Gliding is a recreational activity and competitive
air sport
The term "air sports" covers a range of aerial activities, including air racing, aerobatics, aeromodelling, hang gliding, human-powered aircraft, parachuting, paragliding and skydiving.
Recognized and regulated air sports
Many air sports ...
in which pilots fly
unpowered aircraft
Unpowered aircraft can remain airborne for a significant period of time without onboard propulsion. They can be classified as fixed-wing gliders, lighter-than-air balloons and tethered kites. This requires a trajectory that is not merely a verti ...
known as
gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is also used for the sport.
[
]
Gliding as a sport began in the 1920s. Initially the objective was to increase the duration of flights but soon pilots attempted cross-country flights away from the place of launch. Improvements in aerodynamics and in the understanding of weather phenomena have allowed greater distances at higher average speeds. Long distances are now flown using any of the main sources of rising air:
ridge lift,
thermal
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
s and
lee waves
In meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above ...
. When conditions are favourable, experienced pilots can now fly hundreds of kilometres before returning to their home airfields; occasionally flights of more than are achieved.
Some competitive pilots fly in races around pre-defined courses. These
gliding competitions
Some of the pilots in the sport of gliding take part in gliding competitions. These are usually racing competitions, but there are also aerobatic contests and on-line league tables.
History of competitions
In the early days, the main goal wa ...
test pilots' abilities to make best use of local weather conditions as well as their flying skills. Local and national competitions are organized in many countries, and there are biennial
World Gliding Championships
The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern ...
.
Techniques to maximize a glider's speed around the day's task in a competition have been developed, including the optimum
speed to fly
Speed to fly is a principle used by soaring pilots when flying between sources of lift, usually thermals, ridge lift and wave. The aim is to maximize the average cross-country speed by optimizing the airspeed in both rising and sinking air. Th ...
, navigation using
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
and the carrying of water
ballast
Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...
. If the weather deteriorates pilots are sometimes unable to complete a cross-country flight. Consequently, they may need to land elsewhere, perhaps in a field, but
motorglider
A motor glider is a fixed-wing aircraft that can be flown with or without engine power. The FAI Gliding Commission Sporting Code definition is: a fixed-wing aerodyne equipped with a means of propulsion (MoP), capable of sustained soaring flight ...
pilots can avoid this by starting an engine.
Powered-aircraft and winches are the two most common means of launching gliders. These and other launch methods require assistance and facilities such as airfields, tugs, and winches. These are usually provided by gliding clubs who also train new pilots and maintain high safety standards. Although in most countries the standards of safety of the pilots and the aircraft are the responsibility of governmental bodies, the clubs and sometimes
national gliding associations The sport of gliding is managed in each country by national gliding associations, subject to governmental aviation authorities to varying degrees. Internationally the sport is co-ordinated by the FAI Gliding Commission.
* Australia - Gliding Fede ...
often have delegated authority.
History
The development of heavier-than-air flight in the half century between
Sir George Cayley's coachman
Sir George Cayley, 6th Baronet (27 December 1773 – 15 December 1857) was an English engineer, inventor, and aviator. He is one of the most important people in the history of aeronautics. Many consider him to be the first true scientific aeri ...
in 1853 and the
Wright brothers in 1903 mainly involved gliders (see
History of aviation
The history of aviation extends for more than two thousand years, from the earliest forms of aviation such as kites and attempts at tower jumping to supersonic and hypersonic flight by powered, heavier-than-air jets.
Kite flying in Chin ...
). However, the sport of gliding only emerged after the First World War, as a result of the
Treaty of Versailles
The Treaty of Versailles (french: Traité de Versailles; german: Versailler Vertrag, ) was the most important of the peace treaties of World War I. It ended the state of war between Germany and the Allied Powers. It was signed on 28 June ...
,
which imposed severe restrictions on the manufacture and use of single-seat powered aircraft in
Germany's Weimar Republic. Thus, in the 1920s and 1930s, while aviators and aircraft makers in the rest of the world were working to improve the performance of powered aircraft, the Germans were designing, developing and flying ever more efficient gliders and discovering ways of using the natural forces in the atmosphere to make them fly farther and faster. With the active support of the German government, there were 50,000 glider pilots by 1937.
The first German gliding competition was held at the
Wasserkuppe
The is a mountain within the German state of Hesse. It is a large plateau formation at an elevation of and is the highest peak in the Rhön Mountains. Great advances in sailplane development took place on the mountain during the interwar peri ...
in 1920,
[
] organized by
Oskar Ursinus
Carl Oskar Ursinus (11 March 1877 – 6 July 1952) was a pioneer of German aviation and is remembered mainly for his contributions to sailplane designs and the sport of gliding. He has been nicknamed the ''Rhönvater'' ("Rhön father") because ...
. The best flight lasted two minutes and set a world distance record of .
