Thermal Acquisition Thermal Acquisition and Centeringand Centering

How to Have Fun

Soaring Cross Country

Finding and Centering Lift Finding and Centering Lift

• The most important skill for successful cross country soaring

• Cannot be learned without soaring cross country

How Do You Find LiftHow Do You Find Lift

• Look for it in as many places as you can

• Fly through areas where it is most likely to be

Required Equipment?Required Equipment?

• Audio variometer• Total energy probe• The seat of your pants

Considerations of DistanceConsiderations of Distance

• Long range considerations…20 miles– Choosing your course

• Medium range considerations…5 miles– Sampling individual thermals

• Close range considerations…1 mile– Finding the core

Long Range… Long Range… Choosing Your CourseChoosing Your Course

• Terrain• Clouds• Off-course deviations

Medium Range…Medium Range…Thermal SourcesThermal Sources

• The crest of ridges• High ground• Thermal contrasts

Sampling ThermalsSampling Thermals

• Minimize energy loss while cruising• Optimize your opportunity to find the

best thermals• Sample many, use a few• Connect the dots• Wifferdiddle

Thermal IndicatorsThermal Indicators

• Clouds• Other gliders• Haze domes on blue days• Dust devils

Close Range…Close Range…Finding the CoreFinding the Core

• Other gliders in the thermal• Professionals nearby• Darker areas of cloud• The side of the cloud that has been

working• The firm feel of a core

The Lift Profile of a ThermalThe Lift Profile of a Thermal

Approaching a ThermalApproaching a Thermal

• Keep speed up through sink• Slow down a little as lift increases• Don’t turn too soon, wait for upsurge• Turn toward lifted wing• When you feel it, center it

Bank Angle and AirspeedBank Angle and Airspeed

• Bank steeply…normally 45 °• Fly 20% faster than minimum sink

– 42 kts min sink is 50 kts at 45 degrees

• Fly shallower and slower only in large smooth areas of lift

Centering MethodsCentering Methods

• 1- Decrease bank as climb increases

• 2- Increase bank as climb decreases

• 3- Combine 1 and 2

Blue ThermalsBlue Thermals

• Look for thermal triggers• Look for streeting along the wind line• Turn into the wind

Thermal EtiquetteThermal Etiquette

• Enter a gaggle without causing a disturbance

• Fly predictably• Keep your eyes out of the cockpit• Don’t turn your inside other ships unless

well clear• Avoid a “double-blind” situations

Thermal EntryThermal Entry

Re-Acquiring LiftRe-Acquiring Lift

• Common cause is falling out the downwind side

• Fly into the wind to re-acquire

When to Stay and When to Stay and When to LeaveWhen to Leave

• Never fly through the same bad air twice!

• Don’t waste time in weak lift• Leave when the rate of climb decreases

– But only if you have a high probability of finding a better thermal