Hang gliding is an air sport in which a pilot flies a light and unmotorized foot-launchable aircraft called a hang glider. Most modern hang gliders are made of an aluminum or composite-framed fabric wing. Pilots usually control the aircraft by shifting body weight, but other devices, including modern aircraft flight control systems, may be used. The pilot wears a harness and is hung beneath a lifting wing by flexible straps.
In the sport's early days, pilots were restricted to gliding down small hills on low-performance hang gliders. However, modern technology gives pilots the ability to soar for hours, gain thousands of feet of altitude in thermal updrafts, perform aerobatics, and fly cross-country over large distances. The Fédération Aéronautique Internationale and national airspace governing organizations control some aspects of hang gliding.
Summary: Hang gliding existed in China perhaps by the 4th century AD according to the writing of the Daoist Ge Hong, and certainly by the time of Emperor Wenxuan of Northern Qi (r. 550–559 AD) who used men sentenced to death as test pilots for his man-flying kites launched from a tower. Some glider flights have been recorded as early as 875 AD, when Abbas Ibn Firnas attempted such a flight. Most early glider designs did not ensure safe flight; the problem was that early flight pioneers did not 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. Otto Lilienthal of Germany duplicated some of his contemporaries' work and greatly expanded on it from 1874. He rigorously documented his work, strongly influencing later designers; for this reason, Lilienthal is one of the best known and most influential early aviation pioneers. His type of aircraft is now known as a hang glider.
In 1951 Francis Rogallo and Gertrude Rogallo applied for a patent for a fully flexible 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. It was designer engineer Charles Richards directed by Paul Bikle who showed how to build the wing that would affect a full decade of kited-hang glider constructions. 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 Charles Richards wing for kite-hang glider Skiplane. In 1963, John W. Dickenson adapted the flexible wing airfoil concept to create a hang glider, producing about sixty sold copies. Other types of hang gliders following NASA's guide for higher aspect ratio, rigid-wing hang gliders, and hang gliders with dive-control advanced safer foot-launching from 1975 forward.
Since its inception, hang gliding has traditionally been considered an unsafe sport. Modern hang gliders are very sturdy when constructed by HGMA, BHPA, DHV or other certified standards and using modern materials, though they remain lightweight craft that can be easily damaged, either through misuse or by continued operation in unsafe wind/weather conditions. All modern gliders have built-in stall recovery mechanisms such as luff lines in kingposted gliders. Nevertheless, the inherent danger of gliding at the mercy of thermal and wind currents, has resulted in numerous fatal accidents and many serious injuries over the years, even to experienced pilots, and the resultant adverse publicity has affected the popularity of hang gliding.
As a backup, pilots carry a parachute in the harness. In case of serious problems the parachute is deployed and carries both pilot and glider down to earth. Pilots also wear helmets and generally carry other safety items such as hook knives (for cutting their parachute bridle after impact or cutting their harness lines and straps in case of a tree or water landing), light ropes (for lowering from trees to haul up tools or climbing ropes), radios (for calling for help) and first-aid equipment.
The accident rate from hang glider flying has been dramatically improved by pilot training. Early hang glider pilots learned their sport through trial and error. Training programs have been developed for today's pilot, with emphasis on flight within safe limits, as well as the discipline to cease flying when weather conditions are unfavorable, for example: excess wind or risk cloud suck.
Launch techniques include foot-launching from a hill, tow-launching from a ground-based tow system, aerotowing (behind a powered aircraft), powered harnesses, and being towed up by a boat. Modern winch tows typically utilize hydraulic systems designed to regulate line tension, this reduces scenarios for lock out as strong winds result in additional length of rope spooling out rather than direct tension on the tow line. Other more exotic launch techniques have also been used successfully, such as hot air balloon drops for very high altitude. Flights in non-soarable conditions are referred to as "sled runs".