Within ten years, it had become an international event in which the achieved durations and distances had increased greatly. In 1931, Gunther Grönhoff flew on the front of a storm from
Munich
Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the States of Germany, German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the List of cities in Germany by popu ...
to
Kadaň
Kadaň (; german: Kaaden) is a town in Chomutov District in the Ústí nad Labem Region of the Czech Republic. It has about 18,000 inhabitants. It lies on the banks of the river Ohře. Kadaň is a tourist centre with highlights being the Francisca ...
(Kaaden in German) in Western
Czechoslovakia
, rue, Чеськословеньско, , yi, טשעכאסלאוואקיי,
, common_name = Czechoslovakia
, life_span = 1918–19391945–1992
, p1 = Austria-Hungary
, image_p1 ...
, farther than had been thought possible.
In the 1930s, gliding spread to many other countries. In the
1936 Summer Olympics
The 1936 Summer Olympics (German: ''Olympische Sommerspiele 1936''), officially known as the Games of the XI Olympiad (German: ''Spiele der XI. Olympiade'') and commonly known as Berlin 1936 or the Nazi Olympics, were an international multi-sp ...
in Berlin gliding was a
demonstration sport
A demonstration sport, or exhibition sport, is a sport which is played to promote it, rather than as part of standard medal competition. This occurs commonly during the Olympic Games, but may also occur at other sporting events.
Demonstration spor ...
, and it was scheduled to be a full Olympic sport in the
1940 Games.
A glider, the
Olympia
The name Olympia may refer to:
Arts and entertainment Film
* ''Olympia'' (1938 film), by Leni Riefenstahl, documenting the Berlin-hosted Olympic Games
* ''Olympia'' (1998 film), about a Mexican soap opera star who pursues a career as an athlet ...
, was developed in Germany for the event, but World War II intervened. By 1939 the major gliding records were held by Russians, including a distance record of .
During the war, the sport of gliding in Europe was largely suspended, though several German
fighter aces in the conflict, including
Erich Hartmann
Erich Alfred Hartmann (19 April 1922 – 20 September 1993) was a German fighter pilot during World War II and the most successful fighter ace in the history of aerial warfare. He flew 1,404 combat missions and participated in aerial com ...
, began their flight training in gliders.
Gliding did not return to the Olympics after the war for two reasons: a shortage of gliders, and the failure to agree on a single model of competition glider. (Some in the community feared doing so would hinder development of new designs.)
The re-introduction of air sports such as gliding to the Olympics has occasionally been proposed by the world governing body, the
Fédération Aéronautique Internationale
The (; FAI; en, World Air Sports Federation) is the world governing body for air sports, and also stewards definitions regarding human spaceflight. It was founded on 14 October 1905, and is headquartered in Lausanne, Switzerland. It maintai ...
(FAI), but has been rejected on the grounds of lack of public interest.
In many countries during the 1950s, a large number of trained pilots wanted to continue flying. Many were also
aeronautical engineers
Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...
who could design, build and maintain gliders. They started both clubs and
manufacturers
Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a range ...
, many of which still exist. This stimulated the development of both gliding and gliders, for example the membership of the
Soaring Society of America
The Soaring Society of America (SSA) was founded at the instigation of Warren E. Eaton to promote the sport of soaring in the USA and internationally. The first meeting was held in New York City in the McGraw–Hill Building on February 20, 1932. ...
increased from 1,000 to 16,000 by 1980. The increased numbers of pilots, greater knowledge and improving technology helped set new records, for example the pre-war altitude record was doubled by 1950,
and the first flight was achieved in 1964.
New materials such as
glass fiber
Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass.
Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...
and
carbon fiber
Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
, advances in
wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
shapes and airfoils, electronic instruments, the
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
and improved weather forecasting have since allowed many pilots to make flights that were once extraordinary. Today over 550 pilots have made flights over .
Although there is no Olympic competition, there are the
World Gliding Championships
The World Gliding Championships (WGC) is a gliding competition held every two years or so by the FAI Gliding Commission. The dates are not always exactly two years apart, often because the contests are sometimes held in the summer in the Southern ...
. The first event was held at the Samedan in 1948.
Since World War II it has been held every two years. There are now six
classes open to both sexes, plus three classes for women and two junior classes. The latest worldwide statistics for 2011 indicate that Germany, the sport's birthplace, is still a center of the gliding world: it accounted for 27 percent of the world's glider pilots,
[
] and the three major
glider manufacturers
This is a list of gliders/sailplanes of the world, (this reference lists all gliders with references, where available)
Note: Any aircraft can glide for a short time, but gliders are designed to glide for longer.
By nationality
*List of Americ ...
are still based there. However the meteorological conditions that allow soaring are common and the sport has been taken up in many countries. At the last count, there were over 111,000 active civilian glider pilots and 32,920 gliders,
plus an unknown number of military cadets and aircraft. Clubs actively seek new members by giving trial flights, which are also a useful source of revenue for the clubs.
