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Dealing with high shock loading

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billvon

>Maybe something built into the risers like the “YATES SCREAMER” from the climbing
>world. They are built to reduce shock loads by 3-4 Kilo Newtons.

Leaving you with one riser shorter than the other - which, after an opening hard enough to knock you out on a tiny reserve, could be fatal.

This would be a good topic to discuss in Gear and Rigging.

Bilvon -
First comment: there are already some in the parachute industry using this type of load limiting... Butler uses a similar design in higher-speed PEP bridles to reduce snatch loading. But as you would correctly point out, this is a single attach point load, not multi-point as the canopy is on the risers...

And yet, to me and barring a better solution, I'd buy into this concept for this reason...

Lets assume you will have an openning hard enough to engage the safety on this type designed riser. I'll even assume that part of the problem leading to the unusually hard openning is that we are loading the risers unevenly. So freeze-frame at the point that the shock load is about to hit the harness, here's the three primary scenarios I see coming next:

- shock loading causes a busted harness - OK, we're not having problems with this (currently), but it is an option to acknowledge. Outcome if this happens VERY Critical.

- shock loading transfers to the jumper - this is where we are having the (admittedly rare) problem. And this is what we're wanting to avoid... broken neck, broken internals, or simply incapacitated long enough to not deal with the other aspects of the situation (i.e. broken lines, torn canopy, or simply landing a higher performance main)

- shock load disipated through a weak link such that the jumper can deal with the emergency. Focusing on this weak link option... best case, all four risers "unzip" and you end up with risers 2-3 times normal... cutaway and use reserve since you would not be able to reach the steering toggles (as I envision the risers). Worst case scenario would be that one or two risers are longer than the others... canopy spins up, but the jumper having been spared the shock load is able to deal with the emergency.

Best solution, no... but better than what we have now... so smart people, what else would you do...

JW
Always remember that some clouds are harder than others...

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Second concept:

Noting that we already have a device that is primmed and ready to fire the reserve, lets see what you all think of this:

Add to the cypres:
- accelerometer
- two additional cutters integrated into the cut-away cable housings at the riser end grommets
- logic: if (above 1500'* and g-load above 6G's*) then fire cutaway releases, wait 2* seconds, fire reserve release.

*numbers used in the logic portion are abitrary and made up, testing needed to refine what "appropriate" values would be... that's what R&D is for...

With the speed that the current generation of AAD's can process, I think a G/load value could be found that would be high enough to cause us to want the system to immediately (3ms*?) "break" (release) and go to reserve.

As to concerns over mis-fire releasing you under the wrong/bad conditions... well, most people have cypres' now and how often do we have misfires? And yet, by limiting this action to above 1500' it couldn't release the main "too low" Even if a high performance flier were able to exceed the G load limit (which we'd try to make high enough to keep from happening) the activation above 1500' should result in their being under reserve in plenty of time for landing.

Anyone know if Helmut Cloth or SSK follows this forum?

Personal comment - as someone who wishes to keep jumping long after earlier generations did, I know that we face new geriatric-jumper issues. There is a reason POP's focused on 40, that was an "old" jumper in 1966. Old round jumpers discuss openings hard enough to kick their own helmets, knock them out and do other damage... and that was when they were young and fit enough to jump that gear. As our skydiving population extends the "retirement" age, it is very important that we anticipate and address this type of issue. Even the most fit of us (and I'm not) can't continually take the occasional pounding we could at a younger age. Finally, while the 20-somethings know that they are imortal and immune from all things fragile, even the youngest/fittest of us won't survive the worst this gear can dish out.
Always remember that some clouds are harder than others...

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>so smart people, what else would you do...

If that was something worth protecting against? Probably something _like_ a Screamer, but one that completely detaches over a certain load limit - coupled with a Collins lanyard to ensure a clean cutaway.

However, this is again more stuff that can fail, and would probably cause more problems than it avoided.

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How many fatalities are a direct result of hard openings?

The YATES SCREAMER type device would have the desired effect. But if more than one was used on two load paths(risers). An out of trim condition would be a likely result.

Perhaps an decelerometer circuit in the AAD that would activate a second pyro cartridge initiator connected to the three ring cables.

Perhaps this is a solution in search of a problem that lies in a change of attitude re small rigs, high performance.

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Obviously I'm new here, but would it not be possible to put some sort of replaceable, bungee-like material in/at the riser area, that could absorb opening shock, but be bypassed with some sort of clip or hook of some kind once the canopy is open that would shorten/stiffen the risers back to normal if desired?

