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API Weather > Weather Ch.4 > Flashcards

Weather Ch.4 Flashcards

1
Q

LIST the classifications of turbulence used in Pilot Reports (PIREPs)

A
  • Mechanical
  • Thermal
  • Wind Shear
  • Frontal
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2
Q

LIST the intensities of turbulence used in Pilot Reports (PIREPs)

A
  • Light
  • Moderate
  • Severe
  • Extreme
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3
Q

DEFINE the terms used to report turbulence with respect to time

A
  • Occasional: Less than 1/3 of the time
  • Intermittent: 1/3 to 2/3 of the time
  • Continuous: More than 2/3 of the time
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4
Q

DESCRIBE how thermal turbulence develops

A
  • Also called Convective turbulence
  • Result of heating from below
  • Solar heating
  • Cold Air moving over warmer surface
  • Strength depends on type of surface
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5
Q

DESCRIBE how mechanical turbulence develops

A
  • casued by passage of wind over obstructions
    • Buildings
    • Irregular terrain/mountains
  • Strength and magnitude dependent on
    • wind speed
    • roughness of terrain
    • stability of the air
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6
Q

DESCRIBE the cloud formations associated with mountain wave turbulence

A
  • Rotor Clouds
    • Form downwind from and parallel to mountain range
    • Cylindrical shape
    • downward flow has been known to reach the gorund
  • Cap Clouds
    • Cover top of mountatin
    • Remain stationary
  • Lenticular Clouds
    • Form on leeward side of mountain from standing waves
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7
Q

DESCRIBE techniques for flight in the vicinity of mountain waves

A
  • Approach mountain at 45 degree angle, so it is easy to turn back
  • Circumnavigate if possible
  • fly 50% higher than peak
  • Avoid rotor, cap, and lenticualr clouds
  • Avoid strong downdrafts on leeward side of mountain
  • Pressure changes affect pitot-static instruments
  • Fly reccomended turbulent air penetration speed
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8
Q

DESCRIBE how frontal lifting creates turbulence

A
  • Turbulence is caused by warm air being lifted by the cold front
  • abrupt wind shift between air masses
  • strong vertical currents when warm air is moist and unstable
  • most severe in fast-moving front
  • no turbulence in warm front due to little or no lifting
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9
Q

DESCRIBE how temperature inversions are examples of wind shear turbulence

A
  • Extreme wind shear may be formed when strong inversion exists near the ground
  • conditions near ground are stable
  • Strong wind has to exist in upper warmer air
    • wind shear is then produced at layer boundry
  • Sudden change in wind direction/velocity causes loss of airpseed and lift
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10
Q

DESCRIBE how jet streams are examples of wind shear turbulence

A
  • The change in wind speed in short distance can create a significant amount of wind shear
  • vertical shear is more significant than horizontal shear
  • exit by turning south or changing alttitude
  • jet stream could have winds that reach 250 knots
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11
Q

DESCRIBE the recommended procedures for flying through turbulence

A
  • Maintain PCL setting consistent with desired turnbulent air penetration speed
  • trim aircraft for level flight
  • do not chase airspeed deviations with power corrections
    • severe turbulence causes large rapid variations
  • Allow altitude to vary, do not chase altimeter
    • Vertical gusts cause significant altitude deviations
  • Maintain pitch and bank by reference to attitude indicator
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12
Q

DESCRIBE structural icing, in a classroom

A
  • forms on external surfaces of the aircraft
  • 4 types of icing:
    • Clear
    • Rime
    • Mixed
    • Frost
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13
Q

STATE the requirements for the formation of structural icing

A
  1. there must be visible moisture that super-cooled (liquid water that is below freezing); mainly in clouds
  2. The free air temp and aircraft’s surface temp are below freezing
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14
Q

STATE the temperature range most conducive to structural icing

A
  • -20 C to 0 C
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15
Q

DESCRIBE icing conditions associated with fronts

A
  • Warm fronts
    • stratiform clouds
    • rime icing
    • low rate of accumulation
    • widespread area of icing
  • Cold Fronts
    • cumuliform clouds
    • clear icing
    • high rate of accumulation
    • limited area of icing
  • Occluded Fronts
    • Mixed clouds
    • Stratus and cumulus
    • mixed icing
    • rime, clear, and mixed
    • rapid and heavy accumulation
    • very widespread area of icing
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16
Q

IDENTIFY the hazards of aircraft icing

A
  • Most hazardous: Alters the shape of airfoil changing the stall angle of attack
  • Decreases lift, thrust, and range
  • Increases drag, weight, fuel consumption, and stall speed
  • faulty indications from pitot-static system
  • inhibits control surface movement and antenna transmission
17
Q

DESCRIBE the types of engine icing, in a classroom

A
  • Induction Icing
    • AKA inlet icing
    • happens in clear skies and above freezing temps
    • taxi and departure
    • reduced pressure in intake system lowers temp, causing condensation and ice formation
    • High probability with air temps 10 C or less and high relative humidity
  • Compressor Icing
    • forms on compressor inlet blades
    • restricts airflow to engine could casue FOD
      • causing a flame-out, loss of thrust, rise of Exhaust gas temp, fuel to air ratio to increase
18
Q

