Gliders are mostly fixed-wing aircraft, which have no power plant and are heavier than air. It can be towed by plane, winch or car, sliding up and down a high slope into the air. When there is no wind, the glider relies on the component of its own gravity to get forward power in its downward flight. This unpowered downward flight without altitude is called gliding.
In the updraft, a glider can fly horizontally or soar like an eagle spreading its wings, which is commonly called soaring. ?
Modern gliders are mainly used for sports and can be divided into primary gliders and advanced gliders. The former is mainly used for training flight, the latter is mainly used for competitions and performances, and some can also complete various advanced aerial stunts, such as somersaults and hovering.
After 1970s, hang gliders began to revive on the basis of modern technology (improvement of structural materials and improvement of manufacturing technology), attracting a large number of flying enthusiasts.
Aircraft must overcome gravity with lift and air resistance with thrust to fly. The lift is mainly generated by circulation. The airfoil (wing cross section) of subsonic aircraft is almost symmetrical up and down to reduce the drag, while the airfoil of glider is usually similar to Clark Y airfoil (typical convex and flat down), which can make unpowered glider generate more lift, improve the lift-drag ratio and prolong the stay time.
Gliders have no engine power. It can take off in four ways:
(1) Ejection-Put the glider on the elastic rope and pull it back. After the driver gave the signal, he released the rope and ejected.
(2) Car towing: Tie the glider to the car, and after towing to a proper height, the driver releases the rope.
(3) Winch traction-similar to car traction, except that the glider is towed by a winch fixed on the ground and driven by a motor.
(4) Aircraft towing —— After towing another powered aircraft to a certain height, the glider will be detached and fly freely.
After the glider takes off, unless it encounters updraft, the air resistance will gradually slow down the speed of the plane and the lift will become smaller and smaller. When gravity is greater than lift, the plane will fly lower and lower and finally land on the ground.
In order to make the glider fly far and far, it must have a high lift-drag ratio, which is why the glider's wings are so slender. How to break the record of flight time and altitude is the biggest challenge in the design and manufacture of gliders. Gliding is a sport that requires high skills and flight knowledge, and it travels through the sky with the help of natural energy.
Above reference: Glider-Baidu Encyclopedia