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1、Bell407HelicopterDocumentationINTRODUCTIONTOROTARY-WINGAERODYNAMICSYou’reabouttoembarkonanentirelynewareaofflight:thehelicopter.Althoughflyingahelicoptermaynotbeinherentlymoredifficultthanflyingafixed-wingairplane(afterall,lookatallthehigh-schoolgradswholearnedtoflythemverywellduring
2、theVietnamera),itcanbeverydifferent.Infact,itcanbesodifferentthat,giventhechoice,manyhelicopterinstructors(includingme)finditeasiertoteachsomeonetoflyahelicopterfromscratchthantocross-trainafixed-wingairplanepilot.Thatbeingsaid,however,therearequiteafewparallels—particularlyifyoulook
3、atthehelicopterinthemostliteralinterpretationofitsgenericname:arotary-wingaircraft.Likeanyotherheavier-than-airmachine,ahelicopterfliesbecauseofitswings.Takenindividually,arotorbladeisnothingmorethanaskinnywingflyingataveryhighairspeed;and,takenindividually,itobeysexactlythesameaerod
4、ynamicrulesandprinciplesasanyotherwing.Likeanyotherwing,itcanglidewithoutpowerifnecessary;likeanyotherwing,itcanbestalled.It’swhenweexaminethiswinginthecontextofahelicopter,onwhichit’sspinningaround,thatthingsbecomeabitmorecomplex;andtheybecomemorecomplexyetwhenwestartlookingatthehel
5、icopterasawhole,andthewayitsvariousdynamiccomponentsinteractbothwiththeatmosphereandwitheachother.ALITTLEHISTORY:Thedreamofaheavier-than-airmachinecapableofhoveringmotionlessintheairhasbeenwithusatleastsincethedaysofLeonardodaVinci(ifnot,indeed,sincethefirsttimesomecavemanwatchedahum
6、mingbird).Withtheappearanceofthegasolinethengineinthelate19century,apowersourcewasfinallyavailablethatwasbothlightandstrongenoughtoallowforsomeseriousexperimentation.BythetimeoftheFirstWorldWar,afewexperimentaltestrigs(withrigidrotorlikehorizontalpropellers)hadactuallymanagedtoheavet
7、hemselvesacoupleoffeetoffthegroundforafewmomentsatatime.Somecouldevenhover,afterafashion—but,invariably,assoonastheyattemptedtomovehorizontallyatanykindofspeed,theybecameuncontrollable.Itwasn’tuntilafterWorldWarIthataSpaniard,JuandelaCierva,realizedthatthebladesofanysortofliftingroto
8、rorpropeller
