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Hang gliding is an air activity in which a pilot flies an unpowered, light, foot-launchable aircraft called a hang glider. Hang gliding is mainly a recreational air sport, though it has also been used in commerce and for military applications. Most modern hang gliders are made of an aluminum- or composite-framed fabric wing; however vintage hang gliders are still built with a combination of wood, bamboo, and metal. The most common method of control is by shifting the pilot\'s mass fore and aft or left or right but other devices, including modern aircraft flight control systems, may be used. The pilot is hung beneath a lifting wing, most commonly in a harness hanging from the airframe by flexible hang lines. The Fédération Aéronautique Internationale and national airspace governing organizations control some aspects of hang gliding.
Although hang gliding started out centuries ago as gliding down small hills on low performance hang gliders, modern hang glider 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.
Hang glider launching from Mount Tamalpais
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The first recorded controlled flights in a hang glider were by German engineer Otto Lilienthal, who published all of his research in 1889, influencing later designers. The hang glider lost some importance through the introduction of wing warping control by the Wright brothers in 1902 and subsequently of aileron control by the French. The evolution of airframes and airfoils resulted in hang gliders from 1895 onwards (Percy Pilcher, Augustus Herring, John J. Montgomery, Carl S. Bates, 1922: Gottlob Espenlaub, 1929: George A. Spratt, and many others). The A-frame for hang gliders, trikes, and ultralights gradually simplified hang glider control.
From 1945 to 1948 Francis and Gertrude Rogallo together were involved with inventing a fundamental fully flexible self-inflating wing "workable at any level of stiffening" [1]—also known as Rogallo wing; the wing could be fitted to any airframe or fuselage. On November 23, 1948, Stanford University-trained aeronautical engineer Francis Rogallo and his wife Gertrude Sudgen Rogallo applied together for a patent U.S. Patent 2546078 "Flexible Kite" which was approved in March 20, 1951 Article: How to Fly Without a Plane by Robert Zimmerman, aerospace writer. [2] as 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 evaluate it as a recovery system for the Gemini space capsules and recovery of used Saturn rocket stages.SPACEFLIGHT REVOLUTION [3]In 1965, Jack Swigert, who would later be one of the Apollo 13 astronauts, softly landed a full-scale Gemini capsule using a Para Wing stiffened with inflatable tubes along the wing’s edgesNASA\'s Fleep was tested as a "flying Jeep" for transporting supplies and observation, this two-person aircraft used a small engine for power and Rogallo\'s wing for lift)[4] Because NASA were not able to properly solve the unfolding-from-packed condition for the flexible wings for the space-vehicle reentry project, they suspended the high investment in flexible wing projects like the Paresev in 1965 in favor of round parachutes and hard lifting bodies; NASA kept the files opened on the Rogallo wings and further attention was eventually given to the Rogallo wing.
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, who were already building and flying rigid wing hang gliders. Some designers rapidly adapted Rogallo\'s flexible wing onto elementary flexible wing hang gliders, but performance and control remained a challenge. Barry Hill Palmer explored four levels of control of the Rogallo wing hang glider in 1960-1962 and went on to develop a powered hang glider. In 1962, Mike Burns developed the delta winged manned kite SkiPlane in Australia from information about the Rogallo wing from NASA; then fellow countryman John Dickenson, who had been flying a gyrocopting wing in 1963, set out to build a manned water ski-kite that could be released at altitude for a glide to a safe landing. Dickenson called it the "Ski Wing" Ski Wing [5]; although its gliding performance was not impressive; he finally came to an effective use of the trussed trapeze that had been given to aviation for hang gliders by at least George A. Spratt and also by manned kiting; by October of 1964 he reached the ornamental design for the main lifting wing that had been priorly achieved in the hanging-piloted Paresev 1B wing designed by Charles Richard of NASA. The Dickenson ski-kite\'s low weight, increased control, and portability was used in water-ski kiting from that point forward. Then Bill Bennett and Bill Moyes advanced the Dickenson format of Rogallo wing ski-kite and brought it fully into foot-launch hang gliding by 1971 and 1972. On October/11/1963 Dickenson filed for a patent, and a provisional protection was awarded for his application number 36189/63 but the patent was not finally awarded. A similar ornamental design patent for a tow kite was filed by Bill Bennettin on September 24, 1969, in design patent US Pat. D224248 PASSENGER CARRYING TOW KITE[6] (approved July 11, 1972).
