Re: 777-style cabin windows on 767-400(ER)

Date:         20 Nov 98 02:30:56 
From:         "Brett L. Anderson" <>
Organization: The Boeing Company
References:   1 2 3 4 5
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Marc Schaeffer wrote:
> Tjarko de Jong wrote:
> > Oval windows have less stress-concentrations then more or less square holes in
> > the fusalage. Thus rounder window, less stress thus lighter.
> Even if your reply doesn't answer the question how the weight saving is
> achieved, your reply is technicaly correct. You may note that the most
> know windows are those of the De Havilland Comet, who changed from
> square to round after the well knows reasons ...  Oh ... to conclude the
> best looking windows can still be found on the -few remaining -
> Caravelle's

Close Marc, but no cigar... Now you are just continuing an urban myth.
The Fatal Flaw for the poor comet was a lot of poor fatigue details
combined with a poor material choice.  IIR the  1954 fatigue test of a
Comet only made 3600 pressurization cycles before it failed at the
corner of a passenger detail.  BUT..  the one recovered from the ocean
was determined to have initated a crack at the top corner of the ADF
cutout on the airplanes centerline.  This crack then grew to the forward
butt splice and down into the window belt area leading to a catastrophic

Anyway nothing inherently wrong with square windows but the material
selection and gage had better be sufficient to cover the relative stress
concentration in the corner over the acceptable design life.

Brett L. Anderson
Boeing Wichita