Gliders or Sailplanes are heavier-than-air aircraft primarily intended for unpowered flight. See also gliding and motor gliders for more details. Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes See Also Glider A Motor Glider is a Fixed-wing aircraft that can be flown with or without engine power ^[1]

A single-seat high performance fiberglass Glaser-Dirks DG-808 over the Lac de Serre Ponçon in the French Alps

Terminology

A "glider" is an unpowered aircraft. The most common types of glider are today used for sporting purposes. The design of these types enables them to climb using rising air and then to glide for long distances before finding the next source of lift. This has created the sport of gliding, or soaring. Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes The term "sailplane" is sometimes used for these types, implying a glider with a high soaring performance. In addition to high-performance sailplanes, the term 'glider' also encompasses hang gliders and paragliders. History See also History of hang gliding Summary: Hang gliding existed in China perhaps by the 4th century AD according to the writing of the Paragliding is a recreational and competitive flying sport A paraglider is a free-flying foot-launched Aircraft. Like sailplanes these can use upwardly moving air to soar but differ in not having a fuselage, control surfaces or a control column. Descriptions of these variants are in separate articles and so the rest of this article is only about conventional gliders and sailplanes.

Although many gliders do not have engines, there are some that use engines occasionally (see Motor glider). See Also Glider A Motor Glider is a Fixed-wing aircraft that can be flown with or without engine power The manufacturers of high-performance gliders now often list an optional engine and a retractable propeller that can be used to sustain flight if required; these are known as 'self-sustaining' gliders. Some can even launch themselves and are known as 'self-launching' gliders. There are also 'touring motor gliders', which can switch off their engines in flight though without retracting their propellers. The term "pure glider" (or equivalently, but less commonly "pure sailplane") may be used to distinguish a totally unpowered glider from a motorized glider, without implying any differential in gliding or soaring performance.

History

In China, kites rather than gliders were used for military reconnaissance. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National A kite is a flying tethered object that depends upon the tension of a tethering system However the Extensive Records of the Taiping Era (978) suggests that a true glider was designed in the 5th century BC by Lu Ban, a contemporary of Confucius. The Extensive Records of the Taiping Era ( is a collection of stories compiled under the editorship of Li Fang, first published in 978. Lu Ban ( fl 5th century BC) was a Chinese carpenter philosopher military thinker statesman and contemporary of Mozi, born in the State of Lu Confucius ( lit " Master Kung " September 28, 551 BC - 479 BC) was a Chinese thinker and social philosopher ^[2] There is also a report from the History of Northern Dynasties (659) and Zizhi Tongjian (1084) that Yuan Huangtou in Ye made a successful glide, taking off from a tower in 559. The History of Northern Dynasties ( is one of the official Chinese historical works in the Twenty-Four Histories canon The Zizhi Tongjian ( was a pioneering reference work in Chinese historiography. Yuan Huangtou (Chinese was the son of emperor Yuan Lang of Eastern Wei. Ye ( was an ancient Chinese city located in what is now Linzhang County Hebei and the neighbouring Anyang County Henan. ^[3]

Abbas Ibn Firnas invented the first weight shift aircraft ( hang glider) and is also claimed as the inventor of the first manned glider in 875 by fixing feathers to a wooden frame fitted to his arms or back. Abbas Ibn Firnas (810 &ndash 887 AD) was also known as Abbas Qasim Ibn Firnas and العباس بن فرناس ( Arabic language) History See also History of hang gliding Summary: Hang gliding existed in China perhaps by the 4th century AD according to the writing of the Written accounts at the time suggest that he made a ten minute flight. ^[4] Abbas was seriously injured in the resulting crash. ^[5][6][7]

