thermalling (and how to avoid landing out)

THERMALLINGTHERMALLING(and how to avoid landing out)(and how to avoid landing out)

• Other possible titles:

“How I landed out over 50 times.”

“50 Farming families I’ve met.”

“ S.W. Ontario walking tours.”

John Brennan

I have landed out for every year of my life!

PurposePurpose

• Improve your soaring skills.

• By learning from the mistakes of others.

• Reach the point where you enjoy cross country soaring.

• Give you some insights into current thinking about cross country.

• Pass along your new skills and insights to fellow pilots.

John Brennan

The Need for SpeedThe Need for Speed

• All cross country flights are a race against time.• Essential to understand the importance of a

superior climb rate as compared to high inter- thermal speed.

(Any fool can fly fast!)• Thermal activity – weak in morning and late

afternoon – requires tactical adjustments.• Late in the day – STAY HIGH!

First Cross CountryFirst Cross Country

• The 50 km. task is easy – in a modern glider – assuming decent weather conditions..

• 6,000 feet msl. at SOSA – York Soaring is in the bag.

• The biggest barrier you face is the psychological fear of cutting the apron strings.

YOUR OBJECTIVEYOUR OBJECTIVE

• Badge flying is NOT a competition.• Your purpose is to COMPLETE THE

TASK.• Who cares if you complete a 300km. flight

in 4 hours or 6 hours?• You should ! Higher speed requires mental

discipline and courage.• Yet, enjoy the experience – the journey is

just as important as the achievement.

The Big One – 300km.The Big One – 300km.

• Junior glide ratio is 34:1 at fairly high airspeed.• Most modern fiberglass gliders are in the 33:1 to

37:1 range. Astir, Libelle, Junior, Std. Cirrus.• “Even” a 1-23, 1-34 or a 1-35 are capable of

300 km. + +• The key – good thermalling skills and adequate

planning.• Conclusion – 300 km. flight is possible on many

“average” soaring days in S.W. Ont.

PLANNINGPLANNING

• Check lists.• Weather forecast?• Declaration.• Water*, Food.• Pee system.• Map preparation – do not

rely on GPS.• Course line?• Key radio frequencies.

* Top priority for safety!

• Know how to operate your instruments – vario, computer, radio etc.

• Can you reach everything?• Weather shaping up per

forecast?• Take your time – let the

day develop.• Get input from qualified

pilots.• Be positive – don’t get

psyched out!

The Big DayThe Big Day

• Once airborne, get a feeling for the day.• How do actual conditions compare to the

forecast?• Thermal strength and ease of connecting.• Wind shear – at what height?• Operating band*– thermals consistent above

2,500 feet or higher?• Resist the pressure to start too early!*Note – operating band will change as the day

develops.

Thermal IndicatorsThermal Indicators

• Other gliders – most times.• Birds – hawks and seagulls.• Dust “devils” – ploughed fields.• Debris – plastic bags, hay, small cars.• Slopes, ridges, hills, towns, factories

etc.• Fires – often quite small but powerful.• Remember the rule ……

Thermal IndicatorsThermal Indicators

• WHEN HIGH …..

Use clouds or haze domes.

• WHEN LOW…..

Use terrain features.

On overcast (overdeveloped) days fly to areas of sunshine.

Common Thermalling ErrorsCommon Thermalling Errors

• Look outside – keep your head out of the cockpit!

• Use the audio function.

• Use ALL your senses.

• Speed control – fly attitude – fear of stalling?

• Angle of bank – fear of stalling?

• How do I calculate my bank angle?

Calculate my bank angle?Calculate my bank angle?

• Airspeed – you know.

• # seconds to complete 360° turn – you know.

• Gives you approximate angle of bank.

Circling Time in ThermalsCircling Time in Thermals

Bank angle 30° 35° 40° 45°

40 knots

45 knots

23 sec.

26 sec.

19 sec.

21 sec.

16 sec.

18 sec.

13 sec.

15 sec.

50 knots

55 knots

29 sec.

31 sec.

24 sec.

26 sec.

20 sec.

22 sec.

16 sec.

18 sec.

Circling Time in thermalsCircling Time in thermals

• Better pilots typically fly at 45 to 55 knots @ 19 – 23 seconds per turn.

• If you are wandering around at 20 degree angle of bank – you cannot thermal efficiently.

