Transcript - Royal Charter Composite

Mission Aircrew Course
Weather
(APR 2010)
Aircrew Tasks
 P-2008
DISCUSS THE DANGERS OF ICING (O)
 P-2009 DISCUSS THE DANGERS OF REDUCED
VISIBILITY CONDITIONS (O)
 P-2010 DISCUSS THE DANGERS OF WIND
AND THUNDERSTORMS (O)
 P-2023 DISCUSS HOW REDUCED VISIBILITY
AND TURBULENCE EFFECT SEARCH
OPERATIONS (S)
Objectives
 Discuss
how convection currents affect aircraft
glide path.
 Discuss wind patterns around high- and lowpressure areas.
 Define “freezing level” and “lapse rate”
 Discuss airframe icing and its affect on aircraft
performance.
 Discuss carburetor icing and its affect on aircraft
performance.
Objectives (con’t)
 Discuss
the characteristics of cold, unstable air
masses and warm, stable air masses.
 Concerning reduced visibility conditions, state
the minimums for:
• VFR visibility
• Cloud bases when they cover one-half the sky
• How far aircraft must remain below cloud cover
Discuss the dangers of windshear.
 Describe the ‘stages’ of a typical thunderstorm
and discuss the dangers of flying too close.

Weather
 The
most important aspect of weather is its
impact on flight conditions
 Safety is paramount
 Navigation — Visual verses Instruments
 Effects on Search
• Prevailing visibility
• Search visibility
• Search patterns and altitudes
 Information — National Weather Service,
Flight Service Stations, Flight Watch, PIREP’s
Flight precautions
Each member of the aircrew must be vigilant
during all phases of flight
• Assign each an area to watch
 Characterize visibility in the search area to
establish the proper scanning range
• May be different than assumed
 Visibility conditions or turbulence may
increase fatigue

Weather — Circulation
Weather — Circulation
The earth rotates
 Air moving north is pulled
toward the east
 This builds a high pressure
belt about 30 degrees
latitude
 The northerly air flow cools
and starts southward
 These large circulations
are responsible for mixing
the air and most weather

Upward Convection Currents
Terrain which heats up creates updrafts
 Updrafts tend to keep you from descending
 Normally where there are updrafts there are
also downdrafts

EFFECT OF CONVECTION CURRENTS
NORMAL GLIDE PATH
ROCKY TERRAIN
PLOUGHED GROUND
PAVED ROAD
Downward Convection Currents
 Terrain
which remains cool creates
downdrafts
 Downdrafts cause you to descend
GLIDE PATH DUE TO CONVECTION CURRENTS
NORMAL GLIDE PATH
RIVER
GROWING FIELDS
LANDING FIELD
Turbulence
Planning flight around
high terrain requires
special care
 Wind currents on the
downwind side can
be very strong
 Ridges and peaks
should be cleared by
at least 2000 feet

Flight Path
2000 ft.
Wind
Circulation Around a High
Air Sinks
Moves Clockwise
H
Circulation Around a Low
L
Air Rises
Moves
Counter
Clockwise
LAPSE RATE
 As
altitude increases the temperature decreases
at a fairly uniform rate of 3.6 degrees F per 1000
(2.0 degrees C per 1000) feet; this is known as
lapse rate
• Use this on hot days to determine how high
you should climb to get to a comfortable
temperature

At some altitude the air temperature reaches the
freezing temperature of water; the freezing level
Icing
Rime ice is rougher
Frost
 Snow
 Icing
• Airframe
(lift & weight)
• Carburetor

Lift
Decreases
Drag
Increases
Thrust
Decreases
Weight
Increases
Glaze ice is clearer
The wing of a NASA Twin Otter after landing. This looks to be clear
icing or perhaps mixed. Notice the runback well past the
leading edge and on the underside of the wing.
The rectangular device on the windshield is the "hot plate", a
plate of electrically heated glass which is mounted just ahead
of the plastic windshield. When ice formation is especially bad,
the only view forward is through the upper two- thirds of the
plate, and the area around it becomes crusted with frozen
runoff from the heated area.
Carburetor Icing
 Moisture
in the air can condense, then
freeze, blocking further flow of air and fuel to
the engine.

Airplanes most vulnerable when operated in
high humidity OR visible moisture with
temperatures between 45F and 85F.

