"FactsforMotorists，"etc.etc.
　　AND
　　THOS.H.RUSSELL，A.M.，M.E.，CharterMemberoftheAeroClubofIllinois，Authorof"HistoryoftheAutomobile，""MotorBoats：ConstructionandOperation，"etc.etc.
　　WITHINTRODUCTORYCHAPTERBY
　　OCTAVECHANUTE，C.E.，PresidentAeroClubofIllinois1912
　　PREFACE.
　　Thisbookiswrittenfortheguidanceofthenoviceinaviation——themanwhoseekspracticalinformationastothetheory，constructionandoperationofthemodernflyingmachine.Withthisobjectinviewthewordingisintentionallyplainandnon—technical.Itcontainssomepropositionswhich，sofarassatisfyingtheexpertsisconcerned，mightdoubtlessbebetterstatedintechnicalterms，butthiswoulddefeatthemainpurposeofitspreparation.
　　Consequently，whilefullyawareofitsshortcomingsinthisrespect，theauthorshavenoapologiestomake.
　　Inthestatingofatechnicalpropositionsoitmaybeclearlyunderstoodbypeoplenotversedintechnicalmattersitbecomesabsolutelynecessarytouselanguagemuchdifferentfromthatwhichanexpertwouldemploy，andthishasbeendoneinthisvolume.
　　Nomanofordinaryintelligencecanreadthisbookwithoutobtainingaclear，comprehensiveknowledgeofflyingmachineconstructionandoperation.Hewilllearn，notonlyhowtobuild，equip，andmanipulateanaeroplaneinactualflight，butwillalsogainathoroughunderstandingoftheprincipleuponwhichthesuspensionintheairofanobjectmuchheavierthantheairismadepossible.
　　Thislatterfeatureshouldmakethebookofinteresteventothosewhohavenointentionofconstructingoroperatingaflyingmachine.ItwillenablethemtobetterunderstandandappreciatetheperformancesofthedaringmenliketheWrightbrothers，Curtiss，Bleriot，Farman，Paulhan，Latham，andothers，whoseboldexperimentshavemadeaviationanactuality.
　　Forthosewhowishtoengageinthefascinatingpastimeofconstructionandoperationitisintendedasareliable，practicalguide.
　　Itmaybewelltoexplainthatthesub—headingsinthearticlesbyMr.Chanutewereinsertedbytheauthorswithouthisknowledge.Thepurposeofthiswasmerelytopreserveuniformityinthetypographyofthebook.
　　ThisexplanationismadeinjusticetoMr.Chanute.
　　THEAUTHORS.
　　INMEMORIAM.
　　OctaveChanute，"thefatherofthemodernflyingmachine，"
　　diedathishomeinChicagoonNovember23，1910，attheageof72years.Hislastworkintheinterestofaviationwastofurnishtheintroductorychaptertothefirsteditionofthisvolume，andtorendervaluableassistanceinthehandlingofthevarioussubjects.Heevenmadethetripfromhishometotheofficeofthepublishersoneinclementdaylastspring，tolookovertheproofsofthebookand，athissuggestion，severalimportantchangesweremade.Allthiswas"alaboroflove"onMr.Chanute’spart.Hegaveofhistimeandtalentsfreelybecausehewasenthusiasticinthecauseofaviation，andbecauseheknewtheauthorsofthisbookanddesiredtogivethemmaterialaidinthepreparationofthework——afavorthatwasmostsincerelyappreciated.
　　Theauthorsdesiretomakeacknowledgmentofmanycourtesiesinthewayofvaluableadvice，information，etc.，extendedbyMr.
　　OctaveChanute，C.E.，Mr.E.L.Jones，EditorofAeronautics，andthepublishersof，theNewEnglandAutomobileJournalandFly.
　　CONTENTS
　　ChapterI.EvolutionoftheTwo—SurfaceFlyingMachineIntroductoryChapterbyOctaveChanute，C.E.
　　II.TheoryDevelopmentandUseOriginoftheAeroplane——DevelopmentsbyChanuteandtheWrights——PracticalUsesandLimits.
　　III.MechanicalBirdActionWhattheMotorDoes——PuzzleinBirdSoaring.
　　IV.VariousFormsofFlyingMachinesHelicopters，OrnithoptersandAeroplanes——
　　Monoplanes，BiplanesandTriplanes.
　　V.ConstructingaGlidingMachinePlansandMaterialsRequired——EstimateofCost——
　　SizesandPreparationofVariousParts——PuttingthePartsTogetherVI.LearningtoFlyHowtoUsetheGlider——EffectofBodyMovements——RulesforBeginners——SafestPlacetoGlide.
　　VII.PuttingOntheRudderItsConstruction，ApplicationandUse.
　　VIII.TheRealFlyingMachineSurfaceAreaRequired——ProperSizeofFrameandAuxiliaries——InstallationofMotor——CostofConstructingMachine.
　　IX.SelectionoftheMotorEssentialFeatures——MultiplicityofCylinders——PowerRequired——KindandActionofPropellers——PlacingoftheMotorX.ProperDimensionsofMachinesFiguringOuttheDetails——HowtoEstimateLoadCapacity——DistributionoftheWeight——MeasurementsofLeadingMachines.
　　XI.PlaneandRudderControlVariousMethodsinUse——WheelsandHandandFootLeversXII.HowtoUsetheMachineRulesofLeadingAviators——RisingfromtheGround——ReasonableAltitude——PreservingEquilibrium——
　　LearningtoSteer.
　　XIII.PeculiaritiesofAeroplanePowerPressureoftheWind——HowtoDetermineUponPower——WhySpeedIsRequired——BirdfindFlyingMachineAreas.
　　XIV.AboutWindCurrents，Etc.
　　UncertaintyofDirectForce——TroubleWithGustyCurrents——WhyBirdActionIsImitated.
　　XV.TheElementofDangerRiskSmallUnderProperConditions——TwoFieldsofSafety——LessonsinRecentAccidents.
　　XVI.RadicalChangesBeingMadeResultsofRecentExperiments——NewDimensions——IncreasedSpeed——TheOneGoverningRule.
　　XVII.SomeoftheNewDesigns？AutomaticControlofPlaneStability——InventorHerring’sDevices——NovelIdeasofStudents.
　　XVIII.DemandforFlyingMachinesWonderfulResultsinaYear——FactoriesOver—
　　crowdedwithOrders.
