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 1” hg/1000 ft • Dry adiabatic lapse rate 5.4o (3c)/1000 ft • Wet adiabatic lapse rate less than dry • Dew point decreases 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
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
TraWWhatnsition p wave sketch What is wrong with this picture? 03/09/12
Go/No-Go Decision Making • Use realistic scenarios • Are storms forecast for later in the day/evening? • Effect of strong x-wind • Local vs X-C flight • Pilot experience level • What are your limits?
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
Hazards - 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
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
Weather in the Landing Pattern • What effect does the wind have on landing? • How do you determine the wind? • Wind Shear on Final • Wind Gradient
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 Problem Flying in hazy conditions Flying near a thunderstorm Landing into a decreasing headwind
Scenario – wind shear Themes Pilot low turning final Fence 300 ft before runway threshold Pilot making approach at minimum sink speed
Scenario Pilot issues High time pilot returning forgotten battery Aircraft issues Heavy water ballast load EnVironment issues Gliders launching from runway External issues Need to get back up quickly
Relight Scenario Write the text for this scenario Evaluate this scenario using the P.A.V.E model
ScenarioFlying from Coastal Airport with this Surface Prog Is cross country possible today? What about a local training flight? What hazards will you encounter Coastal Airport
Scenario What are your weather concerns?