The flowering of Rogallo hang gliders stemming from the Barry Palmer and the Dickenson-Bennett-Moyes influence along with other influences formed a kind of renaissance in popular hang gliding in the 1970s when scores of manufacturers and flying meetings occurred.For example, the Swallowtail hang glider was featured in the 1976 movie Sky Riders (filmed in Greece during 1975) starring James Coburn, Robert Culp, Susannah York, and Charles Aznavour. After filming of the action was complete, the Wills Wing team toured Europe and stopped by in England to win the British Championships at Mere, Wiltshire in August 1975. The mechanics of George Spratt\'s 1929 triangle control bar with his pendulumed pilot mass-shifting contol into hang gliding and Charles Richard\'s foldable Paresev 1B wing, allowed foldable hang gliders that dramatically reduced difficulty in control, storage, transport, assembly, and repair. Dickenson\'s efficiencies with the help of aeronautical engineer and aviation-standards manufacturer Mike Burns of the NASA-inspired SkiPlane were further refined and brought to the world market by Austalian sportsmen, ski-kite fliers, and businessmen Bill Bennett and Bill Moyes, who significantly improved hang gliders and hang gliding trends along with hundreds of other innovators around the world. Richard Miller was a prime mover for many kinds of hang glider designs in the United States. Mike Harker strongly introduced hang gliding to Europe for the modern renaissance in 1973. The Roy Haggard Dragonfly hang glider introduced a new generation of hang glider design that spelled the demise of the Paresev-lined wing or "standard Rogallo" wing which had become infamous for its luffing-dive safety challenges. High-level engineering from 1975 forward brought an unending series of improvements in hang gliders; most hang gliders, not all, continued to use the simple cabled or stiff-braced triangle control bar (aka "A-frame") and pendulumed mass-shifting control that was gifted to aviation and hang gliding mechanics by George A. Spratt in 1929, if not by others before him like Gottlob Espenlaub and Percy Pilcher.
Learning to hang glide.
Hang gliding has traditionally been considered an unsafe sport, ever since its inception. Otto Lilienthal died of a fractured spine from a glider crash after a gliding career lasting only five years. Modern hang gliders are very sturdy when constructed by HGMA, BHPA, DHV or other certified manufacturers 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 unpredictable 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.
An aspect that has dramatically improved the safety of the modern hang glider is pilot training. Early hang glider pilots learned their sport through trial and error. Many of those errors have led to effective training techniques and programs developed for today\'s pilot, with emphasis on flight well 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), and powered harnesses. 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".
Good gliding weather. Well formed cumulus clouds, with darker bases, suggest active thermals and light winds.
Good gliding weather. Cumulus clouds with dark flat base.
Glider pilots can stay airborne for hours. This is possible because they seek out rising air masses (lift) from the following sources:
The most commonly used source of lift is created by the sun\'s energy heating the ground which in turn heats the air above it. This warm air rises in columns known as thermals. Soaring pilots quickly become aware of visual indications of thermals such as cumulus clouds, cloud streets, dust devils and haze domes. Also, nearly every glider contains an instrument known as a variometer (a very sensitive vertical speed indicator) which shows visually (and often audibly) the presence of lift and sink. Having located a thermal, a glider pilot will circle within the area of rising air to gain height. In the case of a cloud street thermals can line up with the wind creating rows of thermals and sinking air. A pilot can use a cloud street to fly long straight-line distances by remaining in the row of rising air.
