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I've looked all over this site, and also Web searches - but I can't seem to find any discussion about, and the construction cross-section of, a commercial airliner's pressurized fuselage wall. Not the cross-section of the whole cabin, but just the fuselage wall from inside the cabin to outside.

More specifically, I'm curious as to what layer (and where in the cross-section) contains the pressurized compartment. Do the circular ribs (or whatever they're called) contain this layer, or is the outer skin the pressure vessel?

I've already seen the below questions (and their answers), but they deal primarily with cabin/cockpit window construction.

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The pressure hull is the aluminum tube formed by the outer skin and supporting frames which serve to stiffen it. Within that is a layer of insulation which is fibreglass in a ripstop plastic material envelope made into custom fitted sections clipped into place, then the facia panels that create the interior surfaces. At max pressure differential the hull swells a little bit, maybe a quarter inch in a large airliner. The primary structure is the outer tube.

A big problem with airliners is warm and very humid interior air (from the passengers) is able to circulate between the facia panels and outer hull and some of this air gets between the insulation batts and the outer skin, which at altitude is really cold so the moisture condenses as frost/drops. Over time water starts to get absorbed into the insulation. Airliners can have hundreds of pounds of water in the insulation especially down at the bottom, and at heavy checks the insulation has to be removed and dried out.

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  • $\begingroup$ Thank you for this answer, but after reading that second paragraph, I don't think I'll ever sit inside a pressurized aircraft the same way again knowing all that condensation is lurking in the insulation. Ewww!! $\endgroup$
    – pr1268
    Commented Apr 21, 2018 at 23:08
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    $\begingroup$ It's worse in some airliners than others, and there are aftermarket systems operators can install called "zonal dryers" that circulate low humidity air, which is the super dry air being pumped in from outside, between the insulation and the skin. $\endgroup$
    – John K
    Commented Apr 23, 2018 at 3:03
  • $\begingroup$ By "facia", do you mean "facial" or "fascia"? $\endgroup$
    – Vikki
    Commented Jun 23, 2018 at 16:46
  • $\begingroup$ Oops I guess it should be fascia. $\endgroup$
    – John K
    Commented Jun 23, 2018 at 18:11

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