why is the jumping alti set at around 12.5k?

[Newbie 0]

i know its around 11-14k or whatever, but whats to stop people going up to 15+ regularly? Weather? Extra cost to get the plane there? Hypoxia issues?

[Remster 24]

yes, and regulations
Remster
Muff 914

[riggerrob 562]

To climb above 12,500 - in many parts of Canada - you have to talk to another air traffic controller.
Hypoxia was also a major factor back when piston engines were the norm. Piston engined airplanes simply spend too many minutes above 10,000'.
Now that turbines are common, hypoxia is less common, until ATC puts you on hold at altitude. But what is really scary is that few people recognise hypoxia when they are hypoxic.

[axe96bam 0]

I know that we do not got to 15+ because you need to have oxygen on board over 15000 MSL. So basically if your DZ is not at see level you will need oxygen on board ever lover. I think that 12.5 to 13.5 AGL is common because at most DZ you are still under that critical 15K MSL. But if you go to Colorado or some other high elevated DZ you will see either oxygen on board or lower jump altitudes.
Alex

[billvon 2,471]

As I recall, FAA rules require oxygen above 12,500 if time spent there is >30 minutes, and above 14,000 for pilots 100% of the time. Occupants must have oxygen available if altitude > 15,000 feet. These rules are stretched quite a bit in skydiving, but advertising 12,500 on a DZ with a landing elevation of 1000 feet is _just_ legal without oxygen.
-bill von

[TheMarshMan1 0]

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Occupants must have oxygen available

That is correct. There is no specified altitude at which everyone on board (besides crew) must USE oxygen. See how much the FAA cares about non-flying occupants?
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[skymama 35]

Last weekend, we had to hold at 13,500 for about 5 minutes while we looked for a hole. The pilot said to sit down, but I just thought he meant to relax. I thought we'd find a hole at any second, so I just leaned up against the side and stayed standing. I noticed I got a little light headed, and after I got down, I had a headache forming. I mentioned this to the pilot later on, and he said, "I told you to sit down, all the blood was going to your feet, that's why you felt like that!" Oh...duh!
Andrea
The brave may not live forever, but the timid may not live at all.

[gemini 0]

...and ask a commercial pilot about the oxygen masks that "pop out" when a commercial jet depressurizes! Something about Bournelli's law and unpressurized masks. It's really scary. I was told by a pilot that his job is to get the plane to a breathable altitude as fast as possible if he loses cabin pressure. Want to guess why?
Gemini
... Fear? Fear is riding the plane down ...

[TheMarshMan1 0]

I need not guess my friend...I am a pilot...A rapid decompression of a pressurized aircraft can occur in anywhere from 1 to about 10 seconds. An explosive decompression can occur in less than a second. If a rapid/explosive decomp. happens, then several things can/will happen:
1.) Cabin will fill with fog because any moisture will be condensed immediately.
2.) Unsecured objects will be drawn toward the opening that caused the decomp., which could turn pencils into bullets and create blinding dust.
3.) After the decomp, the cabin will be VERY cold, since number two includes heated air.
The time of useful conciousness at these altitudes is short- you must act fast.
That answer your question?
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[skymama 35]

Well, someone's been paying attention in class!
Andrea
The brave may not live forever, but the timid may not live at all.

[TheMarshMan1 0]

Class? What class? Where?
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[gemini 0]

Ok, I've acted fast and got the unpressurized yellow mask on, the oxy's flowing and we are at a normal cruising (curses?) altitude of say 30k feet. How long am I awake and alert?
Gemini
... Fear? Fear is riding the plane down ...

[TheMarshMan1 0]

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Ok, I've acted fast and got the unpressurized yellow mask on, the oxy's flowing and we are at a normal cruising (curses?) altitude of say 30k feet. How long am I awake and alert?

