Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

22.8 Cutouts in Wings 609

Fig.22.20

Shear flows (N/mm) on wing rib at station 3000 in the wing of Example 22.6.

Fig.22.21

Wing box of Example 22.7.

assumedthereforethattheeffectsofacutoutarerestrictedtospanwiselengthsofthewingequaltothe
lengthofthecutoutonbothinboardandoutboardendsofthecutoutbay.
Weshallnowconsiderthemorecomplexcaseofawinghavingacutoutandsubjectedtoshearloads
whichproducebothbendingandtorsion.Again,themethodisillustratedbyanumericalexample.

Example 22.7
Awingboxhastheskinpanelonitsundersurfaceremovedbetweenstations2000and3000andcarries
lift and drag loads which are constant between stations 1000 and 4000, as shown in Fig. 22.21(a).
Determinetheshearflowsintheskinpanelsandsparwebsandalsotheloadsinthewingribsatthe
inboardandoutboardendsofthecutoutbay.Assumethatallbendingmomentsareresistedbythespar
flanges,whiletheskinpanelsandsparwebsareeffectiveonlyinshear.

Thesimplestapproachisfirsttodeterminetheshearflowsintheskinpanelsandsparwebsasthough
the wing box were continuous and then to apply an equal and opposite shear flow to that calculated
aroundtheedgesofthecutout.Theshearflowsinthewingboxwithoutthecutoutwillbethesamein
eachbayandarecalculatedusingthemethoddescribedinSection19.3andillustratedinExample19.4.
ThisgivestheshearflowdistributionshowninFig.22.22.