AMT 110 Aircra Metal Structural Repair - Gavilan...

AMT110Aircra+MetalStructuralRepair

Statements•  Thesa7sfactoryperformanceofanaircra+requirescon7nuousmaintenance

•  Repairsmustbestrongenoughtocarryalloftheloadswiththerequiredfactorofsafety!  Repairmustnothavetoomuchstrength

•  Extrastrengthcancausedamage

Statements•  Theproblemofrepairingadamagedsec7onisusuallysolvedbyduplica7ngtheoriginalpartinstrength,kindofmaterial,anddimensions.!  “Followthemanufacturer’srecommendedprocedures”

!  Youdon’tknowwhattheengineeringwasthinking!  AC43.13-1BistheFAA’sguidance

•  AC43.13-1Btakeprecedenceovertextbook

•  Ascratchorgougeinthesurfaceofahighlystressedpieceofmetalcausesastressconcentra7onatthepointofdamage(“stressriser”)andcouldleadtofailureofthepart.

Stresses•  Sixtypesofstress:

!  Tension!  Compression!  Shear!  Bearing!  Torsion!  Bending

Tension

The stress that resists a force that tends to pull apart

Compression

The stress that resists a crushing force, tend to shorten or squeeze parts

Shear

The stress that resists the force tending to cause one layer of material to slide over an adjacent layer.

Think of shears cutting

Bearing

The surface pressure acting on a joint face directly as a result of the force applied by a fastener.

Torsion

The stress that resists twisting

Bending

Combination of compression and tension stress

Compression&Tension

Tools•  Alwayshaveatleastonemachinist’srulein1/32”(or1/64”)

•  Pens!  Nopencils!  Sharpies

•  Bluedoesn’tbleedthroughpaintasbad!  Useinsteadofscribing

•  Demo!  Rivetspacer!  Nibbler

Tools•  Demo

!  Deburringtools

•  Drilling!  Markwithacenterpunch!  Metaltwistdrillbitshave118°head

•  Stainlesssteeluse140°!  Topreventsurfaceska7ngonaluminum,handtwistacoupleof7mebeforeapplyingpower

!  CuZngoilhelpsremovechipsandisnotusedonsheetmetal

!  Forlargeholes,startwithasmallbitandthenenlarge

Tools•  Drilling

!  Generalruleforspeed•  Hardmetal–slowandmorepressure,so+metal–fastandlowpressure

!  Useawoodbackerwhendrillingsheetmetal!  Useadrillguide/holdersifpossible!  Useadrillstopsin7ghtareas!  Useadrillpressforcri7calrepairs!  Forcomplicatedpaêrns:

•  Drillsmallerholesfirst•  Alignpaêrn•  Enlargepaêrn

!  Don’tbetooproudorlazytousesupporttools

Tools•  Reamers

!  Usedtoenlargeandsmoothahole!  Usedtocreateapreciseholediameter!  Verybri^le!  Turnonlyoneway!  Followthedirec7onsfordrillingtheini7alhole

Aluminum•  Usedonaircra+becauseitislightandeasytowork

•  Purealuminumisveryweak•  Methodstoincreasestrengthandhardness

!  Otherchemicalsareaddedtomakeanalloy•  2024isthemostcommonsheetmetalalloy•  2117isthemostcommonrivetalloy•  Alloysusuallyreducecorrosionresistance

!  Heattreatmentandtempering!  Workorstrainhardening!  Agehardening

•  Aluminumalloysgetharderwithage

Aluminum•  Wrought(worked/beaten)aluminumdesigna7on:!  (4digitalloy)–(temper&hardness)

•  e.g.2024-T3•  Firstdigit(e.g.2XXX)indicatestheprimaryalloyingagent

•  Alcad™orclad–very,verythinlayerofpurealuminumusetoprotectagainstcorrosion!  Can’tbereheated!  Can’tbewelded

