Tech1 vs Normoxic trimix

[rjack321]

Yes, I understand all of this. It's dumb, makes no sense, and would be the plan of a diver that shouldn't have been certified to begin with. Also not my point.

Maybe we are having different conversations at the same time. I am looking at this from an instructional standard standpoint that a lawyer would get hold of to extract money from the instructor after an incident. I'm not talking about operational use or best practices or good judgement. Once you are in court, the spirit of the standard is irrelevant, it's what the standard actually says that matters.

Having a variable max depth limit for training dives seems like a poor standard from a legal perspective, and I'm not seeing why there would be a variable standard. It doesn't provide any benefit. 170 is max, don't go deeper than 170. If a standard depends on everyone conducting themselves appropriately for it to be effective, it isn't a well written standard.

It reminds me of the student to instructor ratio that are set for ideal conditions, and it is up to the instructor to lower those ratios based on conditions. That is a terrible standard that puts all of the responsibility on the instructor, and after an incident hindsight bias will create a standards violation (Well I thought I was good with 4 divers in these conditions, but I only came back with three of them, so I guess not). But in that situation it is pretty much required unless every class has a 1:1 ratio. With a variable max depth it doesn't provide any benefit. I don't get it.

The cards say "trained to 170ft" on them. Training dives under instructor supervision will never exceed 170ft.

After class Joe diver goes to 190ft with their T1 card in hand and dies. Family sues the instructor, the boat, and the agency based on exactly what?

 

[Karel_de_Goeiste]

I have attached the sheet containing the certification limits from the GUE T1 course material.
"51m/170 ft max depth limit"

Nowhere - on their website, in the course materials or in their standards - GUE states the depth limit for T1 is 51m average depth (although this may be common or uncommon practice).

 

[tursiops]

I'm with @sea_ledford on this. I understand 170 ft max depth.
I do not understand using the word average in connection with that.
GUE can say/teach whatever it wants, of course, but it cannot redefine words that already have meanings.

 

[LanceRiley]

I'm with @sea_ledford on this. I understand 170 ft max depth.
I do not understand using the word average in connection with that.
GUE can say/teach whatever it wants, of course, but it cannot redefine words that already have meanings.

in a dive you are to make a plan for max depth and average depth? so you have 2 numbers. 1 dictates your deco and the other dictates your minimum gas.

 

[tursiops]

in a dive you are to make a plan for max depth and average depth? so you have 2 numbers. 1 dictates your deco and the other dictates your minimum gas.

I'm fine with this so long as no depth in the average exceeds the max depth; hence, the average depth will always be less than the maximum depth. Right?

 

[LanceRiley]

I'm fine with this so long as no depth in the average exceeds the max depth; hence, the average depth will always be less than the maximum depth. Right?

Max depth can be equal to ave depth.

But in class we had to make both different. Every dive we were always asked about our ave depth.

 

[tursiops]

Max depth can be equal to ave depth.

Perhaps, for a square profile, flat bottom, ignoring the descent and ascent phases of the dive.
If you are using average depth to determine your gas usage (which is what i think you said), then you must include descent and ascent phases. Right? So it is an average over the entire dive, not just over a flat bottom that your are lying on for the entire dive?

 

[sea_ledford]

The cards say "trained to 170ft" on them. Training dives under instructor supervision will never exceed 170ft.

Got it. Max depth for training dives is 170. There is no average depth in there. The average depth conversation is about operational practices, not teaching standards.

And agree with post certification dives beyond that being entirely on the diver, not the instructor.

Thanks, that make much more sense that what I was understanding initially.

 

[LanceRiley]

Perhaps, for a square profile, flat bottom, ignoring the descent and ascent phases of the dive.
If you are using average depth to determine your gas usage (which is what i think you said), then you must include descent and ascent phases. Right? So it is an average over the entire dive, not just over a flat bottom that your are lying on for the entire dive?

This was to answer your question. Not to say how i dive.

I usually dont include the descent. Part of conservatism.

Ascent is part of min gas

 

[rjack321]

I'm fine with this so long as no depth in the average exceeds the max depth; hence, the average depth will always be less than the maximum depth. Right?

Not necessarily. If you bomb down to 140ft in 2.5 mins and stay there for 25mins the descent time is functionally immaterial and it's not a big deal to ignore that and just use max depth. Ala Navy table approach.

I don't know how a "depth used in the average exceeds max depth" that's not mathematically possible. Although someone could round a 159ft max for 5 mins to 160ft for 5 mins, plus a variety of shallower times and its generally not a big deal.