Why the dislike of air integrated computers?

[Adobo]

I can think of several things but basically what NetDoc said: my gas planning does not include you not looking at your spg. My "if fecal matter hits the air displacement device" plan includes knowing I can swim 70' up without breathing.


This was triggered by "ATR bad because if your DC says you have X minutes left and you suddenly need to share air and now your DC lied to you". Yes, we know how sharing works: you had X of something, you shared it, now you have less. What's that got to do with AI DC? Then we somehow got to "but if you have an emergency would you CESA?" -- I kinda think that's what the "E" is for so duh.

I really have no idea what your saying.

The best I can figure is that you don't care if you have enough gas to get you and your buddy to the surface in the case your buddy is OOG.

And with that attitude, you are right. Maybe the ATR information you get from your AI computer is all you need.

 

[dmaziuk]

THere's other reasons to get out of air than not looking at your spg, and you have to be a complete moron to not plan for those. They happen on technical diving as well, see here Nylon-Braided Regulator Hose Diving Emergency

Fine. He found out during initial descent when he could safely thumb the dive when nobody was OOA. Similarly, if my buddy's spg was showing full tank when I give her the "T", we'd know something's wrong and we need to go up. With at least my half-tank of air to share for ascent. No OOA there.

---------- Post added July 24th, 2015 at 01:52 PM ----------

The best I can figure is that you don't care if you have enough gas to get you and your buddy to the surface in the case your buddy is OOG.

The way you make sure you don't run out of "X" is you have three. (Reliability and high-availability are in my job description so I know what I'm saying even if you don't.) If you dive with 5 cylinders: 3 for you and 2 for your buddy, then you've planned for that emergency you're describing. Otherwise you're just fooling yourself.

 

[guyharrisonphoto]

Both methods of gas management can be well implemented on AI computers (at least, on my Galileo--and I assume others as well).

If I am a "rock bottom" diver who does my own calculation for my surfacing pressure depending on the cylinder capacity, depth and estimated SAC, I can set a visual or audible alert (or both) at whatever turn pressure I want, based on my rock bottom calculations. This is very easy and gives a good back-up warning for my pre-determined surfacing pressure.

If I am a "be on the surface with 500" diver, I can set that as my surface reserve, and RBT will show "zero" and alert me to surface so that, at the computer's proper ascent rate and performing all stops, I will get to the surface with 500 psi. Here, the computer does all the calculations in real time, taking into account actual depth and actual SAC (no guessing needed). This eliminates the need to "guess" about when to begin the ascent.

This is not a commentary on which gas management strategy is better, only that AI has tangible benefits for either one.

 

[The Chairman]

Whereas I see thinking about how much gas reserves you need to maintain and checking your pressure at regular intervals is part of what defines a good buddy.

Most instructors I know (including myself) teach the 100lbs/10ft rule. An easy way to do this is to simply add a zero to your depth. See? No 'math' needed and it's close enough for OW dives. Unfortunately, most instructors I know don't teach that each diver should track not only their gas, but their buddy's gas as well. This is easily done through extrapolation from an early check, but it should be rechecked at various points in the dive. It's not enough that I don't allow myself to run out of gas: I should be doing the very same for my buddy.

my gas planning does not include you not looking at your spg.

Since I am my buddy's redundant eyes and brain, I'll be taking a look at their gas supply a few times during the dive. I usually do this first when I've gone through 500psi. If they use more, then they are the limiting diver. If I use more, than I am the limiting diver. I'll usually recheck @ 1500psi and then when I think when they've hit their turn pressure. I expect them to do the same for me. So far, through thousands of dives, neither my buddy or I have gone OOA doing this.

 

[guyharrisonphoto]

That rule of thumb is what I use as well. Surprisingly, when I did a "rock bottom" calculation for two divers on an AL 80, it matched pretty closely to this rule. This rule, though is even better because it is self-adjusting for multi-level profiles (go to 120' and your turn pressure is 1200, ascend to 60' and it is 600).

However, I am not sure that very many instructors actually cover this, especially in the abbreviated OW courses. My wife did not get that when she took her course, for example.

Having now used my AI computer for a while, I notice it is somewhat more liberal. At 100' for example, with my surface reserve set for 500 psi, it will send me up at about 750 with an AL 80. This is because it is basing it on my "relaxed enjoy the dive" SAC rate. However, this does not concern me too much because, in a for-real OOA emergency for my buddy, I would push the ascent rate to 60 ft/min until I hit about 30' to increase the available gas, and then slow to 30'/min to the surface, and I would skip any safety stop. My experience (having been through it once long ago with an OOA buddy) is that OOA is a far more serious situation that possible DCS from pushing the ascent rate, and getting to the surface fast but not out of control is best.

