What is the use of wing root seals? What kind of leaks are possible without having wing root seals, and if the seal is broken what kind of issues can airplanes face?

  • $\begingroup$ We just replaced ours and while talking with the A&P came up with the hypothesis that there are three reasons for it: noise reduction, small increase in speed from reduced turbulence at the root, and keeping water out of the joint. $\endgroup$
    – JScarry
    Apr 9, 2021 at 18:50
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    $\begingroup$ @JScarry This is the basis for an excellent answer. $\endgroup$ Apr 10, 2021 at 7:15
  • $\begingroup$ @PeterKämpf I can’t quote an authoritative source for my comment, so it’s just speculation at this point. $\endgroup$
    – JScarry
    Apr 10, 2021 at 21:26

3 Answers 3


One thing the wing root seal does is keep water out of the join between the fuselage and the main spar. Water in there could corrode the spar or, if it is wooden, cause it to rot.

  • $\begingroup$ That's nasty. Does that apply elsewhere? $\endgroup$
    – Abdullah
    Apr 9, 2021 at 16:17
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    $\begingroup$ it's vitally important to keep water out of airplanes- so any break in the fuselage structure needs to be well-sealed. $\endgroup$ Apr 9, 2021 at 16:47
  • $\begingroup$ Water will soften the epoxy matrix but otherwise will only corrode the metal parts, namely the fittings which connect the pushrods in the wing with the linkages in the fuselage. An aluminium structure will not be affected, unless you are close to the sea so that sea salt is added to the water. $\endgroup$ Apr 10, 2021 at 7:11
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    $\begingroup$ Depending on the weather, don't also forget freeze-thaw erosion: small amounts of water in the tiniest of cracks and joints can cause big problems over time. $\endgroup$
    – Landak
    Apr 10, 2021 at 13:43

The wing root seal reduces drag.

In glider aircraft with detachable wings or foldable, the seal is often nothing more than tape.

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    $\begingroup$ do we have any documentation stating that it reduces the drag and can we quantify that? $\endgroup$
    – NitinG
    Apr 15, 2021 at 10:57
  • $\begingroup$ @NitinG That's a good question that I'd like to know the answer to. That sealing gaps improves performance is widely believed. Here's one sailplane pilot documenting the sealing of gaps: members.goldengate.net/~tmrent/soar/docs/135/seal135.htm . See the last picture on the page for wing root sealing. $\endgroup$ Apr 16, 2021 at 11:20

When building kits I have more than a few times come across the explanation of the seals being for water and element protection. It depends on the installation, on something like a Cherokee it would help reduce drag but be most effective in keeping the wing attachment dry and protected from the element, on a composite it finishes off the smoothed out junction but still allows for flexing, there are many installations where the rubber seal is used to allow for movement.


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