Otto Lilienthal in flight

The first heavier-than-air (i. Otto Lilienthal (born 23 May, 1848 in Anklam, Province of Pomerania &ndash died 10 August, 1896 in Berlin e. non-balloon) aircraft to be flown in Europe was Sir George Cayley's series of gliders which achieved brief wing-borne hops from around 1804. Sir George Cayley 6th Baronet ( December 27, 1773 &ndash December 15, 1857) sometimes known as "the father of Aerodynamics" was Santos Dumont, Otto Lilienthal, Percy Pilcher, John J. Montgomery, and the Wright Brothers are other pioneers who built gliders to develop aviation. Alberto Santos-Dumont (July 20 1873 &ndash July 23 1932 was an early pioneer of Aviation. Otto Lilienthal (born 23 May, 1848 in Anklam, Province of Pomerania &ndash died 10 August, 1896 in Berlin Percy Sinclair Pilcher ( 16 January 1866 &mdash 2 October, 1899 John Joseph Montgomery ( February 15, 1858 – October 31, 1911) was an Aviation pioneer inventor professor at Santa Clara WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Aviation refers to activities involving man-made flying devices ( Aircraft) including the people organizations and regulatory bodies involved with them After the First World War gliders were built for sporting purposes in Germany (See link to Rhön-Rossitten Gesellschaft) and in the United States (Schweizer brothers). World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All The Rhön-Rossitten Gesellschaft ( RRG) or Rhön-Rossitten Society was a German Gliding organization the first one in the world that was officially Paul William (Bill and Ernest Schweizer were three brothers who started building gliders in 1930. The sporting use of gliders rapidly evolved in the 1930s and is now the main application. As their performance improved gliders began to be used to fly cross-country and now regularly fly hundreds or even thousands of kilometers in a day, if the weather is suitable.

Military gliders were then developed by a number of countries, particularly during World War II, for landing troops. Military gliders (an offshoot of common gliders) have been used by the military of various countries for carrying troops and heavy equipment (see Glider infantry World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including A glider was even built secretly by POWs as a potential escape method at Oflag IV-C near the end of the war in 1944. Prisoners made numerous attempts to escape Oflag IV-C, one of the most famous German Army Prisoner-of-war camps for officers in World War The space shuttle orbiters do not use their engines after re-entry at the end of each spaceflight, and so land as gliders. The Space Shuttle orbiters are the orbital Spacecraft of the Space Shuttle program operated by NASA, the space agency of the United States. Spaceflight is the use of Space technology to fly a Spacecraft into and through Outer space.

Launch methods

Main article: Gliding

The two most common methods of launching gliders are by aerotow and by winch. Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes When aerotowed, the glider is towed behind a powered aircraft using a rope about 60 meters (about 200 ft) long. The glider's pilot releases the rope after reaching the desired altitude, but the rope can also be released by the towplane in an emergency. Winch launching uses a powerful stationary engine located on the ground at the far end of the launch area. The glider is attached to one end of 800-1200 metres (about 2,500-4,000 ft) of wire cable and the winch then rapidly winds it in. More rarely, powerful automobiles are used to pull gliders into the air, by pulling them directly or through the use of a pulley in a similar manner to the winch launch. Elastic ropes can also be used to launch gliders off slopes if there is sufficient wind blowing up the hill. The glider will then gain height using ridge lift.

Staying aloft without an engine

Main article: Gliding

Glider pilots can stay airborne for hours. Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes This is possible because they seek out rising air masses (lift) or dynamic effects from the following sources:

Thermals

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. The Sun (Sol is the Star at the center of the Solar System. This warm air rises in columns known as thermals. A thermal column (or thermal) is a column of rising Air in the lower altitudes of the Earth's atmosphere. Soaring pilots quickly become aware of visual indications of thermals such as: cumulus clouds, cloud streets, dust devils and haze domes. A thermal column (or thermal) is a column of rising Air in the lower altitudes of the Earth's atmosphere. A cumulus cloud' is a type of Cloud with noticeable vertical development and clearly defined edges 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. The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator 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 straightline distances by remaining in the row of rising air.

Ridge lift (Orographic lift)

Another form of lift occurs when the wind meets a mountain, cliff or hill. The air is deflected up the windward face of the mountain forming lift. Windward is the direction from which the wind is blowing at the time in question Gliders can climb in this rising air by flying along the feature. This is referred to as "ridge running" and has been used to set record distance flights along the Appalachians in the USA and the Andes Mountains in South America. The Appalachian Mountains ( often called the Appalachians, are a vast system of mountains in eastern North America. The Andes form the world's longest exposed Mountain range. They lie as a continuous chain of highland along the western coast of South America. South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a Another name for flying with ridge lift is slope soaring.

