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I have seen that some aircraft have some of their windows painted white. As you can see in this picture, this A340 has many windows painted white. Why is it that? thai a340

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marked as duplicate by SMS von der Tann, Community Jan 28 '16 at 19:08

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If you look at the seating chart for that plane, you'll notice that those windows match the location of toilets and galleys.

Note that the exact position of toilets and galleys may change during the lifetime of an aircraft, so it's easier to have all the windows installed by design, and just obstruct some that are not used. Even if it were just obstructed from within, I suppose it's better if in an emergency, if emergency personnel had to look inside the plane (to check for people still trapped inside), they would be able to identify quickly those windows that do not need looking through.

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It means that there is some sort of internal structuer (like a wall or a cooking unit) behind that window on that particular configuration of the aircraft. Manufacturers are required to certify the planes with windows in place in order to show that they don't suffer from metal fatigue after repeated flights. So moving a window (or covering it up with metal) is a lot harder than just putting a little plastic cover on the inside of the window. Hence, when a particular configuration places a wall or a cooking unit there, they just cover it up.

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    $\begingroup$ As I understand the statement, the aircraft is certified with its maximum number of windows. Changing the window configuration changes the structure of the air frame, requiring a new certification, therefore, the windows are simply covered from the inside, leaving the air frame unmodified and the original certification still valid. $\endgroup$ – FreeMan Jan 28 '16 at 18:12
  • $\begingroup$ That is tested for as part of the certification process. Modifying the frame to plug the window (instead of just covering it) would change the way stress propagates through the metal, and would change the rate of fatigue, thus needing a new round of certification. Covering or painting over the window is much simpler and cheaper. $\endgroup$ – FreeMan Jan 28 '16 at 18:29
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    $\begingroup$ The story of the De Havilland Comet, en.wikipedia.org/wiki/De_Havilland_Comet. shows why "windows" and "metal fatigue" are closely connected... $\endgroup$ – DJohnM Jan 28 '16 at 20:28
  • $\begingroup$ @DJohnM Bingo, I thought about including it but figured people would likely look up metal fatigue on their own. But yes, that is the perfect example of why it matters. $\endgroup$ – Jay Carr Jan 28 '16 at 20:35

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