WEBVTT - Why Are Airplane Windows Round?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,

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<v Speaker 1>Lauren bog Obam. Here, we're used to seeing square and

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<v Speaker 1>rectangular windows in most building structures. There are, of course,

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<v Speaker 1>rounded windows or oculi in architectural parlance, that lend character

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<v Speaker 1>and intrigue to design. But think about airplanes and jetliners

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<v Speaker 1>always round windows. How strange would it be to walk

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<v Speaker 1>down the aisle of a jetliner and buckle up next

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<v Speaker 1>to a square window. Our ancestors may have done just

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<v Speaker 1>that once upon a time, as square windows were in

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<v Speaker 1>fact the norm in early commercial airplane manufacturing. They worked

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<v Speaker 1>just fine for centuries and homes and buildings, so why

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<v Speaker 1>change a perfectly good design. Unfortunately, it took a few

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<v Speaker 1>tragic events for engineers to take a fresh look at

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<v Speaker 1>aircraft window design. It was in the nineteen fifties when

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<v Speaker 1>commercial airliners were getting bigger, and they also started disintegrating

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<v Speaker 1>in mid air. Two of those were to have land Comets,

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<v Speaker 1>which were the first commercial airliner powered by jet engines.

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<v Speaker 1>Their debut flight was May second of nineteen fifty two

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<v Speaker 1>and their last was in September of nineteen eighty one.

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<v Speaker 1>But the two that experienced this type of failure fell

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<v Speaker 1>apart in flight in separate events in nineteen fifty three

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<v Speaker 1>and nineteen fifty four. The cause was found to be

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<v Speaker 1>those square windows. Engineers determined that the sharp edges of

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<v Speaker 1>the plain squared windows created natural weak spots, causing metal

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<v Speaker 1>fatigue failure. Metal fatigue failure is basically what happens when

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<v Speaker 1>a piece of metal is subjected to repeated stresses, which

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<v Speaker 1>cause micro cracks in the metal, which can grow to

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<v Speaker 1>the point that the piece of metal snaps or tears.

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<v Speaker 1>It can be catastrophic, but the cracks can be so

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<v Speaker 1>small that it happens without any visual warning. So the

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<v Speaker 1>corners of these square aircraft windows were easily stressed then

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<v Speaker 1>further weakened by air pressure at high altitude. By the

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<v Speaker 1>nineteen fifties, aircraft like that the Haveland Comets were flying

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<v Speaker 1>faster and higher than industry predecessors, meaning after multiple flights

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<v Speaker 1>and repeated pressurization, those square windows basically broke apart from

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<v Speaker 1>the pressure. Rounded windows, on the other hand, are able

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<v Speaker 1>to distribute the pressure evenly because they have no corners

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<v Speaker 1>for stressed to concentrate, reducing the likelihood of cracks or brakes.

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<v Speaker 1>The circular shapes are also stronger in resist deformation, making

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<v Speaker 1>them more able to withstand the repeated pressure differences between

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<v Speaker 1>the inside and outside of the aircraft. You might also

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<v Speaker 1>notice that there are multiple layers of acrylic, not glass

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<v Speaker 1>between you and the outside of the aircraft. Those layers

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<v Speaker 1>offer additional protection from weather events like rain, wind, and fog,

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<v Speaker 1>and that tiny hole at the bottom. Those are called

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<v Speaker 1>bleed holes, and they add another layer of protection, helping

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<v Speaker 1>keep the air pressure on board at a relatively constant

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<v Speaker 1>level by allowing the air to pass through the various

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<v Speaker 1>window layers. So the next time you're on a flight,

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<v Speaker 1>be thankful for those rounded windows, whether you're enjoying the

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<v Speaker 1>view or avoiding it because you don't want to be

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<v Speaker 1>reminded of just how high off the ground you are.

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<v Speaker 1>Today's episode is based on the article why are airplane

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<v Speaker 1>windows round? On how stuffworks dot com, written by Schrei's Cunningham.

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<v Speaker 1>Brainstuff is production of by Heart Radio and partnership with

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<v Speaker 1>how stuff works dot Com, and it's produced by Tyler Clang.

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