## Why are aircraft windows round?

 Round Aircraft windows - Wikimedia

Ever wondered why aircraft windows are always round in shape?
Aircraft windows were not always in round shape. In the 1950's, the de Havilland Comet aircraft of British Airways had square windows.

 de Havilland Comet square windows - Wikimedia

This aircraft crashed killing all 56 people in total. The crash of this aircraft taught a very important lesson about the shape of aircraft windows to aircraft engineers.

 British Airways Aircraft crash - Wikimedia

As we go higher, atmospheric pressure decreases but the air pressure inside the aircraft is adjusted so that passengers can feel comfortable during the flight. So this means that the air pressure inside the aircraft cabin is higher than the air pressure outside. Hence the high air pressure applies force on the fuselage in the outward direction which causes stress in the fuselage.

In a case of square windows, this stress gets concentrated at corners, where edges of square windows meet at 90° causing damage to the fuselage. Also for any other shape with an angle in it, the force will concentrate on the angles. So we need the shape of the aircraft windows such that there are no angles. So the circle is the apt shape. But oval shape windows are used in a Aircraft as they give a better view of the scenery to passengers.

In such windows, stress is distributed uniformly all over the circumference. So the stress won't concentrate at a single point. And hence it won't damage the fuselage.

Check out this video!

So this is the reason that all aircraft have rounded windows.