Why the dislike of air integrated computers?

[ajduplessis]

Scary stuff...

 

[doctormike]

Example: I know my own RMV and performance with my HP120 tanks and I have experience with dive profiles where I know that I am going to hit my NDL before my tank drops below 1000 psi. If I were diving a profile like that, if I got in the water and noticed that my AI was no longer telling me my tank pressure - but I know (from a pre-dive check) that my tank is full, I might very well proceed with the dive without "knowing" my tank pressure during the dive (and likely planning to give myself some extra margin on my NDL - i.e. get out well before it goes to 0).

I wouldn't do that.

 

[stuartv]

I wouldn't do that.

Yeah... I posted it knowing that there will be a bunch of people that will read it and think "idiot!" and probably a few who will actually post the same thought. Not saying you, specifically, are calling me an idiot. I understand and appreciate the difference between calling someone and idiot and just saying "I wouldn't do that."

This forum has some interesting dichotomies. "You should always have an SPG connected by a HP hose!" And then, so many times I've read "a good/tech diver doesn't generally even need to look at their SPG because they know what their consumption rate is and know, to a very close margin, what their current gas level is without looking at their SPG, just based on their dive time."

 

[doctormike]

Yeah... I posted it knowing that there will be a bunch of people that will read it and think "idiot!" and probably a few who will actually post the same thought. Not saying you, specifically, are calling me an idiot. I understand and appreciate the difference between calling someone and idiot and just saying "I wouldn't do that."

This forum has some interesting dichotomies. "You should always have an SPG connected by a HP hose!" And then, so many times I've read "a good/tech diver doesn't generally even need to look at their SPG because they know what their consumption rate is and know, to a very close margin, what their current gas level is without looking at their SPG, just based on their dive time."

I didn't call you an idiot because I don't know you, other than through what you post. I'm assuming that you aren't trolling, and that you are interested in participating in this discussion.

To be honest, I far prefer your style (of exhaustive but detailed debate) to those who respond to every difference of opinion with the irritating phrase "it's personal preference!". Of course, it's personal preference, but the whole reason that we have this forum at all is to learn from each other and consider things that we hadn't before.

Don't know if your dive count is correct, but you probably knew when you posted that pretty much any experienced diver or instructor will not consider the technique that you proposed to be safe, even for divers with a lot more experience.

And while a good tech diver doesn't need to look at their SPG compulsively like a newbie on a reef, a good tech diver also wouldn't splash after discovering that their SPG wasn't working, and just rely on doing calculations in their head about how much gas they have left. There's a big difference. Believe me, there are situations underwater where having an SPG can help you sort out different failure modes and figure out what to do next.

 

[stuartv]

I didn't call you an idiot because I don't know you, other than through what you post. I'm assuming that you aren't trolling, and that you are interested in participating in this discussion.

To be honest, I far prefer your style (of exhaustive but detailed debate) to those who respond to every difference of opinion with the irritating phrase "it's personal preference!". Of course, it's personal preference, but the whole reason that we have this forum at all is to learn from each other and consider things that we hadn't before.

Don't know if your dive count is correct, but you probably knew when you posted that pretty much any experienced diver or instructor will not consider the technique that you proposed to be safe, even for divers with a lot more experience.

And while a good tech diver doesn't need to look at their SPG compulsively like a newbie on a reef, a good tech diver also wouldn't splash after discovering that their SPG wasn't working, and just rely on doing calculations in their head about how much gas they have left. There's a big difference. Believe me, there are situations underwater where having an SPG can help you sort out different failure modes and figure out what to do next.

Thank you for all that.

I really think my previous post should be taken in the vein of "well, that's what you SAY you would do, but we'll see what you really do if it ever actually happens."

Because, in reality, I have and use an Atom with AI, but I also have an Aeris A300 XT console on my reg set, so I always dive with 2 computers and 2 SPGs. And I do periodically check the computers and the SPGs against each other. So, of course if my AI (or the Atom itself) stops working I'm not going to bail. Thus, saying what I would do if I only had the AI and just the SPG stopped working is pure speculation. I've put my money where my mouth is already when I say I wouldn't let myself get into that situation in the first place.

Also, I didn't say I would splash with no SPG. I said that if I already splashed and my SPG died, and I was diving a profile that I already knew and had confidence that my gas would well outlast even my NDL, then I would probably continue the dive (and keep it to well shorter than my NDL) rather than abort. I would also make sure I stayed dang close to my buddy. And, of course, this is all predicated on talking about Recreational diving where running out of air with no SPG is no worse than running out of air with a working SPG. Which is to say that it's a colossal screw-up on the part of the diver. But, if it happens, a diver who keeps their wits *should* be able to make it to the surface okay - even if their buddy is not to be found, for some reason. I'm sure someone is going to post up some hypothetical conditions that show this idea to be really bad. What if it's a ripping current, so going straight to the surface, instead of following the anchor line is really bad? Right. If it were me, that kind of thing would definitely be a factor in deciding whether to continue the dive or not. I would not automatically continue just because it's a known profile.