　　XIX.LawoftheAirshipRightsofPropertyOwners——SomeLegalPeculiarities——DangerofTrespass.
　　XX.SoaringFlightXXI.FlyingMachinesvs.BalloonsXXII.ProblemsofAerialFlighXXIII.AmateursMayUseWrightPatentsXXIV.HintsonPropellerConstructionXXV.NewMotorsandDevicesXXVI.Monoplanes，Triplanes，MultiplanesXXVII.RecordsofVariousKindsFLYINGMACHINES：CONSTRUCTIONandOPERATION
　　CHAPTERI.
　　EVOLUTIONOFTWO—SURFACEFLYINGMACHINE.
　　ByOctaveChanute.
　　Iamaskedtosetforththedevelopmentofthe"two—
　　surface"typeofflyingmachinewhichisnowusedwithmodificationsbyWrightBrothers，Farman，[1]Delagrange，Herringandothers.
　　[1]Nowdead.
　　ThistypeoriginatedwithMr.F.H.Wenham，whopatenteditinEnglandin1866（No.1571），takingoutprovisionalpapersonly.IntheabridgmentofBritishpatentAeronauticalSpecifications（1893）itisdescribedasfollows：
　　"Twoormoreaeroplanesarearrangedoneabovetheother，andsupportaframeworkorcarcontainingthemotivepower.Theaeroplanesaremadeofsilkorcanvasstretchedonaframebywoodenrodsorsteelribs.
　　Whenmanualpowerisemployedthebodyisplacedhorizontally，andoarsorpropellersareactuatedbythearmsorlegs.
　　"Astartmaybeobtainedbyloweringthelegsandrunningdownhillorthemachinemaybestartedfromamovingcarriage.Oneormorescrewpropellersmaybeappliedforpropellingwhensteampowerisemployed.
　　OnJune27，1866，Mr.Wenhamreadbeforethe"AeronauticalSocietyofGreatBritain，"thenrecentlyorganized，theablestpapereverpresentedtothatsociety，andtherebybreathedintoitaspiritwhichhascontinuedtothisday.Inthispaperhedescribedhisobservationsofbirds，discussedthelawsgoverningflightastothesurfacesandpowerrequiredbothwithwingsandscrews，andhethengaveanaccountofhisownexperimentswithmodelsandwithaeroplanesofsufficientsizetocarrytheweightofaman.
　　SecondWenhamAeroplane.
　　Hissecondaeroplanewassixteenfeetfromtiptotip.
　　Atrussedsparatthebottomcarriedsixsuperposedbandsofthinhollandfabricfifteenincheswide，connectedwithverticalwebsofhollandtwofeetapart，thusvirtuallygivingalengthofwingofninety—sixfeetandonehundredandtwentysquarefeetofsupportingsurface.
　　Themanwasplacedhorizontallyonabaseboardbeneaththespar.Thisapparatuswhentriedinthewindwasfoundtobeunmanageablebyreasonoftheflutteringmotionsofthefabric，whichwasinsufficientlystiffenedwithcrinolinesteel，butMr.Wenhampointedoutthatthisinnowayinvalidatedtheprincipleoftheapparatus，whichwastoobtainlargesupportingsurfaceswithoutincreasingundulytheleverageandconsequentweightofsparrequired，bysimplysuperposingthesurfaces.
　　Thisprincipleisentirelysoundanditissurprisingthatitis，tothisday，notrealizedbythoseaviatorswhoarehankeringformonoplanes.
　　ExperimentsbyStringfellow.
　　ThenextmantotestanapparatuswithsuperposedsurfaceswasMr.Stringfellow，who，becomingmuchimpressedwithMr.Wenham’sproposal，producedalargishmodelattheexhibitionoftheAeronauticalSocietyin1868.Itconsistedofthreesuperposedsurfacesaggregating28
　　squarefeetandatailof8squarefeetmore.
　　Theweightwasunder12poundsanditwasdrivenbyacentralpropelleractuatedbyasteamengineoverestimatedatone—thirdofahorsepower.Itransuspendedtoawireonitstrialsbutfailedoffreeflight，inconsequenceofdefectiveequilibrium.ThisapparatushassincebeenrebuiltandisnowintheNationalMuseumoftheSmithsonianInstitutionatWashington.
　　Linfield’sUnsuccessfulEfforts.
　　In1878Mr.LinfieldtestedanapparatusinEnglandconsistingofacigar—shapedcar，towhichwasattachedoneachsideframesfivefeetsquare，containingeachtwenty—fivesuperposedplanesofstretchedandvarnishedlineneighteenincheswide，andonlytwoinchesapart，thusremindingoneofaSpanishdonkeywithpanniers.
　　Thewholeweighedtwohundredandfortypounds.Thiswastestedbybeingmountedonaflatcarbehindalocomotivegoing40milesanhour.Whentowedbyalinefifteenfeetlongtheapparatusroseonlyalittlefromthecarandexhibitedsuchunstableequilibriumthattheexperimentwasnotrenewed.Theliftwasonlyaboutone—
　　thirdofwhatitwouldhavebeenhadtheplanesbeenproperlyspaced，saytheirfullwidthapart，insteadofone—ninthaserroneouslydevised.
　　Renard’s"DirigibleParachute."
　　In1889CommandantRenard，theeminentsuperintendentoftheFrenchAeronauticalDepartment，exhibitedattheParisExpositionofthatyear，anapparatusexperimentedwithsomeyearsbefore，whichhetermeda"dirigibleparachute."Itconsistedofanoviformbodytowhichwerepivotedtwouprightslatscarryingabovethebodyninelongsuperposedflatbladesspacedaboutone—thirdoftheirwidthapart.Whenthisapparatuswasproperlysetatanangletothelongitudinalaxisofthebodyanddroppedfromaballoon，ittravelledbackagainstthewindforaconsiderabledistancebeforealighting.Thecoursecouldbevariedbyarudder.NopracticalapplicationseemstohavebeenmadeofthisdevicebytheFrenchWarDepartment，butMr.J.P.
　　Holland，theinventorofthesubmarineboatwhichbearshisname，proposedin1893anarrangementofpivotedframeworkattachedtothebodyofaflyingmachinewhichcombinestheprincipleofCommandantRenardwiththecurvedbladesexperimentedwithbyMr.Phillips，nowtobenoticed，withtheadditionofliftingscrewsinsertedamongtheblades.
