Weather hazards

turbulence

any irregular or disturbed airflow in the atmosphere producing gusts and or eddies

4 different types of turbulence

light, extreme, moderate, severe

terms used to reort turbulence with respect to time

occasional -less than 1/3 of the time

intermittent - 1/3 - 2/3 of the time

continuous - more than 2/3 of the time

the causative factors that create different types of turbulence

thermal, mechanical, frontal, large-scale wind shear

clear air turbulence (CAT)

turbulence in the absence of or outside of clouds

thermal turbulence

caused by heating below and strength depends on type of surface being heated

mechanical turbulence

results from wind flowing over or around irregular terrain or other obstructions

frontal turbulence

result of frontal lifting that is associated with the passage of a cold front

wind-shear turbulence and two types

sudden, drastic change in wind speed and/or direction

high level and low level

high level wind shear

associated with clear air turbulence like jet stream

low level wind shear (LLWS)

• why is it the most dangerous

due to local phenomenon such as a temperature inversion

most dangerous due to risk of stall and low altitude

how temperature inversions are a form of wind shear turbulence

turbulence happens at the boundary between the inversion layer and the surrounding atmosphere and can cause a loss of lift and airspeed near the ground such as when a headwind becomes a tailwind

how are jet streams an example of windshear turbulence

rapid change in wind speed in the jet stream

recommended procedures for flying through turbulence

1. maintain thrust settings

2. trim the aircraft for level flight

3. dont make abrupt control inputs

4. dont chase the altimeter

2 requirements for structural icing

atmosphere must have super-cooled visible water droplets

the free air temperature and the aircrafts surface temperature must be below freezing

4 different types of icing and the temperature (in deg C) and characteristics

clear icing - 0-(-10). large

rime icing - -10-(-20) milky white

mixed icing - -8-(-15) combination of clear and rime

frost - thin layer of crystalline ice that forms on exposed surfaces ON THE GROUND

hazards of aircraft icing

decreases lift, thrust, and range

increases drag, weight, fuel consumption, and stall speed

induction icing

icing in the inlet ducts of the aircraft

compressor icing

ice forming on the compresor inlet screen and inlet guide vanes restricting the flow of inlet air, eventually causing a flameout

ground icing

icing that happens due to events on the ground can cause icing

ways to minimize and avoid icing hazards

different flight path to avoid and climb or decend to warmer temperature

anti-icing and de-icing equipment

PIREPS on icing intensity

two things for PIREPs for icing

intensity - trace, light, moderate, severe

what type

obscuring phenomena

any collection of particles that reduce horizontal visibility to less than seven miles

fog

cloud base is within 50 feet of the ground, greater than 20 ft thick and reduces visibility to less than 5/8 mile

3 conditions for fog to form

1. condensation nuclei must be present in the air

2. the air must have a high water content

3. light surface winds must be present

two types of fog

radiation fog

advection fog

radiation fog

nocturnal cooling, ground releases large amounts of radiation into the air

dissipates with the sun

advection fog

warm air mass moves over cooler land and air is cooled to the dew point

basic requirements for thunderstorm formation

moisture, unstable air, some type of lifting action, and building up through the freezing layer

thunderstom hazards

hail

icing

microbursts

extreme turbulence

lightning

tornadoes

gust front

gusty winds that happen 5-20 miles in front of an approaching thunderstorm

microbursts speed

downdraft of 2000-6000 ft per min

micro bursts are very

localized

visual cues of microbursts

virga

localized blowing dust

rain shafts

roll clouds

hazards of microbursts

wind shear, increase in headwind meaning an increase in indicated airspeed and lift

ways to avoid a thunderstorm

fly around it,

fly over (1,000 ft above for every 10 knots of wind). fly under (1/3 the distance from surface to base), fly through it (lower 1/3 of the storm)