# Presentation: 200372

## Mission Aircrew CourseChapter 6: Weather(August 2006)

**Mission Aircrew Course****Chapter 6: Weather****(August 2006)**

## 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)

**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)**

**Aircrew Tasks**

## Discuss how convection currents affect aircraft glide path. {O; 6.1.3}
Discuss wind patterns around high- and low-pressure areas. {O; 6.1.5}
Define “freezing level” and “lapse rate”	        {O; 6.2.1}
Discuss airframe icing and its affect on aircraft performance. {O; 6.2.2}
Discuss carburetor icing and its affect on aircraft performance. {O; 6.2.3}

**Discuss wind patterns around high- and low-pressure areas. {O; 6.1.5}**
**Define “freezing level” and “lapse rate”****	****        {O; 6.2.1}**
**Discuss airframe icing and its affect on aircraft performance. {O; 6.2.2}**
**Discuss carburetor icing and its affect on aircraft performance. {O; 6.2.3}**

**Objectives**

## Discuss the characteristics of cold, unstable air masses and warm, stable air masses. {O; 6.3}
Concerning reduced visibility conditions, state the minimums for: {O; 6.4}
VFR visibility
Cloud bases when they cover one-half the sky
How far aircraft must remain below cloud cover
Discuss the dangers of windshear. {O; 6.6}
Describe the ‘stages’ of a typical thunderstorm and discuss the dangers of flying too close.      {O; 6.7}

**Concerning reduced visibility conditions, state the minimums for: {O; 6.4}**
**VFR visibility**
**Cloud bases when they cover one-half the sky**
**How far aircraft must remain below cloud cover**
**Discuss the dangers of windshear. {O; 6.6}**
**Describe the ‘stages’ of a typical thunderstorm and discuss the dangers of flying too close.      {O; 6.7}**

**Objectives (con’t)**

## 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

**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**

**Weather**

**Notes:**
Weather is a key component for any CAP Operation

Mission Scanners and Observers must become familiar with basic weather conditions.

You are better prepared as a team, if all are familiar, to make the “go-no go” decision.

## 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**

**Notes:**
All crew members are to be vigilant in your flight

Determine your appropriate scanning range pertinent to your flight weather conditions

DID ANYONE HAVE TO ADJUST YOUR SCANNING RANGE DURING MONDAY’S FLIGHT?  WHY?

## Weather — Circulation

**Notes:**
Air circulation is caused by uneven heating of the earth's surface.

The earth receives more heat at the equator than at the poles.   DRAW ON BOARD    

Heated air rises from the equator and moves towards the poles.

 Colder, denser air at the poles moves towards the equator, establishing a constant circulation that might consist of two circular paths. 

## 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**

**Notes:**
Rotation causes air to deflect to the right in the northern hemisphere.  This is CORIOLIS FORCE.

This caused deflection and distortion of the air flow.

An accumulation at the 30 Latitude

As the earth rotates and the heated then cooled air continues on its path----it is further deflected by other forces:

Oceans and continents

Transference of heat by different surfaces

Variation of Temperatures and seasonal changes.

## 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**

**ROCKY TERRAIN      PLOUGHED GROUND    PAVED ROAD**

- NORMAL GLIDE PATH

- EFFECT OF CONVECTION CURRENTS

**Notes:**
Different surfaces can cause the heating and cooling of air.  This is Convection Current.

Ploughed Fields
Rocky Terrain...sand rocks
Pavement

These surfaces HOLD heat and then gives it back off....radiant heat.  

This causes you to jump and bump upward from your normal glide path.  

Could cause you to come in higher than you should for landing.

## Downward Convection Currents

**Terrain which remains cool creates downdrafts**
**Downdrafts cause you to descend**

**Notes:**
Water and vegetation (planted fields, golf courses) tend to absorb and retain heat, causing downward convection currents.

An ideal glide path can be disrupted by a sudden DROP in temperature----causing your glide path to fall short of the end of the runway.

CONVECTION CURRENT RESULTS IN:

PIC working harder to make the constant corrections to overcome the sudden changes in the glide path 

Results in reduction of crew members comfort level.

Both of which effect crew member effectiveness.

## 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**

- Wind

- Flight Path

- 2000 ft.

**Notes:**
obstructions such as bluffs and mountainsides can cause sudden changes in speed and direction ---- Gusts.

Intensity can vary by size of the obstruction.

