B1-11a Aeroplane Aerodynamics SR

SubjectB1-11a: AeroplaneAerodynamicsandFlight AeroplaneAerodynamicsandFlight Controls

Allrightsreserved.Nopartofthisdocum Allrightsreserved.Nopartofthisdocumentmaybereprod entmaybereproduced,transferre uced,transferred,sold,or d,sold,or otherwisedisposedof,withoutthew otherwisedisposedof,withoutthewrittenpermission rittenpermissionofAviationAustralia. ofAviationAustralia.

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CONTENTS Page Definitions

3

Study Resources

4

Introduction

5

AeroplaneAerodynamics AeroplaneAerodynamics

11.1.1-1

High Speed Flight

11.1.2-1

Flight Controls Systems

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11.9-1

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DEFINITIONS 

Todescribethenatureorbasicqualitiesof.

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Tostatetheprecisemeaningof(awordorsenseofaword).



Specifyinwordsorwriting.

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Tosetforthinwords;declare.

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Toestablishtheidentityof.



Itemise.



Representinwordsenablinghearerorreadertoformanideaofanobjectorprocess.



Totellthefacts,details,orparticularsofsomethingverballyorinwriting.



Makeknownindetail.

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Offerreasonforcauseandeffect.

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STUDYRESOURCES JeppesenSandersonTrainingProducts: 

A&PTechnicianGeneralTextbook.

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A&PTechnicianAirframeTextbook.

B1-11aStudentHandout


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INTRODUCTION Thepurposeofthissubjectistoexplainhowbasicaerodynamicsisappliedtoavarietyof differentaeroplanedesigns/typesandeffectsofhighspeedflight.Thepurpoise,functionand opertionofbasicaeroplneflightcontrolsystemsandcomponents. Oncompletionofthefollowingtopicsyouwillbeableto:

Describetheoperationandeffectsofthefollowingprimarycontrolsystems: rollcontrol(aileronsandspoilers) pitchcontrol(elevators,stabilators,variableincidencestabilisersandcanards) yawcontrolandrudderlimiters   

Describeflightcontrolusingelevonsandruddervators. Describethefollowinghighliftdevices: Slots    

Slats Flaps Flaperons

Describetheoperationandeffectsof: Draginducingdevices(spoilers,liftdumpersandspeedbrakes) Wingfencesandsawtoothleadingedges  

Describeboundarylayercontrolusing: Vortexgenerators Stallwedges Leadingedgedevices.   

Describetheoperationandeffectsofthefollowing: Trimtabs Balanceandantibalance(leading)tabs Servotabs Springtabs Massbalance Controlsurfacebias Aerodynamicbalancepanels       


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Describethefollowing: Speedofsound Subsonicflight Transonicflight Supersonicflight Machnumber Criticalmachnumber Compressibilitybuffet shockwave aerodynamicheating arearule          

Describetheairflowconditionsinengineintakesofhighspeedaircraftandthefactors whichaffectthem. DescribetheeffectsofsweepbackoncriticalMachnumber.

Identifythefollowingprimaryflightcontrolsandexplaintheiroperation: Ailerons. Elevators. Rudders. Spoilers.    

Statethepurposeofthefollowingflightcontrolsystemsandexplaintheiroperation: TrimControl. ActiveLoadControl. HighLiftDevices. LiftDump. SpeedBrakes.     

Explaintheoperationofflightcontrolsbythefollowingmethods: Manual. Hydraulic. Pneumatic. Electrical. FlybyWire.     

Explaintheoperationandeffectof: ArtificialFeel. YawDamper. MachTrim. RudderLimiter Gustlocks.     

Explainbalancingandriggingofflightcontrols. Explaintheoperationofstallprotectionsystems.

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TOPIC11.1.1AEROPLANEAERODYNAMICS

AcombinationofrudderandelevatormountedonaVeetailwhichprovidessimultaneous longitudinalanddirectionalcontrol

VeeTailisalsoknownasaButterflytail.

