Jumping at altitude versus sea-level

[CanuckInUSA 0]

I was about to reply to a post in the Incidents forum concerning a comment someone made about jumping at altitude, but then I decided to start a new thread here since my comments didn't really have anything to do with that specific ZHills incident.

Anyway, the other poster was talking about jumping at 2500' MSL and then made a comment about wanting to do a balloon jump in Colorado. But after some thought he decided against it since the surface altitude was 7500' MSL. And then he asked about other skydivers who may have jumped at altitude.

Well the funny thing about my skydiving experience is that I have never jumped at a DZ where the surface altitude was below 5000' MSL. So I have no idea as to what jumping at sea level is like. Now if you look at my profile, you'd see that I fly a large canopy partly due to the fact that I'm a relatively big guy and because I do jump in Colorado. But sometime in the not too distant future I will start flying a canopy which will give me a wing loading a little above 1.2 and I'm sure it will behave differently here than it would at sea level.

Try not to worry about the things you have no control over

[Beachbum 0]

I saw the same post ... and tho I'm sure not the expert on that sort of thing with my low #'s, I have experienced it ... going from about 50' ground elevation in the Houston area to Lost Prairie at about 3200'. I had problems getting myself to flare early enough in spite of having been warned and making a conscious effort to do so ... the elevation definitely DOES make a difference. I felt a little better tho, after watching many much more experienced folks have the same problem (tho they DID seem to make the adjustment much quicker!).

As long as you are happy with yourself ... who cares what the rest of the world thinks?

[quade 4]

Check out; THIS.

quade -
The World's Most Boring Skydiver

[CanuckInUSA 0]

I'm a licensed private pilot, so I'm aware of DA. But thanks for the info anyway. I just wonder how many other people like myself have never flown at sea level?

Try not to worry about the things you have no control over

[wmw999 2,534]

OK, just getting down to specifics. The last time I went to a higher-elevation dropzone (Perris from Houston in 1980), I was jumping a round main.

I'm going to the Eloy boogie from Houston. I just got a new main, and I'm not awesome at no-wind landings yet. Can I anticipate lots and lots of PLFs on no-wind days? How different will it be, going from 25' to 1500'? Fortunately, I'm way past embarrassment, so PLFs are fine with me thanks

Wendy W.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[skycat 0]

Well, Derek can explain it better than me, but the ground speed is much slower, your recovery arc is shorter, your canopy will have a lot more flare. Basically though you won't have any problems flying at sea level, but you may have to take a jump or 2 to readjust to the higher altitude when you get back home.

If you are down at Canon this weekend talk to Derek about it, or if you are at Mile Hi talk to Paul and Melibe since they just got back from LA (the state not the city )

Fly it like you stole it!

[nacmacfeegle 0]

http://www.afn.org/skydive/sta/highperf.pdf

Prints better than it looks, it has a section on density altitude, and its effects on canopy landings.

This should, IMHO be required reading for anyone wanting more fom their canopy.

--------------------

He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. Thomas Jefferson

[crazy 0]

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How different will it be, going from 25' to 1500'?

Assuming that both places are dry, the speed at ground level will be ~3% higher. This is approx half a mile per hour at full glide, probably not something that you can objectively notice.
As a comparison, a variation of temperature of ~30 degrees fahrenheit woud make an equivalent difference.
Now, if you PLF, the impact will be ~7% stronger. As a weak comparison it would be like a PLF with ~10 pounds of lead.

--
Come
Skydive Asia

[riggerrob 643]

I have often thought that it would be fun to take people considering downsizing to other DZs so they could feel the affects of density altitude with their own canopy.
For example, take someone from a sea level DZ to a Perris at 1500', then California City at 2500', then Denver at 5000' then Leadville at 9000', etc.

[skycat 0]

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then Leadville at 9000'

There's a DZ in leadville? Is that the one the used to be near Ft. Collins?

Fly it like you stole it!

[riggerrob 643]

I was pulling your leg about jumping at Leadville, Colorado. At 9,000 feet above sea level, it is the highest airport in the USA. Some flying schol slike to take pilots to Leadville as part of mountain flying training. Most pilots are amazed at how much of Leadville's runway they nedd for takeoff!
Given that most piston-engined jump planes could not take off from Leadville with a full load, it would be almost impossible to turn a profit. You would have to start with a lightly-loaded turbo-prop - like a Porter - and charge much more than normal to cover the longer climb time and on-board oxygen. For serious freefall time, everyone would need to wear oxygen masks in freefall.