DESCRIBE ground icing hazards

A
  • Frost
    • usually found first thing in the morning
    • must remove prior to flight
    • deicing fluid if highly corrosive and should not be sprayed down intakes or other openings
  • Taxiing through mud, slush, or water
    • splashed on aircraft surfaces
    • can freeze later at higher altitudes and colder temps
  • Runway breaking conditions
    • hazardous to control during braking of aircraft
19
Q

IDENTIFY the procedures to minimize or avoid the effects of icing

A
  • Avoid known icing conditions
    • visible moisture (clouds)
    • 0 to -20 C
    • low altitudes or mountainous terrain
  • When encountered
    • Climb or descend
      • Climb: out of visible moisture, to colder temps (frozen moisture not a hazrd), to watmer temps (if below warm front or temp inversion )
      • Descend: out of visible moisture, below freezing level, if visible moisture or freezing level on surface you can’t descend
  • Anti-Ice or De-Ice
    • Anti prevents icing
    • De removes existing ice
  • Do not fly perpindicular to a front in icing conditions
    • Maximizes exposure time
  • Minimze bank angle and high AOA
    • Increased stall speed
  • Use common sense
  • Remove ice or frost prior to takeoff
20
Q

LIST the intensities of icing used in Pilot Reports (PIREPs)

A
  • Trace
    • ice perceptible but not hazardous
  • Light
    • accumulaton maybe a problem if over an hour, ocassional us of anti or de-icing, not a problem if equioment is used
  • Moderate
    • rate of accumulation potentially hazardous, even for short encounters, de-ice/anti-ice equipment or diversion necessary
  • Severe
    • Rate of accumulation extreme, de-ice/anti-ice equipment fails to reduce or control, immediate diversion necessary, emergency
21
Q

LIST the types of icing used in Pilot Reports (PIREPs)

A
  • Rime Ice: Rough, milky opaque ice formed by the instantaneous freezing of small super-cooled water droplets
  • Clear Ice: glossy, clear or translucent ice formed by the relatively slow freezing of large super-cooled water droplets
  • Mixed Ice: A combination of rime and clear ice
22
Q

DEFINE the types of visibility

A
  • Flight Visibility
    • average forward horizontal distance, measured in statute miles from the cockpit of an aircraft in flight
    • pilot can see and identify prominent unlighted objects by day and prominent lighted objects at night
    • in statute miles
  • Prevailing Visibility
    • used on METARS
    • greatest horizontal visibility
      • equaled or exceeded throughout over half horizon circle AKA must be at least 180°
  • Slant Range Visibility
    • distance on final approach at which runway environment in sight
    • May be reported via PIREP
    • can be estimated by meteoroligists
  • Runway Visual Range (RVR)
    • horizontal distance seen by looking down runway from approach end
      • reported in meters or hundreds of feet
23
Q

DEFINE obscuring phenomena

A
  • any collection of particles that reduce horizontal visibility to less than six miles
  • surface based or aloft
  • Ex. fog, haze, smoke, volcanic ash, and blowing spray
  • vis can vary greatly in same location with different points of view
24
Q

DESCRIBE the sky coverage terms that define a ceiling

A
  • A ceiling is the height above the ground (AGL) ascribed to the lowest broken or overcast layer; or the vertical visibility into an obscuring phenomenon (total obscuration)
    • Vertical visibility is the distance that can be seen directly upward from the ground into a surface based obscuring phenomenon
    • Broken= sky cover is 5/8 to 7/8
    • Overcast= sky cover is 8/8
25
Q

DESCRIBE the parameters that define fog

A
  • visible layer of condensed moisture (must meet all 3)
    • Base at or within 50 ft of surface
    • greater than 20 ft thick
    • reduces visibility to less than 5/8 of a mile
  • 2 types
    • Advection
    • Raditation
26
Q

STATE the requirements for fog formation

A
  • condensation nuclei
  • high moisture content
  • small temp/dew point spread
    • near equal (saturation)
  • light surface winds
    • 1-10 knots
27
Q

DESCRIBE the two main types of fog

A
  • Advection
    • warm, moist air moves over cool surface
      • at or near saturation
      • cool surface reduces temp/dew point spread
    • Usually forms over water
      • brough inland by winds
      • winds can be stronger
    • Very thick
      • doesn’t dissipate with sunshine
      • only wind shift can dissipate
      • persistent
  • Radiation
    • caused by nocturnal radiation cooling
    • what you see in the morning
    • Rate depends on:
      • surface composition
      • vegetation
      • cloud coverage
      • ceiling
    • Light winds
    • dissiption begins as sun warms surface
28
Q

DESCRIBE the aviation hazards of ash clouds

A
  • Volcanic ash clouds create an extreme hazard to aircraft operating near (especially downwind) of active volcanoes. Aircraft flying through volcanic ash clouds have experienced a significant loss of engine thrust and/or multiple engine flameouts along with wing leading edges and windshields being sandblasted.
  • multiple engine malfunctions
    • flameout
    • all engines affected on mulit-engine aircraft
  • pitted windscreens
    • affects cockpit vis
  • sandblasting of external surfaces
  • Make 180° turn to escape, fly 20 NM upwind of eruption

API Weather (5 decks)

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