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Slope soaring is an activity whereby a pilot gains height in a full size or radio-controlled glider by flying 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 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 the albatross, can also do this.
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.
Types of model slope soaring
Combat
Combat is usually flown with expanded polypropylene (EPP) models due to their impact resistance. Each pilot tries to knock the other's aircraft physically out of the air. A "kill" is scored only when the opponents aircraft hits the ground. If a hit occurs and each aircraft recovers and remains airborn, the hits generally do not count. Often this activity includes extreme maneuvers and aerobatics.This particular class of slope glider is extremely popular, as novices can learn to fly with a model that is practically indestructible. There is also a wide appeal in owning an inexpensive glider that is also a stand-off scale model, particularly of favourite WWII fighters, e.g. the Spitfire/Seafire, P-51 Mustang, P-47 Thunderbolt.
As of the time of writing, model EPP Jet Fighter Slope Soarers have become extremely popular, usually either 1950s and some 1960s designs e.g. the MiG-15, the P-80 Shooting Star, and the F-86 Sabre, and the Northrop F-5 and F-20. More ambitious modelers are experimenting with more recent jet fighters such as the F-16, F-15, MiG-29 and Su-27.
Equally popular are models of military trainers, such as the Pilatus PC-9, BAe Hawk, and Aermacchi MB 326 and MB 339.
Ridge racing
Ridge racing (or pylon racing where markers are present) is essentially using the slope lift to race along the "lift zone" -- generally parallel to the slope. This can either be done MoM (man-on-man), in heats of 3 or 4, or simply against the clock (timed).Dynamic soaring
Dynamic soaring is a relatively new style of flying model gliders whereby the windshear just downwind of certain slopes can be used to create high speeds.
See also
"Slope soaring"