584 CHAPTER 21 Fuselages
21.4 CutoutsinFuselages.................................................................................
Sofarwehaveconsideredfuselagestobeclosedsectionsstiffenedbytransverseframesandlongitudinal
stringers.Inpractice,itisnecessarytoprovideopeningsintheseclosedstiffenedshellsfor,forexample,
doors,cockpits,bombbays,windowsinpassengercabins,andsoforth.Theseopeningsor“cutouts”
producediscontinuitiesintheotherwisecontinuousshellstructuresothatloadsareredistributedinthe
vicinityofthecutout,therebyaffectingloadsintheskin,stringers,andframes.Frequently,theseregions
mustbeheavilyreinforced,resultinginunavoidableweightincreases.Insomecases—forexample,door
openingsinpassengeraircraft—itisnotpossibletoproviderigidfuselageframesoneachsideofthe
opening because the cabin space must not be restricted. In such situations, a rigid frame is placed
around the opening to resist shear loads and to transmit loads from one side of the opening to the
other.
The effects of smaller cutouts, such as those required for rows of windows in passenger aircraft,
maybefoundapproximatelyasfollows.Figure21.5showsafuselagepanelprovidedwithcutoutsfor
windowswhicharespacedadistancelapart.Thepanelissubjectedtoanaverageshearflowqav,which
Fig.21.5
Fuselage panel with windows.