Aircra&WeightandBalance Chapter4 WeightandBalanceChart WeightandBalance • TheTCDS(TypeCer9ficateDataSheet)specifies therangeofacceptableweightandcenterof gravity ! Aircra&Specifica9onspre1958 • Thepilotmustinsurethattheairplaneisflown withintherangesspecifiedbytheTCDS ! Calcula9onsaremadewiththefuelattakeoffandat landing. • Thejobofthemechanicistomeasureanempty aircra&andprovedthepilotwiththeaircra&’s weightandcenterofgravitybeforeanyloadis added WeightandBalance • WeightandBalanceelements ! Weight–theweightofanobject • Pilot • Passengers • Fuel • Baggage/Cargo • Theaircra&withnothinginit ! Calledtheaircra&’semptyweight • MeasuredinlbsforUSAaircra& ! Arm–theloca9onofanobjectonthehorizontalaxis • MeasuredininchesforUSAaircra& ! Moment=WeightXArm WeightandBalance • CenterofGravity(CG)–Thepointatwhichall theobjectsareinbalance • WeightandBalanceCalcula9ons Findtheweightofeveryobject ! Findthearmofeveryobject ! Findthemomentofeveryobject ! Totalalltheweightstofindthetotalweight ! Totalallthemomentsofeveryobjecttofindthe totalmoment ! FindtheCG=totalmoment/totalweight ! WeightandBalance Center of Gravity? 110” Datum • Datum–thepointalongthehorizontalaxisthat servesasthereferencepointtomeasurearms • SpecifiedintheTCDS • Usuallylocatedatthefirewalloratthenoseof theaircra& • Armsbehindthedatumareposi9ve • Armsaheadorinfrontofthedatumare nega9ve ! Example–Ifthedatumisatthefirewall,theengine armwouldbenega9vebecauseitisaheadofthe firewall WeightandBalance • FAA-H-8083-1Aircra&WeightandBalance Handbook • Emptyweight–theweightoftheairframe, engines,andallitemsofopera9ngequipment thathavefixedloca9onsandarepermanently installedintheaircra& Permanentballast ! Oilandhydraulicfluids ! • CAR(older)–nooil ! Drainoilormathema9callysubtractoil Drainfueltounusableamount ! Nodrinkingwaterorlavatoryprechargewater ! WeightandBalance • Empty-weightCG–EWCG–CGatemptyweight • Maximumallowablegrossweight–the maximumweighttheaircra&canbe DefinedinTCDS ! Maybemorethanmaximumtakeofforlanding weight ! Ifyoufillalltheseats,fuelandbaggage;theaircra& willusuallybeovermaximumallowableweight ! • Usefulload=Maximumallowablegrossweight– emptyweight ! Fuel,passengersandbaggage WeightandBalance • Zerofuelweight–Theweightofanaircra& withoutfuel ! Thisisgivenbecausesomeaircra&requirea minimumnofuelload • Leverarm-thedistancefromthefulcrumtoan object • Tareweight–theweightoftheequipmentused inthemeasuringprocess(e.g.chocksandjacks) ! Tareweightissubtractedbeforemakingcalcula9ons • • • • • • StandardWeights Avgas–6lb/USgal JetA&A-1–6.8lb/USgal JetB–6.5lb/USgal Oil–7.5lb/USgal Water–8.35lb/USgal AveragePassenger(perAC120-27E) Summer(MaythruOct)–190lb ! Winter(NovthruApr)–195lb ! SomeFAAdocumentsuse170lb ! Crea9ngWeightandBalanceInfo • Newaircra&aredeliveredwithweightand balanceinforma9on • Youmustverifythattheweightandbalance informa9oniscurrentateachannual ! Ifnot,weightheaircra& • Persec9on125.91(b),apart125opera9onmust reweightevery36months ! Noperiodicrecheckrequirementforsmallaircra& • A&eranaltera9on,theweightandbalance informa9onmustbeupdatedifthereismore thanan“negligible”amountofweightchange Crea9ngWeightandBalanceInfo • Whatisgreaterthan“negligible”perAC120-27 Large-cabinaircra&-+/-10lborgreater ! Medium-cabinaircra&-+/-5lborgreater ! Small-cabinaircra&-+/-1lborgreater ! • Determiningweightandbalanceinfoa&eran altera9on Weighttheaircra& ! Doamathema9calcalcula9on ! • Noneedtoreweighaircra& • Informa9onusuallycomesfromSTC