360 CHAPTER 11 Structural Components of Aircraft
Fig.11.8
Typical subassembly breakdown.
Although the wings (and tailsurfaces) of fixed wing aircraft generally consist of spars, ribs, skin,
andstringers,methodsoffabricationandassemblydiffer.ThewingoftheaircraftinFig.11.5relieson
fabricationtechniquesthathavebeenemployedformanyyears.Inthisformofconstruction,thespars
comprisethinaluminiumalloywebsandflanges,thelatterbeingextrudedormachinedandarebolted
orrivetedtotheweb.Theribsareformedinthreepartsfromsheetmetalbylargepressesandrubber
diesandhaveflangesroundtheiredgessothattheycanberivetedtotheskinandsparwebs;cutouts
aroundtheiredgesallowthepassageofspanwisestringers.Holesarecutintheribsatpositionsoflow
stressforlightnessandtoaccommodatecontrolruns,fuel,andelectricalsystems.
Finally,theskinisrivetedtotheribflangesandlongitudinalstiffeners.Wherethecurvatureofthe
skinislarge—forexample,attheleadingedge—thealuminiumalloysheetsarepassedthrough“rolls”
to preform them to the correct shape. A further, aerodynamic requirement is that forward chordwise
sections of the wing should be as smooth as possible to delay transition from laminar to turbulent
flow.Thus,countersunkrivetsareusedinthesepositionsasopposedtodome-headedrivetsnearerthe
trailingedge.
The wing is attached to the fuselage through reinforced fuselage frames, frequently by bolts. In
someaircraft,thewingsparsarecontinuousthroughthefuselagedependingonthedemandsofspace.
In a high wing aircraft (Fig. 11.5), deep spars passing through the fuselage would cause obstruction
problems.Inthiscase,ashortthirdsparprovidesanadditionalattachmentpoint.Theidealarrangement
is obviously where continuity of the structure is maintained over the entire surface of the wing. In
most practical cases, this is impossible since cut outs in the wing surface are required for retracting
undercarriages,bombandgunbays,inspectionpanels,andsoforth.Thelastareusuallylocatedonthe