Forums: Skydiving: Safety and Training:
Canopy colapse

 


wayne8577

Nov 17, 2005, 8:24 AM
Post #1 of 9 (1180 views)
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Canopy colapse Can't Post

Ok, I'm not new to the sport but have not jumped in quite sometime. Just starting back! Please explane why a canopy will collapse. Is it wind shear, or something else? Just read about a canopy colapse at 20 ft. alt.


Premier billvon  (D 16479)
Moderator
Nov 17, 2005, 8:34 AM
Post #2 of 9 (1160 views)
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Re: [wayne8577] Canopy colapse [In reply to] Can't Post

>explane why a canopy will collapse.

Many reasons.

The canopy could stall. This will result in a sudden drop; people often interpret this as a collapse. It's really not but it feels that way.

The winds could change such that the top of the canopy becomes loaded. Since the lines have no compression strength, the canopy will collapse instantly, no matter what design it is.

The winds could change such that the air over the canopy slows down a lot. This causes a stall; see above.

The winds could change such that the winds are now coming from the side. If this happens gradually enough the canopy will weathervane into the new wind. If it happens rapidly one side could collapse as the canopy attempts to turn.

Some sources of these changing winds:

-Wake turbulence behind someone else. Slow/heavy canopies (like tandems) have the worst wake turbulence.

-Turbulence off obstacles on the DZ. A 10 foot tree can cause turbulence 100 feet downwind.

-Thermal effects - dust devils and thermals. These can be seen because of the dust/grass/trash they pick up.

-Weather related turbulence, like a thunderstorm gust front.

For a more detailed description of turbulence I recommend "understanding the sky" by Dennis Pagen. Excellent book on weather that affects parachutes.


wayne8577

Nov 17, 2005, 8:49 AM
Post #3 of 9 (1145 views)
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Re: [billvon] Canopy colapse [In reply to] Can't Post

Thanks for the info. I am a Capt for United and do understand a great deal about weather but having jumped rounds mostly ( some squares back in the early 70's) I was wondering about the word calapse. After revieing my foggy memory on squares and reading your post I can see where the top of a canopy can suddenly, or gradually loose some airflow with the lines like they are. Good food for thought for a newbee! including me!


(This post was edited by wayne8577 on Nov 17, 2005, 8:52 AM)


Superman32  (B 28074)

Nov 17, 2005, 11:32 AM
Post #4 of 9 (1053 views)
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Re: [wayne8577] Canopy colapse [In reply to] Can't Post

You should listen to Brian Germain's interview on Skydive radio. He discusses the flight dynamics of parachute and what you can do to reduce it likelyhood.


bob.dino  (E 2185)

Nov 17, 2005, 3:47 PM
Post #5 of 9 (964 views)
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Re: [Superman32] Canopy colapse [In reply to] Can't Post

Direct download link.


wayne8577

Nov 18, 2005, 9:18 AM
Post #6 of 9 (834 views)
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Re: [bob.dino] Canopy colapse [In reply to] Can't Post

Thanks! When is this on the air and what station? I live outside of Atlanta. Is it on every week or what?


sirenoremac  (C 34757)

Nov 18, 2005, 10:53 AM
Post #7 of 9 (804 views)
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Re: [wayne8577] Canopy colapse [In reply to] Can't Post

It's a podcast... it's on the web.


AFFI  (D 25538)

Nov 18, 2005, 11:35 AM
Post #8 of 9 (795 views)
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Re: [wayne8577] Canopy colapse [In reply to] Can't Post

In reply to:
Ok, I'm not new to the sport but have not jumped in quite sometime. Just starting back! Please explane why a canopy will collapse. Is it wind shear, or something else? Just read about a canopy colapse at 20 ft. alt.

Learn all you can about this issue and learn to minimize the probability and severity but one thing I can share with you from my personal experience -

Once when I was low to the ground, say 30 or 40 feet my canopy bucked like a bronco and I looked up and was distracted for just a moment and stopped paying attention to the planet I was about to land on and my landing was much less than perfect resulting in a badly sprained ankle - I got lucky. Lesson learned, when I am that low to the ground looking up at the canopy did not benefit me at all and what good did taking my eyes off the ground do me? Now whenever I am low to the ground I stay focused on my landing and adjust my reactions to changing conditions accordingly by staying focused on what is important - landing safely...

Make it a great day!


popsjumper  (D 999999999)

Nov 20, 2005, 8:00 AM
Post #9 of 9 (683 views)
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Re: [wayne8577] Canopy colapse [In reply to] Can't Post

Skydive Radio...click on "Download a Show"

http://www.skydiveradio.com/



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