[Hooknswoop 19]

There has been some test jumping done at Leadville. PD military stuff.

Hook

[CanuckInUSA 0]

Leadville is actually listed at 9927 feet MSL and jumping there in the summer would likely be extremely difficult under a highly loaded canopy, but much more tolerable in the winter (if you didn't mind the cold). I have landed there for the first time in a Cessna 182, ironically almost one year ago to the day while I was getting my mountain checkout and it has a nice long/wide runway. I'm sure I would have need much more of the runway had I been on a summer time flight, but in the winter, it wasn't an issue. I've actually landed at Colorado 3rd hardest airport (Glenwood Springs known for it's short runway in a box canyon) and that was much more challenging than Leadville was.

But as far as wearing oxygen, jumping at Leadville would be no different than the rest of us who jump at lower altitudes here in Colorado. In fact due to the Class "A" airspace above us, the jump plane can't go above 18000 feet MSL anyway unless it's on an IFR Flight Plan (which they never are) and we routinely climb to 17500 feet MSL at Longmont and elsewhere in Colorado without using oxygen.

Try not to worry about the things you have no control over

[CanuckInUSA 0]

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There's a DZ in leadville? Is that the one the used to be near Ft. Collins?

Kelli ... you're thinking of Loveland which ironically still has the parachutist icon shown on the Denver sectional chart. But to my knownledge there is no skydiving activing there anymore.

Try not to worry about the things you have no control over

[darkwing 5]

It is realistic to consider the effective altitude changes at any one dropzone over the course of a year are in the vicinity of 5000 feet, so if you jump in only one place you have jumped over a wide altitude range. I'm referring to density altitude, the actual density of the air, which is affected by air pressure, temperature, humidity. The variations with "real" altitude are no more than the variations you accommodate just by going from a very hot, muggy day, when the pressure is low, to a cold dry one in the winter when a high pressure is sitting on you.

-- Jeff
My Skydiving History

[flyangel2 2]

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But to my knownledge there is no skydiving activing there anymore.

You can jump there by appointment only

May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view. May your mountains rise into and above the clouds. - Edward Abbey

[bps 0]

Just for gee-whiz comparisons, I have landed a parachute 3 times at 12,200ft. And if you think there is a noticeable difference between sea-level and 6,000ft (there is), it's REALLY noticeable at 12,200.

I was using a 280 for all 3 jumps. The first one, I landed into a 2mph head-wind and even though it was fast, I had no problem standing it up. On the second jump, there was zero winds and even though I stood it up, I was smoking across the ground and it took a roadrunner pace to run it out. The thrid time was with a 4mph downwind, and well, that one wasn't pretty.

Some of the locals around here can probably figure this one out, but I'm looking at a jump next summer that will have me landing a large American Flag at 14,110ft. Now that will be interesting!

Blue Skies,

Bryan

[skycat 0]

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but I'm looking at a jump next summer that will have me landing a large American Flag at 14,110ft.

Dude are you doing a demo on top of Pikes Peak???

I wanna run ground crew!!

Fly it like you stole it!

[indyz 1]

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but I'm looking at a jump next summer that will have me landing a large American Flag at 14,110ft.

Dude are you doing a demo on top of Pikes Peak???

I wanna run ground crew!!

I'd do it for a dozen of those donuts that they make up there.

[bps 0]

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I wanna run ground crew!!

Ok. I'll let you know when the dates are final.


Bryan

[slotperfect 7]

When I was doing demos, I jumped a Star Trac I (265 SQ FT), loaded at .94:1, shooting target accuracy most often on concrete or asphalt. I trained mostly at DZs less than 500 FT MSL.

Two air shows were quite different: Truckee-Tahoe Airport in California (5900 FT MSL), and Cheyenne Airport in Wyoming (6156 MSL). The first noticeable difference was the descent rate under canopy. I really came out of the sky in a hurry. All of us cut our approach pattern altitudes in half. The landings were a bit harder, but we had winds at both places so it was bearable.

My work canopy is a Silhouette 210, loaded at 1.17:1, and I regularly jump it between 200 FT MSL and 1900 FT MSL. There is a noticeable difference in the timing for planing out during landings, but it only takes one or two jumps to adjust. I have also jumped that canopy in Albuquerque, New Mexico at about 5500 FT MSL. I simply throttled back on my manuevers close to the ground and shot more conservative approaches.

Paul's article is great . . . I have passed it on to my comrades for their education as well.

Arrive Safely

John