Hi Mike,

Not sure of the ultimate provenance but I found that quote here:

http://www.airpages.ru/eng/mn/lan_01.shtml

Claims to be extracts from the ‘Maintenance Manual’

For the Comet, pressure differential 8.25 psi:

The skin was generally 22 s.w.g. (0. 028 in.) except along the sides of the fuselage, where 20 s.w.g.
(0. 036 in.) skin contained the windows (Fig. 3). Skin material was D.T.D.546.

( I found this document which is very readable: http://naca.central.cranfield.ac.uk/reports/arc/rm/3248.pdf )

Alarmingly, that’s remarkably similar to the Lancaster, though using different alloy:

This framework is covered with alclad (a light aluminium alloy) sheet, the majority being 22 SWG but in some places 16 SWG. This is riveted to the formers and stringers with dome-head rivets.

From what I can find online, the revised Comet 4 had 18 swg fuselage skin thickening to 16 swg around cut-outs. Designed pressure differential was 8.5 psi.

The Britannia had fuselage skin gauge of 19 swg ( 0.040 inches ) for pressure differential of 8.2 psi.

The Comet 1 windows and its other square cutouts had rounded corners as this figure from the official report shows.

Wow, that completely changes my understanding of the cause!

Indeed here is the ADF window from G-ALYP at the Science Museum, in plain sight.

[ATTACH=CONFIG]235955[/ATTACH]

So the whole ‘square windows’ story is urban legend.

Looking back through the Flight reporting of the Inquiry, thickening of the skin around cut-outs and the revision and reduction of bolt-holes and manufacturing cracks were the actual remedies.

I consider myself re-educated!

Thanks.