the phase diagram of soaring: flight mode …analysen& konzepte • dr. o. liechti • ch-8404...

ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur

The phase diagram of soaring:flight mode transitions in combinations of

isolated and aligned lift patterns

Olivier LiechtiWinterthur, Switzerland

OSTIV congressLüsse, 12 August, 2008


Outline

•Introduction

•PFD with thermals

•PFD with wind and thermals


Soaring in wind and thermals

•Wave•Ridge lift•Thermals•Combination of W and T


Wave: 13 h, 2‘400 km, 192kph


Ridge: 8.5 h, 1‘180 km, 138 kph


Thermals: 7.75 h, 1‘186 km, 153 kph

80 kph

173 kph


Combination: 13.5 h, 1‘400 km, 103 kph

55 kph

142 kph

98 kph



142 kph



172 kph

110 kph


Flight distance in cross-country soaring

thermals

VFR

wind

ridge

wave

rotors streets

Distance•Duration•Speed


Soaring speed

•climb rate•spatial lift distribution: isolated, aligned•flight polar•pilot skill and experience

Weather controls the duration, the strength andthe spatial distribution of updrafts.

Predictions of these weather elements provide thepotential flight distance (PFD).


Outline

•Introduction




Regional thermal forecast

Avg. Lift Clouds

Source: pc-met@DWD

cross-country conditions

Stratiform Clouds

Cumulus Clouds


Climb rate --> cross-country speed

•flight polar

•speed-to-fly theory for isolated lift

•cross-country speed

•potential flight distance (PFD)


Flight polar

0 20 40 60 80 100 120 140 160 180 200

0 10 20 30 40 50

-4

-3

-2

-1

0

Fahrt [km/h]

VZ [m/s]

[km/h]

[m/s]

124 (1:53, 100 km/h)

114 (1:47, 96 km/h)

100 (1:39, 90 km/h)

84 (1:30, 80 km/h)

77 (1:27, 55 km/h)

51 (1:12, 48 km/h)

39 (1: 5, 30 km/h)

Hängegleiter

Gleitschirm

(Beste Gleitzahl, Fahrt)Index

Archaeopteryx

Segelflugzeuge

Handicap(BGR@speed)

Sailplanes

Hangglider

Paraglider

speed


Optimum cross-country speed

Mittleres Steigen [m/s] in der Thermik

VXC [kph] Handicap (BGR)

124 (1:53)

114 (1:47)

100 (1:39)

84 (1:30)

50 (1:12)

38 (1: 5)

77 (1:27) Archaeopteryx

15 m old

15 m

18 m

25 m

Hangglider

Paraglider

0 1 2 30

20

40

60

80

100

120

climb rate [m/s] thermals


Speed-to-fly theory

flight path vectors

track

climbglide

climb

track

glide

climb

track

glide

speed vectors

20 40 60 80 100 120 140 160 180

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0w [m/s]

vG

(v0,w0)

(vG,wG)

w [m/s]

V [kph]


result: VGlide (wThermal) , VTrack(wThermal)

V [kph]

w [m/s]

track

glide

prediction

VXC


Potential flight distance (PFD)


PFD map


Outline

•Introduction




Approach

•Wind induces airmassvertical motion in aligned

patterns

•Speed-to-fly theory withairmass vertical motion

during the glide


Speed-to-fly in sinking airmass

climb

track

Speed vectors

20 40 60 80 100 120 140 160 180

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0w [m/s]

vG

(v0,w0)

(vG,wG)

w [m/s]

V [kph]

Path vectors

track

climb

glide downdraft

glide

climb

track

glide


Speed-to-fly in rising airmass

climb

track

Speed vectors

20 40 60 80 100 120 140 160 180

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0w [m/s]

vG

(v0,w0)

(vG,wG)

w [m/s]

V [kph]

Path vectors

track

climbglideairmass updraft

glide

climb

track

glide

With sufficient airmass updraft theminimum sink of the glider iscompensated ....


0 1 2 3 4 5

10203040505060708090

100110120130140150160170180190200

10203040505060708090100110120130140150160170180190200

0.5 m/s

pure glide

0.3 m/s

1.8 m/s

1.2 m/s

0.6 m/s

2.4 m/saligned lift

Standard class: 44 @ 92 km/h (33 kg/m2)

1.0 m/s

0.8 m/s

0.0 m/s

pure glide mode in strong aligned liftcircle & glide mode in weak aligned lift

1.5 m/s

[kph]track speed

climb rate [m/s] when circling

circle & glide mode

VTrack in rising airmass (standard class)


Vtrack in rising airmass (Open class)

0 1 2 3 4 50

102030405060708090

100110120130140150160170180190200

0102030405060708090100110120130140150160170180190200


[kph]

0.4 m/s

pure glide mode

0.2 m/s

circle & glide mode

1.6 m/s

1.2 m/s

0.5 m/s

1.8 m/saligned lift

Open class: 54 @ 101 km/h (42 kg/m2)

1.0 m/s

0.8 m/s

0.0 m/s

1.4 m/s

0.6 m/s

XC speed

pure glide mode in strong aligned lift

circle & glide mode in weak aligned lift


0 1 2 3 4 5 60.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.71.81.92.0

0.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.71.81.92.0


vertical motion

190 kph

180 kph

170 kph

160 kph

150 kph

140 kph

130 kph

120 kph

110 kph

100 kph

90 kph

80 kph

70 kph

60 kph

weak aligned lift: circling & gliding mode

strong aligned lift: pure gliding mode

Open class: 54 @ 101 km/h (42 kg/m2)

air mass

[m/s]

(e.g. isolated thermal)

Phase diagram of soaring

Climb rate in isolated lift

Air

mas

su

pd

raft

Vtrack = 100 kph


Summary

•Speed-to-fly theory for isolated lift can beextended to aligned lift

•The time fraction spent climbing is theorder parameter controlling the phasetransition from„climb&glide mode“to„pure glide mode“

•Predicted aligned lift can be used for flightplanning ... How about such predictions?

the phase diagram of soaring: flight mode …analysen& konzepte • dr. o. liechti • ch-8404...

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