Soaring
Glider pilots can stay airborne for hours by flying through air that is ascending as fast or faster than the glider itself is descending, thus gaining
potential energy
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Common types of potential energy include the gravitational potentia ...
.
The most commonly used sources of rising air are
*
thermal
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
s (updrafts of warm air);
*
ridge lift (found where the wind blows against the face of a hill and is forced to rise); and
*
wave lift (
standing wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect ...
s in the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
, analogous to the ripples on the surface of a stream).
Ridge lift rarely allows pilots to climb much higher than about above the terrain; thermals, depending on the climate and terrain, can allow climbs in excess of in flat country and much higher above mountains;
wave lift has allowed a glider to reach an altitude of .
In a few countries such as the UK, gliders may continue to climb into the clouds in uncontrolled airspace,
but in many European countries the pilot must stop climbing before reaching the cloud base (see
Visual Flight Rules
In aviation, visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better ...
).
Thermals
Thermals begin as bubbles of rising air that are formed on the ground through the warming of the surface by sunlight.
If the air contains enough moisture, the water will condense from the rising air and form cumulus clouds.
[
]
When the air has little moisture or when an
inversion
Inversion or inversions may refer to:
Arts
* , a French gay magazine (1924/1925)
* ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas
* Inversion (music), a term with various meanings in music theory and musical set theory
* ...
stops the warm air from rising high enough for the moisture to condense, thermals do not create cumulus clouds. Without clouds or
dust devil
A dust devil is a strong, well-formed, and relatively short-lived whirlwind. Its size ranges from small (half a metre wide and a few metres tall) to large (more than 10 m wide and more than 1 km tall). The primary vertical motion is u ...
s to mark the thermals, thermals are not always associated with any feature on the ground. The pilot must then use both skill and luck to find them using a sensitive vertical speed indicator called a
variometer
In aviation, a variometer – also known as a rate of climb and descent indicator (RCDI), rate-of-climb indicator, vertical speed indicator (VSI), or vertical velocity indicator (VVI) – is one of the flight instruments in an aircraft used to in ...
that quickly indicates climbs and descents. Occasionally reliable thermals can be found in the exhaust gases from
power station
A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.
Many p ...
s or from fires.
Once a thermal is encountered, the pilot can fly in tight circles to keep the glider within the thermal, thus gaining altitude before flying toward the destination or to the next thermal. This is known as "thermalling". Alternatively, glider pilots on
cross-country flights may choose to 'dolphin'. This is when the pilot merely slows down in rising air, and then speeds up again in the non-rising air, thus following an undulating flight path. Dolphining allows the pilot to minimize the loss of height over great distances without spending time turning. Climb rates depend on conditions, but rates of several meters per second are common and can be maximized by gliders equipped with
flaps. Thermals can also be formed in a line usually because of the wind or the terrain, creating
cloud street
Horizontal convective rolls, also known as horizontal roll vortices or cloud streets, are long rolls of counter-rotating air that are oriented approximately parallel to the ground in the planetary boundary layer. Although horizontal convective ...
s. These can allow the pilot to fly straight while climbing in continuous lift.
As it requires rising heated air, thermalling is most effective in mid-latitudes from spring through late summer. During winter, the sun's heat can only create weak thermals, but ridge and wave lift can still be used during this period.
Ridge lift
A
ridge soaring pilot uses upward air movements caused when the wind blows on to the sides of hills. It can also be augmented by thermals when the slopes also face the sun.
In places where a steady wind blows, a ridge may allow virtually unlimited time aloft, although records for duration are no longer recognized because of the danger of
exhaustion
Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
.
Wave lift
The powerfully rising and sinking air in
mountain waves
In meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above t ...
was discovered by glider pilot,
Wolf Hirth
Wolfram Kurt Erhard Hirth (28 February 1900 – 25 July 1959) was a German gliding pioneer and sailplane designer. He was a co-founder of Schempp-Hirth, still a renowned glider manufacturer.Segelflugbildkalendar 2011
Hirth was born in Stuttgart, ...
, in 1933.
Gliders can sometimes climb in these waves to great altitudes, although pilots must use supplementary
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
to avoid
hypoxia
Hypoxia means a lower than normal level of oxygen, and may refer to:
Reduced or insufficient oxygen
* Hypoxia (environmental), abnormally low oxygen content of the specific environment
* Hypoxia (medical), abnormally low level of oxygen in the tis ...
.
This lift is often marked by long, stationary
lenticular (lens-shaped) clouds lying perpendicular to the wind.
Wave lift was used to set the current altitude record (to be ratified) of on 2 September 2018 over
El Calafate
El Calafate, also known as ''Calafate'', is a city in Patagonia, Argentina. It is situated on the southern border of Lake Argentino, in the southwest part of the Santa Cruz Province, about northwest of Río Gallegos. The name of the city is deri ...
,
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
. The pilots,
Jim Payne and
Tim Gardner
Tim Gardner (born 1973 in Iowa City, Iowa) is an American-born Canadian painter known for his watercolors of his brothers and friends involved in youthful revels often set in nature.
