Catastrophic Decompression; Small Place Solo

I would never have picked up on it, but the aviation magazines made a big
thing of it at the time.

Bob Gardner

"Robert Moore" wrote in message
. 8...
"Bob Gardner" wrote

This reminds me of the time when LearJet got a jet certified for 51,000
feet...the photograph in the aviation press showed both pilots smiling
into the camera at FL510 without an oxygen mask in sight. Always
wondered how the FAA reacted to that.

They probably had "quick donners" available, which modifies the reg.

Bob Moore

Aviation wrote:

Do they put their oxygen masks on FIRST or start the dive first?

Masks go on first. After the Payne Weber incident, there was some discussion about
instituting a policy whereby at least one of the flight crew is wearing a mask at all
times above a certain altitude. I don't know if that was emplemented. Crews would set
the autopilot to perform the descent even if they lose consciousness.

Someone also pointed out my goof about "holding" your breath
upon going from cabin (8000 ft pressure) to ambient (25-35,000
ft pressure). In estimating how much time the average civilian
passenger could go without TAKING a breath of good air (14,000
ft or below), I used the HOLD your breath estimate. Assuming
there is 3-5 minutes of mask-oxygen and one minute of "holding"
the last breath, they've got 3-6 minutes to get down to breathable
(14,000 ft?) air and then below.

Once again. You cannot hold the last breath for 1 minute. You can't hold it for five
seconds. The air will rush out of your lungs as rapidly as it rushes out of the
plane,
and there isn't a single thing you can do about it. As soon as the pressure gets
below
about 10 psi, the oxygen will start to leave your bloodstream. You have perhaps 45
seconds before you turn into a babbling idiot - probably much less. If they don't get
you down to a decent altitude in less than about 4 minutes, you may stay a babbling
idiot for the rest of your life. A few more minutes, and you will probably die.

For the movie Executive Decision,
they were cruising at 39,000 ft. so they'd have to dive 25,000 ft
to 14,000 ft in 5 minutes, 5,000 ft/minute, average. Doable?

Mike Rappaport posted that his aircraft can descend at 10,000 fpm. He also posted
the opinion that many jets can do better than that.

I found some rate of ASCENT data of about 3850 ft/min at
http://www.altairva-fs.com/fleet/poh...0747%20POH.htm
but descent data isn't clear to me but it looks like 2500 ft/min
from cruise altitude down to 10,000 ft is the recommended ROD.

Recommended descent rate goes out the window in an emergency. Think on it a little.
Most jet airliners top out between 400 and 500 mph. Idle the engines and point the
nose down, you should be able to get a rate of descent in excess of 25,000 fpm. Hit
500 knots straight down, and you're talking 50,000 fpm, but the pullout would
probably
pull the wings off.

The discussion of the ear problem seems unsettled. Upon going
from 8000 ft cabin pressure to 25000+ ft pressure in a couple
of seconds (if loss of pressure is total), some rapid swallowing
should equilibrate your ears to low pressure. Descending from
25,000+ (39,000) ft at 5,000 ft/min could result in reversible
or IRREVERSIBLE damage depending on a person's ability to
equilibrate REALLY fast.

If you have the presence of mind to do the exercises necessary to save your ears
when the pressure drops, perhaps you'd have the presence of mind to hold your
nose and blow into your ears on the way down? Even if you don't, it beats dying.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."

"Mike Rapoport" wrote in message
hlink.net...

"Ralph Nesbitt" wrote in message
m...
Hopefully all realize when referring to "Air Pressure" at altitude this
is
an "absolute" pressure value inside the fuselage irrespective of
ambient.
When referring to air pressures at ground level the pressure reading is
above unadjusted ambient barometric pressure.

This is incorrect, pressurization is the differential between ambient and
cabin preasure.

Mike
MU-2

Please reconsider your statement above as it applies to pressurization of
A/C cabins at altitude.

At altitude A/C cabins are like a pressure vessel. A/C cabins are
pressurized to maintain ~ 12 PSI Gauge, ~ the same as normal atmospheric
pressure @ 11,000' ASL, in the cabin irrespective of altitude above 11,000'
ASL.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

A/C pressure systems are set to operate from departure point. If set
manually from info provided by ATC this is "Unadjusted Barometric
Presser"
read from an instrument at the base of the Tower, a specified height
above
the ramp. Most modern commercial A/C are equipped with automatic systems
that capture relevant data upon command/that is reset for each flight.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

"Robert Moore" wrote in message
...
"Ralph Nesbitt" wrote

Hopefully all realize when referring to "Air Pressure" at altitude this
is
an "absolute" pressure value inside the fuselage irrespective of
ambient.
When referring to air pressures at ground level the pressure reading is
above unadjusted ambient barometric pressure.

In the Boeing aircraft that I flew (B-727,B-707,B-720) there were two
gages on the FE's panel. One was a simple altimeter that indicated the
cabin altitude at all times and the other, a differential pressure gage
that indicated the difference in pressure between outside and inside.
The maximum differential for those aircraft was around 8.6 psi. The only
way to determine the absolute pressure inside the aircraft would be to use
a graph to convert the altimeter indication to pressure.

Bob Moore

The protocols you reiterate above will translate to a ~ constant pressure of
12 PSI Gauge inside the cabin as the A/C moves through it's flight profile
above ~ 11,000'.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

"Jon Woellhaf" wrote in message
news:jvFIb.85543$VB2.191432@attbi_s51...
During the explosive decompression portion of my Air Force altitude
chamber
training, we sat in a small chamber adjacent to the larger main chamber
with
our masks off. The airtight door between the two chambers was closed. The
large chamber was evacuated to 50,000 feet, or so. We were at about 10,000
feet and had our masks off.

