Punctured pressure cabin.

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!

all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

"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).

Brooks


all the best -- Dan Ford

"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.

Put fat people in the window seats. Maybe they can serve as a plug, and save
the rest of us.

Pete

Cub Driver wrote:

A normal bullet hole would be no problem. There's already a much
larger vent to the outside, which stabilizes cabin pressure against
the fresh & heated air being pumped in from the engines. People
smarter than I say that this hole is about three inches in diameter.



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'.

The pressurization regulator normally allows the cabin altitude
to slowly climb to roughly 8,000 - 9,000 feet while the a/c is
climbing to 35,000 - 40,000 feet. This puts the 'differential
pressure' (between the cabin and the outside pressure at roughly
8.5 PSID. (Pounds Per Square Inch Differential). This may not
sound like much but with a huge area such as a 747's cabin
there's a tremendous potential force there. That's why a small
explosion that rips a good sized hole in the skin can have
disastrous effect (No, a bullet hole is no problem as several
have mentioned)
--

-Gord.

"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.

"John R Weiss" wrote:

"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.

I agree...the size of valves that I quoted belong to a Convair
580...VERY much smaller than a 747, but I'm still surprised by
how large the 747 ones are. Anyhow, I agree with you about the
outflow valve compensating for a blown out window. Pretty well a
'nonevent' as far as disaster is concerned.
--

-Gord.

A normal bullet hole would be no problem. There's already a much
larger vent to the outside, which stabilizes cabin pressure against
the fresh & heated air being pumped in from the engines. People
smarter than I say that this hole is about three inches in diameter.

More detail on this: over on rec.aviation.piloting, there's a parallel
and very busy thread on this same subject. Here's what a Big Spam Can
Driver had to say on the subject of the vent hole(s):

"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."

So upon reflection it doesn't seem that even the blow-out of a window
could cause more than terror and discomfort, especially since it would
almost certainly be followed by an emergency descent to lower
altitude.

One of the pilots commented: "I always wear my seat-belt when flying.
Don't you?" Something to add to your resolutions for 2004


all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

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

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

The comments below are applicable to modern commercial Pax A/C. 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", even then impact would have to be near 90 degrees
because of their "Plug design, plus they are thicker in the center
than the edge This curvature is on the inside.

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. All these
components are riveted together through "Lap Joints". All
joints/connections are sealed with "Sealant" of varying strengths.

The structure of an A/C is designed to flex, expand, & contract as the
A/C goes thru pressurization/de-pressurization cycles.

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. Consider all the
materials described above a bullet would have to impact/penetrate,
without its path being diverted by some degree of ricochet.

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

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


all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

"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.