Gardner obtained his BFA from the University of Manitoba in 1996 ...
, wore pressure suits.
The current world distance record of by
Klaus Ohlmann
Klaus Ohlmann (born 1952 in Neustadt, Germany)) is a German glider pilot who has established 36 world records approved by FAI. Among these is the record for a free distance flight with up to 3 turn-points by flying 3,009 km from Chapelco Airpor ...
(set on 21 January 2003)
[
] was also flown using mountain waves in South America.
A rare wave phenomenon is known as
Morning Glory
Morning glory (also written as morning-glory) is the common name for over 1,000 species of flowering plants in the family Convolvulaceae, whose current taxonomy and systematics are in flux. Morning glory species belong to many genera, some of ...
, a
roll cloud
An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus clouds. They most frequently form along the leading edge or gust fronts o ...
producing strong lift. Pilots near Australia's
Gulf of Carpentaria
The Gulf of Carpentaria (, ) is a large, shallow sea enclosed on three sides by northern Australia and bounded on the north by the eastern Arafura Sea (the body of water that lies between Australia and New Guinea). The northern boundary is ...
make use of it in
springtime
Springtime may refer to:
* Spring (season), one of the four temperate seasons
Film and television
* ''Springtime'' (1920 film), an American silent comedy starring Oliver Hardy
* ''Springtime'' (1929 film), a ''Silly Symphonies'' animated Disney ...
.
Other sources of lift
The boundaries where two air masses meet are known as
convergence zone
A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions.
This causes a mass accumulation that eventually leads to a vertical movement and ...
s.
These can occur in
sea breeze
A sea breeze or onshore breeze is any wind that blows from a large body of water toward or onto a landmass; it develops due to differences in air pressure created by the differing heat capacities of water and dry land. As such, sea breezes ar ...
s or in desert regions. In a sea-breeze front, cold air from the sea meets the warmer air from the land and creates a boundary between two masses of air like a shallow
cold front
A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Norther ...
. Glider pilots can gain altitude by flying along the intersection as if it were a ridge of land. Convergence may occur over considerable distances and so may permit virtually straight flight while climbing.
Glider pilots have occasionally been able to use a technique called "
dynamic soaring
Dynamic soaring is a flying technique used to gain energy by repeatedly crossing the boundary between air masses of different velocity. Such zones of wind gradient are generally found close to obstacles and close to the surface, so the technique is ...
"
allowing a glider to gain
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
by repeatedly crossing the boundary between air masses of different horizontal velocity. However, such zones of high "
wind gradient
In common usage, wind gradient, more specifically wind speed gradient
or wind velocity gradient,
or alternatively shear wind,
is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. It is the rate of ...
" are usually too close to the ground to be used safely by gliders.
Launch methods
Most gliders do not have engines or at least engines that would allow a take-off under their own power. Various methods are therefore used to get airborne. Each method requires specific training, therefore glider pilots must be in current practice for the type of launch being used.
Licensing
A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit).
A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...
rules in some countries, such as the US, differentiate between aerotows and ground launch methods, due to the widely different techniques.
Aerotowing
In an aerotow a powered aircraft is attached to a glider with a tow rope. Single-engined light aircraft or
motor gliders
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.
Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...
are commonly used. The tow-plane takes the glider to the height and location requested by the pilot where the glider pilot releases the tow-rope.
[
] A weak link is often fitted to the rope to ensure that any sudden loads do not damage the
airframe
The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system.
Airframe design is a field of aerospa ...
of the tow-plane or the glider. Under extreme loads the weak link will fail before any part of the glider or plane fails. There is a remote chance that the weak link might break at low altitude, and so pilots plan for this eventuality before launching.
During the aerotow, the glider pilot keeps the glider behind the tow-plane in either the "low tow" position, just below the
wake from the tow-plane, or the "high tow" position just above the wake. In Australia the convention is to fly in low tow, whereas in the United States and Europe the high tow prevails. One rare aerotow variation is attaching two gliders to one tow-plane, using a short rope for the high-towed glider and a long rope for the low tow. The current record is nine gliders in the same aerotow.
Winch launching
Gliders are often launched using a stationary ground-based
winch
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable").
In its simplest form, it consists of a spool (or drum) attache ...
mounted on a heavy vehicle.
This method is widely used at many European clubs, often in addition to an aerotow service. The engine is usually powered by
LPG, petrol or
diesel
Diesel may refer to:
* Diesel engine, an internal combustion engine where ignition is caused by compression
* Diesel fuel, a liquid fuel used in diesel engines
* Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...
, though
hydraulic fluid
A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoe ...
engines and
electrical motor
An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force ...
s are also used. The winch pulls in a 1,000 to 2,500-metre (3,000 to 7,500 ft) cable, made of high-tensile steel wire or a
synthetic fiber
Synthetic fibers or synthetic fibres (in British English; see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants (like cotton) ...