• Good training – Blanik @ 42 knots – around 19 to 20 seconds.

• Caution – remember laminar flow … you can also thermal too slowly.


• Turning too soon when you enter a thermal.• Banking at high speed : 60 knots + +.• Chasing the vario – remember vario lag.• Ignoring the yaw string.• Rough control movements once established in

the thermal.• Entering thermals at high speed.• Leaving thermals at high speed.


• Taking every thermal.

• Thermal “love in” – the last to leave?

• Follow the mob or lead?

• Team flying – single file or spread out?

• On blue days it is essential that all gliders on a task spread out.

““Average” thermal strengthAverage” thermal strength

• Typical flight computer – average thermal strength based on:– Start of climb?– Last 10 seconds?– Last 20 seconds?– Last minute?– Duration of flight?– Computers have given us greater insight into

achieved speeds.

Average thermal strengthAverage thermal strength

• Typically based on the past 20 to 30 seconds.

• That is why a 4 knot day really turns out to be a 1.7 to 2.0 knot day when you analyze the data.

• Beware of optimistic radio calls – “5 knots here.”

Thermal strength* in knotsThermal strength* in knots**(Assuming 4 turns to center)(Assuming 4 turns to center)

Height

gained

1 knot

climb

2 knots

climb

4 knots

climb

6 knots

climb

1,000 ft. 0.7 1.1 1.5 1.8

2,000 ft. 0.9 1.7 2.9 3.8

5,000 ft. 1.0 1.9 3.4 4.8

Cruising between ThermalsCruising between Thermals

• This should be a very busy time for you.• How fast to fly? • How slow?• Go left?• Go right?• Fly through the blue hole ahead?• Avoid the overcast on course line?• Catch up with that LS 8 ahead?

Cruising between thermalsCruising between thermals

• How FAST should I fly?

• If I fly too fast, what happens?

• If I fly too slowly, what happens?

• The good old days of “pure” MacCready ring settings.

Impact of Conservative Ring Impact of Conservative Ring SettingSetting

Thermal Strength

4 knots

Achieved!

6 knots

Achieved!

8 knots

Achieved!

# 2 setting costs you:

3% 6% 9%


0 1% 3%


1% 0 1%

Impact of Conservative Ring Impact of Conservative Ring settingssettings

• If you set the MacCready ring at “0”

• How much performance/time do you lose?

• Answer – 20%........ Leading to a high probability of an out-landing!

• Why?

• Reduces your thermal search area.

• Limited amount of thermal activity during the day – you run out of time.

Thermal Probability Thermal Probability S.W. Ontario* S.W. Ontario*

1 mile 5 miles 10 miles

1 knot 20 90 99

2 knot 10 61 84

4 knot 5 30 52

6 knot 2 10 18

* Standard class glider.

KEY LESSONKEY LESSON

• IT TAKES TIME TO CENTER THERMALS!• A “good” pilot will take FOUR turns to core a

thermal. That is 120 seconds, 2 minutes – a long, long time, going nowhere!

• A really superior pilot will center the thermal in two turns. Time saved during a 20 thermal flight?

• 10 minutes!!• An “average” pilot may NEVER center the

thermal.

How to read CloudsHow to read Clouds

• Depth of cloud – vertical development.• Shape, Texture, Curl over.• Solid, dark base.• Firm profile – not fuzzy.• Cloud shadow. (Overdevelopment?)• Growing clouds, Mature clouds and dissipating

clouds.• Learn to recognize the differences!• Beware of towering Cu.

How to Read CloudsHow to Read Clouds

• Rule of thumb – 1 in 3 clouds working.• Thermal height is proportional to distance

between thermals.• 8,000’ cloud base – thermals far apart, lots

of sink.• 3,000’ cloud base – thermals close

together, not much sink.• Thermal cycles - try to get in phase with

growing clouds.

While you are thermalling…..While you are thermalling…..

• Read the sky ahead.

• Pick out growing cloud(s) – have more than one option!

• Avoid blue holes!

• Select best course line based on cloud layout.

• If you deviate – try to deviate upwind.

Between ThermalsBetween Thermals

• Blue holes - course line deviations. How far ? Remember your objective!

• Upwind or downwind?• Cloud shadow.• Overdevelopment – how to handle?• Cloud streets – visible and not so visible.• Sink streets – be decisive – act quickly.• Blue days – sunglasses.

