If you have ever travelled on an airplane and have an inquisitive mind, you may have wondered why airplane windows are oval shaped. Couldn’t they have come in any other shape – square, rectangle, or what have you?
It turns out there’s a very important reason for that. At a time, airplanes had square windows, but the unsuitability of this was learnt the hard way.
In one of the first major crash investigations in aviation history which occurred on January 10 1954 and involved a de Havilland Comet – the world’s first set of commercial jetliners – the wreckage of which was lifted from the seafloor off Elba (an island in the Mediterranean sea, off the coast of Italy), and re-assembled after it began to plunge out of the sky for unknown reasons.
Investigations later revealed that the pressurised cabin had burst from cracks emanating from window corners. It so happened that the windows of the de Havilland comet were square, and as an aircraft rises from seal level to cruising altitude, its fuselage (that is, an aircraft’s main body that holds cargo and crew) has to hold in a lot of pressure, which makes it bend slightly. It was this repeated bending overtime as the aircraft made successive journeys – called metal fatigue – that led to the cracks around its windows, and its eventual disastrous crash.
Learning from this, airplane models from that time onward came to be designed with windows that could withstand such repeated pressure. And as airplanes became more modern, and capable of flying at even higher altitudes, the pressure difference between the cabin and outside air became even much greater. Hence, the window shape became ever more crucial in preventing the level of stress from raising so high that it would crack.
And this, curious minds is the stripped-down story of how airplanes came to have oval-shaped windows that have characterised them to this day.