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Observer Scanner Training
Understanding Weather
Section 10
by 1st Lt. Alan Fenter
Section 1: Reduced Visibility
Objective:
Discuss acceptable flight visibility, fog,
and search area hazards.
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Flight Visibility
Category
Ceiling
IFR
Below
1000 Feet
1000 to
3000 Feet
MVFR
VFR*
Visibility
And /or
And /or
Greater
And
than 3000
Feet
Less than
3 miles
3-5 miles
Greater
than 5
miles
*By definition, VFR is greater or equal to 1,000 Ft. Ceilings &
greater or equal to 3 miles visibility. MVFR is a sub category
of VFR
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Check for Understanding
What does the FAA consider acceptable
visibility for Safe flight?
3 miles lateral visibility with 6/10 of cloud
cover with a base at least 1000 feet
above the surface.
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Check for Understanding
What is the biggest problem caused by fog?
Difficult of impossible to see runways or
landing areas
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Check for Understanding
What type of man-made object becomes a
much greater hazard to search aircraft when
visibility is poor?
Very
tall towers
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Section 2: Haze and Smoke
Objective:
Complete statements concerning haze
and smoke as flight hazards.
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Check for Understanding
A fine dust causing a lack of transparency in
haze
the air is called ________.
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Check for Understanding
A condition in which cooler air is overlain by
Temperature Inversion
warmer air is called ____________________.
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Check for Understanding
A stable atmosphere means the air does not
heat
mix through transfer of ________.
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Check for Understanding
Convection
The transfer of heat is called ____________.
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Check for Understanding
Calm winds that do not move haze and
visibility
smoke out of areas cause poor ________.
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Check for Understanding
In the summer smoke and haze may extend
10,000 feet during the heat of
upward over _______
the day.
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Check for Understanding
In smoke and haze the greatest surprise to
Thunderstorm
small aircraft pilots is the ______________.
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Section 3: Blowing Dust, Snow, & Sand
Objective:
Discuss the conditions and dangers
involved with dust, sand, snow, and
whiteout.
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Blowing Dust or Sand
Wind can spread dust
over hundreds of
miles and upward to
15,000 feet.
One choice…Turn and
LAND!
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Section 4: Turbulence
Objective:
Select true statements from false
ones concerning wake turbulence, its
dangers, and proper procedures to
deal with it.
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Four Categories of
Turbulence:
Light - unsecured objects are displace
slightly
Moderate - unsecured objects are dislodge
Severe - unsecured objects are tossed about
Extreme - aircraft practically impossible to
control
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Turbulence types:
Low-Level Turbulence LLT
Turbulence Near Thunderstorms TNT
Clear Air Turbulence CAT
Mountain Wave Turbulence MWT
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Low-Level Turbulence (LLT)
Turbulence below 15,000 feet
Due to surface heating or friction,
within a few thousand feet of the
ground
LLT includes



Mechanical Turbulence
Convective Turbulence
Frontal Turbulence and Wake Turbulence
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Mechanical Turbulence
Obstructions such as a line of trees,
buildings and hills
Strong winds flowing perpendicular to
mountain ridges - greatest on leeward
side
During gusty wind conditions, approach
and land using power-on
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Convective Turbulence
Cause by thermals produced by daytime
heating of the air in contact with the
hot ground. Bubbles of air (thermals)
rise causing low level turbulence
If the air is moist, cumulus clouds may
be seen
Convective turbulence can be from light
to severe turbulence
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Frontal Turbulence
Just ahead of a fast moving cold front
Updrafts can reach up to 1000 feet per
minute
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CAT - Clear Air Turbulence:
Turbulence in clear air- no visual
warnings
It is usually encountered above 15,000
feet
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CAT - Clear Air Turbulence:
Often develops near the jet stream (narrow
band of very fast winds near the tropopause
When a pilot enters an area where significant
CAT has been reported, an appropriate action
when the first ripple is encountered is to
adjust airspeed to that recommended for
rough air
A curving jet stream (associated with a deep
trough) produces greater turbulence than a
straight jet stream
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Mountain Wave turbulence:
When wind is 40
Kts. or more across
mountain tops
One of the most
dangerous features
of mountain wave is
the turbulent area in
and below rotor
clouds
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Wake Turbulence
A wing generating lift spills the higher
pressure air (from under the wing) at the
wing tip causing wingtip vortices
The greatest vortex strength occurs behind
heavy, clean, and slow aircraft. (After takeoff:
high angle of attack and maximum gross
weight)
When taking off behind a large aircraft on the
same runway, takeoff at a point before the
takeoff point of the departing aircraft
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Wake Turbulence
When landing behind a large aircraft on the
same runway, stay at or above the other
aircraft's final approach flight path and land
beyond that airplane's touchdown point
The wind condition that prolongs the hazards
of wake turbulence on a landing runway for
the longest period of time is a light quartering
tail wind
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Causes of turbulence include
encountering air too close to:
Thunderstorms and cumulus clouds
Atmospheric waves produced by
mountains
Air flowing around hilly terrain
Atmospheric cold and warm fronts
Tropical storms or hurricanes
Edges of jet streams
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Section 5: Icing
Objective:
Discuss the effects and dangers of
icing, particularly glaze and frost on
an aircraft.
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Kinds of Ice
Rime Ice
Clear or Glaze Ice
Mixed Ice
Frost
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10.8% of all
weather
accidents result
from icing
Close-up of leading edge ice
formation
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In-flight wing leading edge ice
formation
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Section 6: Severe Weather
Objective:
Complete statements concerning
weather threats to aircraft,
particularly thunderstorms, their
development, and effects.
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Cumulus Stage
Updrafts form from
heating and can
reach speeds of
several thousand
FPM.
Altitudes can exceed
40,000 Feet
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Mature Stage
Marked by the
beginning of rain on the
ground.
This cloud has become
a cumulonimbus cloud
because it has an
updraft, a downdraft,
and rain.
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Dissipating Stage
After about 30 minutes,
the thunderstorm
begins to dissipate.
This occurs when the
downdrafts in the cloud
begins to dominate over
the updraft.
Longest stage of a
Thunderstorm.
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