Punctured pressure cabin.

"Gord Beaman" wrote...

Dunno about smart but yes the 'hole' is indeed 3 or 4 inches wide
(and there's two usually) but they're not wide open all the time
(only when 'dump' is selected). They have another valve portion
which mates with them and regulates the 'outflow' to regulate the
cabin pressure which controls the 'cabin altitude'.

On the 747 the outflow valves that regulate cabin pressure are about 1 x 3 feet,
and there are 2 of them. Normal opening is in the range of 12-19%, or about
103-164 square inches. A .40 cal bullet has a cross-sectional area of about
0.126 square inches, or about 1/1000 of the normal outflow area.

Even a full pax window, at about 6x8 inches, has less area. Though it would be
noisy and breezy if a window disintegrated (until a serving tray or something
got stuck in it), rapid depressurization would not occur, as the outflow valves
would adjust over the course of about 2 seconds.

Of course, the size of the outflow valves in smaller airplanes would be somewhat
smaller, but the net result would be similar.

"Kevin Brooks" wrote...

A cargo hatch blew out of a DC-10 in 1974, and it took a big chunk of the
cabin floor above, with passengers, out of the aircraft--the rest of the
aircraft then augered in. Face it, rapid decompression *can* (does not mean
*will be*) be a very bad thing, even when it may just involve a window.

The belly cargo door in a DC-10 is on the order of 6x8 feet, or 7,000 square
inches. A window is on the order of 100 sq in or less, and a bullet hole 0.2 sq
in or less.

You cannot compare the rapid decompression from the instantaneous loss of the
cargo door to the outflow from a bullet hole or loss of a window.

Further, the loss of that cargo door caused secondary structural damage --
buckling of the main deck -- which compromised the structural integrity and
controllability of the entire aircraft. Neither of those would occur with a
single bullet hole in the fuselage -- no matter WHERE or WHAT it hit -- or loss
of a cabin window.

"Cub Driver" wrote...

"Actually, a little bigger. There are two outflow valves that work in
tandem. On the 747 they're located on the aft belly, and each is a
touch smaller in area than one aircraft window -- an oval about 4in by
12in. There are also two relief valves on the left side of the
airplane, and they are about 8" in diameter."

I don't know about the 747 Classic, but the -400 has 2 rectangular outflow
valves, each about 1 x 3 feet. The -400 also also has 3 A/C packs vs the 2 in
the Classic for pressurization.

"Kevin Brooks" wrote in message
news



That is the problem with overgeneralization--it is usually wrong. It
"could"
indeed cause more than terror and discomfort. The Brazilian airliner lost
a
passenger when it had two windows taken out; a Piedmont airliner suffered
a
passenger fatality during a rapid decompression that did not involve any
large opening at all. Having been through a few nasty eardrum ruptures, I

Brooks


Direct quote from NTSB report ATL89IA099 concerning the Piedmont
incident: (emphasis added)

THE PASSENGER WAS TAKEN TO A DAYTON HOSPITAL AND
DIED AT ABOUT 6 HOURS AND 50 MINUTES LATER. THE
MONTGOMERY COUNTY CORONER RULED THAT DEATH WAS
DUE TO NATURAL CAUSES.
-----------------------

Henry Bibb

"Cub Driver" wrote...

And more detail yet. This too from rec.aviation.piloting:

************************************************** **********************

Anyone
familiar with the structure of an A/C will immediately ROFL at the
idea of a 9mm bullet penetrating the external skin if fired from
inside the cabin.

It would take a substantially more powerful weapon than a 9mm to cause
a "Window Failure",
.. . .

The same applies to a bullet exiting through the A/C skin. Consider
between what is seen as the interior cabin wall & the "External Skin"
of the A/C is a layer of insulation, assorted wiring, plumbing in
some places, plus untold ribs, stiffeners, & other assorted structural
components all of which have some "Curvature" to them.
.. . .

There are a few places a "Very High Velocity Bullet" of large caliber
could possibly exit the external skin if it the internal point of
impact was at a "very specific angle, very close to 90 degrees to
external skin" if fired from close range internally.
.. . .

************************************************** ******

(Again: the above is quoted from rec.aviation.piloting)

....which doesn't mean anything as far as credibility goes! Who wrote that?!? I
am almost ROTFL at some of the assertions made up there (salient parts
retained)!

Though the plexiglass in the cabin windows is tough, it isn't THAT tough! A 9mm
or .40 S&W round would EASILY penetrate both layers! The flattened edge of a
JHP round would help prevent ricochet when it hit the thin inside layer, and
mushrooming would probably start without any substantial decrease in velocity.
The net result would be a hole of about 1/2" in diameter. Whether or not the
window would fail immediately or eventually is a matter of conjecture, but is
entirely within the realm of possibility.

As for the aluminum skin, it is already stressed by the differential pressure,
and could not resist a similar round. The interior trim and insulation would,
again, start the JHP mushrooming, and maybe slow it down somewhat, but not
enough to prevent it from penetrating the thin aluminum skin.

