Coast Guard Cutter Healy Deaths

[mntdiver]

I find it interesting that they were using FFM, that the air in BM Duque's tank was completely depleted, and that LT Hill's tank had only 90 psig in it. The air tested good. There was no CO, ethanol, or screened drug in either diver's systems.

While these findings of fact are interesting, I don't think they pinpoint the exact cause of these two fatalities. A thorough "Fault Tree Analyses" would be appropriate for this event, which is a Systems Safety methodology of looking at an accident scenario. I may do this a bit later, and post some of it here. But one observation is that with a FFM, divers rarely die of anoxia using air with scuba. Something had to cause them to loose their air supply.

Since this is the ScubaBoard, I have to ask if anyone has experience with AGA Full Face Mask a few questions. I find it curious that these divers were very quickly out-of-air at depth, probably because they had been working extremely hard trying to swim to the surface while greatly overweighted, and in extremely cold (29 degrees F) water. I know that the AGA mask has a positive pressure breathing feature on it too (or at least used to in the 1990s). My question to those familiar with the mask (I've only used it a few times, and in a pool) is this, under extreme workload, with high demand for air in extremely cold water, is the AGA FFM prone to icing-caused free flow? If so, and that happened in a positive pressure mode, how long would it take to drain a 100 cubic foot tank, assuming a break in the seal around the face, at a depth of greater than 150 fsw?

John C. Ratliff (SeaRat), CSP

It's not impossible that there could have been a freeze up of the regulators on the Interspiro (AGA) masks, but unlikely, they perform well in extreme cold environments. Most likely a cold water failure would be the first stage.

Extrapolating from the report, the dive was approximately 38 minutes from the start of the dive to the recovery of the divers, with some breaks in between for the issues stated. However, keep in mind, that when you don a full face mask, you are breathing from your tank unless you're using an ambient breathing valve. My understanding is that these were gray rubber masks, and I don't think they were fitted with ABV's. I'll try to find out. Add to this dive time, at least several minutes (6 minutes at ice edge) of surface time while breathing from the tank, the additional exertion from over weighting, the available air is being consumed. I don't know and it's not stated if the masks were positive pressure or demand regs. I can find this out as well. In the investigation of the equipment, the masks were determined to be in proper functioning condition. The missing protective guard on the regulator is the Shield Ring. This would have no adverse affect on the function of the regulator.

Not knowing at what stage in the dive that the divers made the uncontrolled descent, assuming that it may have been with the rapid payout of line early in the dive, a single 100 cf bottle with an unknown quantity of gas, isn't going to last long at depths in excess of 180 feet, especially with the extreme workload and onset of panic. This is an assumption, but I don't think it's a far stretch.

I would have a significant concern of the fit of the mask, with the hood being fitted over the mask straps. Assuming they were wearing neoprene hoods not properly trimmed for the masks in the first place, then follow-up adjustments would be almost impossible, especially with heavy gloved hands and limited dexterity due to exposure. Pulling the hood over the straps is often an attempt to get the masks to seal directly to the face when the hood isn't trimmed to fit with the mask over the hood. This limits access to the tag end of the straps for adjustment and can interfere with the buckles. It is possible that they could have had fit issues causing leaking of air out of the masks, but this would be jumping to conclusion. Small or narrow faces can be difficult to fit without the interference of an ill fitted and improperly donned hood.

As stated in the report, there was an accumulation of many factors that caused this accident. It appears that with these findings, the directives issued by Adm. Allen are sound and should go a very long way to preventing similar incidents in the future.

 

[shark.byte.usa]

As a ex-Coastie I am disgusted from top to bottom. I really can't say anything else or I will surely violate the TOS, I'll bite my lip. :icosm10:

-Garrett

 

[Doubles]

It is interesting that the accident investigation discusses the appropriateness of split fins, saying that they "are not considered appropriate for heavy diving and lack the power necessary to overcome the drag of a drysuit. Instead, they are better suited for light diving and snorkeling..."

Split fins do not develop a lot of torque. To test this, one need only strap on a pair of steel double tanks, or load themselves up with lead - descend to a shallow bottom, deflate your bc and attempt to swim to the surface - when that fails go back and try it with a pair of blade fins like rockets or jets and compare the difference in effort to make it to the surface.

