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Hang gliding is an air sport in which a pilot flies an unpowered and light foot-launchable glider aircraft known as a hang glider. Most modern hang gliders are made of an aluminum -or composite- framed fabric wing which lacks moving control surfaces. The pilot is mounted on a harness hanging from the airframe and exercises control by shifting his body weight.

Although it started out as simply gliding down small hills on low performance manned kites, hang glider technology has evolved the ability to soar for hours, gain thousands of feet of altitude in thermal updrafts, perform aerobatics, and fly cross country over large distances.

Contents 1 Classes 2 History 3 Training & Safety 4 Launch 5 Soaring Flight 5.1 Thermals 5.2 Ridge lift 5.3 Mountain waves 5.4 Convergence 5.5 Cross-country flying 6 Performance (2006) 7 Stability and equilibrium 8 Costs (2003) 9 Instruments 9.1 Variometer 9.2 Radio 9.3 GPS 10 Records 11 Competition 12 Related sports 13 Comparison with Paragliders 14 References 15 External links

For competitive purposes, there are three classes of hang glider:

• The flexible wing hang glider, having flight controlled by a wing whose shape changes by virtue of the shifted weight of the pilot. This is not a paraglider.
• The rigid wing hang glider, having flight controlled by spoilers, typically on top of the wing. In both flexible and rigid wings the pilot hangs below the wing without any additional fairing.
• Class 2 (designated by the FAI as Sub-Class O-2) where the pilot is integrated into the wing by means of a fairing. These offer the best performance and are the most expensive.

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.^[1]

Main article: History of hang gliding

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 in importance through the introduction of wing warping by the Wright brothers in 1902 and subsequently of aileron control by the French.

In 1948 aeronautical engineer Francis Rogallo invented a self-inflating wing, which he patented in 1951 as the flexible wing, also known as the Rogallo wing. The flexible airfoil was tested by NASA as a steerable parachute for space capsules returning to Earth. Some images of these tests were published in the early 1960s by NASA and by some aviation magazines. Rogallo's wing simplicity, ease of construction, capability of slow flight and its gentle landing characteristics did not go unnoticed by hang glider and ultralight glider enthusiasts, like aeronautical engineer Barry Palmer, who in 1960-1962 pioneered foot-launched Rogallo hang gliders; he built several versions and up to four different control methods including swing seat and control bar among others, founding the Rogallo hang glider movement in the world. Later, in 1963, an Australian John Dickenson fashioned a water ski kite airframe on a Rogallo airfoil; the pilot sat on a swinging seat and made use of a well-known Spratt and flat-kite control frame to push/pull for enhanced weight-shift control. Dickenson's water ski kite eventually did some free-flight releases and thus became a hang glider. Further refined, and by the early 1970s, the shapes of the Palmer and Dickenson hang gliders were copied by homebuilders and manufacturers across the world via published plans and creative innovative advances. The extreme nature of foot-launched hang gliding appealed to the freewheeling culture of the late 1960s across America more as an expression of freedom and the sudden commercial availability of water ski hang gliders starting in 1969, revolutionized hang gliding into a popular airsport.

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 or DHV 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.

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".

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 [3]. A rare phenomenon known as Morning Glory has also been used by glider pilots in Australia.^[2]

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.

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.

• Topless gliders: glide ratio ~17:1, speed range ~30 to >145 km/h, best glide at ~45 to 60 km/h
• Rigid wings: glide ratio ~20:1, speed range ~ 35 to > 130 km/h, best glide at ~50 to 60 km/h.

Ballast 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.

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.

• Roll - most flexible wings are set up with near neutral roll due to sideslip (anhedral effect). In the roll axis, the pilot shifts his body mass using the wing control bar, applying a rolling moment directly to the wing. The flexible wing is built to flex differentially across the span in response to the pilot applied roll moment. For example, under a right roll input, the right wing trailing edge flexes up more than the left, allowing the right wing to drop.

• The yaw axis is stabilized through the sweep back of the wings. The swept planform, when yawed out of the relative wind, creates more lift on the advancing wing and also more drag, stabilizing the wing in yaw. The differential lift causes positive roll due to sideslip like dihedral would. Thus, if one wing advances ahead of the other it presents more area to the wind and causes more drag on that side. This causes the advancing wing to go slower and to fall back. The wing is at equilibrium when the aircraft is traveling straight and both wings present the same amount of area to the wind.

• Pitch - The pitch control response is direct and very efficient and it is partially stabilized by the sweep of the wings. The wing centre of gravity is close to the hang point and at the trim speed, the wing will fly hands off and return to trim when disturbed. A combination of high lift airfoils with moderate pitching moment and washout (tip trailing edge upwards twist) produces a positive pitching tendency in the wing, where increasing airspeed causes increasing pitch-up. The weight-shift control system only works when the wing is positively loaded; To maintain a minimum safe amount of washout when the wing is unloaded or even negatively loaded, positive pitching devices such as reflex lines or washout rods are employed. To fly at other speeds, the pilot applies a pitching moment to the wing by levering his body mass around using the control bar connected directly to the wing. She pushes on the bar to rotate the wing more nose-up and fly slower, vice versa for high speed.

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.

• Rigid wings: ~10000 Euro (approx. $14500US)
• Topless gliders: 5-6000 Euro (approx. $7250-8700US)
• Intermediates: ~4000 Euro (approx. $4400US)
• Beginner gliders: < 3000 Euro (approx. $3375US)
• Harness: 500 - 1500 Euro (approx. $725-2150US)
• Parachute: ~ 500 Euro (approx. $550US)
• Instruments: 200 - 1000 Euro (approx. $290-1450US)
• School: 2-3 lessons (introductory package) 3-400 Euro (approx. $430-575US)
• School: 10 lessons (full course) 800-1000 Euro (approx. $1160-1450US)

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.

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 MacCreadytheory solves the problem of 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 current 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 has flown a distance of 704 km (437 miles) on June 19 2002 in Zapata Texas.^[3]

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:^[4]

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

• United States Hang Gliding and Paragliding Association - USHPA Official US Association.
• Hang Gliding Org webs #1 hang gliding community, videos, images, forum, news.
• The Oz Report - Worldwide Hang Gliding eZine and blog
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• DMOZ Open Directory category: Hang Gliding
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• The Scottish Hang-gliding & Paragliding Federation
• The Longest Running Hang Gliding Competition in the World
• Info about Hang Gliding
• The British Hang Gliding and Paragliding association
• The Hang Gliding Federation of Australia Governing body in Australia for Hang Gliding, Para-Gliding and Microlights
• Hang Gliding Software, Flight logbook