Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised, fixed-wing heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered with synthetic sailcloth to form a wing. Typically the pilot is in a harness suspended from the airframe, and controls the aircraft by shifting body weight in opposition to a control frame. Early hang gliders had a low lift-to-drag ratio, so pilots were restricted to gliding down small hills. By the 1980s this ratio significantly improved, and since then pilots have been able to soar for hours, gain thousands of meters of altitude in thermal updrafts, perform aerobatics, and glide cross-country for hundreds of kilometers. The Federation Aeronautique Internationale and national airspace governing organisations control some regulatory aspects of hang gliding. Obtaining the safety benefits of being instructed is highly recommended and indeed a mandatory requirement in many countries.
History
In 1853, George Cayley invented a slope-launched, piloted glider. Most early glider designs were not conducive to safe flight; the problem was that early flight pioneers did not sufficiently understand the underlying principles that made a bird's wing work. Starting in the 1880s, technical and scientific advancements were made that led to the first truly practical gliders, such as those developed in the United States by John Joseph Montgomery. Otto Lilienthal built controllable gliders in the 1890s, with which he could ridge soar. His rigorously documented work influenced later designers, making Lilienthal one of the most influential early aviation pioneers. His aircraft was controlled by weight shift and is similar to a modern hang glider.
Hang gliding saw a stiffened flexible wing hang glider in 1904, when Jan Lavezzari flew a double lateen sail hang glider off Berck Beach, France. In 1910 in Breslau, the triangle control frame with hang glider pilot hung behind the triangle in a hang glider, was evident in a gliding club's activity. The biplane hang glider was very widely publicized in public magazines with plans for building; such biplane hang gliders were constructed and flown in several nations since Octave Chanute and his tailed biplane hang gliders were demonstrated. In April 1909, a how-to article by Carl S. Bates proved to be a seminal hang glider article that seemingly affected builders even of contemporary times. Many builders would have their first hang glider made by following the plan in his article. Volmer Jensen with a biplane hang glider in 1940 called VJ-11 allowed safe three-axis control of a foot-launched hang glider.
On 23 November 1948, Francis Rogallo and Gertrude Rogallo applied for a kite patent for a fully flexible kited wing with approved claims for its stiffenings and gliding uses; the flexible wing or Rogallo wing, which in 1957 the American space agency NASA began testing in various flexible and semi-rigid configurations in order to use it as a recovery system for the Gemini space capsules. The various stiffening formats and the wing's simplicity of design and ease of construction, along with its capability of slow flight and its gentle landing characteristics, did not go unnoticed by hang glider enthusiasts. In 1960–1962 Barry Hill Palmer adapted the flexible wing concept to make foot-launched hang gliders with four different control arrangements. In 1963 Mike Burns adapted the flexible wing to build a towable kite-hang glider he called Skiplane. In 1963, John W. Dickenson adapted the flexible wing airfoil concept to make another water-ski kite glider; for this, the Fédération Aéronautique Internationale vested Dickenson with the Hang Gliding Diploma (2006) for the invention of the "modern" hang glider. Since then, the Rogallo wing has been the most used airfoil of hang gliders.
Components
Hang glider sailcloth Hang glider sailcloth is normally made from woven or laminated fiber, such as dacron or mylar, respectively. Woven polyester sailcloth is a very tight weave of small diameter polyester fibers that has been stabilized by the hot-press impregnation of a polyester resin. The resin impregnation is required to provide resistance to distortion and stretch. This resistance is important in maintaining the aerodynamic shape of the sail. Woven polyester provides the best combination of light weight and durability in a sail, with the best overall handling qualities. Laminated sail materials using polyester film achieve superior performance by using a lower stretch material that is better at maintaining sail shape, but is still relatively light in weight. The disadvantages of polyester film fabrics are that the reduced elasticity under load generally results in stiffer and less responsive handling, and polyester laminated fabrics are generally not as durable or long-lasting as the woven fabrics.
Triangle control frame In most hang gliders, the pilot is ensconced in a harness suspended from the airframe, and exercises control by shifting body weight in opposition to a stationary control frame, also known as a triangle control frame, or an A-frame. The control frame normally consists of 2 "down-tubes" and a control bar/base bar/base-tube. Either end of the control bar is attached to an upright tube or a more aerodynamic strut (a "down-tube"), where both extend from the base-tube and are connected to the apex of the control frame/ the keel of the glider. This creates the shape of a triangle or 'A-frame'. In many of these configurations additional wheels or other equipment can be suspended from the bottom bar or rod ends. Images showing a triangle control frame on Otto Lilienthal's 1892 hang glider shows that the technology of such frames has existed since the early design of gliders, but he did not mention it in his patents. A control frame for body weight shift was also shown in Octave Chanute's designs. It was a major part of the now common design of hang gliders by George A. Spratt from 1929. The most simple A-frame that is cable-stayed was demonstrated in a Breslau gliding club hang gliding meet in a battened wing foot-launchable hang glider in the year 1908 by W. Simon; hang glider historian Stephan Nitsch has collected instances also of the U control frame used in the first decade of the 1900s; the U is variant of the A-frame.
Training and safety
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