•  Thiswhyaircra+arerivetednotwelded!  Easytoscratchornick

•  Exposesbasemetaltocorrosion

AluminumAlloyIden7fiers

Aluminum

AluminumHardness

AluminumHeatTreatment

CorniceBrake

BoxandPanBrake(FingerBrake)

SlipRollFormer

RotaryMachine

EnglishWheel

English Wheel Video English Wheel Video 2

SimpleandCheap•  Blockofwood•  Rubberorplas7chammer•  Smallsteelballpeenhammer

C-Clamp

Machinist'sVise

SolidRivets•  Solidshankrivetsarethemostcommontypeofrivetusedonaircra+!  Mostusedofallfasters

•  Rive7ngVideo•  RivetHeadTypes:

!  Universal•  470->AN470orMS20470

!  CountersunkorFlush•  426->AN426orMS20426•  100°headangle

SolidRivets

SolidRivets•  A–1100–Purealuminum

!  Tooso+forstructuraluse!  Fordecora7vetrimonly

•  AD–2117!  Mostcommonrivettype!  Heattreatedbythemanufactureranddoes’trequireheattreatmentbeforebeingdriven

•  B–5056!  Usedformagnesiumalloystructures

•  M–Monel!  Usedfornickel-steel

SolidRivets•  D–2017&DD–2024

!  “Icebox”rivets•  Annealedandstoredinafreezertoretardhardening•  Removedfromfreezerjustbeforeuse

!  ModernmanufacturingnowuseEtyperivets!  Mustbereheattreatedifle+outtoolong!  Onceinstalled,cantakeupto4daystofullyageharden

•  MildSteel!  Usedforsteel

SolidRivets•  Materialsubs7tu7on

!  Followthemanufacturer’srecommendedprocedures

!  D-2017–3/16”(#6)orless•  ReplacewithAD–2117of1/32”diameterlarger

!  Onesizebigger

!  DD-2024–5/32(#5)orless•  ReplacewithAD–2117of1/32”diameterlarger

!  Onesizebigger

RivetsGun

RivetGuns

RivetGunSizes

RivetSets

RivetSets

Theradiusofthecupinarivetsetisslightlygreaterthantheradiusoftherivethead.Thisallowstheblowsfromtherivetguntobeconcentratedontherivethead.

BuckingBar

CompressionRivetSqueezer

SolidRivetMaterial•  A–1100–Purealuminum•  B–5056–Usedonmagnesium•  AD–2117–Mostcommontype;hasdimple•  D–2017–“Icebox”•  DD–2024–“Icebox”

RivetDimensioning•  Diameterisin1/32’s

!  #3–3/32,#4-4/32(1/8),#5-5/32

•  Lengthisin1/16!  AN470–sha+length!  AN426–fullrivetlength

RivetDesigna7on•  (HeadType)(Material)(Diameterin1/32s)–(Lengthin1/16’s)

•  Universalhead,2117,3/32diameter,5/16length!  AN470AD3-5orMS20470AD3-5

•  Countersunkhead,1100,1/8(4/32)diameter,1/2(8/16)length!  AN426A4-8orMS20426A4-8

DrillBitsSizes•  #3–3/32-#40drillbit•  #4–1/8(4/32)-#30drillbit•  #5–5/32-#21drillbit

ReadAC43-13.1BPar4-57Rive7ng

RivetLayout•  RivetStresses

!  Shear•  Forcerequiredtocutarivet•  Arepairorpatchshouldbedesignedsoitisundershearstress

!  Tension•  Resistancetotensionisbearing•  Tensionstresspullingapatchapart

Dimpling•  Coindimpling

!  Rivetisthemaledie

•  RadiusDimpling!  Handsqueezer!  Sta7onarydimpler

•  Hotdimpling!  Usesheateddimplingdiestoensurethemetalflowsbe^erduringthedimplingprocess

•  Dimpling,duetothenestlingeffect,givesastrongerjointthanthenon-flushtype.

