AMT 110 Aircra+ Metal Structural Repair
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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! Forcomplicatedpa^erns:
• Drillsmallerholesfirst• Alignpa^ern• Enlargepa^ern
! 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
Shear
CorniceBrake
BoxandPanBrake(FingerBrake)
BoxandPanBrake(FingerBrake)
SlipRollFormer
SlipRollFormer
RotaryMachine
EnglishWheel
English Wheel Video English Wheel Video 2
SimpleandCheap• Blockofwood• Rubberorplas7chammer• Smallsteelballpeenhammer
C-Clamp
Vise
Machinist'sVise
Cleco
Cleco
Cleco
SolidRivets• Solidshankrivetsarethemostcommontypeofrivetusedonaircra+! Mostusedofallfasters
• Rive7ngVideo• RivetHeadTypes:
! Universal• 470->AN470orMS20470
! CountersunkorFlush• 426->AN426orMS20426• 100°headangle
SolidRivets
SolidRivets
SolidRivets
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
Cleco
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
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-Shear™
Hi-Shear™
Hi-Lok™• Installa7onVideo• Canbeinstalledwithstandardtools
HuckLockbolt™
HuckLockbolt™
Rivnut™
Good for thin sheet metal applications
Rivnut™
CherryRivetlessNutplate• Installa7onanima7on
Dzus™Fastener
Dzus™Fastener
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
BendingBrake
BendingBrake
BendRadius
NeutralLine
Bend
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
Crack
Patch
RivetSpacing• Rivetpitch-thedistancebetweenthecentersofadjacentrivetsinthesamerow.! Minimum–3D;Maximum–10D! Typical6Dto8D
• Transversepitch-theperpendiculardistancebetweenrivetrows! 75%ofrivetpitch! Minimum–21/2D
• EdgeDistance–2Dto4D
RivetSpacing
ElongatedOctagonalPatch
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
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