Weather Hazards

Question 1

Thunderstorms

Answer 1

•Ingredients
•Moisture
•Lifting action
•Instability

•Stages
•Cumulus
•Mature
•Dissipating

Question 2

Types of thunderstorms

Answer 2

•Airmass Thunderstorms
•Typically resulting from diurnal (daytime) heating

•Severe Thunderstorms
•Typically associated with frontal systems or drylines.
•Criteria for Severe Thunderstorm:
•Wind in excess of 50 knots, or;
•Hail of ¾ in. diameter or greater, or;
•Tornados

Question 3

Hazards of a thunderstorm

Answer 3

•Turbulence
•Severe or greater turbulence
•Vertical currents could displace aircraft 2,000 to 6,000 feet
•Maximum turbulence is mid-level of storm between 12,000 and 20,000 feet

•Lightning
•Static electricity buildup on airframe increases risk
•Strikes can happen in clear air
•Structural damage or damage to electronics is possible

•Hail
•Can inflict severe structural damage to airframe
•Exists usually between 10,000 and 30,000 feet
•Can be encountered in clear air

•Icing
•Can be severe, especially in upper atmosphere

•Wind/Low Level Wind Shear
•Tornados and gust fronts can occur
•Areas of very strong and rapidly changing wind

Question 4

How to avoid thunderstorms

Answer 4

•Don’t go near or especially through any type of convective activity
•Thunderstorms are hazardous at any altitude
•Don’t attempt a takeoff or landing near or around any convective activity

Question 5

Inflight thunderstorm detection

Answer 5

•Two types of thunderstorm detection
•Radar
•Data Uplink
•Radar: Antenna located on aircraft can be manipulated to avoid and locate TS
•Operating characteristics will vary with model
•Data Uplink: Radar data from US is uplinked to aircraft via satellite or ground antenna

Question 6

Turbulence

Answer 6

•Mechanical: Caused by wind moving around or over objects
•Mountain Waves
•Convective: Vertical currents or air rising or falling due to surface heating and cooling
•Microburst

Question 7

Microburst

Answer 7

•Down drafts can be as strong as 6000 fpm
•Typically associated with convective activity
•Duration rarely in excess of 15 minutes

Question 8

Windshear

Answer 8

•Abrupt change in wind speed or direction
•CAUSES
•Temperature inversion
•Terrain obstructions
•Frontal passage
•Thunderstorms
•Jet Stream—50 kts or greater, further south and stronger in winter
•Clear Air Turbulence (CAT)
•Wake turbulence

Question 9

Turbulence reporting

Answer 9

•LIGHT:
•Slight erratic changes in altitude or attitude; slight strain against seat belts
•MODERATE:
•Changes in attitude/altitude occur, a/c remains in positive control, variations in IAS.
•Occupants feel definite strain against seat belts.
•SEVERE:
•Large abrupt changes in altitude or attitude; large variations in airspeed.
•Aircraft momentarily out of control.

Question 10

Inflight icing

Answer 10

•Induction Icing
•Interferes with the engines ability to produce power
•Carburetor icing
•Structural Icing
•Adheres to aircraft surfaces and adds drag and destroys lift
•Comes in three forms: clear, rime, or mixed

Question 11

Induction icing

Answer 11

•Aircraft do not have to have a carburetor in order to be susceptible to induction icing
•Ice may block engine inlets or plug air filters on fuel injected aircraft
•Most common form of induction icing is carburetor icing
•Does not have to be below freezing
•Can occur in high humidity and temps up to 70 F

Question 12

Icing conditions

Answer 12

•Simple formula to figure out when icing will exist:
•Visible moisture + cold = Ice
•Aircraft surface or water droplets at or slightly below freezing (2 C to -10 C)
•All water will freeze at -40 C
•Airline definition: +10 C or colder

Question 13

Clear icing

Answer 13

•Clear ice is also called glaze ice.
•This ice type appears lumpy and translucent or clear and smooth.
•It results from supercooled liquid water droplets striking the surface but not freezing immediately upon contact.
•Clear ice tends to form horns or other complex shapes which can significantly disrupt the airflow

Question 14

Rime icing

Answer 14

•The ice type that appears rough, milky and opaque.
•Rime ice is formed by the instantaneous freezing of supercooled droplets as they strike the aircraft

Question 15

Mixed icing

Answer 15

•The ice type that appears clear near the stagnation line turning to white rime near the edges.
•It occurs at conditions between those that form pure clear and pure rime ice.
•Like clear ice, mixed ice accretions can significantly disrupt airflow and cause handling and performance problems

Question 16

Structural icing hazards

Answer 16

•Decreases lift (light rime – 30% decrease)
•Increases drag (light rime – 40% increase)
•Decreases thrust
•Decreases visibility
•Increases weight
•Increases stall speed
•Contaminates brakes, gear, gear indicators

Question 17

Tail plane stall

Answer 17

•Ice forms on the thinner surfaces first
•Tail will most likely stall before wing
•Application of flaps increases stall risk
•Nose pitches down due to loss of tail down force
•Recovery is:
•Change what you just did (i.e., flaps)

Question 18

Wing stall

Answer 18

•Application of flaps lowers stall risk
•Nose pitches down due to loss of lift
•Recovery is:
•Lower nose
•Increase power

Question 19

Reporting icing

Answer 19

•TRACE:
•Perceptible, but accumulation is balanced by sublimation
•LIGHT:
•Accumulation could be a problem with exposures over 1 hour
•MODERATE:
•Even short exposures are potentially dangerous without de-icing equipment
•SEVERE:
•Accumulation exceeds de-icing capability