Countersinking•  Removemetaltoinstallrivet•  Reducesstrengthofmetal•  Edgedistanceisgreaterthanwhenuniversalheadfasteners!  2½D

•  100°countersink•  Sheetmetalmustbethickerthanrivethead•  Usemicrostopcountersink

Countersinking

FlushShopHead

Ugly!!!

RemoveRivet

BackRive7ng•  BackRive7ngVideo•  HotRive7ng

BlindRivets•  Canbeinstallfromoneside

!  Installedwith“puller”tool

•  PopRivet!  Poprivetinstalla7on!  Usedforno-structuralworkonly!  Hollowa+erinstalla7on

BlindRivets•  “CherryRivets”

!  Notyourhardwarestorerivets!  Widevariety–CherryLock,CherryMax,Huck-Clinch,HuckMax,Olympic-Loc

!  CherryMaxAnima7on!  CherryMaxcanreplaceasolidrivetofthesamesizediameter

•  Somemechanicsareconcernedabouttherivetsvibra7ngloose

!  InstallCherryMaxRivet!  Hardtoremove

•  Readprocessonpage4-49

CherryRivetRemoval

Hi-Shear™

Hi-Lok™•  Installa7onVideo•  Canbeinstalledwithstandardtools

HuckLockbolt™

Rivnut™

Good for thin sheet metal applications

Rivnut™

CherryRivetlessNutplate•  Installa7onanima7on

Dzus™Fastener

Dzus™Fastener•  Lengthspecifiedin1/100(0.01)inchincrements•  Diameterspecifiedin1/16inchincrements•  Headmarkingsarebodydiameter,typeofhead,andlengthofthefastener

•  Reten7ongrommet/collarcommonlycomeloose

CamLockFastener

AirlocFastener

AnchorNut&Tinnerman

MetalBending

MetalLayout

MetalBendingLayoutProcedure1.  Obtainthedimensionsoftheshape2.  Determinesizeofthestockor“wheretocut”3.  Locatebrakereferencelinesor“whereto

bend”4.  Cutstock5.  Markcentersor“wheretodrill”6.  Drillholes

!  Ifjoiningmul7plepieces,drilla+erbending

7.  Bendmetal

WhyBendAllowance?•  Metalcannotbebentataperfect90°angle

!  Itwillbreakorcrack

•  Aroundbendisusedtopreventbreaking!  Thebendisdefinedbyitsradius–bendradius!  Thebendispor7onofacircle

•  Apor7onofacircleisshorterthanaperfect90°

Radius

WhyShorter?•  Theshortestdistancebetweentwopointsinaline

•  Aperfect90°isthelongest•  Acurvedbendisshorterthanaperfect90°

!  Thebiggertheradius,theshorterdistance

•  Theheartofabendradiuscalcula7onistodeterminethisshorterdistance

TheBendingTool•  ThetooliscalledaBrake

!  CorniceBrake!  FingerBrake

•  Clampingbarholdsthemetalanddeterminesradius!  Clamp/Fingerscanbechangedtosetradius

•  Wheretoplacethemetal?!  Thefront/noseoftheclamp

•  Thegoalofthecalcula7onsaretodeterminewherethenosegoes

BendingBrake

BendRadius

NeutralLine

Calcula7onGoals•  Determinethematerialdimensions/measurements!  Itiseasiertocutthematerialbeforebendingit

•  Markwherebendsshouldbelocated!  Onlyreferenceonthebrakeisthenoseoftheclamp–sightline

!  Determine/markwherethenosewillgo!  Noseloca7oniscalledthe“BrakeReferenceLine”

Terms/Vocabulary•  MoldLinesDimension(MLD)–Themethodofdefiningapartonadrawing!  Example–2”X4”X2”channel!  Thelengthofasideiftherewasnobend!  Drawnasifthebendisaperfect90°(0radiusbend)

•  BendRadius(R)–Thesizeofthecurveusedtobendthemetal!  Radiusofthebrakeclampnose!  Insideradiusofbend