Elevonsprovidesimultaneouscontrolaboutthelateralaxisandthelongitudinalaxisi.e.pitch androll.


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B1-11.1.1: Aeroplane Aerodynamics Page 1 of 6

Controlforcesdependontheairspeed2andareaofsurface,thelargerand/orfasterthe aircraftthehighertheforcerequiredtomanoeuvre. Forthisreasoncontrolsareoftenbalancedtoassistthepilotsinputforceduringmanoeuvres. (Reduceforces)

Trimminghowever,meansremovingallcontrolforcesduringsteadyflightusingaseparate controlinthecockpit.

Aportionofthecontrolsurfaceisextendedoutaheadofthehingeline.Thisutilisesthe airflowabouttheaircrafttoaidinmovingthesurface.Althoughverysimple,itdoes createdrag.


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Thehingedbalancepanelmovesinsideasealedspaceaheadoftheaileron. Whentheaileronisdeflectedupward,(asseenabove)theairoverthebottomsurface speedsupandproducesalowpressurebelowthebalancepanel.(Venturieffect) Thislowpressurepullsthebalancepaneldownandputsaforceontheleadingedgeofthe aileroninsuchadirectionthatitassiststhepilotinholdingtheailerondeflectedupward. Thereisnoextradrag.

Spoilersareflightcontrolsthatriseupfromtheuppersurfaceofthewingtodestroy,orspoil, lift. Flightspoilersareusedathighspeedtodecreaseliftononewingandrolltheaircraft. Asliftdumpers,theyareusedtodestroytheliftoftheaircraftaftertouchdowntoaidin slowingtheaircraft


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Speedbrakes,alsocalleddivebrakes,arelargedragpanelsusedforairspeedcontrol. Theycanalsobeusedtoslowanaircraftaftertouchdown,andreducethelandingroll.

WING FENCE

Boundarylayercontroldevicesaredesignedtodelayairflowseparationoverthewing. Wingfencesarefixedvanesthatextendchordwiseacrossthewingofsweptwingaircraft. Theirpurposeistopreventairfromflowingoutwardalongthespanofthewing,forthisinturn islikelytocauseairflowseparationnearthewingtipsandsoleadtotipstallingandpitch-up


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Tipseparationandstallcanalsobedelayedreducedbyintroducinganotchorsawtoothin theleadingedge.

NOTCH

Eachnotchgeneratesastrongvortexwhichcontrolstheboundarylayerinthetipregion

Thesearesmallplatesorwedges,projectinganinchorsofromthetopsurfaceofthewing, Eachplategeneratesavortexaddingenergytotheboundarylayer. Theboundarylayertravelsfurtheralongthesurfacebeforebeingslowedupandseparating fromthewing.


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TOPIC11.1.2HIGHSPEEDFLIGHT “Theratioofthespeedoftheairplanetothespeedofsoundinthesameatmospheric conditions.”

 

.

M=1iscalledSONICflow

HighspeedflightismeasuredintermsofMachNumber,whichistheratioofthespeedofthe aircrafttothespeedofsound. WhentheaircraftisflyingatMach•75itisflyingat75%ofthespeedofsoundattheambient airtemperature. TheSpeedofSoundvarieswithtemperature,andthetempvarieswithaltitude. SoaircraftreachMach1earlierathigheraltitudes.

TheflightMachnumberatwhichthereisthefirstindicationofsonicairflow,overthewing. AtMach0.5AllairflowovertheaircraftwingislessthanM=1.Astheaircraftaccelerates, theFlightMachNo.atwhichtheairflowoverthewing,(duetotheventurieffect),becomes sonic,isknownastheCriticalMachNumber.


