O2 and Cypriot airliner crash

John Kirksey wrote:

How, then, can someone like Ed Viesturs repeatedly climb the tallest
mountain peaks in the world without supplemental oxygen? Is it because of
the slower ascent and the time spent acclimating to the higher altitudes?

First, acclimatisation.

Second, walking (and climbing) is different from flying. You don't need
much brain to walk. When piloting, however, everything is about
thinking. And it's the brain which needs the most oxygen.

And maybe a third reason: There are exceptional people who are just
better suited for such things than you and me.

Stefan

Partially because he is acclimated and partly because he is Ed Visteurs.

Mike
MU-2


"John Kirksey" wrote in message
news:cZ0Me.4596$H_4.4209@trnddc07...
Tlme of useful
consciousness
Altitude (ft) without oxygen

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds
28,000 1 minute


How, then, can someone like Ed Viesturs repeatedly climb the tallest
mountain peaks in the world without supplemental oxygen? Is it because of
the slower ascent and the time spent acclimating to the higher altitudes?

John K.

wrote

In accounts of the crash of the Cypriot airliner in Greece,

My thoughts on yesterday's accident.

The way the regulations require that it be done.

First........During the preflight, someone ensures that the emergency
oxygen bottles in the lower cargo holds have their valves opened and are
ready for use.

Second...During the cockpit preflight, each pilot tests his oxygen mask
for proper operation and for pressure delivery of oxygen.

Then.......With the engines running and before takeoff, the air
conditioning and pressurization system is turned on (pack valves opened)
and the cruising altitude set in the controller by a crewmember and
verified by the checklist.

The system then functions normally, maintaining a cabin pressure of about
8,000 feet until starting descent.

However if something goes wrong and the cabin altitude rises
uncontrollably............

First.......At 10,000'cabin altitude, A VERY loud warning sounds to alert
the crew. If at cruise altitude, this MANDATES first, immediate donning
of the pilot's oxygen mask followed immediately by an emergency descent
to 14,000'.

Second.. At 13,000' cabin altitude, the outflow valves automatically
close in an attempt to maintain cabin pressure if the system has been
properly turned-on before takeoff. If the system was not properly
turned-on before takeoff, the warning should have occurred during climb.

Third.....At 14,000' cabin altitude, the passenger oxygen masks
automatically drop.

All of these systems are independent. News reports indicate that the
passenger O2 masks did deploy. If so....

Did the warning sound? If it did why was there no emergency descent?
Why was pressure not maintained when the outflow valves closed? Perhaps
the pack valves were not opened before takeoff? Had the pilots O2 bottle
been replaced and the valve not opened or checked during preflight?

Looks like a lot of human error to me. Just speculating.

Bob

Most passenger O2 systems use chemically generated O2.
There are no bottles to check. There are cabin walk around bottles
and the flight deck is bottled O2, but passengers are not. Remember
the Valujet crash. The initiating event was a cargo bay/cabin fire casued
by
improperly shipped O2 generators igniting in flight.

Bruce Hoult wrote:

I personally know glider pilots here in New Zealand who have flown to
betweeen 35,000 and 37,000 ft with only an ordinary oxygen mask, not a
pressure system.

The glider world record of 49,000 ft used a pressure system.

Thanks for getting back on topic for this NG.


Jack

Bucky wrote:

wrote:

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds


I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

If the drop in pressure is rapid, can a person hold in the air? Or
perhaps it is expelled because the pressure in the lungs is double the
cabin pressure?


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

"pbc76049" wrote
Most passenger O2 systems use chemically generated O2.
There are no bottles to check.

Depends on the age of the B-737. Boeing used pax bottles
for a long time. But this is immaterial to the discussion
of why the pilots did not have O2.

Bob Moore
ATP B-707 B-727
PanAm (retired)

Totally crap. Teach someone how lungs work.

If the pressure drop is rapid, they need to exhale, otherwise their lungs
will burst. Just like surfacing in scuba diving.

--
Bert Willing

ASW20 "TW"


"Eric Greenwell" a écrit dans le message de news:
...
Bucky wrote:

wrote:

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds


I don't get it. Can't a person stay conscious for longer than 30
seconds without breathing? Most people can hold their breath for over
a minute.

If the drop in pressure is rapid, can a person hold in the air? Or perhaps
it is expelled because the pressure in the lungs is double the cabin
pressure?


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

wrote:
In accounts of the crash of the Cypriot airliner in Greece, all I've
read say that loss of cabin pressure could not, by itself, incapacitate
the pilot. Yet, I was once told by an ATP that at 40k feet (admittedly
this plane was at 35k) O2 supply by itself will not suffice to keep you
conscious and that the drop down masks only give a false sense of
security. He said that the ambient pressure is so low that even 100% O2
does not provide enough to keep you conscious without a pressure
breathing mask. If he's right, that could explain the crash, especially
given that all it would take is 20 seconds of distraction (i.e., not
donning the mask) to knock out the pilot as indicated in the table
below. On the other hand, I checked and a standard atmosphere at 35k
feet is 7.0 in of Hg, which is more than the partial pressure of O2 at
sea level (6 in = 20% of 30 inches), which would seem to contradict the
info given by the ATP. Any thoughts or corrections to my reasoning?


Tlme of useful
consciousness
Altitude (ft) without oxygen

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds
28,000 1 minute
26,000 2 minutes
24,000 3 minutes
22,000 6 minutes
20,000 10 minutes
15.000 Indefinite


Sure pp is 6" at sea level, but at 35 k ft (using your numbers) the pp
O2 is 20% of 7" or 1.4" Hg. At that pressure only about 50% of the
hemoglobin in your blood is saturated, and it hangs on to that O2 pretty
strongly, so it's not available for use by your brain (or anywhere else).

Shawn