 

[doctormike]

Thank you for all that.

I really think my previous post should be taken in the vein of "well, that's what you SAY you would do, but we'll see what you really do if it ever actually happens."

Well, if it happened to me, I would just abort the dive. I can't imagine a situation where I would continue the dive, but of course, I can't prove a hypothetical like that...

Because, in reality, I have and use an Atom with AI, but I also have an Aeris A300 XT console on my reg set, so I always dive with 2 computers and 2 SPGs. And I do periodically check the computers and the SPGs against each other. So, of course if my AI (or the Atom itself) stops working I'm not going to bail. Thus, saying what I would do if I only had the AI and just the SPG stopped working is pure speculation.

OK, maybe I'm confused by your post. I thought that you were saying that you would continue the dive without a direct readout of tank pressure based on your knowledge of the NDLs, your SAC rate and the profile. Are you referring to a situation where you have two tank pressure readouts and you have lost one of them? Or where you have one and you have lost it?

Also, I didn't say I would splash with no SPG. I said that if I already splashed and my SPG died, and I was diving a profile that I already knew and had confidence that my gas would well outlast even my NDL, then I would probably continue the dive

A minor semantic point. If you would continue a dive when your only SPG failed during the dive, why would that be more reasonable than starting a dive when your only SPG failed before the dive? Not sure I get the distinction... those two things seem pretty equivalent from a risk management point of view (again, not talking about a deco obligation).

 

[stuartv]

OK, maybe I'm confused by your post. I thought that you were saying that you would continue the dive without a direct readout of tank pressure based on your knowledge of the NDLs, your SAC rate and the profile. Are you referring to a situation where you have two tank pressure readouts and you have lost one of them? Or where you have one and you have lost it?

No, my original statement was regarding the hypothetical situation of having only the AI SPG and if it crapped out. Specifically, the post I was responding to was comparing HP hose blow-out to AI transmitter dying. IF that were me, the AI would have the advantage of offering the ability to continue the dive.

A minor semantic point. If you would continue a dive when your only SPG failed during the dive, why would that be more reasonable than starting a dive when your only SPG failed before the dive? Not sure I get the distinction... those two things seem pretty equivalent from a risk management point of view (again, not talking about a deco obligation).

If it died before I got in, I could potentially delay the dive a few minutes and fix the issue and still do the complete dive. If it happened after I got in, then my choice is to abort the dive, which probably really means losing the dive completely (at least, whatever remains of it), including costing my buddy the dive. If it died before I got in, and I couldn't remedy the situation in any way, at least my buddy might have the option to join another buddy pair and still get to do his dive.


Would you be willing to swim an AL80 that you know is full, in a 12' deep pool, for 30 minutes, with an SPG? If so, then I don't think we're any different. We're both saying we would be willing to evaluate the dive conditions and do or continue certain dives, if the conditions are right, without an SPG. At that point, it's a question of where we each choose to draw the line. Somewhere between a pool and 130' in low viz with a ripping current and high seas on the surface. I would not draw that line at either end of the extreme, but rather somewhere in between. I've done 3 dives to 110+ fsw with my 120s, staying down right up to my NDL, and not gotten out with less than 930 psi left. I would feel pretty confident in not running out of gas if I did the same dive, in the same conditions, with only 1 SPG, which happened to die after I got in, and planning to get out with, say, 5 - 7 minutes of NDL left. Of all the safety concerns on a dive like that, do you REALLY feel like continuing with a freshly dead SPG is really that unsafe? Why?


If you would NOT be willing to get in a pool and stay under for 30 minutes, using a known full AL80 and no SPG, then we are definitely different. And, hopefully, my radical disregard for safety won't get me or anyone else killed.

 

[Charles2]

I have made many, many, many dives knowing only that I had a full tank when I started. No spg - no AI. Just using planned depth, time and projected air consumption as a guide. Never been OOA. Never had a buddy go OOA.

I thought the J-valve was a good idea when I got one. I liked using a SPG better. I think AI is the best yet.

But in a pinch, stuartv has a good point.

 

[doctormike]

No, my original statement was regarding the hypothetical situation of having only the AI SPG and if it crapped out. Specifically, the post I was responding to was comparing HP hose blow-out to AI transmitter dying. IF that were me, the AI would have the advantage of offering the ability to continue the dive.

