Air integrated computer and tec diving

[The Chairman]

Wow... 20 dives? Did they lube them with grease at all? You should use a dynamic grease in there. The only leaking ones I have seen were over two years old.

 

[Patoux01]

Didn't seem to be much lube in there. Brand new regs. It wasn't a big failure, but still sufficient for me not to say that "they never fail".

 

[decompression]

Did they tell you that it was written in blood too? That's what transcends this opinion from being reasonable to just plain over the top. Trying to scare people into your way of thinking just rubs me the wrong way. It's like the Scuba version of Reefer Madness!

Cobra Madness!!!
...it's written in blood!!!
​

Pete, does it mean I'm old because I'm getting all your references?


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[The Chairman]

Didn't seem to be much lube in there.

So, I'll add the caveat "competently serviced" o-rings won't fail then. Neglect and incompetence don't make good dive companions even on a purely recreational dive. It's hard for me to blame the gear when either neglect or incompetence are involved. It's why I service my own gear.

Pete, does it mean I'm old because I'm getting all your references?

It probably means you 'get' the irony of it all. A side mounter who criticizes an extra SPG and then says it's 'written in blood' could be called an iron for just that. It's an Alanis Morrisette moment, doncha think?

 

[KenGordon]

Since I uninstalled DM4 as soon as I discovered what they'd done with the program since DM3, I've only been playing around with the dive planner that came with DM3. I've never seen that planner give me anything but 3m deco stops (except the one minute "deep stop" at half max depth). Are you saying that the DM4 dive planner will give you a staged deco profile with multiple stops? How do the deco profiles that DM4 give you compare to those given by e.g. Multideco or V-planner?

I use DM5 now. You can set the last stop depth but that is not synced to the computer (with the Helo2 anyway, maybe it can be set on the Eon Steel) so you still get the Suunto minutes issue doing stops at 6.

The rest of the planning s straight forward, set the gases, MOD for each gas and it spits out a plan. The labelling of the plan sucks slightly so some adding up may be required depending on how you like your slate.

The main problem I have with DM5 is that they always mess up the USB to serial stuff so you are left unable to upload dives for a while following upgrades. Also on a Mac it uses mono which adds a few more rolls of the dice in the game of getting it to be usable.

Still at least they offer a planner.

The plans do match the computer. If it has deep stops etc as per my helo2 and if you dive the plan you come up on time without bending the computer. I mostly dive the plan on the slate but follow the computer up if significantly early leaving the bottom.

You cannot really compare a vplanner or multideco plan with s Suunto plan without choosing how liberal or conservative to be. Set the right way a multideco plan will take the same time as a DM5 one. Whether that is 'right' or not who can tell.

My personal feeling is that in practice RGBM (at least in the Helo2) comes out like Buhlmann with Pyle stops added. I am ok with that.

 

[Storker]

You can set the last stop depth but that is not synced to the computer (with the Helo2 anyway, maybe it can be set on the Eon Steel) so you still get the Suunto minutes issue doing stops at 6.

Ah, OK. That means they've probably done something significant to the planner since v.3.1.

I'm a rec diver myself, but I got a bit curious about deco a year and a half ago, when I got somewhat involved - as a possible subject - in a diving medicine study. They were doing chamber dives for two hours at 18m, then deco according to the Norwegian Navy table (more conservative than the US Navy table, and somewhat different from BSAC-88. On the Norwegian table, deco for 2h@18m is 5 min @6m, 25 min @3m, on air). Just for fun, I ran the schedule through the dive planner in DM3.1. I ended up with owing 1h43min of deco at 3m, but no stops deeper than that. So quite a bit of difference between 3.1 and 4...

 

[Rick Murchison]

Interesting thread...
Just a couple of thoughts.
First, from a safety perspective, I have no problem with someone else using AI transmitters. I personally prefer brass & glass.
Custom tables in caves... if I'm doing a cave dive that requires deco I'll run as close an approximation as I can in V-Planner in advance, and take a review look at the (gasp!) Navy tables.
Then I dive the HelO2, with those other two in my back pocket as a reasonability check on the computer, and for fallback if the whole world turns to worms.
And... if I ain't too cold, I'll find something to interest me in the shallows for a while at the end of the schedule.

Rick

 

[DevonDiver]

As the OP, I'll clarify. I'm not trying to be cavalier with tec. I'll likely by wrist mounted computer as a back up

I don't mean to come across as hard-ass, or know-all.... I hope you understand that. You asked specifically about Tec40/45, so I am presenting the essence of what you'll be taught on those courses. In particular, I am trying to convey the mindset shift that you will encounter on transition from recreational to technical diving.

It's the mindset that matters... because that's what enables you to understand and answer these questions for yourself in the future.

I was curious about the idea of a failure point v redundancy.

This is where tech principles come into it. These principles may sometimes seem contradictory, but in reality there is a prudent method to apply them. The issue to safeguard yourself against is whether you seek to justify violating a principle for invalid reasons; convenience and cost.

