Air integrated computer and tec diving

[The Chairman]

It's about responsibility and control during the dive.

Is it? Either way you're not 'thinking' your way through anything. You're either following a printed out plan based on your fantasy of what the dive should consist of, with maybe a couple of variants for those 'Oh crap!' moments, or you're following a glowing screen with the most up to the moment measurements of how much deco obligation you have. The only decision you've made is which plan to follow. Now, if you somehow feel superior for following a piece of paper based on wishful thinking over a PDC based on reality, then welcome to the world of self deception. Why are more and more rebreathers using PDCs rather than tables? People forget. People make simple mistakes and then make even more exacerbating the issue. Most just shrug and say "Oh well!" When a PDC fails, it's so stinking obvious that it makes your head spin.

There are multiple issues being discussed here: PDCs, AI and wireless AI. If you don't feel comfortable with them, don't dive them. But please, don't pretend that your phobias make your dives any safer. A phobia, by any name, says more about the person holding it than what they're skeered of.

 

[packrat12]

Your controlling factor will be your gas supply. Regardless of your deco obligation if you have not pre-planned accordingly (with contingent plans built in) and you run out of gas, then you have a choice.... risk getting bent or drowning. Pre-Planning will always matter in whatever phase of the dive you're at.

There can be many different ways of thinking about this. Either way it is the same. A normal ascent, Deco will be in control. My stops and times are based on it, not gas supply. If I surface with excess gas, Deco was obviously in control. If I needed more gas and since I cannot get it, I still follow Deco until out of gas. Then, gas becomes in control. I may augment the ascent to get out faster such as following the GF99 value but in the end I will surface early. Semantics can be fun. Either way, since we assume that we are not talking about emergencies, Deco is in control.

I guess you have a different concept of 'precision' in diving a plan and following a runtime...
Assuming we're talking about OC tech in OW... and not, bailouts or contingencies either,.. why would your pre-dive plans become obsolete. Your pre-dive planning should predict, very closely... or exactly, what you computer will subsequently give you.
It does for me.
If your pre-dive deco plan became obsolete (because you didn't follow it).... then so does your gas planning. That can't be justified by any means...
This is why tech divers are best educated by following run-times on tables. It develops precision and an ability to 'plan the dive, dive the plan'. Computers should only be used once this core competency is developed... otherwise they're likely to prevent that learning ever occurring ...
Just a thought... Packrat12, did you learn tech on tables/run-times or by diving computers?

I never stated that your dive plan is obsolete. I only stated that the computer has the more accurate representation of your actual dive. I doubt that if I zoom in on your deco stops that they would be a clean straight line. I doubt that your bottom phase would be a clean straight line. I doubt that you precisely descend and ascend at the planned rates. I doubt that your depths follow precisely with your plan. Are your stop times and gas switches precise to the plan? If not, you cannot say that it accurately represents your dive. I am not sure that anybody could. It is an approximation of your dive.
Your computer has diligently been updating your dive profile probably more than once per second. Your computer calculations represent an accurate profile with all realities and variations taken into consideration. Your planned profile has not done this.

In the end, if the computer and table match – great. If not, I will definitely trust my computer unless given other compelling reasons not to. I can say that none of my dives ever matched my computer. Variations are just too normal.

As for learning tables, yes I learned both tables and computers. During training, we followed tables BUT we never surfaced without verifying with our computers that no deco obligations existed. Tables make a great and necessary out when the computer goes south. Tables are a never exceed item that will allow me to surface safely using just a BT and depth gauge. They are not, however a more accurate indicator of my actual dive profile. I think I can quote a bad movie, Quigley Down Under, here: “I said I never had much use for one. Never said I didn't know how to use it.” When my computer is working, it is the best indication of my actual profile.

As for planning, which I never talked about, I am as diligent as anybody about it. I cut several tables and contingencies for any dive. I am very retentive about my gas supply, etc. But once the dive starts, realities set in and the computer still will have the most accurate representation of my dive!

 

[doctormike]

When I had just finished tech training, I followed the advice to clear the slate, and not worry so much about clearing the computer. But then I started diving more and more with one buddy, an instructor and experienced tech diver. He convinced me that by following your PDC, you get a much more accurate assessment of your deco obligation.

Yes, tech diving is all about making a plan and sticking to it, but sometimes I don't do that and I don't think that makes me a bad diver. There are two ways that your nitrogen loading can deviate from the plan - over or under. Over shouldn't happen at all, and then only if there is a major problem that you weren't successful in avoiding (entanglement, difficulty exiting an overhead environment in a timely fashion, etc..).

But under happens all the time - you cut a dive short because of vis or cold, or you plan for one bottom depth but the wreck turns out to have a lot of relief and you spend more time above that bottom than you thought. There is no great tech obligation to stick to the exact plan that you cut on the slate no matter what the dive turns out to be like. So that's when I started flying the computer and using the slate as backup.

