Ken:

Sorry it's taken me a while to answer, but I needed to get some =

information on the incident.  Please read below.

You wrote:
>----------
>Subject: RE: seeking opinions on isolator valves/Jusw
>CC: "'Cave Diving list'" <cavers@ww*.ge*.co*>,
>        "' techdiver@aquanaut.com '" <techdiver@aquanaut.com>
>Priority: normal
>In-reply-to: <199803300536_MC2-3851-E37B@co*.co*>
>X-mailer: Pegasus Mail for Win32 (v2.53/R1)
>Message-ID: <53A41D60C9A@co*.ci*.uf*.ed*>
>
>Conrad,
>
>Think back, how many people were out of air? Two.
>
>McFadden and Main. Gavin was the only one with air in his tanks.
>
>Now, if Bill Gavin had been using independent doubles, how well do
>you think that would have worked?
>
>Do you sing?
>
>Ken


I've been going over the information which I have, which comes from =

Martyn Farr's book.  If my source is in some way incorrect, so may my =

results. I apologize in advance for any mistakes or incorrections.

Let me first make a quick summary of what happened.  If you have more =

accurate information, please correct me.

Three divers enter Little Dismal, Gavin, Main & McFadden.  Gavin is to =

scooter to one end, the other two to go upstream into a side tunnel for =

surveying, to adepth of about 66 mts. (220 feet).  M&M are in a low =

ceiling area, so bad visibility is unavoidable (zero viz.).  When Main =

calls the dive, he then passes McF, and proceeds to the chamber where =

the downstreanm tunnel leads off.  There he notices he is alone and =

waits for McF.  When he is about to start back to look for McF, he =

notices Gavin arriving on his way to the exit.  After communicating =

Gavin goes to look for McF while Main waits.  Gavin finds McF, who has =

lost the line and is stressed.  As they return to the chamber where =

Main is, McF runs out of air and breather from Gavin's second =

regulator. By now McF is highly stressed.  They start to get out, but =

before reaching their deco tanks, Gavin also runs out of air.  Main has =

air, but not very much of it.  During the swapping process on to one of =

 Main's regulators, McF blacked out.  Gavin was out of air, and Main =

put a regulator in Gavin's mouth, and dragged him through a =

constriction to reach their deco tanks. McF died but Gavin and Main =

were able to survive.


The situation is an extremely difficult one. It's very easy to find =

faults when sitting in front of your computer, with knowledge of the =

events, and I'm almost ashamed of attempting to analyse the accident, =

however I suppose no further harm will come from this.  Also I'd like =

to stress that no attack or criticism of what happened nor the persons =

involved, nor of their actions is intended.   A few things do however =

come to mind:

1- McF probably had a problem which made him lag behind Main.  =

Presumably something that made him lose the line and become =

disoriented.  Could N2 narcosis have been a factor here? If Main hadn't =

lost contact with McF perhaps there would have been no incident?

2- Main waited for McF instead of going back to look for him.  Perhaps =

if he hadn't waited he could have solved the problem while it was more =

manageable.

3- Once Gavin showed up, he was probably in a calmer mood than Main, so =

it was sensible for him to search for McF instead of Main.

4- Gavin returns with McF and has to share air with him.  On the return =

journey, Gavin runs out of air. With IMDs, Gavin and McF ran out of air =

simultaneously.  I agree that with IDs, one of the two would have ran =

out of air before the other, forcing them to buddy-breathe or to have =

McF borrow air from Main. With IMDs they were able to get the most out =

of Gavin's tanks.

5- Main can do nothing for McF, but is able to rescue Gavin & take him =

to the deco tanks.  Ultimately Main cannot share air and attemp to =

rescue two persons, so he rescued the one that was still conscious.  =

Perhapos if he had tried to buddy-breathe with Gavin and put a =

regulator in McF's mouth & drag the two of them through the =

restriction, the result would have been a triple death.

Now back to your original question:

>Now, if Bill Gavin had been using independent doubles, how well do
>you think that would have worked?

It would have been different, if on IDs. If Gavin's tank had emptied =

before McF's.  Then Gavin would have had to retrieve his remaining =

(operational) regulator from McF, who would have had to borrow from =

Main. If McF's borrowed tank would have emptied first, he would also =

have had to borrow from Main.  But in this case, perhaps, and I say =

*perhaps* they could have ALL made it to the deco tanks...  It would =

have depended on the amount of air Main had left, and in their capacity =

to do this gas swithching in an extremely stressful situation.

