safe backup

[land shark]

Ok Im a rank amature when it come to this stuff. Somehow I feel there is an answer out there. Now that DeeperBlue has hit 12000 members perhaps we can put our heads together and come up with a better idea! I Know that we have had threads in the past pehaps we could revive them instead and build on them. It some how seems to simple to let the boat do the work but here is a very simplistic Idea based on an anchoring trick fishermen use.

The pics were constructed rather fast but i feel conveys the idea.

The sled cable is passed through the bouy and bouy with the speader bar is released after the sled is released. Upon intiation the anchor line is released and the boat pulls the whole sled assemby up. a rod at the top of the sled counter weights over to help lock the sled to the ring on the bouy while the boat powers down for the support team.

[azapa]

great Ideas. I was deep in thought about this as well after Loic's sad death. I think the problem is budget related. Freediving is still a new, "weird" sport (not my words, but what I see reflected in the comments of others I explain it to). There are no huge budgets or sponsors. Least for training dives as was Loic's.

The mechanical version, ropes, pulleys etc you mention is great. But my solution would be similar to the freediver safety vest (search this forum): an emergency buoyancy device, triggered by the diver, or from the surface. It would of course, have to be a completely separate unit to the main dive infrastructure. In both deaths, Audrey and Loic, the surface crew were aware that something was wrong, due to the time, but could do nothing to help. Some electronic progress monitoring of the diver would be great.

I have to be fair in stating that I have never tried no limits dives, nor have ever seen one. But I am an engineer, and can solve problems, and feel that these type of deaths have a technological prevention on hand. Lets hope so.

[fcallagy]

Hi azapa,
as far as i know the an inflating vest would not work/provide enough lift from the depths that are now being reached. The counter weight seemed to be the safest option thus far the biggest downside to it possibly being caught in currents or flotsam etc and getting snagged so i.m not sure would your boat idea work as it may pull the diver horizontally rather than vertically. Maybe a superfast winch on a large boat will be the only way in the future that swings out prouud of the boat. with the declining fish stocks there may be a few of these on the market at reasonable prices in the future.

[land shark]

Thats what Im talkin about!
lets those that build these systems see what Ideas we all can build on perhaps we can help with a better mouse trap.

[azapa]

fair point re depths and pressures, although I'm sure that some no limits sledges are lifted by balloons?? Of course, the freedivers saftey vest size balloon would not work at those depths. I can't get out of my head the idea of trying out (just for fun!) a car airbag unit at depth. They should be cheap from the wrecking yards, and just need a 12V buzz to fire.. I know the duration would be a problem... like I said, a fun experiment.

[trux]

As for backup and redundancy, it is necessary to realize that there are basically two categories of possible failure at sled dives - diver failure and equipment failure.

Usually, if there is at least basic safety in place with some security redundancy built-in, such failures are to be expected rather often, but still the redundancy avoids a tragedy. It becomes serious when there is multiple failure, what one cannot exclude in such extreme conditions.

I am not perfectly familiar with the sled at CIPA, but from what I heard and read, they cared about security and built in multiple redundancy. AFAIK, there were two tanks and lift-bags, for the case one fails. Additionally, Loïc had a small bottle integrated in his suit that could lift him if the main lift failed. There was the counterweight system that was regularly tested.

Although we do not know what exactly happened, it seams that Loïc blacked out already on descent (or got blocked, or entangled, or had other technical or physical troubles - they wrote they did not feel him touching the base plate). It seems he did not open the lift bags or his safety ascent bottle. Well, although the primary cause for this might have been technical, the basic problem was that the diver failed to start the ascent (either due to unconsciousness, physical problems, or whatever else). Hence in that moment, all the redundancy that was relying on the freediver was worthless.

Now, not feeling Loïc touching the bottom plate within reasonable time, they initiated the counterweight system - another piece of the safety redundancy. Unfortunately, it failed too. Possibly due to the primary reason (some kind of entanglement on the descent), maybe because of something else. Anyway, there was now very little remaining redundancy - they improvised with pulling the ropes by hand, then by pulling it by another boat, and finally descending on Nitrox to 30m (they did not really know how deep Loïc is).