　　PhillipsFailsonStabilityProblem.
　　In1893Mr.HoratioPhillips，ofEngland，aftersomeveryinterestingexperimentswithvariouswingsections，fromwhichhededucedconclusionsastotheshapeofmaximumlift，testedanapparatusresemblingaVenetianblindwhichconsistedoffiftywoodenslatsofpeculiarshape，22feetlong，oneandahalfincheswide，andtwoinchesapart，setintenverticaluprightboards.
　　Allthiswascarrieduponabodyprovidedwiththreewheels.Itweighed420poundsandwasdrivenat40
　　milesanhouronawoodensidewalkbyasteamengineofninehorsepowerwhichactuatedatwo—bladedscrew.
　　Theliftwassatisfactory，beingperhaps70poundsperhorsepower，buttheequilibriumwasquitebadandtheexperimentswerediscontinued.Theyweretakenupagainin1904withasimilarapparatuslargeenoughtocarryapassenger，butthelongitudinalequilibriumwasfoundtobedefective.Thenin1907anewmachinewastested，inwhichfoursetsofframes，carryingsimilarsetsofslat"sustainers"wereinserted，andwiththisarrangementthelongitudinalstabilitywasfoundtobeverysatisfactory.Thewholeapparatus，withtheoperator，weighed650pounds.Itflewabout200yardswhendrivenbyamotorof20to22h.p.at30milesanhour，thusexhibitingaliftofabout32poundsperh.p.，whileitwillberememberedthattheaeroplaneofWrightBrothersexhibitsaliftingcapacityof50poundstotheh.p.
　　Hargrave’sKiteExperiments.
　　Afterexperimentingwithverymanymodelsandbuildingnolessthaneighteenmonoplaneflyingmodelmachines，actuatedbyrubber，bycompressedairandbysteam，Mr.LawrenceHargrave，ofSydney，NewSouthWales，inventedthecellularkitewhichbearshisnameandmadeitknowninapapercontributedtotheChicagoConferenceonAerialNavigationin1893，describingseveralvarieties.Themodernconstructioniswellknown，andconsistsoftwocells，eachofsuperposedsurfaceswithverticalsidefins，placedonebehindtheotherandconnectedbyarodorframe.Thisflieswithgreatsteadinesswithoutatail.Mr.Hargrave’sideawastouseateamofthesekites，belowwhichheproposedtosuspendamotorandpropellerfromwhichalinewouldbecarriedtoananchorintheground.Thenbyactuatingthepropellerthewholeapparatuswouldmoveforward，pickuptheanchorandflyaway.Hesaid：
　　"Thenextstepisclearenough，namely，thataflyingmachinewithacresofsurfacecanbesafelygotunderwayoranchoredandhauledtothegroundbymeansofthestringofkites."
　　Thefirsttentativeexperimentsdidnotresultwellandemphasizedthenecessityforalightmotor，sothatMr.
　　Hargravehassincebeenengagedindevelopingone，nothavingconvenientaccesstothosewhichhavebeenproducedbytheautomobiledesignersandbuilders.
　　ExperimentsWithGliderModel.
　　Andhereacuriousreminiscencemaybeindulgedin.
　　In1888thepresentwriterexperimentedwithatwo—cellglidingmodel，preciselysimilartoaHargravekite，aswillbeconfirmedbyMr.Herring.Itwasfrequentlytestedbylaunchingfromthetopofathree—storyhouseandglideddownwardverysteadilyinallsortsofbreezes，buttheangleofdescentwasmuchsteeperthanthatofbirds，andtheweightsustainedpersquarefootwaslessthanwithsinglecells，inconsequenceofthelessersupportaffordedbytherearcell，whichoperateduponairalreadysetinmotiondownwardbythefrontcell，sonothingmorewasdonewithit，foritneveroccurredtothewritertotryitasakiteandhethusmissedthedistinctionwhichattachestoHargrave’sname.
　　SirHiramMaximalsointroducedforeandaftsuperposedsurfacesinhiswondrousflyingmachineof1893，buthereliedchieflyfortheliftuponhismainlargesurfaceandthisnecessitatedsomanyguys，topreventdistortion，asgreatlytoincreasetheheadresistanceandthis，togetherwiththeunstableequilibrium，madeitevidentthatthedesignofthemachinewouldhavetobechanged.
　　HowLilienthalWasKilled.
　　In1895，OttoLilienthal，thefatherofmodernaviation，themantowhosemethodofexperimentingalmostallpresentsuccessesaredue，aftermakingsomethingliketwothousandglideswithmonoplanes，addedasuperposedsurfacetohisapparatusandfoundthecontrolofitmuchimproved.Thetwosurfaceswerekeptapartbytwostrutsorverticalpostswithafewguywires，buttheconnectingjointswereweakandtherewasnothingliketrussing.Thiseventuallycosthismostusefullife.
　　Twoweeksbeforethatdistressinglosstoscience，HerrWilhelmKress，thedistinguishedandveteranaviatorofVienna，witnessedanumberofglidesbyLilienthalwithhisdouble—deckedapparatus.Henoticedthatitwasmuchwrackedandwobblyandwrotetomeaftertheaccident："Theconnectionofthewingsandthesteeringarrangementwereverybadandunreliable.I
　　warnedHerrLilienthalveryseriously.Hepromisedmethathewouldsoonputitinorder，butIfearthathedidnotattendtoitimmediately."
　　Inpointoffact，Lilienthalhadbuiltanewmachine，uponadifferentprinciple，fromwhichheexpectedgreatresults，andintendedtomakebutveryfewmoreflightswiththeoldapparatus.Heunwiselymadeonetoomanyand，likePilcher，wasthevictimofadistortedapparatus.Probablyoneofthejointsofthestrutsgaveway，theuppersurfaceblewbackandLilienthal，whowaswellforwardonthelowersurface，waspitchedheadlongtodestruction.
　　ExperimentsbytheWriter.
　　In1896，assistedbyMr.HerringandMr.Avery，I
　　experimentedwithseveralfullsizedglidingmachines，carryingaman.ThefirstwasaLilienthalmonoplanewhichwasdeemedsocrankythatitwasdiscardedaftermakingaboutonehundredglides，sixweeksbeforeLilienthal’saccident.Thesecondwasknownasthemultiplewingedmachineandfinallydevelopedintofivepairsofpivotedwings，trussedtogetheratthefrontandonepairintherear.Itglidedatanglesofdescentof10or11degreesorofoneinfive，andthiswasdeemedtoosteep.ThenMr.Herringandmyselfmadecomputationstoanalyzetheresistances.Weattributedmuchofthemtothefivefrontsparsofthewingsandonasheetofcross—barredpaperIatoncedrewthedesignforanewthree—deckedmachinetobebuiltbyMr.Herring.
