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Teaching Soaring Weather. Soaring Safety Foundation FIRC Rich Carlson. Basic Principles. Obtain the basic weather data Know how the atmosphere works Use some simple calculations to see if soaring is possible Graphs and pictures improve student understanding

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Teaching Soaring Weather

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Teaching Soaring Weather

Soaring Safety Foundation

FIRC

Rich Carlson


Basic Principles

  • Obtain the basic weather data

  • Know how the atmosphere works

  • Use some simple calculations to see if soaring is possible

  • Graphs and pictures improve student understanding

  • Weather analysis continues throughout the flight


Obtaining Weather Data

  • Look Outside

  • Local sounding

  • Flight Service Station (1-800-WXBrief)

  • National Weather Service

  • Duat

  • 3rd party service provider

  • Internet (email and Web)


Atmospheric Assumptions

  • Pressure lapse rate1” hg/1000 ft

  • Dry adiabatic lapse rate5.4o (3c)/1000 ft

  • Wet adiabatic lapse rateless than dry

  • Dew point decreases1o / 1000 ft


Soaring Calculations

  • Thermal Index (TI)

    • measured - adiabatic(minus is better)

  • Cloud base

    • (max surface - dewpoint)/4(in 1000’s of ft)


Obtaining a Weather Briefing

  • FSS call 1-800-992-7433(WXBrief)

    • Identify yourself as a glider pilot

    • Give Aircraft ‘N’ number

    • Say type of flight and location

    • Ask for standard briefing

    • Ask for surface reports

    • Ask for winds aloft forecast

    • Ask for Soaring forecast

    • Ask for other pertinent data (Notams, TFR’s)


Pseudo-Adiabatic plot

Src: Soaring Flight Manual


Typical FSS Soaring Forecast

  • T.I. at 5000 ft-5

  • T.I. at 10,000 ft+2

  • Height of -37200

  • Top of Lift8500

  • Max Expected Temp89

  • Morning Low*50


Step 1, draw the adiabatic line


Step 2, add the T.I. dots


Step 3 Draw the sounding


Internet Sources

  • Kevin Ford - http://www.soarforecast.com

  • NOAA-FSL, Forecast Systems Laboratory - http://www-frd.fsl.noaa.gov/mab/soundings/java/

  • Aviation Digital Data Service - http://adds.aviationweather.noaa.gov

  • Dr Jack BLIPMAP - http://www.drjack.info/BLIP/index.html


Kevin Ford Plots

  • === Interpolations (temps in deg. F, altitudes in feet MSL) ===

  • MSL *TI* Wdir@kts trig VirT 1.2 degrees/division ("`": Dry Adiabatic)

  • ----- ---- -------- ---- . ---- -----------------------------------------

  • 10000 12.4 40 | -9.8 ` :

  • 9500 11.6 39 | -8.6 ` :

  • 9000 10.7 280 27 37 | -7.5 ` :

  • 8500 9.8 35 | -6.5 ` :

  • 8000 8.8 290 25 34 | -5.5 ` :

  • 7500 7.9 32 | -4.5 ` :

  • 7000 6.9 295 24 30 | -3.5 ` :

  • 6500 6.0 29 | -2.6 ` :

  • 6000 3.7 300 27 25 | -4.0 ` :

  • 5500 3.6 24 | -1.5 ` :

  • 5000 3.5 24 | 0.9 ` :

  • 4500 3.3 24 | 3.3 ` :

  • 4000 2.1 22 | 3.7 ` :

  • 3500 0.8 19 | 4.1 `:

  • 3000 -0.5 18 | 4.4 :`

  • 2500 -1.8 16 | 4.8 : `

  • 2000 -2.1 15 | 7.0 : `

  • 1500 -2.1 15 | 9.7 : `

  • 1000 -2.1 15 | 12.3 : `


NOAA Forecast Plot


ADDS METAR/TAF Data


Dr Jack BLIPMAP


Local factors

  • Terrain features

    • Ridges

    • Mountains

    • Rivers

    • Lakes

    • Towns


Local factors

  • Ridge conditions

    • Calculations

    • Predictions

      • 90O +/- 30O to ridge line

      • 10 - 15 kts

    • Ridges

      • Lift extends 2 – 3 times the ridge height

      • Ridge length should be several miles


Ridge Lift Zones


Local factors

  • Wave conditions

    • Calculations

    • Predictions

      • Wind at peak

        • 15 – 20 kts

      • Wind 2000 m above peak

        • Same direction

        • 20 – 25 kts higher


Mountain Wave System


Transition pilot wave sketch


Some rotor research in progress


Some rotor research in progress


Thermal Predictors/Indicators

  • Negative Thermal Index values at alt.

