Traffic and Weather Soaring Safety Foundation Tom Johnson CFIG
Weather Contents Weather Gathering Sources Weather Acquisition Enroute Weather Analysis Weather Hazards Weather in the Landing Pattern
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 Duats Weather Channel Internet (email and Web)
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
Atmospheric Assumptions Pressure lapse rate Dry adiabatic lapse rate Wet adiabatic lapse rate Dew point decreases 1 hg/1000 ft 5.4o (3c)/1000 ft less than dry 1o / 1000 ft
Soaring Calculations Thermal Index (TI) measured - adiabatic (minus is better) Cloud base (max surface - dewpoint)/4 (in 1000 s of ft)
Pseudo-Adiabatic plot Src: Soaring Flight Manual
Typical FSS Soaring Forecast
NOAA Forecast Plot
METAR and TAF
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
What causes this wave system?
Sea Breeze Front
Sea Breeze Front-Chicago Style
Hazards - Cold Front Src: Aviation Weather AC 00-6A
Hazards - Warm Front Src: Aviation Weather AC 00-6A
Hazards - Seasonal Weather Operations Density Altitude Thunderstorms Frost, Snow Ice Temperature extremes Wind shear Microbursts
Wind Indicators
Wind Sock
NTSB Accident Exerpts Wind Gradient? The 360-hour private pilot reported that he was unable to find any thermal lift to assist in gaining altitude to return to TA11, and he elected to land on a nearby open field which he considered suitable for landing. The pilot stated that while on final approach to the open field, he experienced gusty headwinds resulting in an "excessive sink rate." He lowered the landing gear and put in full flaps and set up for landing in a green field. When he recognized the field was a crop he turned toward a dirt field, but he encountered "heavy sink and turbulence." He reported that he leveled the wings prior to landing but landed hard. The pilot further noted that just before turning onto final approach, about 400 feet agl, the glider experienced an increase in sink rate and a decrease in airspeed (about 5 to 10 knots IAS). He lowered the nose in an effort to increase the airspeed and counteract the sink, but the glider continued toward the ground. Notice a pattern?
Wind Gradient.What Do I Do? 1. Assume the Wind Gradient will ALWAYS be there. 2. MAINTAIN Minimum IAS of VL/D + 5 kts Blanik, ASK-21, Grob 103 55kts If you do lose IAS, you slow toward best L/D and decrease drag. Once you get below best L/D you increase drag as you slow. 3. Close spoilers to maintain glidepath as performance decreases. Do not pull back on the stick to maintain glidepath.
Scenario Training Opposing Solo's Landing Long The Weather was fine when we left
Opposing Solo's Bob is on his third solo. He has planned well, and is about to turn his aircraft on a left base at just where he wants to be. At the same time, Brutus calls that he is turning a right base for the same runway.
Landing Long Bob is flying the club single place. The runway is 8000ft long at Former Air Base Field. The club officers think it is best to use ALL of the available runway on every takeoff. It is taboo to land far down the field. Bob takes the necessary steps to ensure he does not land long.
The Weather was fine when we left Bob took off at 3:30 to quickly fly the local 100km triangle. Bob came back to the field to find the wind out of the south at 18kts. Bob prefers to land on the east-west runway that is 2800 ft long. He has repeatedly stated that landing on the 1100 ft north-south runway is dangerous
Scenario Flying from Coastal Airport with this Surface Prog Is cross country possible today? Coastal Airport What about a local training flight? What hazards will you encounter