JX 103 Weather Hazards Flashcards
Define turbulence
Irregular or disturbed atmospheric flow producing gusts and/or eddies
What is the “intensity” classifications for turbulence
Light, moderate, Severe, and extreme
Characteristics of light turbulence
- Momentary “slight” erratic changes with altitude, attitude, pitch, roll, yaw.
- “slight” strain against seatbelt and shoulder straps
- Unsecured objects displaced “slightly”
Characteristics of moderate turbulence
- “larger changes in altitude and or attitude”
- Variations on indicated airspeed
- definite strain against seat belts and should straps
- Unsecured objects dislodged
Characteristics of severe turbulence
- “large abrupt changes in altitude/attitude
- “large” variations in indicated airspeed
- Unsecured objects tossed around
- aircraft may be momentarily out of control
Characteristics of extreme turbulence
- Aircraft “violently” tossed around
- control difficult or impossible
- Possible structural damage
- declare emergency
- Exit area ASAP
What are the durations or Turbulence?
Occasional, intermittent, continuous
How long is occasional turbulence?
less than 1/3 of the time
How long is intermittent turbulence?
1/3 to 2/3 of the time
How long is continuous turbulence?
more than 2/3 of the time
What are the classifications of turbulence by causative factors?
Thermal, mechanical, frontal, wind shear
Describe clear air turbulence (CAT)
- not associated with clouds or convective activity
- usually in a jet stream (more severe there)
- Any of the four classifications can be CAT
- Wind shear is almost always CAT
Describe thermal turbulence
- Also called convective turbulence
- Vertical air movement
- -Result of heating from below
- – Solar heating
- – Cold air moving over warmer air
- Strength depends on what type of surface
- -Result of heating from below
Describe Mechanical turbulence
- Caused by passage of wind over obstructions, such as buildings or irregular terrain/mountains
- Strength and magnitude are dependent on wind speed, Roughness of terrain, and stability of air
Describe mountain waves
- Strong winds blowing perpendicular to a mountain range
- Form standing waves
- Turbulence can be in clear air as well as in clouds
- Clouds best way to determine if turbulence is present
What is a rotor cloud?
- Form downwind from and parallel to mountain range
- Cylindrical shape
- Downward flow has been known to reach the ground
What are Cap clouds?
- Cover the top of the mountain
- Remain stationary
What are Lenticular clouds?
- For on leeward side of mountain from standing waves
Local intensities of turbulence from a mountain (proximity and intenisty)
50 knots wind at altitude of peak - Extreme turbulence
Up to 150 miles downwind - Severe turbulence
Up to 300 miles downwind - Moderate turbulence
Considerations on avoiding mountain wave turbulence
- Circumnavigate if possible
- Fly 50% higher than peak
- Avoid rotor, cap, and lenticular clouds
- Approach mountain at 45 degree angle
- Avoid strong downdrafts on leeward side of mountain
- Pressure changes affect pitot-static system
- fly recommended turbulent air penetration speed
Describe Frontal turbulence
- Caused by warm air lifted by cold front
- most severe in fast-moving fronts
- usually no turbulence is warm fronts due to little or no lifting
What is wind shear turbulence and characteristics?
- sudden changes in wind speed or direction over short distance, vertically or horizontally
- generally occurs in clear air and the greater the change the more severe the turbulence
Three types of wind shear
- Jet streams
- gusty winds
- temperature inversion
- Land/ sea breezes, mountain winds, and thunderstorms also produce wind shear
Describe a Jet stream (wind shear)
- Rapid change of wind speed short distance from the core
- vertical shear more significant than horizontal
- exit by turning south or changing altitude
Describe gusty winds (wind shear)
Gusty winds at low levels can create problems during approach or landing/takeoff
Describe temperature inversion (wind shear)
- Extreme wind shear turbulence may be formed when strong temperature inversions exists near ground
What are the turbulent procedures?
- Maintain PCl setting consistent with desired turbulent air penetration airspeed
- Trim aircraft for level flight
- Do not chase airspeed deviations with power corrections
- Do not chase altimeter
- maintain pitch and bank by reference the attitude indicator
What are the two types of icing?
