Authored by Rich Simerson Revised 01-Apr-2010

Modified by Lt Colonel Fred BlundellTX-129 Fort Worth Senior Squadron

For Local Training Rev 5.0 04-Jan-2014

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This Training Slide Show is a project undertaken by Lt Colonel Fred Blundell of the TX-129 Fort Worth Senior Squadron, Fort Worth, TX for local use to

assist those CAP Members interested in advancing their skills. The information contained herein is for CAP Member’s personal use and is not intended to replace or be a substitute for any of the CAP National Training Programs. Users should review the presentation’s Revision Number at the

end of each file name to ensure that they have the most current publication.

Objectives

Discuss how convection currents affect aircraft glide path.

Discuss wind patterns around high and low-pressure 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.

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Objectives(continued)

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 wind shear. Describe the ‘stages’ of a typical thunderstorm and

discuss the dangers of flying too close.4

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

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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

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Weather — Circulation

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Weather — Circulation(Continued)

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

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UpwardConvection Currents

Terrain which heats up creates updrafts Updrafts tend to keep you from descending Normally where there are updrafts there are also

downdrafts

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ROCKY TERRAIN PLOUGHED GROUND PAVED ROAD

NORMAL GLIDE PATH

EFFECT OF CONVECTION CURRENTS

DownwardConvection Currents

Terrain which remains cool creates downdrafts Downdrafts cause you to descend

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RIVER GROWING FIELDS LANDING FIELD

NORMAL GLIDE PATH

GLIDE PATH DUE TO CONVECTION CURRENTS

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

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Wind

Flight Path

2000 ft.

Circulation Around a High

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HAir Sinks

Moves Clockwise

Circulation Around a Low

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L

Air Rises

Moves Counter

Clockwise

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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

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Icing

Frost Snow Icing

Airframe (lift & weight) Carburetor

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Lift

ThrustDecreases

WeightIncreases

DecreasesDragIncreases

Rime ice is rougher

Glaze ice is clearer

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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.

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Icing

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.

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Icing

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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.

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Causes of Frontal Activity

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DRY AIR

COLD POLAR AIR

TROPICAL MOIST AIR

Warm Front

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St Louis Indianapolis Columbus Pittsburgh

Nimbostratus

Altostratus

CirrostratusCirrus

WARM AIR

COLD AIR

dust/polutants

Cold Front

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St Louis Indianapolis Columbus Pittsburgh

COLD AIRWARM AIR

Cumulonimbus

Occluded Front

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St Louis Indianapolis Columbus Pittsburgh

COLD AIR

WARM AIR

COLD AIR

Cumulonimbus

NimbostratusAltostratusCirrostratus

Cirrus

Clouds

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Altocumulus

Lenticular

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Clouds

Lenticular

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Clouds

Towering Cumulus

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Clouds

Mushroom

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Clouds

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

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Reduced Visibility(CONTINUED)

Fog Haze Snow White out Blowing dust Affected by sun angle and direction Aircrew must increase vigilance during these

conditions

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Wind Shear

Thunderstorms

Fronts - wind shear may advance as far as 15 nm

Air flow around obstacles

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Windward

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 passesIf moving 30kts or more, may exist below 5000 ft for

up to 3 hours Warm front:

Before front passesMay exist below 5000 ft. for up to 6 hoursDanger passes once front passes airport

Pilot must adjust quickly34

WeatherThunderstorms

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Cumulus Stage Mature Stage Dissipating Stage

Lightning In-Cloud (IC)

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Cloud-to-Cloud (CC)

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Flight Planning WX Sources

Telephone National Weather Service

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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

Flight Planning WX SourcesTelephone National

Weather ServiceWinds Aloft

All altitudesNotams

Current AirmetsConvective SigmetsCloud Tops (reported)Pilot Reports (PIREPS)High/Low Pressure AreasFronts

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Flight PlanningComputer WX Sources

AOPA.org Weather Satellite Images Radar Imagery Surface Wx Imagery Upper Air Imagery Textural WX

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Flight PlanningComputer WX Sources

(Continued)

Weatherunderground.com Temperature Heat Index Wind Chill Radar Dew point Visibility

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Flight PlanningComputer WX Sources

(Continued)

Intellicast.com Radar Severe Weather Satellite Surface Analysis Hurricane Watch More Spam

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Flight PlanningComputer WX Sources

(Continued)

NOAA’s National Weather Center (adds.aviationweather.noaa.gov) Turbulence Convection Winds/Temps Prog Charts Metars Tafs Pireps

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Plain Language Interpretation of METAR

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JOT Time 1240Z C-172 at Fl Level 2500. Reported sky cover was overcast from 8000-10000 ft. Occasional light chop. Scattered

Virga Observed

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JOT reported at the same time 1245Z showed surface weather winds from 190 at 4knots,

visibility was 10sm and CLEAR! Temperature was 23C and dew point 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)

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Questions?

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Always Think Safety!