  • Forecast plots

  • Clouds

  • Birds/Gliders circling

  • Dirt, crops, houses, animals rising before your eyes


Go/No-Go Decision Making

  • Use realistic scenarios

    • Storms forecast for later in the day/evening

    • Effect of strong x-wind

    • Local vs X-C flight

    • Pilot experience level


Continuing Weather Analysis

  • Obtaining enroute weather data

    • Flight Watch (122.0 Mhz)

    • Airport automated weather services

  • Obtaining end-of-flight weather data

    • Wind direction for landing

    • Current Altimeter setting


En Route Flight Advisory Service (Flight Watch)

  • AIM section 7-1-5

  • Real-time weather advisories

  • National coverage above 5000 ft on 122.0

  • Available 6:00 am to 10:00 pm

  • State ARTCC facility, N number, & nearest VOR name


Types of Fronts

  • Cold

    • Good soaring conditions

    • squall lines 50 - 300 miles ahead

  • Warm

    • temperature inversion

    • broad cloud system precedes front

  • Occluded

    • both warm & cold cloud patterns


Cold Front

Src: Aviation Weather AC 00-6A


Warm Front

Src: Aviation Weather AC 00-6A


Cold-Occlusion Front

Src: Aviation Weather AC 00-6A


Warm-Occlusion Front

Src: Aviation Weather AC 00-6A


Seasonal Weather Operations

  • Density Altitude

  • Thunderstorms

  • Frost, Snow Ice

  • Temperature extremes

  • Wind shear

  • Microbursts


Determining When to Land

  • What effect does the wind have on landing?


27

9

Effect of 20 Kt wind

Time on Downwind: More, Less, no Change?

Altitude loss: More, Less, no Change?

20 Kts


27

9

Effect of 20 Kt wind

Time on base: More, Less, no Change?

Altitude loss: More, Less, no Change?

20 Kts


27

9

Effect of 20 Kt wind

Time on Final: More, Less, no Change?

Altitude loss: More, Less, no Change?

20 Kts


27

9

Effect of 20 Kt wind

Which path is your student likely to fly?

Which path do you want them to fly?

4

20 Kts

3

1

2


Final Approach(No wind)

60 kts @ 500 ft/m decent rate

12:1 glide slope

24 seconds

200

2400


Final Approach(20 Kt Head Wind)

60 kts @ 500 ft/m decent rate

8:1 glide slope

24 seconds

200

2400

1600


Final Approach(20 kt wind shear)

60 kts @ 500 ft/m decent rate

Maintain constant speed during approach

How much time remains?

200

20 kts

0 kts

X

Y

2400

1600


Decision Time

  • With a 20 kt shear, are you likely to

    • overshoot (into area Y)

    • undershoot (into area X)

  • Said another way, what actions do you need to take to reach your intended touchdown point

    • close the spoilers to extend (undershooting)

    • open the spoilers to sink faster (overshooting)

  • Another variation, what will the aim spot do?

    • move up on the canopy (undershooting)

    • move down on the canopy (overshooting)


Glide Distance


How much Altitude does it take to regain original airspeed?

?


Transition through Wind Shear Line


Final Approach(20 Kt Wind Shear)

2 seconds for the glider to stabilize at the new sink rate

AOA increases from 0.5o to 5.0o

200

20 kts

0 kts

2400

1600

934


Distance & Altitudeduring recovery phase


Final Approach(20 Kt Wind Shear)

3 seconds to accelerate back to 60 Kts

Glider nose is 20o below the horizon

200

20 kts

0 kts

1230

2400

1600


Final Approach(Likely outcome in 3 cases?)

No Wind

Constant headwind

20 Kt Wind Shear

200

2400

1230

1600


Shear Encounters

  • When can this happen?

    • Landing in gusty conditions

    • Landing area shielded by obstructions

    • During good thermal conditions


Recommendations

  • Plan for this loss of energy

    • Pick an approach speed that will allow for some loss

    • Move base leg closer to runway edge

    • Be higher turning Final

    • Be prepared to close the spoilers

    • Be prepared to pitch forward to maintain/recover airspeed


Conclusions

  • Shear line causes loss of Total Energy

  • Large Pitch change required to rapidly recover lost energy

  • Large amount of Time ‘lost’ while total energy changes

  • Immediate action is required to reach original touchdown point!


Effects on Landing

  • Steady wind requires more energy

    • 800 feet closer or 100 ft higher for 20 kt wind

  • Changing wind requires more energy

  • Sink requires more energy

  • Ask yourself “Are you more likely to wind up getting low or high on final?”


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