Gliding
Gliding isrecreational activitycompetitive sport where individuals fly un-powered aeroplanes usually called gliders or sailplanes. Properly, however, "gliding" isterm used fordescending flightany heavier-than-air craft, when its own weightits sole motive force. Whencraft gains altitude or speed fromatmosphere duringflight,correct term"soaring".
Recreation or sport?
While recreational glider enthusiasts enjoyfreedom, scenic views,sheer enjoymentcontrollingplanes, others concentrate on building their own craft, while still others flycompetitions, wheregoal iscomplete circuit around designated "turning-points", as quickly as possible. These competitions testpilot's (andco-pilot,two-seater gliders) abilityrecognisemake uselocal weather conditions as well as their flying skillsnavigational abilities. Therealso glider aerobatics competitions.History
All developmentsheavier-than-air flight between 1853 (Sir George Cayley's coachman),1903 (Wright brothers) involved gliders (See HistoryAviation). However,sportgliding only emerged afterFirst World War, andreasonits development can be traced toTreatyVersailles. The peace settlement imposed severe restrictions onmanufactureusesingle-seater powered aeroplanesGermany. Thus, in1920s1930s, while aviatorsaircraft makers inrest ofworld were workingimproveperformance powered aeroplanes,Germans were designing, developingflying ever more efficient gliders,discovering waysusingnatural forces inatmospheremake them fly furtherfaster. The first German gliding competition was held atWasserkuppe1920, organised by Oskar Ursinus,ten years later had become an international event. The sport has since taken holdmany countries, not only those offering large areasrelatively flat land but also those whereterrain provides more challenging flying. Germany, however, remainsworld centregliding, as evinced byfact that allmajor glider manufacturersbasedthat country.Soaring
Soaringusually achieved by flying throughmassair thatascending as fast or faster thansailplanedescending,thus gaining potential energy. The most commonly exploited rising massesair thermals (updraftshot ground layer air caused by local differencesair temperature), ridge lift (found wherewind blows againstface ofhillis forcedrise),wave lift (standing waves inatmosphere, analogous toripples onsurface ofstream). Ridge lift rarely allows pilotsclimb much higher than about 2,000 ft (600 m); thermals, depending onclimateterrain, can exceed 10,000 ft (3 000 m)flat countrymuch higher inmountains; wave lift has allowed glidersachieve altitudes approaching 50,000 ft (15 000 m).On rare occasions, glider pilots have been ableusetechnique called "dynamic soaring", wheresailplane can be madegain kinetic energy by repeatedly crossingboundary between air massesdifferent horizontal velocity. However, such zoneshigh "wind gradient"usually much too lowbe used safely by aircraft,dynamic soaring istechnique only really usefulbirds, notably toalbatrosses who duringmigrations can be seen repeatedly pulling up, turning,diving back down throughwind gradient close tosurface ofocean.
In thermal flight,glider pilot attemptsfind streamsair thatmoving upwards asresultbeing heated by contactsun-lit earth. Typical spotsfind thermalsover freshly ploughed fieldsasphalt roads, however most oftime thermalshardassociateany feature onground. Asrequires rising heated air, thermallingtypically only effectivemid-latitudes from spring through into late summer, other latitudes tendhave vertical air temperatures-gradients suppressing thermal convection,during winter theretoo little solar heatstart thermals. Oncethermalencountered,pilot banks sharplykeepplane turning insmall circle withinthermal. This way gliders can ride upward untilthermal either entersclouds base (see Visual Flight Rules) orwarmer air layer calledCapping inversion stopsfrom rising any further.
Ridge running instead looksair thatbeing mechanically lifted asflows upsideshills or other vertical changes inlandscape (including buildingssome cases). Ridge running worksany climate or weather, but can only be usedcertain locations. Oftencombinationridgethermal glidingused. Ridge lift can kick off strong thermals.
Mountain wave flying isvariationridge-running allowinggliderclimb much higher. Most sailplane altitude records were set by flying large scale mountain waves intop flowlong mountain ranges all overworld. The current world distance record3008 km by Klaus Ohlmann (on 21 jan 2003) was also flown inmountain waveSouth America.
Glider pilots learnspotcharacteristic cloud formations that usually accompany zonesrising air or "lift". Well-formed cumulus clouds (the fluffy, cotton-wool typecloud)sharply defined flat bases often form attopsstrong thermals,long, stationary lenticular (lens-shaped) clouds, perpendicular towind direction, frequently markcrestsatmospheric waves.
Launch methods
Glidersinitially launched intoair by oneseveral methods, most commonly "aerotowing" (being towed behindpowered aircraft by means ofdetachable cable) or "winching" (usingstationary ground-based winch possibly mounted onheavy vehicle). Other less common methods"auto-towing" (towing behindcar or truck), "reverse auto-towing" (like auto-towing exceptlaunch cablethreaded throughfixed pulley at one end ofairfield, sotruckdriving towardsaircraft)"bungy-launching" (propulsion fromsteep hillside using an elastic rope).Sailplanesnormally launched by aero-tow withsingle engine tow-plane. Lately, strong self-launching motor glidersmicrolight planes have also been permittedtow gliders. A very economical methodlaunching gliders isuse oftruck-mounted diesel-engine purpose-built winch. (Launch costsabout EUR 3an ordermagnitude less comparedan aero-tow.) The winch pulls in1000-1200msteel rope attached tosailplane, which releasesropeabout 400-500m altitude after an amazingly shortsteep ride comparable torocket lauch. This methodprevalentgliding clubs all over Germany orNetherlands.
Outlandings
Outlandingscommoncross country gliding. Theseoften mistaken'emergency landings'. Theyentirely normal, althoughhassle. When this happens, eitherpilot's ground crewcalled inretrievesplane inpurpose-built trailer which can easily be towed bycar, or,some larger countries like Australia,towing planesend inrelaunchplane. To avoid this time consuming hassle, some modern more expensive gliders havevery light retractable propeller/two-stroke engine, too lightself take off but enoughallow themreturntheir home airfield.Related sports
Two minimalistic variations ofsporthang gliding, where instead offully-fledged planefull control surfacesan enclosed cockpitcraft usedbasicallyfabric flying wing,paragliding, wheresophisticated kindparachuteflown.
See also: glider
