Why do airplanes have circular/round windows?

Question

Why do airplanes have circular/round windows?

Answer 1

All these answers are true, stress forms on the 90 degree corner of a square window, easily cracking when flexed.

The round windows pass the stress around the circumference of the circle so there is no focal point.

The same thing applies to ships, and during world war2 a large number of the liberty ships suffered stress fractures due to their construction with square hatches.

Answer 2

The sharp corners on square windows are places where stresses concentrate and multiply their effects, hence the term "stress risers."  Cracks, buckles, and tears in the airplane skin tend to start at these points.  The rounded corners in airplane windows are much less prone to this problem.

Answer 3

first answer was right, sharp corners are "stress risers"

Answer 4

Circular shapes are much stronger and resist deforming much better- ie like an egg! Also corners on external features such as windows would create much more drag on the air, meaning less fuel efficiency

Answer 5

Squire windows look great on a DC-3 so "911" is wrong there.

Go with the the guys who mentioned the British Comet, THAT'S the reason

Answer 6

The above is true regarding stress. They had to find out the sad way. The Comet had 3 fatal crashes just after takeoff and by putting the aircraft in a large water tank found out that the windows were the weak spot.

They filled the tank and emptied it to simulate thousands of flight hours.

Answer 7

Top three people are correct and also because square windows would look ugly.

Answer 8

To prevent stress cracks at the corners of a square window. Look up the Brithsh made Comet, the first passenger jet after World war II. Several were lost over water with loss of all passengers. Sudden structual faiilure of the hull. Tokk a while, but they finnally figured out it was the square window design held over from the prop plane design that caused the problem. Redesigned the window apetures and 'voila', good to go.

Answer 9

They're pressurized.  The shape avoids stress risers.

Answer 10

They didn't want to be "square." lol. The above are correct.