So, although there was some redundancy built in, it was not sufficient, because a single failure (of the diver) erased most of it. The failure of the only remaining redundancy (counter-weight) was unlucky, but wouldn't be necessarily tragic, if there was another backup option (independent on the diver) immediately available.

The no-limits trips should be considered as dangerous as Apollo trips to the Moon, and similar redundancy for all systems should be implemented. Backing up only some of them is definitely not sufficient. Already at Audrey's tragedy, there was a chain of failures (now, it is irrelevant if you think it was on purpose or not). And it will happen in future again, unless we start to look at NLT as a really extreme experiment requiring extreme safety measures.

I agree with Loïc and CIPA that safety scuba divers are not the solution for NLT, though having at least two observers at 20m, ready to descent to some 50-60m in case of need, would not cost much, would not put anyone in a serious risk, and might have helped quite a lot in this particular case (but likely not in many others). We do not even know if Loïc did not black out just shortly after the start. If there were observers in relatively shallow depth, they could have abort the attempt at least in such case.

There are still certainly many ways how to improve the security of sled dives. Besides building lifting systems independent on the freediver conscience or remotely controlled, I find that one of the most important things is a communication and real-time monitoring (camera) system, that should be present even at training dives, not only at record attempts.

If the surface team had live video feed, they'd be able to react faster and better. If there was some kind of communication system - for example simple button for keeping the contact (in similar way as tapping during statics), it would certainly help a lot too. Also, to me it seems to be necessary to be able to trigger the lift bags remotely - similar mechanism like that used in the freediving security vest could be used (lift bags filled automatically whenever one of several conditions met - maximum depth, contact with the bottom plate, maximum time, or even lapse of reaction from the freediver during the descent). I think that also the possibility to remotely detach the bottom plate and sled weight might be considered - in case of entanglement and the necessity of pulling up the entire system, it may help.

As for the communication system - there definitely should be some way of communicating or at least signaling between the surface teams, safety divers, and even the freediver. Protocols for any thinkable situation (including such improbable ones as a squid or shark attack) should be be created and drilled. Already the tragedy of Audrey proved that all the involved persons handled improperly, because they simply did not know what to do, and what others are doing - there were no drills, no protocols, no communication, no signaling (or very little of them, AFAIK).

Yes, I know - some of the measures are not technically trivial, others are expensive (i.e. live video feed), but on the other hand there are other possibilities that can be done rather easily and at low cost. And maybe AIDA and/or multiple clubs + sponsors could finance one or multiple good and safe sled systems that could be then rented for diverse events (record attempts, trainings, courses, competitions).

And please do not take my comments wrong - I did not suggest that CIPA or Loïc were carefree or cavalier with security (I know the opposite is true). I am just telling that whatever tragic and unfortunate the accident was, it is good to learn from it.

[Stavros]

Hallo all
dear land-shark the idea you suggested would work probably as well as a normal counterweight with a slight advantage of speed. The only problem is that you wouldn't e pulling the diver/sled straight up but at an angle. So instead of dragging the diver 180m+ upwards you'd end up dragging them over a much larger distance (+time).

A far simpler solution we've used is to have the dive line going through a pulley with the other side attached to a small boat ready to lift up the whole line+sled+diver. This works well if you combine it with an accurate sonar which can monitor the diver's descent arrival and ascent (so you know if everything is going according to plan). We have been doing some testing this way but the problem is it requires a lot of infrastructure (two boats and a minimum of a 4 person team every time you dive)

Although in theory this doesn't seem like a lot for NLT dives once you start trying to arrange it with a freediver's budget you quickly realise it is not very easy to have such setup every time you dive.

So the solution now seems to be powered counterweight systems...they work - they are expensive - they are heavy - but its an one-off investment.

So thats the new thing...(tested a couple of weeks ago and works nicely)

Later on today we are trying out the new sled...its going to be interesting.

Cheers Stavros

[fcallagy]

Thanks for the info stravos please keep us updated on it. One other idea that comes to mind id that the sled detatches from the line in the event of entanglement and still raised by lift bags surfaceing possibly away from the line but at least surfacing.