Banned from diving for a locked out backup computer?

[BarryNL]

Why would I want to dive if my primary computer is locked out?

In the scenario that it freaked out or in case of incorrect settings on my part prior to the dive. I see stories about that happening a few times. Don't want to loose dive time for a computer snafu be it my fault or the computers.

Well, if it's truly a computer rather than diver screw up I can understand it. Still, I think for most computers you can manually override and reset the residual nitrogen memory. Of course, you DEFINITELY should NOT rely on it to dive with afterwards because it will assume you now have zero nitrogen in your body.

(Well, not zero - 0.78 ATA obviously)

 

[BarryNL]

I personally am a big geek and my main dive buddy is a big geek too.

While we both dive computers, we also carry a set of tables..in our BCD pockets! Hey we like to make each other plan dives on the safety stops.

I'm never quite sure how much use a dive table is if your computer locks out. I notice a couple of dives ago I did 38.9m with 37mins dive time. Ok, I wasn't deep for long and it was within the computer's NDL but I don't think you could convert that one to the RDP - the wheel perhaps.

 

[rockjock3]

Not to pick on you specifically rockjock3, but you and others (Carldarl among others) has posted statements like yours above and such as "But, I also record my basic info after each dive so if I ever have to revert to tables I have the what's needed. ".

How much data on your profile do you record?

What pressure group am I in if my dive sequence on air is 128' 47 min; 65 min SI; 86' 57min; 52 min SI; 55' 52 min. These are all no deco dives, btw.

Or even just the 2 dive sequence of 83' 65 minutes, 71min SI, 53' 64 minutes.

I do have a procedure I use, but I'm curious about what you, or others that advocate keeping track on tables also, would do.

First, I don't take it as picking on me. This is healthy debate and through such things we all can learn and become more skilled/informed divers.

As I said, I am new to diving. As for those dives, on 21%, then they are not NDL dives (128' max 10 min (130' for 10 min)). You are off the charts on all of them. Perhaps on Nitrox but then 128', on standard rec limits of nitrox, can be unsafe. I won't quote on this because I am going to, but haven't yet, taken my nitrox specialy yet.

I record all my dive information (when planning the dive) before the dive. I obviously make any changes once I surface (changed time for some reason, reduced depth maybe)

As for computers. What did people use before computers? Basic guages and tables. I understand that tables are more conservative than computers because they round when computers don't I also understand if you are doing multilevel dives a computer will give you more time than tables. I also understand that the wheel will give you more time on your multilevel dives than standard tables, as it was designed to plan these.

I say your tables should be your primary because they never fail (crash, lock-up, flood, etc.) The way I keep track is to plan my dive, say 60' for 50 minutes, before dive. Once me and my buddy are ready to dive I set my computer for that profile. If my computer dies I then my and my buddy start up. I have the dive time and depth from his computer then will make any changes (reduced time UW) to my profile, make the appropriate calcs for my SI and next dive profile, then I will use my seperate DG and watch to control my next dive. This is as good as a backup computer because unless you are wearing both computers at all times then the backup will only be able to be used as a simple DG and timer, since it has no data from your previous dives in it.

 

[Web Monkey]

If you lock out your computer by setting it incorrectly, I'd go diving and use tables. If it's locked out because it's broken, I'd go diving and use tables.

If it's locked out because you exceeded any of the parameters it monitors, I'd decide if I had any DCS symptoms, get help if I did, or go find a book and take a nap somewhere quiet if I didn't.

Unless there's something actually wrong with the computer, it locks you out when it thinks you either are or will be injured. I'd take it's advice.

It's not trying to annoy you, it's trying to save your life.

Terry

I am looking into doing some dive trips that include multi-day dives. I really don't like the idea of getting in the middle of this and having my computer die. At that point it would be hard to back track and figure out where I am in terms of repetitive diving. A few of the resort dives and live-a-boards I am looking into have this 24 sit out for locked out computer rule. And I have heard a few of those "my Suunto locked out for no good reason" stories.

So I am wondering if for some reason my Suunto gets locked out on one of these trips, will the DMs allow me to continue on the Aeris? Or is that even a concern?

 

[Jarrett]

Wow, who knew my dumb question would bring together such good info on the topic Thanks to all those offering info, especially folks like Charlie99 and NetDoc, great stuff.

I went and got some feedback from a couple LDS owners today. Here are some of the points that really stuck with me, some of which have already been covered. I have no idea if these are wrong or right, but they stuck in my head and I thought I'd throw them out into this interesting discussion:

1. It's hard (maybe impossible?) to do multi-day/repretitive diving with tables only. The tables will show you in deco way before the computer that actually took the ride with you will.

2. Based on the first point, either dive computers or dive tables. On multi-day/repetitive dives, if you begin on a computer, you can't switch to tables.

3. Tables are based on theories, computers are based on tables. There is no proof yet that one theory is better than another. The Haldanian theory has been in practice longer than the RGBM-based theories.

4. Due to low occurance of DCS, there is not enough data to prove that RGBM-ish computers are safer than Haldanian-based computers.

5. Stats for DCS are about 1 in 28,000 worldwide. With most causes being connected to ascending too quickly and dehydration. But not one algorithm over another.

6. Computers will and do fail/glitch at times. See point #2.

What do you think of this info?

 

[Notso_Ken]

Does it apply to backup computers? Meaning, if my primary is fine and my backup is locked out, do I still get to dive?

