Weather Ch.4 Flashcards
1
Q
LIST the classifications of turbulence used in Pilot Reports (PIREPs)
A
- Mechanical
- Thermal
- Wind Shear
- Frontal
2
Q
LIST the intensities of turbulence used in Pilot Reports (PIREPs)
A
- Light
- Moderate
- Severe
- Extreme
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
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
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
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
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
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
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
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
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
12
Q
DESCRIBE structural icing, in a classroom
A
- forms on external surfaces of the aircraft
- 4 types of icing:
- Clear
- Rime
- Mixed
- Frost
13
Q
STATE the requirements for the formation of structural icing
A
- there must be visible moisture that super-cooled (liquid water that is below freezing); mainly in clouds
- The free air temp and aircraft’s surface temp are below freezing
14
Q
STATE the temperature range most conducive to structural icing
A
- -20 C to 0 C
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
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
- Climb or 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
- horizontal distance seen by looking down runway from approach end
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
DESCRIBE the parameters that define fog
* 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
STATE the requirements for fog formation
* condensation nuclei
* high moisture content
* small temp/dew point spread
* near equal (saturation)
* light surface winds
* 1-10 knots
27
DESCRIBE the two main types of fog
* 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
DESCRIBE the aviation hazards of ash clouds
* 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