There are no easy answers, especially to these sad events, just hypothese=
s.

Regards

Conrad


>> Date:          Mon, 30 Mar 1998 05:33:48 -0500
>> From:          Conrad Daubanton <100774.1625@co*.co*>
>> Subject:       RE: seeking opinions on isolator valves/Jusw
>> To:            "Ken Sallot" <ken@co*.ci*.uf*.ed*>
>> Cc:            "'Cave Diving list'" <cavers@ww*.ge*.co*>,
>>                "' techdiver@aquanaut.com '" <techdiver@aquanaut.com>
>
>> Ken:
>>
>> Please remind us about the McFadden accident & in what way Indep.
>> Doubl. would have made things worse.  As far as I can recall it was an=

>> out of gas problem with high stress levels making things difficult for=

>> the three divers.  When two of the three had no more gas, thigs became=

>> overwhelmingly difficult.
>>
>> Also please see more comments below where appropriate.
>>
>> Thanks
>>
>> Conrad
>>
>> >----------
>> >De: "Ken Sallot"
>> >Para: Jsuw; Conrad Daubanton
>> >Cc: "' techdiver@aquanaut.com '"; "'Cave Diving list'"
>> >Asunto: RE: seeking opinions on isolator valves
>> >Fecha: Viernes 27 de Marzo de 1998 3:53
>> >
>> >Sender: ken@co*.ci*.uf*.ed*
>> >Received: from smtp.ufl.edu (sp04.nerdc.ufl.edu [128.227.175.134])
>> >	by hil-img-2.compuserve.com (8.8.6/8.8.6/2.10) with ESMTP id VAA0153=
5
>> >	for <100774.1625@co*.co*>; Thu, 26 Mar 1998 21:53:17 -0500 (E=
ST)
>> >Received: from condor.circa.ufl.edu (condor.circa.ufl.edu [128.227.8.=
24])
>> >	by smtp.ufl.edu (8.8.7/8.8.7/1.5.1) with ESMTP id VAA64254;
>> >	Thu, 26 Mar 1998 21:53:10 -0500
>> >Received: from CONDOR/SpoolDir by condor.circa.ufl.edu (Mercury 1.40)=
;
>> >    26 Mar 98 21:53:09 +500
>> >Received: from SpoolDir by CONDOR (Mercury 1.40); 26 Mar 98 21:52:54 =
+500
>> >Received: from ascentia- (128.227.206.168) by condor.circa.ufl.edu
>> (Mercury 1.40);
>> >    26 Mar 98 21:52:51 +500
>> >Comments: Authenticated sender is <ken@co*.ci*.uf*.ed*>
>> >From: "Ken Sallot" <ken@co*.ci*.uf*.ed*>
>> >To: Jsuw <Jsuw@ao*.co*>, Conrad Daubanton <100774.1625@co*.co*=
>
>> >Date: Thu, 26 Mar 1998 21:56:10 +0000
>> >MIME-Version: 1.0
>> >Content-type: text/plain; charset=3DISO-8859-1
>> >Content-transfer-encoding: Quoted-printable
>> >Subject: RE: seeking opinions on isolator valves
>> >CC: "'Cave Diving list'" <cavers@ww*.ge*.co*>,
>> >        "' techdiver@aquanaut.com '" <techdiver@aquanaut.com>
>> >Priority: normal
>> >In-reply-to: <199803251547_MC2-37EE-2CC5@co*.co*>
>> >X-mailer: Pegasus Mail for Win32 (v2.53/R1)
>> >Message-ID: <4B6966846D8@co*.ci*.uf*.ed*>
>> >
>> >Conrad,
>> >
>> >I have to give you credit for at least trying to think the logic
>> >through, which is a lot better then most. However, one real simple
>> >thing to remember is that with any sort of independent system you'll
>> >never be able to access all of your gas.
>>
>> True, that's one of the disadvantages of I.D.s, you will not have
>> access to gas in the troublesome tank/regulator.  It's an inherent
>> disadvantage of I.D. which one may or may not accept.  That is why you=