Ridge lift occurs when the wind meets a mountain, cliff or hill. The air is deflected up the windward face of the mountain, causing lift. Gliders can climb in this rising air by flying along the feature. Another name for flying with ridge lift is slope soaring.
The third main type of lift used by glider pilots is the lee waves that occur near mountains. The obstruction to the airflow can generate standing waves with alternating areas of lift and sink. The top of each wave peak is often marked by lenticular cloud formations.
Another form of lift results from the convergence of air masses, as with a sea-breeze front.
More exotic forms of lift are the polar vortexes which the Perlan Project hopes to use to soar to great altitudes [7]. A rare phenomenon known as Morning Glory has also been used by glider pilots in Australia. A Guide to the Morning Glory at www.dropbears.com
Once the skills of using thermals to gain altitude have been mastered, pilots can glide from one thermal to the next to fly cross-country (XC). Potential thermals along the route can be identified by land features which typically generate thermals, by soaring birds or by cumulus clouds which mark the top of a rising column of warm, humid air as it reaches the dew point and condenses to form a cloud.
Hang gliding at Hyner, Pennsylvania.
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.
The extra weight provided by ballast is advantageous if the lift is likely to be strong. Although heavier gliders have a slight disadvantage when climbing in rising air, they achieve a higher speed at any given glide angle. This is an advantage in strong conditions when the gliders spend only little time climbing in thermals.
High performance flexible wing hang glider. 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. The most common airframe part&mdahs;the triangle control frame (TCF) is a simple triangle truss cable-stayed or strut-stayed frame—the A-frame for hang gliders, trikes, and ultralights stemming from designs from the sixteeth century onwards; the pilot interacts with the TCF.
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.
Launch of a hang glider
To maximize a pilot\'s understanding of how the hang glider is flying, most pilots carry instruments. The most basic being a variometer and altimeter—often combined. Some more advanced pilots also carry airspeed indicators and radios. When flying in competition or cross country, pilots often also carry maps and/or GPS units. Hang gliders do not have instrument panels as such, so all the instruments are mounted to the control frame of the glider.
Vario-altimeter
People can sense the acceleration when they first hit a thermal, but they cannot detect the difference between constant rising air and constant sinking air, so they turn to technology for help. 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.
GPS (global positioning system) is a necessary accessory when flying competitions, where it has to be demonstrated that way-points have been correctly passed.
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.Mike Barber needed to fly "1% further" than Ruhmer\'s 435 miles (700 km) in order to break the official FAI record; Barber needed to fly only 3 more miles for a total of 440 miles. Barber\'s flight remains the longest hang glider flight ever.
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). For a chronology of the FAI World Hang Gliding Championships, see:Chronology of the FAI World Hang Gliding Championships[8]
Modern \'flexible wing\' hang glider.
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.Dan Buchanan: [9]
The related sports are gliding, in which the gliders have full control surfaces and an enclosed cockpit, and paragliding, where the pilot is sitting on a harness suspended below a fabric wing.
Paragliding and hang gliding are closely related sports: foot-launched gliders with flexible wings, with options for tow launching and for powered flight and there is sometimes confusion about the differences. Beyond sport definitions and sporting association class definitions, there is a perspective that simply treats paragliders as a proper subset of hang gliders (as an over class of aircraft apart from the influence of sporting classes).
The main differences between the "two proper subsets" of generalized hang gliders are:
| Paragliders | Hang gliders | |
|---|---|---|
| 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 |
| 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 |
| 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 90+ mph, hence easier to launch and fly in stronger conditions with better wind penetration, and can out run bad weather, full pitch control |
| Glide angle: | poorer glide performance makes long-distances more difficult | better glide performance enables longer-distance flying, 430+ mile records |
| Turn radius: | tighter turn radius, allowing circling in the higher-rising center of thermals | somewhat larger turn radius, not allowing such a high rate of climb 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 |
| 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; |
| 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 |
| Cost: | cheaper but less durable | more expensive but more durable |
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