资源描述：
《直升机英语介绍》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、Howisahelicoptermade?BackgroundHelicoptersareclassifiedasrotarywingaircraft,andtheirrotarywingiscommonlyreferredtoasthemainrotororsimplytherotor.Unlikethemorecommonfixedwingaircraftsuchasasportbiplaneoranairliner,thehelicopteriscapableofdirectverticaltake-offandlanding;itcanals
2、ohoverinafixedposition.Thesefeaturesrenderitidealforusewherespaceislimitedorwheretheabilitytohoveroverapreciseareaisnecessary.Currently,helicoptersareusedtodustcrops,applypesticide,accessremoteareasforenvironmentalwork,deliversuppliestoworkersonremotemaritimeoilrigs,takephotogr
3、aphs,filmmovies,rescuepeopletrappedininaccessiblespots,transportaccidentvictims,andputoutfires.Moreover,theyhavenumerousintelligenceandmilitaryapplications.Numerousindividualshavecontributedtotheconceptionanddevelopmentofthehelicopter.Theideaappearstohavebeenbionicinorigin,mean
4、ingthatitderivedfromanattempttoadaptanaturalphenomena—inthiscase,thewhirling,bifurcatedfruitofthemapletree—toamechanicaldesign.Earlyeffortstoimitatemaplepodsproducedthewhirligig,achildren'stoypopularinChinaaswellasinmedievalEurope.Duringthefifteenthcentury,LeonardodaVinci,there
5、nownedItalianpainter,sculptor,architect,andengineer,sketchedaflyingmachinethatmayhavebeenbasedonthewhirligig.Thenextsurvivingsketchofahelicopterdatesfromtheearlynineteenthcentury,whenBritishscientistSirGeorgeCayleydrewatwin-rotoraircraftinhisnotebook.Duringtheearlytwentiethcent
6、ury,FrenchmanPaulCornumanagedtolifthimselfoffthegroundforafewsecondsinanearlyhelicopter.However,Cornuwasconstrainedbythesameproblemsthatwouldcontinuetoplagueallearlydesignersforseveraldecades:noonehadyetdevisedanenginethatcouldgenerateenoughverticalthrusttoliftboththehelicopter
7、andanysignificantload(includingpassengers)offtheground.IgorSikorsky,aRussianengineer,builthisfirsthelicopterin1909.Whenneitherthisprototypenorits1910successorsucceeded,Sikorskydecidedthathecouldnotbuildahelicopterwithoutmoresophisticatedmaterialsandmoney,sohetransferredhisatten
8、tiontoaircraft.DuringWorldWarI,HungarianengineerTheodo
