AMT111
Aircra*WoodandStructuralRepair
Chapter6
Whatplaneisthis?
de Havilland Mosquito
DeHavillandMosquito
•  deHavillandDH98Mosquito
•  AusieMosquito
Wood
Nature’scompositematerial
Lightweightandstrong
Canbecreatedwithsimpletools
TypicalconstrucIonmethodsareverylabor
intensive
•  Olderwoodenaircra*aresuscepIbletorotand
delaminaIngbecausetheirgluesandfinishes
didn’tmeasureuptomodernreplacements
•  AC43-13-1BistheulImatereference
•  SitkaSpruceisthereferencewood
•
•
•
•
Wood
ProperIesofaircra*structuralwood.
Wood
•  Allwoodmustbeaircra*approved
•  Laminatedwoodvideo
•  Laminatedwoodisstripsofwoodgluedtogether
Canbeusedtoreplacesolidpiecesandsparsaslong
asitisthesamequalitywoodandthegrainis
parallel
!  Canbeusedtomakecurvedpieces
!  Canbestrongerthansolidpieces
!
•  Plywoodislaminatesheetsofwood
!
Grainsofadjacentlayerscrosseachotherateither
45°or90°toaddstrength
Plywood
Wood
•  Woodgrowthrings
!
Darkringissummergrowth
•  Slowgrowth
•  Denserandheavier
!
Lightringisspringgrowth
•  Fastgrowth
•  Woodshrinksandwarpsalongtherings
•  WoodisquartersawntocreateverIcalgrainand
minimizewarping
Quartersawn
Plankscuttangenttotheannualrings(flatgrain)distort,orwarp,astheir
moisturecontentchanges.Plankscutacrosstheannualrings(verIcalgrain)change
theirdimensionsveryli`leasmoisturecontentchanges.
Quartersawn
Alogisquartersawntoproducethemaximumnumberofplankswith
verIcal“C”grain.Twomethodsofquartersawingareillustrated.
Glue
•  Agluejointisstrongerthanthewood
Awoodjointshouldbreakatthewoodnottheglue
!  Adeterioratedgluejointwillbreakattheglue
!
•  Showimprintsofthewoodintheglue
•  Nowoodfibersstucktotheglue
!
Nailsareusedforclampingonlyanddon’taddto
jointstrength
•  Jointshouldbeflatandstraight
!
Shouldhaveaveryslightroughtexture
•  Thebookssaystouseaglasscu`er
•  AC43sayusesandpaperbutinsureallsawdustis
removed
GlueTypes
•  Resorcinolistheonlyapprovedglueforwood
Two-partsyntheIcresinadhesiveconsisIngofresin
andahardener
!  FederalSpecificaIonMMM-A-181DandMilitary
SpecificaIonMIL-A-22397
!
•  Caseinglues(whiteglueslikeElmers)shouldnot
beused
•  PlasIcresinglue(urea-formaldehyderesinglue)
shouldnotbeused
•  FAAsayssomeepoxiesareOKbutdoesn’t
specifywhichtype
RibConstrucIon
•  EAAVideo1
•  EAAVideo2
Defects
Typicalrequirementsforaircra*spruce.
Defects
Defects
•  Mineralstreaks-acceptable,providingcareful
inspecIonfailstorevealanydecay.
!
LookslikediscoloraIonle*bydriedfluid
•  Decayisnotacceptableinanyform
Discolored–o*enblackmarks
!  So*whenprobed
!
•  Damagedsparholesmustberepaired
!
Elongatedorcracksaroundhole
•  Elongatedboltholesinawingsparshouldnotberepaired
bydrillingtheholeoversizeandusingthenextlargersize
bolt.
!
CutoutdamagedsparsecIonandreplace
SparSplice
Defects
•  Crackedspars(exceptboxspars)maybe
repairedbybondingplatesofspruceorplywood
ofsufficientthicknesstodevelopthe
longitudinalshearonbothsidesofthespar
•  Compressionfailuresmustberepaired
Cracks
!  DeformaIon
!  Bucklingatrightanglestothegrain
!  Lookslikefaintlinerunningacrossthegrainofa
wood
!
ScarfJoint
GrainorientaIonforascarfedgluejoint.
I-Beam