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BeyondMcrit,theshockwavegrows.Airflowthroughthisregionundergoesasuddenstatic pressureincrease. Theeffectofthesuddenpressureriseistocausetheboundarylayertoseparatefromthe wingimmediatelybehindtheshock,takingwithitthelayersofairaboveit,soprecipitatinga “ShockStall”. Theshockwavecausesearlyairflowseparation.(partialstall)

The“ShockStall“andtheordinary\stall,althoughhavingdifferentcauseshavecertain pointsincommon:- Asuddenincreaseindragoftenaccompaniedbycompressibilitybuffetingwhichincreases inintensitywithgrowthofstall,andalossoflift.

Thesuddenextradragwhichisamarkedfeatureofshockstall,isofthesamenatureasform dragandskinfriction. Overcomingthissuddendragrisegivesrisetotheexpression,“breakingtheSoundBarrier”.

Tominimisetheincreaseindragintransonicflighttheaircraft’stotalcrosssectionalarea, alongitslengthshouldincreasegraduallytoamaximumandthendecreasejustasgradually. Thefuselagecrosssectionareashoulddecreaseatthewingroot.The“cokebottleeffect”.


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Shockwavesareusedinthedesignofsupersonicaircraftjetintakestoaidengine performance.AtMach1theairflowwithintheintakewillcausethecompressorsstallandthe enginetoflameout.Thisundesirableeffectiseliminatedbykeepingtheintakeairvelocity belowsonic. AsimplemethodtoslowdowntheairflowwithintheintakeistoinduceaNormalShockwave infrontofthecompressor,airflowbehindanormalshockwaveisalwayssubsonic. Onemethodofachievingthisistobuildinadevicesuch,asamoveableplug,thatwillcause aNormalShockwavetoform.Anothercommonmethodusedisthevariable convergent/divergentintakeduct.Duringsupersonicflight,theNormalshockwavesformsin theconvergentsectionoftheductreducingtheintakevelocitytosubsonic,theairflow velocityisthenfurtherreducedinthedivergentsectionbeforeenteringthecompressor. Dumpandspillvalvesintheintakekeeptheintakepressuretoanoptimum.


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TOPIC11.9FLIGHTCONTROLS

asystemofwingbendingreliefisdevisedforsomelargeraircrafttypes; allowsmanufacturerstobuildlighterwingsandsavemoneyonconstruction; allowaerodynamicstressestobealleviatedand,insometypes,istermedloadalleviation function(LAF). passivewayofachievingloadalleviationistostorefuelinthewings. Anactivemethodofloadalleviationisforhydraulicactuationtorapidlymovetheailerons and/orspoilersinresponsetoturbulencesensedbyaflightmanagementcomputer. Yawdampercomponentsintheruddersystemautomaticallyinputruddermovementto prevent“DutchRoll”.

Asthemachincreases,sothecentreofpressuremovesaftandthenoseoftheaircraftwill tendtodrop.(machtuck). Someaircrafthaveasystemthatwillincreasetheangleofattacktopreventmachtuck. Iftheaircraftapproachesthiscondition,theautopilotwillinputtotheelevatororstabtrimto liftthenoseoftheaircraft.Operation:-machinformationreceivedfromairdatacomputeris usedbym/tcouplertogenerateamachtrimservopositioncommandsignalwhichisrouted tom/tactuator[signalmodified/cancelledifflapnotfullup].theactuatorchangeselevator positionthruelevatorfeelandcenteringunitandelevatorpcuinordertomaintaincorrect pitchattitude.


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B1-11.9: Flight Controls Page 1 of 24

. Allpanelsareusedforgroundspoilers. Panels2.3and4usedasspeedbrakes. Panels2,3,4and5plusaileronsareusedforrollcontrol.. Panel4and5plusaileronsareusedforloadalleviationfunction(LAF). ELAC’sandSEC’sarethecomputersthatarecontrollingthepanelmovement. BlueGreenorYellowhydraulicsystems.


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Thespeedbrakeleverisconnectedtorodswhichoperateaquadrantandcablesystem. Thecablesruntoaspoilercontrolvalvewhichallowshydraulicpowertobeportedtothe speedbrake/spoileractuators. Ifairloadsareexcessiveonthepanelthenitwill“blowdown”viaacheckvalve. Lastpartoftravelissnubbedtopreventdamageofpiston.


