the atmosphere?
Evaporation – change from liquid water to water vapor
Sublimation – change of ice directly to water vapor
What is humidity?
Humidity is the amount of water vapor
present in the atmosphere at any given
time
What is RH?
Relative Humidity (RH) is the amount of
moisture in the air compared to the amount of
moisture the air can actually hold at that
temperature
What is dew point?
The dew point is the temperature at which air
can no longer hold moisture
When temperature and the dew point meet,
fog formation is likely
What is Precipitation Static
P-Static is a form of radio interference caused by rain, snow or dust
particles hitting the sUAS antennas and inducing a small
radio-frequency voltage into it
What are the five kinds of fog?
Raditation Advection Upslope Steam Ice
What is Radiation Fog?
Radiation fog – forms on clear, calm nights in low-lying areas when the ground cools rapidly
and the surrounding air reaches its dewpoint
What is Advection fog?
Advection fog – forms when wind/sea breezes blow warm moist air over cooler land masses,
can persist for days and usually lifts during the day to form low stratus clouds
What is Upslope fog?
Upslope fog – forms when wind/land breezes blow moist stable air up the slope of a mountain
and can persist for days
What is Steam fog?
Steam fog – common over water bodies during cold times of the year, forms when cold dry air
moves over warmer water, looks like smoke (like when you take a hat off in cold weather and
your head creates steam) and can cause icing
What is ice fog?
Ice Fog – needs VERY cold temperatures to occur, and occurs in low lying areas; water vapor
forms directly into ice crystals
