Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Speaker 1: Lauren bog Obam. Here, we're used to seeing square and
Speaker 1: rectangular windows in most building structures. There are, of course,
Speaker 1: rounded windows or oculi in architectural parlance, that lend character
Speaker 1: and intrigue to design. But think about airplanes and jetliners
Speaker 1: always round windows. How strange would it be to walk
Speaker 1: down the aisle of a jetliner and buckle up next
Speaker 1: to a square window. Our ancestors may have done just
Speaker 1: that once upon a time, as square windows were in
Speaker 1: fact the norm in early commercial airplane manufacturing. They worked
Speaker 1: just fine for centuries and homes and buildings, so why
Speaker 1: change a perfectly good design. Unfortunately, it took a few
Speaker 1: tragic events for engineers to take a fresh look at
Speaker 1: aircraft window design. It was in the nineteen fifties when
Speaker 1: commercial airliners were getting bigger, and they also started disintegrating
Speaker 1: in mid air. Two of those were to have land Comets,
Speaker 1: which were the first commercial airliner powered by jet engines.
Speaker 1: Their debut flight was May second of nineteen fifty two
Speaker 1: and their last was in September of nineteen eighty one.
Speaker 1: But the two that experienced this type of failure fell
Speaker 1: apart in flight in separate events in nineteen fifty three
Speaker 1: and nineteen fifty four. The cause was found to be
Speaker 1: those square windows. Engineers determined that the sharp edges of
Speaker 1: the plain squared windows created natural weak spots, causing metal
Speaker 1: fatigue failure. Metal fatigue failure is basically what happens when
Speaker 1: a piece of metal is subjected to repeated stresses, which
Speaker 1: cause micro cracks in the metal, which can grow to
Speaker 1: the point that the piece of metal snaps or tears.
Speaker 1: It can be catastrophic, but the cracks can be so
Speaker 1: small that it happens without any visual warning. So the
Speaker 1: corners of these square aircraft windows were easily stressed then
Speaker 1: further weakened by air pressure at high altitude. By the
Speaker 1: nineteen fifties, aircraft like that the Haveland Comets were flying
Speaker 1: faster and higher than industry predecessors, meaning after multiple flights
Speaker 1: and repeated pressurization, those square windows basically broke apart from
Speaker 1: the pressure. Rounded windows, on the other hand, are able
Speaker 1: to distribute the pressure evenly because they have no corners
Speaker 1: for stressed to concentrate, reducing the likelihood of cracks or brakes.
Speaker 1: The circular shapes are also stronger in resist deformation, making
Speaker 1: them more able to withstand the repeated pressure differences between
Speaker 1: the inside and outside of the aircraft. You might also
Speaker 1: notice that there are multiple layers of acrylic, not glass
Speaker 1: between you and the outside of the aircraft. Those layers
Speaker 1: offer additional protection from weather events like rain, wind, and fog,
Speaker 1: and that tiny hole at the bottom. Those are called
Speaker 1: bleed holes, and they add another layer of protection, helping
Speaker 1: keep the air pressure on board at a relatively constant
Speaker 1: level by allowing the air to pass through the various
Speaker 1: window layers. So the next time you're on a flight,
Speaker 1: be thankful for those rounded windows, whether you're enjoying the
Speaker 1: view or avoiding it because you don't want to be
Speaker 1: reminded of just how high off the ground you are.
Speaker 1: Today's episode is based on the article why are airplane
Speaker 1: windows round? On how stuffworks dot com, written by Schrei's Cunningham.
Speaker 1: Brainstuff is production of by Heart Radio and partnership with
Speaker 1: how stuff works dot Com, and it's produced by Tyler Clang.
Speaker 1: Four more podcasts my Heart Radio, visit the iHeart Radio app,
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.