Air integration for tech dives

[tursiops]

You are 100% correct.
So at that point you advocate to carry on with the dive with a known failure?
Speak into the mic.

Exactly. The protocol doesn't change. You turn the dive.

Again, logic I do not agree with. Suppose I had 5 SPGs. One fails...a "known failure." Do I turn the dive? No, I don't turn the dive until I have no knowledge of my pressure.

 

[Tracy]

Again, logic I do not agree with. Suppose I had 5 SPGs. One fails...a "known failure." Do I turn the dive? No, I don't turn the dive until I have no knowledge of my pressure.

What you would do, and what the right answer is are often different. The correct answer is don't continue a dive with a known failure.
Would I? Maybe, depends on the circumstances.
But it doesn't make it a good decision. It is one of those things that people point to during accident analysis.
"Why would he do that, he knew he had a failure and did the dive anyway. What an idiot, I would never do that."

 

[boulderjohn]

You are 100% correct.
So at that point you advocate to carry on with the dive with a known failure?
Speak into the mic.

Exactly. The protocol doesn't change. You turn the dive.

Actually, yes, I would continue the dive, just as I do on every dive now. You see, I do not presently use AI, so I start every dive with one functioning SPG. So I would be in the same boat if my AI failed and I had one functioning SPG.

You are using the phrase "known failure" as a substitute for thought. Whether or not you continue a dive after a failure depends upon the nature of the failure and the risk involved with continuing despite it. Some failures are barely worth mentioning, but others end the dive ASAP.

In my original tech training, the mantra was to end the dive after a major failure or two minor failures.

 

[jlcnuke]

Yeah, I'm not ending the dive just because something failed. I've never been taught that and it wouldn't make sense. A major failure (something I can't do the dive safely without) is something that causes you to end the dive, not simply "anything fails at all". Heck, if I have a backup primary light in addition to my two other backup lights, I'm not even calling the dive if I have a primary light failure (I often carry a backup primary because it functions as my video/picture light as well so this is a realistic thing that I could have happen).

 

[stuartv]

All of this is assuming a shearwater AI setup is less reliable than a spg. Which any tech diver knows is BS but won't admit too as they glance over at their box of broken SPGs

SOME tech divers won't admit...

I use AI (and no SPG) on everything I dive. Single tank OC, BM doubles (OC), SM (OC), and on the Dil and O2 on my CCR. I totally agree that SPGs are less reliable than a properly maintained AI setup (of the type that uses the PPS transmitters - aka the ones Shearwater uses).

I do not use AI on bailout or deco cylinders (I do use SPGs on them). I can't see a reason to bother with AI on those. They start full and the pressure in them is not the basis for a turn point in the dive. If/when I use them they either have enough gas or I royally screwed up in my dive planning. The pressure in the cylinders on my back (or sides) is what I need to monitor during the dive, to ensure I don't stay down too long. Those are what I use AI on.

 

[boulderjohn]

Heck, if I have a backup primary light in addition to my two other backup lights, I'm not even calling the dive if I have a primary light failure (I often carry a backup primary because it functions as my video/picture light as well so this is a realistic thing that I could have happen).

I raised this issue in cave diving circles a while ago. We teach 3 lights, and if your primary light goes, you call the dive.

With today's lights, your first backup light is probably far more powerful and dependable than the primary lights in use when that rule was first created. If you take 4 lights with you and your primary fails, then you are back to the rule of 3 lights, and there is no reason to end the dive for a primary light failure. (Yes, the dive is over if you have only 2.)

My cave instructor carried 5 lights, 2 of them of normal primary quality, for that reason.

 

[AJ]

What *should* the gauge say? If you just start the dive and the transmitter fails, if the SPG reads full then it’s working. You can extend that to all phases of the dive.

Your pressure should never be a surprise when you look at your gauge, AI or analog.

Exactly, you don't even need a gauge because you need to know you have enough gas to get back safe from the start. Gauge (AI or otherwise) is to verify during the dive if you have somekind of issue. If you don't know from the start of the dive there's enough gas to get back, you should not even consider to go diving.

Anything can break, but not having enough gas from the start of the dive is not a instrument failure. Adding more instruments doesn't solve the real potential problem = not enough gas.