You might say that you should follow your dive plan even if your actual dive involves less N2 loading than you had anticipated, after all, what's the problem with doing more deco? But at some point, you may be just trading one risk for another. Assuming that you have done enough deco to reduce your DCS risk to a reasonable level (based on your actual dive profile), isn't it safer to be back on the boat than hanging on the line in the ocean, clearing your slate just because it represents your original plan? There are plenty of stories of people having shallow water issues (medical or otherwise).

 

[boulderjohn]

So many things to which to respond.

First of all, let's be clear that the PADI tech curriculum does not refuse to use computers the way a GUE or UTD program would. Quite the opposite. It is further not as rigid as things are being made out to be. Students are encouraged to make intelligent decisions about the options of their diving. I recently had to ask PADI about a student's prerequisites for crossing over to PADI trimix after being previously certified in lower level courses by UTD. PADI has a table for prerequisites for students crossing over, but UTD is not on it, so they had to look at its curriculum to see at what level the student could be accepted. When they responded to me, one of their criticisms of the UTD curriculum was its rigidity, meaning the student did not have the experience making decisions that a PADI student is expected to have. If a PADI instructor is being rigid about equipment choices and practices beyond the basic core level associated with all tech diving, then that is an instructor decision and not part of the curriculum.

When I got my PADI Trimix instructor certification, I had to intern for a trimix class, and during that class we planned and executed dives both by run times with a computer backup or by computer with a written backup. (We always had at least 3 written plans with us.) The instructor trainer's personal preference was for all members of the team to have two computers each of the same model for backup, but we did not have that possibility. The key idea was for the student to have knowledge and ability with different ways of divig it so the student could make an intelligent choice after the class was over.

My own early tech training never used computers, and for years I never had a computer on my wrist for tech dives. As I indicated earlier, my first real problem with this came when two friends got bent on a dive like that, and because one of them was using a computer in gauge mode, we were able to see from the log how very far their actual dive was from what they thought it had been. I wondered how many times my own dives had deviated from what I thought they were because I had made mental errors that were invisible after the dive without a computer log to record them. For the last few years I have carried a computer and a bottom timer with written plans, using one or the other as the primary ascent guide depending upon the circumstances. I teach my students both ways. I just placed an order for a second computer.

 

[DevonDiver]

I never stated that your dive plan is obsolete. I only stated that the computer has the more accurate representation of your actual dive. I doubt that if I zoom in on your deco stops that they would be a clean straight line. I doubt that your bottom phase would be a clean straight line. I doubt that you precisely descend and ascend at the planned rates. I doubt that your depths follow precisely with your plan. Are your stop times and gas switches precise to the plan? If not, you cannot say that it accurately represents your dive. I am not sure that anybody could. It is an approximation of your dive.!

My standard for stops is +/- 25cm.

Bottom depth is +/- 2m. Very square profile as it's deep wrecks.

Ascent rate is a big factor for me..I think gas tissue differential plays a big factor. Accuracy is quite easy.

For typical extended range scope dive... say 45 min at 55m...On, say VPM-B +3 with 50%/100%. I'd be pissed if my computer runtime varied by more than 1 minute from my planned runtime.

My job is to role-model this stuff... I'll admit that my advantage is that I've done the same training dives, same sites, same conditions, same profiles, hundreds of times... So there's a high element of repetition and practice behind that.

Let me be clearer on an earlier point... I've had access to tech computers for years... and used them often. There is no phobia, whatsoever. I simply saw no dire need for one.

When I started in tech diving, we planned our dives on MS-DOS software. I even ran the same software on an emulator when I upgraded my machine to XP.

Things have progressed immensely since then... All for the good. I'm no technophobe.

Regards spending $800....well, I'm a full-time, independent, tech instructor..... not a desk bound webmaster.... So incomes and finances are obviously tighter for me. I'd also rather gift such money to help struggling friends here in the Philippines, a developing country, than buy superfluous gadgets and chase a materialistic existence. I didnt own a TV until last year... and that's just to keep my girlfriend happy.

Knowing what you NEED, versus what you WANT, can enable both a happy, simple life... and safe, satisfying tech dives.

I wouldn't pour scorn on divers who love kit and gadgets... I wouldn't expect scorn in return for not worshipping such things. I acknowledge and accept that people have different interests, preferences and ideals of lifestyle.

But I do spend the vast majority of my disposal income on tech diving.... and it IS expensive. For me, money well spent is on developing skills and gaining practical experience. I'm lucky that my job is also my hobby... and my passion..... I'd hate to be stuck behind a desk all week dreaming of diving, or diving vicariously via the internet. I can appreciate how that existence can lead to an open wallet approach to kit. Boredom, frustration and denial is often alleviated through retail therapy...

 

[Storker]

Bottom depth is +/- 2m. Very square profile

Which IMO indicates - quite clearly - that your diving is mainly on sites you've dived several times before. Far from everyone dives the same site over and over again. IJS.

 

[boulderjohn]

Bottom depth is +/- 2m. Very square profile as it's deep wrecks.

