This is a featured article. Click here for more information. This article is about soaring flight manual pdf aerial sport of gliding.
Gliding as a sport began in the 1920s. Initially the objective was to increase the duration of flights but soon pilots attempted cross-country flights away from the place of launch. Improvements in aerodynamics and in the understanding of weather phenomena have allowed greater distances at higher average speeds. Some competitive pilots fly in races around pre-defined courses. If the weather deteriorates pilots are sometimes unable to complete a cross-country flight. Powered-aircraft and winches are the two most common means of launching gliders.
These and other launch methods require assistance and facilities such as airfields, tugs, and winches. These are usually provided by gliding clubs who also train new pilots and maintain high safety standards. Thus, in the 1920s and 1930s, while aviators and aircraft makers in the rest of the world were working to improve the performance of powered aircraft, the Germans were designing, developing and flying ever more efficient gliders and discovering ways of using the natural forces in the atmosphere to make them fly farther and faster. With the active support of the German government, there were 50,000 glider pilots by 1937.
Within ten years, it had become an international event in which the achieved durations and distances had increased greatly. In the 1930s, gliding spread to many other countries. Germany for the event, but World War II intervened. Gliding did not return to the Olympics after the war for two reasons: a shortage of gliders, and the failure to agree on a single model of competition glider. Some in the community feared doing so would hinder development of new designs. In many countries during the 1950s a large number of trained pilots wanted to continue flying. 1,000 to 16,000 by 1980.
The first event was held at the Samedan in 1948. Since World War II it has been held every two years. However the meteorological conditions that allow soaring are common and the sport has been taken up in many countries. Clubs actively seek new members by giving trial flights, which are also a useful source of revenue for them.
Thermals begin as bubbles of rising air that are formed on the ground through the warming of the surface by sunlight. If the air contains enough moisture, the water will condense from the rising air and form cumulus clouds. Once a thermal is encountered, the pilot can fly in tight circles to keep the glider within the thermal, so gaining altitude before flying towards the destination or to the next thermal. This is known as “thermalling”. This is when the pilot merely slows down in rising air, and then speeds up again in the non-rising air, thus following an undulating flight path. Dolphining allows the pilot to minimize the loss of height over great distances without spending time turning.
These can allow the pilot to fly straight while climbing in continuous lift. As it requires rising heated air, thermalling is most effective in mid-latitudes from spring through late summer. During winter the sun’s heat can only create weak thermals, but ridge and wave lift can still be used during this period. It can also be augmented by thermals when the slopes also face the sun. Schematic cross section through a sea breeze front. If the air inland is moist, cumulus often marks the front. Glider pilots can gain altitude by flying along the intersection as if it were a ridge of land.
Convergence may occur over considerable distances and so may permit virtually straight flight while climbing. Most gliders do not have engines or at least engines that would allow a take-off under their own power. Various methods are therefore used to get airborne. Each method requires specific training, therefore glider pilots must be in current practice for the type of launch being used.
USA, differentiate between aerotows and ground launch methods, due to the widely different techniques. In an aerotow a powered aircraft is attached to a glider with a tow rope. The tow-plane takes the glider to the height and location requested by the pilot where the glider pilot releases the tow-rope. Under extreme loads the weak link will fail before any part of the glider or plane fails. There is a remote chance that the weak link might break at low altitude, and so pilots plan for this eventuality before launching. In Australia the convention is to fly in low tow, whereas in the United States and Europe the high tow prevails.
One rare aerotow variation is attaching two gliders to one tow-plane, using a short rope for the high-towed glider and a long rope for the low tow. The current record is nine gliders in the same aerotow. This method is widely used at many European clubs, often in addition to an aerotow service. A strong headwind will result in higher launches. Winch launches are much cheaper than aerotows and permit a higher launch frequency.
A winch may also be used at sites where an aerotow could not operate, because of the shape of the field or because of noise restrictions. The height gained from a winch is usually less than from an aerotow so pilots need to find a source of lift soon after releasing from the cable, otherwise the flight will be short. Another method of launching, the “autotow”, is rarer nowadays. The direct autotow requires a hard surface and a powerful vehicle that is attached to the glider by a long steel cable. A variation on the direct autotow is known as the “reverse pulley” method. In this method, the truck drives towards the glider being launched. The cable passes around a pulley at the far end of the airfield, resulting in an effect similar to that of a winch launch.