Terms/Vocabulary•  DevelopedWidth(DW)–Materialneededtomakeapiece/item!  YoubookcallsitTotalDevelopedWidth(TDW)!  TotalofallBendTangentLineDimensions(BTLD)plusallBendAllowances(BA)

•  Allthestraightpartsplusthebentareas

Terms/Vocabulary•  DevelopedWidth(DW)=BTLD(Sec7onA)+BA+BTLD(Sec7onC)

Terms/Vocabulary•  BrakeReferenceLine–Wherethebrake’ssightlinewillbeplaced–some7mescallSightLine

OpenAngle•  OpenAngle–Bentlessthan90°

ClosedAngle•  ClosedAngle–Bentgreaterthan90°

Calcula7onOrder1.  MLD-DetermineMoldLineDimensionsfrom

problem2.  R-Radius

!  Getfromproblem!  OrMinimumbendradius

•  AC43.13-1BTable4-6•  FAA-H-8083-31Vol.1Figure4-125

Calcula7onOrder3.  BA–BendAllowance

!  FAA-H-8083-31Vol.1Figure4-129!  BA=(0.01743XR+0.0078XT)Xdegreeofbend

•  Bookhastypos•  R=Radius&Tisthicknessofmaterial

!  SampleR=.25”&T=.040”and90°bend»  BA=(0.01743X0.25)+(0.0078X0.04)X90=0.420255”»  BA=0.421”fromFAA-H-8083-31

Calcula7onOrder4.  SB–Setback

!  For90°,SB=T+R•  Tisthicknessofmaterial&R=Radius

!  SB=K(T+R)•  For90°,K=1•  Kcharts

!  AC43.13-1BTable4-7!  FAA-H-8083-31Vol.1Figure4-123

Calcula7onOrder5.  BTLD–BendTangentLineDimension

!  MoldLineDimension–Setback!  BTLD=MLD–SB(s)

Calcula7onOrder6.  DW-DevelopedWidth

!  TotalofalltheBendTangentLineDimensions+alltheBendAllowances

!  DW=TotalofalltheBTLD(s)+allBA(s)

Calcula7onOrder7.  BrakeReferenceLine(SightLine)

!  BrakeReferenceLine=BendTangentLineDimension+Radius

!  BrakeReferenceLine=BTLD+Radius

Example•  Example:.032”2024-T3Dimension=2”forbothside,90°bend!  MinimumRadius=R=0.128->roundto0.125”!  BA=0.218”!  SB=T+R

•  SB=0.032”+0.125”=0.157”!  BTLD=MLD–SB

•  BTLD=2”–0.157”=1.843”!  DW=BTLD+BA+BTLD

•  DW=1.843”+0.218”+1.843”=3.904”

!  BrakeReferenceLine=BTLD+R•  BrakeReferenceLine=1.843”+0.125”=1.968”

Example•  Example:.0807075-T6–5”X6”X5”channel

!  MinimumRadius=R=0.44”or(7/16)=0.438”!  BA=0.745”!  SB=T+R

•  SB=0.080”+0.438”=0.518”!  BTLD=MLD–SB

•  BTLD(side)=5”–0.518”=4.482”•  BTLD(bo^om)=6”–2X0.518”=4.964”

!  DW=BTLD+BA+BTLD+BA+BTLD•  DW=4.482”+0.745”+4.964”+0.745”+4.482”=15.418”

!  BrakeReferenceLine=4.482”+0.438”=4.92”(frombothsides)

Prac7ceProblems•  .032”2024-T5,Side1=23/8”,Side2=5.4”,90°bend

•  .040”6061-T5–2.5”X1”X2.75”channel,allbends90°

•  .100”2024-T5,Side1=13/8”,Side2=29/16”,110°bend

MetalWorking•  Followmanufacturer’srecommendedprocedures

•  FollowAC43-13•  Heattreatuntreatedmetals

!  Treatedmetalsmustbeformedcold

•  Topreventcorrosion,useaprotec7velayerbetweendissimilarmetals!  Paintortape

•  Whenusingaformblock,startattheedgesandworktothecenter

•  Usereliefholesatbendintersec7ons

ReliefHoles

Flu7ngSheetMetal•  Video1•  Video2

InspectforDamage•  Lookfor:

