[na85]

>Yet none ever wonder or look at why cockpit windows remain decidedly rectangular. :)

Aerospace engineer here. It's not the shape of the window but the radius of the corner. A circle is just a square with large-radius corners, really, and it's the sharp corner that causes stress concentrations.

If you look closely at modern jet liner cockpit windows you'll see they are in fact still rounded at the corners.

[FigBug]

The radius of cockpit windows doesn't look that different than the radius on the Comet's square windows.

https://upload.wikimedia.org/wikipedia/commons/2/2e/Boeing_7...

http://www.c-and-e-museum.org/marville/photos/planes/comet-6...

[na85]

Perhaps not, but remember that the metal fatigue phenomenon responsible for cracking in the Comet was not yet fully understood at that time.

Nowadays we have a very good understanding of how metals degrade/respond to repeated load cycles and can design around it. I have not personally worked on airliner window structures but there are a number of avenues that one could take to retain the general shape of the window and still avoid structural compromise due to cracking.

[NeedMoreTea]

I'm sure my brain had another sentence that never made it to keyboard when I was writing that, as I've given completely the wrong impression, opposite to intended. No idea what I was thinking. :)

Comet windows did have rounded corners, as seen in the wreckage photo, similar to the 707's and others. The cause was stress at rivet holes and lack of strength in those areas. After strengthening it had oval windows. The popular view continues to believe the cause was windows with corners.

[na85]

I believe you're correct, but they did also find that the magnitude of stress concentrations around the windows were much higher than design analysis predicted.