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pchapman

3-ring flip-through on opening (Sigma tandem jump)

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This weekend as an instructor on a tandem jump at near maximum allowed weight, I discovered one riser's 3-ring to be partially 'flipped through' after opening, where the middle ring had slid back part way through the large ring, and the middle ring was angled well forwards rather than vertically, as was the bottom of the riser itself. This configuration greatly reduces the lever effect of the 3-ring system. The yellow cable was jammed up against the AMP fitting and riser, with a slight bend in the cable, although not actually being sucked through the grommet.

Under canopy, the top of the small ring can normally be moved with only a couple pounds of pressure (showing how little force there is on the white loop), but this time I found I couldn't budge the small ring while squeezing the riser and small ring with one hand.

I landed OK with my first jump student. The middle ring shows distinct indentations where it was 'hammered' by the large and small rings during opening. The indentations are much deeper and sharper edged than the minor flat spots that occur on the middle ring over the course of many jumps. I think the middle ring is slightly distorted (bent, not ovalled), but it's hard to tell by eye. The cutaway cable is nicked and kinked slightly.

A couple questions:

a) Anyone know of similar incidents?
I haven't found anything quite like it in the dropzone.com archives, although it has been mentioned that jumping with a flip through could or has broken risers due to the non-normal forces on the system.

b) What to do with the riser? Given that the white loop for the 3-ring APPEARS undamaged, does that mean that it IS undamaged or not? One theory is that if no torn strands are seen, and no elongation is seen compared to another loop, then there is no loss of strength. (I don't know anything about stress, strain, yield strengths, etc. in woven fabric material.)

At the DZ, we've grounded the rig for the moment, and we'll talk with RWS after the weekend.

========== Other details:

It was a tandem jump on an RWS Sigma rig with a Sigma 395 canopy. The student weighed 280 lbs (at least as reported by the student), with an instructor weight of 150 lb. With the rig weighing about 50 lbs, that's a total of 480+ lbs, getting close to the Sigma certification weight of 500 lbs.

(No I didn't check what the canopy weight limits would be after density altitude corrections are taken into effect -- PD-designed canopies tend to have that kind of thing listed, although at the moment I don't have info on paper about whether that is applied to Sigma canopy for recommended or certificated weights. We were close to the limits in any case.)

Droguefall was normal but fast as expected. (125mph SAS average on the ProTrack). The opening was hard but not unusually so. Openings on the Sigmas are noticeably harder as the passenger weights increase. In particular, there tends to be a harder jolt and shake at the end of the opening, which is what occurred. The opening was on-heading as usual.

After popping toggles, checking airspace, getting my passenger comfortable, etc., I checked the 3-rings. To check them after opening was taught when taking the tandem instructor course 3 years ago, although it is easy to get casual about it because one expects the 3-rings to be fine. As I didn't check right away after opening, we were getting down a bit in altitude by the time I thought through the situation, although still above recommended tandem emergency procedure altitude.

It seemed most likely that if the riser and loop withstood the opening, it would be fine under canopy. So I chose to land the canopy. Still, there was the disquieting notion that there might be a not insignificant chance that the loop could let go from damage during opening, which can lead to not being alive. No spirals for the student! (I coached the student through the steering during some of the flight while I squeezed the top of the small ring towards the riser with one hand -- that seemed worth trying even though the forces on the top of the small ring were probably so high that one couldn't keep the 3-ring from releasing.)

How did the flip through happen? Flip throughs on tandem rigs do occur on the ground from time to time and have to be fixed during packing. I can't imagine that there had been a flip through that remained undetected by the packer or the instructor (me). Is there anything packing-related that might make a flip through more likely? Say, if a riser were a little loose over the shoulder (rather than snugly pulled down towards the main container & putting slight tension on the 3-ring assembly)?

Could the flip through have happened in the somewhat jerky opening? Perhaps one riser rotated away from the pack, yet unloaded for a moment, allowing the middle ring to slip 'back' through the harness ring? Would the unloading happen as the main bag lifted and lines stretched, with some whipping back and forth of the risers, or later during some part of an asymmetrical canopy opening? I'm not quite sure.

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That's common to flip it through when gathering up the canopy after landing when the risers are hanging down in front of you.