Crea9ngWeightandBalanceInfo • Themajorsourceofweightchangeformost aircra&astheyageiscausedbyrepairsand altera9ons ! Inreality,itisfromallthe“junk”le&intheaircra&by thepilotandrepairs WeighinganAircra& • Cleanaircra& • Getdowntothe“requireequipmentlist” FromTCDS ! Consultall337sformodifica9onrequirements ! Cleanthejunkout ! • Securepermanentballasts(weights)andremove temporaryballasts WeighinganAircra& • Drainfuel Getdowntounusablefuel ! Ifunabletodrainfuel,filltanksandthen mathema9callysubtractfuel ! • Useanega9veweighofusablefuel ! (minus)usablefuelingallonsXweighoffuelpergallon(6lb/gal forAvgas) • FindthearmforthefuelintheTCDS • Filloil ! CARcer9fiedaircra&–drainoil(canusemath) • Fillhydraulicfluids • Drainotherfluids WeighinganAircra& • Moveaircra&toalevelspotwithnowind • Rollaircra&ontoscales Jackinganaircra&onascalecancauseerrors becausethelandinggearcompresseswhenlowered ! Releasebrakes ! Remembertousechockstopreventrolling ! • Levelaircra&perTCDS FAArecommendsusingaspiritlevel ! Adjustpressureinnosegear ! • Finddatumandtransfertothegroundusinga plumbbob WeighinganAircra& • Transferlandinggearloca9onstotheground Useplumbbob ! Usethecenterofthewheelaxis ! • Determinethelandinggeararmsbymeasuring thedifferencebetweenthedatumandthe landinggearloca9ons ! Measurelongitudinalpor9ononly • Notthedirectslantdistance • Remembertorecord(+)forbehindthedatumand(-)for aheadofthedatum • Remembertosubtracttareweightfrom measurements WeightandBalancePrac9ce • WeightA–Weight100lb,armat0” • WeightB–Weight100lb,armat40” • WeightC–Weight200lb,armat100” WhatistheemptyweightandCG Empty Weight is 400 lb with CG at 60” (Remember units) WeightandBalancePrac9ce • WeightA–Weight100lb,armat-100” • WeightB–Weight100lb,armat40” • WeightC–Weight200lb,armat10” WhatistheemptyweightandCG Empty Weight is 400 lb with CG at -10” WeightandBalancePrac9ce • Nosewheel–Weight1,210lb,armat82.5” • Le&main–Weight2,510lb,armat197.5” • Rightmain–Weight2,515lb,armat197.5” WhatistheemptyweightandCG Empty Weight is 6,235 lb with CG at 175.2” WeightandBalancePrac9ce • Tailwheel–Weight50lb,armat120” • Le&main–Weight800lb,armat-11” • Rightmain–Weight806lb,armat-11” WhatistheemptyweightandCG Empty Weight is 1,656 lb with CG at -7.0” WeightandBalancePrac9ce Anaircra&withanemptyweightof1,500poundsandan emptyweightCGof+28.4wasalteredasfollows: 1.two12-poundseatslocatedat+58.5wereremoved; 2.structuralmodifica9onsweighing+28poundsweremadeat +73; 3.aseatandsafetybeltweighing40poundswereinstalledat +70.5 4.radioequipmentweighing35poundswasremovedat-8.5 5.Radioequipmentweighing15poundwasaddedat-8.5 Whatisthenewemptyweight&CG? Empty Weight is 1,524 lb with CG at 30.3” WeightandBalancePrac9ce Datumisforwardofthemaingearcenterpointat30.24 Actualdistancebetweentailgearandmaingearcenterpoints is360.26inches Netweightatrightmaingearis8,100pounds Netweightatle&maingearis8,025pounds Netweightattailgearis645pounds Theseitemswereintheaircra&whenweighed: 1.Lavatorywatertankfull(43poundsat+352). 2.Hydraulicfluid(22poundsat-8). 