Catastrophic Decompression; Small Place Solo

running with scissors wrote in
message om...
"John Gilmer" wrote in message
...
"Bob Gardner" wrote in message
news:QODIb.85072$VB2.187788@attbi_s51...
No way. You start off at sea level, of course, and they pump the
chamber
pressure down to 25000 feet with masks on...then they do some
experiments
with a few of the pilots taking their masks off, just to show how
severely
their abilities are affected. Then comes the explosive decompression,
which
takes the chamber from 25K back down to sea level in a second or two.

SIlly question but ...

Why would "they" pressurize the aircraft to sea level? Why not some
compromise "pressure" like that equivalent to, say, 6,000 or 8,000 feet?


EMWTK

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances
(eg medevac operations where pressurization is a factor)

Sec. 25.1 Applicability.

(a) This part prescribes airworthiness standards for the issue of type
certificates, and changes to those certificates, for transport category
airplanes.
http://www.astech-engineering.com/sy...apart25d.html#
Pressurization

Sec. 25.841 Pressurized cabins.

"(a) Pressurized cabins and compartments to be occupied must be equipped to
provide a cabin pressure altitude of not more than 8,000 feet at the maximum
operating altitude of the airplane under normal operating conditions."

Transport category:

* All jets with 10 or more seats or greater than 12,500lb Maximum
Takeoff Weight.
* All propeller driven airplanes with greater than 19 seats or greater
than 19,000lb Maximum Takeoff Weight.


Obviously the rule would not normlly apply to Medivac operations.

HTH,

Paul Nixon

"running with scissors" wrote in
message m...
"C J Campbell" wrote in message
...
"Ron Natalie" wrote in message
m...
|
| "C J Campbell" wrote in
message
...
|
| We do not really know any such thing. If the passenger is bigger
than
the
| window he simply cannot be pulled through it any more than he can
sucked
up
| through a vacuum cleaner hose.
|
| Passengers are pretty flexible. Some might plug up the hole, others
will
| go through holes that looked like they ought not to fit through.
|

The windows are surprisingly large, too. I have no doubt that a small
person
could get through one, especially if his seatbelt is not properly
fastened.
However, you are not going to lose a whole planeload of passengers this
way.
Given a choice, I would shoot a hijacker with the off chance of killing
an
innocent bystander rather than allow the hijacker to drive the plane
into a
crowded building.


ok.. interesting scenario. but what would be the option if the
hijacker was a midget ??

Shoot him with a .22?

"running with scissors" wrote in
message
FAR 91.211
Supplemental oxygen.

????

"Ron Natalie" wrote in message
m...

"Gary Mishler" wrote in message
news:eBoKb.745162$HS4.5776347@attbi_s01...
"running with scissors" wrote
in
message om...

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances

Actually, it depends on the aircraft. Aircraft are certified to certain
"differential pressures" which is the difference between in the inside
cabin
pressure and the outside ambient air pressure.

We were talking about transport aircraft. US certificated transport
aircraft
must keep the cabin altitude below 8000'.

Yup, I know. The Lear 60 is a transport category aircraft, certified under
Part 25, and it's cabin is normally around +/- 6,500ft. Previous poster
said cabin pressure is normally *at* 8,000 and I was just pointing out that
it depends on the aircraft.

Manufactures of transport category corporate jets seem to take pride in
pointing out to potential customers that their jet can maintain a lower
cabin altitude at cruise than the competitors, which all depends on the
certificated max psid.

Yup, but the butterfly is not necessarily all the way open at cruise
altitude... Anyway, us ga airplane folks generally don't appreciate how
much air flow the compressors can deliver to the cabin, especially if you by
pass the cooler - any idea what the cabin temperature go up to if direct
feed off the compressor was delivered to the cabin?... Might be a good
behavior modification tool...
Denny
"Jack Davis" wrote That would not be a good
guess! The main outflow valve on a 737 is
much larger than that.

"Gary Mishler" wrote in message news:eBoKb.745162$HS4.5776347@attbi_s01...
"running with scissors" wrote in
message om...

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances

Actually, it depends on the aircraft.


uh huh. i know it does. though if i posted an exact figure for a
specific aircraft type, then a whole flood of posts saying i am wrong
because "xx" type is pressurized to "yy"




Aircraft are certified to certain
"differential pressures" which is the difference between in the inside cabin
pressure and the outside ambient air pressure. An airframe must be designed
to handle the differential pressure required to maintain acceptable cabin
altitude up to the max flight level the aircraft is certified to.

As an example, the King Air I fly has a normal differential pressure of 6.6
psid. This provides for a cabin altitude of 2,700 up to 20,000 cruise
altitude, an 8,700 foot cabin altitude at 31,000 cruise altitude, and a
10,200 foot cabin altitude at 35,000 cruise altitude.

In contrast, the Lear 60 I fly has a normal psid of 9.5 (9.7 max) which
typically results in a cabin altitudes of around aprox 6,500 up in the
40,000 ish cruise altitudes.

Michael Williamson wrote in message ...
running with scissors wrote:
Michael Williamson wrote in message ...

John Gilmer wrote:



SIlly question but ...

Why would "they" pressurize the aircraft to sea level? Why not some
compromise "pressure" like that equivalent to, say, 6,000 or 8,000 feet?


Typically, they start at whatever the local pressure altitude
happens to be (which of course may or may not be sea level, depending
on where you happen to have the chamber). Also, I've never
experienced in any altitude chamber ride a rapid REcompression
down to sea level- it strikes me as a good way to have sinus
or ear problems.

