INSTRUMENT ORAL QUESTIONS AND ANSWERS SET
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✔✔Types of structural ice - ✔✔a) clear ice - large drops strike aircraft surface, slowly
freeze
b) rime ice - small drops strike surface, rapidly freeze
c) mixed ice - combination of clear and rime, building a rough accumulation
✔✔Intensity categories of aircraft structural icing - ✔✔a) Trace - ice becomes
perceptible; deicing/anti-icing equipment not used unless encountered for over 1 hour
b) Light - occasional use of deicing/anti-icing to ensure safe flight
c) Moderate - short encounters become potentially hazardous; use deicing/anti-icing
equipment or divert
d) Severe - divert immediately; deicing/anti-icing equipment will not reduce or control
hazard
✔✔What is a freezing level, and how can you determine it? - ✔✔Lowest altitude at
which air temperature is 0 degrees C. Use icing forecasts and PIREPs to determine
approximate freezing level. Area forecasts, AIRMETs, SIGMETs, and Low-Level
Significant Weather Charts are examples of aviation weather products that contain icing
information.
✔✔Factors necessary for thunderstorm - ✔✔a) source of lift (heating, fast-moving front)
b) moisture (temp and dew point close)
c) unstable air (nonstandard lapse rate)
✔✔"Squall line" thunderstorms - ✔✔non-frontal, narrow band of active thunderstorms
that often develops ahead of cold front in moist, unstable air. Presents single most
intense weather hazard to aircraft; usually forms rapidly during late afternoon.
✔✔Two ways for fog to form - ✔✔a) cooling air to dew point
b) adding moisture to air
, ✔✔Name several types of fog - ✔✔a) radiation
b) advection
c) upslope
d) precipitation-induced
e) ice
✔✔Cause of radiation fog - ✔✔clear sky, little-to-no wind, and small temperature-dew
point spread (high relative humidity). Fog forms almost exclusively at night or near
daybreak.
✔✔Advection fog, and where it usually forms - ✔✔Forms when moist air moves over
colder ground or water. Most common along coastal areas; may occur with winds,
cloudy skies, over a wide geographic area, and at any time. Deepens as wind speed
increases up to 15 knots; stronger winds lift fog into a layer of low stratus or
stratocumulus.
✔✔Up-slope fog - ✔✔Moist, stable air cooled adiabatically while moving up sloping
terrain (because of wind). Can often be dense and extend to high altitudes (can form
under cloudy skies, unlike radiation fog).
✔✔Ice fog - ✔✔Occurs in cold weather when temperature is below freezing and water
vapor sublimates directly as ice crystals. Same conditions as radiation frog, though
colder (-25 deg C or colder).
✔✔Precipitation-induced fog - ✔✔Relatively warm rain or drizzle falls through cool air,
evaporation from precipitation saturates cool air and forms fog. Commonly associated
with warm fronts, but can occur in slow-moving cold fronts and stationary front.s Can be
quite dense and continue for long time.
✔✔Several other examples of IFR weather producers - ✔✔Low clouds (stratus), haze,
smoke, blowing obstructions to vision, and precipitation. Fog and low stratus restrict
navigation by visual reference more often than all other weather phenomena.
✔✔Sources of weather information - ✔✔a) Telephone information briefing service
(TIBS) (AFSS): 1-800-WX-BRIEF
b) Weather and aeronautical info from private industry sources (e.g. Foreflight)
c) Direct User Access Terminal System (DUATS)
d) Transcribed Weather Broadcast in Alaska (TWEB)
✔✔Pertinent information from weather briefing - ✔✔S - synopsis
A - adverse conditions
C - current conditions
r
E - enroute forecast
D - destination forecast
A+
✔✔Types of structural ice - ✔✔a) clear ice - large drops strike aircraft surface, slowly
freeze
b) rime ice - small drops strike surface, rapidly freeze
c) mixed ice - combination of clear and rime, building a rough accumulation
✔✔Intensity categories of aircraft structural icing - ✔✔a) Trace - ice becomes
perceptible; deicing/anti-icing equipment not used unless encountered for over 1 hour
b) Light - occasional use of deicing/anti-icing to ensure safe flight
c) Moderate - short encounters become potentially hazardous; use deicing/anti-icing
equipment or divert
d) Severe - divert immediately; deicing/anti-icing equipment will not reduce or control
hazard
✔✔What is a freezing level, and how can you determine it? - ✔✔Lowest altitude at
which air temperature is 0 degrees C. Use icing forecasts and PIREPs to determine
approximate freezing level. Area forecasts, AIRMETs, SIGMETs, and Low-Level
Significant Weather Charts are examples of aviation weather products that contain icing
information.
✔✔Factors necessary for thunderstorm - ✔✔a) source of lift (heating, fast-moving front)
b) moisture (temp and dew point close)
c) unstable air (nonstandard lapse rate)
✔✔"Squall line" thunderstorms - ✔✔non-frontal, narrow band of active thunderstorms
that often develops ahead of cold front in moist, unstable air. Presents single most
intense weather hazard to aircraft; usually forms rapidly during late afternoon.
✔✔Two ways for fog to form - ✔✔a) cooling air to dew point
b) adding moisture to air
, ✔✔Name several types of fog - ✔✔a) radiation
b) advection
c) upslope
d) precipitation-induced
e) ice
✔✔Cause of radiation fog - ✔✔clear sky, little-to-no wind, and small temperature-dew
point spread (high relative humidity). Fog forms almost exclusively at night or near
daybreak.
✔✔Advection fog, and where it usually forms - ✔✔Forms when moist air moves over
colder ground or water. Most common along coastal areas; may occur with winds,
cloudy skies, over a wide geographic area, and at any time. Deepens as wind speed
increases up to 15 knots; stronger winds lift fog into a layer of low stratus or
stratocumulus.
✔✔Up-slope fog - ✔✔Moist, stable air cooled adiabatically while moving up sloping
terrain (because of wind). Can often be dense and extend to high altitudes (can form
under cloudy skies, unlike radiation fog).
✔✔Ice fog - ✔✔Occurs in cold weather when temperature is below freezing and water
vapor sublimates directly as ice crystals. Same conditions as radiation frog, though
colder (-25 deg C or colder).
✔✔Precipitation-induced fog - ✔✔Relatively warm rain or drizzle falls through cool air,
evaporation from precipitation saturates cool air and forms fog. Commonly associated
with warm fronts, but can occur in slow-moving cold fronts and stationary front.s Can be
quite dense and continue for long time.
✔✔Several other examples of IFR weather producers - ✔✔Low clouds (stratus), haze,
smoke, blowing obstructions to vision, and precipitation. Fog and low stratus restrict
navigation by visual reference more often than all other weather phenomena.
✔✔Sources of weather information - ✔✔a) Telephone information briefing service
(TIBS) (AFSS): 1-800-WX-BRIEF
b) Weather and aeronautical info from private industry sources (e.g. Foreflight)
c) Direct User Access Terminal System (DUATS)
d) Transcribed Weather Broadcast in Alaska (TWEB)
✔✔Pertinent information from weather briefing - ✔✔S - synopsis
A - adverse conditions
C - current conditions
r
E - enroute forecast
D - destination forecast