　　Beingabuilderofbridges，Itrussedthesesurfacestogether，inordertoobtainstrengthandstiffness.Whentestedinglidingflightthelowersurfacewasfoundtooneartheground.Itwastakenoffandtheremainingapparatusnowconsistedoftwosurfacesconnectedtogetherbyagirdercomposedofverticalpostsanddiagonalties，specificallyknownasa"Pratttruss."ThenMr.HerringandMr.Averytogetherdevisedandputonanelasticattachmenttothetail.Thismachineprovedasuccess，itbeingsafeandmanageable.Over700glidesweremadewithitatanglesofdescentof8
　　to10degrees，oroneinsixtooneinseven.
　　FirstProposedbyWenham.
　　Theelastictailattachmentandthetrussingoftheconnectingframeofthesuperposedwingsweretheonlynoveltiesinthismachine，forthesuperposingofthesurfaceshadfirstbeenproposedbyWenham，butinaccordancewiththepopularperception，whichbestowsallthecredituponthemanwhoaddsthelasttouchmakingforsuccesstothelaborsofhispredecessors，themachinehassincebeenknownbymanypersonsasthe"Chanutetype"ofgliders，muchtomypersonalgratification.
　　Ithassincebeenimprovedinmanyways.WrightBrothers，disregardingthefashionwhichprevailsamongbirds，haveplacedthetailinfrontoftheirapparatusandcalleditafrontrudder，besidesplacingtheoperatorinhorizontalpositioninsteadofupright，asIdid;andalsoprovidingamethodofwarpingthewingstopreserveequilibrium.FarmanandDelagrange，undertheveryableguidanceandconstructiveworkofVoisinbrothers，thensubstitutedmanydetails，includingaboxtailforthedart—liketailwhichIused.Thismayhaveincreasedtheresistance，butitaddstothesteadiness.NowthetendencyinFranceseemstobetogobacktothemonoplane.
　　MonoplaneIdeaWrong.
　　Theadvocatesofthesinglesupportingsurfaceareprobablymistaken.Itistruethatasinglesurfaceshowsagreaterliftpersquarefootthansuperposedsurfacesforagivenspeed，buttheincreasedweightduetoleveragemorethancounterbalancesthisadvantagebyrequiringheavysparsandsomeguys.Ibelievethatthefutureaeroplanedynamicflierwillconsistofsuperposedsurfaces，and，nowthatithasbeenfoundthatbyimbeddingsuitablyshapedsparsinthecloththeheadresistancemaybemuchdiminished，Iseefewobjectionstosuperposingthree，fourorevenfivesurfacesproperlytrussed，andthusobtainingacompact，handy，manageableandcomparativelylightapparatus.[2]
　　[2]Aeronautics.
　　CHAPTERII.
　　THEORY，DEVELOPMENT，ANDUSE.
　　Whileeverycraftthatnavigatestheairisanairship，allairshipsarenotflyingmachines.Theballoon，forinstance，isanairship，butitisnotwhatisknownamongaviatorsasaflyingmachine.Thislattertermisproperlyusedonlyinreferringtoheavier—than—airmachineswhichhavenogas—bagliftingdevices，andaremadetoreallyflybytheapplicationofenginepropulsion.
　　MechanicalBirds.
　　Allsuccessfulflyingmachines——andthereareanumberofthem——arebasedonbirdaction.Thevariousdesignershavestudiedbirdflightandsoaring，mastereditstechniqueasdevisedbyNature，andthemodernflyingmachineistheresult.Onanexaggerated，enlargedscalethemachineswhicharenownavigatingtheairarenothingmorenorlessthanmechanicalbirds.
　　OriginoftheAeroplane.
　　OctaveChanute，ofChicago，maywellbecalled"thedeveloperoftheflyingmachine."Leavingballoonsandvariousformsofgas—bagsoutofconsideration，otherexperimenters，notablyLangleyandLilienthal，antedatedhiminattemptingthenavigationoftheaironaeroplanes，orflyingmachines，butnoneofthemwerewhollysuccessful，anditremainedforChanutetodemonstratethepracticabilityofwhatwasthencalledtheglidingmachine.Thistermwasadoptedbecausetheapparatuswas，asthenameimplies，simplyaglidingmachine，beingwithoutmotorpropulsion，andintendedsolelytosolvetheproblemofthebestformofconstruction.Thebiplane，usedbyChanutein1896，isstillthebasisofmostsuccessfulflyingmachines，theonlyradicaldifferencebeingthatmotors，rudders，etc.，havebeenadded.
　　CharacterofChanute’sExperiments.
　　ItwastheprivilegeoftheauthorofthisbooktobeMr.Chanute’sguestatMillers，Indiana，in1896，when，incollaborationwithMessrs.HerringandAvery，hewasconductingtheseriesofexperimentswhichhavesincemadepossibletheconstructionofthemodernflyingmachinewhichsuchsuccessfulaviatorsastheWrightbrothersandothersarenowusing.Itwasawildcountry，muchfrequentedbyeagles，hawks，andsimilarbirds.Theenthusiastictrio，Chanute，HerringandAvery，wouldwatchforhourstheevolutionsofsomebigbirdintheair，agreeingintheendontheverdict，"Whenwemastertheprincipleofthatbird’ssoaringwithoutwingaction，wewillhavecomeclosetosolvingtheproblemoftheflyingmachine."
　　AeroplanesofvariousformswereconstructedbyMr.
　　ChanutewiththeassistanceofMessrs.HerringandAveryuntil，atthetimeofthewriter’svisit，theyhadsettleduponthebiplane，ortwo—surfacemachine.Mr.
　　Herringlaterequippedthiswitharudder，andmadeotheradditions，butthegeneralideaisstillthebasisoftheWright，Curtiss，andothermachinesinwhich，bytheaidofgasolenemotors，longflightshavebeenmade.
　　DevelopmentsbytheWrights.