Most likely to form at low power settings such
as in descents and approaches to landings.

Fuel injected engines are not vulnerable to
carburetor icing.
Causes of Frontal Activity
COLD POLAR AIR
DRY AIR
TROPICAL MOIST AIR
Warm Front
WARM AIR
Cirrus
Cirrostratus
Altostratus
COLD AIR
Nimbostratus
dust/polutants
St Louis
Indianapolis
Columbus
Pittsburgh
Cold Front
COLD AIR
St Louis
Cumulonimbus
Indianapolis
WARM AIR
Columbus
Pittsburgh
Occluded Front
Cirrus
Cumulonimbus
WARM AIR
Nimbostratus
Cirrostratus
Altostratus
COLD AIR
COLD AIR
St Louis
Indianapolis
Columbus
Pittsburgh
Clouds
Altocumulus
Lenticular
Lenticular
Towering Cumulus
Mushroom Cloud
Reduced Visibility

Under almost all circumstances, VFR daytime
flight requires:
• At least three miles visibility
• When clouds cover more than one-half
the sky, cloud bases must be no lower
than 1,000 ft. AGL
• Search aircraft must usually remain at
least 500 ft. below the cloud deck
Reduced Visibility
Fog
 Haze
 Snow
 White out
 Blowing dust
 Affected by sun angle and direction
 Aircrew must increase vigilance during these
conditions

Wind Shear

Thunderstorms

Fronts - wind
shear may
advance as far
as 15 nm
Windward

Air flow around
obstacles
Wind Shear

Two potentially hazardous situations, dangerous mainly
during landing:
• Tailwind turns calm or to a headwind
• Headwind turns calm or to a tailwind

Critical conditions for potential low-level wind shear:
• Cold Front:
– After front passes
– If moving 30kts or more, may exist below 5000 ft for up to 3
hours
• Warm front:
– Before front passes
– May exist below 5000 ft. for up to 6 hours
– Danger passes once front passes airport

Pilot must adjust quickly
Weather — Thunderstorms
Cumulus Stage
Mature Stage
Dissipating Stage
Lightning In Cloud (IC)
Cloud to Cloud (CC)
Flight Planning WX Sources
Telephone National Weather
Service
1-800 –WX Brief (1-800-992-7433)
Standard Briefing
– METARS (updated as significant change has
occurred)
– Terminal Area Forecast (i.e. IND)
• Good for 12 hours
• 3 x per day
– Area Forecast (entire state or area you designate)
• Every 12 hours
• Route of Flight
– Winds Aloft
• All altitudes
• Notams
– Current Airmets
– Convective Sigmets
– Cloud Tops (reported)
– Pilot Reports (PIREPS)
– High/Low Pressure Areas
– Fronts
Flight Planning WX Sources
Computer
 AOPA.org
•Weather
•Satellite Images
•Radar Imagery
•Surface Wx Imagery
•Upper Air Imagery
•Textural Wx.
Flight Planning WX Sources
Computer

Weatherunderground.com
• Temperature
• Heat Index
• Wind Chill
• Radar
• Dewpoint
• Visibility
Flight Planning WX Sources
Computer

Intellicast.com
• Radar
• Severe Weather
• Satellite
• Surface Analysis
• Hurricane Watch
• More Spam
Flight Planning WX Sources
Computer

NOAA’s National Weather Center
(adds.aviationweather.noaa.gov)
• Turbulence
• Convection
• Winds/Temps
• Prog Charts
• Metars
• Tafs
• Pireps
Plain Language
Interpretation
of METAR
JOT Time 1240Z
C-172 at Fl
Level 2500.
Reported sky
cover was
overcast from
8000-10000 ft.
Occasional
light chop.
Scattered Virga
Observed.
JOT reported at
the same time
1245Z showed
surface weather
winds from 190 at
4knots, visibility
was 10sm and
CLEAR!
Temperature was
23C and dewpoint
19C.
Radio Services
Flight Service Station (FSS)
 Flight Watch (122.0)
 Automatic Terminal Information Service(ATIS)
 Transcribed weather broadcasts (TWEB)
 Scheduled weather broadcasts
• Fifteen minutes after the hour
• Alerts, hourly weather, Advisory, Pilot
Reports, Radar
 Pilot Weather Reports (PIREP)

Questions?