Mike



nope. when the doors on an aircraft are shut the pressure is ambient.
thats it. when bleed air pressures the cabin its noramlly to about
8000ft.

While the final (steady state) pressure of the aircraft
(as determined by the cabin pressurization controller) will end
up at its cruise setting, the aircraft is pressurized from
takeoff and the cabin altitude will typically climb slowly
toward its set value (about 8,000' in this case) rather than
follow ambient- the pressurization system is indeed pressurizing
the aircraft its initial field elevation up to the cruise
pressurization setting.

In addition, my above response was poorly worded and I actually
was commenting on the pressurization of the altitude chamber- which
begins at whatever the ambient pressure happens to be. My bad for
not reading the question closely enough.

Mike


ditto, my bad for not reading closely. although you used the words
cabin pressurization, you did use the word chamber too !

"khobar" wrote in message news:W_qKb.17919$7D3.14891@fed1read02...
running with scissors wrote in
message om...
"John Gilmer" wrote in message
...
"Bob Gardner" wrote in message
news:QODIb.85072$VB2.187788@attbi_s51...
No way. You start off at sea level, of course, and they pump the
chamber
pressure down to 25000 feet with masks on...then they do some
experiments
with a few of the pilots taking their masks off, just to show how
severely
their abilities are affected. Then comes the explosive decompression,
which
takes the chamber from 25K back down to sea level in a second or two.

SIlly question but ...

Why would "they" pressurize the aircraft to sea level? Why not some
compromise "pressure" like that equivalent to, say, 6,000 or 8,000 feet?


EMWTK

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances
(eg medevac operations where pressurization is a factor)

Sec. 25.1 Applicability.

(a) This part prescribes airworthiness standards for the issue of type
certificates, and changes to those certificates, for transport category
airplanes.
http://www.astech-engineering.com/sy...apart25d.html#
Pressurization

Sec. 25.841 Pressurized cabins.

"(a) Pressurized cabins and compartments to be occupied must be equipped to
provide a cabin pressure altitude of not more than 8,000 feet at the maximum
operating altitude of the airplane under normal operating conditions."

Transport category:

* All jets with 10 or more seats or greater than 12,500lb Maximum
Takeoff Weight.
* All propeller driven airplanes with greater than 19 seats or greater
than 19,000lb Maximum Takeoff Weight.


Obviously the rule would not normlly apply to Medivac operations.

HTH,

Paul Nixon

medevac ops are not exempt. though under certain medical conditions
the cabin my not be pressurized or pressurized to a lower altitude.
nitrogen narcosis is one condition that springs to mind.

"Tom Sixkiller" wrote in message ...
"running with scissors" wrote in
message m...
"C J Campbell" wrote in message
...
"Ron Natalie" wrote in message
m...
|
| "C J Campbell" wrote in
message
...
|
| We do not really know any such thing. If the passenger is bigger
than
the
| window he simply cannot be pulled through it any more than he can
sucked
up
| through a vacuum cleaner hose.
|
| Passengers are pretty flexible. Some might plug up the hole, others
will
| go through holes that looked like they ought not to fit through.
|

The windows are surprisingly large, too. I have no doubt that a small
person
could get through one, especially if his seatbelt is not properly
fastened.
However, you are not going to lose a whole planeload of passengers this
way.
Given a choice, I would shoot a hijacker with the off chance of killing
an
innocent bystander rather than allow the hijacker to drive the plane
into a
crowded building.


ok.. interesting scenario. but what would be the option if the
hijacker was a midget ??

Shoot him with a .22?


lol

running with scissors wrote in
message om...
"khobar" wrote in message
news:W_qKb.17919$7D3.14891@fed1read02...
running with scissors wrote
in
message om...
"John Gilmer" wrote in message
...
"Bob Gardner" wrote in message
news:QODIb.85072$VB2.187788@attbi_s51...
No way. You start off at sea level, of course, and they pump the
chamber
pressure down to 25000 feet with masks on...then they do some
experiments
with a few of the pilots taking their masks off, just to show how
severely
their abilities are affected. Then comes the explosive
decompression,
which
takes the chamber from 25K back down to sea level in a second or
two.

SIlly question but ...

Why would "they" pressurize the aircraft to sea level? Why not
some
compromise "pressure" like that equivalent to, say, 6,000 or 8,000
feet?


EMWTK

"they" dont. cabin pressurization is normally at 8000ft though crew
may elect to use different cabin pressures under certain circumstances
(eg medevac operations where pressurization is a factor)

Sec. 25.1 Applicability.

(a) This part prescribes airworthiness standards for the issue of type
certificates, and changes to those certificates, for transport category
airplanes.

http://www.astech-engineering.com/sy...apart25d.html#
Pressurization

Sec. 25.841 Pressurized cabins.

"(a) Pressurized cabins and compartments to be occupied must be equipped
to
provide a cabin pressure altitude of not more than 8,000 feet at the
maximum
operating altitude of the airplane under normal operating conditions."

Transport category:

* All jets with 10 or more seats or greater than 12,500lb Maximum
Takeoff Weight.
* All propeller driven airplanes with greater than 19 seats or
greater
than 19,000lb Maximum Takeoff Weight.


Obviously the rule would not normlly apply to Medivac operations.

HTH,

Paul Nixon

medevac ops are not exempt. though under certain medical conditions
the cabin my not be pressurized or pressurized to a lower altitude.
nitrogen narcosis is one condition that springs to mind.

I was thinking about medivac helicopters. Dunno why since medivac goes
beyond helicopter operations. Oh well...

Paul Nixon