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 Whentakingoff,leverselectedtodowndetent,uponreversethrustbeingselected(rejected takeoffabove60knots)thespeedbrakeleverwillbeliftedbyacamandtheelectricactuator willdrivetheleverandcableruntodeployallgroundspoilers. Whenlanding(leversettoARMinflight)ifawheelspeedissensed(60knotsB737)andthe throttlesareretarded,spoilerswillbedeployed.Absenceofwheelspeedsensingwillmean thatthesystemwillsensesquatswitchongroundanddeployspoilers. Advancingeitherthrottleretractsspoilers.


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

Lateralcontrol,providedbytheailerons,isinitiatedbycontrolwheelorstickmovement. Inthisschematicthepistonisfixed,thecylindermovesandrepositionsitselfwiththespool thereby“followingup”and cancellinghydraulic inputwhen desiredtravelofcontrolsurface hasbeenachieved. Ifspoolisdisplacedtotherightbycablemovement,thiswillopenR/Hpxportandalsoopen returnforL/Hsideofactuator.PxwillflowtoR/Hsideofactuatoranditwillmovetotheright (panelwillraise).Asthishappensthepressureandreturnportswillbeblockedoffagain(will catchuptothespool). Outboardaileronsonlyabletobeusedduringlowspeedflight.On747thisiswhenflapsare notup,andon767aircraftspeedisusedtolockoutoutboardaileron. Yaw damper components in the rudder system automatically input rudder movement to prevent “Dutch Roll”:- (directional and lateral oscillation that swept back wings are susceptible to.) Flight management computers sense uncommanded roll and pitch movementsthenwillinputtorudder.

Someaircrafthaveasystemthatwillincreasetheangleofattacktopreventmachtuck. Iftheaircraftapproachesthiscondition,theautopilotwillinputtotheelevatororstabtrimto liftthenoseoftheaircraft.(MachTuck:-asthemachincreases,sothecentreofpressure movesaftandthenoseoftheaircraftwilltendtodrop).


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Someaircraftneedtolimittheamountofruddertravelathighspeedtoavoidoverstress. Thisisusuallyaccomplishedbyalteringtheamountofmechanicalinputbasedonairspeed. Anelectricactuatoralterstheamountofmechanicalinputthattherudderpedalscan cause. Ona747atabout165knots,therudderdeflectioncapabilitygoesfrom25degto5deg.

Highspeedaircraftneedamorecomplicatedfeelcomputerthanthesimplespringdueto severalfactors: 

variationinCofGandgrossweight;



variationinaltitude.

ThereisconsiderablevariationinelevatoreffectivenessbetweenanaftCofGandaforward CofG.Toachieveaconstantstickforce,thefeelsystemmustbuildinstiffnessforaftCof GandreducethestiffnessforaforwardCofG. Feel computers have inputs from two hydraulic systems, pitot / static air pressure and stabiliserposition. AvariablefeeliscreatedasCofGchangesduringfuelburn,andatdifferingairspeedsand altitudes. Thefeelistransmittedasahydraulicresistancetothepilotcontrolinputs.


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Lefthand diagramshows controlwheelinputwith controlcablesmovingquadrantwithfeel gainedbyrollerriding upcamagainstspringpressure.Whencontrolwheelisreleased the springreturnswheeltocentre(neutral). Rightdiagramis triminput,whereactuatorextendsorretractsandthecammoveswiththe cam follower (aileron system friction forces are less than spring force) to produce a new neutralposition.Controlwheelmoves. Triminputwithouthydraulicswillhavethesameeffectasfeelintheaboveschematics.The system will be ready to move as soon as hydraulics are applied, causing dangerous situation.

Duringflight,ifsmalllateralcontrolmovementsareneeded,thepilotwill‘trim’theaircraft. Ailerontriminthissystemisprovidedbyanelectricactuatordisplacingthecontrolquadrant.