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I would argue that we have this now in the form of mini risers. The problem with that is that we have RSL's. You could call the collens lanyard a fix for that problem but I see it as a fix for a fix and would argue that simplifying the system removing the RSL would be a cleaner way to go.

Another thought is to reevaluate the way we are building risers. A riser where the break point would be above the RSL connection. I have seen mini risers break above the confluence point, front riser snapped, so we're not that far off. I think the problem is the internal stresses in the three ring. I've seen several tapes break on the third ring. If we went to an Aerodyne stile riser with an elongated second ring we might move the break point up above the release. Another thought is risers with a lower tinsel strength webbing. And you can have webbing woven to any speck. For example we had a tape woven for a raideal seam that was 1200 lb vs the normal 500. So if we built a lighter riser, with good reinforcing tape in the grommet, and an Icon ring we could move the failure point up above the junction. Pick the strength and set the limit to the load you want the jumper and harness to endure.

And this isn't a speculative goofy discussion. People have died from opening shock. I've known several who ether died or might have died from opening shock and one that's paralised. And... remember the Racer that blew up? Broke all the stitching on the chest strap. I've seen several leg junctions blow partially or completely. Fortunately they were on rigs with redundant stitching. Or the russion rig that blew up at the upper junction. Or the base rig that blew up at the upper junction, built just like a skydiving reserve riser. Point is you can and we have broken shit. Both our harnesses and our selves. I don't consider this to be a theoretical discussion.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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It's a real problem. I've known 3 people that died from hard openings on mains and one quadriplegic.

A screamer or bungee would not work because there is not enough energy absorption. It's force over distance and the numbers are too high. I work with them in several designs, we have a screamer on our nose cone. Just built a system with a break tape followed by a large screemer for the attachment points for hover test of our air frame to protect the crane truck. And they are really bulky by the way. Snapping the riser is the way to go to limit the load.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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The problem we're trying to solve is to prevent an opening shock going above some number of Gs. Tapes and webbing break at a certain number of lbs. For the same limit in lbs, a 5G shock for a heavy jumper would be a 10G shock for someone half the weight. The first one might be ok, the second one might be fatal.

An AAD could measure Gs, but the measurement might be delayed or underestimated because the sensor is not attached directly to the MLW. For calibrated tape/webbing solutions, you'd need different breaking strengths for different jumper exit weights, which means many more variations in riser manufacturing. I keep asking UPT to build mini risers with standard rings, but they keep saying no. :P

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That's valid. I think it's fair to say that these aberrant openings only happen when some thing goes wrong but there are a lot of things to go wrong. The quad was sit flying when he lost a main. Best if that never happened but... shit happens. Was it just the air speed? I think a riser got caught under his reserve tray and caused an out of sequence opening but that's just my theory. People are free flying all the time. Short of building 170 mph canopies I don't see a solution to that.

Remember the video of the wing suter that sucked their canopy all the way back onto to their back on opening and then had basically a slider down opening on his main? I know a woman that I think that happened to. Almost destroyed her shoulder.

I don't think it's a small canopy problem. Historically I've seen way more problems with small canopies then large ones.

This is one of the reasons I am very skeptical about new goofy stowless bag designs. I think those things are asking for trouble.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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You've obviously been in the sport for a long time. Have you noticed any trends regarding equipment technology and changes to it compared to the frequency and severity of hard openings? Have fatal or maiming hard openings always been a problem to the degree they are today or did the trend go up with the introduction of ZP/microline? Is there any correlation that you can discern? Just curious.
What's right isn't always popular and what's popular isn't always right.

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How about risers designed to separate (fail at a predetermined point) to act like the weakest link, or a fuse like in electronics? They would separate at forces less than those that would kill or seriously injure the jumper. They would have to be built into a location so that it wouldn't interfere with the RSL. Worst case is that the jumper would have to replace his risers after a very hard opening (I.e. replace the fuse).
What's right isn't always popular and what's popular isn't always right.

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>I would argue that we have this now in the form of mini risers.

A few problems with that I can see.

1) While they do in fact fail under load, they are in no way calibrated to do so. You'd need to design them to fail before X lbs loading but never fail up to Y lbs loading - not easy to do, nor easy to guarantee over riser life.

2) You would often then get one riser broken and one not, which isn't a good situation without an RSL and Collins lanyard. (And if the failure is above the confluence, even Stevens/Collins lanyards don't help.)

