Re: FAIR WARNING: A GUN cartoon. I happen to like this one...

From: Mike Lorrey (
Date: Wed Sep 26 2001 - 13:51:59 MDT

jeff davis wrote:
> I wrote:
> "I don't see how fifty or a hundred or even two
> hundred
> bullet holes through the fuselage of a large airliner
> would do anything more than depressurize the plane."
> "I think this is something like an urban legend."
> To which Mike replied:
> >The bullet would create a hole that would be spread
> >open like a peeled spam can for at least a foot or
> >two by the pressure differential.
> No disrespect meant, but I really need an
> authoritative reference in support of this assertion.
> Aluminum is tough and ductile, and the pressure
> differential is only 14.7 psi. If the bullet rips a
> long gash, as it penetrates the outer skin at a
> shallow angle, combined with strong (~700mph) airflow
> forces impinging on the rough edges of the "exit
> wound", then perhaps, a large blow-out might occur.

How do windshield cracks form (and why do many windshields fail as a

They have a small nick from a bouncing rock on them, then the small
cracks produced slowly creep across the windshield from heating and
cooling of the sun and precipitation, as well as the very minor low
pressure stresses of 60 mph winds and ground vibrations.

Sharp angles in any material act to focus stress at the apex of the
angle, and cracks are simply highly acute sharp angles in such
materials. This is the same reason why aircraft makers discovered in the
Comet airliner crashes that square windows focused stresses at the
corners, which is why all aircraft windows are now round.

In the event of a bullet rupturing an aircraft pressure cabin, it would
peel outward 3-10 flanges of metal in its passing. It won't just punch a
round hole. The stresses of the wind outside passing at 600 mph
laterally across the hole, combined with the escaping gasses will all be
focused on the narrowest parts of the cracks between the flanges of
metal, causing the cracks to spread outward rather quickly.

If you shoot through a window, only the window will open up, but that is
enough to suck out anyone within 2-6 feet without any real trouble. If
you shoot through the wall of the cabin, a much larger hole will result,
going a few feet to each adjacent rib and stringer in the airframe, and
perhaps beyond until pressure equalizes. If the plane does not slow down
rather quickly, the skin will continue to peel backward over time.

This archive was generated by hypermail 2b30 : Fri Oct 12 2001 - 14:40:57 MDT