直升机的英文

Howisahelicoptermade?

Background

Helicoptersareclassifiedasrotarywingaircraft,andtheirrotarywingiscommonly

themorecommonfixedwing

aircraftsuchasasportbiplaneoranairliner,thehelicopteriscapableofdirectvertical

take-offandlanding;eaturesrenderitidealfor

uwherespaceislimitedorwheretheabilitytohoveroverapreciareaisnecessary.

Currently,helicoptersareudtodustcrops,applypesticide,accessremoteareasfor

environmentalwork,deliversuppliestoworkersonremotemaritimeoilrigs,take

photographs,filmmovies,rescuepeopletrappedininaccessiblespots,transportaccident

victims,er,theyhavenumerousintelligenceandmilitary

applications.

Numerousindividualshavecontributedtotheconceptionanddevelopmentofthe

aappearstohavebeenbionicinorigin,meaningthatitderivedfroman

attempttoadaptanaturalphenomena—inthisca,thewhirling,bifurcatedfruitofthe

mapletree—ffortstoimitatemaplepodsproducedthe

whirligig,achildren'the

fifteenthcentury,LeonardodaVinci,therenownedItalianpainter,sculptor,architect,and

engineer,t

survivingsketchofahelicopterdatesfromtheearlynineteenthcentury,whenBritish

theearly

twentiethcentury,FrenchmanPaulCornumanagedtolifthimlfoffthegroundforafew

r,Cornuwasconstrainedbythesameproblems

thatwouldcontinuetoplagueallearlydesignersforveraldecades:noonehadyet

devidanenginethatcouldgenerateenoughverticalthrusttoliftboththehelicopterand

anysignificantload(includingpasngers)offtheground.

IgorSikorsky,aRussianengineer,itherthis

prototypenorits1910successorsucceeded,Sikorskydecidedthathecouldnotbuilda

helicopterwithoutmoresophisticatedmaterialsandmoney,sohetransferredhisattention

WorldWarI,HungarianengineerTheodorevonKarmanconstructeda

helicopterthat,whentethered,lyearslater,

SpaniardJuandelaCiervadevelopedamachinehecalledanautogiroinrespontothe

tende

coulddesignanaircraftinwhichliftandthrust(forwardspeed)wereparatefunctions,

Ciervaspeculated,ogirohesubquently

inventedincorporatedfeaturesofboththehelicopterandtheairplane,althoughit

ogirohadarotorthatfunctionedsomethinglikea

tinmotionbytaxiingontheground,therotorcouldgenerate

supplementallift;however,theautogirowaspoweredprimarilybyaconventionalairplane

dlandingproblems,theenginecouldbedisconnectedandtheautogiro

broughtgentlytorestbytherotor,whichwouldgraduallyceaspinningasthemachine

rduringthe1920sand1930s,autogirosceadtobe

producedaftertherefinementoftheconventionalhelicopter.

esinaerodynamic

theoryandbuildingmaterialshadbeenmadesinceSikorsky'sinitialendeavor,and,in

1939,rslater,an

improveddesignenabledhimtoremainaloftforanhourandahalf,ttingaworldrecord

forsustainedhelicopterflight.

Thehelt

wasnotutilizedextensivelyduringWorldWarII,thejungleterrainofbothKoreaand

Vietnampromptedthehelicopter'swidespreaduduringbothofthowars,and

technolog

recentyears,however,privateindustryhasprobablyaccountedforthegreatestincrea

inhelicopteru,asmanycompanieshavebeguntotransporttheirexecutivesvia

tion,helicoptershuttlerviceshaveproliferated,particularlyalongthe

,amongciviliansthehelicopterremains

bestknownforitsmedical,rescue,andreliefus.

Design

Ahelicopter'spowercomesfromeitherapistonengineoragasturbine(recently,the

latterhaspredominated),whichmovestherotorshaft,

standardplanegeneratesthrustbypushingairbehinditswingasitmovesforward,the

helicopter'

proportionaltothechangeintheair'smomentum(itsmasstimesitsvelocity):thegreater

themomentum,thegreaterthelift.

Helicopterrotorsystemsconsistofbetweentwoandsixbladesattachedtoacentralhub.

Usuallylongandnarrow,thebladesturnrelativelyslowly,becauthisminimizesthe

amountofpowernecessarytoachieveandmaintainlift,andalsobecauitmakes

ight-weight,general-purpohelicoptersoftenhavea

two-bladedmainrotor,heaviercraftmayuafour-bladedesignortwoparatemain

rotorstoaccommodateheavyloads.

Tosteerahelicopter,thepilotmustadjustthepitchoftheblades,whichcanbetthree

ollectivesystem,thepitchofallthebladesattachedtotherotorisidentical;

inthecyclicsystem,thepitchofeachbladeisdesignedtofluctuateastherotorrevolves,

thehelicopterinany

direction,thepilotmovestheleverthatadjustscollectivepitchand/orthestickthatadjusts

cyclicpitch;itmayalsobenecessarytoincreaorreducespeed.