Interesting. In a thread on a similar topic a number of years ago, John Chatterton cited deep wrecks as the reason he rarely dives a square profile. In fact, he cited deep wrecks as the reason he can't really predict his dive profile with great accuracy ahead of time. I have dived with him (on the same boat--not as a buddy) when he is doing instruction, and he is indeed not doing square profiles on those dives.

I find the same thing. I will be teaching a Trimix class in South Florida in early March, and I just worked with the dive operator to schedule the dives. They will all be to deep wrecks. I have been to most of them, but I certainly don't have them memorized. I have not been to two of them at all. I know the depth to sand for each of them (with variations due to tides), but I don't expect to go to the sand. These are all pretty big wrecks, with a big difference between the bottom of the structure and the top. I intend to go to our deepest planned depth first and then work my way up before starting the final ascent. I do not expect to have anything like a square profile on any of those dives.

My job is to role-model this stuff... I'll admit that my advantage is that I've done the same training dives, same sites, same conditions, same profiles, hundreds of times... So there's a high element of repetition and practice behind that.

You don't see an obligation to role model anything except well-known, square profile dives?

 

[Nasser]

There can be many different ways of thinking about this. Either way it is the same. A normal ascent, Deco will be in control. My stops and times are based on it, not gas supply.

You stated earlier that your pre-dive planning no longer matters once you start your accent or is a controlling factor...

Once you start your ascent, your pre-dive planning no longer matters or is the controlling factor. Your deco obligations are the controlling factor,

If you are planning a dive and one of the main reasons for planing is to insure adequate gas supply for the required deco, then of course it matters... if you have undershot your calculations or not planned for any possible emergencies, then it makes the deco obligation almost irrelevant - you need to get out when you run out of gas. Granted that during the planning phase you are balancing various elements. - the most obvious being required deco and amount of gas needed and so deco can seem to be the controlling factor, but if this requirement exceeds how much gas is practical to carry (particularly in open circuit) then you will not be able to complete the dive safely, you need to re-adjust your plan... and gas was the determining factor for this adjustment.

If I needed more gas and since I cannot get it, I still follow Deco until out of gas. Then, gas becomes in control. I may augment the ascent to get out faster such as following the GF99 value but in the end I will surface early. Semantics can be fun. Either way, since we assume that we are not talking about emergencies, Deco is in control.

That's a mighty big IF... and reinforces the notion that your pre-dive plan is all the more relevant... it can make the difference between a smooth uneventful deco dive and and an emergency - and that's not taking into account a real emergency! It's not the same thing looked at in a different way or just mere semantics - it's poor planning - and that speaks to the heart of why regardless of the tools you use, pre planning will always be a relevant factor throughout the entire course of the dive.

 

[DevonDiver]

You don't see an obligation to role model anything except well-known, square profile dives?

I thought we're talking about tec40/45, or at least OW tech...not technical wreck (same as cave... profile dictated by topography).

But yes, at entry level tech, I focus on 'plan the dive, dive the plan'... as I believe that, once ingrained, a precision approach forms the foundations of all that follows.

Its also one of the biggest mindset shifts that needs to be achieved with students emerging from the recreational training system..

I'm kinda lucky here in Subic Bay, as we've got a plethora of great wrecks spanning DSD to Advanced Trimix ranges. But I'm not a weekend diver, I dive more frequently... and I've been here 8 years.... So the wrecks are intimately familiar to me, inside and out.

Regards square profiles... The variation is very relative to the overall depth. A 4m variation makes a 12m dive sawtoothed. It's pissing in the wind on a 90m dive.

But let's also not forget that multideco etc do allow multiple levels. Plan the dive, dive the plan. It needn't be 'square', but what you plan must predict what you do underwater...

That said, I'd plan series (non-penetration) dives on the same wreck in levels. Why not?

 

[packrat12]

Nasser,

I have lost two write-ups so this one will be short. Never said pre-planning was unimportant. It is critical in determining requirements and contingencies. Once the dive begins, you cannot change your equipment configuration with regards to supplies and any unforeseen or unplanned contingencies that may avail themselves. You have what you have. You might lose some supplies but you are unlikely to gain supplies. You still have options so a pre-plan that determined your supplies and dive profile is important but the dive profile in is control. You can go deeper, shallower, longer, shorter, abort etc. Once you start your ascent, you really cannot change much. Follow a GF99 value to reduce deco stops, use different gas switches etc but for the most part, your min deco obligation is what it is, your gas supply is what it is, your times to surface are what they are, your swim or other requirements are also what they are. So as you start your ascent your deco obligations are in control. It is possible for something else to take control, e.g. gas loss, gas exhaustion, thermal considerations, medical issue etc, but in a non-emergency ascent, deco obligations are in control. So it really does not matter what the pre-plan or even the dive plan states, as your deco obligations are what they are and you will either complete them or not with your current supplies (short of borrowing from buddies or the boat). Even if you run out of gas, only then is gas supply in more control than deco obligations. I may be concerned during deco but until I run out or nearly run out, gas is not in control. I have even seen it written and generally agree, although I do not do, deco bottles do not really need a pressure during the dive as it serves minimal purpose - all you can really do is watch your gas run out, hence you have what you have.