12000 ft ASL low Jump

[guest]

Hello everybody, somebody know about the canopys deployment at 12000 ft ASL(4000 mts.).
I need information about a 180 ft.(63 mts) Bridge jump in a Mountain location at 12000 ft.
Direct bag or PC asist.?
How pressurise the Canopy at 12000 ft.?
Is jumpeable or maybe no.

Tanks for the data.

Nik

[guest]

My guess is that the air is so thin up there that the opening distance would have to be greater. You can keep this one thanks.

[guest]

The one time I jumped at 12k was with a Dragon 235 with a ZP topskin loaded at .70.

I didn't notice a longer opening time, but the landing was definitely faster and harder.

Of course, I was doing a 650-foot wall with a very steep talus slope that makes it 800+ just a few meters from the wall, so even a 50 percent increase in opening time would not have been a problem.

If your bridge is over deep water, I'd consider it, but if it's over ground, I wouldn't even think about it unless I did a bunch of test jumps with a non-breathing dummy to see what happened.

[guest]

Where's your sense of adventure mate?

[guest]

Gave it to Dwain, mate.

[Dwain]

>How pressurise the Canopy at 12000 ft.?

I have one static line jump at this altitude which really doesn’t mean much (there are too many variables in any BASE jump to form opinions or draw conclusions from just one jump), but here are my impressions anyway (from memory 2 years ago):

The cliff was sub 200' to impact with the exit point at 12,600' ASL (interestingly enough next to a bridge - could this be the same mountain you speak of Nikito?).
I was using a Mojo220 loaded at about 0.74 lbs / square foot. Two other Australians and one New Zealander followed once they ascertained I would survive (there was some debate about this prior to exiting with heated arguments over who had the ownership rights to my rigs – standard Australian BASE protocol }> ).
Deployment and pressurization of the canopy was not noticeably slower. I'm not sure how much extra altitude was used during pressurization as the surrounding environment was just rock and ice making distances difficult to judge. However I still had substantial vertical height on full deployment – enough to consider freefalling if I ever returned.
To clarify, deployment and pressurization of the canopy took about the same amount of time (compared to a sea level jump) but I suspect slightly more altitude was used due to a slower deceleration in the less dense air.
We deployed in a very narrow canyon and a 90-degree left turn was required soon after deployment. The time frame from deployment to smacking the opposite wall was less than what I had estimated. What we all noticed was a radical increase in speed of our canopies. My 220 felt like maybe a 150 square foot canopy at that altitude. The glide ratio of the canopy did not appear to suffer. Landing was at 3,000' ASL (after a 9,600' canopy ride down the mountain).
Due to the increased speed of the canopy and the proximity of the wall (it was somewhat underhung), I felt I could not have avoided an object strike in the event of a bad offheading.

So in regards to your question, in my one-jump experience (and from watching three others) the canopy should be pressurized and flying from 180' on a static line deployment at 12,000’ ASL. However I can't comment on how you will land at this height with that little canopy time (I have seen various footage of people landing BASE canopies well at these altitudes, however they had ample canopy time to set up). If you intended to land at 12,000' then I'd recommend using as large a canopy as possible with bottom surface inlets.
As Slim would always say "Big canopy, Pad up and Pound in".

[guest]

Tanks Dwain for your appreciation.
I take in mind your data.
Nik

[guest]

At 12000 ft the air has half it's density as compared to sea level (for the same temperature). I'm not going to predict the outcome of a jump but it's going to make a BIG difference. 180 ft is a hell of a tight testing ground for something you're unsure of.

Sorry, can't help more.
Be safe. Walk away if you're not 100%.

[Dwain]

>At 12000 ft the air has half it's
>density as compared to sea level

At an altitude of 18,000 feet, the density of the air is half the air density at sea level.

See: http://avstop.com/AC/1-8.html for one of thousands of articles which mention this.

[guest]

Does anyone know what the density graph looks like?

Does the density decrease at an arithmetic, goemetric, or logarithmic rate?

In some of these scenarios, you could both be right.

If only I'd paid more attention in Physics class...

--Tom Aiello
tbaiello@ucdavis.edu

[guest]

>Does anyone know what the density
>graph looks like?
>

Approximation for normalized air density valid up to 5 Km:

NormalisedAirDensity= 1 - 0.09H + 0.002H^2 where H is in kilometers

This means that the value at sea level = 1, then the air is ~.91 times as dense at 1 km, and so on.

The density of air at sea level is 1.225 kg/m^3 so if you want the actual values use the equation above and multiply the density at sea level by your answer.

bsbd,

BakerBoy

[guest]

I will try and keep a crib sheet at the exit point, 'cuz my brain is fading

[guest]

Nice work BakerBoy. I should have believed you about that Other Thing.
You know, last Friday, YOUR brain seemed to be fading...must be ....the alcohol??....nah.

[guest]

The exact formula for calculating the air density knowing the altitude is an exponential formula but that presently I do not have ready by hand to write it down.
But I report here as follows few values of air density at various altitudes (drawn from a weather book reporting standard air values according to ICAO):
sea level......................1.225 kg/m^3
..5000 ft - 1524 m........1.057 kg/m^3
20000 ft - 6096 m........0.653 kg/m^3
25000 ft - 7620 m........0.551 kg/m^3
As soon as I find the exact formula, I shall write it down here.
In the meanwhile, from my very low experience, I can say that my unique jump with exit and landing at 1000 m - 3280 ft of altitude (jumping a Fox 245 loaded at 0.72 lb/ft^2), a bridge 145 m - 476 m high, resulted in a very swift flying with open canopy and in a very fast landing, in which my left foot had quite a strong close encounter with a nasty boulder: nothing broken but lots of pain!!!
I do not even want to imagine how fast would be a canopy (normally loaded) flown at 4000 m - 13123 ft!!!!! Unless you choose to jump a canopy that is at least 1.5 times the size of your usual canopy!!!
While evaluating all the details, stay safe!!!
Blue Skies
Andrea

[guest]

Yeah Dwain you're right. That's what happens when you use too many numbers from memory without reference. There's a lesson to be learned there. The consequence of getting a phone number or two wrong is a long way from the result of basing a jump on poorly memorized data. Thanks for the correction.