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”