🚀 go-pugleaf

M. W. Eglestone 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.
> 
>  If a bullet is fired inside an aircraft, and that aircraft is
> pressurized, you have a pressure inside the skin and what amounts to a
> vacuum on the outside of the skin. The bullet will punch a hole
> "instantly" in skin that thin. The bullet, since it is a impacting
> from the inside (pressure) to the outside (vacuum) will more than
> likely RIP a good size section of metal out as it passes through.
> Having seen explosive decompression before, I would venture to say
> that an average .22 slug would rip out a hole about the size of a
> softball. IOW, the bullet will create a jagged hole which (because of
> the pressure inside that aircraft) will cause the metal to RIP along
> the grain boundary and you will get a blow out around that size. In
> the absence of pressurization, the hole would be about 3/4th of an
> inch in diameter if you include the portions that shatter because of
> the impact. Keep in mind that thin cross sections of Hardened Aluminum
> do NOT bend like steel does, they crack and shatter!
> 
>  Bottom line. A .22 short could, with very little difficulty, cause
> explosive decompression in an aircraft flying as low as 15,000 feet.
> The higher you go, the more likely it will happen.
> --
> 

Uh, I am no metalurgist, but the aluminum sheets that
they make aircraft skins out of is NOT brittle. they are
QUITE ductile.  I could believe that a tear would propagate
to a frame or a sheet edge.  I have seen pictures of DC-3s
which flew home and landed safely with DOZENS of 20mm holes
in the skin.  Modern alloys and materials are even better.

Baring a hit on a fuel, hydraulic, electric, etc line(not a 
trivial threat) a gunfight in a jet liner would not
threaten a catasrophic failure of the airframe.

>    (Mike Eglestone)
> 
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-- 
doug
--
No truce with Kings.