It seems nearly impossible to have it occur unless it was put on your back that way. I realize you performed a gear check, but it seems to be the only way. I've been proven wrong before so it happening afterwards isn't ruled out. Does there happen to be video of the jump?

Try and push that ring through while it's unloaded. Then squeeze the middle and the small ring together and it will pass through. I'm not sure how it could pass through under any sort of load, but ya never know.
My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

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That's common to flip it through when gathering up the canopy after landingand the risers are hanging down in front of you.



I concur with that as well. We have seen what you described as the rig was being closed by the packer. It happens after landing or during the laying down/packing process. My guess is that it was like that when you put the rig on and went unnoticed on the ground.
"It's just skydiving..additional drama is not required"
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That's common to flip it through when gathering up the canopy after landing and the risers are hanging down in front of you.



I concur with that as well. We have seen what you described as the rig was being closed by the packer. It happens after landing or during the laying down/packing process. My guess is that it was like that when you put the rig on and went unnoticed on the ground.



_____________________________________________

Strong TIs knew about this (flip through) problem 15 years ago. That is one of the reasons why we switched to Type 7 risers.
Your next step is delivering a stern warning to your packers to the effect that if they ever pack another rig with a riser flipped through: they are fired.
The second step is to loudly and angrily tell your TIs that if they ever don another rig with a riser flipped through: they are fired.
Your fourth step is to order a new set of risers.

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It seems nearly impossible to have it occur unless it was put on your back that way. I realize you performed a gear check, but it seems to be the only way. I've been proven wrong before so it happening afterwards isn't ruled out. Does there happen to be video of the jump?



Nope no video.

As it is hard to come up with ways for the rings to flip through during freefall or opening (or even, say, while hooking up in the aircraft), it comes back to the question whether I got in the airplane with the flip through. I can't avoid that question but I just can't see myself having missed that during inspection & gear up.

I still need to talk to the other tandem instructor on the C-182 and to find the records of who packed the rig. And I'll play around with tandem 3-rings next time I'm at the DZ.

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That is so common with tandem rigs, I have a hard time believing that this comes as a surprise to someone in 2005! I mean, it is the reason for many many broken tandem risers and reserve rides; for everyone I know that makes tandem jumps it is a mandatory pre-jump check by the instructor before putting the rig on. And it CERTAINLY should be checked by anyone packing tandems. It is so common that many tandem rigs have the tendency to do this after every jump and must be straightened out before packing.

Oh, and like has been said earlier, that pair of tandem risers is trash and MUST be replaced with new main risers.

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Oh, and like has been said earlier, that pair of tandem risers is trash and MUST be replaced with new main risers.



I have had this very often - nearly after every jump - on a Strong/SET400 Tandem. It happens on the ground, not during opening. I always correct this while packing and never saw a problem.
The risers are new (less than 100 jumps). Do you really think they must be replaced?

alex

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www.tandemmaster.net
www.skydivegear.de

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The risers are new (less than 100 jumps). Do you really think they must be replaced?



Here's part of the original post...
"The middle ring shows distinct indentations where it was 'hammered' by the large and small rings during opening. The indentations are much deeper and sharper edged than the minor flat spots that occur on the middle ring over the course of many jumps. I think the middle ring is slightly distorted (bent, not ovalled), but it's hard to tell by eye. The cutaway cable is nicked and kinked slightly."

So yes, the risers should be replaced, as well as the cutaway cable.

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Ok, that's quite the revival of an old thread.

I see the video shows a flip through existing before exit, on a Strong rig, for a tandem instructor who was probably sitting with nobody looking at him due to how the seating was in that plane. (Other than the guy in the copilot seat turning and videoing the tandem exits.)

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I have seen it personally on one jump and have at least 3 more recountings of it's occurrence. I believe it is caused by instability causing uneven ruser/line group tension durring the trapdoor.
----------------------------------------------
You're not as good as you think you are. Seriously.

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Nice to hear that someone knows of the flip through occurring during a jump on opening, as nobody wanted to believe me that I was sure the rings were OK in the plane! (A C-182 with I and another instructor looking across the 3 ring at each other.)

Makes sense that it somehow could involve uneven tension, with a loss of tension on one side during the trapdoor, with made worse if there's any unevenness like a shoulder down.

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