　　In1900theWrightbrothers，WilliamandOrville，whoweretheninthebicyclebusinessinDayton，Ohio，becameinterestedinChanute’sexperimentsandcommunicatedwithhim.TheresultwasthattheWrightstookupChanute’sideasanddevelopedthemfurther，makingmanyadditionsoftheirown，oneofwhichwastheplacingofarudderinfront，andthelocationoftheoperatorhorizontallyonthemachine，thusdiminishingbyfour—fifthsthewindresistanceoftheman’sbody.
　　ForthreeyearstheWrightsexperimentedwiththegliderbeforeventuringtoaddamotor，whichwasnotdoneuntiltheyhadthoroughlymasteredthecontroloftheirmovementsintheair.
　　LimitsoftheFlyingMachine.
　　Intheopinionofcompetentexpertsitisidletolookforacommercialfuturefortheflyingmachine.Thereis，andalwayswillbe，alimittoitscarryingcapacitywhichwillprohibititsemploymentforpassengerorfreightpurposesinawholesaleorgeneralway.Therearesome，ofcourse，whowillarguethatbecauseamachinewillcarrytwopeopleanothermaybeconstructedthatwillcarryadozen，butthosewhomakethiscontentiondonotunderstandthetheoryofweightsustentationintheair;orthatthegreatertheloadthegreatermustbetheliftingpower（motorsandplanesurface），andthatthereisalimittothese——aswillbeexplainedlateron——beyondwhichtheaviatorcannotgo.
　　SomePracticalUses.
　　Atthesametimetherearefieldsinwhichtheflyingmachinemaybeusedtogreatadvantage.Theseare：
　　Sports——Flyingmachineracesorflightswillalwaysbepopularbyreasonoftheelementofdanger.Itisastrange，butneverthelessatrueproposition，thatitisthiselementwhichaddszesttoallsportingevents.
　　Scientific——Forexplorationofotherwiseinaccessibleregionssuchasdeserts，mountaintops，etc.
　　Reconnoitering——Intimeofwarflyingmachinesmaybeusedtoadvantagetospyoutanenemy’sencampment，ascertainitsdefenses，etc.
　　CHAPTERIII.
　　MECHANICALBIRDACTION
　　Inordertounderstandthetheoryofthemodernflyingmachineonemustalsounderstandbirdactionandwindaction.Inthisconnectionthefollowingsimpleexperimentwillbeofinterest：
　　Takeacircular—shapedbitofcardboard，likethelidofahatbox，andremovethebent—overportionsoastohaveaperfectlyflatsurfacewithaclean，sharpedge.
　　Holdingthecardboardatarm’slength，withdrawyourhand，leavingthecardboardwithoutsupport.Whatistheresult？Thecardboard，beingheavierthanair，andhavingnothingtosustainit，willfalltotheground.
　　Pickitupandthrowit，withconsiderableforce，againstthewindedgewise.Whathappens？Insteadoffallingtotheground，thecardboardsailsalongonthewind，remainingafloatsolongasitisinmotion.Itseekstheground，bygravity，onlyasthemotionceases，andthenbyeasystages，insteadofdroppingabruptlyasinthefirstinstance.
　　Herewehaveahomely，butaccurateillustrationoftheactionoftheflyingmachine.Themotordoesforthelatterwhattheforceofyourarmdoesforthecardboard——
　　impartsamotionwhichkeepsitafloat.Theonlyrealdifferenceisthatthemotiongivenbythemotoriscontinuousandmuchmorepowerfulthanthatgivenbyyourarm.Theactionofthelatterislimitedandtheendofitspropulsiveforceisreachedwithinasecondortwoafteritisexerted，whiletheactionofthemotorisprolonged.
　　AnotherSimpleIllustration.
　　Anothersimplemeansofillustratingtheprincipleofflyingmachineoperation，sofarassustentationandtheelevationanddepressionoftheplanesisconcerned，isexplainedintheaccompanyingdiagram.
　　Aisapieceofcardboardabout2by3inchesinsize.
　　BisapieceofpaperofthesamesizepastedtooneedgeofA.Ifyoubendthepapertoacurve，withconvexsideupandblowacrossitasshowninFigureC，thepaperwillriseinsteadofbeingdepressed.Thedottedlinesshowthattheairispassingoverthetopofthecurvedpaperandyet，nomatterhowhardyoumayblow，theeffectwillbetoelevatethepaper，despitethefactthattheairispassingover，insteadofunderthecurvedsurface.
　　InFigureDwehaveanoppositeeffect.HerethepaperisinacurveexactlythereverseofthatshowninFigureC，bringingtheconcavesideup.Nowifyouwillagainblowacrossthesurfaceofthecardtheactionofthepaperwillbedownward——itwillbeimpossibletomakeitrise.Theharderyoublowthegreaterwillbethedownwardmovement.
　　PrincipleInGeneralUse.
　　Thisprincipleistakenadvantageofintheconstructionofallsuccessfulflyingmachines.Makersofmonoplanesandbiplanesalikeadheretocurvedbodies，withtheconcavesurfacefacingdownward.Straightplanesweretriedforatime，butfoundgreatlylackinginthepowerofsustentation.Bycurvingtheplanes，andplacingtheconcavesurfacedownward，asortofinvertedbowlisformedinwhichtheairgathersandexertsabuoyanteffect.Justwhattheratioofthecurveshouldbeisamatterofcontention.Insomeinstancesoneinchtothefootisfoundtobesatisfactory;inothersthisisdoubled，andthereareafewcasesinwhichacurveofasmuchas3inchestothefoothasbeenused.
　　Righthereitmightbewelltoexplainthattheword"plane"appliedtoflyingmachinesofmodernconstructionisinrealityamisnomer.Planeindicatesaflat，levelsurface.Asmostsuccessfulflyingmachineshavecurvedsupportingsurfacesitisclearlywrongtospeakof"planes，"or"aeroplanes."Usage，however，hasmadethetermsconvenientand，astheyaregenerallyacceptedandunderstoodbythepublic，theyareusedinlikemannerinthisvolume.
　　GettingUnderHeadway.
　　Abird，onfirstrisingfromtheground，orbeginningitsflightfromatree，willflapitswingstogetunderheadway.Hereagainwehaveanotherillustrationofthemannerinwhichaflyingmachinegetsunderheadway——
　　themotorimpartstheforcenecessarytoputthemachineintotheair，butrightherethesimilarityceases.
