Flying a Hang Glider
To launch, the pilot must run down a slope to get air moving across the wing at about 15 to 25 miles per hour (24 to 40 kph). This movement of air over the surface of the wing generates lift, the force that counters gravity and keeps the glider aloft. Once aloft, gravity (the weight of the hang glider and pilot) pulls the glider back toward Earth and propels the glider forward, continually causing air to flow over the wing.
In addition to the horizontal movement of air, hang gliders can get lift from rising currents of air, such as columns of hot air (thermal lift) or air deflected upward by mountainous or ridge topography (ridge lift). As the hang glider and pilot move through the air, they collide with air molecules. The frictional force caused by these collisions is known as drag, which slows the glider down. The amount of drag is proportional to the airspeed of the hang glider: The faster the glider moves, the more drag it creates (see How Gliders Work for details).
As with soarplane gliders, the balance of these three forces (lift, drag, gravity) determines how high the hang glider can go, how far it can travel and how long it can stay aloft. The performance of a hang glider and the distance it can travel is determined by its glide ratio (lift/drag ratio), the ratio of the forward distance traveled to the vertical distance dropped. Unlike soarplane gliders, hang gliders have neither movable surfaces on the wing nor a tail to deflect airflow and maneuver the craft. Instead, the pilot is suspended from the hang glider's center-of-mass (hence the term "hang" glider) by way of a harness, maneuvering the hang glider by shifting his or her weight (changing the center-of-mass) in the direction of the intended turn.
The pilot can also change the angle that the wing makes with the horizontal axis (angle of attack), which determines the airspeed and the glide ratio of the hang glider. If the pilot pulls back on the glider, tipping its nose down, the glider speeds up. If the pilot pushes forward on the glider, tipping its nose up, the glider slows down or even stalls. In stalling, no air flows over the wing so the glider can't fly.