It doesn't replace the primary; but it is available if needed. We don't stop training it just because something better came along. Astronauts don't stop training backups just because there is a better system installed.
Of course having a plan-b is a good idea, but the better backup for a failed computer while diving is another computer. In your example above, if, during the ultimate holiday, the diver fell back to tables and continued to dive the rest of the trip with them then they would ultimately get less bottom time for the trip than if they did a 12-18 hour SI and carried on with a new computer.
The issue I see isn't backup and even though tables are a lousy option for this as compared to other options, it seems to be the only thing people bring up in every one of these discussions as a reason to keep training them.
How would you address the problem I have mentioned a couple of times in this thread that after a period of time, people generally do not remember how to use the tables correctly? I see a risk in this that I believe can be better addressed by recommending using a 2nd computer as a backup.I support teaching computers; it should be the primary means- but the alternate should be taught as well.
I see no benefit in assigning blame for this. It doesn't address the fact. The fact remains that if people do not use the tables on a regular basis most of them will forget over time how to apply them correctly.Then this is where you failed as an instructor, to instruct properly. If they were taught properly, then it is their fault for letting a skill deteriorate.
On this we agree. We just disagree about what form that backup should take.You simply don't grasp the concept of backup, do you? There always exists a viable need to have an alternate plan if one system fails. If your computer fails on a trip, having a backup can save time and money.
They are not incompatible, I agree. However, as I've said above, I see tables as an inferior way of backing up a computer, *especially* during that trip of a lifetime. On a one or two dive day, sure, go ahead and use tables from time to time. Nothing wrong with it and manually working it out is a good mental exercise. I understand what you're trying to say, but I disagree with you that learning tables makes one a more skilled diver. It might make them a more knowledgeable diver, but as time goes by we will see more and more highly skilled divers who can't easily find their way around a table.Teaching tables does not infringe on the ability or need to teach computers. Nor should it replace computers. Both should be taught side-by-side. This produces a more skilled diver, one that can better handle an failure.
R..
---------- Post added March 16th, 2014 at 10:57 AM ----------
This is why computers must be taught. It takes a while to learn how to use a computer properly.
This point often gets overlooked and deserves repeating. Regardless of whether or not the instructor is teaching tables the computer should *always* be taught. I still see instructors around me failing to teach computers and as a result they are teaching something the student isn't going to use and failing to teach something that the student WILL be using.
I see teaching tables as optional, but I see teaching to use computers as mandatory.
R..
---------- Post added March 16th, 2014 at 11:00 AM ----------
I almost always calculate my dive profiles after each dive using the tables, for practice, and just in case my computer fails. I have a waterproof watch and a depth gauge as backup. If my computer failed mid-dive (unlikely), or if I accidentally left the computer at home (happened once), I could still dive based on the tables and a square profile. In other words, I would act as if I had been diving on tables all day.
The last dive I made was made to a maximum depth of 38 metres for a total bottom time before reaching the safety stop depth of 37 minutes.
The NDL at 38 metres is 9 minutes IIRC. What was my pressure group after that dive?
This is the reason we can only use tables as a back up for computers if the dive *happens* to fall somewhere on the same map. Often times it does not.
R..