Mountain wave

The third main type of lift used by glider pilots are the lee waves that occur near mountains. In Meteorology, lee waves, are atmospheric Standing waves. The most common form is mountain waves, which are atmospheric internal Gravity The obstruction to the airflow can generate standing waves with alternating areas of lift and sink. A standing wave, also known as a stationary wave, is a Wave that remains in a constant position The top of each wave peak is often marked by lenticular cloud formations. Lenticular clouds are stationary lens-shaped Clouds that form at high altitudes normally aligned at right-angles to the wind direction

Convergence

Another form of lift results from the convergence of air masses, as with a sea-breeze front. In the absence of a more specific context convergence denotes the approach toward a definite value as time goes on or to a definite point a common view or opinion or A sea-breeze (or onshore breeze) is a Wind from the sea that develops over land near coasts

Dynamic events allowing dynamic soaring

Gusts and wind-shear have been used by the flyers of models, but these phenomena are almost always too close to the ground to be useful to glider-pilots. See Dynamic soaring. Dynamic Soaring is a Gliding technique used to gain Kinetic energy by repeatedly crossing the boundary between air masses of significantly different horizontal

Other forms of lift

Among the more exotic forms of lift is the phenomenon known as Morning Glory which is used by some glider pilots in Australia. The Morning Glory cloud is a rare meteorological phenomenon observed in Northern Australia 's Gulf of Carpentaria. ^[8] It had also been hoped to use the polar vortex in the Perlan Project to soar to great altitudes^[9]. The polar vortex is a persistent large-scale Cyclone located near the Earth's Poles, in the middle and upper Troposphere and the Stratosphere The Perlan Project is a current research project to fly a sailplane to an altitude of 100000 feet (30480 meters

Moving forward

A typical training glider, Schleicher ASK 21 just before landing

After climbing in lift, gliders move on to find the next source of lift, or to land. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout As the glider descends, the air moving over the wings generates lift. In the context of a Fluid flow relative to a body the lift force is the component of the Aerodynamic force that is Perpendicular to the flow The lift force acts slightly forward of vertical because it is created at right angles to the airflow which comes from slightly below as the glider descends, see Angle of attack. Angle of attack ( AOA, \alpha Greek letter alpha) is a term used in Aerodynamics to describe the Angle between the This horizontal component of lift is enough to overcome drag and allows the glider to accelerate forward. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a The ratio of lift to drag is the same as the height lost for each metre of forward travel, Glide ratio^[10]. Glide ratio, also called Lift-to-drag ratio, glide number or finesse is an Aviation term that refers to the distance an Aircraft will move forward for

Glider design

Early gliders had no cockpit and the pilot sat on a small seat located just ahead of the wing. A cockpit is the area usually near the front of an Aircraft, from which a pilot controls the aircraft These were known as "primary gliders" and they were usually launched from the tops of hills, though they are also capable of short hops across the ground while being towed behind a vehicle. Primary Gliders are a category of Aircraft that enjoyed worldwide popularity during the 1920s and 1930s as people strove for simple and inexpensive ways to learn to To enable gliders to soar more effectively than primary gliders, the designs minimized drag. Gliders now have very smooth, narrow fuselages and very long, narrow wings with a high aspect ratio and winglets. The fuselage (from the French fuselé "spindle-shaped" is an Aircraft 's main body section that holds crew and passengers or Cargo In Aerodynamics, the aspect ratio of a wing is defined as the square of the wing span divided by the wing area Wingtip devices are usually intended to improve the efficiency of Fixed-wing aircraft.

Cockpit of a Typical Modern Glider. Click for details.

The early gliders were made mainly of wood with metal fastenings, stays and control cables. Later fuselages made of fabric-covered steel tube were married to wood and fabric wings for lightness and strength. New materials such as carbon-fiber, glass-fiber and Kevlar have since been used with computer-aided design to increase performance. The first glider to use glass-fiber extensively was the Akaflieg Stuttgart FS-24 Phönix which first flew in 1957. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout This material is still used because of its high strength to weight ratio and its ability to give a smooth exterior finish to reduce drag. Drag has also been minimized by more aerodynamic shapes and retractable undercarriages. Flaps are fitted on some gliders so that the optimal lift of the wing is available at all speeds. Flaps are hinged surfaces on the trailing edge of the wings of a Fixed-wing aircraft. Lift, or more precisely "static lift" is rising air used by Soaring birds and by humans in Gliding, Hang gliding and Paragliding

