From: mayne@eta.cs.fsu.edu (William Mayne)
Subject: Re: DPV info wanted
Reply-To: mayne@cs.fsu.edu
Organization: Florida State University Computer Science Department
Date: Mon, 5 Oct 92 17:11:25 GMT

In article <1992Oct5.105129.10114@meiko.com> gordon@meiko.com (Gordon Henderson) writes:
>There is an interesting incident reported in the BS-AC incident report of
>a diver running out of air while using an DPV of some kind .. Apparently
>the jet of water caused his octopus to freeflow, draining his tank
>without him noticing! I'll dig it out & post the actual report if anyones
>interested, but I think it was only a few lines.

I'm interested. It may sound like someone would have to be a real idiot
to let this happen, but I can see how it could happen to someone using
a DPV for the first time without proper instructions. Even with proper
technique (like not being in the prop wash) the task loading of operating
a DPV can be significant for the inexperienced. I am just beginning to
feel comfortable enough to look around at the sights and enjoy the ride
after 20-30 scooter dives. I still don't enjoy it as much as swimming
most of the time, but for commuting to areas of interest it is great.
Being in a cave makes it more difficult, of course. Tasks include
avoiding running into the wall, handling a light at the same time, keeping
track of the line and a buddy, adjusting bouyancy as the passage goes up
and down, and still keeping track of depth, time, and air supply.

While on the subject of problems using scooters, here is my sad story.
This is long. Needless to say, don't imitate my example.

On about my second scooter dive in a cave, while trying out a scooter
I had just bought (used) I had a scooter flood on the way in. At first
I noticed that it seemed nose heavy, but I attributed this to the fact
that I was trying out a new harness and still not used to the way they
were supposed to handle. Then I stopped and saw water in the headlight.
I decided to park the scooter and continue in swimming, since my partner
and I had gone to a lot of trouble to make this dive. I swam on so I'd
be certain not to get too far for my air supply, being extra cautious
because we were then down to one scooter. My partner set his on low speed
and continued with it. After turning around (well before thirds, allowing
for extra time to drag the dead scooter out) I let him tow me back to
where I'd parked.

When I picked up the scooter and unclipped it from the line I hit
the trigger and it came on at full speed and wouldn't quit. It
got away from me and went to the floor, still running, where it
blew up an enormous cloud of silt. My partner who was about 20
feet away said it looked like an atomic bomb blast with me at
ground zero - a column of silt shooting up to the ceiling and
spreading out into a mushroom cloud. At first I held on to the line
with one hand and the scooter with the other, but I quickly decided
to get out of the silt cloud and survey the situation. I found my
partner waiting in clear water a short distance down stream, toward the
exit. The flow was almost zero so the silt wasn't moving
toward him at any significant rate. After exchanging okays and
signaling for him to wait I went back into the silt cloud and
managed to retrieve the scooter, which was still running. I worked
with the switch but couldn't get it to stop.

I got control of it and we proceeded toward the exit. Then
at a point where the passage went down into a big room I had
to take one hand off the scooter to adjust my bouyancy and
I again lost control of it. The silt here was at least two
feet deep all the way across this big room, and the distance
from the line to the floor where the scooter went after I let
go to maintain contact with the line was more than I could reach.
Besides, by then my experience had by then taught me that I probably
wouldn't be able to handle a runaway scooter through the restriction
just before the exit. At that point I decided to leave the scooter
and go out. We had a short decompression and did an extra safety stop
as usual. We were okay and apart from trouble with the scooter it had
been a good dive.

After getting out I briefly considered waiting for it run
down and going back in to recover the scooter, which was only a
few hundred feet from the entrance. We still had enough air to do
another short dive under normal conditions, even by cave diving
safety standards. But we were cold. Waiting around wasn't a very
attractive prospect and to do the recovery dive safely would require
more planning and full tanks. So we went home, leaving the scooter
temporarily to its fate, running full blast.

The next night, about 30 hours after the ill fated dive,
I went back with an improvised lift bag and recovered the
scooter. I had been concerned that someone would find it
in the mean time and take it, but I needn't have worried.
It had kicked up so much silt visibility was still
only about five feet where it had been unlimited before.
I knew exactly where the abandoned scooter was and I could barely
find it. Although everything went well on the recovery that was
one of my more challenging dives.

My initial worry, as I planned the recovery dive, was that
I had left the charging port plug out and was responsible for
the damage. It turned out I hadn't. The shop I had just bought
the scooter from took it back and refunded what I'd paid for
it. I never did find out what caused it to flood or its
ultimate fate. Most likely it had leaked around the propeller
shaft because the back compartment was completely flooded.
I assume that flooding with fresh water wouldn't do irreparable
damage.

I chastised myself for taking a scooter into a cave
without a test in deep open water and for not calling the dive
as soon as I saw water in the headlight. But I felt good that
even though Murphy's law had been proved correct - the worst
possible failure at just about the worst possible time - I had
survived, trying as much as was reasonable to get out with the
scooter but never putting myself or my partner in mortal danger.

Bill Mayne

From: boell@hpcc01.corp.hp.com (Donald P Boell)
Date: Wed, 30 Sep 1992 17:06:33 GMT
Subject: Re: Re: SCAPA-FLOW  Scotland (Long) comments from my trips
Organization: the HP Corporate notes server