OK, maybe I'm not following your thread, or maybe you are referring to another one of your posts. In post 520, it sure seems like you said that you would complete a dive when your only pressure measuring device failed rather than aborting the dive.

If it died before I got in, I could potentially delay the dive a few minutes and fix the issue and still do the complete dive. If it happened after I got in, then my choice is to abort the dive, which probably really means losing the dive completely (at least, whatever remains of it), including costing my buddy the dive. If it died before I got in, and I couldn't remedy the situation in any way, at least my buddy might have the option to join another buddy pair and still get to do his dive.


Would you be willing to swim an AL80 that you know is full, in a 12' deep pool, for 30 minutes, with an SPG? If so, then I don't think we're any different. We're both saying we would be willing to evaluate the dive conditions and do or continue certain dives, if the conditions are right, without an SPG. At that point, it's a question of where we each choose to draw the line. Somewhere between a pool and 130' in low viz with a ripping current and high seas on the surface. I would not draw that line at either end of the extreme, but rather somewhere in between. I've done 3 dives to 110+ fsw with my 120s, staying down right up to my NDL, and not gotten out with less than 930 psi left. I would feel pretty confident in not running out of gas if I did the same dive, in the same conditions, with only 1 SPG, which happened to die after I got in, and planning to get out with, say, 5 - 7 minutes of NDL left. Of all the safety concerns on a dive like that, do you REALLY feel like continuing with a freshly dead SPG is really that unsafe? Why?

Hypotheticals are useful, but less so when you add conditions after you get a response. My reading of your post (520) was as a general statement that if you knew your RMV and your typical NDL for a profile that you knew well, you would complete a dive after an SPG failure. But I guess there are very specific situations in which you could do that (the pool dive example). I still don't like your plan to use NDL as a means of guessing tank pressure, but I'm sure that you know that.

If you would NOT be willing to get in a pool and stay under for 30 minutes, using a known full AL80 and no SPG, then we are definitely different. And, hopefully, my radical disregard for safety won't get me or anyone else killed.

You know, I'm treating you with respect and answering your posts. This sort of flippant, mocking language, especially from a very inexperienced diver, makes me feel like you don't respect the sport.

I know that you are a rightfighter, and that's OK, I do that myself sometime. I think that you are worth engaging with because you actually care enough about diving to have learned a lot of theory in your short dive career, and I respect that.

But this stuff is just trolling, and you know it. Maybe I'm just sensitive since I lost a very good friend on a dive last week. You really should tone down the arrogance. The idea of killed on a dive isn't just a rhetorical tool. It really happens, and accident analysis often shows that it starts with this sort of attitude.

 

[boulderjohn]

You know, I'm treating you with respect and answering your posts. This sort of flippant, mocking language, especially from a very inexperienced diver, makes me feel like you don't respect the sport.

I know that you are a rightfighter, and that's OK, I do that myself sometime. I think that you are worth engaging with because you actually care enough about diving to have learned a lot of theory in your short dive career, and I respect that.

But this stuff is just trolling, and you know it. Maybe I'm just sensitive since I lost a very good friend on a dive last week. You really should tone down the arrogance. The idea of killed on a dive isn't just a rhetorical tool. It really happens, and accident analysis often shows that it starts with this sort of attitude.

A little learning is a dangerous thing;
drink deep, or taste not the Pierian spring:
there shallow draughts intoxicate the brain,
and drinking largely sobers us again.

---Alexander Pope​

Stuart, I am going to echo and reinforce doctormike on this point. I made an oblique reference to this a few days ago, I believe in another thread, and you laughed that off in a mocking tone as well.

I recall well when you first joined ScubaBoard as a brand new diver, and everyone was stunned by the way you lectured highly experienced divers on things you really knew very little about. Now you are back with a total of 35 dives (according to a recent post in another thread), and you seem to believe your accumulated experience and knowledge surpasses all other divers. When divers with a relative wealth of experience disagree, you mock and insult them as if they were simple-mindeed fools.

I am concerned for you to some degree, but that is not why I am writing this. If you choose to ignore the advice of experienced and highly trained divers, that is your choice. I think it is clear that you will not be dissuaded by anything anyone says. The people I am concerned about are the other less experienced divers who are reading these posts and trying to learn. As I post this warning, my real audience is that other group of divers. I am asking them to make a careful consideration about issues and not just follow the advice of someone on the Internet who seems very sure of himself.

The PADI technical diving program requires students to identify the key character traits of technical divers. One of them is humility. You gain that humility when you do enough training to fully understand how much there is to know and be able to do. At that point you begin to understand how far you have to go. Ironically, I feel less sure of my own total knowledge and ability than I did 600-700 dives ago, and I look forward to every opportunity to continue my education.