From "The RSL & Skyhook debate" article

[Hooknswoop 19]

Quote

Think about the configuration of a skyhook deployment, you have the malfunctioning canopy at the apex attached to the bridle with a free bag, still with the locking stows, on one side of the bridle and the spring loaded pilot chute on the other side. Now as the spinning main is deploying the system there seems to be the possibility of the main spinning violently enough to have the reserve pilot chute wrap underneath the free bag trapping the locking stow from coming out. So until some real testing has been done proving that this is not possible I’m not going to be the first skydiver to have that malfunction while doing hop n pops or if jumping something loaded that high.”

Has anyone ever seen a reserve pc entangle with a freebag during a skyhook reserve deployment?

I do not see how this is possible. The Skyhook is not in the center of the bridle. From billbooth; "
1. Bridle Length

With the Skyhook, timing is everything. In a partial mal breakaway, the Skyhook must pull the main out of the container after the pilot chute is launched and "out of the way", but before the pilot chute begins to open and produce enough enough drag to release the Skyhook connection, like it would in a total malfunction situation. To make this equation work out with our particular pilot chute, we found that locating the Skyhook hardware 5 feet below the pilot chute, and 7 feet from the bag, gave the best results. Add these numbers up and you get 12 feet overall bridle length. "Standard freebag bridles are much longer. "

How would the PC get to the freebag when it has 2-feet shorter bridle length from the Skyhook than the freebag has?

Derek V

[RiggerLee 61]

That's the point. One consideration in the choosing of those measurements is to avoid that situation.

Interesting note. Remember the non skyhook rig that had this very type of problem. I'm trying to remember the details. I want to say that it was a vilant spinning mal. RSL. He cutaway. The free bag was thrown out of the tray in the tumble. It spun twisting the lines and bridle together. The PC caught air pulling it tight. So the lines and bridle were twisted at the top of the bag and then the bag just flopped down and the square corner of the bag locked the twist in. Game over.

It's an example of the importance of staging in all aspects of the deployment. It was a case where there was just not enough bag retention to keep every thing in sequence.

A mard might have forced the extraction of the bag before any of this had the opportunity to entangle. Really a compensation for a design issue in the container but they all interrelate. Just one example where a Mard could save you but there are also ways that it can kill you... All design is trade offs.

Lee

Lee
[email protected]
www.velocitysportswear.com

[mark 102]

Hooknswoop

Has anyone ever seen a reserve pc entangle with a freebag during a skyhook reserve deployment?

Morten Pederson.

-Mark

[Hooknswoop 19]

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Morten Pederson

Googled and just got some NSL results.

Derek V

[billbooth 10]

Please let me toss in a few statistics in favor of one of my children...The Skyhook:

It has been in the field for 17 years now.
UPT, Sunpath, Aerodyne, and Avocet have filmed more than 300 Skyhook test jumps.
Our demo program has allowed over 700 "average" jumpers to try a Skyhook breakaway.
It has been installed on over 30,000 rigs.

IF we assume an average of 500 jumps on each of these rigs, we get 15,000,000 (Yes, 15 million!) live jumps on Skyhook equipped rigs. (Assume more or less if you wish, but I bet I'm close.)

IF we use the USPA statistic that a reserve is used every 607 jumps, we get about 25,000 actual reserve deployments on Skyhook equipped rigs in emergency situations. (I would like to take this moment to thank my loyal customers for providing all those test jumps for me, free of charge. I knew I could depend on you.) By comparison, TSO testing requires less than 100 jumps.

In responce to some people's assertions that Skyhooks can cause line twists, or that Skyhooks were never tested on today's super hot mains, let me say this:

I believe that with so many uses, we can safety assume every conceivable malfunction, on every conceivable canopy combination has happened , and I can't remember many (if any) occasions where a jumper has been injured of killed by reserve line twists, whereas MANY MANY jumpers have been killed by low reserve pulls. Besides, Skyhooks don't cause line twists. By getting your reserve directly over your head in half a second, I believe they actually lessens your chance of line twists. (What did you just breakaway from after all? Probably a main with line twists. And those line twists happened just fine without a Skyhook, didn't they.)

AAD's and Skyhooks are not designed to help you when you do everything right. They are designed to give you a better chance of survival when you really screw up. So saying, "I always pull high", just doesn't hold water.

That said: Nothing I have ever designed is perfect. Every device has malfunction modes. Every "safety device", from AAD's to airbags has "killed" people. However, the Skyhook has had far fewer problems than either my Hand Deployed Pilot Chute or my 3 Ring release. It has truly stood the test of time.

[gowlerk 1,903]

I pretty much 100% agree with you about the Skyhook. But not quite on this:

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I can't remember many (if any) occasions where a jumper has been injured of killed by reserve line twists,

I have been injured by reserve line twists. I walk with a limp from the broken heel that I got landing a 5 cell Swift on the tarmac with the brakes still set because the canopy was still in line twists. It opened at about 200 feet. About 20 years ago. My talus joint is now full of arthritis. If I had Skyhook on that jump I do believe I would not have had that particular problem and I would not need my special orthopedic shoes.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[Deimian 43]

billbooth

I can't remember many (if any) occasions where a jumper has been injured of killed by reserve line twists

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=4810702

Being said that, I agree with everything else you said and my rig has a Skyhook. I see it as a probability game.