, attached to the glider. The cable is released at a height of about 35% of the cable length after a short, steep ride.
A strong headwind will result in higher launches.
Winch launches are much cheaper than aerotows and permit a higher launch frequency. A winch may also be used at sites where an aerotow could not operate, because of the shape of the field or because of noise restrictions. The height gained from a winch is usually less than that from an aerotow, so pilots need to find a source of lift soon after releasing from the cable, or else the flight will be short. A break in the cable or the weak link
[A ''weak link'' is a specially calibrated element, connecting two parts of the winch cable, designed to break if the tension on the winch cable exceeds safe values.] during a winch launch is a possibility for which pilots are trained.
Auto-tow
Another method of launching, the "autotow", is rarer nowadays.
The direct autotow requires a hard surface and a powerful vehicle that is attached to the glider by a long steel cable. After gently taking up slack in the cable, the driver
accelerates hard and as a result the glider rises rapidly to about 400 metres (1,300 ft), especially if there is a good
headwind
A tailwind is a wind that blows in the direction of travel of an object, while a headwind blows against the direction of travel. A tailwind increases the object's speed and reduces the time required to reach its destination, while a headwind has ...
and a
runway
According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt concrete, as ...
of or more. This method has also been used on desert
dry lake
A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappears when evaporation processes exceeds recharge. If the floor of a dry lake is covered by deposits of alkaline c ...
s.
A variation on the direct autotow is known as the "reverse pulley" method. In this method, the truck drives towards the glider being launched. The cable passes around a pulley at the far end of the airfield, resulting in an effect similar to that of a winch launch.
Bungee launch
Bungee launching was widely used in the early days of gliding, and occasionally gliders are still launched from the top of a gently sloping hill into a strong breeze using a substantial multi-stranded rubber band, or "
bungee".
[
] For this launch method, the glider's main wheel rests in a small concrete trough. The hook normally used for winch-launching is instead attached to the middle of the bungee. Each end is then pulled by three or four people. One group runs slightly to the left, the other to the right. Once the tension in the bungee is high enough, the glider is released and the glider's wheel pops out of the trough. The glider gains just enough energy to leave the ground and fly away from the hill.
Gravity launch
A glider can simply be pushed down a slope until gravity can create enough speed for it to take off.
Cross-country
One of the measures of a glider's performance is the distance that it can fly for each meter it descends, known as its
glide ratio
In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...
. Glide ratio is dependent on an aircraft's class, and can typically range from 44:1 (for modern designs in the Standard Class) up to 70:1 (for the largest aircraft). A good gliding performance combined with regular sources of rising air enables modern gliders to fly long distances at high speeds.
The weather is a major factor in determining cross-country speeds. The record average speed for is
and required unusually good conditions, but even in places with less favorable conditions (such as
Northern Europe
The northern region of Europe has several definitions. A restrictive definition may describe Northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other g ...
) a skilled pilot can expect to complete flights over every year.
[
]
As the performance of gliders improved in the 1960s, the concept of flying as far away as possible became unpopular with the crews who had to retrieve the gliders. Pilots now usually plan to fly around a course (called a ''task'') via
turn-points, returning to the starting point.
In addition to just trying to fly further, glider pilots also race each other in
competitions
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
. The winner is the fastest, or, if the weather conditions are poor, the furthest round the course. Tasks of up to 1,000 km have been set and average speeds of 120 km/h are not unusual.
Initially, ground observers confirmed that pilots had rounded the turn-points. Later, the glider pilots photographed these places and submitted the film for verification. Today, gliders carry secure
GNSS Flight Recorders
The International Gliding Commission (IGC) is the international governing body for the sport of gliding. It is governed by meetings of delegates from national gliding associations.
It is one of several Air Sport Commissions (ASC) of the Fédéra ...
that record the position every few seconds from
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
satellites. These recording devices now provide the proof that the turn-points have been reached.
![Gliding competition grid](https://upload.wikimedia.org/wikipedia/commons/2/28/Gliding_competition_grid.JPG)
National competitions generally last one week, with international championships running over two. The winner is the pilot who has amassed the greatest number of points over all the contest days. However, these competitions have as yet failed to draw much interest outside the gliding community for several reasons. Because it would be unsafe for many gliders to cross a start line at the same time, pilots can choose their own start time. Furthermore, gliders are not visible to the spectators for long periods during each day's contest and the scoring is complex, so traditional gliding competitions are difficult to televise. In an attempt to widen the sport's appeal, a new format, the
Grand Prix
Grand Prix ( , meaning ''Grand Prize''; plural Grands Prix), is a name sometimes used for competitions or sport events, alluding to the winner receiving a prize, trophy or honour
Grand Prix or grand prix may refer to:
Arts and entertainment ...
, has been introduced. Innovations introduced in the Grand Prix format include simultaneous starts for a small number of gliders, cockpit mounted cameras, telemetry giving the positions of the gliders, tasks consisting of multiple circuits, and simplified scoring.
