Must I abort if computer fails?

SCUBASailor · Jan 16, 2010

I saw in a recent thread several posts saying that a dive should be thumbed if your dive computer fails.

I'm wondering...if you have redundant gauges, would it not be of benefit to have made a square profile "worst case" dive plan from the tables before the dive? That way if the computer craps out, you don't have to abort, just stick to the conservative worst case plan. (Assuming of course, that you know that your max depth had not exceeded your worst case scenario dive plan.)

Is it really always necessary to abort, or is my idea impractical, weighed against the remote chance that your computer will fail?

TSandM · Jan 16, 2010

As long as you have incorporated all relevant information from prior dives, your idea is fine.

paddler3d · Jan 16, 2010

TSandM:
As long as you have incorporated all relevant information from prior dives, your idea is fine.

How would you do this?

You can't interchange tables and dive computers in the same day. This is the logic why a computer will lock you out of computer mode for 24-48 hours if you dive it using the 'guage' mode.

Assuming you made previous dives on the computer and it crapped out, how would you know what your nitrogen load is in order to calculate the dive?

Gombessa · Jan 16, 2010

SCUBASailor:
I saw in a recent thread several posts saying that a dive should be thumbed if your dive computer fails.

I'm wondering...if you have redundant gauges, would it not be of benefit to have made a square profile "worst case" dive plan from the tables before the dive? That way if the computer craps out, you don't have to abort, just stick to the conservative worst case plan. (Assuming of course, that you know that your max depth had not exceeded your worst case scenario dive plan.)

Is it really always necessary to abort, or is my idea impractical, weighed against the remote chance that your computer will fail?

I don't see a problem with this either, assuming you still had some way to determine your depth and bottom time. Unfortunately, most computer "failures" I'd expect would crap out one or both of these functions.

MauiScubaSteve · Jan 16, 2010

You do not even have to have a prior backup plan, per se. If you set the bezel of your dive watch at the beginning of the dive and carry the dive tables, that are sized to fit in a BC pocket, in your BC pocket, when your dive computer dies you look at your max depth depth gauge, look at the tables, look at your watch. If you have time left on a square profile dive, continue diving. If you do not have time left, abort.

Arizona_SVO · Jan 16, 2010

Assuming you had all the relevant infomration as TS&M states, you will probably find that when transitioning that information to the dive tables that you would find yourself outside of their accepted limits since computers only 'charge' you for the time you spend at a certain depth - the tables are worked using the square profile (but you of course know this). If you go into your log and attempt to re-work your dives, you will probably find that you had (according to the tables) gone into a deco obligation and thus, should have stayed out of the water for your subsequent dives. It's a good thought, but usually not easy to do in all practicality.

Better to dive 2 computers - if one dies, obviously use the other.

Mr Carcharodon · Jan 16, 2010

SCUBASailor:
Is it really always necessary to abort, or is my idea impractical, weighed against the remote chance that your computer will fail?

A lot of this depends on your dive profile (depth v. time). If your average depth is less than 35 fsw there is not much to worry about. In some locations you have a hard bottom at that is in that range. I would certainly continue the dive in that sort of location. Also if you add in stops at every 10 fsw from the 30 feet to the surface you will have done a lot to mitigate the risk on somewhat deeper dives.

The other end of the spectrum is doing the deeper end of recreational diving say 110 fsw or deeper. I would find the risk too great to accept for those dives. Getting information from your buddy is an option as well but you need to stay within 5 fsw of each other and have a tight team for that to work. Not something to try with someone you are diving with the first time.

SteveAD · Jan 16, 2010

Here's one backup theory that I have heard of that seems quite logical.

Works best with Pelagic computers or others that use the DSAT algorithm, and PADI/DSAT tables.

Upon surfacing from each dive, immediately run the DC through a diveplan mode and note NDL for 100 feet. Use this NDL to find an equivalent pressure group from the tables. It is now theoretically possible to pick up tables from that point.

Mr Carcharodon · Jan 16, 2010

paddler3d:
You can't interchange tables and dive computers in the same day. This is the logic why a computer will lock you out of computer mode for 24-48 hours if you dive it using the 'guage' mode.

Those sort of factoids are usually presented as immutable wisdom. It will come as a surprise to some some that not everyone buys into this.

Some would keep the surface intervals longer than an hour and add in shallow stops.

Notso_Ken · Jan 16, 2010

SCUBASailor:
I saw in a recent thread several posts saying that a dive should be thumbed if your dive computer fails.

I'm wondering...if you have redundant gauges, would it not be of benefit to have made a square profile "worst case" dive plan from the tables before the dive? That way if the computer craps out, you don't have to abort, just stick to the conservative worst case plan. (Assuming of course, that you know that your max depth had not exceeded your worst case scenario dive plan.)

Is it really always necessary to abort, or is my idea impractical, weighed against the remote chance that your computer will fail?

TSandM:
As long as you have incorporated all relevant information from prior dives, your idea is fine.

Absolutely correct. I was taught to "Plan your dive, then dive your plan." EACH dive, not just the first. If the computter dies on first dive it's easy to switch over. Past the first dive, as another poster pointed out, you may quickly run out of NDL time on the tables, but if you went to the tables preior to that dive, you should know where you are in relation to the limits! If at or past, yep, it's time to thumb the dive. But, then yopu just revert to being limited by the tables until you can get the computter fixed, or buy a better one!

Ken

Must I abort if computer fails?

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