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Double mal

 


377  (F 666)

Sep 2, 2009, 4:21 PM
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Double mal Can't Post

http://news.bbc.co.uk/.../england/8234173.stm

Question: if you are down to your last chute and it is all spun up like in this video, is there anything that can be done?

What would happen if you threw out a 4 ft diameter pilot chute attached to your harness? Would it slow the spin down enough to make the canopy more parallel to the ground and slow the rate of descent to something survivable? I know its a wacky idea but I was just wondering... I cant quite figure out the aerodynamics. I am an EE not an ME or Aero E.

No, I am not advocating three chutes so don't flame me.

377


(This post was edited by 377 on Sep 2, 2009, 4:21 PM)


D22369  (D 22369)

Sep 2, 2009, 6:41 PM
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Re: [377] Double mal [In reply to] Can't Post

not so sure a 4' drag chute would help in any way as the main would probably spin just the same - your body would have less spin speed I am sure, but the canopy might still be pointed at the ground and would it slow the decent? I am not sure it would make an appreciable difference.

several points on the video -
unless the TI's where that jump was made deploy at a lower altitude than here then the tandem pulled at 5000' - 5500'

the cameraman waited 4-5 seconds (not the 10 he stated on the interview) before deploying his main so he was around 3500ish at the lowest when it became obvious that the main was screwed.

He pulled his reserve on his back, not sure if there was an rsl involved but you can clearly see the reserve bridal and pilot chute in the video...
not once did I see him check an altimeter.

unless I missed something he had plenty of time to get stable and pull the reserve which would likely have resulted in a non-incident ...
In my mind the only time an unstable reserve pull is acceptable is when humming through 1k or thereabouts.

being as stable as time allows in my mind is a better option than a drag chute *however that said, it is an interesting idea and I am not sure if it would help or hinder

Roy


377  (F 666)

Sep 2, 2009, 10:25 PM
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Re: [D22369] Double mal [In reply to] Can't Post

Quote:
your body would have less spin speed I am sure, but the canopy might still be pointed at the ground

hmmm. You might be right. Unless the canopy plane became less vertical it wouldn't really help.

Anyone else have a response? Where is Brian Germain when we need him?

377


(This post was edited by 377 on Sep 2, 2009, 10:27 PM)


Arvoitus  (D 3917)

Sep 2, 2009, 11:07 PM
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Re: [D22369] Double mal [In reply to] Can't Post

He didn't have RSL.

Quote:
TSE Teardrop, Pilot 132 and Techno 128, no RSL, Cypres 1



http://www.dropzone.com/...;;page=unread#unread


BrianSGermain  (D 11154)

Sep 3, 2009, 1:48 PM
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Re: [377] Double mal [In reply to] Can't Post

It is most likely that the extra drag from a small round canopy, if attached to the jumper, would increase the decent rate of the system. Remember that the flight path of a parachute is based in part on the balance of drag between the canopy drag (D1) and the pilot drag (D2).

When you increase the drag source at the bottom of the equation (D2), you effectively keep the canopy in the dive. If it is already spinning, it will continue to spin, but most likely on a different axis.

If, however, a larger round canopy was deployed, say 20-30 feet in diameter, the spin would have stopped and the second canopy would become dominant. That assumes that the reserve avoids entangling with the main, which is not a certainty. Tossing the canopy itself, in a bag, in the direction of the spin can reduce the risk of entanglement however, and there are lots of people have done this successfully. This is, in fact, how paraglider reserves work, although I would take a cutaway and reserve deployment over that if I had the choice.

Hope this clarifies things.

BSG


377  (F 666)

Sep 3, 2009, 1:55 PM
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Re: [BrianSGermain] Double mal [In reply to] Can't Post

Thanks Brian. Your explanation makes sense.

So much for my idea for a pocket sized solution for a spinning reserve.

377


dragon2  (D 101989)

Sep 4, 2009, 1:50 AM
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Re: [377] Double mal [In reply to] Can't Post

That idea is called a terts/tersh/tertiary reserve (bigger than a pilotchute, much smaller than a round reserve). Been in use by CRWdawgs for a long time. System can solve problems (I know at least 2 jumpers who are alive today because of a terts) and it can CAUSE a lot of problems hence not many people jump with one.



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