- Structural icing
- Engine Icing
Types of structural icing
- Clear
- Rime
- Mixed
- Frost
Types of Engine icing
- compressor icing
- induction icing
Icing requirements
- Visible moisture
- super cooled water droplets
- – liquid water at air temperatures below freezing
- – clouds most common
- free air temperature and aircraft surfaces below freezing
Description of clear icing
- Found at temperatures between 0 and -10 degrees celcius
- large water droplets freeze slowly, spreading out and assuming shape of airfoil
- found in cumulous clouds : unstable conditions
description of rime icing
- found at temperature between -10 and -20 degrees celcius
- small water droplets free instantaneously, retaining shape
- air bubbles do not escape, causing opaque ( milky white ) color and brittleness
- found in stratiform clouds : stable conditions
description of mixed icing
- combination of clear and rime
- most common
- found at temperatures between -8 and -15 degrees celcius
- lumpy (like rime) but hard and dense (like clear)
description of frost
- occurs on clear calm nights
- lack of clouds promotes radiation cooling
- little or no wind allows moisture to deposit ice crystals (deposition)
- may also form in flight when descending from below freezing temperatures into high humidity
- does not add weight, but still disrupts boundary layer airflow over the winds, increasing stall speed
Characteristics of Frontal icing - Warm Front
- Stratiform clouds
- rime icing
- low rate of accumulation
- widespread area of icing
Characteristics of Frontal icing - Cold Front
- Cumuliform clouds
- Clear icing
- High rate of accumulation
- Limited area of icing
Characteristics of Frontal icing - Occuluded Front
- Mixed clouds of stratus and cumulus
- mixed icing (rime, clear, and mixed)
- rapid and heavy accumulation
- very widespread area of icing
Aerodynamic effects of icing
Alters shape of airfoil, changing the stall angle of attack (most hazardous)
Performance effects of icing
- Decreases lift, thrust and range
- Increases drag, weight, fuel consumption, and stall speed (can not be predicted)
Other effects of icing other than performance
- Pitot static system will have faulty instrument indications
- inhibits control surfaces and antenna transmissions
Description of induction icing
- also known as inlet icing
- clear skies and above freezing temperatures
- usually happens on taxi and departure
How does induction icing work?
Lowers temperature, condensation performs, then icing occurs from the water molecules being cooled.
- High probability with air temperatures +10 degrees celcius or less and high relative humidity
What is Compressor icing?
- forms on compressor inlet guide vanes
- both induction and compressor icing restrict airflow and could FOD engine
Two options to avoid icing
Climb or descend
What will climbing to avoid icing do?
- Out of visible moisture to a colder temperature, which allows you to get to frozen moisture (not a hazard).
- Could also be warmer if an inversion is present or below a warm front
What will descending to avoid icing do?
Out of visible moisture, below freezing levels, but if visible moisture or freezing level on surface, the descending is not an option
What is anti-ice?
PREVENTS ice
What is De-icing?
REMOVES existing ice
Three types of anti-ice/de-ice equipment
Fluid, mechanical, and heat
What does fluid anti/de icing equipment do?
- lowers freezing point of water
- ground fluids sprayed on aircraft
- Could be inflight
What does mechanical anti/de icing equipment do?
It is rubber blabbers (expands and contracts)
- most common on thicccc winged aircraft
What does heat anti/de icing equipment do?
Could be electrically heated or hot air bled off from engine to melt ice
What are the four types of Icing intensities?
Trace, light, moderate, severe
Characteristics of Trace icing
- ice becomes perceptible
- rate of accumulation slightly greater than sublimation
- de-icing/anti-icing not used unless encountered for long time
Characteristics of light icing
- Rate of accumulation can be a problem over an extended time (over 1 hour)
- Occasional use of anti icing equipment prevents accumulation (not a problem if equipment is used)
Characteristics of moderate icing
- Rate of accumulation potentially hazardous (even for short encounters)
- de icing equipment used or diversion if necessary
Characteristics of severe icing
- Rate of accumulation extreme
- de icing equipment fails to remove
- immediate diversion necessary
What is flight visibility?
Average forward horizontal distance from cockpit
-measured in statute miles
What is prevailing visibility?
Greatest horizontal visibility
- Equaled or exceeded throughout over half of horizon circle
- measured in statute miles
- does not need to be continuous
What is Slant Range visibility?
Distance on final approach at which runway environment is in sight.
- must be reported on a PIREP
- can be estimated by meteorologists
- indicates when an aircraft will breakout on final
What is Runway visual range (RVR) ?
Horizontal distance seen by looking down the runway
- reported in meters or hundred of feet
What is obscuring phenomena?
When visibility is obscured and reduced to less than 6 miles
What are the types of obscuring phenomena?
Fog, Haze, Smoke, Rain/drizzle, snow, and blowing snow/dust/sand
When is vertical visibility (VV) used ?
- When sky is totally hidden
- base within 50 feet of surface
- also referred to as the indefinite ceiling
What is the definition of fog?
Visible layer of condensed moisture which reduces visibility to less than 5/8 mile
What are the two types of fog?
Radiation and advection
requirements for the formation of fog
- condensation nuclei
- high moisture content
- small temperature/dew point spread
- light surface winds
What is radiation fog?
caused by nocturnal radiation cooling
- depends on surface composition, vegetation, cloud coverage, ceiling, and light winds
- dissipation begins as sun warms surface
What is advection fog?
Warm moist air moves over cool surface
- at or near saturation
- usually forms over water
- -brought inland by winds
- very thick layer
- only winds can get rid of it
