When traveling by plane, we all like to choose a window seat, through the plane window to see the sea of clouds and the blue sky.
But have you ever noticed that these portholes on airplanes are usually round?
This is certainly not for aesthetic reasons, considering that every design on an airplane is closely related to the safety of passengers, and so are these round portholes.
Airplanes were invented in 1903, and for years they had square portholes, but that changed in the 1950s.
The Havilland Comet, the first commercial jetliner in history, entered service in 1952 with square portholes, but this proved to be a flawed design.
At the time, little was known about metal fatigue, but the investigation of successive crashes led the aviation community to pay attention to the impact of repeated pressure changes on aircraft structures and to study metal fatigue.
According to the principle of physics and mechanics, the pressure will be accumulated at sharp angles, which means that the design of the square porthole causes 70% of the pressure in the cabin to be concentrated here, so there will be cracks caused by metal fatigue at the corner of the square porthole.
Since then, Havilland engineers have redesigned the portholes to be round or with large rounded corners to reduce pressure and increase fatigue strength.
Since then, the round porthole quickly replaced the square porthole to become the new standard in the field of civil aviation.
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