With each generation of materials and with the improvements in aerodynamics, the performance of gliders has increased. One measure of performance is the glide ratio. Glide ratio, also called Lift-to-drag ratio, glide number or finesse is an Aviation term that refers to the distance an Aircraft will move forward for A ratio of 30:1 means that in smooth air a glider can travel forward 30 meters while only losing 1 meter of altitude. Comparing some typical gliders that might be found in the fleet of a gliding club - the Grunau Baby from the 1930s had a glide ratio of just 17:1, the glass-fiber Libelle of the 1960s increased that to 39:1, and nowadays flapped 18 meter gliders such as the ASG29 have a glide ratio of over 50:1. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The largest open-class glider, the eta, has a span of 30. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 9 meters and has a glide ratio over 70:1. Compare this to the infamous Gimli Glider, a Boeing 767 which ran out of fuel mid-flight and was found to have a glide ratio of only 12:1, or to the Space Shuttle with a glide ratio of 3:1^[11]. Gimli Glider is the nickname of an Air Canada aircraft which was involved in an infamous Aviation incident WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States

Due to the critical role that aerodynamic efficiency plays in the performance of a glider, gliders often have state of the art aerodynamic features seldom found in other aircraft. The wings of a modern racing glider have a specially designed low-drag laminar flow airfoil. Laminar flow, sometimes known as streamline flow occurs when a fluid flows in parallel layers with no disruption between the layers An airfoil (in American English) or aerofoil (in British English) is the shape of a Wing or blade (of a Propeller, rotor After the wings' surfaces have been shaped by a mold to great accuracy, they are then highly polished. Vertical winglets at the ends of the wings are computer-designed to decrease drag and improve handling performance. Wingtip devices are usually intended to improve the efficiency of Fixed-wing aircraft. Special aerodynamic seals are used at the ailerons, rudder and elevator to prevent the flow of air through control surface gaps. For the band with a similar name see The Ailerons Ailerons are hinged control surfaces attached to the Trailing edge of the Wing of a Fixed-wing A rudder is a device used to steer a Ship, Boat, Submarine, Hovercraft, or other conveyance that move through a fluid (generally air or Elevators are control surfaces usually at the rear of an Aircraft, which control the aircraft's orientation by changing the pitch of the aircraft and so also Turbulator devices in the form of a zig-zag tape or multiple blow holes positioned in a span-wise line along the wing are used to trip laminar flow air into turbulent flow at a desired location on the wing. A turbulator is a device for improving the flow of air over a wing This flow control prevents the formation of laminar flow bubbles and ensures the absolute minimum drag. Bug-wipers may be installed to wipe the wings while in flight and remove insects that are disturbing the smooth flow of air over the wing.

A glider releasing its water ballast

Modern competition gliders are also designed to carry jettisonable water ballast (in the wings and sometimes in the vertical stabiliser). The extra weight provided by the water ballast is advantageous if the lift is likely to be strong, and may also be used to adjust the glider's center of mass. 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. The pilot can jettison the water ballast before it becomes a disadvantage in weaker thermal conditions. To avoid undue stress on the airframe, gliders must jettison any water ballast before landing.

Pilots can land accurately by controlling their rate of descent using spoilers, also known as air brakes. In Aeronautics a spoiler (sometimes called a lift dumper) is a device intended to reduce lift in an aircraft These are metal devices which extend from either the upper-wing surface or from both upper and lower surfaces, thereby destroying some lift and creating additional drag. A wheel-brake also enables a glider to be stopped after touchdown, which is particularly important in a short field.

Classes of glider

A DG Flugzeugbau DG-1000 of the Two Seater Class

For competitions seven classes of glider have been defined by the FAI. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Competition classes in Gliding, as in other sports mainly exist to ensure fairness in competition The Fédération Aéronautique Internationale (FAI is the world governing body for Air sports and Aeronautics and Astronautics world records They are:

• Standard Class (No flaps, 15 m wing-span, water ballast allowed)
• 15 metre Class (Flaps allowed, 15 m wing-span, water ballast allowed)
• 18 metre Class (Flaps allowed, 18 m wing-span, water ballast allowed)
• Open Class (No restrictions except a limit of 850 kg for the maximum all-up weight)
• Two Seater Class (maximum wing-span of 20 m), also known by the German name "Doppelsitzer"
• Club Class (This class allows a wide range of older small gliders with different performance and so the scores have to be adjusted by handicapping. For "handicap" as it refers to disabled persons see Disability. Water ballast is not allowed).
• World Class (The FAI Gliding Commission which is part of the FAI and an associated body called Organisation Scientifique et Technique du Vol à Voile (OSTIV) announced a competition in 1989 for a low-cost glider, which had moderate performance, was easy to assemble and to handle, and was safe for low hours pilots to fly. The International Gliding Commission (IGC is the international governing body for the sport of Gliding. Organisation Scientifique et Technique du Vol à Voile (OSTIV is a body associated with the FAI Gliding Commission (IGC The winning design was announced in 1993 as the Warsaw Polytechnic PW-5. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout This allows competitions be run with only one type of glider.

