What happened - rapid ascent

I was just on a dive off of Catalina Island. Gear wise, I had on a 7-mil wetsuit and my new'ish Tusa X-Wing BCD. I was a couple pounds underweighted. We got down to around 70' max depth. From there, the bottom sloped up to around 50'. As we followed the bottom, I started to become positively bouyant. My BCD has two deflators. A standard one, and a powered deflator. I typically use the powered deflator. I was deflating as we were ascending, but it didn't feel like was dumping air. I ascended a few feet and switched to the manual deflator. It didn't help and I again rose a couple feet. At this point, I was in trouble and at about 40'. I pulled my my shoulder dump and my dive buddy pulled my butt dump, but barely anything came out and I just got more and more positively bouyant until the point of no return. My inflator wasn't stuck, but at about 20' I did end up pressing just to make sure and it definitely pumped more air into my BCD.

I'm a bit freaked out with my BCD now. It was like it was retaining air that it couldn't release. This is only my 4th dive with it.

Ensure that your are properly weighted and do some easy
dives focusing on maneuvering the air in the BCD and getting it to the exhausts. It's probable with jacket style bcds that there was air trapped somewhere. Get to know the BCD really well.



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Aluminim tanks become positive buoyant when air is used up. Do a buoyancy check with a near empty tank next time.

under water some where

You may recall from your open water training that air has weight and depending on the cylinder you were using it could be 4-6 pounds for an aluminum 80. So if you were a "couple pounds underweight", in reality it could have been closer to 6-8 pounds.

"I'm a bit freaked out with my BCD now. It was like it was retaining air that it couldn't release."
It is possible your BC had air trapped, I'm not familiar with TUSA X-wing.
Were you vertical when you were trying to vent or horizontal?
If horizontal and the butt dump is on the divers right and you rolled to divers right, trying to get inflator to vent, you could trap air in the BC.

Good thing is you're OK, a bit shaken, but OK.

Do a proper buoyancy check either in a pool or shallow water and make a couple dives in shallow water until you can either sort the issue out or have confidence you can make a controlled ascent.

Just a guess but try this on for size:
Ascending wet suit becomes more buoyant, AL 80 is moving from negative to 4 Pounds positive. So if you were 2 pounds underweighted at the start as you moved to 1000 PSI you would be 4-6 pounds underweight.

Melvin Pasley
NAUI Instructor 50764
Handicapped SCUBA Association International Instructor 3017

Please excuse my ignorance....but how does a power deflator actually work?

pjhansman:

Please excuse my ignorance....but how does a power deflator actually work?

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This is the first I'm hearing of it too. Some sort of vacuum empty system?

pjhansman:

Please excuse my ignorance....but how does a power deflator actually work?

Click to expand...

The details are pretty thin, but it sounds like it somehow uses tank air to power-deflate the BC.

Based on absolutely nothing, I'm guessing some sort of venturi or air-powered air pump. Not sure how else it could work.

flots.

flots am:

The details are pretty thin, but it sounds like it somehow uses tank air to power-deflate the BC.

Based on absolutely nothing, I'm guessing some sort of venturi or air-powered air pump. Not sure how else it could work.

flots.

Click to expand...

Manufacture Site:

TUSA’s Active Purge Assist system is a revolutionary BCJ accessory technology. This pneumatically assisted purge system and newly designed OPEV (Over Pressure Exhaust Valve) offers significantly enhanced flow rates over a standard inflator system, which allows for immediate purge and inflation response.

Click to expand...

Tusa

Watching the video it appears there is a third button which opens the OPV on the shoulder

Scott:

Tusa

Watching the video it appears there is a third button which opens the OPV on the shoulder

Click to expand...

...does it also have a remote control ? or a twin-scroll turbo ?