As mentioned before, technical diving courses give extensive training in the mindset necessary for technical diving. In the Tech Deep Diver manual, each chapter contains a sub-section entitled 'Thinking Like A Technical Diver'.

The question you asked initially...."and, why?" is answered by understanding that mindset. It is a very different mindset to that of recreational diving. You can see the difference in mindsets even within this thread. There are some very enlightening examples of "non-technical mindsets" in some of the posts. You can fail technical training for not displaying the right mindset.... that's one big difference between tech and recreational courses.

Just so you know, here are the six principles identified in the TecRec Tech Deep Diver manual (p193):

Principles for Surviving a Tec Dive​

You may have noticed that this course focuses on being alive and unhurt after a tec dive. (A Good Diver’s Main Objective Is To Live). Therefore, the six principles for surviving a tec dive should be nothing new to you. Think of these as survival principles you never violate, though there may be different ways to follow them, depending upon the environment.​

1. The Principle of Secondary Life Support. You should have at least two independent usable regulators, at least two independent sources of time, depth and decompression information, and at least two methods for controlling buoyancy. You should have at least two of anything that keeps you alive. If any one fails, you abort the dive on the other.​

2. The Principle of Gas Reserve. You should have ample gas to handle reasonably possible emergencies and still complete your decompression (usually thirds). During an emergency, time is what you need to solve the problem — your reserve gives you that time.​

3. The Principle of Self Sufficiency. At any point in a dive, you should be able to complete it independently.​

4. The Principle of Depth. Your dive plan should account for narcosis, decompression, oxygen toxicity and gas supply needs based on a planned depth and/or a maximum contingency depth (and times) that you do not exceed.​

5. The Principle of Simplicity (KISS principle). Your dive should be planned as simple as possible, with complexities eliminated.​

6.The Principle of Procedure and Discipline. You follow the rules and work the procedures without exception on every dive, no matter how familiar the dive and no matter how much experience you have. To state this in a negative context: Cutting corners kills.​

The principles that apply to the question of redundancy versus failure points are #1 #3, #5 and #6.

You consider redundancy for two clear purposes: staying alive and finishing the dive alone (as a contingency). Thus, we have two regulator systems, two gas systems (either independent or able to isolate), two information systems (computer/bottom timers). These are critical.

We have two computer/bottom timers because we have to complete a decompression ascent. If we didn't have that information, then we would probably hurt ourselves though DCI. As we're self-sufficient, it is not acceptable to defer that redundancy to a team-mate.

Some divers get confused why a computer/bottom-timer is 'life support', but an SPG isn't. As explained in my previous post; loss of SPG information doesn't jeopardize life support. That's because you've already calculated a gas plan and have ensured that you have sufficient gas to complete the dive. If you lost SPG information, then you would immediately abort the dive. Having a second SPG wouldn't give you more gas. Losing SPG information doesn't prevent you doing a planned ascent.

So... SPG redundancy brings no tangible benefit in respect to safety, self-sufficiency or life-support.

On the other hand, we have the principle of simplicity... K.I.S.S. (keep it simple stupid). This principle stems from the military... and it covers equipment, protocols/procedures and dive planning. The tech manual explains, in detail, why this is an important principle.

The issue of failure points can be considered under the umbrella of K.I.S.S. The less you have, the less that can go wrong. The less that goes wrong, the less risk of an accident.

Failure points can be many things... o-rings, connections, hoses, buckles, electronic items.

Failure points also have different consequences....such as; loss of information, loss of gas, loss of buoyancy.

Loss of gas is always critical. Loss of information may be critical.

One major difference between technical and recreational divers is the assumption of things going wrong. Technical divers are taught that "if something can go wrong, it will go wrong". We are trained to consider the worst-case scenario, not to assume the best-case.

Here's how the Tech Deep Diver Manual explains it (p115):

One good characteristic to develop if you want to last a long time in tec diving is a moderate dose of paranoia. Tec divers dedicate themselves to applying, following and responding to the world’s most quoted aphorism, Murphy’s Law:​

Anything that can go wrong, will go wrong.​

Tattoo that on the back of your hand if you have to. Murphy’s Law serves you well as a tec diver if you assume that everything that can fail will fail. Assuming failures prompts you to plan for them....

​

As you plan each step in a dive, simply ask yourself, “What aspect of this can fail and hurt or kill me?” For every reasonably possible failure or problem you can imagine, have a workable solution before beginning the dive. Within reason, make contingency plans that do not require your teammate’s assistance as your first option. Remember that it’s impossible to anticipate all problems — but you can anticipate the most common and likely.​

Technical divers are taught to identify failure points through the process of contingency planning. Having considered failure points in a system, we then seek to eliminate them.... or as many as possible.

How do we eliminate failure points? We balance the NEED for a component against it's RISK. The NEED is determined by the six principles mentioned earlier (and nothing else).