>> must turn around when there's enough gas on any one of your two tanks
>> to allow you to exit safely.  Rule of thirds.
>>
>> On the positive side of I.D.s,  it's extremely unlikely that you will
>> lose all your gas.  A double failure is much more improbable than on
>> Isolated Manifold Doubles (IMD), though of course it can still happen
>> if Murphy decides to make your day ... .;-(
>>
>> > Independents have so much
>> >more convolution to them beyond just the "task loading" aspect to
>> >hem.
>>
>> >Overall I like a lot of the CDAA policies for cave training, except
>> >the requirement for independents.. Once again, the logic wasn't all
>> >thought through. Remember, if you have a first stage failure on a
>> >manifolded system (and the handwheel is intact), you can still access=

>> >all of your gas in doubles.
>>
>> According to Sue, not if you are wearing North. Diver Compressed
>> neoprene suits!....;-)
>>
>> Seriously now, it's one of the situations where the IMD have an
>> advantage...but not always.
>>
>> >You might hope, think, and pray you'll never need to get to all of
>> >that gas, but there have been recorded Charlie Foxtrots where if
>> >people had the added problems of independents there would have been
>> >multiple fatalities (the McFadden fatality comes to mind, if those
>> >guys were diving independents and had a failure then more then just
>> >Bill McFadden would have died).
>>
>> See above...
>>
>> >Ken
>>
>> Thanks to your comments, Jusw will be able to make a logical decision
>> based on sound reasoning, not dogma, which is what he was asking for i=
n
>> the first place.
>>
>> Perhaps, as Josep commented, unless you will be in a situation that ma=
y
>> place you out of reach of the handwheels, IMD may be superior to ID.
>> But if you get into those difficult situations, (sumps, zero viz. etc.=
)
>> or when (God forbid) diving solo, then IDs are better.
>>
>> Regards
>>
>> Conrad
>>
>> > Date:          Wed, 25 Mar 1998 15:42:38 -0500
>> > From:          Conrad Daubanton <100774.1625@co*.co*>
>> > Subject:       RE: seeking opinions on isolator valves
>> > To:            Jsuw <Jsuw@ao*.co*>
>> > Cc:            "'Cave Diving list'" <cavers@ww*.ge*.co*>,
>> >                "' techdiver@aquanaut.com '" <techdiver@aquanaut.com>=

>>
>> > JUSW
>> >
>> > I quote you...
>> >
>> > > Others say that it is an unlikely problem to occur, so an isolator=
 is
>> > not necessary.>
>> >
>> > Careful,...  it may be unlikely, but what's the price you'd pay if i=
t
>> > happens? (And it will happen, we just don't know how nor when)
>> >
>> > Ken Sallot has already explained the logic, now here's another set o=
f
>> > questions:
>> >
>> > a)-	Should the isolator valve be open or closed during a dive, if so=
 why?
>> >
>> > 	If it's open you can breathe from one regulator out of the two tank=
s,
>> > but depending on how quickly you can close the isolator, if at all, =
you
>> > may lose half your gas or all of it, in case of trouble.
>> >
>> > 	If it's closed you'll never lose more than half your remaining gas,=

>> > provided you breathed from both regulators evenly, that is making
>> > switches every 10 bar/20 bar or so.  This is similar to using
>> > independent doubles.
>> >
>> > b)-	What could happen if it were open & trouble happens?
>> >
>> > 	It happened to Exley's partner in a dive in the Atlantida lava hole=
 in
>> > the Canary Islands.  The diver in question didn't realize the noise
>> > came from his own gear, thinking Exley had a problem, by the time th=
e
>> > mistake had been cleared, almost all the gas in both tanks had been
>> > lost.   Only their great experience & training allowed them to get t=
o
>> > the stage cylinders and eventually survive the dive.
>> >
>> > c)-	What could happen if it were closed & trouble happens?
>> >
>> > 	In the previous example, exit from the cave would have been
>> > considerably less stressing, as Exley's partner would have had a ful=
l
>> > third in one of his tanks.
>> >
>> > d)-	With a regular manifold, how redundant is your gear?
>> >
>> > 	Only as quick as you are in closing the valves... if they can be
>> > closed, and if the problem is not a tank neck O-ring.  I don't like =
the
>> > idea of using a regular manifold (without isolator) in an overhead
>> > environment or in a decompression dive.  For me it's either with
>> > isolator, or else independent doubles.
>> >
>> > e)-	Are there any advantages/disadvantages to independent doubles?
>> >
>> > 	Advantage: It's very improbable that you will be left without gas
>> > provided you balance tank consumption.  It would require a double
>> > system failure something very improbable (has happened though! Partn=
er
>> > provided gas to exit cave).  If a low cave ceiling forces you to
>> > side-mount your tanks, then you have no choice but to have independe=
nt
>> > tanks.  Also you KNOW for sure that both regs are in perfect working=

