Canopy opening / flight V altitude

[greeny]

Questions,

Does any body know how altitude affects canopy opening and canopy flight ( glide angles )?

I understand that at a higher altitude the air is less dense. This to me means that my canopy will use more vertical height to open, as the less dense air will need more time to inflate the canopy. I also understand that the canopy will not glide as far as the less dense air will create less lift. Less lift means less flare and harder landings. What I'm looking for specificly is:

1) Is there a chart or a calculation (maybe in aircraft flight manuals) that will tell me:

a) If I know my canopys (aircrafts) glide angle for a given air pressure. Can I work it out for any given air pressure?

b) If I know the vertical height my canopy uses to open after a specific delay / set up for a given air pressure. Can I work out the vertical height my canopy will use to open after the same delay and with the same set up but in my new air pressure?

c) If I want to open and land my canopy at high altitude can I simply increase the size of my canopy and pilot chute relative to the drop in air pressure?

eg. If I halve the air pressure I'm jumping in, can I double the canopy size and expect similar flight performance ( I mean glide ratio and flare as I believe it would turn and react to input slower ).

Thank you.
Greeny

[sean]

Dude...i think you need to get out more..:*

[sean]

Seriously though....there are so many factors that can effect glide angles and opening heights that without jumping in a high altitude location that had the same ambient conditions 24/7 and using a jumper whose body position and weight stayed the same for those conditions...you would no doubt get a different set of results every time.

You are trying to quantify exactly a system built by a human,packed by a human,operated by a human in conditions that you cant control exactly..tailwinds,headwinds,crosswinds,sidewinds, updrafts and down drafts could all throw your results..

Good luck with your quest


Sean:o

[3ringheathen]

For starters, I don't think you'll find any hard numbers on your canopies glide ratio. As Sean stated, there are just way too many variables.
This is one of those areas where there's no substitute for experience.
You have to make a number of jumps off of objects that you know you can make the landing area from, pay attention to details such as wind conditions, canopy input - risers, toggles, etc. and go from there.
Unless you are comfortable not making the landing area, and going into the trees, hillside, whatever, don't jump something you're not sure of.

Anyway, IMO, any change in the glide ratio and opening speed due to altitude aren't going to be critically different. If they are, you're pulling too low or the landing area's too far away. As a general rule, if you're unsure what pc size to use, go with the bigger one.

What really does matter is how the canopy will land. I know from first hand experience that my Mojo 220 lands me like a lawn dart at 5000'.

Assuming all other factors are equal, a *rough* rule of thumb I'd propose is:
If the smallest canopy you feel comfortable landing at sea level is a 220, you'll want to jump a 240 when the landing area is at 1500+, and a 260 above 4000.
-Josh