Airplanes have circular windows for a reason. It took two plane crashes to find out.

When you get on a plane, have you ever wondered why the windows of this means of transport They have an oval shape. If you look closely, it’s not just the windows: also the armrests, trays, screens and any interior furniture. has a circular shape. Although it may seem something purely aestheticthere is actually scientific reasoning behind this choice. But before getting into the technical details, we need to talk a little about the history of aviation and how two fatal accidents changed everything.

In their early days, airplanes had rectangular windows like those found in any house. As taking to the skies became more popular in the 1950s, airlines started flying at higher altitudes. This guaranteed them considerable economic savings, since the thin air generates less resistance and, therefore, less fuel is consumed, as well as allowing more comfortable driving with less turbulence.

But in order for planes to fly at those heights, manufacturers were also forced to make design changes. The cabin had to be pressurized so that the pilots could breathe without problems. And a pressurized cabin requires a cylindrical shape to function, which creates a pressure difference between indoor air and outdoor air which increases as the plane rises. The flat body expands very slightly and therefore stress is applied to the material.

And this is where the shape of the windows come into play. In 1954 there were two fatal accidents which caused the death of 56 passengers and crew. The reason the fuselage disintegrated had to do with a design flaw, which was that they had kept the windows square. Due to its right angles, Cabin pressure was concentrated in its corners and it was multiplied by three, more than in the rest of the fuselage. That caused the windows to end up exploding.

It must be taken into account that airplanes usually fly at an altitude of 10,000 meters or more and that level atmospheric pressure It is about a third of normal. As Real Engineering explains in this video“When a material changes shape like this, stress is created in the material. Eventually, the stress can increase so much that the material breaks.” This is exactly what happened in the aforementioned accidents.

The problems

However, in a circular plane, tension flows smoothly through the material, a flow that is interrupted by the introduction of a window. But if the window is oval, stress levels are more evenly balanced. The same principle applies to the cargo and cabin doors. And that’s why we also see it in the windows of ships and spaceships. Unfortunately, it took two plane crashes and several decades of research to realize the evils that square windows were causing.

Furthermore, as commented Anthony Harcup, director of the Teague design company, which has worked with Boeing for more than 75 years in this article from Travel + Leisure: “Sharp edges hurt elbows, knees, hips… or any part of the body they come into contact with. Rounding of all parts of the plane is also done for the “deletalization”a design principle that ensures that when subjected to Murphy’s Law, a passenger cannot be injured anywhere in the airplane seat.”

It’s not just the shape of airplane windows that has changed over the years, but also their material. The windows you see on airplanes actually They are not glass, but acrylicwhich is more durable than the first. Also, as you may have noticed, there are three layers in each window. In fact, the interior window that faces passengers is not even part of the structure of the plane (it is just a safety measure so that the exterior window does not get touched or scratched). And the second layer exists as reinforcement to maintain the pressure on the end in case the exterior window is damaged.

If you looked at the window, you will also have seen a small hole in this layer. Its role is essential since it serves as a valve to equalize pressure between this inner window and the outer window. Between the interior and exterior window there is a small air chamber and this hole regulates the pressure between the two sheets automatically. In addition, it balances the humidity level, preventing the window from fogging up or freezing. Everything on an airplane is pure science.

Images | Unsplash

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