3) You would need to sell different risers based on jumper's weight.

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It wouldn't and it doesn't do so now. It shouldn't be too much to ask for people to replace their shit when it wears out. And yes that's a problem now as it is. I don't think the over all life span would change that much do to wear. The areas we are talking about are not the wear areas. There is much more wear around the three rings. All of the failures I've seen on third ring tapes and grommets have been on older risers. Interestingly, the risers I saw break above the junction were almost new. So in an asymmetric opening most of the load on the right front riser it failed the riser above the junction before it broke the three ring or grommet. So with a brand new riser, built properly, correct dimensions, I think the strength of the three ring is greater then that type 17. But as the three ring wears it drops below the strength of the riser and becomes the failure point. What I'm suggesting is that we build the riser such that the leg, which isn't the main wear point, would remain the weak link through out it's expected service life. Looked at from that perspective It wouldn't be that much weaker then a used riser.
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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Turning the riser into a fuse is basically what we are talking about. I'd say build lighter slinks but they are much more of a wear area. The riser leg is less of a wear and less prone to change over a reasonable life span.

This problem has come in waves. Once we had good sliders and good staging the problems of hard openings was basically solved. Then as micro line and ZP showed up it reared it's head again. Now as fall rates pick up with free flying we are seeing it again.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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gowlerk

Rouge openings like this can only happen it the slider fails to do it's job. It would probably be better and simpler to focus on finding ways of ensuring that sliders stay all the way up until line stretch.



That's the simple solution. Why not just put a tailgate on the slider? It can be done while propacking and only takes a few extra seconds.

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Quote

Once we had good sliders and good staging the problems of hard openings was basically solved. Then as micro line and ZP showed up it reared it's head again.


This is exactly the point I've been debating with another poster on another thread.
What's right isn't always popular and what's popular isn't always right.

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Has it ever been determined which contributes more to hard openings, ZP or microline? I think that both came out within three years of each other (microline in 1986 and ZP in 1989) so time of introduction to determine this would be difficult since a three year spread isn't really enough to determine a trend for the microline.
What's right isn't always popular and what's popular isn't always right.

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I think nether. It was staging. The change to micro and ZP created staging issues. Packing practices that worked, or that we go away with, on dacron lined f-111 canopies would not work with the new materials. And although they came out together they were not necessarily used together. we saw f-111 with micro and ZP with dacron.

Lee
Lee
lee@velocitysportswear.com
www.velocitysportswear.com

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Phil1111

How many fatalities are a direct result of hard openings?



You would need to count direct and indirect. If you open hard enough to knock you out, you break a riser and then you plummet to the earth unconscious and unable to cut away, do we really need to argue schematics over whether that was a broken riser that caused the death or a hard opening? btw. that was a real fatality not that long ago.

So if you use that as the standard, than I think hard openings are responsible for many deaths, at least a few last year alone. Several of the fatality reports I've read from the last few years have mentioned hard openings. Not necessarily killed on opening, but disabled or otherwise affected enough that the hard opening ended in death. Almost everyone I know who has at least 1000 jumps has mentioned having at least one hard opening that was hard enough to cause injury (ranging from moderate to serious). So I think hard openings are far more common than they should be.

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gowlerk

Rogue openings like this can only happen it the slider fails to do it's job. It would probably be better and simpler to focus on finding ways of ensuring that sliders stay all the way up until line stretch.



Thumbs up to that. Snaps (as on a couple canopies), elastics, elastics on slider mounted tailgates, whatever .....?

Currently we basically follow the method of "Pack it well, wrap the tail, don't lose control sticking the canopy in the bag....and hope the slider stays in place. "

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Would utilizing a pilot chute controlled reefing system (pilot chute attaches through the canopy to the slider to help slow/control its descent down the lines) potentially help with this? No idea what potential issues those have but I'm sure someone's tried it before, right?

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pchapman

***Rogue openings like this can only happen it the slider fails to do it's job. It would probably be better and simpler to focus on finding ways of ensuring that sliders stay all the way up until line stretch.



Thumbs up to that. Snaps (as on a couple canopies), elastics, elastics on slider mounted tailgates, whatever .....?

Currently we basically follow the method of "Pack it well, wrap the tail, don't lose control sticking the canopy in the bag....and hope the slider stays in place. "

Snaps would be even easier and dummy proof than a tailgate.

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