California resident Spencer Lisenby just set the world record for dynamic hover for radio-controlled (RC) gliders at 882 km / h, using only wind power.
Back in the 60s of the last century, RC glider pilots noticed that the wind reaches its highest speed when it is moving along a hill. In this case, it becomes a reliable source of energy for the hovering glider, which, thanks to this, can stay in the air, in fact, indefinitely.
Flight slows down when the glider is on the leeward side of a hill, where the air flow decreases. Here, the apparatus falls into a zone of turbulence. As a result, the glider can accelerate to about the speed of the tailwind when it goes down, and slow down on the way back, gaining energy and speed at each turn.
This flight technique was “invented” by nature. For millennia, albatrosses have used the difference in wind speeds created by ocean waves to travel enormous distances with a minimum of energy.
Dynamic soaring is a rather harmless name, but it is precisely this name that extreme pilots use, accelerating controlled gliders to transonic speeds at a dangerously close distance from the Earth.