Dive with ONLY computer?

[Charlie99]

nomoreno once bubbled...
You are right that I want to improve my odds... So you are saying that my analog gauges will provide addtional failure points. How likely?

I was just responding to your comment that you "want to prepare for the worst case scenario".

Loss of gas pressure indications isn't anywhere as bad as the actual loss of gas.

A broken HP hose, or a leak from the o-ring in the SPG will dump your air. Computer failure just causes you to gracefully abort the dive.

You have to figure in both the probabilities and the consequences.

Or you can just go dive. None of the above failures should be a big deal.

Although the "correct" procedure is to abort if you loss gas pressure indication, I've seen a couple of cases where the divers just went ahead and finished the dive. One woman whose AI computer failed said, "I alway have more air than my husband, so I just asked him how much air he had, and stayed closer than normal". This was a typical rec dive that starts off deep, then most of the dive is spent relatively shallow and the overall risk of continuing the dive really wasn't all that great.

 

[nomoreno]

Thank you all for your comments.

BTW, does computer need to be serviced annually?

 

[Roncone]

I had been diving with a hoseless computer (Oceanic DataTrans+) since 1998. Each dive would have the occasional loss of pressure info. I would have to reorient my arm to get the signal back. Over the past 5 years, I did have 2 dive trips where I could not get the transmitter linked to the computer at all and I was forced to borrow analog gauges to replace my transmitter. I never had a backup SPG. I always thought that if I lost the signal at depth, I could always just ascend and end the dive, because I managed my gas properly. By the way, I had the unit replaced by Oceanic and I still had the same problems.

In the past year, I started diving more frequently/seriously and decided to buy the seemingly very reliable Vytek. I brought it with me to the Bahamas last month for a week of diving. I never got a signal loss. However, on 2 occasions during a dozen dives I got wildly erroneous pressure readings for about 20 seconds, and then it self corrected. The first time, my tank started showing 205 psi 15 minutes into the dive. The second time this happened was a day or so later where I read nearly 3000 psi at my safety stop. Needless to say, my Vytek is now in the shop. I also have a small OMS backup SPG on a hose, clipped to my D-ring just for peace of mind, after 5 years of sporadic signal problems with multiple computers. I highly recommend backup info. It's one thing to lose a reading and then abort if need be, but if the pressure reading is wrong, you may not know what to believe...

My 0.02

Dive safe,

Ron

 

[jplacson]

Hmm... interesting... any news on why your Vytec was giving wrong pressure readings? Could it be that someone else in the area was using a Vytec on the same channel code?

Just wondering, cuz I just purchased a Vytec w/o the transmitter... if and when I do decide to go hoseless, and not DIR... I just wanna know the existing problems and limitations of the Vytec transmitter. Thanks!

 

[Roncone]

I was the only diver with a Vytek (and the only diver with a hoseless computer).

I hope I just have a lemon and that this isn't a periodic problem. The fact that nobody else with the setup has experienced supports the theory that I have a lemon.

Suunto has the unit and is testing it.

Ron

 

[buttermanr]

I notice that the replies are all focusing on the SPG, which is really not all that relevant. This may sound strange, but the simple fact is that if your SPG fails, whether it's built in a computer or not, you need to abort the dive and get to the surface as quickly as safely possible .

The key question is how to achieve this if you have no working gauges and the answer is that it depends on your dive-profile.
- If you are not near any non-deco limits, you can just do a slow visual ascent and you really don't need any gauges.
- If you need to make deco stops the situation becomes difficult without gauges: you would have to remember the deco times and depths from just before the computer failure and then visually judge the depth and clock the time by counting seconds. Extremely difficult to do even under perfect conditions, let alone in an emergency situation.

Another key consideration is your buddy. If your buddy has analog gauges these can help get you to the surface safely. If your buddy only has a computer this can work too providing that you both have the same dive profiles for the last couple of days.

As for myself: I usually dive with only a computer (Aeris 300G) but always with a buddy and stay away from the non-deco limits.

RB

 

[MikeFerrara]

A significant percentage of dives do require decompression. If my SPG fails, I'm still ok. I know how much gas I have at the time of failure and I have an adequate reserve planned. While I will turn the dive at this time I will not abreviate any stops. On a recreational dive I would handle it much the same way. While I would end the dive I would not ruch my ascent in any way. A broken gauge isn't the same as being OOA.

In the case of a bottom timer or computer failure, it's again much the same. Sometimes I have a backup but if not, I just use my buddies for the ascent. I do have several computers (that I use for bottom timers) in addition to my bottom timer but I never rely on them to calculate my decompression. They just tell me depth and time. When it fails, I know what my profile has been and my buddies gauges can guid me through my ascent if I don't have a backup.

OTOH, if you're totally reliant on the computer for decompression status you're hose for the rest of the day. Sorry about your luck. Me, I'll just grab a spare out of my bag and keep diving.

 

[jplacson]

Well, I'm just lucky that the group I dive with basically has the same profile as me... we all go diving for the weekend and dive at the same time so everyone with a computer is basically a redundant system since we all stick close.

 

[Sean326]

I have dove with an air z nitrox hoseless for quite a while, every 5 or 10 dives i lose signal for a few seconds, but then it comes back.

I check my air enough so that i always have a good idea of what i have. If it ever were to die completely i would just end the dive and take a long safety stop.

I do have a small pony bottle SPG screwed directly into my first stage (no hose) so i can check my gas on the boat before the dive without waiting to boot up my air Z.