Without warning, the hatch between the chambers was suddenly opened. There
was a loud bang, and the pressure in the two chambers very quickly
equalized
to about 30,000 feet. The whole chamber filled with thick fog. I felt for
my
mask and put it on.

Ever after, I have been amused at the flight attendant's briefing, "In the
unlikely event of a sudden loss of cabin pressure, the oxygen masks in
front
of you will automatically deploy. Simply put the mask over your mouth and
nose and breath normally. Etc. etc."

Yeah, right! First there's a loud bang and everyone thinks a bomb has gone
off. Then the cabin fills with super cold thick fog. The pilot puts the
plane in a dive to get to breathable air and the masks are hanging a
couple
feet in front of you. I think it would be absolute chaos.

Have any of you experienced an actual explosive decompression while in
flight?

Jon

Never experienced it personally, but have met 4 A/C that have over my 40+/-
years of CFR/ARFF experience.

There were a few injuries from flying stuff, otherwise many had "Bloody
Noses", while some had "bleeding from the ears. In most instances those
injured by various "Flying Objects" showed signs of hypoxia.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

Jim, if I install a transponder pin with a carbon fiber ground plane,
inside a fiberglass fuselage, what equipment is needed to see how well
it's working? Or do I just fly around and ask ATC "Can you see me
now? Can you see me now?"

(actually, I've already installed it, but I'm not flying yet.)


On Wed, 31 Dec 2003 15:57:13 -0800, Jim Weir wrote:

:Yes, I got results on the carbon fiber and I would have SWORN that I posted them
:to this site.
:
:Putting a GPS antenna UNDER a small bowl-shaped carbon fiber radome immediately
:killed any GPS signal into a 27 dB gain active antenna INCLUDING satellites that
:were directly overhead.
:
:Figuring that the carbon was so lousy a transmissive path, I drilled a hole on
:the top of the bowl and used the bowl as the groundplane. VIOLA. The GPS
:antenna worked every bit as well on TOP of the carbon fiber as it did on a metal
:ground plane of approximately the same size.
:
:I can't say this is true for any other service than GPS (transponder, vhf nav &
:com, etc.) but it did test well for GPS.
:
:Jim
:
:
:
:Richard Riley
:shared these priceless pearls of wisdom:
:
:-
:-Did you ever get results on the carbon?
:
:Jim Weir (A&P/IA, CFI, & other good alphabet soup)
:VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
:http://www.rst-engr.com

"Cub Driver" wrote in message
...

Was that in reference to a stray bullet causing the decompression?
If so, I'd have to agree that he's full of it.

Yes, just so. He agreed that the sky marshal would have frangible
bullets, but argued that the terrorist would not. That would lead to a
bullet through the airplane (he didn't specify window, which I
understand to be a problem) followed by explosive decompression "and
all that that entails."

all the best -- Dan Ford
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.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

On Wed, 31 Dec 2003 16:04:08 -0500, "Ron Natalie"
wrote:


"Bob Gardner" wrote in message news:bgFIb.16418$I07.44872@attbi_s53...
Well, it's been awhile, John, and I can hardly remember things that happened
last week, much less things that happened in the 70s. However, I do not
recall anything odd happening to my body during the ascent to 25000 but do
recall my lips doing the blub-blub-blub thing during the decompression. As
the pressure in the chamber rapidly increased, it kinda pushed the trapped
gas out.
It's the other parts of your body doing the blub-blub-blub thing that's problematic.

Just remember it's absolutely essential to drink lots of beer, eat a
lot of chips with a hot dip and baked beans the night before to make
the altitude chamber a truely memorable experience.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Ralph Nesbitt wrote in message
news

"Robert Moore" wrote in message
...
"Ralph Nesbitt" wrote

Hopefully all realize when referring to "Air Pressure" at altitude
this
is
an "absolute" pressure value inside the fuselage irrespective of
ambient.
When referring to air pressures at ground level the pressure reading
is
above unadjusted ambient barometric pressure.

In the Boeing aircraft that I flew (B-727,B-707,B-720) there were two
gages on the FE's panel. One was a simple altimeter that indicated the
cabin altitude at all times and the other, a differential pressure gage
that indicated the difference in pressure between outside and inside.
The maximum differential for those aircraft was around 8.6 psi. The
only
way to determine the absolute pressure inside the aircraft would be to
use
a graph to convert the altimeter indication to pressure.

Bob Moore

The protocols you reiterate above will translate to a ~ constant pressure
of
12 PSI Gauge inside the cabin as the A/C moves through it's flight profile
above ~ 11,000'.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

http://books.nap.edu/books/030908289...6.html#pagetop

http://print.nap.edu/pdf/0309082897/pdf_image/36.pdf


Paul Nixon

"Ralph Nesbitt" wrote:

"Cub Driver" wrote:

Was that in reference to a stray bullet causing the decompression?
If so, I'd have to agree that he's full of it.

Yes, just so. He agreed that the sky marshal would have frangible
bullets, but argued that the terrorist would not. That would lead to a
bullet through the airplane (he didn't specify window, which I
understand to be a problem) followed by explosive decompression "and
all that that entails."

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.

Really? I saw a movie in the 1960s where a guy with a .38 revolver
tried to shoot another pax on an airliner (I think it was a DC-7), and
he missed and the slug went through the cabin wall and hit an engine and
set it on fire. :-]