Why are the windows of planes round or curved?

Did you ever ask yourself why the plane windows are round? Whether you prefer to sit beside a window or not in your flight, after reaching your seat and putting your belongings in the overhead bin, you look around and notice the rounded edges of the window and wonder why this shape?

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Over years, the engineering of aerospace made great jumps in the aviation industry, which helped in carrying more passengers and going faster. Shapes of planes also changed to achieve safety, these changes included window shapes.

In the mid of the 20th century, airlines began to fly their aircraft at higher altitudes which allowed them to save money thanks to the thinner air, which produces less drag and a more comfortable ride with less turbulence. These altitudes were a problem as human beings cannot survive at 30,000 feet high. To make this possible, the cabin shape was changed to cylindrical to support the internal pressure. Previously, plane windows were designed in a square shape which was totally unsafe.

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In 1950, The de Havilland Comet manufactured a pressurized cabin that can fly higher and faster than other aircraft. At the same time, in 1953, three airplanes fell apart and 43 persons were killed – the reason was the windows.

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Where a corner is found, a weak spot is found. Each squared window corner means four weak spots, that lead to crashes under pressure such as air pressure. Through curved windows, the pressure which may break and crush windows can be reduced. The rounded windows are stronger and more resistant to deformation, so the difference of pressure inside and outside the plane can be avoided.

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Also as a traveler, you can notice the existence of multiple layers of acrylic between you and the outside of the plane. These layers provide additional protection against some events related to weather changes such as rain, winds, and fog. The tiny holes which are found at the bottom are called “bleed holes” that keep the air pressure safe by allowing air to pass through the multiple layers of the window.

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Anthony Harcup, senior director at the design house „Teague“, a design firm that has worked with Boeing for 75 years, said that the rounding of edges is done for “delethalization,” which is a design that ensures Murphy’s law and passengers can’t hurt themselves on any part of the aircraft seat. Harcup notes it’s not just for our protection, but for the planes as well.

“Whether a part is molded, machined and painted, or covered in laminate, the finish is far more likely to get stress fractures or have the finish wear off at the high-point when manufactured with sharp edges.”

Anthony Harcup


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