A glider is continuously "falling" through the air yet glider pilots can stay airborne for hours. This is possible because they seek out rising air masses (lift) from the following sources:Thermals
With each generation of materials and with the improvements in aerodynamics, the performance of hang gliders has increased. One measure of performance is the glide ratio. For example, a ratio of 12:1 means that in smooth air a glider can travel forward 12 meters while only losing 1 meter of altitude.
Some performance figures as of 2006:
Because hang gliders are most often used for recreational flying, a premium is placed on gentle behavior especially at the stall and natural pitch stability. The wing loading must be very low in order to allow the pilot to run fast enough to get above stall speed. Unlike a traditional aircraft with an extended fuselage and empennage for maintaining stability, hang gliders rely on the natural stability of their flexible wings to return to equilibrium in yaw and pitch. Roll stability is generally set up to be near neutral. In calm air, a properly designed wing will maintain balanced trimmed flight with little pilot input. The flex wing pilot is suspended beneath the wing by a strap attached to his harness. The pilot lies prone (sometimes supine) within a large, triangular, metal control frame. Controlled flight is achieved by the pilot pushing and pulling on this control frame thus shifting his weight fore or aft, and right or left in coordinated maneuvers. Roll
Furthermore, the fact that the wing is designed to bend and flex, provides favorable dynamics analogous to a spring suspension. This allows the wing to be less susceptible to turbulence and provides a gentler flying experience than a similarly sized rigid-winged aircraft.
Some costs as of 2008:
Gliding pilots are able to sense the acceleration forces when they first hit a thermal, but have difficulty gauging constant motion. Thus it is difficult to detect the difference between constantly rising air and constantly sinking air. A variometer is a very sensitive vertical speed indicator. In other words, the variometer indicates climb rate or sink rate with audio signals (beeps) and/or a visual display. These units are generally electronic, vary in sophistication, and often include an altimeter and an airspeed indicator. More advanced units often incorporate a barograph for recording flight data and/or a built-in GPS. The main purpose of a variometer is in helping a pilot find and stay in the ‘core’ of a thermal to maximize height gain, and conversely indicating when he or she is in sinking air and needs to find rising air. Variometers are sometimes capable of electronic calculations based on the MacCready Speed Ring to indicate the optimal speed to fly for given conditions. The MacCready theory answers the question on how fast a pilot should cruise between thermals, given both the average lift the pilot expects in the next thermal climb, as well as the amount of lift or sink he encounters in cruise mode. Some electronic variometers make the calculations automatically, after allowing for factors such as the glider's theoretical performance (glide ratio), altitude, hook in weight and wind direction.
Pilots use radio for training purposes, and for communicating with other pilots in the air – particularly when traveling together on cross-country flights.
Radios used are PTT (push-to-talk) transceivers, normally operating in or around the FM VHF 2-metre band (144–148 MHz). Usually a microphone is incorporated in the helmet, and the PTT switch is either fixed to the outside of the helmet, or strapped to a finger. It should be emphasized that operating a 2-meter band radio without an appropriate Amateur Radio license is illegal in most countries (such as the United States) that have regulated airwaves.
It can also be interesting to view a GPS track of a flight when back on the ground, to analyze flying technique. Computer software is available which allows various different analyses of GPS tracks (e.g. CompeGPS).
Other uses include being able to determine drift due to the prevailing wind when flying at altitude, providing position information to allow restricted airspace to be avoided, and identifying one’s location for retrieval teams after landing-out in unfamiliar territory.
More recently, the use of GPS data, linked to a computer, has enabled pilots to share 3D tracks of their flights on Google Earth. This fascinating insight allows comparisons between competing pilots to be made in a detailed post-flight analysis.
Records are sanctioned by the FAI. The world record(s) (as of 2005) for "free distance" is held by Manfred Ruhmer with 700.6 km (435.3 miles) in 2001 and Michael Barber flew a distance of 704 km (437 miles) on June 19, 2002 in Zapata Texas.
Other records include:
Out-and-Return distance - 332.5 km (206.6 mi), July 5th, 2007 by George Stebbins, starting and ending just South of Lone Pine, California.