Between ThermalsBetween Thermals

• Lake effect.

• Turn point in blue air – what to do?

• First – decide how far you have to fly in blue air.

• Second – climb as high as possible.

• Slow down and be patient.

• Work weak lift in blue air – particularly after turn point- wind at your back.

Course deviationsCourse deviations

• Remember your mission !

• A 30° course deviation causes you to fly 15% further.

• At 80 knots, 3 miles and 30° deviation costs you 20 seconds.

• If you gain a mere 100 feet, you are better off than the blue hole puncher.

Course DeviationsCourse Deviations(The Tortoise and the Hare)(The Tortoise and the Hare)

• High personal confidence in my thermalling ability.

• Shortest distance (best speed) between two points? Straight line ?

• Flying with others showed that the most effective way to fly between two points is frequently made by deviating under “wimpy” lift.

• Fly with purpose! Don’t let the thermals push you around

Effective Inter-thermal FlyingEffective Inter-thermal Flying

Effective Inter-thermal FlyingEffective Inter-thermal Flying

• When you feel lift always slow down and turn into it

• Anytime you can climb while flying straight on course is advantageous

Turn point TacticsTurn point Tactics

• Take upwind turn point……….. LOW.*

• Take downwind turn point…… HIGH.

*( Within reason, of course!)

• Bartell – “ a 2 knot thermal going downwind is as good as an 8 knot thermal going upwind.”

Key PointsKey Points

• Read clouds carefully.• Enter and leave thermals correctly.• Turn tightly.• Be selective with thermals you take.• Use conservative MacCready settings.• Speed up by slowing down between

thermals.• Be flexible!

Thermalling RulesThermalling Rules

• First glider in thermal establishes direction of turn.

• When joining a thermal do NOT interfere with other gliders.

• Keep yourself visible to other pilots in the thermal.

• If you are climbing faster than other gliders – you must not impede other pilots

• Maintain a good lookout at all times.

Psychological FactorsPsychological Factors

• The importance of flexibility - learn to adjust your pace.

• At 7,000 feet ignore weak lift.

• At 2,000 feet take anything!

• High = Fast

• Low = Slow

• Be patient – a 1.5 knot thermal at 1,200 feet may be a 4 knot thermal at 3,000 feet


• Develop stamina – both physical and mental.• Fight the urge to “do something”. Be patient!• Avoid follow the leader – fly your own flight.• Fight the urge to “catch up” – the need for

companionship.• Remember your objective – finish the task

safely.


• The need for companionship – follow the leader often puts your brain in neutral.

• Think for yourself – avoid the herd mentality.

• The other guy is just a dumb as you are.

(Most of the time, anyway!)


• Don’t get sucked in by higher performance gliders.

• Be realistic about your gliders performance:

Astir versus VentusHornet versus LS 6LS 6 versus Nimbus 3

• McMaster strategy – optimize your gliders performance envelope.

Airport HoppingAirport Hopping(Airport hoping?)(Airport hoping?)

• Seductive for the low time pilot.• Pros and cons. Silver distance – o.k.• Dangerous for longer flights?• Your energy and concentration is on the next

airport and NOT on weather reading.• Actually slows your speed dramatically.• Many airstrips are very narrow!• Target fixation – final glides…. The mind stops

working!

PRACTICAL STEPSPRACTICAL STEPS

• The importance of weak days.

• Use 1 knot thermals around the field.

• Work on low saves around your Club.

(Just brief the Duty Instructor!)

Work on stamina.

• Release early. The Tow pilot creed – “if he fails to release in lift, he must want sink”.

SummarySummary

• Develop thermalling skills – particularly on weak days.

• Constant angle of bank, constant airspeed.• Tight turns !• CONSERVATIVE ring setting.• Make haste slowly and steadily.• Read the sky ahead.• Avoid blue holes.• Work on long inter thermal glides – 15 to 20km.• Lead – don’t follow.• Have fun!

Recommended reading listRecommended reading list

• Soaring Cross Country Reichmann

• New Soaring Pilot Welch & Irving

• Winning 11 Moffat

• The Platypus Papers Bird

• Meteorology for glider pilots Wallington

• Transition to gliders Knauff

Recommended Reading ListRecommended Reading List

• A comprehensive reading list will be

e-mailed along with a copy of this presentation.

E-mail address:

[email protected]

thermalling (and how to avoid landing out)

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