One thing that hasn't been mentioned yet I had a situation that could have turned out to be just like yours. I have noticed that I have become positively buoyant and started dumping air. I saw air leaving the hose (and lots of it) but was still positive. It turned out that I was pressing inflator button with the palm of my hand. Once I've realized what I was doing I could correct my mistake.
uncontrolled ascent
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DEEPLOU
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I am-a gonna get blasted for this. The heritic I am. But I would rather be heavy any day than light.
Remember that when u check bouyancey it shoult be w/ an empty tank (500psi). If u using an aluminum it is 4 lb bouyant at that time. I forget off hand how negative it is when full. If your perfectly neutral at the beginning of the dive, u gonna be very bouyant at the end.
Remember that when u check bouyancey it shoult be w/ an empty tank (500psi). If u using an aluminum it is 4 lb bouyant at that time. I forget off hand how negative it is when full. If your perfectly neutral at the beginning of the dive, u gonna be very bouyant at the end.
Not a lot to add other than "it happens". Learn from the event, think it through, work out where things didnt work, what can be improved and try to prevent it happening next time.
As others have said, learn where your dumps are (ALL of them) and learn to tell immediately if you're moving vertically in the water (ears, visual reference, gauge etc).
Also worth noting that your position will affect air dumping - air will always move to the highest point so if you're dumping from a valve that isnt the highest point, nothing will happen so you need to know which dump to use and where (and alter body angle if needed).
You mentioned suit expansion and yes that can speed up an ascent.
Another issue maybe were you overweighted? If so you'd have more air in the BC so expansion would be quicker and more pronounced than normal so its worth checking that.
If the worst comes to the worst and you know you're destined for the surface remember to breathe out forcefully all the way. Also go into the flare position to create drag to slow the descent (a combination of this flare and dumping can occasionally stop a seemingly out of control ascent).
If it makes you feel better i just did my first dive of the year with a brand new drysuit and had must first ever out of control ascent. As we all had new kit and months out of practice we decided a shallow warm up dive so no deeper than 20m (~60ft).
A shoulder dump instead of my old suit with a cuff dump that decided no matter what i did wouldnt dump air. It was find below about 30ft but above that i was going up and couldnt dump, had to hold onto rocks until i got to about 20ft then, no more rocks, had to let go and ascend. Decided not to grab my buddy as it isnt really his problem
Ascent wasnt too fast or too steep but im still annoyed i let it happen.
My shoulder dump is being replaced immediately by a cuff dump as i cant trust a valve that MIGHT not dump when i have stops to do. Again, a learning experience.
Other highlights from that dive, got my reg kicked out, mask kicked off and snapped the zip to my BC pocket leaving it fully locked closed and cant repair.
Not bad for 36 mins work
As others have said, learn where your dumps are (ALL of them) and learn to tell immediately if you're moving vertically in the water (ears, visual reference, gauge etc).
Also worth noting that your position will affect air dumping - air will always move to the highest point so if you're dumping from a valve that isnt the highest point, nothing will happen so you need to know which dump to use and where (and alter body angle if needed).
You mentioned suit expansion and yes that can speed up an ascent.
Another issue maybe were you overweighted? If so you'd have more air in the BC so expansion would be quicker and more pronounced than normal so its worth checking that.
If the worst comes to the worst and you know you're destined for the surface remember to breathe out forcefully all the way. Also go into the flare position to create drag to slow the descent (a combination of this flare and dumping can occasionally stop a seemingly out of control ascent).
If it makes you feel better i just did my first dive of the year with a brand new drysuit and had must first ever out of control ascent. As we all had new kit and months out of practice we decided a shallow warm up dive so no deeper than 20m (~60ft).
A shoulder dump instead of my old suit with a cuff dump that decided no matter what i did wouldnt dump air. It was find below about 30ft but above that i was going up and couldnt dump, had to hold onto rocks until i got to about 20ft then, no more rocks, had to let go and ascend. Decided not to grab my buddy as it isnt really his problem
Ascent wasnt too fast or too steep but im still annoyed i let it happen.
My shoulder dump is being replaced immediately by a cuff dump as i cant trust a valve that MIGHT not dump when i have stops to do. Again, a learning experience.
Other highlights from that dive, got my reg kicked out, mask kicked off and snapped the zip to my BC pocket leaving it fully locked closed and cant repair.
Not bad for 36 mins work
DEEPLOU:
Thats one bit of advice im a bit dubious with. In theory if you're exactly neutral at 500psi then fine. HOWEVER in an emergency situation your air can be lower than that, maybe a leak, maybe a buddy on octopus etc. If you have say 150psi left instead and are neutral with 500 you are going to be positive and therefore have problems.