There is a decentralized Internet-based competition called the
Online Contest
The aerokurier Online Contest (OLC), a worldwide decentralized soaring competition for glider, hang glider, and paraglider pilots. The OLC is operated by Segelflugszene Gemeinnützige GmbH, a German not-for-profit founded in 2000. "Segelflugszene" ...
, in which pilots upload their GPS data files and are automatically scored based on distance flown. Worldwide, 6,703 pilots registered for this contest in 2010.
Maximizing average speed
Soaring pioneer
Paul MacCready
Paul B. MacCready Jr. (September 25, 1925 – August 28, 2007) was an American aeronautical engineer. He was the founder of AeroVironment and the designer of the human-powered aircraft that won the first Kremer prize. He devoted his life to dev ...
is usually credited with developing mathematical principles for optimizing the speed at which to fly when cross-country soaring,
[
] although it was first described by
Wolfgang Späte
Wolfgang Späte (8 September 1911 – 30 April 1997) was a German Luftwaffe fighter pilot during World War II. He was a recipient of the Knight's Cross of the Iron Cross with Oak Leaves. For fighter pilots it was a quantifiable measure of skill an ...
in 1938. The
speed to fly
Speed to fly is a principle used by soaring pilots when flying between sources of lift, usually thermals, ridge lift and wave. The aim is to maximize the average cross-country speed by optimizing the airspeed in both rising and sinking air. Th ...
theory allows the optimal cruising speed between thermals to be computed, using thermal strength, glider performance and other variables. It accounts for the fact that if a pilot flies faster between thermals, the next thermal is reached sooner. However at higher speeds the glider also sinks faster, requiring the pilot to spend more time circling to regain the altitude. The MacCready speed represents the optimal trade-off between cruising and circling. Most competition pilots use MacCready theory to optimize their average speeds, and have the calculations programmed in their flight computers, or use a "McCready ring", a rotatable bezel on the glider's variometer to indicate the best speed to fly. The greatest factor in maximizing average speed, however, remains the ability of the pilot to find the strongest lift.
On cross-country flights on days when strong lift is forecast, pilots fly with water ballast stored in tanks or bags in the wings and fin. The fin tank is used to reduce trim drag by optimizing the
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
, which typically would shift forward if water is stored only in the wings ahead of the spar.
Ballast enables a sailplane to attain its best lift-to-drag ratio (L/D) at higher speeds but slows its climb rate in thermals, in part because a sailplane with a heavier wing loading cannot circle within a thermal as tightly as one with a lower, unballasted wing loading. But if lift is strong, typically either from thermals or wave, the disadvantage of slower climbs is outweighed by the higher cruising speeds between lift areas. Thus, the pilot can improve the average speed over a course by several percent or achieve longer distances in a given time.
If lift is weaker than expected, or if an off-field landing is imminent, the pilot can jettison the water ballast by opening the dump valves.
On days with particularly strong and widespread lift pilots can attain high average speeds by alternating periods of fast flight with pull-ups, merely slowing down in areas of lift without deviating from the course. This 'dolphining' technique can result in high average speeds because the height lost can be minimised until particularly strong lift is encountered when circling would be most effective.
Badges
Achievements in gliding have been marked by the awarding of
badges
A badge is a device or accessory, often containing the insignia of an organization, which is presented or displayed to indicate some feat of service, a special accomplishment, a symbol of authority granted by taking an oath (e.g., police and fi ...
since the 1920s.
[
] For the lower badges, such as the first solo flight, national gliding federations set their own criteria. Typically, a bronze badge shows preparation for cross-country flight, including precise landings and witnessed soaring flights. Higher badges follow the standards set down by the
Gliding Commission of the Fédération Aéronautique Internationale (FAI).
[
]
The FAI's Sporting Code defines the rules for observers and recording devices to validate the claims for badges that are defined by kilometres of distance and metres of altitude gained.
The Silver-C badge was introduced in 1930.
Earning the Silver Badge shows that a glider pilot has achieved an altitude gain of at least , made a five-hour duration flight, and has flown cross-country for a straight-line distance of at least : these three attainments are usually, but not invariably, achieved in separate flights. A pilot who has earned the Gold badge has achieved an altitude gain of , made a flight of five-hours duration, and flown cross-country for a straight-line distance of at least . A pilot who has completed the three parts of the Diamond Badge has flown to a pre-defined goal, has flown in one flight (but not necessarily to a pre-defined goal) and gained in height. The FAI also issues a diploma for a flight of and further diplomas for increments of .
Landing out
If lift is not found during a cross-country flight, for example because of deteriorating weather, the pilot must choose a location to "land out".