This creates hazards at takeout and landings.  FAIL TO GIVE YOU ALTITUDE DURING TAKEOFF AND CAUSE SUDDEN SINKING UPON LANDING.

Be aware of these obstructions ahead of time in order to avoid the problems.

If any doubt whether you can clear the obstruction by 2000’, turn away and make another approach at a higher altitude.

Narrow Canyons and small valleys can pose problems as wind can increase substantially in these areas.

## Circulation Around a High

**Air Sinks**
**Moves Clockwise**

**Notes:**
Pressure is the force exerted per unit area on a surface by the weight of air above it.  

High pressure systems usually form where the air converges aloft. As the air converges in the upper-levels of the atmosphere, it forms an area of higher pressure and is forced to sink. The sinking air spirals outward, clockwise in the Northern Hemisphere

High pressure systems deplete the quantity of air causing it to sink.  This is caused by air flow converging in the atmosphere and causing the sinking effect.

This causes clouds to dissipate.

This is why we associate High Pressure systems with GOOD WEATHER.

## Circulation Around a Low

**L**

**Air Rises**
**Moves Counter Clockwise**

**Notes:**
Low pressure systems are pushing air upward causing cloudiness and precipitation

This pressure system is associated with bad weather.

## Slide 14

**Notes:**
Slide shows the High and Low symbols

Occluded 

Stationery

## 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

**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***

**LAPSE RATE**

**Notes:**
You can use simple math to give you a good idea of at what altitude freezing level is:

For example:

The freezing temperature of water is 0 degrees.

If airport elevation is 1000 feet and temperature is 12C

Freezing level would be approximately at 6000’ AGL (or 7000’ MSL)

This is a good approximate formula for determining freezing levels prior to flight.  However, give yourself a good margin as temperatures are always changing.

## Icing

**Frost**
**Snow**
**Icing**
**Airframe**
**   ****(lift & weight)**
**Carburetor**

- Lift

- Thrust

- Decreases

- W

- eight

- Increases

- Decreases

- Drag

- Increases

**Notes:**
Ice is a major problem in aviation. 

Experiments have shown that as little as one half-inch of ice accumulation on the leading edge of some airfoils in use today can reduce their lift by about 50%.

There are two requirements for ice to form: 1) the aircraft must be flying through visible water in the form of rain or cloud droplet, 

2) when the liquid water droplets strike, their temperature, or the temperature of the airfoil surface must be at or below 32

Types of ice –

 Clear ice (glaze), is a transparent coating of ice which has a glassy appearance and looks similar to ice that forms on trees and other surfaces after a freezing rain has fallen. 

 Rime ice is a white or milky, opaque, granular deposit which forms on aircraft surfaces. 
In the summer this can occur at altitudes below 10,000 ft. while flying in air which is above 32 F. 

Good Operating Practices  Plan flights to avoid area of icing or minimize time in these areas. 
 Caution should be exercised when flying through rain or wet snow with temperature levels at flight levels near freezing. 
 Maintain 4,000 to 5,000ft clearance above the crest of ridges or mountains if flying into clouds at freezing temperatures.
  Watch for ice when flying through cumulus clouds with the temperature level near freezing. 
 When ice forms on the aircraft, avoid maneuvers that will increase the wing loading. 
 Remember that fuel consumption will increase due to increased drag and additional power required. 
Consult the latest forecasts for expected icing conditions.

**Notes:**
FAR’s state there should be no frost, ice or snow on the aircraft prior to flight

THESE AOPA STATS shows the dramatic affect of icing on air safety.

**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. **

**Notes:**
This is an example of a  NOAA forecast for potential icing

This information is available for general aviation levels of flight.  This one is for FL030.

The blue dot shows the area of flights for MAS.

## 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.  **

**Notes:**
Why is it important to have your carb heat on during landings?

## Causes of Frontal Activity

**DRY AIR**

**COLD POLAR AIR**

**TROPICAL MOIST AIR**

**Notes:**
Large, high pressure systems frequently stagnate over large areas of land or water with relatively uniform surface conditions. 

They take on the characteristics of their source regions...polar coldness....tropics heats,,, moisture oceans.

As they move from their source they are modified. We see them as WARM and COLD Fronts

## Warm Front

**dust/polutants**

**Notes:**
If the air is warmer than the surface, there is no tendency for convection currents to form, trapping dust, and other pollutants near the surface, resulting in poor visibility. These air masses are considered 'stable'.

Warm air slides up over colder air. 