Electricactuatorcontrolledbythetwoswitchesrepositionstheaileroncableswhichcause aninputtotheaileronhydraulicactuator.

Cablesoperateagainstthespringtogivethepilotfeel.


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Hydraulicmotorsinthewheelwelldrivetorquetubesalongthewing.Thetorquetubesdrive gearboxeswhichrotatejackscrews.Thejackscrewsdrivetheflappanelviatheballnut.The flap drive system also normally incorporates an electric motor which can drive the same torquetubesintheeventofhydraulicpowerfailure. Atanyflappositionorwhileintransit,theleftandrightflappositionsarecompared. Ifadifferenceisdetectedthentheflapasymmetryprotectionsystemisactivated.Theflaps willbede-activatedorlockoutifonesideissensedtobemovingatadifferentratetothe otherside.


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Movementoftheflapleverpositionsthecontrolvalvewhichportshydraulicfluidtooneport ofthehydraulicmotor.Thelinkageisalsomovedbutasthemotorturnsthefollowupdrum is rotated which repositions the cam on the linkage and nulls the input at the position selected.(followup) Theloadlimiterisadevicethatwillmovetheflapsfrom40unitsto30units(737)toprotect thetrailingedgeflapsagainstexcessiveairloads.


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Theseaircraftuseanelectronicstallwarningsystem. A stall warning computer uses airspeed, angle of attack, flap position and engine power setting to determine approachingstall andwillactivatea stick shaker andprovidemaster warningwithauraltones. Withlargeaircraftthemarginbetweenpre-stallbuffetandactualstallisverysmall.Some manufacturers incorporate a stick nudger, which will push the control column forward if a stallisimminent.

The aileron that movesdownward creates both more lift and drag, and this drag way out nearthewingtippullsthenoseoftheairplanearoundinthedirectionoppositetotheway theairplaneshouldturn.

Toovercomethisproblemtheaileronmovingupwardtravelsagreaterdistancethantheone movingdownwardandarecalled IssueB:January2008

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1. SolenoidValve 2. PressureLineClosingValve 3. ReturnLineClosingValve 4. Servovalve 5. ModeSelectorValve 6. DampingOrifice 7. CheckValve 8. ReturnReliefValve 9. FluidReserve 10 FeedbackTransducer 11.ModeSelectorValveTransducer ThisisanAirbusflybywireaileronservocontrol.Hydraulicpressuregoestoaservowhich isthesameprincipleastheantiskidservo.Howmuchsidestickdeflectionismeasuredbya displacementtransducerwhichissentasasignaltoacomputerandthenontotheservo. Theamountof flapperdeflectioninservoiscontrolled bythecoilin servo,whichdisplaces thespoolandmovesaileron.Movementofaileronispickedupbythefeedbacktransducer and when input signal and output signal match, the spoolwill bebackin null. This isthe principleofallairbusflightcontrols.Internalstopsfortravelthrowsandathumbwheelateye endforrigging.


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Ingeneral,controlforceswhichthepilothastoexertinordertomovethecontrols,dependon theairspeedandareaofsurface.Thelargerand/orfastertheaircraft,thehighertheforce requiredtomanoeuvre.Forthisreasoncontrolsareoftenbalancedtoassistthepilotsinput forceduringmaneuvers.(Reduceforces) Flight,especiallyhighspeedflight,demandsthatallcontrolsurfacesbewellalignedand balanced. Surfacesareaerodynamicallyandstatically/massbalanced. Aerodynamicbalancingmakesiteasierforpilotstooperatethecontrolsinflight–requires lessinputforce. Staticbalancingpreventscontrolsurfaceflutterandsubsequentvibration. Oneformofaerodynamicbalanceiswhenaportionofthecontrolsurfaceoftheaircraftis extendedoutaheadofthehingeline.TheportionisknownasaHornBalance.Thisutilises theairflowabouttheaircrafttoaidinmovingthesurface.

