Canopy equivalent charts for MSL changes..

[jose 0]

I am looking for a conversion chart that gives the equivalant canopy size as you jump at increasing MSL altitudes. IE, I jump a 119 and it flies like a 119 at MSL, but what would it fly like at 4500MSL? Is there such a chart?

Thanks

[quade 4]

No such chart exists (or in reality -could-).

That said, you might want to look at http://futurecam.com/densityAltitude.html.

quade -
The World's Most Boring Skydiver

[lifewithoutanet 0]

Haven't seen a chart like you mention, and I'm not sure how well you could really draft it out, given so many variables, but do a search of the forums on 'air density'. You'll get 'a few' posts, but it should direct you to the more appropriate threads.

From personal experience, I was back in CO this past weekend. My canopy (Sabre 150) was fast as fcuk up there w/o me trying to speed it up.

-C.

[jose 0]

Well, it was worth a try. I of course was looking for approximations, not actual scientific data.

Heres the short. I currenly am flying a Xfire2 119 and have about 40 jumps on it now. I am flying it quite well and enjoy its characteristics. I am planning on attending the Moab boogie and the MSL there is 4500'. What, in theory, would my canopy be flying like with the change in air density. Maybe a 107? Less? What kind of altitude loss changes am I going to be experiencing during manouvers.

I have only jumped at that alti once, at MileHigh, but I was too green to grasp any such changes and probably shouldnt have been jumping there at 80 jumps. Wiser now, I am looking for info that will give me insight, so I can make the right decisions.....before I jump.

[TomAiello 26]

Have you considered just calling up Clint and asking him what his experience was moving to Moab? He ought to be able to give you a rough estimate, anyway.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[quade 4]

Quote

What, in theory, would my canopy be flying like with the change in air density.

What elevation have you been jumping at and what have been the average temperatures? What are the expected temps for the Moab boogie?

quade -
The World's Most Boring Skydiver

[DrewEckhardt 0]

Quote

I am looking for a conversion chart that gives the equivalant canopy size as you jump at increasing MSL altitudes. IE, I jump a 119 and it flies like a 119 at MSL, but what would it fly like at 4500MSL? Is there such a chart?

Thanks

Mathematically:

At low altitudes airspeed increases about 5%/3000 feet.

So you'll be going over 7.5% faster than you would down at sea level with the same temperature (hot air is less dense) and humidity (humid air is less dense).

Airspeed also increases with the inverse square of canopy size.

So the speed would be as if you had a canopy 1/(1.075^2) = .865 the size of what you have at sea level.

.865 * 119 = 103 square feet.

Recovery arc also increases substantially with altitude. Subjectively it isn't too different compared to jumping the smaller canopy at sea level although I haven't looked at the math.

Annecdotally: I usually jump at 5050 or 4500 feet MSL but also have a few hundred jumps at sea level boogies. The altitude increase is like loosing over a full canopy size compared to sea level except with regard to control sensitivity (the parachute still has the same line length + dimensions).

We tell people from sea level to be careful, that they need to start any high performance landings much higher, etc. The people who don't listen usually bruise or sprain themselves but sometimes leave with broken bones.

[jose 0]

Cheers Drew...that was what I was looking for. Some relativity that was both scientific and personal experience. Thanks.

[Miami 0]

Damn...so I'll need to downsize again when I leave Colorado?

Jose, Drew's chart is a pretty good estimate. Best advise really when going to a high elevation dz is to treat your canopy like have never jumped it before. Take it easy and slow and get to know your canopy at the new elevation before you try any maneuvers.
Hope this helps...

Miami