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220:
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172:
339:. This creates a narrow band of soarable lift with winds as light as 10 knots (19 km/h). These permit the gaining of altitude by flying along the intersection as if it were a ridge of land. Convergence may occur over considerable distances and so may permit virtually straight flight while climbing.
140:
Once a thermal is encountered, the pilot flies in circles to keep within the thermal, so gaining altitude before flying off to the next thermal and towards the destination. This is known as "thermalling". Climb rates depend on conditions, but rates of several meters per second are common. Thermals
204:
In ridge lift, pilots typically fly long straight legs parallel to the ridge. If the maximum height of the lift is not achieved, the pilot may turn around and fly in the other direction above the same slope. With winds of 20 to 25 knots (46 km/h), it is possible for aircraft to soar at an
167:
As it requires rising heated air, thermalling is only effective in mid-latitudes from spring into late summer. Despite these limitations, it is the most common source of lift used by glider pilots, as ridge lift and lee waves require mountainous terrain, and may thus not be found near a given
230:
occur when a wind of 25 knots (46 km/h) blows over a mountain. Provided that there is a steady increase in wind strength with altitude without a significant change in direction, standing waves may be created. They were discovered by a glider pilot,
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rather than the result of flying in rising air. Gliders are equipped with instruments that are compensated to prevent indications of stick thermals but the phenomenon is evident in aircraft whose compensation is inadequate.
201:, is caused by rising air on the windward side of a slope. Ridge lift is used extensively by sea birds and by aircraft. In places where a steady wind blows, a ridge may allow virtually unlimited time aloft.
106:
are columns of rising air that are formed on the ground through the warming of the surface by sunlight. If the air contains enough moisture, the water will condense from the rising air and form
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stops the warm air from rising high enough for the moisture to condense, thermals do not create cumulus clouds. Typical locations to find thermals are over towns, freshly
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from the sea that develops over land near coasts. In a sea-breeze front, cold air from the sea meets the warmer air from the land and creates a boundary like a shallow
248:
592:
235:, in 1933. These waves reach heights much greater than the original obstruction and so can permit gliders to climb to the stratosphere. Pilots use supplementary
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airfield. During the off-season, when thermals are weaker, ridge and wave lift can still be used and some pilots travel to more mountainous areas to fly.
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is gained by repeatedly crossing the boundary between air masses of different horizontal velocity rather than by rising air. Such zones of high "
160:
roads, but thermals are often hard to associate with any feature on the ground. Occasionally thermals are caused by the exhaust gases from
456:
Thermals were known to the Wright
Brothers in 1901, but were first really discovered in 1921 by William (sic) Leusch at the Wasserkuppe...
637:
612:
247:(lens-shaped) clouds lying perpendicular to the wind. A mountain wave was used to set the record for highest altitude by a glider when
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altitude up to twice the height of the obstacle. Ridge lift can also be augmented by thermals when the slopes also face the sun.
747:
593:"Airbus Perlan Mission II glider soars to 76,000 feet to break own altitude record, surpassing even U-2 reconnaissance plane"
567:
522:
411:
441:
706:
681:
481:
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390:"). This is not true lift because the increase in potential energy of the aircraft is achieved from decreasing
473:
256:
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Schematic cross section through a sea breeze front. If the air inland is moist, cumulus often marks the front.
732:
137:
in
Germany. It was not until about 1930 that the use of thermals for soaring in gliders became commonplace.
742:
501:
81:
it is also possible to gain energy, though this uses differences in wind speeds rather than rising air.
752:
243:
because most gliders do not have pressurized cockpits. This lift is often marked by long, stationary
737:
336:
251:
and Tim
Gardner soared to an altitude of 22,657 metres (74,334 ft) on September 2, 2018 over
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17:
8:
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can also be formed in a line usually because of the wind or the terrain, creating
38:. The most common human application of lift is in sport and recreation. The three
348:
283:
198:
126:
78:
31:
571:
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130:
259:. The current world distance record of 3,008 km (1,869 statute miles) by
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114:
47:
35:
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27:
361:" are usually too close to the ground to be used safely by gliders, but
670:
Meteorology and Flight: Pilot's Guide to
Weather (Flying & Gliding)
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316:
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Birds have been observed using wave lift to cross mountainous regions.
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39:
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instruments by entering a climb by pulling back on the stick (hence "
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227:
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145:. These can allow flying straight while climbing in continuous lift.