Major manufacturers of gliders

• DG Flugzeugbau GmbH
• Schempp-Hirth GmbH
• Alexander Schleicher GmbH & Co
• Rolladen-Schneider Flugzeugbau GmbH (taken over by DG Flugzeugbau)

See also the full gliders and manufacturers list, past and present. DG Flugzeugbau GmbH is a manufacturer of sailplanes based in Bruchsal near Karlsruhe, Germany. Schempp-Hirth Flugzeugbau GmbH is a Glider manufacturer based in Kirchheim, Germany. Alexander Schleicher GmbH & Co is a major manufacturer of Sailplanes located in, near Fulda in Germany. Rolladen-Schneider was a major glider manufacturer. It originally made rolling doors and shutters and was run by Willi and Walter Schneider based in Egelsbach near Abbott-Baynes Sailplanes Ltd Abrial Abrial A-12 Bagoas Abrial A-2 Vautour Advanced

Instrumentation and other technical aids

Schempp-Hirth Janus-C in flight, showing instrument panel equipped for "cloud flying," configured in the basic-T, with airspeed, attitude and altitude display across the top row; below a GPS-driven computer, with wind and glide information, drives two electronic variometer displays to the right. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Most aircraft are equipped with a standard set of flight instruments which give the pilot information about the aircraft's attitude airspeed and altitude The airspeed indicator or airspeed gauge is an instrument used in an Aircraft to display the craft's Airspeed, typically in knots, to the In Aviation, the turn and bank indicator shows the rate of turn and the coordination (slip or skid of the turn An altimeter is an instrument used to measure the Altitude of an object above a fixed level Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator The yaw string and compass are above the glare shield

Gliders must be equipped with an altimeter, compass, and an airspeed indicator in most countries, and are often equipped with a variometer, turn and bank indicator and an airband radio (transceiver), each of which may be required in some countries. The yaw string, also known as a slip string, is a simple device for indicating a slip or skid in an Aircraft in flight A compass, magnetic compass or mariner's compass is a navigational instrument for determining direction relative to the earth's Magnetic poles It consists An altimeter is an instrument used to measure the Altitude of an object above a fixed level A compass, magnetic compass or mariner's compass is a navigational instrument for determining direction relative to the earth's Magnetic poles It consists The airspeed indicator or airspeed gauge is an instrument used in an Aircraft to display the craft's Airspeed, typically in knots, to the The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator In Aviation, the turn and bank indicator shows the rate of turn and the coordination (slip or skid of the turn The airband or air band is the band of frequencies used for radio communication in Aviation. A transceiver is a device that has both a Transmitter and a receiver which are combined and share common circuitry or a single housing An Emergency Position-Indicating Radio Beacon (ELT) may also be fitted into the glider to reduce search and rescue time in case of an accident. In the field of Search and Rescue (SAR distress radio beacons, also collectively known as distress beacons, emergency beacons, or simply beacons For the TV series of this title see Search and Rescue (TV series.

Much more than in other types of aviation, glider pilots depend on the variometer, which is a very sensitive vertical speed indicator, to measure the climb or sink rate of the plane. The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator This enables the pilot to detect minute changes caused when the glider enters rising or sinking air masses. Both mechanical and electronic 'varios' are usually fitted to a glider. The electronic variometers produce a modulated sound of varying amplitude and frequency depending on the strength of the lift or sink, so that the pilot can concentrate on centering a thermal, watching for other traffic, on navigation, and weather conditions. Rising air is announced to the pilot as a rising tone, with increasing pitch as the lift increases. Conversely, descending air is announced with a lowering tone, which advises the pilot to escape the sink area as soon as possible. (Refer to the variometer article for more information). The term Variometer also refers to a type of tunable Electrical Transformer A variometer (also known as a rate-of-climb indicator

Gliders' variometers are sometimes fitted with mechanical devices such as a "MacCready Ring" to indicate the optimal speed to fly for given conditions. Speed to fly is a principle used by soaring pilots when flying between sources of lift usually Thermals Ridge lift and wave. These devices are based on the mathematical theory attributed to Paul MacCready^[12] though it was first described by Wolfgang Späte in 1938. Paul B MacCready Jr ( September 25, 1925 - August 28, 2007) was an American Aeronautical engineer. ^[13] MacCready theory 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. Electronic variometers make the same calculations automatically, after allowing for factors such as the glider's theoretical performance, water ballast, headwinds/tailwinds and insects on the leading edges of the wings. A polar curve is a Graph of the rate of sink of an Aircraft, often a Glider, versus its horizontal speed