However that is mostly theoretical. Like you, my current buddy and I check each other's gas when we hit bottom, and when one of us hits half of their starting pressure, and usually one or two other times as well. I can't imagine diving without doing this basic thing. We have never come close to OOA

 

[Adobo]

Most instructors I know (including myself) teach the 100lbs/10ft rule. An easy way to do this is to simply add a zero to your depth. See? No 'math' needed and it's close enough for OW dives. Unfortunately, most instructors I know don't teach that each diver should track not only their gas, but their buddy's gas as well. This is easily done through extrapolation from an early check, but it should be rechecked at various points in the dive. It's not enough that I don't allow myself to run out of gas: I should be doing the very same for my buddy.

I'm actually okay with these kinds of rules that help us remember what our minimum reserves should be. Although we are then taking it on faith that someone else did the math before us to prove that this rule makes sense. And correct me if I am wrong but I imagine that these rules of thumbs are inclusive of the notion that your buddy might need gas from you as a result of some gas emergency.

We also need to keep in mind the constraints of the rule. For example, this rule might work well with an al80 but not an al63. Or another example, this rule works well but it assumes that you are making a direct ascent as soon as the gas donation is complete. There is no time to swim away from the wall or to deploy an SMB at depth.

The way you make sure you don't run out of "X" is you have three. (Reliability and high-availability are in my job description so I know what I'm saying even if you don't.) If you dive with 5 cylinders: 3 for you and 2 for your buddy, then you've planned for that emergency you're describing. Otherwise you're just fooling yourself.

After reading that, all I can do is echo what eelnoraa said:

It is actually quite sad that OW class don't teach proper gas management anymore.

 

[The Chairman]

We also need to keep in mind the constraints of the rule. For example, this rule might work well with an al80 but not an al63. Or another example, this rule works well but it assumes that you are making a direct ascent as soon as the gas donation is complete. There is no time to swim away from the wall or to deploy an SMB at depth.

I try to simplify all things to eliminate confusion. Divers on an AL63 usually have a spectacular SAC as opposed to those who would dive a 100 or a 120. So really, adding the zero works pretty well.

It's always been my belief that the best way to handle any emergency is to prevent it. If you ascend when the first buddy hits their turn pressure, then the other buddy should have at least that and probably more. This is why it's so important that buddies take the onus to keep track of each other's gas supply. Either diver in a buddy team going OOA is unconscionable on so many levels that it boggles my mind.

After reading that, all I can do is echo what eelnoraa said:

It is actually quite sad that OW class don't teach proper gas management anymore.

Gas management is taught in many OW classes. I know that NASE requires it's students to calculate their SAC and plan their dives accordingly. PADI recently made it a mandatory part of their OW class and while I haven't seen what they are teaching in that regard, I applaud any improvements. The gloom and doom that classes have been dumbed down is mostly FUDDDD (Fear, Uncertainty, Doubt, Deception, Distortion and Drama). On the contrary, certain skills such as gas management and trim/neutral buoyancy have never enjoyed this much emphasis.

 

[boulderjohn]

Quote Originally Posted by eelnoraa
It is actually quite sad that OW class don't teach proper gas management anymore.

Gas management is taught in many OW classes. I know that NASE requires it's students to calculate their SAC and plan their dives accordingly. PADI recently made it a mandatory part of their OW class and while I haven't seen what they are teaching in that regard, I applaud any improvements. The gloom and doom that classes have been dumbed down is mostly FUDDDD (Fear, Uncertainty, Doubt, Deception, Distortion and Drama). On the contrary, certain skills such as gas management and trim/neutral buoyancy have never enjoyed this much emphasis.

That was my point earlier. When I took my OW class in the last millenium, there was next to nothing on gas management. When I became an instructor a decade ago, there was next to nothing on gas management. Many of us added it to the course, and we also talked to PADI about that lack--sometimes at great length. I don't know what influence that had, but right now there is a pretty fair amount of gas management at the OW level. I don't get the idea that it is not taught as much it used to be--in my experience, it is taught a lot more now than it used to be.

 

[The Chairman]

It's good old revisionism, John. The "good ol' days" syndrome. Everything was better back 'in the day'. I like the direction classes have taken as of late. In reality, classes have gotten safer and smarter with more emphasis on meeting the needs of the students: not the egos of the instructor.

 

[guyharrisonphoto]

I did not mean to join the ranks of those trashing the new OW courses. My wife was certified 5 years ago and "formal" gas management was not covered for her, was all. Her instructor did tell her to begin surfacing at 750 psi (AL 80) for safety, and drilled into her to check her SPG regularly and that is probably enough for the basic OW diver who is limited to 60'. I don't fault him and in fact I thought he was excellent when I went on her OW checkout dives.

It was not covered for me, either, in 1974 .

I am glad to hear PADI and others are adding a little more formal training as part of OW.