PADI OW and AOW

[xyrandomyx]

I'll be doing my deep dive for my PADI AOW course tomorrow (if the good weather holds out). After thinking about the feedback from my last thread and doing a bit more reading, I'm trying to do a bit more preparation and be more pro-active in planning for tomorrow's dive.

I've calculated my RMV and SAC for 12 and 15 litre tanks (I've probably erred quite far on the conservative side, but it seems prudent given my lack of experience). I used that to compile a table for rock bottom pressures for various. I've also compiled a table for the pressure needed to ascend to and complete safety and deep stops, so that I can add easily add that to my reserve when calculating a turnaround pressure. I also have a table showing how much pressure I expect to use in 5 and 2 minutes at various depths.

My plan, then, is to let the instructor come up with the dive plan and then double-check it against my own calculations. I'll ask questions until I'm happy that I understand completely and agree with it. I've decided that I wouldn't be comfortable doing a dive where conditions wouldn't allow me to ascend at any point with minimal complications: so, very obviously, no overhead or 'virtual overhead' environments; but also not anywhere where it'd be unsafe to ascend without an anchor line or in certain areas. But, a bit more of a surface swim seems OK to me.

I think that, given my experience, I can't be completely confident in my ability to execute the plan. So, I need a backup plan: checking my gauges often and knowing what I expect to see. That way, I'll be able to identify early (long before rock bottom, with plenty time for safety stops) that I'm consuming more air than expected and, if I can surface safely at any point, thumb the dive. That said, I'm hoping that all my calculating and thinking will turn out a sound dive plan that I can execute successfully.

Lastly, I'll be harassing my instructor with questions about dive planning. PADI OW and AOW might not cover as much as many think it should, but he seems like a fairly knowledgeable and experienced guy, so I'm sure he'll be able to add some useful information beyond what's required for the course.

Does my reasoning seem sound?

 

[Bubbletrubble]

FYI, so long as gas consumption is expressed in volume per unit time, gas consumption rate is independent of the tank used.

You sound prepared. Be sure to discuss with your buddy all of the elements of the dive plan. Pay particular attention to gas planning (turn pressure, gas reserves), lost buddy procedures, and air sharing protocol.

In my experience, for the PADI AOW deep dive, the plan as outlined by the instructor consists of:

• Descend to a depth of approx. 100 fsw.
• Perform a task at depth to demonstrate the effects of narcosis. (The tasks I've seen/heard of/experienced -- unlock combo lock, simple math exercise, etc. -- are insufficient in my opinion.)
• The student notifies the instructor when he/she gets down to 1500psi.
• Ascend to safety stop depth.
• Conduct 3 minute safety stop.
• Ascend to surface.

Unfortunately, there is usually no discussion of gas planning beyond what was outlined above since PADI standards don't specify that such a discussion should take place. This is a glaring omission in the AOW curriculum.

Ask your instructor about the benefit of deep stops, the usefulness of extending safety stops, and how to do on-the-fly gas management during a dive (calculating whether a given gas supply will last long enough to make a safe ascent from a certain depth).

Good luck with your class. Have fun.

 

[tddfleming]

Please report back to us on how well this went. I am wondering if he will be able to answer your questions. From what little contact I have had with different inst. around here, I would think they would not be able to answer questions like this. But I could be wrong. I have come to realize there are a couple to a few different inst out there, some will be able to answer this and then some and those at will look at you like a deer in headlights. I only say this from my personal experience of ones that I have had some dealings with.

Good Luck and let us all know.

 

[Scott]

In my experience, for the PADI AOW deep dive, the plan as outlined by the instructor consists of:

• Descend to a depth of approx. 100 fsw.
• Perform a task at depth to demonstrate the effects of narcosis. (The tasks I've seen/heard of/experienced -- unlock combo lock, simple math exercise, etc. -- are insufficient in my opinion.)
• The student notifies the instructor when he/she gets down to 1500psi.
• Ascend to safety stop depth.
• Conduct 3 minute safety stop.
• Ascend to surface.

The outline for the deep adventure dive was changed recently. It now consists of the following:

• 
  Performance Requirements
  1. Descend using a line, wall or sloping bottom.
  2. Compare changes in color at the surface and at depth.
  3. Compare a depth gauge to another diver’s depth gauge.
  4. Ascend at a rate not to exceed 18 metres/60 feet per
  minute using a dive computer (or depth gauge and
  timing device).
  5. Make a safety stop at 5 metres/15 feet for at least three
  minutes.

If your instructor adds a 'narcosis' test or something else to your dive, consider it a bonus.

 

[Bubbletrubble]

@Scott: Thanks for the update on the revised standards. Out of curiosity, did the previous standards specify that a "narcosis test" be performed at depth?

 

[xyrandomyx]

FYI, so long as gas consumption is expressed in volume per unit time, gas consumption rate is independent of the tank used.

You sound prepared. Be sure to discuss with your buddy all of the elements of the dive plan. Pay particular attention to gas planning (turn pressure, gas reserves), lost buddy procedures, and air sharing protocol.

