The problem here is really much bigger than a failed computer, isn't it? I don't understand what kind of backup is being talked about here. Is it 1)A backup so that you can continue to dive after primary fails?? or 2)A back up that you can still monitor your depth and time, so that you can abort the dive safely? I hope it is 2. And to do that, all you need is a depth gauge and timer, so that you can make the safe ascent, do safety stop is desired.
Hmmm, I am not sure what you think I may have implied, but I believe we are saying the same thing here... the point I was making in the larger paragraph, from which you have taken this quote, is that a person needs to be able to execute a safe ascent, ideally with the help of an appropriate time and depth measuring device to ensure proper ascent rates, maintain proper stop depth, etc.
So it should really be a computer set to gauge mode. The problem with two computers is that what is the backup show you a drastic different information. Say your primary says you are still within NDL right before it fails, but you back up is in deco mode. Will you follow the back up and complete the deco?? At least for Oceanic/Aeris recreation computer, their deco mode gives ridiculous stop depth and time.
You should not have allowed any of your computers, whether backup or primary, to go into deco mode in the first place (on a recreational dive), and the more conservative computer should have been the primary. Throughout the dive, you would have been following the information provided by the least aggressive among all your computers, and the dive plan that has been prepared beforehand, hence in the case of a failure, what you would be left with is the (possibly) more aggressive bailout schedule (which, of course, shouldn't really contain any deco stops to begin with). If you are not willing to stay within the limits computed by your backup, then I agree that there is no point pretending that it is anything more than a bottom timer, and you might as well set it to gauge mode at this point.
I am not so sure that is the right way to do deco at all.
Of course it is not, a recreational diver on a single tank should not even go anywhere near deco, which requires technical training and redundancy, and all divers regardless of training or redundancy should plan their dives, and dive their plans...
Unfortunately, many divers push their limits, and ride their computers up to the NDL, which is very easy on a 100-130 foot dive, especially if someone is going to get narced. If a diver is going to ride their computer (which of course they shouldn't), then they better have a fully functioning backup that can get them out of trouble safely... if the skills are lacking, or if someone refuses to improve their skills, and yet they continue to make aggressive near-NDL dives to 130 feet (which of course they shouldn't), having an equipment solution to the problem (backup comnputer, or at least a bottom timer and tables) still seems to be the lesser evil. Then again, of course, the better way to go would be to abstain from making these sorts of dives if a diver finds herself repeatedly cutting it close, and take up proper training ASAP.