3.Removableballast(110poundsat+380). Whatisthenewemptyweight&CG? Empty Weight is 16,617 lb with CG at 41.1” WeightandBalancePrac9ce Datumisforwardofthemaingearcenterpointat30.24 Actualdistancebetweentailgearandmaingearcenterpoints is360.26inches Netweightatrightmaingearis8,100pounds Netweightatle&maingearis8,025pounds Netweightattailgearis645pounds Theseitemswereintheaircra&whenweighed: 1. Fullfuel(Avgas)–50galat50.5”(1.2galunusable) Whatisthenewemptyweight&CG? Empty Weight is 16,447.2 lb with CG at 44” Adverse-LoadedCGChecks • Adverse-LoadedCGCheck–aweightand balancecheckforextremecondi9ons • FromFAA-H-8083-1A IftheEWCG(EmptyWeightCenterofGravity)is locatedwithinthisrange,itisimpossibletolegally loadtheaircra&sothatitsloadedCGwillfalloutside ofitsallowablerange. ! IftheTCDSlistanempty-weightCGrange,anda&er thealtera9oniscompleted,theEWCGfallswithin thisrange,thenthereisnoneedtocomputeafore anda&checkforadverseloading. ! Adverse-LoadedCGChecks • FromFAA-H-8083-1A ! ButiftheTCDSliststheEWCGrangeas“None”(and mostofthemdo),acheckmustbemadeto determinewhetherornotitispossiblebyany combina9onoflegalloadingtocausetheaircra&CG tomoveoutsideofeitheritsforwardora&limits. FAAQues9on • When,orunderwhatcondi9on(s)areadverse loadingchecksconducted? a.Atorbelowthemaximumgrossweightofthe aircra&. ! b.Any9mearepairoraltera9oncausesEWCGtofall withintheEWCGrange. ! c.Atspecifiedflighthourorcalendar9meintervals. ! FAAQues9on • When,orunderwhatcondi9on(s)areadverse loadingchecksconducted? ! b.Any9mearepairoraltera9oncausesEWCGtofall withintheEWCGrange. FAAQues9on • IftheemptyweightCGofanairplanelieswithin theemptyweightCGlimits, a.itisnecessarytocalculateCGextremes. ! b.itisnotnecessarytocalculateCGextremes. ! c.minimumfuelshouldbeusedinbothforwardand rearwardCGchecks. ! FAAQues9on • IftheemptyweightCGofanairplanelieswithin theemptyweightCGlimits, ! b.itisnotnecessarytocalculateCGextremes. Adverse-LoadedCGChecks • Mustincludeminimums Pilot ! Minimumfuel ! • Nominalpilotweightis170lb • Minimumfuel-1/12gallonX“maximumexcept fortakeoffhorsepower”(METO) ! SinceAvgasweights6lb/gallon • 6lb/gX1/12gXMETO • 1/2lbXMETO • METO/2lb Adverse-LoadedCGChecks • ForwardAdverse-LoadedCGCheck Includeminimums ! EverypointinfrontoftheforwardCGlimitmustbe filledtothemaximum ! • A&(back/rearward)Adverse-LoadedCGCheck Includeminimums ! Everypointbehindthea&CGlimitmustbefilledto themaximum ! • SeeFAA-8083-1Apages5-5&5-6 MeanAerodynamicChord(MAC)&CG • • • • • Usedforlargeaircra& LEMAC–LeadingedgeoftheMAC TEMAC–TrailingedgeoftheMAC LEMACandTEMACarereferencetodatum CGin%MAC=CGfromLEMACX100/MAC CGfromLEMAC=CG–LEMAC ! Usethestandardweightandbalanceworksheetand thenconvertto%MAC ! DeterminingNeededBallast • Aircra&isoutofCG,howdoyoucorrectit ! AddballastontheoppositesideoftheCG • Ballastweight=(Aircra&weightXDistanceout oflimits)÷(Distancebetweenballastand desiredCG) ! Distanceoutoflimits=ClosestCGlimit–CurrentCG • Mustbeposi9ve ! DistancebetweenballastanddesiredCG=Where youareplacingtheballast–desiredCG • Mustbeposi9ve • Ballastloca9onsareusuallypredefined DeterminingNeededBallast • Aircra&weighs4,954lbwithCGat30.5” CGrangeis32.0”to42.1” Ballastcanbeplacedat162” • Ballastweight=(Aircra&weightXDistanceout oflimits)/(Distancebetweenballastanddesired CG) Distanceoutoflimits=32.0”–30.5”=1.5” ! DesiredCG=Forwardlimit=32” ! DistancebetweenballastanddesiredCG=162”– 32”=130” ! Ballastweight=(4,954lbX1.5”)/130”= ! 57.16lb ! POHInfo POHInfo CGmomentenvelopefromPilot’sOpera9ngHandbook. WeightandBalancePrac9ce A&eraltera9on,anN123ABPA-28-160S/N28-1650was weighedwithfullfuelandoil 1. Nosewheel–400lb@31” 2. Le&main–510lb@109.7” 3. Rightmain–520@109.7” Whatisthenewemptyweight&CG? Hint1:FullfuelandunusablefuelhavedifferentCG Hint2:Whataboutoil? Hint3:Themomentstotal=96679.6 Hint4:7itemslistedinworksheet Empty Weight is 1,119 lb with CG at 86.4”