In my experience, for the PADI AOW deep dive, the plan as outlined by the instructor consists of:

• Descend to a depth of approx. 100 fsw.
• Perform a task at depth to demonstrate the effects of narcosis. (The tasks I've seen/heard of/experienced -- unlock combo lock, simple math exercise, etc. -- are insufficient in my opinion.)
• The student notifies the instructor when he/she gets down to 1500psi.
• Ascend to safety stop depth.
• Conduct 3 minute safety stop.
• Ascend to surface.

Unfortunately, there is usually no discussion of gas planning beyond what was outlined above since PADI standards don't specify that such a discussion should take place. This is a glaring omission in the AOW curriculum.

Ask your instructor about the benefit of deep stops, the usefulness of extending safety stops, and how to do on-the-fly gas management during a dive (calculating whether a given gas supply will last long enough to make a safe ascent from a certain depth).

Good luck with your class. Have fun.

Thanks. I do realise that gas by volume is independent of cylinder size, but it seemed more useful to convert to a cylinder-size dependent pressure unit as the last step. I want to know that I need to turn around at 120 bar, not have to divide 1440 litres by 12 to figure that out (especially not underwater).

I've been discussing the gas management aspect with my buddy this week (while doing my own calculations). I've done all of my dives with him so far, so we're quite clear on lost-buddy and air-sharing procedures, though we generally do a quick confirmation of them before a dive (and usually an instructor or divemaster mentions them too, in my limited experience).

I've made a note of your suggested questions and will be sure to ask them tomorrow (and let tddfleming know if I get any answers).

Also, sorry for the thread title (I realised after posting that I couldn't edit it). It was meant to say 'PADI AOW Deep Dive', but my brain was switched off when I clicked 'Post'. It's a little bit misleading or at least unhelpful.

Oh. And thanks to 'Bob (Grateful Diver)' for his article on gas management. Useful and interesting. I do think that he and his fellow citizens should learn to use the metric system, though.

 

[Scott]

@Scott: Thanks for the update on the revised standards. Out of curiosity, did the previous standards specify that a "narcosis test" be performed at depth?

From memory, be it limited
The standard did not call it a narcosis test, they called it a timed task.
The timed task was moved to dive three of the deep diver specialty and the color comparision was moved from dive three to dive one of the AOW.

 

[chuck34gboro]

I did mine in Cancun with Aqua World in April of 2010 and there was no "narcosis" or "timed" test. Just the mentioned reading guages to detect differences in equipment. Determined my console guage to be off by about 8ft at 90fsw. Also the differences in colors between some gear we looked at on the surface and at depth. And there was no mooring or anchor and no wall so it was a free descent and ascent. But it's drift diving.

As for the planning, she walked me through it on the boat orally. She asked things like time and air on what i felt like I needed to return safely. She agreed and we went over communications. Even got to penetrate C-58.

 

[Crowley]

The Timed Task - which was indeed intended to demonstrate the effects of narcosis at depth, was removed from the curriculum - er - about 2 years ago. I actually disagree with this removal but there you have it.

Descending without a reference of some type on the Deep adventure dive is a violation of standards. Adding the "narcosis" test would also be a violation of standards. Much as people might disagree with them, there are liability issues involved and therefore we are required to teach what is required to be taught - sorry about that.

Gas management - okay - you know a lot more than the average recreational-type AOW candidate. The discussion about the name of the course and what is actually taught has been around this forum so many times I would rather people didn't start it here, but although the specific standards do not include gas management in terms of "at this tank pressure you should start to ascend, then make this or that stop, then do the next thing", the concept of careful gauge observation and diving conservatively is a requirement of all PADI courses.

It might be rather simplistic in the approach - as in "maximum depth 30 metres, when the first person in the group indicates 100 bar or approaches 5 minutes to their NDL on their dive computer (or table) we will ascend to 15 metres; at 60 bar we will ascend to 8 metres, at 50 bar we will make our safety stop and surface with 40 bar" - or a variation thereof, that's just an example.

Now - this is a simplistic approach without SAC or decompression calculations being involved, but it's a broad-spectrum approach to recreational diving. Understandable and conservative.

xyrandomyx you have a good approach to diving, and after you stick a few dives under your weight belt, you may wish to look into some of the more advanced diving courses.

Good luck, have fun!

C.

 

[xyrandomyx]

The dive didn't exactly go as planned. The visibility was pretty terrible. We descended to about 17m, my buddy wasn't feeling comfortable going down into the seemingly bottomless bucket of pea soup and thumbed the dive. We made a normal ascent with a safety stop. Not a catastrophic failure by any means. I was a little disappointed, but very much glad he thumbed it instead of trying to push on through when he was unhappy. We had a good second dive in much shallower water and better visibility later in the day, at least.

As for my questions -- they didn't really go as planned either. I didn't get the deer-in-headlights thing, more like creative handwaving. I'm disappointed. I did discuss the plan in a fair bit of detail, asked enough questions until I was sure it fitted with what I'd calculated was a good idea. But I couldn't get a clear answer as to how he got to the plan.

So, um, I'll probably complete the course and then consider various ways to carry on learning. Either a course through another agency or perhaps finding someone local who's experienced and can teach me informally (you know, answer questions and discuss).

Eh. I'm a bit disappointed with the day on the whole, but at least the second dive was fun. And I got some sun and fresh air and a ride on a boat.