Unlikeairplanes,whicharedesignedtominimizebulkandprotuberancesthatwould

weighthecraftdownandimpedeairflowaroundit,helicoptershaveunavoidablyhighdrag.

Thus,designershavenotutilizedthesortofretractablelandinggearfamiliartopeople

whohavewatchedplanestakingofforlanding—theaerodynamicgainsofsuchasystem

ral,helicopterlandinggearis

sthelatterrequirelongrunwaysonwhichto

reduceforwardvelocity,helicoptershavetoreduceonlyverticallift,whichtheycandoby

,theydon'tevenrequireshockabsorbers:theirlanding

gearusuallycomprisonlywheelsorskids,orboth.

Oneproblemassociatedwithhelicopterrotorbladesoccursbecauairflowalongthe

ansthatliftanddragfluctuateforeachblade

throughouttherotationalcycle,therebyexertinganunsteadyinginfluenceuponthe

edproblemoccursbecau,asthehelicoptermovesforward,thelift

beneaththebladesthatentertheairstreamfirstishigh,butthatbeneaththebladesonthe

effectoftheproblemsistodestabilizethe

lly,themeansofcompensatingfortheunpredictablevariationsinlift

sign

allowachbladetoshiftupordown,adjustingtochangesinliftanddrag.

Torque,anotherproblemassociatedwiththephysicsofarotatingwing,causthe

helicopterfulage(cabin)torotateintheoppositedirectionfromtherotor,especially

etthisreaction,many

helicoptersuatailrotor,anexpodbladeorductedfanmountedontheendofthetail

rmeansofcounteractingtorqueentails

installingtworotors,attachedtothesameenginebutrotatinginoppositedirections,while

athird,morespace-efficientdesignfeaturestwinrotorsthatareenmeshed,something

onalalternativeshavebeenrearched,andatleastone

NOTAR(notailrotor)designhasbeenintroduced.

RawMaterials

Theairframe,orfundamentalstructure,ofahelicoptercanbemadeofeithermetalor

organiccompositematerials,performance

requirementswillinclinethedesignertofavorcompositeswithhigherstrength-to-weight

ratio,oftenepoxy(aresin)reinforcedwithglass,aramid(astrong,flexiblenylonfiber),or

lly,acompositecomponentconsistsofmanylayersof

fiber-impregnatedresins,randsheetmetal

substructuresareusuallymadeofaluminum,thoughstainlesssteelortitaniumare

litatebendingduringthe

manufacturingprocess,thestructuraltubingisoftenfilledwithmoltensodiumsilicate.A

helicopter'srotarywingbladesareusuallymadeoffiber-reinforcedresin,whichmaybe

icopter's

windscreenandwindowsareformedofpolycarbonatesheeting.

TheManufacturing

Process

Airframe:Preparingthetubing

Eachindividualtubularpartiscutbyatubecuttingmachinethatcanbequicklytto

producedifferent,requiringangular

bendsisshapedtotheproperangleinabendingmachinethatutilizesinterchangeable

erthanminorbends,tubesarefilledwith

moltensodiumsilicatethathardensandeliminateskinkingbycausingthetubetobendas

-calledwaterglassisthenremovedbyplacingthebenttubeinboiling

water,thatmustbecurvedtomatchfulage

contoursisfittedoverastretchformingmachine,whichstretchesthemetaltoaprecily

,thetubulardetailsaredeliveredtothemachineshopwherethey

areheldinclampssothattheirendscanbemachinedtotherequiredangleandshape.

Thetubesarethendeburred(aprocessinwhichanyridgesorfinsthatremainafter

preliminarymachiningaregroundoff)andinspectedforcracks.

Gusts(reinforcingplatesorbrackets)andotherreinforcingdetailsofmetalare

machinedfromplate,angle,orextrudedprofilestockbyrouting,shearing,blanking,or

ter

proces

thetemplatehasbeenformed,itisdippedinmoltenmetalasmanytimesasnecessaryto

eparthasdried,itisheatedsothatthewaxor

toahighertemperaturetopurifyitand

placedinamoldboxwhereitissupportedbysand,themoldisthenreadytoshape

emovalandcooling,thepartsarethen

finish-machinedbystandardmethodsbeforebeingdeburredonceagain.

Thetubesarechemicallycleaned,fittedintoasubasmblyfixture,andMIG(metal-arc

inertgas)process,asmallelectrodewireisfedthroughaweldingtorch,

andaninert,shieldinggas(usuallyargonorhelium)ispasdthroughanozzlearoundit;

elding,thesubasmblyisstress

relieved—heatedtoalowtemperaturesothatthemetalcanrecoveranyelasticityithas

y,theweldsareinspectedforflaws.