Largest triangle - 357.12 km (221.9 mi), December 16, 2000 by Thomas Suchanek, starting and ending from Riverside Australia.
Competitions started with "flying as long as possible" and spot landings. With increasing performance cross-country flying replaced them. Usually two to four waypoints have to be passed with a landing at a goal. In the late 1990s low-power GPS units were introduced and have completely replaced photographs of the goal. Every two years there is a world championship. The Rigid and Women's World Championship in 2006 was hosted by Quest Air in Florida Big Spring, Texas hosted the 2007 World Championship Hang gliding is also one of the competition categories in World Air Games organized by Fédération Aéronautique Internationale (World Air Sports Federation - FAI), which maintains a chronology of the FAI World Hang Gliding Championships.
For competitive purposes, there are three classes of hang glider:
In addition to typical launch configurations, a hang glider may be so constructed for alternative launching modes other than being foot launched; one practical avenue for this is for people who physically cannot foot-launch.
Paragliding, hang gliding and gliding are closely related sports, but there is sometimes confusion about the differences. In particular paragliders and hanggliders are both foot-launched gliders with flexible wings, with options for tow launching and for powered flight. Beyond sport definitions and sporting association class definitions, there is a perspective that simply treats paragliders as a subset of hang gliders rather than a different class of aircraft.
The main differences between the types of glider are:
|Wing structure:||entirely flexible, with shape maintained purely by the pressure of air flowing into the wing in flight and the tension of the lines. prone to collapse in turbulence.||supported on a rigid frame which determines its shape and thus does not collapse in turbulence||rigid surface to wings that totally encases structure|
|Pilot position:||sitting ‘supine’ in a seated harness||usually lying ‘prone’ in a cocoon-like harness suspended from the wing. Seated, and 'supine' are also possible||sitting in a seat with a harness surrounded by a crash-resistant structure|
|Speed range (stall speed – max speed):||slower – hence easier to launch and fly in light winds, can get into trouble when winds pick up, poor wind penetration and no pitch control, cannot dive for speed, although some pitch variation can be achieved with speed bar.||faster – much faster, up to 145 km/h (90+ mph), hence easier to launch and fly in stronger conditions with better wind penetration, and can out run bad weather, full pitch control||even faster - maximum speed up to about 280 km/h (170 mph); stall speed typically 65 km/h (40mph). Able to fly in windier turbulent conditions and can outrun bad weather. Exceptional penetration into the wind. Semi- or fully aerobatic.|
|Glide angle:||poorer glide performance makes long-distances more difficult||better glide performance enables longer-distance flying, 700km (430+ mile) record||high glide performance enabling long distances, 3000km (1800+ mile record)|
|Turn radius:||tighter turn radius, allowing circling in the rapidly rising center of thermals||somewhat larger turn radius, not allowing such a high rate of climb in thermals||even greater turn radius but still able to circle tightly in thermals|
|Landing-out:||smaller space needed to land, offering more landing options from cross-country flights. Also easier to carry back to the nearest road||longer approach & landing area required, but can reach more landing areas due superior glide range||can land in less than 200 metres and can often reach another airfield. Specialised trailer needed to retrieve by road|
|Learning:||quicker to get ‘into the air’ with most skills learned in the air; flying tandem with an instructor is rarely necessary during instruction||basic control skills are learned in ground school, and in flights close to the ground prior to high flights;||teaching is done in a two seat glider with dual controls|
|Convenience:||pack smaller (easier to transport and store); lighter (easier to carry); quicker to rig & de-rig; transported in the trunk of a car||more awkward to transport & store; longer to rig and de-rig; transported on the roof of a car||trailers are typically 10 m (30 ft) long. Rigging & de-rigging takes about 20 minutes|
|Cost:||cheaper but less durable||more expensive but more durable...||long lasting (several decades), so active second hand market in all price ranges, but cost of new gliders very high. Often syndicated|