Thecontrolsurfaceisbalancedonaknife-edgemandrel.Aslidingweightofknownweightis movedalongagraduatedscaleuntiltheflightcontrolisbalanced(usespiritlevel). Theweightmustbeacertaindistancefromthehingetoachieveequilibrium. Forexample,iftheweightisonepoundanditmustbepositionedoneinchforwardofthe hingetoachieveequilibrium,themomentarmissaidtobeoneinchpound. Twopoundsplacedhalfaninchforwardofthehingewillachievethesameresult.


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Therefore,itisnecessarytoknowthedistancefromthehingethattheprovisionforinstalling thebalanceweightsisonthecontrolsurface. Aformulacanthenbeusedforbalanceweightsrequired: , whereM1isthemassusedalongtheslidingscaleandM2isthemasstobeinstalled onthecontrolsurface. S1isthedistanceofthebalanceweightfromthehingelineandS2isthedistancefromthe hingethattheweightsaremountedonthecontrolsurface. IfS2isknownalready(forexample,2inches),theformulacannowread:

If,ontheslidingscale,amassof0.5poundsatadistanceof1inchfromthehingeachieved balance,then:



Therefore,amassof0.25poundsisinstalledtobalancethiscontrolsurface.

Rebalanceisrequiredafteranyrepairorrepaintandshouldbecarriedouttoaircraft manufacturersspecifications.


Revision 2


Acommoncharacteristicisthatallcontrolsystemsneedtoberigged,takingintoaccount: 

correctcontrolsystemrouting,



wearanddamageofanysystemhardware,



correctadjustmentandtensionofadjustablecomponents,



safetyofalladjustablecomponents,



correctsense,thatis,thecontrolinputdoeswhattheoperatorwantstoachieve (instinctivecontrol).



correctneutralfairingandcorrecttravel(throw)ofallcontrolsurfacesand,



freedomofmovementofthewholesystem.

Thefollowingpagesexaminethesesevenpointstoconsiderwhenriggingacontrolsystem.


Revision 2


Meansthatallhardwarecomponentsareintheircorrectlocationwithrespecttoother components.Forexample,itisveryimportantforacableruntopassthecorrectwayover pulleysandcableguards,fairleadsandcabledrums. Ifthesecablespicturedabovewereroutedthewrongsideofthecableguard,thecable wouldgrindontheguard,causingprematurewearandroughsystemoperation,possibly leadingtocablebreakage. Anyroughnesswhenoperatingacablesystemiscausetocheckforcorrectroutingalongthe entirecablerun.

Shouldbeassessedwhencarryingoutanysystemriggingoradjustment.


Revision 2


Isrequiredtoensurecorrectsystemoperation.Adjustmentofcableandchainends,pushpullrodendsandadjustablestopswilldeterminecableandchaintension,controlsurface neutralpositionandcontrolsurfacetravel.Cabletensiometerisreadonthescaleandthen convertedtocabletensioninpounds.Eachunithasacalibratedcardandthescalereading isconverteddependingontheriserbeingusedandthegaugeofthecable.


Revision 2


Itisessentialtoensurethesystemcomponentsdonotloosenoff.Thiswillfirstlyaffect systemlengthortensionandeventuallycompromisesystemintegrity.Lockwiringon turnbucklesmustbeterminatedwithatleastfourwrapsaroundtheshankoftheturnbuckle.If acablerunhasbecomeloose,orthereislostmotioninacontrolrun,itisimportanttocheck thatallturnbucklesandendfittingsarestillsecure.Precautionsforensuringthatpush-pull rodadjustableeyeendsandcableturnbucklesaresecure

Isabsolutelycriticaltoaircraftoperation.Imaginetheconsequencesifacontrolrunwas riggedsothattheaircraftstartedtoclimbwhenthecontrolcolumnwaspushedforward, ratherthandescendorrolledtotheleftwhenthepilotwantedtorolltotheright.