　　Ifthemachineistobekeptafloatthemotormustbekeptmoving.Aflyingmachinewillnotsustainitself;
　　itwillnotremainsuspendedintheairunlessitisunderheadway.Thisisbecauseitisheavierthanair，andgravitydrawsittotheground.
　　PuzzleinBirdSoaring.
　　Butabird，whichisalsoheavierthanair，willremainsuspended，inacalm，willevensoarandmoveinacircle，withoutapparentmovementofitswings.Thisisexplainedonthetheorythattherearegenerallyverticalcolumnsofairincirculationstrongenoughtosustainabird，butmuchtooweaktoexertanyliftingpoweronaflyingmachine，Itiseasytounderstandhowabirdcanremainsuspendedwhenthewindisinaction，butitssuspensioninaseemingdeadcalmwasapuzzletoscientistsuntilMr.Chanuteadvancedthepropositionofverticalcolumnsofair.
　　ModeledCloselyAfterBirds.
　　Sofaraspossible，buildersofflyingmachineshavetakenwhatmaybecalled"thearchitecture"ofbirdsasamodel.Thisisreadilynoticeableintheformofconstruction.Whenabirdisinmotionitswings（exceptwhenflapping）areextendedinastraightlineatrightanglestoitsbody.Thisbringsasharp，thinedgeagainsttheair，offeringtheleastpossiblesurfaceforresistance，whileatthesametimeabroadsurfaceforsupportisaffordedbytheflat，undersideofthewings.
　　Identicallythesamethingisdoneintheconstructionoftheflyingmachine.
　　Note，forinstance，themarkedsimilarityinformasshownintheillustrationinChapterII.HereAisthebird，andBthegeneraloutlineofthemachine.Thethinedgeoftheplaneinthelatterisalmostaduplicateofthatformedbytheoutstretchedwingsofthebird，whiletherudderplaneintherearservesthesamepurposeasthebird’stail.
　　CHAPTERIV.
　　VARIOUSFORMSOFFLYINGMACHINES.
　　Therearethreedistinctandradicallydifferentformsofflyingmachines.Theseare：
　　Aeroplanes，helicoptersandornithopers.
　　Ofthesetheaeroplanetakesprecedenceandisusedalmostexclusivelybysuccessfulaviators，thehelicoptersandornithopershavingbeentriedandfoundlackinginsomevitalfeatures，whileatthesametimeinsomerespectsthehelicopterhasadvantagesnotfoundintheaeroplane.
　　WhattheHelicopterIs.
　　Thehelicoptergetsitsnamefrombeingfittedwithverticalpropellersorhelices（seeillustration）bytheactionofwhichthemachineisraiseddirectlyfromthegroundintotheair.Thisdoesawaywiththenecessityforgettingthemachineunderaglidingheadwaybeforeitfloats，asisthecasewiththeaeroplane，andconsequentlythehelicoptercanbehandledinamuchsmallerspacethanisrequiredforanaeroplane.This，inmanyinstances，isanimportantadvantage，butitistheonlyonethehelicopterpossesses，andismorethanovercomebyitsdrawbacks.Themostseriousoftheseisthatthehelicopterisdeficientinsustainingcapacity，andrequirestoomuchmotivepower.
　　FormoftheOrnithopter.
　　Theornithopterhashingedplaneswhichworklikethewingsofabird.Atfirstthoughtthiswouldseemtobethecorrectprinciple，andmostoftheearlyexperimentersconductedtheiroperationsonthisline.Itisnowgenerallyunderstood，however，thatthebirdinsoaringisinrealityanaeroplane，itsextendedwingsservingtosustain，aswellaspropel，thebody.Atanyratetheornithoperhasnotbeensuccessfulinaviation，andhasbeeninterestingmainlyasaningenioustoy.
　　Attemptstoconstructitonascalethatwouldpermitofitsusebymaninactualaerialflightshavebeenfarfromencouraging.
　　ThreeKindsofAeroplanes.
　　Therearethreeformsofaeroplanes，withallofwhichmoreorlesssuccesshasbeenattained.Theseare：
　　Themonoplane，aone—surfacedplane，likethatusedbyBleriot.
　　Thebiplane，atwo—surfacedplane，nowusedbytheWrights，Curtiss，Farman，andothers.
　　Thetriplane，athree—surfacedplaneThisformisbutlittleused，itsonlyprominentadvocateatpresentbeingElleLavimer，aDanishexperimenter，whohasnotthusfaraccomplishedmuch.
　　Whateverofrealsuccesshasbeenaccomplishedinaviationmaybecreditedtothemonoplaneandbiplane，withthebalanceinfavorofthelatter.Themonoplaneisthemoresimpleinconstructionand，whereweight—
　　sustainingcapacityisnotaprimerequisite，mayprobablybefoundthemostconvenient.Thisopinionisbasedonthefactthatthesmallerthesurfaceoftheplanethelesswillbetheresistanceofferedtotheair，andthegreaterwillbethespeedatwhichthemachinemaybemoved.Ontheotherhand，thebiplanehasamuchgreaterplanesurface（doublethatofamonoplaneofthesamesize）andconsequentlymuchgreaterweight—
　　carryingcapacity.
　　DifferencesinBiplanes.
　　Whileallbiplanesareofthesamegeneralconstructionsofarasthemainplanesareconcerned，eachaviatorhashisownideasastothe"rigging."
　　Wright，forinstance，placesadoublehorizontalrudderinfront，withaverticalrudderintherear.Therearenopartitionsbetweenthemainplanes，andthebicyclewheelsusedonotherformsarereplacedbyskids.
　　Voisin，onthecontrary，dividesthemainplaneswithverticalpartitionstoincreasestabilityinturning;usesasingle—planehorizontalrudderinfront，andabigbox—
　　tailwithverticalrudderattherear;alsothebicyclewheels.
　　Curtissattacheshorizontalstabilizingsurfacestotheupperplane;hasadoublehorizontalrudderinfront，withaverticalrudderandhorizontalstabilizingsurfacesinrear.Alsothebicyclewheelalightinggear.
　　CHAPTERV.
　　CONSTRUCTINGAGLIDINGMACHINE.
　　Firstdecideuponthekindofamachineyouwant——
　　monoplane，biplane，ortriplane.Foranovicethebiplanewill，asarule，befoundthemostsatisfactoryasitismorecompactandthereforethemoreeasilyhandled.
