Incident due to battery change on dive computer

[boulderjohn]

Good post, Frank.

The newer OW classes that are based on the computers try to teach as much of this as they can. They teach what computers do in a generic sense. They teach them that when they get their specific computers, they need to know how to use it to plan the dive. It tells them they need to know how it is telling them when they are approaching NDLs, and it tells them how to dive conservatively within those limits. It tells them to learn how it will guide them in case they go past NDLs and have a decompression obligation. That way when they pick up that computer manual, they are not just looking at a mass of information, they are looking for specific functions to look for in that manual, and they have been taught how to apply them to their diving when they find them.

The courses have a dive simulator that takes through dives, showing how the computer tracks nitrogen ongassing and offgassing as they descend and ascend. It takes them through multiple scenarios. They can practice to their heart's content with that simulator before they actually purchase a compute, and thereby know what to look for in the models they evaluate.

Contrary to popular belief, if the instructor takes the required time to go through the computer portion of the course as it is designed, it takes at least as much time as it takes to teach the tables, and probably more.

 

[RJP]

They have been told that computers "let them dive longer than tables", so the "computer will keep you safe".

As I tell students "Believing that 'my computer will keep me safe' while diving is like believing 'my speedometer will keep me safe' while driving."

Like a speedometer in a car, a dive computer is a very useful tool that provides valuable information. But ultimately a computer is only "as safe" as the person using it. If you don't consult it at all during your dive, or ignore what it's telling you, or fail to modify what you do with the information it provides based on the current environment and conditions... it's not really going to do you much good.

A diver should no more look at their computer and say "Oh crap... how did I rack up 33min of deco at 90ft!?" than a driver should look down at their speedometer and say "Oh crap... how am I doing 95mph around this curve in the rain?!"

 

[KenGordon]

Contrary to popular belief, if the instructor takes the required time to go through the computer portion of the course as it is designed, it takes at least as much time as it takes to teach the tables, and probably more.

How long is that?

 

[SubAquatix]

Contrary to popular belief, if the instructor takes the required time to go through the computer portion of the course as it is designed, it takes at least as much time as it takes to teach the tables, and probably more.

John,

While I agree in context, the question is, what is the required time?

In the dark ages, when a normal OW course was divided into 20 hours class and 20 hours pool, we did 2 hours of one night just running tables for a single dive followed by 6-8 dives of homework, before doing multi-dives the next class. AN EASY 4-7 hours, with homework, just on tables, as a beginning to dive planning.

There is a shop on the Carolina coast that doesn't have 4 hours of TOTAL classroom, yet calls themselves "one of the top three ____ Instruction Centers worldwide". Clearly, they can't be training planning, computers or even what the beeps mean, effectively, but there it is! Sadly, they are becoming the norm!!!!

 

[boulderjohn]

Back in the old days when dive instruction actually had times listed, the instruction was delivered primarily by lecture, which is known by all educational theorists as the worst way to deliver instruction. Today students study on their own first and then come to the instructor to help with any problems they had with their private learning and to make sure they understood it all. That is true whether you learn the tables or a computer. When students come to me for instruction on either tables or the computer, they are supposed to have studied it on their own before I see them. If they have not even done that, I send them home.

So how long does it take for my part of the process?

Whether it is tables or computers, the amount of time it takes for me to help them depends upon how well they learned it on their own. I have had people who came in with everything perfectly clear in their minds, and I have had people come in honestly stumped. I remember one class of 8 students who breezed through the table knowledge reviews so quickly, with no questions asked, that I told them they were scaring me. I normally would not give the final exam until we had done enough extra problems to convince me they were ready for it, and they were saying they were ready with no extra help from me at all. Everyone insisted they were ready, and not a single one of them missed a single question. I have also had classes in which I spent a very long time giving people extra help until they got it.

The same is true when I teach the computer version of the class. Some come in with everything nailed. Some need a lot of work.

In my experience with students who did the online instruction, they all come in with the course material down cold, and they need little help from me.

 

[Wookie]

In my experience with students who did the online instruction, they all come in with the course material down cold, and they need little help from me.

I don't rail against online instruction, I have a Bachelor's degree I obtained that way. I got a 3.98. I test well. I didn't learn as much information in my online bachelors degree, which I completed in 9 months forced march as I did in 4 years of lectures, but both methods resulted in a sheepskin in my name. I didn't get nearly as good a grades in a 4 year program as I did in the 9 month program, in fact, I barely got out, but I did graduate.

i can still recite the neutron life cycle, tell you all about heat transfer across the reactor core, etc., because I was given the time to learn the material. I can't tell you much about environmental science, but I have a degree in it.

 

[Redshift]

This incident could very well turned into an accident.
Accidents usually happen after a series of incidents which are not caught on time or dealt with. In your case there were several times when I question how things were done.

After changing the battery on my dive computer I had to reset the date/time and units of measure but forgot to change the Personal Safety Factor to "Medium"

This was the first incident, but I don't even think it was that much of a problem.