2 ways around this, either calculate the mass of air present at 500psi and add that onto the weight calculation so its neutral empty or just use a tank on fumes, take it down quickly sort the weight and do it that way.
lamont
Contributor
So, i had a runaway ascent the weekend before last (dive with max depth of 35 fsw, so i wasn't concerned about DCS). My equipment config was with my drysuit, AL80 and 18 lbs of weight. This was dive number 10 for me, and dive number 6 on my drysuit.
What I don't know about this ascent is if I was under-weighted or if I just failed to dump out of the drysuit. Until last weekend I hadn't been consciously dumping out of the drysuit shoulder valve -- last weekend I learned how to roll my shoulder and watch the bubbles come out. When I had the ascent though I was in a vertical (standing) position and I'm sure that there wasn't any trapped air in the wing. I handn't been dumping air consciously out of the suit though (but with that 'trim' shouldn't it have been dumping out the suit when I went up?). I hit the surface feeling a little chagrined that I hadn't been able to stop it and then swam down to the bottom (15-20 ft) and let the suit sqeeze tight and didn't have any more bouyancy issues.
I suspected being underweighted, so the next time i dove I used 20 lbs. I wonder though if I just wasn't managing the airspace in my suit at all which caused it?
I will say that learning the shoulder roll to dump gives me a lot more confidence in my ability to consciously manage the air in my drysuit. Now I only wonder when or if that button on the dump gets used...
------------------
I'd also like to add a couple ofcomments to this thread which I don't think I saw addressed enough:
1. Listen to what your ears are telling you. The crackling sound of the reverse sqeeze letting go when i'm ascending lets me know that I'm going up -- it is generally a much better safe ascent meter and warning to dump than my computer. I know that if my ears are crackling that I have to be going up (irregardless of what my eyes think the bottom is doing) and that I need to think about dumping. If my ears are crackling continuously then I'm going up too fast.
2. I've read a bunch of accident reports (DAN, etc) where I see a common thread which is runaway ascent -> fear of DCS -> descent -> buddy separation -> drowning. It seems better to me to stay out of the water -- 1. if you're within the NDLs then there's a good chance you wont have a DCS hit 2. any DCS hit from OW NDL diving probably will not kill you and will completely resolve from chamber treatment, even if it takes a few hours or even a day to get to the chamber 3. a DCS hit coming on as you're descending back down has a much better chance of killing you through drowning you....
What I don't know about this ascent is if I was under-weighted or if I just failed to dump out of the drysuit. Until last weekend I hadn't been consciously dumping out of the drysuit shoulder valve -- last weekend I learned how to roll my shoulder and watch the bubbles come out. When I had the ascent though I was in a vertical (standing) position and I'm sure that there wasn't any trapped air in the wing. I handn't been dumping air consciously out of the suit though (but with that 'trim' shouldn't it have been dumping out the suit when I went up?). I hit the surface feeling a little chagrined that I hadn't been able to stop it and then swam down to the bottom (15-20 ft) and let the suit sqeeze tight and didn't have any more bouyancy issues.
I suspected being underweighted, so the next time i dove I used 20 lbs. I wonder though if I just wasn't managing the airspace in my suit at all which caused it?
I will say that learning the shoulder roll to dump gives me a lot more confidence in my ability to consciously manage the air in my drysuit. Now I only wonder when or if that button on the dump gets used...
------------------
I'd also like to add a couple ofcomments to this thread which I don't think I saw addressed enough:
1. Listen to what your ears are telling you. The crackling sound of the reverse sqeeze letting go when i'm ascending lets me know that I'm going up -- it is generally a much better safe ascent meter and warning to dump than my computer. I know that if my ears are crackling that I have to be going up (irregardless of what my eyes think the bottom is doing) and that I need to think about dumping. If my ears are crackling continuously then I'm going up too fast.
2. I've read a bunch of accident reports (DAN, etc) where I see a common thread which is runaway ascent -> fear of DCS -> descent -> buddy separation -> drowning. It seems better to me to stay out of the water -- 1. if you're within the NDLs then there's a good chance you wont have a DCS hit 2. any DCS hit from OW NDL diving probably will not kill you and will completely resolve from chamber treatment, even if it takes a few hours or even a day to get to the chamber 3. a DCS hit coming on as you're descending back down has a much better chance of killing you through drowning you....
DEEPLOU
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String:
I used 500 psi as that is the general dictum of what to have left at the end of the dive.
To calculate the mass of air present @500psi seems to be a bit tedious for the average (and probably the above average) diver. The difference in bouyance between 500psi and 150psi is neglegible. The main point is adjust your bouyance based the end of the dive not the beginning.
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