Slope soaring
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Slope soaring is a technique to gain height in a full size glider or with a radio-controlled glider by flying it in the updraft produced by wind blowing up the face of a steep slope. Model glider pilots commonly refer to this as "slope gliding" or "sloping". Pilots of full-sized gliders also call the lift "ridge lift" and its use "ridge flying". They use it to potentially fly hundreds of kilometers where there is suitable terrain. Birds, such as many seabirds, also use slopes in this way.
[edit] Basic requirements
Slope soaring requires a hill and a wind that is blowing on the face of the hill. The wind will create a region of rising air directly in front of the hill which may extend quite a distance upwards and outwards from its face because the airflow follows the contour of the hill (this is called orographic lift). However at near vertical cliffs, there is usually an area of turbulence with descending air near the base of the cliff. Downwind of the hill, standing waves can form that are also used by glider pilots to gain height but this should not be confused with slope lift.
The rising air from the slope is used to keep gliders airborne. Although a glider is always descending through the air, it will climb if the surrounding air is rising faster than the glider's sink rate.
