CRUISING FOR SPEEDCRUISING FOR SPEED

TECHNIQUES FOR EFFICIENT TECHNIQUES FOR EFFICIENT INTERTHERMAL SOARINGINTERTHERMAL SOARING

INTRODUCTIONINTRODUCTION

CRUISING = 60%-80% OF FLIGHTCRUISING = 60%-80% OF FLIGHT HOW FAST TO FLY BETWEEN HOW FAST TO FLY BETWEEN

THERMALS?THERMALS? MACREADY STILL RULES – BUT WITH MACREADY STILL RULES – BUT WITH

NUANCES WORTH UNDERSTANDINGNUANCES WORTH UNDERSTANDING OUT MACREADYING MACREADY – OUT MACREADYING MACREADY –

FOLLOW THAT ENERGY PATH!FOLLOW THAT ENERGY PATH!

PROGRAM PLANPROGRAM PLAN

REVIEW CLASSIC MACREADY THEORYREVIEW CLASSIC MACREADY THEORY

WIL SCHUEMANN’S PAPERWIL SCHUEMANN’S PAPER– The Price You Pay For Macready SpeedsThe Price You Pay For Macready Speeds

JOHN COCHRANE’S PAPERJOHN COCHRANE’S PAPER– Just A Little Faster PleaseJust A Little Faster Please

TECHNIQUES FOR SPECIFIC SITUATIONSTECHNIQUES FOR SPECIFIC SITUATIONS

Classic Macready TheoryClassic Macready Theory

AssumptionsAssumptions– All thermals same strength at all altitudesAll thermals same strength at all altitudes– Strength of next thermal is knownStrength of next thermal is known– Interthermal sink/lift is assumed constant Interthermal sink/lift is assumed constant

Three PilotsThree Pilots– Hair on fire Pilot CHair on fire Pilot C– Namby pamby Pilot BNamby pamby Pilot B– Ollie Optimal Pilot AOllie Optimal Pilot A

PRINCIPLE OF OPTIMIZATIONPRINCIPLE OF OPTIMIZATION

Classic Macready TheoryClassic Macready Theory Optimal inter-thermal speed for maximum Optimal inter-thermal speed for maximum

average cross country speed can be average cross country speed can be calculatedcalculated

Effect of inter-thermal sink/lift– essentially Effect of inter-thermal sink/lift– essentially subtracts from/adds to achieved climb ratesubtracts from/adds to achieved climb rate

Effect of Headwind/Tailwind--none except Effect of Headwind/Tailwind--none except on final glideon final glide

Water ballast-- shifts polar down to rightWater ballast-- shifts polar down to right Put in an anticipated thermal strength, a Put in an anticipated thermal strength, a

polar and a wing loading to the on-board polar and a wing loading to the on-board computer and a speed to fly emerges as a computer and a speed to fly emerges as a tone and needle indicationtone and needle indication

PROBLEMS WITH MACREADYPROBLEMS WITH MACREADY

Don’t know next climb rateDon’t know next climb rate

Climb rate varies with altitudeClimb rate varies with altitude

And time to center the climb – achieved climb rateAnd time to center the climb – achieved climb rate

Don’t know sink/lift between thermals– varies Don’t know sink/lift between thermals– varies constantlyconstantly

Wil Schuemann- renaissance soaring manWil Schuemann- renaissance soaring man– Total energy compensation boxTotal energy compensation box– Water ballastWater ballast– WingletsWinglets– Discus plan-formDiscus plan-form– Seminal paper on modified MacCready flightSeminal paper on modified MacCready flight

Soaring symposia—1972– see referencesSoaring symposia—1972– see references

The Price You Pay For Macready The Price You Pay For Macready Speeds Speeds

by Wil Schuemannby Wil Schuemann

Cruise speed vs. achieved Average speed Cruise speed vs. achieved Average speed – minimal difference +/- 8 to10 knotsminimal difference +/- 8 to10 knots– Big difference at best L/DBig difference at best L/D

Effect on range – does slower speed Effect on range – does slower speed increase range? Yes with respect to increase range? Yes with respect to airmass- more range, larger chance to find airmass- more range, larger chance to find special thermal (Remember Pilot B?)special thermal (Remember Pilot B?)

Who would you rather be if you don’t Who would you rather be if you don’t know where the next thermal is?know where the next thermal is?