　　Thiswillbeeasilyunderstoodwhenwerealizethatthesurfaceofaflyingmachineshouldbelaidoutinproportiontotheamountofweightitwillhavetosustain.
　　Thegenerallyacceptedruleisthat152squarefeetofsurfacewillsustaintheweightofanaverage—sizedman，say170pounds.Nowitfollowsthatifthese152squarefeetofsurfaceareusedinoneplane，asinthemonoplane，thelengthandwidthofthisplanemustbegreaterthanifthesameamountofsurfaceissecuredbyusingtwoplanes——thebiplane.Thisresultsinthebiplanebeingmorecompactandthereforemorereadilymanipulatedthanthemonoplane，whichisanimportantitemforanovice.
　　GlidertheBasisofSuccess.
　　Flyingmachineswithoutmotorsarecalledgliders.Inmakingaflyingmachineyoufirstconstructtheglider.
　　Ifyouuseitinthisformitremainsaglider.Ifyouinstallamotoritbecomesaflyingmachine.Youmusthaveagoodgliderasthebasisofasuccessfulflyingmachine.
　　Itwillbewellforthenovice，themanwhohasneverhadanyexperienceasanaviator，tobeginwithagliderandmasteritsconstructionandoperationbeforeheessaysthemorepretentioustaskofhandlingafully—
　　equippedflyingmachine.Infact，itisessentialthatheshoulddoso.
　　PlansforHandyGlider.
　　Agliderwithaspread（advancingedge）of20feet，andabreadthordepthof4feet，willbeaboutrighttobeginwith.Twoplanesofthissizewillgivethe152squareyardsofsurfacenecessarytosustainaman’sweight.
　　Rememberthatinreferringtoflyingmachinemeasurements"spread"takestheplaceofwhatwouldordinarilybecalled"length，"andinvariablyappliestothelongoradvancingedgeofthemachinewhichcutsintotheair.
　　Thus，agliderisspokenofasbeing20feetspread，and4feetindepth.Sofarasmasteringthecontrolofthemachineisconcerned，learningtobalanceone’sselfintheair，guidingthemachineinanydesireddirectionbychangingthepositionofthebody，etc.，allthismaybelearnedjustasreadily，andperhapsmoreso，witha20—
　　footgliderthanwithalargerapparatus.
　　KindofMaterialRequired.
　　Therearethreeall—importantfeaturesinflyingmachineconstruction，viz.：lightness，strengthandextremerigidity.Spruceisthewoodgenerallyusedforgliderframes.Oak，ashandhickoryareallstronger，buttheyarealsoconsiderablyheavier，andwherethesavingofweightisessential，thedifferenceislargelyinfavorofspruce.Thiswillbeseeninthefollowingtable：
　　WeightTensileCompressivepercubicft.StrengthStrengthWoodinlbs.lbs.persq.in.lbs.persqin.
　　Hickory5312，0008，500
　　Oak5012，0009，000
　　Ash3812，0006，000
　　Walnut388，0006，000
　　Spruce258，0005，000
　　Pine255，0004，500
　　Consideringthemarkedsavinginweightsprucehasagreaterpercentageoftensilestrengththananyoftheotherwoods.Itisalsoeasiertofindinlong，straight—
　　grainedpiecesfreefromknots，anditisthiskindonlythatshouldbeusedinflyingmachineconstruction.
　　YouwillnextneedsomespoolsorhanksofNo.6
　　linenshoethread，metalsockets，asupplyofstrongpianowire，aquantityofclosely—wovensilkorcottoncloth，glue，turnbuckles，varnish，etc.
　　NamesoftheVariousParts.
　　Thelongstrips，fourinnumber，whichformthefrontandrearedgesoftheupperandlowerframes，arecalledthehorizontalbeams.Theseareeach20feetinlength.
　　Thesehorizontalbeamsareconnectedbyuprightstrips，4feetlong，calledstanchions.Thereareusually12ofthese，sixonthefrontedge，andsixontherear.Theyservetoholdtheupperplaneawayfromthelowerone.
　　Nextcomestheribs.Theseare4feetinlength（projectingforafootovertherearbeam），andwhileintendedprincipallyasasupporttotheclothcoveringoftheplanes，alsotendtoholdtheframetogetherinahorizontalpositionjustasthestanchionsdointhevertical.
　　Thereareforty—oneoftheseribs，twenty—oneontheupperandtwentyonthelowerplane.Thencomethestruts，themainpieceswhichjointhehorizontalbeams.Allofthesepartsareshownintheillustrations，referencetowhichwillmakethemeaningofthevariousnamesclear.
　　QuantityandCostofMaterial.
　　Forthehorizontalbeamsfourpiecesofspruce，20feetlong，11/2incheswideand3/4inchthickarenecessary.
　　Thesepiecesmustbestraight—grain，andabsolutelyfreefromknots.Ifitisimpossibletoobtainclearpiecesofthislength，shorteronesmaybespliced，butthisisnotadvisedasitaddsmateriallytotheweight.Thetwelvestanchionsshouldbe4feetlongand7/8inchindiameterandroundedinformsoastoofferaslittleresistanceaspossibletothewind.Thestruts，therearetwelveofthem，are3feetlongby11/4x1/2inch.Fora20—footbiplaneabout20yardsofstoutsilkorunbleachedmuslin，ofstandardoneyardwidth，willbeneeded.Theforty—oneribsareeach4feetlong，and1/2inchsquare.ArollofNo.12pianowire，twenty—foursockets，apackageofsmallcoppertacks，apotofglue，andsimilaraccessorieswillberequired.Theentirecostofthismaterialshouldnotexceed$20.Thewoodandclothwillbethetwolargestitems，andtheseshouldnotcostmorethan$10.Thisleaves$10forthevarnish，wire，tacks，glue，andotherincidentals.Thisestimateismadeforcostofmaterialsonly，itbeingtakenforgrantedthattheexperimenterwillconstructhisownglider.Shouldtheservicesofacarpenterberequiredthetotalcostwillprobablyapproximate$60or$70.
　　ApplicationoftheRudders.