Formingsheetmetaldetails

Sheetmetal,whichmakesupotherpartsoftheairframe,isfirstcutintoblanks(piecescut

topredeterminedsizeinpreparationforsubquentwork)byabrasivewater-jet,blanking

dies,umblanksareheat-treatedtoannealthem(givethemauniform,

strain-freestructurethatwillincreatheirmalleability).Theblanksarethenrefrigerated

u

forming,thesheetmetaldetailsareagedtofullstrengthandtrimmedbyroutingtofinal

shapeandsize.

Sheetmetalpartsarecleanedbeforebeingasmbledbyrivetingoradhesivebonding.

Aluminumpartsandweldedsubasmbliesmaybeanodized(treatedtothickenthe

protectiveoxidefilmonthesurfaceofthealuminum),whichincreascorrosion

alpartsarechemicallycleanedandprimer-painted,andmostreceive

finishpaintbysprayingwithepoxyorotherdurablecoating.

Makingthecoresofcompositecomponents

Cores,thecentralpartsofthecompositecomponents,aremadeofNomex(abrandof

aramidproducedbyDuPont)oraluminum"honeycomb,"whichiscuttosizebybandsaw

ssary,thecoresthenhavetheiredgestrimmedandbeveled

erialwithwhich

eachcomponentisbuiltupfromitscores(eachcomponentmayumultiplecores)is

esarelayersoforientedfibers,usuallyepoxyorpolyimide,that

ingwritteninstructionsfromthedesigners,

workerscreatehighlycontouredskinpanelsbyttingindividualpliesonbondmoldtools

andsandwichingcoresbetweenadditionalpliesasdirected.

Completedlayups,asthelayersofprepregaffixedtothemoldarecalled,arethen

claveisamachinethatlaminatesplastics

byexposingthemtopressurizedsteam,and"curing"isthehardeningthatoccursasthe

resinlayers"cook"intheautoclave.

Visibletrimlinesaremoldedintothepanelsbyscribelinesprentinthebondmoldtools.

anelsmaybe

nspection,trimmedpanels

aes

mustbewellaledbypainttopreventmetalcorrosionorwaterabsorption.

Makingthefulage

Canopiesorwindscreensandpasngercompartmentwindowsaregenerallymadeof

anelssubjecttobirdstrikeorotherimpactmaybelaminated

hpartsaremadebyplacinganoversizedblank

onafixture,heatingit,andthenformingittotherequiredcurvaturebyuofairpressure

method,notoolsurfacetouchestheopticalsurfacesto

caudefects.

Installingtheengine,transmission,

androtors

Modernhelicopterenginesareturbineratherthanpistontypeandarepurchadfroman

icoptermanufacturermaypurchaorproducethetransmission

asmbly,issioncasaremadeof

aluminumormagnesiumalloy.

Aswiththeabove,themainandtailrotorasmbliesaremachinedfromspecially

lec

torblades

mayhaveasheetmetallayeradhesivelybondedtoprotecttheleadingedges.

Systemsandcontrols

Wiringharnessareproducedbylayingouttherequiredwiresonspecialboardsthat

,orknitted

protectivecovers,areplacedonthewirebundles,andthepurchadconnectorsare

lictubingiitherhand-cuttolengthandhand-formed

bycraftsmen,ormeasured,formned,eflared,

andtubesareinspectedfordimensionalaccuracyandtoensurethatnocracksare

licpumpsandactuators,instrumentation,andelectricaldevicesare

typicallypurchadtospecificationratherthanproducedbythehelicoptermanufacturer.

Finalasmbly

Finishedandinspecteddetailairframeparts,includingsheetmetal,tubular,andmachined

andweldeditems,aredeliveredtosubasmblyjigs(fixturesthatclamppartsbeing

asmbled).Centralpartsarelocatedineachjig,andassociateddetailsareeitherbolted

inplaceor,whererivetsaretobeud,match-drilledusingpneumaticallypowereddrills

odynamicsmoothnessonsheetmetalor

compositeskinpanels,holesarecountersunksothattheheadsofflat-headedscrews

won'ntisoftenappliedin

esituations,mi-automatedmachines

maybeudformovingfromoneholelocationtothenext,drilling,reaming,aling,and

installingtherivetsunderoperatorcontrol.

Aftereachsubasmblyisacceptedbyaninspector,ittypicallymovestoanotherjigtobe

furted

"toplevel"subasmbliesarethendeliveredtofinalasmblyjigs,wheretheoverall

helicopterstructureisintegrated.

Uponcompletionofthestructure,thepropulsioncomponentsareadded,andwiringand

,windows,doors,instruments,andinterior

-paintingandtrimmingare

completedatappropriatepointsduringthisprocess.

Afterallsystemsareinspectedinfinalform,alongwithphysicalasmbliesand

appearanceaspects,thecompletedocumentationofmaterials,process,inspection,

icopter

propulsionsystemistested,andtheaircraftisflight-tested.