What responsible technical divers DON'T do is negotiate away those failure points by asking how often they might occur.

Dive for long enough and you'll encounter failures. Both for yourself or for others you know. It's a given.

You will also know people who suffer consequences from those failures... the tech community is relatively small... so over time you'll confronted with people actually having close near-misses... or getting DCI, or dying (and when they do... you'll see the principles they broke to cause it...)

Each hose is a potential failure point. Theoretically we could reduce that by just diving one LP and 1 HP, but clearly we would lack redundancy and safety. How much of a failure threat is an HP hose with computer as a back up only when an HP hose would release gas slower than the LP hose.

Each hose, each o-ring, each connection, each battery, each microchip, each digital screen, each digital depth sensor, each wire..... There are a LOT of failure points in a computer compared to an analogue gauge.

What's important to convey, in respect to technical mindset, is that this process isn't one of negotiation and compromise. If something isn't optimal... if it's not NEEDED.... but it poses any failure threat, then the answer is evident.

Asking "how much of a failure threat" is a negotiation. It's contrary to the technical diving mindset that we assume what can go wrong, will go wrong. Yes, we can ask if a failure is 'reasonable', but we don't play a game to discount risks based on presumptions or an inability to directly quote failure statistics or incident reports.

With that in mind, I will re-word your question:

[-]How much of a failure threat[/-] is an HP hose with computer as a back up only a failure threat? Yes or no? ...

In respect to technical principles:

Argument Yes:
1. Electronic SPG has more failure points than analogue SPG.
2. Older computer more failure potential than new bottom timer.
3. Hose-mounted computer less simple to monitor than wrist-mounted gauge.
4. Failed AI computer removes two sources of dive information.

Argument No:
1. AI computer failure removes sole source of gas information, but is only the back-up deco information. A safe ascent can still be conducted on the primary computer/bottom-timer.

So....in respect to information loss, the failure of the SPG isn't safety critical. Neither is the loss of a back-up computer. The diver is equipped and prepared to carry out a safe, independent deco ascent anyway. It's not a 'safety' decision, but rather, a question of whether or not to follow principles and exhibit appropriate mindset.

The issue of whether an AI computer failure is more/less likely to cause gas loss than an analogue SPG failure is an issue. But I doubt there are statistics available to give us a clear answer. Both have an HP hose, with two o-ring sealed connections at each end. A brass/glass SPG is pretty robust. An AI computer... who knows? So... unless someone can definitively prove that AI computers are more prone to gas loss in physical failures, we have to discount that. Err on the side of caution, if you feel it prudent.

Back to principles... it boils down to Simplicity.

Using a hose-mounted back-up is less simple than a wrist-mounted, dedicated, bottom timer. That simplicity does count, because on a technical deco ascent you'll already have a lot of task loading; especially in your early development as a technical diver and even more so under the rigors of training.

You need to constantly monitor your computer, ideally it needs to be within your field-of-vision the whole time. You need to keep an accurate ascent rate. You need to maintain accurate stop depths; even whilst conducting gas switches or deploying DSMBs. In training (at least) you'll have to deal with simulated contingencies and emergencies; shut-down drills, flooded masks, gas-sharing, failed buoyancy, lost gas, omitted deco, Most technical students find their training very stressful... and it should be. Adding the stressor of a hose-mounted back-up computer is not prudent... it's something else to juggle, to distract, to irritate you... another function to perform when you're already at your limit.

As a technical instructor... if you had an AI computer as back-up.... I'd want to test and assess the impact it had on you. I'd want YOU to know that impact. So you'd do multiple ascents using only that back-up. We'd see how it effected your performance. If it's a potential weak-link, then I want you to learn that in supervised, simulated training... not discover it at a later date, where the consequences might be severe.

In that respect, the "opinions" of others are useless. It's a matter for YOU to decide. Does it degrade your performance or not? Does it increase task-loading and stress? Does that cause knock-on problems that do effect potential safety? Is it simple enough for you, not others.

There's no perfect answer. Your future tech instructor may have a different opinion. They may take the decision out of your hands... or may not see it as a problem at all. What they should ALL do though... is encourage you to make an educated decision for yourself... and provide you with the circumstances by which to test your decision before you will rely upon it.

**I am not discussing the issue of two (2) SPGs because you haven't asked about that. From the information presented, relevant to the Tec40/45 course, you should now be able to make a simple evaluation of that. **

 

[Divetech99]

Perhaps I'm mistaken but doesn't the HelO2 just provide the ceiling and ascent time and it's up to you to curve your ascent? I think this is the way all Suunto's (old and new) function on deco. Thus rendering them useless in deco situations.

 

[decompression]

Perhaps I'm mistaken but doesn't the HelO2 just provide the ceiling and ascent time and it's up to you to curve your ascent? I think this is the way all Suunto's (old and new) function on deco. Thus rendering them useless in deco situations.

Not the tec computers (Vytec, HelO2).


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