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103:
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61:
43:
263:(set on 21 January 2003) was also flown using mountain waves in
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Example of a thermal column between the ground and a cumulus
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Energy can be gained by using rising air from four sources:
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171:
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The boundaries where two air masses meet are known as
129:
in 1901, it was not exploited by humans until 1921 by
70:
Wave lift, where a mountain produces a standing wave,
179:
glider ridge soaring in Lock Haven, Pennsylvania, US
67:
Ridge lift, where air is forced upwards by a slope,
719:
278:producing strong lift. Pilots near Australia's
30:phenomenon used as an energy source by soaring
223:A lenticular cloud produced by a mountain wave
113:Thermal lift is often used by birds, such as
379:A pilot can create an indication of lift on
148:When the air has little moisture or when an
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125:. Although thermal lift was known to the
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288:
218:
170:
94:
365:and model gliders use this phenomenon.
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435:
73:Convergence, where two air masses meet
467:
368:
300:
442:World Scientific Publishing Company
270:A rare wave phenomenon is known as
13:
342:
14:
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255:, Argentina in the purpose-built
470:The Story of Gliding 2nd edition
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661:
655:
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560:
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461:
429:
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257:Windward Performance Perlan II
64:(where air rises due to heat),
1:
748:Severe weather and convection
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183:
42:that use soaring flight are:
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7:
438:The Paths of Soaring Flight
84:
10:
769:
697:Reichmann, Helmut (2005).
372:
346:
304:
212:
187:
88:
15:
548:"Article about wave lift"
319:or in desert regions. A
523:"Diagram of ridge lift"
668:Bradbury, Tom (2000).
568:"Diagram of wave lift"
436:Irving, Frank (1998).
294:
224:
180:
100:
412:"Diagram of thermals"
315:. These can occur in
292:
222:
174:
98:
733:Aviation meteorology
701:. Motorbuch Verlag.
16:For other uses, see
468:Welch, Ann (1980).
353:In dynamic soaring
280:Gulf of Carpentaria
743:Gliding technology
295:
282:make use of it in
225:
181:
101:
699:Streckensegelflug
613:"Distance record"
498:"Duration record"
369:Illusions of lift
313:convergence zones
301:Convergence zones
760:
753:Unpowered flight
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665:
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640:. Archived from
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615:. Archived from
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414:. Archived from
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307:Convergence zone
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738:Gliding animals
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638:"Morning Glory"
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127:Wright Brothers
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79:dynamic soaring
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444:. p. 53.
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373:Main article:
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347:Main article:
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325:onshore breeze
305:Main article:
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213:Main article:
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188:Main article:
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162:power stations
131:Wilhelm Leusch
108:cumulus clouds
89:Main article:
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28:meteorological
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728:Animal flight
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683:0-7136-4226-2
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644:on 2006-08-25
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619:on 2008-03-11
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574:on 2006-07-18
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529:on 2006-07-18
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504:on 2005-02-19
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418:on 2006-07-18
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381:uncompensated
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375:Stick thermal
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36:soaring birds
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646:. Retrieved
642:the original
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621:. Retrieved
617:the original
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48:hang gliding
23:
22:
474:John Murray
363:Albatrosses
317:sea breezes
253:El Calafate
156:fields and
135:Wasserkuppe
52:paragliding
722:Categories
648:2006-09-27
623:2006-08-24
598:2020-07-18
578:2006-09-05
553:2006-09-28
533:2006-09-05
508:2006-08-24
422:2006-09-05
399:References
337:shear line
333:cold front
321:sea-breeze
284:springtime
276:roll cloud
245:lenticular
233:Wolf Hirth
195:Ridge lift
190:Ridge lift
184:Ridge lift
40:air sports
249:Jim Payne
239:to avoid
228:Lee waves
215:Lee waves
209:Wave lift
150:inversion
440:. City:
392:airspeed
335:along a
177:Scimitar
154:ploughed
119:vultures
104:Thermals
85:Thermals
62:Thermals
32:aircraft
388:thermal
327:) is a
241:hypoxia
158:asphalt
133:at the
115:raptors
91:Thermal
44:gliding
705:
680:
480:
448:
355:energy
237:oxygen
123:storks
386:stick
197:, or
26:is a
703:ISBN
678:ISBN
478:ISBN
446:ISBN
329:wind
323:(or
274:, a
121:and
50:and
34:and
24:Lift
18:Lift
77:In
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286:.
267:.
175:A
117:,
110:.
54:.
46:,
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20:.
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