The only qualified dive supervisor was in the water diving; these two duties can not be done concurrently.

Actually Lt Hill qualification had lapsed.

While these findings of fact are interesting, I don't think they pinpoint the exact cause of these two fatalities.

I believe it does - the minute they deviated from established procedures the probabilities of a fatal accident in that environment would be very high. And its important for all divers to realize this fact as it may save others in the future.

I find it curious that these divers were very quickly out-of-air at depth, probably because they had been working extremely hard trying to swim to the surface while greatly overweighted, and in extremely cold (29 degrees F) water. (SeaRat)

I am more surprised that Lt Hill had 90 psi left. Relatively inexperienced divers who were overweighted, runaway descent, in drysuits with cold water gloves, wearing splitfins. It might only take minutes to consume 100cft of gas in that cold water scenario. Drysuit squeeze may have also impacted their mobility at depth, requiring even more effort to move, resulting in heavier breathing. I do not believe the report mentioned whether the suits were overly inflated when they were pulled to the surface. It would be helpful to know of the suits were venting - the report did mention a lack of bubbles.

Their fins would be useless in arresting the descent, their breathing rates had to be high, and at 180 feet they would be consuming gas at a minimum rate of 6.45 times that at the surface. Consider hyperventilating with this minimum gas consumption rate.

Another item I don't think has been mentioned yet, is that regulators don't work well when tank pressure is below 250 psi. There may have been a period of time at a certain depth where that 90 psi was not available or could not be drawn from the tank.

John I would be very interested in the results of your "Fault Tree Analyses", feel free to pm them to me if you decide not to post them here

Best Regards

Steve

 

[Rick Murchison]

... I am more surprised that Lt Hill had 90 psi left. ... There may have been a period of time at a certain depth where that 90 psi was not available or could not be drawn from the tank. ...

90/6=15.
Yep... empty.
Especially if the pressure was measured back aboard after the tank had warmed back up a bit.
Rick

 

[rongoodman]

There are pictures here: http://www.uscg.mil/ccs/cit/cim/foia/Healy/Number 199/, including several of the tanks mounted backwards on the BCs, with the regulator pointing backwards and the valve on the diver's left instead of right side.

 

[mntdiver]

There are pictures here: http://www.uscg.mil/ccs/cit/cim/foia/Healy/Number 199/, including several of the tanks mounted backwards on the BCs, with the regulator pointing backwards and the valve on the diver's left instead of right side.

In addition, they have the hoses for the FFM's routed over their right shoulder and then folded over the left shoulder. It would have been proper routing if they had the tanks mounted correctly.

Referring to the previous post, the masks were positive pressure and they have no ambient breathing valves.

 

[DeepBound]

This is really very sad.
It sounds like this dive was a purely recreational dive. The ship stopped to give the crew a break, some of them drank beer and lied in the sun, and a couple decided to do some scuba diving for fun. Even so, it's unfortunate that the Coast guard rules weren't followed

 

[John C. Ratliff]

I am continuing to read the report, and am getting some more information. The photos were very helpful, and changed my perception of the dives. I had originally, from the initial reading, thought that the icebreaker had simply come up to the ice, and that this was an open water dive off the ice. But the photos show this not to be the case. This was an under ice dive through a hole in the ice. In other words, this dive was in an overhead environment. As such, it was a technical dive, and special training was necessary to conduct it; this was also referred to in the report, but was easy to miss.

Mntdiver, your confirmation that these AGA masks were positive pressure masks confirms my suspicions about the dive. The reason one diver had zero guage pressure on the surface, and bubbles were observed coming from the mask even though he was not breathing, was either that there was a break in the seal, and the mask was leaking, or that there was an ice-up situation with a second stage free flow. The other diver had 90 pounds in her tank because it was at zero at depth, and lost no air upon ascent.

I am working on a time line, and will probably also put together the analysis I described above just to see where it takes us.

SeaRat

 

[John C. Ratliff]

My reading of this accident investigation is going places I don't want to pursue in a public forum, and out of respect for the families involved, and some who have PMed me, I will proceed no further discussing this event.

John

 

[MikeFerrara]

My reading of this accident investigation is going places I don't want to pursue in a public forum, and out of respect for the families involved, and some who have PMed me, I will proceed no further discussing this event.

John

That's exactly where I ended up after a quick read of the report and one PM.