Characteristics:

Stratus and stratocumulus clouds
Lower ceilings
Poor visibility....fog, haze, smoke, dust 
Smooth stable air with little or no air turbulence
Slow steady precip or drizzle

## Cold Front

**Notes:**
If the air is colder than the surface, it will be warmed from below, causing convection currents, which rise and take with them dust, smoke and other atmospheric pollutants, improving visibility at the surface. These air masses are 'unstable'. 

Cold air plows underneath the warmer air ahead of it.  

As it advances, the warm moist air rises quickly, producing cloud types that depend on the stability of the air. 

With a fast moving cold front, friction retards the front near the ground, causing a steep frontal surface. 

Characteristics:

Cumulus and cumulonimbus clouds
Unlimited ceilings (except during precip)
Excellent visibility (except during precip)
Unstable air causing pronounced turbulence in lower levels...because of hot air rising  causing convection current.
Thunderstorm, showers, hail sleet.

## Occluded Front

**Notes:**
Occluded Front occurs when an air mass is caught between two colder air masses. The warmer air is forced aloft to higher and higher levels until if finally spreads out and loses its identity. As far as the pilot is concerned, the weather encountered with an occlusion is a combination of warm front and cold front conditions. Initially, warm front conditions prevail, with lowering ceilings, visibility and precipitation, followed almost immediately by cold front conditions with squalls, turbulence and thunderstorms.

## Clouds

**Altocumulus**

**Notes:**
Associated with a cold front

## Lenticular

**Notes:**
CAUSED BY WARM FRONT PASSING OVER COLD.  Formed near high mountain ranges

## Lenticular

**Notes:**
Can drift away from source of origination.

## Towering Cumulus

**Notes:**
Cold front.....unstable air.

## 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**

**Notes:**
6.4
Objective 6.7 – Concerning reduced visibility conditions, state the minimums for: visibility, under visual flight rules; cloud bases when clouds cover over one-half the sky; how far aircraft must remain below cloud cover.

## Reduced Visibility

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

**Notes:**
Fog is comprised of water droplets suspended in the air. Expect fog anytime the temperature and dew point are within 2F of each other in weather observations. Fog can severely reduce visibility and therefore constitute a serious hazard to aircraft.
Snow is another form of precipitation that presents unique problems. A whiteout is an optical phenomena that can occur with snow covered ground, and a low level cloud deck in certain low light conditions. As sunlight is diffused through the clouds, it reflects off the snow in various directions. The net result is the loss of any reference to horizon and lack of depth perception.

## Wind Shear

**Thunderstorms**
**Fronts - wind shear may advance as far as 15 nm**
**Air flow around obstacles**

- Windward

**Notes:**
Thunderstorms - any storm accompanied by thunder and lightning.

 They commonly form along cold fronts.

 Require warm, moist air that is lifted. 

Should stay at least 20 miles away from a thunderstorm.

Windshear can precede the actual storm up to 15 miles.

Downdraft from thunderstorm strikes the ground and moves outward in a radius. 

 These may be visible as dust rings or arcs in dry areas.

Wind shear appears to a given location as a sharp, distinct change in wind speed and or direction.

## 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**

**Notes:**
6.6
Objective 6.10 – Discuss the dangers of windshear.

## Weather — Thunderstorms 

**Cumulus Stage**

**Mature Stage**

**Dissipating Stage**

**Notes:**
Cumulus stage - Characterized by strong updrafts, and cumulus to cumulonimbus cloud formation
Mature Stage - Characterized by falling precipitation and mixture of updrafts and downdrafts.
Dissipating Stage - Downdrafts dominate, without supply of moisture, cloud evaporates, cloud develops characteristic anvil shape
Downwind hazards include clear air hail and turbulence.

## 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.**

**Weatherunderground.com**
**Temperature**
**Heat Index**
**Wind Chill**
**Radar **
**Dewpoint**
**Visibility**
**SPAM**

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

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

**Notes:**
Java interactive

**Notes:**
Can get it in translated format if you’re not comfortable reading the raw format

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

**Notes:**
It’s important to check the pireps for your areas of flight.

Here is a pirep of Jot

**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.   **

**Notes:**
Metar reported CLEAR.  The pirep said otherwise.

## 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)**

**Notes:**
TWEB - Continuous broadcast over VOR and NDB frequencies
In the case of severe weather, if a pirep is made, it is broadcast within 150 miles of the affected area.

**Notes:**
When all else fails......consult the ROCK