Revision 2


Isimportantbecauseanydeviationofacontrolsurfacefromastreamlinedpositionwill: 

Causeanetresultsimilartoacontrolmovementinthatdirection,e.g.ifanelevator issittingbelowitsnormalfairedposition,theaircraftwilladoptaconstantnose-down attitude.Pilotsmustactivelycorrectthis.



Causeincreasedfuelburnbecauseofincreaseddrag



Causeundueaerodynamicstressontheairframe.

Controlsystemriggingis usuallydoneinaneutralpositionandpartsofthesystemmaybe heldintheneutralbytheuseofrigpins. Rigpinsareusedtoeasilysetportionsofthecontrolsysteminneutral.Theremaybeapin tobefittedatthecontrolcolumnoratitsbase,forexample,thenanotherinabellcrankor pulley half way throughthesystem. Finally,there may bea rig pin orrigging boardto be fittedatthecontrolsurfacetolockitatneutralortoadjustthebiasofthesurfacetheamount itshouldsitawayfromneutral,ifapplicable. Rigging any control system requires that step-by-step methodical procedures be followed fromtheaircraftmaintenancemanual.Thebasicmethodhasmorestepswithincreasing aircraftcomplexitybutfollowsthesameformat:


Revision 2


Lockthecockpitcontrol,bellcranksandcontrolsurfacesintheneutralposition. Adjustthecabletension,maintainingtherudder,elevatorsoraileronsintheneutralposition. Adjustthecontrolstopstolimitthecontrolsurfacetraveltothedimensionsgiven. Whenalladjustmentshavebeenmade,checkthattherigpinsarenotundertension,should beabletoberemovedeasily,indicatingthatthecableor push-pull rodadjustmenthasnot disturbedthesystemawayfromitsoriginalneutralposition.

The control surfaces themselves move through an arc which is determined by the manufacturer.Maximumdeflectionfromneutralmaybemeasuredindegreesbyusingan inclinometer.


Revision 2


Thesetwotypesofinclinometersorprotractorsaremountedonthecontrolsurface.Asthe surface moves either way from neutral, the vernier graduations will show the amount of deflectionindegrees.Anothermethodofcheckingmaximumcontrolsurfacedeflectionisby


Revision 2


measuringthelineardistancefromthetrailingedgeofthecontrolsurfacetothetrailingedge of the surface on which the control is mounted e.g. elevator trailing edge to horizontal stabilisertrailingedge.

It is important for the primary stops to contact first then, with further control column movement,thesecondarystopstocontact. Thisfurthercontrolcolumnmovementistermed‘springback’. Thisensuresfulltravelofthesurfacewillbeachievedbeforefullcontrolcolumndeflection.If acontrolsurfacedoesnotachieveitsspecifiedtravelrange,primaryandsecondarystops mustbecheckedforcorrectdimension. Also,assumingcable riggingis correctandrig pinsareeasilyremoved,ensureanypushpullhardwareinthesystemnearthecontrolsurfaceisthecorrectlength.


Revision 2


isthefinalchecktobemadeonacontrolsystemafteranyworkhasbeencarriedout. Thecontrolsystem shouldbeoperatedthrough thewholerangeofmovementin allmodes ofoperatione.g.hydraulicpoweronandoff. Any binding,grinding, restrictionsin movementor failureof the controlsystemto returnto neutralmustbeinvestigated. Check for correct routing of system elements and excessive deflection of cables as they passthroughfairleadsetc. Look, also, for any worn, rusted or seized bearings, either quadrant and bellcrank pivot bearingsorpush-pullrodeyeendbearings.

Oncompletionofallriggingandbeforeflight,aduplicateinspectionmustbecarriedout. DuplicateinspectionsarerequiredbyallRegulatoryAuthoritiesafterassemblyoradjustment ofaircraftofflightandenginecontrols,airlinesmayrequiresduplicateinspectionsofother systemsincluding: 

fuel,



landinggear



andothersystemsvitaltoaircraftsafety.


Revision 2


B1-11a Aeroplane Aerodynamics SR

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