Here are some of the opositions brought up by some of our members...
If the tender and profiler are doing their job and know the diver's SAC rate and counting bubbles, they should be able to estimate how much air the diver has and know whether the contingency bottle should be brought down or not..
- If most of the time the problem is an entanglement the extra contingency bottle is just another thing the divers have to deal with. If its not needed don't bring it
- If the primary has 2 air sources all is well. Work to free him. If it takes a long time get the back up to bring the contingency bottle -- so far we don't have a need to pass any pony to anyone; we deal with the problem as easily as possible
Having said that if the tender gets a 3+3+3 and sees a large mass of continuous bubbles that looks like a free flow by all means bring down the extra bottle
I guess the problem IMO with calculating the need for the contingency is that it isn't for sure. You're not going to take it if you don't need it (because we rarely do actually need it) and things can change fast. having a pony that can be donated gives you the option of leaving the primary if you have to (ie get more air, tools etc). If the primary is OOA (empty main and little to nothing in the pony) and you can't pass him the pony you either stay with him and both drown or you leave him with no air (he drowns)
If the primary is entangled and the back-up passes his pony off to him to go back for the contingency, there is a good chance that the back up can also become entangled in the same obstacle and now he has no back up air supply.
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Nothing is definate for sure. There's always a risk of entanglement but for the back up it is reduced quite a bit. Here's why
- he is approaching the primary from a different angle - mid water vs searching through the bottom where most of the obstacles are
- he is following the tether and not actively searching (arms/legs sweeping), turning etc.
- he is more alert to entanglements because thats probably why he is going and can be more diligent
- he shouldn't encouter any until he reaches the primary if the tether is tight as it should be. The line should be clear if the tender is doing his job - he would notice any snags as they occur and should stop the diver before they escalate.
These are common concerns - we've had these same discussions too and hopefully I'm describing things clearly enough for you. We should be able to address ALL the "what ifs" so that we can be assured that we can bring our divers home. We also want to deal with the problems as easily as possible - more task loading may make things worse but we also need to adapt as things change. A Q/R pony will give you another option
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