🚀 go-pugleaf

In ca.general M. W. Eglestone <smsmike@bellsouth.net> wrote:
:  Qualifications: 26 Years as an Aircraft Structural Repair Specialist.

:  The average thickness of the Aluminum skin on commercial aircraft is
: between .040 and .050 of an inch. Around the thickness of 3 to 4
: playing cards stacked together. In other words, it's real damn thin.

:  It doesn't need to be any thicker than that because it doesn't carry
: much of a load. The structure of the aircraft carries 65 to 70 percent
: of the loading placed upon the average airframe. The aluminum is
: normally one of two alloys 2024-T3 or 7075-T6. Both are strong, both
: are light weight. Both will crack like glass if subjected to shear
: forces at 90 degree angles to the heat treated grain of the metal. The
: skin gets its strength by being attached to the structure, it has very
: little stand along strength in thin cross section applications.
....

     Do they still use 7075 alloy for aircraft??  I thought that they
quit using this alloy (light and strong though it is) because it is
so  brittle.  Wasn't it brittle crack propagation in 7075 that caused
the Comet I crashes in the mid-50s?