Although inconvenient and often mistaken for "
emergency landing
An emergency landing is a premature landing made by an aircraft in response to an emergency involving an imminent or ongoing threat to the safety and operation of the aircraft, or involving a sudden need for a passenger or crew on board to term ...
s", landing out (or "outlanding") is a routine event in cross-country gliding. A location needs to be identified where the glider can land safely without damaging the glider, the pilot, or property such as crops or livestock. The glider and the pilot(s) can then be retrieved by road from the outlanding location using a purpose-built trailer. If this is not possible due to an inaccessible location such as a mountain range, the glider may be loaded into its trailer and airlifted by helicopter. In some instances, a tow-plane can be summoned to re-launch the aircraft.
Use of engines or motors
Although adding to the weight and expense, some gliders are fitted with small power units and are known as
motor glider
A motor glider is a fixed-wing aircraft that can be flown with or without engine power. The FAI Gliding Commission Sporting Code definition is: a fixed-wing aerodyne equipped with a means of propulsion (MoP), capable of sustained soaring flight ...
s. This avoids the inconvenience of landing out. The power units can be
internal combustion
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
engines, electrical motors, or retractable
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s. Retractable propellers are fitted to high performance sailplanes, though in another category, called
touring motor gliders, non-retractable propellers are used. Some powered gliders are "self launching", which makes the glider independent of a tow plane. However some gliders have "sustainer" engines that can prolong flight but are not powerful enough for launching. All power units have to be started at a height that includes a margin that would still allow a safe landing out to be made, if there were a failure to start.
In a competition, using the engine ends the soaring flight. Unpowered gliders are lighter and, as they do not need a safety margin for starting the engine, they can safely thermal at lower altitudes in weaker conditions. Consequently, pilots in unpowered gliders may complete competition flights when some powered competitors cannot. Conversely, motor glider pilots can start the engine if conditions will no longer support soaring flight, while unpowered gliders will have to land out, away from the home airfield, requiring retrieval by road using the glider's trailer.
Aerobatic competitions
World
In its most general sense, the term "world" refers to the totality of entities, to the whole of reality or to everything that is. The nature of the world has been conceptualized differently in different fields. Some conceptions see the worl ...
and
European
European, or Europeans, or Europeneans, may refer to:
In general
* ''European'', an adjective referring to something of, from, or related to Europe
** Ethnic groups in Europe
** Demographics of Europe
** European cuisine, the cuisines of Europe ...
Aerobatic
Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...
competitions are held regularly.
[
] In this type of
competition
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
, the pilots fly a program of
maneuvers
A military exercise or war game is the employment of military resources in training for military operations, either exploring the effects of warfare or testing strategies without actual combat. This also serves the purpose of ensuring the com ...
(such as inverted flight, loop, roll, and various combinations). Each maneuver has a rating called the "K-Factor". Maximum points are given for the maneuver if it is flown perfectly; otherwise, points are deducted. Efficient maneuvers also enable the whole program to be completed with the height available. The winner is the pilot with the most points.
Hazards
Unlike
hang gliders
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...
and
paragliders
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched Glider (aircraft), glider aircraft with no rigid primary structure. The pilot sits in a :wikt:harness, harness o ...
, gliders surround the pilots with strong structures and have undercarriages to absorb impacts when landing. These features prevent injuries from otherwise minor incidents,
but there are some hazards. Although training and safe procedures are central to the ethos of the sport, a few fatal accidents occur every year, almost all caused by pilot error.
In particular there is a risk of mid-air collisions between gliders, because two pilots might choose to fly to the same area of lift and so might collide. To avoid other gliders and
general aviation
General aviation (GA) is defined by the International Civil Aviation Organization (ICAO) as all civil aviation aircraft operations with the exception of commercial air transport or aerial work, which is defined as specialized aviation services ...
traffic, pilots must comply with the Rules of the Air and keep a good lookout. They also usually wear
parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
s. In several European countries and Australia, the
FLARM
FLARM is proprietary electronic system used to selectively alert pilots to potential collisions between aircraft. It is not formally an implementation of ADS-B, as it is optimized for the specific needs of light aircraft, not for long-range commun ...
warning system is used to help avoid mid-air collisions between gliders. A few modern gliders have a ballistic emergency parachute to stabilize the aircraft after a collision.
Training and regulation
![Schleicher ASK13 glider](https://upload.wikimedia.org/wikipedia/commons/3/35/Schleicher_ASK13_glider.jpg)
In addition to national laws controlling aviation, the sport in many countries is regulated through national gliding associations and then through local gliding clubs. Much of the regulation concerns safety and training.
Many clubs provide training for new pilots. The student flies with an instructor in a two-seat glider fitted with dual controls. The instructor performs the first launches and landings, typically from the back seat, but otherwise the student manages the controls until the student is deemed to have the skill and the
airmanship
Airmanship is skill and knowledge applied to aerial navigation, similar to seamanship in maritime navigation. Airmanship covers a broad range of desirable behaviors and abilities in an aviator. It is not simply a measure of skill or technique, b ...
necessary to fly solo.
Simulators
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the ...
are also beginning to be used in training, especially during poor weather.