IF the bullet happened to hit a rib, it may well be stopped. An overlapped skin
section would not stop it, however. Air ducts wouldn't affect it much at all;
hydraulic lines would deflect it rather than stop it or cause it to "ricochet";
and a THICK wire bundle MIGHT slow it enough to prevent penetration.

---------------------
John Weiss
Retired Naval Aviator
current 747-400 pilot

FWIW, tomorrow (Friday) night on The Discovery Channel's "Myth Busters"
program, one of their projects is rapid decomp of an airliner.

"Emmanuel.Gustin" wrote...

In
extreme cases, rapid pressure loss (or perhaps
more accurately, an internal pressure differential) can
lead to major structural failures, especially around
bulkheads that are insufficiently vented -- the pressure
differential is enough to make these collapse -- or in
fuselages that are already 'tired'.

AFAIK, all current airliners have sufficient blow-out doors in interior
bulkheads to prevent that sort of structural failure.


There is also the risk of bullets bouncing around inside
the plane and doing damage to power lines, fuel systems,
etc. Historically, fire has been the major killer of
aircraft following projectile damage.

Since almost everything aft of the cockpit in an airliner is "soft" (aluminum,
fabric, plastic, fiberglass...), the likelihood of multiple ricochets is
extremely low. Also, the likelihood of hitting a pressurized fuel line in a
low-wing airliner is negligible. Even in a high-wing airplane like a BAE-146 or
ATR, it is also unlikely in any credible scenario I can think of. A single
inert bullet into a fuel tank would not likely cause a fire.


The worst problem is the prospect of a gun battle in a cabin
packed with people. Almost every stray bullet is going to
hit someone; even if the sky marshall hits the right man
(or woman) the bullet seems likely to hit others as well.

Considering the alternative of an uncontrolled crash into the ground, which do
you prefer?


I don't
think it is wise at all to give guns to pilots after
minimal training.

First, the training is NOT "minimal"! It is intense and specialized.

Second, the pilots' use of their weapon is restricted to the case where the
terrorist already has gained access to the cockpit (likely in an airplane where
there are NO Air Marshals). Again, there is only one credible alternative
today. Which do you prefer?

In article ,
"Kevin Brooks" wrote:

"Cub Driver" wrote in message
...

Dan, you are forgetting that there was indeed documented evidence of a
passenger being sucked out of a blown window brought out during that
discussion--a TAM Fokker F28 turboprop somwhere over Brazil

I'd rather give up the guy in the window seat than go down with the
airplane onto Times Square.

Again I say: fasten your seat-belt when flying!

You must have missed the rest of the message where I acknowledged that the
decompression threat did not outweigh the threat from hijacker(s).

Here's the thing: if it takes you more than about a second to unlock
your seat belt to go after a hijacker, you're not exactly the first
string. Wait for the coordinated people to go first, then help if you
can.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

On Wed, 31 Dec 2003 23:06:55 +0000, "M. J. Powell"
wrote:


There has been a bit of a furore over here concerning the new US
requirement to airlines to supply air marshals when requested. The
concern is mainly over the possible puncture of a pressure cabin.
What do readers think is the result of decompression via a bullet hole?

A little more noise in the cabin, at least near the hole.

Mary

--
Mary Shafer Retired aerospace research engineer

"John R Weiss" wrote in message
news:LVZIb.187838$8y1.595561@attbi_s52...
"Kevin Brooks" wrote...

A cargo hatch blew out of a DC-10 in 1974, and it took a big chunk of
the
cabin floor above, with passengers, out of the aircraft--the rest of the
aircraft then augered in. Face it, rapid decompression *can* (does not
mean
*will be*) be a very bad thing, even when it may just involve a window.

The belly cargo door in a DC-10 is on the order of 6x8 feet, or 7,000
square
inches. A window is on the order of 100 sq in or less, and a bullet hole
0.2 sq
in or less.

You cannot compare the rapid decompression from the instantaneous loss of
the
cargo door to the outflow from a bullet hole or loss of a window.

Nobody has said you could. What I have said, repeatedly, is that evidence
does indeed exist that rapid decompression from relatively small "holes"
(used vicariously--I don't know that the Piedmont 737 decompression incident
even involved a "hole") can be fatal, with two cases cited. The DC-10
incident was mentioned as just another example of the possible consequences
of *rapid* decompression, though in that case the door in question was
indeed quite a bit larger than a window (but then again, it was not directly
accessing the passenger compartment, either).


Further, the loss of that cargo door caused secondary structural damage --
buckling of the main deck -- which compromised the structural integrity
and
controllability of the entire aircraft. Neither of those would occur with
a
single bullet hole in the fuselage -- no matter WHERE or WHAT it hit -- or
loss
of a cabin window.

But you cannot classify the loss of a window (or two) as a nominal event, as
others apparently have. That Brazilian passenger who left that TAM Fokker at
altitude would have disagreed with you if you did, as would also the poor
fellow who died in the Piedmont incident, and as would those folks who
suffered ruptured eardroms and the like during the Aer Lingus 737
decompression. A bulet hole in the fuselage is a minor inconvenience and not
arapid decompression cause--a bullet hole in a window that leads to rapid
decompression is quite a bit more serious, and potentially fatal.

Brooks