Soaring flight computers, often used in combination with PDAs running specialized soaring software, have been specifically designed for use in gliders. Using GPS technology these tools can:

The track of a glider while thermalling in the Austrian Alps using SeeYou(C) visualization software. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth

• Provide the glider's position in 3 dimensions by a moving map display
• Alert the pilot to nearby airspace restrictions
• Indicate position along track and remaining distance and course direction
• Show airports within theoretical gliding distance
• Determine wind direction and speed at current altitude
• Show historical lift information
• Create a secure GPS log of the flight to provide proof for contests and gliding badges
• Provide "final" glide information (ie showing if the glider can reach the finish without additional lift). Airspace means the portion of the atmosphere controlled by a particular country on top of its territory and Territorial waters or more generally any specific three-dimensional
• Indicate the best speed to fly under current conditions

After the flight the GPS data may be replayed on specialized computer software for analysis and to follow the trace of one or more gliders against a backdrop of a map, an aerial photograph or the airspace. A 3-D view is shown here with a topographical background. 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer

Because collision with other gliders is an ever-present risk, the anti-collision device, FLARM is becoming increasingly common in Europe and Australia. FLARM is an electronic device to selectively alert pilots to potential collisions between Aircraft. In the longer term, gliders may eventually be required in some European countries to fit transponders once devices with low power requirements become available. A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation

Glider markings

Like all other aircraft, gliders are required to be painted with a national aircraft registration number, known as a "tail number" or in the U. An aircraft registration is a unique Alphanumeric string that identifies an Aircraft, in similar fashion to a licence plate on an automobile S. as an "N-number". The required size of these numbers varies from country to country. The size range is from 1 cm to 30 cm, sometimes depending on the age of the aircraft.

To distinguish gliders in flight, very large numbers/letters are sometimes displayed on the fin and wings. These numbers were added for use by ground-based observers in competitions, and are therefore known as "competition numbers" or "contest ID's". They are unrelated to the glider's registration number, and are assigned by national gliding associations. They are useful in radio communications between gliders, so glider pilots often use their competition number as their call-signs. In Broadcasting and Radio communications a call sign (also known as a callsign or call letters, or abbreviated as a call, or otherwise

Fibreglass gliders are white in color after manufacture. Fiberglass (also called fibreglass and glass fibre see Spelling differences) is material made from extremely fine Fibers of Glass. Since fibreglass resin softens at high temperatures, white is used almost universally to reduce temperature rise due to solar heating. Color is not used except for a few small bright patches on the wing tips; these patches (typically bright red) improve gliders' visibility to other aircraft while in flight. Non-fibreglass gliders (those made of aluminum and wood) are not subject to the temperature-weakening problem of fibreglass, and can be painted any color at the owner's choosing; they are often quite brightly painted.

S-1 Swift - modern aerobatic glider

Aerobatic gliders

Another - less widespread - form of gliding is aerobatics. The Swift S-1 is a single seat aerobatic Glider manufactured by Swift Ltd. Aerobatics is the demonstration of flying maneuvers for Training, Recreation or Entertainment. Gliders have been developed specifically for this type of competition, though most gliders can perform simpler aerobatic maneuvers such as loops and chandelles. The chandelle is an aircraft control maneuver where the pilot combines a turn with a climb in a certain way Aerobatic gliders usually have stronger and shorter wings than the gliders that are used in cross-country racing to withstand the high g-forces that are experienced in some maneuvers. g-force (also G-force, g-load) is a measurement of an object's Acceleration expressed in g s

See also

• Gliding
• Gliding competitions
• Hang Glider
• Foot-Launched Powered Hang Glider
• Military glider
• Gimli Glider
• Paraglider
• Underwater gliders

References

External links

• For more information on gliders and learning to glide, see article on gliding and contact the national gliding federation
  • Links to all national gliding federations

• Information about all types of glider:
  • Sailplane Directory - An enthusiast's web-site that lists manufacturers and models of gliders, past and present. Gliding is a Recreational activity and competitive Sport in which pilots fly un-powered aircraft known as Gliders or sailplanes

• FAI webpage
  • FAI records- sporting aviation page with international world soaring records in distances, speeds, routes, and altitude