After the first solo flights glider pilots are required to stay within gliding range of their home airfield. In addition to solo flying, further flights are made with an instructor until the student is capable of taking a glider cross-country and of handling more difficult weather. Cross-country flights are allowed when they have sufficient experience to find sources of lift away from their home airfield, to navigate, and to select and land in a field if necessary. In most countries pilots must take a written examination on the regulations, navigation, use of the radio, weather, principles of flight and human factors. Proposals are being made to standardise the training requirements across European countries.
In addition to the regulation of pilots, gliders are inspected annually and after exceeding predetermined flight times. Maximum and minimum
payload
Payload is the object or the entity which is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of ...
s are also defined for each glider. Because most gliders are designed to the same specifications of safety, the upper weight limit for a pilot, after allowing for a parachute, is usually . There is also a limit, 193 centimetres (6 ft 4 in), on the tallest pilots who can safely fit into a typical glider's cockpit.
Challenges for the gliding movement
According to the FAI President, gliding as a sport faces challenges in the years ahead. These include:
*Time pressures on participants: gliding typically takes whole days that many people today find harder to devote. As a result, the average age of glider pilots is increasing.
*In some countries, the need for more land for housing is threatening small airfields. These airfields may also be used for other general aviation activities, and the addition of gliding may be difficult to accommodate. This can limit the number of available airfields and so it can require longer drives to reach them.
*
Airspace
Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. It is not the same as aerospace, which is the ...
: in many European countries, the growth of
civil aviation
Civil aviation is one of two major categories of flying, representing all non-military and non-state aviation, both private and commercial. Most of the countries in the world are members of the International Civil Aviation Organization and work ...
is reducing the amount of
uncontrolled airspace
In aviation, uncontrolled airspace is airspace where an Air Traffic Control (ATC) service is not deemed necessary or cannot be provided for practical reasons. It is the opposite of controlled airspace. It is that portion of the airspace that has ...
. In the U.S. new security requirements, and the growth of controlled airspace around cities, has also had some impact on where to fly.
*Competition from other activities: there is now a greater variety of similar sports such as
hang gliding
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...
and
paragliding
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure. The pilot sits in a harness or lies supine in a cocoon-like 'po ...
that may attract potential glider pilots.
*Lack of publicity: without coverage by television or popular publications, many people are unaware that gliding is even a sport. Without this knowledge the public may have a poor understanding of how flying without an engine is possible and safe.
*Increasing costs: due to higher costs of fuel and insurance, and due to greater regulation requiring equipment such as new radios, or in some cases
transponder
In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend word, blend of ''transmitter'' and ''responder''.
In air navigation or radio frequency identification, a T ...
s, gliding costs have increased, although without the continuous use of engines and fuel, they are still considerably lower than traditional power flying.
Related air sports
The two air sports that are most closely related to gliding are
hang gliding
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...
and
paragliding
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure. The pilot sits in a harness or lies supine in a cocoon-like 'po ...
. Although all three sports rely on rising air, there are significant differences which are listed in detail in
a comparison of sailplanes hang gliders and paragliders. The main difference is that both hang gliders and paragliders are simpler, less sophisticated and cheaper aircraft that use the pilot's feet as the undercarriage. All paragliders and most hang gliders have no protective structure around the pilot. However, the dividing line between basic gliders and sophisticated hang-gliders is becoming less distinct. For example, hang gliders typically use fabric wings, shaped over a framework, but hang gliders with rigid wings and three-axis controls are also available. The lower air speeds and lower glide ratios of typical hang gliders means that shorter cross-country distances are flown than in modern gliders. Paragliders are more basic craft. They are also foot-launched, but their wings usually have no frames and their shape is created by the flow and pressure of air. The airspeeds and glide ratios of paragliders are generally lower still than the typical hang gliders, and so their cross-country flights are even shorter.
Radio-controlled gliding uses scale-models of gliders mainly for ridge soaring; however thermic aeromodelling craft are also used.
[
]
See also
*
Glider (sailplane)
A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding (also called soaring). This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailpla ...
*
Glossary of gliding and soaring
This is a Wikipedia:Manual of Style (glossaries), glossary of acronyms, initialisms and terms used for gliding and soaring. This is a specialized subset of broader aviation, aerospace, and aeronautical terminology. Additional definitions can be fou ...
*
Flying and gliding animals
A number of animals are capable of aerial locomotion, either by powered flight or by gliding. This trait has appeared by evolution many times, without any single common ancestor. Flight has evolved at least four times in separate animals: inse ...
*
List of notable glider pilots
This list of notable glider pilots contains the names of those who have achieved fame in gliding and in other fields:
Notable in gliding
* Ruth Alexander - female altitude record breaker, first woman glider instructor in the U.S.
* Sergei Anokhin ...
Notes
References
Further reading
*
*
*
External links
Gliding at FAI
{{Authority control
Former Summer Olympic sports
Air sports
Articles containing video clips