Radio Controlled Glider
In the late 1990s, radio-controlled gliding awoke to the idea of dynamic soaring (a "discovery" largely credited to RC soaring luminary Joe Wurts). Radio controlled glider pilots perform dynamic soaring using the leeward side of ground features such as ridges and saddles. If the ridge faces the wind, and has a steep back (leeward) side, it can cause flow separation off the top of the hill, resulting in a layer of fast air moving over the top of a volume of stagnant or reverse-flow air behind the hill. The velocity gradient, or wind shear, can be much greater than those used by birds or full scale sailplanes. The higher gradient allows for correspondingly greater energy extraction, resulting in much higher speeds for the aircraft. Models repeatedly cross the shear layer by flying in a circular path, penetrating a fast-moving headwind after flying up the back side, turning to fly with the wind, diving down through the shear layer into the stagnant air, and turning again to fly back up the back side of the hill. Because of the speeds involved, significant structural reinforcement in the fuselage and wing is important. Because of this, dynamic soaring models are commonly built using composite materials.
As of March 2012, the highest reported speed for radio control dynamic soaring was 498 mph (801 km/h). There is no official sanctioning organization that certifies speeds, so records are listed unofficially based on readings from radar guns, although analysis from video footage and other sources is also used. Lately, some models have begun carrying on-board telemetry and other instruments to record such things as acceleration, air speed, etc.
Read more about this topic: Dynamic Soaring
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