C

B

A

Pilots

Flying MaCready accurately ain’t Flying MaCready accurately ain’t easyeasy

What is the next (achieved) thermal strength??What is the next (achieved) thermal strength??

Chasing the needle may do more damage than Chasing the needle may do more damage than goodgood– Control dragControl drag– Non-optimal G loadingNon-optimal G loading– Damp out airframe responsesDamp out airframe responses– Scare the s--- out of fellow pilotsScare the s--- out of fellow pilots

Distracts from other tasksDistracts from other tasks

Lessons learnedLessons learned

Speed variations 8-10 knots from ideal Macready Speed variations 8-10 knots from ideal Macready minimal impact on ave. x/c speedminimal impact on ave. x/c speed

Speeding in sink gains littleSpeeding in sink gains little

Range gained with slowingRange gained with slowing

But But perfectperfect speed adherence would give slightly speed adherence would give slightly higher speeds. higher speeds.

Schuemann’s conclusionsSchuemann’s conclusions– A moderate speed with little variation costs very A moderate speed with little variation costs very

little speedlittle speed– Reducing MacCready intensity yields more time Reducing MacCready intensity yields more time

to think!!! And look outsideto think!!! And look outside– Increasing range may improve thermal selectionIncreasing range may improve thermal selection– Slower flight makes air easier to assessSlower flight makes air easier to assess

John CochraneJohn Cochrane

– PHD economics, U. of Chicago dept. FinancePHD economics, U. of Chicago dept. Finance– Highly successful competition pilotHighly successful competition pilot– Regular contributor to Soaring magazineRegular contributor to Soaring magazine

Just A Little Faster PleaseJust A Little Faster PleaseJohn CochraneJohn Cochrane

Speed and modern MacCready theory-Speed and modern MacCready theory-observationsobservations– MacCready still key to in-flight speed decisionsMacCready still key to in-flight speed decisions– MacCready determines cruise speed--- the MacCready determines cruise speed--- the

mathematical solution is still validmathematical solution is still valid– But what is the correct MacCready value?But what is the correct MacCready value?

Reichmann’s elliptical thermal lift concept- bottom and top are Reichmann’s elliptical thermal lift concept- bottom and top are usually less than mid-level climb rateusually less than mid-level climb rate

Likelihood of finding best thermals goes down with altitudeLikelihood of finding best thermals goes down with altitude

Random lift distribution curve plotted against Random lift distribution curve plotted against altitudealtitude– Assumes thermals vary in strength quite a bitAssumes thermals vary in strength quite a bit– There are many weak thermals to use to save a There are many weak thermals to use to save a

flight lowflight low– There are a few really good thermalsThere are a few really good thermals

Seems to fit with pilots’ real world Seems to fit with pilots’ real world observationsobservations

Proper MacCready setting drifts Proper MacCready setting drifts down as glider gets lowerdown as glider gets lower

John CochraneJohn Cochrane(cont.)(cont.)

CENTERING TIME-AT THERMAL ENTRYCENTERING TIME-AT THERMAL ENTRY– Often several circlesOften several circles– Dilutes average rate of climbDilutes average rate of climb– Makes stopping for short climbs less efficientMakes stopping for short climbs less efficient– Longer down low and on windy daysLonger down low and on windy days– Effect larger for strong thermalsEffect larger for strong thermals– Supports trying to pick easily centered thermalsSupports trying to pick easily centered thermals

Implications for Flying TacticsImplications for Flying Tactics

Recognize that thermals are variableRecognize that thermals are variable Steadily reduce MacCready as altitude Steadily reduce MacCready as altitude

lowerlower Leave weak thermals to search as get Leave weak thermals to search as get

higherhigher Average MacCready much lower than best Average MacCready much lower than best

seenseen Always adjust MacCready to expected Always adjust MacCready to expected

future—save altitude now!!!future—save altitude now!!!

DJ Practical ObservationsDJ Practical Observations

In a modern glass shipIn a modern glass ship– Fly 60-70 knots if nervousFly 60-70 knots if nervous– Fly 80 knots if feels OKFly 80 knots if feels OK– Fly 90-100 knots if great dayFly 90-100 knots if great day

MaCready on 2 and leave it aloneMaCready on 2 and leave it alone No zoomies - gentle pull-ups and pushovers to No zoomies - gentle pull-ups and pushovers to

feel the airfeel the air Concentrate instead on following the max energy Concentrate instead on following the max energy

pathpath Other observations???Other observations???

