[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.