　　Thefiguresgivenalsoincludetheexpenseofrudders，butthedetailsofthesehavenotbeenincludedasthegliderisreallycompletewithoutthem.SomeofthebestflightsthewritereversawweremadebyMr.A.M.Herringinagliderwithoutarudder，andyettherecanbenodoubtthatarudder，properlyproportionedandplaced，especiallyarearrudder，isofgreatvaluetotheaviatorasitkeepsthemachinewithitsheadtothewind，whichistheonlysafepositionforanovice.Forinitialeducationalpurposes，however，arudderisnotessentialastheglideswill，orshould，bemadeonlevelground，inmoderate，steadywindcurrents，andatamodestelevation.Theadditionofarudder，therefore，maywellbeleftuntiltheaviatorhasbecomereasonablyexpertinthemanagementofhismachine.
　　PuttingtheMachineTogether.
　　Havingobtainedthenecessarymaterial，thefirstmoveistohavetheribpiecessteamedandcurved.Thiscurvemaybeslight，about2inchesforthe4feet.Whilethisisbeingdonetheotherpartsshouldbecarefullyroundedsothesquareedgeswillbetakenoff.Thismaybedonewithsandpaper.Nextapplyacoatofshellac，andwhendryrubitdownthoroughlywithfinesandpaper.Whentheribsarecurvedtreattheminthesameway.
　　Laytwoofthelonghorizontalframepiecesonthefloor3feetapart.Betweentheseplacesixofthestrutpieces.Putoneateachend，andeach41/2feetputanother，leavinga2—footspaceinthecenter.Thiswillgiveyoufourstruts41/2feetapart，andtwointhecenter2feetapart，asshownintheillustration.Thismakesfiverectangles.Besurethatthepointsofcontactareperfect，andthatthestrutsareexactlyatrightangleswiththehorizontalframes.Thisisamostimportantfeaturebecauseifyourframe"skews"ortwistsyoucannotkeepitstraightintheair.Nowgluetheendsofthestrutstotheframepieces，usingplentyofglue，andnailonstripsthatwillholdtheframeinplacewhiletheglueisdrying.Thenextdaylashthejointstogetherfirmlywiththeshoethread，windingitasyouwouldtomendabrokengunstock，andovereachlayerputacoatingofglue.Thisdone，theotherframepiecesandstrutsmaybetreatedinthesameway，andyouwillthusgetthefoundationsforthetwoplanes.
　　AnotherWayofPlacingStruts.
　　Inthemachinesbuiltforprofessionaluseastrongerandmorecertainformofconstructionisdesired.Thisissecuredbytheplacingthestrutsforthelowerplaneundertheframepiece，andthosefortheupperplaneoverit，allowingthemineachinstancetocomeoutflushwiththeouteredgesoftheframepieces.Theyarethensecurelyfastenedwithatieplateorclampwhichpassesovertheendofthestrutandisboundfirmlyagainstthesurfaceoftheframepiecebytheeyeboltsofthestanchionsockets.
　　PlacingtheRibPieces.
　　Takeoneoftheframesandplaceonittheribs，withthearchedsideup，lettingoneendoftheribscomeflushwiththefrontedgeoftheforwardframe，andtheotherendprojectingaboutafootbeyondtherearframe.
　　Themanneroffasteningtheribstotheframepiecesisoptional.Insomecasestheyarelashedwithshoethread，andinothersclampedwithametalclampfastenedwith1/2—inchwoodscrews.Whereclampsandscrewsareusedcareshouldbetakentomakeslightholesinthewoodwithanawlbeforestartingthescrewssoastolessenanytendencytosplitthewood.Onthetopframe，twenty—oneribsplacedonefootapartwillberequired.Onthelowerframe，becauseoftheopeningleftfortheoperator’sbody，youwillneedonlytwenty.
　　JoiningtheTwoFrames.
　　Thetwoframesmustnowbejoinedtogether.Forthisyouwillneedtwenty—fouraluminumorironsocketswhichmaybepurchasedatafoundryorhardwareshop.
　　Thesesockets，asthenameimplies，provideareceptacleinwhichtheendofastanchionisfirmlyheld，andhaveflangeswithholesforeye—boltswhichholdthemfirmlytotheframepieces，andalsoservetoholdtheguywires.
　　Inadditiontotheseeye—boltholestherearetwoothersthroughwhichscrewsarefastenedintotheframepieces.
　　Onthefrontframepieceofthebottomplaneplacesixsockets，beginningattheendoftheframe，andlocatingthemexactlyoppositethestruts.Screwthesocketsintopositionwithwoodscrews，andthenputtheeye—boltsinplace.Repeattheoperationontherearframe.Nextputthesocketsfortheupperplaneframeinplace.
　　Youarenowreadytobringthetwoplanestogether.
　　Beginbyinsertingthestanchionsinthesocketsinthelowerplane.Theendsmayneedalittlerubbingwithsandpapertogetthemintothesockets，butcaremustbetakentohavethemfitsnugly.Whenallthestanchionsareinplaceonthelowerplane，lifttheupperplaneintoposition，andfitthesocketsovertheupperendsofthestanchions.
　　TrussingwithGuyWires.
　　Thenextmoveisto"tie"theframetogetherrigidlybytheaidofguywires.ThisiswheretheNo.12pianowirecomesin.Eachrectangleformedbythestrutsandstanchionswiththeexceptionofthesmallcenterone，istobewiredseparatelyasshownintheillustration.
　　Ateachoftheeightcornersformingtherectangletheringofoneoftheeye—boltswillbefound.Therearetwowaysofdoingthis"tieing，"ortrussing.Oneistorunthewiresdiagonallyfromeye—bolttoeye—bolt，dependinguponmainstrengthtopullthemtautenough，andthentwisttheendssoastohold.Theotheristofirstmakealoopofwireateacheye—bolt，andconnecttheseloopstothemainwireswithturn—buckles.Thislattermethodisthebest，asitadmitsofthetensionbeingregulatedbysimplyturningthebucklesoastodrawtheendsofthewireclosertogether.Aglanceattheillustrationwillmakethisplain，andalsoshowhowthewiresaretobeplaced.Theproperdegreeoftensionmaybedeterminedinthefollowingmanner：
　　Aftertheframeiswiredplaceeachendonasaw—horsesoastolifttheentireframeclearofthework—shopfloor.Getunderit，inthecenterrectangleand，graspingthecenterstruts，oneineachhand，putyourentireweightonthestructure.Ifitisproperlyputtogetheritwillremainrigidandunyielding.Shoulditsageversoslightlythetensionofthewiresmustbeincreaseduntilanytendencytosag，nomatterhowslightitmaybe，isovercome.