I read the original post as a question that most instructors would answer as 'if you cut your schedule, you run a higher risk.' As far as taking a hit, according to DAN, sometimes, even when doing your dive on schedule, you can be hit. Period. And, there are cases where people blow off most if not all of their stops and seem fine. Obviously, if you are doing any form of technical diving, you are going to want to KNOW WHAT IS GOING ON, be PROPERLY equiped and trained. There are possibilities of being put in a situation where you will not have the gas to do the stops. A severe entanglement at the end of the dive, a current that came out of nowhere, followed by a catastrophic failure, wreck collapses, trying to save someone, etc, etc. To say I will never have any of these problems means you are lying to yourself. Or you are diving in absolutely perfect conditions all the time. Must be nice. So, before you all flame me with whatever (as a DIR GUE, I'd have my buddy free me-let's say he had his head bitten off by a giant triggerfish,or if you enter a wreck that collapses, you shouldn't have gone in-didn't one of the team end in a collapsed cave.....)lets get back to the OP's question- which to skip and why. I am not trying to start anything, I just get sick of people flaming me with their straight from the manual responses. Really, Really, Really sick of it......
'-J
Well, first off let's not make this an agency-specific issue ... because it is certainly not that. My first tech training was with IANTD. My Advanced Nitrox/Deco class was NAUI, but we used TDI materials for the classwork (because, frankly, they're better than what NAUI was offering at the time). And my Trimix 1 and 2 classes were NAUI. And there are certain things they ALL emphasized. One of those things is planning for things to go wrong ... and in particular, planning in such a way that if they DO go wrong, you will not be left with an inadequate gas supply.
Most agencies train you to be able to handle any combination of two failures without compromising your safety. What this means is that if you lose gas, you will be able to make up that gas with reserves in some fashion that will not require you to skip any mandatory deco. So if you follow your training, having things go wrong won't require you to make an unsafe ascent.
So thinking along those lines ... there are certain things you should ALWAYS include in your dive plan.
- Bring sufficient backgas that if you lose your deco gas you have enough to extend your schedule and deco on backgas.
- Bring sufficient deco gas that if you or your buddy lose a deco bottle you have enough that you can extend your schedule and share what's left and honor your deco obligation.
Planning the dive so that both (or all three in some cases) divers on the team observe the two rules above means that even if you encounter two or three simultaneous problems, the possibility of having to reduce your deco schedule due to inadequate gas supplies is extremely remote ... and if it happens, you've got bigger problems than just a risk of DCS.
You JUST SHOULDN'T be doing the dive the OP described with no redundancy, and insufficient reserves to accommodate a problem. Once you get to the point where you're doing tech dives, the mindset that goes into recreational protocols doesn't apply ... that's why the training is so important.
Now, if you WANT TO take those risks, go ahead ... there aren't any scuba police gonna stop you. But if you're going to come to ScubaBoard ... or any other dive forum ... and ask how to accommodate a situation that just shouldn't occur, then don't complain when people tell you not to plan your dive in such a way that it could happen.
As I said earlier ... we did talk about reducing a deco schedule in my classes. But in no circumstance did we frame it in such a way that the issue was that you failed to bring adequate gas for a lost-gas contingency. That's just poor planning, and has no place in tech diving. If you want to dive that way, then my advice is stick to NDL profiles, where there's always a possibility for a direct ascent.
Or ... stop living in denial and just recognize that you're flying by the seat of your pants and are doing a dive without really understanding or planning for dealing with the risks involved.
... Bob (Grateful Diver)