Flying Energy PathsFlying Energy Paths

Well Formed Cu’sWell Formed Cu’s

Isolated or random cumulus cloudsIsolated or random cumulus clouds read tops as well as bottoms read tops as well as bottoms

Cumulus congestusCumulus congestus

Cu-nimCu-nim

Cruising techniquesCruising techniques Cruising with cumulus cloudsCruising with cumulus clouds

– Classic StreetsClassic Streets Speed to fly– MacCready still appliesSpeed to fly– MacCready still applies Altitude-- higher better but need to seeAltitude-- higher better but need to see Deviation angles up to 30 degrees, occ. moreDeviation angles up to 30 degrees, occ. more Bridging to next streetBridging to next street Often best speed will cause falling away from cloudsOften best speed will cause falling away from clouds ““End of street” planningEnd of street” planning

– Get highGet high

Cruising techniquesCruising techniques– ““Make your Make your

owns”owns”

Even a random Even a random pattern of dots pattern of dots can be can be connectedconnected

Optimize the Optimize the time spent “in the time spent “in the shade” shade”

Fully utilize the Fully utilize the clouds you haveclouds you have

Departing the Cloud Departing the Cloud When the lift drops off, not necessarily at When the lift drops off, not necessarily at

cloudbase!cloudbase! Want to maximize average climbWant to maximize average climb

plan ahead – while you’re topping outplan ahead – while you’re topping out speed choices – maximize the weak liftspeed choices – maximize the weak lift use the rest of the clouduse the rest of the cloud look for bridges to next energy path steplook for bridges to next energy path step Ideally should have idea where next stop Ideally should have idea where next stop

will bewill be

When to stop in generalWhen to stop in general Long cruise legs reduce centering lossLong cruise legs reduce centering loss No point in stopping high – centering time No point in stopping high – centering time

lossloss Set a height band floor—usually ~ top 30- Set a height band floor—usually ~ top 30-

40% of thermal– 40% of thermal– – Below 50%, lift begins to disconnect from Below 50%, lift begins to disconnect from

cloudsclouds Try to end streets highTry to end streets high Understand the thermal strength profile for Understand the thermal strength profile for

the day- changes with heightthe day- changes with height

Big Blue HolesBig Blue Holes Assess– why blue??Assess– why blue??

– Lake/sea shadow?Lake/sea shadow?– Airmass changeAirmass change– Wave influenceWave influence– High wind streetingHigh wind streeting

Get high and try to stay highGet high and try to stay high Go slow until you’ve had time for Go slow until you’ve had time for

assessment –may be good but dry– or not!!! assessment –may be good but dry– or not!!! Look for gliders- good thermal markersLook for gliders- good thermal markers

Blue thermal cruisingBlue thermal cruising

Read the groundRead the ground Streeting prominent on blue daysStreeting prominent on blue days Wind direction key!!!Wind direction key!!!

– Wind arrow on Ilec or GNII, etcWind arrow on Ilec or GNII, etc– Streets almost always on the windStreets almost always on the wind– Feel for the lines of lift and do this Feel for the lines of lift and do this

continuouslycontinuously– Deviate onto the lines of lift (energy paths)Deviate onto the lines of lift (energy paths)

Blue thermal cruising Blue thermal cruising

– Go slower?– greater range when weak Go slower?– greater range when weak and blueand blue

– Practice centering lines of lift on blue daysPractice centering lines of lift on blue daysFeel for asymmetric lift, and make small Feel for asymmetric lift, and make small

turns into itturns into itTry to sustain reduced sink – can Try to sustain reduced sink – can

augment achieved L/D substantially, augment achieved L/D substantially, extend range, lead to a thermalextend range, lead to a thermal

Weak blue day strategyWeak blue day strategy

Greater uncertainty warrants more conservative Greater uncertainty warrants more conservative

MacCreadyMacCready Find some company 3-5 gliders not 20Find some company 3-5 gliders not 20 Spread out when cruising with other gliders—don’t Spread out when cruising with other gliders—don’t

hide behindhide behind Lift asymmetries and lift lines –lead to thermalLift asymmetries and lift lines –lead to thermal Read the groundRead the ground