!  Corrosion•  Treatorreplace

!  Cracks!  Elongatedholes!  Dents,scratches,nicks,pits&cuts!  Wrinklesorbents!  Looserivets

•  “Smoking”rivetsareindica7onofrubbingorfreZng•  Tippedrivets

!  Ifthereisone,thereisusuallyawholerowinthesamedirec7on

!  Lookforforcetransmission

SmokingRivets

PatchingSheetMetalDamage•  ConsultManufacturer’srepairmanualand/orAC43-13forbestrepairmethod!  Thegoalistoreturnthestructuretoitsoriginalstrength

!  Manufacturermaylimitwhatyoucanrepair

•  Supportdamagedarea•  Stopdrillcracksorcutoutdamage.

!  Leavenostressrisers–nosharpcorners

•  Calculatethenumberofrivets!  Trytomakeyourrepairbasedontherivetshearstrength

PatchingSheetMetalDamage•  Makeapaperdesignofapatch

!  Markholestoinsurenointerference!  Usetransparencyifpossible

•  Createapatch!  Samematerialandsamethicknessorgreater!  Patchwillgounderskinifpossible

•  Makefillerplugifneeded–flushpatch•  Drillholes•  Applycorrosioninhibitor/primer•  Applysealantforpressurizedrepairs

PatchingSheetMetalDamage•  Rivet•  PrimeandPaint•  Complete337andlogrepair

StopDrill

FlushPatch

NumberofRivets–AC43.13-1B•  UseTables4-9,4-10or4-11forrivetsperinch.

!  Page4-37,4-38or4-39!  Checknotes

•  #Rivets=LengthofcrackXRivetsperinch•  #Rivetsisonlyforoneside.•  Thetotalrivetsusedis2X#Rivets

RivetSpacing•  Rivetpitch-thedistancebetweenthecentersofadjacentrivetsinthesamerow.!  Minimum–3D;Maximum–10D!  Typical6Dto8D

•  Transversepitch-theperpendiculardistancebetweenrivetrows!  75%ofrivetpitch!  Minimum–21/2D

•  EdgeDistance–2Dto4D

RivetSpacing

ElongatedOctagonalPatch

RoundPatch

TurnDownEdge

PanelRepair

PatchIdeasAC43.13 Fig. 1-15

Page 1-29

PatchIdeas

YourGuides•  Followmanufacturer’sinstruc7ons

!  Maintenance/Repairmanual!  Copyrivetholepa^ern!  Usesamematerialandrivets

•  UseAC43.13-1BPar4-58

SampleQues7ons•  Shallowscratchesinsheetmetalmayberepairedby!  burnishing

•  Whenapieceofaluminumalloyistobebentusingaminimumradiusforthetypeandthicknessofmaterial!  thelayoutshouldbemadesothatthebendwillbe90°tothegrainofthesheet.

!  AC43-13-1B4-55Bsays“preferably”

SampleQues7ons•  Ifitisnecessarytocomputeabendallowanceproblemandbendallowancetablesarenotavailable,theneutralaxisofthebendcanbe!  foundbyaddingapproximatelyone-halfofthestockthicknesstothebendradius.

•  Youcandis7nguishbetweenaluminumandaluminumalloyby!  tes7ngwitha10percentsolu7onofcaus7csoda.

SampleQues7ons•  Themostimportantfactorsneededtomakeaflatpa^ernlayoutarea.  radius,thickness,andmoldline.b.  radius,thickness,anddegreeofbend.c.  thelengthsofthelegs(flatsec7ons).

•  Answer:b

AMT 110 Aircra Metal Structural Repair - Gavilan...

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