At 30,000 ft.? Probably for as long as your oxygen supply lasts. Its not until about 40,000 feet that you will have respiratory trouble even with 100% oxygen. The reason for this is the exremely low atmospheric pressure, and the fact that it is so low it does not support proper oxygen saturation into the bloodstream. There is another type of oxygen mask that can be used above 40k, but it is positive-pressure and requires special training to use.
Maybe diverdriver can back me up here, if I'm off a little or wrong...
Oh, and I forgot earlier....rapid decompression can also cause altitude-induced decompression sickness.
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[billvon 2,471]

>...and ask a commercial pilot about the oxygen masks that "pop out" when a commercial jet depressurizes!
> Something about Bournelli's law and unpressurized masks.
Do you mean Bernoulli's Law? Not sure how that applies. Basically it states that when the speed of a fluid increases its pressure decreases. As the air near your face (even with a mask) is essentially stationary, Bernoulli doesn't play a big role.
Perhaps you're talking about insufficient partial pressure of oxygen? Sea level available PPO2 is 3 PSI; you can make do with 2 PSI. When the surrounding pressure drops below 2 PSI, even pure oxygen won't keep your blood saturated. You need either a pressure suit or a positive-pressure mask to survive.
Fortunately, commercial aircraft do not fly at altitudes above 2 PSI pressure altitude, which is around 50,000 feet, so this is not much of an issue. Note that the Concorde _does_ fly near these levels, which is one reason it has tiny windows - to limit the rate of pressure loss when one blows.
>I was told by a pilot that his job is to get the plane to a breathable altitude as
>fast as possible if he loses cabin pressure. Want to guess why?
Because a) barotrauma is possible, as is decompression sickness (going rapidly from 3000 feet to 39,000 feet pressure altitude can give you the bends) and b) the oxygen generators used on commercial aircraft have limited lifetimes.
-bill von

[TheMarshMan1 0]

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the oxy's flowing and we are at a normal cruising (curses?) altitude of say 30k

Oh yeah...and another thing. After any kind of depressurization...you wont be at a normal crusing altitude of 30,000 ft. That altimeter will be unwinding rather quickly......
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[skymedic 0]

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Oh, and I forgot earlier....rapid decompression can also cause altitude-induced decompression sickness.

among other things...working on lear jets transporting patients I have read too much on altitude physiology...also problem is you can also have problems with say an absess in a tooth....if you have a sudden depressuriztion...you can have that tooth litearly explode in your mouth....OUCH....
marc
BSBD

[TheMarshMan1 0]

ah yes....i had heard that, but forgotten that too. That would hurt like a bitch....
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[axe96bam 0]

Well than, with all of my dental work I should never fly a pressurized cabin plane again. Good thing the jump planes are not pressurized.
Alex

[lazerq3 0]

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why is the jumping alti set at around 12.5k

Any higher and I'd be afraid to jump!!....
jason

[Billy 0]

Isn't it Boyle's Law,, as pressure drops, gas expands,,, like a coke can when ya pop it open,, all C02 dissolved in the can expands making bubbles,, so will the C02 in your bloodstream,, after a rapid decomp the pilot will dive the plane to a safer altitude so be ready for that also,, it's normal,,,
Don't read this shit down here,, it's nonsense,,,

[xybe 0]

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So basically if your DZ is not at see level you will need oxygen on board ever lover

Symtoms of hypoxia would not include erotic freudian slips when posting to the boards now, would they?
You are so busted, since your SO cannot see you at the DZ you meet with your lover over there! Ha!
Someone get an O2 mask on that guy! Oh, wait, it's not hypoxia, it's sleep deprivation from all those nights of crazed sex at the DZ!
Just joking, sorry, I feel hypoxic and underslept.
Still shedding whuffo-ness
Check out the Hardcore Whuffo pages

[axe96bam 0]

ha-ha-ha. I did not even notice that until now. I will go with your excuse because I cannot think of a better one.
Alex

[lazerq3 0]

We jump at a DZ here that is 4500ft msl and we get out at 12500-13000ft agl which would put us at 16 to 17000ft msl......and we've never had to us O2.......Now when we do the 16000ft agl jumps there is O2 on the plane!!
jason

[TheMarshMan1 0]

Just curious.....Does your pilot wear oxygen?
"If I could be like that, I would give anything, just to live one day, in those shoes..."

[lazerq3 0]

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Just curious.....Does your pilot wear oxygen?

First let me say this inst at my home DZ.... Second ummmm I think maybe I should plead the 5th!!!!! Ohnestly I dont know...I mean I've never really looked up at him when were on jump run!!! Its in a caravan and since I'm jumping formation I'm usaully the first out so I'm in the back.
jason