The dive computer decided that I went into deco and demanded a stop at 39 feet for 2 minutes

The computer didn't just decide. It had always been calculating (and correctly, based on its settings and your profile) your NDL throughout the dive and you should have noticed it way before you were in deco, even when doing a dive that you had already done. There's no point in having a computer if you don't look at it.

I realized at that point what happened and only did three minutes at 15 feet.

Did you at this point ask your buddy what was his computer saying or those 3 min at 15 feet came out of thin air?

Did a second dive 1-3/4 hours later to find that my dive computer refused to compute/display deco time because I had violated my deco on the earlier dive and it was only providing depth, bottom time and temperature. Since I was buddied with a Dive Master and understood what happened and since the buddy and I were glued together on the first dive I thought I would just rely on his computer.

Why did you decide to only rely on your buddy's computer and not plan the dive with tables and take your computer which was now working as a bottom timer?

20 minutes into the second dive I looked at his computer to discover that it was displaying the word "UP" instead of time remaining till deco.

Had you told him before the dive that you didn't have a functioning computer and that you'd rely on his? Was his ok after the first dive or also locked?
Otherwise I don't understand that "UP" message. Was it not displaying any diving info at all?
Was your buddy also not looking at his computer?
A computer is a tool, not an accessory. It's worthless if divers don't look at them, follow their advice and understand what is happening.

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet.

Without any info, why a 5 min stop at 15 feet? After the first dive where you had already pushed it, not planning the second dive to have an idea of the limits and not having any info about the second dive, I think I'd have stayed there for as long as I had gas...

I was not happy with my decision to dive without a properly working computer and also very unhappy to find that a Dive Master certified diver would do the same.

Again, you could have planned your dive with tables and taken your computer. (Oh, did you learn tables?)
Did the DM go in already with a locked computer? If so, this should have been caught in the briefing!
If not, he did the same mistake of not looking at the computer during the dive.

 

[doctormike]

I called the dive and we ascended from 80 feet taking 19 minutes to do so with a five minute stop at 15 feet.

Great thread. I'm pretty sure that the OP now knows what the SB crowd thinks about this incident, his decision making, and his lack of situational awareness. Thanks for posting, I hope you learned something (and I hope that this has been useful for other, less experienced divers).

I didn't see this mentioned in the thread (sorry if I missed it), but I just want to comment on one thing that is often a point of confusion for new divers. The importance of slow ascents are stressed early in training, and some people think that means the slower the better. This is not always the case, especially for the deeper portions of the dive.

The OP ascended from 80 to 15 feet in 19 minutes, which means a bit over 3 feet per minute. If the OP meant that the 19 minutes included the five minute stop, it would be just over 4 fpm. Either way, this is much slower than the commonly accepted 30 FPM (for the shallower portion of the dive). By doing this - I'm guessing in an attempt to make the ascent "safer" - the divers probably made their DCS risk greater by increasing their nitrogen loading, ongassing during much of the ascent.

So while ascents that are too rapid can accelerate bubble formation and add to decompression stress (in addition to making barotrauma more likely), ascents that are too slow can also be dangerous. Different agencies have different recommendations, but 30 fpm above 60 feet and 60 fpm below that point are good rules of thumb.

Once you realize that you are inadvertently in deco, the most important thing is to get shallow and to stop ongassing. That's why the DM's computer just showed "UP" - the computer was not designed for technical diving, and it was trying to get these guys to start offgassing as quickly as possible.

 

[Rich Keller]

Have you read the thread?

The computer did not fail at all. The diver did not use it properly.

When students are taught in their courses to use computers, they are taught how to plan with them. They are taught how to use them to stay within decompression limits. They are taught how to use them to guide their ascents. They are taught how to follow the computer guidance in case they accidentally go into decompression. The diver did none of the above--not one.

They are also taught what to do if the computer fails, but in this case the computer did not fail.

Is it your contention that if he had been taught how to use the tables, he would have known how to use the computer properly?

Yes I read the thread, it was operator error. Does it matter if it was a hardware failure, operator error or a software problem? The end result is the same, the computer could not get him back to the surface safely and he had no plan B. If he had the tables with him and knew how to use them he would have had a plan B. If he was never taught how to use them then that option did not exist for him. Even if the OP were diving with two computers in this case it probably would not have helped. If he made every dive with identical computers dialed into the same setting what are the odds that he would have changed both batteries at the same time? I think those odds would have been about 100%.

 

[DavidFL]

Reading Frank's post about online vs. 'traditional schoolhouse' instruction, and the rest of the thought-provoking context of this thread got me thinking about the importance of meta-cognition....each of our very own knowledge about our knowledge. My best open-source reference on this subject is:
How People Learn: Brain, Mind, Experience, and School: Expanded Edition

What is a very important driver, illustrated in Frank's comparison of Navy nuclear power training vs online general education degrees, comes back to the importance of our own self-paced choices when we believe we either know what we want and need to know, or we don't believe we know it and keep exploring until we do.

The challenge in this discussion is partly about the training agencies and the material and the delivery of the material and how much time is spent on the material....but it is at least equally about each individual's internal, dynamic metacognition. To oversimplify it, when someone doesn't know what he or she doesn't know....