Thanks in advance.

Why not plan your dive on tables, then as long as the ONE computer is operating, use the longer bottom time it allows. If the computer dies, then you revert to the tables.

They can't give you a 24 hour sit out for diving tables. Can they?


Ken

 

[Charlie99]

As for those dives, on 21%, then they are not NDL dives.

I record all my dive information (when planning the dive) before the dive. I obviously make any changes once I surface (changed time for some reason, reduced depth maybe)

As for computers. What did people use before computers? Basic guages and tables.

My point was that those dive were NDL dives and the various statements of "just keep track on the tables" really aren't a reasonable answer once your SAC is low enough that reasonable, safe, multilevel dives routinely exceed table limits. While one could theoretically track the various levels and times of a multilevel dive, in practice I don't and I doubt that any other divers routine do this, UNLESS they are not using a computer and instead using the wheel. (I do have a rough plan, such as 6 at 130', 10 at 80', 20 at 50 when getting in, but often modify that during the dive.)

My simple solution to tracking dives and moving over to tables is to decide whether or not I have 1) violated the DSAT model, i.e. have omitted deco, and 2) whether my previous dives would invoke the special 3+ dives W,X,Y, or Z rules that come into play when the slower than 60 minute compartment is the limiting one. If 1 is true, then I should be on O2 and no longer diving. If number 2 is true, then I need to observe the extended 1 or 3 hour SIs.

Otherwise, I simply assume that I got out of the water in PADI RDP pressure group Z and run my plan from that point.

I'd also dig my spare computer out of my gearbag and start wearing it on my dives. My dives are limited to table planning for the rest of the day. Starting the next day, my backup computer is the primary guide.

So far, I have never had to use this plan since my computer has never failed. However, that plan is ready to be executed without having to cook up a solution on the spot.

 

[Charlie99]

1. It's hard (maybe impossible?) to do multi-day/repretitive diving with tables only. The tables will show you in deco way before the computer that actually took the ride with you will.

2. Based on the first point, either dive computers or dive tables. On multi-day/repetitive dives, if you begin on a computer, you can't switch to tables.

3. Tables are based on theories, computers are based on tables. There is no proof yet that one theory is better than another. The Haldanian theory has been in practice longer than the RGBM-based theories.

4. Due to low occurance of DCS, there is not enough data to prove that RGBM-ish computers are safer than Haldanian-based computers.

5. Stats for DCS are about 1 in 28,000 worldwide. With most causes being connected to ascending too quickly and dehydration. But not one algorithm over another.

6. Computers will and do fail/glitch at times. See point #2.

What do you think of this info?

In general I agree, but ........

1. You can use table of multi-day repetitive diving. You just won't be staying down as long.

2. My plan for moving over to tables, and then to a backup computer that had previously been left on the boat, is in my post just above this.

3. There is a deco model. Computers are based upon that model. Computers aren't really based upon tables at all. Tables are much cruder tracking methods that are consistent with the model. In particular, tables track 1 and only 1 compartment (60 minute halftime in PADI RDP/wheel, 120 minute halftime in USN tables and the modified USN tables of NAUI, YMCA, SSI, etc.). Like Newtonian physics, Haldanean models are a pretty good start. VPM, RGBM and various other dual phase models, as well as empirical experience have taught us ways to modify the haldanean model to better reflect real life. Deep stops is a good example. Gradient factor hacks on the Haldanian/Buhlmann model is another good improvement.
Although Suunto markets their computers as "Suunto RGBM" computers, they are really Haldanian computers with some tweaks that reflect our improved knowledge of decompression.

4. The same "lack of hard data" argument is also sometimes used to debate whether diving a profile on nitrox is safer than diving that same profile on air. I both believe nitrox is safer, and diving an "rgbm" or a "bubble friendly" PROFILE is safer than either a very slow linear ascent, or a 60fpm pop up to a safety stop. Profile is capitalized because it is the PROFILE that you actually dive that determines safety, not what device you are using to track or plan the dive. On a normal recreational dive that does not go into deco, even a true RGBM computer would not give any guidance as to what is the best ascent profile. YOU set the profile.

 

[scubabrandon]

What is a dive table?

Kidding...

I always plan my dives with the tables, but I still use my Smartcom computer to back me up.

 

[mason]

This is a classic case of a "trust me" dive. Very bad idea. You WERE an idiot, not for asking questions, but for NOT asking the question and getting it resolved before you got into the water. That may sound harsh, but you really are responsible for your own planning. Blindly following along, relying upon someone else's computer is a Very Bad Idea.

Get a computer. Get a wheel and do a multilevel plan. Dive a more limited profile that you have planned on a table. Sit out the dive. Any of those are acceptable options. Doing the dive because someone else says it's OK isn't an acceptable option.

Charlie99,

In general, I would agree with you; however, the boat we were on wasn't a "dive operation," and I was with two divemasters, one master diver, and a guy who is contracted to the Department of Homeland Security to do national callout rescue diving, and shortly after our trip, did so following the hurricane. The master diver was my former assistant chief and headed our dive rescue/recovery team for 10 years. I would trust some of these guys with my life.

The fact that we were on my first ocean spearfishing trip, I was following their lead. I knew if I felt out of place or uncomfortable, or if we stayed at our max depth for anything close to what I had planned, I would have signaled them and began an appropriate ascension.

Otherwise, I would never had done anything other than my plan.