High altitude loads - no more.

[diverdriver 5]

Ok. I know I'm at my legal limit for posts in a row on a thread but I'll risk it.

The proper way to do high altitude loads is what we did on the World Record flights at SDC in 1998 and attempts in 2000. EVERYONE started breathing oxygen at 10,000 MSL (what you read on the aircraft's altimeter) and had it on until the climbout command came. EVEN when we did loads to 17K MSL before we needed the extra working time for the record. It is that important to not let yourself get hypoxic. You need to breath oxygen BEFORE you get high so that you do not lose the level of oxygen you have. Once you get hypoxic it can actually take quite awhile to get your levels back up. Just like a hangover, hypoxic hangovers can linger and effect your performance on subsequent jumps. You will feel fatigue onset sooner through the day if you do not take time to replenish your blood oxygen.

Chris Schindler
ATP
www.DiverDriver.com

[billvon 2,990]

> A lot of it is caused by the decreased pressure in the atmosphere
> and that pressure does not decline evenly (linearly) as you climb. It
> actually decreases more as you get higher.

Actually, the opposite is true. The pressure difference between 1000 and 2000 feet is 33 millibars; the pressure difference between 15000 and 16000 feet is 22 millibars. It decreases more slowly as you get higher.

>So the onset of hypoxic symptoms will come quicker the higher you
> are. We refer to this as Time of Useful Consciousness (TUC).

This is definitely true, but due to how flexible the human oxygen transport system is. Above a certain partial pressure of oxygen, hemoglobin actively accepts oxygen; it has a very strong affinity for it. Below this pressure, though, it does not readily accept oxygen. This partial pressure of oxygen is found between about 12,000 and 20,000 feet, depending on acclimation. Mountain climbers, for example, can tolerate lower partial pressures of oxygen because their bodies actually shift their hemoglobin's oxygen affinity curve. Above 20,000 feet, the body can no longer adapt well, which is one reason the region above 20,000 feet is often called "the death zone" - the levels of oxygen in their blood drop dramatically.

Skydivers generally do not have this acclimation, although people in very high areas (Denver) are somewhat better acclimated.

What this all means is that your body does a very good job dealing with dropping pressures to a certain point. Even though the air pressure at 10,000 feet is only 68% of sea level air pressure, oxygen saturation of your blood can still remain near 100%. Above a certain point, though, that ability to adapt goes away very quickly - which is why you can be perfectly fine at 10,000 feet but be very handicapped by hypoxia at 16,000.

[kallend 2,026]

Quote

Mountain climbers, for example, can tolerate lower partial pressures of
oxygen because their bodies actually shift their hemoglobin's oxygen affinity
curve. Above 20,000 feet, the body can no longer adapt well, which is one
reason the region above 20,000 feet is often called "the death zone" - the
levels of oxygen in their blood drop dramatically.

Th red cell count also increases during acclimatization. When Kevin Uliassi made his attempt to fly round the world in an unpressurized balloon in 2000 he slept for weeks beforehand in an altitude chamber. His blood became so "thick" it became difficult for the medics to draw a sample with a regular needle. He had become sufficiently acclimatized that he could stay indefinitely at 19,000ft without supplemental oxygen. Kevin only made it 1/2 way round the world when his oxygen mask regulator blew out at 31,000ft over Calcutta. His acclimitazation was good enough that he was able to make a controlled descent to 20,000ft without oxygen (not something you can do quickly in a huge balloon), and then set up for an "out" landing in Myanmar.

Steve Fossett also acclimatized in an altitude chamber before his flights, but I don't know the details.

Everest has been climbed without oxygen on several occasions, mostly by sherpas, but some by well acclimatized non-indigenous climbers.

[diverdriver 5]

Quote

> A lot of it is caused by the decreased pressure in the atmosphere
> and that pressure does not decline evenly (linearly) as you climb. It
> actually decreases more as you get higher.

Actually, the opposite is true. The pressure difference between 1000 and 2000 feet is 33 millibars; the pressure difference between 15000 and 16000 feet is 22 millibars. It decreases more slowly as you get higher.

Thanks for the correction Bill. Yah....what he said.

Chris Schindler

[Jayboz 0]

For what it's worth...

Alti and Pressure.pdf

[Jayboz 0]

Found this kicking around my lower left hand desk drawer too.

only goes up to 6,000 ft. The non-linearity becomes more apparent as altitude increases.

alti vs atmos pressure.pdf

[kallend 2,026]

This is a nice interactive atmosphere calculator.

aero.stanford.edu/StdAtm.html

[Staso 0]

Quote

This is a nice interactive atmosphere calculator.

aero.stanford.edu/StdAtm.html

according to this calculator the highest speed i've achieved
so far is almost 0.4 Mach ! :) 0.3926 to be precise.
0.074 shy. damn ! :)

stan.

--
it's not about defying gravity; it's how hard you can abuse it. speed skydiving it is ...
Speed Skydiving Forum

[christoofar 0]

You should never be in an unpressurized cabin going above 15 w/o a bailout bottle in your hand. Plain and simple.

O2 asphyxiation has killed plenty of GA non-skydiver pilots in the past.

Oxygen is the fuel that keeps your brain working. Breate it. :)

____________________________________________________________
I'm RICK JAMES! Fo shizzle.

[PhreeZone 20]

You only need the bail out bottle above about 24k, the Useful time of consiouseness that that altitude is enough that you can freefall to 15k where the O2 levels are enough that the UTC is pretty much unlimited. You do need active flow O2 above 15k.

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