Pick apart my rescue: air-share ascent from 110'

[Zef]

One thing to consider is that with the depth you were diving to your gas plan was not conservative enough. However brief your descent to 41m was it was still your deepest depth...at 40meters with an average consumption rate of 25L/min for each diver the pressure you planned to begin ascending should have been more around 165bar for 12L tank (AL80) or 140bar for a 15L tank. Those gauge readings include arriving at the surface with 50bar left in the tank that both divers are breathing off of in an emergency, with an ascent time based on 9m/min with a 2.5min stop at half the max depth and a 1min stop at 5 meters.

One other thing about your depth...your post reads as if you saw something in the sand and dropped down to check it out....it does not read as if you originally planned to dive to 41 meters. I can't stress enough that one should "Plan your dive and dive your plan"...you should normally only stray from your plan if there is an emergency...dropping down to check out something in the sand was not an emergency.

Recommend reading up on Rock Bottom.

Good job getting to yourself on your buddy to the surface safely. Luckily things did not go further south than they did.

-Z

 

[Lorenzoid]

It was very kind of @dewdropsonrosa to focus the thread on "picking apart" her actions as rescuer rather than on the actions (or inactions) of the rescued diver. Looks like you did a great job. Not much to pick apart. But of course the burning question is what led to there being an incident in the first place. The diver failed to switch to his pony. It sounds like he hadn't practiced with it enough for it to be ingrained in muscle memory.

 

[Marie13]

It was very kind of @dewdropsonrosa to focus the thread on "picking apart" her actions as rescuer rather than on the actions (or inactions) of the rescued diver. Looks like you did a great job. Not much to pick apart. But of course the burning question is what led to there being an incident in the first place. The diver failed to switch to his pony. It sounds like he hadn't practiced with it enough for it to be ingrained in muscle memory.

Pony practice issue is addressed in post 41 of the other thread.

 

[Lorenzoid]

Pony practice issue is addressed in post 41 of the other thread.

Then what more can be said here? Diver 1 free-flowed. Diver 2 shared air. Good. From the other thread, I thought Diver 1 was the real topic of interest?

 

[Neilwood]

What I take from this is a number of points:
1) If you are going to add safety equipment such as a pony to your gear, make sure you are practised in how to use it. That does not mean 30 mins in the pool the day before. Practise shutting down your tank and deploying the pony and the reverse procedure (you may wish to switch back onto back gas if the free flow was arrested quickly
enough
2) If you are adding a pony, remember to use it otherwise it is just added weight.
3) Make sure your rescue skills have had some practise in case of a buddy like that.

Another one is , if you are paired with an instabuddy like that, don't just assume that they know how to (and will) use their equipment in the event of a situation.

@dewdropsonrosa well done on the rescue. Had you not been as aware, this could have been a lot worse

 

[Diving Dubai]

Given than on Con Ed courses most students make pig's ear out of a (Briefed) OOA/Airshare event which I use as a skills check on the course, I congratulate you for a job well done.

Contrary to other opinions, I wouldn't' have put them on their pony straight away. You had a known good air supply in your Alt so that was step one (Get air to your buddy). Step 2 wss to manage the situation, you chose to shut down their gas, others suggested to stop the free flow - also possible, but in these situations you act without thinking too much. Either way was correct, but turning the tank off was the surest way.

Your controlled ascent was good and you chose to get him to switch regs at the SS. Given his lack of experience this was the safest rather than get him to remove and replace a reg at depth.

One never knows how they will react in a sticky situation until they have one for real. You it seems handled it well.

Hopefully the buddy will take away some lessons, but it's quite common for a new diver faced with a real incident to be like a rabbit in the headlights, so some careful counselling would be the best solution

 

[seeker242]

9. Once we had a good air source in his mouth and his tank off, we signaled OK and immediately started our ascent. I wasn’t sure how much of our remaining NDL we used up and I wanted to (a) avoid incurring a deco obligations and (b) get to a depth where our air would last longer. I believe I had 1200-1500 psi (~80-100 bar) in the tank at the start of our ascent.

10. We ascended almost within kissing distance (36’/1m octo hose) for about 100’ to reach our safety stop.

Overall sounds pretty good but you asked to pick it apart so here we go. One question that comes to mind reading this was "If you weren't sure how much of remaining NDL was used, then how do you know it wasn't exceeded?" Of course a simple computer check would tell you that. I'm assuming you had checked at some point to make sure you were not in deco and did not actually have any obligations.

 

[dewdropsonrosa]

Overall sounds pretty good but you asked to pick it apart so here we go. One question that comes to mind reading this was "If you weren't sure how much of remaining NDL was used, then how do you know it wasn't exceeded?" Of course a simple computer check would tell you that. I'm assuming you had checked at some point to make sure you were not in deco and did not actually have any obligations.

This is a good question and I'm glad you asked for clarification! I checked my computer at the start of our ascent and *I* was not in deco.

I did not have the presence of mind to check Buddy's computer to ensure that *he* hadn't entered deco yet. However, he was not locked out or in penalty at the surface - I'll make a guess that he was still in NDL.

A very good lesson for next time!

 

[dewdropsonrosa]

This can't be a common issue or else it would be talked about over and over again during the course, so could you do a new diver a favour and expand on this a little more please?

Or if it isn't really what this thread is for, then please feel free to PM me with an explanation.

As a side note.........great job on the save. That can't happen every day?

Below is my understanding, but I sincerely welcome more detail from someone who's more of a gearhead than I am.

When using regulators that are not designed for cold water (roughly speaking, <50°F or 10°C) in low temperatures, it's possible to induce a freeflow if you are (1) breathing hard from the regs and (2) inflating for a sustained period of time.

My understanding of the science is that this causes rapid adiabatic cooling in the first stage and an ice crystal might form. The regulator "fails safe" and free-flows instead of jamming and leaving you OOA.

This issue is largely obviated by using regulators that are designed to handle cold water conditions.

 

[peeweediver]

Thanks for sharing this experience for all of us to both "pick apart" but also learn from. Since spouse and I are diving the Wisconsin for the first time next month, the post certainly got my attention. I have been thinking about free flow due to what I've been told is the temp at the boat, 41 degrees. Recently serviced, cold-water regs should avoid that, but you never know. From my end, you stayed calm, handled the situation extremely well and, most importantly, returned healthy. I can't think of any situation that, in hind-sight, I couldn't have done better. Sharing this experience with us shows your intent to be the best you can be. Spouse and I tend to give each other a wide berth when buddying. Think I may stay more in "kissing" distance for this wreck. We will certainly discuss your experience and plan our response actions accordingly.
Thanks again

Rob