[KellyF 16]

Hooknswoop

Quote

Morten Pederson

Googled and just got some NSL results.

Derek V

https://youtu.be/4tF6iXI70-Y?list=FLpzksUDjnFCkYtFrUztdcZA

[JohnMitchell 14]

KellyF

https://youtu.be/4tF6iXI70-Y?list=FLpzksUDjnFCkYtFrUztdcZA

Damn, that raised the pulse rate a bit just watching it.

[gowlerk 1,903]

JohnMitchell

***https://youtu.be/4tF6iXI70-Y?list=FLpzksUDjnFCkYtFrUztdcZA

Damn, that raised the pulse rate a bit just watching it.


Meh....he just had a stable reserve with line twists. But he used poor technique on the probably overloaded canopy and started it to turn before he figured it out!

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[pchapman 261]

gowlerk

***https://youtu.be/4tF6iXI70-Y?list=FLpzksUDjnFCkYtFrUztdcZA

Meh....he just had a stable reserve with line twists. But he used poor technique on the probably overloaded canopy and started it to turn before he figured it out!

So for reference this is the Morten Pederson case.

Did you watch the video in detail? I only went thru it a few times. What were you considering the "poor technique"? While we have all sorts of techniques floating about for getting out of line twists, we don't really have any set of them listed in any sort of order of preference or decision tree in any formal instructional manual. I have some ideas, and others do too, but I don't think you can go to the SIM for that.

He was trying to kick out it seems which is pretty standard. (Although there can be stuff added like not swinging around too much; or one can try to level the risers -- I think they were uneven for part of his ride; and at some point I think he did a desperation move of popping both brakes which may have just sped up the dive for the ground while in line twists?)

Despite lots of good comments of yours on dz, I just thought that comment about poor technique was a wee bit harsh on a guy who just had an issue getting his reserve out of the freebag and to stop snivelling. Or at least it could use more explanation.

(Other background: The case was discussed a little at http://blueskiesmag.com/2011/08/30/not-your-day-to-die-evidently/ but with no big conclusions either.)

I'll also note from the youtube discussion:

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Kolla Kolbeinsdottir
3 years ago
Hi Victor - well, manufacturers have looked at the gear and the video, but so far none of them have issued a statement or suggestions as to what took place. There is no debate that the WL is not a factor, the Optimum has been tested and proven to work far beyond the wingloading this jumper was at.
If we ever find out the cause or what contributed, we will be sure to share it. 

The reserve wing loading debate will never end, but sometimes I find that "too high a wing loading" is an excuse used after something goes wrong -- "Oh his reserve problem? While within the legal limits, I think it was too high so he kinda sorta deserved it!"

[gowlerk 1,903]

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What were you considering the "poor technique"?

Yes, I suppose you are right. What I really should have said is that I believe my technique would have worked better. What I saw was a canopy with line twists that started out flying level. But then as he worked it I believe he induced the harness and therefore the lines to become uneven which started the canopy turning. At that point he was nearly done for, and it almost seemed miraculous that he recovered.

What I have found works with a level flying canopy is to simply draw my extremities inward. Become long and narrow like a spinning dancer. That allows the twists to come out quickly and easily. And yes, I also believe that the wing loading allowed on small reserves is just plain foolish.

Then there is also the ongoing debate about the speed of Optimum openings. That one seemed a little slow for a Skyhook opening. The longer it sniveled the more it twisted up.

Edit to add, I just noticed that the Skyhook must have released prematurely. I can plainly see that the P/C was definitely having trouble clearing the freebag for some reason.

Edit one more time to add, I should probably spend more time watching vids before I comment. The more I watch it the deeper the questions get.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[KellyF 16]

gowlerk

Edit to add, I just noticed that the Skyhook must have released prematurely. I can plainly see that the P/C was definitely having trouble clearing the freebag for some reason.

I talked to Morten sometime after I first saw this video, and he said that he had another camera that got knocked off, but was still connected by a lanyard. There was a frame of video from that camera that showed everything still connected when the reserve was at line stretch, then the red lanyard broke.

This one has puzzled me for years. Most of the explanations I hear don't hold water. I've heard the bagged reserve fell out of the container before the MARD started to deploy it. So the reserve FELL out of the container in the split second between the RSL pulling the pin and the jumper and main getting 7-8 feet of separation after a high G spin? I don't think so...

I've heard the rig was one of the Javelin's that had the cutaway cables trimmed incorrectly (so the RSL riser would release first), but that shouldn't matter if the Collin's lanyard was used.

I've been told that the left riser locked up momentarily, allowing the MARD to start deploying the reserve into the main. MAYBE, but I'm not clear on what would cause the riser to lock up if the riser covers were open, which it clearly seems they were, given the location of the main riser ends during the line twists. Come to think of it, I don't know what side of Morten's helmet the camera that got knocked off was on...

To me, this is a "MARD malfunction", whereas every other MARD related incident has been related to the nature of the specific MARD used.