>> > order, as you're switching from one to the other regularly. The natu=
re
>> > of many caves/sumps  make the porterage of single tanks easier than
>> > manifolded ones through complicated extensive dry cave sections.
>> >
>> > 	Disadvantage: More task loading (frequent regulator changes), requi=
res
>> > a diver that switches regulators instinctively, therefore training i=
s
>> > longer. If you don't change regulators properly, then you'll not hav=
e a
>> > balanced redundancy in case of failure.  Some divers may have a hard=

>> > time adjusting to perpetual exchange...  some argue that this produc=
es
>> > excessive task load, but most tech divers and cave divers in Europe
>> > dive this way.
>> >
>> > No system is pefect nor foolproof, just pick the one you think best
>> > suits you diving needs and use caution and common sense.
>> >
>> >
>> > Conrad Daubanton
>> >
>> >
>> > >----------
>> > >De: Jsuw
>> > >Para: ;
>> > >Asunto: seeking opinions on isolator valves
>> > >Fecha: Mi=E9rcoles 25 de Marzo de 1998 3:00
>> > >
>> > >Sender: owner-techdiver@aquanaut.com
>> > >Received: from bighorn.terra.net (bighorn.terra.net [199.103.128.2]=
)
>> > >	by arl-img-6.compuserve.com (8.8.6/8.8.6/2.10) with ESMTP id VAA27=
618;
>> > >	Tue, 24 Mar 1998 21:00:27 -0500 (EST)
>> > >Received: (mail@lo*)
>> > >	by bighorn.terra.net (8.8.6/jr3.9) for
>> > >	id UAA17579; Tue, 24 Mar 1998 20:50:35 -0500
>> > >Precedence: bulk
>> > >Errors-To: owner-techdiver@aquanaut.com
>> > >Received: from bighorn.terra.net (root@lo*)
>> > >	by bighorn.terra.net (8.8.6/jr3.9) with EXEC for techdiver
>> > >	id TAA14654; Tue, 24 Mar 1998 19:44:29 -0500
>> > >Received: from imo28.mx.aol.com (imo28.mx.aol.com [198.81.17.72])
>> > >	by bighorn.terra.net (8.8.6/jr3.9) with ESMTP for =

<techdiver@aquanaut.com>
>> > >	id TAA14646; Tue, 24 Mar 1998 19:44:29 -0500
>> > >Received: from Jsuw@ao*.co*
>> > >	by imo28.mx.aol.com (IMOv13.ems) id 7QKUa06523;
>> > >	Tue, 24 Mar 1998 19:40:45 -0500 (EST)
> >> >From: Jsuw <Jsuw@ao*.co*>
>> > >Message-ID: <e2d30005.3518528f@ao*.co*>
>> > >Date: Tue, 24 Mar 1998 19:40:45 EST
>> > >To: cavers@ww*.ge*.co*, techdiver@aquanaut.com
>> > >Mime-Version: 1.0
> >> >Subject: seeking opinions on isolator valves
> >> >Content-type: text/plain; charset=3DUS-ASCII
> >> >Content-transfer-encoding: 7bit
> >> >X-Mailer: AOL 4.0 for Windows 95 sub 120
>> > >
>> > >I am in the market for doubles for cave diving and also for tech
>> diving.  The
>> > >one thing I still have a question about is whether to get a =

manifold with or
>> > >without an isolator valve.
>> > >
>> > >Some people seem to like having a way to preserve the gas in at lea=
st one
>> > >cylinder in case of a problem.  Others say that it is an unlikely =

problem to
>> > >occur, so an isolator is not necessary.
>> > >
>> > >I'm interested in hearing opinions, along with your rationale.
>> > >
>> > >Thanks!
>> > >--
>> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.co=
m'.
>> > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.c=
om'.
>> >
>>>
--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]