Catastrophic Decompression; Small Place Solo

"Jim Weir" wrote in message ...

There's a hell of a good question -- why did the OUTFLOW valve on the 727
(located on the starboard side of the aircraft back in the aft airstairs
compartment) have a FILTER on it?

Don't want all that nasty nicotine polluting the upper atmosphere?

Possibly because at ground level, it's possible that air might go in the outflows?

Dr. George O. Bizzigotti wrote:

"G.R. Patterson III" wrote:

Basically, the pilots need to get their masks on and get the plane down below
25,000' as rapidly as it can possibly be done. The descent to 10,000' can be made
a little more leisurely, but not much - there's always someone in the cattle
section who panicked and isn't wearing a mask.

One aspect that I have not seen addressed in this thread is the fact
that most oxygen systems can provide supplemental oxygen for a few
minutes only (I dimly recall figures like 3-5 minutes, but that may be
inaccurate). The pilots also need to get down to 10,000 feet within
that time before everyone's oxygen generators run out.

How could an SST like the Concorde get from cruising altitude down to
10,000 feet in 3-5 minutes?

"G.R. Patterson III" wrote in message

If the aircraft is much above 25,000', the masks will do little good. You
need
a pressure mask to survive long at (for example) 35,000'. Those used by
the
airlines for passengers are not good enough for that.

Passenger masks generally only need to provide sustenance for a couple of
minutes.

....the jet would have to go from let's say 30000 feet to 5000 feet in
30-45 seconds. My ears would explode.)

Basically, the pilots need to get their masks on and get the plane down
below
25,000' as rapidly as it can possibly be done. The descent to 10,000' can
be made
a little more leisurely, but not much - there's always someone in the
cattle
section who panicked and isn't wearing a mask. If that's one of the flight
attendants, you're really in trouble.

Ten thousand is where supplemental O2 is no longer legally required. In
reality, you're back in survivable atmosphere, for most people, at about
14,000 or so. Emergency descent procedures are predicated on descending
from cruise altitude to 10,000 MSL (or an altitude where you can maintain a
cabin alt of 10K) as rapidly as is safely possible. As a practical matter,
you won't be descending at much over 12-15 thousand f/m or so, so the
descent will take a minute and a half or more.

Jim Weir wrote
There's a hell of a good question -- why did the OUTFLOW valve on the
727 (located on the starboard side of the aircraft back in the aft
airstairs compartment) have a FILTER on it?

My B-727 Flight Manual does not confirm that this is the location
of the aft outflow valve and with 5 years experience flying the a/c,
(one year as FE) I don't recall it being there.

Bob Moore

"Ron Natalie" wrote in message news:3ff1fd08$0$32339

"Bob Gardner" wrote in message news:cLmIb.79193
I have no direct knowledge of how big an airliner
outflow valve is, but I am going to guess three inches in diameter

I think this is a good guess. It sort of looks like the top of a can of
parmesan cheese.

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.

JG

Different dash models perhaps? PSA had some of the first units to come off the
line. Later models may have found a better location? I dunno. I do remember
changing them at 3 am just after graveyard shift lunchtime. Barfo.

Then again, that was 40+ years ago. Things get hazy when you haven't done them
in a while.

Jim


Robert Moore
shared these priceless pearls of wisdom:

-Jim Weir wrote
- There's a hell of a good question -- why did the OUTFLOW valve on the
- 727 (located on the starboard side of the aircraft back in the aft
- airstairs compartment) have a FILTER on it?
-
-My B-727 Flight Manual does not confirm that this is the location
-of the aft outflow valve and with 5 years experience flying the a/c,
-(one year as FE) I don't recall it being there.
-
-Bob Moore


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Easily. My MU-2 can descend 10,000fpm. Any jet can easily do it.

Mike
MU-2


"Scott M. Kozel" wrote in message
...
Dr. George O. Bizzigotti wrote:

"G.R. Patterson III" wrote:

Basically, the pilots need to get their masks on and get the plane down
below
25,000' as rapidly as it can possibly be done. The descent to 10,000'
can be made
a little more leisurely, but not much - there's always someone in the
cattle
section who panicked and isn't wearing a mask.

