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Ridge lift (or slope lift) is created when a

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

strikes an obstacle, usually a mountain ridge or cliff, that is large and steep enough to deflect the wind upward. If the wind is strong enough, the ridge lift provides enough upward force for gliders,

hang glider Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised, fixed-wing heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...

paraglider Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched Glider (aircraft), glider aircraft with no rigid primary structure. The pilot sits in a :wikt:harness, harness or in ...

s and birds to stay airborne for long periods or travel great distances by 'Ridge soaring'. Although unpowered aircraft are usually descending through the air, they will climb if the surrounding air is rising faster than their sink rates. Model glider enthusiasts refer to this technique as "slope gliding" or "sloping".

Orville Wright The Wright brothers, Orville Wright (August 19, 1871 – January 30, 1948) and Wilbur Wright (April 16, 1867 – May 30, 1912), were American aviation pioneers generally credited with inventing, building, and flying the world's first succes ...

used ridge lift, setting a duration record of 11 minutes in 1911. However the sport of soaring started in Germany after the First World War. In 1921, Dr. Wolfgang Klemperer broke the Wright Brothers’ 1911 soaring duration record with a flight of 13 minutes. In 1922, Arthur Martens became the first glider pilot to use an updraft rising along a mountain slope to stay aloft for a lengthy period, with a flight over an hour.

Basic requirements

Ridge lift is generated when the wind blows against a

hill A hill is a landform that extends above the surrounding terrain. It often has a distinct summit, and is usually applied to peaks which are above elevation compared to the relative landmass, though not as prominent as Mountain, mountains. Hills ...

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Due to the similarity, the term '' scarp'' may mistakenly be incorrectly used inte ...

or ocean wave, causing the air to rise. In meteorology this is known as

orographic lift Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and cr ...

. The wind creates a region of rising air directly above the slope, which may extend some distance upwards and outwards from its face because the airflow follows the upward contour of the hill. However, at near vertical

cliff In geography and geology, a cliff or rock face is an area of Rock (geology), rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. ...

s, there is usually an area of

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...

with descending air near the base of the cliff. Downwind of the hill,

lee waves In meteorology, lee waves are Earth's atmosphere, atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, :de:Hans_Deutschmann ...

can form; these are also used by glider pilots to gain height, but this should not be confused with slope lift. Near slopes rather than vertical cliffs, the strongest lift is often to be found in a flight path that intersects with an imaginary line emerging at right angles from the slope. Long mountain ranges such as those found in

Ridge-and-valley Appalachians The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian Highlands division. The physiographic province is divided into three se ...

in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, and

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

have been used by glider pilots to fly in excess of a thousand kilometers in a single flight. Birds, such as many

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

s (in particular

albatross Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Paci ...

) and raptors, also use slopes in this way.

References

External links

Ridge flying the Mifflin task area

flying the Kittatinny Ridge

{{Authority control Gliding meteorology Mountain meteorology Radio-controlled aircraft

Basic requirements

See also

References

External links