When to slow upWhen to slow up(changing gears)(changing gears)

Cochrane’s theory– progressiveCochrane’s theory– progressive When going from cu to blueWhen going from cu to blue Approaching overdeveloped areaApproaching overdeveloped area Cirrus overcast aheadCirrus overcast ahead Known or visible wet area ahead—lake, known Known or visible wet area ahead—lake, known

shower history, standing water, shower history, standing water, Multiple low gliders aheadMultiple low gliders ahead Lots of whining on the radioLots of whining on the radio ““No see-um’s” aheadNo see-um’s” ahead

Low savesLow saves

Go slow for max rangeGo slow for max range Look for birds, other gliders, dust devilsLook for birds, other gliders, dust devils ridges, rock piles, fire, smoke, edge of lake ridges, rock piles, fire, smoke, edge of lake

or woodsor woods Take anything and work its edges, Take anything and work its edges,

especially up-wind-- be patientespecially up-wind-- be patient Quit at a safe altitude– know your limitsQuit at a safe altitude– know your limits

Water ballastWater ballast

Adjustable wing-loadingAdjustable wing-loading– Slows climb directly, increased circle speed and Slows climb directly, increased circle speed and

diameter (farther away from core)diameter (farther away from core)– Improves glide performance-greater range, ave. Improves glide performance-greater range, ave.

speedspeed– Rule of thumb-keep water if ave. lift 350 ft./min Rule of thumb-keep water if ave. lift 350 ft./min

or moreor more– Especially helpful on long streets, ridgesEspecially helpful on long streets, ridges

Water ballast use (cont.)Water ballast use (cont.)

Don’t dump too soonDon’t dump too soon May need to dump a portionMay need to dump a portion

– Low savesLow saves– Thermals generally small in diameterThermals generally small in diameter

Don’t dump in gaggle thermalsDon’t dump in gaggle thermals

Water ballast (cont.)Water ballast (cont.)

Check your systemCheck your system Practice before you go to a contestPractice before you go to a contest

– Loading’s a hassleLoading’s a hassle– Flies differentlyFlies differently

Adds an interesting element of complexityAdds an interesting element of complexity

What we really doWhat we really do

Conservative MacCready dictates ave. SpeedConservative MacCready dictates ave. Speed Plan ahead, WAY AHEADPlan ahead, WAY AHEAD Not a lot of zooming—gentle speed changesNot a lot of zooming—gentle speed changes Slower with lower highly variable Slower with lower highly variable Major emphasis on best track (thus improved L/D)Major emphasis on best track (thus improved L/D) Extreme emphasis on finding best thermalsExtreme emphasis on finding best thermals Leave mediocre thermals as soon as safeLeave mediocre thermals as soon as safe

What we do (cont.)What we do (cont.)

Major deviations are the normMajor deviations are the norm Do what it takes to avoid out-landingsDo what it takes to avoid out-landings Remember the sky usually is not fallingRemember the sky usually is not falling Have fun, don’t obsess about falling behindHave fun, don’t obsess about falling behind Everybody has a bad day sometimeEverybody has a bad day sometime Practice, practice, practicePractice, practice, practice Fly for speed every time you flyFly for speed every time you fly Get better!!!Get better!!!

Recommended readingRecommended reading

Cross-Country Soaring: Helmut ReichmannCross-Country Soaring: Helmut Reichmann Introduction To Cross-Country Soaring: Kai Introduction To Cross-Country Soaring: Kai

Gertson Gertson http://www.flsc.org/XCountry/Cross-Countryhttp://www.flsc.org/XCountry/Cross-CountryB0202.pdfB0202.pdf

The Price You Pay For MacCready Speeds: The Price You Pay For MacCready Speeds: Wil Schuemann Wil Schuemann http://www.betsybyars.com/guy/soaring_syhttp://www.betsybyars.com/guy/soaring_symposia/mposia/

Just A Little Faster Please: john Cochrane Just A Little Faster Please: john Cochrane http://faculty.chicagogsb.edu/john.cochrane/http://faculty.chicagogsb.edu/john.cochrane/research/Papers/#maccreadyresearch/Papers/#maccready

Let’s flyLet’s fly

The end The end