One aspect that I have not seen addressed in this thread is the fact
that most oxygen systems can provide supplemental oxygen for a few
minutes only (I dimly recall figures like 3-5 minutes, but that may be
inaccurate). The pilots also need to get down to 10,000 feet within
that time before everyone's oxygen generators run out.

How could an SST like the Concorde get from cruising altitude down to
10,000 feet in 3-5 minutes?

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

"Ralph Nesbitt" wrote in message
m...

"Jeff Franks" wrote in message
...

Witnessed the result of "Port Hole Window" on the starboard side of a
C-5
blowing out during "Initial Factory Pressure checks" on a new C-5". The
window itself went through the side of a "Tin Sided Building" ~ 200'
from
where the window/port hole came from. A substantial number of the
insulation/batting blankets were torn from their normal place in the
cargo
bay & piled on the cargo bay floor near the opening. A large number of
the
insulation blankets/bats, along with seat cushions from the upper aft
troop
compartment were piled around the entrance to the stairs from the troop
compartment down to the cargo bay, plus scattered along the cargo bay
floor
in the direction of the failed port hole/window. Seat cushions,
mattresses
from bunks, & insulation bats/blankets from the upper front area were
piled
against the exit stairs from the upper from lobe & along the cargo bay
floor
toward the failed port hole/window. A few of the insulation
bats/blankets
were blown out the failed port hole/window.

A/C being tested were instrumented to record/document test protocols as
appropriate. According to instrumentation on the A/C, at time of port
hole/window failure the air pressure dropped from 14.5 lbs to 0 in .003
seconds.

Factory Pressure Check on C-5's was 15 pounds, slightly over 1
atmosphere.
This was worked up to in stages. This incident occurred.
Ralph Nesbitt
Professional FD/CFR/ARFF Type


This is not the same situation. First the preasurization was set to twice
what it will be in flight. Second the preasure dropped because the
engines
were not pumping air in. Take a bicycle tire pump it up to 8psi (almost
flat) and then let the air out. This it the same preasure differential.

Mike
MU-2

Agreed.

The purpose of the pressure test in question is to assure structural
pressure integrity to 1 atmosphere above AGSL.

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.

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

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.

Bob Gardner

"Kiwi Jet Jock" wrote in message
...
In the pressure chamber,
from 25000 to sea level is instantaneous and you do a sustained
burp-and-fart.

Bob Gardner

Other way around Bob. (sea level to 25,000)

Gotta admit that I am working from memory of events many long years ago and
may easily have screwed up the details. With regard to the fog, however,
there has to be moisture from somewhere...simple expansion is not the whole
story. Fog is, after all, a gazillion eensy-teensy droplets.

Bob

"Viperdoc" wrote in message
...
The FAA has opportunities for a chamber ride to actually experience rapid
decompression, and we have to do it periodically in the Air Force while on
flying status. On of our classmates volunteered to take off his oxygen
mask
at 25,000 feet. He turned green immediately and started seizing, and
despite
being prepared, he was unable to gang load his oxygen regulator and put
his
mask back on. I wonder how many brain cells he killed.

The rapid decompression was pretty uneventful- there was kind of a loud
pop,
and a lot of fog. This is the result of condensation due to cooling of the
air from expansion, not moisture from our bodies.

If you ate a lot of Mexican food the night before the pain from the gas
expanding comes on the ascent, not on the descent. Likewise, ear blocks
(feels like sticking an ice pick in your ear from personal experience)
comes
during descent only, as the increased ambient pressure pushes inward on
your
ear drum.

The most valuable part of the ride was the ability to recognize symptoms
of
hypoxia, like decreased color vision, etc. A

Anyone who ever flies over 10,000 feet (or less at night) should consider
a
chamber ride a valuable and potentially life saving experience.