Glider (sailplane) - Launch and Flight

Launch and Flight

The two most common methods of launching sailplanes are by aerotow and by winch. When aerotowed, the glider is towed behind a powered aircraft using a rope about 60 meters (about 200 ft) long. The glider pilot releases the rope after reaching the desired altitude. However, the rope can be released by the towplane also. Winch launching uses a powerful stationary engine located on the ground at the far end of the launch area. The glider is attached to one end of 800–1200 metres (about 2,500–4,000 ft) of cable and the winch rapidly winds it in. The glider can gain about 900–3000 feet of height with a winch launch (about 300 – 900 metres), depending on the head wind. Less often, automobiles are used to pull gliders into the air, by pulling them directly or through the use of a reverse pulley in a similar manner to the winch launch. Elastic ropes (known as bungees) are occasionally used at some sites to launch gliders from slopes, if there is sufficient wind blowing up the hill. Bungee launching was the predominant method of launching early gliders. Some modern sailplanes can self-launch with the use of retractable engines and/or propellers, which can also be used to sustain flight once airborne (see motor glider).

Once launched sailplanes try to gain height using thermals, ridge lift, lee waves or convergence zones and can remain airborne for hours. This is known as 'soaring'. By finding lift sufficiently often experienced pilots fly cross-country, often on pre-declared tasks of hundreds of kilometers, usually back to the original launch site. Cross-country flying and aerobatics are the two forms of competitive gliding. For information about the forces in gliding flight, see lift-to-drag ratio.