Ground effect
Ground effect (or Wing In Ground effect) isphenomenonaerodynamics whereflowair around partan aircraft orracing carinterrupted byground.Ground effectaircraft
Aircraft obtain increased lifttherefore better efficiency by flying very close toground: onfixed-wing monoplane, about halfdistance fromwingtip tofuselage. Ground effect therefore affects most aircraft only at takeofflanding.
Most pilots, especiallysmall aircraft, will experience ground effects on landing -factartlanding largely comes downunderstanding when these effects needbe taken into account. Asaircraft descends towardsrunway,will not be affected by ground effect, but asaircraft flaresdescendslast few feet, ground effect will causepronounced increaselift. This can causeaircraftrise suddenlysignificantly - an effect known as"balloon". Left uncorrected,balloon can lead todangerous situation whereaircraftrising yet decelerating,condition which can rapidly lead tostall, especially when itconsidered that landing speedsgenerally onlyvery small margin abovestall speed. A stall even fromfew tensfeet aboveground can causemajor, possibly fatal, crash. A balloon may be corrected given sufficient runway remaining, butnovice pilotsbetter option isgo around. A good landing approach allowsground effect such thataircraft flaresis held offground effect untilgently decends ontorunway.
Hovercraft rely onground effectfly.
Ground effectcars
In racing cars,designer's aimnotincreased lift butincreased downforce, allowing greater cornering speeds. (By1970s 'wings', or inverted aerofoils, were routinely used indesignracing carsincrease downforce, but thisnot ground effect.)
However, substantial further downforceavailable by understandinggroundbe part ofaerodynamic systemquestion. The basic idea iscreatevolumelow pressure underneathcar, which suckscar toroad. Naturally,maximizeforce one wantsmaximal volume atminimal pressure. Racing car designers have achieved low pressuretwo ways: first, by usingfansuck air out ofcavity; second,designunderside ofcar as an inverted aerofoil so that large amountsincoming airaccelerated throughnarrow slot betweencar andground, lowering pressure by Bernoulli's principle. Official regulations currently (2003) disallow ground effectsmany typesracing, such as Formula One.
Jim Hall (engineer),first car aerodynamicistharness downforce, built Chaparral carsboth these principles. His 1961 car attempteduseshaped underside method but there were too many other aerodynamic problems withcaritwork properly. His 1966 cars useddramatic high wingtheir downforce. His Chapparal 2J "sucker car"1970 was revolutionary. It had two fans atrear ofcar driven bydedicated two-stroke engine;also had "skirts", which left onlyminimal gap between carground, so assealcavity fromatmosphere. Althoughdid not quite winrace,competition lobbiedits ban, which came into place atendthat year. Movable aerodynamic devices were banned from most branches ofsport.
Formula 1 inlate 1970s wasnext settingground effectracing cars. In 1977 Lotus brought out their "Wing Car",Lotus 78, designed by Peter Wright, Colin Chapman,Tony Rudd. Its sidepods, bulky constructions between frontrear wheels, were shaped as inverted aerofoilssealedflexible "skirts" toground. The team won 5 races that year,21978 whiledevelopedmuch improved Lotus 79. The most notable contender1978 wasBrabham BT46B "fan car", designed by Gordon Murray. Its fan, spinning onhorizontal, longitudinal axis atback ofcar, took its power frommain gearbox. The car avoidedsporting ban by claims thatfan's purpose wasengine cooling. It raced just once,Niki Lauda winning atSwedish Grand Prix. The team though, led by Bernie Ecclestone who had recently become president ofFormula One Constructors Association, withdrewcar beforehadchancebe banned. The Lotus 79, onother hand, went onwin 6 races andworld championshipMario Andretti. In following years other teams copiedimproved onLotus until, afterseriesfatal accidents, flat undersides became mandatory from 1983 .
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