Question for the TDI people out there - computer use

[Shinythings]

Hi all, after many years of kicking around the idea of tech, I've finally taken the plunge and bought a doubles set up and will be taking ADV. nitrox and DECO procedures in the fall.

I've had trouble communicating with my instructor so I figured the TDI divers of SB could probably answer my question.

Question is this:

How does TDI train divers to use a computer? Are they trained to plan dives on tables with the computer in gauge mode, or do they allow for more flexibility and use the computer for gas switching during the dive.

Obviously they will teach you to plan the dive, dive the plan - but how much flexibility is their between your plan and your dive? Are new tech divers taught only to plan a dive using tables and then execute the plan using a bottom timer?

Thanks.

 

[KevinNM]

I can't answer this question, but I'll ask another: but how hard have you tried to get an answer and how long have you waited for an answer? If you have asked more than once and you have waited over a few days it seems kind of odd. This seems like an easy question they should be able to dash off an answer to in a minute or two during a SI. To me this seems like a bit of red flag here if they can't get around to answering simple questions from students (or even prospective students).

 

[Jim Lapenta]

Initially for those classes you plan the dives using tables cut on v planner or some other software. You can also use existing tables. It really depends on the instructor. My instructor trainer was Steve Lewis and we used v planner. It's proven, easy to use, inexpensive foe the full version, and is compatible with my shearwater with vpm unlocked. One reason for using tables and using the computer as a bottom timer or back up is that you could end up with a team using a shearwater, lynx, cochran, or a simple veo in gauge mode. You need to be able to plan the dive so that everyone is on the same page. No deco dives it's often no big deal to have people on different models. With mandatory decompression however if you are indeed going to dive as a team your required stops should match. Down the road once you've developed the discipline to plan dives and stick to the plan you can start to use the computer. It does help if your team is using the same one. And even then hopefully you're using similar conservative settings. I don't mind doing my stops alone. But I prefer to have my team members on them with me for the same schedule just in case something goes wrong. Even then it's not a guarantee they could help. Look at this most recent Doria accident. I've been banned from the A&I forums here but from other sources the missing diver was last seen by his buddy on their 20 ft stop. There have been other incidents where someone discovered their deco bottle empty. Nice to have a buddy there for the same duration to share theirs.

 

[Seya]

Yeah multi deco is great also as a dive planning program. That way you are not trapped to VPM

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[Aquavelvet]

When I took my Adv Nitrox / Deco class we used Baltic Deco with gradient factors that matched my Kaon. We also used a Ratio Deco algorithm to plan our dives and compared it to the Buhlman deco plan. The more conservative plan was chosen. The training was more about planing and executing the dive according to plan. Not as much about the differences between algorithms or deco programs.


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[Nasser]

Deco dives will be taught using tables. You will probably start out learning to use the Buhlmann tables as examples and run simulated deco dives. Then you will learn to cut tables with any of the available decompression software and do actual full on staged decompression dives. In all cases computers in gauge mode and/or bottom timers will be used to follow run times.

BTW when I did my course we also used Baltic Deco with Gradient Factors. I love that app. it's got an excellent user friendly interface and is very stable.

 

[KenGordon]

My instructor took a realistic view that people will dive their computers. He made sure everyone understood the principles of planning with tables. This was very revealing of some diver's speed of learning and ability to count. We actually planned the course dives with PC software and executed them by the book.

You need to be sure your gas planning is correct when doing a complicated, multi gas dive however it will be executed. The execution may be leave the bottom at x minutes and follow the computer. To do that though you need a workable fall back which will probably involve a slate and another computer or a timer. Personally since I did the planning to be sure on gas I think I might as well take the plans on a slate.

Practice starts to deviate from the strict book in particular for second dives when you will not know the exact surface interval ahead of time.

 

[currier]

We used MultiDeco to plan our AN/DP dives and contingency schedules, and ran them on slates. Both myself and buddy used bottom timers and backups, instructor had bt and pdc. When it came time to return for Ext. Range and Trimix (same instructor and buddy) we followed the same protocol.

I can‘t speak about ‘agency standards‘ or whatnot, but I‘ve always thought TDI left their instructors a bit of wiggle room on points like these. I‘m certainly thankful for the approach we took. Training is about theory and practice, etc., but more importantly education about the mindset and discipline required for more advanced diving.

 

[WarrenZ]

We did vplanner profiles and both of us were running computers for the dive with the plan of follow the vplanner schedule unless on of our computers hadnt cleared. If the computer was still in deco we would ride out the computers deco. my petrels with 30/70 were showing deco clear before the vplanner +4 schedule was finished. The computers were just a backup to our plan.

 

[doctormike]

Interesting question. When I did my TDI training, we generated a dive plan using multi deco and put it on a slate, then followed that for our ascents. I have a bottom timer and a Petrel, and generally the Petrel cleared before I was done running the planned schedule. So we are basically diving the slate and using the computer as an extra check - in case you made an error in your planned profile, the computer will keep you from running a schedule with insufficient deco.

One of my current buddies (who is also an OW instructor) disagrees with this approach and feels that instead of the computer being a backup for the slate, the slate should be a backup for the computer. His argument is that the main point of computer diving (same as in rec diving) is that the computer gives you credit for time spent above the bottom of a square profile, so that if you just follow your slate, you will be doing more deco than you really need. While a computer can fail, it's probably not going to fail in the way that it is still apparently working but generating an incorrect schedule.

Now, most people say "what's the problem with more deco? Isn't that just being more conservative?". His argument is that once you have cleared an appropriate schedule - INCLUDING whatever conservatism you want to build in by gradient factors - then you are safer getting out of the water at that point. And, since the computer knows what you are ACTUALLY doing in the water, if the reverse happens and you incur a greater deco obligation than you planned, then following the computer's ascent schedule will be safer. Sure, you probably planned +5 minute and over-depth contingency profiles as well, but the computer will calculate on the fly ANY deviation from your plan, whether it involves more or less deco.

Still not sure what to think. They are both reasonable approaches, and I really respect my dive buddy's insights (he is a very experienced diver), but I also really respect my instructor! So I guess I'll keep thinking about this...