I've been trying to research various methods on the joints between the winglet and the wingtip out of interest. I'm aware that the airfoil is attached to the underbody of the fuselage by means of a butt joint, but with companies like Aviation Partner who offer options such as BBJ's, how are these winglets attached?

  • 3
    $\begingroup$ This is pedantic, but isn't the wingLET attached to the wingTIP? (Hey guys, I've got this winglet, now let's build a plane...) $\endgroup$
    – CGCampbell
    Commented Sep 17, 2016 at 13:50
  • $\begingroup$ Is a butt joint some kind of aerostructures term I'm not familiar with? Typically the wing spar extends into the fuselage quite a bit where it is structurally connected to the fuselage bulkhead(s) and the other wing... $\endgroup$
    – Daniel
    Commented Sep 19, 2016 at 2:45

1 Answer 1


There are a number of winglets available in market for retrofitting and their method of attachment will also vary. Boeing details the procedure for attaching a winglet to their BBJ and it is quite instructive. According to the article the main issue is modifying the wing to accommodate the winglet, rather than the attachment itself.

The more time-consuming part of the retrofit is installation of the wing modification to accommodate the winglet.

For this particular aircraft, the following steps are given:

  • Removal and replacement of the outboard upper and lower skin panels

  • Removal and replacement of rib 25, which is third from the outermost rib

  • Installation of stiffeners across rib 25.

  • Cutting of the closure rib (rib 27) and trimming of the two spars

  • Installation of the new center section of rib 27 and the new winglet attach fitting

  • Installation of the spar attach fittings

  • Installation of the aft-position light.

which is followed by installation of the winglet.

Winglet installation

Installation of winglet, from Boeing Aero.

  • $\begingroup$ How many ribs would say a B737-800 have without a winglet? $\endgroup$ Commented Sep 18, 2016 at 15:43
  • $\begingroup$ @PravinPradeep it says that rib 27 is already there, they just modify it, so there are still 27 ribs. $\endgroup$
    – fooot
    Commented Sep 19, 2016 at 14:39
  • $\begingroup$ @PravinPradeep - sounds like a whole new question - you should ask it! $\endgroup$
    – FreeMan
    Commented Sep 19, 2016 at 17:58

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