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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Outline
•Introduction
•PFD with thermals
•PFD with wind and thermals
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Soaring in wind and thermals
•Wave•Ridge lift•Thermals•Combination of W and T
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Wave: 13 h, 2‘400 km, 192kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Ridge: 8.5 h, 1‘180 km, 138 kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Thermals: 7.75 h, 1‘186 km, 153 kph
80 kph
173 kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Combination: 13.5 h, 1‘400 km, 103 kph
55 kph
142 kph
98 kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Combination: 10.5 h, 1‘430 km, 142 kph
142 kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Combination: 14.5 h, 1‘900 km, 132 kph
172 kph
110 kph
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Flight distance in cross-country soaring
thermals
VFR
wind
ridge
wave
rotors streets
Distance•Duration•Speed
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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).
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Outline
•Introduction
•PFD with thermals
•PFD with wind and thermals
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Regional thermal forecast
Avg. Lift Clouds
Source: pc-met@DWD
cross-country conditions
Stratiform Clouds
Cumulus Clouds
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Climb rate --> cross-country speed
•flight polar
•speed-to-fly theory for isolated lift
•cross-country speed
•potential flight distance (PFD)
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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]
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
result: VGlide (wThermal) , VTrack(wThermal)
V [kph]
w [m/s]
track
glide
prediction
VXC
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Potential flight distance (PFD)
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
PFD map
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Outline
•Introduction
•PFD with thermals
•PFD with wind and thermals
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Approach
•Wind induces airmassvertical motion in aligned
patterns
•Speed-to-fly theory withairmass vertical motion
during the glide
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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 ....
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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)
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
Vtrack in rising airmass (Open class)
0 1 2 3 4 50
102030405060708090
100110120130140150160170180190200
0102030405060708090100110120130140150160170180190200
climb rate [m/s] when circling
[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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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
climb rate [m/s] when circling
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
ANALYSEN& KONZEPTE • Dr. O. Liechti • CH-8404 Winterthur
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?